The evolution and control of detrital sediment provenance in the middle and northern Okinawa Trough since the last deglaciation: Evidence from Sr and Nd isotopes

Palaeogeography, Palaeoclimatology, Palaeoecology 522 (2019) 1–11

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The evolution and control of detrital sediment provenance in the middle and northern Okinawa Trough since the last deglaciation: Evidence from Sr and Nd isotopes

T

Fuqing Jianga,b, , Zhifang Xiongb,d, Martin Frankc, Xuebo Yina, Anchun Lia ⁎

a

Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, 266071, China Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China c GEOMAR, Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany d Key Laboratory of Marine Sedimentology and Environmental Geology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China b

ARTICLE INFO

ABSTRACT

Keywords: Yellow River Yangtze River Taiwan orogen Volcanic material Kuroshio current

The Okinawa Trough (OT) is a large sink of sediments supplied by the East Asian continent. Identifying the provenance of the OT sediments is key to reconstructing the temporal and spatial variations of the terrigenous supply to this area and is important for understanding the impact of paleoclimatic and paleoceanographic variability on the sediment supply to this marginal sea over the late Quaternary. In this contribution, we show that radiogenic strontium (Sr) and neodymium (Nd) isotopes allow to efficiently distinguish Yellow and Yangtze/Taiwan River detrital sediments, and can be used to reconstruct distinct changes in the provenance of the detrital fraction of marine sediments from the middle and northern OT since the last deglaciation. The Sr and Nd isotope signatures are compared to those of the potential sediment sources, namely the Yellow and Yangtze Rivers, the Taiwan orogen, and volcanic material from the OT and nearby islands, and the relative contributions of these sources are reconstructed. The Sr and Nd isotope compositions of the detrital fraction in the two sediment cores recovered from the middle and northern OT show that the sediments mainly originated from the Yangtze River between 18 and 10.5 ka, which was caused by low sea level and a widely developed channel system on the continental shelf. During the period between 10.5 and 7.0 ka, the rising sea level resulted in elevated Yangtze and Yellow Rivers sediment input into the OT. Simultaneously, large-scale volcanic activity also contributed significant amounts of material to the OT. During the last 7.0 ka, besides important contributions from the Yellow River, the intensification of the Kuroshio Current resulted in increased delivery of sediment from Taiwan to the OT.

1. Introduction The Okinawa Trough (OT) is located in the southeastern part of the East China Sea (ECS, Sibuet et al., 1987) and is an active back-arc basin behind the Ryukyu arc-trench system (Fig. 1). The OT resulted from the northwestward subduction of the Philippine Sea Plate underneath the Eurasian Plate since the Late Miocene (Letouzey and Kimura, 1986; Sibuet et al., 1987). As a large sedimentary sink area, the OT has recorded the evolution of climate, oceanography, and continent-ocean interactions since the late Quaternary (Liu et al., 2001; Li et al., 2001; Liu et al., 2007a; Xiang et al., 2007; Dou et al., 2010a). Major changes in the paleoenvironment and paleoclimate, such as fluctuations in sea level (Wang and Sun, 1994; Liu et al., 2004), variability in the strength and pathway of the Kuroshio Current (Ujiié et al., 2003; Ujiié and Ujiié,

⁎

1999; Jian et al., 1998, 2000; Xu and Oda, 1999), shifts in East Asian Monsoon (EAM) precipitation on the Chinese continent (An et al., 2000), and development of the Chinese coastal current (Liu et al., 2007b) have potentially influenced the supply of terrigenous material to the OT. Changes in the sources of the detrital fraction in the OT sediments can be used to reconstruct the temporal and spatial variations of the terrigenous supply, which allows for a better understanding of the interactions between climatically driven detrital sediment supply and the paleoceanographic and paleoclimatic variability in this area. The sediments in the OT are mainly composed of terrigenous material, volcanic material and biogenic carbonate (Zhao et al., 1984; Qin et al., 1987). However, the contributions from different sources of terrigenous material in the OT are still not well constrained for two reasons: (1) Complex sediment provenance; Yangtze River, Yellow

Corresponding author at: Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China. E-mail address: [email protected] (F. Jiang).

https://doi.org/10.1016/j.palaeo.2019.02.017 Received 30 September 2018; Received in revised form 31 January 2019; Accepted 26 February 2019 Available online 01 March 2019 0031-0182/ © 2019 Elsevier B.V. All rights reserved.

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Fig. 1. Regional map of the ECS and the OT including the locations of cores E017 and Y127 (represented by red stars). (Reference sites of surface sediments (Meng et al., 2001) are represented by black open circles, other sediment core sites (Dou et al., 2016; Zheng et al., 2016; Bi et al., 2017) are represented by solid black circles. The approximate pathways of the Kuroshio Current (KC) and its branch are adopted from Xu and Oda (1999) and regional circulation patterns in the ECS, Yellow Sea and adjacent area are adopted from Guan (1994) and Yuan et al. (2008). YSCC-Yellow Sea Coastal Current, ZFCC-Zhejiang and Fujian Coastal Current and TWC-Taiwan Warm Current. The major tectonic blocks and faults in continental China (modified from Deng et al. (2017) are also presented in this figure). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

River and Taiwan orogen sediments are believed to be the major contributor, but it is difficult to distinguish the contributions from the end members. (2) The influence of strong and extensive volcanic activity within and around the OT (Qin et al., 1987; Liu et al., 2007c; Jiang et al., 2010). Over recent decades, many mineralogical (Sun, 1990; Yang, 1988; Eisma et al., 1995) and geochemical (Zhao and Yan, 1992; Meng et al., 2000a; Yang et al., 2002, 2007; Jiang et al., 2009; Dou et al., 2015) methods have been developed to distinguish the fractions of different end member sediments, some of which have been applied to identify the sources of the OT sediments (Jiang et al., 2009; Dou et al., 2012; Li et al., 2015; Wang et al., 2015; Zheng et al., 2016). However, controversy and discrepancies still exist. Detrital mineral assemblage (amphibole-epidote-quartz-feldspar etc.) and heavy mineral

characteristics based on BP artificial neural network analyses of surface sediments from the western slope of the OT indicate for example, that the modern sediments of the OT mainly originate from the Yangtze River (Yuan et al., 1987; Lin et al., 2003), whereas other studies indicated that the terrestrial sediments in the OT are mainly supplied by the old Yellow River submarine delta (Milliman et al., 1985; Yuan et al., 2008; Bian et al., 2010). In contrast, geochemical evidence (e.g. enrichment factors of transition elements and rare earth element patterns) has shown that the surface sediments in the northern OT have received contributions from both Yangtze and Yellow Rivers (Jiang et al., 2006; Jiang et al., 2008). In the geological past, due to the influence of changes in sea level, ocean currents, and climate on sediment supply to the OT, tracing past changes in sediment sources is even more difficult 2

