Late Paleozoic supradetachment basin configuration in the southwestern Barents Sea — Intrabasement seismic facies of the Fingerdjupet Subbasin

Abstract

Late to post-Caledonian, Devonian extension remains unresolved in the SW Barents Sea, despite considerable knowledge from onshore Norway, East Greenland and Svalbard. We analyse intrabasement seismic facies in high-resolution 3D and reprocessed 2D data to investigate evidence for Caledonian deformation and post-Caledonian detachment faulting in the central SW Barents Sea. These results are compared to published potential field models and analogue field studies from onshore Svalbard and Bjørnøya, substantiating that structures inherited from post-orogenic extension influenced the Late Paleozoic and Mesozoic basin evolution. The Late Paleozoic Fingerdjupet Subbasin is underlain by a NNE-striking, ESE-dipping extensional detachment fault that records a minimum eastwards displacement of 22 km. The detachment fault and associated shear zone(s) separate post-orogenic metamorphic core complexes from the syn-tectonic deposits of a presumed Devonian supradetachment basin. Spatial variability in isostatically induced doming likely governed Devonian basin configurations. Pronounced footwall corrugations and faults splaying from the detachment indicate eastward extensional transport. This ultimately led to two interacting but subsequent, east-stepping detachments. Local reactivation of the detachment systems controlled the extent of Carboniferous carbonate and evaporite basins in the Bjarmeland Platform area. Further, the Mesozoic Terningen Fault Complex and Randi Fault Set testify to how the inherited Devonian structural template continued to control spatial localisation and extent of rift structures during subsequent periods of extensional faulting in the Fingerdjupet Subbasin.