Recent Muddy Sediments of China Shelf Sea and their Formation Environments and Origin
Anchun Li, Shangbin Xiao, and Fangjian Xu
Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
Muddy sediment is one of main sediment types and widely distributed in the eastern China Shelf Sea. The muddy sediments can be mainly devided into three categories: muddy sediment of the river estuary, coastal currents and small circulation. Muddy sediments in Bohai Sea, Yellow Sea and northern East China Sea are mainly from Huanghe River with minor supply of adjacent rivers and coastal erosion, of which muddy sediments in the southern Yellow Sea and northern East China Sea also slightly have Changjiang River origin. Muddy sediments (clinoform) of inner shelf of East China Sea mainly come from Changjiang River in middle and northern parts. Southern part may be partially supplied by matter from Taiwan Island, Min River and Ou River.
The formation of muddy deposits has close relation to shelf circulation system during the Holocene. Recent work indicates that depocenters of muddy deposit aren’t only located in river mouths but near coast zones also. For example, although muddy wedge sediments (cinoforms) located in the nearshore of northern and eastern Shandong Peninsula and inner shelf of East China Sea are as far as more than 600 Km from Huanghe River mouth and Changjiang River mouth, respectively, their sediment depth exceed 40m in some location. They mainly formed since high stand of sea level during the Holocene. Formation time of muddy sediments in the shelf seas can go back approximately to middle and late Holocene with variation in different areas. Muddy wedge deposits in the inner shelf of East China Sea have been formed since 7-8ka B.P. corresponding with global modern delta build up, which show that sediments of Changjiang River commenced to influence the area, meanwhile coastal current off Fijian and Zhejiang provinces began while the sea level approach or reached the present height. The formation of muddy sediments located in northern East China Sea and middle northern and southern Yellow Sea formed since 6.4 ka B.P. indicating when Yellow Sea Warm Current entered and cold eddies formed. The formation time of muddy sediments in the Bohai Sea is almost sametime with the muddy patch of the central Yellow Sea.
AAPG Datapages/Search and Discovery Article #90180©AAPG/SEPM/China University of Petroleum/PetroChina-RIPED Joint Research Conference, Beijing, China, September 23-28, 2013