Sedimentary environment and paleo-tidal evolution of the eastern Bohai Sea, China since the last glaciation

Quaternary International xxx (2016) 1e10

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Sedimentary environment and paleo-tidal evolution of the eastern Bohai Sea, China since the last glaciation Zhengquan Yao a, b, Xuefa Shi a, b, *, Xiaoyan Li a, b, Yanguang Liu a, b, Jian Liu b, c, Shuqing Qiao a, b, Yazhi Bai a, b, Xin Wang d, Aimei Zhu a, b, Xuchen Wang e a Key Laboratory of Marine Sedimentology and Environmental Geology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China b Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266061, China c Qingdao Institute of Marine Geology, Qingdao 266071, China d Ludong University, Yantai 264025, China e Ocean University of China, Qingdao 266100, China

a r t i c l e i n f o

a b s t r a c t

Article history: Available online xxx

Numerical simulation suggests that the Holocene sediments re-suspension and distribution in the Bohai Sea was mainly controlled by tidal current regime, which was closely related with sea-level change. Study on sediments in the Bohai Sea thus can provide insights into the evolution of tidal-influenced sedimentary environment and its links with sea-level change. Our understanding of this issue remains incomplete, however, owing to the lack of comprehensive study on sediment core with high-resolution proxies to test such inference. In this study, analyses of sedimentary facies, proxies (grain size, total organic carbon and total nitrogen, X-ray fluorescence scanning Sulfur and Chlorine ratio) and accelerator mass spectrometry 14C dates of a sediment core recovered from the eastern Bohai Sea were carried out to clarify the Holocene sedimentary environment, tidal current change and its relation to the sea-level. The results indicate that the eastern Bohai Sea was dominated by fluvial-coastal environment prior to 12,400 cal a BP due to the sea-level lowstand and changed to tidal-influenced environment from 12,400 to 6700 cal a BP following the rapid sea-level rising. Thereafter shelf environment with minor tidal influence dominated the eastern Bohai Sea under the condition of a deceleration of sea-level rise. The significant change at ~6700 cal a BP both in sedimentary environment and sediment proxies, indicating an environmental transition from strong tidal-influenced to less tidal-influenced setting. With the sealevel rising from the early Holocene to the mid-Holocene, tidal-current was much strong due to the low sea-level stand and became weak after the maximum transgression at ~6700 cal a BP. These results are consistent with the numerical simulation, which suggested that less strong tidal current were the consequence of the most highstand sea-level since the mid-Holocene. Our study thus provides a sedimentary record to support the interpretation of numerical simulation-based tidal-influenced depositional process in the eastern Bohai Sea since the deglacial period. © 2016 Elsevier Ltd and INQUA. All rights reserved.

Keywords: Bohai Sea Tidal current The deglacial period Sea-level

1. Introduction The Bohai Sea is a semi-enclosed sea of China that connects to the northern Yellow Sea by the narrow Bohai Strait. The sedimentary environment in the Bohai Sea has been strongly affected by the sea-level fluctuations and sediments supply due to the shallow

* Corresponding author. Key Laboratory of Marine Sedimentology and Environmental Geology, First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China. E-mail address: xfshi@fio.org.cn (X. Shi).

water depth (average: ~18 m; Qin et al., 1990). The tidal current is one of the most energetic oceanic components of the present Bohai Sea, especially in the eastern area close to the Bohai Strait, and thus plays an important role in sedimentary processes such as deposition, erosion, and re-suspension (Liu et al., 1998; Zhu and Chang, 2000; Chen and Zhu, 2012). Therefore exploring the links between tidal current and the sedimentary process is crucial to understand the sedimentary environment change in this region. Both field data (Qin et al., 1990; Liu et al., 1998; Qiao et al., 2010) and numerical simulation results (Uehara and Saito, 2003; Chen and Zhu, 2012) show that tidal-current field is the dominant

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Please cite this article in press as: Yao, Z., et al., Sedimentary environment and paleo-tidal evolution of the eastern Bohai Sea, China since the last glaciation, Quaternary International (2016), http://dx.doi.org/10.1016/j.quaint.2016.04.010

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Z. Yao et al. / Quaternary International xxx (2016) 1e10

factor for controlling the sediment types and distribution in the Bohai Sea. The model results are fairly consistent with the investigation on modern sediments distribution in the Bohai Sea (Qin et al., 1990; Liu et al., 1998; Shi, 2012). However, how the tidal current regime evolved to influence the sedimentary process since the last deglacial period, as well as its underlying causes remains poorly understood. Numerical simulations suggested that sediment types in the Chinese shelves were closely related to tidal-current regime during the Holocene transgression (Uehara and Saito, 2003; Chen and Zhu, 2012), while the latter was mainly dominated by the postglacial sea-level rise and resultant changes in coastline configuration (Chen and Zhu, 2012). This inference is very important to understand the sedimentary process in the Bohai Sea, because the Bohai Sea was exposed subaerially during the last glacial maximum (LGM), and then was followed by a large-scale Holocene transgression which can be found in coastal region worldwide (Violante and Parker, 2004; Gao and Collins, 2014), responding to the global sea-level rising from
120 m to the present level (Siddall et al., 2003). However, there is still lacking of sedimentary record spanning the last deglacial period to test the model results up to now, in spite of its paleoenvironmental significance. Recently, a 212.4-m core (BH08) was recovered from the eastern Bohai Sea, close to the Bohai Strait. In this study, we focus on the upper ~8 m portion, which has been well dated using accelerator mass spectrometry (AMS) 14C method and proved to be spanning the last deglacial period. We present the sedimentology and proxies (grain size, XRF core scanning elements, carbon and nitrogen content) records of the core sediments. The specific objectives of the current research are (1) to perform detailed facies analyses and establish the sedimentary history in the eastern Bohai Sea and (2) to tentatively discuss the tidal current evolution of the eastern Bohai Sea since the deglacial period as well as its relation to the sealevel change. 2. Regional setting The Bohai Sea is a semi-enclosed sea of China connecting to the northern Yellow Sea by the narrow Bohai Strait (Fig. 1). The water depth is less than 30 m throughout the Bohai Sea with a mean value of ~18 m (Fig. 1a, b; Qin et al., 1990). The main rivers flowing into the Bohai Sea are the Yellow River, Luanhe, Haihe and Liaohe Rivers, which originate from the Tibetan Plateau, Taihang and Yanshan Mountains (Fig. 1). Among them, the Yellow River is the largest and is the main source of sediments in this region. As the second largest river in the world in terms of sediment loads, the Yellow River discharges eastward huge amounts of sediments into the Bohai Sea (Milliman and Meade, 1983). The circulation in the Bohai Sea is mainly composed of the predominant extension of the Yellow Sea Warm Current (YSWC), the Liaonan Coastal Current (LCC) and the southern Bohai Sea Coastal Current (BSCC) (Fig. 1a, Guan, 1994; Fang et al., 2000). The saltier water enters the Bohai Sea from the northern Yellow Sea through the northern Bohai Strait, circulating as LCC and BSCC along the Bohai Sea coastal area (Fig. 1a). Although the direction of LCC follows the clockwise and anticlockwise during the winter and summer season, respectively, the water finally flows out through the southern part of the Bohai Strait (Guan, 1994). In addition to the current circulation, the modern Bohai Sea is also affected by tidal currents (Qin et al., 1990), with the strongest tidal currents in the eastern part close to the Bohai Strait (Xie et al., 1990). The tidal regime is dominated by semi-diurnal tides (M2). The absolute ellipticities values of the M2 tidal are less than 0.4 in the study area, dominated by reciprocatingcurrent (Liu et al., 1998). The mean velocity of tidal currents

