Abstract: Resolution of Lower and Higher Frequency Sequences in Neogene Coastal Deltas, Offshore Mid Norway

Sverre Henriksen, Paul Weimer

Extensive deltaic coastal progradation occurred along the mid-Norwegian continental shelf in the early Pliocene. The deltaic sedimentation is tentatively dated between 5.0 Ma and 4.2 Ma, and constitute a third order highstand system tract above a regional second order flooding surface. Twenty-seven well developed, seismically resolvable, type 1, high frequency sequences are identified within the deltaic unit. Deposition of the high frequency sequences was probably in response to relative high frequency sea level cycles produced by low subsidence, high sedimentation rates and high frequency eustatic cycles within a lower frequency system. A very marked type sequence boundary, formed by the conjunction of lower and higher order falling inflection points, terminates the deltaic coast sed mentation. Further sequence development are of a completely different style and high frequency sequences are generally not resolvable by the seismic system. Increased plate tectonic activity in the Norwegian-Greenland Sea are thought to have been essential in the unique accommodation development needed for the high frequency sequence development in the area. Deposition of the high frequency delta sequences are close in time to the onset of glaciations in the Northern Hemisphere, and glacial conditions on the surrounding land areas have probably contributed significantly to the elevated depositional rates and high frequency sea level changes.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994