Sediment sources and their contribution along nort

Continental Shelf Research 47 (2012) 156–164
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Continental Shelf Research
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Research papers
Sediment sources and their contribution along northern coast of the South
China Sea: Evidence from clay minerals of surface sediments
Jianguo Liu, Wen Yan n, Zhong Chen, Jun Lu
Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 4 August 2011
Received in revised form
28 May 2012
Accepted 20 July 2012
Available online 31 July 2012
Clay minerals of surface sediment samples from nine bays/harbors along northern coast of the South
China Sea (SCS) are used for sediment sources and contribution estimation in the study areas. Results
reveal that sediments in the study bays/harbors seem to be a mixture of sediments from the Pearl,
Hanjiang River and local islands/rivers, but their clay mineral assemblage is distinct from that of Luzon
and Taiwan sediments, indicating that sediments are derived mainly from the neighboring sources
through riverine input and partly from localized sediments. Due to input of local sediments in the
northern SCS, sediments from both east of the Leizhou Peninsula (Area IV) and next to the Pearl River
estuary (PRE, Area II) have high smectite percent. Affected by riverine input of the Pearl and Hanjiang
Rivers, sediments in west of the PRE (Area III) and east of the PRE (Area I) have high illite (average 47%)
and kaolinite (54%) percents, respectively. Sediment contributions of various major sources to the study
areas are estimated as the following: (1) the Hanjiang River provide 95% and 84% sediments in Areas
I and II, respectively, (2) the Pearl River supply 79% and 29% sediments in Areas III and IV, respectively
and (3) local sediments contribute the rest and reach the maximum ( 71%) in Area IV.
& 2012 Elsevier Ltd. All rights reserved.
Keywords:
Sediment sources
Contribution estimation
Surface sediments
Clay minerals
Bays/harbors
South China Sea
1. Introduction
The northern South China Sea (SCS) annually receives terrigenous sediments from major rivers, the Red River (sediment load of
130 million tons, Mt) to the northwest, Pearl River (69 Mt) to the
north, Taiwanese rivers (187.5 Mt) to the northeast and some
rivers on Luzon Islands ( 48.2 Mt) to the east (Milliman and
Syvitski, 1992; Z. F. Liu et al., 2010). Surface current in the SCS is
driven by southwester winds in summer and northeaster winds in
winter (Fang et al., 1998). In deep water of the northeastern SCS,
sediments from Taiwan and Luzon islands were transported into
sea and accumulate as drift deposition on the continental slope,
¨
probably related to deep water current intrusion (Ludmann
et al.,
2005; Shao et al., 2007). Based on the records of clay minerals,
grain size and mass accumulation rate of terrigenous materials
from the northern SCS slope sites, Wan et al. (2010) found that
increasing terrigenous supply from Taiwan was related to deepwater current. Z. F. Liu et al. (2010) revealed source and transport
of detrital sediments from the northeastern SCS, considering the
impact of the Guangdong coastal current, deep water current, and
Kuroshio Current intrusion. Recently, J. G. Liu et al. (2011) further
discussed the inﬂuence of Kuroshio Current intrusion on depositional environment based on multi-proxies of surface sediments
from the northern SCS. Moreover, Liu et al. (2009) concluded that
n
Corresponding author. Tel.: þ86 20 89023150; fax: þ 86 20 84451672.
E-mail address: [email protected] (W. Yan).
0278-4343/$ - see front matter & 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.csr.2012.07.013
sediments from the Pearl River were partly transported alongshore while the major sediments from the Pearl River were
trapped inside the estuary. However, we do not yet know how
sediments from South China through river runoff are transported
and distributed along coast of the northern SCS.
