The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes

YQRES-03596; No. of pages: 12; 4C: Quaternary Research xxx (2014) xxx–xxx

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The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes Zhuyou Sun a, Gang Li b,⁎, Yong Yin a a b

MOE Key Laboratory of Coastal and Island Development, Nanjing University, Nanjing 210093, China Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guang Zhou 510300, China

a r t i c l e

i n f o

Article history: Received 18 January 2014 Available online xxxx Keywords: Yangtze River Channel deposits Marine Oxygen Isotope Stage 3 Sea level

a b s t r a c t The depositional history of the lower Yangtze River and sea-level changes during Marine Oxygen Isotope Stage (MIS) 3 was established using three long drill cores from the northern Yangtze deltaic plain and southern Yellow Sea by using sedimentary analysis and AMS 14C dates. Voluminous channel deposits of the lower Yangtze River in MIS 3 were found from the northern deltaic plain and offshore area, with a thickness of over 30 m. The thick channel deposits are characterized by massive medium-to-fine sand deposits with sporadic tidal influence. During MIS 3, the Yangtze River appears to have mainly migrated between the modern river mouth and middle Jiangsu coastal plain, and likely built a delta complex in the field of Yangtze Sand Shoal in northern East China Sea. A large sediment supply and rapid sea-level variations promoted rapid progradation of the delta onto the flat shelf. The highest sea levels during MIS 3 are estimated to have reached 25 ± 5 m below the present sea level. © 2014 University of Washington. Published by Elsevier Inc. All rights reserved.

Introduction During the past few decades, global sea-level curves in the late Quaternary have been reconstructed by studies on oxygen isotope of deep-sea foraminifers, ice core and coral reef records (Chappell and Shackleton, 1986; Chappell, 2002; Siddall et al., 2008). The reconstructed sea-level curves have been widely used to interpret depositional evolution of river systems on continental margins (Wellner and Bartek, 2003; Anderson et al., 2004; Busschers et al., 2007; Liu et al., 2009, 2010). Well-dated sedimentary sequences and relatively accurate sea-level reconstructions have deepened the understanding of river–sea interaction history in the late Quaternary. The Yangtze River, one of the largest rivers in the world, has formed a broad tide-dominated delta since the Holocene sea-level highstand (Hori et al., 2001a). Studies on the depositional evolution of the Yangtze River system responding to the sea-level changes mostly concentrate on the last transgression (Chen et al., 2000; Li et al., 2000; Hori et al., 2001a, b; Li et al., 2002). The pre-Holocene depositional history of Yangtze River is poorly known, however, especially during Marine Oxygen Isotope Stage (MIS) 3. Studies on sea-level changes around the Yangtze River delta during MIS 3 (Lin et al., 1989; Yang et al., 2004; Wang et al., 2013) conflict with the sequence stratigraphic studies on the shelf in the Yellow Sea and East China Sea (Saito et al., 1998; Liu et al., 2003). Oxygen isotope

⁎ Corresponding author. E-mail address: [email protected] (G. Li).

records in Sulu Sea (Linsley, 1996), coral reef records in Vanuatu (Cabioch and Ayliffe, 2001) and coastal depositional records in Red River delta (Hanebuth et al., 2006) indicate that the sea level during MIS 3 in the tropical Pacific was much higher than the global eustatic sea level, which fluctuated at around 60–80 m below present sea level (bpsl) (Siddall et al., 2008). Along the east coast of China, researches on Quaternary stratigraphy widely identified the transgression during MIS 3 (named the Gehu transgression) (Zhao and Qin, 1985; Lin et al., 1989). The highest sea level was estimated at about 10 m bpsl during the late MIS 3 on southern Yangtze deltaic plain (Wang and Wang, 1980; Yang et al., 2004). In contrast, seismic studies found deltaic sequences in southern Yellow Sea and East China Sea and inferred that the regional sea-level change during MIS 3 was almost consistent with the global eustatic sea levels (Saito et al., 1998; Xia and Liu, 2001; Berné et al., 2002; Wellner and Bartek, 2003; Lee et al., 2013). The divergent judgments about the sea-level changes during MIS 3 have been rarely evaluated because the deep incision of Yangtze River (60–80 m) during the last glacial maximum (LGM) has made old deposits poorly preserved on inner shelf and in modern deltaic plain. The preserved deposits of MIS 3 potentially record the depositional environment in the lower Yangtze River and the highest sea-level position in this stage. In order to acquire the information about the pre-Holocene deposition of Yangtze River, three long cores were drilled in southern Yellow Sea (Fig. 1). Three cores were located out of the LGM-incised valley where pre-Holocene strata are preserved (Li et al., 2002; Wang et al., 2012). In this study, the pre-Holocene depositional history of Yangtze River system was established from these three cores. Previously reported cores with detail sedimentary records and chronological dates from

http://dx.doi.org/10.1016/j.yqres.2014.08.008 0033-5894/© 2014 University of Washington. Published by Elsevier Inc. All rights reserved.

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

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Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

Figure 1. Schematic map of the bathymetry in the southern Yellow Sea and northern East China Sea. Gray area and dark solid lines on Yangtze deltaic plain show the scales of the LGM incised valley and the pre-LGM incised valley, respectively (from Li and Wang, 1998; Wellner and Bartek, 2003). Red lines mark the outlines of the MIS 3 delta complex identified by seismic studies (Xia and Liu, 2001; Liu et al., 2003, 2010; Lee et al., 2013). Drill cores in this study are shown as squares. Main reference cores are labeled using triangles (Zheng, 1989; Jin, 1992; Tang, 1996; Liu et al., 2010; Wang et al., 2012; Lee et al., 2013; Li and Yin, 2013; Wang et al., 2013). The locations of two sedimentary profiles are shown. The chronologic framework of Core MFC is from Wang et al. (2013). YSTSR: Yellow Sea Tidal Sand Ridges. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Yangtze River delta and adjacent continental shelf were collected and were integrated to analyze the sea-level change during MIS 3.

Regional setting The continental shelf of Yellow Sea and East China Sea is one of the largest shelves in the world, with the maximum width of over 600 km. The East China Sea shelf extends from the coast of China to the Okinawa Trough, having a smooth and flat topography. The continental shelf is shallower than 150 m with an obvious shelf-break. Surficial sediments on the shelf are mainly supplied by Yellow River and Yangtze River. Vast fluvial sediment supply makes the sea-bed topography in the western Yellow Sea obviously higher than that in the east. The Yellow River shifted south of the Shandong Peninsula and flowed into the southern Yellow Sea from AD 1128–1855, forming the Old Yellow River delta (OYRD) (Zhang, 1984) (Fig. 1). In the southern Yellow Sea, a field of tidal sand ridges (Yellow Sea Tidal Sand Ridges: YSTSR) is distributed between the OYRD and the Yangtze River subaqueous delta. The YSTSR consist of more than 70 sand ridges separated by tidal channels and cover an area of 22,470 km2 (Wang et al., 2012). On the inner shelf of the northern East China Sea, a large sand shoal, named the Yangtze Sand Shoal (YSS), is distributed at water depths of 25–55 m (Fig. 1). Bottom sediments are dominated by fine sand.

