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306.Журнал Сибирского федерального университета. Сер. Техника и технологии №1 2010

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Журнал Сибирского федерального университета
2010
Journal of Siberian Federal University
3 (1)
Техника и технологии
Engineering & Technologies
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CONTENTS / СОДЕРЖАНИЕ
Dallas H. Abbott, Perri Gerard-Little, Sarah Coste,
Stephanie Coste, Dee Breger and Simon K. Haslett
Exotic Grains in a Core from Cornwall, NY $ Do They Have
an Impact Source?
?5?
Richard B. Firestone, Allen West, Zsolt Revay,
Jonathan T. Hagstrum, Tamas Belgya,
Shane S. Que Hee and Alan R. Smith
Analysis of the Younger Dryas Impact Layer
? 30 ?
Editorial Advisory Board
Chairman:
Eugene A. Vaganov
Members:
Kirill S. Alexandrov
Josef J. Gitelzon
Vasily F. Shabanov
Andrey G. Degermendzhy
Valery L. Mironov
Gennady L. Pashkov
Vladimir V. Shaidurov
Veniamin S. Sokolov
Editorial Board:
Editor-in-Chief:
Mikhail I. Gladyshev
Founding Editor:
Vladimir I. Kolmakov
Managing Editor:
Olga F. Alexandrova
Executive Editor for Engineering &
Technologies:
Vitaly S. Biront
Edward Bryant, Simon K. Haslett, Sander Scheffers,
Anja Scheffers and Dieter Kelletat
Tsunami Chronology Supporting Late Holocene Impacts
? 63 ?
Kord Ernstson, Werner Mayer, Andreas Neumair,
Barbara Rappenglьck, Michael A. Rappenglьck,
Dirk Sudhaus and Kurt W. Zeller
The Chiemgau Crater Strewn Field: Evidence of a Holocene
Large Impact Event in Southeast Bavaria, Germany
? 72 ?
Konstantin V. Simonov
Computational Experiment in the Problem of the Recent Traces
of Oceanic Cosmic Impacts
? 104 ?
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????????? ? ?????? 9.03.2010 ?. ?????? 84x108/16. ???. ???. ?. 10,7.
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?????????? ? ??? ???. 660041 ??????????, ??. ?????????, 82a.
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Editorial board for Engineering &
Technologies:
Yury D. Alashkevich
Viktor G. Anopchenko
Sergey M. Geraschenko
Gennadiy I. Gritsko
Lev V. Endjievsky
Sergey V. Kaverzin
Valery V. Kravtsov
Vladimir A. Kulagin
Sergey A. Mikhaylenko
Vladimir V. Moskvichev
Anatoli M. Sazonov
Vasiliy I. Panteleev
Sergey P. Pan?ko
Peter V. Polyakov
Viktor N. Timofeev
Galina A. Chiganova
Oleg Ostrovski
Harald Oye
????????????? ? ??????????? ???
?? ? ??77-28-722 ?? 29.06.2007 ?.
Jonathan T. Hagstrum, Richard B. Firestone,
Allen West, Zsolt Stefanka and Zsolt Revay
Micrometeorite Impacts in Beringian Mammoth Tusksand a
Bison Skull
? 123 ?
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??????????? ? ????????).
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?? ????? ?????????? ? ?????. ??? ? 1980 ???? ?????? ?????? Alvarez L.W., Alvarez W.,
Asaro F., Michel H.V. Extraterrestrial cause for the Cretaceous-Tertiary extinction. ? Science,
1980, V. 208, ? 4448, P. 1095-1108 ??????? ??????? ??????? ??????????? ?????????
? ???????? ?????????? ?????????? ? ?????? ????? ???????? ? ????????. ??????
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Journal of Siberian Federal University. Engineering & Technologies 1 (2010 3) 5-29
~~~
??? 5551.3
Exotic Grains in a Core from Cornwall,
NY ? Do They Have an Impact Source?
Dallas H. Abbotta*, Perri Gerard-Littlea,
Sarah Costea, Stephanie Costea,
Dee Bregerb and Simon K. Haslettc
a
Lamont Doherty Earth Observatory of Columbia University,
Palisades, NY 10964, USA
b
Micrographic Arts,
Greenfield Center, NY 12833, USA
c
CELT, University of Wales,
Newport, Lodge Road, Caerleon, South Wales, NP18 3QT, UK 1
Received 3.02.2010, received in revised form 27.02.2010, accepted 9.03.2010
We have found seven discrete layers in a bog core from Cornwall, NY about 80 km away from
the Atlantic Ocean. All but two layers contain material that is unlikely to be locally derived.
In most cases, the material in the layers has been transported thousands of kilometers from its
source area. Six out of the seven layers are diffi cult to explain except through impact processes.
If all of these layers are derived from impacts that produced craters, the data imply a very high
impact rate during late Holocene time. In addition, we have been able to associate two of the
impact ejecta layers with dated tsunami events that span the Atlantic Ocean. If this discovery is
validated by further research, it implies a much larger tsunami hazard in the Atlantic Ocean than
previously reported.
Keywords: sedimentation rate, sediment transport, scanning electron microscope (SEM) analysis,
impact ejecta layer, impact hypothesis during late Holocene time, tsunami hazard in the Atlantic
Ocean.
Introduction
Impact ejecta travel thousands of kilometers away from their source crater. They
are deposited within seconds to minutes of the impact event [11]. If impact ejecta could be
discerned within cores with rapid sedimentation rates, they would constitute marker horizons
with geologically instantaneous ages. In this paper, we discuss seven layers from a bog core
with a sedimentation rate of ~100 cm per 1000 years. In each case, some component of the layer
suggests transport over long distances. Each layer also contains components that are suggestive
of impact. However, a confirmation of the impact origin and the source crater for each layer is
still in progress.
*
1
Corresponding author E-mail address: dallas@ldeo.columbia.edu
© Siberian Federal University. All rights reserved
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Background
In 2006, we used a piston corer to take a core from Tamarack Pond in Black Rock Forest
near Cornwall, NY. Tamarack Pond is an artificial lake that was a bog until about 100 years ago.
Approximately 1 km away, an earlier core from Sutherland Pond is known to have a sedimentation rate
of about 100 cm per thousand years [22]. We are interested in determining if Tamarack Pond also had
a similar sedimentation rate and geological history.
In our initial studies, we sampled for pollen and found that the sedimentation rate was similar to that
of the Sutherland Pond core. We then searched for datable seeds and twigs. These were used to define a
dated stratigraphy for the Tamarack Pond core [13]. We found that the sedimentation rate for the upper
part of the core was identical within error to that of the previously dated Sutherland Pond core. The lower
part of the Tamarack Pond core had no material that could be dated. Therefore, we extrapolate our ages
downward assuming that the sedimentation rate is the same as that in Sutherland Pond.
Regional Geological Setting
The area around Tamarack Pond consists of Proterozoic age rocks of the Hudson Highlands.
With the exception of a few granites and pegmatites, most of the rocks are hornblende-granulite grade
gneisses [3]. None of the rocks have fossils. There are no active volcanoes in the area. The closest
source of glassy volcanic rocks of Holocene age is the volcanic arc in the Caribbean. Tamarack Pond
is on a local topographic high with low relief. Thus, there is no expectation of any long distance of
sediment transport sourced from younger rocks.
Laboratory Methods
We took our core sample on an island mat of vegetation in the center of Tamarack Pond (Fig. 1).
The upper 260 cm of the «core» contained only water. To avoid transposition errors, we have retained
our original estimates of depth. Thus, the top of the sediment layer and the 2006 A.D. age horizon is
at 260 cm depth.
Samples were processed in two different ways. Our initial samples were taken at 10 cm intervals.
They were burned in an oven at 400°C and then sieved with stainless steel sieves and dried in an oven
at 60°C. Our samples for dating and pollen analysis were not burned but were sieved in stainless steel
sieves and dried in an oven at 60°C. The sieved samples were divided into 3 different size fractions:
>150 ?m, >63 ?m, and >38 ?m. We also kept all sieving residues. The two largest size fractions were
examined optically with a microscope with a maximum magnification of 110 times. Interesting grains
that did not look detrital were selected for examination with a scanning electron microscope.
The scanning electron microscope (SEM) analysis consisted of two parts. We first examined
the samples using an FEI XL30 ESEM in both secondary and backscatter modes. Secondly, we used
the EDAX energy dispersive X-ray analyzer (EDS) to determine the composition of the sample. We
combined all of this data to determine the origin of each grain.
Layer A. 350-355 cm. Corrected 14C Age: 1006±67 A.D.
This layer contains four grains that appear either distally transported and/or impact related. The
first is a fresh basaltic glass shard with no vesicles (Fig. 2). The nearest source of basaltic glass from
recent volcanism is either along the mid-Atlantic spreading ridge (2800 km away) or in the western
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Fig. 1. Location map. Inset. Location of Black Rock Forest relative to east coast of North America. Large map:
Red circle: Location of Tamarack Pond. Gray circles: Locations of Sutherland Pond and central administration
building of Black Rock forest in Cornwall, NY. Black Rock forest is in the Hudson Highlands just west of the
Hudson River. Image from Geomapapp. Layer A. 350-355 cm. Corrected 14C Age: 1006±67 A.D
Fig. 2. Fresh basaltic glass shard and radiolarian. A. SEM image of glass shard. Note curved broken surfaces
which are characteristic of glass. B. X-ray analysis (EDS) of surface of glass shard. Composition does not match
that of any mineral. It does match the composition of basaltic glass. C. Radiolarian-species is not identifiable but
the genus is Cenosphaera. D. Analysis of the surface of the radiolarian showing that is dominantly composed of
SiO2. The minor Al, Ca, and C peaks may be from material coating the radiolarian test
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 3. Glauconite microfossil cast and C rich spherule. A. Microfossil cast composed of glauconite clay. The
cast is green in color. B. X-ray analysis (EDAX) of the composition of the microfossil cast. C. Perfectly round,
vesicular spherule. D. X-ray analysis (EDAX) of the composition of the spherule
United States (3700 away). The nearest Caribbean volcano is 2600 km away but Caribbean volcanic
glass is generally more silicic than basalt. Thus, we infer that if this basaltic glass is volcanic in origin,
it has been transported a minimum distance of 2800 km.
The second grain is a radiolarian belonging to the genus Cenosphaera (James Hayes, written
comm.). Cenosphaera is most commonly found in the mid-high latitudes 40°-50° N and 40°-50°S or in
upwelling areas. It is very uncommon in the tropics [21].
The third grain is a glauconitic microfossil cast (Fig. 3). Close-ups of the grain show that it has
morphology like that of other clay minerals. The compositional analysis matches the composition of
glauconite. The last grain is a vesicular, perfectly round Carbon-rich spherule with a smooth surface in
between the holes. Round, vesicular C-rich spherules have been found in the impact ejecta layer from
the younger Dryas [12].
Discussion of Origin of Layer A
Two of the components of layer A are of undoubted marine origin. Glauconite casts form exclusively
in the marine environment, either within marine microfossils or as a replacement of faecal pellets.
Glauconite is considered to be so unstable that it cannot survive reworking [31]. The glauconite we have
found is a microfossil cast, most probably of a foraminifer. The radiolarian is also of marine origin and
is most probably from 40° to 50° N or an upwelling region in the North Atlantic. A third component of
layer A is a basaltic glass. Because the glass has no vesicles and no significant potassium, it is unlikely
to come from a continental basalt flow or an arc volcano. As basalt is deeply buried on older oceanic
crust, the most probable nearby sources are the mid-Atlantic ridge or thinly sedimented oceanic crust.
If we look for marine sediments in the Atlantic that contain both glauconite and radiolarians, are
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 4. Locations of marine sediment cores containing both radiolarians and glauconite (source of data, Lamont
core curator Rusty Lotti)
between 40° and 50° N, and are close to a mid-ocean ridge, there are only three sites with the correct
sedimentary assemblage and geographic location (Fig. 4). These sites are approximately 3800 to 4000
km away from Black Rock Forest.
Because these locations are so far away from Black Rock Forest, the only viable method for
transporting the material to Black Rock Forest is an impact event. This hypothesis would fit with the
inclusion of a perfectly round carbon spherule with a smooth surface in layer A. In known impact
ejecta layers, there are many perfectly round spherules with smooth surfaces of varying compositions
[9, 23, 33]. The perfect roundness and smoothness of impact spherules is the result of solidification in
a vacuum or near vacuum produced by the impact. The carbon spherules in layer A closely resemble
carbon impact spherules from the impact ejecta layer of the younger Dryas [12]. The impact hypothesis
has several testable predictions. Because the impact must have been relatively large in order to produce
a discernable ejecta layer over 3700 km from the source area of its marine components, it should also
have produced a tsunami. Therefore, we have searched the geological record for a tsunami in the
Atlantic sometime between 939 A. D. and 1073 A.D.
Tsunami in the Atlantic between 939 A.D. and 1073 A.D.
We have found tsunami events with the right age range in two locations. The first tsunami event
has a known age of Sept 28, 1014 A.D [8, 16]. This event is reported in several different historical
sources (Fig. 5). From the Anglo-Saxon chronicle «and in this year on St. Michaels mass eve came the
great sea flood widely through this country and ran up so far as it had never done before and drowned
many vils and of mankind a countless number».
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Table 1. Locations and Azimuths to Tsunami Sources for Events circa 1014 A.D
Location
Curacao-N
Curacao-N
Porth Cwyfan
Porth Terfyn
Mounts Bay
Kent
Sussex
Hampshire
Max_Age, AD
893
906
>1180
>1180
1014
1014
1014
1014
Min_Age, A.D.
1028
1045
>1460
>1460
1014
1014
1014
1014
Azimuth
N45E
N45E
S47W
S43W
unknown
unknown
unknown
unknown
Lat.
Lon
12.37618
12.39583
53.19125
53.18437
50.12142
51.11491
50.82057
50.81342
-69.12700
-69.15107
-4.50448
-4.46661
-5.47675
1.32091
-0.16187
-1.22543
The second tsunami event is in the Lesser Antilles. Two 14C dates of a tsunami (Table 1) have the
right age range to match the age of layer A [27]. The tsunami came in from the northeast of the Lesser
Antilles [29], consistent with a source northeast of the Lesser Antilles.
White circle: source area with glauconite and radiolarians in marine sediment that also has young
basalt close to the surface. Blue circle: Location of Black Rock Forest. Yellow circles: Locations of
tsunami deposits that are circa 1014 A.D. (Caribbean) or have an exact calendar year date of September
28, 1014 A.D. (Great Britain). Arrows: Inferred direction to tsunami source derived from the elongation
direction of tsunami boulder deposits.
Fig. 5. Proposed source area of transported layer in Black Rock forest and locations of 1014 A.D. or circa 1014
A.D. tsunami layers
Discussion of Tsunami Data
Of the three possible impact sites, the northernmost site would not produce a tsunami in
the English Channel area. Either one of the other two possible impact sites could have provided
a source for the two known tsunami events on opposite sides of the Atlantic that occurred about
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 6. Ammonium values in ice core samples. A: Ammonium values in the GISP2 ice core from Greenland [24,
34]. B: Ammonium values in the Taylor dome ice core
from Antarctica [25]
1000 years ago. There is also a lack of tsunami deposits that are circa 1000 B.P. near Lisbon,
Portugal. The bay in Lisbon faces southwest and contains tsunami deposits that are roughly the
age of the 1775 earthquake and an older set of deposits that are roughly 2440±50 B.P. in age [30].
The lack of tsunami deposits that are circa 1000 years old near Lisbon can be explained if the
source for the 1014 A.D. tsunami was somewhat north of the latitude of Lisbon (38.7°N). The
tsunami data are therefore consistent with the hypothesis of an impact into the North Atlantic
above 40°N but cannot prove it.
Ice Core Data and the Impact Hypothesis
An impact origin for the tsunami in Great Britain in 1014 A.D. is proposed based on its association
with a prominent ammonium anomaly in the GRIP ice core [6]. The youngest prominent ammonium
anomaly in the GISP2 ice core is the same age as the Tunguska impact event (Fig. 6A) [4, 28, 35]. We
have also found a prominent ammonium anomaly in the Taylor Dome ice core that occurs at the same
time (August 13.1930) as an impact event in Brazil, South America [5] (Fig. 6B). Thus, we infer that
some ammonium anomalies in ice cores were produced by impact events.
Conclusions: Layer A
A core from Tamarack Pond in Cornwall, NY has a layer containing a transported radiolarian
in association with a glauconite microfossil cast, low-K basaltic glass, and a perfectly round, smooth
carbon spherule. There are three LDEO cores in the north Atlantic near the ridge crest that could be
close to the source of this layer. Because these cores are all at least 3700 km away from Cornwall,
NY, an impact into the Atlantic is the only viable method of transport of glauconite, radiolarians, and
basaltic glass to Black Rock Forest.
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 7. Red coral with coccoliths in its interstices. A: SEM photomicrograph of red coral. B: X-ray analysis of the
composition of the red coral. C: SEM photomicrograph of coccolith from the interstices of the red coral. Species:
Gephyrocapsa oceanica. D: SEM photomicrograph of second coccolith from the interstices of the red coral. Species: Emiliana huxleyi
The temporal correlation of circa 1014 A.D. tsunami events in the Caribbean and Great Britain
with the age of layer A provides further support for our Atlantic impact hypothesis. The azimuths of
the tsunami sources for both events are consistent with a source area that is located close to two of
our three proposed impact sites. The results are encouraging but not definitive. A search for a crater
candidate must be undertaken near our proposed impact sites and the presence of thick layers of impact
ejecta close to any crater candidates should then be investigated. In addition, future work on the solid
fraction of the 1014 A.D. horizon in the GISP2 core should show the presence of impact ejecta that
includes marine components. Nevertheless, our initial work is intriguing and a follow up should be
vigorously pursued.
Layer B. 382-384 cm. Age: 925±76 A.D.
This layer contains at least one undoubtedly transported component, a red coral fragment with
two coccoliths trapped in its cells (Fig. 7).
There is no red coral in the Atlantic Ocean near Black Rock Forest. Red coral is found predominantly
in the Mediterranean Sea. However, the closest location with red coral is the Cape Verde Islands. One of
the coccoliths is Gephyrocapsa. The angle between the long axis of Gephyrocapsa and the orientation
of the bridge across the middle is called the bridge angle. The bridge angle varies as a function of
the temperature in which the coccolith precipitated. Bridge angles greater than 56 degrees denote
equatorial associations [7]. The Gephyrocapsa in Fig. 7 is Gephyrocapsa Equatorial. Gephyrocapsa
Equatorial lives at latitudes between 17°N and 17°S [7].
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 8. Ilmenite grain with usual texture and splashed on Ni metal and calcium phosphate. The Ni metal appears as
the bright drops on the upper left side of the image. A: SEM photomicrograph of ilmenite grain. B: X-ray analysis
of composition of ilmenite grain. Some Mg and Al are included in the structure and this is unusual. C. X-ray
analysis of the composition of the splashed on Ni metal. The Fe and Ti peaks are from the surrounding ilmenite
grain. All of the oxygen can be accounted for by the ilmenite. Thus, the Ni is likely to be Ni metal rather than Ni
oxide. D: X-ray analysis of splashed on Ca phosphate
The layer also contains at least one defi nite piece of impact ejecta, an ilmenite grain with
splashed on Ni metal and splashed on Ca phosphate (Fig. 8). In addition, the layer contains one
partially dissolved and apparently melted foraminiferal fossil of a type that lives in brackish
water. This layer is discussed in more detail in a separate publication (Gerard-Little et al., in
preparation).
Layer C. 452-454 cm. Age: 28±92 B.C. (120 B.C to 64 A.D.)
This layer contains glauconite rosettes on a glassy looking fragment, basaltic glass with lens
shaped fractures, a quartz grain with tiny micrometer scale Sn-rich silicate spherules in holes in the
surface, and titanomagnetite grains with odd craters on their surfaces (Fig. 9, 10, 11). Glauconite
rosettes have been found in continental basalts on the surface of cracks in basalt or on open
weathering surfaces [17]. In one case, glauconite rosettes were discovered on the surface of samples
from a borehole in basalt [18]. The metamorphic grade of the basalt is extremely low. Basaltic glass
with lens shaped fractures has not been reported elsewhere, to our knowledge. We found three Snrich silicate spherules from an unknown source on the surface of the quartz grain. The surface of
the titanomagnetite grain is extremely fresh, and it cannot have been exposed to weathering for any
length of time. The craters in the titanomagnetite grain are similar to craters produced by high speed
projectiles.
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Fig. 9. Comparison of glauconite in two different forms. A: Glauconite rosette on top surface of rock fragment
from Layer C. B: X-ray analysis of glauconite rosette to left. C: Microfossil cast composed of glauconite from layer A. D. X-ray analysis of glauconite cast to left. Note in particular the three iron peaks in both X-ray analyses
Fig. 10. Unusual components of layer C. A: Ilmenite grain with unusual craters on its surface. B: X ray analysis
of ilmenite. C: Sn-rich silicate spherules in hole in quartz grain. D: X-ray analysis of spherules
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 11. Basaltic glass with lens-shaped fractures. A. Entire grain showing conchoidally fractured, fresh surfaces.
There is no apparent cleavage. B. X-ray analysis of the grain in A showing a composition like that of typical
basaltic glass. C and D. Close ups of the lens shaped fractures in the surface of the glass. Note that the length to
width ratio of the fractures is about 10 to 1 with width measured at the center of the fractures
Discussion-Layer C
Some sort of catastrophic explosion must have produced the glass and the fractured
titanomagnetite. The basaltic glass has discernable K in it and could be derived from an explosive
volcanic eruption. The closest volcanoes that produce K-rich glass are in the Caribbean, over 2600
km away. However, Caribbean volcanism is typically more silica rich than basalt. The closest
volcanoes producing basaltic rocks are near the mid-Atlantic ridge, about 2900 km away [32].
Microprobe work on the chemistry of the basaltic glass is needed to determine its probable source
area (Fig. 11). The Sn-rich silicate spherules resemble impact spherules but are not defi nitive due
to their small size. If they are impact related the Sn may be derived from the impactor. Impact
ejecta from presumed cometary impactors have enrichments in Sn, Sb, and Pb [20], all elements
with low melting points that are thought to be enriched in comets. Thus, the presence of Sn
does not necessarily tell us anything about the chemistry of the source rocks for this layer. The
glauconite rosettes are derived from basalt that has never experienced high-grade metamorphism.
With the data we have so far, the materials in this layer could be either from a continental impact
event or a large explosive volcanic eruption. If the layer is from a continental impact event, it
could be derived from a local impact site in the Triassic basalts of the Newark group. If so, the
extremely small diameters of the spherules imply a very small source crater only a few meters in
diameter. Alternatively, if the layer is derived from an explosive volcanic eruption, it must have
traveled over 2600 km from its source volcano.
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 12. Possible shocked quartz grain (unpolished). A: SEM image of surface of the grain. Three directions of
planar features are visible. The spacing between the planar fractures is less than a micron, one defining characteristic of shock lamellae. B: X-ray analysis of the composition of the grain. C: Enlargement of the best-resolved
planar features in Fig. A. Edges of the best resolved planar features are delineated by lines on the left side of the
image. The height of the image is equal to a distance of 3.1 micrometers. The planar features in this image have a
spacing of much less than 1 micrometer and thus are clearly PDFs resulting from shock metamorphism [19] rather
than metamorphic deformation features
Layer D. 490-494 cm. Age: 327±113 B.C.
This layer contains two possible shocked quartz grains (Fig. 12). One of the two grains with
shocked quartz also has glauconite. The origin of the grains in this layer is unknown. In theory,
the planar features in the grain are PDFs, as their spacing is much less than 1 micrometer [19].
However, the mainstream impact community will not accept these grains as shocked quartz unless
the grains are imaged in a polished thin section. More grains need to be characterized to pin
down the source location and origin of the layer. The layer has the same age within error as the
Chiemgau impact crater field. It also has the same age within error as a tsunami layer in the
Hudson [14] that contains the following shocked minerals: impact diamond (lonsdaleite), shocked
olivine, and shocked limonite [10]. So far, shocked quartz has not been found in the tsunami layer.
Our papers devoted to the tsunami layer and the confi rmed shocked minerals in the layer are in
preparation.
Layer E. 522-524 cm. Age: 605±97 B.C.
This layer contains a high-Mg carbonate microfossil (Fig. 13). It also contains a glass with
a composition similar to Mg-rich pyroxene or basalt and a glass with a composition similar to
albite feldspar (Fig. 14). The latter glass appears vesicular but only in some areas. The layer also
contains an optically translucent grain with a surface that appears vesiculated in some places.
The grain has an average composition akin to marine clay but has abundant bright material, a
combination of Ni and Fe, on the surface. The Si in the sample can account for all of the minor
oxygen in the analysis.
Discussion Layer E.
The combination of components in layer E (Figs. 13, 14, 15, 16) suggests an impact into an oceanic
area, possessing a basaltic substrate covered by a thin layer of clay rich sediment. Some of the basaltic
glass (Fig. 14) has a small percentage of K so it is most likely from a source that is not on a midocean ridge. The very high Ni content of the material splashed onto the clear grain in Fig. 15, and its
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Fig. 13. Marine carbonate fossil. A: SEM image of marine fossil. B: X-ray analysis of composition of fossil. Note
that there is a strong Mg peak, consistent with either aragonite or high Mg calcite. The carbonate contains about
26 mol% Mg
Fig. 14. Basaltic glass with lens-shaped fractures. A: SEM image of black basaltic glass with lens shaped fractures. B: X-ray analysis of composition of the glass
Fig. 15. Glass Grains. A: SEM image of grain with conchoidal fracture. B: X-ray analysis of composition of the
grain in A. C: SEM image of grain with conchoidal fracture. Parts of the grain appear vesiculated. D: X-ray
analysis of the composition of grain in C
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 16. Metal on Clear Grain. A. SEM backscatter image of entire grain. B. X-ray analysis of composition of
grain matrix. C. SEM backscatter detail of grain showing melted, vesiculated surface and bright material of
higher atomic number splashed on surface. D. X-ray analysis of composition of bright material (includes contribution from surrounding matrix)
apparent lack of oxygen, suggest an event that vaporized and reduced extraterrestrial material. The
high Mg content of the marine fossil suggests a marine platform in very shallow water. The closest
marine platform is Bermuda, over 1200 km away. However, basalt is not exposed near the surface in
Bermuda; it is deeply buried by the subsidence of the islands over time. Because we are seeing fresh
basaltic glass, the source area most likely has very thin sediment cover over a basalt layer. The high
Mg content of the marine fossils precludes a source on most of the crest of the mid-Atlantic ridge, as
it is too deep for aragonite or high Mg calcite to be stable. Taking these factors into account, the next
most plausible source is near a marine hotspot or volcanic arc in the tropics. The closest hotspot islands
in the tropics are the Canary Islands, over 5100 km away. The closest volcanic arc is in the Caribbean,
over 2600 km away.
The size of the grains we have found is relatively large. Making an analogy to the average size of
shocked quartz grains versus distance from the K/T impact site, the source area for Layer E should be
within 9000 km of Black Rock forest [26].
The hypothesis of an impact near the Canary Islands or in the Caribbean around 600 B.C. can be
tested further by looking for tsunami deposits of that age in Spain, Portugal and the Caribbean. Using
ages determined by electron spin resonance dating (ESR), there is one tsunami deposit of that age on
the Caribbean island of Curacao. The tsunami source is NE of Curacao, either in the Atlantic or in the
Caribbean arc. An older tsunami deposit from Portugal has an uncorrected 14C age of 2440±50 B.P.
This age overlaps with the uncorrected 14C age of the tsunami deposit in Curacao of 2511±43 B.P. Thus,
it is possible that all of the ages are derived from the same tsunamigenic event. If so, the tsunami source
is somewhere in the northern tropical Atlantic Ocean or the Caribbean arc.
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Layer F. 542-544 cm. Age: 794±83 B.C.
Layer F contains a carbonate fossil from the ocean, glasses of many types, mineral grains and an
iron chloride spherule. The carbonate fossil is high in Mg, implying a source in shallow water at low
latitudes (Fig. 17). The glasses range in composition from high-Na silicic glass to high-Mg basaltic
glass (Fig. 18). There are mineral grains as well. Fig. 19 (A, B) shows a translucent pink grain with
conchoidal fracture. It is most probably Mg rich garnet (pyrope) from a relatively high-grade terrane.
Fig. 19 (C, D) is of a black glassy looking mineral with relatively high K, Al, and Si. It most resembles
K-feldspar but the black appearance and minor Fe and Mg are typical of glass. Part of the grain is
pulled back like the lid of a sardine can. The glass in Fig. 20 is basaltic glass. It has a pyrite spherule
that is indenting and making a track in it. Fig. 21 shows a perfectly smooth FeCl spherule containing
small amounts of Cr and Ni.
Fig. 17. High Mg carbonate fragment. A: SEM image of submarine fossil. B: X-ray analysis of surface of fossil
near metal contamination from stainless steel sieve
Fig. 18. Conchoidally fractured grains that appear to be glass. A: SEM image of optically clear glass shard. B:
X-ray analysis of the composition of the glass shard. C: Optically clear greenish grain with conchoidal fracture
and gouges. D: X-ray analysis of the composition of C
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Fig. 19. Possible mineral grains. A: Optically clear pink grain with conchoidal fracture. B: X-ray analysis of the
composition of the grain in A. C: Optically clear grain with section pealed back like sardine can. D: X-ray analysis
of the composition of the grain in C
Fig. 20. Pyrite spherule indenting basaltic glass. A: SEM image of entire grain. Pyrite spherule is colored red. B:
X-ray analysis of the composition of the glass. C: Close up of iron sulfide spherule indenting glass. The pyrite is
following a single track. The offset of the track is an optical illusion. D: X-ray analysis of the composition of the
spherule
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Fig. 21. Iron chloride impact spherule. A: SEM image of smooth, perfectly round iron chloride spherule. B: X-ray
analysis of composition of the spherule. Note the Fe, Cr and Ni peaks
Discussion: Layer F
Many unusual features of this layer are most consistent with an impact event. Iron chloride is
a common alteration product of meteoritic iron. However, an iron chloride spherule with a perfectly
smooth surface cannot be a simple ablation product of a fireball or a small meteorite. Cosmic spherules
do not contain large amounts of Cl. If the Cl was added by alteration in situ, the alteration should also
have roughened the surface of the spherule. The Ni in the iron chloride spherule provides further
evidence of an impact origin. The basaltic glass that is being indented by an iron sulfide spherule is
not volcanic glass. The formation of an indentation track without breaking the grain or the spherule
requires the indentor to have a very high speed. In addition, the iron sulfide spherule contains a small
amount of Ni. As far as we know, this sort of feature has never been observed in volcanic ejecta. The
K-rich grain that has been peeled back like the cover of a sardine can is also hard to explain with
normal earth surface processes. However, the high speeds and shock deformation that accompany
impacts can produce fluid like deformation of solid material. The most unusual features of this layer
can all be interpreted as impact ejecta.
The layer also contains material that is geologically normal but is out of place in a fresh water bog.
For example, Mg rich carbonates are typically found in tropical oceans, not in the ocean near New York
City. The New York area has no active volcanoes, making the presence of fresh glass unusual as well.
None of the fresh glass is vesicular. There is no pumice and the glass has highly variable chemistry.
All of these features are most consistent with material transported to this location by an impact rather
than a volcanic eruption.
There are several lines of evidence leading to the conclusion that the impact was under the ocean.
First, there is the presence of a transported marine fossil from a tropical location. Second, an impact
spherule composed of iron chloride would be most likely to form in an oceanic impact where there is
an ample supply of Cl. We have never heard of anyone finding such a spherule before. As most impacts
that have been studied are continental, this is consistent with our inferences about the oceanic origin
of the iron Cl spherule.
There is one piece of data that seems at odds with an oceanic impact. This is the occurrence of a
broken garnet grain of pyrope composition. This is the one grain that might be locally derived from the
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Hudson Highlands or glacial debris. It has probably not been transported for a great distance, as it is
not rounded and it has a very fresh broken surface. The fresh conchoidal fractures on the grain surface
might be from frost weathering. Because, the origin of the grain of pyrope is equivocal, it cannot be
used to infer the location of the impact source.
Conclusions-Layer F
Layer F most likely originated from an impact into the ocean between 30°N and 30°S, where
calcareous organisms with high Mg contents are abundant. There are no known tsunami layers of this
age in the Atlantic Ocean. The spectacular nature of the deposits suggests a large impact. The time
series of tsunami activity from western Australia shows a peak at 785±100 B.C. [8]. The direction to
the source for this tsunami is to the northeast of Australia. Thus, the most probable location of this
impact is in the tropical Pacific Ocean. Because many of the grains we have found are larger than 150
micrometers in diameter, we use the data of [26] to infer that the impact source was within 9000 km of
Black Rock Forest. This rules out an impact source in the western Pacific or the Tasman Sea.
We have found chevrons in Hawaii that point to a site to the northeast of the Hawaiian Islands. We
interpret chevrons as tsunami deposits produced by point sources, i.e. landslides, impacts or volcanic
eruptions. Chevrons cannot form as the result of a tsunami generated by a line source such as a large
subduction zone earthquake. The chevrons we have found in Hawaii are the only chevrons in the
Pacific that point to a possible tropical point source of tsunami. There are several sites along the coast
of Baja California that have shallow carbonate platforms and thin sediment cover over basalt. These
are our candidate source areas for the impact event. This source area would explain why we have such
a spectacular deposit in North America.
Layer G. 562-564 cm. Age: 1082±99 B.C.
Layer G contains 6 shards of glass. None of the glass shards have vesicles and none have the
appearance of volcanic glass. The most unusual of the glass shards is shown above. The surface of the
glass contains three marine microfossils entombed in the glass. The microfossils have some relief and
are not flat on the surface of the glass. Because the fossils appear like coccoliths, we infer they have been
silicified as they were entombed in the glass. Coccoliths are normally composed of calcium carbonate.
Discussion: Layer G
So far as we know, no submarine volcanic eruption has ever been observed to produce silicified
marine microfossils. Recent experimental work on impact ejecta from South America has found that
organic matter can only be preserved in glass if temperatures are ~1600°C [23]. If temperatures are lower,
the organic matter will burn up. We infer that the similar temperatures would be required to preserve
silicified coccoliths. If so, the glass fragment above (Fig. 22) could only have formed during an impact.