Certain clay mineral parameter (e.g. illite crystallinity) was
utilized to semi-quantitatively evaluate contribution of various
sources (including Taiwan, Luzon and Pearl River) from the land
in the northeastern SCS (Z. F. Liu et al., 2008). In the Okinawa
Trough, contribution of various sources is estimated using three
extrapolated equations of four clay minerals in three end members (Dou et al., 2010). Along the northern SCS coast, annual
sediment discharge of the Hanjiang and Jianjiang Rivers is 7.6 and
2.0 Mt, respectively (Zhao et al., 1999). These small rivers,
together with the Pearl River, collectively transfer 80 Mt sediments annually to the coastal oceans. In addition, these rivers can
also signiﬁcantly affect sedimentary process on the continental
shelf and slope environments due to a narrower and steeper shelf
than those next to Luzon Island and Red River, especially during
the last glacial maximum when sea level was 120 m below the
present (Liu et al., 2004; J.P. Liu et al., 2007). In Hanjiang River
delta, clay minerals of the Quaternary sediments were mainly
controlled by the variations of sedimentary environments correlated with interchanges of sea and land (Wang and Zheng, 1990).
As river-derived sediments input to ocean play a key role in
inshore and offshore environmental change (Bianchi and Allison,
2009), how they are distributed and contributed in these environments become an important question. Nowadays, with the
J. Liu et al. / Continental Shelf Research 47 (2012) 156–164
development of agricultural and industrial activities along northern-most coast of the SCS, the estuaries and bays are intensively
affected by anthropogenic activities (Morton and Blackmore,
2001; Y. Liu et al., 2011). Since 1980s rapid expansions of
urbanization, aquaculture and industry have resulted in environmental deterioration, such as water quality degradation (Wu
et al., 2009; Zhang et al., 2010), organic contaminants increasing
(Yan et al., 2009; Bottcher et al., 2010), and episodes of harmful
algal blooms (Yu et al., 2007; Song et al., 2009) in some bays of
the northern SCS. So we should ﬁrstly understand distribution of
various sediment sources along northern coast of the SCS in order
to provide reference for further environmental management in
the study areas.
This paper reports clay mineralogical data of surface sediments in nine bays/harbors along the northern-most part of SCS,
all located in the coast of Guangdong Province, South China
(Fig. 1). The aims of this study are (1) to investigate the spatial
variations of clay minerals in surface sediments, (2) to identify the
dominant sediment sources using clay mineralogy, and (3) to
estimate sediment contribution in the study areas considering
sediment provision of the Pearl and Hanjiang River and local
islands/rivers.
2. Materials and methods
A total of 119 surface sediments along northern-most coast of
the SCS (Fig. 1) were collected using a box sampler in autumn
2008 during a cruise of Guangdong Province 908 Special Project
on Investigation and Research of Water Environment. Based on
sample spatial distribution, our study region was divided into
four areas (Fig. 1): east of the Pearl River Estuary (PRE) (Area I,
including Zhelin Bay and Shantou Harbor), next to the PRE (Area
II, including Shanwei Harbor, Daya Bay and Dapeng Bay), west of
the PRE (Area III, including Hailing Bay and Shuidong Harbor) and
east of the Leizhou Peninsula (Area IV, including Zhanjiang Harbor
and Leizhou Bay). Sediment types vary greatly in nine bays/
harbors, silt and clayey silt dominated in the Zhelin Bay, Shanwei
Harbor and Hailing Bay, but silty sand and sand dominated in the
Zhanjiang Harbor and Leizhou Bay (unpublished data).
Clay minerals ( o2 mm) were separated according to Stoke’s
settling velocity principle after removing carbonate and organic
matter with 10% H2O2 and 0.5 N HCl, respectively (Wan et al.,
2006). Clay mineralogy determinations were performed by standard X-ray diffraction (XRD) on a D8 ADVANCE diffractometer
with CuKa radiation (40 kV, 25 mA) in the Key Laboratory of
Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences. Identiﬁcation of clay minerals was
made mainly using the position of the (001) series of basal
reﬂections on the XRD diagram of ethylene glycol salvation.
