Labrador Sea: the extent of continental and oceanic crust and the timing of the onset of seafloor spreading

Abstract The continental margins of the South China Sea (SCS) have undergone episodic rifting since the Cenozoic, and there are ongoing debates surrounding the processes of crustal deformation and seafloor opening. In this work, we present a P ‐wave velocity model extending from the north of Xisha Trough to the Zhongshanan Basin in the northwestern SCS margin, using ocean bottom seismometer data of the wide‐angle seismic profile OBS2013‐1. The results show that the crust thins symmetrically across the western Xisha Trough, from more than ∼20 km at the flanks to ∼10 km in the central valley where the sedimentary layers thicken to over 6 km. In the Zhongsha Trough, closer to the deep basin, the upper crust is detached in a ∼20 km wide region and the lower crust has seismic velocities increased by more than ∼0.3 km/s. The top boundary of the lower crust is located at a depth of ∼13 km across the Zhongsha Trough, and a ∼5 km thick midcrustal ductile layer is imaged. A ∼50 km wide ocean‐continent transition region beneath the Zhongshanan Basin characterizes a ∼6 km thick continental crust underlain by serpentinized and magnetized upper mantle. These observations, together with plate reconstructions based on gravity and magnetic analysis, suggest that deformation of the continental margin was controlled by a ductile crustal layer. Magmatism, associated with the early stage oceanic accretion, has mixed with the highly extended continental crust. Developments of the failed rifted basins were controlled by the westward propagation of the continental breakup.

Seafloor Spreading

Continental Margin

Trough (economics)

10.1029/2020tc006260

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Citations (23)

Magnetic evidence for slow seafloor spreading during the formation of the Newfoundland and Iberian margins

Earth and Planetary Science Letters (2000)

S. P. Srivastava Jean‐Claude Sibuet S. C. Cande W. R. Roest I. Reid

Seafloor Spreading

Continental Margin

Oceanic basin

10.1016/s0012-821x(00)00231-4

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Citations (238)

Labrador Sea: the extent of continental and oceanic crust and the timing of the onset of seafloor spreading

Marine and Petroleum Geology (1995)

James A. Chalmers Kirsten Holt Laursen

Seafloor Spreading

Continental Margin

10.1016/0264-8172(95)92840-s

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Citations (142)

Prebreakup Sedimentary and Volcanic Sequences on Rifted Continental Margin of Wilkes Land, Antarctica: ABSTRACT

AAPG Bulletin (1986)

Monty A. Hampt Stephen L. Eittreim

The transition zone from continental crust to oceanic crust on the Wilkes Land, Antarctica, margin was surveyed with 24-fold multichannel seismic reflection along 1800 line-km in 1984. The northward transition from extended continental crust to normal oceanic crust is characterized by a progression through three distinct volcanic sequences. The first, deposited on extremely thin continental crust, is interpreted to be a flood basalt, presumably deposited during the late rifting stage. The second, which overlaps the first at its northern end, is a seaward-dipping reflector sequence that forms anomalously thick oceanic crust. The third, which in turn onlaps the second, is normal oceanic crust with a rough upper surface and no internal reflectors.

Continental Margin

Margin (machine learning)

10.1306/94886420-1704-11d7-8645000102c1865d

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Citations (0)

The crustal structure of the Enderby Basin, East Antarctica

Marine Geophysical Research (2018)

J K Davis Lawrence A. Lawver Ian O. Norton Ian W. D. Dalziel Lisa M. Gahagan

Seafloor Spreading

Oceanic basin

Continental Margin

10.1007/s11001-018-9356-5