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Quaternary International xxx (2017) 1e10
Contents lists available at ScienceDirect
Quaternary International
journal homepage: www.elsevier.com/locate/quaint
Characteristic grain-size component - A useful process-related
parameter for grain-size analysis of lacustrine clastics?
Yin Lu a, *, 1, Xiaomin Fang a, **, Oliver Friedrich b, Chunhui Song c
a
CAS Center for Excellence in Tibetan Plateau Earth Sciences and Key Laboratory of Continental Collision and Plateau Uplift, Institute of Tibetan Plateau
Research, Chinese Academy of Sciences, Beijing, 100101, China
b
Sedimentology and Marine Paleoenvironmental Dynamics Group, Institute of Earth Sciences, Heidelberg University, Im Neuenheimer Feld 234-236, 69120,
Heidelberg, Germany
c
School of Earth Sciences & Key Laboratory of Western China's Mineral Resources of Gansu Province, Lanzhou University, Lanzhou, 730000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 November 2016
Received in revised form
10 July 2017
Accepted 21 July 2017
Available online xxx
Lacustrine sediments are important archives for paleoclimate reconstructions. The application of grainsize analysis as palaeoclimatic proxy in lacustrine clastics is valuable but also difficult because the typical
polymodal grain-size distribution in these clastics. To better understand the grain-size distribution of
lacustrine clastics and to promote the application of grain size in paleoenvironmental interpretation, this
study investigates lacustrine clastics from northern and southern China. The grain-size distribution of
these sediments was decomposed by log-normal distribution function fitting method. Based on the
results, and drawing upon the concept of paleomagnetic demagnetization and “Characteristic Remnant
Magnetization” from paleomagnetism, a conceptual system has been established and defined for grainsize distribution analysis. The system is composed of four components: (I) Characteristic Grain Size
Component (ChGSC), (II) Affiliated Grain Size Component, (III) Meaningful Grain Size Component, and
(IV) Combination Feature of Grain Size Components (CFGSCs). Based on the proposed system, ChGSC and
CFGSCs were used to detect the grain-size distribution of clastics from the different lake zones investigated. Our results show the number, modal size, and percentage of ChGSC(s) in grain-size distributions
are sensitive to changes in the lacustrine environment. The ChGSC(s) mirrors the dominant depositional
process and hydrodynamic conditions. The modal size of ChGSC(s) is more sensitive to hydrological
conditions than the widely used mean grain-size approach. Thus, the ChGSC(s) provide a useful processrelated parameter for paleoenvironmental reconstructions. To test this promising application, we applied
this approach to a deep drill core from the Qaidam Basin in the northeastern Tibetan Plateau.
© 2017 Elsevier Ltd and INQUA. All rights reserved.
Keywords:
Lacustrine sediments
Grain-size distribution
Grain-size curve fitting
Paleoenvironment
1. Introduction
Lakes are typically hypersensitive to climatic changes
(Verschuren, 2009; Yu and Shen, 2010; Wolff et al., 2011; Herb et al.,
2013; Liu et al., 2017) and therefore provide an ideal archive of
continental climate change because of the preservation of long (a
hundred thousand years to million-year time scale), uninterrupted
sedimentary records (Kashiwaya et al., 2001; Wang et al., 2012; Lu
* Corresponding author.
** Corresponding author.
E-mail addresses: yinlu@post.tau.ac.il, yinlusedimentology@yeah.net (Y. Lu),
fangxm@itpcas.ac.cn (X. Fang).
1
Present address: Sedimentology and Marine Paleoenvironmental Dynamics
Group, Institute of Earth Sciences, Heidelberg University, Germany.
et al., 2015). These conditions in a continental setting, allow for
high-resolution palaeoclimatic studies that are crucial to better
understand the pattern and dynamics of the global climate system
(An et al., 2011; Brauer et al., 2007; Kashiwaya et al., 2001; Litt et al.,
2014; Torfstein et al., 2015; Elbert et al., 2015; Tian et al., 2017).
Furthermore, clastic sediment sequences in large lakes have not
been investigated sufficiently to examine their climatic and sedimentary significances.
As climate change is typically the main driver of the hydrological
conditions within a lake, the nature and arrangement of clastic
sedimentary facies in lacustrine sediments, both of which are
closely related to the hydrological conditions, can be used to
reconstruct (palaeo)climatic changes. Grain size is a particularly
valuable indicator of the hydrodynamic evolution of lakes because
it corresponds to the hydraulic energy that is needed for clast
http://dx.doi.org/10.1016/j.quaint.2017.07.027
1040-6182/© 2017 Elsevier Ltd and INQUA. All rights reserved.