Mixed-layers mainly of smectite–illite in the northern SCS were
included in ‘‘smectite’’ and mixed-layers mainly of chlorite–illite
with very minor abundance were not calculated referred as Z. F.
Liu et al. (2010). Relative percentages of the four main clay
mineral groups were estimated by weighting integrated peak
˚
areas of characteristic basal reﬂections (smectite—17 A,
˚ and kaolinite/chlorite—7 A)
˚ in the glycolated state
illite—10 A,
using the Topas 2P software with the empirical factors from
Biscaye (1965). Relative proportions of kaolinite and chlorite were
˚
determined using the ratio of 3.57 A/3.54
A˚ peak areas.
˚
The illite chemistry index is inferred from the ratio of 5 A/10
A˚
peak areas on the XRD diagrams of the ethylene glycol salvation
condition. The measurement of illite crystallinity is made by
computing the integrated breadth of the glycolated 10 A˚ peak.
More details of methods can be found in Wan et al. (2010) and
J. G. Liu et al. (2011). Data of Taiwan, Luzon and Pearl River are
157
recalculated from Z. F. Liu et al. (2010), while data of Hanjiang
River from Boulay et al. (2005).
Hierarchical cluster analysis was performed using the Statistical Product and Service Solutions (SPSS) software to test
whether the differences between various sources are statistically
signiﬁcant. The percentages of four clay minerals (smectite, illite,
kaolinite and chlorite) from 119 samples were used for cluster
analysis.
3. Results
Clay mineral assemblage of 119 surface sediments from the
study areas mainly consists of kaolinite (average 46%) and illite
(41%), with lesser amount of smectite (10%) and scarce chlorite
(3%). Average illite chemistry index and illite crystallinity were
0.381 and 0.321D2y, respectively. Clay mineral assemblage in nine
bays/harbors is different for surface sediments along the northern
SCS coast. Smectite percent is obviously high in the Leizhou Bay
(average 21%), Dapeng and Daya Bays (18%), but low in the
Shantou Harbor ( 3%). Illite percent in the Hailing Bay is the
highest (average 50%), while illite percent in the Leizhou Bay is
the lowest (33%) among nine bays/harbors. Kaolinite percent is
the highest in the Shantou Harbor (average 56%) but low in the
Daya Bay ( 39%) and Dapeng Bay ( 40%).
For sediments from east of the PRE (Area I), smectite and illite
percents are relatively high ( 46% and 440% respectively) in the
eastern and southern Zhelin Bay, but low ( o2% and o35%
respectively) in the western Shantou Harbor and the western
Zhelin Bay (Fig. 2 and Table 1). However, kaolinite percent in the
western Shantou Harbor and western Zhelin Bay is the highest
( 460%), but low ( o50%) in the southern and eastern Zhelin Bay
and northeastern Shantou Harbor. Illite chemistry index is high
(average 0.46) in the southern Shantou Harbor, but low (0.30) in
the northern Shantou Harbor.
Next to the PRE (Area II), smectite percent in the Daya and
Dapeng Bays (average 18%) is clearly higher than that in the
Shanwei Harbor (8%) (Fig. 3). Illite percent in the Shanwei Harbor
and southeastern Daya and Dapeng Bays is high ( 441%), but low
( o38%) in the northwestern Daya and Dapeng Bays. Illite crystallinity is higher in the Daya and Dapeng Bay (average 0.331D2y)
than that in the Shanwei Harbor (0.301D2y).
For west of the PRE (Area III), illite percent increases from
44% in the southwestern Shuidong Harbor, 47% in the northeastern Shuidong Harbor, to 50% in the Hailling Bay (Fig. 4).
Contrarily, kaolinite and smectite percents northeastward decrease from 47% and 7% in the southwestern Shuidong Harbor,
42% and 6% in the northeastern Shuidong Harbor, to 41% and 4%
in the Hailing Bay, respectively. Illite crystallinity in the Shuidong Harbor (0.361D2y) is higher than that in the Hailing Bay
(0.341D2y).