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and there is an ongoing debate. Clay minerals (Diekmann et al., 2008; Dou et al., 2010a; Wang et al., 2015), Rare Earth Elements (Dou et al., 2010b), and detrital minerals (Chen et al., 2011) were used to reconstruct sediment sources of the OT since the last glacial period. However, the exact temporal and spatial variations of the different sediment sources and their relative contributions to the OT remain unclear. Radiogenic Sr and Nd isotopes have been extensively used to characterize sediment provenance and to reconstruct temporal variations in sediment supply to ocean basins (e.g. Grousset et al., 1988; Revel et al., 1996; Asahara et al., 1999; Colin et al., 1999; Weldeab et al., 2002; Yokoo et al., 2004; Colin et al., 2006; Chen et al., 2007; Yang et al., 2007; Ali et al., 2015). While the Sr isotope composition can be influenced by grain size sorting and diagenesis of the sediment (Walter et al., 2000), the Nd isotope composition is hardly affected by grain size differences between the sediment fractions and is also not significantly influenced by changes in the weathering regime if the sediment sources have remained unchanged (Goldstein et al., 1984; Walter et al., 2000; Ehlert et al., 2011). There have been studies on Sr and Nd isotopic characteristics of the potential source rock areas and corresponding sediments in the OT area, such as sediment and suspended matter of the Yellow and Yangtze Rivers (Meng et al., 2000a, 2008; Yang et al., 2007; Luo et al., 2012; Rao et al., 2017; Hu et al., 2018), and Taiwan Rivers (Chen and Lee, 1990; Bentahila et al., 2008; Zheng et al., 2016; Dou et al., 2016), as well as rocks in the OT area (Notsu et al., 1987; Shinjo et al., 1999, 2000; Meng et al., 2000b; Huang et al., 2006; Zeng et al., 2010; Guo et al., 2018). These studies contributed valuable data for establishing the end member isotopic characteristics and for identifying the sediment sources of the OT. A study on the Sr and Nd isotopic characteristics of sediments in the ECS shelf and western slope of the middle OT demonstrated that the detrital fractions are mainly a mixture of two end members, which are volcanic and terrigenous materials (Meng et al., 2001), but the different terrigenous detrital sources could not be distinguished. Although Sr and Nd isotopes have been used to trace the OT sediment sources (Dou et al., 2012; Li et al., 2015; Zheng et al., 2016; Dou et al., 2016), the end member components, such as the Yangtze River and Yellow River, are not fully constrained, which strongly affects the provenance discrimination and may lead to ambiguous paleoenvironmental reconstructions. In this contribution, we analyzed the Sr and Nd isotope compositions of sediment from the Yangtze and Yellow Rivers combined with the published Sr and Nd isotopic data of sediments and suspended matter from both rivers and other potential source areas (e.g. Taiwan and volcanic material). We find that the sediments of the Yellow and Yangtze/Taiwan rivers can be distinguished using radiogenic Sr and Nd isotopic data. Using this result and by analyzing the sediment endmember variability since the last deglaciation, we characterize the relative contributions of detrital sediment sources in the OT as a function of climatic and oceanographic driving mechanisms over time.

1826 m water depth 298 cm total length) was recovered from the middle-southern OT (Fig. 1). Both cores record the depositional history since the last deglaciation (Xiang et al., 2007; Jiang et al., 2010). The age model is based on thirteen AMS (accelerator mass spectrometry) 14 C ages on planktonic foraminifers (six ages for core E017 and seven ages for core Y127, Xiang et al., 2007; Jiang et al., 2010), which have been converted to calendar years using the Calib 7.0 program (available at http://radiocarbon.pa.qub.ac.uk/calib/) (Stuiver et al., 1998). In the conversion, ΔR (the local difference in reservoir age from 400 yr in the OT) was assigned as 35 ± 25 yr (Hideshima et al., 2001; Wei, 2006). All ages were generated based on a linear interpolation of sedimentation rates between the AMS 14C ages. A sequential leaching procedure was adopted to remove the nondetrital fractions from approximately 1 g of dried bulk sediment to determine the pure detrital radiogenic Sr and Nd isotope signatures. Each sediment sample was treated with distilled water and acetic acid (10%) at room temperature to remove sea salts and biogenic carbonates. Then, a 2 M Na2CO3 solution was used to remove opal in an 85 °C water bath for 5 h, and subsequently, a 1 M NaOH solution was employed to further dissolve opal in a 100 °C water bath. Early diagenetic iron and manganese oxides were removed using a 1 M hydroxylamine hydrochloride solution in 25% (v/v) acetic acid (Chester and Hughes, 1967; Bayon et al., 2002) on a hotplate (90 °C) for 3 h. The remaining organic material was removed using 5% H2O2. Finally, the residual detrital fraction was dried (at 50 °C), ground and homogenized for the Sr and Nd isotope separation. Approximately 0.1–0.2 g of each sample was used for total dissolution in a concentrated HF–HNO3–HClO4 solution on a hot plate. Sr and Nd were separated and purified for mass spectrometric analyses by application of standard ion chromatographic procedures (Cohen et al., 1988; Horwitz et al., 1992; Lugmair and Galer, 1992). Radiogenic Sr and Nd isotope measurements were performed on an IsoProbe-T thermal ionization mass spectrometer at the analytical laboratory of the Beijing Research Institute of Uranium Geology. The analytical blank was < 200 pg for Sr and < 50 pg for Nd. Sr isotopes were measured using single Re filaments and a Ta activator in static mode. The measured 87Sr/86Sr ratios were corrected for internal mass bias by applying 86 Sr/88Sr = 0.1194. The 87Sr/86Sr result for the reference material NBS 987 is 0.710250 ± 7 (2σ, n = 10), while the recommended value is 0.710248. Nd isotopes were measured using triple Re filaments in static mode. Data were corrected for internal mass bias by applying 146 Nd/144Nd = 0.7219. The 143Nd/144Nd result for the reference material JNdi-1 was 0.512118 ± 3 (2σ, n = 10), while the recommended value is 0.512115 (Tanaka et al., 2000). The 143Nd/144Nd ratios were normalized to the value for the Chondritic Uniform Reservoir (CHUR) and reported as εNd(0) = ((143Nd/144Nd/0.512638) − 1) × 104 (Jacobsen and Wasserburg, 1980). The Sr and Nd isotope characteristics of potential end members were established by compiling published Sr and Nd isotope data, including sediment and suspended material data of the Yangtze and Yellow Rivers (Yang et al., 2007; Meng et al., 2008; Luo et al., 2012; Rao et al., 2017; Hu et al., 2018), Taiwan orogen sediments (Chen and Lee, 1990; Zheng et al., 2016; Dou et al., 2016), volcanic material in the OT (Shinjo et al., 1999, 2000; Meng et al., 2000b; Huang et al., 2006; Zeng et al., 2010; Guo et al., 2018), and sediments from the middle OT (Meng et al., 2001).

