苏北浅滩成因的最新研究

THE LATEST STUDY ON ORIGIN OF THE NORTH JIANGSU SHOAL

本文指出苏北浅滩在全新世海侵发生前,有可能为独立的“沙漠堆积体”,而不是所谓古长江—古黄河三角洲沉积。晚更新世末期,冰期气候使蒙古高压增强,在风蚀出露的陆架上产生了沉积分异作用,较粗的物质在“苏北浅滩”附近集中,形成沙丘群;较细的物质被搬运至扬州—南京一带,形成了黄土沉积。来自黄河、长江等河流带来的陆源物质,随沿岸流的搬运而将过去的沙漠堆积复盖。所以“苏北浅滩在全新世海侵前是古风暴活动区;而海侵后又为风暴潮活动区,全新世海侵发生以后,陆架沙漠化作用终止。

Continental-shelf transgressions since late Pleistocene can be divided into two types: one is climatic type, represented by the last-interglacial and Holo-cene transgressions (also called warm-type transgressions), the other is tectonic type, such as the two sub-interglacial transgressions in Wurm glaciation (also called cold-type transgressions). When the last-interglacial transgression happened, sea water did not wholy drown the North Jiangsu shoal, due to the sea-level height and transgression range at that time. After Wurm glaciation, two tectonic-type transgressions took place in the South Huanghai Sea, with their influence reaching, to the area west of Yancheng and. near 33°18'N, 122°45'E in the Wunansha uplifted zone. Thus it can be said that most of the North Jiangsu shoal area was in a terrestrial environment. Only when the Holocene transgression happened did sea water, for the first time, completely occupy the North Jiangsu shoal. This information got from shallow stratigraphic profile has been proved by analysis data of Jianggang core. Therefore, the North Jiangsu shoal may not be the previously inferred extension of the ancient Changjiang and Huanghe River Deltas, but an inherited desert body.