For surface samples at east of the Leizhou Peninsula (Area IV),
smectite percent in the Leizhou Bay (average 21%) is obviously
higher than that in the Zhanjiang Harbor ( 8%) (Fig. 5). Kaolinite
percent in the Zhanjiang Harbor sediments (52%) is apparently
higher than that in the Leizhou Bay sediments (43%).
4. Discussion
4.1. Sediment provenance
Sediments in the northern SCS are mainly ﬂuvial input from
both the South China loaded by the large Pearl River, and Taiwan
and Luzon Islands via small mountainous rivers (e.g. Kaoping
River) on them (Wan et al., 2007; Z. F. Liu et al., 2010; Liu et al.,
158
J. Liu et al. / Continental Shelf Research 47 (2012) 156–164
Fig. 1. Locations of study areas and surface sediment samples along the coast of Guangdong Province. Pink, green, orange and purple lines with arrow represent
Guangdong summer coastal current (GDSCC), Guangdong winter coastal current (GDWCC, after Fang et al., 1998), South China Sea warm current (SCSWC) and South China
Sea Branch of Kuroshio (SCSBK, after J. G. Liu et al., 2011), respectively. Areas I, II, III and IV correspond to east of the Pearl River estuary (PRE), next to the PRE, west of the
PRE and east of the Leizhou Peninsula, respectively. Dashed black dividing lines in four areas denote delimit among different bays/harbors. Pink stars and N below them
refer to sample locations and numbers of the corresponding rivers. (For interpretation of the references to color in this ﬁgure legend, the reader is referred to the web
version of this article.)
J. Liu et al. / Continental Shelf Research 47 (2012) 156–164
159
Fig. 2. Distribution of clay mineral parameters in surface sediments from east of the PRE (Area I): (a) smectite, unit: %, (b) illite, unit: %, (c) kaolinite, unit: %, (d) chlorite,
unit: %, (e) illite chemistry index, and (f) illite crystallinity (1D2y).
2010a,b). The Luzon sediments related with weathering of volcanic materials are typically characterized by high smectite percent
(average 46%). Strong physical weathering and moderate chemical weathering (Selvaraj and Chen, 2006) may explain the reason
of high illite (69%) and chlorite (30%) percents for the Taiwansourced sediments (Table 1) 30% 10 bays/harbors in the study
region. Because of intensive chemical weathering of rocks by
warm and humid climate in the South China, sediments
160
J. Liu et al. / Continental Shelf Research 47 (2012) 156–164
from the Pearl River are characterized by high kaolinite percent
(Z. F. Liu et al., 2007). Sediments from the Hanjiang River are
characterized by high kaolinite percent (69%) but nearly no
smectite (Boulay et al., 2005).
Previous studies revealed that the westward branches of the
North Paciﬁc deep water and the Kuroshio Current in the western
Paciﬁc crossing the Luzon Strait might transport the Taiwan- and
Luzon-sourced sediments to the northern SCS slope and even
¨
shelf environments (Ludmann
et al., 2005; Shao et al., 2007; Wan
et al., 2010; J. G. Liu et al., 2011). On the shelf of the northern SCS,
however, there is a current named the South China Sea warm
current (SCSWC) that ﬂows northeastward from offshore area in
the east of the Hainan Island and ﬁnally enters the East China Sea
Table 1
Clay mineral assemblages of surface sediments from various areas along coast of
the northern South China Sea.