There are no Holocene lavas extruded at temperatures above 1600°C. Thus, the most likely
explanation is that the silicified coccoliths formed during a submarine impact.
Possible Correlation to Climate Downturns
Three of the seven layers in Fig. 22 have roughly the same age as prominent climate downturns
(Fig. 23, Table 2). Layers D, C and G have ages that roughly match those of climate downturns at 41
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Fig. 22. Glass shard with embedded silicified coccoliths. A. SEM image of entire glass shard. B. X-ray analysis of
glass shard. C, D and E. Embedded silicified cocoliths
Fig. 23. Time series of impact events compared to nonvolcanic Cl anomalies and climate downturns. A: Nonvolcanic Cl anomalies in the GISP2 ice core. B: Prominent climate downturns proposed by Mike Baillie based on
the analysis of tree ring records. All are proposed to have an extraterrestrial source. C: Discrete impact layers
identified so far in the Tamarack Pond core
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Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
Table 2. Layers in Tamarack Pond Core vs. Climate Downturn and Tsunami Events
Layer Name
Age
Climate Downturn?
Regional Tsunami?
A
1006±67 A.D.
No
Yes, Atlantic
B
925±76 A.D.
No (nonvolcanic Cl)
No
C
28±92 B.C
Yes
No
D
327±113 B.C.
Yes
No (local tsunami)
E
606±97 B.C.
No
Yes, Atlantic
F
794±83 B.C.
No
Yes, Pacific?
G
1082±99 B.C.
Yes
No
B.C., 207 B.C. and 1132 B.C. However, much more work remains before any of these layers can be
linked unequivocally to a climate downturn.
Layer B has an age that roughly matches nonvolcanic Cl anomalies at 921 and 923 A.D. in the
GISP2 ice core. This is important because the largest nonvolcanic Cl anomaly in the last 2000 years is
at 536 A.D. The nonvolcanic Cl anomaly at 536 A.D. corresponds to a time of greatly increased input
of impact ejecta into the GISP2 ice core [2]. The increased input of impact ejecta matches the time
of a dust veil event that lasted from March 536 until August of 537. Thus, at least one nonvolcanic Cl
anomaly and climate downturn can be linked precisely to impact ejecta. The present data is intriguing
but cannot prove that impacts produced the climate downturns at 41 B.C., 207 B.C. and 1132 B.C. In
the short term, more work is needed to more fully characterize each layer in the Tamarack Pond Core
and also to pinpoint the depths of maximum concentration of impact ejecta. In the long term, all of the
layers must be located and precisely dated within ice core samples.
Relationship to Tsunami
The layers that we have not been able to relate to climate downturns or nonvolcanic Cl
anomalies are those that have the same age as regional tsunamis. Two of the postulated tsunamis
are in the Atlantic and might represent smaller impact events. If the third tsunami started in the
eastern Pacific and reached Australia, it should have been quite large. We do not know why the
third event did not produce a climate downturn. Perhaps it occurred in relatively deep water and
produced less dust to cloud the atmosphere. Clearly the water depth of impacts is important.
If we assume that most of these impactors are just barely big enough to produce a crater, an
impactor that hits deep water should produce less atmospheric dust and more water vapor. A
tsunami originating from a deep-water impact event will have a greater initial wave height and is
more likely to travel long distances without significant attenuation. Thus, the inverse relationship
we see between climate downturns and regionally significant tsunami makes sense in terms of the
amount of dust generated by shallow water impacts compared to deep-water impacts. Because we
infer a very high Holocene impact rate compared to the long-term rate of impacts, the simplest
assumption to make is that most impactors are «small», just above the threshold size needed to
generate widely dispersed atmospheric dust.
Further testing of the relationship to tsunami will require searches for impact ejecta within tsunami
layers. We have found evidence of impact ejecta within a local tsunami layer in the Hudson River that
is circa 300 B.C. [10]. This layer contains impact diamonds and shocked minerals. The impact ejecta
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were found in layers deposited below mean sea level. Particularly in the Atlantic, tsunami layers from
bogs and marine cores need to be routinely examined for impact ejecta. Only then can we determine
how many tsunami events are produced by impacts.
Summary of Results
The seven youngest layers in a bog core from Cornwall NY all contain exotic components
that did not form in the Proterozoic age basement of Black Rock Forest. Six out of the seven layers
contain material that is difficult to explain except with an impact event. The youngest layer, layer
A, contains probable impact glass, an equatorial radiolarian, a probable impact spherule, and a
glauconite fossil cast. It is also temporally associated with an ammonium anomaly in the GRIP
ice core and tsunami deposits in Great Britain and the Caribbean. It may have a calendar year age
of 1014 A.D., the age of the ammonium anomaly and the tsunami event in Great Britain. Layer B
contains transported red coral and a grain with native Ni on its surface. Layer C contains glauconite
rosettes, a fresh glass fragment, tiny Sn-rich silicate spherules, and titanomagnetite with odd craters
on its surface. This layer may have a local source from a small impact or it may have a distal
volcanic source. Layer D contains possible shocked quartz grains that must be further verified. One
of the quartz grains appears to be associated with glauconite. This layer could have a local or distal
source. Layer E contains a transported marine microfossil from the tropical ocean, a basaltic glass,
and an albite feldspar or albite rich glass. It also contains a glassy grain with splashed-on Ni metal.
All of these components suggest a tropical source. Layer E has the same age as tsunami deposits
in Portugal and Curacao. It may have originated from an impact into the tropical Atlantic. Layer F
contains a rich variety of material that is likely to be impact-related: an Fe chloride impact spherule
with trace Ni, impact glass indented by a pyrite spherule with trace Ni, and numerous other glasses.
It also contains a high Mg carbonate fossil that was transported from the tropical ocean. Based
on its rich assemblage of material and data on point sources of tsunami in the Pacific, its probable
source area is in the eastern tropical Pacific. Layer G contains silicified coccoliths entombed in
impact glass. It most likely formed during a low latitude impact event. Most of our data suggests
long distance transport of exotic material, in particular fresh glass, marine fossils, Ni rich material,
and possible impact spherules. However, we have not yet identified unequivocal shocked minerals or
impact diamonds in any of these layers in the Tamarack Pond core. This will be required to convince
the mainstream impact community that we have found impact ejecta. Our results are tantalizing and
exciting, but are still equivocal.
Acknowledgements
We thank Academ Gorodok in Krasnoyarsk for providing wonderful hospitality for a HIWG
meeting and for the chance to present our research results to a receptive audience. We thank the National
Science Foundation for their support of Sarah and Stephanie Coste. We thank Black Rock Forest for
their support of Sarah Coste, Stephanie Coste, Perri-Gerard Little and for their support of SEM work
on the Tamarack Pond core. We thank the Climate Center of Lamont-Doherty Earth Observatory of
Columbia University for their support of the geochronological work on the Tamarack Pond core. The
SEM/EDS work was conducted in the Centralized Research Facilities of Drexel University?s College
of Engineering.
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????????? ??????? ? ?????? ?? ????????,
???? ???-???? ? ????? ?? ??? ????????? ??????????????
?. ???????, ?. ???????-??????, ?. ??????,
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??????????? ??????,
?????????????? NP18 3QT, ????? ?????, ???????
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???-????, ????????????? ????? 80 ?? ?? ?????????????? ??????. ??? ????????? ?????,
????? ????, ????????? ????????, ??????? ???? ?? ???????? ???????. ? ???????????
??????? ???? ???????? ? ?????????? ????????? ?? ?????? ?????????? ?? ?????? ??
?????????????. ????? ?? ???? ???????? ?????? ?????????, ???????? ????????? ???????.
???? ??? ??? ????????? ???????? ?? ????????? ??????????? ? ?????????? ?????????????
????????, ?? ??? ?????? ????????????? ????? ??????? ??????? ????????? ???????????
? ?????? ???????? ????????. ????? ????, ?? ?????? ??????? ??? ?????????, ??????????
??????? ?? ????????? ???????????, ? ??????? ? ??????, ??????? ??????????
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?? ??? ????????????? ??????? ??????? ????????? ?????? ? ????????????? ??????, ???
?????????? ?????.
# 28 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Dallas H. Abbott, Perri Gerard-Little?Exotic Grains in a Core from Cornwall, NY-Do They Have an Impact Source?
???????? ?????: ???????? ????????????????, ????????? ???????, ?????? ? ???????
???????????? ???????????? ?????????? (???), ????????? ? ??????????? ????????
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? ????????????? ??????.
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Journal of Siberian Federal University. Engineering & Technologies 1 (2010 3) 30-62
~~~
??? 551.3
Analysis of the Younger Dryas Impact Layer
Richard B. Firestonea, Allen Westb, Zsolt Revayc,
Jonathan T. Hagstrumd*, Tamas Belgyac,
Shane S. Que Heee and Alan R. Smitha
a
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
b
GeoScience Consulting, Box 1636, Dewey, Arizona 86327, USA
c
Institute of Isotopes of the Hungarian Academy of Sciences,
H - 1525 Budapest, P.O.B. 77, Hungary
d
U.S. Geological Survey, 345 Middlefield Road MS 937,
Menlo Park, CA 94025, USA
e
University of California, Los Angeles, ICP-MS Facility,
Los Angeles, CA 90095, USA 1
Received 3.02.2010, received in revised form 27.02.2010, accepted 9.03.2010
We have uncovered a thin layer of magnetic grains and microspherules, carbon spherules, and
glass-like carbon at nine sites across North America, a site in Belgium, and throughout the rims of
16 Carolina Bays. It is consistent with the ejecta layer from an impact event and has been dated to
12.9 ka BP coinciding with the onset of Younger Dryas (YD) cooling and widespread megafaunal
extinctions in North America. At many locations the impact layer is directly below a black mat
marking the sudden disappearance of the megafauna and Clovis people. The distribution pattern
of the Younger Dryas boundary (YDB) ejecta layer is consistent with an impact near the Great
Lakes that deposited terrestrial-like ejecta near the impact site and unusual, titanium-rich
projectile-like ejecta further away. High water content associated with the ejecta, up to 28 at. %
hydrogen (H), suggests the impact occurred over the Laurentide Ice Sheet. YDB microspherules
and magnetic grains are highly enriched in TiO2. Magnetic grains from several sites are enriched
in iridium (Ir), up to 117 ppb. The TiO2/FeO, K/Th, TiO2/Zr, Al2O3/FeO+MgO, CaO/Al2O3, REE/
chondrite, FeO/MnO ratios and SiO2, Na2O, K 2O, Cr2O3, Ni, Co, U, Th and other trace element
abundances are inconsistent with all terrestrial and extraterrestrial (ET) sources except for
KREEP, a lunar igneous rock rich in potassium (K), rare-earth elements (REE), phosphorus
(P), and other incompatible elements including U and Th. Normal Fe, Ti, and 238U/235U isotopic
abundances were found in the magnetic grains, but 234U was enriched over equilibrium values
by 50 % in Murray Springs and by 130 % in Belgium. 40K abundance is enriched by up to 100 %
in YDB sediments and Clovis chert artifacts. Highly vesicular carbon spherules containing
nanodiamonds, glass-like carbon, charcoal and soot found in large quantities in the YDB layer
are consistent with an impact followed by intense burning. Four holes in the Great Lakes, some
deeper than Death Valley, are proposed as possible craters produced by the airburst breakup of
a loosely aggregated projectile.
Keywords: impact ejecta layer, impact crater, methods of elemental analysis, magnetic grain and
microspherule analysis, analysis of carbon spherules and glass-like carbon.
*
1
Corresponding author E-mail address: jhag@usgs.gov
© Siberian Federal University. All rights reserved
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
We have reported [16] a narrow layer of magnetic grains and microspherules, dated to 12.9 ka,
at seven Clovis sites across North America, glacial Lake Hind in Manitoba, Canada, a drumlin in
Alberta, Canada, a comparably dated site in Lommel, Belgium, and throughout the 1-5 m thick rims
of 15 Carolina Bays. Additional markers found in the YD boundary layer (YDB) at most sites include
high concentrations of iridium, glass-like carbon containing nanodiamonds and fullerenes with ET
3
He abundance, carbon spherules, soot, and charcoal. At many sites, a «black mat» lies directly above
the YDB layer, which has also been identified by C. Vance Haynes at 57 sites in North America [23].
Haynes [24] reported that no evidence of extinct megafaunal remains or in situ Clovis artifacts is found
above the black mat and suggested that «the sudden extinction of the Pleistocene megafauna would be
dramatically revealed by explaining that all were gone an instant before the black mat was deposited».
The age of the YDB layer was determined as 12,938±25 cal yr BP from the average of youngest dates
determined at various sites summarized in Table 1. This age coincides with the onset of YD cooling
~12,900 yr BP determined from GISP2 methane and paleotemperature analysis (Fig. 1).
Table 1. Youngest dates available for the sites examined containing YDB markers. In most cases, the sites were
independently dated by other researchers and recalibrated here using IntCal04 [40]. Two sites were not previously radiocarbon dated: (1) Morley drumlin is constrained by the end of local deglaciation to ~13 ka; and (2)
the Chobot site is of Clovis age because of an abundance of Clovis artifacts, limiting the site?s age, according to
Waters and Stafford [49], to a minimum range of ~200 years between 13,125 to 12,925 cal. B.P. Seven of the 10
sites exhibit a black mat immediately overlying the YDB layer
YDB TEST SITES
Da
tes
Black
Mat
Cal BP
± (1?)
14
C Date
± (1?)
500
SOURCE
Blackwater Draw, NM
1
Yes
12982
575
11040
Chobot, AB, CAN
1
Yes
~13000
--
Archaeology --
Staff (2000) [11]
Daisy Cave, CA
1
Yes
13090
140
11180
Erlandson, et al. (1996) [14]
130
Taylor, et. al (1996) [41]
Gainey, MI
1
No
12400
1000
TL
--
Simons, et al. (1984) [39]
Lake Hind, MB, CAN
1
Yes
12755
87
10610
25
UCIAMS 29317 (this work)
Lommel, Belgium
1
Yes
12943
30
10950
50
Morley, AB, CAN
1
Yes
~13000
--
Deglaciation --
Murray Springs, AZ
8
Yes
12916
25
10890
50
Taylor, et al. (1996) [41]
Wally?s Beach, ABA CAN 1
No
12966
61
10980
80
Kooyman, et al. (2001) [31]
Weighted Average 12938
25
Van Geel, et al. (1989) [45]
Boyce, et al. (1991) [6]
Sample collection and preparation
Sediment samples were collected from the YDB layer at each site which was identified by its
proximity to the black mat and/or its association with Clovis-age artifacts. Sediment samples from
above and below the YDB layer were also collected to determine the distribution of YDB markers. The
magnetic and carbon components of the impact layer were separated from sediment as follows.
Separation of the magnetic component of the impact layer
A 2?Ч1?Ч0.5? grade-42 neodymium magnet was used for qualitative in situ field testing to locate
the peak in magnetic grains in the YDB. This worked best in loose, dry sediment with a high grain
concentration. For quantitative analysis several methods were used to separate magnetic grains from
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 1. Haynes, in Taylor, et al. (1996)1, correlated the end of Clovis cultural adaptations with the onset of Younger
Dryas cooling and provided end-Clovis 14C dates that have been calibrated to 12.92 ka for Murray Springs and
12.98 ka for Blackwater Draw, two of the sites we analyzed. This graph displays a corresponding date of 12.9
ka for the onset of the YD in Greenland GISP2 ice core data based on paleotemperature analyses (Alley, 20002,
in red) and changes in methane concentrations (Brook, et al.,20003, in blue). The onset of the YD was marked
by a dramatic 8 °C drop in Greenland temperature in less than 150 years with an associated abrupt decrease in
atmospheric methane concentrations. We propose that these climatic changes were triggered by the YD event at
~ 12.9 ka
sediment, depending upon the type of sediment. For large-scale processing, the following basic
procedures were used with automated equipment and a bank of magnets, which were placed in a
moving stream of either wet or dry sediment. Small samples were processed manually.
For loose or sandy sediment about 500-1000 g of friable sand or silt was first dehydrated at room
temperature and weighed. Then the samples were put into a container and any lumps were broken up.
All processing was done with non-metallic tools to avoid contaminating the sample with foreign metal.
The magnet was placed in a 4-mil plastic bag to prevent grains from adhering directly to the magnet.
Sediment sample was poured over the tightly bagged magnet into an empty container. Magnetic grains
sticking to the magnet were collected in a separate container when the magnet was removed from the
bag. This process was repeated until all of the magnetic grains were recovered. In order to remove dust
and debris still adhering to the magnetic grains and spherules the magnetic fraction was placed in a
beaker of water. The bagged magnet was gently agitated in the beaker to attract the magnetic grains
which were then deposited on to a dry laboratory dish after the magnet was removed from the bag.
After drying, the samples were weighed, catalogued, and examined microscopically.
For sediment that was sticky or clayey and difficult to pulverize about 4 liters of water were added
to each 500-1000 g of sediment and homogenized it into slurry. The bagged magnet was used to extract
magnetic grains from the fluidized mixture and the magnetic grains were then released from the magnet
into a separate container of water and then retrieved onto a laboratory dish as discussed above.
1
2
3
Taylor R.E., Haynes, C.V., and Stuiver M. (1996) Antiquity 70, 515-525.
Alley R.B. (2000) Quaternary Science Reviews 19:213-226.
Brook E. J., Harder, S., Severinghaus J., Steig E.J., and Sucher, C. M. (2000) Global Biogeochem. Cycles, 14(2), 559?572.
# 32 #
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 2. Representative sample of magnetic grains and microspherules extracted from the YDB layer at Blackwater Draw. Grains very from rounded to subrounded to highly angular and colors range from mostly white quartz
to metallic black. Magnetic grains were found in all sediment layers but peaked sharply in the YDB
Although sonication is a common way of separating magnetic grains from sediment, this process
was not used here because that procedure typically collects only the smallest most highly magnetized
grains missing up to 90 % of the remainder, including many of the most interesting items such as
the titanium-rich microspherules. Fig. 2 shows a representative collection of magnetic grains and
microspherules collected at the Blackwater Draw site. The magnetic grains have a continuum of shapes
ranging from sub-round to highly angular and very in color from white to black.
Extraction of magnetic microspherules
The magnetic fraction was extracted from a weighed sediment sample as discussed above. The
concentration of microspherules in bulk sediment is low and it was often necessary to search nearly
the entire magnetic fraction to find them. Approximately 100 mg aliquots of the magnetic fraction were
weighed, deposited sparsely across a microscope slide, and scanned microscopically. Microspherules,
typically ranging from 10-100 ?m, were counted, and their abundance extrapolated to quantity per kg.
Selected microspherules were manually removed from the magnetic fraction with a moistened probe
and placed onto either an SEM mount or double-sided tape on a microscope slide. The spherules were
either left whole or sectioned and given a microprobe polish for analysis by laser ablation or X-ray
fluorescence (SEM/XRF). Representative microspherules from various sites are shown in Fig. 3.
Extraction of carbon spherules, glass-like carbon, and charcoal
Low density carbon spherules were separated by floatation in water. Typically one kg samples
were added to about 4 liters of water and agitated. The floating fraction was collected with a 150-?m
sieve. A second carbon fraction with specific gravity slightly greater than water was manually removed
from the surface of the wet sediment. After drying the carbon spherules at low temperatures they were
collected either manually or gravimetrically by vibrating the dried sample on an inclined, polished
surface. Glass-like carbon and charcoal, in the samples were extracted manually and weighed. Typical
samples of carbon spherules, glass-like carbon, and charcoal are shown in Fig. 4.
# 33 #
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Murray Springs
Chobot
Lommel
Arlington Springs
Gainey
Topper
Blackwater Draw
Carolina Bay
Fig. 3. Titanium rich magnetic microspherules were only found in the YDB at Clovis-age sites
Research site descriptions
The distribution of YDB markers found at research sites described below is summarized in
Table 2.
Murray Springs, near Sierra Vista, Arizona, is one of several local Clovis mammoth kill-sites
associated with a chain of end-Pleistocene ponds at 12.9 ka. Sediments from the YDB layer are mostly
fine to coarse fluvial or lacustrine sand. A distinctive black mat, most likely of algal origin, drapes
conformably over the bones of butchered mammoths, and a thin layer (<2 cm) that contains YDB
markers lies at the base of the black mat and immediately overlies the bones [23]. The upper surfaces
of some Clovis-butchered mammoth bones, which were in direct contact with the YDB and the black
mat, exhibit slightly higher radioactivity and magnetic susceptibility than the lower surfaces. Fig. 5A
shows that the distribution of magnetic grains and spherules, carbon spherules, charcoal, iridium and
nickel peaks in a narrow layer immediately beneath the black mat.
Blackwater Draw in New Mexico is southwest of the town of Clovis, which gave its name to
the type of projectile points first found there. It was a PaleoAmerican hunting site on the bank of a
spring-fed waterhole, where the black mat was found draped over bones of butchered mammoths and
Clovis artifacts. YDB markers are concentrated in a ~2-cm layer of fine-grained fluvial or lacustrine
sediment that lies at the base of the black mat in the uppermost stratigraphic horizon containing in situ
mammal bones and Clovis artifacts. The upper surfaces of some mammal bones were in direct contact
with the YDB or the black mat and exhibited very high levels of radioactivity. We sampled a 2-meter
stratigraphic sequence spanning the YDB down into the deep gravels that date to >40 ka and possibly
to 1.6 Ma [23]. ET markers peaked only in the YDB. Fig. 5B shows that the distribution of magnetic
grains and spherules, glass-like carbon, and iridium peaks in a narrow layer immediately beneath the
black mat.
Lake Hind in Manitoba, Canada, was an end-Pleistocene proglacial lake. Various analyses by
Matthew Boyd, et al., show that at ~12.76 ka, the ice dams on the lake failed catastrophically as part of
a regional pattern of glacial lake drainages. At the YDB, the failure rapidly transformed the lake from
deep to shallow water [7], as shown by pollen analysis and the start of peat accumulation. The sample
# 34 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Vesicular carbon spherules and a copal spherule from the Carolina
Gainey, MI
Murray Springs, AZ
Topper, SC
Glasslike carbon particles
Charcoal from Chobot
Fig. 4. Vesicular carbon spherules, copal (amber) spherules, glass like carbon, and charcoal were abundant in the
YDB layer. Some carbon spherules can be produced in high temperature forest fires. Many carbon spherules contained nanodiamonds which are clear evidence of production during an impact. The association of carbon spherules and copal spherules suggests that they have a common origin, perhaps in different temperatures regimes
of fires following the impact. Glass-like carbon and charcoal may have been produced by the burning of forests
under reduced oxygen conditions caused by the atmospheric shockwave emanating from the impact site
33.00554N 81.49001W
33.00545N 81.49056W
Wally?s Beach, AB
Topper, SC -- T-1
Topper, SC -- T-2
(with paleosol beneath)
33.36120N 81.30440W
CAROLINA BAYS:
Blackville, SC -- T13
33.81883N 78.74181W
33.83118N 78.72379W
33.84034N 78.70906W
34.70992N 78.62043W
34.75566N 79.10870W
Myrtle Beach, SC -- M24
Myrtle Beach, SC -- M32
Salters Lake, NC -- B14
Lumberton, NC -- L33
CAROLINA BAYS:
Myrtle Beach, SC -- M33
35.51865N 76.267917W
(no paleosol reached)
Lk Mattamuskeet ? LM
33.83776N 78.69565W
51.14853N 114.93546W
Morley drumlin, AB
34.81417N 78.84753W
51.23580N 5.26403E
Lommel, BELGIUM
Howard Bay, NC ? HB
49.43970N 100.69783W
Lake Hind, MB, CAN
Myrtle Beach, SC -- M31
34.04207N 120.32009W
Daisy Cave, CA
CLOVIS-AGE SITES:
31.57103N 110.17814W
49.34183N 113.15440W
Murray Springs, AZ
52.99521N 114.71773W
42.93978N 83.72111W
Gainey, MI
34.27564N 103.32633W
Chobot, AB, CAN
(with artifacts)
Blackwater Draw, NM
2
CLOVIS SITES:
1
Latitude--Longitude
0.08
0.53
--
--
0.45
16.12
1.27
0.86
2.8
9.90
0.75
0.28
Yes
1.95
0.51
7.79
2.62
3.20
1.92
2.14
3
--
42
--
--
20
--
22
36
205
1020
16
No
Yes
97
--
6
109
2144
578
768
4
0.14
0.42
Yes
Yes
16.25
.007
0.01
0.21
0.03
Yes
0.06
0.22
Yes
0.07
0.06
--
0.03
0.08
0.11
0.03
5
Yes
777
Yes
Yes
142
No
1458
492
803
16
No
184
Yes
--
257
--
No
1232
11
No
6
Yes
0.20
Yes
Yes
Yes
Yes
2.12
0.73
0.03
0.06
0.13
Yes
Yes
No
No
--
0.06
0.12
0.19
0.03
7
Magnetic
Magnetic
Glass-like Carbon
Charcoal
Grains Microspherules Carbon Spherules
(g/kg)
(g/kg)
(#/kg)
(g/kg)
(#/kg)
Table 2. Summary of the distribution of YDB markers found at the sites as discussed in this paper
--
--
--
1969
--
No
No
No
--
--
--
21
--
No
No
--
--
--
--
9
Carbon
Soot
(ppm)
--
--
--
--
84 (max 682) No
--
--
--
--
--
--
--
81 (max 108)
--
--
--
29 (max 87)
--
--
3 (max 11)
8
He R/Rair in
Fullerenesa
3
No
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
No
No
No
Yes
No
Yes
Yes
10
Black
Mat
No
No
No
No
2.1
No
15
No
15
No
117
3.0
No
No
2.8
51
2.2
No
No
24
11
Iridium
(max.
ppb)
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
35.30104N 78. 84753W
34.95800N 78.70280W
35.78412N 76.434383W
Moore Cty, NC -- MC1
Sewell, NC ? FS3
Lake Phelps ? LP
3
3.40
17.10
--
0.91
--
--
--
389
--
--
--
--
--
--
4
0.99
.013
0.11
0.02
Yes
Yes
Yes
5
489
No
126
152
Yes
Yes
Yes
6
7
1.39
Yes
0.03
11.63
Yes
Yes
Yes
8
--
--
--
--
--
--
9
49 (max 222) 995
--
--
--
--
--
--
No
No
No
No
No
No
10
No
No
No
No
No
No
11
The first value = the total 3He (as R/Rair) released at all temperatures. «Max»= the highest ratio measured for ET helium (3He as R/Rair) during step-heating of the fullerenes
or acid-resistant residue.
a
34.79324N 79.01871W
Lumberton, NC -- L32
AVERAGES
34.78117N 79.04774W
Lumberton, NC -- L31
2
3477766. N 79.05008W
Lumberton, NC -- L28
1
Table 2 continued
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
sediments are fine-grained lacustrine silt and peat. Fig. 5C shows that the distributions of magnetic
grains, carbon spherules, iridium and nickel peak in the Clovis layer.
Chobot is southwest of Edmonton, Alberta, Canada. In Clovis times, it was located along the shore
of a proglacial lake, where a supply of quality flint attracted hunter-gatherers. The presence of Clovis
artifacts [11] dates this level to an interval of ~200 years ending at 12,925 cal B.P. [50]. The Clovis level
is capped by the YDB layer, above which there is a black mat similar to other sites. The YDB sediment
samples are mostly fine-grained and colluvial. Fig. 5D shows that the distributions of magnetic grains
and spherules, carbon spherules, glass-like carbon and charcoal peak in the Clovis layer.
Topper, located on a high bank of the Savannah River near Allendale, South Carolina, was a
Clovis-age flint quarry containing thousands of artifacts. Sediments are eolian, fluvial, colluvial, and
alluvial in origin and are comprised mostly of coarse to medium quartz sand. YDB markers occur
within a ~5-cm interval immediately in and above a distinct layer of Clovis artifacts. Lower sediments
in the sequence have been dated to >55 ka [21], and no ET markers appear in the stratigraphic sections
above or below the YDB. There is no black mat at this site. Fig. 5E shows that the distributions of
magnetic grains and spherules and carbon spherules peak in the Clovis layer. At a new excavation
the neodymium magnet and a magnetic susceptibility meter were used to help identify the YD layer
based on the high iron content. Shortly afterward, the excavators recovered part of a Clovis point
immediately beneath the YD layer (Fig. 6), illustrating the usefulness of the YDB markers for locating
the Clovis horizon in new locations.
Morley is a non-archaeological site west of Calgary in Alberta, Canada. The site is on a raised
drumlin, a sub-glacial erosional landform that formed at the end of the Pleistocene during deglaciation
[6]. The largest drumlin field near Ontario (5000 km2) contains 3,000 drumlins that date to shortly
after 13 ka, and the age of the Morley drumlin field appears to be similar. Later, the ice sheet melted
away leaving atop the drumlin glacial debris containing numerous YDB markers. Samples are mostly
gravel grading down through coarse and medium sand. Fig. 5F shows that the distributions of magnetic
grains and spherules peak in the Clovis layer.
Gainey, north of Detroit, Michigan, was a PaleoAmerican campsite located tens of kilometers
from the southern margin of the Laurentide Ice Sheet at 12.9 ka. Sediments containing YDB markers
are mostly fine alluvial sand and glacial silt. The Gainey site has been closed and hence inaccessible
for many years, and only archived samples from the ~5-cm YDB layer were available for analysis. No
black mat was observed. Fig. 5G shows that the distribution of magnetic grains and spherules peaks
in the Clovis layer.
Wally?s Beach at St. Mary Reservoir, southwestern Alberta, Canada, was a stream-fed valley
that, at 12.9 ka, supported many species of now-extinct megafauna, including mammoths, camels, and
horses. Hundreds of their footprints were found there during prior excavations. A sediment sample of
fine-grained and silty alluvium was provided to us by Dr. Brian Kooyman from the brain cavity of a
horse skull found (Fig. 7) in the YDB layer amidst Clovis points that tested positive for horse protein,
providing some of the first evidence that Clovis peoples hunted horses [31].
Daisy Cave is a cave/rockshelter on San Miguel Island, one of the Channel Islands off the Southern
California coast. This cave does not appear to have been occupied until about 11.5 ka, but a Clovis-age
human skeleton was found on nearby Santa Rosa Island, demonstrating that the PaleoAmericans had
boats capable of reaching the islands [29]. Several markers were found, but others, including Ir, were
# 38 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Fig. 5. Sediment profiles for the A) Murray Springs, B) Blackwater Draw, C) Lake Hind, D) Chobot, E) Topper,
F) Morley drumlin, and G) Gainey sites. Magnetic grains peak in the YDB at all sites and magnetic microspherules are only found in or near the YDB. Carbon spherules, glass-like carbon, charcoal, and iridium also peak in
the YDB. The Blackwater Draw image is a composite of three photos and there is no photo for Gainey
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 6. In a new excavation at the Topper site the Clovis layer was identified with the Nd magnet and a magnetic
susceptibility meter. Subsequently a Clovis point (arrow) was uncovered at that location. This demonstrates that
the magnetic properties can be used to identify the YDB layer at many undated sites
Fig. 7. Horse skull uncovered among Mammoth footprints and Clovis artifacts at the Wally?s Beach (St. Mary
Reservoir) site in Alberta, Canada. Sediment retrieved from this skull was unusually enriched in magnetic grains
(7.5 g per kg sediment) and iridium (51 ppb). Few magnetic microspherules were found inside the skull suggesting
it was buried before the microspherules were deposited
not found, possibly because the protected cave shelter prevented accretion. The sediment with YDB
markers dates to ~13.09 ka [15] and varies from fine sand to silt.
Lommel is in northern Belgium, near the border with the Netherlands. At 12.94 ka [45], this site
was a large late Glacial sand ridge, covered by open forest at the northern edge of a marsh. More than
50 archaeological sites in this area indicate frequent visits by the late Magdalenians, hunter-gatherers
who were contemporaries of the Clovis culture in North America [46]. Throughout the BцllingAllerod, eolian sediments known as the Coversands blanketed the Lommel area. Fig. 8 shows that
the distributions of magnetic grains and spherules, charcoal, iridium, and rare earth elements peak
beneath the Usselo layer, the European analog to the black mat.
Carolina Bays are a group of ?500,000 highly elliptical and often overlapping depressions scattered
throughout the Atlantic Coastal Plain from New Jersey to Alabama (see Fig. 9). They range from ~50 m
to ~10 km in length [37] and are up to ~15 m deep with their parallel long axes oriented predominately
# 40 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Fig. 8. Sediment profile from the Lommel, Belgium site. Numerous YDB markers peak beneath the Usselo layer
the European analog to the black mat. Lommel magnetic grains contained the highest concentration of iridium
(117 ppb) found at an site
Fig. 9. DEM (digital elevation model) image of hundreds of Carolina Bays in Bladen County, NC (left). Like impact craters, many bays overlap other bays, while keeping rims intact. The DEM is color-coded by elevation and
is vertically exaggerated for clarity. The orientation of the major axes of the Carolina Bays (right) points towards
the Great Lakes and Hudson Bay
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
A
B
C
Fig. 10. Sediment profiles for Carolina Bays A) B14, B) M31, and C) M33.
YDB markers, which are distributed in a narrow layer at most Clovis-age
sites, are found throughout the rims of the Carolina Bays. The similar
composition of markers found in the Bays suggests a common origin, but
it remains unclear whether the Bays were formed by the shockwave following the YDB impact or by later Aeolian forces
to the northwest. The bays have poorly stratified, sandy, elevated rims (up to 7 m) that often are higher
to the southeast. All of the Bay rims examined were found to have, throughout their entire 1.5-5-m
sandy rims, a typical assemblage of YDB markers (magnetic grains, magnetic microspherules, iridium,
charcoal, soot, glass-like carbon, nanodiamonds, carbon spherules, and fullerenes with helium-3). In
Howard Bay, markers were concentrated throughout the rim, as well as in a discrete layer (15 cm thick)
located 4 meters deep at the base of the basin fill and containing peaks in magnetic microspherules
and magnetic grains that are enriched in Ir (15 ppb), along with peaks in charcoal, carbon spherules,
and glass-like carbon. In two Bay-lakes, Mattamuskeet and Phelps, glass-like carbon and peaks in
magnetic grains (16-17 g/kg) were found about 4 meters below the water surface and 3 m deep in
sediment that is younger than a marine shell hash that dates to the ocean highstand of the previous
interglacial. Fig. 10 shows how various YDB markers are distributed throughout Carolina Bays near
Elizabethtown NC (B14), Myrtle Beach SC (M31), and Marion SC (M33).