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
2
Y. Lu et al. / Quaternary International xxx (2017) 1e10
transport, sorting, and deposition. Grain-size analysis provides
paleoenvironmental information at the high temporal resolution
that is needed to reconstruct and understand the dynamics of
climate change. However, the typical polymodal grain-size distribution in lacustrine sediments has hindered the wide application of
grain-size analysis as a standard tool. This polymodal grain-size
distribution comes from different transporting media (e.g., floods,
aeolian input, lake currents, and waves) and the re-sorting of
sediment. Within a lake, however, different depositional zones are
characterized by distinctive combination of grain size components,
as was shown for Hulun Lake (Inner Mongolia) (Xiao et al., 2012).
This shows that decomposition polymodal grain-size distribution is
a potential tool for paleoenvironmental reconstructions based on
lacustrine sediments.
Recently, two different approaches have been carried out to
obtain reliable results from grain-size distribution analyses of
lacustrine sediments: (1) end-member modeling analysis (EMMA)
(Dietze et al., 2012, 2013, 2014; Ijmker et al., 2012; Liu et al., 2016;
Parris et al., 2009; Yu et al., 2016), and (2) the log-normal distribution function fitting method (Xiao et al., 2009, 2012, 2013, 2015;
Gammon et al., 2017). The log-normal distribution function fitting
method is based on single sample fitting and subsequent decomposition. In contrast, the EMMA method requires an eigenspace
decomposition with different scaling procedures that extract
genetically meaningful end-member grain-size distributions and
their percentages in each sample (Dietze et al., 2013).
The log-normal distribution function fitting method has been
successfully applied to obtain paleohydrological information of
ancient lakes (Xiao et al., 2009, 2012, 2013, 2015; Gammon et al.,
2017). Based on grain-size component fitting and decomposition,
percentage of each individual component was acquired. Subsequently, the sequence of percentage variation on the individual
component was compared with other proxies. However, in our
Miocene-Pleistocene deep drill core studies, we expect to get the
variation sequence of component(s) that reflects the dominant
sedimentary process, not simply to do statistics of each individual
component. Therefore, an effective conceptual analysis system is
needed to extract the most essential elements from the large
number of decomposed components. In this study, we establish
such a system for grain-size distribution analysis using lacustrine
sediments from southwestern, western, and northern China as
representative sedimentary archives. We further propose the
Characteristic Grain Size Component (ChGSC) as a useful processrelated parameter for paleoenvironmental research and apply this
approach to a deep drilling core (SG-1b) from the Qaidam Basin in
the northeastern Tibetan Plateau to test its applicability.
receives high-suspension dust input (An et al., 2012) (Fig. 1A, C).
Angulinao Lake in northern China is controlled by the East Asian
winter monsoon (during the winter half-year) and the Westerlies
and is therefore characterized by significant high-suspension (Sun
et al., 2008a,b) and low-suspension (Prins et al., 2007; Sun et al.,
2008a,b) dust input.
2.2. Grain-size measurement and component decomposition
Grain-size distribution was determined using a Malvern Mastersizer 2000 laser particle sizer after the organic matter and carbonates were removed by H2O2 and HCl, respectively. The fractions
<4 mm (84) and >63 mm (44) were regarded as clay and sand,
respectively. In between, fractions 4e8 mm (74), 8e16 mm (64) and
16e63 mm indicate very fine silt, fine silt and medium to coarse silt,
respectively. The fractions 63e125 mm (34), 125e500 mm (14) and
>500 mm indicate very fine sand, fine to medium sand and coarse
sand, respectively.
Polymodal sediments are typically formed by various combinations of unimodal components (Ashley, 1978; Inman, 1949;
Tanner, 1964; Visher, 1969) of which the grain-size distribution
generally follows a log-normal distribution (Krumbein, 1938; Passe,
1997). Using the log-normal distribution function, the grain-size
distribution can therefore be described with sufficient accuracy
(Ashley, 1978; Passe, 1997; Qin et al., 2005). Based on these findings,
the log-normal distribution function fitting method described by
Qin et al. (2005) was used to quantitatively fit and partition the
grain-size components within individual distributions of the
sampled lake sediments.
