The South China Sea has yet to receive a DSDP investigation; consequently, numerous untested models have been proposed for its post-Cretaceous evolution. From a compilation of regional oceanographic heat-flow measurements with offshore and onshore bore-hole temperatures, we thermally model and constrain possible interpretations of its tectonic evolutionary path. The heat-flow data, together with magnetic profiles, depth to basement determinations, and regional sediment isopachs, characterize two principal subbasin extensional elements--one trending east-west (northern area between Hainan and Luzon) and the other trending northeast-southwest (central area between Palawan and Vietnam). The thermal models of simple lithosphere cooling suggest the central area began spreading 55-58 m.y.B.P. and the northern region 34-35 m.y.B.P. These dates of incipient extension correspond to two principal unconformities in Paleocene and Oligocene strata of both offshore China and Palawan, and together they indicate regional uplift of the South China Sea owing to thermal expansion prior to the spreading events. The thermal models also suggest that in the northern region, spreading ceased approximately 19 m.y.B.P., which compares favorably with published magnetic estimates of 17.7 m.y.B.P. A late Cenozoic heating event is evidenced by a thermal anomaly in the southern portion of the central region (southern Vietnam margin) that may be related to incipient spreading along a zone of crustal weakness inherited from the Jurassic-Cretaceous Sunda-Tethys suture. Overall, these data tend to support the hypothesis of spreading occurring first in the central region and then in the northern region.

From the geophysical data and observations of Cretaceous ophiolites cropping out to the south in Sabah and Brunei, we kinematically border our model to the south and propose the Palawan Ulugan fault to be a right-lateral suture between continental and intermediate crust. Structurally, within limits of the data presently available, our model further predicts the southern China shelf to have experienced two principal episodes of extension with a net result of younger (<34 m.y.B.P.) east-west trending graben normal faults superimposed upon older (<55 m.y.B.P.) northeast-striking pregraben normal faults. In terms of thermal maturity, geochemical kinetic modeling of Late Cretaceous source rocks suggests depths to the oil ceiling to range from 1.3 to 1.8 km in the northern region and rom 0.98 to 1.6 km in the central region. Similarly, depths to the oil floor are estimated to range from 2.4 to 3.4 km and from 1.8 to 3.2 km in the two respective regions.

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