Paleolandscapes recorded by the Top Basement surface in the Norwegian North Sea

Mapping the diachronous Top Basement in the North Sea reveals a complex amalgamation of paleolandscapes and provides valuable insights into the Late Paleozoic and Mesozoic geologic history. To illuminate the temporal geologic and geomorphic evolution, we document and analyze geomorphic characteristics and relate these to the regional tectonostratigraphic events. The paleolandscapes represented by the Top Basement surface generally fall into the following categories: rough, irregular terrains; rough, confined drainage networks; and smooth, planar landscapes. Notably, the irregular landscape found at the base of the deep basins is covered by Upper Paleozoic sediments and represents a potential late stage of the Devonian denudation of the Caledonian mountain chain. A distinct drainage network on the Top Basement of the Patch Bank Ridge represents two exposure phases: one related to extension during Devonian exhumation and the other associated with Carboniferous exhumation. Two regional tectonic events are candidates for such Carboniferous exhumation, one is Variscan contraction, the other is the Pennsylvanian event dated onshore Greenland and Fenoscandia. Preserved drainage networks observed on various basement highs correspond to local Late Permian to Early Triassic fault block uplift. In tilted fault blocks, these features are significant, while in horst block structures, smooth, planar landscape expression occurs. This is linked to repeated uplift of horst block structures, while tilted fault blocks get buried sooner. A distinct terrain observed in a confined area on the western Måløy Slope exhibits geomorphic characteristics comparable to those found on the tilted Vette and Tusse fault blocks overlain by sediment of Triassic or older origin. Thus, we suggest that this is a strong indication that Late Permian to Early Triassic rifting impacted the Måløy Slope. Tectonic and climatic processes controlled the relief and spatial extent of these landscapes. Our findings correlate with onshore exhumation and landscape development documented from other studies onshore East Greenland and Fennoscandia. These insights highlight the potential for identifying further paleolandscape features across the wider North Sea region and beyond.