The late Mesozoic and Cenozoic evolution of the Sørvestsnaget Basin: A tectonostratigraphic mirror for regional events along the Southwestern Barents Sea margin?

Abstract

Seismic interpretation and mapping of the Sørvestsnaget Basin at the southwestern Barents Sea Margin has revealed a complex basin history, related to large scale plate tectonic movements in the Norwegian-Greenland Sea area. The pre-Cenozoic evolution of the Sørvestsnaget Basin is poorly understood, due to lack of well data and poor seismic data quality. Regional pre-Cenozoic geologic models, that includes the Sørvestsnaget Basin, should await more and better data. Prior to break-up and sea-floor spreading in the Norwegian-Greenland Sea, Late Cretaceous and Palaeocene shear movements along the Senja Fracture Zone led to structuring and possibly elevation of the southern part of the basin. As sea-floor spreading took place and propagated northwards along the Senja Fracture Zone, the western areas of the basin were uplifted and eroded. Two large and two smaller intrabasinal features in the southern Sørvestsnaget Basin are characterised by: (a) low values on the gravimetric anomaly maps; (b) surrounding synforms; and (c) little response on magnetic anomaly maps. The features have been interpreted as salt structures. The Tertiary evolution of intrabasinal salt-structures seems to have been governed by extensional faulting and subsidence of the margin during the Late Palaeocene and Eocene periods. The Oligocene and Miocene periods were characterised by local and regional uplift of the Sørvestsnaget Basin, respectively. During these periods, the area in particular the western part of the basin, was subjected to transpressional/compressional forces, which can be tentatively correlated to contemporaneous, large scale plate reorganisations and variations of sea-floor spreading rates in the Norwegian-Greenland Sea. The Oligocene and Miocene transpressional/compressional events influenced the salt structures, and is here suggested to be partially responsible for the complex expression of the largest salt structures. The Late Neogene and Pleistocene periods are represented by a thick, westward prograding wedge, indicating subsiden3e with coinciding high sediment input to, and minor adjustment of the salt structures in, the Sørvestsnaget Basin.