Sun, Sea and Sand; Cretaceous Source to Sink Systems of Senegal, NW Africa

Abstract

Paleo source to sink system analysis requires a complete earth systems model approach, utilising regional geology, tectonics, climate and modern-day source to sink analogues. This study examines the Cretaceous source to sink systems of Senegal, NW Africa, integrating a broad regional dataset using a multidisciplinary mineralogical approach. The most significant regional geological and tectonic events to affect Senegal since the Pan-African Orogenies (800–520 Ma) are the Hercynian Orogeny (320–290 Ma), Pangea break-up and rifting between S. America and Africa, with associated Central Atlantic Magmatic Province volcanism (200 Ma) and uplift of the Mauritanide hinterland (113–66 Ma). In addition to tectonic controls, climate is the principal driver for paleo-drainage reorganisation. During the Cretaceous an antithetical shift in climate from warm and arid (145–115 Ma), to hot and humid (100–88 Ma), increased fluvial catchment and energy. Antecedent paleo-drainage of the Cretaceous Senegalese Basin is governed by subsurface grabens striking hundreds of kilometres into the continent formed during Atlantic rifting. Early Cretaceous aridity restricted fluvial catchments to recycling pre-Cretaceous basinal sediments. Climate change triggered expansion of paleo-drainage catchments during the Aptian caused fluvial incision and erosion of the Gaouâ Group Hercynian to Pan-African age source rocks along the western flank of the Mauritanides. Exhumation increased significantly throughout the Cretaceous Thermal Maximum during the Cenomanian–Turonian, with exhumation of the Gadel Group Pan-African source rocks, evidenced from a shift between a garnetiferous to staurolitic basin mineralogy. Inclusion of 200 Ma zircons into the central Senegalese Basin during the Albian is evidence of possible catchment shifts to include CAMP detritus from the Fouta Djallon Plateau. Cretaceous basinal sediments are almost exclusively sourced from the Mauritanide belt which includes Hercynian metamorphic host rocks and Palaeozoic sediments ultimately derived from the erosion of the Pan-African orogenic belts. During the Maastrichtian, the central fluvial systems breached the southern Mauritanides, sourcing Cambrian zircons from the south.