Shallower structure and geomorphology of the southern Puerto Rico offshore margin



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Granja Bruña, José Luis and Ten Brink, Uri S. and Muñoz Martín, Alfonso and Carbó Gorosabel, Andrés and Llanes Estrada, Pilar (2015) Shallower structure and geomorphology of the southern Puerto Rico offshore margin. Marine and Petroleum Geology, 67 . pp. 30-56. ISSN 0264-8172

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Oblique convergence between the North American and Caribbean plates along the eastern Greater Antilles island arc has yielded the asymmetric Muertos thrust belt in the backarc region. Offshore south of Puerto Rico, this thrust belt disappears and is replaced by a succession of NEeSW- and EeW-trending deep basins and steep ridges that characterize the western Anegada passage, resulting in a complex deformation pattern. Using new high-resolution multibeam bathymetry and seismic reflection profiles, we studied the geomorphology and shallower structure of the southern Puerto Rico offshore margin. We have identified four morphotectonic provinces: the Puerto Rican sub-basin and Muertos trough, the Muertos margin, the insular shelf and the western Anegada passage. The Muertos margin province shows two distinct slope sub-provinces: the active Muertos thrust belt e which includes lower and upper thrust belts with distinct deformational styles and lateral continuity e and the shelf slope highly-incised by a dense canyon network. This network is disrupted by the Investigator fault zone consisting of a 130 km-long EeW-trending band of active extensional deformation. The Investigator fault zone shows differential surface expression caused by along-strike changes in the magnitude and distribution of the deformation, though this deformation is driven by a NeS-oriented extension. In the western Anegada passage province, the Whiting basin and Whiting and Grappler ridges are formed by large dip-slip normal faults driven by a NWeSE-oriented extensional regime. The western St. Croix rise shows a complex structure where the NEeSW-trending NW-dipping normal faults observed at the summit of the rise predate the EeW-bounding faults that could accommodate the extensional deformation at the Present. This study provides detailed observations on the active tectonic and sedimentary processes to help future studies assessing the natural resources and the seismic and tsunamigenic hazard in the Puerto Rico region.

Item Type:Article
Uncontrolled Keywords:Caribbean plate, Puerto Rico, Thrust belt, Accretionary system, Imbricate structure, Normal faults, Block tilting
Subjects:Sciences > Physics > Geophysics
Sciences > Geology
Sciences > Geology > Geodynamics
ID Code:33036
Deposited On:21 Sep 2015 08:38
Last Modified:22 Sep 2015 10:22

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