长江三角洲北翼兴化-通州地区第四纪地层划分及古环境分析

选取长江三角洲北翼兴化-通州地区(分属东台和南通第四纪地层小区)的5个实测钻孔,以岩石地层、年代地层和磁性地层为基础,应用层序地层学理论与方法,对研究区第四纪地层进行初步划分,共划分出下更新统(Qp1)、中更新统(Qp2)、上更新统(Qp3)和全新统(Qh)4个地层单元。讨论了区内第四纪以来岩相古地理演化特征及古河道变迁的过程。研究区内北部东台地层小区第四纪以来以陆相河湖沉积为主;南部南通地层小区第四纪早期以陆相河湖沉积为主,中晚期为海陆交互沉积。第四纪以来古河道在海安以南区域摆动,至晚更新世晚期南移接近现长江位置。

Stratigraphic division of Quaternary strata and paleoenviroment analysis for Xinghua-Tongzhou region in the north flank of the Yangze River delta

Basing on measured drill cores selected from 5 bore holes located respectively along Xinghua （ZK10）-Dongtai （ ZK02 ）-Haian （ ZK01 ）-Tongzhou （ ZKA4 ）-Tongzhou （ ZK03 ） section in the north flank of the Yangtze River delta, of which Xinghua and Dongtai belonging to the Dongtai Quaternary stratigraphic subregion and Haian,Tongzhou belonging to the Nantong Quaternary stratigraphic subregion, using lotho- stratigraphic, chronostrtigraphic and magnetostratigraphic analyses in combination with theory and meth- od of sequence stratigraphy, a preliminary division of Quaternary strata in the studied area was made. The Quaternary strata of the two stratigraphic subregions can be divided into 4 stratigraphic units, namely, Lower Pleistocene（QP^1 ）, Middle Pleistocene （QP^2）, Upper Pleistocene （QP^3） and Holocene （Qh） from lower to upper. Quite different lithofacies and paleogeographic evolution characterisrics and shifting of ancient stream channels of the two stratigraphic subregions since Quaternary in the studied area were also discussed. Since Quaternary, the sediments of the Dongtai stratigraphic subregion in the north part of the studied area were mainly dominated by continental lacustrine facies sediments, while the sediments of the Nantong stratigraphic sudregion were doninated by continental lacustrine facies sediments in early Quater- nary and marine-continental alternate facies sediments in middle-late Quaternaty. The shifting of ancient stream channels since Quaternary were occurred in the south part of Haian,the deep river-cut valleys were developed in Haian in middle-late pleistocene, and the ancient stream channels shifted southwards and ap- proached the present site of the Yangtze River in the late stage of late pleistocene.