Journal of Asian Earth Sciences 152 (2018) 52–68

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Journal of Asian Earth Sciences

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Full length article Holocene evolution of the Liaohe Delta, a tide-dominated delta formed by T multiple rivers in Northeast China ⁎ Lei Hea,b, Chunting Xuec, Siyuan Yea,b, , Edward Allen Lawsd, Hongming Yuana, Shixiong Yanga, Xiaolei Due a Key Laboratory of Coastal Wetland Biogeosciences, China Geologic Survey, Qingdao, China b Laboratory for Marine Mineral Resources, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China c Department of Coastal Geology, Qingdao Institute of Marine Geology, Qingdao, China d College of the Coast & Environment, Department of Environmental Sciences, Louisiana State University, Baton Rouge, USA e Inspection & Test Center of Marine Geology, Ministry of Land and Resources, Qingdao, China

ARTICLE INFO ABSTRACT

Keywords: The Liaohe Delta in Northeast China is one of the ecologically important estuarine deltas in China. It has been Sedimentary evolution formed via the accumulation of sediment discharged by four rivers in the Liaohe Plain that enter Liaodong Bay. Climate changes Twenty-seven 30–40 m long cores recovered from the Liaohe Plain and Liaodong Bay were analyzed for sedi- Human impacts mentary characteristics, grain size, foraminifera species, and ages determined by accelerator mass spectrometry Holocene (AMS) 14C to document the stratigraphical sequence and the spatio-temporal evolution of the Liaohe Delta. Our Liaohe Delta results revealed that the sedimentary environments have evolved from fluvial, tidal flat/estuarine, to neritic and finally to a deltaic environment since the Late Pleistocene. The Holocene transgression arrived at the present coastline at ∼8500 cal a BP and flooded the maximum area of land at ∼7000 cal a BP. A deltaic environment prevailed in this area after 7000 cal a BP. Bounded by the modern Liaohe River mouth, the present deltaic sedimentary system can be divided into the eastern and western components. The rate of seaward progradation of the eastern paleocoastline was estimated to be ∼8.6 m/a since 7000 cal a BP; the eastern cores in the present coastline began receiving the deltaic sediments at ∼5000 cal a BP. The rate of seaward progradation of the western paleocoastline was estimated to be only ∼2.8 m/a since 7000 cal a BP. The coastline on the western side began accumulating deltaic sediments about 2000 years later than the eastern coastline. Depocenter shifting was hypothesized to be the reason for the spatial differences in the sedimentary processes. However, the change of sediment fluxes of the western rivers due to climate changes and ancient human impacts might be the reason for the differences of the temporal evolution of the eastern and western sedimentary systems in the Liaohe Delta.

1. Introduction (Penland et al., 1985; Xue, 1993), and (3) the morphologies of deltaic coastal plains and coast processes(Tanabe et al., 2006; Tamura et al., During the last several decades, a number of studies have focused on 2012). The deltas noted above, however, are associated with a single the geological history of the mega deltas of the world, including the river. Nile Delta (Coutellier and Stanley, 1987; Stanley and Warne, 1993), A few studies have concerned major deltas formed by multiple Mississippi River Delta (Penland et al., 1985; Penland and Suter, 1989), rivers, such as the Ganges–Brahmaputra Delta (Goodbred and Kuehl, Yangtze River Delta (Li and Wang, 1998; Li et al., 2000a; Hori et al., 2000; Allison et al., 2003; Sarkar et al., 2009), Pearl River Delta (Li 2001, 2002), Yellow River Delta (Xue, 1993; Cheng and Xue, 1997; et al., 1991; Zong et al., 2009), Chao Phraya Delta (Tanabe et al., 2003), Saito et al., 2000) and Mekong River Delta (Nguyen et al., 2000; Ta and Rhine-Meuse Delta (Bos and Stouthamer, 2011). These studies have et al., 2002; Tamura et al., 2009). These studies have greatly increased provided a somewhat diﬀerent perspective on the evolution of deltaic understanding of the relationships between (1) the initiation of major coastal plains. Allison et al. (2003) found that the coastal plain of the river deltas and sea level change (Stanley and Warne, 1994; Hori et al., Ganges–Brahmaputra Delta could be roughly divided into three sections 2004; Hori and Saito et al., 2007; Nguyen et al., 2010), (2) pa- associated with the Ganges—G1 (5–2.5 ky), G2 (4–1.8 ky), G3 (< 4–0.2 leochannel shifting and several periods of deltaic superlobe formation ky) and a GB1 section associated with the Ganges and Brahmaputra

⁎ Corresponding author at: 62 Fuzhou south Rd., Shinan District, Qingdao Institute of Marine Geology, China Geological Survey (CGS), Qingdao 266071, China. E-mail address: [email protected] (S. Ye). https://doi.org/10.1016/j.jseaes.2017.11.035 Received 22 June 2017; Received in revised form 23 November 2017; Accepted 24 November 2017 Available online 24 November 2017 1367-9120/ © 2017 Elsevier Ltd. All rights reserved. L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 1. (a) map of China and location of the study area. (b) drainage areas of Liaohe – Daliao Rivers, Daling River, and Xiaoling River. The yellow dotted line indicates the boundary of each drainage area. (c) a total of 7 sampling cores (solid red triangles) and 20 open-pit cores (solid black circles) were recovered for the stratigraphical study in this area during 2012–2014. The blue dashed line indicates the approximate limit of the Holocene transgression (modified from Fu, 1988). The red solid lines indicate the longitudinal profile and transverse profile. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

(0.2–0 ky). Nevertheless, most previous studies of deltas controlled by 2. Regional setting multiple rivers have tended to include all rivers together (e.g., the Chao Phraya Delta, Tanabe et al., 2003) or to focus on the main river (e.g., The Liaohe Delta is located at the junction of the lower Liaohe River the Po Delta, Amorosi et al., 2003). Because much work is required to Plain and Liaodong Bay in the northern Bohai Sea (121°25′–123°55′E, address the paleochannel history of more than one river, it is much 40°40′–41°25′N) (Fig. 1b). It has formed from the accumulation of se- more complex and challenging to reconstruct the evolutionary history diments discharged by the Liaohe River, Daliao River, Daling River, and of deltas accumulated by multiple rivers. Xiaoling River, all of which enter Liaodong Bay (Fig. 1c). The area of The Liaohe Delta is the northernmost coastal delta in China the delta is approximately 5200 km2 (Zhang et al., 2009), of which (Fig. 1a). It has been formed by sediment discharged by four rivers that ∼1280 km2 is wetland (Li et al., 2012). About 786 km2 of the wetland enter Liaodong Bay in the Bohai Sea (Fig. 1b). Based on a compre- is marsh vegetated by common reed (Phragmites australis (Cav.) Trin.Ex hensive analysis of 27 drilling cores in the Liaohe Delta during Steud). The reed marsh in the Liaohe Delta represents probably the 2012–2014 (Fig. 1c), the goal of this paper was to: (1) document largest reed ﬁeld in the world (Brix et al., 2014) and is an important characteristics and depositional patterns of the sediment in the Liaohe breeding area for many endangered bird species. It has been designated Delta and its response to Holocene sea level changes, (2) reveal the as the Shuangtaizihekou National Nature Reserve since 1986 and has contributions of the four rivers to the delta evolutionary processes and also been listed as a Ramsar Site since 2004 (Li et al., 2012). mechanisms, (3) improve understanding of the fate of deltas formed by multiple rivers. 2.1. River system characteristics

The four rivers that discharge into the northern Liaodong Bay

53 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

include the Xiaoling River, Daling River, Liaohe River, and Daliao River (joined by the Hunhe River and Taizi River) from west to east, respectively (Fig. 1c). The runoff and sediments are mainly derived from the Liaohe River, Daliao River, and Daling River in the Liaohe Delta. Of these, the Daliao River is the largest contributor to runoff, whereas the Wang and He (1993) Wu et al. (2005) Wang and He (1993) Zhang et al. (1995) Daling River is the largest contributor to sediment discharge (Table 1). The Liaohe River and Daliao River have not been isolated throughout their history. According to historical records, the Liaohe River and Daliao River entered the sea through the same channel from the Han Dynasty (206 BCE to 24 A.D.) to 1861 CE (Pan, 2005). They partially separated after a crevasse formed in the right bank of the 1979 1993 1979 1987 – – – – Liaohe River in 1861. The crevasse led to part of the Liaohe River’s 1969 1954 1954 Period of measurement Reference entering Liaodong Bay by Panjin, while the rest of the river still entered the bay by Yingkou. The Liaohe River and Daliao River were separated completely when a dam was built to cut off the connection between

and sediment discharge data shown here should be smaller them in 1958, the result being formation of two independent river ﬀ systems since then (Pan, 2005). Topographically, the catchment of the –

1987) Liaohe Daliao River system is low in the center and high on both sides (Fig. 1b). The eastern portion of the Liaohe–Daliao River catchment is mainly mountainous, with high vegetative coverage and relatively high )

3 precipitation. This eastern area yields ∼70% of the annual runoﬀ from 9.98 3.23 Sediment concentration (kg/ m 5.59 (1955 – the combined catchments (Wang et al., 2002). In contrast, the vegetative coverage of the western area is < 30%; the result is severe soil loss, and the western area is therefore the main source of sediments in the catchment (Zhao et al., 2008).

