A grey, homogeneous, somewhat marly claystone, exhibiting a uniform, low acoustic-velocity and resistivity response on wire-line logs.
Conformably upon the more calcareous Middle Werkendam Member.
In complete successions it is covered by the Brabant Formation. The basal member of the Brabant Formation displays an upward increase in limestone and sandstone content, reflected by a clear funnel shape on most wire-line logs (lower GR, higher sonic-velocity and resistivity readings). The base of the Brabant Formation has been placed at the base of the first clean limestone bed, marked by a sharp log peak.