Sedimentary Records For Cenozoic Tectonic Event In Northwest Sub-basin Of South China Sea (SCS)

South China Sea（SCS） is the largest marginal sea in the western Pacific. In thestructure，it locates in intersection of India_Australian Plate,Eurasian Plate andPacific_Philippine Sea plate.On the geological history,it located in the junction of thePacific tectonic domain and Tethys tectonic domain. As a typical marginal sea in thewestern Pacific, SCS experienced the whole evolution from continental margin splitto seafloor spreading.By determining the sedimentary age of sea basin in the northwest SCS, this paperanalyses Cenozoic tectonic deformation and sedimentary characteristics. Thenorthwest sub-basin of SCS deposited from late Oligocene, but the slop of thesub-basin deposited from Eocene. By analyzing response relationship betweensedimentary and seafloor spreading, Cenozoic evolution model was proposed.Thesub-basin underwent three structure evolution,continental margin split-seafloorspreading and past seafloor spreading.Achieved the following results.①Northwest sub-basin accepted the deposition since the lateOligocene; but the North slope of the sub-basin accepted thedeposition since Eocene. Seven seismic reflectors can be traced,from top to bottom respectively S1.8(T2), S5.5(T3), S10.5(T4),S16.4(T5), S23.3(T6), S28.0(T7)。②The sub-basin underwent three structure evolution,continental marginsplit-seafloor spreading and past seafloor spreading③The seafloor spreading of sub-basin started at the same time with centerbasin of SCS.