1987) The Daling and Xiaoling River catchments are mainly mountainous – and hilly. The sediment discharged by the Daling River mainly origi- ux of sediments entering the sea is therefore smaller than the sediment discharge in this table. ﬂ t/yr) nates from the upstream reaches of the river, where clastic rocks and 4 loess are widely exposed. About 83% of the sediment in the Daling 889 1217 Sediment discharge (10 River is derived from the upstream portion of its catchment (Li et al., / 3

m 2000b). The sediments in the Xiaoling River are also mainly derived 8

uvial fan. The from its upstream catchment, as are ∼85% of the sediments in the ﬂ Xiaoling River (Zhang et al., 1995). 1987) 224 (1955

2.2. Marine hydrology 1985 in the upper reaches of the Hunhe River and Taizi River, the runo 27.5 12.19 Water discharge (10 yr)

and sediment discharge data shown here should therefore be smaller than the values under natural conditions. The estuary of the four rivers is located in Liaodong Bay, Bohai Sea

ff which is a semi-enclosed epeiric sea. The area of Liaodong Bay is ∼1×104 km2, and the average depth of the water is about 18 m, with 32 m as the maximum depth (Xu et al., 1997). The average salinity of Liaodong Bay is < 30‰ (Xu et al., 1997). The waves in Liaodong Bay are primarily driven by the wind. The ) 2 annual prevailing wind direction is SW, and the average wind speed is 23,048 (km ∼4.30 m/s (IOCAS, 1985). The orientation of the waves is mainly NNE, with N as the second most common orientation. The average height of the waves is less than 1 m, with 5 m as the maximum height (Liu, 1996). The average tidal range is ∼2.70 m at the Liaohe River mouth (Zhu et al., 2007). The coastal area of the Liaohe Delta is classified as tide- dominated (low) to mixed energy (tide-dominated) based on the dia- Tangmazhai 11,203 Linghai Liujianfang 136,500 Hydrologic station Controlling area gram of mean tidal range vs. mean wave height of Davis and Hayes (1984). This same classification also characterizes the Yangtze River Delta and Mekong River Delta (see Hori et al., 2002). The delta may also be classified with respect to tide-wave domination and is close to 1981 in the upper reaches of the Liaohe River. The runo – )

2 the boundary with the wave-dominated ﬁeld in Galloway’s river-tide-

(km wave ternary diagram (Galloway, 1975). Tidal currents are the main currents in the northernmost sector of Liaodong Bay, where they govern the irregular semidiurnal tides. The main ﬂood and ebb tides move back and forth in a NE-SW direction 415 11,480 Xingjiawopu 11,090 42.21 899 2.13 1954 3971430 23,549 195,500 (Liu, 1996). The maximum speed of the tidal currents ranges from 0.70 to 2 m/s (Liu, 1996). The tidal currents are stronger in the eastern part ) 353.4 13,880 c of the northernmost sector of Liaodong Bay than in the western part because of the incised river channel on the eastern side (Fig. 1b), which b a is a favorable passage for modern tidal currents (Lin, 1983; Liu, 1996). ) c The tidal waterway of the Liaohe River can reach Panjin, which is R. Several reservoirs were built during 1958 The hydrologic station for the Daling river is in a mountain pass, and some river-derived sediments accumulate on the The Daliao River is joined by the Hunhe and Taizi Rivers. Because several reservoirs were built during 1954 – ∼61 km from the river mouth. The tidal waterway of the Daliao River a b c River Length (km) Drainage area Daliao R. (Taizi R. Liaohe R. Daliao R. (Hunhe Xiaoling R. 206 5475 Jinzhou 3115 3.456 (1954 – Daling R. ∼ Table 1 Hydrology of the Liaohe, Daliao, Daling, and Xiaoling Rivers. than the values under natural conditions. can reach 94 km from the river mouth (SLWRC, 2004).

54 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 2. Subaqueous sedimentation of the modern Liaohe Delta. (a) particle size distribution of modern surface sediments in the northern Liaodong Bay (modiﬁed after Zhang, 2013). SG = sandy gravel, S = sand, TS = silty sand, T = silt, ST = sandy silt, YT = clayey silt; (b) distribution of sedimentary environments in the modern Liaohe Delta.

The alongshore currents of the northernmost part of Liaodong Bay shells, peat, plant materials were sampled. As shown by Liu et al. are much weaker than the tidal currents. Except for some individual (2004) and Xue (2014), the sea level was estimated to be ranged from months (July or August), the coastal currents move in a clockwise di- −70 m to −50 m during the period from 13–11 ka. A rapid sea-level rection (Zhao et al., 1995). This pattern may be related to the Yellow rise occurred during 11–8 ka BP and the sea level approached or ex- Sea Warm Current and thermohaline gradients in this area (Liu, 1990; ceeded its present level around 6–7 ka BP. Based on appropriate dating Zhao et al., 1995). The speed of the residual current ranges from 0.05 to materials from terrestrial-marine environments, Tian et al. (2016) re- 0.32 m/s on the surface water and from 0.04 to 0.18 m/s at the bottom constructed the Holocene relative sea-level curve of the Laizhou Bay on the eastern coast; it ranges from 0.06 to 0.23 m/s on the surface and (one of bays in the Bohai Sea), especially after 8 ka BP. Compared with below 0.08 m/s at the bottom on the western coast (Liu, 1990). the buried sea level curve referred from Yan et al. (2006), the curve from Tian et al. (2016) may be more reliable to explain the history of 2.3. Subaqueous sedimentation in the modern Liaohe Delta sea level changes in the Bohai Sea.

The subaqueous sedimentary system of the modern Liaohe Delta 3. Materials and methods gradually stabilized after the separation of the Liaohe and Daliao Rivers in 1958. From land to sea, the system can be divided into three parts: Table 2 shows all the data from the 27 cores recovered in the Liaohe tidal flat, delta front, and prodelta (Fig. 2). Delta. Cores ZK1–ZK7, 90 mm in diameter, were taken from the present The tidal flat sediments are primarily composed of gray silt and delta plain and subaqueous delta by rotary drilling during 2012–2014. sandy silt (Zhu et al., 2007)(Fig. 2a). It extends along the present The mean coring recovery rate of these seven cores was > 85%. Cores coastline, river mouths, and several shoals seaward of the Liaohe and GCZ01–GCZ20 were open-pit cores that were described and sampled Daliao River mouths (Fig. 2b). The width of the tidal flat is ∼3–9 km. during field engineering drilling in 2014. The sedimentary accumulation rate was ∼0.13–0.19 m/a during the Samples for grain size were collected from cores ZK1–ZK7. The last decade (Zhu et al., 2010). sample interval was ∼0.10 m, with a smaller sample interval The delta front sediments are composed of gray sand and sandy silt (∼0.05 m) in some layers where there were visible differences in tex- which appear as several lobes at the outside of rivers that discharge into ture. The weight of each sample was about 10 g. All grain sizes were Liaodong Bay (Zhang, 2013)(Fig. 2b). The widths of the Xiao- determined using a Mastersizer-2000 laser particle size analyzer and – – ∼ – ling Daling and Liaohe Daliao delta fronts are 3 10 km and standard sieving methods after pretreating with 10% H2O2 and 0.10 N ∼10–30 km, respectively. HCl to remove organic matter and biogenic carbonates. The range of The prodelta sediments are composed of dark gray clayey silt and particle sizes was from 0.02–2000 μm; the standard deviations silt (Zhang, 2013)(Fig. 2a). The prodelta can extend ∼50–60 km from were < 1% of the mean values; the reproducibility (φ50) was also < the present coastline in northern Liaodong Bay. However, there are two 1%. The samples were classified into three categories: clay (< 2 μm), sets of underwater incised channels in eastern Liaodong Bay, namely silt (2–63 μm), and sand (> 63 μm). The ranges of particle sizes cor- the Daling R. incised channel and the Liaohe R. incised channel responding to the three classes were based on the Krumbein phi (Ф) (Fig. 1c). These incised channels, characterized as residual underwater scale (Krumbein and Sloss, 1963), which is a logarithmic scale com- landscapes, were presumably formed during the period of low sea level puted by the equation: Ф = –log2 (D/Do), where D is the diameter of (Lin, 1983). They became important conduits for the influx of riverine the particle (mm) and Do is a reference diameter equal to 1 mm. Size sediments into Liaodong Bay (Lin, 1983). Thus, some of the delta se- parameters were calculated based on the methods of Folk and Ward diments were dispersed into the middle of the Bohai Sea though this (1957). channel after the initial formation of the Liaohe Delta (Xu et al., 1997). The average interval of microfossil sampling was ∼0.25 m in the cores, with a smaller sample interval (∼0.10 cm) in some layers. All 2.4. Sea-level changes in the Bohai Sea during past 13 ka samples were dried at 40 °C in an oven, weighed at about 50 g per sample, and washed over a 63-μm sieve. After drying, foraminifera

Four sea-level curves in the Bohai Sea and its adjacent seas are were concentrated and separated using the CCl4 ﬂotation method exhibited in Fig. 3 during the last 13 ka (Liu et al., 2004; Yan et al., (Wang et al., 1985). Sample division was carried out when the for- 2006; Xue, 2014; Tian et al., 2016). These curves were constructed by aminiferal abundance of a sample was very high. Samples were split dating ages (mainly from AMS 14C dating, occasionally from OSL) into fractions using a splitter, and tests were picked until a re- against the depths at which the dated materials, such as molluscan presentative number of more than 200 individuals was obtained for

55 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 3. Sea-level curves in the Bohai Sea and its adjacent seas during the past 13 ka.

