Mantle-induced subsidence and compression in SE Asia since the early Miocene

Abstract

Rift basins developed extensively across Sundaland, the continental core of Southeast Asia, since the Eocene. Beginning in the early Miocene, basins in southern Sundaland experienced widespread synchronous compression (inversion) and marine inundation, despite a large drop in long-term global sea level. The mechanism for this large-scale synchronous regional sea level rise, basin inversion, and subsidence is not well understood and contrary to expectations from traditional basin models and eustatic sea level trends. We present geodynamic models of mantle convection with both deformable and rigid plate reconstructions to investigate this enigma. Models suggest that a slab stagnates within the transition zone beneath Southeast Asia before the Miocene. The stagnant slab penetrated through the 660 km mantle discontinuity during the early Miocene and formed a slab avalanche event, due to continuous subduction and accumulation of negatively buoyant slabs. This avalanche may have induced large-scale marine inundation, regional compression, and basin inversion across southern Sundaland. We argue mantle convection induced large-scale basin compression, in contrast to conventional plate margin-induced compression; this suggests mantle convection may exert a much stronger control on surface processes than previously recognized.

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