Plumbing the Depths of the Caribbean-South American Arc-Continent Collisional Zone Using Long Seismic Reflection and Refraction Transects

Paul Mann¹, Gail Christeson², Alejandro Escalona¹, Alan Levander³, Colin Zelt³, Beatrice Magnani³, Dale Sawyer³, and Michael Schmitz^4
1 Jackson School of Geosciences, The University of Texas at Austin, Austin, TX
² Institute for Geophysics, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX
³ Department of Earth Science, Rice University, Houston, TX
⁴ Seismology Department, FUNVISIS, Caracas, Venezuela

We present five 300-630-km-long transects spanning the northern margin of South America to illustrate large-scale and time-transgressive (65-0 Ma) subduction and collision-related processes. Four out of the five transects merged an offshore profile with an onland prolongation; one transect is entirely marine. Each transect was acquired as a reflection profile recorded to 14 seconds TWT, as a refraction profile using up to 49 ocean bottom seismometers, and as an onshore-offshore profile using up to 550 RefTek receivers. These data reveal the crustal and upper mantle structure of the collided Caribbean arc province with a 27-km-thick crust, a suture zone now occupied by the active right-lateral El Pilar fault zone and characterized by high crustal velocities, and the South American continental margin with a 40-km-thick crust. In addition to these elements, we imaged a slab of the Caribbean seafloor with a crustal thickness of 8-10 km that is subducting as far as 350 km southward beneath the collided arc. We interpret the southward-dipping slab as the product of subduction flipping and continued mid to late Cenozoic convergence between South America and the Caribbean following aborted early Cenozoic northward subduction of thick South American continental crust beneath the arc. The easternmost marine transect shows the structure of the ongoing arc-continent collision with the Lesser Antilles volcanic arc, arc-related basins on the Caribbean plate, the arc-continental suture zone near eastern Trinidad, and the evolving Columbus foreland basin above the flexed continental margin.