Paleogene transgression process and environmental evolution in the deepwater area of the Baiyun Depression in the northern South China Sea  

作　　者：Peijun Qiao Yuchi Cui Qiong Ma Qiang Yu Lei Shao 

机构地区：[1]State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China [2]CNOOC Energy Technology&Services-Drilling&Production Co.,CNOOC Central Laboratory Shenzhen Branch,Guangdong 516000,China

出　　处：《Acta Oceanologica Sinica》2024年第4期15-24,共10页海洋学报（英文版）

基　　金：The National Natural Science Foundation of China under contract No.42076066。

摘　　要：Multiple borehole samples are collected from the Baiyun Depression in deep-water area of the northern South China Sea(SCS)in an effort to reconstruct transgression processes during the Paleogene based on palynalgal analysis.This study indicates that the Baiyun Depression generated a large group of palynopore assemblages and fluvial/lacustrine-related algae during the early and middle Eocene when the Wenchang Formation was deposited.The entire depression was dominated by fluvial and lacustrine facies before transgression.Its eastern and southeastern sags transitioned to shallow marine environment by generating a large abundance of marine dinoflagellates during the Enping deposition of the late Eocene.Meanwhile,the southern uplift zone simply yielded fluvial/lacustrine-related palynopores and algae,and was dominated by the fluvial and lacustrine environment during the early stage of the Enping Formation,prior to shifting into transitional setting in the later period.Northwestern sags remained extensive fluvial and delta facies without existence of marine dinoflagellates.It was until the depositional stage of the Zhuhai Formation(Oligocene)that the overall depression was strongly impacted from transgression process.Both eastern and southeastern sags were mainly under deep marine setting on a continental slope while northwestern and southern areas developed transitional facies.Although distribution and accumulation patterns varied greatly among sub-sags,the overall Baiyun Depression was characterized by widespread development of marine dinoflagellates.It should be noted that the northwestern sag also partly generated large-scale river delta deposits.Due to the eustatic rise and change of SCS spreading axis,the overall Baiyun Depression was mostly influenced by the deep marine environment on a continental slope during the early Miocene.Both northwestern sag and southern uplift zone were found plentiful marine dinoflagellates.In summary,transgression initiated from the eastern and southeastern Baiyun Depression before

关 键 词：South China Sea PALEOGENE TRANSGRESSION sedimentary environment plant ecology 

分 类 号：P618.13[天文地球—矿床学]