varies from 20 cm/s to 80 cm/s with the strongest value in the northern Bohai Strait and the eastern part of Liaodong Bay (Huang et al., 1999). In the Bozhong Shoal close to the core location, the maximum speeds of flood currents are ~58e79 cm/s with an average of 68.5 cm/s and the maximum ebb current speeds are ~50e65 cm/s with an average of 57.5 cm/s (Liu et al., 1998). The flood current enters the Bohai Sea along the northern part of the Bohai Strait and leads to the counterclockwise tidal circulation in Liaodong and Bohai Bays, due to the Coriolis force, while the ebb current flows out of the Bohai Sea along its southern part (Qin et al., 1990; Liu et al., 2009). The sediments distribution in the Bohai Sea varies with tidalcurrent energy under the influence of tidal current field, because sediments erosion and re-suspension in the Bohai Sea are mainly controlled by tidal currents (Milliman et al., 1985; Liu et al., 1998). Modern sediments distribution in the Bohai Sea (Qin et al., 1990; Shi, 2012) show that muddy deposits composed of silts/sandy silts dominated in the estuarine and the central part, while sandy deposits (mainly sand/silty sand) dominated in the north-eastern Bohai Sea, close to the Bohai Strait where strong tidal currents occurs. The north-eastern Bohai Sea is mainly composed of mixed sediments with sand fraction ranging from 20% to 60% (Shi, 2012).

3. Material and methods The BH08 core (212.4 m) was recovered in the eastern Bohai Sea (119.99 E, 38.28 N; Fig. 1) with a mean recovery of 86% in length. The current water depth at the site location is ~25 m. In laboratory, the core was split into two sections, photographed, described and subsampled. In the present study, we have selected the above ~8 m portion with well-constrained AMS 14C dates for study. Grain-size analysis was performed at ~5e10 cm intervals throughout the core to characterize the sediment texture using Malvern Mastersizer 2000. We have used the chemical procedure introduced by Konert and Vandenberghe (1997) in the experimental pretreatment to remove carbonate and organic material before the measurements. A total of 60 samples have been selected at ~10 cm intervals for total organic carbon (TOC) and total nitrogen (TN) analyses. After samples being freeze-dried, homogenized and pulverized, sediments were treated with 1 N HCl to remove carbonate and subsequently rinsed with deionized water to remove salts. The residue was centrifuged and oven dried at 60  C. Then the carbonate-free samples were analyzed for TOC and TN in duplicates in a Vario EL-III Elemental Analyzer. Elemental abundances, given in peak area (count per second; cps), were obtained at 1 cm resolution using the Itrax XRF core scanner, using 20 s count times, 30 kV X-ray voltage. Although elemental concentrations are not directly available from the microXRF measurements, the obtained values can be used as estimates of relative concentrations. All the above analyses were performed at the First Institute of Oceanography, State Oceanic Administration, China. We here focus on the sulfur (S) and chlorine (Cl) which are obtained directly from the XRF scanning. A total of six foraminifera samples and well-preserved mollusks (Table 1) were taken for AMS 14C dating at the Woods Hole Oceanographic Institution, USA. Radiocarbon ages were corrected for the regional marine reservoir effect (DR ¼
139 ± 59 years, a regional average value determined for the Bohai Sea; Stuiver et al., 2005) and calibrated using Calib 6.0.1 program (Stuiver et al., 2005) with a one standard deviation (1s) uncertainty (Table 1).

Please cite this article in press as: Yao, Z., et al., Sedimentary environment and paleo-tidal evolution of the eastern Bohai Sea, China since the last glaciation, Quaternary International (2016), http://dx.doi.org/10.1016/j.quaint.2016.04.010

Z. Yao et al. / Quaternary International xxx (2016) 1e10

3

41

e

oh

Liaodong Bay 0

Lia

100 km

50

he

Pe on

g

an

Bohai Sea

od

Haihe

Lu

nin

LC C Winter Summer Winter+Summer

Lia

Latitude N

40

su la

China

39

Bohai Bay

M5-5

TP23

Bo

M7-4

BSC

C

M7-6

ha

BH08

38

w ello

Yellow Sea

er

Riv

Y 37

i S YSWC tra it

Laizhou Bay

Shandong Peninsula

a 118

119

120

121

122

Longitude E

41

40

Latitude o N

Li

39

a

o od

ng

Pe

ni

u ns

la

-10 -20

Bohai Sea

Bohai Bay

0

-30

Bohai Strait

Yellow Sea

BH08

38

Leizhou Bay 37

b

S

118

119

do han

120

ng

Pen

ul ins

121

-50

Water depth (m)

Liaodong Bay

-70

a

-90 122

123

Longitude oE Fig. 1. Geographic (a) and bathymetry (b) of the Bohai Sea, including the location of the BH08 core site (solid square) and the sites mentioned (solid circle) in the text. Circulation pattern (modified from Guan, 1994; Fang et al., 2000) is indicated by the arrows with black (winter), red (summer) and green (both summer and winter). YSWC: Yellow Sea Warm Current; LCC: Liaonan Coastal Current; BSCC: Bohai Sea Coastal Current. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

4. Results 4.1. Sedimentary units of the BH08 core

depositional units (I, II, III and IV) from the bottom to the top of the core. Detailed characteristics of the units and their interpretations are described below.

