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Due to tectonic uplift in the Cenozoic and numerous shelf-wide glaciations during the Quaternary, -1-2.5 km of sedimentary overburden has been eroded from the Barents Sea shelf, leading to the exhumation and partial uncapping of hydrocarbon accumulations. Widespread natural gas and oil leakage from the glacially eroded middle-upper Triassic reservoir directly into the water column has been documented at the Sentralbanken high in the northern Norwegian Barents Sea. However, it remains unclear whether the hydrocarbon leakage occurs only from the middle-upper Triassic reservoir units in geological settings exceptionally conducive to hydrocarbon leakage, or if other reservoir formations contributed to the release of hydrocarbons into the water column. It is also not clear whether complete erosion of the caprock is a prerequisite for widespread liberation of natural gas and oil from glacially eroded reservoirs across Arctic continental shelves. Here we analyze multibeam echosounder data covering -5,000 km2 and a suite of high-resolution P-cable seismic lines from a range of geological structures across the northern Norwegian Barents Sea. Our analyses reveal that -21,700 natural gas seeps originate from exhumed, faulted and variably eroded structural highs bearing a range of Mesozoic reservoir formations. All investigated structural highs fuel seabed methane release hotspots with no exception. Evident from observations of seismic anomalies, fluid accumulations are pervasive in the subsurface and likely to continue fuelling seabed gas seepage into the future. We also document that gas seepage through faults piercing overburden, caprocks and reaching potential reservoir levels is pervasive at all investigated structural highs. On the Storbanken high and the Kong Karl platform, such fault-controlled seepage is more prevalent than seepage from reservoir formations subcropping below the seafloor. Using a simple parametrization approach, we estimate that seeps identified within our multibeam data coverage produce a seabed methane flux of 61 x 107 mol/yr (9,803 ton/yr), which is one to two orders of magnitude higher than other globally known submarine methane seepage provinces. Fluxes of methane from sea water to the air above the thermogenic gas seep provinces in the northern Norwegian Barents Sea remain to be determined. [ABSTRACT FROM AUTHOR]

The late Pliocene-Pleistocene paleoenvironment has been reconstructed based on three-dimensional seismic data from the southwestern Barents Sea continental margin. During the late Pliocene-early Pleistocene, continental slope sediments were predominantly deposited from meltwater overflows and underflows. The seismic stratigraphy of the early-middle Pleistocene shows both glaciomarine sediment input from channelized meltwater discharge and the first indications of large debris-flow deposits on the continental slope, originating from input of subglacial deformation till eroded and transported by ice streams. During the middle-late Pleistocene, large debris flows dominated the slope succession. From the above results we infer the following evolution in the Barents Sea: (1) a temperate Barents Sea Ice Sheet with channelized meltwater flow developed during the late Pliocene-early Pleistocene; (2) alternating glacial periods of ice with channelized meltwater flow and the first periods of ice, including ice streams, characterized the early and middle Pleistocene; and (3) more polar ice conditions and a Barents Sea Ice Sheet that mainly included large ice streams, with little or no channelized meltwater flow, occurred in the middle and late Pleistocene. doi: 10.1130/G30193.1

Three-dimensional seismic data from the southern flank of the outer Bear Island Trough at the western Barents Sea margin show former ice-stream activity; the interpretation of such activity is based on megascale lineations and long chains of megablocks and rafts buried in thick till units between glacially eroded horizons. In several units the sediment blocks and rafts are aligned in chains up to 2 km wide and 50 km long. Individual megablocks have an areal extent of up to 2.2 [km.sup.2] and their internal structure is well preserved, providing information about the processes involved in their incorporation into the ice, subsequent detachment, and partial disintegration. Previous discussions of sub-ice-stream processes have focused on ductile deformation of weak sediments and molding of subglacial landforms. This work also demonstrates the importance of brittle sediment deformation in these settings, adding to the understanding of ice streams as agents of glacial erosion, transport, and sedimentation. Keywords: ice-stream erosion, brittle sediment deformation, chains of megablocks and rafts, megascale glacial lineations, three-dimensional seismic data, Barents Sea.