Formation and Evolution of the Northern Jiangsu Plain
|Keywords||major elements trace elements REE C-N isotopes land-sea interaction climate recorder north Jiangsu Plain|
The Northern Jiangsu Basin which has developed from the Yangtze plate since late Mesozoic times, is a large sedimentary basin composed of several small sub-basins shaped as a“dustpan”. It is dominated by deep faults which controlled the sedimentation since late Tertiary. The west-tilting topography of East Asia was reversed with the uplift of the Tibetan plateau and the opening of marginal seas, resulting in an Asian fluvial system radiating from the uplifted center of the continent. The Northern Jiangsu Plain, which is above sea level, comprises the continental component of the southern Yellow Sea Basin. It is located on the northern side of the Yangtze River and south of Lan-Shan Tou cape, 32o10’-35 o 05’N, and 118 o 40’-120 o 30’E.Historical records and previous studies have indicated that the outer part of the Northern Jiangsu plain was formed from marine sedimentation during a Holocene high sea level period at 5000 a BP, as defined by a series of abandoned shell beach ridges. These are about 200 km long from north to south, and located some 60 km landward of the modern coastline. The present study is focused upon the formation of the inner part of the Jiangsu plain which is located inside of the beach ridges and to the west of the Grand Canal.Geomorphic features relating to the formation of the inner plain west to the Fan-Gong dike, include (1) A series of surrounding rocky hills forming an arc-shaped embayment. (2) A series of lakes, such as Hongze, Gaoyou, and Shaobo Lake, located to the west of the Grand Canal, which are almost connected to each other either by lowland or swamps. Indeed, the Grand Canal was constructed partly utilizing the pre-existing channels connecting these lowland swamps and lakes (3) Several rivers have produced deltaic forms on the western side of the lakes;(4) A series of artificial islands have been constructed upon the natural bars or barriers located in the lakes and wetlands, and are locally termed Duo, Dun or Wei (meaning artificial bars or crossways in Chinese). These are now valuable lands for settlements for local people living in the wetland areaa. All of the islands or barriers are aligned in a North to South direction i.e. parallel to the present coastline. Sea shells and their fragments have been found on these islands indicating a marine origin.