Cenozoic Tectonics of Central Hispaniola and Adjacent Caribbean Sea

Abstract

ABSTRACT Seismic reflection profiles across the island margin south of the Dominican Republic indicate the presence of geologic structures similar to structures in the forearc regions seaward of Pacific island arcs. The thick, mildly deformed Tertiary section in San Pedro Basin south of Santo Domingo is separated from the highly deformed sediments of the north slope of the Muertos Trench by an anticlinal ridge. San Pedro Basin is homologous to numerous forearc basins bounded seaward by structurally high trench-slope breaks. The transition landward from subsiding San Pedro Basin to rising Llanos Costeros del Seibo is homologous to the upper-slope discontinuity present in many Pacific arcs. Structures within the sediment wedge beneath the north slope of the Muertos Trench that have homologs in Pacific trench inner slopes include trench-floor turbidite fill, landward-tilted ponded terraces, landward-dipping internal reflections, and a landward continuation of ocean crust beneath the sediment wedge. The northwest-southeast trending basins and ridges parallel with the Cordillera Central in central Hispaniola may be caused by compression between the Beata Ridge and the Bahama platform. These compressional basin-and-ridge structures die out eastward in Hispaniola where thinner ocean crust apparently under-thrusts Hispaniola from the south. Right-lateral offset along the northeast-trending Beata Ridge lineament may explain the pattern of central Hispaniola mountain ridges terminating eastward against subsiding basins, and vertical offset along the same lineament may explain the topographic and structural rise from the Venezuela Basin westward up to the east flank of the Beata Ridge. The basin-and-ridge structure of Hispaniola has probably developed in a manner similar to the basin-and-ridge province of southern California which has formed as a consequence of shear along the San Andreas fault.physiographic provinces of the Venezuela Basin and Colombia Basin separated from each other by the southwest-trending Beata Ridge (Fig. 1). South of the Dominican Republic the sea floor slopes down to the Muertos Trench (Fig. 2A), which is the northern edge of the floor of the Venezuela Basin. At its western end the Muertos Trench curves northwestward and dies out as a bathymetric feature against Barahona Peninsula, but the structural expression of the trench on the seismic sections discussed in this report extends northwestward into the Bahia de Azua (Peter Goreau, personal commun., 1978) on strike with the Enriquillo Basin. Higher on the insular slope the bathymetric contours define a basin which we call San Pedro Basin bounded on the east by Isla Saona and on the west by a southward extension of the Cordillera Central to Punta Palenque (Fig. 2A). San Pedro Basin is partly bounded on the south by two submarine topographic ridges—one extending southeast from Punta Palenque and the other extending southwest from Isla Saona (Fig. 2A).