Full-Fit Reconstruction of the Central Atlantic Ocean: 3d Crustal Models of Eastern North America and Northwest Africa

A new, full-fit tectonic plate reconstruction is established for the Central Atlantic Ocean. Earlier plate reconstructions applied mappable elements to fit North American and African plates, but few incorporated crustal thinning in their models; instead, relying on simple geometries that limit deformation estimates. Workers also failed to evaluate crustal deformation structures in West Africa, preventing realistic assessments of rifting processes. This study built 3D crustal models of the North American and African margins of the Central Atlantic, constrained by geophysical data, to estimate Moho and crustal thickness via gravity inversion. These 3D crustal models required higher resolution basement surfaces than available. Therefore, basement structure maps were created using the Tilt-Depth Method on magnetic data. Current, open-source magnetic anomaly maps have gaps over northwest Africa, so vintage magnetic stations were incorporated with the open-source data to produce a more complete magnetic anomaly map. In North America, 3D crustal model results suggest narrow Triassic rift basin connectivity along strike (~NE-SW) in the north, but shallow, wide rifts in the southern portion, which are offset along NW-SE striking transfer zones, interpreted as inherited crustal heterogeneities which reactivated based on their oblique orientation to overall Triassic-Jurassic extension direction. In northwest Africa, the 3D crustal model suggests that crustal thinning begins 400 km eastward of the farthest previously interpreted extensional structures. Crustal extension is narrow in the southern and northern parts of this margin, but wide in the central portion, where crustal thickness and basement structures suggest horst and graben like morphology between transfer zones oriented NW-SE. Plate reconstruction results reveal that these zones are parallel to sub-parallel to the transfer zones observed in southern North America, implying they are also reactivated, inherited features of similar origin. Overall, rift geometries and deformation amounts are compatible along strike for the conjugate margins. Using these results, a new, full-fit plate reconstruction model of the Central Atlantic is presented, in which present-day extended continental crust is restored to pre-rift thicknesses and geometries. Based on reconstruction overlaps and gaps, magmatic and/or amagmatic histories are estimated. Sections of the margin characterized by overlaps suggest additional crustal material is present, interpreted as excess magmatic activity during formation. Conversely, gaps along the reconstructed margins suggest missing crustal material, interpreted as mantle exhumation.