Sedimentary units were classified based on lithology, sediment color, sedimentary structure, grain-size characteristics and biofacies. The 8-m core sediments can be divided into four

4.1.1. Unit I (8.1e6.5 m; 14,100e12,400 cal a BP) Unit I mainly consists of massive relatively well-sorted grayishyellow (2.5Y 6/2) fine sand (Fig. 2a), with sand fraction ranging

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Z. Yao et al. / Quaternary International xxx (2016) 1e10

Table 1 AMS 14C dates from the BH08 core. C age (a BP) Calibrated age range (1s, cal a BP) Mid-point calibrated age (cal a BP)

Sample number Lab number Depth (m) Material

AMS

14

BH08-1 BH08-2-16 BH08-3-26-1 BH08-3-26-2 BH08-4-37 BH08-4

600 5570 7370 8490 9010 8770

± ± ± ± ± ±

OS-83189 OS-83200 OS-83201 OS-83190 OS-83202 OS-83191

0.18 1.69 2.89 3.47 4.09 4.30

Mollusk (Mactra quadrangularis) Mixed foraminifera Mixed foraminifera Mollusk (Donax sp.) Mixed foraminifera Mollusk (Cyclosunetta)

20 30 30 40 35 40

312e437 6023e6197 7900e8044 9214e9405 9827e10,092 9488e9653

375 6110 7972 9310 9960 9571

abundant shell fragments (Fig. 2b and c), indicating a relatively high-energy marine environment. Most sand layers have relatively sharp contacts with the underlying and overlying mud layers. Overall this unit is characterized by an upward-thinning succession (Fig. 3a and c). Well-preserved mollusks of Donax sp. and Cyclina sinensis (Gmelin) are distributed at the depth range of 4.0e4.3 m. In addition, large foraminifers can be seen visually in this unit. Combining all these features, this unit is interpreted as tidal-flat environment, similar to those described by Reineck and Singh (1980). Sand layers are deposited during ebb and flood currents, whereas mud layers accumulate from suspension during or near tidal slack water (Dalrymple, 1992). Compared with the unit I, the grainsize of unit II is highly variable (Fig. 3a, c and d), with sand fraction ranging from 1.3% to 74.9% (Mean: 37.1 ± 23.5%, n ¼ 39; Fig. 3c). Correspondingly, the silt and clay fraction displays large variations (Fig. 3c), ranging from 20.1% to 78.2% (Mean: 48.9 ± 18.7%) and 4.9% to 25.7% (Mean: 14.0 ± 5.3%). The overall grainsize distribution is bimodal with fine (5e10 F) and coarse (2e5 F) fractions (Fig. 3f), characteristic of tidal-influenced setting, partly supporting the sedimentary interpretation. While the distribution pattern in the single silt and sand layers shows single modal, with fine fraction at 4e10 F in the silts and coarse fraction at 2e5 F in the sands (Fig. 3f). The AMS 14C dating in this unit gives dates of 9571, 9960 and 9310 cal a BP from the bottom to the top (Table 1) and thus indicates an age rang of 12,400e9310 cal a BP based on interpolation of sedimentary rates.

Fig. 2. Photographs of four units (a) unit I: 6.60e6.92 m; (b) lower part of unit II: 4.67e5.02 m; (c) upper part of unit II: 3.89e4.21 m; (d) unit III: 3.18e3.46 m; (e) unit IV: 1.48e1.80 m; (f) the boundary (dashed line) between unit III and IV of the BH08 core. Note the iron encrustation in unit I, wavy-, flaser-bedding and abundant broken mollusk in unit II, and sand-filled burrows in unit III and IV.

from 56.3% to 87.2% (Mean: 81.2 ± 6.2%, 1s; n ¼ 24; Fig. 3c). The silt and clay fraction are low and relatively stable, with a mean value of 14.8 ± 5.4% and 4.0 ± 1.0% (Fig. 3c), respectively. The sediments show multimodal grain-size distribution, with one dominant coarse fraction at 2e5 F (Fig. 3g). The presence of iron encrustation in the unit (Fig. 2a) indicates an environment under oxygenated conditions. No brackish mollusks have been observed in this unit except that foraminifers occur occasionally. These results suggest that unit I might be deposited in fluvial-coastal transitional environments. Exploration based on the AMS 14C dates of 3.47 m and 4.09 m (Table 1) assuming constant sedimentation rate suggests an age range of 14,100e12,400 cal a BP for this unit (Fig. 3b).

4.1.2. Unit II (6.5e3.4 m; 12,400e9310 cal a BP) This unit is characterized by dark gray (N 3/0) wavy-, lenticularand flaser-bedded sand and mud. The sand layers normally contain

4.1.3. Unit III (3.4e1.85 m; 9310e6700 cal a BP) This unit consists of dark gray (N 3/0) silts with abundant sandfilled burrows (Fig. 2d). The grainsize of sediments is relatively uniform, with silt fraction dominated, ranging broadly from 43.1% to 69.9% (58.1 ± 7.7%; n ¼ 14; Fig. 3c), while the sand and clay fraction is relatively low, with a mean value of 23.6 ± 10.0% and 18.3 ± 2.8% (Fig. 3c), respectively. The grainsize distribution is similar to unit II, showing bimodal pattern (Fig. 3f). Foraminifers can be seen visually throughout this unit. A slight fining-upward trend can be observed due to the decreased portion of sand-filled burrows. This unit is interpreted to be a tidal-influenced shelf environment. The lenticular sand distributed in the silts-dominant deposits suggests a tidal-influenced environment, but with less strong tidal current compared with the unit II. The AMS 14C dating in this unit gives date of 7972 cal a BP at 2.89 m (Table 1) and thus indicates an age rang of 9310e6110 cal a BP based on AMS 14C of 6110 cal a BP and 9310 cal a BP at 1.69 m and 3.47 m, respectively. 4.1.4. Unit IV (1.85e0 m; 6700 cal a BPepresent) Unit IV consists of well-sorted grayish brown (2.5Y 5/2) silts with sand-filled burrows (Fig. 2e). Two well-preserved brackish mollusks, Mactra quadrangularis are distributed at the depth of 0.18 m and 1.0 m. Abundant foraminifers can be observed visually in this unit. Although the presence of sand-filled burrows, its proportion is much lower, compared with the unit III. A general finingupward trend can be observed (Fig. 3a and c). The grainsize of this unit is very uniform, with silt fraction dominated, ranging from

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Z. Yao et al. / Quaternary International xxx (2016) 1e10

375

Content(%) 20 40 60 80 100

Mz

Grainsize distribution

e 0.48 mm/a

a

b

d

c

0.5

Ω

f

0.43 mm/a 0.95 mm/a

»

2.49 m 2.99 m 4.49 m 5.19 m 5.49 m

10 8 6 4 2 0

Frequency

9310 Ω

9960 9571

II

Ω

Depth(m)

12

III 7972

4.5 5.0

4 8 Grainsize

0.64 mm/a

3.5 4.0

0.29 m 0.69 m 1.49 m 1.79 m

8 6 4 2 0 0

»

Ω

3.0

Sand

6110 Ω

2.5

Silt

Ω

1.5 2.0

IV

0.26 mm/a

1.0

Frequency

0.0

0

FS

Silt Ss

Lithology

5

0

Clay

4 8 Grainsize

12

»

5.5 6.0 Ω

7.0

7.09 m 7.49 m 8.05 m

10

I

7.5 8.0

Marine shell

Burrow

»

Sand

»

Silt

0 Ω

Clay

5 0

14100 a

Ω

Legend

g

15

12400 a

Frequency

6.5

Bioturbation

4 8 Grainsize

Parallel lamination

12 AMS C (cal. a BP)

Fig. 3. Lithology (a), age-depth (b), contents of sand, silt, clay fraction (c), mean grainsize (Mz, d), along with grainsize distribution pattern (e, f and g) of the core BH08. Dashed lines denote the boundary between units. AMS 14C dates in (b) are labeled using solid circles, while the dates labeled with squares were obtained by extrapolation based on the age at the depth of 3.47 m and 4.09 m.

