--> Development of Cenozoic Carbonate Platform in the Conjugated Margin of the South China Sea: Response on Tectonic Evolution

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Development of Cenozoic Carbonate Platform in the Conjugated Margin of the South China Sea: Response on Tectonic Evolution

Abstract

The huge thicknesses of Cenozoic carbonate platform are widely developed in the South China Sea. However, most of which have been drowned since the Late Cenozoic, also named drown carbonate platform. The carbonate platforms are unique in the South China Sea and contain rich information on tectonic evolution. The carbonate platforms were developed by the rifting processes, and were initiated on the faulted block shoulder in the conjugated rifting margin. Tectonic subsidence provides the accumulation of platform growth. Tectonic tilts, faulting and foreland basin for bulge migration control distribution, thickness and seismic reflection horizontal variation. Tectonic induced relative sea-level change control the sedimentary cycles of carbonate platforms. Based on the latest drilling and 2D/3D seismic data and regional geological document, a study was carried out mainly on the Xisha carbonate platform. Innovative results had been achieved as follows. 1) Combined with well YC35-1-1, we established three margin symbols of carbonate platforms, tidal channels, fault escarpments and lithological shifts. Tidal channels mainly distribute on the gradual slope of the Xisha Uplift and Guangle Uplift, fault escarpments centralize on the two uplift margins, while the shifts of carbonate rock and clastic rock locate on the relative steep slopes around uplifts. 2) We straightened out the space-time of the Xisha carbonate platform and identified seven periods of carbonate platform evolution which were divided into four stages, preliminary stage, flourishing stage, recessed stage and surviving stage. 3) Restored palaeogeomorphology of Miocene carbonate platforms suggested that carbonate platform mainly deposited on the shallow water and reefs centralized on the steep cliffs in this area. 4) The results from quantitatively calculated factors of extension and subsidence by balanced cross-section and backstripping techniques demonstrated that the carbonate platforms initialized on the tectonic high in early Miocene and flourished during the middle Miocene dependent on the stable tectonic conditions. However, later rapid subsidence in Late Miocene led to the demise of carbonate platforms. 5) The change of relative sea level had a very important influence on the evolution of carbonate platforms. The second order of relative sea level controlled evolutionary trend of carbonate platforms and the third order of relative sea level affected the evolutionary periods in each stage.