Grey and red-brown marl or calcareous, fissile claystone, frequently with intercalated bituminous claystone beds. In the West Netherlands Basin developed as fossiliferous, glauconitic and intensely bioturbated, greenish grey, silty to very silty or sandy, marls and claystones. Alternation of sandy/silty claystones and argillaceous sandstones along the basin edge in the southwesten Netherlands.
Moderately- to fairly deep-marine setting (middle- to outer-neritic), where fines and carbonates settled. Bituminous deposits indicate periods of stagnant basin-floor circulation. Rare, thin sand layers were formed during storms.
Mildly unconformable with the Vlieland Claystone Formation or the De Lier Member. In halokinetically disturbed and very proximal onlap settings the interval can rest unconformably upon the Altena Group or older deposits.
Conformably or unconformably covered by the Middle Holland Claystone Member, Holland Greensand Member or Spijkenisse Greensand Member, which are easily recognised on log character.
