Ordovician sedimentary facies and faunas of southwest Europe: palaeogeographic and tectonic implications

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Abstract
The term st European Platform is introduced for an Ordovician shelf now within the western Variscides. The geometry of the sedimentary facies belts and their faunal variation suggest that it formed a promontory on the Gondwanan margin. The palaeogeography of the platform is discussed with particular reference to the Centro-Iberian/Armorican area, especially central Portugal. The sedimentary history of the Centro-Iberian/Armorican area was controlled by basement structures. Rapid local subsidence during Early Ordovician extension was followed by later differential subsidence along these early structures. The thin sequences indicate low overall rates of subsidence. The dominantly clastic shallow marine sediments show strong storm influence. Individual sediment packets occur over wide areas indicating little syndepositional relief. The linear nature of facies belts allows reconstruction of the relative orientation of some blocks within the Variscides, and indicates strike-slip faulting during early Variscan events, with subsequent (Carboniferous) rotation of most of Iberia. Faunas from SW Europe from a homogeneous group related to those of the classic 'Mediterranean Province' areas of Bohemia and Morocco, and more distantly to those of the Avalonian terrane. Faunal migration into the West European Platform from Avalonia accompanied progressive northward drift of the platform, occuring particularly during periods of eustatic sea-level rise in the early Llanvirn, the early Caradoc and the early Ashgill