Mid–Late Miocene sedimentation on the southwestern Barents Shelf margin

Abstract

This paper discusses six mid and upper Miocene seismic stratigraphic sequences. The sequences comprises mainly lowstand fans and lowstand prograding complexes whereas the transgressive and highstand systems tracts are largely missing due to erosion. This erosion occurred during mid Miocene to mid Pleistocene periods of low relative sea-level stand and during periods of upper Pleistocene glacial erosion on the Barents Shelf. The mid Miocene sequences are dominated by large submarine canyons, lowstand fan systems comprising both basin floor and slope fans and westward prograding lowstand prograding complexes. Large submarine canyons are closely related to major fault zones west of the Stappen High and not found within the upper Miocene sequences where the margin had a position more than 15 km west of the major faults. The presence of basin floor fans within the mid Miocene sequences indicates input of sand to the basin during falling relative sea-level. The provenance area for sand probably was located northeast of the study area and volcanic basinal highs in the northern parts of the area together with southward flowing deep currents were of importance for the deposition of the basin floor fans west of the Stappen High. Changes within the northern drainage system prior to deposition of the upper Miocene sequences ended the deposition of sandy basin floor fans within the study area. The best hydrocarbon potential are suggested to be within massive sandstones within the mid Miocene basin floor fans. These are overlain by a condensed, mid and upper Miocene section of hemipelagic shales. Other potentials may occur within thick mid Miocene slope fan deposits near the northern submarine canyons. Mid Miocene submarine canyon fills and shallow marine, deltaic/shoreface sandstones within the lowstand prograding complexes may also represent potential reservoirs. However, the preservation potential within these plays is expected to be relatively poor due to shallow depths and upper Pleistocene glacial erosion.