Testing Models of Caribbean Tectonics in Global and Regional Contexts

Abstract

Two distinct end member models have been proposed to explain Caribbean tectonics: an in situ model and a Pacific-derived model. The in situ model interprets the crust underlying the Caribbean Plate as stretched, thinned and attenuated continental crust, which was deformed as a consequence of the break-up of Pangaea. In a Pacific-derived model, the Caribbean Plate is underlain by oceanic crust and plateau basalt which originate in the eastern Pacific Ocean and become trapped between the American continents as a consequence of their westward drift during the opening of the Atlantic Ocean. The Pacific origin model may exclude the possibility of Cretaceous age source rocks, equivalent to those found onshore Colombia and Venezuela, extending to the deep offshore. In this paper we test the end member hypotheses for Caribbean tectonics in the context of a Global Plate Model that includes high-resolution tectonic reconstructions for the South and Equatorial Atlantic and for Gulf of Mexico regions. The Global Plate Model was constructed using marine gravity and magnetic data to constrain crustal architecture, COBs and plate motion paths for large continental plates during the break-up of Pangaea and by using onshore geological and geophysical relationships to constrain the motion of smaller terranes. High-resolution regional tectonic models (including detailed structural analysis, 2D potential field profiles and crustal models, along with public-domain seismic data) were incorporated into the Global Plate Model. We constructed a model for each end member hypothesis using the constraints on geometry, space and timings provided by the Global Plate Model (particularly the motion of North America relative to South America during the formation of the Atlantic Ocean and the formation of oceanic crust in the Gulf of Mexico). While models representing both end members can be constructed, a Pacific origin model fits better within the global plate circuit as it does not require long-lived (>100 My) phases of continental extension with high stretching factors; it also better explains the subduction-accretion geology onshore in northern South America and is supported by tomographic evidence of up to 900 km of subducted oceanic crust beneath Colombia. Our models do not discriminate between variants of the Pacific-derived model, such as the origin of large igneous province like basalts and the timing of subduction reversal between the Pacific and proto-Caribbean regions.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016