Late Ordovician shelly faunas from Jämtland: palaeocommunity development along the margin of the Swedish Caledonides

Abstract

Late Ordovician shelly faunas occur at several localities in the Ostersund area of Jamtland (Sweden) and developed against a background of intense and rapid global climate change. In the eastern part, approximately in the middle parts of the Krykas Quartzite, and in the western part in the uppermost Kogsta Siltstone changes in faunas and sedimentary patterns provide regional evidence of these global events. In both areas the faunas occur in shale and siltstone facies and are used to effect correlations between the eastern and western parts of the region, which show major differences in facies development. These sub-basins, situated on the margins of a developing mountain belt, reacted differently to global signals providing further evidence of the heterogeneous responses to climate change at the end of the Ordovician Period.