Seismic Stratigraphy of the Lower Cretaceous Valhall Formation, Danish Graben, North Sea

Detailed seismic stratigraphic analysis of a 3D seismic survey covering the southern part of the Danish Central Graben in the North Sea has revealed a complex stratigraphic infill pattern controlled by eustatism and local tectonics in the Lower Cretaceous Valhall Formation. The success of this analysis is due to the combination of (a) the choice of a geological meaningful flattening horizon in order to bring out the basin morphology, (b) the attenuation of multiples generated by the overlying chalk deposits, (c) a systematic use of horizon slices in the analysis of the depositional geometries, and (d) the application of a geological modelling technology using (guided) autotracking. This approach showed that the southern part of the Danish Central Graben was filled by a westward prograding depositional system that consists of clinoform packages organised at two different scales. This prograding is clearly expressed in the southern part of the basin by coast-parallel features, which are visible in horizon slices and interpreted as shelf margin breaks. It is interpreted as the result of a dominantly eustatic control. The break down of this pattern towards the north of the study area is caused by strong, local subsidence.