2. Materials and methods Four sediments samples were recovered from the channel of the lower reaches of the Yangtze River (from Wuhu to Shanghai, Fig. 1; Table 1). Seven sediment samples were collected from the Yellow River at Guide, Lanzhou, Qingtongxia, Tongguan, Baotou, Beizhen and Lijin (Table 1; Jiang et al., 2009). The sediments are mainly composed of fine sand, silt and silty clay and are dominantly composed of detrital minerals, such as quartz, plagioclase and orthoclase, and clay minerals (e.g. illite and chlorite). The sediments do essentially not contain any biogenic debris (Jiang et al., 2009). Two gravity cores (Y127 and E017) were recovered from the OT during the investigation of the ECS shelf and marginal seas with RV Ke Xue Yi Hao in May 1999. The site of core Y127 (128°18.26′ E, 30°32.97′ N, 739 m water depth, 422 cm total length) is in the northern OT. Core E017 (126°01.38′ E, 26° 34.45′ N,

3. Results 3.1. Sr and Nd isotope compositions of the Yellow and Yangtze River sediments The Sr and Nd isotope compositions of sediments from the lower reaches of the Yangtze and Yellow Rivers are shown in Table 1. The 87 Sr/86Sr ratios of Yangtze River sediments are between 0.71730 and 0.71880, with an average of 0.71804. Yellow River sediments are 3

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Table 1 Sr and Nd isotope compositions in Yangtze and Yellow River sediments. Sites

Sediment type

87

Sr/86Sr

2σ(×10−6)

143

Nd/144Nd

2σ(×10−6)

εNd(0)

Sediments in the Yangtze River CJR1 Fine sand CJR5 Silty clay CJR6 Silty clay CJR2-2 Silty clay

0.71730 0.71840 0.71764 0.71880

9 9 12 12

0.512066 0.512087 0.512037 0.511999

4 4 6 6

−11.2 −10.7 −11.7 −12.5

Sediments in the Yellow River HHR Fine sand HHR2 Medium-coarse sand HHR5 Find sand HHR6 Fine sand HHR9 Silt HHR31 Fine sand HHR36 Fine sand

0.71597 0.71517 0.71470 0.71592 0.71504 0.71650 0.71588

15 25 17 13 16 10 32

0.511821 0.512115 0.512136 0.512067 0.512078 0.511891 0.511900

6 20 7 7 6 5 13

−15.9 −10.2 −9.8 −11.1 −10.9 −14.6 −14.4

Note: All the sediment in the Yangtze River is recovered from the channel of lower ranches of Yangtze River (from Wuhu to Shanghai); HHR-riverbed at Tongguan port, HHR2-north side of the river terrace at Guide, HHR5-south side of the river at Lanzhou, HHR6-east side of the river at Qingtongxia, HHR9-west side of the river at Zhaojun Tomb of Baotou, HHR31-riverbed at Beizhen, HHR36-riverbed at Lijin (Jiang et al., 2009).

somewhat less radiogenic in Sr, ranging from 0.71470 to 0.71650, with an average of 0.71560. The εNd(0) values of sediments from the lower reaches of the Yangtze River are between −12.5 and −10.7. The εNd(0) values of the Yellow River sediments show a larger variability and range from −15.9 to −9.8. All measured Sr and Nd isotopes of the Yangtze and Yellow River sediments are within the range of previously published data (Yang et al., 2007; Luo et al., 2012; Meng et al., 2008; Luo et al., 2012; Rao et al., 2017; Hu et al., 2018).

radiogenic than the younger part of the core. Similar to Core E017, the Sr and Nd isotope compositions of Core Y127 sediments can also be divided into two sections (Fig. 2). The 87 Sr/86Sr ratios of the top 20 cm (the most recent 10.5 ka), ranging from 0.71301 to 0.71398 (with an average of 0.71345), are less radiogenic than the sediments between 20 cm and 422 cm (from 18 ka to 10.5 ka), which range from 0.72031 to 0.72343 (with an average of 0.72245). The εNd(0) is between −8.9 and −8.1 (with an average of −8.5) in the top 20 cm and is significantly more radiogenic than the sediments between 20 cm and 422 cm, which range from −13.5 to −11.5 (with an average of −12.6).

3.2. Sr and Nd isotope characteristics of the detrital fraction in the OT The 87Sr/86Sr and 143Nd/144Nd signatures of the detrital fractions in cores E017 and Y127 are plotted in Fig. 2 and listed in Table 2. The Sr and Nd isotope compositions can be divided into two sections in the core E017 sediments (Fig. 2). The 87Sr/86Sr ratios of the top 120 cm of the sediment (the past 10.5 ka) range from 0.70767 to 0.72009. The average Sr isotope ratio of the last 10.5 ka is 0.71849 if the samples with abundant volcanic glass are excluded. The Sr isotope ratios between 120 cm and 298 cm depth (from 18 to 10.5 ka) are more radiogenic overall and vary from 0.72025 to 0.72437, resulting in an average of 0.72230. The εNd(0) is between −12.4 and −2.1 (with an average of −10.3) in the top 120 cm. The average εNd(0) is −11.7 over the last 10.5 ka if the samples bearing abundant volcanic glass are excluded. The εNd(0) signatures in the sediments between 120 cm and 298 cm range from −14.4 to −11.7, with an average of −13.0, overall less

