Climate changes control offshore crustal structure at South China Sea continental margin

Rifted continental lithosphere subsides as a consequence of combined crustal thinning and mantle lithosphere cooling yet basins on some continental margins experience anomalous subsidence events that postdate active extension. Deep basins on the northern margin of the South China Sea, notably the Baiyun Sag, show basement subsidence accelerating after ∼21 Ma, postdating extension by several million years.

We combine geophysical observations and numerical forward modeling to show that loading of the offshore basins by increased sediment flux caused by faster onshore erosion following Early Miocene monsoon intensification is a viable trigger for ductile flow after the cessation of active extension. This illustrates that offshore basin dynamics at continental margins with weak crust can be controlled by onshore surface processes in a newly recognized form of climate–tectonic coupling. 

Present-day topography of South East Asia and the thickness of sedimentary fans – shown in the same colour scale. In this article why investigate the impact of sediment loading on post-rift tectonics at passive margins. (Credits: Topography data: GMRT v2.6, Sediment thickness: Divins (2006), Visualisation: GeoMapApp)

Numerical model of a wide rift evolution until break-up. Post-rift sediment loading starts at 21 Ma and increasing to full load until 11 Ma (indicated by orange triangle). (A)–(C) Weak crust decouples deformation of crust and mantle. A wide rift develops into two symmetric margins. (D)–(E) Post-breakup sediment loading is accommodated by lateral flow of the low-viscosity crust.

Cite as:

Clift, P.D., Brune, S., Quinteros, J., 2015. Climate changes control offshore crustal structure at South China Sea continental margin. Earth and Planetary Science Letters 420, 66–72. doi:10.1016/j.epsl.2015.03.032


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