SEDIMENTOLOGICAL CHANGES ACROSS THE ORDOVICIAN-SILURIAN BOUNDARY IN HADELAND AND THEIR IMPLICATIONS FOR REGIONAL PATTERNS OF DEPOSITION IN THE OSLO REGION
Cjr. Braithwaite et al., SEDIMENTOLOGICAL CHANGES ACROSS THE ORDOVICIAN-SILURIAN BOUNDARY IN HADELAND AND THEIR IMPLICATIONS FOR REGIONAL PATTERNS OF DEPOSITION IN THE OSLO REGION, Norsk geologisk tidsskrift, 75(4), 1995, pp. 199-218
Basin faulting and global eustatic sea-level fluctuations during the l
atest Ordovician and early Silurian generated new and complex sediment
ation patterns in the Oslo Region. In eastern Hadeland a fall in sea l
evel, possibly in the earliest Hirnantian, resulted in the incision of
channels which were later filled by carbonate debris flows and finall
y became emergent during the period of maximum withdrawal, The drownin
g of these deposits as sea level rose was followed by the deposition o
f storm-dominated shelf-derived carbonate and siliciclastic sediments.
During this period transport was from the north and east. A subsequen
t 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 e
astern pattern of derivation is thought to have been a general feature
of the basin during the late Ordovician and early Silurian.