Olive-grey to grey-brown claystones. The claystones are non- to slightly calcareous, silty to very fine sandy, locally slightly bituminous, micaceous and pyritic.
Open-marine shelf conditions prevail, near-normally oxygenated basin-floor circumstances.
Conformably underlain by the glauconitic Scruff Greensand Formation (Stortemelk Member in the southern Central Graben and Terschelling Basin, e.g. well F18-02).
Coincides with the Berriasien-Valanginian boundary (Sequence 3 / Sequence 4 transition sensu Abbink et al. 2006). It is associated with the Late Kimmerian unconformity. Covered (sometimes virtually conformably) by sediments of the Rijnland Group (or the Chalk or Lower North Sea Group). Top is not always easy to pick on logs. Quite often, an intra Schill Grund ‘kick’ (Sequence 3) is mistaken for the base of the Rijnland Group (Sequence 4).
