MIOCENE DINOFLAGELLATE AND SEA SURFACE TEMPERATURE IN THE DEEP AREA OF SONGNAN SAG,QIONGDONGNAN BASIN,SOUTH CHINA SEA
70 samples were collected for organic-walled dinoflagellate cyst from the interval 2 005～3 285.85 m of Well ST35-A in Songnan Sag,Qiongdongnan Basin,South China Sea.Abundant dinoflagellates were found in most samples.It contains the Miocene index species Tuberculodinium vancampoae,Hystrichosphaeropsis obscura and Selenopemphix quanta,indicating that the stratigraphic age of this interval is Miocene.Based on the species appearance and abundance of dinoflagellate,the sea surface temperature has undergone three changes during the Miocene,namely:(1)Early Miocene-late Early Miocene(3 285.85～2 005 m),it is dominated by Spiniferites spp.,with relatively low content of Polysphaeridium zoharyi,which likes extreme warm,and moderate content of Operculodinium centrocarpum,with a mean W/C of 0.59,indicating a warm surface water temperature.(2)Late Early Miocene-Middle Miocene(2 886～2 350 m),Spiniferites spp.and Polysphaeridium zoharyi increased while Polysphaeridium zoharyi decreased,the average W/C index is 0.72.The sea surface temperature increased significantly compared with the previous stage and reached a peak,which may correspond to the most suitable warm period of the Middle Miocene climate.(3)Late Miocene(2 340～2 005 m),Operculodinium centrocarpum content increased,Spiniferites spp.and Polysphaeridium zoharyi decreased,with an average W/C index of 0.50,indicating relatively cool surface water temperature.
Dinoflagellatessea surface temperatureMioceneSongnan SagQiongdongnan BasinSouth China Sea
NETL
NSTL
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