Modern fire sites. Four recent modern sites were surface-sampled. Two were taken from forest
underbrush fires in North Carolina that burned near Holly Grove in 2006 and Ft. Bragg in 2007. Trees
mainly were yellow pine mixed with oak. There was no evidence of carbon spherules and only limited
evidence of glass-like carbon, which usually was fused onto much larger pieces of charcoal. The glasslike carbon did not form on oak charcoal, being visible only on pine charcoal, where it appears to have
formed by combustion of highly flammable pine resin.
Two surface samples also were taken from recent modern fires in Arizona; they were the Walker
fire, which was a forest underbrush fire in 2007 and the Indian Creek Fire near Prescott in 2002, which
# 42 #
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 11. Prompt Gamma-ray Activation Analysis (PGAA) analysis of a typical magnetic grain sample from the
Topper site. The sample was placed in the guided neutron beam at the Budapest Reactor where the induced
prompt gamma-ray spectrum was measured with an Compton-suppressed HPGe detector. Each point represents
a separate simultaneous determination of the elemental concentration based on a different gamma ray observed
in the PGAA spectrum. The results are then averaged giving 49±1 % TiO2 and 43±1 % FeO. PGAA is a complimentary method to Instrumental Neutron Activation Analysis with the advantage that it is sensitive to all elements
and provides more rapid results
was an intense crown fire. Trees mainly were Ponderosa pine and other species of yellow pine. Only
the crown fire produced carbon spherules, which were abundant (~200 per kg of surface sediment) and
appeared indistinguishable from those at Clovis sample sites. Both sites produced glass-like carbon
fused onto pine charcoal.
Methods of elemental analysis of the YDB layer samples
Sediments, magnetic grains and microspherules, carbon spherules, and glass-like carbon were
analyzed by Instrumental and Prompt Gamma-ray Neutron Activation Analysis (INAA/PGAA),
Scanning Electron Microscope X-ray Fluorescence (SEM/XRF), Induced Coupled Plasma Mass
Spectroscopy (ICP/MS), low-background gamma ray counting, and Thermal Ionization Mass
Spectroscopy (TIMS). These methods are described below.
Prompt Gamma-ray Activation Analysis (PGAA) of samples from many sites was performed
at the Department of Nuclear Research, Institute of Isotopes in Hungary. PGAA is a non-destructive
technique [17, 36] using neutron beams to excite the samples producing gamma-ray spectra unique
to each element. Typically, several gamma-rays are excited for each element, which can be used for
analysis as shown in Fig. 11. PGAA is sensitive to all of the principal sample constituents, except oxygen,
and many trace elements. Concentrations are typically normalized to the total sample composition
assuming standard oxidation states.
Bulk samples of magnetic grains and microspherules, ranging in size from 9 mg to 13 g, were
analyzed with PGAA for H, B, F, Na, Al, S, Si, Mg, Cl, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Cd,
Sm, Eu, and Gd.
Instrumental Neutron Activation Analysis (INAA) of samples from many sites was performed at
Becquerel and Activation Laboratories in Canada and at the Department of Nuclear Research, Institute
of Isotopes in Hungary. NAA was used to analyze trace element concentrations in bulk magnetic grain
# 43 #
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
samples and these results are complimentary to the PGAA measurements. Bulk magnetic grain and
sediment samples were analyzed by NAA for Be, Na, Si, Ca, Sc, Cr, Fe, Co, Zn, As, Se, Br, Rb, Zr, Mo,
Ag, Cd, Sn, Sb, Te, Cs, Ba, Ce, La, Nd, Sm, Eu, Tb, Yb, Lu, Hf, Ta, W, Ir, Au, Hg, Th, and U.
X-ray Fluorescence (XRF) analyses of magnetic microspherules were done with a Scanning
Electron Microscopes (SEM) at Cannon Microprobe and the USGS in Menlo Park. Representative
microspherules were sliced, polished, and mounted for analysis. The grains were examined using
energy dispersive x-ray detector (EDS). Elements with atomic number >10 were detected at Cannon
Microprobe and with atomic number >5 at the USGS. Different regions of the microspherules were
randomly analyzed to obtain average elemental concentrations.
Inductively Coupled Plasma Mass Spectrometry (ICP-MS) Analysis. The isotopes 52,53Cr,
58,60,61,62,64
Ni and 191,193Ir were analyzed by ICP-MS. This analysis process involved digestion with
concentrated Fisher OPTIMA nitric acid (HNO3) followed by concentrated Fisher OPTIMA hydrofluoric
acid (HF) with evaporation of the hydrofluoric acid before ICP-MS analysis in 5 % (v/v) HNO3. All
vessels and containers were acid washed in 10 % nitric acid overnight, rinsed with ASTM I water, and
dried beforehand. Initially, large sample weights of about 100 g were used to screen the various isotope
ratio changes to detect changes in uranium (U) isotopes. A method blank and a positive control (NIST
Buffalo River Sediment SRM 8704) were analyzed in parallel.
Low background gamma-ray counting techniques were used at the Lawrence Berkeley National
Laboratory to measure the concentration of the natural radioactive isotopes 40K, 232Th, and 235,238U.
Gamma rays from the decays of these isotopes were measured with HPGe detectors.
Thermal Ionization Mass Spectrometry (TIMS) analysis of 234,235,238U was performed using the
USGS-Stanford Finnegan-Mat 262 TIMS to collect and isolate the uranium isotopic ratios. Chemical
separation of uranium from the sample was accomplished using acid dissolution and then processed
using anion exchange resins. The Finnegan-Mat262 Thermal Ionization Mass Spectrometer (TIMS)
utilizes a surface ionization technique in which nitrates of uranium are placed on a source filament.
Upon heating, positive ion emission occurs. The ions are then accelerated and focused into a beam
which passes through a curved magnetic field dispersing the ions by mass. Faraday cups and/or an ion
counter capture the ions and allow for quantitative analysis of the various isotopes.
Results of the sediment, magnetic grain and microspherule analysis
Results of the elemental analysis of bulk sediment profiles at various Clovis-age sites by PGAA,
INAA and ICP-MS are summarized in Table 3. At most sites there is little difference between the YDB
impact layer and adjacent sediment layers because the impact was deposited as a thin layer of ejecta
at each site and was later diluted by turbation. This is a fundamental difference between the YDB
impact layer that is distributed within a few centimeters of sediment and the K-T boundary layer that is
often over a meter thick. At the Lommel, Belgium site background trace element concentrations were
unusually low and significant increases in the concentrations of Sc, V, Co, Zn, Br, Sr, Y, Zr, Ba, rare
earth elements (REE), Hf, Ta, Th, and U were observed.
Magnetic microspherules were only found in the YD impact layer. SEM/XRF analysis of 14
microspherules is shown in Table 4. Ten microspherules from Gainey, Morley drumlin, Blackwater
Draw, and Lommel are highly enriched in TiO2, averaging 34 wt. %, and FeO, averaging 44 wt. %
resulting in an usually high average ratio TiO2/FeO=0.77. Four microspherules from Gainey and
# 44 #
3.3
Upper Continental Crust
0.8
13
5.2
1
1.1
0.8
1.0
1.1
1.3
0.5
2.8
0.8
3.2
4.6
0.2
0.12
0.05
0.07
0.07
Na2O
0.3
0.1
0.09
0.1
0.8
H 2O
Gainey.MI
Chobot, AB (8)
Wally?s Beach, AB
Murray Springs, AZ (244.8)
Murray Springs, AZ (246.5)
Murray Springs, AZ (247.1)
Murray Springs, AZ (247.7)
Murray Springs, AZ (248.3)
Murray Springs, AZ (262.0)
Blackwater Draw, NM (1237.74)
Blackwater Draw, NM (1238.17)
Blackwater Draw, NM (1238.36)
Blackwater Draw, NM (1238.38)
Blackwater Draw, NM (1238.48)
Blackwater Draw, NM (1239.60)
Topper, SC (20)
Topper, SC (40)
Topper, SC (80)
Topper, SC (120)
Topper, SC (155)
Lommel, Belgium (30)
Lommel, Belgium (42)
Lommel, Belgium (48)
Lommel, Belgium (55)
Lommel, Belgium (70)
Site (depth cm)
Element
6
0.9
2.5
0.07
0.02
15
2.5
10
9
1.3
0.9
0.01
0.05
0.01
7
Al2O3
0.5
MgO
67
87
85
55
66
83
SiO2
K 2O
0.15
0.05
0.07
0.2
0.2
2.8
0.7
<0.01
1.6
<0.01
<0.01
2.8
3.4
Weight( %)
0.1
2.1
<0.01
<0.01
P 2O 5
3.6
<2
0.1
<2
<2
<2
<2
0.64
0.2
0.2
0.3
0.3
1.4
0.9
0.6
0.6
0.6
0.8
0.1
0.2
0.3
0.7
0.7
0.2
<1
5.6
2.8
8.8
6.1
<2
<2
<2
<2
0.8
<2
<2
<2
<2
0.4
TiO2
1.0
CaO
Table 3. PGAA/INAA analysis of bulk sediment from Clovis-age sites. The YDB layer is indicated in green
0.01
0.008
0.010
0.006
0.012
0.006
0.007
0.01
0.005
0.011
0.002
0.005
0.009
0.006
0.008
0.001
0.001
0.001
0.002
0.001
0.01
0.003
0.005
0.010
0.006
0.010
Cr2O3
0.1
0.004
0.010
0.025
0.09
MnO
5
2.1
3.3
2.0
2.7
1.6
2.6
1.7
1.5
2.7
0.8
0.9
1
0.8
1.5
0.4
0.5
0.2
0.6
0.2
0.5
0.7
0.4
0.4
0.3
0.5
FeO
Ir
0.02
ppb
<1
<1
<1
<5
<1
<0.5
2
<5
<0.01
<5
<1
2
<1
2
<5
<1
<5
<1
<5
<1
<1
<1
<1
<1
<1
Th
10
ppm
5.5
8.6
5.8
13
13
13
12
12
16
1.8
3.5
5.4
4.3
5.7
1.6
3.4
2.4
4.5
4.9
4.3
1.2
3.9
1.3
0.9
0.8
U
3
ppm
2.0
2.8
2.3
6.9
4.1
3.8
4.3
3.2
6.8
2.3
4.1
5.6
9.7
46.8
0.5
1.1
0.9
1.4
1.1
1.4
0.3
1.3
0.5
0.5
0.4
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Table 4. X-ray fluorescence (XRF) analysis of the YDB Microspherules shows that they are highly enriched in
titanium and iron with a TiO3/FeO ratio comparable to YDB magnetic grains and very different than all terrestrial
and meteoritic sources except for lunar KREEP
Site-sample
Blackwater-1
Al203
3.7
SiO2
5.8
TiO2
13
FeO
MnO
74
1.7
3.5
Blackwater-2
2.3
3.1
53
37
Gainey-1
2.7
5.1
0
92
Gainey-2
24.8
55
2
18
Gainey-3
2.9
4.0
68
25
0.1
Gainey-4
6.4
40.1
25
7
Gainey-5
1.9
3.7
29
64
1.0
1.7
Morley-1
2.7
4.5
47
44
Morley-2
3.0
4.6
40
50
Morley-3
1.7
1.9
0
84
Morley-4
3.4
11.5
0
84
Lommel-1
74
16
Lommel-2
54
11
Lommel-3
74
16
TiO2/FeO
Spherule Average
5.0
12.7
34
44
0.7
0.77
Grain Average
6.1
44
22
30
0.9
0.73
Crustal
15
67
0.6
5
0.1
0.12
Ocean trench
10
59
0.5
7.6
2.2
0.07
Laurentian Basalt
15
50
2.2
13
0.2
0.17
Cretaceous Tertiary
15
70
0.3
4.5
0.01
0.07
PT layer
9
24
0.45
2.3
0.02
0.20
CI Chondrite
1.6
23
0.07
24
0.3
0.003
KREEP
9
14
12
19
0.14
0.63
Fig. 12. Distribution of magnetic grains and microspherules, SiO2, TiO2, FeO, and H2O at Clovis-age sites as a
function of distance from the Gainey site. All markers except TiO2 are most abundant at Gainey indicating that
the impact site was near Gainey and the projectile was unusually rich in TiO2
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Morley drumlin contained little or no titanium and may be micrometeorites from other sources that
were redeposited by the melting glaciers.
Elemental analysis of magnetic grains from various Clovis-age sites by PGAA, NAA and ICP-MS
are compared with various terrestrial, impact layer, meteoritic and lunar sources in Table 5. Magnetic
grains extracted from the YDB at Gainey contain 14 wt. % FeO and 1.6 wt. % TiO2 with a ratio TiO2/
FeO=0.11 that is similar to the ratio TiO2/FeO=0.19 in adjacent sediment and nearly the crustal average
ratio TiO2/FeO=0.13. This is consistent with a terrestrial, possibly local, origin for the Gainey magnetic
grains. The five Gainey magnetic microspherules have an average ratio TiO2/FeO=0.55 suggesting
a different origin than that for the magnetic grains. The average TiO2 and FeO concentrations for
magnetic grains from sites far from Gainey are 22 wt. % and 30 wt. % respectively with a ratio TiO2/
FeO=0.73. This suggests that all magnetic microspherules and magnetic grains from all sites except
Gainey may have a common origin. The high concentrations of TiO2 in both microspherules and distant
magnetic grains appear inconsistent with concentrations in all terrestrial, impact layer, and meteoritic
sources except for lunar KREEP where a nearly identical ratio TiO2/FeO=0.73 was observed.
The geographical distribution of YDB ejecta is shown in Fig. 12. Most YDB impact markers,
including the number of microspherules and the mass of magnetic grains, water, FeO, and SiO2, are far
more enriched at Gainey than at other sites. This is consistent with an impact near the Great Lakes that
deposited low-velocity terrestrial ejecta near the impact site. Microspherules and magnetic grains from
sites far from Gainey are enriched in TiO2 which is consistent with the deposition of high-velocity,
titanium-rich ejecta from airburst of an unusual object far from the impact site. The TiO2 distribution is
also asymmetric with lower concentrations to the south and west (8-16 wt. %) and higher concentrations
to the east (21-49 wt. %). That is consistent with a ballistic correction to the projectile ejecta motion
due to Earth?s rotation [1] for an object approaching from the north. The distribution of FeO and SiO2
is more symmetrical as expected if its origin is terrestrial.
The magnetic microspherules were presumably formed by impact ejecta launched above the
atmosphere that melted upon reentry. Magnetic grains would include material melted by the impact
and carried by an atmospheric shockwave spreading across the continent creating a wind-driven
pattern of destruction across the landscape. Microspherules would continue to rain down long after
the impact and the deposition of the magnetic grains. This scenario appears to have occurred at the
Wally?s Beach site where magnetic grains were recovered from inside an extinct horse skull which
had protected them from redeposition and postdepositional contamination. At Wally?s Beach the
magnetic grain concentration is higher than at any other Clovis site (7.5 g/kg) with an unusually high
iridium concentration (51 ppb). Conversely the number of microspherules in the horse skull is very
low (0.02 per cm 2) possibly because the shockwave buried the skull before many microspherules
could fall into it.
Previous analyses of magnetic grains and microspherules found very different compositions. El
Goresy [13] reported only one of 47 grains and spherules in Greenland ice that contained measurable
Ti (29.7 wt. %). Gounelle et al analyzed 67 Antarctic micrometeorites [22] finding none with more
than 0.2 wt. % TiO2. A single large magnetic microspherule containing 26 wt. % TiO2 was found in
the KT Maastrichtian bone bed [35] and one particle ascribed to the Tunguska impact was reported
to contain 75 wt. % Ti [34]. Iyer et al [28] summarized the average Ti concentrations in 202 volcanic
spherules from the Pacific Ocean (0.7-7 wt. %) and Central Indian Ocean Basin (0.3 %). The average
# 47 #
1.8
0.7
4
Tonga Trench
2
0.4
Apollo 12 PKT
SNC Meteorite (Mars)
0.7
SAU 169 Lunar Meteorite
0.4
1.2
CI Chondrite Meteorite
0.4
0.9
PT Boundary (Slovenia)
Lunar feldspathic meteorite
0.07
KT boundary (Denmark)
Apollo 17 Basalt
0.92
0.09
Australasian Tektites
0
3.3
Upper Continental Crust
3.8
0.14
Howard Carolina Bay (L)
Laurentian Basalt
0.18
0.08
Howard Carolina Bay (U)
8.4
1.3
0.3
6
5.5
8.5
9.1
6.9
16
8.8
3.1
3.2
6.0
2.7
2.5
0.03
0.5
0.6
10
28.0
9.0
14.4
16.3
1.6
8.9
8
15
15
10
15
5.6
9.8
1.9
5.8
4.3
49
44
39
46
53
23
24
29
70
49
59
67
12
12
50
51
33
0.07
0.8
0.12
0.8
1.0
0.15
6.1
0.3
0.22
0.09
0.11
0.06
1
6.2
0.36
1
0.27
0.09
Carolina Bay B14
0.5
51
36
0.3
0.03
0.06
0.05
0.4
0.9
0.07
3.11
2.5
1.8
0.9
2.1
2.8
0.06
0.04
0.04
0.03
0.9
0.08
11
16.4
10.8
10.6
10.6
1.3
23
23
3.5
7.0
2.1
3.6
0.09
0.03
1.1
0.15
0.32
0.28
1.3
<1
0.25
Carolina Bay M33
0.19
1.9
1.4
1.1
0.2
2
1.3
0.06
0.06
Carolina Bay M31 (L)
0.05
4.8
21
0.8
1.9
1.9
0.8
0.3
3.5
3.8
Carolina Bay M31 (U)
0.4
0.5
1.7
1.6
Lommel, Belgium
0.11
0.19
0.07
0.2
1.3
0.7
51
41
34
2.5
10
2.2
0.6
6.5
6.7
6.9
0.2
2
1.1
CaO
Topper, SC Site 2
2.1
2
62
0.2
0.2
K 2O
Topper, SC Site 1
0.53
0.75
12
50
60
S
Weight ( %)
P 2O 5
1.5
5.1
Murray Springs, AZ
11
4.8
SiO2
4.2
1.6
Wally?s Beach, AB
1.5
2.7
2.9
Al 2O3
1.5
5
Chobot, AB
3
0.64
MgO
Blackwater Draw, NM
3.7
Na2O
Murray Springs black sand
3.2
Morley Drumlin, AB
H 2O
Gainey.MI
Site
Element
1.4
0.24
11.9
5-15
1.5
0.07
0.45
0.32
0.82
3.7
0.5
0.64
39
48
29
21
33
34
21
49
36
8.1
0.7
16
8.3
0.9
1.4
1.6
TiO2
0.10
0.10
0.32
0.34
0.12
0.4
0.05
0.02
0.01
0.03
0.01
0.15
0.13
0.07
0.07
0.12
0.04
0.89
0.09
0.07
0.15
0.04
0.03
0.18
0.02
0.02
0.06
Cr2O3
0.5
0.16
0.19
0.12
0.3
0.02
0.01
0.26
2.2
0.1
0.6
0.7
1.3
1.2
1.5
1.9
1.4
2.3
1.7
1.1
2
0.32
0.53
0.14
0.41
MnO
19
4.7
19
5-20
8.8
24
2.3
4.5
5.1
14
7.6
5
19
20
18
18
25
26
23
43
41
27
92
21
41
14
14
14
FeO
0.2
6
0.05
3
481
64
<1
0.02
15
<2
4
117
2
24,2*
2*
51
<2
ppb
Ir
0.5
0.4
0.4
9
22
0.029
8.5
7.1
16
1.8
10
10
2110
205
11
4
11
5
24
13
15
28
10
34
9
12
4
9
ppm
Th
0.2
0.2
0.12
3
6
0.08
4.1
8.6
1.8
1.4
3
453
27
2
<1
4
3
<1.5
2
2
14
3
8
3
3
1
2
ppm
U
Table 5. Comparison of PGAA/NAA analysis of YDB magnetic grains from Clovis age sites and Carolina Bays with terrestrial sources, impact ejecta layers, meteoritic and
lunar sources. Ir concentrations designated with a * were measured in bulk sediment
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
4
4
6
Carolina Bay M31 (U)
Carolina Bay M31 (L)
Carolina Bay M33
2.1
Upper Continental Crust
52
121
97
760
1020
370
320
480
490
560
62
SNC Meteorite (Mars)
51
37
Lunar feldspathic meteorite
36
Apollo 17 Basalt
2.7
Apollo 12 PKT
240
8
71
100
36
56.5
5.8
CI Chondrite Meteorite
18
48
8
PT Boundary (Slovenia)
SAU 169 Lunar Meteorite
391
KT boundary (Denmark)
47
14
20
32
12
502
6
142
12
217
17
46
36
21
22
35
22
92
2
<60
312
13
1027
13
62
67
563
210
240
220
320
350
240
240
252
47
<200
<200
<200
<200
<100
190
<200
256
<100
40
<200
38
159
190
1.1 %
12
1137
38
96
1
5
14
18
10
7
15
9
14
4
5
11
3.3
14
7
18
10
12
As
0.4
1.86
ppm
<200
240
54
Ni
39
14
22
14
77
94
22
27
41
27
47
47
169
<50
190
230
400
<200
160
Zn
100
704
370
76
90
22
610
590
38
27
44
31
35
24
34
Co
Australasian Tektites
0.9
17
36
118
23
19
13
35
620
1980
900
210
310
302
V
Laurentian Basalt
0.025
1
Howard Carolina Bay (L)
Tonga Trench
8
Howard Carolina Bay (U)
Carolina Bay B14
<1
Lommel, Belgium
6.1
36
4
Topper, SC Site 2
151
4
Topper, SC Site 1
3.2
30
130
4.2
188
3
Blackwater Draw, NM
39
19
16
9
18
Sc
Murray Springs black sand
170
41
Murray Springs, AZ
183
114
60
Chobot, AB
135
182
Cl
Wally?s Beach, AB
30
B
34
5
Be
Morley Drumlin, AB
Site
Element
Gainey.MI
Table 5 continued
0.7
1.2
3.6
0.4
1.6
<2
5
<2
3
13
<2
<2
<0.5
<0.5
6.6
<2
<2
5
2.1
Br
7
0.8
9
20
2.3
27
76
19
40
84
<30
<30
<30
<30
<20
<30
<30
56
36
100
41
110
30
61
Rb
57
198
153
166
230
7.8
115
144
410
233
320
27
16
10
29
15
40
17
104
128
Sr
19
81
338
1.6
315
39
173
21
9670
574
10
127
66
121
119
64
207
Y
69
32
730
1397
3.94
115
144
315
270
123
193
7720
1120
920
1000
2700
1100
750
530
<200
280
850
<500
<500
<500
<200
Zr
0.686
0.09
<10
0.4
<10
<10
<9
<10
0.25
<10
<10
<10
0.31
0.7
Cd
0.02
0.02
0.14
0.5
8
0.3
0.4
9.3
7.5
2.1
1.5
3.7
1.5
4.8
1.8
1.1
2.2
0.7
2.2
1
1.1
1
1
Sb
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
340
Cs
<1
<1
Carolina Bay M33
Carolina Bay B14
6.9
0.187
0.9
0.4
40
0.05
0.5
CI Chondrite Meteorite
SAU 169 Lunar Meteorite
Apollo 12 PKT
Apollo 17 Basalt
Lunar feldspathic meteorite
SNC Meteorite (Mars)
1.9
KT boundary (Denmark)
PT Boundary (Slovenia)
475
4.3
Australasian Tektites
52
115
74
600
1351
2.34
250
1175
1000
Laurentian Basalt
3
2.2
6.3
49
113
0.235
27
61
48
40
134
2.4
Tonga Trench
1680
31
628
5
Upper Continental Crust
162
11
<5
12
6
92
12
17
32
22
96
33
34
17
34
La
476
363
<200
<200
<200
<200
<200
<200
460
<50
360
470
1200
320
19
Ba
Howard Carolina Bay (L)
Howard Carolina Bay (U)
<1
<1
<1
Lommel, Belgium
Carolina Bay M31 (L)
<1
Topper, SC Site 2
Carolina Bay M31 (U)
2
Murray Springs black sand
<1
2
Murray Springs, AZ
Topper, SC Site 1
6
Wally?s Beach, AB
Blackwater Draw, NM
5
<1
Chobot, AB
2
Site
Element
Morley Drumlin, AB
Gainey.MI
Table 5 continued
7
5.8
21.2
128
297
0.603
32
57
96
95
196
63
8450
334
19
<10
20
<10
157
22
27
61
40
170
62
86
32
Ce
7
3.4
21.5
82
162
0.45
16
63
44
37
158
27
3240
184
31
14
16
22
<5
28
30
25
18
110
35
31
23
16
Nd
2
1.1
9.3
22
45
0.15
3
12
8.5
9.4
35
4.7
640
29
2.1
1
2
1.1
12
2.4
2.9
3.9
4.8
15
5.5
6
3
3
Sm
0.8
0.8
1.9
1.8
2.4
0.06
0.5
2.8
1.6
3.1
8
1
33
2.2
<2
<2
<1
<2
2.1
<2
<2
4.8
0.6
2
<2
<2
<2
0.9
Eu
Gd
3
13.6
50
0.2
2.3
7.2
38
4
0.8
2
4.2
2.7
4.9
4.6
2
5.4
18
5.4
5.6
2.9
3.2
ppm
0.6
0.2
2.5
3.5
10
0.04
0.5
1.8
1.2
1.4
0.7
130
5
<1
<1
1
<1
<0.5
<1
<1
<0.5
0.9
4.6
<1
1
<1
<0.5
Tb
2
0.9
9.1
17
36
0.162
1.6
5
3.9
3.4
17
2
407
23
5
11
13
11
20
6
<5
6
5
13
<5
<5
<5
2.4
Yb
0.3
0.1
1.3
2.4
5.2
0.024
0.2
0.6
0.6
0.5
3
0.3
56
3.4
0.8
1.7
2.1
1.8
3.2
0.9
0.6
1
0.8
1.8
<0.5
<0.5
<0.5
0.3
Lu
26
15
87
306
715
1.91
83
203
211
190
589
144
13430
799
70
30
70
45
291
76
80
139
102
429
141
164
78
79
REE
3
0.8
8.6
18
35
0.104
3.2
4
9
3.5
5
102
20
24
21
60
25
20
9
7
20
18
19
9
5
4
5
Hf
0.2
0.1
1.6
2
4.2
0.014
0.5
1.6
0.6
1
155
46
11
13
23
13
16
23
22
10
2
36
4
1
<1
2
Ta
0.3
0.08
13
2.5
0.093
1.5
2
71
10
4
<4
8
<4
68
<4
5
83
6
36
<4
<4
<4
2
W
Au
20
0.09
2
140
<0.1
3
1.5
5
<10
<10
<10
<10
<10
<9
15
14
<2
<1
<10
<10
<10
<2
ppb
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 13. Comparison of FeO+MgO and Al2O3 concentrations. Microspherules and magnetic grains from sites
south and east of Gainey have very different FeO+MgO/Al2O3 ratios than Gainey or terrestrial sources but are
very similar to extraterrestrial material. This figure is adapted from Fig. 4 in R.L. Korotev, Invited review Lunar
geochemistry as told by lunar meteorites, Chemie der Erde 65, 297-346 (2005)
TiO2 concentration observed in YDB microspherules and distant magnetic grains greatly exceeds
concentrations in nearly all previously studied ET and volcanic spherules.
TiO2/Zr ratios in YDB magnetic grains ratios are comparable to lunar KREEP and higher than
all terrestrial and impact layer sources except Laurentian Ocean Island basalt (LOIB). High TiO2/Zr
ratios are also observed in chondrites, shergottites, and lunar feldspathic meteorites, although SAU-169
has a very low TiO2/Zr ratio.
H2O content in magnetic grains was measured by PGAA which is unusually sensitive to hydrogen
in small samples. The concentration is high at all sites ranging up to 28 at. % H at Murray Springs.
At Gainey the magnetic grains contain 18 at. % H compared to 5 at. % H in the adjacent sediment.
Tektites and ET sources typically contain little H2O so it is likely that this excess must have a terrestrial
origin. It appears that this water is trapped in the magnetic grains because they often will explode in a
microwave oven. Large amounts of water (?20 wt. %) have also been observed in granite silicate melt
inclusions [43] suggesting that the water may have been trapped in the ejecta at the time of impact. This
would be consistent with an impact into the Laurentide Ice Sheet north of Gainey combining ejecta
with stream from the ice explosion.
Al2O3 and FeO+MgO concentrations for magnetic grains, microspherules, terrestrial and ET
sources are compared in Fig. 13. Microspherules and magnetic grains from the distant sites have Al2O3/
FeO+MgO ratios similar to CI chondrites, shergottites, and lunar meteorites [33]. Magnetic grains from
Gainey have Al2O3/FeO+MgO ratios comparable to crustal, oceanic, volcanic, and terrestrial impact
layer values. The Al2O3/FeO+MgO ratios at Gainey are consistent with terrestrial composition from a
nearby impact site, and the ratios at distant sites are consistent with an ET projectile composition.
CaO/Al2O3 at Gainey (0.20) is comparable to crustal (0.24) and ocean trench (0.21) values. At
distant sites, CaO/Al2O3 values vary widely and are terrestrial at Topper (0.18) and Blackwater Draw
# 51 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
(0.23) At Wally?s Beach (0.51), Murray Springs (0.57), and Lommel (0.93) the CaO/Al2O3 ratios are
comparable to Lunar PKT (0.75), SAU-169 (0.65), and CI chondrite (0.81) values. However, total CaO
and Al2O3 concentrations at all sites are well below crustal or lunar abundance, possibly due to the
magnetic selection, and the ratios may be contaminated by local sources. The CaO/Al2O3 ratios are
consistent with an ET origin at three of five sites.
SiO2 concentration in magnetic grains is comparable at Gainey (60 wt. %) to the continental
crust (67 wt. %) and ocean trenches (59 wt. %). At distant sites, except for Topper, SiO2 concentrations
vary from 34-51 % which is comparable to lunar meteorites (43-48 wt. %) [32], PKT (53 wt. %), and
shergottites (49 wt. %). Topper values (5 wt. %) are much lower possibly indicating significant postimpact alteration of the magnetic grains at this site. Lower SiO2 concentrations at some sites may
also be an artifact of magnetic separation and no strong conclusions can be drawn from the SiO2
concentration.
Na2O concentration is 3 wt. % at Gainey, which is similar to shergottites (2 wt. %), crustal (3.3
wt. %) and ocean trench (4 wt. %) values. At distant sites Na2O concentration varies from 0.1-0.8
wt. %, which is comparable to ET value in the lunar PKT (0.7 wt. %), SAU-169 (1.2 wt. %), lunar
meteorites (0.3-0.5 wt. %), and CI chondrites (0.9 wt. %).
K 2O concentration is 2.0 wt. % at Gainey, which is similar to crustal (2.8 wt. %) and ocean
trench (2.1 wt. %) values. At distant sites, the K 2O concentration varies from 0.2-1.1 wt. %, which is
comparable to ET values in the lunar PKT (0.4 wt. %), SAU-169 (0.7 wt. %), and lunar meteorites (0.11.0 wt. %). Shergottites contain far less K 2O (0.03 wt. %).
Cr2O3 concentration is 0.06 wt. % at Gainey, which is slightly above the crustal (0.01 wt. %) and
ocean trench (0.03 wt. %) values. At the distant sites, Cr2O3 averages 0.25 wt. %, which is comparable
to ET values in the lunar PKT (0.34 wt. %), SAU-169 (0.12 wt. %), lunar meteorites (0.1-1.0 wt. %), and
CI chondrites (0.4 wt. %).
FeO/MnO ratios vary widely ranging from 34 at Gainey to 10-25 at distant sites. These ratios
are lower than in the continental crust (50), CI chondrites (80), shergottites (38) and SAU-169 (38) and
higher than in ocean trenches (3.5). Enrichment of MnO has been observed in Bahaman sediments
following the previous four glaciations [5, 48] and MnO increased suddenly, from 0.3 wt.. % to 1.2
wt. %, in Pacific sediments at the onset of the YD [4]. YDB microspherules have a much higher
average FeO/MnO ratio (75) that is comparable to the average (71.5) for a wide range of lunar
meteorites [32].
Rare Earth Element (REE) concentrations normalized to volatile-free CI chondrite [3] as
suggested by Korotev [32] are shown in Fig. 14 for YDB magnetic grains. YDB magnetic grains, lunar
PKT, and lunar KREEP REE concentrations range between crustal and oceanic values.
Gainey magnetic grains have REE abundance ratios that are comparable to crustal and oceanic
values. Unlike terrestrial sources, distant magnetic grains have a negative Eu signature comparable
to lunar KREEP-rich brecchia [32]. Lunar feldspathic meteorites are very different with a positive Eu
signature. Shergottites have REE chondrite ratios similar to chondrites.
Iridium is found in high concentrations in YDB magnetic grains and/or sediments at ten sites; Lake
Hind (3 ppb), Murray Springs (2 ppb), Blackwater Draw (24 ppb), St. Mary (51 ppb), Topper (2 ppb),
Carolina Bay T13 (4 ppb), Carolina Bay M31 (4 ppb), Carolina Bay M33 (2 ppb), Howard Bay (15 ppb)
and Lommel (117 ppb). Iridium is below INAA detectable limits (~1 ppb) in 41 sediment samples taken
# 52 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 14. CI chondrite normalized rare earth (REE) concentrations at Murray Springs, Lommel, Blackwater Draw,
and Topper have a negative Eu anomaly similar to that observed in lunar KREEP and SAU 169. Gainey and terrestrial crustal or oceanic sources have no Eu anomaly, lunar feldspathic basalts have a positive Eu anomaly, and
Martian basalt meteorites have REE concentrations similar to CI Chondrites
from above or below the YDB at various sites. Crustal iridium concentration is 0.02 ppb, although
higher concentrations (0.5 ppb) have been observed in volcanic ash [27]. Iridium concentrations in the
magnetic grains are lower than in CI chondrites (481 ppb) but comparable to that in the KTB (64 ppb)
and lunar meteorites (?25 ppb) [33]. High iridium concentrations in the YDB magnetic grains from
many sites are classic evidence [2] that they are from an impact event.