The log-normal distribution function fitting method assumes
that a polymodal grain-size distribution is composed of several
unimodal log-normal distributions (Qin et al., 2005). The prototype
formula of the log-normal function is as follows:
2
Z∞
n
X
6 Ci
FðXÞ ¼
exp
4 pffiffiffiffiffiffi
i¼1 si 2p
∞
3
!
ðX ai Þ2
7
dX 5
2s2i
where X ¼ lnðdÞ, d is the grain size in mm, n is the number of modes,
ci is the content of the ith mode, si is the variance of the ith mode,
and ai is the mean value of the ith mode's logarithm grain size, ai ¼
lnðdi Þ (Xiao et al., 2009, 2012). The fitting residual is calculated as
follows:
dF ¼
m 2
1X
F Xj G Xj
m j¼1
2. Material and methods
2.1. Lacustrine sediment sampling
For this study, surface sediments in the deep/central, the
shallow/transitional and the lakeshore zones of Lugu Lake, Dian
Lake, Yangzonghai Lake and Yilong Lake in southwestern China
(Fig. 1A and B), the Qinghai Lake in western China (Fig. 1C) and
Angulinao Lake in northern China (Fig. 1D) were sampled for grainsize distribution measurement and decomposition. Sedimentary
sequences in these lakes both are dominated by clastics with low
levels of organic materials. The location of these lakes and detailed
information about the sample collection are given in Fig. 1 and
Table 1. Lugu Lake, Dian Lake, Yangzonghai Lake and Yilong Lake in
southwestern China (Yunnan-Guizhou Plateau) are mainly
controlled by the Indian monsoon and show no significant aeolian
input (Fig. 1A and B). Qinghai Lake in western China (Tibetan
Plateau) is impacted by the Westerlies throughout the year and
where m is the number of grain-size intervals and GðXÞ is the
measured grain-size distribution of a sample (Xiao et al., 2009,
2012). The fitting process of each sample is accomplished until a
minimum fitting residual is yielded. Then, the modal size (median
size) and the relative percentage of each component are given. The
technical aspects of this procedure are described in detail by Qin
et al. (2005) and Xiao et al. (2012).
3. Results
3.1. Grain-size component decomposition of sediments from the
deep/central lake zone
The grain-size distributions of sediments from the deep/central
lake zone are composed of three to four unimodal components,
designated C1, C2, C3 and C4, from the finest to the coarsest modes,
respectively (Fig. 2). All analyzed grain-size distributions are
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
Y. Lu et al. / Quaternary International xxx (2017) 1e10
3
Fig. 1. Location of the study area. (A) Map showing location of the sampled lakes in southwestern, western and northern China and the main atmospheric circulation systems. CLP:
Chinese Loess Plateau; TP: Tibetan Plateau. (B) Magnification from rectangle B in Fig. 1A showing the location of four sampled lakes in southwestern China. The Indian monsoon is
the main atmospheric circulation system that controls the area. (C) Magnification from rectangle C in Fig. 1A showing the location of Qinghai Lake in western China. The area is
impacted by the Westerlies throughout the year. (D) Magnification from rectangle D in Fig. 1A showing the location of Angulinao Lake in northern China. During the winter half year,
the East Asian winter monsoon is the controlling climate system in this area. Hulun Lake, Daihai Lake and Dali Lake are the places referred in this study. Detailed sampling-related
information of the studied lakes are listed in Table 1.
characterized by a unimodal component (red dashed curves in
Fig. 2) that not only has a non-overlapping area with other adjacent
components > 12 but also has a percentage value > ~10%. The
modal size of these components occurs in the very fine silt size
range (4.4e7.5 mm, the average value is 5.9 mm), and observed
percentages vary between 75.92% and 90.52% (average value:
81.96%) (Fig. 2).
3.2. Grain-size component decomposition of sediments from the
shallow/transitional lake zone
The grain-size distributions of sediments from the shallow/
transitional lake zone are composed of three to five unimodal
components, C1, C2, C3, C4 and C5 (Fig. 3). In each sample, two
unimodal components (red dashed curves in Fig. 3) occur that have
a non-overlapping area with other adjacent components > 12 and
a percentage of > ~10%. The modal size of these components occurs
in (1) the clay to fine silt size range (2.3e12.4 mm, average value:
5.2 mm) for the finer component and (2) the fine silt to very fine
sand size range (11.9e77.4 mm, average value: 50.7 mm) for the
coarser component. Percentages for the finer and coarser components varies between 34.77% and 69.06% (average value: 54.58%)
and 13.50%e46.17% (average value: 28.29%), respectively. The
combined total percentage of the two components varies between
73.13% and 96.86% (average value: 82.85%).
