The Ordovician of France and neighbouring areas of Belgium and Germany

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.

Ordovician sedimentation and basin development in the North Armorican Massif, NW France: Field evidence from the northern Cotentin Peninsula

“…Water depth may, likewise, be inferred to increase northwards. This is an interpretation different to that currently in place for the Ordovician of the whole Armorican Massif which suggests water depth increased southwards (Lefebvre et al 2023). It is stressed the revised interpretation of northwards deepening is only for the North Armorican Massif which was probably separated from the Central and South Armorican massifs by 100's to 1000's km at the time of deposition (Fig.…”

“…The variations in thickness and minor conglomerate beds seen in the initial Ordovician deposits of both the north and central sectors of the Armorican Massif are explained by the sediment thinning onto erosionally modified precursor relief, rather than as tectonically active rift-fills. Rising sea levels associated with steady thermal subsidence resulted in the back-fill of valleys, initially with locally sourced conglomerate, sand and mud (initial red beds), and subsequently with mature sand sourced from Gondwana (the Grès Armoricain) (Noblet & LeFort, 1990; Dabard et al 2021; LeFebrevre et al 2023).…”

“…They include sharp changes in sediment thickness (this study) indicating more than 300 km lateral displacement, and detrital zircon studies which point to separate source areas for the Ordovician of the Central and North Armorican Massifs (Dabard et al 2021). These data highlight that the Central Armorican Massif and North Armorican Massif were not contiguous blocks in the Ordovician, and moreover, they were likely to have been separated by many 100’s to 1000’ km (Lefebvre et al 2023). For this reason, the current study restricts interpretation of the Cambrian and Ordovician strata to those rocks of the North Armorican Massif.…”

“…Some favour a scenario, which envisions the opening of three oceans in the Ordovician, the Rheic, Conquet-Tepla and Medio-European (Faure et al 2005; Ballèvre et al 2009; Ballèvre et al 2012; Faure & Ferrièr, 2022). Furthermore, regardless of the preferred model, many authors view the rift-drift phase of ocean development, to have occurred entirely within the Ordovician (Brun et al 1991; Robardet et al 1994; Ballèvre et al 2012; Dabard et al 2021; LeFebrevre, 2023).…”

The Ordovician System: Key concepts, events and its distribution across Europe

“…Scotese (2023) has provided a new global sea-level curve. Many authors have included regional sea-level curves in their chapters, with such curves available for Bohemia (Kraft et al 2023), East Baltic (Meidla et al 2022, western France (Lefebvre et al 2023), the Laurentian margin in Scotland (Molyneux et al 2023) and Sardinia (Loi et al 2022).…”