Ni and Co concentrations only slightly exceed crustal abundance at most sites and Ni concentrations
are much lower than in chondrite values. The Ni and Co concentrations are comparable to both the
lunar meteorites and in shergottites.
Trace element concentrations in magnetic grains and SAU-169, normalized to crustal abundance,
are shown in Fig. 15. Heavy element (Hf, Ta, W, Th, and U) concentrations are terrestrial at Gainey
and significantly exceed crustal values elsewhere.
They are comparable to SAU-169 for the distant sites. K 2O/Th ratios for magnetic grains (Table 6)
from Gainey (2200) are comparable to crustal values (2800), but much lower at distant sites (400) and
comparable to values in the PKT (440), SAU-169 (410), and most lunar sediments (360) [42].
As and Sb concentrations at all YDB sites significantly exceed terrestrial and ET values but are
similar to the KT and PT boundary layers. The reason for the enrichment of As and Sb in magnetic
grains is unknown.
# 53 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 15. Comparison of trace elemental concentrations normalized to crustal abundance for magnetic grains from
various Clovis-age sites. Magnetic grains from Topper, Blackwater Draw, Murray Springs, and Lommel are very
different from terrestrial sources but similar to each other. Gainey magnetic grains have trace elemental abundances similar to terrestrial values
Isotopic abundance ratios
Fe, Ti, and U isotopic ratios were analyzed by ICP-MS and TIMS. Samples were digested in high
purity HNO3 and HF with evaporation before analysis in 5 % (v/v) HNO3. All vessels and containers
were acid washed in 10 % nitric acid overnight, rinsed with ASTM I water, and dried beforehand.
50
Ti/48Ti ratios were determined by PGAA/INAA. Isotope abundance ratios 54,56,57,58Fe, 46,47,48.49,50Ti,
and 238U/235U in YDP magnetic grains and sediments are consistent with normal solar system values
(Table 6). The 234U/235U ratio is terrestrial at Wally?s Beach, but 234U is enriched by 50 % compared to
equilibrium concentrations at Lommel and by 130 % at Murray Springs. 234U is often enriched by up to
15 % in seawater [12] and up to 50 % in river sediment [25], but 234U/235U enrichment in relict glacial
lakes can exceed 500 %. The large 234U enrichment at Murray Springs may result from an airburst over
a 234U-rich glacial lake near the Laurentide Ice Sheet.
40
K/39,41K ratios in Clovis-age cherts and sediments were measured by gamma ray counting (40K),
PGAA (39K), and INAA (41K). These cherts, found in fire pits at several Clovis sites, have a high
density of impact pits and particle tracks on only one side as if they were bombarded from above [18].
40
K abundance is enriched by a factor of ?2 in samples with lowest total potassium concentration and
the enrichment decreases with increasing potassium concentration. No 40K anomalies were observed
in control sediments and cherts. Voshage [47] has shown that 40K abundance is enriched in iron
meteorites by spallation up to 2000Ч terrestrial abundance (0.012 %). Similar enrichments in 40K were
also observed in cosmic rays [8]. Shimamura et al [38] reported a 40-70 % 40K enrichment in magnetic
microspherules from South Pacific sediments. Analysis of lunar PKT sediment indicates that potassium
concentration measured by the Lunar Prospector Gamma-ray Spectrometer (GRS) (40K) is consistently
50-100 % higher than «ground-truth» data (39K) [19]. Although this was attributed to GRS calibration
error, it is also consistent with 40K enrichment. Addition of a small amount of highly enriched 40K to
the YDB could notably increase the 40K/39,41K ratio, especially where the total potassium concentration
is low. Anomalous 40K/39,41K ratios in the YDB layer are only consistent with an ET source.
# 54 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Table 6. Fe, Ti, U, and K Isotope ratios. Uncertainties in the least significant digits are given in parenthesis
Iron
Fe/56Fe
6.37
6.7(2)
6.6(2)
6.8(2)
6.7(2)
6.6(2)
46
Ti/48Ti
11.04
11.1(3)
10.9(3)
238
U/235U
137.88
138.01(26)
138.03(12)
138.05(9)
137.8(5)
%K
2.09
Fe/56Fe
2.31
2.39(7)
2.40(7)
2.38(7)
2.39(7)
2.38(7)
47
Ti/48Ti
9.95
10.0(3)
9.8(3)
234
U/235U
0.0076
0.00760(11)
0.01744(3)
0.011353(12)
0.00742(20)
40
K/39K
0.000125
Upper Mercer
Bayport
0.058
0.061
0.00024(8)
0.000188(25)
Bay T13
Murray Springs -1
Topper-2U
Topper-2L
Topper-2L
Lommel
Bay M31
Lake Hind
Blackwater Draw - 1
Wally?s Beach
Gainey
Murray Springs -2
Murray Springs - 3
Blackwater Draw-2
Controls
Fossil Hill (Chert)
Onondaga (Chert)
Loomis-O (Sed)
Loomis-A (Sed)
Loomis-B (Sed)
Loomis-C (Sed)
0.075
0.18
0.35
0.36
0.38
0.57
0.82
1.12
1.30
1.44
1.75
2.30
2.80
3.05
Terrestrial
Gainey
Murray Springs
Wally?s Beach
Morley drumlin
Lommel-Maatheide
Titanium
Terrestrial
Gainey
Murray Springs
Uranium
Terrestrial
Wally?s Beach
Lommel-Maatheide
Murray Springs
NIST Standard
Potassium
Terrestrial
54
57
Fe/56Fe
0.307
0.314(9)
0.269(8)
58
Ti/48Ti
7.24
7.1(5)
7.5(5)
49
K/41K
0.00174
40
Ti/48Ti
6.93
6.5(22)
6.6(6)
50
Ratio?
1.00
Chert
1.9(6)
1.5(2)
Sediment
?
0.045
0.061
1.16
1.12
1.19
1.29
0.0030(6)
0.0039(6)
0.0020(2)
0.0023(2)
0.0023(2)
0.0018(2)
0.023(2)
0.0015(2)
0.0019(2)
0.0023(2)
0.000143(9)
0.0019(2)
0.0018(2)
0.0016(2)
0.000113(25)
0.000119(10)
0.000124(4)
0.000129(4)
0.000124(4)
0.000124(4)
Ratio of measured 40K abundance to the terrestrial value
1.7(3)
2.2(3)
1.2(1)
1.3(1)
1.3(1)
1.0(1)
1.3(1)
0.9(1)
1.1(1)
1.3(1)
1.14(7)
1.1(1)
1.0(1)
0.9(1)
0.95(21)
0.90(8)
0.99(3)
1.03(3)
0.99(3)
0.99(3)
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Analysis of carbon spherules and glass-like carbon
Table 7 shows the PGAA bulk analysis of carbon spherules from a Carolina Bay. As expected the
carbon spherules are mostly carbon (82±12 wt. %) but they contain a substantial amount of hydrogen
(5.3±0.8 wt. %), nitrogen (6.8±1.1 wt. %), Al2O3 (2.0±0.4 wt. %), SiO2 (2.2±0.4 wt. %), and several
other impurities with <1 wt. %. The high atomic ratio of hydrogen to carbon C10H8 in carbon spherules
is slightly less than C12H20 for copal (amber) spherules usually found with the carbon spherules.
Carbon spherules can be formed from tree sap in high temperature forest fires suggesting that these
spherules were formed in fires following the YD impact. Kennett et al [30] have reported the presence
of nanodiamonds inside of some carbon spherules. Nanodiamonds cannot be produced by forest fires
indicating that some carbon spherules were produced directly by the impact. It is likely that both impact
and forest fire carbon spherules were produced during the YD impact event. The high concentration
of nitrogen impurity is consistent with formation of the carbon spherules in an airburst, and the high
TiO2 (0.09 wt. %) and FeO (0.2 wt. %) concentrations are consistent with the magnetic grain chemistry
suggesting that the carbon spherules formed amidst the exploding impact ejecta.
Table 8 shows the PGAA bulk analysis of glass-like carbon from a Carolina Bay. The glass-like
carbon is also mostly carbon (90±1 wt. %), with significant amounts of hydrogen (3.0±0.1 wt. %),
and SiO2 (4.8±0.1 wt. %). The hydrogen to carbon ratio C10H4 is lower than for carbon spherules and
consistent with the formulation expected for burning wood in the absence of air. This formulation is
not very different from charcoal C7H4O which should also be produced at the same time. Unlike carbon
spherules glass-like carbon lacks significant nitrogen content suggesting that it was formed from trees
burning under anaerobic conditions in the shockwave from the impact. This is consistent with a sample
that we found where glass-like carbon on one side of sample graded into yellow pine on the other side
suggesting that a very hot wind had passed through the sample. Significant amounts of SiO2 and TiO2
(0.067 wt. %) may have been carried into the sample by the shockwave.
Discussion
The geographical distribution and composition of the magnetic grains are consistent with
an airburst 12.9 ka ago near the Great Lakes of an object unusually enriched in titanium and
other incompatible elements. Terrestrial-like ejecta fell close to an impact site near Gainey while
projectile-rich ejecta fell farther away. High water content in the ejecta favors an airburst over
the Laurentide Ice Sheet north of Gainey. This is also consistent with the thinness of the YDB
impact layer suggesting that relatively little terrestrial ejecta were created due to shielding of the
airburst from the ground by the ice sheet. Microspherules from various sites including Gainey and
magnetic grains from Wally?s Beach, Murray Springs, Blackwater Draw, Topper, and Lommel
sites were unusually enriched in TiO2 with TiO2/FeO, TiO2/Zr, REE/chondrite, Al 2O3/FeO+MGO,
CaO/Al 2O3, K/Th, FeO/MnO, and 40K/K ratios and SiO2 , Na 2O, K 2O, Cr2O3, Ni, Co, Ir, and trace
element abundances that are comparable to lunar KREEP and inconsistent with other terrestrial or
meteoritic sources except for meteorite SAU-169 whose KREEP-like composition is attributed to
a lunar Procellarum KREEP Terrane origin. The unusual KREEP-like composition of the object
that impacted Earth 12.9 ka ago has never been observed in meteorites before. It seems unlikely
to have come directly from the moon however it is coincidental that SAU-169 fell in Oman near
the time of the YD impact [20].
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Table 7. PGAA analysis of Carolina Bay carbon spherules
Element
Table 8. PGAA analysis of Carolina Bay glass-like
carbon
Wt. % or ppm
Element
Wt. % or ppm
H2
5.3 %
H2
3.0 %
B
61 ppm
B
10.2 ppm
C
82 %
C
90 %
N
6.8 %
N
0.66 %
Al2O3
2.0 %
Al2O3
0.97 %
SiO2
2.2 %
SiO2
4.8 %
S
0.39 %
Cl
181 ppm
Cl
0.073 %
K 2O
120 ppm
K 2O
0.12 %
CaO
0.49 %
CaO
0.5 %
TiO2
0.067 %
TiO2
0.09 %
Cd
0.22 ppm
FeO
0.2 %
Sm
0.19 ppm
Cu
0.06 %
Gd
0.22 ppm
Cd
0.8 ppm
Sm
0.8 ppm
Gd
0.9 ppm
Analysis of carbon spherules found in the YDB layer at many sites indicates that they were likely
formed both from the impact and from extensive hot forest fires ignited by the ensuing atmospheric
shockwave and falling hot debris. Evidence of nanodiamonds in carbon spherules which is only
consistent with an impact event will be discussed in later papers. High concentrations of soot, evidence
of very high temperature burning following the impact, were found in the YDB at several sites [16] and
will be discussed elsewhere. Similarities in the bulk composition of carbon spherules and associated
copal (amber) spherules suggest that these spherules were produced by the high temperature burning of
tree sap. Glass-like carbon and charcoal found in the YDB at many sites appears to have been produced
by the burning of trees under low oxygen conditions as the YD impact atmospheric shockwave raced
across North America. The black mat which overlays the YDB layer at many sites, marking the point
above which no megafauna fossils or Clovis points are found, was not formed by the impact but instead
appears to consist mainly of algal material produced by dying organic matter and burned material. It
is likely that the YD impact caused the failure of the Laurentide Ice Sheet sending large quantities of
ice into the North Sea, shutting down the thermohaline ocean circulation, and initiating 1300 years
of Younger Dryas cooling. This was accompanied by the injection of dust and water into the upper
atmosphere blocking sunlight for an extended period of time and lowering temperatures suddenly. The
impact event followed by extensive fires and sudden climate change likely contributed together to the
rapid extinction of the megafauna and many other animals.
No impact crater has yet been identified with the YD impact. Toon et al. [44] suggest that it requires
an airburst with energy of 107 megatons, a>4 km-wide comet, to cause continent-wide destruction on
a scale observed at the YDB. Such an object undoubtedly would have left a significant crater. We have
speculated that multiple 2-km objects struck the 2-km thick Laurentide Ice Sheet at a low angle leaving
negligible traces after deglaciation. A problem with this argument is that it would require at least eight
# 57 #
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Death Valley
282?
Fig. 16. NOAA bathymetry maps of the Great Lakes indicate four deep holes in the Lakes Superior, Michigan,
Huron, and Ontario that may be YD impact craters. Three of these holes are the lowest points in North America,
deeper than Death Valley. The origin of these holes in unknown and they are unlikely to have been formed by
glacial action
such objects and it seems unlikely that none of these would leave a lasting mark on the planet. Another
possibility is that the impact left craters that have yet to be recognized. Fig. 16 shows a depth profile
of the Great Lakes where it has long been known that four of the deepest holes in North America exist
in Lakes Superior, Michigan, Huron and Ontario. Three of these holes are deeper than Death Valley.
They are unlikely to have been caused by the action of glaciers or moving water [10]. The Finger Lakes
region of New York radiate out from the hole in Lake Ontario as if they were formed by the force of
the impact pushing water and ice to the south. Charity Shoal, shown in Fig. 17, has been identified as
a smaller, 1-km crater in Lake Ontario of approximately the correct age to be associated with the YD
impact event [26]. Further research is necessary to prove that these Great Lake basins are the craters
from the YD impact event.
Toon et al [44] also noted that the impact of a >4 km-wide comet is expected to occur only once
every few million years. This estimate is based largely on solar system cratering rates and has little
# 58 #
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
Fig. 17. NOAA bathymetry image of Charity Shoal, a 1-km diameter crater, in Lake Ontario. It dates approximately to the time of the YD impact and sits directly above a magnetic anomaly
relevance to the timing of the YD impact. Culler et al [9] determined the ages of lunar microspherules,
many enriched in TiO2, by 40Ar/39Ar dating and found that lunar impacts began increasing dramatically
400 Ma years ago and peaked very recently. These results were not corrected for lunar 40K/K ratios
which would make this increase even more recent and dramatic. It appears that Toon et al?s estimate
could be off an order of magnitude too high.
Acknowledgements
This work was supported, in part, by the U.S. Department of Energy under contract DE-AC0205CH11231. The authors thank C. Vance Haynes (University of Arizona), B. Kooyman and colleagues
(University of Calgary), Jane Pike-Childress (BLM), M. Boyd and colleagues (Lakehead University),
G. Howard, D. Kimbel, and W. Newell for providing samples, helpful comments, and/or access to their
research sites. We especially thank Jim Bischoff (USGS) and Ross Williams (LLNL) for analysis of the
uranium isotopic abundances. M. Gifford is thanked for help with ICP-MS analyses. We thank Henry
Wright (University of Michigan) and Denise Henry and Terrence Rettig (NSF) for their encouragement
early in this project. J. Talbot (K/T GeoServices, Inc.), B. Cannon (Cannon Microprobe), J. Edwards
(Process NMR Assoc., LLC), E. Hoffman (Activation Laboratories. Ltd.), J. Feathers and J. Johnson
(Luminescence Dating Lab, University of Washington), S. Simpson (Becquerel Laboratories), and J.
Southon (Keck Carbon Cycle AMS Facility) were very helpful analyzing research sample.
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Richard B. Firestone, Allen West? Analysis of the Younger Dryas Impact Layer
?????? ?????????? ???? ???????? ??????
?. ???????????, ?. ?????, ?. ??????,
??. ?????????, ?. ???????, ?. ??? ???, ?. ?????
?
???????????? ??????????? ??. ???????? ? ??????
??? 94720, ??????????, ??????,
?
????????? ??????????,
??? 86327, ???????, ?????, ?/? 1636
?
???????? ???????? ?????????? ???????? ????,
??????? ?-1525, ????????, ?/? 77
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????????????? ?????? ??????????? ??????,
??? 94025, ??????????, ????? ????, ???????? ????, 345
?
?????????????? ???????????,
??? 90095, ??????????, ???-????????
?? ?????????? ?????? ???? ????????? ????? ? ??????, ?????? ????????, ? ????? ??????
??????????????? ?? ???????? ? ?????? ??????? ?? ???? ???????? ???????, ??????? ? ?? ????
16 ??????? ????????. ??? ??????????? ?? ?????? ? ????????? ????????? ? ?????????? ? 12,9
???. ??? ?????, ???????? ? ???????????? ? ???????????? ????????????? ????????? ? ????????
??????? ? ?????? ???????? ?????? (YD). ?? ?????? ?????? ???? ? ????????? ?????????
?????????? ??????????????? ??? ??????????? ?????????? ???????????? ????????? ? ????????
???????. ??????? ????????????? ???? ?????????? ???????? ?? ??????? ???????? ?????? (YDB)
??????????? ? ????????? ???????????? ????? ??????? ????, ??????? ???????? ????????,
??????????? ?????? ?? ????? ?????????? ?????????? ???????????, ? ??????? ???????
???????, ??????????? ??????. ??????? ?????????? ???? ? ????? ?????????? ???????? (??
28 % ????????) ???????????????, ??? ??????????? ????????? ?? ????????????? ??????????
????. ???????????? ? ????????? ????? ? ???? YDB ?????? ????????? TiO2. ????????? ?????
?? ?????????? ???? ????????? ??????? (Ir), ?? 117 ?????? ?? ????????. ????????? TiO2/FeO,
K/Th, TiO2/Zr, Al2O3/FeO + MgO, CaO/Al2O3, REE / ????????, FeO / MnO, ? ????? SiO2, Na2O, ?2?,
??2?3, Ni, Co, U, Th ? ?????? ????? ????????? ???????? ?????????????? ?? ????? ??????? ?
?????????? ???????????, ?? ??????????? KREEP ? ?????? ????????????? ??????, ???????
?????? (K), ??????????????? ?????????? (???), ???????? (P) ? ??????? ??????????????
??????????, ??????? ???? ? ?????. ?????????? Fe, Ti ? ??????? 238U/235U ? ???????? ????
??????? ? ????????? ??????, ?? 234U ??????????? ????? ???????????? ?????????? ?? 50 % ?
??????-??????? ? ?? 130 % ? ???????. 40K ???????? ?? 100 % ???????? ?? YDB ? ???????????
??????????? ???????? ??????. ??????? ?????????????? ?????????? ???????, ??????????
??????????, ??????, ??? ?? ??? ???????, ????????? ????? ? ????, ?????????? ? ???????
??????????? ? ???? YDB ? ??????????? ? ????????????? ???????????? ???????. ??????
???????? ??????? ? ?????? ??????? ????, ????? ????????, ??? ? ?????? ??????, ???????????? ?
???????? ????????? ???????? ? ?????????? ?????? ? ??????? ? ??????? ????? ??????????????
???????????.
???????? ?????: ????, ?????????? ??????? ?????????? ????????, ????????? ??????,
?????? ??????????? ???????, ????????? ??????? ? ?????? ???????????, ?????? ???????? ?
?????????? ?????? ????????.
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Journal of Siberian Federal University. Engineering & Technologies 1 (2010 3) 63-71
~~~
??? 551.3
Tsunami Chronology Supporting Late Holocene Impacts
Edward Bryanta*, Simon K. Haslettb, Sander Scheffersc,
Anja Scheffersc and Dieter Kelletatd
a
Science Faculty Office, University of Wollongong,
NSW, Australia, 2516
b
CELT, University of Wales, Newport, Caerleon Campus,
Lodge Road, Caerleon, South Wales, NP18 3QT, UK
c
Southern Cross University, School
of Environmental Management and Science,
Lismore, NSW, Australia, 2480
d
University of Cologne, Institute of Geography,
50623 Cologne, Germany 1
Received 3.02.2010, received in revised form 27.02.2010, accepted 9.03.2010
The Holocene Impact Working Group (HIWG) has identified the location of at least eight impacts
into the world?s oceans in the Late Holocene. Each of these was capable of generating large tsunami
that should have left a geological footprint on adjacent shorelines. We have identified from shoreline
tsunami deposits five known impact events (Fig. 1), two of which are associated with impact craters
identified by the HIWG. The other three are associated with legends and historical descriptions. This
paper presents the chronology of tsunami events in New South Wales (NSW) and Western Australia
(WA)?on opposite coasts of Australia, and in the UK that are linked to impact events.
Keywords: mega-tsunami, shoreline tsunami deposits, radiocarbon calendar distributions, impact
craters late Holocene.
New South Wales (NSW) and the Mahuika Impact Event
Research along the east coast of Australia since 1989 [7, 8] indicates that mega-tsunamis have
struck and eroded the rocky shores of New South Wales over a distance of 600 km throughout the
Late Holocene. Sixty-eight radiocarbon dates have been obtained from marine shell found along the
New South Wales Coast in disturbed Aboriginal middens, deposited in tsunami dump deposits and
sand layers, and protected beneath boulders transported by tsunami. Radiocarbon dates do not simply
represent a calendar age. Each can be plotted as a frequency distribution over a span of radiocarbon
years. These «radiocarbon» distributions were then converted to calendar ones at ten year intervals
using a carefully constructed calibration table based on marine species [33]. The «calendar» frequency
distributions were then summed over time to produce a composite time series of tsunami events.
Radiocarbon calendar distributions are very noisy and suffer from age reversals. In order to assess
*
1
Corresponding author E-mail address: ebryant@internode.on.net
© Siberian Federal University. All rights reserved
# 63 #
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Edward Bryant, Simon K. Haslett? Tsunami Chronology Supporting Late Holocene Impacts
Fig. 1. Location of impact events supported by the chronology of tsunami events in New South Wales, Western
Australia or the UK
whether or not the timing of our dates was random, a simulated time series of calendar distributions
was constructed with mid-points at 10 year intervals over the same time span. This «background» time
series was then scaled to the total number of samples in our dataset. The simulated times series was
subtracted from the NSW one to remove this background «noise».
The technique reduced the possibility of a single radiocarbon date being considered a tsunami
event. The resultant time series since 6000 BC is plotted in Fig. 2. The y-axis has arbitrarily been set
in this figure to a maximum value of 1.0. The time series shows the clustering of dates?supported by
more than one radiocarbon date?centred on one of ten times: 5000 BC, 4200 BC, 3200 BC, 1400 BC,
700 BC, AD 440, AD 790, AD 1300, AD 1490, and AD 1690. The latter three events may be part of
the same event because the biggest age reversals occur over this period. Comet impacts with the ocean
are probably responsible for many of these events given the spread and magnitude of deposits along the
coast. The most prominent peak centres on AD 1500±85, which corresponds with the largest number
of asteroid observations for the past two millennia and a peak in observable comets [7]. The location
of the impact probably responsible for this event has recently been discovered lying in 300 m depth
of water on the continental shelf 250 km south of New Zealand at 48.3° S, 166.4° E [1, 9]. The crater
is 20 km in diameter and could have been produced by a comet 1.6 km in size travelling at a speed
of 51 km s-1 (based on calculations by [20]). When it struck, it would have generated an earthquake
with a surface wave magnitude of 8.3. The lack of sediment that normally settles over time from the
ocean suggests that the crater is less than 1000 years old. The comet has been named Mahuika after
the Maori God of fire. Tektites found in sediments to the southeast indicate a trajectory for this comet
from the northwest, across the east coast of Australia [22]. A likely time for this impact was in the
late evening on the 13 February 1491. Korean astronomers were observing the small and not very
active comet X/1491 B1 (formerly 1491 II) in the evening sky of 20 January 1491. This comet appears
to have been a Jupiter family object with a period of less than 20 years. The Koreans followed the
comet?s movement in the constellation Cetus and last sighted it brightly on 12 February. It disappeared
by the 14th. According to calculations by [12], X/1491 B1 was making a close approach to the Earth.
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Edward Bryant, Simon K. Haslett? Tsunami Chronology Supporting Late Holocene Impacts
Fig. 2. Time series of probable tsunami events affecting the New South Wales coast of eastern Australia
Sekanina and Yeomans [32] calculate that a collision with the Earth was possible on 13 February. From
the perspective of the east coast of Australia, this comet approached the Earth around midnight from
the northwest, most likely at a 45° angle to the horizon. The direction, season, and time of day agree
with Aboriginal legends. Baillie [4] also recognized the potential of this comet for an impact with the
Earth. He points out that its timing matches the largest ammonium spike in a millennium in Antarctic
ice cores that can be interpreted as the signature of a comet impact.
Western Australia (WA)
The presence of tsunami deposits along the coast of Western Australia has been described in a
number of studies [7-9, 24-27, 31]. Fifty-four radiocarbon dates have been obtained from marine shell
found along this coast. A similar analysis was applied to these dates as for those described above.
The results are plotted in Fig. 3. There again are ten significant tsunami events. This time centred on
4200 BC, 2870 BC, 2150 BC, 100 BC, AD 540, AD 790, AD 1040, AD 1300, AD 1440, and AD 1680.
Again the latter three events may be part of the same event. A more recent event in the last 250 years
cannot be ruled out, but is impossible to date using radiocarbon because the ages come out as modern.
By far the most extensive event is the one that has occurred within the last 800 years. Its signature is
preserved at more than six locations along the coast, from Kalbarri in the south to Cape Leveque in the
north?a distance of 1800 km.
Three of the events are noteworthy because they occur at times of other calamities in the region.
The 1440 event overlaps with the AD 1491 mega-tsunami event documented along the New South
Wales coast of Australia. Any tsunami generated by this impact would not have affected the west
coast of Australia to the degree documented in this paper. This point will be discussed later. The
second event dated at AD 540 coincides with a catastrophic event triggered in AD 535 by an unknown
explosion or eruption in the Indonesian-Northern Australian region [18]. Bryant E.A., Walsh G., Abbott
D. [9] believe that the explosion has its source in a comet that fragmented into two and struck the Gulf
of Carpentaria in northeast Australia. However, any tsunami generated in the Gulf would not have
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Edward Bryant, Simon K. Haslett? Tsunami Chronology Supporting Late Holocene Impacts
Fig. 3. Time series of probable tsunami events affecting the West Australian coast of Australia
entered the Indian Ocean. The event around 2870 BC corresponds to a global catastrophe caused by a
comet impact in 2807 BC documented by [21] and linked to the Burckle Impact crater shown in Fig.
1. Finally, an event centred on 2150 BC may also have a cosmic origin although the evidence is less
conclusive. Its timing corresponds with the fall of the Akkadian empire in the Middle East at around
2200 BC, which has been linked to an impact [21].
United Kingdom (UK)
On 28th September 1014 widespread coastal flooding occurred in Britain [13]. William of
Malmesbury in The History of the English Kings (vol. 1) states that «a tidal wave, of the sort which
the Greeks call euripus and we ledo, grew to an astonishing size such as the memory of man cannot
parallel, so as to submerge villages many miles inland and overwhelm and drown their inhabitants»
[23]. For the same year, the Anglo-Saxon Chronicle states that «on the eve of St. Michael?s Day [28th
September], came the great sea-flood, which spread wide over this land, and ran so far up as it never
did before, overwhelming many towns, and an innumerable multitude of people» [16]. Some accounts
suggest that this flood affected Kent, Sussex, Hampshire [11], and even as far west as Mount?s Bay in
Cornwall, where the Bay was «inundated by a ?mickle seaflood? when many towns and people were
drowned» [29]. Healy [15] describes organic deposits in Marazion Marsh, that lie behind a coastal
barrier in Mount?s Bay, that is dated to no later than AD 980 and overlain by a sand layer, which could
be a signature of the flood event. In North Wales, it has been suggested that recently described field
evidence for tsunami impact may be related to this Celtic event [14]. The flood is also mentioned in the
Chronicle of Quedlinburg Abbey (Saxony), where it states many people died as a result of the flood in
The Netherlands, and it is remembered in a North American account by [17].
This collection of records implies a significant event in 1014 affecting a number of locations
around the British Isles (southeast England, Cornwall, possibly Cumbria). Storm surge can be ruled
out because a single storm could not generate a surge over so wide an area in different bodies of water.
The event has characteristics of a tsunami given the geography and apparent severity of the flood [13].
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Edward Bryant, Simon K. Haslett? Tsunami Chronology Supporting Late Holocene Impacts
Fig. 4. Summary of tsunami events and corresponding impacts
Indeed, [5] considers the 1014 flood to have been a tsunami caused by a comet impact. He cites GRIP
ice core data indicating a high ammonium spike in 1014. Investigations of Comet Hale-Bopp and
others indicate that ammonium is a major component (1-2%) of a comet?s composition. His theory is
supported by another high ammonium anomaly recorded in the GISP2 ice core data coincident with
the 1908 Tunguska bolide over Siberia. Haslett and Bryant [13] have shown that a single impact in the
ocean west of Ireland could generate a tsunami that would strike all the coastlines of northwest Europe
associated with this event. This UK event clearly requires further investigation.
Discussion and Conclusions
Fig. 4 summarises the chronology presented in this paper. In essence, our data for New South
Wales, Western Australia, and Western Europe are evidence of impacts in three oceans: the southwest
Pacific, the Indian and the North Atlantic. The North Atlantic region has additional evidence for at
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Edward Bryant, Simon K. Haslett? Tsunami Chronology Supporting Late Holocene Impacts
least seven major tsunami documented on the Iberian Peninsula. These events occurred in 60 BC,
218-216 BC, 1763 BC, 1862 BC, 2153 BC, 3309 BC and 4000-5000 BC [19, 28, 30]. In addition, three
pre-historic tsunami are known from the northern British Isles. These events occurred at AD 500,
3250-3150 BC and 3300 BC [6, 10]. The source of all of these events remains unknown, but Baillie
[5] points out that the size and association of some events with climatic anomalies begs for an impact
explanation. These events are also listed in Fig. 4.
Except for the Burckle event of 2807 BC, all of the impact events we have identified in this
paper are linked to tsunami deposits in more than one ocean. By far the most prominent event is
Mahuika, which most likely occurring in AD 1491. However, the event is associated with age reversals
in radiocarbon, which may have resulted from overturning of carbon-rich ocean waters or injection of
vaporised carbonates into the atmosphere. It is difficult to separate any tsunami deposit dated between
AD 1300 and AD 1700 into more than one event because of this issue. AD 1491 has been chosen as the
likely date of the impact because it is associated with the disappearance of an observed comet close to
the Earth and one of the largest ammonium spikes in Antarctic ice cores.
There are possibly four synchronous events occurring in more than one ocean that have not been
linked yet to an identifiable impact. These occurred around AD 790, 60 BC, 3200 BC and 4200 BC
(Fig. 4). Baillie [5] has already identified the 3200 BC event as being a prime candidate for an impact
event that affected more than one ocean. If the results presented in this paper are correct, then they
indicate that impactors generating tsunami are more likely to be clustered in time or to occur as a
swarm that has a widespread impact path across the Earth?s surface. Swarming has already been
identified at two sites on land, at Campo del Cielo and Rio Cuarto, both in Argentina [21]. Campo del
Cielo consists of 26 small craters and an associated meteorite field covering an area of 238 sq km dating
around 2500 BC. Rio Cuarto consists of an impact area covering 48,000 sq km dating between 4000
BC and AD 1000. It released over 1000 Mt of energy [21]. Had it occurred over the ocean, the resulting
mega-tsunami would have been more than sufficient to produce many of the deposits mentioned in this
paper. The threat from comets may not be as a single object occurring at rare intervals. Instead, the
idea of phases of coherent catastrophism from comet impacts, formulated by [3] is more likely.
More difficult to detect are impacts occurring as a swarm over the ocean. Unless such a swarm
contains pieces approaching 500 to 1000 metres in size, it will leave no crater as evidence of its impact.
Its only signature, besides the myths and legends of people who saw it, would be the type of megatsunami evidence that forms the bases of the chronology presented in this paper.
?????? ???????????? ??? ????????? ????????? ???????? ?????????? ????????????
????????????.
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Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Edward Bryant, Simon K. Haslett? Tsunami Chronology Supporting Late Holocene Impacts
?????????? ?????? ????????????? ????????? ????????
? ??????? ????????
?. ????????, ?. ????????, ?. ????????,
?. ????????, ?. ?????????
?
?????????????? ???????????, ????????? ???????????? ????,
????????? 2516, NSW
?
??????????? ??????,
?????????????? NP18 3QT, ????? ?????, ???????
?
??????????? ?????? ??????,
????????? 2480, NSW, ??????
?
????????? ???????????, ???????? ?????????,
???????? 50623, ?????
??????? ??????? ????????? ??????????? ? ???????? (HIWG) ?????????? ?????, ?? ???????
????, ?????? ????????? ??????????? ? ??????? ?????? ? ??????? ????????. ?????? ?? ???
??? ???????? ????????????? ?????????? ??????, ??? ??? ?????? ???? ???????? ?????????????
???? ?? ??????????? ??????????. ?? ?????????? ?? ?????????? ?????????? ?????? ????
????????? ????????? ???????, ??? ?? ??????? ??????? ? ?????????, ??????????? HIWG.
????????? ??? ??????? ? ????????? ? ????????????? ??????????. ? ?????? ??????????
?????????? ??????? ?????? ? ????? ????? ????? ????? (NSW) ? ???????? ?????????
(WA) ? ?? ??????????????? ??????? ?????????, ? ????? ? ??????????????, ??????? ???????
? ?????????? ?????????.
???????? ?????: ??????????, ????????? ???????? ??????, ???????????? ????????????????
