Contrasting thermal evolution of the West African Equatorial and Central Atlantic continental margins

Abstract

The landscape of the West African continental margins is the product of tectonic, thermal and surface processes acting in concert during and following the breakup of Gondwana. Central Atlantic opening was marked by the emplacement of the Central Atlantic Magmatic Province (CAMP) and continental breakup proceeded through Late Jurassic and Early Cretaceous divergent tectonics while opening of the Equatorial Atlantic was dominated by early and mid-Cretaceous transform movement. The onshore erosional response to these events is poorly constrained yet is a crucial component of our understanding of topographic evolution and sediment transfer across continental margins. We present new apatite fission-track (AFT) data for 24 samples from Guinea and 11 samples from Ivory Coast, and thermal histories from inverse modelling. Our data and thermal histories show the following: the thermal effect of the CAMP across Guinea and Ivory Coast; rapid cooling along the coast during the early to mid-Cretaceous related to erosion of short-wavelength rift-shoulders; moderate cooling across longer wavelengths reflecting a pattern of erosion across flexural margin upwarps; and low cooling rates from the start of the Cenozoic to present day, consistent with low magnitudes of erosion inferred by onshore geomorphological data. We present our results alongside the published regional AFT dataset and draw inferences on the thermal and tectonic evolution of the onshore margin.