Stress field modeling of northwestern South China Sea since 5.3 Ma and its tectonic significance
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Stress field modeling of northwestern South China Sea since 5.3 Ma and its tectonic significance YANG Fengli1*, ZHOU Zuyi1, ZHANG Na1, LIU Ning1, NI Bin1 1 School
of Ocean and Earth Science, Tongji University, Shanghai 200092, China
Received 18 May 2013; accepted 4 August 2013 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2013
Abstract Tectonically, the northwestern South China Sea (SCS) is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Yinggehai Basin, the Qiongdongnan Basin and Xisha Trough in the east, and the Zhongjiannan Basin in the south. Since the Pliocene (5.3 Ma), the Yinggehai Basin has experienced repeated accelerating subsidence, high thermal fluid, and widely developing mud-rich overpressure chambers, abundant mud diapers and crust-mantle mixed CO2. While a large central canyon was developed in the Qiongdongnan Basin, new rift occurred in the Xisha Trough. These characteristics demonstrate a single tectonic unit for the northwestern SCS, for which we have undertaken stress field modeling to understand its plate deformations and sedimentary responses. Our results demonstrate that an extension tectonic event occurred after 5.3 Ma in the Yinggehai-Qiongdongnan-Xisha trough area, which is characterized by thinner crust (3 500 m). A new rift system subsequently was developed in this area; this event was mainly driven by the combined effects of different movement velocity and direction of the three micro-plates, and the far-field effect of the continental collision between the Indian Plate and the Tibetan Plateau, and subduction of the Pacific Plate underneath the Eurasian Plate. Key words: northwestern South China Sea, Pliocene, stress field modeling, rift system Citation: Yang Fengli, Zhou Zuyi, Zhang Na, Ni Bin. 2013. Stress field modeling of northwestern South China Sea since 5.3 Ma and its tectonic significance. Acta Oceanologica Sinica, 32(12): 31–39, doi: 10.1007/s13131-013-0385-2
1 Introduction The geodynamic mechanism for the formation of active continental marginal basins has become a focus of research since the establishment of the plate tectonic theory. After decadal endeavors, geodynamic mechanism remains a problem in the global plate tectonic theory, and a systematic approach is required for a solution. Today, the western Pacific continental margin is located at the junction of the EuropeanAsian, the Pacific and the Indian-Australian Plates, and over the geological history, this area had been restrained by the evolution of the Tethys and paleo-Pacific Plates. Globally, around 70% of the present-day marginal basins are located here, and they are characterized by a variety of morphologies and formation times in the trench-arc-basin systems of the region (Fig. 1). This unique tectonic-geomorphic chain has long occupied a position in the research of global continental marginal basins. Many studies have been undertaken for this region and some models have been p
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