?????????, ????????? ??????? ???????? ????????.
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Journal of Siberian Federal University. Engineering & Technologies 1 (2010 3) 72-103
~~~
??? 551.3
The Chiemgau Crater Strewn Field: Evidence of a Holocene Large
Impact Event in Southeast Bavaria, Germany
Kord Ernstson*a, Werner Mayerb, Andreas Neumairb,
Barbara Rappenglьckb, Michael A. Rappenglьckb,
Dirk Sudhausc and Kurt W. Zellerd
a
University of Wьrzburg,
Am Judengarten 23, 97204 Hцchberg, Germany
b
Institute for Interdisciplinary Studies,
BahnhofstraЯe 1, 82205 Gilching, Germany
c
Institute of Geography, University of Augsburg,
UniversitдtsstraЯe 10, 86135 Augsburg, Germany
d
Цsterreichisches Forschungszentrum Dьrrnberg,
Pflegerplatz 5, 5400 Hallein, Austria 1
Received 30.01.2009, received in revised form 27.02.2010, accepted 9.03.2010
The Chiemgau strewn field in the Alpine Foreland discovered in the early new millennium comprises
more than 80 mostly rimmed craters in a roughly elliptically shaped area with axes of about 60 km and
30 km. The crater diameters range between a few meters and a few hundred meters. Geologically, the
craters occur in Pleistocene moraine and fluvio-glacial sediments. The craters and surrounding areas
so far investigated in more detail are featuring heavy deformations of the Quaternary cobbles and
boulders, abundant fused rock material (impact melt rocks and various glasses), shock-metamorphic
effects, and geophysical anomalies. The impact is substantiated by the abundant occurrence of metallic,
glass and carbon spherules, accretionary lapilli, and of strange matter in the form of iron silicides
like gupeiite and xifengite, and various carbides like, e.g., moissanite SiC. The hitherto established
largest crater of the strewn field is Lake Tьttensee exhibiting an 8 m-height rim wall, a rim-to-rim
diameter of about 600 m, a depth of roughly 30 m and an extensive ejecta blanket. Physical and
archeological dating confine the impact event to have happened most probably between 1300 and 300
B.C. The impactor is suggested to have been a low-density disintegrated, loosely bound asteroid or a
disintegrated comet in order to account for the extensive strewn field.
Keywords: ?hiemgau crater, shock-metamorphic effects, geophysical anomalies, Chiemgau material,
Chiemgau impactor.
1. Introduction
In the last decade, an increasing interest in Holocene catastrophic impact events is documented
by numerous international meetings, workshops and publications [1, 4, 28, 36, 56, 57, 65]. This interest
reflects the public awareness of a realistic cosmic threat, and the centenary of the Tunguska event with
*
1
Corresponding author E-mail address: kernstson@ernstson.de
© Siberian Federal University. All rights reserved
# 72 #
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Kord Ernstson, Werner Mayer? The Chiemgau Crater Strewn Field: Evidence of a Holocene Large Impact Event?
Fig. 1. The Chiemgau crater strewn field. The craters are not drawn to scale, but the relative sizes more or less hold
true. The numbers attached to a few craters are the true diameters (in meters).
worldwide considerable resonance in the media underlines the importance of the subject matter. The
real threat to Earth and possible defense strategies [12, 60, 61] are controversially disputed, and here
statistics and impact probabilities play a major role [5, 7, 52]. While in general the threat by asteroid
impact is considered much larger than by comet impact [60], there are scientists who suggest the
probability of cometary impacts is largely underestimated [62]. The debate demonstrates that statistics
has limited importance only and that a sound and complete as possible record of young impact events
based on thorough field observations and precise dating are fundamental.
Here we report on a large impact event some 2,500 years ago in the Celtic period that produced
an unusually large crater strewn field that was discovered in the early new millennium by a group of
local history researchers (W. Mayer and co-workers). In the subsoil they detected pieces of metallic
material (ferrosilicides Fe3Si, mineral gupeiite, and Fe5Si3, mineral xifengite) hitherto unknown in the
region of the rural districts of Altцtting and Traunstein near Lake Chiemsee (Chiemgau, southeastern
Bavaria) [2]. They noticed that the material was regularly associated with striking craters, which
mostly showed a clear rim, though some of them had been leveled by plowing. After having performed
an extraordinary field work over three years till 2004 they came to the conclusion that both the peculiar
metallic matter and the craters could be related with the impact of an extraterrestrial object and that
the impact must probably have happened in historical time. Their discovery in the Inn-Salzach region
(Fig. 1) widely raised skepticism, but they nevertheless were able to interest scientists e.g., from the
Munich and Tьbingen universities resulting in a few early publications [25-27, 41, 67, 78]. In the year
2004, W. Mayer and co-workers entered into a new cooperation constituting a group of researchers
(Chiemgau Impact Research Team, CIRT) that now comprises the early discoverers together with earth
scientists, astronomers, impact researchers, archeologists and historians. The constitution of the CIRT
went hand in the insight into a much larger dimension of the proposed impact event comprising both
the areal dimension (Fig. 1) and the host of related phenomena. The present paper intends to give an
overview of the research as it now (late 2008) stands.
2. Scattering ellipse and crater dimensions of the Chiemgau strewn field
On earth, seven meteorite crater strewn fields are known. These are the Kaalijarvi field in Estonia,
the Morasko field in Poland, the Sikhote Alin field in Russia, the Henbury field in Australia, Campo
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Fig. 2. Aerial photographs of leveled craters on farmland (near Mehring, left, and Perach) after image processing.
The Perach crater exhibits a distinct ejecta blanket and, although leveled by farming, a clear concentric zoning.
Photos by courtesy of G. Benske and Bayer. Landesamt f. Denkmalpflege
Fig. 3. The 6 m-diameter Hohenwarth and 11 m-diameter # 004 craters
del Cielo in Argentina, the Wabar field in Saudi Arabia [39], and the Macha meteorite crater field in
Yakutia [35]. Recently, a group of a few young meteorite craters with diameters of the order of 300 m
has been discovered in Russia east of Moscow [17].
Compared with these known occurrences, the newly discovered crater strewn field in southeastern
Germany (Fig. 1) is exceptional. Our investigations up to now count more than 80 craters that have been
identified, measured and catalogued on the basis of topographic mapping, satellite imagery, systematic
aerial photography, and ground inspection establishing the scattering ellipse shown in Fig. 1. Recent
sonar soundings in Lake Chiemsee and relevant deposits in and around the lake [85] suggest impacts
to have happened also in the water. Most conspicuous is a rimmed doublet crater of the size roughly
900 m x 400 m.
The preservation of the craters varies depending on their location on, e.g., farmland or in forests.
On farmland, many of the craters recorded on older topographic maps have meanwhile been leveled out.
Despite the leveling, they are often visible by satellite imagery or on aerial photographs especially when
image processed (Fig. 2). On the other hand, many well-preserved craters are probably if not certainly
hidden in forests that cover large areas of the scattering ellipse.
The diameters of the documented craters range between 3 m and several 100 m (a few of them
shown in Figs. 3, 4). At present, Lake Tьttensee, located near the well-known Lake Chiemsee, proves to
be the largest crater (Fig. 1; more about the Lake Tьttensee crater below (chapter 12.1)). The depths of
the craters range between 0.4 m (for the smallest 3 m-diameter craters) and an estimated depth of about
30 m for the largest crater, Lake Tьttensee. In Fig. 5, the depths and diameters for 42 fully preserved
smaller craters are plotted exhibiting a general increase of the depths with increasing diameters. On
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Fig. 4. The 16 m diameter Murshall crater and the 55 m-diameter # 024 semi-crater (punched out of the Inn river
embankment; to the right). The # 024 crater is conserved at half only (see the broken line encircling the crater)
because of the destruction by the nearby Inn river erosion. Aerial photo: G. Benske
Fig. 5. Diameters and depths for 42 fully preserved smaller craters of the Chiemgau strewn field. On average, a
diameter-to-depth ratio of 7 has been determined (given by the straight line)
an average, a diameter-to-depth ratio of r = 7 applies. Depth determinations for the larger craters is in
general problematic because of lacking soundings in water-filled structures and frequent back filling.
On average, the diameter of the craters increases from the northern end of the strewn field to
its southern end (Fig. 1). This is remarkably similar to other meteorite crater strewn fields (Morasko,
Henbury, Kaalijarvi, Sikhote Alin) showing a comparable distribution [39]. Such a distribution
is generally assumed to be related with an atmospheric break-up of the impactor implying a rough
grading of the fragments and of the diameters of the associated craters.
3. Target geology
Apart from the most northern part of the strewn field, where Miocene gravels, sands and marls
are exposed in the hilly terrain, the target is predominantly composed of Pleistocene and Holocene
moraine sediments and fluvial deposits (Fig. 6). Pebbles, cobbles and boulders up to the size of 30
cm are intermixed with sands, clays and loamy material. The components represent Alpine material
in the form of sedimentary rocks (mostly limestones, dolostones and sandstones), magmatic rocks
(mostly granitoids) and metamorphic rocks (mostly quartzites, gneisses, amphibolites, serpentinites
and schists). Occasionally, meter-sized erratic blocks and larger blocks of cemented conglomerates
(Nagelfluh) are observed. Locally, lacustrine clays, peat, loess and loamy soils contribute to the target
layers.
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Fig. 6. Rim zone of the # 024 semi-crater (located to the left) exposing typical gravelly target rocks in the Inn
river embankment (see Fig. 4). Note that the layers are markedly folded probably due to the impact excavation
flow field
Fig. 7. Simplified sketch map of glacial signature in the crater strewn field area. Note that a large part of the crater
distribution is located outside the most recent Wьrm glaciation not allowing a confusion of the craters with young
dead-ice depressions there. A = Altцtting, B = Burghausen, O = Obing, Tn = Traunstein, Tt = Traunreut
Because of the glaciation-dominated target geology, confusion has been introduced by critics of
the impact hypothesis. Most commonly, the craters are claimed to be dead-ice depressions [16, 76, 91]
without stating any reasons. As shown in Fig. 7, the crater strewn field is to a large extent located in
the gravel plains outside the ice thrust of the latest Wьrm glaciation basically excluding a dead-ice
origin for the numerous craters found here. Because of the markedly fresh shape of the craters an
interpretation as remnants from earlier glaciations can likewise be excluded. With regard to other
geological processes to have possibly formed the craters, we find that neither volcanism nor tectonics
are known for the region under discussion and for the Holocene geological time of the phenomenon.
Deep-seated dissolution and collapse processes like karstification may account for those depressions
lacking a ring wall but can be excluded for all the craters exhibiting such a wall. Recent ideas and
investigations [24] suggest that some of the smaller craters may have been formed indeed in the impact
event, however from beneath instead of from above. Like strong earthquake shocks, impact shock may
lead to liquefaction of water-saturated soft rocks causing sand explosion craters as happened widespread in the strong 1811/1812 New Madrid earthquake series [83].
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4. Crater structure and material
Only a few craters have so far been examined in more detail. Digging vertical trenches through
them reveals the typical bowl-shaped profile well known from meteorite craters of comparable size.
The majority of the craters have clear walls, with a steep gradient inside towards the center and a
flat one outside. Ground penetration radar (GPR) measurements [79] across a 11 m-diameter crater
reveal strong reflexions from the crater floor, and the layering down to a depth of several meters
continuously reflects the rim wall morphology. Often, the craters show a slightly elliptical form. On
aerial photographs, the zone of ejecta around some craters may become visible (Fig. 2).
The gravel in the center of the craters studied so far is sharp-edged broken and looks basically
different compared with the usually well-rounded pebbles found in the field (Fig. 8). At the rim of the
craters, strongly deformed cobbles and boulders are regularly observed. They may be accompanied by
melt rocks, pumice-like stones and low-density, foamy, vesicular carbonate material (for more details
of the deformations and the melt rocks see below).
Fig. 8. Broken, sharp-edged clasts from within the craters (to the left) sharply contrasting with well-rounded
clasts from the Quaternary material in the field
5. Macroscopic deformations
Craters having so far been investigated in more detail exhibit strong mechanical deformations
at the floor and the walls and in the ejected material forming the rim (Figs. 9, 10). Heavily fractured
but coherent cobbles and boulders (Fig. 9) prove in situ high-pressure/short-term deformation. A
deformation by Alpine tectonics or by glaciers can be excluded, because the clasts would not have
survived any significant transport. Comparable in situ high-pressure/short-term deformation established
by Ernstson and Claudin [20] and Ernstson [23], have also been reported earlier for the Ries impact
structure (Nцrdlinger Ries) [11, 15, 70, 71].
Likewise, the widely open fractures in the otherwise coherent cobbles with smooth surface and
without any shearing (Fig. 10, upper) cannot possibly have originated from tectonics. Instead, these
so-called spallation features are the typical result of dynamic shock deformation well known from
shock experiments in fracture mechanics (Fig. 10, lower right) and also observed in conglomerates
near large impact structures [22-23], (Fig. 10, lower left). We emphasize that the examples shown in
the figures do not represent scarce finds but regularly occur in and around the strewn field craters. In
the wall surrounding the largest crater, Lake Tьttensee, estimated 40-50% of the so far examined larger
cobbles and boulders exhibit strong deformations, whereas all gravel pits next to the crater are void of
these characteristically deformed rocks.
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Fig. 9. Strongly deformed cobbles from the Chiemgau crater field. The cobble to the left has completely been
crushed to form a monomictic movement breccia [75] partly exhibiting mortar texture. The heavily squeezed
and sharp-edged fractured however coherent cobbles sampled from a soft matrix prove high-pressure/short-term
deformation and exclude any significant transport
Fig. 10. Shock-induced spallation fractures in cobbles from the Chiemgau crater field (upper). For comparison,
widely-open spallation fissures in a shocked quartzite cobble from the Azuara-Rubielos de la Cйrida impact
structures ([23]; lower left) and in an experimentally shocked ARMCO iron (courtesy M. Hiltl)
More impact-related deformations are observed in the form of heavily striated and polished
cobbles found in various craters (Fig. 11). It is true, striated and polished clasts are well-known from
glacier transport, the clasts shown here, however, originate from craters formed in fluviatile gravel
deposits outside the Wьrm glaciation (see Fig. 7), and the striae and the polish would not have survived
any water transport. Striated and polished clasts are moreover well-known from other impact sites like
the Ries impact structure [11], the Azuara-Rubielos de la Cйrida impact structures [20, 23] and the
Chicxulub impact ejecta [54, 64].
In the fluviatile gravel material from craters in the Chiemgau strewn field, distinct concussion
marks have been observed to occur on the surfaces of quartzite cobbles (Fig. 12). They strongly
resemble similar deformations reported for shocked conglomerates near the Azuara-Rubielos de la
Cйrida impact structures [20-21], and a comparable formation for both, that is a highly energetic shock
acceleration of cobbles in contact, is suggested.
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Fig. 11. Striation and mirror polish on quartzite clasts from # 024 semi-crater (to the left) and the Einsiedeleiche
crater. The craters are located in fluvial deposits and, therefore, the deformations cannot be confused with a
glacial signature
Fig. 12. Probably shock wave-induced concussion marks on the surface of a quartzite cobble from the # 024 semicrater (Fig. 4). The close-up shows the strong microfracturing of the quartz grains causing a whitish color of the
otherwise grayish stone
6. Rock corrosion
One of the most remarkable observations in the Chiemgau strewn field is the abundant heavy
corrosion of Alpine cobbles and boulders of both carbonate and silicate lithology including, e.g.,
sandstones and amphibolites. They are observed to occur on the surface, in the shallow subsurface and
within ejected material. The corrosion, abundantly deep-reaching to the point of residual rock skeletons
(Fig. 13) is explained by decarbonization/melting and/or nitric-acid dissolution of carbonate rocks
(limestones, dolostones) and by nitric-acid corrosion of silicate rocks. The production of considerable
amounts of nitric acid (and other acids) in the explosion cloud of large impacts has repeatedly been
proposed [53, 55, 66, 93], and precipitation of acid rain has also been suggested for the 1908 Tunguska
event [50, 74].
7. Melt rocks and glass
Pumice-like melt rocks constitute striking impact rocks (impactites) in the strewn field (Fig. 14).
They occur around the Lake Tьttensee crater and have been observed at the Lake Chiemsee shore.
Near the Lake Tьttensee crater and north of Lake Chiemsee they have been used as building stones
for the construction of 18th and 19th century farmhouses. Around the Lake Tьttensee crater, the melt
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Fig. 13. Deeply corroded clasts from the Chiemgau crater strewn field
Fig. 14. Melt rock as occurring around the Lake Tьttensee crater and near lake Chiemsee. A, B: Various aspects
of the strongly vesicular melt rock show analogy to the Chapadmalal (Argentina; [81]) impact melt rock (image
inserted in Fig. 14 A). Superficially, the vesicular melt rock may pass over into a dense glass (C), and a «ropy pahoehoe» (D) reminds of well-known lava flow features
rocks must have been abundant in the past, but now they are rare. The reason is a popular game played
by children some 50 years ago. They threw melt rock clasts («swim stones») into the Lake Tьttensee
water betting on whose stone would sink last. The rock reflects an in general volatile-rich melt (Fig. 14
A, B) with frequent superficial transitions to a dense, often greenish glass (Fig. 14 C). Flow texture
is indicated by alignment of elongated vesicles and a kind of «ropy pahoehoe» (Fig. 14 D) otherwise
well known from volcanic lava flow. Frequently, melt rock clasts are superficially caked with gravel
reflecting the emplacement of the melt. The macroscopically fairly homogeneous melt rock may be
deduced from a homogeneous parent rock, for example from Lake Chiemsee lacustrine clays. In an
experimental approach, wet lacustrine clay could be transformed to a vesicular glass on exposing the
clay to some 2,500 °C for only a few seconds.
A second group of wide-spread melt rocks comprises cindery glass fragments in most cases
interspersed with small rock fragments (Fig. 15). Among impact melt rocks the vesicular glass melt
rocks from the Henbury (Australia) meteorite crater strewn field are most similar to this Chiemgau
cindery glass.
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Fig. 15. Cindery glass fragment interspersed with quartzite splinters. This type of melt rock is widespread found
in the Chiemgau strewn field
Fig. 16. A large sandstone boulder from the Lake Tьttensee crater completely coated by a thin film of glass. The
darker spots show the original rock where the glass has flaked off
Fig. 17. SEM image of a broken vesicular glass spherule; Stцttham impact layer
A further variety of melt glass is found to in most cases completely coating silicate cobbles and
boulders (Fig. 16). For the # 004 crater in the northern part of the strewn field, the cobbles and boulders
more or less completely transformed to glass are a special characteristic that will be discussed in a
separate chapter (12.3). More glass in the form of small glass spherules is found in the subsoil and
embedded in impact breccia layers (Fig. 17).
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8. Shock metamorphism
It is generally accepted that shock metamorphism in rocks must be considered as in proof of
meteorite impact [31-32, 34]. Depending on their intensity, shock waves leave quite different traces
in a mineral. Planar deformation features (PDFs) belong to the most important ones. Fig. 18 shows
photomicrographs of PDFs in quartz from the Chiemgau strewn field. At least two (left) and five (right)
sets with varying orientation are occurring.
These peculiar structures are closely spaced parallel, optically isotropic lamellae following
crystallographic planes in the quartz grain. According to current knowledge [84], multiple sets of
these closely spaced isotropic lamellae can originate from extreme shock pressure only. The mottled
appearance of the quartz in Fig. 18 (right) can also be attributed to shock. This so-called «toasted
quartz» is well known from shocked quartz from other impact structures and is explained by extremely
tiny fluid inclusions [88]. PDFs in quartz have been shown to exist in several samples from crater # 004
(Fig. 18), from the Lake Tьttensee rim wall (Fig. 18) and in rocks from the Lake Tьttensee ejecta layer
(see 12.1). In quartz from the # 004 crater diaplectic glass as a further strong shock indicator could be
established. More distinct shock metamorphism in the form of PDFs and glass (probably maskelynite)
is found in feldspar from the Lake Tьttensee melt rock (Fig. 19).
Fig. 18. Planar deformation features (PDFs) in quartz from the Chiemgau strewn field; photomicrographs crossed
polarizers. Left: Two sets of PDFs in quartz, quartzite clast from crater # 004. Right: Five sets of PDFs in «toasted» quartz, quartzite cobble from the Lake Tьttensee crater rim wall. Not all sets can be seen on the image, but
they become visible on rotation of the thin section on the microscope stage
Fig. 19. Twin lamellae, multiple sets of PDFs partly showing «ladder» texture [31], and spots of glass (probably
maskelynite) in plagioclase; photomicrograph, plane-polarized light. Melt rock from the Lake Tьttensee crater
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Fig. 20. Two sets of closely spaced kink banding in biotite (NNW ? SSE and NNE ? SSW trending); photomicrograph, crossed polarizers. Gneiss clast from the Lake Tьttensee ejecta layer (excavation pit # 10)
Fig. 21. Five sets of closely spaced and partly curved deformation features in calcite; photomicrograph, crossed
polarizers. The spacing of the microtwins is in part 2 ?m only. Calcite dikelet in quartzite, Lake Tьttensee crater
excavation pit # 21
Apart from the PDF signature in quartz and feldspar and the diaplectic glass in quartz, the
study of thin sections from 31 rock samples taken from seven different excavations at Lake Tьttensee
establishes a rich inventory of mineral deformations that with reasonable certainty have also originated
from shock load. The shock effects are moderate and comprise planar fractures (PFs; cleavage) in
quartz, extreme and abundant kinking in mica (Fig. 20) [31, 43], and regularly occurring multiple sets
of microtwinning in calcite (Fig. 21) [58]. With regard to the relatively small impact crater, the frequency
of occurrence of the presumed shock deformations, although of moderate intensity, is conspicuous.
Therefore, the special target conditions, that is hard and dense cobbles and boulders in an uncemented
soft matrix, are discussed to have enabled a focusing of shock intensity as has earlier been considered
for the Barringer crater Coconino sandstone [48] and for a shocked conglomerate [22].
9. Geophysics
Anomalous magnetic signature of craters and the subsoil have been revealed in the early phase of
the investigations restricted to the Burghausen area in the very north of the strewn field. While Fehr et
al. [27] considered inconclusive the measurements across a few craters, Rцsler et al. [79] and Hoffmann
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et al. [42] discussing the strong magnetic signature of an 11 m-diameter crater (crater # 004 in our
nomenclature; also see 12.3) favored a relation to an impact event. Extensive soil magnetic susceptibility
measurements in forests in the northern part of the strewn field [40] revealed significantly enhanced
values at depth. The authors exclude industrial and geologic delivery, but they avoid to discuss a third
possibility. Meanwhile, we were able to show that the anomalous magnetic signature extends also to
the most southern part of the strewn field. A rimmed 6 m-diameter crater some 2 km north of the Lake
Tьttensee crater is characterized by a 15 m-diameter halo of enhanced soil magnetic susceptibility up
to one order of magnitude larger than the normal soil susceptibility outside the halo. Also, the subsoil
enhanced magnetic susceptibility as recorded in the northern strewn field [40] has been found to have
its counterpart in the southern crater strewn ellipse. In a forest about 1 km north of the Lake Tьttensee
crater we measured several soil susceptibility profiles regularly showing a peak at some decimeter
depth (Fig. 22). The magnetic peak is related with a horizon enriched in fractured pebbles, cindery glass
and carbonaceous spherules. Rock-magnetic studies remain to be done. More evidence of anomalous
rock-magnetic behavior in the strewn field is given by the abundant occurrence of strongly magnetic
rock clasts of quite different lithologies. The high, dominantly remnant magnetization seems to be
unusual compared with typically magnetic rocks from the Alps (e. g., amphibolites, serpentinites).
Although a systematic investigation has not been done so far, the cobbles and boulders thus featured
seem to be confined to a superficial deposition, while lithologically comparable rocks sampled from
e.g. nearby gravel pits are lacking this property. More geophysics in the form of a gravity survey is
discussed in a special section on the Lake Tьttensee crater (12.1).
Fig. 22. Soil magnetic susceptibility profile near Lake Tьttensee revealing an anomalous peak at 30-35 cm depth.
Comparable anomalous soil susceptibility has been shown to exist also in the northern part of the crater strewn
field
10. Strange matter
The discovery and investigation of the Chiemgau meteorite crater strewn field is inextricably
related to the occurrence of widespread peculiar matter that may generally be classified into metallic
and carbonaceous matter. Since early analytical results from the northern crater strewn field have been
published elsewhere, the present article confines to a short summary of the existing data and to a few
exemplarily discussed new findings.
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Fig. 23. Metallic iron silicide particle typically found in the Chiemgau impact strewn field
Fig. 24. Comparison of analyses of Chiemgau gupeiite and meteoritic suessite. Suessite data from [46]
and [89]
Fig. 25. SEM image of moissanite (SiC) crystals in iron
silicide matrix. Scale bar 1 mm
Metallic matter. The first finds of peculiar metallic matter were often done near rimmed craters
in the Burghausen area suggesting both occurrences were related to each other. The particles were
millimeter to centimeter-sized forming spherules and irregular pieces, often seemingly aerodynamically
shaped and with a peculiar surface sculpture reminding of regmaglypts (Fig. 23).
Surprisingly, these phenomena in turn correlated with anomalous data of a completely independent
prospective biomonitoring campaign with honey bees over a considerable part of the sampling area
[68] leading to the hypothesis both observations could be related to a possible cosmic impact. In early
analyses, the metallic matter proved to be iron silicides FexSiy, among them the minerals Fe3Si, gupeiite,
and Fe5Si3, xifengite [80]. The similarity to gupeiite and xifengite occurences in cosmogenic globular
particles from the Yanshan area in China [95-96] strengthened the hypothesis of an impact event in
the Salzach-Inn region. A more recent electron microprobe analysis of a gupeiite particle from the
Chiemgau strewn field showed clear affinity to meteoritic suessite (Fig. 24). The moissanite (SiC)
crystals growing out of a iron silicide matrix (Fig. 25) also point to extraterrestrial origin of this
Chiemgau sample if anthropogenic formation can be excluded.
Carbonaceous matter. Carbonaceous material of different, partly very peculiar character has
abundantly been found in the Chiemgau strewn field. The most common occurrence is charcoal more
or less regularly intermixed in the impact breccia layers from the Stцttham archeological excavation
and the Lake Tьttensee crater ejecta blanket (see sections 12.1, 12.2). Moreover, carbonaceous
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Fig. 26. Carbonaceous matter from the Chiemgau strewn field. Millimeter scale
Fig. 27. Raman spectra collected from a carbonaceous piece sampled in the Chiemgau impact strewn field. The
doublet peak at approximately 1360 cm-1 (D ? disordered ? band) and 1560 cm-1 (G ? graphitic -band) indicates the
matter to be mostly amorphous carbon
matter occurs in the form of black glassy fragments up to the size of a few centimeters (Fig. 26) and
carbonaceous spherules with diameters of the order of millimeters (Fig. 28). The EDX analysis of a
glassy fragment reveals mostly carbon, a high amount of oxygen (up to 25 wt. %), small amounts of Al,
Si and Ca, and traces of Na, Mg, S, Cl, K and Fe. Raman spectra of the sample (Fig. 27) show greatly
disordered elemental carbon mostly in an amorphous state. Similar Raman spectra of disordered
carbon are known from, e.g., Allende carbonaceous chondrite, carbon matter from the Sudbury impact
structure and artificially shocked graphite [38]. The inexplicably high oxygen content needs further
analyses and may be related to a similar discovery of glassy amorphous particles of carbon and oxygen
as the only major components in a microbreccia from the Mid-Tertiary Rubielos de la Cйrida impact
structure in Spain [23].
Like the unusual metallic matter, the carbon spherules (Fig. 28) have originally been discovered
in the northern part of the strewn field and later also in the south when the much larger crater strewn
field was established. Here they have been shown to be enriched in the layer of enhanced soil magnetic
susceptibility (see above, Fig. 22).
For nanodiamond-bearing carbonaceous spherules sampled from the soil and embedded in the
melt crust of rocks in the northern strewn field an impact-related origin has been suggested [92].
Both a formation in the impact process and constituents of the impactor are considered. Carbon
spherules of similar qualities have been found also in soils widespread over Europe [92] and in an
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Fig. 28. Carbonaceous spherules
Fig. 29. Accretionary lapilli from the Chiemgau impact strewn field (left). Middle: A lapillo under the SEM showing the onion skin structure typically found in accretionary lapilli. Right: Cut lapillo composed of finegrained
sandy matter hosting metallic particles (dark)
archeological context at the Dьrrnberg (Austria) some 50 km off Lake Chiemsee thus pointing to a
fallout phenomenon.
Accretionary lapilli. In the Chiemgau strewn field a special type of spherically shaped particles
can abundantly be sampled from the ground that show the character of accretionary lapilli (Fig. 29).
Although outwardly appearing very similar (Fig. 29 left), internal texture and chemical composition
are quite different. Frequently they are composed of a dense fine-grained sandy material sometimes
hosting a core of metallic matter (Fig. 29 right). Others show the sandy material to form a skeletal
vesicular structure, and transitions to the vesicular glass spherules as shown in Fig. 17 can be observed.
A broad spectrum from strongly magnetized to non-magnetic lapilli exists. Preliminary EDX analyses
show strong elemental inhomogeneity even in one single lapillo.
Although accretionary lapilli are basically known from volcanism, they are more and more
reported to have formed also in meteorite impacts, e.g. in the Ries [33], Azuara-Rubielos de la Cйrida
[21], Tookoonooka [6], Chicxulub [10] and in the Alamo [87] impacts. In the Chiemgau impact event
the accretionary lapilli may attest a large explosion cloud. More analyses, however, are
necessary.
11. The anthropogenic/industrial component
From the beginning, field and analytical work in the Chiemgau strewn field were confronted with
the clear perception that there might be a strong anthropogenic signature concerning both the craters
and the proposed impact-related material. In the region of the impact strewn field quite a few industrial
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firms are residing, and it is common knowledge that from the beginning of settlement human activities
left various kilns, among them well-known lime kilns, glassworks and smelting works and related
high-temperature material like various slags and glass always implying also carbonaceous matter. In
addition, typical steel stabilizers are the same elements as are typical chemical elements in meteorites.
In a few cases, after systematic inquiries in population and industry, a competition between proposed
impact related findings and anthropogenic material clearly became evident. Thus, glass-coated silicate
cobbles have convincingly been attributed to meteorite craters (e.g., crater # 004), but externally very
similar cobbles are reported to may have casually been produced in lime kilns in earlier times. Much
more problematic is the realization that in the Chiemgau industry the extremely rare iron silicide
minerals gupeiite and xifengite are regularly produced as a hitherto completely unknown byproduct
(Schьssler, written comm.), and from an enquiry it seems possible that iron silicides intermixed in
fertilizer could be brought out on farmland during a few years after World War II. In this case, we have
to explain why the particles under discussion are found also in many hundred years old forests, in peat
mires at about two meter depth and in alp regions at more than 1,000 m altitude, unless also these areas,
hardly imaginable, were fertilized in former times. Moreover, gupeiite and xifengite particles were
detected below a medieval hoard of coins and below ground work of the Burghausen medieval castle.
Hence, a so-called effect of convergence, that is the inserting of the same kind of ferrosilicide particles
by fertilizing as well as by impact processes, cannot be excluded. As has been described above, impact
melt rocks from Lake Tьttensee and Lake Chiemsee have been used as building stones for farmhouse
construction in the 18th and 19th century. Likewise, true smelting slag served for the same purpose, and
both were generally lumped together.
An origin other than from the impact has been considered also for the craters, and especially
a possible anthropogenic formation of the many craters (e.g., housing estates, exploitation of earth
materials, water reservoirs, charcoal piles, production of quicklime and glassworks, medieval limonite
mining and smelting, explosion cratering from artillery fire or extensive bombing during World Wars
One and Two) has been investigated and discussed by us in very detail, and in summary, for the most
part of the craters under discussion a man-made origin can practically be excluded.
12. Selected impact sites
12.1. The Lake Tьttensee crater.
Lake Tьttensee is located a few kilometers east-southeast of Lake Chiemsee and north of the
Foothills of the Alps (Fig. 1). The main dimensions of the lake (Fig. 30) is roughly 400 m. A seismic
survey conducted on the lake has revealed the maximum water depth to be about 16 m, however no
clear reflection signals from deeper layers probably due to energy-absorbing thick mud (G. Daut, pers.
comm.). A gravity survey on the frozen lake [19] suggests roughly 30 m total depth including this
thick layer of organic material. The lake is surrounded by a rim wall merging in the north into a glacial
moraine. About one hundred years ago, the 8 m-height rim wall continuously encircled the lake but
now exhibits three artificial gaps (Fig. 30). The rim crest diameter amounts to roughly 600 m, which
therefore is the diameter of the proposed meteorite impact crater. Apart from the artificial gaps, the rim
and crater area have sustained significant morphological modifications probably beginning already in
Roman times.
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Fig. 30. The Lake Tьttensee crater and the 8 m-height rim wall exhibiting an artificial gap
Lake Tьttensee has always been considered a dead-ice relic from glaciation although the considerable
size and the pronounced, originally continuous rim wall have never favored the interpretation of a
kettle hole, the more so as there are not any exposures that have supplied the necessary geologicsedimentological evidence. Moreover, outlet records of Lake Tьttensee [3] and dominating gravelly
material reported for the peripheral lake bed are speaking against a bottom sealing otherwise typical
for glacial lakes in the Alpine Foreland. Nevertheless, critics of the impact event maintain the deadice origin for Lake Tьttensee [16]. Planned boreholes into Lake Tьttensee have categorically been
prohibited by the authorities because of feared negative impacts on nearby drinking water fountains.
Consequently, the impact nature of Lake Tьttensee has been revealed by accessible geology of the rim
wall and an extensive impact ejecta blanket.
The study of the rim wall is mostly restricted to the outcrops of the artificial gaps with in general
poor insight into its structure and material, the latter in principle being Quaternary moraine and gravel
material. From the gaps, and especially from quite a few additional superficial excavations into the
rim wall, great quantities of pebbles, cobbles and boulders were sampled exhibiting the unusual strong
deformations and peculiar textures already described in paragraph 5 and shown in Figs. 9, 10.
