A conceptual geological model for Utsira Nord offshore wind site in the Norwegian North Sea

Summary Geoscience has a fundamental role to play in the development of safe, cost-effective offshore wind installations. Conceptual geological models of the seabed and shallow subsurface are key to planning efficient data acquisition programs and designing appropriate infrastructure at prospective sites in the early phases of development. Additionally, a better understanding of the soil-structure interactions of offshore wind turbines is urgently required if renewable energy goals are to be met. A detailed geological understanding of the turbine foundation or anchor substrates within new offshore wind areas will be an important component of this. In this study, a conceptual geological model for the Utsira Nord site in the Norwegian North Sea is presented, bringing together an overview of previous knowledge about the complex ice streaming history of the Norwegian Channel together with key observations from high resolution bathymetric data, 2D seismic data, sub-bottom profiles, and shallow cores. Despite limited data coverage, four main geological-geotechnical provinces can be defined: 1) buried lodgment till, 2) buried to exposed sub-glacial traction till suitable for suction-type anchors, 3) exposed glacimarine to marine sediments suitable for suction-type anchors and 4) shallowly buried to exposed crystalline bedrock which will likely require a pile-based or novel anchoring solution.