3.3. Grain-size component decomposition of sediments from the
lakeshore
The grain-size distributions of lakeshore sediments are
composed of four unimodal components, C1, C2, C3 and C4 (Fig. 4).
Like the grain-size distributions of sediments from the shallow/
transitional lake zones, the grain-size distributions of the sediments from lakeshores also have two unimodal components (red
dashed curves in Fig. 4) that have a non-overlapping area with
other adjacent components of > 12 and a percentage of > ~10%.
The modal sizes of these components occur in (1) the very fine to
fine silt size range (5.3e10.8 mm, average value: 7.7 mm) for the finer
component and (2) the very fine to medium sand range
(68.3e301.3 mm, average value: 189.3 mm) for the coarser component. The percentages of the fine component vary between 16.78%
and 28.98% (average value: 21.63%), while percentages of the
coarser component vary between 58.83% and 77.01% (average
value: 68.45%). The combined total percentage of the two
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
4
Y. Lu et al. / Quaternary International xxx (2017) 1e10
Table 1
Locations and sampling-related information of the studied lakes.
Type
Lake
Hydrological information
Sample
name
Lake area: 48.5 km2, MWD: 93.5 m,
AWD: 40.3 m
Yilong Lake Lake area: 38.0 km2, MWD: 6.2 m,
AWD: 2.4 m
Qinghai Lake Lake area: 4340.0 km2, MWD: 27.0 m,
AWD: 17.9 m
Angulinao
Lake area: 31.7 km2, MWD: 30.0 m,
Lake
AWD: 19.5 m
Qinghai Lake
Modern deep/central lake sediments Lugu Lake
Ancient deep lake sediments
Modern shallow lake (transition
zone) sediments
Dian Lake
2
Lake area: 297.9 km , MWD: 5.9 m,
AWD: 2.9 m
Lugu Lake
Modern lakeshore sediments
Yangzonghai Lake area: 31.7 km2, MWD: 30.0 m,
AWD: 19.5 m
Lake
Angulinao
Lake
Qinghai Lake
Angulinao
Lake
Sample location
27.691320 N,
100.804959 E
YlL-1
23.67744 N,
102.5748 E
QhL-1, 2 36.811306 N,
100.137083 E
AglnL-1
41.316667 N,
114.35 E
QhL-3
36.661861 N,
100.389639 E
DL-1
24.768611 N,
102.664167 E
LgL-2
27.695944 N,
100.809250 E
YzL-1
24.90764 N,
103.01031 E
AglnL-2, 41.316667 N,
114.35 E
3, 4
QhL-4,
36.811306 N,
100.137083 E
5,6, 7,
AglnL-5, 6 41.316667 N,
114.35 E
LgL-1
Water depth Plots in
(m)
figure
Remark
38.4
2A
Sag pond
2.0
2B
2C, D
Top 2 cm of core
QH-1A
2E,
2F
Erlangjian deep
drilling
5.4
3B
35.1
3C
Sag pond
22.1
3A
Sag pond
3D, E, F
4A, B, C, D Erlangjian deep
drilling
4E, F
Note: MWD: max water depth, AWD: average water depth. Hydrological information about related lakes cited from Wang and Dou (1998).
Fig. 2. Grain-size component fitting and decomposition of sediments from the deep/central lake zone of various lakes. In Fig. 2AeF, the black-coloured curves represent the
measured grain-size distribution, the green-coloured curves represent the fitted grain-size distribution (above the black-coloured curves), and the dashed curves with different
colours represent the decomposed grain-size components. Modal size and percentage of each component and fitting residual of each sample are given. CM, component modal size.
(For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
components varies between 86.69% and 94.92% (average value:
90.08%).