Quaternary strata in the Yellow Sea and East China Sea consist of alternating marine and terrestrial sediments in response to glacioeustatic sea-level changes (Qin et al., 1987). The thickness of Quaternary sediments varies between 100 m and 200 m on the shelf (Jin, 1992; Yang, 1994). About eight marine units were identified from the Quaternary strata in the southern Yellow Sea (Yang, 1994). In the late Quaternary stratigraphy, the most remarkable marine units were dated in MIS 5 and MIS 1 (Yang et al., 1993). In Yellow Sea and inner East China Sea, at least two marine units separated by terrestrial units were discriminated within the strata of MIS 3 (Yang et al., 1993). No terrestrial deposits of MIS 5–3 were found in the strata on the outermost shelf of East China Sea (Tang, 1996). The Yangtze River delta is tide-dominated with a funnel-shaped topography and several wide distributary channels. Tidal water annually reaches an average of 210 km upstream from the river mouth (Shen, 1998). Modern sandy sediments from Yangtze River are mainly deposited in the river mouth in depths shallower than 10 m (Chen et al., 2000). The modern Yangtze River delta was built in the deep incised valley of the Yangtze dating from the LGM lowstand, which formed when sea level reached its present position at 6–7 cal ka BP (Hori et al., 2001a) (Fig. 1). Seismic analysis on the shelf showed the incised valleys from Yangtze River mainly extended southeastward to the outer East China Sea (Wellner and Bartek, 2003). Submarine relief above the main incised valley depicts a V-shaped trough, south of the YSS

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

(Fig. 1). A small LGM-incised valley from the river mouth trends eastward to the middle YSS (Fig. 1).

Material and methods Three cores were drilled in the field of southern YSTSR in 2007 (Fig. 1 and Table 1). Core 07SR11 (SR11) was taken on the oyster reef platform at the lowest tidal level. Core 07SR09 (SR09) was drilled in one tidal trough at a water depth of 10.8 m. Core 07SR04 (SR04) was drilled on one sand ridge at a water depth of 11.2 m. Rotary drilling was used, with a recovery ratio of 70%–80%. Core SR11 is located near the edge of the LGM-incised valley of the Yangtze River, whereas the other two cores were taken farther north (Fig. 1). A preliminary interpretation of the stratigraphy of Core SR04 was reported by Wang et al. (2012). In the laboratory, cores were split lengthwise and visually described, including the sediment color, grain size, and sedimentary structures. Subsamples were taken according to the variation of lithology, including 396 subsamples for grain-size analysis, 171 subsamples for magnetic susceptibility measurement and 88 subsamples for foraminifer identification. Before measuring grain size, samples were pretreated with 10% H2O2 and 0.1 N HCl to remove organic matter and biogenic carbonate. Grain-size analysis for the particles smaller than 2 mm was carried out on a Malvern Mastersizer 2000 laser particle size analyzer. Grain sizes over 2 mm were determined using the sieving method. Measurements by the two methods were integrated to get the whole grain size distribution. After drying at b 40°C, mass magnetic susceptibility was measured on a Bartington MS2 magnetic susceptibility system. For micropaleontological analysis, standard treatment methods were used and the fraction over 63 μm was examined. Results were recalculated on the basis of the wet sample weight of 100 g. Mollusk shells present in the cores were picked and identified. Multiple 14C ages were obtained from all three cores (Table 2). Radiocarbon-14 dating was mainly conducted on mollusk shells, plant debris and organic-rich clay using an accelerator mass spectrometry (AMS) system in Peking University. All radiocarbon age determinations were calibrated by using Calib 7.0 (Reimer et al., 2013). Radiocarbon age determinations of bivalve and gastropod shells were corrected for the regional marine reservoir effect (DR), which was regarded as − 96 ± 60 yr, obtained from Qingdao (Southon et al., 2002). Calendar ages are given with a two standard deviation (2σ) uncertainty (Table 2). Radiocarbon age determinations from SR04 were published by Wang et al. (2012). Dates from core NS1, drilled at the same location as SR11, were reported by Wang et al. (2009) and are listed in Table 2.

Results Borehole sediments were divided into three main units, Unit I, Unit II and Unit III from bottom to top. Sub-units within every unit were divided based on the color, sedimentary features and sedimentary structures (Fig. 2). Units I to III were described individually and interpreted, and then 14C ages of the core sediments are discussed.

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Depositional units and facies interpretation Unit I (71–24 m in SR11; 66.7–32.9 m in SR09; 30.8–21.5 m in SR04) Sub-unit I.1 in cores SR11 and SR09 is primarily composed of yellowish-brown medium sand, fine sand and silty sand. The sand layers consist of N 75% sand fraction. Sand layers are mostly structureless, with occasional cross-bedding and parallel bedding (Figs. 3a, b, e, f). Muddy layers are thin and variable in grain size. Rounded quartz gravels, muddy granules and carbonate nodules are occasionally found in sandy layers (Figs. 3a, d). Plant debris is mostly concentrated as laminae or decimeter-thick gyttja beds in the upper part of sand beds (Fig. 3b). Mud-dominant intervals contain a few sandy lenses with cross lamination (Fig. 3c). Magnetic susceptibility of this sub-unit is highest in all sections and is variable in the scale of 40–350 × 10−8 m3 kg−1. Mollusk shells found in sandy layers include freshwater and brackish water species. Freshwater gastropods present are Bithynia robusta hongkongensis Yen, Gyraulus albus Müller, Parabithynia longicornis Benson, Parafossarulus striatulus Benson, P. subangulatus von Martens, Tritonella festiva Powys, Turbonilla nonlinearis Wang, T. nonnota Nomura and T. Shanghaiensis Wang. Brackish water bivalves are Barbatia parallelogramma Busch, Meretrix meretrix Linnaeus and Potamocorbula sp. Foraminifers are rare in this subunit, with rare Ammonia beccarii var. and Pseudorotalia schroeteriana in Core SR11 at depths of 51.3 m and 70.7 m. The scarcity of foraminifers and abundance of the freshwater mollusks suggest that this sub-unit was mainly of terrestrial origin. Thick sandy deposits are mostly of fluvial origin and they correspond to channel and the point-bar deposits in a highly dynamic environment (Meckel, 1975; Okazaki and Masuda, 1995). Leaves and wood fragments concentrated in the sandy layers indicate that some organic debris was transported and deposited during flood period. Muddy sediments and gyttja deposits overlying sand beds correspond to the waning period during floods. A few tide-influenced sedimentary structures are present in some sections of the lower sub-unit. The sand– mud alternation facies present in some sandy sections (Figs. 3b, e) is similar to the sand–mud couplet structure (type b) defined by Hori et al. (2001b) and sandy deposits with muddy drapes found in the Rhine and Meuse valleys (van den Berg et al., 2007). Sand–mud alternation facies forms in the fluvial–tidal transition zone where the deposition was dominated by fluvial processes but could be influenced by the tide (Allen, 1991; Allen and Posamentier, 1993). Brackish mollusks also indicate that this part of the fluvial deposition was influenced by marine water. Sub-unit I.2 in Core SR11 (33.8–24 m) is a homogeneous clayey silt with faint lamination (Fig. 3g). The lower part of this sub-unit is transitional with the underlying sub-unit I.1 and contains sandy lenses and thin sandy beds. Organic materials are rare in this sub-unit, but some thin organic laminae are present within the sandy deposits. Magnetic susceptibility of this sub-unit is relatively uniform within the range of 20–40 × 10−8 m3 kg−1. Mollusk shells are scarce and no foraminifers were found. The absence of foraminifers and the homogeneous character of subunit I.2 indicate that these sediments are lacustrine deposits. The low content of organic material in the sediments suggests that it was an

