ABSTRACT: Tertiary Tectonostratigraphic Evolution of the South China Sea
KAHN, PETER G., and SIMON P. TODD,* BP Exploration, Uxbridge, Middlesex, United Kingdom
Sequence stratigraphic principles have been adopted in the investigation of the Tertiary tectonostratigraphic evolution of the depositional basins of the South China Sea (SCS). Sequence boundaries and maximum flooding surfaces have been picked in well logs, core and seismic and correlated with available biostratigraphic data. Some boundaries assume greater significance than others, so that the Late Oligocene and younger stratigraphy can be considered in terms of a series of eight composite sequences (or cycles).
Paleogeographic maps depicting the facies distribution in these composite sequences illustrate the interaction of sediment supply, eustasy and tectonic subsidence/uplift. Regional changes in sea level (eustatic) are modified by local tectonics. For example, the effects of the top Middle Miocene eustatic lowstand are variable: in the Yinggehai and SE Hainan basins, the clastic shelf was eroded; in the Xisha trough, these erosion products were shed as turbidites; in the rapidly subsiding Baram delta, the sequence boundary is much diminished or absent; in Luconia and East Natuna, the carbonate buildups were exposed to karstification; in the Saigon Basin, the lowstand coincided with transtension and fault-block rotation and thus produced a major angular unconformity upon which carbonate b ildups developed in the succeeding transgression.
The tectonostratigraphic evolution has profound effects on the hydrocarbon habitat and hence on exploration strategy in the SCS. For example, the stratigraphic relationships of Miocene carbonate buildups relative to source rocks, angular unconformities and regional seals at maximum flooding surfaces exerts an important influence on hydrocarbon migration pathways and hence degree and phase of fill in the buildups.
AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)