3.4. Establishing a conceptual system for grain-size distribution
analyses using the log-normal distribution function fitting method
Based on the log-normal distribution function fitting method
(Qin et al., 2005), the notion of paleomagnetic demagnetization and
the concept of “Characteristic Remnant Magnetization” (Tauxe,
1998) from paleomagnetism have been used in this study to
establish a conceptual system for grain-size distribution analysis of
lacustrine clastics. The reasoning behind this argument is that both
concepts share the same aim, which is to extract the component(s)
that carries the main information. The conceptual analysis system
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
Y. Lu et al. / Quaternary International xxx (2017) 1e10
5
Fig. 3. Grain-size component fitting and decomposition of sediments from the shallow/transitional lake zone of various lakes. In Fig. 3AeF, the black-coloured curves represent the
measured grain-size distribution, the green-coloured curves represent the fitted grain-size distribution (above the black-coloured curves), and the dashed curves with different
colours represent the decomposed grain-size components. Modal size and percentage of each component and fitting residual of each sample are given. (For interpretation of the
references to colour in this figure legend, the reader is referred to the web version of this article.)
used in herein is composed of four components: (I) the Characteristic Grain Size Component (ChGSC), (II) the Affiliated Grain Size
Component (AfGSC), (III) the Meaningful Grain Size Component
(MeGSC), and (IV) the Combination Feature of Grain Size Components (CFGSC). Based on the statistical analysis of fitting results
from lacustrine clastics (Figs. 2e4), the conceptual analysis system
was defined and interpreted as below.
3.4.1. Characteristic Grain Size Component (ChGSC)
This component is characterized by a non-overlapping area with
other adjacent components of > 12 and a percentage >~10% (red
dashed curves in Figs. 2e4). Each grain-size distribution of a given
sediment must have at least one ChGSC. Our grain-size component
fitting and decomposition results suggest the total percentage of
ChGSC(s) in one grain-size distribution is generally >70%. Sedimentologically, this ChGSC indicates a particular sedimentary
environment with one dominant sedimentary process. If more than
one ChGSC is present, this indicates a sedimentary environment
that was dominated by different sedimentary processes. From the
highest to the lowest percentages of the ChGSCs in one sample,
they can be divided into the first ChGSC, the second ChGSC, the
third ChGSC, etc.
3.4.2. Affiliated Grain Size Component (AfGSC)
This component has a non-overlapping area with other adjacent
components between 0 and 13 (yellow dashed curves in
Figs. 2e4). Our grain-size component fitting and decomposition
results reveal the percentage of individual AfGSC varies between 1%
and 15%. The total percentage of AfGSC(s) in one grain-size distribution is generally <20%. Each grain-size distribution of a given
sediment can have one or more AfGSC(s) (e.g., Figs. 2F, 3A, 4E, 6CeF
and 7D). In some case, there is no AfGSC in one grain-size distribution (e.g., Figs. 2D, 3F and 6B). This parameter will improve fitting
accuracy of the percentage of the ChGSC.
3.4.3. Meaningful Grain Size Component (MeGSC)
This component has a non-overlapping area with other adjacent
components between 13 and 12 or a non-overlapping area with
other adjacent components > 12 but a percentage that is <~10%
(blue dashed curves in Figs. 2e4). The percentage of individual
MeGSC varies between 1% and <20%. The total percentage of
MeGSC(s) in one grain-size distribution is generally < 20%. Like the
AfGSC, each grain-size distribution of a given sediment can have
one or more MeGSC(s) (e.g., Figs. 2D, 3F, 6B and 7E), or no MeGSC
(e.g., Figs. 2F, 3A, 4E, 6A and 7B). This parameter does not reflect the
dominant sedimentary processes but may indicate some sedimentary processes that are related to either a special transport
medium or a change in the dynamic conditions of the respective
transport medium. Its sedimentology meaning still needs to further
explore.
3.4.4. Combination feature of grain size components (CFGSCs)
The CFGSCs is mainly depicted by the number, modal size and
percentage of the ChGSC(s) in a grain-size distribution. For
example, only one ChGSC in each grain-size distribution of sediments from the deep/central lake zone (Fig. 2). The combination
feature makes the grain-size distribution of sediments from the
deep/central lake zone are different with sediments from the
shallow/transitional lake zone and lakeshore. Grain-size distributions in the latter two types of sediments have more ChGSC(s),
which with different modal size and percentage. CFGSCs indicates a
particular sedimentary environment with dominant sedimentary
process (es), and superimposed by some minor processes.
We choose the brackets for the components just based on our
grain-size component fitting and decomposition of ~1100 samples.
