Palaeozoic sedimentary deposits and basement structures in the Danish area

We find that seismic methods can be used for distinguishing betaveen upper and lower Palaeozoic rocks. It is possible that rocks from the upper Palaozoic sedimentary series have generated hydrocarbons, which are still present in the area; in some areas even the lower Palaozoic series may potentially contain source rocks, in particular in the Kattegat area, far from the Caledonian Deformation Front. The thickness of the Palaeozoic series is up to 6-7 km, mainly around 3-5 km, depending on the degree of erosion. The Palaeozoic rocks are usually found under a 4-6 km cover of Mesozoic and Cenozoic rocks, but in places the cover is very thin (down to less than 1 km), e.g. on the Ringkøbing-Fyn High, ground the Baltic Sea, and in parts of Kattegat. This project has shown that the Ringkøbing-Fyn 'basement high' consists of uplifted series of Palaeozoic sedimentary rocks, and not, as often claimed, of crystalline basement rocks. These sedimentary sequences were deposited during a complex series of rifting episodes since early Palaeozoic times and in the Caledonian foreland basin. Each rifting episode was followed by general subsidence. The depths to source and reservoir rocks are important for assessment of the their hydrocarbon potential. It is likely that hydrocarbons have been bumt in deeply seated rocks, whereas shallower still may contain hydrocarbons even after long time spans. The latter case appears possible in parts of the Danish region, e.g. in Kattegat and perhaps in parts of the Ringkøbing-Fyn High