--> Carboniferous Graben Structures, Evaporite Accumulations and Inversion in the Southeastern Norwegian Barents Sea

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Carboniferous Graben Structures, Evaporite Accumulations and Inversion in the Southeastern Norwegian Barents Sea

Abstract

2D regional seismic reflection profiles and well data are used for the investigation of the deep basin architecture in the southeastern Norwegian Barents Sea. The study area contains thick upper Paleozoic to Mesozoic sedimentary strata with prominent structural features comprising the Haapet, Veslekari, and Signalhorn domes; the Tiddlybanken Basin, Fedynsky High, and eastern Finnmark Platform. Interpretation of selected seismic profiles and time-structure maps are presented focusing on the positions, extent, and configurations of the Carboniferous basins. Furthermore, we investigate the relation between the Carboniferous graben structures, evaporite accumulations and inversion in the area. The basin boundary faults of the Carboniferous structures strike NW-SE, and the syn-rift Carboniferous sequences were deposited in half and full grabens. Basins are separated by platforms and structural highs, while basin infill generally dip towards the axis of the grabens, except for the half-graben on the Finnmark Platform where strata dip towards the north and the half-grabens beneath the Haapet Dome where strata dip to the south. In the study area, evaporites are accommodated in the Carboniferous basins and carbonates occupy the structural highs. The deposition of evaporites was constrained by the master faults of the grabens, except for an evaporitic body, which oversteps the rift margins and connects with the southeastern and central parts of the Nordkapp Basin. Furthermore, a thick Triassic succession, with provenance mainly in the southeast, was deposited in the region, while thin Jurassic sediments outcrop at seafloor over the Veslekari Dome and the salt diapir of the Tiddlybanken Basin. Prograding Cretaceous strata mark another phase of regional subsidence in the study area. Several domes are identified at the near base Triassic to the base Cretaceous levels with different shapes, orientation and sizes. The distribution and evolution of the younger domes are partially controlled by the deep-seated Carboniferous structures. Distinct observations including the lateral thickness variations for the uppermost Triassic to the lowermost Cretaceous sediments, the rim syncline development and the onlap at various stratigraphic levels all suggest several phases of doming. We propose a Paleogene timing for the main phase of reactivation of the inverted domes due to Carboniferous graben structures, probably in response to regional compressional stresses.