Table 1 Locations, water depths, and core lengths of the cores in this study. Core no.

Latitude

Longitude

Water depth (m)

Core length (m)

Recovered length (m)

SR04a SR09 SR11 NS1b SMc

33°27.18′N 32°32.74′N 32°8.99′N 33°27.16′N 32°27.8′N

122°5.62′E 121°36.28′E 121°32.82′E 122°5.61′E 121°18.6′E

−11.2 −10.8 0 0 +3.1

30.8 66.7 71 33.2 60.3

24.8 45.9 51.2 27

a b c

Core SR04 was named as Core Kuishuiyang in the paper by Wang et al. (2012). After Wang et al. (2009). After Wang et al. (2012).

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

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Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

Table 2 List of radiocarbon age determinations from four cores in this study. Core no.

Depth/m

Material

Species

Conventional 14C age (yr BP)

Calibrated 14C age (cal yr BP; 2σ)

Lab no.

Commenta

07SR04b

−11.53 −14.34 −17.18 −21.53 −24.68 −30.38 −0.65 −2.85 −15.61 −28.5 −38.36 −47.2 −53.34 −54.14 −64.92 −0.05 −0.79 −1.93 −24.9c −29.1c −31.19 −37.3 −38.72 −39.73 −43.67 −48.5 −52.1 −60.47 −64.11 −66.9 −68.6 −69.93 −70.75 −5.52 −13.95 −19.67 −26.15

Mollusk shell Mollusk shell Single mollusk shell Single mollusk shell Organic rich clay Organic rich clay Mollusk shell Mollusk shell Mollusk shell Organic rich clay Organic rich clay Gyttja Mollusk shell Single gastropod gyttja Single oyster shell Single oyster shell Single oyster shell Organic rich clay Organic rich clay Mollusk shell Gyttja Single leaf Gyttja Gyttja Gyttja Gyttja Clayey siltd Mollusk shell Single mollusk shell Single mollusk shell Mollusk shell Mollusk shell Organic rich clay Organic rich clay Organic rich clay Organic rich clay

Shell fragment Shell fragment Dosinia gibba Corbicula fluminea

2005 ± 40 3375 ± 30 4290 ± 40 27,830 ± 100 31,975 ± 100 31,655 ± 170 2815 ± 40 3455 ± 30 7255 ± 35 15,190 ± 70 26,890 ± 120 N43,000 30,695 ± 170 42,005 ± 390 N43,000 530 ± 30 360 ± 30 535 ± 30 N43,500 N43,500 2075 ± 30 N43,000 N43,000 N43,000 42,665 ± 485 42,965 ± 300 N43,000 22,130 ± 60 785 ± 30 40,935 ± 370 N43,000 34,440 ± 235 715 ± 35 5630 ± 700 6824 ± 125 8056 ± 120 42,535 ± 305

1687 3345 4576 31,315 35,440 35,140 2647 3441 7806 18,460 30,990

BA090484 BA090485 BA090486 BA090487 BA090488 BA090489 BA090438 BA090448 BA090439 BA090440 BA090442 BA090443 BA090444 BA090445 BA090447 BA090449 BA090450 BA090451

Reliable Reliable Reliable Reliable Reliable Reliable Reliable Reliable Reliable Reliable Reliable Reliable Unreliable Reliable Reliable Reliable Reliable Reliable Reliable Reliable Unreliable Reliable Reliable Reliable Reliable Reliable Reliable Unreliable Unreliable Reliable Reliable Unreliable Unreliable Reliable Reliable Reliable Reliable

07SR09

07SR11

NS1

a b c d e

e

Shell fragment Shell fragment Shell fragment

Shell fragment Assiminea sp. Ostrea denselamellosa Ostrea denselamellos Ostrea denselamellosa

Shell fragment

Shell fragment Meretrix meretrix Parafossarulus striatulus Shell fragment Shell fragment

± ± ± ± ± ± ± ± ± ± ±

170 174 209 203 340 400 194 171 140 190 200

34,374 ± 359 45,094 ± 715 255 ± 175 118 ± 118 263 ± 173

1755 ± 168

45,940 ± 940 46,170 ± 670 26,340 ± 240 501 ± 127 44,148 ± 751 38,650 416 5900 7330 8600 45,790

± ± ± ± ± ±

586 121 1600 240 310 620

BA090455 BA090456 BA090457 BA090458 BA090459 BA090460 BA090461 BA090462 BA090463 BA090464 BA090465 BA090466 BA090467 KF06090 KF06087 KF06088

Dates on multiple shell hash in unit I are mostly abnormal and out of the sequence. After Wang et al. (2012). After unpublished thesis by Li, Y.J. (pers. comm). Organic content of this sample is low. After Wang et al. (2009).

