Abstract
The Imsdalen Submarine Fan Complex is a gravel and coarse sand dominated turbidite fan system. The fan complex was deposited in the Neoproterozoic Hedmark rift basin close to a basin margin bordered by the Imsdalen Fault. The Imsdalen Fault is supposed to be inherited
from a syn-sedimentary strike-slip fault zone that was reactivated during the Caledonian nappe emplacement.
Ten sedimentary logs cover a stratigraphic section more than 4 km thick. Thirteen facies have been organized into five facies associations, representing architectural elements including
base-of-slope to upper fan feeder channel complex, upper fan distributary channel complex, middle to lower fan channel-lobe complex, fringed sheets, and fi ne-grained overbank and
basin-plain deposits. The Imsdalen Submarine Fan Complex is divided into eleven fan systems, separated by erosional surfaces, interpreted as sequence boundaries, except for the boundary at the base of fan 6, interpreted to be a maximum fl ooding surface. Overall, the eleven fan systems form a turbidite succession that records a long history of aggradation to retrogradation, as shown by the fans 1 to 8, followed by a phase of marked progradation, displayed by the fans 9 to 11, from middle to lower, to upper fan positions. It is suggested
that the main factor in control of the development of the Imsdalen Submarine Fan Complex was related to fault activity at the basin margin and sediment supply.
The Imsdalen Submarine Fan Complex shows that gravity fl ow processes have the capacity and competence to transport huge amounts of coarse sand and gravel at least 40 to 60 kilometres into a deep-marine basin. The long transport distance of the coarse-clastic
material is interpreted as a result of the combined effects of very high rates of coarseclastic sediment supply, high potential energy along the submarine slope, high slope gradient, creation of accommodation due to high rate of basin subsidence, channelized transport, and effective mechanisms of clast support in the gravity fl ow system. These observations suggest that the high and low effi ciency concept of submarine fan systems, as a function of grain
size distribution of the available sediment should be modifi ed.