Tectonic differences between eastern and western sub-basins of the Qiongdongnan Basin and their dynamics
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ORIGINAL RESEARCH PAPER
Tectonic differences between eastern and western sub-basins of the Qiongdongnan Basin and their dynamics Jianbao Liu · Zhen Sun · Zhenfeng Wang · Zhipeng Sun · Zhongxian Zhao · Zhangwen Wang · Cuimei Zhang · Ning Qiu · Jiangyang Zhang
Received: 21 January 2014 / Accepted: 1 December 2014 / Published online: 18 December 2014 © Springer Science+Business Media Dordrecht 2014
Abstract The central depression of the Qiongdongnan Basin can be divided into the eastern and western subbasins by the Lingshui–Songnan paleo-uplift. To the northwest, the orientation of the faults turns from NE, to EW, and later to NW; In the southwest, the orientation of the faults turns from NE, to NNE, and then to NW, making the central depression much wider towards the west. In the eastern sub-basin, the NE-striking faults and the EWstriking faults made up an echelon, making the central depression turn wider towards the east. Fault activity rates indicate that faulting spreads gradually from both the east and west sides to the middle of the basin. Hence, extensional stress in the eastern sub-basin may be related to the South China Sea spreading system, whereas the western sub-basin was more under the effect of the activity of the Red River Fault. The extreme crustal stretching in the eastern sub-basin was probably related to magmatic setting. It seems that there are three periods of magmatic events that occurred in the eastern sub-basin. In the eastern part of the southern depression, the deformed strata indicate that the magma may have intruded into the strata along faults
around T60 (23.3 Ma). The second magmatic event occurred earlier than 10.5 Ma, which induced the accelerated subsidence. The final magmatic event commenced later than 10 Ma, which led to today’s high heat flow. As for the western sub-basin, the crust thickened southward, and there seemed to be a southeastward lower crustal flow, which happened during continental breakup which was possibly superimposed by a later lower crustal flow induced by the isostatic compensation of massive sedimentation caused by the right lateral slipping of the Red River Fault. Under the huge thick sediment, super pressure developed in the western sub-basin. In summary, the eastern sub-basin was mainly affected by the South China Sea spreading system and a magma setting, whereas the western sub-basin had a closer relationship with the IndoChina extrusion system. Keywords Fault activity · Tectonic subsidence · Magma intrusion · Stretching factor · Lower crustal flow
Introduction J. Liu School of Resource and Environment, Henan Institute of Engineering, Zhengzhou 451191, China e-mail: [email protected] J. Liu · Z. Sun (&) · Z. Zhao · Z. Wang · C. Zhang · N. Qiu · J. Zhang CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China e-mail: [email protected] Z. Wang · Z. Sun China National Offshore Oil Corporation, Western Branch, Zhanjiang 524000, Guangdong, China
The Qiongdongnan Basin (QB)
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