4. Discussion 4.1. Characterizing the potential sediment sources Tracing the detrital fraction back to its source regions requires detailed and systematic information on the SreNd isotopic signatures of the potential source regions. Previous studies showed that the sediment provenance of the detrital fraction in the OT includes volcanic material from within and near the OT (Jiang et al., 2010), terrigenous sediment supplied by the major rivers of East Asia, particularly the Yangtze and Yellow Rivers (Katayama and Watanabe, 2003), lateral transport along the ECS shelf (Honda et al., 2000; Iseki et al., 2003; Oguri et al., 2003), and sediments from the Taiwan orogen carried by the Kuroshio Current Fig. 2. Age model of cores E017 and Y127, and downcore variability of Sr and Nd isotope compositions of the detrital sediments plotted against age in cores E017 and Y127 (numbers indicate the AMS 14C ages (converted to cal kyr B.P.). Core E017 is marked with baby blue curve and symbols, and Core Y127 is marked with orange curve and symbols. The age of 10.5 ka was derived using a linear interpolation between neighboring ages of the two cores). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

4

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Table 2 Sr and Nd isotope compositions of detrital fraction in core E017 and core Y127 sediments. Cores

Layer/cm

Age (ka)

E017

0–2 4–6 8–10 16–18 26–28 34–36 42–44 50–52 58–60 66–68 74–76 82–84 86–88 90–92 98–100 106–108 110–112 114–116 118–120 122–124 130–132 138–140 146–148 154–156 162–164 170–172 178–180 186–188 194–196 202–204 210–212 218–220 226–228 234–236 240–242 250–252 258–260 264–266 274–276 286–288 280–282 290–292 0–2 2–4 4–6 18–20 36–38 48–50 56–58 68–70 88–90 106–108 120–122 148–150 170–172 190–192 210–212 248–250 274–276 290–292 314–316 340–342 360–362 380–382 400–402 420–422

0.15 0.73 1.31 2.47 3.38 4.01 4.64 5.27 5.90 6.53 7.16 7.78 8.10 8.41 9.04 9.43 9.63 9.83 10.02 10.22 10.61 11.00 11.40 11.79 12.17 12.54 12.91 13.28 13.66 14.03 14.40 14.77 15.14 15.49 15.73 16.14 16.47 16.72 17.13 17.38 17.63 17.79 0.66 1.99 3.32 10.50 12.66 12.73 12.78 12.84 13.21 13.55 13.89 15.49 15.84 16.03 16.22 16.57 16.82 17.00 17.27 17.56 17.79 18.01 18.24 18.46

Y127

87

Sr/86Sr

2σ (×10−6)

0.71830 0.71815 0.71821 0.71913 0.71814 0.71837 0.71867 0.72009 0.71892 0.71876 0.71621 0.71170 0.70767 0.71745 0.71953 0.71072 0.71896 0.71648 0.71581 0.72179 0.72025 0.72246 0.72308 0.72309 0.72327 0.72191 0.72163 0.72233 0.72261 0.72313 0.72293 0.72342 0.72293 0.72243 0.72136 0.72437 0.72140 0.72320 0.72233 0.72288 0.72202 0.72229 0.71335 0.71301 0.71398 0.71346 0.72240 0.72031 0.72103 0.72121 0.72181 0.72167 0.72143 0.72233 0.72287 0.72308 0.72312 0.72322 0.72308 0.72312 0.72328 0.72296 0.72343 0.72308 0.72281 0.72272

10 9 9 8 10 11 9 14 17 14 14 17 15 17 14 14 14 28 13 35 13 10 9 12 8 15 14 11 14 12 15 13 13 16 11 9 9 9 9 7 8 14 11 10 10 11 36 14 12 9 36 10 8 17 8 11 11 11 11 10 9 12 13 9 12 7

(Dou et al., 2010b; Dou et al., 2012; Zheng et al., 2016). A large variation in the 87Sr/86Sr ratios of detrital sediments (ranging from 0.71312 to 0.74432) in all Yangtze River reaches has previously been found (Yang et al., 2007). Compared with those of the Yangtze River, the 87Sr/86Sr ratios of the Yellow River sediments have a

143

Nd/144Nd

0.512056 0.512067 0.512030 0.512027 0.512014 0.512014 0.512051 0.512064 0.512019 0.512050 0.512061 0.512350 0.512528 0.512001 0.512023 0.512327 0.512029 0.512209 0.512188 0.511988 0.512010 0.511989 0.511966 0.511980 0.511953 0.511968 0.511982 0.51204 0.511938 0.511960 0.511965 0.511902 0.511983 0.511975 0.511912 0.511954 0.511974 0.511927 0.512006 0.511961 0.511987 0.511968 0.512183 0.512200 0.512214 0.512223 0.511998 0.511958 0.512051 0.511989 0.511963 0.511998 0.511956 0.511991 0.511978 0.511950 0.512004 0.511948 0.512029 0.512006 0.511974 0.511972 0.512031 0.512038 0.512031 0.511952

2σ(×10−6)

εNd(0)

11 7 7 6 6 5 7 13 7 7 7 11 9 9 9 6 5 6 14 17 8 6 6 8 13 7 8 24 18 7 34 19 14 17 19 10 8 15 12 7 11 9 10 7 21 27 27 16 21 10 9 14 13 11 14 14 17 11 12 12 9 24 13 27 14 13

−11.4 −11.1 −11.9 −11.9 −12.2 −12.2 −11.5 −11.2 −12.1 −11.5 −11.3 −5.6 −2.1 −12.4 −12.0 −6.1 −11.9 −8.4 −8.8 −12.7 −12.3 −12.7 −13.1 −12.8 −13.4 −13.1 −12.8 −11.7 −13.7 −13.2 −13.1 −14.4 −12.8 −12.9 −14.2 −13.3 −13.0 −13.9 −12.3 −13.2 −12.7 −13.1 −8.9 −8.5 −8.3 −8.1 −12.5 −13.3 −11.5 −12.7 −13.2 −12.5 −13.3 −12.6 −12.9 −13.4 −12.4 −13.5 −11.9 −12.3 −13.0 −13.0 −11.8 −11.7 −11.8 −13.4

much narrower variation range (0.71287 to 0.71886) and are overall less radiogenic (average 0.71548; Meng et al., 2008). Thus, most of the 87 Sr/86Sr signatures of the Yellow River are within the range of the Yangtze River ratios. In addition, the 143Nd/144Nd ratios of the Yangtze and Yellow Rivers are similar. Therefore, it is difficult to differentiate 5

