Upper-plate deformation in response to flat slab subduction inboard of the aseismic Cocos Ridge, Osa Peninsula, Costa Rica

Abstract

Along the Middle America Trench in southern Costa Rica, flat slab subduction of the aseismic Cocos Ridge has uplifted and exposed the outer forearc, shortened the Térraba forearc basin sequence in the inner forearc (i.e., the Fila Costeña thrust belt), and uplifted the magmatic arc. The Osa Peninsula, an outer forearc high ̃20 km inboard of the Middle America Trench and 3 km to 10 km above the plate interface at its trenchward edge, is deforming in response to variations in the bathymetry of the subducting aseismic Cocos Ridge where relief locally exceeds 1 km. Modern topography of the Osa Peninsula, elevation of the basement rocks (Early to Middle Tertiary Osa mélange), elevations of Quater..