Shell-bearing calcareous sands, dominant grain-sizes: 105-210 µm, coarse sand (210-420 µm) in tidal channel deposits. The sands alternate with thin silt and clay-layers, often showing disturbance of the layering by organisms such as molluscs and crustacea (bioturbation structures).
Back-barrier tidal basin behind an ‘open coast’. The open coast featured barrier islands separated by large inlets with ebb and flood-tidal deltas (Beets et al. 2000). The Wormer Member includes five main lithofacies units: sandy point bar deposits, sandy tidal flat deposits, mud flat deposits, supra-tidal flat and tidal marsh deposits, and clayey lagoonal deposits (Van Straaten 1963; De Mulder & Bosch 1982; Westerhoff et al. 1987; Ebbing et al. 2003; Vos & Van Kesteren 2000; Donselaar & Geel 2007).
In most places the Wormer Member overlies with a sharp, erosive contact the Basisveen Bed (Nieuwkoop Formation). Alternatively it overlies fine and coarse-grained Pleistocene sediments.
Usually characterized by a 1-2 m thick blue-grey coloured clay layer in the top, known (in Dutch) as ‘oude blauwe zeeklei’. The Wormer Member is overlain by peat (Hollandveen Member, Nieuwkoop Formation).