Shortening, Exhumation, and “Flip” in Tectonic Vergence of the Cordillera Central and Southern Dominican Republic

In a subduction zone, variability in the buoyancy and structure of the downgoing plate impacts deformation patterns in the overriding plate. Thick and buoyant lithosphere or smaller-scale indentors entering the trench can lead to significant relief development and exhumation. To investigate such processes, we target the Cenozoic reorganization of the Northern Caribbean Plate Boundary (NCPB), hosting sequential episodes of subduction, backarc underthrusting, and ridge impingement. The island of Hispaniola was at the locus of the reorganization, resulting in transpressional deformation and the formation of mountain chains with peaks up to 3 km. To reconstruct the deformation and exhumation phases that shaped the NCPB, we apply zircon and apatite (U-Th)/He thermochronology, U-Pb geochronology, and 1D thermal history modeling to samples gathered in the Cordillera Central and southern sierras of the Dominican Republic portion of the island. Our results constrain three main cooling sequences: (a) (Formula presented.) 100–50 Ma: magmatic emplacement during intra-arc strike-slip and subsequent cooling; (b) (Formula presented.) 50–20 Ma: SW-directed continental impingement and change in plate motion leading to backarc thrusting and accelerated exhumation of the arc in the axial zone of a NE-SW bivergent structure (rates (Formula presented.) 1.7 mm/yr); (c) (Formula presented.) 20 Ma-present: progressive NE-directed impingement of the Caribbean Large Igneous Province leading to a southward “flip” in tectonic vergence and focused exhumation, climaxing from (Formula presented.) 5 Ma-present with a ridge indentation event (rates (Formula presented.) 1.5 mm/yr). This two-sided impingement scenario led to the highly segmented present-day plate configuration through the formation of large-scale strike-slip and thrust fault systems that remain active to the present day.