Coupled tectonic and surface processes in the Guerrero forearc, Mexico: Insights from the basin-averaged erosion rates

The complex interactions among erosion, tectonic uplift, and climate are fundamental to understanding the mechanisms that drive landscape evolution and govern the recycling of crustal materials. In this study, we used basin-averaged erosion rates based on 10 Be concentrations in river sediments from eight medium- to large-sized drainage basins across the Guerrero forearc to investigate the interplay between lithology, climatic conditions, and tectonic factors in shaping the topography above the flat-slab subduction zone. The calculated erosion rates range from 0.8 mm/yr and show an apparent eastward increase. This spatial pattern appears to be primarily controlled by the tectonic processes associated with the subduction of the Cocos Plate beneath the North American Plate, particularly the seismogenic activity of crustal faults, with climate variability exerting a secondary influence and limited lithology impact. The eastward increase in erosion rates across the Guerrero forearc appears to correspond to the activity of trench-parallel, W-striking crustal faults, most notably the La Venta Fault, and aligns with observed patterns of exhumation rates, increasing convergence rate, and roughness of the subducting Cocos Plate. The relatively low erosion rates may be attributed to the flat-slab subduction observed in the Guerrero sector of the Mexican subduction zone, consistent with global observations that associate forearc regions above flat slabs with reduced erosion rates. A secondary climatic influence on erosion patterns is indicated by correlations with mean annual discharge and the potential impact of extreme precipitation events at the individual basin scale.