51.2% to 75.4% (66.5 ± 7.8%; n ¼ 17; Fig. 3c). The sand and clay fraction decreases relative to the unit III, ranging 8.5%e34.4% (19.4 ± 7.5%) and 12.2%e16.9% (14.1 ± 1.5%), respectively. The mean grainsize is very stable, ranging from 5.5 F to 6.3 F (Fig. 3d), relative to the other units. The sediments distribution is similar with the unit III, and shows bimodal with 5e6 F as the boundary between the coarse and fine fraction (Fig. 3e). Considering the vertical facies pattern, this unit is interpreted as shelf deposits with minor tidal influence. The AMS 14C date at the bottom of this unit (1.69 m) and 0.18 m is 6110 and 375 cal a BP, respectively (Table 1), and thus yield a basal age of 6700 cal a BP assuming a constant sedimentation rate between 1.69 and 0.18 m. 4.2. Relationship between grainsize and TOC, TOC/TN The sulfur/chlorine (S/Cl) ratio in marine sediments has been chosen to reveal the presence of additional S associated with pyrite or organic matter in excess of the constant S/Cl ratio in seawater (Passier et al., 1999; Thomson et al., 2006). Because pyrite and organic matter are inclined to be present and enriched in the anoxic environments (Kohnen et al., 1990; Lin and Morse, 1991), this ratio thus can be used to indicate the paleo-redox condition of the sedimentary environments. Generally, TOC/TN weight ratio has been used for source identification of organic matter. It was reported by Redfield et al. (1963) to be 5e7 for marine organic matter and >15 for terrestrial organic matter by Meyers (1997). Although

the early diagenesis would affect the preservation of organic matter in sediments (Henrichs, 1992), TOC/TN ratio, combined with other proxies indicating sedimentary environment may provide a clue for addressing the relative influence of marine and terrestrial settings. Previous study also revealed the influence of hydrodynamic effects on the soil organic matter (SOM) accumulation in the Bohai Sea (Hu et al., 2009). In order to explore the relationship between the sediment texture and TOC, TOC/TN, contents of sand, silt and clay fraction are plotted with TOC (Fig. 4aec) and TOC/TN (Fig. 4def), respectively. The results show that the TOC in the unit I, II and III are positively correlated with silt and clay (Fig. 4b and c), whereas are negative with sand fraction (Fig. 4a), suggesting the major influence of grainsize effects. Samples in unit IV lies beyond the regression line, implying other process also contribute the TOC variations, in addition to the grainsize. Similarly, the TOC/TN are correlated positively with fine-grained silt and clay fraction (Fig. 4e and f) and are negative with sand fraction (Fig. 4d) in the unit I, II and III, whereas the TOC/TN in unit IV are much lower relative to the regression line. These results indicate that TOC and TOC/TN in the unit I, II and III are mainly grainsize dependent and prone to be enriched in fine-grained fraction, except for the unit IV. 4.3. Variations in S/Cl, TOC and TOC/TN of the units The unit divisions in the Section 4.1 are also consistent with the measured sediments proxies, such as micro-XRF scanning S/

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Fig. 4. Correlation between grainsize and TOC (%), TN (%) contents for units form I to IV. (a) Sand contents and TOC; (b) Silt contents and TOC; (c) Clay contents and TOC; (d) Sand contents and TOC/TN; (e) Silt contents and TOC/TN; (f) Clay contents and TOC. Higher regression coefficient (outside brackets) can be observed when the data for unit IV were not included in the regression.

Cl and TOC, TOC/TN ratio (Fig. 5). The S/Cl ratio of the unit I is quite lower and shows very small variations, ranging from 0.02 to 0.10 (0.05 ± 0.01; n ¼ 111; Fig. 5a), due to the well-sorted sandy deposits, suggesting a relative stable and oxidized environment. The TOC content in the sediments of this unit is very low (Fig. 5c), ranging broadly from 0.02% to 0.08% with a mean value of 0.04 ± 0.02% (n ¼ 11). The TOC/TN is also very low with a mean value of 4.08 ± 1.25 (n ¼ 11; Max: 6.31; Min: 1.59; Fig. 5d). Such low TOC/TN value can be attributed to the very low TOC content, rather than prominent marine organic matter fingerprint, because this unit is interpreted to be formed under a fluvialcoastal environment. Low TOC content was due to the influence of hydrodynamic effects on the SOM accumulation in Bohai Sea (Hu et al., 2009), because this unit is mainly composed of wellsorted fine sand. Compared with the unit I, The S/Cl ratio in the unit II is significantly higher and variable, ranging from 0.02 to 0.25 with a mean value of 0.12 ± 0.03 (n ¼ 369) (Fig. 5a), indicating reduced and unstable sedimentary environments. The measured TOC contents in this unit are ranging from 0.11% to 1.4% with a mean value of 0.42 ± 0.32% (n ¼ 32; Fig. 5c), much higher than for the unit I. Although TOC/TN ratio in BH08 are closely related with the sediment texture, a finer trend in mean grainsize parallels with decreasing TOC/TN for the upper ~6 m portion (Fig. 5b and d), suggesting the validity of using TOC/TN to discriminate relative contribution of terrestrial and marine organic matter. The TOC/TN ratios in this unit varied from 4.1 to 21.9 with a mean value of 10.5 ± 4.5 (Fig. 5d), suggesting a terrestrial-dominant mixed marine and terrestrial setting.

Fig. 5. Variations of S/Cl ratio (a), mean grainsize (Mz, b), TOC contents (c) and TOC/TN (d). Vertical lines denote the boundary between units. AMS 14C date are labeled using solid triangle, while the dates labeled using hollow triangle were obtained by extrapolation.

