Cenozoic tectonic subsidence from 2D depositional simulations of a regional transect in the northern North Sea basin

Abstract

Abstract The Cenozoic depositional history along a regional E–W profile across the northern North Sea has been simulated using a forward process-based simulation program of dynamic-slope type. It involves a depth-dependent, dual-lithology diffusion equation that handles transport, erosion and deposition of sediments. The data used in the simulation were derived from a seismic line calibrated against wells, and from the regional literature concerning the northern North Sea. The most important of the factors used are: the initial basin form (Paleocene bathymetry), tectonic subsidence, isostatic variables, sediment supply (sand-shale), sediment compaction (porosity-depth relationships for sand-shale) and eustatic sea-level changes. The interaction between the data values extracted from the literature could not reproduce a cross-section similar to the observed cross-section from seismic data. Therefore, the subsidence pattern and the initial basin form were reconsidered. The resulting model gave an anomalous Cenozoic subsidence pattern, different from the expected post-rift thermal subsidence, with deviations corresponding to Paleocene and Late Miocene-Pliocene times. The model-derived Paleocene subsidence might have been overestimated by using an over-shallow palaeobathymetric value, although a deepening of the basin is also indicated by biostratigraphic data. The pronounced Neogene subsidence created accommodation space for a thick Pliocene sequence, derived from the uplifted eastern source area.