Abstract

UGHI, Antonio. Gravimetric survey of the cortical structure in the Grenade basin and the Lesser Antilles. Rev. mex. cienc. geol [online]. 2012, vol.29, n.2, pp.432-449. ISSN 2007-2902.

The Grenada basin is a geological structure that separates the Aves swell form the Lesser Antilles; it has a concave shape with 140 km width and 600 km length. Several geodynamical models have been proposed to explain the opening and later formation of the Grenada basin, based on magnetic anomalies, geological data, gravity and deep seismic data. There is a broad range of alternative models to explain the opening of the basin, which consider north-south or east-west orientations, through all intermediate options. An alternative model considers that the Grenada basin formed as result of the rollback of the Atlantic slab to the east and then the primitive basin was intruded by the Lesser Antilles island arc separating the Grenada and Tobago basins (Christeson et al., 2008, J. Geophys. Res., 113,1-19; Aitken et al., 2011, Marine and Petroleum Geology, 28(1), 235-258). In this research I used enhanced altimetric gravity, topography and bathymetry data to develop gravity models along profiles crossing the Caribbean - Atlantic subduction zone. The obtained results show evidence of cortical structures associated with the migration of the island arc to the east. The cortical blocks are also visible as a cortical prolongation of the Lesser Antilles linked to the cortical basement of the Leeward Antilles and Margarita Island. The Margarita Island appears to be the most southern superficial morphological expression of the Lesser Antilles island arc.

Keywords : Lesser Antilles; Grenada basin; subduction; tectonics; geodynamics.

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