Sedimentary Evolution of Paleogene Series in Deep Water Area of Zhujiangkou and Qiongdongnan Basin

Key words: 
• continental margin /
• sequence stratigraphy /
• lake /
• ocean /
• deep water area

Abstract: Three sedimentary sequences have been divided in the deep water area from the Paleogene system of ZhujiangkouQiongdongnan basin, i.e. Eocene Wenchang, EnpingYacheng and ZhuhaiLingshui sequences. In combination with the data from well facies, strata isopach, seismic facies and seismic sandstone index maps, together with depositional characteristics of faulted basin and tectonic background, the integrated sedimentary facies maps have been figured out for each systems tract in the study area. Three large lacustrine area were developed in the deep water area around the northern part of South China Sea, including the Baiyun depression in the east, SongnanBaodao depression and Lingshui Ledong depression in the west. During this period, the segment features were obvious,i.e. five or six smallscaled lakes were also developed apart from the three large lake basins. During the early Eocene, the sea transgression area was mainly in Qiongdongnan basin, and sea water was probably flushed into the basin from both the west and east directions to form two shallow sea areas divided by the erosion area while the Baiyun depression was not influenced by sea transgression to keep lacustrine environment. At the same time, ShundeKaiping depression also maintained the lacustrine environment which was gradually enlarged from small lakes into the united giant lake. During the late period, the overall sea transgression took place in the study area, but there existed the difference of transgression directions, e.g. the sea water emplaced from the east in the BaiyunShundeKaiping depression, and there might exist two sea mouths in the Qiongdongnan basin for sea transgression which inherited the sea flushing direction of Yachengnian.