Episodic Rifting and Subsidence in the South China Sea

The South China Sea experienced at least three stages of rifting and two intervening stages of sea-floor spreading since the Early Cretaceous. Its evolution can be described by an episodic model of tectonism, one of thermal cooling and subsidence, pulsed by temporally and spatially confined heating events. Analysis of regional geologic and geophysical data suggests episodes of rifting and associated thermal activities initiated during the Late Cretaceous, the late Eocene, and the late early Miocene. The rift system corresponding to the first episode trends northeast-southwest, whereas those of the second and third trend east-west. These two trends coincide with the orientations of the major tectonic lineations within the basin. Age estimates from heat-flow and bathymetric data suggest the oceanic crust in the Southwest subbasin is considerably older (55 Ma) than that in the Northwest (35-36 Ma) or East (32 Ma) subbasins. The episodic tectonic model is supported by basin subsidence analysis. Subsidence, especially subsidence rate curves derived from the regional well data, demonstrates that unlike a classic Atlantic passive margin, thermal subsidence in the South China Sea was punctuated by rapid subsidence events which are chronologically consistent with the rifting episodes. In terms of hydrocarbon potential, the episodes of rifting and drifting would be conducive to the development of overprinted structures and the deposition of several discrete transgressive packages of source rocks and reservoirs, separated by widespread unconformities. The thermal maturity of sedimentary organic matter affected by episodic rifting and subsidence may be greater than expected on a purely passive margin of equivalent age that had not experienced repeated heating.

[1]  A. G. Fischer.  Origin and Growth of Basins , 1975 .

[2]  P. Vail,et al.  Seismic stratigraphy and global changes of sea level, Part 4 : Global cycles of relative changes of sea level , 1977 .

[3]  D. Falvey.  THE DEVELOPMENT OF CONTINENTAL MARGINS IN PLATE TECTONIC THEORY , 1974 .

[4]  John G. Sclater,et al.  Continental stretching: An explanation of the Post-Mid-Cretaceous subsidence of the central North Sea Basin , 1980 .

[5]  R. Freund,et al.  The formation of rift valleys and their zigzag fault patterns , 1976, Geological Magazine.

[6]  Naresh Kumar,et al.  Profiler-sonobuoy measurements in the South China Sea Basin , 1979 .

[7]  S. Barr,et al.  Geochemistry and geochronology of late Cenozoic basalts of Southeast Asia: Summary , 1981 .

[8]  R. Folk.  Areal standard deviation on scatter plots: Objective method for excluding extremes and portraying density concentrations , 1973 .

[9]  J. Mammerickx.  Bathymetry of the east and southeast Asian seas , 1976 .

[10]  N. Holloway.  North Palawan Block, Philippines--Its Relation to Asian Mainland and Role in Evolution of South China Sea , 1982 .

[11]  N. Sleep.  Thermal Effects of the Formation of Atlantic Continental Margins by Continental Break up , 1971 .

[12]  D. Karig.  Plate convergence between the Philippines and the Ryukyu islands , 1973 .

[13]  C. Reyes,et al.  Late Tertiary Geologic History of the Continental Shelf off Northwestern Palawan, Philippines , 1973 .

[14]  D. McKenzie,et al.  Some remarks on the development of sedimentary basins , 1978 .

[15]  J. May,et al.  Well Log and Seismic Character of Tertiary Terumbu Carbonate, South China Sea, Indonesia , 1985 .

[16]  P. Williams,et al.  Global Basin Classification System , 1983 .

[17]  Warren Hamilton.  Tectonics of the Indonesian region , 1979 .

[18]  D. Karig.  Origin and development of marginal basins in the western Pacific , 1971 .

[19]  C. S. Hutchison.  Ophiolite in Southeast Asia , 1975 .

[20]  S. D. Lewis,et al.  A geophysical study of the Manila Trench, Luzon, Philippines: 1. Crustal structure, gravity, and regional tectonic evolution , 1984 .

[21]  S. Uyeda,et al.  The evolution of the China Basin and the mesozoic paleogeography of Borneo , 1973 .

[22]  B. Parsons,et al.  An analysis of the variation of ocean floor bathymetry and heat flow with age , 1977 .

[23]  J. Mcmanus,et al.  Volcanic Control of Structures in North and West Borneo , 1976 .

[24]  L. Desheng.  Geologic Evolution of Petroliferous Basins on Continental Shelf of China , 1984 .

[25]  R. S. Lu,et al.  Plate Convergence and Accretion in Taiwan-Luzon Region , 1978 .

[26]  J. A. Wolfe.  North Palawan Block, Philippines--Its Relation to Asian Mainland and Role in Evolution of South China Sea: DISCUSSION , 1984 .

[27]  M. Steckler,et al.  Subsidence of the Atlantic-type continental margin off New York , 1978 .