Central Atlantic Ocean-Continent Transition Structure, Continent Ocean Boundary Location and Crustal Type from OCTek Gravity Inversion

Abstract

The determination of continent-ocean boundary (COB) location, ocean-continent transition (OCT) structure and crustal thickness for the continent-ocean margins of the Central Atlantic, and the prediction of their heat-flow history, presents a substantial scientific and technical challenge common to all frontier deep-water hydrocarbon exploration. Using OCTek satellite gravity anomaly inversion, we have produced comprehensive regional maps of Moho depth, crustal thickness, continental lithosphere thinning and oceanic lithosphere distribution for this region and its West African continental margins. These results from gravity inversion provide estimates of COB location which are independent of magnetic isochrons. Crustal cross-sections using Moho depth from OCTek gravity inversion allow continent-ocean transition structure to be determined and provide constraints on their magmatic type (magma poor, “normal” or magma rich).

Superposition of illuminated satellite gravity data onto crustal thickness maps from gravity inversion provides improved determination of pre-breakup conjugacy and post-breakup trajectory of the North American and West African margins. By restoring crustal thickness & continental lithosphere thinning to their initial post-breakup configuration we show the geometry and segmentation of the rifted continental margins at their time of breakup, together with the location of highly-stretched failed breakup basins and rifted micro-continents. Restoration of crustal thickness maps for the Central Atlantic to Jurassic breakup time shows a string of isolated rift basins (and proto-ocean basins) comparable in scale and geometry with the Malawi-Rukwa-Tanganyika-Albert Lakes rift system of East Africa. These restorations indicate that the eastern Canary Islands of Fuerteventura and Lanzarote are underlain by continental crust located at the southern end of a continental sliver (micro-continent) extending northwards which was pulled out of the Moroccan continental margin.

Maps and grids of continental lithosphere thinning (and beta factor) and residual thicknesses of radiogenic continental crust determined from OCTek gravity inversion provide valuable input to petroleum systems basin modelling.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015