The role of rifting in the development of the continental margins of the southwest subbasin, South China Sea: Insights f
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ORIGINAL RESEARCH PAPER
The role of rifting in the development of the continental margins of the southwest subbasin, South China Sea: Insights from an OBS experiment Chuanchuan Lu¨1
•
Tianyao Hao1 • Jian Lin2 • Xuelin Qiu3
Received: 21 June 2016 / Accepted: 15 November 2016 Ó Springer Science+Business Media Dordrecht 2016
Abstract The continental margins of the southwest subbasin in the South China Sea mark a unique transition from multi-stages magma-poor continental rifting to seafloor spreading. We used reflection and refraction profiles across the margins to investigate the rifting process of the crust. Combining with the other seismic profiles acquired earlier, we focused on the comparative geological interpretation from the result of multichannel seismic analysis and wideangle seismic tomography. Our result provides the evidence of upper crustal layer with abundant fractures below the acoustic basement with a P-wave velocity from 4.0 to 5.5 km s-1. It indicates extensive deformation of the brittle crust during the continental rifting and can make a good explanation for the observed extension discrepancy in the rift margins of the South China Sea. The seismic chronostratigraphic result shows the possibility of the intracontinental extension center stayed focused for quite a long time in Eocene. Additionally, our evidence suggested that continental margin of the southwest subbasin had experienced at least three rifting stages and the existence of the
Electronic supplementary material The online version of this article (doi:10.1007/s11001-016-9295-y) contains supplementary material, which is available to authorized users. & Chuanchuan Lu¨ [email protected] 1
Key Lab of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
2
Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
3
Key Lab of Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
rigid blocks is an appropriate explanation to the asymmetric rifting of the South China Sea. Keywords South China Sea Southwest subbasin Magma-poor rifted margins Hyper-extended crust Wide-angle reflection and refraction
Introduction Before the oceanic crust accretion of the South China Sea (SCS), the passive margins of the SCS experienced progressive rifting starting from the early Paleocene (Taylor and Hayes 1983; Ru and Pigott 1986; Cullen et al. 2010; Franke 2013). As a consequence, an ultra-wide attenuated continental crust progressively dislocated from the South China continent and was rifted where a series of marginal basins formed within (Buck 1991; Clift and Lin 2001; Huismans and Beaumont 2008; Hall 2009; Franke et al. 2014). Additionally, as there is no evidence of salt or a Seaward Dipping Reflector, the margins of the SCS have been categorized as magma-poor rifted margins (Nissen et al. 1995; Qiu et al. 2001, 2011; Yan et al. 2001; Clift et al. 2002; McIntosh et al. 2005; Wang et al. 20
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