Oslo Region: the Ordovician-Silurian transition

The Ordovician–Silurian transition marked a major taxonomic turnover in marine faunas, particularly within the dominant sessile benthos, the Brachiop-oda. Ecological changes across the boundary were less severe but nevertheless significant. Within the Oslo Region, southern Norway, the Ordovician– Silurian transition is represented by a number of contrasting faunal successions in different environ-mental settings (Baarli et al. 2003), each revealing different aspects of this event. In the central Oslo Region relatively deep-water facies may have formed a refugium for a variety of more typically Ordovician taxa within this part of the basin during the early Rhuddanian (Baarli & Harper 1986). In the northern part of the region tw