High palaeolatitude (Hodh, Mauritania) recovery of graptolite faunas after the Hirnantian (end Ordovician) extinction event

Marine shales directly overlying lower Hirnantian (uppermost Ordovician) glacially related sediments in Mauritania (North-West Africa) have produced a rich graptolite fauna spanning the Ordovician-Silurian boundary in an area of high palaeolatitude. The lowermost transgressive sandy shales are barren of graptolites, but overlying shales show a sudden appearance of a diverse fauna indicative of the terminal Ordovician persculptus Zone, suggesting that with improving conditions, colonisation by a relatively cold-tolerant fauna was possible. This fauna is replaced by a low diversity assemblage dominated by long ranging taxa, probably representing the basal Silurian acuminatus and atavus Zones. With the extinction of the persculptus Zone fauna, conditions were still hostile to warm water Silurian graptolites, and a Normalograptus fauna was again established. A sudden influx of fairly diverse taxa marks the base of the acinaces Zone and the establishment of a typical Lower Silurian fauna with the establishment of warmer water conditions

The Ordovician of France and neighbouring areas of Belgium and Germany

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 compa-rable, poorly preserved Ordovician successions, suggesting affinities with the Teplá-Barrandian and/or Molda-nubian zones of Central Europe.This paper is a contribution to the International Geoscience Programme (IGCP) projects 653 "The onset of the Great Ordovician Biodiversification Event" and 735 “Rocks and the Rise of Ordovician Life: Filling knowledge gaps in the Early Palaeozoic Biodiversification". The authors are particularly grateful to Annalisa Ferretti, David A.T. Harper and Petr Kraft for their careful and constructive reviews, comments and suggestions, which greatly improved the quality and relevance of the paper