SEISMIC FACIES OF THE PERMIAN SECTION OF THE BARENTS SHELF - ANALYSIS AND INTERPRETATION

The Palaeozoic succession of the Barents Shelf has been investigated with data from only a few wells. However, a considerable amount of high-quality seismic data complements the sporadic well control, permitting an extensive seismic study of the three major intervals distinguished in the Permian section. The lowermost Interval I consists of an evaporitic sequence. Both vertical and horizontal gradations of the seismic facies are recognized and interpreted in terms of basin evolution. In the centre of the basin, a lower unit characterized by high-amplitude parallel reflections grades upwards to a mounded reflection-free upper unit. The mounds are interpreted as salt pillows overlying a lower unit with lithology dominated by anhydrite. A rather thick evaporite interval in basinal setting passes laterally to a mixed carbonaceous-anhydritic section on the margins and basinal highs. The thickness distribution and the areal extent of the seismic facies provide information on the configuration of the evaporite basin, on syn-sedimentary tectonism and on evaporite diagenesis. As a result of renewed transgression, the overlying Interval II was deposited in open-marine conditions on a shallow shelf. Belts and patches of seismic mounds, interpreted as carbonate build-ups, are widely spread on the basinal highs and on the basin margins. Depositional environments are inferred from the distribution of build-ups. During the progressive drowning of the shelf, a back-stepping belt of seismic mounds were deposited on the southern basin margin. This transgressive episode, which constitutes Interval III, culminated in the generalized deposition of deep-water facies. © 1990.