Ejecta blanket. ? The most striking geological evidence of the Tьttensee impact cratering
process, however, has been supplied by numerous excavation pits around Lake Tьttensee (Fig. 31).
Modifications included, they exhibit in general a three-layer sequence of autochthonous target rocks
(moraine material or lacustrine clay), a fossil soil and a diamictite layer that in general is overlain
Fig. 31. Map of excavation pits around the Lake Tьttensee crater with a concentration of the excavations in the
larger quadrangle
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Fig. 32. A multicolored polymictic breccia constitutes a large part of the Lake Tьttensee crater ejecta layer. Note
the heavily fractured however coherent quartzite clasts (to the right) proving deformation under high confining
pressure and excluding any fluvio-glacial transport
Fig. 33. Organic material (splinters of wood, charcoal, bones, teeth; to the left) and Neolithic/ Bronze Age artifacts (a quartzite hammerstone and the fragment of a drilled quartzite boulder, possibly an inchoate stone ax)
from the Tьttensee impact layer
by colluvium or immediately by the plowing horizon. The up to more than 1 m thick diamictite is
interpreted to represent the Lake Tьttensee impact ejecta blanket that was in part overprinted and/
or reworked by tidal waves emerging from companion impacts into Lake Chiemsee [85]. The basal
diamictite is dominated by sub-angular carbonate and silicate boulders in a muddy matrix which are in
part strongly deformed plastically and are abundantly corroded down to a skeletal sculpture (Fig. 13).
An intermediate bed, not always present, has the character of a polymictic matrix-rich breccia composed
of heavily fractured cobbles and boulders of Alpine lithology (Fig. 32), while the uppermost part of
the diamictite is especially enriched in humus material. The diamictite contains abundant splinters of
wood and charcoal as well as fractured animal bones and teeth (Fig. 33). Tufts of hair from the base
of the diamictite may be human hair. Thin-section analyses reveal abundant mineral deformations
evident of shock metamorphism (see 8). From the matrix of the diamictites a couple of prehistoric
artifacts could be recovered in the form of potsherds and Neolithic/Bronze Age stone tools (Fig. 33).
A more comprehensive article on the Lake Tьttensee crater as matters stood in 2006 has been written
by [13].
Gravity survey. ? A gravity survey on the frozen lake and in its surroundings had the principal
aim to get knowledge of the crater shape. The maximum gravity anomaly of Lake Tьttensee (Fig. 34) is
about -0.8 milligals mainly resulting from the density contrast of water/mud and rock. Surprisingly, a
ring of relatively positive anomalies is measured surrounding the Tьttensee negative anomaly (Fig. 34).
The positive anomalies are modeled [19] by a 1000 m-diameter flat lens of slightly enhanced density. It
is explained by a model of soil liquefaction and post-liquefaction densification well known from large
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Fig. 34. Bouguer gravity residual anomaly for the Lake Tьttensee crater. Note the ring-like zone of relatively positive anomalies explained by impact densification
Fig. 35. Gravity horizontal second derivative of the Lake Tьttensee Bouguer residual anomaly suggesting interference of smaller circular features
earthquakes [51, 59, 86]. Moreover, mass flow behind the impact shock front could have contributed to
the compaction of the loose, highly porous and water-saturated target rocks. The impact densification
model is substantiated by a gap in the northern part of the positive ring-like anomaly (Fig. 34). Here, a
moraine ridge of densified glacial rock material obviously resisted further densification upon impact, in
contrast with the otherwise highly porous Quaternary fluvial sediments. More strong rock liquefaction
suggested to be the result of the Chiemgau impact event is observed to occur widespread in the southern
part of the strewn field [24].
From the computed field for the horizontal second derivative of the Tьttensee Bouguer anomaly
(Fig. 35), the circular shape of the crater anomaly becomes more accentuated, at the same time
exhibiting an outline of interfering smaller circles. This may indicate a pre-impact disintegration of
the Lake Tьttensee projectile.
12.2. The Stцttham exposure.
In the course of an archeological excavation at Chieming-Stцttham located a few hundred
meters apart from the shoreline of Lake Chiemsee (47°54?25.3??N; 12°31?28.5??E), a diamictic layer
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very similar to the Lake Tьttensee impact diamictite has been encountered outcropping in a clear
archeological stratigraphic context (see 13). The several decimeters thick diamictite is embedded
in layers of colluvium contains brecciated and strongly corroded clasts, abundant organic material
like wood, charcoal, fractured animal bones and teeth, and intermixed archeological artifacts. Hightemperature signature is given by partly melted silica limestone, a typical rock from the Alps, and
a sandstone clast with sporadically interspersed glass. A formation of the melt from shock release
is possible. Moderate shock is indicated by abundant and strong kink banding of micas in gneiss
clasts from the diamictite. Millimeter-sized glass and carbonaceous spherules were extracted from
the diamictite mud. Lacking serious alternate explanations, the Stцttham layer must be considered an
impact horizon belonging to the same catastrophic event as does the formation of the Lake Tьttensee
crater. Different from the Lake Tьttensee crater diamictic ejecta no crater has so far been found as a
source for ejected material constituting the Stцttham deposit. A nearby possible candidate is a 200
m-diameter depression that however was completely filled in the past not allowing simple geological
access. A delivery of the Stцttham proposed impact ejecta material from craters located offshore in
Lake Chiemsee is also discussed [85].
12.3. The # 004 crater.
In the first time of the strewn field investigations, the crater # 004 (Fig. 3) located in the northern
part of the strewn field raised special interest because of its conspicuous deformation features and
exceptional high-temperature signature. The bowl-shaped circular depression with a complete rim
wall measuring 11 m in diameter was excavated from fluvial gravel material comprising common rocks
from the Alps like quartzites or basic metamorphic rocks. Apart from a great number of mechanically
deformed and fractured cobbles and boulders in and around the crater, a high-temperature process the
crater area must have undergone is given by numerous clasts exhibiting a drastic melting signature up
to practically complete transformation to glass. Rцsler et al. [79] report temperatures that must have
exceeded 1,500 °C across the crater area and a halo of about 20 m diameter. From these observations
and additional geophysical radar and magnetic measurements, an impact-related origin of the crater is
considered possible [79], although the authors were not able to establish shock metamorphism. From
detailed petrographic and geochemical analyses of rocks taken from crater # 004, new insights into
the cratering process are available. 17 cobbles of various lithology have been studied by thin-section
inspection and microprobe analyses (Mineralogical Institute, University of Wьrzburg). The thin
sections clearly show that the cobbles have experienced shock metamorphism at high temperatures
and pressures. Apart from extreme fracturing of quartz and feldspar including multiple sets of planar
fractures (PFs) in quartz, we observe multiple sets of planar deformation features (PDFs) in quartz
and feldspar, diaplectic SiO2 glass and extreme subgrain formation. Heavy tensile fracturing of whole
rocks and quartz grains indicates spallation by dynamic shock pulses. Melt glass is in general found
in five different occurrences: as nearly completely foamed-up cobbles (Fig. 36), as a thin crust often
completely coating the cobbles, as vesicular, partly recrystallized feldspar glass interspersing quartzite
rocks, as recrystallized glass filling open spallation fissures (Fig. 36), and as allochthonous melt lumps
fused to the cobbles? surface. The field observations and the lab analyses exclude normal tectonic
processes as well as human activities but, especially with regard to the shock metamorphism, clearly
establish a meteorite impact event. Obviously, this event that formed crater # 004 must have been
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Fig. 36. Glass from crater # 004. Left: Cobble practically completely transformed to a foamy glass. Right: Glass
filling tensile, probably shock spallation fissures in quartz grain. Photomicrograph, crossed polarizers; field width
0.8 mm
different from a normal solid-body impact shedding some light on the impactor(s) and the process of
the Chiemgau impact event and the emplacement of the meteorite craters. From scaling laws and from
comparison with the recent Carancas (Peru) meteorite impact that formed a roughly 14 m-diameter
crater [37, 82], a solid projectile of the size of the order of 1 m could have formed crater # 004. This
small size categorically excludes the formation of the abundant and widespread melt glass and the
heating of the 20 m-diameter crater halo to more than 1,000 °C from shock release. Total-rock melting
from shock release requires shock pressures of more than 50 GPa (= 500 kbar) [18] attained, if at all, at
the impact point of crater # 004. Consequently, the crater formation must have been accompanied by
a discrete strong thermal event independent of impact shock, and we suggest a local superheated gas
explosion bubble near above or immediately at the ground surface.
For the present, details of this peculiar process have to remain unanswered, for example the
question whether there was a solid impactor at all or whether the crater could have been formed solely
by a near-surface extreme gas explosion. Assuming this to be true, the question arises whether the
heavy mineral deformations in the crater # 004 cobbles could in part be produced by extreme thermal
shock stress waves. The production of cleavage (PFs) in quartz by thermal shock has been reported
earlier [29].
13. Dating the Chiemgau impact event
An approximation to the date of the Chiemgau impact is so far realized by quite different methods.
The stratigraphic context of the Lake Tьttensee (12.1) and Stцttham (12.2) ejecta layers clearly establishes
a post-glaciation, Holocene age. A thermoluminescence dating of a sample from crater # 004 revealed
an age of a few hundred years BC (B. Raeymaekers, pers. comm.). Various radiocarbon (C14) datings
supplied a broad time span and in part puzzling results that must still be analyzed thoroughly. Dating
wood from an excavation into the Lake Tьttensee impact layer gave reasonable ages that places the
impact to have happened after 2,900 BC. A radiocarbon age for charcoal from crater # 005 suggests
the crater formed before 200 AD [27].
For the Chiemgau event, the currently most stringent age is given by archeological artifacts.
Intermixed in the ejecta layer of Lake Tьttensee crater potsherds have been discovered. In temper and
texture they show great similarity with the so-called «Kultplatz» ceramics found at the Durrnberg
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(Austria) Celtic archeological site, only 50 km afar. Due to new dendrochronological data and the
archeological context at the Dьrrnberg, the «Kultplatz» ceramics can be dated between 470-430 (+/10) BC. Unfortunately, the Lake Tьttensee potsherds lack important attributes that would enable to
distinguish them with certainty from ceramics used in the Bronze Age. But from the mere existence of
these potsherds in the impact-related layer a 1300 BC terminus post quem of the impact is warranted.
Several artifacts of the Roman Imperial Period found at the rim wall of the Lake Tьttensee crater
establish a terminus ante quem that can be further narrowed down by a potsherd of middle/late La
Tene graphite ceramics found in the topsoil above the ejecta layer. It provides a terminus ante quem of
about 300 BC further substantiated by abundant middle/late La Tиne artifacts in the affected region
excluding an impact later than 300 BC.
At the Chieming-Stцttham excavation site (12.2), the unique chance for studying the situation
of an impact layer being embedded in an archeological stratigraphy was gambled away by the
strict opposition of the excavating archeologist and the Bayerisches Landesamt fьr Denkmalpflege
(Bavarian State Office for the Preservation of Historical Monuments) to cooperate and to establish
a joint geological and archeological stratigraphy. Nevertheless, within the impact layer a slightly
graphitized potsherd was found that may be ascribed to the late Hallstatt/early La Tиne period thus
possibly scaling up the terminus post quem to 700-500 BC when this kind of potsherd was used. The
impact layer is overlaid by colluvium as bed of a Roman pavement (ca. 2nd century AD). Summarizing,
archeological artifacts establish a date of the Chiemgau impact event definitely between 1300 and 300
BC and possibly narrowed down to 700-300 BC.
The Chiemgau impact may further be dated by analyzing traditions of ancient people. The Celtic
fear of the collapsing sky is handed down to us as being mentioned in 335 BC (Strabo, Geography
7.3.8). In general, the respective story has been interpreted as an anecdote illustrating the fearlessness
of the Celts. On the background of the Chiemgau impact we offer an alternative interpretation: The
Celts did not point to a possible catastrophe in the future but reminded of a real event in the past that
could recur anytime. The date of 335 BC is coherent with the terminus ante quem of 300 BC provided
by the archeological data.
A thorough analysis [72-73] provides a good basis to interpret the Greek myth of Phaethon as
an allegorization of the Chiemgau impact. Details of the mythical tradition handed down in classical
texts can well be compared with astronomical, geological, geophysical and geographical details of
the Chiemgau impact. The application of criticism of sources and text hermeneutics suggests to date
the event reflected in the myth of Phaethon to 600-428 BC. Hence, the time frames provided by three
different dating methods fit very well together, possibly narrowing down the date of the Chiemgau
impact to 700-300 BC, if not to 600-428 BC.
14. The nature of the Chiemgau impactor
While for the known Holocene impacts iron meteorite projectiles are established, the nature of
the Chiemgau impactor must for the time being left to assumptions. Preliminary computer modeling
(by M.A. Rappenglьck) of the impact that formed the unusually large crater strewn field yielded a
low density (<1.3 g/cm3), roughly 1,100 m sized projectile that fragmented on entering the atmosphere
on a low-angle trajectory (~ 7°) at a velocity of about 12 km/s. Hence, a comet nucleus or a lowdensity asteroid like 253 Mathilde must be taken into consideration. The ~50 km-diameter asteroid
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253 Mathilde probably is a kind of a gravity-bound rubble pile to account for the low density of 1.3 g/
cm3 only, and apart from a comet nucleus a fragment of such a cosmic body could have constituted
the Chiemgau impactor. The discussion of the peculiar # 004 crater (12.3) suggesting a superheated
gas explosion bubble near the ground may substantiate the idea of a complexly composed projectile
comprising both solid meteoritic matter and explosive gaseous, possibly frozen methane constituents.
So far, no material has been sampled from the Chiemgau strewn field that can unambiguously be
attributed to the impactor. It is true, the strange matter (10), e.g., the nanodiamonds, the ferrosilicides
xifengite and gupeiite, the latter resembling meteoritic suessite, and the silicon carbide moissanite
have substantial extraterrestrial counterparts, and current SEM and TEM analyses of the Chiemgau
material (M. Hiltl, F. Bauer, pers. comm.) are strengthening the idea of a cosmic source. A conclusive
relation between the strange matter and the impactor has to be provided eventually.
15. Conclusions and final remarks
In meteorite impact research there are quite a few criteria as a base for the evaluation of a meteorite
crater, and some of them are regarded as in proof of impact. Impact criteria, compelling and less
compelling, as compiled by, e.g., Norton [63] and French [31] are morphology, geophysical anomalies,
geologic evidence implying exotic layers, high-temperature evidence, high-pressure evidence, shock
metamorphism, shatter cones, meteorite fragments or geochemical evidence of meteoritic matter, direct
observation (historical record), and special evidence like spherules, accretionary lapilli and micro- and
nanodiamonds. According to current understanding, shock metamorphism, shatter cones, meteorite
matter, and direct observation are each one by itself accepted as a confirmation of an impact event.
Beginning with shatter cone fracture markings, they are not expected to occur in the Chiemgau impact
strewn field because of the unconsolidated target rocks. The other criteria are definitely, probably
and possibly fulfilled. Morphologically significant are numerous bowl-shaped craters exhibiting clear
rim walls. Geophysical anomalies are measured showing abnormal magnetic and gravity signature.
Strong geologic evidence is given by exotic layers constituting polymictic breccias that could hardly
have been formed by geologic processes other than impact. The abundant occurrence of impact melt
rocks and various kinds of natural rock glasses proves a high-temperature overprint of the region.
High-pressure effects are indicated by plastic and brittle strong deformation of cobbles and boulders
including spallation, striations, polish and concussion marks definitely unrelated to glaciation.
Abundant heavily fractured however coherent cobbles and boulders in a soft matrix prove short-term
deformation under high confining pressure. Clear shock metamorphism, unanimously considered as in
proof of impact, has been attested in form of planar deformation features (PDFs) in quartz and feldspar
and diaplectic glass requiring shock pressures >10 GPa. More evidence of (moderate) shock (planar
fractures (PFs) in quartz, strong kink banding in micas, multiple sets of microtwins in calcite has been
shown to occur in Lake Tьttensee rocks in an intensity and frequency incompatible with deformation
from possible Alpine tectonics. Various kinds of spherules, accretionary lapilli, nanodiamonds and
strange metallic and carbonaceous matter can be considered a probable impact signature, while an
unambiguous evidence of meteoritic matter remains to be given. Possibly, the geomyth of the fall of
Phaethon allegorizes the observed Chiemgau impact [72-73].
Despite this clear, comprehensive and compelling impact evidence brought before the public by
Internet presence and numerous website articles (on www.chiemgau-impact.com, www.chiemgau# 95 #
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impakt.de), notable magazines, many public presentations and lectures, and several TV documentary
reports, the fact of the Chiemgau impact event has greatly been challenged by both a group of regional/
local geologists ([16]; Darga, verbal messages; and others) and part of the so-called impact community
[49, 76, 91]. The criticism of the first group is the criticism well acquainted in impact research. Whenever
a new meteorite crater/impact structure is put up for discussion, there are geologists claiming the impact
nature is not compatible with regional-geology features. These classic discussions are well known for
the Ries, Sudbury, Vredefort, Azuara and a large number of other impact structures worldwide. In the
case of the Chiemgau impact, this regional-geology context is the Alpine glaciation, and craters are said
to be glacial kettle holes and dead-ice depressions, and all deformed cobbles were carried from the Alps
where the rock experienced tectonic overprint. Moreover, all high-temperature signature is considered
anthropogenic. While this discussion is in principle accessory only, the challenge of the impact event
by part of the impact community is more crucial. Not a single one of the addressed impact community
members has ever contacted our research group, has ever visited the Chiemgau impact sites or has ever
been willing to jointly examine the impact exposures and impact rocks. The challenge is motivated by
remote image diagnosis of our impact material, by theoretical computer modeling of impacts and by
repeating the regional geologists? arguments of a glacial origin of the impact features [47, 49, 76-77,
91]. Among their arguments, the large size of the strewn field and the asserted impossibility of the
formation of the smaller craters in a comet impact are most commonly used. The assertion [47] that
according to numerical simulation the width of strewn fields cannot exceed 1 km is simply confuted
by the dimensions of the Campo del Cielo (Argentina) crater field measuring 19 km x 3 km [90]. One
order of magnitude larger (390 km x 120 km) is the Gibbeon (Namibia) strewn field of a fragmented
iron meteoroid (however without the formation of craters). The argument [76-77] smaller craters cannot
possibly have been formed in a comet impact because small-sized cometary fragments would not have
survived atmospheric passage ignores that we don?t exclusively consider a comet to have been the
impactor (see 14) and that the old idea of comets mostly composed of ice [75, 76] is no longer maintained
by astronomers and cosmochemists (e.g., [8, 9, 30, 44, 45, 94]. It is just the Chiemgau multiple impact
with the in part unusual crater formation and the abundant strange matter that could possibly enormously
contribute to the new understanding of asteroids, comets and the NEO threat.
Acknowledgements. ? Our work would not have been possible without the great assistance of
many persons and institutions, too many to be all itemized here. We especially thank Dr. F. Bauer,
R. Beer, G. Benske, T. Bliemetsrieder, T. Ernstson, F. Gцth, Dr. M. Hiltl, J. Konhдuser, J. Lex, H.-P.
Matheisl, E. Neugebauer, Dr. B. Raeymaekers, Prof. Dr. U. Schьssler, Dr. C. Soika, P. Spдthe, R.
Sporn, R. Wehweck and Baron D. Freiherr von Wrede for manifold support. For generous analytical
assistance we are indebted to Mineralogical Institute, University of Wьrzburg, and to Carl Zeiss SMT,
Nano Technology Systems Division, Oberkochen. Special thanks go to Dr. V. Gusiakov and Prof. V.
Shaidurov having enabled the print of this paper.
Note added in proof
In 2009, Acevedo et al. [Acevedo R.D. Bajada del Diablo impact crater-strewn field: The largest
crater field in the Southern Hemisphere / R.D. Acevedo, J.F. Ponce, M. Rocca, J. Rabassa, and H.
Corbella // Geomorphology, 110. ? 2009 ? P. 58-67] report on the discovery of an impact crater strewn
field in the Chubut Province, Argentina. In an area of about 27 km x 15 km more than 100 crater# 96 #
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type structures occur with diameters ranging from 100 to 500 m. The proposed impact event is dated
between Early Pleistocene and Late Pleistocene (0.78?0.13 Ma ago). According to the authors the
extensive strewn field may have originated from multiple fragmentation of an asteroid that broke up
before impact, perhaps traveling like a rubble pile. Alternatively, a collision of comet fragments is
discussed. A relationship to the Chiemgau impact event is obvious, and the authors when considering
the nature of the impactor explicitly refer to the Chiemgau impact.
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Journal of Siberian Federal University. Engineering & Technologies 1 (2010 3) 104-122
~~~
??? 551.46
Computational Experiment in the Problem
of the Recent Traces of Oceanic Cosmic Impacts
Konstantin V. Simonov*
Institute Computational Modeling SB RAS
Akademgorodok, Krasnoyarsk, 660036 Russia 1
Received 3.02.2010, received in revised form 27.02.2010, accepted 9.03.2010
The paper aims to fill the gap between geological practice on the problem of the recent traces of
oceanic cosmic impacts and computational experiment on tsunami geology problem. Computational
experiment and numerical analysis data of the oceanic comet impacts could be more effective for
mega tsunami understanding and prediction than the traditional geological methods. We explored the
depositional traces of large-scale water impact on the coast and modeling of mega tsunami given the
steep waves and Mach reflection on the rocky shore and described chevron dunes form on the base
of neural network technology to solve the inverse tsunami problem. The ocean impact craters were
explored using the wavelet analysis digital data of the ocean bottom.
Keywords: ocean impact crater, tsunami geology problem, mega tsunami, chevron dunes, depositional
traces, computational experiment, neural network technology, wavelet analysis.
Introduction
One of the most significant current discussions on the problem of the recent traces of oceanic
cosmic impacts is tsunami geology [2, 3, 5, 6, 11]. Computational experiment is becoming increasingly
fruitful in the complex investigation of the problem of tsunami formation deposits on the coastline.
We believe that computational experiment is the leading way in this problem solution, because it is a
universal approach [21].
Now computational experiment is a common methodology characterized by a complex approach
for solution of direct and inverse tasks in this problem. Computational experiment is an important
component in the investigation and plays the key role in study of the recent traces of oceanic cosmic
impacts. In the investigation computational experiment has become a central issue for dune-chevrons
study. The issue of dune-chevrons has received considerable critical attention, because they have the
amazing geomorphologic forms.
Recent developments in the mega tsunami problem have raised the need to use computational
experiment for the digital data numerical analyses of the ocean bottom relief on the base of wavelet
transformation for the search and selection impact craters.
In recent years there has been an increasing interest in use of neural network processing for the
solution of nonformalized tasks. Recent developments in the field of computational experiment have
*
1
Corresponding author E-mail address: simonovkv@icm.krasn.ru
© Siberian Federal University. All rights reserved
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
led to a renewed interest in use of this modern technology in the research of ocean cosmic impacts and
tsunami geology. Recently, on the Tunguska phenomena conference in Krasnoyarsk, researchers have
also shown an increased interest in computational experiment use to solve the problem of Holocene
impacts and mega tsunami modeling for formation and describing chevrons form.
Abbott D., Breger D., Bryant E., Gusiakov V., Kelletat D., Masse W., Scheffers A., Scheffers
S. and et. all. (2001?2008) show how the past research into dune-chevrons was mainly concerned
with geology and geomorphology aspects [2, 3, 5, 6, 11, 20]. Recently, investigators have examined
the effects of mega tsunami on coast and dune-chevrons formation. Previous studies have reported
especially the geometry and relative position deposits and candidate crater. A considerable
amount of literature has been published on tsunami deposit and dune-chevrons. These studies
showed geomorphologic, geological and physical aspects of formation tsunami deposit and dunechevrons.
Surveys, such as that conducted, showed that chevrons can describe the origin of tsunami caused
by the collapse of cosmic bodies into the ocean. Previous studies have based their criteria for selection
the form of geometric images obtained by a satellite against quality characteristics. Recent evidence
suggests that without a quantitative description of the studied processes there will be no progress in
understanding the geological aspects of the problem tsunami deposits.
More recently, literature has emerged that offers contradictory findings about the causes of the
chevron formation and their connection with tsunami, caused by the impact forces in the ocean. In
many conferences a debate take place between supporters and opponents of impact formation of
chevron. The controversy about scientific evidence for relation chevron with mega tsunami has raged
unabated for over a last decade. Traditional natural experiment suffers from several major drawbacks:
it is labor demanding and expensive.
So far, however, there has been little discussion about the possibility of the chevron formation
with tsunami waves at rocky shores, which can be described by a wave effect, which is called Mach
reflection, when the height of waves in the coastal zone increases by several times. However, far
too little attention has been paid to quantitative analysis of the qualitative data on the occurrence of
floods in different regions due to cosmic impact on ocean. Most studies on chevron have only been
carried out in a small number of areas: geomorphology and physical aspects. The research to date
has tended to focus on qualitative description of the data rather than on numerical simulation and
modeling.
So far, methodology of computational experiment has only been applied to normal wave tsunami,
but not to cosmic tsunami impact. However, there have been no controlled studies which compare
differences in approaches for chevrons description. However, few scientists have been able to draw
on any structured research into the opinions and attitudes of this subject. This indicates a need to
understand the various perceptions of phenomenon that exist among different researches, because the
evidence for this relationship is inconclusive. What is not yet clear, is detailed impact of mega tsunami
on coast. The physical basis of these phenomena is also poorly understood. No previous study has
investigated these phenomena by computational technology, because the experimental data are rather
controversial.
The purpose of this study is to develop an understanding of the potential of computational
experiment to address the major challenges in the problem of the traces recently ocean cosmic impacts.
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This article seeks to explain the development of coastal sediments, and other qualitative information
based on the arsenal of modern computing. This case study seeks to examine the changing form of
dune-chevrons by means of numerical experiments. The central question in this report is how the
following impacts (craters) and coastal sediments (chevron) can promote the solution of the inverse
problem of tsunami impact from space sources. In particular, this article will examine 3 main research
questions also related to the construction of efficient technologies of computing experiment, in relation
to this issue. The hypothesis that will be tested is that existing hydrodynamic models can describe the
devastating waves and their run-up in relation to chevron formation.
Due to the practical constraints (insufficient empirical data), this paper cannot provide a
comprehensive review of available capacity for numerical analysis. Part of the tsunami modeling,
wavelet analysis and the use of neural networks were considered briefly, since is beyond the scope of
this study to examine the practical aspects of the tsunami geology. The reader should bear in mind that
the study is based on a small sample of digital data provided by: V. Gusiakov and D. Abbot, and also
contained in the relevant articles. Our main reason for choosing this topic is personal interest to this
problem, because for us it was an incomparable pleasure of communicating with the participants of
the HIWG conference on Tunguska problem, which was held in Krasnoyarsk in summer 2008, where
we got acquainted with famous scientists ? Abbott D., Bryant E, Breger D., Gusiakov V., Hagstrum J.,
Masse W.
The overall structure of the study takes the form of 3 chapters and an introduction, an overall
description of computational experiment, as the approach to the tasks solution. Finally, the conclusion
gives a brief summary and critique of the finis area. While a variety of definitions of the term
computational experiment have been suggested, this article uses the definition first suggested by
A. Samarsky who understood it as a modern methodology and technology scientific research [17-18].
1. Numerical experiments of the submarine impact selection
A fast algorithm for two-dimensional wavelet transformation in the numerical experiment studied
the data, as well as special procedures for the visualization of the earth?s surface topography and the
ocean floor. The potential of the computational method for the allocation of submarine impact craters
shows that it can also be applied to the study of ring morphostructure an origin at the Earth?s surface
and ocean bottom [9-10].
Organization of the numeral process in solving these problems takes the form of computational
experiment and includes the detection and identification of the required forms on the surface,
followed by its contrast. Numerals experiments using the developed technology were carried
out on the data describing the shape of the land surface in Central Siberia and Kazakhstan. The
results obtained are very promising. Well-known ring structure (impact craters Papigay, Lagoncha,
Zhimanshin and Chicxulub crater) effectively detected and clearly identified on the surface under
study, the quantitative information being presented in the form suitable for subsequent processing
and analysis.
The aim of this section is to describe a computational method for the allocation of submarine
impact craters, presumably associated with the formation of chevron studied on the basis of digital
bathymetry with the developed algorithm and software of the wavelet analysis of the data. We selected
Burckle crater, presumably responsible for the initiation mega tsunami and of the chevron formation
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
on shores Madagascar. The technique is suitable for large-scale numerical experiments for different
areas of the ocean.
Wavelet transformation of one signal is the basis for its expansion, designed with certain properties
of the solution function (wavelet) by means of large-scale changes and transfers [1]. An element of the
basis of wavelet transformation is a well localized function, rapidly tending to zero outside a small
interval, so that each function describes the basis of a spatial (temporal) frequency and its localization in
physical space (time). In the case of two-dimensional data wavelet is a surface with a central symmetry
that meets the same set of requirements, which in one case.
Consider the algorithm for constructing two-dimensional wavelet diagram, which was developed
under a specific task ? to search for the ring structures on the surface of the Earth. The initial data
represent the D matrix NxM elements that contain values of some characteristics of the nodes of a
rectangular grid. It is necessary to identify the structure of a given shape, weakly expressed on the
background of the heterogeneity of the environment. For practical application, it is important to know
the characteristics of a wavelet:
? Localization in space (time) and in frequency;
f
f
і і M ( x , y ) dxdy
Zero mean:
f f
f f
і і M ( x, y )
Limited:
2
(1.1)
0;
dxdy f;
(1.2)
f f
Self-basis.
Next, we introduce the following symbols and functions:
x , y Џ ( M , M ),
M (t )
)
(1 t ) � e t ,
xM ,yM
(1.3)
§ 1 0 (( x M ) 2 ( y M ) 2 ) ·
M Ё
ё;
M
©
№
where M ? scale wavelet transform, ?x+M,y+M ? matrix of the base wavelet.
Fig. 1 shows the type of wavelet. Now the wavelet transform can be rewritten as an integral sum
of:
Wx , y
'x'y § M M
� ЁЁ ¦¦ ) M k , M l � ( Dx k , y l Dx k , y l Di k , j 1 Di k , j 1 ) Mi ©k 1l 1
M
·
k 1
№
¦ ) M k ,M � ( Dx k , y Dx, y l Di k , j Di , j 1 ) ) M ,M Dx, y ёё.
(1.4)
Because both components of the matrix are constant, the procedure of wavelet-transformation is
reduced to multiplying the folding of a set of constants. These matrixes are organized in such a way that
the numbers of operations in the computation of the elements of their coefficients were minimal. This
greatly reduces the amount of computer time required for the calculations. The developed algorithmic
and software demonstrated high efficiency in the real data processing.
Numerical data simulation using the wavelet transformation was carried out by the example of the
allocation of the Burckle crater in the Indian Ocean at the depth of 3800 m, with 29 km in diameter. A
summary of the Burckle crater is presented in Fig. 2.
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Fig. 1. Wavelet forms
Fig. 2. Data on the location of the Burckle crater [http://tsun.sscc.ru/hiwg/hiwg.htm]
Calculations were carried out with the computing environment MathSad14, which has a built in
function to calculate the wavelet transform based Dobe?. The result of wave function is a vector linked
to a few coefficients with a wavelet spectrum.
Figs. 3?5 present the results of the filtering data. Fig. 5 clearly allocated to the location of the
Burckle crater.
Further simulations were performed in the Burkle crater through Haar functions. The size of the
area to the Burkle crater was 400*300 km with a step of 1 km, the effective diameter of a «cap» wavelet
being 20 km, the results of calculations are shown in Figs. 6?8.
So, sections 1?3 present the findings of the research, focusing on the three key themes that have
been identified in the data analysis: the search of impact craters on the basis of wavelet transformation
of the digital ocean bottom, an effective visualization of the seabed topography and the land required
in the solution of hydrodynamic problems, the use of the above models of neural networks for solving
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Fig. 3. Baseline data shows an array of the data for analysis [5-6]
Fig. 4. Dobe? wavelet
?
b
c
Fig. 5. Phased wavelet filter surface of the ocean floor topography: a ? filter M30; b ? filter |M30|-M15; c ? the
result of filtering
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Fig. 6. Haar wavelet
Fig. 7. Output filtering of the Haar wavelet, Burkle crater
Fig. 8. View of the Burckle crater, obtained using Global_mapper
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
the problem of reconstruction of the characteristics of waves in the run-up on the coast and chevron
formation.
2. Neural network analysis of the observational data of coastal structures
In addition to scientific and technical tasks, allowing a rigorous formal description, there are
challenges when a formal description of the phenomenon does not exist, or it is difficult to analyze
it. Numerical (information) simulation of mega tsunami traces ? in chevron form represents an ideal
type of task. Neural algorithms allow the search of regularities in large data arrays with an arbitrary
statistical distribution of random variables. When the patterns are identified, then the developed
numerical network model can be put into performance [24].
Proposed numeric experiments are based on observations of chevron and the relief of the coastal
areas, construction of their models being approximating the spatial functions. Proposed use of the
numerical network analysis technology is a rapid multi-parameter regression model of observational
data, including procedures for constructing the model (learning) and its testing. As a result, appropriate
algorithmic and software numerical network modeling of coastal structures is adapted.
In most cases, the regression (neural networks) optimization principles are used. A functional,
assessing the quality of the regression model, is optimized by gradient or other methods. The classical
approach is the method of least squares. It minimized functional, estimating the model with the
experiment:
& &
2
H ¦ ( y ( xi , p ) ~
yi ) ,
(2.1)
i
&
* *
i ? number of experimental; y ( x , p) ? approximating function; x ? the vector of variables, which is
&
yi ? the experimental value. As a result, the
addiction; p ? adjusts the parameters of vector function; ~
parameters are standard functions (usually linear), which approximate the experimental dependence.
But in the experiment not all data may have the same credibility; therefore, weighted least squares
method introduces weights reflecting the impact of each experiment:
H
2
& &
§ y ( xi , p ) ~
yi ·
ё ,
¦ ЁЁ G~y
ё
i ©
i
№
(2.2)
yi is confidence interval, the precision with which the determined ~
yi .