oligotrophic lake. Intercalated medium-sand layers in the lower part of sub-unit I.2 show the transitional character with underlying deposits. The lake was probably an oxbow lake produced by migration of a river channel. The fining-upward sequence may reflect the decreasing influence from river and the deepening of the lake. The lower part of sub-unit I.3 in Core SR04 (30.8–22.5 m) is characterized by bioturbated clayey silt with abundant sand layers and lenses. Cross lamination and parallel lamination are common in the sand layers (Fig. 3h). The upper part of sub-unit I.3 (22.5–21.5 m) is a sandy silt bed with concentrations of shells and dispersed reddish oxidized spots (Fig. 3i). The shell layer has high organic content characterized by dark gray color and dispersed organic spots. Mollusk shells include freshwater and brackish water species that are common on the modern tidal flats in the Yellow Sea, such as Arca sp. Corbicula fluminea Müller. Foraminifers in sub-unit I.3 have low abundance compared with the overlying Holocene stratum, less than 35 tests per 100 g wet sample (Fig. 2). The assemblage is dominated by the littoral species A. beccarii var. with secondary shelf species including Bolivina striatula, Nonion grateloupi and Uvigerina schwageri. Magnetic susceptibility of sub-unit I.3 is mostly lower than 30 × 10−8 m3 kg−1. Sedimentary characteristics and the fossil assemblage indicate that sub-unit I.3 is a tidal-flat deposit. C. fluminea Müller is a common mollusk on the tidal flat in the Yellow Sea (Liu and He, 2003). Low abundance and low diversity of foraminifers in the sediments suggest that sub-unit I.3 corresponds to supratidal flat to upper tidal flat

environments (Hua and Wang, 1986). The heavily bioturbated clayey silt deposits with frequent sandy lenses are in accord with the sedimentary characteristics of supratidal flat and upper tidal-flat sediments on the Jiangsu coast described by Zhu and Xu (1982) and Wang et al. (2002). The 1-m-thick shell layer with oxidized spots corresponds to the deposits of cheniers and shelly ridges, which are commonly distributed on erosive tidal flats in the western Yellow Sea (Wang and Ke, 1989). The shelly ridges and cheniers mostly lie adjacent to the shoreline on the high tidal mud flat (Zhu and Xu, 1982; Lee et al., 1994).

Unit II (24–22.2 m in SR11; 32.9–24 m in SR09) Sub-unit II.1 in Core SR11 includes two types of sediments with a yellowish brown color. The upper part of the section is mainly sandy deposits and the lower is stiff mud (Fig. 4a). The sandy deposits have more than 50% sand. The stiff mud is composed of 25% clay, 60% silt, and 15% sand. Abundant oxidized spots and organic patches are visible in the stiff mud. Stiff mud contains a few carbonate nodules. Magnetic susceptibility of this sub-unit is around 23 × 10−8 m3 kg−1. Sub-unit II.2 in Core SR09 is characterized by brown muddy deposits intercalated with sand layers (Figs. 4b, c). The sandy deposits are mostly composed of 25–30% medium sand and ~ 50% fine sand. A few reddish muddy clasts were found in some sandy deposits (Fig. 4c). Only one foraminifer sample was found in this sub-unit at 30.5 m. Thirteen tests were found in this sample and include Ammonia annectens, Noin sp., and

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

depth/m

SR11

0

Sand Foram -1 % n(100g)

SR09

255±175

5

SR04

Sand Foram -1 % n(100g)

Sand %

Foram n(100g) -1

2,647±194

263±173 3,441±171 5,900±1,600*

6,320±80

10

III

III

III 1,687±170

7,330±240*

3,345±174 7,806±140 4,576±209

20

8,600±310* 31,315±203

II.1

35,440±340 >43,500 #

45,790±620*

I.2

I.3 18,460±190

II.2

>43,500#

30

35,140±400 1,755±168

10 2 1

0

10 3

>43,000

30,990±200

>43,000 >43,000

40

Legend Stiff mud

Lenticular bedding

Cross bedding

Trough cross bedding

Bipolar cross bedding

Sand-mud couplets

Contorted

Carbonate nodules

Oyster

Erosional boundary

Freshwater mollusk

Bivalve shells

Muddy block

Gastropod

Plant debris

Peat

45,940±940

>43,000

46,170±670

50

I.1 I.1 >43,000

34,374±359 45,094±715

Silic gravels

60

Unrecovered

mud 186±55 Calibrated age (cal yr BP) silt fine sand 410±80 unreliable age medium sand coarse sand

26,340±240

501±127 >43,000

0

10 2 1

10

3

44,148±751 >43,000

70

38,650±586 416±121

0

10 2 1

10 3

Figure 2. Sedimentary column of each core. Calibrated 14C ages are labeled. Radiocarbon age determinations with asterisk and pound were measured by Wang et al. (2009) and Li, Y.J. (pers. comm), respectively.

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

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Figure 3. Representative core photographs. (a–f): Examples from sedimentary sub-unit I.1. (a) Massive medium sand deposits with mollusk shells and carbonate nodules. (Below) Closeup of carbonate nodules. (b) gyttja deposits with abundant micas overlying sand deposits with parallel bedding. The brown clay at the top was intruded during coring. (c) Sandy layers within the muddy section have cross lamination and parallel lamination. Muddy deposits also contain thin sandy laminae. (d) Rounded muddy gravels present in the sandy layers. Weathered shells and plant debris are mixed within sand deposits. (e and f) Thick sand layers alternating with thin mud layers. (g) Homogeneous clay silt with faint lamination. (h–i): Examples from sedimentary sub-unit I.3. (h) Bioturbated clay silt containing sandy lens. The sandy lens has normal grading and parallel lamination. (i) Shell-concentrated sandy silt deposits. Reddish oxidized spots are visible on the split surface. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Spiroloculina lucida. The magnetic susceptibility of this sub-unit is higher than subunit II.1 and is around 50 × 10−8 m3 kg−1. Stiff mud present in core SR11 has been widely discovered around the Yangtze River delta and it was deposited on an alluvial plain between river channels during the late Pleistocene (Li et al., 2002). Reddish ferruginous nodules in the mud indicate that the stiff mud layer was exposed and experienced pedogenesis (Chen and Li, 1997). Although this characteristic layer was not found in Core SR09, a few reddish ferruginous muddy clasts also suggest that a few sections in this unit were exposed. The absence of foraminifers in most sediment supports the interpretation of unit II as a terrestrial facies. Brackish foraminifers found in one samples may have been eroded from old marine sediments and redeposited in fluvial sands.

Unit III (22.2–0 m in SR11; 24–0 m in SR09; 21.5–0 m in core SR04) Unit III in all three Cores has a coarsening-upward succession. The lower section is characterized by bioturbated clayey silt inter-bedded or inter-laminated with fine sand (Figs. 4d, g). In the middle section of SR11 and SR09, sandy sediments were deposited as thicker beds intercalated with thin muddy layers (Fig. 4e). Cross-laminations are commonly present in the sandy deposits and some show bidirectional orientations. The upper section of SR11 is mainly composed of well sorted silt and fine sand. Cross-lamination and parallel lamination are the main structures visible in this section (Fig. 4f). The upper section of SR09 is dominated by medium sands. Muddy sediments were deposited as thin layers (Fig. 4h). The upper part of SR04 is dominated by well sorted fine sand. Sand–mud lamination is the main structure in the