In the unit III, the S/Cl ratio is also variable and ranges from 0.03 to 0.22 (0.10 ± 0.05; n ¼ 144; Fig. 5a), suggesting variable and reduced conditions. The TOC content in this unit is similar with the unit II, fluctuating from 0.16% to 0.52% (0.39 ± 0.09%; n ¼ 13; Fig. 5c). The TOC/TN ratios varied from 5.7 to 11.8 with a mean of 9.0 ± 1.5 (Fig. 5d), suggesting a similar environment with unit II, influenced by both marine and terrestrial settings. Furthermore, a clear decreasing trend from ~13 to ~9 can be observed in TOC/TN (Fig. 5d), due to the enhanced influence of marine setting. The S/Cl ratio in the unit IV decreases greatly, with much less variations ranging from 0.01 to 0.06 (0.03 ± 0.01; n ¼ 283; Fig. 5a), suggesting stable and increased oxidized conditions. The TOC content in this unit decreases relative to the unit III, fluctuating from 0.15% to 0.48% (0.22 ± 0.08%; n ¼ 15; Fig. 5c). The TOC/TN ratios in this unit is relatively stable and varies from 4.2 to 7.2 with a mean of 6.2 ± 0.8 (Fig. 5d), suggesting a predominant marine origin when compared with the unit II and III.

5. Discussion 5.1. Sedimentary environmental evolution in the eastern Bohai Sea since the deglacial The Bohai Sea is a subsiding basin initiating from the Eocene until the present day (Allen et al., 1997), and more than 400 m thick sediments have accumulated during the Quaternary (Qin et al., 1990). The sedimentary environment of this region is mainly controlled by sea-level variations and sediments discharge from surrounding rivers, because of very shallow water depth. The BH08 core records three main depositional systems in vertical profile from the bottom to the top: fluvial-coastal, tidal-influenced and shelf environment (Fig. 6).

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The fluvial-coastal transitional environment dominated prior to 12,400 cal a BP in response to the sea-level lowstand (Zhao et al., 1979; Bard et al., 1990a; Clark and Mix, 2002) during the last glacial period (Fig. 6). Previous studies showed that the eastern China (Zhao et al., 1979) and global (Clark and Mix, 2002) sea-level was 120e135 m below the present sea-level during the last glacial maximum (Fig. 6d). The remarkable sea-level drop led to the entire Bohai Sea, even the northern Yellow Sea (Liu et al., 2007a) subaerially exposed. Our interpretation of fluvial-coastal transitional environment is consistent with previous studies. The presence of peat layer and limnetic ostracods from the M7-6 core deposits in the central Bohai Sea suggests that seawater had not yet significantly influenced this region by ~12,900 cal a BP (Liu et al., 2010). A tidal-influenced setting developed between approximately 12,400 and 6700 cal a BP, which overlie the lower fluvial-coastal system (Fig. 6). During this time period, the global sea-level rose from
100 m to almost the present level rapidly (Fig. 6d, Zhao et al., 1979; Bard et al., 1990b, 1996; Fairbanks, 1990; Peltier and Fairbanks, 2006). The formation of tidal-influenced setting is believed to be correlated with rapid sea-level rising during the early Holocene (Zhao et al., 1979; Bard et al., 1990b). High sedimentary accumulation rate (SAR) of 0.43e0.95 mm/a during this time period (Fig. 3b) partly attest to the abrupt increase in the accommodation due to the rapid sea-level rising (Zhao et al., 1979; Bard et al., 1990b). The tidal-influenced environments recorded in the BH08 core are consistent with the early to mideHolocene paleoenvironment in the Bohai Sea and adjacent onshore area (Qin et al., 1990; Liu et al., 2010; Qiao et al., 2011; Yao et al., 2012; Zhou et al., 2014). The shelf environment dominated the eastern Bohai Sea since ~6700 cal a BP (Fig. 6). During the last ~7000 cal a BP, the sea-level

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changed little and fluctuated within ~5 m ranges (Fig. 6d, Bard et al., 1990b, 1996; Fairbanks, 1990; Peltier and Fairbanks, 2006). Meanwhile, the SAR of the core was significantly lower compared with previous time period, with a mean value of 0.26 mm/a (Fig. 3b). Previous study showed that sea water first entered the Bohai Sea at around 11,600 cal a BP (Liu et al., 2007a) and reached the maximum transgression at ~6000e7000 cal a BP (Qin et al., 1990). Thereafter, the Yellow River delta began to develop on the western shore of the Bohai Sea (Xue, 1993; Xue et al., 2004). The sedimentary environmental change from fluvial/coastal to shelf-dominated settings is largely consistent with previous results in this region, implying the dominant control of sea-level change since the deglacial period. 5.2. Evolution of tidal-current regime since the deglacial period and implications The sedimentation in the Bohai Sea is controlled by multiple factors, including fluvial-transported sediment provenance, wave action and tidal current (Milliman et al., 1985; Graber et al., 1989; Qin et al., 1990; Liu et al., 1998). While the tidal currents play an important role in modulating the final sediments distribution (Liu et al., 1998; Zhu and Chang, 2000; Chen and Zhu, 2012), especially in the eastern Bohai Sea close to the Bohai Strait where tidal currents are much stronger (Bao et al., 2000). Previous studies demonstrated that not only sandy deposits in the Bohai Sea were the products of tidal-current, but also for fine-grained mud deposits (Zhu and Chang, 2000). Investigation on surface sediments (Qin et al., 1990; Shi, 2012) shows that the modern sediment distribution is largely consistent with the present tidal current regime. Because the Bohai Sea is dominated by the semi-diurnal tide and M2 component can approximately represent the total tidal current, the tidal-induced deposition are mainly controlled by the speed Mn (ug/g) 1000 2000

b

c

d

e 0.5 1.0

5016 a

1.5 2.0 Depth (m)

Unit II and Unit III Tidal-influenced facies

Strong tidal current

Weak tidal current

a

Unit IV Shelf/shallow marine facies

0

2.5 8134 a 3.0 3.5 4.0

Unit I Fluvial-coastal facies

4.5 5.0

Fig. 6. Temporal variations in mean grainsize (a), S/Cl (b), TOC/TN (c) ratios and comparison with global (Bard et al., 1996; Peltier and Fairbanks, 2006) and Eastern China (Zhao et al., 1979) sea-level change (d), as well as manganese content (e; Liu et al., 2007b) from core M1-3 in the Bohai Sea.

