Finite extension across the South Vietnam basins from 3D gravimetric modelling: relation to South China Sea kinematics

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We derive a crustal thickness map over the south Vietnam basins from a 3D inversion of gravity data that takes into account the sedimentary infill and its density variation with depth. This map is used to estimate the total amount of stretching across these basins, that varies from 190 km to the east (at 111°E) to 30 km to the west (at 107°E). Comparison with South China Sea kinematics (amount and timing of oceanic opening) implies large decoupling with respect to the Indochina block and supports the hypothesis of formation of the South China Sea in upper Oligocene to lower Miocene by southward subduction of the proto-South China Sea.