Oblique subduction modelling indicates along-trench tectonic transport of sediments

Abstract

Convergent plate margins are currently distinguished as 'accretional' or 'erosional', depending on the tendency to accumulate sediments, or not, at the trench. Accretion and erosion can coexist along the same margin and we have noticed that this mostly occurs where subduction is oblique. Here we show that at oblique subduction zones, sediments that enter the trench are first buried, and later migrate laterally parallel to the trench and at various depths. Lateral migration of sediments continues until they reach a physical barrier where they begin to accumulate. The accretionary wedge size decreases along the trench moving away from the barrier. We therefore suggest that the gradual variation of the accretionary wedge size and sediment amount at the trench along one single subduction zone, as observed in many active plate margins worldwide, can be explained by the lateral tectonic migration of sediments driven by obliquity of subduction as well.

Interplate deformation at early‐stage oblique subduction: 3‐D thermomechanical numerical modeling

“…The lateral tectonic migration of sediments is active during the entire subduction process and occurs at different depths both in the accretionary prism and along the slab. As described by Malatesta et al (2013), such migration causes the formation of a trench with variable sediment amount along its axis. The domain from which sediments are removed as they enter the subduction zone generally exhibits a tiny accretionary prism ( Figure 1c).…”

“…In the last years a variety of models studied subduction zones in 3D using either physical (e.g., Boutelier et al, 2014;Dominguez et al, 2000;Duarte et al 2013;Funiciello et al, 2008;Malavieille and Trullenque, 2009), semianalytical (Royden and Husson, 2006) or numerical methods (e.g., Capitanio et al, 2007;Jadamec and Billen, 2010;Malatesta et al, 2013;Manea et al, 2014;Schellart et al, 2007;Stegman et al, 2010;Sternai et al, 2014;Yamato et al, 2009;Hampel, 2015, 2016); these works tested several subduction-related topics as e.g. the deformation mechanisms and the influencing parameters of accretionary wedges, the role of margins geometry, interplate rheology and mantle processes on upper plate deformation and on subduction kinematics and dynamics.…”

“…The evolution of subduction-related processes in an oblique setting is therefore more complex compared to the case of orthogonal platesconvergence (e.g., Boutelier et al, 2012;Malatesta et al, 2013;McCaffrey, 1992). For this reason, 2D models, lacking the third dimension, are not suitable to fully reproduce these particular patterns and 3D models should be used.…”

“…In our previous work (Malatesta et al, 2013) we discussed the along-trench tectonic transport of sediments at oblique oceanic subduction zones. In this new work we use similar highresolution 3D thermomechanical modelling approach, to study if and how long-term deformation, topographic evolution and tectonic erosion of the upper plate can vary along the same margin, when involved in an oblique subduction during its early history (15)(16)(17)(18)(19)(20).…”

Implementing nonlinear viscoplasticity in ASPECT: benchmarking and applications to 3D subduction modeling

“…To demonstrate ASPECT's promise in this field, we here present 3D models of free-plate intraoceanic subduction. Recent 3D subduction models have been applied in the study of along-strike effects such as oblique convergence (Malatesta et al, 2013), toroidal flow (Schellart and 10 Moresi, 2013), varying lithospheric structure (Mason et al, 2010;van Hunen and Allen, 2011;Capitanio and Faccenda, 2012;Duretz et al, 2014), slab width (Stegman et al, 2006;Schellart et al, 2007;Stegman et al, 2010) and the presence of lateral plates (Yamato et al, 2009). Four-dimensional (3D plus time) modeling allows us to investigate more realistically the generics of subduction (e.g.…”