Journal of Asian Earth Sciences 152 (2018) 52–68 Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes 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, re- spectively (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.