Delineating confined slope turbidite systems offshore mid-Norway: The Cretaceous deep-marine Lysing Formation

摘要

The Dønna Terrace is part of the morphologically complex continental slope offshore mid-Norway and contains a series of tectonically confined subbasins. These subbasins all have different sizes, shapes, and locations that strongly controlled the development of the deep-marine, Upper Cretaceous Lysing Formation. Careful mapping of the entrance points and internal faults within each subbasin is crucial for constructing a depositional model for these slope turbidite complexes. The key to successful delineation of the turbidite systems and complexes in the study area is a four-step process: (1) understanding the main structural elements on a semiregional scale; (2) mapping all structural features in detail that can impact the sediment fill within and prior to the studied interval to build a structural framework of the area; (3) performing a thorough integration of seismic, biostratigraphy, wire-line, core, and formation-pressure data for each subbasin, identifying the geometry and reservoir architecture of turbidite systems and complexes; and (4) developing a sequence-stratigraphic framework to establish if the deep-marine sedimentary fill of the subbasins is genetically linked. The importance of establishing a genetic linkage between slope basins is related to the reservoir quality of the deep-marine turbidite systems; if a cannibalization of a sandstone-dominated sedimentary fill of an updip slope basin can be demonstrated, lower risk can be assigned for reservoir quality of lower-slope-basin reservoirs. In addition, onlap style and pinch-out character of the turbidite systems yield important information of sand deposition within the turbidite systems.