Late Jurassic rift physiography of the Froan Basin and Frøya High, offshore Mid-Norway: development of a syn-rift shallow-marine system

The Froan Basin and Frøya High are two major structural elements located on the Mid-Norwegian Continental Shelf and are separated from the Halten Terrace by major west-dipping normal fault zones. Compared to the Halten Terrace, the Froan Basin and Frøya High are relatively under-explored and remain poorly understood in terms of their Late Jurassic tectono-stratigraphic evolution. Upper Jurassic, shallow marine, syn-rift deposits (i.e. Rogn Formation) are present locally, but their source, delivery system and depositional environment are not yet well understood. Improving our understanding of how fault activity and rift-shoulder uplift influenced rift physiography and paleowater depths is crucial when developing depositional models in this region. In this study, we present a model of the Late Jurassic rift physiography of the Froan Basin and Frøya High based on seismic reflection and well data and reverse subsidence modelling. We show that during the Late Jurassic to Early Cretaceous, major footwall uplift caused the Frøya High and the western margin of the central Froan Basin to be subaerially exposed, forming an intra-rift footwall island. Shallow marine areas to the east, immediately adjacent to the footwall island, accumulated sediment supplied from the uplifted and partially eroded footwall. In contrast, the Trøndelag Platform, north of the Froan Basin and Frøya High, remained submerged throughout the rift episode. We therefore suggest that the extent of the shallow marine system was controlled by the magnitude of footwall uplift along the western margin of the basin and that sediment dispersal was influenced by the coastal paleogeomorphology of the back-tilted footwall.