Source
Smectite (%)
Illite (%)
Kaolinite (%)
Chlorite (%)
Area I
Area II
Area III
Area IV
Luzon
Taiwan
Leizhou Peninsula
Hanjiang
Pearl River
4(4)
15(8)
5(3)
14(9)
76
2
25
0
1
39(7)
41(7)
47(5)
35(4)
3
70
32
27
52
54(10)
41(7)
43(5)
48(8)
9
3
41
69
39
3(2)
4(2)
5(3)
3(3)
12
25
2
4
8
Note: Numbers in bracket refer to standard deviations.
throughout the Taiwan Strait (Guan and Fang, 2006; Wang et al.,
2010). This current might prevent the Luzon-sourced sediments
from further transporting and then depositing into the study
areas. Clay mineral assemblage of sediment in nine bays/harbors
along the northern SCS coast is distinct from that of Luzon
sediments, and long distance between the study areas Luzon
Island also indicates that sediments in the study areas is not likely
derived from Luzon. Meanwhile in the Qiongzhou Strait, current
ﬂows westward in most of months, and slowly ﬂows eastward
only in June and July when the southwest monsoon wind prevails
(Ke, 1986; Shi et al., 2002). Current investigation further revealed
that the Qiongzhou Strait was main pathway of sediments and
seawater transport from the SCS to the Beibu Gulf (Li and Ke,
2000; Chen et al., 2009). Clay mineralogy of surface sediments
already revealed that the northeastern SCS is less affected by the
Red River sediments (Z. F. Liu et al., 2008, 2010). Therefore, the
Red River sediments discharged into the Beibu Gulf is not
considered to be signiﬁcant sediment sources in the study areas.
Recent study on sediments from inner shelf of the East China Sea
further revealed that Yangtze River-derived clays were characterized by low smectite percent, but very limited sediments
appeared to reach the northern SCS throughout the Taiwan Strait
(Xu et al., 2009). To sum up, sediment sources of Luzon, Red and
Yangtze Rivers are minor in the study areas.
The Pearl River drains through the South China where the west
is dominated by Paleozoic–Mesozoic carbonate rocks and the east
mainly consists of Mesozoic–Cenozoic granitic rocks and Plaeozoic sedimentary rocks (limestone, shale and sandstone, Z. F. Liu
et al., 2007). Affected by the Guangdong Coastal Current and
Fig. 3. Distribution of clay mineral parameters in surface sediments next to the PRE (Area II): (a) smectite, unit: %, (b) illite, unit: %, (c) kaolinite, unit: %, (d) chlorite,
unit: %, (e) illite chemistry index, and (f) illite crystallinity (1D2y).
J. Liu et al. / Continental Shelf Research 47 (2012) 156–164
161
Fig. 4. Distribution of clay mineral parameters in surface sediments from west of the PRE (Area III): (a) smectite, unit: %, (b) illite, unit: %, (c) kaolinite, unit: %, (d) chlorite,
unit: %, (e) illite chemistry index, and (f) illite crystallinity (1D2y).
longshore current (Z. F. Liu et al., 2010), sediments from the Pearl
River are mostly transported southwestward to be distributed in
sea between the Pearl River mouth and southeast of Hainan
Island, but hardly enters the abyssal basin (J. G. Liu et al., 2011).
During the transport process from low drainage basin to river
mouth, clay mineral assemblage of sediments from the Pearl River
changes less (Z. F. Liu et al., 2007). Clay mineral assemblage of
sediments in four areas ﬂuctuates around that of the Pearl River
sediment (Fig. 6), indicating that the Pearl River sediment is a
signiﬁcant source in the study areas.
Under the nearly identical latitude (20–241N) with a low-relief
and stable morphology, the study bays/harbors experiences warm
and humid climate conditions with alike geological background,
probably contributed to the intensive weathering process there.
Cluster analysis reveals that sediments in four areas is related with
provision of different sources. To the west of the Pearl River mouth,
Area III is dominated with sediments from the Pearl River, and Area
IV approaches sediments from the Leizhou Peninsula. Annual 2
million tons of sediments loaded by the Jianjiang River mostly
deposits in estuaries and the delta-front, and their transport near
estuaries is largely subjected to tidal current and wave (Ye and
Huang, 1994). Close to the Jianjiang River, clay mineral assemblage
in Zhanjiang Harbor is characterized by high kaolinite percent but
low smectite percent. However, clay mineral assemblage in Leizhou Bay is characterized by high smectite percent but low kaolinite
percent. These indicate that sediments from Leizhou Peninsula or
localized weathering of volcanic materials instead of the Jianjiang
River are primary source for smectite in the study area.
