Basement inheritance and salt structures in the SE Barents Sea: Insights from new potential field data

Abstract

The tectonic evolution of the former ‘grey zone’ between Russia and Norway has so far remained poorly constrained due to a lack of geophysical data. In 2014, the Geological Survey of Norway (NGU) carried out a new state-of-the-art aeromagnetic survey (BASAR-14) in the southern part of the new Norwegian offshore territory. The new BASAR-14 survey completes and extends the pre-existing aeromagnetic compilation and mapping of the Norwegian Barents Sea. We present this new magnetic dataset and its interpretation combined with gravity and seismic data. Caledonian and Timanian structures, highlighted by the new potential field data, dominate the basement patterns and have exerted a strong influence on the structure and development of the overlying basins and basement highs. Clearly associated with NW-SE-oriented Timanian trends, the Tiddlybanken Basin represents an atypical sag basin that developed at the southern edge of the Fedynsky High. Quantitative modelling along 2D seismic transects was also carried out to constrain the structural and basement composition of the study area. The predominant NE-SW Mesozoic trend of the Nordkapp Basin represents a major crustal hinge zone between the Finnmark Platform, poorly affected by major crustal deformation, and the Bjarmeland Platform where Late Palaeozoic rifting controlled the widespread accumulation of salt deposits in Late Carboniferous-Early Permian time. The entire structure and segmentation of the Nordkapp Basin have been influenced by the inherited basement configuration highlighted by the new aeromagnetic data. At present, quite a few large diapiric salt domes along the Nordkapp and Tiddlybanken basins are relatively shallow, locally reaching the seabed and thus show a clear bathymetric and magnetic signature. Both the Nordkapp and the Tiddlybanken basins appear to lie at the edge of a peculiar thick and rigid crustal feature that coincides with a highly magnetic region. The abrupt termination of the eastern Nordkapp Basin at the edge of this magnetic domain suggests the presence of an old and thick Precambrian continental block. This magnetic and rigid tectonic buffer controlled the Late Palaeozoic pre-salt and Mesozoic post-salt tectonic development of the southeastern Barents Sea.