The value of the “non-overlapping area with other adjacent
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
6
Y. Lu et al. / Quaternary International xxx (2017) 1e10
Fig. 4. Grain-size component fitting and decomposition of lakeshore sediments from various lakes. In Fig. 4AeF, the black-coloured curves represent the measured grain-size
distribution, the green-coloured curves represent the fitted grain-size distribution (above the black-coloured curves), and the dashed curves with different colours represent
the decomposed grain-size components. Modal size and percentage of each component and fitting residual of each sample are given. (For interpretation of the references to colour
in this figure legend, the reader is referred to the web version of this article.)
components” was used to define how one component stands out
from the rest. One component that stands out from the rest (i.e.,
having a non-overlapping area with other adjacent components of
> 12), indicates one specific sedimentary process. The percentage
of one component used to evaluate the relative importance of it.
The quantitative definitions of the three components, e.g., ChGSC is
characterized by a non-overlapping area with other adjacent
components of > 12 and a percentage >~10%, are based on our
subjective experience. Thus, it is an open system that might need a
slight adjustment under certain boundary conditions.
4. Discussion
4.1. Sedimentary implications of Characteristic Grain Size
Component (ChGSC)
The grain-size distributions of sediments from the deep/central
lake zone are characterized by one ChGSC with an average percentage up to ~82% and a modal size in the very fine silt range
(Fig. 2). This observation accords with the fact that sediments in the
deep/central lake zone are mainly composed of offshore suspension
particles (clay to fine silt). Because of the depositional processes in
these areas, sediments are deposited under relatively still lake
water and weak hydrodynamic conditions.
In sediments from the shallow/transitional lake zone, each
grain-size distribution shows two ChGSCs. One ChGSC has a modal
size that is comparable to the ChGSC in sediments from the deep/
central lake zone. The other is much coarser and characterized by a
modal size in the fine silt to very fine sand range (Fig. 3). These
results are consistent with the fact that the shallow/transitional
lake zone receives much more sediment from transporting media
near the lake margin, such as rivers.
The grain-size distribution of lakeshore sediments also shows
two ChGSCs. However, the coarser ChGSC has a much higher percentage than the finer ChGSC and is generally much coarser than
the ChGSCs of sediments from other lake zones (Fig. 4). These results accurately reflect depositional processes at the lakeshore that
are dominated by fluvial transport and lake waves. This strong
hydrodynamic regime leads to the deposition of a small amount of
fine silt that is combined with a larger amount of sand particles
(Schieber et al., 2007).
Overall, the similar results of our conceptual analysis system
show that the investigated lacustrine deposits have inherent and
stable grain-size distribution features for a variety of modern lakes
with different sediment sources and different climatic regimes (i.e.,
the westerlies, Indian monsoon, East Asian monsoon) (Fig. 1A).
Moreover, the above mentioned observations suggest that the
ChGSC(s) of sediments from different lake zones closely mirror the
dominant depositional processes and hydrodynamic conditions.
Our new grain-size fitting results as well as previous studies of
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
Y. Lu et al. / Quaternary International xxx (2017) 1e10
lacustrine clastics from Hulun Lake (Xiao et al., 2012), Daihai Lake
(Xiao et al., 2013) and Dali Lake (Xiao et al., 2015) in northern China
indicate that sediments along a transect from the lakeshore to the
lake centre are characterized by a decrease in the percentage of
their coarser ChGSCs that corresponds to an increase in the percentages of their finer ChGSCs. Therefore, the number, modal size,
and percentage of ChGSC(s) in grain-size distributions of lake
sediments can be used to obtain paleoenvironmental information.
4.2. Application of Characteristic Grain Size Component (ChGSC)
To test the promising application of ChGSC based on the conceptual grain-size distribution analysis system, we applied it to a
clastics dominated sedimentary sequences in a huge lake, paleoQaidam Lake. The lake was located in the western Qaidam Basin,
northeastern Tibetan Plateau (Fig. 1A), developed during the late
Oligocene-Quaternary (Yang, 1986; Zhang et al., 1987; Wu and Xue,
1993; Wang et al., 2012). A ~723 m-deep drill core SG-1b (as part of
a joint Sino-German project) was recovered in the paleo-Qaidam
Lake with an average sediment recovery rate of ~93% (Zhang
et al., 2014; Lu et al., 2015). Detailed paleomagnetic dating of
Core SG-1b constrains its age at ~7.3e1.6 Ma (Zhang et al., 2014).
