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.