Geological Evolution And Hydrocarbon Potential Of Cenozoic Carbonate Platforms, Southern South China Sea

Based on available seismic and well data, the Cenozoic carbonate platforms inthe southern South China Sea are identified from seismic reflection profiles and theirsedimentary characteristics as well as spatial and temporal distributions aredocumented in detail. These carbonate platforms initiated in the late Early Mioceneand reached their widest extent in the Middle Miocene, showing north-southorientation, and mainly occurring on the hanging wall of the strike-slip fault block inthe centre of the basin and the southern basin margin. The carbonate platform can bedivided into the east band and the west band according to its forming from twodifferent sedimentary tectonic backgrounds,where the west side was the slopedipping towards the east fractured by faults and approached land-source areasresulting in alternating clastic and carbonate rocks, while the east side was close to theSouth China Sea basin and far from terrigenous areas showing thick and purecarbonate rocks. After the sequence stratigraphic analysis, it showed that thecarbonate platforms existed mainly in transgressive and highstand system tracts. Thesedimentary facies of single carbonate platform showed ring construction in the planeview, and they were relatively narrow but regular, which may be divided into innerplatform facies, fringing platform facies, foreslope facies (gentle and steep slope) and basin floor facies. However, the basin floor facies were only in the eastern side ofcarbonate platform which may be related to the geological settings near the SouthChina Sea.We have mapped the platforms, reconstructed their evolution, and evaluated thecontrols on platform growth and demise within the regional geological setting. Theplatform margins were controlled by synsedimentary faults, associated with carbonateslope failure deposits and/or reef talus. The platforms are of two types: shelf platformsand isolated platforms. Platform growth history involves six phases: start-up, catch-up,keep-up, exposure, renewal and drowning phases. Quantitative studies on theextension and subsidence were carried out in the study area. Using balancedcross-section and backstripping techniques, we reconstructed the stratigraphicdeposition history and tectonic evolution history of the study basin. Quantitativeanalysis of the basin evolution indicates that tectonism, eustasy, the supply of bothterrigenous sediment and nutrients are the dominant controls on platform developmentand demise in the southern South China Sea.