Table 2 preferentially assayed in a given layer. Additionally, foraminifers were Location, elevation, and core depths of cores collected in the Liaohe Delta. also selected for AMS 14C dating when no available sample was obtained in some layers. Age determination was based on a Libby half-life Core Latitude Longitude Elevation (m)a Core depth (m) of 5568 yr. Radiocarbon ages were corrected for the regional marine ZK1 40°51′53.01″ 121°50′29.89″ 2.42 31.2 reservoir effect (ΔR=−178 ± 50 a, a regional average determined ZK2 40°45′18.33″ 122°07′11.23″ 4.24 32 for the Bohai Sea after Southon et al., 2002) and calibrated using Calib ′ ″ ′ ″ ZK3 40° 52 14.59 121° 36 12.07 2.73 36.7 Rev. 7.02 with one standard deviation (1σ) uncertainty (Reimer et al., ZK4 40°48′36.60″ 121°59′41.42″ 2.71 35.92 ZK5 40°59′34.19″ 122°09′33.94″ 4.16 0.0–14.56 2013). Table 3 summarizes all radiocarbon dates, which obtained from 40°59′34.20″ 122°09′33.96″ 4.23 14.56–31.25 either sampling cores or the open-pit cores. ZK6 40°33′00.58″ 121°45′25.08″ −8.6 30 ′ ″ ′ ″ − ZK7 40°25 05.31 121°39 07.25 16 30.9 4. Results GCZ01 40°57′21.77″ 121°34′62.65″ 4.33 32 GCZ02 40°58′0.45″ 121°18′24.55″ 4.83 32 GCZ03 40°56′0.80″ 121°26′26.79″ 2.94 31 4.1. Depositional units and sedimentary facies in the Liaohe Delta GCZ04 41°07′31.73″ 121°19′28.57″ 5.13 33 GCZ05 40°53′37.06″ 121°32′42.31″ 3.07 32 Based on the analysis of lithological and sedimentary character- ′ ″ ′ ″ GCZ06 40°53 27.05 121°41 39.31 3.89 32 istics, fossils, and dating results of all cores in the Liaohe Delta, four GCZ07 40°59′42.54″ 121°40′35.82″ 4.51 33.2 GCZ08 41°03′55.11″ 121°43′34.38″ 3.96 34.3 main depositional units (DUs) and their facies are summarized and GCZ09 40°58′38.77″ 121°56′30.58″ 3.19 33 detailed as follows. GCZ10 40°54′09.86″ 121°55′07.77″ 3.61 32 GCZ11 40°51′06.17″ 121°53′24.78″ 3.95 34.2 4.1.1. DU1: fluvial sediments GCZ12 40°55′53.27″ 122°06′59.29″ 4.48 32.2 GCZ13 40°52′31.04″ 122°02′58.84″ 3.23 33.3 The DU1 recovered from the lower part of the sedimentary sequence GCZ14 40°47′01.73″ 122°02′20.85″ 2.43 32.5 in the Liaohe Delta could be divided into three related facies: channel- GCZ15 40°51′03.04″ 122°15′36.3″ 2.87 33 filled facies, channel-margin facies, and inter-channel flood basin fa- ′ ″ ′ ″ GCZ16 40°48 05.46 122°11 48.34 3.57 32 cies. GCZ17 40°40′23.18″ 122°09′44.53″ 3.77 32.8 GCZ18 40°35′0.99″ 122°16′31.57″ 3.08 33.7 GCZ19 41°02′39.9″ 122°15′50.28″ 4.22 33.3 4.1.1.1. Channel-filled facies. Depth: Core ZK1, 11.6–21.6 m; ZK2, GCZ20 40°29′30.37″ 122°17′59.46″ 3.53 33.8 23.8–32 m; ZK3, 23.3–31.3 m; ZK4, 13.4–33.4 m; ZK5, 10.5–23.9 m; ZK6, 21–30 m; ZK7, 6.6–31 m. a Elevation of cores are relative to 1956 Yellow Sea height datum of China. This facies consisted of sand, interbedded silt and silty clay in as- cending order. The sediments displayed an overall fining-upward se- each assemblage. Otherwise, all the available tests were picked and quence; they were rich in plant fragments and contained no marine studied under a Zeiss optical stereoscope. The “foraminiferal abun- shell or shell fragments. dance” parameter in this paper is the number of foraminifera per 50 Subfacies 1.1 (core ZK1 16.3–21.6 m; ZK2, 23.8–32 m; ZK3, grams of dry sediment. The “simple diversity” is the number of for- 23.3–31.3 m; ZK4, 17–33.4 m; ZK5, 10.5–23.9 m; ZK6, 21–30 m) was aminiferal species in each sample. dominated by a huge set of gray white to yellowish gray fine-medium A total of 80 samples for 14C dating were measured by Beta Analytic sand. The mean grain sizes of the sandy layers in core ZK1 ranged from using accelerator mass spectrometry (AMS). These samples included 1.94 Ф to 4.11 Ф (standard deviations: 0.53–1.57 Ф). Wood fragments mainly mollusk shells, organic matter, and plant fragments. Mollusk or organic materials were occasionally found together in this subfacies shells and plant fragments with relatively large diameters were (Fig. 4-1).

56 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Table 3 AMS 14C dating results of cores in the Liaohe Delta.

Core Sample Beta no. Depth (m) Materials δ13C (permil) Conventional age (a BP) Calendar ages (cal a BP)

Intercept Range (1σ)

ZK1 FA-3 349,364 4.18 Mactra chinensis +0.6 1030 ± 30 755 679–805 FA-4 349,365 4.26 Umbonium thomasi +1.1 1190 ± 30 915 835–975 FA-8 349,368 8.45 Umbonium thomasi +0.1 2240 ± 30 2300 2154–2359 FA-13 349,373 10.95 Talonostrea talonostrea −0.9 3250 ± 30 3295 3223–3368 FA-9 349,370 10.96 Scapharca sp. −1.5 7590 ± 40 8240 8171–8308 FA-15 349,374 11.35 Mactra chinensis −7.2 7780 ± 40 8420 8354–8485 FA-12-2 349,372 11.55 Barbatia sp. −2.6 6270 ± 30 6940 6848–7016 C-1 349,350 27.95 Plant materials −27.0 22,180 ± 100 26,385 26,212–26,524

ZK2 ZK2FA-1 339,942 4.33 Mactra veneriformis −2.6 2350 ± 30 2200 2135–2285 ZK2FA-2 339,943 5.4 Mactra chinensis −2.6 2900 ± 30 2850 2772–2913 ZK2F39C 342,136 5.65 Foraminifers (mix) NA 4210 ± 30 4545 4434–4616 ZK2FA-5 339,946 7.42 Mactra chinensis −1.8 4300 ± 30 4670 4594–4777 ZK2F54C 342,137 7.85 Foraminifers (mix) NA 4020 ± 30 4285 4214–4387 ZK2F75C 342,138 9.95 Foraminifers (mix) −3.8 5280 ± 30 5830 5756–5896 ZK2FA-3 339,944 9.96 Arca subcrenata −1.7 4870 ± 30 5400 5316–5457 ZK2FA-4 339,945 10.72 Mactra chinensis −6.1 6830 ± 30 7500 7451–7553 ZK2F85C 342,139 11.15 Foraminifers (mix) −8.3 6340 ± 30 7030 6958–7120 ZK2FA-6 339,947 12.9 Mactra chinensis −7.0 7330 ± 30 7965 7906–8029 ZK2FA-7 339,948 13.05 Mactra chinensis −5.9 7680 ± 40 8320 8258–8391 ZK2C14B-5 402,657 13.3 Organic sediment −25.5 8840 ± 40 9925 9777–9940 ZK2CB-1 402,658 15.8 Organic sediment −26.6 9310 ± 40 10,520 10,488–10,575

ZK3 ZK3S1 367,650 3.5 Mactra veneriformis 0 390 ± 30 190 130–274 ZK3S9 419,398 11.2 Corbicula ﬂuminea −9.6 7640 ± 30 8425 8400–8446 ZK3S25 379,336 12.45 Ruditapes philippinarum −0.4 4390 ± 30 4775 4693–4845 ZK3S3 367,652 12.83 Organic sediment −25.3 9980 ± 40 11,425 11,308–11,410 ZK3S27 379,338 16.05 Biomphalaria sp. −12.2 12,850 ± 50 15,320 15,206–15,414 ZK3S8 367,657 29.05 Organic sediment −22.7 35,990 ± 340 40,625 40,246–41,030

ZK4 ZK4S10 367,659 8.1 Arca subcrenata −1.0 2130 ± 30 1925 1848–1994 ZK4S28 379,339 8.49 Potamocorbula ustulata −2.9 4160 ± 30 4475 4397–4554 ZK4S11 367,660 9.48 Volachlamys hirasei −0.7 4580 ± 30 5015 4889–5087 ZK4S29 379,340 10.05 Foraminifers (mix) −2.3 6010 ± 40 6625 6546–6710 ZK4S12 367,661 11.6 Arca subcrenata −1.9 7270 ± 40 7905 7839–7968 ZK4S13 367,662 12.65 Potamocorbula ustulata −3.1 7350 ± 30 7985 7920–8046 ZK4S15 367,664 29.1 Plant materials −28.4 32,200 ± 260 36,090 35,804–36,356

ZK5 ZK5S31 379,342 8.95 Plant materials −26.0 7270 ± 30 8095 8089–8157 ZK5S20 367,667 9.84 Organic sediment −23.9 7660 ± 40 8450 8405–8461 ZK5S21 367,668 12.65 Plant materials −27.0 7210 ± 50 8025 7961–8051

