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NEW BIO- AND MAGNETOSTRATIGRAPHIC DATA AT THE JURASSIC-CRETACEOUS BOUNDARY OF THE CHIGAN СAPE (VLADIVOSTOK REGION, RUSSIA)

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NEW BIO- AND MAGNETOSTRATIGRAPHIC DATA
AT THE JURASSIC-CRETACEOUS BOUNDARY
OF THE CHIGAN ?APE
(VLADIVOSTOK REGION, RUSSIA)
Guzhikov A.Yu.1,
Arkadiev V.V.2,
Baraboshkin, E.Yu.3,
Feodorova A.A.4,
Shurekova O.V.4,
Baraboshkin E.E.3,
Manikin A.G.1,
Surinsky A.M.1,
Golozubov V.V.5,
Kasatkin S.A.5,
Nechaev V.P.5
1Chernyshevsky
Saratov State
University, Saratov, Russia,
2Saint
Petersburg State University,
St. Petersburg, Russia,
3Lomonosov
Moscow State
University, Moscow, Russia,
4Research
and Production
Enterprise Geologorazvedka, St.
Petersburg, Russia,
5Far
East Geological Institute FEB
RAS, Vladivostok, Russia,
42�'37.8''N
123�'47.0''E
In September 2014 we have studied the well-known Chigan section
(Chigan Cape, Podiapolsky Town region). Some geologists
(Konovalov, Konovalova, 1997) supposed that the section contains
Jurassic?Cretaceous (J/K) boundary interval.
This section previously referred to Berriasella jacobi ammonite zone (Konovalova, Konovalov, 1997; Sey, Kalacheva, 1999)
because of ammonite findings: Pseudosubplanites cf. grandis, P. aff. combesi, Berriasella ex gr. jacobi, Dalmasiceras, and
others.
(Konovalova, Konovalov, 1997)
in calcite cement
(Sey, Kalacheva, 1999)
Outcrops 3046 and 3047 consist
of gray sandstones, poorly sorted
and muddy. These layers crop
out in steep cliffs at a distance of
500 meters to the north from the
section 3046. Its bedding is
nearly subhorizontal and they are
crossed by a number of Late
Cretaceous gabbro dikes.
The ichnogenus and lithology are typical for
the lower shoreface zone (Members 1-3 and 5).
A specific 1.5-m level of middle-upper
shoreface massive sandstones (Member 4) was
recognized in the middle part of the section. It
is limited by the erosional surfaces at the base
and at the top. The upper surface is a
transgressive surface, which is overlaid by 10cm cross-bedded sandstone, replaced laterally
by bioclastic rudstones. The visible thickness
of the section is 33 m.
5
4
3
2
1
Recrystallised rudstones with quartz
grains and bioclasts of bivalves (Bi)
and crinoids (Cr) in calcite cement.
Member 5.
Thin-section 1314-3, nicols +.
Polymictic sandstones of lower shoreface
with Schaubcylindrichnus coronus. Member
2. Thin-section 1314-1-11, nicols +.
For the comparison we have studied
section 3050 to the south (~1.1 km),
which continues the Chigan Formation
(Sey, Kalacheva, 1999) and has the
same stratigraphic age (Konovalov,
Konovalova, 1997).
Berriasella cf. jacobi Mazenot, cast.
Pseudosubplanites cf. combesi Le H間arat.
Collection of V.P. Nechaev, 2014.
Collection OAO ?Primorgeologiya?, sample 15-1547.
Collection of I.V. Konovalova, 1993. Scale bar = 10 mm.
In the rockfall at the base of the section we found the remains of ammonites: an imprint of Pseudosubplanites cf. combesi Le
H間arat and living chamber fragment of Pseudosubplanites sp. In addition, in the collection of I.V. Konovalov? (1993),
courtesy of the "Primorgeologiya" Company, we have determined Berriasella cf. jacobi Mazenot and Pseudosubplanites sp.,
also found in the debris at the base of the same sections. All these findings characterize the Lower Berriasian Jacobi Zone. It
should be noted that P. cf. combesi differs from other Pseudosubplanites by evolute shell and prevalence of bifurcate ribs. It
is also very similar to some Upper Tithonian forms (Oloriziceras type).
Palynology. The plant detritus,
poor preserved gymnosperms
pollen and spores, rare
indeterminate proximochorate ?
proximate cysts and dinocysts
Sirmiodinium grossii Alberti,
Systematophora areolata Klement
? Tubotuberella rhombiformis
Vozzhen. were found in only one
sample (3046/3) of 14. This
assemblage ranges from Oxfordian
to Early Valanginian. Dark brown
organic residues indicates the
mesocatagenetic stage with
paleotemperature about 200�.
3050
uppermost
3046
3047
3050
lowermost
Generic rate of foraminifers from Chigan formaition
The differential thermomagnetic analysis and
magnetic saturation demonstrate that
magnetite or related titanomagnetite are
principal magnetic minerals in the sandstones.
The hematite was fixed at one level only
(sample 3046/21 near the base of member 4).
Results of thermomagnetic and alternating field cleanings.
Statistic paleomagnetic characteristics of the Chigan cape section
n
D?? (o)
I?? (o)
?
?95 (o)
(R-) ??? ????????? ??? ??????????
43
262.6
-79.4
8.23
8.1
(R-) ?????????, ????????? ??? ?
????????? ???????? ????????????
40
259.3
-81.9
11.75
6.9
(N+) ??? ?????????
12
311.6
64.9
24.68
8.9
(N+) ?????? (?????? ?????) ? ????
????????
17
279.2
84.5
45.05
5.4
Results of contact test
Thank you for attantion!
Автор
Nastya
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