珠三坳陷珠三南断裂形成演化及其对沉积中心迁移的控制

Formation and evolution of Zhu-3 south fault and its control on the depocenter shift in Zhu-3 depression,Pearl River Mouth Basin

应用断裂三维定量构造几何学和不同时期断裂活动多参数-走向长度关系分析方法,对珠三南断裂几何特征、形成演化、分段和连锁、活动强度的差异及其对沉积中心迁移的控制,进行较细致和定量的研究。珠三南断裂总体分3大段:东段、西段北支和西段南支,依次细分为2小段、4小段和3小段,各段几何特征和活动差异较大。早期,断裂自西向东分段延伸发育;中期,西段南支活动停止、西段北支和东段强烈差异活动下连锁;晚期,断裂自西向东分段停止活动。整个断裂体系随断裂"弱→强→弱"活动特征,呈"分→合→分"的演化状态。沉积中心随断裂活动强度差异变化表现为"跷跷板式"的迁移规律:古新世在文昌C凹陷的西部→始新世—渐新世早、中期在文昌A凹陷→渐新世晚期在文昌B凹陷的西部→渐新世以后不受断裂控制。

Geometric features, formation and evolution, division and linkage, and active intensity differential of Zhu-3 south fault and its control on the depocenter shift in Zhu-3 depression were investigated in detail and quantitatively by applying the 3-D quantitative structure geometry of faults and analysis of multi-parameters and strike length of fault activity at different stages. The fault has three major segments：the eastern one, western north one and western south one, each can be further divided into 2, 4 and 3 sub-pieces, respectively. Geometric features and activities of each segment were quite different at various stages. For instance, at the early stage, the fault extended by pieces from west to east; at the middle stage, the western north one and eastern one linked under a strongly differential movement while the western south one stopped; and at the late stage, the fault stopped from west to east by pieces. The entire fault system characteristic of ＂weak -〉strong -〉 weak＂ activities experienced a ＂division -〉 linkage -〉 division＂ evolutionary episode correspondingly. The depocenter showed a ＂teeterboard＂-type shift rule with variances in active intensity of the fault, i.e. from the western Wenchang-C sag in Paleocene to Wenchang-A sag in Eocene and early-middle Oligocene, then to the western Wenchang-B sag in late Oligocene, and with no fault control after Oligocene.