Previous detailed examination of lithofacies, seismostratigraphy
and grain-size records, suggest that the drilling site was in a deep to
semi-deep lake environment during ~7.3e3.6 Ma (~723-245 m), in
a shallow lake environment during ~3.6e1.9 Ma (245-35 m), and
finally in a lakeshore-like environment during ~1.9e1.6 Ma (350 m) (Lu et al., 2015). The millimeter-to centimeter-scale thin
interbedded marl and limestone layers are mainly deposited in the
core with depth <600 m, gypsum crystals frequently occurrenced
in the core with depth <250 m (Zhang et al., 2014). Detailed mineral
composition study (Fang et al., 2016) reveals the very low content of
halite, gypsum, celestite, calcite and aragonite in the lower part of
the core (with core depth >600 m). Thereby, in this study, we chose
the lower 100 m of the Core SG-1b (720-620 m) to apply the
concept of ChGSC based on the conceptual analysis system. Paleomagnetic dating constrains the age of the investigated core interval
to be between ~7.3e6.8 Ma (Zhang et al., 2014). Lithofacies of the
investigated interval comprise fine siltstones with horizontal
millimeter-scale laminae (Fig. 5), suggesting that the sediments
were deposited in a deep to semi-deep lake environment (Lu et al.,
2015).
Within the investigated core interval, our fitting and decomposition experiment reveals fitting residuals that are in the range of
~2.74e1.18% (average value: ~1.76%), suggesting a very good fitting
process. The grain-size distribution of each sample is composed of
three to five unimodal components, designated C1, C2, C3, C4 and C5,
from the finest to the coarsest modes, respectively. In the grain-size
distributions of 95 analyzed samples, 90 samples (94.7%) are
7
characterized by one ChGSC and five samples (5.3%) are characterized by two ChGSCs. Fig. 6 shows representative grain-size distributions of the 90 samples. In these samples, observed
percentages of ChGSC vary between ~62.08% and 96.02%, with an
average value at ~79.46%. Modal size of these ChGSCs vary between
~5.01 mm and 19.0 mm, with an average value of ~9.1 mm.
One may note that the average value in modal size of ChGSC in
the Core SG-1b (~9 mm) is slightly larger than in the investigated
sediments from the deep/central lake zone in the modern lakes
(very fine silt, < 8 mm). This difference should mainly result from
different instruments that used for grain-size measurement. The
sediments from the deep/central lake zone in the modern lakes are
measured by Malvern Mastersizer (2000) laser particle sizer, while
sediments from Core SG-1b are measured by Microtrac S3500 laser
particle sizer. Mudstone (late Miocene lacustrine deposits) were
collected from one drill core located in the Nanyishan anticline,
western Qaidam Basin, northeastern Tibetan Plateau. Twenty parallel samples were pre-treated in the Institute of Tibetan Plateau
Research, Chinese Academy of Sciences. Subsequently, they were
measured at the Institute of Tibetan Plateau Research using a
Microtrac S3500 laser particle sizer and in the Key Laboratory of
Western China's Environmental Systems, Lanzhou University with
a Malvern Mastersizer 2000 laser particle sizer, respectively in
2012. The parallel experiments reveal the Microtrac S3500 laser
particle sizer with lower sensitivity to clay and very fine silt particles than the Malvern Mastersizer 2000 laser particle sizer. The
differences in mean grain-size measured by the two different instruments are varying between 0 and 5 mm. Thus, the average value
in percentage (~79.5%) and modal size (~9 mm) of ChGSC in the Core
SG-1b are identical to the investigated sediments from the deep/
central lake zone in the modern lakes (~82.0% and ~6 mm).
The five samples which characterized by two ChGSCs are also
shown (Fig. 7). Grain-size distribution of these samples are similar
with investigated sediments from the shallow/transitional lake
zone. Among the five samples, grain-size distribution of four
samples have one coarse ChGSC (Fig. 7BeE). Percentage of the
coarse ChGSC are in the range of ~8%e10%. Thus, these samples
were inferred to be mass movement deposits.
These fitting and decomposition results of Core SG-1b suggest
that the sediments in the investigated core interval are mainly
composed of offshore suspension particles (clay to fine silt) and
have been deposited under relatively still lake water and weak
hydrodynamic conditions. These quantitative characteristics suggest deposition in a deep to semi-deep lake environment, which is
in agreement with the qualitative observations of the respective
lithofacies (Lu et al., 2015).
