Basin faulting and global eustatic sea-leve! fluctuations during the latest Ordovician and early Silurian generated new and complex sedimentation patterns in the Oslo Region. In eastern Hadeland a fall in sea leve!, possibly in the earliest Hirnantian, resulted in the incision of channels which were later filled by carbonate debris flows and finally became emergent during the period of maximum withdrawal. The drowning of these deposits as sea level rose was followed by the deposition of storm-dominated shelf-derived carbonate and siliciclastic sediments. During this period transport was from the north and east. A subsequent gradual shallowing culminated in local emergence. The early Silurian was marked by new shelf-flooding and by the delivery of siliciclastic sediments, again from the east. In contrast with earlier models, an eastern pattern of derivation is thought to have been a general feature of the basin during the late Ordovician and early Silurian.

C. J. R. Braithwaite & A. W. Owen, Department of Geology and Applied Geology, The University of Glasgow, Glasgow G12 8QQ, Scotland;
Rachel A. Heath, 4 Lammerton Terrace, Dundee DD4 7BW, Scotland.