Submarine morpho-structure and active processes along the North American-Caribbean boundary plate (Dominican Republic sector)

Abstract

Oblique collision between the Bahamas Carbonate Province and the Hispaniola island arc accompanied by underthrusting are being recorded along the northern margin of Hispaniola. That oblique convergence is the primary cause of major devastating earthquakes and tsunamis affecting the north-eastern Caribbean. Using new swath multibeam bathymetry data and vintage single- and multi-channel seismic profiles, we have performed the analysis and interpretation of the shallow surface and active processes along the northern margin of the Dominican Republic. We have identified three morphotectonic provinces: the Bahamas Banks, the Hispaniola Trench and the Insular Margin, which are divided into two tectonic domains; the Collision Domain and the Underthrusting Domain. The southern slope of Bahamas Banks Province shows a very irregular morphology produced by multi-scale active erosive processes and gravity failures, indicating an extensional tectonic regime and margin collapse. This collapse is larger in the Collision Domain where there are longer erosive and fault escarpments with higher dip-slip throws. The Hispaniola Trench Province, formed by the extended Caicos and Hispaniola basins in the Underthrusting Domain and by the isolated SantÌsima, Trinidad, and Navidad basins in the Collision Domain. The trench floor have a flat bottom with a sedimentary fill of variable thickness consisting of horizontal or sub-horizontal turbiditic levels. The turbiditic fill is mostly sourced from the Hispaniola island arc through wide channels and canyons which transports sediment from the shelf and upper slope. The Insular Margin Province comprises the Insular Shelf and the Insular Slope sub-provinces. The active tectonic processes observed on the Insular Slope have been developed in the context of the Northern Hispaniola Deformed Belt. This deformed belt shows a very irregular morphology, with a WNW-ESE trending north-verging imbricate fold-and-thrust system. This system is the result of the accommodation of the oblique collision/underthrusting between the North American and the Caribbean plates. In the Underthrusting Domain, the along-strike shape of the imbricate system is highly variable in map view forming broad salients and narrow recesses. This variability is due to along-strike changes in the sediment thickness of the Hispaniola Trench as well as the variable topography of the underthrusting Bahamas Carbonate Province. In the Collision Domain the morphology of the Insular Slope and the development of the deformed belt show significant differences. Here, the imbricate system is barely visible and lies in the upper slope. These changes are due to the active collision of Bahamas Banks Province with the Insular Margin and the partial closure of the Deformation Front south of the Navidad Bank. Throughout the entire area studied, multi-scale gravitational instabilities have been observed, especially on the Insular Margin Province and to a lesser extent on the southern slope of the Bahamas Banks Province. These instabilities are a direct consequence of the active underthrusting/collision process. We mapped large individual slumps north of Puerto Plata in the Underthrusting Domain and zones of major slumps in the Collision Domain. All the above observations of active deformation have to be considered in future studies of the assessment of seismic and tsunami hazards in the region.

AAPG Datapages/Search and Discovery Article #90330©2018 AAPG Hedberg: Geology of Middle America – the Gulf of Mexico, Yucatan, Caribbean, Grenada and Tobago Basins and Their Margins “Integration of the geology of the area from the southern onshore of North America to the northern onshore of South America”, Siguenza, Guadalajara, Spain, July 2-5, 2018