December **** Vol.** No.**: **** ****

Oceanology

doi: 10.1007/s11434-010-4149-5

SPECIAL TOPICS:

A high-resolution clay mineralogical record in the northern South

China Sea since the Last Glacial Maximum, and its time series

provenance analysis

LIU ZhiFei1*, LI XiaJing1, COLIN Christophe2 & GE HuangMin1

1

State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China;

2

Laboratoire IDES, UMR 8148 CNRS, Universit de Paris XI, Orsay 91405, France

Received May 4, 2010; accepted August 12, 2010; published online October 19, 2010

High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea (SCS) covering the period since

the Last Glacial Maximum shows that illite (29% 48%), smectite (14% 45%), chlorite (17% 28%), and minor kaolinite

(6% 14%) comprise the clay mineral assemblage, and that time series variation does not present glacial-interglacial cyclicity.

Provenance analysis indicates three end-member sources: almost all smectite derives from Luzon, all kaolinite is sourced from the

Pearl River, and illite and chlorite originate from both the Pearl River and Taiwan. By comparing clay mineral compositions in

surface sediments from the three major source areas and of the SCS, we reconstructed a time series of clay mineral contribution

from the major provenances to the northern slope of the SCS using the linear separation method for illite crystallinity. There were

three stages of provenance change. (1) During 24.1 17.5 ka BP, contributions from Taiwan and Luzon were similar (30% 40%),

while that from the Pearl River was only 25%. (2) During 17.5 14.0 ka BP, the contribution from Luzon decreased rapidly to

20% 25%, while that from Taiwan increased to 35% from an average of 25% at 18 ka BP, and that from the Pearl River increased

largely to 40%. (3) During the Holocene, differences in contributions from the three major provenances increased: the contribu-

tion from Luzon increased slightly and then remained at 27% 35%, that from Taiwan increased rapidly and then remained at

55% 60%, and that from the Pearl River decreased to 15%. The change in clay mineral contributions from different provenances

is influenced mainly by clay mineral production, monsoon rainfall denudation, oceanic current transport, and sea-level change.

clay minerals, illite crystallinity, provenance, Last Glacial Maximum, sea level change, East Asian monsoon, South China

Sea

Citation: Liu Z F, Li X J, Colin C, et al. A high-resolution clay mineralogical record in the northern South China Sea since the Last Glacial Maximum, and its time

series provenance analysis. Chinese Sci Bull, 2010, 55: 4058 4068, doi: 10.1007/s11434-010-4149-5

The most important component in sediments of the world s widely distributed in almost all oceanic environments. Clay

oceans is terrigenous clastic particles, which have an im- minerals have been applied successfully to studying sedi-

portant role in studies of the formation and evolution of ment source determination, oceanic current transport and

oceans and associated tectonic and climatic change histories paleoclimate evolution [4 8]. The South China Sea (SCS) is

[1]. Their application is particularly effective for marginal the largest marginal sea in the low-latitude western Pacific.

seas between continents and oceans, where high-sedimen- Because it is located next to the Asian continent and the

tation deposits may provide high-resolution, continuous, island arc belt of the western Pacific, terrigenous clastic

and long-sequence paleoenvironmental change information particles make up ~80% of total sediments in the sea since

[2,3]. Among the terrigenous clastic particles in oceans, the Oligocene [3], and provide excellent materials for global

clay minerals are the most important because they are paleoenvironmental and tectonic evolution studies, espe-

cially for the Asian paleo-monsoon history reconstruction.

Therefore, the SCS is receiving more international attention

*Corresponding author (email: abphuk@r.postjobfree.com)

Science China Press and Springer-Verlag Berlin Heidelberg 2010 csb.scichina.com www.springerlink.com

4059

LIU ZhiFei, et al. Chinese Sci Bull December (2010) Vol.55 No.35

for studying past global change [9,10]. northern SCS, we focus on clay mineral variations in the

Clay minerals can be used to track oceanic current varia- northern SCS since 24 ka BP (marine oxygen isotope stage

tions and to reveal contemporaneous paleoclimatic changes (MIS) 2), and discuss the time series provenance analysis.

prevailing in continental source areas [7,8], and have a sig-

nificant role in sedimentation and paleoenvironment studies

1 Materials and methods

of the SCS [11 16]. Most previous studies were based on

analysis of sediment cores obtained from the Ocean Drilling

Core MD05-2904 is located on the northern slope of the

Program (ODP) Leg 184 and International Marine Past

SCS, southwest of the Dongsha Islands, and almost overlaps

Global Change Study (IMAGES) cruises in the SCS. Those

ODP Site 1146 (9 27.40 N, 116 16.37 E, water depth 2092

results showed that the time series variation in late Quater-

m). The core is 44.98 m long and consists of homogenous

nary clay mineral assemblages presents mostly glacial-

ooze with slight bioturbation [21]. A high-resolution age

interglacial cyclicity, and they were interpreted either as

model reconstructed from planktonic foraminifera oxygen

chemical weathering closely related to contemporaneous

isotopes of the whole core and AMS14C dates on the top

climatic changes of source areas or as oceanic current

indicates an age of 257 ka BP at the core bottom with an

transport. For example, variations in clay mineral assem-

average sedimentation rate of 17.5 cm ka 1 [22], in accord

blages on the northern slope of the SCS have been suggest-

with a value of 18.9 cm ka 1 from the similar core interval

ed to be related to oceanic surface currents that are reversed

between winter and summer [12,16,17], or to the contem- at ODP Site 1146 [12]. A total of 267 samples with a depth

poraneous chemical weathering of source areas forced by resolution of 2 4 cm were taken from the top 9.4 m (at 24.1

the East Asian monsoon rainfall [13,15,18]. Studies in the ka BP), with a 4-cm resolution for 0 6.0 m (at 17.0 ka BP)

southern SCS considered chemical weathering driven by and a 2-cm resolution for 6.0 9.4 m. The average temporal

contemporaneous climatic changes of source areas to be the resolution of the measured core interval is 90 a, with 173 a

major mechanism, with a case study off the Mekong River for 0 6.0 m and 42 a for 6.0 9.4 m. Clay mineral data from

mouth showing that the Mekong River basin serves as the 300 surface argillaceous samples from potential prove-

major provenance of the southwestern SCS [14,19]. A study nances of Core MD05-2904 and from the SCS seafloor are

in the summer upwelling region of the western SCS, how- referred in the discussion of provenance, and are from the

ever, considered surface current transport controls, i.e., Pearl River [23,24], Taiwan [25], Luzon [26], and north-

north-southerly dominant surface currents during glacials eastern SCS [27] (Figure 1).

transported kaolinite originating mainly from the Pearl Riv- Clay minerals were identified by X-ray diffraction (XRD)

er to the south, whereas south-northerly dominant surface on oriented mounts of clay-sized particles (

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