Contemporary stress orientations in the Faroe–Shetland region

Abstract

The Faroe–Shetland region of the NE Atlantic continental margin contains a number of complexly structured Mesozoic–Palaeogene-age rift basins, but in comparison with the contiguous British Isles and North Sea Basin, the state of crustal stress in the Faroe–Shetland region is poorly understood. The orientation of maximum horizontal compressional stress (σHmax) across most of NW Europe is roughly NW–SE, which is considered to be controlled by forces acting at the plate boundaries. We have determined 16 B–D quality σHmax orientations based on borehole breakouts interpreted in petroleum wells, and define three distinct stress provinces within the Faroe–Shetland region. Stress orientations in the NE are roughly NW–SE, consistent with the regional pattern of stresses in NW Europe and local neotectonic structural trends. However, contemporary stress orientations in the central and SW of the Faroe–Shetland region exhibit short-wavelength (distances <10–50 km) variation, with NE–SW, north–south and east–west orientations that are parallel or subparallel to underlying structural trends. This variation is interpreted in terms of stress deflections towards weak faults that downthrow the Mesozoic–Cenozoic sedimentary successions against basement highs. These local-scale sources are superimposed on a background roughly WNW–ESE σHmax orientation that is controlled by both plate boundary forces and regional-scale sources of stresses.