Arenig-Llandovery stratigraphy and faunas across the Scandinavian Caledonides

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Abstract
Summary: The nature and development of Arenig-Llandovery sedimentary environments is reviewed with reference to 18 allochthonous-parautochthonous sections in the Scandinavian Caledonides. The faunas suggest that age constraints are imprecise, and direct correlations with sequences on the adjacent platform are difficult. However, it is possible to recognize a northerly transition from near-shore to offshore facies on Hardangervidda and a platform to slope transition in Jämtland and E Jotunheimen during the early Ordovician. There is no direct evidence of a distinct Finnmarkian orogenic event (late Cambrian-early Ordovician) in the lower Allochthon, while the central Scandinavian upper Allochthon, containing N American shelly fossils, has a pre-Caradoc history far removed from that of the Baltic platform. In the Bergen area no fossils older than Ashgill age are known and the youngest marine rocks are early Llandovery. Locally-important features of the platform sequences, including breaks in sedimentation, the deposition of bentonites, basement faulting and the early termination of marine sedimentation (late Llandovery in the N and W), cannot be directly related to discrete tectonic events in the orogen.