植物生态学方法在沉积环境恢复中的应用:以南海北部白云凹陷为例OA北大核心CSTPCD

The palaeogeography in the northern South China Sea changed drastically in the Early Ce-nozoic era and the sedimentary environment underwent a transition from land to sea.The plant ecology methods are powerful in accurately revealing the transition time and processes,which is of great signifi-cance for the restoration of palaeogeography in this region.In this study,representative borehole samples are collected from the deep-water area of the Baiyun sag in the northern South China Sea to investigate the Paleogene transgression based on sporopollen algae analysis.The results show that the Baiyun sag was do-minated by fluvial and lacustrine facies that was not affected by marine transgression of the Wenchang For-mation in the Early to Middle Eocene.In the Enping Formation of Late Eocene,eastern and southeastern parts of the Baiyun sag developed into a shallow marine environment characterized as the development of a large number of marine sporopollen algae.The fluvial and lacustrine environments developed in the sou-thern part in the early stage,and it transforms into marine and land transition environment.The north-western part was dominated by large river delta environment.For the southern uplift zone of the Baiyun sag,it was characterized by fluvial lacustrine facies environment in the early stage,while it transformed into the marine and land transition environment in the late stage.The northwestern part of the depression was dominated by the large river delta environment.During the depositional period of the Zhuhai Formation in the Oligocene,it revealed a continental slope-deep sea environment in eastern and southeastern parts of the Baiyun sag,a transitional depositional environment occurred in northwestern and southern parts,and the large river delta appeared in the northwest part of the sag.Due to global sea level rise and sudden shift of the South China Sea spreading axis,most parts of the Baiyun sag were located in the continental slope environment in the early Miocene.Transgression initiated from the eastern and southeastern parts of the Baiyun sag and subsequently advanced towards the western areas,which is completely consistent with the gradual opening of the South China Sea oceanic crust from east to west.