ZK6 ZK6S8 393,088 3.7 Potamocorbula laevis 2.4 1240 ± 30 970 909–1035 ZK6S9 398,912 5.05 Pelecyora trigona −0.5 1240 ± 30 970 909–1035 ZK6S14 419,399 6 Oysters 0.4 6460 ± 30 7170 7107–7246 ZK6S10 398,912 6.25 Talonostrea talonostrea 0.3 6420 ± 30 7120 7041–7199 ZK6S2 393,082 6.45 Talonostrea talonostrea 0.3 6470 ± 30 7180 7123–7254 ZK6S3 393,083 7.6 Potamocorbula ustulata −3.9 7700 ± 30 8340 8287–8401 ZK6S4 393,084 8.55 Plant materials −26.0 9060 ± 30 10,225 10,210–10,238 ZK6S12 398,915 9.75 Plant materials −26.8 8450 ± 30 9480 9461–9503 ZK6S13 398,916 10.8 Plant materials −28.5 8250 ± 30 9220 9137–9287 ZK6S6 393,086 16.75 Plant materials −26.6 8670 ± 30 9605 9551–9630

ZK7 ZK7S1 393,089 0.45 Glossaulax didyma 0.0 280 ± 30 90 1–126 ZK7S3 393,091 2.2 Theora sp. −0.3 540 ± 30 365 301–419 ZK7S8 398,918 4.75 Talonostrea talonostrea 0.6 6140 ± 30 6780 6708–6857 ZK7S4 393,092 5 Talonostrea talonostrea −0.5 6500 ± 30 7210 7150–7268 ZK7S9 398,919 5.35 Oysters 0.6 6260 ± 30 6925 6838–7004 ZK7S10 398,920 6.4 Organic sediment −27.7 10,970 ± 40 12,810 12,740–12,857 ZK7S5 393,093 8.35 Plant materials −28.3 14,030 ± 50 17,050 16,947–17,156 ZK7S6 393,094 13.85 Plant materials −27.3 10,930 ± 40 12,775 12,734–12,806 ZK7S7 393,095 23.53 Plant materials −24.4 20,520 ± 80 24,700 24,514–24,872

GCZ02 GCZ02S1 398,899 10.1 Potamocorbula laevis −0.7 5410 ± 30 5985 5903–6052

GCZ03 GCZ03S1 398,900 9.05 Ruditapes philippinarum −2.2 1610 ± 30 1340 1275–1387 GCZ03S2 398,901 10.4 Ruditapes philippinarum −1.7 3800 ± 30 3980 3896–4065

GCZ05 GCZ05S1 398,902 10.8 Potamocorbula ustulata −3.3 7830 ± 30 8465 8400–8523

GCZ06 GCZ06S1 386,299 13.7 Crassostrea ariakensis −4.3 7290 ± 30 7925 7863–7983 GCZ06S2 419,401 30.5 Plant materials −24.1 38,610 ± 380 42,605 42,341–42,862

GCZ07 GCZ07S1 398,904 27.7 Corbicula ﬂuminea −10.5 7800 ± 30 8580 8551–8598

GCZ08 GCZ08S1 386,300 24.6 Potamocorbula ustulata −0.7 3190 ± 30 3230 3158–3317 GCZ08S2 398,905 24.5 Potamocorbula ustulata −4.0 3220 ± 30 3265 3194–3343

(continued on next page)

57 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Table 3 (continued)

Core Sample Beta no. Depth (m) Materials δ13C (permil) Conventional age (a BP) Calendar ages (cal a BP)

Intercept Range (1σ)

GCZ09 GCZ09S1 398,906 9.9 Potamocorbula ustulata −3.8 6400 ± 30 7095 7010–7165

GCZ10 GCZ10S1 398,907 16.9 Ruditapes philippinarum −2.1 5170 ± 30 5715 5627–5784

GCZ12 GCZ12S1 386,301 16.4 Crassostrea ariakensis −3.3 5540 ± 30 6130 6045–6208

GCZ13 GCZ13S1 386,302 18.3 Potamocorbula ustulata −5.5 7120 ± 30 7760 7688–7822

GCZ14 GCZ14S1 419,402 11.4 Potamocorbula ustulata −5.4 7290 ± 30 7925 7863–7983

GCZ15 GCZ15S1 419,403 14.4 Plant materials −27 37,110 ± 340 41,635 41,380–41,921

GCZ16 GCZ16S1 386,303 7.2 Crassostrea ariakensis −3.3 6200 ± 30 6850 6773–6927 GCZ16S2 386,304 9.2 Crassostrea ariakensis −5.5 6670 ± 30 7365 7309–7418 GCZ16S3 386,305 12.6 Organic sediment −22.7 8410 ± 30 9505 9489–9528

GCZ17 GCZ17S1 419,404 20.9 Corbicula ﬂuminea −10.9 8080 ± 30 9010 8995–9025 GCZ18 GCZ18S1 398,908 9.95 Potamocorbula ustulata −5.2 7660 ± 30 8305 8242–8369 GCZ18S2 398,909 14.7 Potamocorbula laevis −8.1 7690 ± 30 8475 8425–8480

GCZ19 GCZ19S1 419,406 7.5 Organic sediment −28.1 7230 ± 30 8035 7982–8052

GCZ20 GCZ20S1 398,910 8.3 Mactra veneriformis −0.4 590 ± 30 405 335–467 GCZ20S2 419,407 14.5 Plant materials −25.9 29,970 ± 160 34,040 33,876–34,180

Subfacies 1.2 (core ZK1 11.6–12.7 m; ZK4, 13.4–14.4 m) was char- deposit during a period of slow flow as this part was dominated by fine- acterized by dark gray silty clay and thin silty layers containing some grained sediments. Calcareous concretions are well preserved plant/wood fragments and rootlets (Fig. 4-2). The mean grain sizes of throughout the facies, an indication of a partly subaerial and leaching this subfacies in core ZK4 ranged from 5.02 Ф to 6.81 Ф (standard environment, which is very common in a natural levee or crevasse splay deviation: 1.61–1.91 Ф). Small terrestrial gastropods, such as Radix sp., (Galloway and Hobday, 1983). Thus, this facies is interpreted as a were found in this subfacies. channel-margin depositional environment, such as crevasse splay. The Interpretation: The lack of marine fossils and abundant plant frag- AMS 14C ages of this facies fall after 40,000 cal a BP, the indication ments indicate a terrestrial environment in this unit (Galloway and being that it is a Late Pleistocene channel-margin facies. Hobday, 1983). An overall fining-upward succession is characteristic of lateral accretion of point bar in a meandering river system (Visher, 4.1.1.3. Inter-channel flood basin facies. Depth: Core ZK2, 15.7–23.8 m; 1965; Galloway and Hobday, 1983; Miall, 1992). Thus, subfacies 1.1 is ZK3, 12.4–23.3 m; ZK4, 33.4–36 m; ZK5, 8.8–10.5 m. considered to be a channel-filled sediment deposit because of the coarse This facies is dominated by gray to dark gray silty clay and silt, grain size, good sorting, and thick deposits. Subfacies 1.2 is probably a partly interbedded with sandy silt layers (Fig. 4-4). The mean grain swamp environment rather than a lacustrine environment, because the sizes of the clayey and silty beds in core ZK2 ranged from 3.95 to 7.10 Ф plant materials and rootlets are relatively abundant in this subfacies (standard deviations: 1.42–2.43 Ф). This facies displays horizontal (Galloway and Hobday, 1983). The gradational boundary between bedding and bioturbation, and also contains some freshwater gastro- subfacies 1.1 and the overlying subfacies 1.2 is interpreted to reflect pods, including Radix sp. and Biomphalaria sp. gradual channel abandonment or lateral channel shifting (e.g. Amorosi Interpretation: Floodbasin sediments are often found in cores near 14 et al., 2008). AMS C ages of plant fragments ranged from the mouths of the Liaohe River, Daliao River, and Daling River, such as 9.0 ± 0.9 ka to > 40,000 cal a BP in this facies, the indication being cores ZK2 and ZK3 (Fig. 1c). The sediments are fine and always sharply that the facies includes a long period of time and multiple cycles of overlay channel-filled depositions, reflecting the abrupt channel aban- fluvial processes from the Late Pleistocene to the Early Holocene in this donment (e.g. Amorosi et al., 2008). Horizontal beddings and bio- area. turbation are well displayed in this facies. It is thus interpreted as a mud plug or backswamp after the river channel laterally shifted. Compared 4.1.1.2. Channel-margin facies. Depth: Core ZK3, 31.3–36.7 m; ZK5, with a mud plug, fine and organic rich sediment is common in a ve- 14 23.9–25 m. getated backswamp (e.g. Hori et al., 2004). The AMS C dates in this This facies generally consists of two parts, and shows an overall facies fall between 10,000 cal a BP and 28,000 cal a BP implies an in- fining-upward succession. The lower part is characterized by brownish terchannel flood basin deposition before the Holocene transgression. yellow fine sand and gray silty clay. The mean grain sizes of the sandy and clayey layers in core ZK5 ranged from 2.95 Ф to 6.66 Ф (standard 4.1.2. DU2: estuarine sediments deviations: 1.65–2.89 Ф). Calcareous concretions (0.5–5 cm in dia- Depth: Core ZK6, 7.7–20.9 m. meter) and mud clasts (0.5–4 cm in diameter) were scattered Based on its lithological characteristics and fossils, the estuarine throughout this part of the core (Fig. 4-3). Small-scale cross beddings facies of DU2 in the Liaohe Delta can be divided into three subfacies. could also be easily discerned in these layers. The upper part, however, Subfacies 2.1 (core ZK6 12.1–20.9 m) is mainly composed of gray was dominated by homogenized silty clay that contained some calcar- fine sand containing some marine and brackish water mollusk shells eous concretions (0.5–2 cm in diameter) and some plant/wood frag- (Fig. 4-5), such as Ruditapes philippinarum, Talonostrea talonostrea, Po- ments or rootlets. The mean grain sizes of the clayey layers in core ZK5 tamocorbula ustulata, and Corbicula fluminea. The mean grain sizes of ranged from 5.78 Ф to 6.41 Ф (standard deviations: 1.99–2.39 Ф). No this layer in core ZK6 ranged from 1.94 Ф to 5.34 Ф; the standard marine fossils were found in this facies. deviations (0.64–1.76 Ф) indicated good to moderate sorting. The Interpretation: Compared with the deposition of point bar, the lower average foraminiferal abundance and simple diversity were 240 and 6, part of the unit contains poorly sorted sand and clayey silt and scattered respectively. This subfacies was dominated by euryhaline foraminifera mud clasts, an indication of a chaotic and rapid pattern of deposition such as Ammonia beccarii vars. (average percentage: 39%) and Cavar- (Galloway and Hobday, 1983). The upper part, however, was likely to otalia annectens (25%) (Fig. 5).