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and ellipticity of the M2 (Liu et al., 1998). An absolute ellipticity value less than 0.4 for the M2, combined with high rate tidal current, favor the formation of reciprocating tidal currents, especially in shallow seas near the coast under the influence of the coastal outline and topography (Liu et al., 1998). While when the ellipticity value is more than 0.4, rotating tidal currents are prone to be formed (Liu et al., 1998). Numerical simulation results show that during the last deglacial period, the tidal current field in the Bohai Sea had been dominated by reciprocating tidal current (Chen and Zhu, 2012). Uehara and Saito (2003) suggested that the evolution of maximum bottom-stress field in the Chinese shelves is closely related with the deglacial sea-level change, illustrated by using a two-dimensional tidal model. The maximum bottom-stress decreased significantly after the mid-Holocene transgression maximum when the sea-level reached the most highstand (Uehara and Saito, 2003). Recent numerical simulation results also confirmed that the strength of tidal current was controlled by the marked changes in coastline configuration since the last glacial maximum, as a response to sea-level change (Chen and Zhu, 2012). During the early Holocene when sea-level was lower than the present, the tidal currents were strong and became much weaker during the Holocene maximum transgression (Uehara et al., 2002; Chen and Zhu, 2012). Examination on sedimentary facies and the associated proxies of BH08 sequence, including grainsize, S/Cl, TOC and TOC/TN has revealed three main evolutionary stages of tidal currents in the eastern Bohai Sea during the deglacial period. During 12,400e9960 cal a BP, the study area was dominated by tidal-influenced environment. The presence of large-scale coarse sandy deposits with high amplitude variations in grainsize (sand, silt and clay; Fig. 3c) indicates that the tidal current was very strong. During this time period, sea-level was low and was rising rapidly from
80 m to
60 m (Fig. 6d, Zhao et al., 1979; Siddall et al., 2003), and thus relatively small Bohai Sea area led to the strengthened tidal current (Chen and Zhu, 2012). The basal age of ~10,000 a BP for the marine transgression in the Bohai coastal area (Wang, 1999; Wang et al., 2008) suggested similar shoreline position as the present. During the time interval of 9960 to 6100 cal a BP, the sedimentary environment in the study area was still influenced by tidal currents, but with less strong tidal currents, as evidence by both lithology and proxies. The phenomenon of only small-scale lenticular bedding (Fig. 2d) and much less variation in grainsize can be observed in the sequence (Fig. 3c) support the above inference. Numerous dating for the basal marine transgression in the coastal area display younger trend from ~10,000 a to ~6000 a BP towards inland, far from the present shoreline (Peng et al., 1980; Li et al., 1995, 2005; Wang, 1999; Wang et al., 2008). These results suggested that the Bohai Sea area had been expanding due to the continuous sea-level rising from
60 m to
10 m (Zhao et al., 1979; Siddall et al., 2003). Thus less strong tidal currents are regarded as the result of expanded Bohai Sea area (Chen and Zhu, 2012). The maximum bottom-stress in this period was high (Uehara and Saito, 2003) although, a decreasing trend due to the sea-level rising from
30 m to
16 m (Siddall et al., 2003) is possibly responsible for the decreased strength of tidal current, compared with the previous period. An obvious and sudden sedimentary environmental change from tidal-influenced setting to shelf with minor tidal influence at ~6700 cal a BP can be deduced based on the sedimentary facies analyses, indicating a marked transition of tidal currents from strong to weak condition. Since ~6700 cal a BP, the sediments texture was more homogenous with an upward-fining trend (Figs. 2e and 3). S/Cl decreased abruptly at this moment (Fig. 6b) suggesting more oxidized setting, in spite of as a consequence of

increased fine-grained sediments. This abrupt change can also be observed in the lithology of unit III and IV with sharp boundary between them (Fig. 2f). All these results suggest that abrupt and great decrease of tidal current occurred at this moment. During ~6000e7000 cal a BP, global sea-level reached the highest stands (Fig. 6d, Siddall et al., 2003) and the Bohai Sea area reached maximum, as revealed by many studies that the coastline can reach western Tianjin area, ~40e80 km far from the present shoreline (Peng et al., 1980; Wang, 1999; Wang et al., 2015). The abrupt decrease in maximum bottom-stress and much weakened tidal current was concluded based on the numeral simulation (Uehara and Saito, 2003; Chen and Zhu, 2012). The inference of enhanced marine influence on the sedimentary environment is also witnessed in the decreased TOC/TN ratio from 9.7 to 6.4 began at ~6700 cal a BP (Fig. 6c), due to the most highstand sea-level. Furthermore, an abrupt decrease in SAR (almost 3 times less; Fig. 3b) since the mid-Holocene revealed by core BH08 can also be observed in other cores (M5-5, M7-4; Fig. 1; Liu et al., 2008) in the central-eastern Bohai Sea. As the Yellow river delta progradation began at this time period (Xue et al., 2004) that would deliver more sediments into the Bohai Sea, the decreased sediments accumulation in the study area can be attributed to the final establishment of the modern Bohai Sea circulation, and thus most sediment have been transported along the coastal area into the Yellow Sea through the Bohai Strait (Bi et al., 2011). It is also noted that the abrupt redox change from reduced to oxidized condition recorded in the S/Cl ratio of the BH08 core can also be observed in other cores from the Bohai Sea (Liu et al., 2007b, 2008). Heavy minerals and chemical compositions of two gravity cores (M5-5 and M7-4; Fig. 1) in the Bohai Sea suggest that a very dynamic sedimentary event, which the ambience was transformed from reductive to oxidative occurred between 5900 and 6600 a BP (Liu et al., 2008). Abrupt increase in manganese content was widely distributed in the central Bohai Sea at proximately 6000 a BP based on geochemical study (Fig. 6e; Liu et al., 2007b; Liu et al., 2008), further supporting the abrupt environmental change at the midHolocene. However, the transition in these studies was ascribed to the influence of YSWC into the Bohai Sea (Liu et al., 2008, 2010), which would lead to the stronger ventilation as a result of more effective exchange with the open ocean water (Xiang et al., 2008). Because S/Cl is greatly influenced by grainsize and prone to be enriched in fine sediments, and direct evidence indicating the YSWC is absent in our core, whether this abrupt change in paleoredox can be attributable to the influence of YSWC is still unknown which need to be examined further. Anyway, our results present the direct evidence that sedimentary environment change due to the tidal current field evolution is as a response to the sea level rising since the deglacial period, and provide the field data to constrain the boundary condition for numerical simulation. 6. Conclusions Detailed analyses of sedimentary facies and sediment proxies, including grainsize, TOC, TN and micro-XRF scanning S/Cl ratio of the BH08 core, in conjunction with AMS 14C dates lead to the following conclusions. (1) Prior to 12,400 cal a BP, the eastern Bohai Sea was dominated by fluvial-coastal transitional environment because of sealevel lowstand during the last glacial period. Following the rapid sea-level rising, tidal-influence environments were dominant during the time interval of 12,400e6700 cal a BP. Thereafter shelf environments with minor tidal influence dominated this region due to the deceleration of sea-level rise.

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(2) Sediment proxies of grainsize, TOC, TN and S/Cl changed abruptly at ~6700 cal a BP, also indicating a transition to decreased tidal-influenced environment, as well as from reduced to oxidized condition, which can be observed in the Bohai Sea widely. The abrupt decline of tidal current since ~6700 cal a BP was largely corresponding to the midHolocene transgression maximum in the eastern China. These results are consistent with the numerical simulation, which suggested that decreased maximum bottom-stress and less strong tidal current were the consequence of the sea-level highstand and thus expanded Bohai Sea area during this period. Our study not only highlights the important control of sea-level in the tidal-current regime, and thus paleoenvironmental change in the Bohai Sea during the deglacial period, but also provide a case for numerical simulation of tidal-influenced depositional process in the Bohai Sea.

