Abstract The inundated Doggerland in the North Sea Basin has been a coveted research target for many years owing to its key location with respect to geological evolution since the last glaciation and its archaeological potential related to prehistoric hunter–gatherer populations. Still, many uncertainties related to glacial and sea-level forcing on erosion and deposition remain, and the first discovery of submerged settlements is yet to be reported. In this study, we present a range of seismic morphologies and facies characteristic for the late glacial and Holocene succession near a major drainage system at the eastern Dogger Bank. Five of these facies are dominant in the area while two facies can be associated with a terrestrial–fluvial landscape buried 0–22 m below the seafloor. We detect various erosion levels of the terrestrial–fluvial landscape that are greatest towards the south where sediment has been removed, probably owing to combined terrestrial–fluvial and marine erosion. We find that five subareas show geo-archaeological potential in terms of (1) the preservation degree of terrestrial strata based on erosion estimates, (2) the accessibility of terrestrial strata based on burial depths and (3) the palaeolandscape configuration based on the spatial setting in relation to the drainage system and the palaeocoastlines. We further document a geological evolution of the study area, which is comparable with the evolution at the western Dogger Bank. However, we find more evidence for an extended flooding period because of the vicinity to the major drainage system and the Elbe Paleo Valley. We propose that our approach can be used as a workflow for marine investigations that focus on submerged hunter–gatherer heritage.

Abstract This paper presents the results of a cross-border study of the Middle Jurassic–Early Cretaceous rift phase in the Danish–German–Dutch Central Graben area. Based on long-distance correlations of palynologically interpreted wells, a stepwise basin evolution pattern was determined. Four phases are defined and described as tectonostratigraphic mega-sequences (TMS). The TMS are governed by changes in the tectonic regime. TMS-1 reflects the onset of rifting, triggered by regional east–west extension. Rift climax was reached during TMS-1, reflected by thick mudstone accumulations. TMS-2 reflects a change in the tectonic regime from east–west to NE–SW extension. NW–SE-trending normal faults became active during this phase, switching the depocentres from the graben axis into adjacent basins. TMS-3 displays divergent basin development. In the Dutch Central Graben area, it is characterized by a basal unconformity and widespread sandstone deposition, indicating continued salt and fault activity. Organic-rich mudstone deposition prevails in the Danish and German Central Graben area, indicating sediment starvation and water-mass stratification. With TMS-4 the rift phase ended, reflected by regionally uniform mudstone deposition. The basin evolution model presented here coherently places the lithostratigraphic units occurring in a stratigraphic framework and provides a valuable basis for hydrocarbon exploration activities in the region.

Abstract Foraminiferal palaeoecological analyses were carried out on 124 upper Maastrichtian chalk samples from the M-10X and E-5X wells of the Danish Central Graben. The two wells demonstrate similar trends, with some notable differences. Both are strongly dominated by planktic foraminifers, of which the small, biserial Heterohelix globulosa is by far the most common species. Based on variations within five significant, benthic foraminiferal morphogroups and the plankton/benthos ratio, eight specific foraminiferal intervals have been described. The faunal and palaeoenvironmental changes observed during the late Maastrichtian period were, in most places and especially in the lower part, not very distinct, and it is believed that the palaeoenvironment during the majority of the interval was a mostly stable, deep outer-shelf environment characterized mainly by pelagic sedimentation under temperate, suboxic conditions. More unstable conditions characterized the latest Maastrichtian. The analyses show that the sediments in the M-10X well were deposited in a generally deeper palaeoenvironment than those from E-5X. The influx of common Pseudotextularia elegans (three acmes), together with scattered specimens of the typical Tethyan species Abathomphalus mayaroensis and Pseudoguembelina hariaensis (in E-5X only), indicate that relatively warm conditions prevailed, at least periodically, during the latest part of the late Maastrichtian in both areas.

Abstract The chalk reservoir of the Gorm Field, southern North Sea is dome-shaped and faulted owing to a combination of salt diapirism and regional east–west extension. Fractures developed in the structure considerably enhance permeability. The dataset discussed here records fractures in horizontal wells from more than 10 km of image logs and provides a special opportunity to test theoretical models of fracture development with quantitative observations. In an effort to forecast fracture density and fracture orientation, we have estimated the strains in the structure using an elastic dislocation model that incorporates mechanical boundaries in the form of the tectono-stratigraphic interface with salt and tectonic faults. More than 50% of the angular differences between poles to the planes of simulated and observed fractures are less than 30°; 75% are less than 45°. Relative strain magnitude appears to be a useful indicator of fracture density. At the field scale, small strain magnitudes correspond with small non-zero fracture densities and relatively large strain magnitudes correspond with high fracture densities.

Abstract Deposition of the Upper Cretaceous–Danian Chalk Group in the Salt Dome Province of the southern Danish Central Graben took place during a tectonic period dominated by post-rift subsidence, halokinesis and structural inversion. This resulted in highly variable chalk distribution with >1300 m of chalk located in synclines and <200 m preserved on inversion highs and salt structures. The area is mature with respect to exploration with most of the chalk fields located in structural traps discovered in the 1970s. However, the Halfdan discovery in 1999 illustrates the existence of off-structural traps, leading to renewed exploration interest. To locate additional off-structural traps, a detailed geological model is necessary for prediction of chalk intervals with reservoir potential. To unravel basin development, we combine 3D seismic interpretation, well log correlation and 2D seismic inversion to estimate acoustic impedance along selected profiles. The 2D acoustic impedance profiles are converted to total porosity and used to identify areas with potential untargeted reservoirs. A prominent high-amplitude reflection is interpreted as a regional unconformity separating two distinctly different chalk deposition patterns. Nannofossil biostratigraphy suggests a latest Campanian to early Maastrichtian age for the unconformity. It corresponds to an increase in acoustic impedance and decrease in porosity in wells. The Tor Formation contains porous intervals while the underlying Hod Formation contains less porous chalk. The Hod Formation has a maximum porosity of <20% based on well log and inversion data. In contrast, inversion data indicate that the Tor Formation comprises reservoir-grade porosity at several locations on downflank structures. In several areas, the inversion-based maximum porosity is predicted to be higher than expected, compared with porosity/depth trends derived from well data. Therefore, the spatial porosity variation in chalk is complex and controlled by factors other than burial depth.