Lithospheric warping underlies the formation of back-arc basins

Abstract

Back-arc basins represent intriguing phenomenon of the lithospheric evolution. They are the places of potential subduction initiation, what makes them highly important features within the theory of plate tectonics. The circumstances of their origin and life cycle are not well understood and whether the retreat of subduction is a cause or consequence of back-arc basin development remains an open issue. In the presented work, the new approach has been used, based on the model of thin shell warping. Within this concept, the plate warps due to proximity of translational boundary when its forward movement is constrained. During the process, the lithospheric slab can steepen and sink to the 660 km transition layer, reaching an amphitheatre-like geometry. The specific shape of deformation resembles the topology of several reference basins from the Western Pacific region. Results show that subduction retreat, back-arc extension and arcuate geometry may represent only different demonstrations of one underlying physical mechanism. Modelling suggests that the movement of plates and their interactions, together with the curvature of the Earth’s surface, could be responsible for the formation of back-arc basins.