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

Abstract Combined U–Pb, Lu–Hf and O isotope data of detrital zircons from the Devonian sandstone of southern Libya provide important new boundary parameters for reconstruction of palaeosource areas and sediment transport and may lead to novel approaches to test current plate tectonic models, with important implications for our understanding of the evolution of northern Gondwana (in present-day coordinates) during the Palaeozoic. Detrital zircon U–Pb ages from Devonian sandstone of the eastern margin of the Murzuq Basin show four main age populations: 2.7–2.5 Ga (13%), 2.1–1.9 Ga (10%), 1.1–0.9 Ga (25%) and 0.7–0.5 Ga (46%). The ubiquitous occurrence of c. 1.0 Ga detrital zircons is characteristic of the Saharan Metacraton sedimentary cover sequence and provides new insights into palaeogeographic reconstructions of Gondwana-derived terranes in the Eastern Mediterranean and SW Europe. The Lu–Hf isotope data suggest that zircons crystallized within a narrow time interval from magmas with heterogeneous Hf isotope compositions. These magmas were derived by melting of pre-existing rocks, rather than being juvenile. The calculated Hf model ages range from 3.7 Ga to 1.3 Ga, with a major population between 2.8 Ga and 1.9 Ga, indicating prominent recycling of Archaean and Palaeoproterozoic crust.