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Fig. 3. 87Sr/86Sr ratios plotted vs. 143Nd/144Nd ratios of sediments of the potential sediment sources in the OT (error bars for the Sr and Nd isotopes are smaller than the symbol size; data of the Yangtze and Yellow River sediments are from Yang et al. (2007), Meng et al. (2008), Luo et al. (2012), Rao et al. (2017), Hu et al. (2018), and this study; Taiwan River sediments (circled by magenta solid line) are from Chen and Lee (1990), Dou et al. (2016), and Zheng et al. (2016); Volcanic material refers to signatures of volcanic material in and around the OT published in Shinjo et al. (1999, 2000), Meng et al. (2000b) and Huang et al. (2006), Zeng et al. (2010), and Guo et al. (2018)).

Fig. 4. 87Sr/86Sr ratios plotted vs. 143Nd/144Nd ratios of detrital fractions in typical sediment (Sr and Nd isotope data of ODP Site 1202, MD06-3040, Oki02 and A7 are from Dou et al. (2016), Bi et al. (2017) and Zheng et al. (2016), respectively).

River sediment have not changed for at least the past 10 ka. The SreNd isotope relationships of Core MD06-3040 show that the sediment samples are entirely within the range of the Yangtze River and significantly different from the Yellow River sediments (Fig. 4). Clay mineral evidence has shown that Cores Oki02 and A7 sediments are mainly composed of Yangtze and Taiwan river sediments since the last deglaciation (Zheng et al., 2016). By using SreNd isotope data of Cores Oki02 and A7 (Fig. 4), it is also clear that Yangtze and Taiwan river sediments have been the two major contributors to the sediments of the two investigated cores. All above results demonstrate that Yangtze and Yellow River sediments can be distinguished reliably based on their Sr and Nd isotope compositions. The Taiwan orogen is an area of very high sediment discharge because of the ongoing arc-continental collision and high uplift rates. The erosion rates in the eastern central range have been on the order of 3–6 mm yr−1 across all timescales of the past several million years (Dadson et al., 2003). Based on Rare Earth Element evidence, Dou et al. (2010b) demonstrated that Taiwan sediments can be carried to the OT by the northward flowing, warm Kuroshio Current. The Sr and Nd isotope data of rocks reported by Lan et al. (1995) have been used to constrain the Taiwan origin end member (Dou et al., 2012). However, the sediments delivered from the Taiwan orogen do not only include basement rocks (e.g., metapelites and granitoids) with less radiogenic Sr isotope values but also old, recycled continental crustal material with somewhat more radiogenic Sr isotope compositions (Lan et al., 1995). The OT sediments derived from the Taiwan orogen have been suggested to mainly originate from the Lanyang River (Li et al., 2009a), a large river northeast of the Taiwan orogen. In fact, the Sr and Nd isotope data of the Lanyang River sediment resemble those of other large rivers in northern Taiwan (e.g., Tanshuiho River, Tachiahsi River and Choshui River) (Chen and Lee, 1990; Zheng et al., 2016; Dou et al., 2016). We argue that the Sr and Nd isotope signature of the northern Taiwan River sediment represents a large-scale, integrated sample of the Taiwan eroded sediments supplied to the southern OT (Fig. 3). The Sr isotope compositions of the Taiwan sediments are more radiogenic than the Yellow River sediments, which makes it possible to differentiate the sediments. However, the Taiwan orogen and Yangtze River sediments are similar, which makes it difficult to distinguish these sources of

the sediments originating from the Yangtze and Yellow River based on the Sr and Nd isotopes. The variability and wide range of Sr isotopes in the Yangtze River sediments result from a complex source rock distribution (e.g., younger igneous rocks in the upper Yangtze River reaches, old metamorphic rocks and Sinian-Cambrian siliceous rocks in the middle-lower Yangtze River reaches) and strong fractionation of the Sr isotopes during chemical weathering (Yang et al., 2007). Therefore, the average Sr and Nd isotope signature of the Yangtze River catchment does not represent the end member discharged into the ocean. In contrast, the sediments in the lower reaches of the Yangtze River are well mixed (Table 1) and represent integrated samples of the Yangtze River supplied to the ECS and OT. The source rock composition in the Yellow River catchment is simpler and yields a relatively homogeneous Sr isotope composition along its reaches. Therefore, all Yellow River reaches sediments represent the end member of the Yellow River supplied to the ocean. If we only consider sediments from the lower reaches of the Yangtze River, the Sr and Nd isotopic compositions of the sediments are significantly different from those of the Yellow River sediment (Fig. 3). Sediments of the lower reaches of the Yangtze River show a wider range of variation in 87Sr/86Sr ratios, from 0.71638 to 0.73033, and most of the 87Sr/86Sr ratios of the Yangtze River are higher than 0.71800. In contrast, the Sr isotope signatures of Yellow River (most are < 0.71800) are overall less radiogenic than those of the Yangtze River and show a narrower range of variability. To testify the reliability of this proxy, we compiled published Sr and Nd isotope data from the literature, e.g., core MD06–3040 on the inner shelf of the ESC (Bi et al., 2017), ODP Site 1202B (Dou et al., 2016), Core Oki02 in the southern OT (Zheng et al., 2016), and Core A7 in the middle OT (Zheng et al., 2016). The detrital fractions of all of these sediments show clear provenances. Core MD06–3040 sediments have been demonstrated to be dominantly derived from Yangtze River sediments for the last 10 ka (Bi et al., 2017). Nd isotope variations of Core MD06-3040 are very small (−12.5 < εNd(0) < −11.5, Bi et al., 2017), which indicate that the composition and contribution of Yangtze 6

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Fig. 5. 87Sr/86Sr ratios plotted vs. 143Nd/144Nd ratios of detrital fractions of Core E017 sediment and the potential sediment sources in the OT (two end members of the mixing curve are the volcanic materials in the OT and the homogenized sediments in the lower reaches of the Yangtze River. The concentrations of Sr and Nd, and isotopic compositions of the two members adopted are [Sr] = 129 ppm (n = 2, 112–146 ppm), [Nd] = 33.6 ppm (n = 4, 26.8–38.4 ppm), 87Sr/86Sr = 0.72137 (n = 10, 0.71715–0.72562) and 143 Nd/144Nd = 0.512036 (n = 10, 0.511968–0.512188) for the Yangtze River sediments; [Sr] = 188.6 ppm (n = 5, 111–217 ppm), [Nd] = 15.9 ppm (n = 5, 12.6–20.6 ppm), 87Sr/86Sr = 0.70463 (n = 21, 0.70406–0.70544) and 143 Nd/144Nd = 0.512781 (n = 21, 0.512648–0.512896) for the volcanic material source in the OT. The data are from Meng et al. (2000b), Huang et al. (2006), Meng et al. (2008), and Yang et al. (2007)).

