THE MESOZOIC TECTONIC CHARACTERISTICS AND SEDIMENTARY BASINS IN THE EASTERN MARGIN OF SOUTH CHINA

Through the researches on the distribution of Mesozoic sediments and it's characteristics in the South China and offshore,we realize that there occur two tectonic stages.In the first stage from Triassic to early Jurassic,the Yindosinian block collided with the South China block and pushed the later moving northeastward.At the same time,the Sino-Korean block collided with the South China block and pushed the later moving southwestward.In the second stage from the later Jurassic to early Cretaceous,the Izangi block (the ancient South China Sea block in South China Sea area) subducted under the South China block and in the early Cretaceous the Nansha block collided with the South China block along the present ocean-continent boundary,and pushed the later moving northwestward.Therefore,the sediments before Cretaceous were deformed and denuded.Under such a tectonic framework there deposited deep to shallow marine sediments of the late Triassic to early Jurassic,with passive margin sediments at the eastern margin.In the second stage,there were continental sediments deposited in back arc rifting basins,with deep to shallow marine sediments in the fore arc basins.It is observed from the seismic profile across the well LF35-1 in the Chaoshan depression (the fore arc basin in the second stage) that the early Cretaceous sediments had obducted northwestward.Therefore,the southeastern margin of the South China block had been an Alpine collision-type margin during the Yanshan movement.