Contemporary stress orientations in the Faroe-Shetland region

The Faroe-Shetland Region (FSR) of the NE Atlantic continental margin contains a number of complexly structured Mesozoic-Palaeogene-age rift basins, but in comparison to the contiguous British Isles and North Sea Basin, the state of crustal stress in the FSR is poorly understood. The orientation of maximum horizontal compressional stress (σHmax) across most of NW Europe is ~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 FSR. Stress orientations in the NE are ~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 FSR exhibit short-wavelength (distances <10-50 km) variation, with NE-SW, N-S and E-W orientations that are parallel or sub-parallel 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 superposed on a background ~WNW-ESE σHmax orientation that is controlled by both plate boundary forces and regional-scale sources of stresses.