To the east of the Pearl River mouth, clay mineral assemblage
of sediments in Area I approaches that of sediments from the
Hanjiang River, and sediments in Area II seem to be a mixture of
sediments from Pearl River, Hanjiang River and local source.
If sediments along the coast of South China are conﬁrmed to be
transported southwestward, how can we explain reversal directions for smectite distribution in the east and west of Pearl River
mouth (Figs. 2–5), where smectite percent increased southwestward in the west but decreased northeastward in the east?
Therefore, here we assume that localized process resulting in high
smectite percent is activated and cannot be neglected in Area II.
4.2. Contribution estimation
In this paper, we estimate sediment contribution of various
sources through the method named minimum error between the
estimating and real values. Firstly, various sediment sources and
their compositions (Xij, i sample¼1, 2,y,n, j parameter¼1, 2, y, m)
are assigned in the study areas. Here sediment sources in nine bays/
harbors include the Pearl River, Hanjiang River, localized materials
(e.g. Leizhou Peninsula), Taiwan and Luzon islands. Secondly, the
preliminary coefﬁcients of each source (oi, i¼1, 2,y,n, Soi¼1) are
designated. Thirdly, estimating values (Xijoi, i¼1, 2,y,n, j¼1,
2,y,m) are acquired together with the corresponding real values
(Yj, i¼1, 2,y,m). Finally, the coefﬁcients are continuously adjusted
until the error between the estimating and real values
(Z¼ S X ij oiYj, i¼1, 2,y,n, j¼1, 2,y,m) reaches the minimum.
Sediments in east of the PRE (Area I) may be mixed with
sediments derived from the Hanjiang River and local islands/
rivers. Remote sensing analysis revealed that the suspended
sediments outside of the Hanjiang River estuary were transported
along the boundary affected by the southwestward current (Ding
and Xu, 2007). Using the above method, sediment contribution of
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J. Liu et al. / Continental Shelf Research 47 (2012) 156–164
Fig. 5. Distribution of clay mineral parameters in surface sediments from east of the Leizhou Peninsula (Area IV): (a) smectite, unit: %, (b) illite, unit: %, (c) kaolinite,
unit: %, (d) chlorite, unit: %, (e) illite chemistry index, and (f) illite crystallinity (1D2y).
the Hanjiang River is estimated to be 95%, while local sediments
only contribute 5% for surface sediments in this area.
The Hanjiang River contributes 84% sediments next to the PRE
(Area II), while the rest is provided by local sediments. Although
no major rivers discharge into the Daya Bay, but there are three
small rivers that discharge into the Dapeng Bay (Han, 1995).
Because most of water in the Daya Bay originates from the SCS,
water from the neighboring PRE affects the Daya Bay during the
ﬂood seasons (Yu et al., 2010). Local sediments characterized by
relatively high smectite percent (18%) in Daya and Dapeng Bays
might be partly transported northeastward driven by the southwest wind in summer (Fang et al., 1998) and then deposited in
the study area (Yan et al., 2009; Yu et al., 2010).
In west of the PRE (Area III), sediments from the Pearl River
contribute 79% while local sediments supply the rest. However, in
east of the Leizhou Peninsula (Area IV), only 29% sediments are
derived from the Pearl River, and local sediments contribute
71%. High-resolution Chirp sonar proﬁles indicated that the
majority of sediments from the Pearl River were trapped inside
the PRE, and that sediments escaped to the shelf had not yet
formed a large remote nearshore depocenter (Liu et al., 2009). 3-D
suspended sediment transport model also simulated that suspended sediments discharged from riverine gates of the PRE were
southwestward transported by coastal ﬂows (Ying, 1999; Chen
and Chen, 2008). The synthetic analysis results on tract data of
drifting bottles and Acoustic Doppler Current Proﬁlers (ADCP) in
the west coast of Guangdong Province showed that the coastal
currents in the west of the Pearl River mouth ﬂowed mainly
southwestward in summer during 1964–1972 (Yang et al., 2003).
