Transpressional margins are widespread, and their dynamics are relevant for plate boundary evolution globally. Though transpressional orogen evolution involves a topographic response to deformation, many studies focus only on the structural development of the system ignoring surface processes. Here, we present a new set of analog models constructed to investigate how tectonic and surface processes interact at transpressive plate boundaries and shape topography. Experiments are conducted by deforming a previously benchmarked crustal analog material in a meter-scale plexiglass box while controlling erosion through misting nozzles mounted along the transpressional wedge. We used a laser scanner to generate digital elevation models throughout the model evolution and photos for particle image velocimetry analysis. We focus on three experiments that cover a range of rainfall and convergence settings, with two end-member erosion settings and a dry reference. In all experiments, a bivergent wedge forms, and strain partitioning broadly evolves according to previously established models. Regarding drainage networks, we find that the streams in our models develop differently through feedback between fault development and drainage rearrangement processes. Differences between end-member erosional models can be explained by the varying response of streams to structure modulated by rainfall. Additionally, erosion may influence the structural evolution of transpressional topography, leading to accelerated strike-slip partitioning. From these results, we create a model for developing structures, streams, and topography where incision and valley formation along main structures localize exhumation. We apply insights from the models to natural transpressional systems, including the Transverse Ranges, CA., and the Venezuelan Andes.

The evolution of subduction zones influences the rise and demise of forearc and back-arc basins on the overriding plate. We conducted 2D elasto-visco-plastic numerical models of oceanic subduction and subsequent continental collision which include erosion, sedimentation, and hydration processes. The models show the evolution of wedge-top and retro-forearc basins in the continental overriding plate, separated by a forearc high. These forearc regions are affected by repeated compression and extension phases. Higher subsidence rates are recorded in the syncline structure of the retro-forearc basin when the slab dip angle is higher and the subduction interface is stronger and before the slab reaches the 660 km upper-lower mantle discontinuity. The 3-4 km negative residual topographic signal is produced by the gradually steepening slab, which drags down the overlying upper plate. Extensional back-arc basins are either formed along inherited crustal or lithospheric weak zones at large distance from the arc region or are created above the hydrated mantle wedge originating from arc rifting. Back-arc subsidence is primarily governed by crustal thinning controlled by slab roll-back. Onset of collision and continental subduction is linked to the rapid uplift of the forearc basins; however, the back-arc region records ongoing extension during the initial phase of soft collision. Finally, during subsequent hard collision both the forearc and back-arc basins are ultimately affected by compression. Our modelling results provide insights into the evolution of Mediterranean subduction zones and propose that the Western-Eastern Alboran, Paola-Tyrrhenian, Transylvanian-Pannonian Basins should be considered as genetically connected forearc –back-arc basins, respectively.