Lithospheric-mantle modification beneath the thick sedimentary fan of Bay of Bengal: Inference from the 3D gravity model

Abstract

A lithospheric density structure of the Bay of Bengal (BoB), which includes the thickest sedimentary layers deposited after continental rifting, is determined from constrained 3D/2D gravity modeling, to understand intricate tectonics processes of the region. The results suggest lateral density variation in the sub-crustal lithospheric mantle and high-density upper mantle is found beneath the thick sedimentary region of BoB. The present density model also predicts the thick lithosphere beneath the huge pile of sediments. The dense and thick lithospheric mantle results are supported by global tomographic and other geophysical results. It is also noticed that the dense mantle and thick sedimentary region have high elastic strength. We propose that the density and strength of the lithospheric mantle in the northern BoB are increased with age and sedimentation since rifting. The cause of density changes in the mantle is indistinct and could occur due to numerous reasons such as the transformation of mantle material catalyzed by a change in pressure and temperature conditions, or mantle flow.