The effect of low-viscosity sediments on the dynamics and accretionary style of subduction margins

Abstract. Observations of sediments at subduction margins appear to divide them into two classes: accretionary and erosive. Accretionary are dominated by accretion thick piles (>1 km) from the subducting plate, while tectonic erosion is favored in regions with little or no sedimentary cover (<1 km). The consequences styles for dynamics remain poorly resolved. In this study, we used 2-D numerical simulations investigate how low-viscosity influence margin type through plate coupling. We vary thickness viscosity sediment layer entering subduction, upper driving velocity (i.e., kinematic boundary conditions). Diagnostic parameters extracted automatically analyze differentiate between modes margin. identify three types based on extent viscous coupling interface: (a) margin, (b) low-angle wedge (c) high-angle case – analogous an erosive high-viscosity thin-layer increase interface. On other hand, when reduced, scrapped off slab form wedge. Models that develop show small radii curvature, slow convergence rates, thin interfaces, models large faster dynamic wedges. These diagnostic then linked observations present-day zones.