Figure 4. Representative core photographs. (a–c): Examples from sedimentary sub-unit II. (a): Reddish yellow medium sand overlying the stiff mud; (b and c): Brown mud interbedded with medium sand. Oxidized mud blocks are sporadically visible; (d–i): Examples from sedimentary sub-unit III. (d): Mud dominant deposits with sand layers. Some sand layers display small-scale scour-and-fill structures and cross lamination. (e): Sand dominant deposits interbedded with mud layers. Cross-lamination structures are commonly present in sand layers. (f): Sand dominant deposits with thin mud layers. Parallel lamination and cross lamination are common. (g): Mud dominant deposits interbedded with thin sandy layers. (h): Thick medium sand layer with thin muddy layers. (i): Interlaminated mud/sand deposits. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

upper section (Fig. 4i) and pure fine sands are present in the uppermost section. Magnetic susceptibility of unit III in the three cores is mainly variable within the range of 20–50 × 10−8 m3 kg−1. At the top of the three cores, the coarsest part of this unit has higher magnetic susceptibility close to 100 × 10−8 m3 kg−1. Foraminifers within unit III have high abundance and high diversity. Test abundances per 100 g wet sample are 100–300 in SR11, 40–120 in SR09 and 200–400 in SR04. Dominant species are littoral to shelf species (A. beccarii var., Cribrononion frigidum, Quinqueloculina complanata, Q. lamarckiana) and shelf species (B. striatula, N. grateloupi). A. annectens is commonly present in sediments of SR09 and SR04. Elphidium kiangsuensis is only found in the upper 5 m of SR11. There are also some A. pauciloculata, B. pseudopunctata, Lagena striata, L. clavata, L. hispidula, Florilus decorus, Massillina secans, Nonionella opima, Sigmoilina subtenuis, and Spiroloculina lucida. Foraminiferal assemblages indicate that sediments of unit III are marine facies. In the lower part of the three cores, the shelf facies is characterized by bioturbated mud with occasional storm deposits. In Core SR09, mud–sand couplets dominate the lower section, indicating that the shelf deposits were strongly influenced by tides. The succession from mud-dominated to sand-dominated in Core SR11 reflects shallowing upward. Sedimentary structures in the upper section of SR11 (Fig. 4f) indicate that the sandy deposits correspond to the finesand flat at the low tide level (Zhu and Xu, 1982; Wang et al., 2002). E. kiangsuensis in the upper section of SR11 is a characteristic species of tidal flats in the East China Sea and Yellow Sea (Hong, 1985). Deposits in the upper SR09 are mainly composed of medium sands intercalated with muddy drapes, reflecting the strong hydrodynamic conditions in the tidal channel. In the top of SR04, pure sand reflects the effect of waves on the sorting of sediments on the tidal ridge. Radiocarbon age determinations The AMS 14C results indicate that unit III was deposited in the Holocene (Table 2 and Fig. 2). Radiocarbon age determinations show an orderly downward progression, except one date on bulk organic-rich clay in the upper part of SR04 that appears anomalously old. The thickness of the Holocene stratum in SR04 (21.5 m) is comparable with Core SYS702 (20.22 m) on the OYRD, north of Core SR04 (Fig. 1), where the Holocene stratum was mainly deposited after 2500 cal yr BP (Liu et al., 2010). According to previous studies (Chen and Li, 1997), stiff mud below Holocene stratum is the stratigraphic marker bed of MIS 2 in Yangtze deltaic plain. The stiff mud present in Core SR11 thus indicates that unit II corresponds to MIS 2. In SR09, one date of 18.5 cal ka BP on organic rich clay at a depth of 28.5 m confirms that unit II formed during MIS 2. In unit I of the three cores, twenty three AMS 14C dates were acquired (Table 2). Fourteen of these are infinite and others are close to the limit of reliable dating (N 45 14C ka BP). A few dates in this unit are problematic and out of the sequence. Most dates on organic clay, gyttja, single leaf and single mollusk shell are consistent and can be compared, except one date at 60.47 m in Core SR11. The dated clayey silt does not have rich organic material and supplied an abnormally young age (26 cal ka BP). Most dates on mollusk shell hash are problematic and not reliable. In Core SR11 a few dated samples were contaminated by young carbon during core collection in the field, with three late Holocene dates on mollusk shell hash being clearly inconsistent with the stratigraphic position. A young date (1755 ± 168 cal yr BP) at 31.19 m in Core SR11 is contradicted by newly acquired dates and one date on organic-rich clay in Core NS1 (= SR11) (Table 2). Two dates on shell hash in Core SR09 (53.34 m) and Core SR11 (69.93 m) are obviously younger than the dates above and below on single mollusk shell and gyttja. Yim (1999) questioned the reliability of pre-Holocene radiocarbon age determinations because of admixtures of younger carbon during transport, deposition and post-depositional processes. However, the

7

radiocarbon dating method has been widely used to constrain the chronology of pre-Holocene depositional sequences on the shelf (Chough et al., 2004; Liu et al., 2010; Lee et al., 2013) and on the coast (Hanebuth et al., 2006; Cohen et al., in press) with consistent results. Wang et al. (2013) verified the reliability of radiocarbon age determinations approaching the dating limit in Core WJ in southern Yangtze deltaic plain. Two radiocarbon age determinations approaching the dating limit were in accord with OSL (optically stimulated luminescence) dates. The chronologic study on OYRD by Liu et al. (2010) also showed that in the age range of MIS 3 radiocarbon age determinations were not contradictory with OSL dates. In the strata of MIS 3 constrained by OSL dates, finite and infinite radiocarbon age determinations were both present. However, in the strata older than MIS 3 all radiocarbon age determinations were infinite. In this study over half the dates in unit I were finite. Based on the good finite dates discussed above, it is suggested that unit I formed during MIS 3. One OSL date is available for Core 11DT02 in inner YSTSR, in tidal-flat deposits below stiff mud, corresponding to subunit I.3 in Core SR04. The OSL age in the tidal-flat deposits is 57,500 yr (Li and Yin, 2013), similar within likely error to the ~45 ka radiocarbon age determination. Discussion Sedimentary environment during MIS 2 and MIS 1 In order to clarify the late Quaternary sedimentary sequence in the northern Yangtze deltaic plain and the adjoining inner shelf, four reference cores and the three cores in this study were used to build a sedimentary profile crossing the LGM incised valley. These cores were published by Jin (1992), Zhao et al. (2008), Wang et al. (2012) and Li and Yin (2013). The chronological correlation of these cores in this study is shown in Figure 5. The youngest sedimentary unit in this study, unit III, represents Holocene sedimentary sequence. In cores SM and 11DT02 (Wang et al., 2012; Li and Yin, 2013), tidal-flat deposits in the lowest section of this unit record the marine transgression during the early Holocene (Fig. 5). Within the three cores in this study, unit III shows a shallowing-upward facies succession with no typically transgressive lag deposits. The lower part of the unit III in the cores SR11, SR09 and SR04 represents the inner-shelf deposits during the middle Holocene when sea level rose to its present level (Fig. 5). More frequent storm beds and tidal deposits are present in the upper inner-shelf deposits. Tidal currents strengthened in the central tidal channel after 3–4 cal ka BP, recorded by Core SR09. AMS 14C dates in SR04 indicate that most sediment has been deposited since 4.4 cal ka BP with an upward increase in accumulation rate. The significant increase of sedimentation rate in SR04 after ca. 1500 cal yr BP indicates that the sedimentation in the northern YSTSR was influenced by the newly formed Yellow River subaqueous delta after AD 1128. At the site of SR11, coastal aggradation was slow in the late Holocene according to 14 C dates, obviously slower than the aggradation speed of the Yangtze River delta (Hori et al., 2001a). The crossing sedimentary profile (Fig. 5) highlights the different sedimentary thicknesses between the incised valley and interfluve during MIS 2. Most sediment from Yangtze River was deposited in the incised valley and thick fluvial sands were accumulated. On the interfluve, low sediment supply produced only a thin sedimentary layer in MIS 2 and pedogenesis of surficial fluvial mud. There is no MIS 2 sedimentary layer in Core SR04, and an erosional marine transgression in the early Holocene probably created the hiatus between unit III and unit I. Yangtze River deposition during MIS 3 According to radiocarbon age determinations in this study and OSL dates by Li and Yin (2013) and Wang et al. (2013), Unit I defined in this study was deposited during MIS 3. The crossing sedimentary profile