58 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 4. Typical depositional units and facies in the Liaohe Delta. (1) channel-filled channels subfacies 1.1 from depth 16.7–17.1 m in core ZK5; (2) channel-filled channels subfacies 1.2 from depth 12.3–12.7 m in core ZK1. white arrow (a) are thin organic-rich layers, white arrows (b) are plant materials and rootlets, white arrows (c) is a scratch; (3) channel-margin facies from depth 24.5–24.9 m in core ZK5, white arrows (d) are calcareous concretions and white arrows (e) are mud clasts; (4) interchannel floodbasin facies from depth 19.5–19.9 m in core ZK3; (5) estuarine subfacies 2.1 from depth 13.9–14.3 m in core ZK6, white arrows (f) are small oyster fragments; (6) estuarine subfacies 2.2 from depth 9.5–9.9 m in core ZK6, white arrow (g) indicates a small cross bedding; (7) estuarine subfacies 2.3 from depth 7.8–8.2 m in core ZK6; (8) tidal flat-neritic facies from depth 7.5–7.9 m in core ZK4, white arrow (h) indicates a shell-rich layer; (9) prodelta from depth 10.3–10.7 m in core ZK3; (10) delta front from depth 6.8–7.2 m in core ZK3; (11) lower delta plain from depth 3.2–3.6 m in core ZK4, white arrows (i) are rusty speckles; (12) upper delta plain from depth 1.2–1.6 m in core ZK3, white arrow (j) indicates common reed rootlets. All column lengths are 40 cm.

Subfacies 2.2 (core ZK6 9.3–12.1 m) was dominated by light gray silt Protelphidium tuberculatum, increased sharply in this subfacies. interbedded with gray clayey silt (Fig. 4-6). Wavy and lenticular tidal Interpretation: Subfacies 2.1 is preliminarily considered to be a beddings were well presented in the sediments. The mean grain sizes of channel–filled facies because of the very large set of well sorted sandy this layer in core ZK6 range from 3.83 Ф to 6.59 Ф. The standard de- deposits. However, the presence of mollusk shells, such as viations (1.36–2.24 Ф) were indicative of poor sorting. The average Potamocorbula ustulata, Corbicula fluminea and a few of foraminifers foraminiferal abundance and simple diversity were 2480 and 8, re- indicated that the subfacies 2.1 was deposited in a brackish environ- spectively. This foraminifer assemblage was dominated by the eur- ments (e.g. Hori et al., 2001, 2004; Tanabe et al., 2006). Thus, subfacies yhaline species Ammonia beccarii vars. (average percentage: 65.16%), 2.1 is considered to be a tide river-filled facies. but it also included Protelphidium tuberculatum (9.38%) and Elphidium Subfacies 2.2 was well represented by rhythmic sand-mud couplets magellanicum (2.58%) (Fig. 5). The abundance of microfossils increased and wavy and lenticular tidal beddings with some plant materials. The from subfacies 3.1 to subfacies 3.2. foraminifer assemblages were dominated by Ammonia beccarii vars., a Subfacies 2.3 (core ZK6 7.7–9.3 m) was primarily composed of fine species characteristic of low-salinity environment in the coastal area gray sand and sandy silt interbedded with thin silt beds (Fig. 4-7). The (Wang et al., 1985). Thus, it indicates the coastal marsh to tidal flat mean grain sizes of this layer range from 3.24 Ф to 6.12 Ф. The stan- environments in this subfacies (e.g. Hori et al., 2004; Tanabe et al., dard deviations (1.34–2.17 Ф) were indicative of poor sorting. The 2006). average foraminiferal abundance and simple diversity were 4100 and The subfacies 2.3 was also characterized by interbedded sand and 11, respectively. These sediments were dominated by the foraminifera mud and typical tidal beddings. However, the sand content is generally Ammonia beccarii vars. (average percentage: 57%) and Protelphidium more than 80%. Abundant foraminifers and a greatly increasing tuberculatum (20%), with minor contributions from Elphidium magella- abundance of stenohaline species suggests that it should be deposited in nicum and Cribrononion subincertum. The foraminiferal abundance and a sedimentary environment deepen upward from subfacies 2.2 to sub- simple diversity were relatively high, and the stenohaline species, facies 2.3 (Wang et al., 1985). On the basis of the lithofacies and

59 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 5. Comprehensive geological log of core ZK6. (a)–(c): charts of particle size analysis; (d)–(k): charts of foraminiferal analysis, including foraminiferal abundance (per 50 g dry sample), simple diversity, and percentage composition of each dominant species; (l)–(m): sedimentary environment and depositional units of core ZK6. assemblages of benthic foraminifera, it is appropriate to interpreted as (28.34%), Elphidium magellanicum (9.39%), Cribrononion subincertum tidal sand bar in the estuary (Dalrymple and Choi, 2007). (4.80%), Elphidium advenum (3.27%) and Cavarotalia annectens (1.28%) An overall fining-upward succession from medium sand to inter- (Fig. 6). bedded sand and mud in this facies is similar to tidal estuarine sand and Interpretation: On the basis of the lithofacies, sedimentary texture mud sediments in the Gironde estuary (Allen and Posamentier, 1993) (e.g. lenticular bedding), this unit is interpreted as a tidal flat and and Fly River delta in the Gulf of Papua (Dalrymple et al., 2003). Thus, neritic environment because of the abundance of marine micro- and these subfacies were interpreted as estuarine facies as a whole in this macrofossils (Galloway and Hobday, 1983). The marine shells and depositional unit. A few AMS 14C dates revealed that the bottom of the microfossils increased upward in the sequence. Relatively stenohaline estuarine facies was deposited at ∼9000 cal a BP in the cores around species, such as the foraminifera Protelphidium turberculatum, reached the present coastline. This observation indicates that the forefront of maximum abundance as the tidal flat environment transitioned to a the Holocene transgression may have influenced the rivers in the Liaohe neritic one. However, it is difficult to identify the tidal flat and neritic River Plain at ∼9000 cal a BP, whereas the ages in cores ZK6 were a facies in all cores of the Liaohe Delta. The difficulty may be related to little earlier than 10,000 cal a BP. the rapid sea level rise during the Early Holocene (Liu et al., 2004; Hori and Saito, 2007; Xue, 2014), which led to a relatively thin deposition of tidal flat facies. Another reason may be erosion caused by the strong fl 4.1.3. DU3: Tidal at and neritic sediments tidal currents and waves in this area (Zhu et al., 2010; Ji et al., 2011). – – – Depth: Core ZK1, 10.7 11.8 m; ZK2, 8.6 13.3 m; ZK3, 11 12.4 m; The hydrodynamic conditions may have led to the hiatus between the – – – ZK4, 8 13.4 m; ZK6, 6.2 7.7 m; ZK7, 3.8 5.6 m. late Pleistocene terrestrial facies and the Early Holocene marine facies This unit generally consisted of dark gray silt and gray clayey silt (e.g., in cores ZK3 and ZK5); they may also have reversed some neritic and clayey sand (Fig. 4-8). The silty layers were distributed at the shell-abundant layers and thereby caused a reversed time sequence in Ф Ф bottom of DU3. The mean grain sizes range from 3.82 to 5.27 this facies (e.g., cores ZK1 and ZK3). – Ф (standard deviations: 2.08 2.54 ). Lenticular beddings were common The facies succession was quite different in core ZK4, which could in the layers. A few oyster fragments were found in this unit. In core be divided into two subunits. The first subunit consisted of gray fine- ZK2, the average foraminiferal abundance and simple diversity were medium sand. The mean grain sizes ranged from 3.08 Ф to 3.44 Ф ∼ 700 and 8, respectively (Fig. 6). The euryhaline Ammonia beccarii (standard deviations: 0.51–1.09 Ф). The second subunit was char- vars. (average percentage: 36%), Elphidium magellanicum (19%), Cri- acterized by gray clayey silt and silty sand. The mean grain sizes ranged brononion subincertum (7.8%) and E. advenum (6%), were the dominant from 4.41 Ф to 5.66 Ф (standard deviations: 1.61–2.37 Ф). The second foraminifera species (Fig. 6). subunit contained abundant marine shells and lenticular or wavy bed- The upper part of DU3 was dominated by clayey silt and clayey dings. The first and second subunits alternated within the depth interval Ф Ф sand. The mean grain sizes in core ZK2 range from 4.13 to 6.19 , 8.0–13.4 m in core ZK4; each set of two subunits had an average – Ф and the standard deviations were 1.87 2.55 . These sediments were thickness of 1.5 m. We interpreted the unit in core ZK4 as a tidal sand rich in mollusk shells (Fig. 4-8), including mainly Ruditapes philippi- ridge which a similar lithology has been reported from core JS98 in the narum, Mactra veneriformis, Talonostrea talonostrea, Potamocorbula us- Yangtze River Delta (Hori et al., 2001). The well-sorted sand re- tulata, and Anomia chinensis. The average benthic foraminiferal abun- presented a sand ridge, and the poorly sorted sand with abundant shell ∼ dance was 3880, and the simple diversity reached 20 in core ZK2 fragments was interpreted as inter-ridge deposits. (Fig. 6). The dominant foraminifera species were Protelphidium tu- The majority of AMS 14C dates in the tidal flat and neritic sediments berculatum (average percentage: 45.92%), Ammonia beccarii vars.