Acknowledgments We are grateful to Woods Hole Oceanographic Institution for AMS 14C measurements, and to Yoshiki Saito for helpful discussion. This study is jointly supported by the National Program on Global Change and Air-Sea Interaction (No. GASI-04-01-02), the National Natural Science Foundation of China (Grant No. 41476055, U1606401) and Project of State Oceanic Administration, China (Grant No. 908-01-BC15).

References Allen, M.B., Macdonald, D.I.M., Xun, Z., Vincent, S.J., Brouet-Menzies, C., 1997. Early Cenozoic two-phase extension and late Cenozoic thermal subsidence and inversion of the Bohai Basin, northern China. Marine and Petroleum Geology 14, 951e972. Bao, X.W., Gao, G.P., Yan, J., 2000. Three dimensional simulation of tide and tidal current characteristics in the East China Sea. Oceanologica Acta 24, 135e149. Bard, E., Hamelin, B., Arnold, M., Montaggioni, L., Cabioch, G., Faure, G., Rougerie, F., 1996. Sea level record from Tahiti corals and the timing of deglacial meltwater discharge. Nature 382, 241e244. Bard, E., Hamelin, B., Fairbanks, R.G., 1990a. U-Th ages obtained by mass spectrometry in corals from Barbados: sea level during the past 130,000 years. Nature 346, 456e458. Bard, E., Hamelin, B., Fairbanks, R.G., Zindler, A., 1990b. Calibration of the 14-C timescale over the past 30,000 years using mass spectrometric U-Th ages from Barbados corals. Nature 345, 405e409. Bi, N., Yang, Z., Wang, H., Fan, D., Sun, X., Lei, K., 2011. Seasonal variation of suspended-sediment transport through the southern Bohai Strait. Estuarine, Coastal and Shelf Science 93, 239e247. Chen, Q.Q., Zhu, Y.R., 2012. Holocene evolution of bottom sediment distribution on the continental shelves of the Bohai Sea, Yellow Sea and East China Sea. Sedimentary Geology 273e274, 58e72. Clark, P.U., Mix, A.C., 2002. Ice sheets and sea level of the Last Glacial Maximum. Quaternary Science Reviews 21, 1e7. Dalrymple, R.W., 1992. Tidal depositional systems. In: Walker, R.G., James, N.P. (Eds.), Facies Models-response to Sea Level Change. Geological Association of Canada, pp. 195e218. Fairbanks, R.G., 1990. The age and origin of the “Younger Dryas climate event” in Greenland ice cores. Paleoceanography 5, 937e948. Fang, Y., Fang, G., Zhang, Q., 2000. Numerical simulation and dynamic study of the wintertime circulation of the Bohai Sea. Chinese Journal of Oceanology and Limnology 18, 1e9. Gao, S., Collins, M.B., 2014. Holocene sedimentary systems on continental shelves. Marine Geology 352, 268e294. Graber, H.C., Beardsley, R.C., Grant, W.D., 1989. Storm-generated surface waves and sediment resuspension in the East China and Yellow Seas. Journal of Physical Oceanography 19, 1039e1059. Guan, B., 1994. Patterns and structures of the currents in Bohai, Huanghai and East China seas. In: Zhou, D., Liang, Y., Tseng, C.K. (Eds.), Oceanology of China Seas. Kluwer Academic Publishers, Dordrecht, pp. 17e26. Henrichs, S.M., 1992. Early diagenesis of organic matter in marine sediments: progress and perplexity. Marine Chemistry 39, 119e149. Hu, L., Guo, Z., Feng, J., Yang, Z., Fang, M., 2009. Distributions and sources of bulk organic matter and aliphatic hydrocarbons in surface sediments of the Bohai Sea, China. Marine Chemistry 113, 197e211.

