3D modeling of coupled tectonics and surface processes: the role of active erosion/deposition in continental rift systems

During the last decades, numerical modeling has become a crucial approach to study and understand continental rifting. Although numerous studies have treated the role of rheology, geometry and inherited structures on the formation and evolution of rift systems, little is known on the role of surface processes during lithosphere extension. The redistribution of mass related to erosion/deposition is, however, key to assess as it provides a primary control on fault activity, which in turn controls strain localization and ultimately the rift geometry. Here we present results obtained from coupling long-term tectonic modeling (using pTatin3D) and surface processes including erosion/deposition (using FastScape). Our starting geometry consists of a 500x500x250 km box, comprising a 35 km thick continental crust and a 85 km thick lithosphere. Weak seeds located atop the mantle are used to simulate rift linkage and oblique rifting with relay zones. We explore the interaction and feedback between surface processes and tectonics during crust-lithosphere extension by systematically varying rift offset and fluvial erosion efficiency. We find that the structural style of rift linkage and rift segmentation depends strongly on rift offset and erosion efficiency with inefficient linkage and fault migration for large offset and low surface process efficiency. In contrast, our models predict efficient rift linkage at high surface process efficiency in the limit promoting transform faults between individual rift segments. At intermediate surface process efficiency and rift offset, the models exhibit complex rift linkage structures with horst like structures in the linkage area, fault and depocentre migration with time.