On seismic sequence stratigraphy since the Pliocene in Yazhou Bay, Sanya, Hainan Island

The stability of the geological environment is an important prerequisite for the development of the marine economy in China. It is of scientific significance to this region's environmental evolution and future trend. In sequence stratigraphy, based on the 2D seismic data, the strata in the marine area of Yazhou Bay could be divided into three third-level sequences, namely, SQA, SQB, and SQC from the bottom to top. In the SQA and SQB sequences, transgressive and highstand systems tracts are divided by the maximum transgressive surface, and the SQC sequence is not fully developed except for the transgressive system tract. In the sequence stratigraphic framework of the study area, three types of seismic facies, i.e., parallel sub-parallel reflection facies, depressed reflection facies, and progradational reflection facies, were recognized from the sequence. The pattern of seismic facies distribution shows that the sedimentary strata in Yazhou Bay developed mainly coastal, shore, and shallow marine types. Since the Pliocene, the sedimentation evolved landward from shallow sea to delta, and finally to the coastal facies. The controlled factors in the study area are mainly climate change and sea level fluctuation.