9

Huang, D.J., Su, J.L., Backhaus, J.O., 1999. Modelling the seasonal thermal stratification and baroclinic circulation in the Bohai Sea. Continental Shelf Research 19, 1485e1505. Kohnen, M.E.L., Damste, J.S., Kock-van Dalen, A.C., Haven, H.L.T., Rullkotter, J., De Leeuw, J.W., 1990. Origin and diagenetic transformations of C25 and C30 highly branched isoprenoid sulphur compounds: further evidence for the formation of organically bound sulphur during early diagenesis. Geochimica et Cosmochimica Acta 54, 3053e3063. Konert, M., Vandenberghe, J.E.F., 1997. Comparison of laser grain size analysis with pipette and sieve analysis: a solution for the underestimation of the clay fraction. Sedimentology 44, 523e535. Li, F.L., Wang, H., Wang, Y.S., Zhang, J.Q., Li, J.F., Lin, F., Yan, Y.Z., Long, T.C., 2005. Stratigraphic division and establishment of a formation for the Holocene stratotype section in the coastal plain of the Bohai Bay. Geological Bulletin of China 24, 124e135 (in Chinese with English Abstract). Li, H.D., Wang, S.Z., Leng, X.T., Bai, Y., 1995. Formation mechanism and time-space distribution of coastal peat of the Bohai Bay. Marine Geology and Quaternary Geology 15, 11e16 (in Chinese with English Abstract). Lin, S., Morse, J.W., 1991. Sulfate reduction and iron sulfide mineral formation in Gulf of Mexico anoxic sediments. Journal of American Science 291, 55e89. Liu, J., Saito, Y., Wang, H., Yang, Z.G., Nakashima, R., 2007a. Sedimentary evolution of the Holocene subaqueous clinoform off the Shandong Peninsula in the Yellow Sea. Marine Geology 236, 165e187. Liu, J., Saito, Y., Wang, H., Zhou, L.Y., Yang, Z.G., 2009. Stratigraphic development during the Late Pleistocene and Holocene offshore of the Yellow River delta, Bohai Sea. Journal of Asian Earth Sciences 36, 318e331. Liu, J.G., Li, A.C., Chen, M.H., 2010. Environmental evolution and impact of the Yellow River sediments on deposition in the Bohai Sea during the last deglaciation. Journal of Asian Earth Sciences 38, 26e33. Liu, J.G., Li, A.C., Chen, M.H., Xiao, S.B., Wan, S.M., 2008. Sedimentary changes during the Holocene in the Bohai Sea and its paleoenvironmental implication. Continental Shelf Research 28, 1333e1339. Liu, J.G., Li, A.C., Xu, Z.K., Xu, F.J., 2007b. Manganese abnormity in Holocene sediments of the Bohai Sea. Journal of China University of Geosciences 18, 135e141. Liu, Z.X., Xia, D.X., Berne, S., Wang, K.Y., Marsset, T., Tang, Y.X., Bourillet, J.F., 1998. Tidal deposition systems of China's continental shelf, with special reference to the eastern Bohai Sea. Marine Geology 145, 225e253. Meyers, P.A., 1997. Organic geochemical proxies of paleoceanographic, paleolimnlogic, and paleoclimatic processes. Organic Geochemistry 27, 213e250. Milliman, J.D., Beardsley, R.C., Yang, Z.S., Limeburner, R., 1985. Modern Huanghederived muds on the outer shelf of the East China Sea. Continental Shelf Research 4, 175e188. Milliman, J.D., Meade, R.H., 1983. World-wide delivery of river sediment to the oceans. Journal of Geology 91, 1e21. Passier, H.F., Middelburg, J.J., De Lange, G.J., Bottcher, M.E., 1999. Modes of sapropel formation in the eastern Mediterranean: some constraints based on pyrite properties. Marine Geology 153, 199e219. Peltier, W.R., Fairbanks, R.G., 2006. Global glacial ice volume and Last Glacial Maximum duration from an extended Barbados sea level record. Quaternary Science Reviews 25, 3322e3337. Peng, G., Zhang, J.W., Jiao, W.Q., Chen, Y.J., Li, D.M., Li, G.Y., 1980. Chronology of late Quaternary deposits along the coast of the Bohai Bay. Seismic Geology 2, 71e77 (in Chinese with English Abstract). Qiao, S.Q., Shi, X.F., Saito, Y., Li, X.Y., Yu, Y.G., Bai, Y.Z., Liu, Y.G., Wang, K.S., Yang, G., 2011. Sedimentary records of natural and artificial Huanghe (Yellow River) channel shifts during the Holocene in the southern Bohai Sea. Continental Shelf Research 31, 1336e1342. Qiao, S.Q., Shi, X.F., Zhu, A.M., Liu, Y.G., Bi, N.S., Fang, X.S., Yang, G., 2010. Distribution and transport of suspended sediments off the Yellow River (Huanghe) mouth and the nearby Bohai Sea. Estuarine, Coastal and Shelf Science 86, 337e344. Qin, Y.S., Zhao, Y.Y., Chen, L.R., Zhao, S.L., 1990. Geology of Bohai Sea. China Ocean press, Beijing. Redfield, A.C., Ketchum, B.H., Richards, F.A., 1963. The influence of organisms on the composition of sea water. In: Hill, M.N. (Ed.), The Sea Wiley, New York, pp: 26e77. Reineck, H.E., Singh, I.B., 1980. Depositional Sedimentary Environments. Springer, Berlin, p. 551. Shi, X.F., 2012. Chinese Marginal Seas: Marine Bottom Sediments. China Ocean Press, Beijing. Siddall, M., Rohling, E.J., Almogi-Labin, A., Hemleben, C., Meischner, D., Schmelzer, I., Smeed, D.A., 2003. Sea-level fluctuations during the last glacial cycle. Nature 423, 853e858. Stuiver, M., Reimer, P.J., Reimer, R.W., 2005. CALIB 6.0.1 html. http://www.calib.org. Thomson, J., Croudace, I., Rothwell, R., 2006. A geochemical application of the ITRAX scanner to a sediment core containing eastern Mediterranean sapropel units. In: Rothwell, R. (Ed.), New Techniques in Sediment Core Analysis. Geological Society, London, pp. 65e77. Uehara, K., Saito, Y., 2003. Late Quaternary evolution of the Yellow/East China Sea tidal regime and its impacts on sediments dispersal and seafloor morphology. Sedimentary Geology 162, 25e38. Uehara, K., Saito, Y., Hori, K., 2002. Paleotidal regime in the Changjiang (Yangtze) Estuary, the East China Sea, and the Yellow Sea at 6 ka and 10 ka estimated from a numerical model. Marine Geology 183, 179e192.

Please cite this article in press as: Yao, Z., et al., Sedimentary environment and paleo-tidal evolution of the eastern Bohai Sea, China since the last glaciation, Quaternary International (2016), http://dx.doi.org/10.1016/j.quaint.2016.04.010

10

Z. Yao et al. / Quaternary International xxx (2016) 1e10

Violante, R.A., Parker, G., 2004. The post-last glacial maximum transgression in the de la Plata River and adjacent inner continental shelf, Argentina. Quaternary International 114, 167e181. Wang, Q., Zhang, Y.F., Yuan, G.B., Zhang, W.Q., 2008. Since MIS 3 stage the correlation between transgression and climate changes in the North Huanghua area, Hebei. Quaternary Science 28, 79e95 (in Chinese with English Abstract). Wang, Q., 1999. Preliminary study of age of the basal peat during the early Holocene in the western Bohai Sea. Quaternary Science 1, 99 (in Chinese with English Abstract). Wang, F., Li, J., Chen, Y., Fang, J., Zong, Y., Shang, Z., Wang, H., 2015. The record of mid-Holocene maximum landward marine transgression in the west coast of Bohai Bay, China. Marine Geology 359, 89e95. Xiang, R., Yang, Z., Saito, Y., Fan, D., Chen, M., Guo, Z., Chen, Z., 2008. Paleoenvironmental changes during the last 8400 years in the southern Yellow Sea: benthic foraminiferal and stable isotopic evidence. Marine Micropaleontology 67, 104e119. Xie, L.S., Hsieh, W.W., Helbig, J.A., 1990. A tidal model of Bohai. Continental Shelf Research 10, 707e721.

Xue, C.T., 1993. Historical changes in the Yellow River delta, China. Marine Geology 113, 321e330. Xue, C.T., Zhou, Y.Q., Zhu, X.H., 2004. The Huanghe River course and delta from the end of Late Pleistocene to the 7th century BC. Acta Oceanologica Sinica 26, 48e61 (in Chinese with English abstract). Yao, Z.Q., Guo, Z.T., Xiao, G.Q., Wang, Q., Shi, X.F., Wang, X.Y., 2012. Sedimentary history of the western Bohai coastal plain since the late Pliocene: implications on tectonic, climatic and sea-level changes. Journal of Asian Earth Sciences 54e55, 192e202. Zhao, X.T., Geng, X.S., Zhang, J.W., 1979. Sea level changes of the Eastern China during the past 20000 years. Acta Oceanologica Sinica 1, 269e281. Zhou, L.Y., Liu, J., Saito, Y., Zhang, Z.X., Chu, H.X., Hu, G., 2014. Coastal erosion as a major sediment supplier to continental shelves: example from the abandoned Old Huanghe (Yellow River) delta. Continental Shelf Research 82, 43e59. Zhu, Y.R., Chang, R.F., 2000. Preliminary study of the dynamic origin of the distribution pattern of bottom sediments on the continental shelves of the Bohai Sea, Yellow Sea and East China Sea. Estuarine, Coastal and Shelf Science 51, 663e680.

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