Abstract In Denmark, mapping and preliminary investigations of Palaeogene and Early Neogene clay deposits have been performed over the past 5 years. The goal was to locate potential host rocks for the final disposal of low- and intermediate-level radioactive waste from the Danish Research Centre Risø, which has to be decommissioned within the next 5–8 years. Five areas with low-permeability Paleocene and Oligocene clay formations, situated in northern Jylland, NE Fyn and southern Lolland, not far from the Baltic coast at Femern Belt, have been suggested. The clay formations are between 75 and 150 m thick, and have large lateral distribution. They are covered by thin layers of glacial clayey tills and the shallow depth to the clay formations is attractive, partly because they are easy to access and partly because there are no groundwater aquifers situated above or below the clay deposits. The paper gives an overall review of the characteristics of the six different clay formations within four of the areas.

Abstract The lower limit of this package is defined by the basin-wide sedimentary discontinuity close to the Eocene-Oligocene boundary. This is apparently a combination of a tectonic episode, marked by inversion in areas of the North Sea Basin, with major uplift and erosion in some areas (Chapter 8), and sea-level fall consequent on the Early Oligocene cooling event(s) (Chapter 4). The temporal relationship between these events is difficult to establish owing to the widespread unconformity(ies) in this interval (Figs 72, 76 & 81). The earliest Oligocene sediments overlying this surface are characterized by extensive reworking of Eocene palynomorphs and nannofossils. In extreme cases (e.g. in Denmark), this can present significant problems in identifying the Eocene-Oligocene boundary.