Episodic Rifting and Subsidence in the South China Sea
Episodic Rifting and Subsidence in the South China Sea
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DOI：
10.1306/94886a8d-1704-11d7-8645000102c1865d
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发表时间：
1986-09
期刊：
影响因子：
3.5
通讯作者：
Ke Ru;J. Pigott
中科院分区：
文献类型：
--
作者：
Ke Ru;J. Pigott
自早白垩世以来，南中国海至少经历了三次裂谷作用和两次海底扩张作用。它的演化可以用时间和空间受限的加热事件驱动的热冷却和下沉的构造作用的幕式模型来描述。对区域地质和地球物理资料的分析表明，裂谷作用和相关的热活动始于晚白垩世、晚始新世和早中新世晚期。第一幕对应的裂谷系走向为东北-西南走向，而第二幕和第三幕对应的裂谷系为东西走向。这两个趋势与盆地内主要构造线理的走向相吻合。根据热流和测深数据进行的年龄估算表明，西南次盆地的洋壳年龄(55 Ma)远大于西北次盆地(35-36 Ma)或东部次盆地(32 Ma)的洋壳年龄。幕式构造模式得到了盆地沉降分析的支持。由区域测井资料得到的沉降量曲线表明，与经典的大西洋被动边缘不同，南中国海热沉降期伴随着与裂谷事件在时间上一致的快速沉降期。在油气潜力方面，裂谷和漂移的幕式有利于叠置构造的发育和由广泛的不整合隔开的多个离散的烃源岩和储集层的海侵组合的沉积。受幕式裂陷和沉陷影响的沉积有机质的热成熟度可能大于预期，在没有经历过重复加热的相同年龄的纯被动边缘上。
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.