The Hectoroceras kochi Zone (Ryazanian) in the North Sea Central Graben and remarks on the Late Cimmerian Unconformity

Ammonites, inoceramids and dinofl agellate cysts found in core material from the E-1 well in the Tail End Graben of the Danish part of the Central Graben are described. The core be longs to the upper, highly radioactive part of the Kimmeridge Clay Formation (unit J-4) and includes the ammonite Hecroroceras
kochi indicating the basal Cretaceous, Lower Ryazani an H. kochi Zone. Dinoflagellates indicate the Cannosphaeropsis thula Subzone. Dinoflagellates from cuttings immediately below and above the boundary between the Kimmeridge Clay Formation and the overlying Valhall Formation indicate a Valanginian age for the boundary (Spiniferites ramosus Zone). No hiatus between the two formations is discernible in the din oflagellates. The "Late Cimmeri an unconformity" is discussed in the light of the new stratigraphic data from the well.