Evolution of Rifting and Paleobathymetry During the Opening of Central Atlantic Ocean

Summary We examine the rifting history, crustal structure and palaeobathymetric evolution of the conjugate Nova Scotian and Moroccan rifted margins. The deposition of Late Triassic to Early Jurassic evaporites and shallow marine carbonates within rift basins raises questions about the timing and magnitude of continental lithospheric thinning and subsidence history. We apply 3D flexural backstripping and post-breakup reverse thermal subsidence modelling on Jurassic to Late Triassic sequences. Variations in crustal thickness and breakup-related melt production along the margins are calibrated using seismic reflection and gravity anomaly data. Crustal scale sections and stratigraphic-tectonic charts reveal along-strike differences in rifting style and transition from magma-rich to magma-poor breakup. Predicted base salt palaeobathymetry exceeds 2 km in highly thinned distal rifted margins, while it restores to near sea level in weakly thinned proximal domains at the time of breakup. Our interpretation of this is that proximal salt experienced post-rift thermal subsidence only, whereas distal salt deposited during the final rifting underwent both tectonic subsidence from crustal thinning and post-rift thermal subsidence. A period of basin isolation likely occurred in the early stage of the Central Atlantic opening but does not appear to be the primary control on basin bathymetry during salt deposition.