Grey fine to medium sand, mostly calcareous with marine shells that may be concentrated in layers (dominant outside of basins). Dark grey to greenish grey clay, silty, mostly calcareous with shells or shell layers, locally organic (dominant in basins). Subordinate shell crags, diatomite.
In former glacial basins, succession of shallow freshwater (locally diatomite) to brackish coastal (silty organic clay) to fully marine (shelly clay and sand), driven by sea-level rise, followed by renewed brackish coastal, governed by sea-level fall and basin fill (shallowing) (Cleveringa et al. 2000; Van Leeuwen et al. 2000; De Gans et al. 2000). Elsewhere, especially offshore, primarily fully (shallow) marine.
Locally, diatomite or gyttja at base. Gradual transition into glaciolacustrine clay (Uitdam Member, Drente Formation). Sharp contact with till (Gieten Member, Drente Formation), less shelly fluvial siliciclastics (Kreftenheye (Twello Member), Urk and Sterksel Formations), or Neogene sediments (marine Oosterhout, Rupel and Dongen Formations, fluvial Waalre Formation).
Highly variable. Generally, sharp and unconformable contact with usually non-calcareous periglacial aeolian and local river sand (Boxtel Formation), coarse fluvial channel lags (Kreftenheye Formation), or tidal-channel siliciclastics (Naaldwijk Formation). Gradual to diffuse transition into fluvially reworked marine sand from the Eem Formation (Ockenburg Member, Kreftenheye Formation) or tidal sand and clay (Naaldwijk Formation). Locally, gradual to sharp boundary with Eemian to early Weichselian peat (Woudenberg Formation) or sharp boundary with Holocene peat (Basisveen Bed, Nieuwkoop Formation).
