In the Roer Valley Graben predominantly light grey to green grey, very fine-grained (63-150 µm) micaceous sand followed by (dark) green-grey clay that coarsens upward into sands. On the Peel Block and the Venlo Block, the formation consists predominantly of sands. There, it is difficult to discriminate between the Voort and Someren members without the help of biostratigraphic data. Outside the Roer Valley Graben and the adjacent blocks, the formation consists of clays and silty clays with silty to sandy intervals at the base and in the middle part.
Shallow-marine. Inner to outer neritic environment. Waterdepth was less than 200 m.
Southern Netherlands: conformably or mildly unconformably overlies the Steensel Member of the Rupel Formation. The boundary is sharp and has been defined at the base by a distinct clay layer. Wherever the Steensel Member is missing, the formation mildly unconformably overlies the Boom Member (Rupel Formation).
Overlain by the Breda Formation from which it is separated by a distinct unconformity, except presumably in the axial area of the Roer Valley Graben. The upper boundary is characterized by a transition from relatively light to darker coloured glauconite sands.