?~
To build a regression (neural networks) models are used in the developed software «Models». The
used the approximation depending exits from the entrances to the following:
D ta
ba ca ¦ sin(Maj ¦ w ji X t i ),
j
(2.3)
i
where X ? input data; i ? number of inputs; j ? number of harmonics; t ? number of tasks in the sample;
a ? adjusts the parameters, b, c, w, ? ? number of exit.
Nonsmoothness function was assessed as the mean first-order sensitivity of the output:
¦
a
U
§ waa
Ё
Ё wx j
©
¦
aa
·
ё
ё
№
2
2
a
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¦¦ w2ji .
j
i
(2.4)
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Array of inputs («causes»), order of
o
o
o
output x1 , x 2 , , x n
o
o
o
array output («consequences») y1 , y 2 , , y n
Learning, the selection of
the best features of the
model: number of
harmonics, spectrum
The input
data
o
o
Model
o
o
f ( x)
y
o
x1c , x 2c , , x kc
Testing
o
o
o
y1c , y 2c , , y nc
o
y ic
o
f ( xic )
Fig. 9. Present the modeling of the observational data using the software «Models»
Fig. 10. The dialog program «Models»
This value restricts the top, depending on the task. During the training, by adjusting the parameters
w are changed in such a way that they do not exceed user-defined limits. For optimization the method
of conjugate gradient is used.
The program «Models» is designed for the rapid synthesis of large amounts of empirical and
analytical models to experimental data (Fig. 9). Synthesized approximate analytical models reproduce
the original object of cause-effect relationships, to the extent that they regard themselves in the
collection of empirical data. The analytical model can replace experiments with the original object to
resort to numerical experiments with the model.
Fig. 10 presents a dialog window «Models» to work in the computing environment «Excel». It is
necessary to specify the location of a book «Excel» source of empirical data, as well as items that will
be posted the results of the program. It is assumed that the empirical data are organized in b-array
consisting of two related arrays ? an array of inputs («causes») and the array outputs (responses,
«consequences»).
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Another two b-array need to display results: b-array «Projections», which has the same structure
and size as the b-array of empirical data and their accuracy, and b-array «Model» (address placement
is given in paragraph «Model» dialog box) with the same horizontal size as the other b-array, but
differs in the vertical size, user (Item «Size»).
In b-array «Projections» posted the results of model smoothing of empirical data, b-array
«Model» stored information about the parameters of the analytical model. Two upper rows b-array
«Model» are of informational status ? in particular, in the first line of the first input column posted on
the error model of the last instruction and the range of values in the second row indicate the significance
of the relevant input parameter for the predictions ? the smaller the figure, the less important is its
corresponding to input information. The remaining positions adjust the model parameters.
Synthesis of the model performs the «Learning» procedure, by the iterative search of the model
parameters, where the standard deviation of responses (opinions) models and related empirical data in
an array of responses are minimized. The number of iterations is defined by «Iteration» paragraph. For
the training the restriction on nonsmoothness function (item «Spectrum») must be set strictly greater
than zero level of the spectral density. If the observation occurs, plaque indicating the number of past
iterations, estimate (error), the proportion of the fall assessment on the last iteration and the current
spectral density are defined.
The calculation shows the actual observations of the spectral density, while the dialog is established
recommended. If the actual spectral density is significantly (by several tens of percent) greater than
recommended, it implicitly refers to the fact that raising the level recommended by the spectral density
decreases error learning, but does not necessarily diminish the bug testing. If the actual spectral
density is significantly lower than recommended, it is advisable to try to reduce the spectral density.
Based on the results of the testing calculated the most suit-user spectral density may be, so that both the
training and testing errors were smaller. At high spectral density it is easier to achieve error reduction
training without the requirement of smoothness of interpolation, but the deteriorating performance of
test predictions can occur. Also selecting the size of the model, take into substantially, that large sizes
and, consequently, increase of the model machine time.
Thus, non-linear regression (neural networks) analysis allows information to build predictive
models of studied phenomena (the process) and use them in the systems of control and monitoring.
We were having outlined the general scheme of computational experiment and a brief description
of its main stages. Be aware, that computing experiment in a narrow sense, as the creation and study of
mathematical models of the object with the help of computational tools, can be identified as the basis
for the triad: a model ? an algorithm ? a program. Broadly (methodological) sense of computational
experiments is understood as techniques of research [17]. For the investigated object (chevron) first,
a mathematical (neural networks) model is developed. Computing experiment, in essence, provides
a study group near regression (approximation) model. Initially, we construct a simple, but quite
meaningful model for description of the object in terms of proximity to the experimental data neural
networks (information) model.
In the computational experiment, the subsequent cycles of the model states new developments
are taken into account, etc. Therefore, we can write about the orderly recruitment (hierarchy) of
mathematical models, each with an accuracy of describing reality. Thus, in the most simple model, it is
necessary to seek agreement with the experiment, it is the aim of the computational experiment.
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Here are the basic elements of numerical experiments on simulation of chevron structures: a fullscale experiment, the construction of a mathematical model, the choice and application of numerical
method for finding solutions, building a software implementation of mathematical models to find the
numerical solution, processing the results of calculations, compared with full-scale experiment, the
decision on continuation of full-scale experiments, the continuation of full-scale experiment to obtain
the data necessary to refine the model, the accumulation of experimental data. Adapted, depending on
the specifics of the problem, the chain of these phases of computational experiment, implemented in a
single software system, and is «technology» computing experiment.
Thus, the proposed computational technique based on neural networks modeling of observational
data for the numerical description of mega tsunami builds a model (approximation of spatial functions
to study the structure-surface) in form chevron. It can also simulate bottom topography and land
in their expressions for the detection of these interactions and processes, their formation at up rush
mega tsunami on rocky shores. Later, on that basis the numerical analysis of the diversity of chevron
geometries was performed for the assessment of the predominant angle of the axis of chevron to the
coastline. Grade azimuth geometry chevron indicates a possible source area of the epicenter and the
tsunami probable submarine impact craters. The contours of chevron in the depths of the land would
allow detailed modeling of run-up of the mega tsunami.
Baseline data of coastline and chevron, digitized with a step of 2 mm (1 mm = 125 m), are
expressed in b-arrival on the worksheet «Excel» (Fig. 11?12). Two arrays with the input X (common to
the shoreline and chevron) and the output Yb (to shore) and Ych (for chevron) are located nearby ? on
the left array of consequences, on the right ? an array of reasons. This calculation is one an «input»
and one an «output». After placing the initial data on the «Excel» sheet, turn to the procedure for the
synthesis of the model, filling in a dialog window «Models». Then, after filling the required fields in
the dialog box appears b-arrival «Model», which contains adjusted parameters of the base dependence.
Two tops of the array contain the values of average error and the spectrum. Then it is necessary to
compare the original data with the results of testing and by changing the settings range from 20 to 200
and size from 20 to 100, making the best result compared field and calculated data (smallest error).
Based on the results of numerical simulation data of the studied chevron forms and coastline we
have come to the following conclusions: the best result in the simulation is obtained for the range = 200
for all the input data and the number of subscript parameters ? 35 for the first chevron, and 40 ? for the
second chevron, revealed that chevron, along the coast, remain in a general form similar to the form
of appropriate shoreline, which in turn can characterize the run-up catastrophic waves, as a result of
which the respective chevron is formed.
3. Numerical simulation mega tsunami in the coastal zone
We were reviewed of the results of hydrodynamic modeling of the single wave?s interaction with
oblique wall to form a Mach leg. In Future, the numerical study of chevron distribution, its orientation
to the coastlines, the relationship to a coastal forms (cliffs, coastal embankments), will disclose the
mystery of the impact of mega tsunami cosmic origin in the coastal area.
Let us consider the hydrodynamic models that can estimate the nonlinear transformation of
tsunami waves of types in the coastal zone within the above tasks. Palmer and others [15] performed
laboratory experiments to model the anomalous strengthening of the tsunami in Hilo Bay, which had
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Fig. 11. Chevron form (Australia) [20]
Fig. 12. Placement of data numeric experiments on the sample «Excel» sheet
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Fig. 13. Wave scheme of Mach reflection
occurred in 1946, 1952, 1957 and 1960. They believed that the anomalous strengthening of the tsunami
caused by a combination of several characteristics of the geometrical of the bay: underwater ridge at
the entrance to the bay led to refraction of tsunami waves, sending them into the bay, the bay having
a triangular configuration due to wave of accumulating effect in the bay top where the port of Hilo. In
this paper, [23] described the experiments of [16] to study the interaction solitary wave ai amplitude
with a flat vertical wall, to which the wave come at some angle ?i. The reflected waves from the
wall to be were found regular or irregular (Mach) depending on the amount ?i. Regular reflection
of ridges crossing the incident and reflected waves occurred at the wall, and at Mach formed a third
wave, called the Mach leg, which is located between the wall and the point of the first two wave crests
intersection.
Mach reflection scheme let us consider in detail, following [8], which is depicted in Fig. 13.
Theoretical studies of skew run-up on a wall in were made be Miles [13-14]. These analytical
formulas for the maximum run-up R, the amplitude ai of the reflected waves ?i, the angle and the angle
of reflection, which is visible to the Mach leg from point A, were obtained through the study some
nonlinear-dispersion model of shallow water of solutions. At the same time many possible schemes for
the wave interaction with a wall to use the wave configurations that have been observed in experiments
[16]: double and triple configurations. The distance from the zone of interaction of all waves are
assumed to be in the form of solutions, as in the case of Mach reflection wave parameters are related
to additional terms of the resonant interaction. When assumptions are specified the following formula
for the maximum run-up is suggested:
R
ai
­
\2
4
, i t 1;
°
1
2
2
3ai
°°1 1 3 ai \ i
®
2
°§
\ i ·ё \ i2
Ё
,
d 1.
°Ё1 1 2
°Ї© 3ai ё№ 3ai
(3.1)
Thus, if the solitary wave at the free-wall falls at an angle, then the run-up value may reach
the value R 4ai . In the Melville experiments [12] the depth of the pool reaches 30 cm, but for the
magnitude of R is found, not to exceed 2ai.
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Fig. 14. Free surface wave, its contours and grid for free surface at the relevant time [8]
The authors of [19] proved that such a small R value was due to the fact that [12] actually examined
only the initial phase of the wave interaction with a wall, and to achieve steady-state R values is
required that the wave to pass a distance of at least ten times longer than in Melville experiments.
Currently the creation of large experimental facilities for the study of skew run-up solitary waves is
problematic computational experiments have become the best solution.
Numerical simulation of oblique run-up was described in [4] Miles received the theoretical
dependence by calculations based on a mathematical model. At the same time, is for practical interest
the process of roll waves of finite and not infinitely small amplitude. In the absence of reliable
experimental data and the theory of skew roll waves of finite amplitude, numerical simulation is the
only tool to study this phenomenon. Funakoshi [4] used the finite-difference method for calculating the
wave with an amplitude of ai = 0.05, Tanaka [22] ai = 0.3 applied to the spectral method. A large series
of calculations in the range of amplitudes ai = 0.05?0.30 carried out complied by Serebrennikova and
Frank [19] was based on the discrete model of an incompressible fluid. Given the existing differences
of numerical results for some parameter values calculations based on other mathematical models and
algorithms should be undertake.
Khakimzyanov G.S. [7, 8] presented the results of calculations in the nonlinear-dispersion model
Zheleznyak-Pelinovsky (NDM) and three-dimensional models of potential flows from the finitedifference method using a dynamically adaptive grid, and provided a comparison of the results obtained
in the calculations of other authors. In numerical solution of the problem curvilinear grid used adapted
to the field form, and depending on the solution, so that the concentration of grid nodes increased in
areas of the phenomena to be investigated: ridges in the vicinity of the incident and reflected waves,
legs, and the Mach zone run-up. A fragment of such a grid, lying on the free surface, is shown in
Fig. 14. One can see that from the grid tracks the main features of the modeled currents, in particular
Mach leg.
Fig. 15 shows the dependence of the R/ai value of values for different \ i 3ai values of free-wave
amplitude (MPF ? a model of potential flows [8]).
In this paper [13] was obtaining the dependence run up wave of small amplitude at regular
reflection:
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
§
·
3
3 2 sin 2 \ i ёё.
2 ai ЁЁ
2
© 2 sin \ i
№
Fig. 15 contains two curves (3.2): ai=0.1 (I) and ai=0.5 (II).
R
ai
(3.2)
Points ? calculation results, solid line ? theoretical dependence (3.1); bar ? the theoretical
dependence (3.2) (I ? ai= 0.1; II ? ai = 0.5): ai= 0.05: 1 ? [4]; 2 ? MPF; ai= 0.1: 3 ? NDM, 4 ? MPF;
ai= 0.3: 5 ? [22]; 6 ? [19]; 7 ? MPF; ai= 0.5: 8 ? MPF.
Thus, Fig. 15 shows graphs of theoretical dependence (3.1). We see that at finite values of amplitude
ai the results of the calculations are close the curve (3.1) Mach reflection. Fig. 16 shows the chevron
form of southern coast of Madagascar.
Conclusions
This paper has given an account of and the reasons for the widespread use of computational
experiments in the recent issue of the cosmic impacts of ocean traces. This paper has argued
that a computational experiment is the best instrument to research this complex interdisciplinary
problem. The purpose of the current investigation was to determine the possibility of computational
experiments to refi ne our understanding of the studied effects. This project was undertaken to
design computing technology of numerical data analysis and evaluate the quality of these data to
address relevant problems. Returning to the hypothesis posed at the beginning of this research, it is
now possible to state that calculations make it possible to disclose material aspects of the physical
phenomena.
This investigation has shown that pooling disparate data and computational algorithms helps to
solve the tasks more efficiently. These findings suggest that in general the hypothesis adopted at the
beginning of the study of recent cosmic impact effects in marine waters is justified. One of the most
significant findings to emerge from this study is that it identified a set of computational techniques
that allow most effectively. It also showed that the present computational technology it is important
to integrate in a single computational experiment. This research has found that on the whole iterative
procedures, computational experiment provided the necessary evidence and the validity of obtained
solutions.
The most obvious finding to emerge from this study is that in this problem there is a set of
interconnected data, which allows answering the fundamental question of the space object of the
origin. Multiple regression analysis revealed that the form of dune-chevron reflect not only the relief of
the coast line, but the bathymetry offshore.
The evidence from this study suggests that the results of numerical simulations do not contradict
the empirical data. The results of this study indicate that the hydrodynamic models are consistent with
the geomorphologic data. The results of this research support the idea that outer impact marine water
was most probable cause of a research of natural phenomena. Taken together, these results suggest
that hypothesis on the significant prevalence of recent cosmic impact of marine influences is much
unsubstantiated.
The computational experiment that we have identified therefore assists in our understanding
of the role of simulation in solving the problem. This research will serve as a base for future
investigations and introduce a new productive hypothesis on this issue. The current fi ndings add
substantially to our understanding of the physical nature of the phenomenon. The research has gone
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Fig. 15. The dependence runs up wave R/aifrom yi
3ai [8]
Fig. 16. Chevron forms of southern coast of Madagascar
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
some way towards enhancing our understanding of the overall relationship of the investigated sites.
The methods used for this object may be applied to other similar elsewhere in the world. Taken
together, these fi ndings suggest a role for our methodology in promoting solution to this pressing
problem.
Finally, a number of important limitations need to be considered. The most significant limitation
lies in the fact, that important data are fragmented and characterized by a qualitative description.
Therefore, the current study was limited to individual objects, the data on which enables the main
stages of the computational experiment. Note that the current study was not specifically designed to
evaluate factors related to geochronology and computer data processing, analysis, obtained with the
help of a microscope. Therefore, with a small sample number, caution must be applied, as the findings
might not be transferable to other unique objects.
Of course, this research has thrown up many questions in need of further investigation. Further
work needs to be done to establish whether the model obtained is adequate for use in justifying the basic
concepts in the problem of the recent cosmic impact space traces. The further research is recommended
to be undertaken in the following areas: building models related to the recent variability of the climate,
the creation of an expert database of forms and parameters of chevron in various maritime areas, the
adaptation of the hydrodynamic models megatsunami of run-ups for specific coastal areas, collection
and systematization of manifestations of the recent cosmic catastrophes.
Further experimental investigations are needed to estimate constructed hydrodynamic and
statistical models. More broadly, a new research is also necessary to determine the reliability of
the assumptions made and the hypotheses, as well as their adequate justification. It is suggested
that the association of these factors is investigated in future studies. Further research can explore
more detailed and subtle effects of the studied phenomenon. Further research in this field regarding
the role of the computational experiment would be of great help in numerical processing and the
rationale for experimental studies. Note also that more information on marine space impact trace
would help us to establish a greater degree of accuracy on matter of the nature of the studied
processes. It would be interesting to assess the effects of (damage) of the new catastrophic event
that would occur, for example, in the vicinity of the Burkle crater with characteristics close to the
site.
These findings suggest several courses of action for the development of technologies of
computational experiment to study the issue of the recent cosmic impact ocean traces. However, the
findings of this study have a number of important implications for future practice of searching these
traces, their systematization and the creation of an expert database dune-chevron is constriction. At
the same time, there is a number of important changes to be made to enhance the opportunities of
mathematical modeling of the phenomenon and the numerical analysis. Another important practical
implication is that the results of numerical experiments can be used and compared with the new data
to be received during the field work. This information can be used to develop targeted interventions
aimed at building a new physical and mathematical model of the studied phenomenon. Our work here
is just the first step in this endeavor.
?????? ???????????? ??? ????????? ????????? ???????? ?????????? ????????????
????????????.
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
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Conference of ICCM-2004 ? Novosibirsk: SB RAS ICM&MG, 2004 ? P. 110-115.
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K.?. ???????
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?????? ? ???????????? ??????????? ????? ?? ????? ????? ???? ????? ???????????? ???
????????? ? ??????????????? ??????????, ??? ???????????? ????????????? ??????. ??
????????????? ????? ????????? ?? ???????????????? ??????????? ???? ?? ????????? ?
????????????? ?????????? ? ?????? ???????? ????? ? ????????? ???? ?? ????????? ??????,
? ????? ???????? ????? ???-???????? ?? ?????? ???????????? ?????????? ??? ???????
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???????-??????? ???????? ?????? ?????????? ???.
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????-???????, ????????? ??????, ?????????????? ???????????, ?????????? ?????????
?????, ???????-??????.
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Journal of Siberian Federal University. Engineering & Technologies 1 (2010 3) 123-132
~~~
??? 551.3
Micrometeorite Impacts in Beringian Mammoth Tusks
and a Bison Skull
Jonathan T. Hagstruma*, Richard B. Firestoneb,
Allen Westc, Zsolt Stefankad and Zsolt Revayd
a
U.S. Geological Survey, 345 Middlefield Road, Menlo Park,
CA 94025, United States
b
Lawrence Berkeley National Laboratory, Berkeley,
CA 94720, United States
c
GeoScience Consulting, Box 1636, Dewey, AZ, 86327, United States
d
Institute of Isotopes of the Hungarian Academy of Sciences,
H - 1525 Budapest, P.O.B. 77, Hungary 1
Received 3.02.2010, received in revised form 27.02.2010, accepted 9.03.2010
We have discovered what appear to be micrometeorites imbedded in seven late Pleistocene Alaskan
mammoth tusks and a Siberian bison skull. The micrometeorites apparently shattered on impact
leaving 2 to 5 mm hemispherical debris patterns surrounded by carbonized rings. Multiple impacts
are observed on only one side of the tusks and skull consistent with the micrometeorites having come
from a single direction. The impact sites are strongly magnetic indicating significant iron content. We
analyzed several imbedded micrometeorite fragments from both tusks and skull with laser ablation
inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray fluorescence (XRF). These
analyses confirm the high iron content and indicate compositions highly enriched in nickel and depleted
in titanium, unlike any natural terrestrial sources. In addition, electron microprobe (EMP) analyses of
a Fe-Ni sulfide grain (tusk 2) show it contains between 3 and 20 weight percent Ni. Prompt gamma-ray
activation analysis (PGAA) of a particle extracted from the bison skull indicates ~0.4 mg of iron, in
agreement with a micrometeorite ~1 mm in diameter. In addition, scanning electron microscope (SEM)
images and XRF analyses of the skull show possible entry channels containing Fe-rich material. The
majority of tusks (5/7) have a calibrated weighted mean 14C age of 32.9 ± 1.8 ka BP, which coincides
with the onset of significant declines <36 ka ago in Beringian bison, horse, brown bear, and mammoth
populations, as well as in mammoth genetic diversity. It appears likely that the impacts and population
declines are related events, although their precise nature remains to be determined.
Keywords: global climate changes, megafauna, micrometeorites, multiple impacts, Siberian bison skull,
Pleistocene Alaskan mammoth tusks, plasma mass spectrometry analyses, X-ray fluorescence analyses,
electron microprobe analyses, gamma-ray activation analysis, scanning electron microscope images.
1. Introduction
During the late Pleistocene, Beringia was largely an ice-free continental region that consisted of
northeastern Siberia, northwestern North America, and the emerged Bering Strait. Major events that
*
1
Corresponding author E-mail address: jhag@usgs.gov
© Siberian Federal University. All rights reserved
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Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
occurred at that time were global climate changes, migration of humans from Asia to America (~13 ka
BP), and large-scale megafaunal extinctions (~12 ka BP). The cause of these extinctions has long been
controversial and has been attributed predominantly to either climate change or overkill by humans
[9]. A period of marked decline in population and genetic diversity for many large mammal species
happened earlier, however, beginning at about 36 ka BP before the last glacial maximum, human entry
into the New World, or the final megafaunal extinctions. For instance, no brown bear fossils have been
found in eastern Beringia (Alaska) that date between 35 and 21 ka BP, and different haplotypes at
either end of this hiatus likely indicate a local extinction event [1]. Similarly, between 35 and 28 ka BP,
caballoid horse fossils show a significant decline in metacarpal size and a coeval drop in the number of
dated specimens, possibly reflecting lower population numbers, and Alaskan wild asses apparently were
extinct by ~31 ka BP [6]. The genetic diversity of Beringian Steppe bison dropped sharply after ~37 ka
BP [10], and one of two major mammoth mitochondrial lineages also disappeared around this time [2].
The final extinctions of megafauna were apparently contemporaneous with the abrupt onset of
Younger Dryas cooling and termination of Clovis culture in North America. A carbon-rich black
layer or "mat" lying above both megafaunal fossils and Clovis tools has been identified at over 50
sites across North America, which dates to ~12.9 ka BP [7]. Directly beneath the black-mat horizon,
Firestone et al. [4] have found, at a number of places, a thin magnetic layer (<5 cm) containing
magnetic particles, iridium, charcoal, soot, carbon microspherules, glass-like carbon containing
nanodiamonds, and fullerenes with extraterrestrial helium. Firestone et al. [4] have proposed that one
or more extraterrestrial objects collided with and/or exploded over northern North America at this
time leading to intense biomass burning. In addition, large spikes in ammonium and nitrate contents
in layers of the Greenland GISP2 ice core at the beginning of the Younger Dryas are consistent with
massive biomass burning at ~12.9 ka BP.
In this report we present preliminary evidence that supports a link between the ~36 ka BP decline
in Beringian megafaunal populations and genetic diversity, and an extraterrestrial accretion event.
Seven Alaskan mammoth tusks and one Siberian bison skull have been found with small magnetic
(Fe-rich) particles embedded in them. We have radiocarbon dated the tusks and skull, and subjected
the embedded magnetic particles to a battery of non-destructive tests to determine their chemical
compositions and their possible origin as micrometeorites.
2. Analytical methods
To the naked eye, the dark particles embedded in the Alaskan mammoth tusks, and Siberian bison
skull, appear to be composed of an oxidized metallic material. Upon closer inspection, the particle
sites may or may not have raised rims, concentric "burn" rings, bulged centers, and/or "entry" pits
(Fig. 1). Their attraction to a small neodymium magnet indicates that they are iron rich, and this quick
and easy test was useful in sorting them from a large collection of fossils. The seven tusks and one
skull with embedded particles are from a commercial supplier, and represent ~0.1% of the samples
inspected at Canada Fossils, Ltd. Thus, no field notes documenting the source localities are available,
and only general provenances can be assigned (Alaska or Siberia). Particles are found only on one side
of any given fossil, and this is consistent with bombardment from a single direction. An X-ray image
shows that the particles penetrated the tusks, presumably at high velocity, forming 2 to 5 mm diameter
hemispherical debris patterns (Fig. 2).
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Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
Fig. 1. Close-up photograph and enlagement of metallic particles embedded in tusk 1. Several features can be seen
associated with these particles; raised rim (A), "burn" ring (B, C), and bulged center (B)
Fig. 2. (a) Close-up photograph of a particle embedded in tusk 2. (b) X-ray image of the same particle in cross
section showing hemispherical debris pattern. This particle is about the same size as particle B in Fig. 1
Sectioning and polishing of tusk/particle samples below (<1 mm) the zone of concentrated debris
show many small particles (<20 ?m diameter) widely dispersed within the tusk matrix. The number
and fundamental complexity of the embedded particles suggest that they are the result of a natural
explosive event, and determining their chemical compositions is key to discovering their origin and
the nature of this ancient event.
We analyzed particles extracted from six of the tusks and bison skull with laser ablation inductively
coupled plasma mass spectrometry (LA-ICP-MS). In particular, we determined Ni/Fe ratios, as these
are diagnostic of meteoritic and terrestrial compositions. Our results are given in Table 1, which
also include, for comparison, values for a variety of extraterrestrial and terrestrial samples. These
analyses confirm the high Fe content of the particles and indicate compositions highly enriched in Ni
and depleted in Ti, unlike any terrestrial values. A particle from tusk 1 also has a Ti/Fe ratio of 0.004,
which is 3% of terrestrial values and comparable to those for CI chondrites. From X-ray fluorescence
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Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
(a) Tusk 4
O
Fe
Counts per Second (cps)
Counts per Second (cps)
20
15
10
(b) Tusk 4
20
15
10
5
Fe
5
C
O
C
0
0
0
2
4
6
8
0
2
Energy (keV)
(c) Tusk 2
6
8
O
Fe
(d) Tusk 2
S
20
Counts per Second (cps)
20
Counts per Second (cps)
4
Energy (keV)
15
10
Ni
5
O
K
S Si
15
Al
10
C
5
Fe
Ca
Mg
Na
0
K
Ni
Ca
0
0
2
4
6
8
Energy (keV)
0
2
4
6
8
Energy (keV)
Fig. 3. X-ray fluorescence (XRF) spectra showing the compositional variability within and between particles
from two different tusks. Compositions range between native Fe (a), FeO (b), FeNiS (c, d). Silicate compositions
in d are probably due to contamination from host sediments during burial
(XRF) analyses, we determined that the composition of the Fe-rich particles varies between native Fe,
FeS, and FeO (Fig. 3), all typical of meteoritic compositions. Particles from tusks 2 and 3 are highly
enriched in Ni (Table 1), and electron microprobe (EMP) analyses of a Fe-Ni sulfide grain from tusk 2
(Table 2) show two different phases within the grain that each contain Ni contents averaging 3 and 20
weight percent, respectively.
Particles embedded in the bison skull appear more angular (Fig. 4) than those embedded in the
tusks (Fig. 1). Prompt Gamma-ray Activation Analysis (PGAA) of a particle extracted from the bison
skull indicates that it contains 0.36 mg of iron, an amount consistent with an impacting particle ~1 mm
in diameter. Furthermore, scanning electron microscope (SEM) images and XRF analyses of a broken
section of bison skull show possible entry channels with straight sharp edges that contain Fe-rich
material within them (Fig. 5).
Samples from all but one of the tusks, and bison skull, were submitted for 14C dating to
radiocarbon laboratories at the University of Arizona and the University of California at Irvine
(Table 3). Samples from tusk 1 were dated twice at Arizona and once at UC Irvine. In general,
the calibrated ages range between 31 and 36 ka with three exceptions: tusk 2 has an age of 20.1 ±
0.4 ka, the bison skull has an age of 26.3 ± 0.2 ka, and tusk 7 has an assigned age of >47.5 ka. The
samples from tusk 2 and the bison skull might have been contaminated with younger carbon, and no
detectable 14C in tusk 7 indicates that it is radiocarbon "dead". Additional samples from these three
specimens need to be dated. A weighted mean average for the 5 tusks with similar ages is 32.9 ± 0.2
ka. The 1? error estimate for this overall mean is based only on laboratory error and, therefore, is
probably too low. The range in ages for the three repeat measurements on tusk 1 is 3.6 ka or ± 1.8 ka,
and is a better estimate of the true error.
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Table 1. Comparisons of Ni/Fe ratios between particles and meteoritic compositions
Sample
(Ni/Fe)/(Ni/Fe)Terrestrial
Sample
(Ni/Fe)/(Ni/Fe)Terrestrial
Tusk 1
6.4
Iron meteorite
110
Tusk 2
415
CI Chondrite
51
Tusk 3
190
H Chondrite
67
Tusk 4
10
K-T (Danish)
28
Tusk 5
22
Urelite
6
Tusk 6
5.6
Carb. Chondrite
3
Bison
8.5
Laurentian basalt
0.7
Notes: Ni/Fe ratios normalized by a bulk terrestrial value. K-T (Danish) indicates a sample from the Cretaceous-Tertiary
boundary layer at Stevns Klint in Denmark.
Table 2. Microprobe data for a particle from Tusk 2
Site
S
Ni
1 (red-org)
37.148
15.409
39.757
92.314
2 (gray)
15.402
4.777
46.796
66.975
3 (red-org)
40.850
20.727
32.726
94.303
3.151
0.816
52.382
56.349
5 (red-org)
39.913
24.129
30.591
94.651
6 (gray)
12.810
4.328
49.392
66.530
Red-org avg.
39.304
20.088
34.358
93.756
Gray avg.
10.454
3.307
49.523
63.285
4 (gray)
Fe
Total
Notes: Under plain light, the particle appeared to be a mixture of two phases: one phase with a reddish-orange hue, and the
other grayish in color. Compositional values are reported in weight percent. Totals do not sum to 100% indicating that other
elements are present (Fig. 3c, d). Bottom two entries are averages (avg.) for each phase.
Fig. 4. (a) Photograph of Siberian bison skull showing general locations of embedded metallic particles. (b) Close
up photograph of particles in bison skull, and (c) enlargement of partcle about the size of particle B in b. Embedded particles in the bison skull appear more angular than those found in the tusks (Figs. 1, 2)
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Fig. 5. Scanning electron microscope (SEM) images of a cross section of the bison skull. The particles appear to
have formed straight channels (a-c) where particle shards penetrated the bone. Clusters of iron particles at greatest
enlargement (c) are seen inside the channel. A second channel is also shown (d). Black line segments and arrows
indicate channel walls
Table 3. 14C dates for Mammoth tusks and Bison skull
Sample
Tusk 1
Age
Error
34479
323
Lab
Lab No.
33050
520
Arizona
AA63886
36600
2300
Arizona
AA64879
35340
420
UC Irvine
29597
Tusk 2
20960*
350
Arizona
AA64881
Tusk 3
31800
1300
Arizona
AA64880
Tusk 4
31250
330
UC Irvine
36479
Tusk 5
32030
360
UC Irvine
36480
Tusk 7
>47500*
UC Irvine
36481
Tusk 8
34510
500
UC Irvine
36482
Bison
26310*
150
UC Irvine
29596
Mean
32870
179
N=5
Notes: Tusk 1 was dated twice at the University of Arizona radiocarbon lab, and once at the UC Irvine lab (italics); a weighted
mean of the three dates is given fi rst. Tusk 6 has not been dated, and Tusk 7 has no detectable 14C and is considered radiocarbon
"dead". *, values omitted from weighted mean.
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Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
3. Discussion of results
The high Ni concentrations and other Fe and sulfide compositions measured in the particles
extracted from seven Alaskan mammoth tusks, and a Siberian bison skull, are in agreement with
meteoritic compositions. Ni is relatively rare at the Earth?s surface, and it is difficult to imagine any
terrestrial process that would concentrate it within late Pleistocene fossils. Moreover, the particles
are highly fragmented and appear to have exploded upon impact within the tusks. The apparent entry
channels filled with Fe-rich material and more angular particles in the bison skull are consistent with
impact into more porous and much softer bone, compared to the tooth-like hardness of tusks. In
addition, the embedded particles are found only on one side of the fossils indicating that the particles
arrived from a single direction, as they would from a micrometeorite shower.
Micrometeorites traveling at hypervelocities, however, cannot penetrate the Earth?s atmosphere
and reach the surface at high velocity due to atmospheric drag. Thus, we believe that the particles most
likely arrived from an airburst, or from multiple airburst events over Beringia at around 33 ± 2 ka
(perhaps similar to the 1908 Tunguska event), which locally pushed the atmosphere aside allowing the
particles to travel greater distances at high velocity. Multiple airbursts would appear more likely due
to the large area (several thousand km across) from which these fossils were recovered. Large-body
impacts also produce high-speed ejecta particles, but these consist primarily of target material having
terrestrial compositions. The 33 ± 2 ka age of the impacted fossils agrees with the onset of Beringian
population declines around 36 kyr ago that has been documented from the fossil record [1, 2, 6, 10].
These declines preceded major megafaunal extinctions and the onset of Younger Dryas cooling in
Beringia at ~12.9 ka, which also has been associated with an accretionary event [4].
Sithylemenkat Lake is at the bottom of a topographic bowl-shaped depression in central Alaska
(Fig. 6) and might be an impact crater also related to the 33 ka micrometeorite event. Located at
66.117°N and 151.383°W, the depression is 12.4 km in diameter and 500 m deep. Found during a
search of Alaskan Landsat imagery for possible impact features, the Sithylemenkat Lake depression
was selected because of its shape, and also because it is located in terrain unsuited for the formation
of circular periglacial lakes or volcanic centers [3]. Analysis of aerial photographs of the basin shows
radial and concentric fractures similar to those associated with other known impact structures. Glacial
features are absent within the basin indicating that it was not formed by glacial action and that it is
probably late-to-post Wisconsin in age (<100 ka). Sediments from streams peripheral to the basin
contain high Ni concentrations of up to 5000 ppm [8] consistent with an impact, although ultramafic
bedrock in the vicinity could be the source of the nickel. In addition, a pronounced aeromagnetic
low is centered over the depression [11], and these are commonly associated with other large impact
structures due to the intense fracturing of bedrock immediately below the crater floor [3].