60 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 6. Comprehensive geological log of core ZK2. (a)–(c): charts of particle size analysis; (d)–(k): analyses of foraminifera, including foraminiferal abundance (per 50 gram dry sample), simple diversity, and percentage composition of the six dominant species; (l)–(m): sedimentary environment and depositional units of core ZK2. The OSL dates are quoted from Liu et al. (2017). ranged from 8500 to 3000 cal a BP in the cores near the present vars. (average percentage: 32.42%) and Protelphidium tuberculatum coastline, the implication being that the Holocene transgression arrived (28.94%). in the Liaohe Plain at ∼8500 cal a BP. It should be noted that there is a Subfacies 4.3 (core ZK1, 2.4–3.6 m; ZK2, 2.6–5.2 m; ZK3, 2.6–3.8 m; ∼2000 yr time lag between the eastern cores and western cores in the ZK4, 2.2–4.2 m; ZK5, 2–4.8 m) was mainly composed of gray to grayish- present coastline before it was covered by the subaqueous delta. This yellow silt alternating with clayey silt (Fig. 4-11). Wavy and lenticular time lag will be detailed in a subsequent report. beddings were well displayed in this subfacies. The mean grain sizes in core ZK2 range from 3.77 Ф to 6.45 Ф (standard deviations: 0.93–2.20 Ф). The average abundance and simple diversity in core ZK2 were 500 4.1.4. DU4: Deltaic sediments and 8, respectively. The foraminiferal species were dominated by Am- Depth: core ZK1, 0–10.7 m; ZK2, 0–8.6 m; ZK3, 0–11 m; ZK4, monia beccarii vars. (average percentage: 40.72%), whereas the rela- 0–8.0 m; ZK5, 0–8.0 m; ZK6, 0–6.2 m; ZK7, 0–3.8 m. tively stenohaline species Protelphidium turberculatum averaged only of This unit consisted of gray silty clay, clayey silt, and sand in as- 10.33% (Fig. 6). cending order. The sediments displayed an overall coarse-upward suc- Subfacies 4.4 (core ZK1, 0–2.4 m; ZK2, 0–2.6 m; ZK3, 0–2.6 m; ZK4, cession. Marine shells were commonly found in some layers, whereas 0–2.2 m; ZK5, 0–2 m) was dominated by grayish yellow clayey silt and wood/plant fragments were abundant in the upper part of the unit. silt beds containing many common reed roots and ferruginous nodules Subfacies 4.1 (core ZK1, 9.8–10.7 m; ZK3, 10–11 m; ZK6, 3.6–6.2 m; (Fig. 4-12). The mean grain sizes of these beds in core ZK2 range from ZK7, 0–3.8 m) was composed of gray clayey silt alternating with light 5.43 Ф to 6.52 Ф (standard deviations: 1.82–2.03 Ф). The average gray silt layers or lenses (Fig. 4-9). The mean grain sizes in core ZK2 foraminiferal abundance and simple diversity in core ZK2 decreased to range from 5.89 Ф to 7.17 Ф, (standard deviations: 1.55–2.01 Ф). 125 and 4, respectively. The dominant foraminifera species were Am- Lenticular bedding was well displayed in this subfacies. Shells of a few monia beccarii vars. (average percentage: 45.62%) and Pseudononionella marine mollusks, such as Glossaulax didyma, Scapharca subcrenata, and variabilis (42.24%) (Fig. 6). Theora sp., were found in this subfacies. In core ZK2, the abundance and Interpretation: Fine sediments, abundant marine microfossils, and simple diversity averaged 2300 and 19, respectively. The dominant lenticular beddings in the subfacies 4.1 were good indicators of the low- foraminifera species were Protelphidium tuberculatum (average percen- energy prodeltaic suspended deposition (Coleman and Wright, 1975). tage: 31.49%), Ammonia beccarii vars. (26.78%), Elphidium magella- Well sorted coarse sediments and a few marine shells and microfossils nicum (20.84%), Elphidium advenum (3.59%), and Cribrononion sub- were commonly found in the river mouth. The relatively low abundance incertum (2.6%) (Fig. 6). and simple diversity of benthic foraminifera may reflect high energy Subfacies 4.2 (core ZK1, 3.6–9.8 m; ZK2, 5.2–8.6 m; ZK3, 3.8–10 m; conditions and high sediment accumulation rates in the delta front, ZK4, 4.2–8 m; ZK5, 4.8–8.8 m; ZK6, 0–3.6 m) was dominated by gray consistent with the near absence of bioturbation and few shell frag- fine sand and silt (Fig. 4-10) containing a few shell fragments of mol- ments in the subfacies 4.2 (e.g. Abrahim et al., 2008; Liu et al., 2009). lusks such as Mactra veneriformis, M. chinensis, and Umbonium thomasi in Wavy bedding and lenticular beddings were well displayed in the tidal some layers. The mean grain sizes in core ZK2 range from 2.74 Ф to flat in the subfacies 4.3 (Galloway and Hobday, 1983); common reed 5.96 Ф (standard deviations: 0.48–1.51 Ф). The average foraminiferal roots and rusty speckles were good indicators of the saltmarsh and abundance in core ZK2 of this stratum was 1370, lower than those of supratidal environment in the subfacies 4.4 (e.g. Tanabe et al., 2006; the subfacies 4.1. The average of the simple diversity decreased to 14; Liu et al., 2016). On the whole, the quantity of marine microfossils and the dominant foraminiferal species in core ZK2 were Ammonia beccarii

61 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 7. Longitudinal profile A–A′ in the Liaohe Delta. relatively stenohaline foraminiferal species decreased in upward suc- western cores and ∼4 m in the eastern cores of the present coastline cession, whereas the abundance of euryhaline species increased, the (Fig. 8). This difference may be related to the differences of accumu- indication being that the environment changed from marine to terres- lation time between the eastern and western cores. The sediments of trial (Wang et al., 1985). We interpreted this unit as a deltaic en- DU3 in the western cores might experience more washout, transporta- vironment because of its typical deltaic sedimentary characteristics and tion, and erosion by waves and tidal currents. In addition, the amounts textures (Galloway and Hobday, 1983). It evolved from prodelta (sub- of suspended sediment transported to the neritic sea by the Liaohe River facies 4.1) to delta front (subfacies 4.2) and delta plain (subfacies 4.3 and Daliao River were greater than the amounts transported by the and 4.4) in the upward succession. Daling and Xiaoling Rivers. The neritic facies gradually tailed out landward in the longitudinal profile (Fig. 7), and they were covered by 4.2. Sedimentary sequence and spaito-temporal differential evolutions of deltaic sediments in the upward sequence. the Liaohe Delta The delta facies (DU4) were widely distributed in all 27 cores. The thickness of DU4 ranged from 2.5 m to 13 m in these cores. Portions of Longitudinal profile A–A′ and transverse profile B–B′ basically il- DU4, such as core GCZ04 at the edge of the Holocene transgression, did lustrate the spatio-temporal sedimentary evolution of the Liaohe Delta not show the three typical deltaic types, namely prodelta, delta front on the whole (Figs. 7 and 8). The depositional facies of the 27 cores and delta plain. record the evolution of the area from a fluvial environment, to an es- Notably, we used an age-depth plot (accumulation curve) of the tuary or tidal flat, to a neritic sea, and finally to a deltaic environment. cores around the present coastline to elucidate the overall trend of se- A fluvial environment (DU1) prevailed in the Liaohe Plain during dimentary evolution in the Liaohe Delta. This plot clearly revealed two the low stand of sea level at the Late Pleistocene. Compared with the distinctive trendlines (Fig. 9). The first trendline was apparent in the channel-filled facies, the channel-margin facies were not as well re- radiocarbon dates of the eastern cores, which were mainly related to presented in most cores, perhaps because of erosion due to fluvial the depocenter of the Liaohe and Daliao Rivers. The accumulation rate washout during channel shifting. It should be noted that inter-channel was low to ∼0.07 cm/a from 8000 cal a BP to 5000 cal a BP, but high flood basin facies were widely distributed in cores GCZ05, ZK3, and accumulation rate (∼0.28 cm/a) existed after 5000 cal a BP in this GCZ06 between the Daling and Xiaoling Rivers (Fig. 8), the implication trendline. The other trendline was apparent in the radiocarbon dates of being that the Daling River might have been relatively stable between the western cores, which were related to the depocenter of the Daling- 20,000 cal a BP and 11,000 cal a BP based on the radiocarbon dates of Xiaoling Rivers. The sediment accumulated quite slowly (∼0.02 cm/a) core ZK3. between 8500 cal a BP and 3000 cal a BP, but it increased abruptly to an The estuary originated from the filling of an incised river channel average of ∼0.21 cm/a from 3000 cal a BP to the present in the DU4. during the transgression. The estuarine environment (DU2) could be Thus, there is a temporal differential evolutions in the Liaohe Delta area found in cores GCZ12, GCZ13, ZK6, GCZ11, GCZ17, and GCZ18 in the where the eastern depocenter area received the deltaic sediments profiles (Figs. 7 and 8), which in our study were mainly distributed near ∼2000 a earlier than the western one. the present mouths of the Liaohe River and the Daliao River (Fig. 1c). The bottom elevations of DU2 were commonly 5–12 m lower than those 5. Discussions of tidal flat facies in the surrounding cores (Fig. 8), because the estu- aries were highly incised during the low-stand tract system in the Late 5.1. Holocene evolution and paleocoastline changes in the Liaohe Delta area Pleistocene (see Allen and Posamentier, 1993). AMS 14C dates revealed that estuarine facies was deposited at the Early Holocene, approxi- Based on the 27 cores of this study and previous studies in this re- mately ∼9000–10,000 cal a BP in the Liaohe Delta area. gion (Wang and Gu, 1980; Fu, 1988; Wang et al., 2000, 2015; Li et al., Tidal flat and neritic environments (DU3) prevailed after the early 2009; Xu et al., 2014; Sun et al., 2015; Ma et al., 2016; He et al., 2016a, Holocene transgression; they reached the Liaohe Delta region at b; Liu et al., 2017), the Holocene evolution of the Liaohe Delta can be ∼9000–8500 cal a BP. The average thickness of DU3 was ∼6 m in the divided into four depositional stages: Stage I (10–8.5 cal ka BP), Stage II

