Palaeogeographic and palaeoenvironmental characteristics of major marine incursions in northwestern Europe during the Westphalian C (Bolsovian)

Abstract

The Westphalian C was a time of marked tectonic and climatic changes within the Variscan Foreland, but our understanding of these changes is hampered by a poor appreciation of large-scale palaeogeography and palaeogeographic evolution within this key stratigraphic interval. The distribution of tonsteins, marine bands and faunal occurrences related to marine incursions or the proximity of marine conditions in Britain and on the European mainland during the Westphalian C (Bolsovian) is briefly summarised. The favoured environmental conditions of some selected fossil taxa (Lingula, arenaceous foraminifers, Geisina, conchostracan faunas and Torispora producing tree ferns) are highlighted. A palaeogeographic model shows the relationship between major sedimentary facies belts in the Westphalian C of western Europe and the influence of major marine incursions on the distribution pattern of incursion-related faunas. The frequent succession of transgressive-regressive faunal phases in beds with marine faunas and the close correlation between the distribution of these beds and the distribution of upper delta plain environments in the Westphalian C of northwestern Europe suggest that marine incursions were long-lived, related to glacio-eustatic events, and cannot be regarded as catastrophic « flash floods ».