D219孔和渤海湾北部晚第四纪地质环境

对渤海湾北部D219孔岩心样品进行了沉积地层学、生物地层学和年代地层学分析测试，将该孔自上而下划分为海相—滨海相、陆相、海相、陆相4个地层，按单井划相方法阐述了本区晚第四纪层序沉积历史。39 ka BP所处的时期相当于献县海侵，本区的陆地平原被淹没；23 ka BP海水退出渤海，本区又成为陆地；8~9 ka BP(或8.5 ka BP)海水再次侵入本区至今。以D219孔为主，与本区30余孔进行对照认为，本区在全新世海侵前是低缓平原，东西向总坡度约1.7‰，其上分布南堡和歧口两古河道系统。前者河宽小、曲率小，是流量较小的平原河系；后者河宽大、曲流汊道多，是流量较大的自SW向NE流的河系。

THE HOLE D219 AND THE LATE QUARTERNARY PALEOGEOGRAPHIC ENVIORMENTS

Lithological, biological and chronological stratigraphic studies are carried out for the hole D219 which is located at the northern Bohai Bay. The deposits of the hole may be divided into four sets, i.e. marine-littoral facies, continental facies, marine facies and continental facies again in a descending order. Single well facies analysis reveals that seawater invaded into the northern Bohai Bay at 39 ka BP, corresponding to the Xian Country Transgression. It then retreated from the Bohai Sea at 23 ka BP. Around 8.5 ka BP the research area was covered by seawater again. Based on the data from D219 and another 30 boreholes, it is concluded that the northern Bohai Bay was a plain in Late Quaternary with two paleochannel systems. The topographic gradient of the plain is no more than 1.7‰. The Nanpu River was small, but the Qikou River flowing from southwest to northeast was a meandering river with high discharge and multiple branches.