Underthrusting of the Eastern Margin of the Antilles by the floor of the western North Atlantic Ocean, and origin of the Barbados Ridge

Two seismic reflection profiles of the southeastern end of the Puerto Rico trench show that the strata forming the ocean floor, including the oceanic basement, dip westward beneath the eastern flank of the Antilles arc. Farther south a profile across the eastern margin of the northern end of the Barbados ridge shows a similar westward dip of oceanic strata beneath the ridge and suggests that thrust faults dipping 20°–30° west cut the overlying sediments that form the east flank of the ridge. Similar thrust-faults appear in a profile southeast of Barbados. The evidence from the reflection profiles is compatible with seismological and magnetic evidence that suggests that the ocean floor is spreading west from the mid-Atlantic ridge and is being thrust westward beneath the Antilles. The Barbados ridge is composed of sedimentary material that formerly formed a continental rise overlying the oceanic crust along the northern margin of South America. Thrusting of oceanic crust beneath the Lesser Antilles arc and displacement of South America westward relative to the Antilles during the Cenozoic resulted in the crumpling, thickening, and accumulation of the material of the continental rise in front (east) of the Antilles arc to form the Barbados ridge.