Controls on Miocene Carbonate Platform Evolutlon around the South China Sea Region

Steven L. Dorobek

A preliminary compilation of subsurface data from Miocene carbonate platform around the South China Sea region shows that they have unique morphologies, internal stratal relationships, long-term depositional histories, and ages of platform termination. Variability in platform evolution reflects differences in local tectonic setting, proximity to sources of siliciclastic sediment, paleo-circulation patterns, or other environmental factors.

Miocene platforms from the western side of the South China Sea are located on remnant fault-bounded highs that formed during earlier extension or transtension Basement tilting during platform sedimentation is recorded within the internal stratigraphy of the platforms as subtle divergence or convergence of stratal reflectors. Basement tilting may be related to limited extension and rotation of fault bounded basement blocks, flexural loading by Pliocene-Recent progradational shelf facies, or both.

Along the eastern side of the South China Sea, synorogenic carbonate platforms on the distal side of Miocene foreland basins typically have ramp profiles that mimic the flexural profile produced by tectonic loading. During active convergence, the flexuraI profile migrated in unison with the advancing orogenic wedge; lower-middle Miocene ramps on the distal side of the foreland basin were forced to backstep before burial by upper Miocene(?) to Recent hemipelagic sediment.

Miocene carbonate platforms on fault-bounded highs in the Pearl River Mouth Basin area illustrate the complex interactions between influx of siliciclastic sediment and tectonics. Siliciclastic sediment supplied by fluvial-deltaic point sources to the northwest was dispersed through interplatform structural lows; platforms on structural highs continued to develop. Once structural lows were filled, siliciclastic facies could prograde, terminate, and ultimately bury carbonate platforms on structural highs.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California