Comprises (brownish-) grey to black claystones. The base is usually more silty. The claystones are generally rather bituminous, but locally less organic matter may be present.
Shelf environment. Basin circulation stagnated which resulted in dysoxic to anoxic basin-floor conditions and in the deposition of bituminous claystones.
Unconformably on the undifferentiated Scruff Greensand Formation (block F03) or Kimmeridge Clay Formation. The bituminous claystones of the Clay Deep Member can be distinguished easily from the main Kimmeridge Clay Formation by their higher GR- and resistivity-log response. The contact with the Scruff Greensand Formation below is clear because of the change in lithology.
Coincides with the Berriasian-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 the Rijnland Group (or the Chalk or Lower North Sea Group).