Pan-African tectonic evolution and glacial events registered in Neoproterozoic to Cambrian cratonic and foreland basins of West Africa

Abstract This paper attempts to describe the Neoproterozoic–Cambrian lithostratigraphic successions occurring on the West African craton and in the surrounding Pan-African fold belts, with special reference to glacial or glacially influenced deposits. It provides a brief synthesis of these terrains in order to propose inter-regional correlations, and to place the glacial events already described in the literature within the tectonic framework of this part of the world. Correlations are based on facies associations and isotopic databases, and supported by the occurrence of glacial deposits when these are ascribed to continental-scale glaciation. As expected, there is a diachronism of the main tectonic events around the craton when the mobile belts display a roughly similar overall facies trend reflecting the successive stages of the Pan-African orogenic cycle from rifting to collision. Contrary to most of the Neoproterozoic glacial strata elsewhere, which consist generally of marine diamictites preserved in marginal basins, West Africa displays the cratonic counterpart (tillites and associated terrestrial facies) deposited on exposed land surface by continental ice sheets. Lithostratigraphic correlations and a combination of relative dates on sedimentary rocks and on tectonic markers show that a major West African glaciation occurred between 630 and 610 Ma and can be correlated with the Marinoan ice age. This major climatic event is contemporaneous with the final stages of the Pan-African orogenic cycle. Under favourable climatic conditions (mid to high latitudes), the presence of surging reliefs at the rim of a wide cratonic platform may account for the development of the West African Marinoan ice sheet. The diachronism around the craton of collision-surrection events may also account for the occurrence of unrelated local mountain-type glaciation that could be mistaken with the craton-scale glaciation.