Fig. 6. 87Sr/86Sr ratios plotted vs. 143Nd/144Nd ratios for detrital fractions in surface sediments from the ECS shelf and slope, the middle OT and in Core Y127 sediment, and the potential sediment sources of the OT. The mixing line is the same as in Fig. 5.

sediment samples deposited during the 9.0–7.0 ka period are located in the Yellow array, which indicates that the Yellow River may also have influenced this area during this period. The Sr and Nd isotopic characteristics of five sediment layers (82–84 cm, 86–88 cm, 106–108 cm, 114–116 cm and 118–120 cm) are distinctly different from the other sediments, with significantly lower 87Sr/86Sr ratios and higher 143 Nd/144Nd ratios. These characteristics document elevated abundances of volcanic material. Mineral and chemical compositions support that these five layers are mainly composed of volcanic material, and the most abundant volcanic material is present in the sediment between 86 and 88 cm depth (Jiang et al., 2002, 2010). The estimated content of volcanic materials in the detrital fraction is close to 80% in this layer based on the mixing curve (Fig. 5). Previously published Sr and Nd isotopic data (Meng et al., 2001) were collected to trace surface sediment sources on the ECS shelf and western slope of the OT. We only chose the sites with 100% terrigenous sediments to draw 87Sr/86Sr-143Nd/144Nd plots in order to avoid contamination with volcanic material (Fig. 6). The results show that most of the samples from the ECS shelf and slope are located in the Yellow River field. We thus argue that the sediment in this area is mainly derived from the Yellow River. Several samples are located in the Yangtze River and Taiwan sediment fields, which may indicate that the surface sediments were derived from these source areas. Yangtze River and/or Taiwan sediments carried by Kuroshio may contribute some of the sediment to this area. In addition, we note that two surface samples in the middle OT (Meng et al., 2001) are located in the Yangtze and Yellow River fields in the 87Sr/86Sr vs 143Nd/144Nd plot (Fig. 6). This phenomenon is similar the Sr and Nd isotopic compositions of the core top sediment of core E017 (Fig. 5) and strongly implies that the modern surface sediment in the central OT was influenced by contributions from the Yangtze River and/or Taiwan orogen (more detailed discussions will be given in Section 4.4) and Yellow River inputs.

sediment by only their Sr and Nd isotope compositions, and thus, additional evidence based on other proxies and analyses of the geological settings will be required. Volcanic material mainly composed of volcanic glass and rocks has been another important source for the detrital fraction in the middle and northern OT since the last deglaciation (Liu et al., 1999; Jiang et al., 2010). The radiogenic Sr and Nd isotope data of volcanic glass and basalt (Shinjo et al., 1999, 2000; Meng et al., 2000b; Huang et al., 2006; Zeng et al., 2010; Guo et al., 2018) are very homogeneous and completely different from the other potential source area sediments due to their highly unradiogenic Sr and radiogenic Nd isotope signatures (Fig. 3). This difference provides a sensitive proxy to identify whether volcanic material has contributed sediment to the OT. 4.2. Sediment provenance variation in the middle OT In Fig. 5, the Sr and Nd isotope compositions of the detrital fraction of Core E017 sediments are compared to those of potential sources. During the period between 18 and 10.5 ka (between 298 and 120 cm depths, Jiang et al., 2002), the sediments plot in the Yangtze River area field. We thus argue that the sediments at that time were mainly derived from the Yangtze River. This view is supported by clay mineral assemblages (Dou et al., 2010a), Rare Earth Element distributions (Dou et al., 2010b), and trace element evidence (Jiang et al., 2002). Fig. 5 also shows that although most of the sediments of the last 10.5 ka plot in the Yangtze River field, their Sr and Nd isotope compositions are different from the sediments during 18–10.5 ka. The sediments of the past 10.5 ka are less radiogenic in Sr isotopes, more radiogenic in Nd isotopes, and very similar to Taiwan River sediments. This may indicate that Taiwan and Yangtze River sources together dominated the sediment contributions to the OT. In addition, two

4.3. Sediment provenance variation in the northern OT The Sr and Nd isotopic compositions of the detrital fraction in Core Y127 sediments can be divided into two parts (Fig. 6). The bottom layer sediments (422–20 cm) recorded the sedimentary history of the 7

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northern OT between 18 ka and 10.5 ka (Fig. 2; Jiang et al., 2010). The Sr and Nd isotope signatures of the detrital fractions in the sediment samples are located in the Yangtze River field, show very little variation and are unambiguously different from the Yellow River sediments. We infer that the detrital fractions mainly originated from the Yangtze River during this period. Rare Earth Element evidence also supports the dominant contribution of the Yangtze River to the area during this period (Jiang et al., 2008). Compared with the sediments of the older part, the sediments of the last 10.5 ka (topmost 20 cm) showed less radiogenic Sr and more radiogenic Nd isotope signatures. The samples nearly plot on the calculated mixing line of the Yangtze/Taiwan and volcanic material in the OT (Fig. 6). We suggest that detrital sediments of the last 10.5 ka in the northern OT have been a mixture of volcanic material (30–40%) and Yangtze River and/or Taiwan sediments (60–70%) based on the Sr isotope signatures in the mixing model. Because the differences in the average Sr and Nd isotope compositions between the Yangtze River and Taiwan sediments are very small, it is difficult to distinguish these sediments based only on Sr and Nd isotopes. However, more detailed analysis (see Section 4.4) indicates that the Taiwan orogen and Yangtze River area may both have contributed sediment to the northern OT, but their relative contributions are difficult to estimate.

