Paleoenvironmental evolution and sedimentological significance of the Beibuwan Basin in the Eocene
Sporopollenin fossils preserved in strata are important for studying ancient vegetation and climate change.They can be used to reconstruct the ancient environment,predict the enrichment of the source rocks for hydrocarbons,and guide oil and gas exploration.In this study,we considered the WS-X1 and WS-X2 wells in the Wushi Sag of the Beibuwan Basin in the South China Sea,WZ-X3 well in the Haizhong Sag,and JH-X4 well in the Fushan Sag to analyze the data on sporopollenins from the Eocene period,and identify the characteristics of vegetation of the Beibuwan Basin and its paleoenvironmental evolution.We identified 49 types of sporopollenin fossils belonging to four major categories that were dominated by angiospermic pollens.Quercoidites(microchrici+minutus),Tricolpopollenites,and Alnipollenites were found to have higher content in oak pollens.Pinuspollenites were the main pollen in gymnosperms,while the spores of ferns were mainly Polypodiaceae and Osmundacites.A large number of algae were observed,most of which were the disk-shaped Pediastrum.The four wells considered here were abundant in subtropical taxa,and had had a high pollen content during the Eocene,which reflected the development of forests that were characterized by abundant evergreen species of oak in the Beibuwan Basin in this period.Forest vegetation mainly consisted of evergreen and deciduous broad-leaved mixed forests in the low mountain areas of the basin,with fern vegetation below it indicating a warm and humid tropical-subtropical climate during the Eocene.Thermophilic vegetation was more widely distributed in the Early Eocene than in the Late Eocene.We think that the climate of the area cooled gradually trend from the Early to the Late Eocene.In addition,a large volume of algae appeared in the sporopollenin assemblage,indicating that the sedimentary environment at the time had been dominated by lake and coastal river swamp facies.
万方数据
维普