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

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Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

MI S

MFC

Ch4

SR11

0

SM 11DT02

255±175

Elevation relative to present sea level (m)

5,900±1,600

1

*8.4±0.2 ka *9.15±0.25 ka

2

*16.23±1.56 ka *21.59±1.93 ka

767±126

SR09 2,647±194 3,441±171

7,330±240 8,600±310

Incised valley during LGM

45,790±620

7,283±134

1,687±170 3,345±174 4,576±209

*57.5 ka

31,315±203 35,440±340

7,806±140 >35,000

*32.35±2.91 ka

SR04

*3.2 ka

>43,000 >43,000

18,460±190

35,140±400

45,940±940

-50

3

peat *43.42±2.61 ka

46,170±670 >43,000

14,900±1,000

>43,000 45,094±715

44,148±751 >43,000

*66.62±4.14 ka

4

>43,000

MIS-3 Yangtze River main channel deposits -100

30,990±200

5

Mud **95±4.7 ka

Silt

Legend

*116.4±11.25 ka

**137±6.5 ka

Sand

Shelf

Lake

Prodelta Delta front and mouth bar

Alluvial plain Fluvial channel Tide-influenced fluvial channel

**95±4.7 ka TL age

Lagoon

*137±6.8 ka OSL age

Gravel

Tidal flat

Stiff mud

Estuary

#45.3±3.7 ka U-series age 9,796±203

14

C age ( cal yr BP )

Figure 5. Stratigraphic section in the Yangtze deltaic plain and the offshore area. The Yangtze River channel deposits during MIS 3 were highlighted by yellowish mask. Reference cores are from Jin (1992); Li and Wang (1998); Wang et al. (2012); Li and Yin (2013) and Wang et al. (2013). The location of this profile is shown in Figure 1. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

(Fig. 5) shows that different paleo-environments existed in modern Yangtze River deltaic plain and the adjoining shelf during MIS 3. The stratigraphy of two cores (SR11 and SR09) shows that fluvial sands, over 35 m thick, were deposited in the northern Yangtze deltaic plain during MIS 3. A similar sand layer over 30 m thick was reported in cores SM and T08, north of Core SR11 (Fig. 1). One radiocarbon age determination (N35 14C ka BP) in Core SM placed this sandy unit into MIS 3 (Wang et al., 2012). Zhu et al. (1999) studied fossil forams (larger than 55 μm) in Core SM and found continuous occurrence of forams in the lower sand layer of MIS 3. The species assemblage was found to be similar to the species assemblage in modern tide-influenced channel of Table 3 Mollusk species and foram species found in unit I of cores SR11, SR09 and SR04. Depth

Species

SR11 42.8– 42.9 m 52.1– 52.6 m 53.1– 53.2 m 60.4– 61.2 m 67.9– 70.8 m

Mollusk species: Assiminea cf. sculpta Yen

SR09 53.3– 53.4 m SR04 21.5– 22.5 m 22.5– 30.8 m

Mollusk species: Gyraulus albus Müller Foram species: Ammonia beccarii var. Mollusk species: Parabithynia? sp. Mollusk species: Barbatia parallelogramma Busch, Bithynia robusta hongkongensis Yen, Gyraulus albus Müller, Meretrix meretrix Linnaeus, Nassarius sp., Parabithynia longicornis Benson, Parafossarulus striatulus Benson, Parafossarulus subangulatus von Martens, Potamocorbula sp., Tritonella festiva Powys, Turbonilla nonlinearis Wang, Turbonilla nonnota Nomura and Turbonilla Shanghaiensis Wang Foram species: Pseudorotalia schroeteriana Mollusk species: Assiminea sp. Mollusk species: Arca sp., Corbicula fluminea Müller, Corbicula leana Prime Foram species: A. beccarii var., A. pauciloculata; Bolivina striatula; Lagena substriata; Nonion grateloupi; Uvigerina schwageri; Rotaliids

Yangtze River, from the river mouth to the tidal limit (Zhu et al., 1999). The study by Wang et al. (1980) pointed out that foraminiferal shells within bottom sediments in the Yangtze Estuary were transported by tidal currents and most had small test size. Because the sieve of 63 μm was used in this study and some small forams might be sieved out, fossil forams were only sporadically found in sub-unit I.1. However, sedimentary structures and brackish fossils present in of the lower part of Core SR11 indicate that during some periods in MIS 3 seawater intruded into the main channel and tides influenced the deposition in channels (Fig. 2 and Table 3). In the northern sand ridge field and the middle Jiangsu coastal plain, most sedimentary records such as cores SR04, 11DT02 and By1 show that tidal flats developed there during MIS 3. In the southern Yangtze deltaic plain and in Hangzhou Bay, tidal flats during this stage were also widely distributed (Wang et al., 2006; Zhao et al., 2008). Zhao et al. (2008) identified deltaic sandy deposits within the MIS 3 section from Core MFC (Fig. 5), but the thickness of the sandy layer is not comparable with the sandy deposits in the northern plain. Overall, thick fluvial deposition was dominant in the northern Yangtze deltaic plain between Qianggang and modern river mouth and the adjoining shallow-water area during MIS 3. The distribution of these thick sand deposits overlaps the zone of pre-LGM incised valley in the Yangtze deltaic plain mapped by Li and Wang (1998). The thickness and the location of fluvial sands suggest that the medium to fine sand was sourced from the main channel of Yangtze River. The fluvial sands represent the main channel deposits in the lower Yangtze River. In the northern East China Sea, seismic and sedimentological studies found a few buried deltaic bodies of MIS 3 from the inner to outer shelf (Zheng, 1989; Jin, 1992; Saito et al., 1998; Xia and Liu, 2001; Berné et al., 2002; Liu et al., 2003; Wellner and Bartek, 2003; Lee et al., 2013). All identified deltaic bodies are summarized and shown in Figure 6. At water depths of 40–70 m, seismic profiles by Xia and Liu (2001) recorded the deltaic layer below the modern sand layer in the field of YSS (Xia and Liu, 2001). Core S5207, drilled on one seismic profile into this deltaic layer, provided one 14C age of N35 14C ka BP (Jin, 1992). The marine

