Generally soft, tough and sticky to hardened and friable clay. A subdivision into two parts can be recognised regionally. The lower part is characterised by its brown-grey colour, tending to beige or red-brown locally. The unit contains pyrite, is non-calcareous, and coalified plant remains are locally present at the base (possibly reworked material). The upper two-thirds have a characteristic green-grey colour. It has a sandy upper part with a number of larger sandstone intercalations and it is somewhat calcareous and glauconitic. Along the palaeo-coastline the clays are silty with some sand stringers, which become less common distally.
Open-marine environment. Estimated waterdepth up to 200 m.
Generally shows as a sharp transition from the underlying Oosteind Member or De Wijk Member to the clay of the Ieper Member.
Very variable trasition to overlying Brussels Sandstone Member. Regionally there is an unambiguous boundary between the clay, sand and sandstone. However, near the palaeo-coastline and on palaeo-highs in the southern and eastern part of the basin, the boundary is gradual and complex, because locally, different parts of the succession are missing as a result of various phases of erosion and/or non-deposition. The nature of these breaks in sediments is not well documented.