4. Conclusions
We propose that the metallic particles found embedded in late Pleistocene mammoth tusks and
bison skull (assuming an incorrect age) are micrometeorites from low-level airbursts that occurred
over Beringia sometime between 31 to 35 kyr ago. The result of these impacts likely caused the death
of these seven Alaskan mammoths and one Siberian bison, as well as the overall decline in megafaunal
populations observed throughout Beringia [2, 10]. Another of these meteors might have penetrated the
atmosphere intact and formed the Sithylemenkat Lake crater in central Alaska.
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Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
Fig. 6. Sithylemenkat Lake (66.117°N, 151.383°W) at the bottom of a bowl-shaped topographic depression in
central Alaska. Contour interval is 30.5 m (100 ft) and the level of the lake is at 219 m (720 ft)
As our sample population is small, the next step in our investigation is to contact and/or visit
museums throughout North America and Siberia having collections of late Pleistocene Beringian
fossils to see if we can discover more fossils embedded with micrometeorites. Also, an expedition
to Sithylemenkat Lake crater is needed to collect geologic samples and confirm the proposed
extraterrestrial origin and age of this topographic feature.
Acknowledgements
The LA-ICP-MS and PGAA analyses were made at the Institute of Isotopes in Budapest, Hungary.
We thank the technical staff there for their assistance in making these measurements. Also, we are
grateful to Robert Oscarson at the USGS in Menlo Park, CA, for his assistance in making the SEM
images, and the XRF and EMP analyses.
?????? ???????????? ??? ????????? ????????? ???????? ?????????? ????????????
????????????.
References
1. Barnes I. Dynamics of Pleistocene population extinctions of Beringian brown bears / I. Barnes,
P. Matheus, B. Shapiro, D. Jensen, A. Cooper // Science, 295 ? 2002. ? P. 2267-2270.
2. Barnes I. Genetic structure and extinction of the woolly mammoth / I. Barnes, B. Shapiro,
A. Lister, T. Kuznetsova, Andrei Sher, D. Guthrie, M.G. Thomas // Mammuthus primigenius, Current
Biology, 17. ? 2007. ? P. 1072-1075.
3. Cannon P.J. Meteorite impact crater discovered in central Alaska with Landsat imagery /
P.J. Cannon // Science, 196. ? 1977. ? P. 1322-1324.
4. Firestone R.B. Evidence for an extraterrestrial impact 12,900 years ago that contributed to the
megafaunal extinctions and the Younger Dryas cooling / R.B. Firestone et al. // Proc. Nat. Acad. Sci.,
104. ? 2007. ? P. 16016-16021.
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Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
5. Firestone R. The Cycle of Cosmic Catastrophes / R. Firestone, A. West, S. Warwick-Smith //
Bear and Company, Rochester, Vermont. ? 2006. ? 392 p.
6. Guthrie R. D. Rapid body size decline in Alaskan Pleistocene horses before extinction /
R.D. Guthrie // Nature, 426. ? 2003. ? P. 169-171.
7. Haynes C. V. Jr. Clovis, Pre-Clovis, climate change, and extinction / C. V. Haynes, Jr. // In
Paleoamerican Origins: Beyond Clovis, Bonnichsen R., B. T. Lepper, D. Sanford, M. R. Waters, Eds.,
Texas A&M Univ. Press, College Station, Texas. ? 2005. ? P. 113-132.
8. Herreid G. Geology and geochemistry, Sithylemenkat Lake area, Bettles Quadrangle /
G. Herreid // Alaska, Alaska Div. Mines Geol. Rep. 35. ? 1969. ? 22 p.
9. Martin P.S. Twilight of the Mammoths / P.S. Martin // University of California Press, Berkeley,
CA. ? 2005. ? 250 p.
10. Shapiro B. Rise and fall of the Beringian Steppe Bison / B. Shapiro et al. // Science, 306. ?
2004. ? P. 1561-1565.
11. U.S. Geological Survey. Aeromagnetic survey, eastern part of Bettles quadrangle, northeast
Alaska. ? Open-File Report 73-305. ? 1973.
????? ???????????????? ??????
? ?????? ???????? ? ?????? ??????
??. ?????????, ?. ???????????,
?. ?????, ?. ?????????, ?. ??????
?
????????????? ?????? ??????????? ??????,
??? 94025, ??????????, ????? ????, ???????? ????, 345
?
???????????? ??????????? ??. ???????? ? ??????,
??? 94720, ??????????, ??????
?
????????? ??????????,
??? 86327, ???????, ?????, ?/? 1636
?
???????? ???????? ?????????? ???????? ????,
??????? ?-1525, ????????, ?/? 77
?? ??????????, ??? ??????????????, ?????????????? ? ????? ???? ?????? ??????? ?
?????? ???????? ??????????? ? ? ?????? ?????????? ??????. ??????????????, ????????,
?????????? ?? ????? ???????, ???????? ??????????????? ????????? ?? 2 ?? 5 ??, ??????????
?????????? ???????. ????? ??????????? ??????????? ?????? ? ????? ??????? ????? ? ??????,
??? ????????????? ??????? ??????????????? ? ?????? ???????????. ????? ?? ???????????
???????? ?????? ??????????, ??? ??????????????? ? ???????????? ?????????? ??????.
?? ???????????????? ????????? ????????? ?????????? ??????????????? ?? ?????? ?
?????? ? ??????? ????-????????????? ???????? ??????? ??????????-????????? ???????
(LA-ICP-MS) ? ????????????? ????????????? (???). ??? ??????? ???????????? ???????
?????????? ?????? ? ????????? ?? ??????, ?????? ??????????? ??????? ? ??????????
???????, ? ??????? ?? ?????? ????????????? ????????? ?????????. ????? ????, ???????
? ??????? ???????????? ?????????? (???) ???????????????? ??????????? ????? (?????? 2)
??????????, ??? ??? ???????? ?? 3 ?? 20% ???? Ni. ????? ?????-?????????????? ???????
# 131 #
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
(PGAA) ??????, ??????????? ?? ?????? ???????, ????????? ?? ~ 0,4 ?? ??????, ??? ????????? ?
???????? ? ???????????????? ~ 1 ?? ? ????????. ????? ????, ??????????? ?? ????????????
???????????? ?????????? (???) ? ???-??????? ?????? ???????? ????????? ??????
?????????? ????????????????? ?????????. ??????????? ?? ?????? (5 ?? 7) ????? ???????,
????????????? ???????????????? ????????? 14C ?? ?????? (32,9 ± 1,8) ???. ???, ??? ?????????
? ??????? ????????????? ???????? ????? 36 ???. ??? ????? ? ?????????? ???????????? ???????,
???????, ????? ???????? ? ????????, ? ????? ????????????? ???????????? ????????.
????????, ??? ????????? ??????????? ? ?????????? ?????????? ????????? ????????????
????? ????????? ???????, ???? ?? ?????? ??????? ??? ????????? ??????????.
???????? ?????: ??????????????, ??????????? ????????? ???????????, ????? ??????????
??????, ????? ??????? ? ?????? ???????? ???????????, ?????? ?????????? ?????????????????, ????????????? ?????????????? ??????, ?????? ??????? ????????????
??????????, ?????? ????????? ?????-?????, ???????????? ??????????? ???????????
???????????.
zero outside a small
interval, so that each function describes the basis of a spatial (temporal) frequency and its localization in
physical space (time). In the case of two-dimensional data wavelet is a surface with a central symmetry
that meets the same set of requirements, which in one case.
Consider the algorithm for constructing two-dimensional wavelet diagram, which was developed
under a specific task ? to search for the ring structures on the surface of the Earth. The initial data
represent the D matrix NxM elements that contain values of some characteristics of the nodes of a
rectangular grid. It is necessary to identify the structure of a given shape, weakly expressed on the
background of the heterogeneity of the environment. For practical application, it is important to know
the characteristics of a wavelet:
? Localization in space (time) and in frequency;
f
f
і і M ( x , y ) dxdy
Zero mean:
f f
f f
і і M ( x, y )
Limited:
2
(1.1)
0;
dxdy f;
(1.2)
f f
Self-basis.
Next, we introduce the following symbols and functions:
x , y Џ ( M , M ),
M (t )
)
(1 t ) � e t ,
xM ,yM
(1.3)
§ 1 0 (( x M ) 2 ( y M ) 2 ) ·
M Ё
ё;
M
©
№
where M ? scale wavelet transform, ?x+M,y+M ? matrix of the base wavelet.
Fig. 1 shows the type of wavelet. Now the wavelet transform can be rewritten as an integral sum
of:
Wx , y
'x'y § M M
� ЁЁ ¦¦ ) M k , M l � ( Dx k , y l Dx k , y l Di k , j 1 Di k , j 1 ) Mi ©k 1l 1
M
·
k 1
№
¦ ) M k ,M � ( Dx k , y Dx, y l Di k , j Di , j 1 ) ) M ,M Dx, y ёё.
(1.4)
Because both components of the matrix are constant, the procedure of wavelet-transformation is
reduced to multiplying the folding of a set of constants. These matrixes are organized in such a way that
the numbers of operations in the computation of the elements of their coefficients were minimal. This
greatly reduces the amount of computer time required for the calculations. The developed algorithmic
and software demonstrated high efficiency in the real data processing.
Numerical data simulation using the wavelet transformation was carried out by the example of the
allocation of the Burckle crater in the Indian Ocean at the depth of 3800 m, with 29 km in diameter. A
summary of the Burckle crater is presented in Fig. 2.
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Fig. 1. Wavelet forms
Fig. 2. Data on the location of the Burckle crater [http://tsun.sscc.ru/hiwg/hiwg.htm]
Calculations were carried out with the computing environment MathSad14, which has a built in
function to calculate the wavelet transform based Dobe?. The result of wave function is a vector linked
to a few coefficients with a wavelet spectrum.
Figs. 3?5 present the results of the filtering data. Fig. 5 clearly allocated to the location of the
Burckle crater.
Further simulations were performed in the Burkle crater through Haar functions. The size of the
area to the Burkle crater was 400*300 km with a step of 1 km, the effective diameter of a «cap» wavelet
being 20 km, the results of calculations are shown in Figs. 6?8.
So, sections 1?3 present the findings of the research, focusing on the three key themes that have
been identified in the data analysis: the search of impact craters on the basis of wavelet transformation
of the digital ocean bottom, an effective visualization of the seabed topography and the land required
in the solution of hydrodynamic problems, the use of the above models of neural networks for solving
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Fig. 3. Baseline data shows an array of the data for analysis [5-6]
Fig. 4. Dobe? wavelet
?
b
c
Fig. 5. Phased wavelet filter surface of the ocean floor topography: a ? filter M30; b ? filter |M30|-M15; c ? the
result of filtering
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Fig. 6. Haar wavelet
Fig. 7. Output filtering of the Haar wavelet, Burkle crater
Fig. 8. View of the Burckle crater, obtained using Global_mapper
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
the problem of reconstruction of the characteristics of waves in the run-up on the coast and chevron
formation.
2. Neural network analysis of the observational data of coastal structures
In addition to scientific and technical tasks, allowing a rigorous formal description, there are
challenges when a formal description of the phenomenon does not exist, or it is difficult to analyze
it. Numerical (information) simulation of mega tsunami traces ? in chevron form represents an ideal
type of task. Neural algorithms allow the search of regularities in large data arrays with an arbitrary
statistical distribution of random variables. When the patterns are identified, then the developed
numerical network model can be put into performance [24].
Proposed numeric experiments are based on observations of chevron and the relief of the coastal
areas, construction of their models being approximating the spatial functions. Proposed use of the
numerical network analysis technology is a rapid multi-parameter regression model of observational
data, including procedures for constructing the model (learning) and its testing. As a result, appropriate
algorithmic and software numerical network modeling of coastal structures is adapted.
In most cases, the regression (neural networks) optimization principles are used. A functional,
assessing the quality of the regression model, is optimized by gradient or other methods. The classical
approach is the method of least squares. It minimized functional, estimating the model with the
experiment:
& &
2
H ¦ ( y ( xi , p ) ~
yi ) ,
(2.1)
i
&
* *
i ? number of experimental; y ( x , p) ? approximating function; x ? the vector of variables, which is
&
yi ? the experimental value. As a result, the
addiction; p ? adjusts the parameters of vector function; ~
parameters are standard functions (usually linear), which approximate the experimental dependence.
But in the experiment not all data may have the same credibility; therefore, weighted least squares
method introduces weights reflecting the impact of each experiment:
H
2
& &
§ y ( xi , p ) ~
yi ·
ё ,
¦ ЁЁ G~y
ё
i ©
i
№
(2.2)
yi is confidence interval, the precision with which the determined ~
yi .
?~
To build a regression (neural networks) models are used in the developed software «Models». The
used the approximation depending exits from the entrances to the following:
D ta
ba ca ¦ sin(Maj ¦ w ji X t i ),
j
(2.3)
i
where X ? input data; i ? number of inputs; j ? number of harmonics; t ? number of tasks in the sample;
a ? adjusts the parameters, b, c, w, ? ? number of exit.
Nonsmoothness function was assessed as the mean first-order sensitivity of the output:
¦
a
U
§ waa
Ё
Ё wx j
©
¦
aa
·
ё
ё
№
2
2
a
# 111 #
¦¦ w2ji .
j
i
(2.4)
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Array of inputs («causes»), order of
o
o
o
output x1 , x 2 , , x n
o
o
o
array output («consequences») y1 , y 2 , , y n
Learning, the selection of
the best features of the
model: number of
harmonics, spectrum
The input
data
o
o
Model
o
o
f ( x)
y
o
x1c , x 2c , , x kc
Testing
o
o
o
y1c , y 2c , , y nc
o
y ic
o
f ( xic )
Fig. 9. Present the modeling of the observational data using the software «Models»
Fig. 10. The dialog program «Models»
This value restricts the top, depending on the task. During the training, by adjusting the parameters
w are changed in such a way that they do not exceed user-defined limits. For optimization the method
of conjugate gradient is used.
The program «Models» is designed for the rapid synthesis of large amounts of empirical and
analytical models to experimental data (Fig. 9). Synthesized approximate analytical models reproduce
the original object of cause-effect relationships, to the extent that they regard themselves in the
collection of empirical data. The analytical model can replace experiments with the original object to
resort to numerical experiments with the model.
Fig. 10 presents a dialog window «Models» to work in the computing environment «Excel». It is
necessary to specify the location of a book «Excel» source of empirical data, as well as items that will
be posted the results of the program. It is assumed that the empirical data are organized in b-array
consisting of two related arrays ? an array of inputs («causes») and the array outputs (responses,
«consequences»).
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Another two b-array need to display results: b-array «Projections», which has the same structure
and size as the b-array of empirical data and their accuracy, and b-array «Model» (address placement
is given in paragraph «Model» dialog box) with the same horizontal size as the other b-array, but
differs in the vertical size, user (Item «Size»).
In b-array «Projections» posted the results of model smoothing of empirical data, b-array
«Model» stored information about the parameters of the analytical model. Two upper rows b-array
«Model» are of informational status ? in particular, in the first line of the first input column posted on
the error model of the last instruction and the range of values in the second row indicate the significance
of the relevant input parameter for the predictions ? the smaller the figure, the less important is its
corresponding to input information. The remaining positions adjust the model parameters.
Synthesis of the model performs the «Learning» procedure, by the iterative search of the model
parameters, where the standard deviation of responses (opinions) models and related empirical data in
an array of responses are minimized. The number of iterations is defined by «Iteration» paragraph. For
the training the restriction on nonsmoothness function (item «Spectrum») must be set strictly greater
than zero level of the spectral density. If the observation occurs, plaque indicating the number of past
iterations, estimate (error), the proportion of the fall assessment on the last iteration and the current
spectral density are defined.
The calculation shows the actual observations of the spectral density, while the dialog is established
recommended. If the actual spectral density is significantly (by several tens of percent) greater than
recommended, it implicitly refers to the fact that raising the level recommended by the spectral density
decreases error learning, but does not necessarily diminish the bug testing. If the actual spectral
density is significantly lower than recommended, it is advisable to try to reduce the spectral density.
Based on the results of the testing calculated the most suit-user spectral density may be, so that both the
training and testing errors were smaller. At high spectral density it is easier to achieve error reduction
training without the requirement of smoothness of interpolation, but the deteriorating performance of
test predictions can occur. Also selecting the size of the model, take into substantially, that large sizes
and, consequently, increase of the model machine time.
Thus, non-linear regression (neural networks) analysis allows information to build predictive
models of studied phenomena (the process) and use them in the systems of control and monitoring.
We were having outlined the general scheme of computational experiment and a brief description
of its main stages. Be aware, that computing experiment in a narrow sense, as the creation and study of
mathematical models of the object with the help of computational tools, can be identified as the basis
for the triad: a model ? an algorithm ? a program. Broadly (methodological) sense of computational
experiments is understood as techniques of research [17]. For the investigated object (chevron) first,
a mathematical (neural networks) model is developed. Computing experiment, in essence, provides
a study group near regression (approximation) model. Initially, we construct a simple, but quite
meaningful model for description of the object in terms of proximity to the experimental data neural
networks (information) model.
In the computational experiment, the subsequent cycles of the model states new developments
are taken into account, etc. Therefore, we can write about the orderly recruitment (hierarchy) of
mathematical models, each with an accuracy of describing reality. Thus, in the most simple model, it is
necessary to seek agreement with the experiment, it is the aim of the computational experiment.
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Here are the basic elements of numerical experiments on simulation of chevron structures: a fullscale experiment, the construction of a mathematical model, the choice and application of numerical
method for finding solutions, building a software implementation of mathematical models to find the
numerical solution, processing the results of calculations, compared with full-scale experiment, the
decision on continuation of full-scale experiments, the continuation of full-scale experiment to obtain
the data necessary to refine the model, the accumulation of experimental data. Adapted, depending on
the specifics of the problem, the chain of these phases of computational experiment, implemented in a
single software system, and is «technology» computing experiment.
Thus, the proposed computational technique based on neural networks modeling of observational
data for the numerical description of mega tsunami builds a model (approximation of spatial functions
to study the structure-surface) in form chevron. It can also simulate bottom topography and land
in their expressions for the detection of these interactions and processes, their formation at up rush
mega tsunami on rocky shores. Later, on that basis the numerical analysis of the diversity of chevron
geometries was performed for the assessment of the predominant angle of the axis of chevron to the
coastline. Grade azimuth geometry chevron indicates a possible source area of the epicenter and the
tsunami probable submarine impact craters. The contours of chevron in the depths of the land would
allow detailed modeling of run-up of the mega tsunami.
Baseline data of coastline and chevron, digitized with a step of 2 mm (1 mm = 125 m), are
expressed in b-arrival on the worksheet «Excel» (Fig. 11?12). Two arrays with the input X (common to
the shoreline and chevron) and the output Yb (to shore) and Ych (for chevron) are located nearby ? on
the left array of consequences, on the right ? an array of reasons. This calculation is one an «input»
and one an «output». After placing the initial data on the «Excel» sheet, turn to the procedure for the
synthesis of the model, filling in a dialog window «Models». Then, after filling the required fields in
the dialog box appears b-arrival «Model», which contains adjusted parameters of the base dependence.
Two tops of the array contain the values of average error and the spectrum. Then it is necessary to
compare the original data with the results of testing and by changing the settings range from 20 to 200
and size from 20 to 100, making the best result compared field and calculated data (smallest error).
Based on the results of numerical simulation data of the studied chevron forms and coastline we
have come to the following conclusions: the best result in the simulation is obtained for the range = 200
for all the input data and the number of subscript parameters ? 35 for the first chevron, and 40 ? for the
second chevron, revealed that chevron, along the coast, remain in a general form similar to the form
of appropriate shoreline, which in turn can characterize the run-up catastrophic waves, as a result of
which the respective chevron is formed.
3. Numerical simulation mega tsunami in the coastal zone
We were reviewed of the results of hydrodynamic modeling of the single wave?s interaction with
oblique wall to form a Mach leg. In Future, the numerical study of chevron distribution, its orientation
to the coastlines, the relationship to a coastal forms (cliffs, coastal embankments), will disclose the
mystery of the impact of mega tsunami cosmic origin in the coastal area.
Let us consider the hydrodynamic models that can estimate the nonlinear transformation of
tsunami waves of types in the coastal zone within the above tasks. Palmer and others [15] performed
laboratory experiments to model the anomalous strengthening of the tsunami in Hilo Bay, which had
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Fig. 11. Chevron form (Australia) [20]
Fig. 12. Placement of data numeric experiments on the sample «Excel» sheet
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Fig. 13. Wave scheme of Mach reflection
occurred in 1946, 1952, 1957 and 1960. They believed that the anomalous strengthening of the tsunami
caused by a combination of several characteristics of the geometrical of the bay: underwater ridge at
the entrance to the bay led to refraction of tsunami waves, sending them into the bay, the bay having
a triangular configuration due to wave of accumulating effect in the bay top where the port of Hilo. In
this paper, [23] described the experiments of [16] to study the interaction solitary wave ai amplitude
with a flat vertical wall, to which the wave come at some angle ?i. The reflected waves from the
wall to be were found regular or irregular (Mach) depending on the amount ?i. Regular reflection
of ridges crossing the incident and reflected waves occurred at the wall, and at Mach formed a third
wave, called the Mach leg, which is located between the wall and the point of the first two wave crests
intersection.
Mach reflection scheme let us consider in detail, following [8], which is depicted in Fig. 13.
Theoretical studies of skew run-up on a wall in were made be Miles [13-14]. These analytical
formulas for the maximum run-up R, the amplitude ai of the reflected waves ?i, the angle and the angle
of reflection, which is visible to the Mach leg from point A, were obtained through the study some
nonlinear-dispersion model of shallow water of solutions. At the same time many possible schemes for
the wave interaction with a wall to use the wave configurations that have been observed in experiments
[16]: double and triple configurations. The distance from the zone of interaction of all waves are
assumed to be in the form of solutions, as in the case of Mach reflection wave parameters are related
to additional terms of the resonant interaction. When assumptions are specified the following formula
for the maximum run-up is suggested:
R
ai
­
\2
4
, i t 1;
°
1
2
2
3ai
°°1 1 3 ai \ i
®
2
°§
\ i ·ё \ i2
Ё
,
d 1.
°Ё1 1 2
°Ї© 3ai ё№ 3ai
(3.1)
Thus, if the solitary wave at the free-wall falls at an angle, then the run-up value may reach
the value R 4ai . In the Melville experiments [12] the depth of the pool reaches 30 cm, but for the
magnitude of R is found, not to exceed 2ai.
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
Fig. 14. Free surface wave, its contours and grid for free surface at the relevant time [8]
The authors of [19] proved that such a small R value was due to the fact that [12] actually examined
only the initial phase of the wave interaction with a wall, and to achieve steady-state R values is
required that the wave to pass a distance of at least ten times longer than in Melville experiments.
Currently the creation of large experimental facilities for the study of skew run-up solitary waves is
problematic computational experiments have become the best solution.
Numerical simulation of oblique run-up was described in [4] Miles received the theoretical
dependence by calculations based on a mathematical model. At the same time, is for practical interest
the process of roll waves of finite and not infinitely small amplitude. In the absence of reliable
experimental data and the theory of skew roll waves of finite amplitude, numerical simulation is the
only tool to study this phenomenon. Funakoshi [4] used the finite-difference method for calculating the
wave with an amplitude of ai = 0.05, Tanaka [22] ai = 0.3 applied to the spectral method. A large series
of calculations in the range of amplitudes ai = 0.05?0.30 carried out complied by Serebrennikova and
Frank [19] was based on the discrete model of an incompressible fluid. Given the existing differences
of numerical results for some parameter values calculations based on other mathematical models and
algorithms should be undertake.
Khakimzyanov G.S. [7, 8] presented the results of calculations in the nonlinear-dispersion model
Zheleznyak-Pelinovsky (NDM) and three-dimensional models of potential flows from the finitedifference method using a dynamically adaptive grid, and provided a comparison of the results obtained
in the calculations of other authors. In numerical solution of the problem curvilinear grid used adapted
to the field form, and depending on the solution, so that the concentration of grid nodes increased in
areas of the phenomena to be investigated: ridges in the vicinity of the incident and reflected waves,
legs, and the Mach zone run-up. A fragment of such a grid, lying on the free surface, is shown in
Fig. 14. One can see that from the grid tracks the main features of the modeled currents, in particular
Mach leg.
Fig. 15 shows the dependence of the R/ai value of values for different \ i 3ai values of free-wave
amplitude (MPF ? a model of potential flows [8]).
In this paper [13] was obtaining the dependence run up wave of small amplitude at regular
reflection:
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
§
·
3
3 2 sin 2 \ i ёё.
2 ai ЁЁ
2
© 2 sin \ i
№
Fig. 15 contains two curves (3.2): ai=0.1 (I) and ai=0.5 (II).
R
ai
(3.2)
Points ? calculation results, solid line ? theoretical dependence (3.1); bar ? the theoretical
dependence (3.2) (I ? ai= 0.1; II ? ai = 0.5): ai= 0.05: 1 ? [4]; 2 ? MPF; ai= 0.1: 3 ? NDM, 4 ? MPF;
ai= 0.3: 5 ? [22]; 6 ? [19]; 7 ? MPF; ai= 0.5: 8 ? MPF.
Thus, Fig. 15 shows graphs of theoretical dependence (3.1). We see that at finite values of amplitude
ai the results of the calculations are close the curve (3.1) Mach reflection. Fig. 16 shows the chevron
form of southern coast of Madagascar.
Conclusions
This paper has given an account of and the reasons for the widespread use of computational
experiments in the recent issue of the cosmic impacts of ocean traces. This paper has argued
that a computational experiment is the best instrument to research this complex interdisciplinary
problem. The purpose of the current investigation was to determine the possibility of computational
experiments to refi ne our understanding of the studied effects. This project was undertaken to
design computing technology of numerical data analysis and evaluate the quality of these data to
address relevant problems. Returning to the hypothesis posed at the beginning of this research, it is
now possible to state that calculations make it possible to disclose material aspects of the physical
phenomena.
This investigation has shown that pooling disparate data and computational algorithms helps to
solve the tasks more efficiently. These findings suggest that in general the hypothesis adopted at the
beginning of the study of recent cosmic impact effects in marine waters is justified. One of the most
significant findings to emerge from this study is that it identified a set of computational techniques
that allow most effectively. It also showed that the present computational technology it is important
to integrate in a single computational experiment. This research has found that on the whole iterative
procedures, computational experiment provided the necessary evidence and the validity of obtained
solutions.
The most obvious finding to emerge from this study is that in this problem there is a set of
interconnected data, which allows answering the fundamental question of the space object of the
origin. Multiple regression analysis revealed that the form of dune-chevron reflect not only the relief of
the coast line, but the bathymetry offshore.
The evidence from this study suggests that the results of numerical simulations do not contradict
the empirical data. The results of this study indicate that the hydrodynamic models are consistent with
the geomorphologic data. The results of this research support the idea that outer impact marine water
was most probable cause of a research of natural phenomena. Taken together, these results suggest
that hypothesis on the significant prevalence of recent cosmic impact of marine influences is much
unsubstantiated.
The computational experiment that we have identified therefore assists in our understanding
of the role of simulation in solving the problem. This research will serve as a base for future
investigations and introduce a new productive hypothesis on this issue. The current fi ndings add
substantially to our understanding of the physical nature of the phenomenon. The research has gone
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Fig. 15. The dependence runs up wave R/aifrom yi
3ai [8]
Fig. 16. Chevron forms of southern coast of Madagascar
Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
some way towards enhancing our understanding of the overall relationship of the investigated sites.
The methods used for this object may be applied to other similar elsewhere in the world. Taken
together, these fi ndings suggest a role for our methodology in promoting solution to this pressing
problem.
Finally, a number of important limitations need to be considered. The most significant limitation
lies in the fact, that important data are fragmented and characterized by a qualitative description.
Therefore, the current study was limited to individual objects, the data on which enables the main
stages of the computational experiment. Note that the current study was not specifically designed to
evaluate factors related to geochronology and computer data processing, analysis, obtained with the
help of a microscope. Therefore, with a small sample number, caution must be applied, as the findings
might not be transferable to other unique objects.
Of course, this research has thrown up many questions in need of further investigation. Further
work needs to be done to establish whether the model obtained is adequate for use in justifying the basic
concepts in the problem of the recent cosmic impact space traces. The further research is recommended
to be undertaken in the following areas: building models related to the recent variability of the climate,
the creation of an expert database of forms and parameters of chevron in various maritime areas, the
adaptation of the hydrodynamic models megatsunami of run-ups for specific coastal areas, collection
and systematization of manifestations of the recent cosmic catastrophes.
Further experimental investigations are needed to estimate constructed hydrodynamic and
statistical models. More broadly, a new research is also necessary to determine the reliability of
the assumptions made and the hypotheses, as well as their adequate justification. It is suggested
that the association of these factors is investigated in future studies. Further research can explore
more detailed and subtle effects of the studied phenomenon. Further research in this field regarding
the role of the computational experiment would be of great help in numerical processing and the
rationale for experimental studies. Note also that more information on marine space impact trace
would help us to establish a greater degree of accuracy on matter of the nature of the studied
processes. It would be interesting to assess the effects of (damage) of the new catastrophic event
that would occur, for example, in the vicinity of the Burkle crater with characteristics close to the
site.
These findings suggest several courses of action for the development of technologies of
computational experiment to study the issue of the recent cosmic impact ocean traces. However, the
findings of this study have a number of important implications for future practice of searching these
traces, their systematization and the creation of an expert database dune-chevron is constriction. At
the same time, there is a number of important changes to be made to enhance the opportunities of
mathematical modeling of the phenomenon and the numerical analysis. Another important practical
implication is that the results of numerical experiments can be used and compared with the new data
to be received during the field work. This information can be used to develop targeted interventions
aimed at building a new physical and mathematical model of the studied phenomenon. Our work here
is just the first step in this endeavor.
?????? ???????????? ??? ????????? ????????? ???????? ?????????? ????????????
????????????.
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Konstantin V. Simonov. Computational Experiment in the Problem of the Recent Traces of Oceanic Cosmic Impacts
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K.?. ???????
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????????? ? ??????????????? ??????????, ??? ???????????? ????????????? ??????. ??
????????????? ????? ????????? ?? ???????????????? ??????????? ???? ?? ????????? ?
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? ????? ???????? ????? ???-???????? ?? ?????? ???????????? ?????????? ??? ???????
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Copyright ??? «??? «??????» & ??? «A???????? K????-C?????»
Journal of Siberian Federal University. Engineering & Technologies 1 (2010 3) 123-132
~~~
??? 551.3
Micrometeorite Impacts in Beringian Mammoth Tusks
and a Bison Skull
Jonathan T. Hagstruma*, Richard B. Firestoneb,
Allen Westc, Zsolt Stefankad and Zsolt Revayd
a
U.S. Geological Survey, 345 Middlefield Road, Menlo Park,
CA 94025, United States
b
Lawrence Berkeley National Laboratory, Berkeley,
CA 94720, United States
c
GeoScience Consulting, Box 1636, Dewey, AZ, 86327, United States
d
Institute of Isotopes of the Hungarian Academy of Sciences,
H - 1525 Budapest, P.O.B. 77, Hungary 1
Received 3.02.2010, received in revised form 27.02.2010, accepted 9.03.2010
We have discovered what appear to be micrometeorites imbedded in seven late Pleistocene Alaskan
mammoth tusks and a Siberian bison skull. The micrometeorites apparently shattered on impact
leaving 2 to 5 mm hemispherical debris patterns surrounded by carbonized rings. Multiple impacts
are observed on only one side of the tusks and skull consistent with the micrometeorites having come
from a single direction. The impact sites are strongly magnetic indicating significant iron content. We
analyzed several imbedded micrometeorite fragments from both tusks and skull with laser ablation
inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray fluorescence (XRF). These
analyses confirm the high iron content and indicate compositions highly enriched in nickel and depleted
in titanium, unlike any natural terrestrial sources. In addition, electron microprobe (EMP) analyses of
a Fe-Ni sulfide grain (tusk 2) show it contains between 3 and 20 weight percent Ni. Prompt gamma-ray
activation analysis (PGAA) of a particle extracted from the bison skull indicates ~0.4 mg of iron, in
agreement with a micrometeorite ~1 mm in diameter. In addition, scanning electron microscope (SEM)
images and XRF analyses of the skull show possible entry channels containing Fe-rich material. The
majority of tusks (5/7) have a calibrated weighted mean 14C age of 32.9 ± 1.8 ka BP, which coincides
with the onset of significant declines <36 ka ago in Beringian bison, horse, brown bear, and mammoth
populations, as well as in mammoth genetic diversity. It appears likely that the impacts and population
declines are related events, although their precise nature remains to be determined.
Keywords: global climate changes, megafauna, micrometeorites, multiple impacts, Siberian bison skull,
Pleistocene Alaskan mammoth tusks, plasma mass spectrometry analyses, X-ray fluorescence analyses,
electron microprobe analyses, gamma-ray activation analysis, scanning electron microscope images.
1. Introduction
During the late Pleistocene, Beringia was largely an ice-free continental region that consisted of
northeastern Siberia, northwestern North America, and the emerged Bering Strait. Major events that
*
1
Corresponding author E-mail address: jhag@usgs.gov
© Siberian Federal University. All rights reserved
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Jonathan T. Hagstrum, Richard B. Firestone? Micrometeorite Impacts in Beringian Mammoth Tusks and a Bison Skull
occurred at that time were global climate changes, migration of humans from Asia to America (~13 ka
BP), and large-scale megafaunal extinctions (~12 ka BP). The cause of these extinctions has long been
controversial and has been attributed predominantly to either climate change or overkill by humans
[9]. A period of marked decline in population and genetic diversity for many large mammal species
happened earlier, however, beginning at about 36 ka BP before the last glacial maximum, human entry
into the New World, or the final megafaunal extinctions. For instance, no brown bear fossils have been
found in eastern Beringia (Alaska) that date between 35 and 21 ka BP, and different haplotypes at
either end of this hiatus likely indicate a local extinction event [1]. Similarly, between 35 and 28 ka BP,
caballoid horse fossils show a significant decline in metacarpal size an
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