62 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 8. Transverse proﬁle B–B′ in the Liaohe Delta.

Fig. 9. Age-depth curves of eastern and western cores in the present coastline during the last 16 ka BP. Notice that there were two distinctive trendlines (dark gray and light gray) that originated from the eastern cores and western cores around the present coastline.

63 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68

Fig. 10. Changes of paleocoastline and sedimentary environments since the Holocene in the Liaohe Delta (modiﬁed after Fu, 1988; Pan, 2005; Chen et al., 2010).

(8.5–7 cal ka BP), Stage III (7–3 cal ka BP), and Stage IV (3 cal ka BP to average of –12 m (the bottom elevation of the tidal flat at ∼8500 cal a the present). BP) (Fig. 9) around the present coastline, the implication being that the average rate of sea level rise reached 12 m/ka during Stage I. 5.1.1. Stage I (10–8.5 cal ka BP) An Early Holocene sea-level jump had widely occurred all over the The Holocene transgression crossed the Bohai strait before 10 cal ka world (Blanchon et al., 2002; Liu et al., 2004; Hori and Saito, 2007), BP as revealed by Liu et al. (2004), and the paleocoastline was still far which was generally considered to be related to the melt water pulse from the present one in the Liaohe Delta area. According to the studies associated with the collapse of the Laurentide Ice Sheet and cata- of drilling core BH08 and gravity core M7-6, the sedimentary en- strophic drainage of glacial lakes (Barber et al., 1999; Teller et al., vironment had transitioned to a shallow subtidal- neritic sea at 2002). Obviously, rapid sea-level rise is the main reason for the Early ∼10,000 cal a BP in the middle of the Bohai Sea (Liu et al., 2010; Yao Holocene sedimentary evolution which led to the transition from the fl fl et al., 2014). In the northern side, Wang et al. (2000) noted that core uvial/estuarine environment to tidal at in the Liaohe Delta area C05 (39°35′25″N, 120°47′50″E) in southern Liaodong Bay began re- during Stage I. However, the estimated sea-level rising rate (12 m/ka) ceiving marine sediments at ∼9700 cal a BP. Sun et al. (2015) found during Stage I appears to be less than the one (an average of 24 m/ka) fi that the neritic sea sediments had already been deposited in core LDD7 in the West Paci c(Liu et al., 2004), presumably due to compaction (39°40.73′N, 120°25.12′E) at ∼10,030 cal a BP at the edge of the and tectonic subsidence in this region. Liaodong Bay. Thus, the sea level and paleocoastline was roughly ex- 1 tended to the red dotted line shown in Fig. 10a. 5.1.2. Stage II (8.5–7 cal ka BP) fl Our study revealed that a uvial environment prevailed in the The neritic environment prevailed at the study area from 8.5 to Liaohe River Plain during Stage I. However, tides might have arrived at 7 cal ka BP. A large part of the present delta plain was submerged under the site of core ZK6 because the bottom elevation of the tidal river a shallow sea. Our data and previous studies of several cores (lp15, – sediments was about 29.60 m in core ZK6, which was approximately lp16, lp37, and sipu2) in this area indicate that the east paleo-coastline fl equal to the elevation of the tidal at sediments in core BH08 (Yao approached Niuzhuang-Haicheng-Shaling, 50–60 km north of the pre- et al., 2014). It means that the tidal river might have extended sent coastline (Fu, 1988)(Fig. 10c). The west paleocoastline, however, ∼ ∼ 130 km beyond the paleo-river mouth at 10,000 cal a BP (Fig. 10a). arrived at Goubangzi-Youwei-Jincheng, 20–30 km from the present The ancient Liaohe and Daling Rivers may have become tidal rivers at coastline at the end of Stage II (Fu, 1988). Actually, the Daling and ∼ 9000 cal a BP, because cores GCZ11 and GCZ17 had already received Xiaoling Rivers in the western plain are typical mountainous rivers, and deposits of tide-river sand around the present coastline. their alluvial fan was formed when fluvial sediments were rapidly fl The Liaohe Delta region quickly changed from a uvial to an es- discharged onto the Liaohe Plain because of abrupt topographic fl tuarine or tidal at environment between 10,000 and 8500 cal a BP changes (Yang, 1989). Fu (1989) found the front edge of the alluvial fan (Fig. 10b), the indication being that sea level rose quickly during this was ∼10–12 km from the present coastline during the Late Pleistocene period, a transition quite similar to the Yangtze River Delta (Hori and in the Daling–Xiaoling River region. Thus, differences of paleo-topo- Saito, 2007). In the absence of tectonic subsidence, erosion, and com- graphy may be the main reason for the different transgression limits – paction, sea level would have risen from an average of 30 m (the during Stage II: the eastern area was quite flat, whereas the western fl ∼ bottom elevation of the tidal at at 10,000 cal a BP) (Fig. 10a) to an area was covered by the Daling-Xiaoling alluvial fan. Sea-level rise continued during 8500–8000 cal a BP, and became fl 1 For interpretation of color in Fig. 10, the reader is referred to the web version of this stagnation for a short time before the maximum ooding surface at article. 6000–7000 cal a BP in Bohai Sea (Tian et al., 2016). The collapse of

