Morphological expressions of recent and past fluid flow expulsion of the SW Barents Sea

Abstract

ABSTRACT Three 3D seismic cubes (EL0001, St0309 and ST05M09) from different parts of the SW Barents Sea basin were studied to decipher processes causing depressions in the seabed and subseabed. Since the investigated areas were under the influence of various depositional and erosional conditions during ice ages special attention was given to the potential of ice driven morphologies. Depressions identified at the seafloor and at the upper regional unconformity (URU) sub surface vary in shape, size and depth. Their distribution is governed by large scale glacial morphology and deeper fluid accumulation and migration pathways as inferred from seismic anomalies. The formation of fluid flow related depressions could be a result or a combination of both external (glacial erosion and accumulation) and internal factors (gas expansion). Evidence for fluid flow exists in deeper layers and thus fluids could migrate upward along faults and porous sediment strata and spread laterally in upper sediment layers. A second class of depressions exists that is mainly related to glacier driven surface processes in for example subglacial melt-water channels without any obvious relation to deeper fluid sources. Generally, glacial morphological elements influence sediment facies distributions, the thickness of the deposits and therefore the location and frequency of pockmarks and/or pockmark fields. The pockmarks tend to occur inside iceberg-plough marks, mega scale glacial liniations (MSGL), all regions with reduced sediment thickness through which fluids may penetrate more easily. The timing of pockmark creation varies depending on fluid source areas, the thickness of the glacial sediment blanket and ice sheet retreat.