Regional Geophysics of the Caribbean and Northern South America: Implications for Tectonics.

The Caribbean plate is an enclosed oceanic basin whose formation and evolution are controversial. In the most commonly accepted model, the Caribbean plate is mainly composed of the Caribbean Large Igneous Province (CLIP) and the buoyant characteristic of this oceanic plateau resisted subduction and allowed an eastward migration to its present position north of South America. In this study, we integrate a broad range of geophysical and geomorphological data to define structural elements and present‐day tectonics of the Caribbean plate and the surrounding region. We present a Bouguer gravity anomaly map and a new crustal thickness map that documents large areas of normal‐thickness oceanic crust within the Venezuela and Colombia basins of the Caribbean plate. Selected cross sections of seismicity and P‐wave anomalies from a seismic tomographic model depict the present‐day geometry of subducting oceanic plates within the Caribbean region. We observe that rather than resisting subduction, as expected for the thick crust of a buoyant large igneous province, the subduction of the Caribbean plate can be traced to a depth of 600 km beneath NW South America. This, together with the crustal thickness map, implies that a significant area of the Caribbean plate, including the subducted portion, is composed of normal‐thickness oceanic crust. As proposed by the Pacific origin model, the Caribbean plate likely migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism (CLIP). Plain Language Summary: The Caribbean plate and northern South America are studied using topography and multiple geophysical data sets, including gravity, magnetics, crustal thickness, seismicity, and seismic images of the upper mantle. These data sets were used to analyze crustal properties as well as the past and present interaction of tectonic plates in this region. Our results show large areas of ocean crust with normal thickness within the Caribbean plate. Seismicity in the circum‐Caribbean subduction zones rarely exceeds 200 km in depth, whereas seismic imaging shows subducting slabs reach a depth of 600 km or more. This implies that subduction has been long‐lived at these active margins. These results also show that the Caribbean plate is subducting beneath NW South America, something that would not be expected for the thick crust of a buoyant large igneous province. As proposed by the Pacific origin model, the Caribbean plate migrated eastward from the Pacific Ocean as an oceanic plate mostly with normal‐thickness crust and limited portions of the crust thickened by hot spot volcanism. Key Points: A new crustal thickness map and gravity maps reveal large areas of normal‐thickness oceanic crust within the Caribbean plateP‐wave seismic tomography images show that the subducted Caribbean plate reaches 660 km depth, but slab seismicity terminates at 200 kmCombined seismicity, gravity, and magnetic maps reveal the active tectonics of the circum‐Caribbean accretionary and magmatic boundary [ABSTRACT FROM AUTHOR]