Clay mineral, element and magnetic susceptibility in surface
sediments from the offshore of the area also revealed that
sediments from the Pearl River were transported southwestward
on the continental shelf between the Pearl River mouth and the
east of Hainan Island (Liu et al., 2010a,b). So these could well
J. Liu et al. / Continental Shelf Research 47 (2012) 156–164
163
Fig. 6. (a) Ternary and Correlation diagram showing variation in clay minerals composition of surface sediments along coast of South China. (b) Hierarchical clustering
analysis of various areas and sources using the clay mineral parameters. The height of the Y-axis indicates the cluster distance between the objects. All clay mineralogical
results used in this study have been calculated according to the Biscaye (1965) method. Data of Taiwan, Luzon and Pearl River are recalculated from Z. F. Liu et al. (2010),
while data of Hanjiang River from Boulay et al. (2005). On legend, red label symbols as sources, solid circles as ‘‘east of the PRE (Area I)’’, hollow circles as ‘‘next to the PRE
(Area II)’’, solid squares as ‘‘west of the PRE (Area III)’’, and hollow squares as ‘‘east of the Leizhou Peninsula (Area IV)’’. (For interpretation of the references to color in this
ﬁgure legend, the reader is referred to the web version of this article.)
explain decreasing illite percent and increasing smectite percent
southwestward in the west of Pearl River mouth. Nevertheless,
impact of sediments from the Pearl River is very limited in this
area, despite that large amount of sediments are transported
southwestward along the coast and greatly affects sedimentation
process in west of the PRE.
It must be point out that quantitative estimation is just based
on clay fraction ( o2 mm) of surface sediments in the study areas,
neglecting grain size effect of sediments along coast of the
northern SCS. At the same time, results of cluster analysis should
be used with caution because the analytical error of XRD clay
mineralogy is about 10% and the difference of clusters shown in
ternary diagram (Fig. 6a) is small.
5. Conclusions
Clay mineral parameters in surface sediments from nine bays/
harbors along the northern SCS coast have been discussed for
sediment provenance and contribution estimation of various
sources in the study areas:
1. Clay mineral assemblage of sediments from four study areas is
distinct. Clay minerals in sediments from east of the PRE (Area I)
mainly include kaolinite (average 54%) and illite (39%), and
these in sediments from west of the PRE (Area III) normally
contain illite (average 47%) and kaolinite (43%). Smectite percent is relatively high for sediments from both next to the PRE
(average 15%) and east of the Leizhou Peninsula (14%).
2. Overall, sediments in the study areas come from the large
rivers (e.g. Pearl and Hanjiang Rivers) and local islands/rivers.
The Hanjiang River provides most sediments in east of the PRE
( 95%) and major sediments next to the PRE (84%). The Pearl
River supplies the majority of sediments in west of the PRE
(79%) and limited sediments in east of the Leizhou Peninsula
(29%). Local islands/rivers input the rest sediments in the
study area, and its contribution reaches the maximum in the
east of Leizhou Peninsula ( 71%).
Acknowledgments
We appreciate the editor and two anonymous reviewers for
their critical reviews and helpful suggestions. This work was
jointly supported by the National Natural Science Foundation of
China (41006026), the Key Project of NSFC-Guangdong Joint
Foundation (U1133002), the National Special Project on Basic
Research of Science and Technology (2008FY110100) and the intergration project (GD908-JC-07), and the State Key Program of National
Natural Science of China (91128206).
Appendix A. Supporting information
Supplementary data associated with this article can be found in
the online version at http://dx.doi.org/10.1016/j.csr.2012.07.013.
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