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

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Figure 6. Stratigraphic section from the Yangtze deltaic plain to the outer shelf, showing the channel deposits on land (yellowish mask) and the deltaic deposits on the shelf (blue mask). Labels are the same as in Figure 5. Reference cores are from Zheng (1989); Jin (1992); Tang (1996) and Lee et al. (2013). Deltaic deposits identified by seismic profiles (Xia and Liu, 2001 [1]; Lee et al., 2013 [2]; Saito et al., 1998 [3]) are labeled besides the core logs. The chronologic framework of Core DZQ4 is from Liu et al. (2000) and Berné et al. (2002). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

muddy deposits in the lower section of Core S5207 correspond to the prodelta facies. In the north, Core QC3 recorded three marine sandy layers separated by terrestrial deposits below the Holocene sands (Zheng, 1989). Based on the geomagnetic chronology and a few 14C dates, Zheng (1989) put the lower unit of Core QC3 in the range of MIS 3. Sedimentary features and fossil forams indicate that these sandy layers in the lower unit were probably the river-mouth bar deposits. Lee et al. (2013) reported a few recent seismic stratigraphic studies in the northern East China Sea, which covered the deep part of YSS and the outer shelf (from 50 m to 120 m). The deltaic layer of unit J2 was dated at MIS 3, constrained by Core ESCDP-102 (Fig. 1). The seismic study by Wellner and Bartek (2003) mainly showed deltaic deposits during MIS 3 in deep water, southeast of YSS. Saito et al. (1998), Berné et al. (2002) and Liu et al. (2003) identified deltaic deposits from seismic profiles on the outer shelf of northern East China Sea and mapped the scale of the MIS-3 subaqueous delta, which was constrained by Core DZQ4. Until now, all identified deltaic bodies of MIS 3 age were located in the southeast of channel belts of Yangtze River (Fig. 1) and in water depth of 40–100 m. Marine-influenced fluvial sandy deposits in cores SM and SR11 indicate tidal currents in the main channel of Yangtze River intruded to the modern coast during the highest stand of MIS 3. By analogy with the modern tidal current limit in lower Yangtze River, the Yangtze River delta during n the highest stand was probably located in a water depth of ca. 40 m bpsl (near the cores QC3 and S5207). In the middle Jiangsu coastal plain and the southern Yangtze deltaic plain, widely distributed tidal-flat deposits (Yang et al., 2004; Zhao et al., 2008; Zhang et al., 2010; Wang et al., 2013) indicate that the paleocoastlines during the highest stand of MIS 3 were located in the plain, west of the modern coast. During the highest stand of MIS 3, a large

protruded delta was probably built on the middle shelf of northern East China Sea. The outline of the delta complex in the northern East China Sea (Fig. 1) suggests that Yangtze River deltas built during MIS 3 were distributed over a broad area and a wide range of water depths. The deposition of Yangtze River deltas during MIS 3 shows different characteristics from the Holocene deltaic systems which were mainly built in the LGM-incised valley on land (Li et al., 2000). Several factors influenced the formation of the Yangtze River delta during MIS 3. As the sea-level fall in MIS 4 was less than in MIS 2, the MIS 4 incised valley was shallower than that in MIS 2. The large sediment load in the Yangtze River in MIS 3 could have filled available accommodation during periods of sea-level rise in MIS 3 with fluvial sand because of base level rise. In addition, rapid sea-level excursions during MIS 3 (Yokoyama et al., 2001) are unfavorable for the creation of large accommodation space. The huge sediment supply and sea-level fluctuation probably promoted rapid progradation of the Yangtze River delta onto the flat shelf. Sea-level implications Eustatic sea-level variations during MIS 3 were recently reviewed by Siddall et al. (2008). Eustatic sea level was approximately at 60 m bpsl in the early MIS 3 and dropped to 80 m bpsl in the late MIS 3, with sealevel fluctuations of the magnitude of 20–30 m. Table 4 lists the collection of MIS 3 sea-level records in the southern Yellow Sea and on the surrounding coast. The relative sea-level data show large discrepancies, and most sea-level positions are higher than eustatic sea level. A similar record of relative sea-level positions was reported by Hanebuth et al. (2006) in Southeast Asia. Several effects on the sea-level records have been summarized, including local subsidence/uplift due to differential sediment load, glacio-hydro-isostatic adjustment, and tectonic

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

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Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

Table 4 Sea-level records in southern Yellow sea and around Yangtze River delta. Core

Water depth (m)

Age (yr)

07SR04 07SR04 11DT02 S5207 By1 By1 By1 By1 WJ WJ SG07 FX MFC MFC YQ0902 YQ0902 XZK169 XZK169 SYS701 SYS702 YS01A YSDP104 YSDP104 YSDP105 YSDP105 YSDP105

−11.2 −11.2 −5.7 −50 +5 +5 +5 +5 +3 +3 +4.3 +3 +3 +3 +4.6 +4.6 −10.56 −10.56 −33 −32 −58.5 −45 −45 −64 −64 −64

31,315 35,140 57,500 N35,000 30,370 36,430 42,840 35,990 44,684 46,024 45,000 39,200 32,350 43,420 31,510 42,650 29,400 39,400 46,870 37,550 31,640 31,300 44,100 30,900 33,490 37,200

Error (2σ) (yr) 203 400

350 440 310 400 843 1003 4000 2930 2910 2610 350 880 1000 1000 2374 950 686 340 1300 330 590 1400

Depth (m)

Sedimentary facies

Materials

Sea level (m PMSL)a

Dating method

21.5 30.4 24.2 1.9 20.8 24.1 28.8 32 11.8 14.2 52.7 49 39 54.5 34.5 37.6 30.75 40.75 16.64 39.36 15.8 3.5 19.4 40.2 46.3 56

Upper tidal flat Tidal flat Upper tidal flat Estuarine Tidal flat Tidal flat Tidal flat Tidal flat Tidal flat Tidal flat Beach Tidal flat Proximal delta front Tidal flat Lagoon Lagoon Tidal flat Tidal flat Proximal delta front Proximal delta front Shallow marine Upper tidal flat Subtidal flat Tidal flat Tidal flat Upper tidal flat

