The Ordovician record of North and West Africa: unravelling sea-level variations, Gondwana tectonics, and the glacial impact

Abstract The Ordovician of North and West Africa comprises three main transgressive–regressive sequences understood as ‘second-order’ cycles 10–15 myr duration. Tide- to wave-dominated shallow-marine clastic successions, preserving incidental bryozoan carbonates the north, include fluvial deposits over most proximal southern stretches platform. boundary with Cambrian strata remains unclear but latter are progressively less represented south in undifferentiated ‘Cambro-Ordovician’. To graptolites, brachiopods trilobites combined palynomorphs provide a robust biostratigraphic frame. Maximum flooding intervals occurred early middle Tremadocian, Darriwilian late Katian. Two events interfered an overall long-term transgressive trend. ‘intra-Arenig’ (late Floian?) tectonic event highlighted palaeohighs coinciding Paleoproterozoic basements. Gondwanan drainage basins were reorganized, which had impact on sediment sourcing distribution detrital material (e.g. zircons) feeding pre-Variscan Europe. second is end-Ordovician glaciation. domain supported greatest part Hirnantian glaciers may also have preserved pre-Hirnantian glacial archives. It not until very latest that offshore conditions developed far inland; it however suspected this inundation benefited from transient postglacial isostatic flexure.