hand, the influence of the abandoned Yellow River on the ECS and OT was very small during this period. An investigation of shallow seismic profiles, combined with the chemical and mineralogical compositions of sediments in the south Yellow Sea show that the paleo-channel system in the northern part of the south Yellow Sea belonged to the paleo-Yellow River system and that the southern part of the south Yellow Sea belonged to the paleo-Yangtze River system prior to 9 ka (Li et al., 1991). These records indicate that the Yellow River sediments were mainly trapped north of the Yellow Sea. The Taiwan orogen sediment was also less important during this period because a significant portion of the sediments supplied by the Lanyang River were trapped in the Lanyang Plain (Wei et al., 2003), and the Kuroshio Current was very weak during this period of time recorded by planktonic foraminifera (Xu and Oda, 1999), sea surface temperature and sortable silt content (Fig. 7h, i; Zhao et al., 2005; Diekmann et al., 2008). Correspondingly, the OT received less sediment from the Lanyang River. Therefore, the sediments in the middle OT and northern OT were mainly derived from Yangtze River during this period, which is supported by our radiogenic Sr and Nd isotope analysis (Figs. 5 and 6). During the early Holocene (11.8–7 ka), East Asia received a large amount of precipitation resulting from the strengthened EAM (Fig. 7j; Yuan et al., 2004; Wang et al., 2005), reaching a maximum between 10 and 7.0 ka ago north of eastern and central China (An et al., 2000). The stronger Asian monsoon precipitation was responsible for flooding of the Yellow River (Huang et al., 2007) and Yangtze River reaches (Zhang et al., 2013) and stronger continental erosion. During this period, sea level rose to approximately 50 to 40 m below the present level (Fig. 7g, Chen and Liu, 1996; Lambeck et al., 2002). Part of the ECS shelf and the Yellow Sea were flooded by the rising sea level, and the Yangtze River mouth was more distant from the OT. Most of the increased terrigenous sediment supply resulted from continental erosion products that were trapped on the continental shelf. Meanwhile, the rising sea level washed and winnowed the ECS continental shelf and continuously released reworked fine particles into the water column, some of which were deposited in the OT. Studies on micropaleontological proxies (Xu and Oda, 1999; Xiang et al., 2007; Ujiié and Ujiié, 1999; Wei, 2006; Li et al., 2009b), sea surface temperature (Fig. 7h, Zhao et al., 2005) and sortable silt content (Fig. 7i, Diekmann et al., 2008) documented the

4.4. Factors controlling sediment provenance changes Sea level during the Last Glacial Maximum (LGM) was approximately 130–155 m lower than at present (Lambeck and Chappell, 2001), the coastline of the ECS advanced eastward, and almost the entire Yellow Sea and most of the ECS continental shelf were exposed. Sea level began to rise during the early stage of deglaciation (between 19.5 and 15 ka) and accelerated between 15 and 10.5 ka (Fig. 7g, Chen and Liu, 1996; Lambeck et al., 2002). High-resolution seismic profiles document that deep channels developed on the exposed ECS and Yellow Sea shelf between the LGM and the deglaciation (Li et al., 2005; Liu et al., 2014). This widespread paleo-Yangtze River channel system (Li et al., 2005) on the ECS shelf implies that the paleo-Yangtze River mouth was significantly closer to the OT than at present and that the Yangtze River sediment could more readily reach the OT. On the other

Fig. 7. Downcore variability of Sr and Nd isotope ratios of the detrital fraction and volcanic glass plotted against the age of cores E017 and Y127 (a and b, 87Sr/86Sr ratio and εNd(0) of core E017 respectively, this study; c, content of volcanic glass (%) of core E017 is adopted from Jiang et al. (2010). d and e, 87Sr/86Sr ratio and εNd(0) of core Y127 respectively, this study; f, content of volcanic glass (%) of core Y127 is adopted from Jiang et al. (2010); g, sea level variation compiled from Lambeck et al. (2002), Chen and Liu (1996); h, sea surface temperature (SSTs) are derived from Zhao et al. (2005); i, the percentage of sortable silt (10–63 μm) in the silt fraction is adopted from Diekmann et al. (2008); j, the δ18O (‰) data were obtained from the Dongge Cave stalagmite (Yuan et al., 2004)). 8

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intensification of the Kuroshio Warm Current in the OT since the early Holocene. The Taiwan orogen erosion products were likely carried by the Kuroshio Current and contributed some of the sediments to the OT during this period. Although our Sr and Nd isotope data cannot discriminate between these sediment sources in detail, based on the above analysis, we argue that the terrigenous sediments were a mixture of Yangtze River, Yellow River and Taiwan orogen sources during this period. Previous studies documented that volcanism in and around the OT have strengthened since the early Holocene (Machida, 1999; Jiang et al., 2010). Large-scale explosive volcanism (Kikai-Akahoya (K-Ah)) in and around Japan produced a number of ignimbrites and widespread fallout tephra sheets between 8 and 6 ka (Machida and Arai, 1983; Machida, 1999), which is also documented in the sediments of the middle and northern OT (Jiang et al., 2010). These volcanic materials are characterized by less radiogenic Sr (87Sr/86Sr < 0.706) and more radiogenic Nd isotope values (εNd(0) > −2), markedly different from other, potential old and continentally derived sediment (e.g., Yangtze and Yellow Rvier sediment, and Taiwan orogen materials) with more radiogenic Sr (87Sr/86Sr > 0.710) and less radiogenic Nd isotope (εNd(0) < −10). Because of the significant difference in Sr and Nd isotope compositions, the input of volcanic materials significantly modified the compositions of the OT sediments. In our record, the least radiogenic Sr and most radiogenic Nd isotope compositions occurred at approximately 7.0–9.0 ka and matched the elevated contents of volcanic glasses (Fig. 7c). Therefore, the explosive volcanic activity of the early Holocene was another important controlling factor that modified the sediment composition of the OT. After sea level had reached the mid-Holocene highstand (approximately 7.0 ka), the Yangtze River sediment was transported southward and deposited in the Yangtze River estuary and deltaic system as a consequence of the establishment of the Chinese coastal current (Liu et al., 2007b). The abandoned Yellow River mouth was located south of the Shandong Peninsula before 1855 (Fig. 1) and directly discharged sediments into the Yellow Sea. Because of the strong coastal erosion (Yu et al., 1986; Zhou et al., 2014), the Yellow River delta has continued supplying almost the same amount of sediment annually as the Yangtze River (Saito and Yang, 1995), and these sediments have been transported to the outer shelf and even to the ECS by the Yellow Sea Coastal Current (YSCC). The Sr and Nd isotope compositions of the surface sediments in the ECS continental shelf and slope (Fig. 6) demonstrate that Yellow River sediment has been the major sediment source of the ECS. During this period, the Kuroshio Warm Current in the OT intensified further and reached present day strength as shown by sea surface temperature (Fig. 7h; Zhao et al., 2005) and sortable silt content (Fig. 7i; Wei, 2006; Diekmann et al., 2008). The stronger erosion of the Taiwan orogen and strengthening of the Kuroshio Current together resulted in more Taiwan sediment being delivered to the OT, which was marked by an increase in the sedimentation rate in the southern OT (Li et al., 2009a) and by enhanced deposition of sortable silt (Wei, 2006; Fig. 7i). The less radiogenic Sr isotope compositions (Fig. 7a, d) together with the other geochemical and isotopic evidence (Dou et al., 2010b; Dou et al., 2012) support that the sediment in the OT mainly originated from the Taiwan orogen during the most recent period. Although the northeastward Kuroshio Current blocked the sediment from dispersing eastward to the OT, the bottom nepheloid layer and upper layer transport (Iseki et al., 2003; Zheng et al., 2014) and some episodic events, such as winter storms, turbidity flows and intertidal waves (Bian et al., 2010), have washed the Yellow and Yangtze sediment onto the ECS continental shelf and have released fine particles into the OT.

