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 This contribution addresses the current state of knowledge of the mainly siliciclastic Ordovician rocks in Jordan, Syria and southern Turkey, including advances in palaeontology, stratigraphy, depositional facies analysis and supra-regional correlation. The extensive and excellent exposures of the sedimentary succession in southern Jordan represent the regional reference for the Ordovician System in the southern Levant. We discuss the sedimentological and faunal characteristics as well as the stratigraphy and correlation of the succession. For the northern Levant (especially southeastern Turkey) and the western and eastern Taurides, the Ordovician succession and an updated sedimentary architecture is explained, and a comprehensive correlation for the region is presented. Increased knowledge on the fossil content from these regions enables correlation across the southern parts of the Arabian Plate to southern Turkey, and with the greater Gondwanan regions, far field as southwestern Europe and northern Africa. The depositional environments in the southern and northern Levant and southern Turkey encompass non-marine to shallow-marine areas in the lower part of the Ordovician that are followed upsection by shelf deposits of variable proximity up to the glacial episode in the Late Ordovician that is traceable in each of the areas. Characteristic signals in the Ordovician succession are represented by the trans-regional early Darriwilian unconformity and by the base of the Hirnantian glacial-related deposits followed by lower Silurian strata, visible across the entire region. New data from zircon-based provenance analysis clearly implicate the Arabian Shield as the main source of a huge amount of the clastic detritus within the Ordovician succession. In the course of the entire Cambrian–Ordovician interval, progressive deeper erosion of the Arabian Shield occurred. Sediment sources from regions farther away indicate long time of exposure and resedimentation, and some long-distance transportation, but their sedimentary influence was only of minor extent. The excellent outcrops mainly in southern Jordan, in southeastern Turkey and in the Taurides represent potential regions for further research.

Abstract The Ordovician successions of France and neighbouring areas of Belgium and Germany are reviewed and correlated based on international chronostratigraphic and regional biostratigraphic charts. The same three megasequences related to the rift, drift and docking of Avalonia with Baltica can be tracked in Belgium and neighbouring areas (Brabant Massif and Ardenne inliers), western (Rhenish Massif) and northeastern Germany (Rügen). The remaining investigated areas were part of Gondwana in the Ordovician. The Armorican Massif shares with the Iberian Peninsula a Furongian–Early Ordovician gap (Toledanian or Norman gap), and a continuous Mid–Late Ordovician shelf sedimentation. The Occitan Domain (Montagne Noire and Mouthoumet massifs), eastern Pyrenees and northwestern Corsica share with southwestern Sardinia continuous shelf sedimentation in the Early Ordovician, and a Mid Ordovician ‘Sardic gap’. In the Ordovician, the Maures Massif probably belonged to the same Sardo-Occitan domain. The Vosges and Schwarzwald massifs display comparable, poorly preserved Ordovician successions, suggesting affinities with the Teplá-Barrandian and/or Moldanubian zones of Central Europe.

Abstract This review illustrates the most important features of the Ordovician successions of the Sardinian basement. We focus on the stratigraphy and tectonic structures in the tectonic units of the External and Nappe zones of the Variscan basement. The Ordovician successions are characterized by unconformities related to tectonic events ascribed to the Sardic and Sarrabese phases. The different durations of the unconformity-related gaps in the External (17 myr) and Nappe (6 myr) zones, recent work on the trilobite fossil content, and the occurrence of a volcanic arc only in the Nappe Zone (Sarrabus and Gerrei units) highlight significant discrepancies suggesting that these domains did not share the same geodynamic setting and palaeogeographical position during the Ordovician. This implies they were amalgamated only in Variscan times. Whereas for the external and nappe zones the Ordovician features are clear, the high-grade metamorphic Inner Zone, where numerous Ordovician ortho- and para-gneiss occur, more detailed studies are needed to define a complete framework for the Ordovician evolution of Sardinia. The present revision of data for the best-preserved succession of Sardinian tectonic units suggests that at least two distinct terranes, which did not share the same Ordovician evolution, were only amalgamated during the Variscan Orogeny.

Abstract Deglacial sedimentary sequences recording the decay and final demise of ice sheets result from intricate interactions between the pattern of ice margin retreat, inherited basin physiography and relative sea-level (RSL) changes. A specific emphasis is here given to the glacio-isostatic adjustment (GIA), which may force postglacial local RSL fall in spite of concomitant glacio-eustatic rise. In this contribution, we characterize a Quaternary deglacial succession emplaced in such a setting, subsequently used as an analogue to interpret an end-Ordovician deglacial record. The Quaternary deglacial succession, tens of metres thick, formed under condition of RSL fall forced by the GIA in c. 10 000 years in the aftermath of the deglaciation. This sedimentary succession consists of a lower, fining-upward sequence representing the backstepping of ice-contact depocentres following the retreat of the ice margin, and an upper, coarsening-upward sequence that relates to the subsequent progradation of a glaciofluvial delta system. A very similar stratigraphic stacking pattern characterizes the Ordovician analogue, suggesting a comparable deglacial sequence. By analogy with the Quaternary succession, this ancient deglacial record would have hence been emplaced under conditions of RSL fall forced by the GIA. Moreover, it must only represent a very short time interval that could be viewed as virtually instantaneous regarding the Late Ordovician glaciation. Such a vision is at odds with commonly accepted interpretations for such successions.