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Depositional architecture and structural evolution of a region immediately inboard of the locus of continental breakup (Liwan Sub-basin, South China Sea)

Lei, Chao, Alves, Tiago M., Ren, Jianye, Pang, Xiong, Yang, Linlong and Liu, Jun 2019. Depositional architecture and structural evolution of a region immediately inboard of the locus of continental breakup (Liwan Sub-basin, South China Sea). Geological Society of America Bulletin 131 (7-8) , pp. 1059-1074. 10.1130/B35001.1

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Abstract

New 3D seismic data and regional 2D seismic profiles from the northern South China Sea, the most extensive dataset imaging a distal rifted margin in the world, are used to characterize a region located immediately inboard of the locus of Cenozoic continental breakup. The interpreted dataset images a ~6 km thick continental crust in which the Moho and the base of syn-rift sediment are observed as clear, well-resolved seismic reflections. This extremely thinned continental crust was offset at its base by a complex detachment fault system from which oceanward-dipping listric faults propagated vertically to bound six separate tilted blocks, in a style akin to tectonic rafts. The seismic reflection data in this work allowed us to investigate the thickness of synand post-rift strata above tilt blocks to reveal that the early-middle Eocene syn-rift topography was gradually blanketed in the late Eocene (~38 Ma). After 33 Ma (earliest Oligocene), the main depocenter on the margin migrated to the south of the Liwan Sub-basin, i.e. oceanward, as recorded by the thickening of strata within a breakup sequence. This work is important as it demonstrates how closely structures and sedimentation within the Liwan Sub-basin were controlled by a basal, rift-related detachment system, which is imaged in detail by 3D seismic data for the first time on a rifted continental margin. Continental breakup was marked by a shift in the locus of subsidence (and crustal stretching) toward ocean crust, within a time period spanning ~16 m.y. We extrapolate our findings from the South China Sea to the development of asymmetric passive margins across the world.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Publisher: Geological Society of America
ISSN: 0016-7606
Date of First Compliant Deposit: 14 November 2018
Date of Acceptance: 6 November 2018
Last Modified: 08 Sep 2020 09:00
URI: http://orca-mwe.cf.ac.uk/id/eprint/116802

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