Corbicula fluminea Müller Organic rich clay

36b 41–44c 33b 42–52e 15–18c 18–21c 23–26c 26–29c 8–11c 10–13c ~48.4f 45–48c 26–31g 51–54c 25–30h 28–33h 40–43c 50–53c 40–48g 61–68g b54d 48–50b 59–64i 103–106c 112–109c 122–119b

AMS14C AMS14C OSL 14 C AMS14C AMS14C AMS14C AMS14C AMS14C AMS14C U-series OSL OSL OSL AMS14C AMS14C 14 C 14 C AMS14C AMS14C AMS14C AMS14C AMS14C AMS14C AMS14C AMS14C

Organic clay Organic clay Organic clay Organic clay Organic clay Mollusk shells Mollusk shells

Organic debris Organic debris Organic clay Organic clay Cobulidae gen. et sp. indet. Organic debris Foraminifers Peat Foraminifers Organic debris Organic debris Peat

References: 07SR04 (this study); 11DT02 (Li and Yin, 2013); S5207 (Jin, 1992); By1 (Zhang et al., 2010); WJ and FX (Wang et al., 2013); YQ0902 from Oujiang deltaic plain, south of Hangzhou Bay (Shang et al., 2013); YS01A (Wang et al., 2014); YSDP104 and YSDP105 off Korea Peninsula (Chough et al., 2004). The location of cores is shown in Figure 1. a PMSL, present mean sea level. b Interpreted paleo-water depths at +3 m. c Interpreted paleo-water depths at +3 to −1 m. d Interpreted paleo-water depths at b−20 m. e Interpreted paleo-water depths at 0 to −10 m. f Interpreted paleo-water depths at 0 m. g Interpreted paleo-water depths at −5 to −10 m. h Interpreted paleo-water depths at 0 to −5 m. i Interpreted paleo-water depths at 0 to −5 m.

displacement (Hanebuth et al., 2006; Wang et al., 2013). Obvious differences of sea level existed between the coast and the shelf (Table 4). Hanebuth et al. (2006) inferred that this sea-level difference on the Southeast Asian margin was mainly caused by differential sediment load and hydro-isostatic adjustment. The effect of local subsidence due to high deltaic sediment load could be found in Table 4. The sea-level positions are lower in the sites close to Yangtze River delta and Yellow River delta. Liu et al. (2010) showed that the MIS 3 deltaic layers in two cores on the OYRD have a depth discrepancy of over 20 m, which is produced by differential sediment load. In order to compare with eustatic sea level, the sea-level records need to be corrected for tectonic subsidence, sediment compaction (subsidence), and hydro-isostatic uplift. Both Liu et al. (2009) and Wang et al. (2013) used the depth of the MIS 5e deposits to estimate approximately the overall subsidence rate in specific sites. Wang et al. (2013) assumed that the highstand of sea level during MIS5e is 5 m above the present sea level and calculated the subsidence rate of 0.69 m/ka in southern modern Yangtze River delta. In the northern Yangtze River delta, Core QC05 drilled in 1984 (Fig. 1) penetrated to early Pleistocene (Zheng, 1989). The fourth transgression layer in Core QC05 was thought to be deposited during MIS 5 (Fig. 6) (Zheng, 1989). The maximum subsidence rate was estimated to be ~0.83 m/ka according to the depth of MIS 5 layer in Core QC05. Cores SR11 and SM are close to QC05, and we assume a similar subsidence rate. The basal marine-influenced facies at 47–71 m bpsl in cores SM and SR11 appears to have an age of early MIS 3 (45–60 cal ka BP). This is equivalent to a subsidence of 37–50 m, implying a sea-level highstand of 15–25 m bpsl. Taking tidal range into account (at present the maximum tidal range is 5 m) would imply a highstand of at least 20–30 m bpsl.

Core SR04 in northern YSTSR recorded tidal-flat deposits in the late MIS 3 (31–35 cal ka BP). If using the subsidence rate calculated from Core SYS-702, the sea level was estimated to be ca. 25–32 m bpsl in northern YSTSR in the late MIS 3. These estimates of sea level in northern Yangtze deltaic plain are close to the sea level in southern Yangtze deltaic plain reported by Wang et al. (2013). The sea level records in the Yangtze River deltaic plain and the adjoining inner shelf represent the highest sea level during MIS 3 which reached 20–30 m bpsl. Deltaic deposits identified by seismic studies on outer shelf of East China Sea (Saito et al., 1998; Berné et al., 2002; Liu et al., 2003; Lee et al., 2013) recorded the sea-levels in lowstands during MIS 3, which fluctuated at 70–90 m bpsl.

Conclusions Drill cores from southern Yellow Sea and northern Yangtze deltaic plain recorded the deposition of Yangtze River and relative sea level during MIS 3. Sandy deposits of MIS 3 were found on the northern Yangtze deltaic plain and on the inner shelf with the maximum thickness of over 30 m. The thick sandy deposits represent the main channel deposits of lower Yangtze River with sporadic tidal influence. The distribution of sandy deposits suggests that during MIS 3, the Yangtze River mainly migrated between the modern river mouth and Qianggang on the middle Jiangsu coastal plain and flowed southeastward to build a delta complex in the northern East China Sea. High sediment supply, as well as the fluctuated sea-levels, resulted in the rapid progradation of the Yangtze River delta onto the flat shelf. The highest sea levels during MIS 3 are estimated to reach 25 ± 5 m bpsl.

Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

Z. Sun et al. / Quaternary Research xxx (2014) xxx–xxx

Acknowledgments The research of this study was supported by the National Natural Science Foundation of China (Grant no. 40776023). Our best thanks to Professor Qiang Wang in Tianjin Institute of Geology and Mineral Resources for helping analyze foraminifer assemblage in this study. We thank the editor D. Booth for his useful comments on the manuscript and D. J.W. Piper for correcting the language. We acknowledge the useful comments by two anonymous reviewers. References Allen, G.P., 1991. Sedimentary processes and facies in the Gironde estuary: a recent model for macrotidal estuarine systems. In: Smith, D.G., Reinson, G.E., Zaitlin, B.A., Rahmani, R.A. (Eds.), Clastic Tidal Sedimentology. Canadian Society of Petroleum Geologists Memoirs. 16, pp. 29–40. Allen, G.P., Posamentier, H.W., 1993. Sequence stratigraphy and facies model of an incised valley fill: the Gironde Estuary, France. Journal of Sedimentary Research 63, 378–391. 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Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008

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Please cite this article as: Sun, Z., et al., The Yangtze River deposition in southern Yellow Sea during Marine Oxygen Isotope Stage 3 and its implications for sea-level changes, Quaternary Research (2014), http://dx.doi.org/10.1016/j.yqres.2014.08.008