Caribbean Slab Segmentation Beneath Northwest South America Revealed by 3-D Finite Frequency Teleseismic P-Wave Tomography

Abstract

The Caribbean plate subducts beneath northwest South America at a shallow angle due to a large igneous province that added up to 12 km of buoyant crust. The overriding plate lacks volcanism and exhibits Laramide-style uplifts over 500 km from the trench. Here, we illuminate the subduction structures through finite frequency teleseismic P-wave tomography and connect those structures to the Laramide-style deformation on the overriding plate. We use a new data set collected from the Caribbean-Mérida Andes seismic experiment comprised of 65 temporary broadband stations integrated with permanent stations from the Colombian and Venezuelan national networks. We identify three segments of subducting Caribbean plate with one segment completely detached from the surface. The timing of the detachment aligns with other regional events, including the uplift of the Mérida Andes, about 10 Ma. Slab buoyancy post-detachment likely resulted in recoupling with the overriding plate, reactivation of Jurassic-aged rift structures and subsequent uplift of the Mérida Andes. Mantle counterflow over the broken segment induced by rollback of the attached slab likely contributed to the uplift of the Mérida Andes. We conclude that the northern limit of subduction lies south of the Oca-Ancón fault, though the fault itself may be the surface expression of the boundary. The southern limit of subduction lies south of our study area.