64 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68 glacial lakes (Agassiz and Ojibway) in the front of Laurentide Ice Sheet western one is controlled by the Daling-Xiaoling Rivers (He et al., led to a melt water pulse to the North Atlantic which may be the main 2016a,b). Milliman and Syvitski (1992) considered that the sediment reason for the sea-level rise during this period (Barber et al., 1999; loads of rivers were mainly controlled by basin area and maximum Clark et al., 2001). The sedimentary environments changed from tidal elevation of the river basin and secondarily by climate and runoff. Al- flat to neritic sea at the present coastline, suggesting the sea-level rise in though the most recent estimate of the sediment load in the Daling the study area during this period. However, it seems that the char- River (∼12.17 mt/yr) is bigger than those of the Liaohe River acteristic of paleo-topography is also a key factor to control the ex- (∼8.89 mt/yr) and Daliao River (∼8.99 mt/yr) (Table 1), this differ- pansion of the paleocoastline, at least in the Daling–Xiaoling River re- ence is more related to human impacts (e.g., building reservoirs or gion during Stage II. artificial drainage in the upper reaches of the rivers) in this area (SLWRC, 2002). The combined catchment area of the Liaohe-Daliao 5.1.3. Stage III (7–3 cal ka BP) Rivers is eight times larger than that of the Daling-Xiaoling Rivers The initiation of mega river deltas in the world is considered to be (Fig. 1b). Thus, the seaward rate of progradation of the eastern depo- highly related to the deceleration of sea-level rise around 7–8.5 ka BP center was likely faster and its reception of deltaic sediments in the (Stanley and Warne, 1994; Hori et al., 2004; Tamura et al., 2009; modern coastline occurred earlier than the western depocenter. Nguyen et al., 2010). Deltaic sediments were widely deposited in the However, it should be noted that whereas cores around the western Liaohe Plain after sea level became almost stable at 7 cal ka BP, and the coastline have received deltaic sediments since ∼3000 cal a BP, cores paleo-coastline gradually moved seaward. A river mouth sandbar GCZ08, GCZ07, and GCZ02 near the transgression limit also had a rapid formed the delta front, whereas fine suspended sediments were trans- accumulation rate after 3000 cal a BP. Previous work has revealed that ported further to the prodelta environment. Small-scale northeast- a deltaic environment prevailed in cores LZk03 and ZK04 in the middle trending tidal sand ridges were formed at the site of cores ZK4, GCZ11, of the western Liaohe Delta region after ∼3000 cal a BP (Li et al., 2009; and GCZ14 because of strong tidal currents in the NE-SW direction (Ji Ma et al., 2016). The radiocarbon data, as noted above, indicate that a et al., 2011). deltaic sedimentary environment existed throughout the western de- It is noteworthy that the eastern paleocoastline advanced faster than pocenter after ∼3000 cal a BP; the implication is that depocenter the western one during Stage III (Fig. 10d). The eastern paleocoastline shifting cannot perfectly explain the sedimentary evolution of the may have extended to Panshan-Guchengzi-Sanchahe at ∼4 cal ka BP, Liaohe Delta. Two reasonable hypotheses have been suggested to ex- whereas the western paleocoastline rarely changed. Our records also plain the sedimentary evolution of the Liaohe Delta as below. reveal that cores around the present eastern coastline received deposits of deltaic sediments and there was a sharp increase in the accumulation 5.2.1. Did sediment influxes sharply increase around 3000 cal a BP in the rate after ∼5000 cal a BP (see Wang et al., 2015; Liu et al., 2017). The western depocenter? western cores, however, still received deposits of neritic facies during The first hypothesis is that sediment influxes from the Daling- Stage III. Thus, paleocoastline changes were basically controlled by Xiaoling Rivers increased sharply after 3000 cal a BP. On the basis of delta progradation rather than sea level changes during this stage. this hypothesis, deltaic sediments could have been deposited in the western depocenter instead of being transported primarily by strong 5.1.4. Stage IV (3 cal ka BP to the present) NE-SW–flowing tidal currents and clockwise-flowing alongshore cur- During this stage, deltaic sediments began to accumulate rapidly in rents (Zhao et al., 1995; Zhu et al., 2010). Actually, there are many the western side of the Liaohe Plain (Fig. 9). He et al. (2016b) and Ma dating hiatuses and chaotic dating sequences in our study cores which et al. (2016) found that the deltaic deposition began at 3–4 cal ka BP at may be reworked, eroded, or redeposited caused by the strong tidal the mouth of the Daling River. Meanwhile, the deltaic depocenter of the currents and waves in this area. eastern side continued to migrate seaward, and cores ZK6 and ZK7 It is generally accepted that the growth and evolution of a river began to accumulate deltaic sediments after ∼1000 cal a BP (Fig. 7). delta depends on three principal factors: (1) fluvial conditions (e.g., There was a small bay named the Panjin Bay between the ancient number of major rivers discharging into the sea, water discharge and Daling River delta plain and the ancient Liaohe River delta plain during sediment fluxes, number and positions of river mouths), (2) marine this stage (Fig. 10e). A crevasse formed in the right bank of the Liaohe dynamics (direction and strength of the tidal currents, volume and di- River in 1861 led to part of the Liaohe River’s entering Panjin Bay, and rection of alongshore currents, dominant wave direction), (3) accom- it turned to be an important channel of the Liaohe River after dredging modation space (the maximum area flooded by the rise of relative sea by the local government in 1894 (Pan, 2005). Recent studies of pa- level, the limit of regional geography, the bathymetry of basin). Marine leotopographic maps and remote sensing (RS) data have revealed that dynamics and accommodation space hadn’t changed much yet in Panjin Bay was rapidly filled after the shift of the Liaohe River channel Liaodong Bay since the Holocene (Ji et al., 2011), thus the fluvial in 1894 (Pan, 2005; Chen et al., 2010). Thus, the paleocoastline conditions are the main controlling factors to the development of delta changes have been more and more influenced by human activities in in this area. The fluvial conditions are usually influenced by climate the Liaohe Delta area, at least since the last two century. changes which may have had a large impact on weathering denudation rates and the discharges of these rivers (De Rham et al., 2008; Gislason 5.2. Climate changes and human impacts: possible reasons for the et al., 2009) as well as their sediment loads (Syvitski, 2002; West et al., differential delta evolution in the Liaohe Delta 2005; Liu et al., 2008; Lu et al., 2013) during the Late Holocene. The Daling-Xiaoling Rivers are small mountainous rivers, and their Based on preamble analysis, the Liaohe Delta is a tide-dominated catchments are located at the edge of the East Asian monsoon region delta that has accumulated as the result of discharges by four main (Zhao et al., 2007). Previous works revealed that East Asian summer rivers from east to west. Bounded by the modern Liaohe River mouth, monsoon became weak and climate deterioration occurred during the coastline on the eastern side began receiving deltaic sediments at 4000–3000 cal a BP, e.g. in the Bohai Sea (4.1 ka BP, Wang and Van ∼5000 cal a BP. The seaward progradational rate of the paleocoastline Strydonck, 1997), Yangtze River Delta (3.8 ka BP, Liu et al., 1992), has been roughly estimated to be ∼8.6 m/a since 7000 cal a BP; the Okinawa Trough (3.3 ka BP, Jian et al., 2000), North Japan (4.1 ka BP, coastline on the western side began receiving deltaic sediments at Kawahata et al., 2009). The paleoclimate changed from warm and wet ∼3000 cal a BP; the seaward progradational rate of the paleocoastline to cool and dry in the Liaohe River catchment (including Daling- has been estimated to be only ∼2.8 m/a since 7000 cal a BP. Xiaoling River catchments) between 4.1 and 3 ka BP (Li et al., 2014). These results seem reasonable because the depocenter of the eastern Additionally, the archaeological research revealed that the relatively Liaohe Plain is dominated by the Liaohe-Daliao Rivers, whereas the prosperous agricultural civilization had been replaced by the animal

65 L. He et al. Journal of Asian Earth Sciences 152 (2018) 52–68 husbandry civilization in the Liaohe and Daling River catchments, important western branch of the ancient Liaohe River that could caused by an abrupt climate change during 3.3–3.6 ka BP (Hu et al., transport massive amounts of sediment to the western depocenter by 2002; Li et al., 2003; Wang, 2012). This climate change may greatly ∼3000 cal a BP, although the stratigraphical research in this area has impact the vegetation covering rate and fluvial hydrological conditions, produced no direct evidence to support this hypothesis until now. especially in the Daling and Xiaoling River catchments, as they are Further work on provenance analysis is needed to test the above hy- mainly exposed by Quaternary unconsolidated sediments, Mesozoic pothesis. shale-sandstone and some pyroclastic rocks (Wang et al., 2013; He et al., 2016b). It is presumably that the water loss and soil erosion 6. Conclusions might abruptly enhance during 3000–4000 cal a BP in the Daling and Xiaoling River catchments, leading to a large increase of sediment in- The Liaohe Delta is a tide-dominated delta that has accumulated as fluxes around ∼3000 cal a BP in the western depocenter. the result of discharges by several rivers that enter Liaodong Bay in In addition, anthropogenic activities couldn’t be ignored which Northeast China. The sedimentary environment in this deltaic area has impacted the sediment loads of these rivers as a result of regional evolved from fluvial and lacustrine, to tidal flat, to estuarine, to neritic, erosion caused by deforestation, agricultural production, and stock- and finally to a deltaic environment since the Late Pleistocene. The breeding (Milliman et al., 1987; McCulloch et al., 2003; Syvitski and Holocene transgression began to influence the Liaohe River at the Kettner, 2011). Syvitski and Kettner (2011) considered that human present coastline ∼9000 cal a BP, and it finally reached the present impacts on sediment production began at 3000 a BP but accelerated coastline at ∼8500 cal a BP. The delta began to form after the max- more widely after 1000 a BP. Syvitski et al. (2005) estimated that an- imum transgression at ∼7000 cal a BP. The deltaic area since then can thropogenic activities led to an increased sediment transport be divided into two entirely different sedimentary systems: an eastern (∼2.3 ± 0.6 × 109 t/yr) by global rivers through soil erosion nowa- sedimentary system and a western sedimentary system. The eastern days. cores in the present coastline received a rapid deposition around The Liaohe River catchment and the Daling-Xiaoling River catch- 5000 cal a BP while the western cores occurred 2000 years later. The ments played important roles in the cultures of earlier civilizations, in shifting of the depocenter was the main reason for the spatial differ- particular Hongshan Culture (6000–4000 cal a BP) and the continuation ences of the geological evolution of this area. Sediment influxes related of the Late Stone age–Early Bronze Age (4000–3000 cal a BP) agri- to climate change and human impacts may have played an important cultural cultures in China (Hu et al., 2002; Li et al., 2003). The habi- role in the differences of the temporal evolution of sedimentation in the tations of ancient human and farming areas were prior placed on the Liaohe Delta. However, further studies are needed to test our hy- river terraces where were vulnerable on the soil and water loss during potheses. the primitive and extensive agricultural production (Han et al., 2008). Li et al. (2003) found that the decreased productivity caused by severe Acknowledgements soil and water loss was one of reasons for the decline of ancient agricultural civilization in the Liaohe and Daling River catchments during This study was jointly funded by the Key Program for International 4100–3300 a BP. Additionally, climate deterioration during S&T Cooperation Projects of China (Grant No. 2016yee0109600), 4000–3000 cal a BP might inspire ancient human to enlarge the de- Ministry and Land and Resources program: “Special foundation for forestation and ancient agricultural production which led a feedback of scientific research on public causes” (Grant No. 201111023), the more intensive regional erosion in this area. Thus, it is possible that the National Natural Science Foundation of China (Grant Nos. 41706057, sediment influxes of the Daling-Xiaoling Rivers had increased greatly by 41506062, 41406082) and China geological survey projects (Grant Nos. roughly 3000 cal a BP, the result being a rapid accumulation of deltaic DD20160144, GZH201200503). We thank Dr. Xigui Ding, Guangming sediments in the western side of the Liaohe Delta Plain after ∼3000 cal Zhao, Shaofeng Pei and Jin Wang for their help in the geological survey a BP. or in preparing this manuscript. We would also like to thank three anonymous reviewers for their helpful comments and suggestions 5.2.2. Did sediment inputs to the western depocenter from eastern rivers during the review stage. after 3000 cal a BP? The other hypothesis is that there were additional sediment inputs References from eastern rivers to the Daling River depocenter. 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