Quaternary deformation and uplift of coral reef terraces produced by oblique subduction and underthrusting of the Bahama Platform below the northern Hispaniola forearc

Abstract

Active tectonics linked to the rise of the Hispaniola forearc explain the morphological characteristics, spatial distribution and U-Th geochronological ages of the uplifted coral reef terraces of the La Isabela Formation in both the eastern Cordillera Septentrional and the Samaná Peninsula of northeastern Dominican Republic. Depositional coral reef terraces of MIS 5e (TII), 7e (TIII) and 9 (TIV) stages occur respectively at maximum heights of about 25 m, 80 m and 120 m above the current sea level. The development of heterogeneous brittle deformation structures in the coral limestone at all scales document active tectonics and include small faults, shear fractures, extensional joints and calcite veins. Their geometric and kinematic characteristics, as well as the stress tensors calculated from fault-slip and fracture orientation data, are all compatible with ENE to NE-trending regional shortening, and indicate that a left-lateral transpressive regime is deforming the forearc during the Quaternary.Along the northern Hispaniola coastline, the tectonic uplift mimics the distribution of the bathymetric features on the subducting Bahamas Platform, outboard the Hispaniola-Puerto Rico Trench. The highest calculated uplift rates in the eastern Cordillera Septentrional and Samaná Peninsula correspond to the collision zone of the Silver Spur and Navidad Bank (≥0.4 m/ka), respectively. Uplift rates decrease towards the west (≤0.2 m/ka), where the oblique collision of carbonate ridges and related forearc deformation would not have been recorded since at least the Early Pleistocene. Oblique subduction and underthrusting of the Bahamas Platform followed by basal erosion at the subduction channel explain the observed time-transgressive pattern of uplift and subsidence in the northern Hispaniola forearc and the change from accretionary to erosive processes in the convergent margin.