东海陆架盆地第三纪海平面变化

THE TERTIARY SEA LEVEL CHANGES IN THE EAST CHINA SEA SHELF BASIN

东海陆架盆地是建立西太平洋新生代海平面变化的关键地区。本文以层序地层和沉积体系分析为基础，利用微体古生物带化石资料，建立了东海陆架盆地第三系相对精度较高的年代地层格架。通过古生态分析、成因相及特征沉积构造分析和反射地震剖面的海岸上超分析，辅以地球化学参数变化研究，首次编制了东海陆架盆地第三纪海平面变化曲线。自第三纪以来，能识别的长周期二级旋回海平面变化４次，短周期三级旋回变化２６次，相对海平面变化幅度在０—１５０ｍ。分析发现海平面变化具有不对称性，即海侵作用速度大于海退作用速度。与Ｈａｑ曲线对比也有较大的差异。

The East China Sea Shelf Basin is a part of the East China Sea Basin.It is the key area to set up the sea level change cycles of Cenozoic ear in the West Pacific.Huge data have been accumulated including geology,geophysics,geochemistry and paleobiofossil throughout the process of oil and gas exploration in the recent decades.Based upon the analyses of sequence stratigraphy and depositional system,the relative high resolution chronostratigraphic framework has been set up using the data of micropaleontology biozone fossils.The depth and its change scope of sea water have been constructed according to the analyses of paleoecology,genetic facies and sedimentary structures.The relative sea level change curve has been finished combining the study of depositional systems and system tracts alternately,the analyses of on lamp recognized from the reflect seismic profiles with the study of geochemical characteristics(B,Ga,Sr,Ba).There are 4 2nd order cycles showing the long term and high order sea level changes,and 26 3rd order cycles showing short term and low order ones with relative change ranges from 0 to 150 m.Transgression and regression showing the long term sea level changes have unsymmetric feature,which indicate that the speed of transgression is faster than the speed of regression. Comparing the curve with Haq's one (1988) both of them have the same tendency in long term and high order sea level change cycles before pliocene.But there are obvious differences in several aspects:a) the sea level cycles show rising tendency from Pliocene in the East China Sea Shelf Basin,while Hag’s curve indicates falling in the same period;b) the quantity and the frequency in sub cycles’ change are quite different;c) there is no response in the change directions and degrees of sub cycles;d) there exist three times large scale transgressions in the Haq’s eustatic curve from Oligocene to Middle Miocene,but there are very small transgressions in the East China Sea Shelf Basin at the same period.The further work is necessary to answer the questions.