Sedimentary record of environmental evolution off the Yangtze River estuary, East China Sea, during the last w13,000 years, with special reference to the influence of the Yellow River on the Yangtze River delta during the last 600 years Jian Liu a, b, * , Yoshiki Saito c , Xianghuai Kong b , Hong Wang b , Lihui Xiang d , Chun Wen e , Rei Nakashima c a Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, PR China b Qingdao Institute of Marine Geology, Qingdao, 266071, PR China c Geological Survey of Japan, AIST, Central 7, Higashi 1-1-1, Tsukuba, Ibaraki 305-8567, Japan d Eastern China Geoexploration Development Bureau for Non-ferrous Metals, Nanjing, 210007, PR China e Ocean University of China, Qingdao, 266003, PR China article info Article history: Received 12 September 2009 Received in revised form 5 June 2010 Accepted 9 June 2010 abstract A 35.60-m-long core (ECS-0702) recovered from a water depth of 22 m in the muddy area off the Yangtze River estuary was analyzed for sedimentary characteristics, clay and detrital mineral components, and element geochemistry as well as by AMS 14 C dating to document sediment provenance changes and envi- ronmental evolution during the postglacial period in the study area. On the basis of the lithology, the benthic foraminiferal and ostracod assemblages, and the AMS 14 C ages, we divided the core into four depositional units (DU1eDU4 in descending order) representing the postglacial sedimentary sequence during the last w13,000 years. DU 4 was deposited in a littoral to tidal-flat environment during w13,000e11,500 cal yr BP; DU 3 in a nearshore, subtidal environment upwards to the nearshore shelf with tidal influence in response to the postglacial sea-level rise during w11 500e7400 cal yr BP; DU 2 in a tide-affected, nearshore shallow-sea environment during w7400e540 calyr BP, on the delta-front of the Yangtze River when the delta was actively prograding; and DU 1 in a nearshore shallow-sea environment during the last w540 years, on the delta-front under modern marine conditions. In DU 1, the depositional rate was much higher than in the underlying units, and the sediment composition reflects more influence from the Yellow River; this unit can therefore be logically linked to the period when the Yellow River last discharged into the South Yellow Sea, from AD 1128 to 1855. According to historical records, this period can be divided into an early stage (AD 1128e1494), when the shoreline near the Yellow River mouth was advancing slowly eastward, and a late stage (1495e1855), when the shoreline was advancing rapidly. The initiation of DU 1 deposition corresponds to the latter part of the early stage, suggesting that since that time, a relatively large amount of sediment from the Old Yellow River mouth area has been transported to the offshore area of the Yangtze River mouth. Our study has identified a high-resolution sedimentary signature associated with the last course shift of the Yellow River in the Yangtze River delta-front, thus highlighting the intricate relationship between sediment sources and sinks in coastal areas. A significant contribution of the Old Yellow River sediments to the Yangtze subaqueous delta during the last w600 years must be considered when the evolutional history of the Yangtze delta is examined and especially when the influence of the Three Gorge Dam construction on the future changes of the Yangtze Estuary and ecological environments in the East China Sea is estimated. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The Yangtze River (Changjiang) is one of the five largest rivers in the world in terms of both sediment load and water discharge, transporting a vast amount of sediments annually to the East China Sea (ECS) (Huang et al., 2001)(Fig. 1). Over the last 7000 years, more than half of the Yangtze-derived sediment has been deposited in the delta and estuary system and in the nearshore subaqueous deltaic area, and the remaining sediment has been transported southward to form a “mud belt” on the inner shelf along the coasts of Zhejiang and Fujian provinces (Liu et al., 2007)(Fig. 2). Most previous research has been restricted to the Yangtze delta and estuary and to the mud belt, focusing mainly on delta initiation and evolution, modern sedimentation, topographic features, the late * Corresponding author at: Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Ministry of Land and Resources, PR China. Tel.: þ86 532 85755832; fax: þ86 532 85720553. E-mail address: liujian0550@vip.sina.com (J. Liu). Contents lists available at ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev 0277-3791/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2010.06.016 Quaternary Science Reviews 29 (2010) 2424e2438