reconstruct the provenance of the detrital fraction in the middle and northern OT sediment since the last deglaciation and to provide constraints on changes in the sediment sources and contributions. We show that well homogenized sediment from the lower reaches of the Yangtze River has Sr and Nd isotopic compositions distinct from Yellow River sediments, which can be used to identify the sediment provenance of this marginal sea. The Sr and Nd characteristics of the detrital fractions in the two sediment cores from the OT show that the sediments in the middle and northern OT were derived mainly from the Yangtze River sediment during the period from 18 to 10.5 ka. Sea level fluctuations and material provided from the widely developed Yangtze River channel system caused the Yangtze River sediments to dominate the OT. The Sr and Nd isotope signatures of the middle OT were consistent with the Yangtze River array during the last 10.5 ka but were closer to the Taiwan and Yellow River areas than the sediments of the older part, which indicates that the Yellow River and/or Taiwan contributed most of the sediment to the middle OT. During the period between 10.5 and 7.0 ka, the rising sea level resulted in higher amounts of Yangtze and Yellow River sediment supplied to the OT. In addition, volcanic material was an important contributor to the northern and central OT during the early to mid-Holocene. Since approximately 7.0 ka, more intense erosion has led to higher amounts of sediment from Taiwan which has been transported to the OT by the strengthened Kuroshio Current. The formation of the coastal current resulted in the delivery of higher amounts of old Yellow River sediments to the Yellow Sea and the ECS shelf and slope since 7.0 ka. Acknowledgments We thank Professor Nathalie Fagel and another reviewer for the constructive comments. We are grateful to Professor Zhigang Zeng of the Institute of Oceanology, Chinese Academy of Sciences for his valuable comment on the manuscript. This research is supported by, the National Natural Science Foundation of China (grant numbers 41576050, 41776065, 41876068), the Strategic Priority Research Program of the Chinese Academy of Sciences (grant number XDA11030302), the National Program on Global Change and Air-Sea Interaction (grant numbers GASI-GEOGE-02 and GASI-GEOGE-04), and Qingdao National Laboratory for Marine Science and Technology (grant number QNLM2016ORP0205). References Ali, S., Hathorne, E., Frank, M., Gebregiorgis, D., Stattegger, K., Stumpf, R., Kutterolf, S., Johnson, J.E., Giosan, L., 2015. South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea. Geochem. Geophys. Geosyst. 16, 505–521. An, Z.S., Porter, S.C., Kutzbach, J.E., Wu, X.H., Wang, S.M., Liu, X.D., Li, X.Q., Zhou, W.J., 2000. Asynchronous Holocene optimum of the East Asian monsoon. Quat. Sci. Rev. 19, 743–762. Asahara, Y., Tanaka, T., Kamioka, H., Nishimura, A., Yamazaki, T., 1999. Provenance of the north Pacific sediments and process of source material transport as derived from Rb-Sr isotopic systematics. Chem. Geol. 158 (3–4), 271–291. Bayon, G., German, C.R., Boella, R.M., Milton, J.A., Taylor, R.N., Nesbitt, R.W., 2002. An improved method for extracting marine sediment fractions and its application to Sr and Nd isotopic analysis. Chem. Geol. 187, 179–199. Bentahila, Y., Othman, D.B., Luck, J.-M., 2008. Strontium, lead and zinc isotopes in marine cores as tracers of sedimentary provenance: a case study around Taiwan orogen. Chem. Geol. 248, 62–82. Bi, L., Yang, S., Zhao, Y., Wang, Z., Dou, Y., Li, C., Zheng, H., 2017. Provenance study of the Holocene sediments in the Changjiang (Yangtze River) estuary and inner shelf of the East China sea. Quat. Int. 441, 147–161. Bian, C., Jiang, W., Song, D., 2010. Terrigenous transportation to the Okinawa Trough and the influence of typhoons on suspended sediment concentration. Cont. Shelf Res. 30, 1189–1199. Chen, C.-H., Lee, T., 1990. A Nd–Sr isotopic study on river sediments of Taiwan. P. Geol. Soc. China 33 (4), 339–350. Chen, Y.-G., Liu, T.-K., 1996. Sea level changes in the last several thousand years, Penghu Island, Taiwan Strait. Quat. Res. 45, 254–262. Chen, J., Li, G.J., Yang, J.D., Rao, W.B., Lu, H.Y., Balsam, W., Sun, Y., Ji, J.F., 2007. Nd and Sr isotopic characteristics of Chinese deserts: implications for the provenances of Asian dust. Geochim. Cosmochim. Acta 71, 3904–3914.

5. Conclusions The radiogenic Sr and Nd isotopic compositions of sediments in the potential sediment source areas of the OT including the Yangtze River, Yellow River, Taiwan orogen, and volcanic material are compared to 9

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