If compared to the mean grain-size, the modal size of the ChGSC
in the investigated core interval shows a strikingly similar trend
(Fig. 8). However, the observed variations in the modal size of
Fig. 5. Lithofacies of the investigated section in Core SG-1b. The core interval is characterized by gray to dark-gray fine siltstones with horizontal millimeter-scale laminae (Lu et al.,
2015).
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
8
Y. Lu et al. / Quaternary International xxx (2017) 1e10
Fig. 6. Representative grain-size distributions of sediments from the lower part of Core SG-1b. The black-coloured curves represent the measured grain-size distribution, the greencoloured curves represent the fitted grain-size distribution (above the black-coloured curves), and the dashed curves with different colours represent the decomposed grain-size
components. Modal size and percentage of each component and fitting residual of each sample are given. These grain-size distributions are both characterized by one ChGSC. (For
interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 7. Grain-size distributions of sediments that inferred to be mass movement deposits in the Core SG-1b. The black-coloured curves represent the measured grain-size distribution, the green-coloured curves represent the fitted grain-size distribution (above the black-coloured curves), and the dashed curves with different colours represent the
decomposed grain-size components. Modal size and percentage of each component and fitting residual of each sample are given. These grain-size distributions are both characterized by two ChGSCs. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Please cite this article in press as: Lu, Y., et al., Characteristic grain-size component - A useful process-related parameter for grain-size analysis of
lacustrine clastics?, Quaternary International (2017), http://dx.doi.org/10.1016/j.quaint.2017.07.027
Y. Lu et al. / Quaternary International xxx (2017) 1e10
9
Fig. 8. Grain-size component fitting and decomposition of sediments in Core SG-1b. (A) Comparison the modal size of ChGSC(s) with the mean grain-size (from Lu et al., 2015). (B)
Percentage of ChGSC in the measured samples. (C) Fitting residual of each sample.
ChGSC show relatively high amplitude variations compared to the
mean grain-size (Fig. 8). This observation suggests that the modal
size of ChGSC is more sensitive to fluctuations in the hydrological
conditions than the mean grain-size; this inference is reasonable
because the mean grain-size represents mixed information, while
the modal size of ChGSC reflects only information of the dominant
depositional process.
Overall, the conceptual grain-size distribution analysis system
that is established herein will greatly improve and promote the
application of the log-normal distribution function fitting method
in grain-size distribution analysis of lacustrine clastics by extracting
significant sedimentological processes from a set of sediments
deposited in different lake environments.
5. Conclusions
A conceptual system for grain-size distribution analysis of
lacustrine clastics has been established and defined based on the
log-normal distribution function fitting method. The system is
composed of four components: (I) Characteristic Grain Size
Component (ChGSC), (II) Affiliated Grain Size Component (AfGSC),
(III) Meaningful Grain Size Component (MeGSC), and (IV) the
Combination Feature of Grain Size Components (CFGSC).
Our data from modern lakes and a drill core show that the
investigated lacustrine clastics from different lake environments
are characterized by their inherent and stable grain-size distribution features. Furthermore, the ChGSC(s) of sediments from
different lake zones are suggested to mirror the dominant depositional processes and hydrodynamic conditions. Therefore, the
modal size of ChGSC is more sensitive to hydrological conditions
than the widely used mean grain-size approach. The ChGSC(s)
provide(s) a useful process-related parameter that can be applied in
paleoenvironmental reconstructions.
Acknowledgements
This study was co-supported by the (973) National Basic
Research Program of China (2013CB956400), the Strategic Priority
Research Program of the Chinese Academy of Sciences (Grant No.
XDB03020400) and the Priority Programme 1372 ‘Tibetan Plateau:
Formation, Climate, Ecosystems (TiP)’ of the German Research
Foundation (DFG; Grant No. AP34/34-1,2,3). We thank Yougui Song,
Hucai Zhang and Zhiqiang Yin for providing some grain-size data.
We thank Qiong Li (Lanzhou University) for grain-size measuring.
Special thanks to Prof. Jule Xiao for providing the log-normal distribution function fitting software and Prof. Erwin Appel for supporting Y.L.’s research at the Univ. of Tübingen, Germany, during the
year of 2013e2014. We thank Philip L. Gibbard (University of
Cambridge), Ge Yu and one anonymous reviewer for their
constructive comments, which improved the quality of the manuscript substantially.
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