黄海南部陆区冰后期沉积环境的演变

THE EVOLUTION OF POSTGLACIAL SEDIMENTARY ENVIRONMENTS IN THE SOUTHERN YELLOW SEA COASTAL LAND

研究区内全新统与上更新统间普遍发现沉积间断。晚更新世古地形呈东个完南向西北逐渐抬高的掀斜状。本文以李堡孔为例,讨论了全新统垂向层序,自下而上由滨海,河口海湾,近岸浅海和潮坪相组成,为一个完整的海浸海退层序。全新世海侵层受古地形及三角洲进积、主河道南偏影响,表现明显的水平相变。通过对区内十几个钻孔剖面的对比分析,揭示了垂向演替及水平相变的规律及其两者间的关系,恢复了全世以来沉积环境的演化过程。

Sedimentary characteristics and environmental evolution have been discussed in the studied area, based mainly upon data of eight drill-holes and also upon other several dozens of reference drill-holes. The conclusions are described as follows:(1)It is non-marine facies of Pleistocene that underlay the sediment of Holocene in uncomformity with Pleistocene.(2)The topography of the area at the end of Pleistocene inclined from northwest towards southeast which influenced the Holocene transgression obviously.(3)The Holocene sedimentary sequence can be divided into the lower transgression and the upper regression one, consisting of coastal marsh, bankshore, beach, tidal flat, estuary-bay, tidal sand body facies etc.. The best developed area is the southeast part of the studied area.(4)In the early Holocene, the sea level rapidly rised. The area gradually changed into beach, estuary or bay. Since 8. 0 ka B. P. , the coast line was near the line of Qutang-Haian-Shenzao. Then, the transgression was at 7. 0-6. 5 ka B. P. , with the mouth of Changjiang River near the area of Zhenjiang- Yangzhou. The middle and east part of the studied ares became nearshore neritic environment. Afterwards, regression occurred and most part of the area became tidal flat or coastal marsh to 1. 0 ka B. P.. At 1. 0-0. 5 ka B. P. ,the coast line approached that of present and little chang has happened since then.