Stratigraphic correlation of the Danish onshore and offshore Tertiary successions based on sequence stratigraphy

The results of a sequence stratigraphic study of the Tertiary sedimentary succession in the Danish North Sea sector, and the adjacent parts of the Norwegian, German, and Dutch sectors are reviewed in the present paper. Lithology and thickness variations of seven major sequence stratigraphic units, comprising twentyone sequences, are shortly described. The chronostratigraphic and genetic relationships between the North Sea sequences and the Danish onshore lithostratigraphic formations are emphasized. Six major sequence stratigraphic boundaries are pointed out, being time-equivalent with regional unconformities in the onshore area. The six surfaces bound five sedimentary packages, which are isochronous in their recognized lateral extension, and comprise genetically related deposits. It is suggested to define the five units as allostratigraphic units, and thus to create a stratigraphic subdivision, which is mappable in the southeastern North Sea region, possibly in the main part of the North Sea. The five allostratigraphic units can be identified in all areas by the available data; seismic sections and logs in the offshore area, and lithology in onshore outcrops and shallow wells. The definition of an allostratigraphic scheme would create a common nomenclature across the national borders and the present coastlines, and hopefully increase the accuracy of the chro­nostratigraphic correlation between profiles in the North Sea region.