Formal (NAM & RGD 1980). Amended (Van Adrichem Boogaert & Kouwe 1993).
Interval of dark-grey, silty to pebbly, micaceous, glauconitic claystones to marls, often with a thin, glauconitic, argillaceous sandstone bed at its base. Dispersed iron oolites are encountered.
Definition of lower boundary
Unconformably covers the Ruinen Member, or the Bentheim Sandstone Member of the Vlieland Sandstone Formation.
Definition of upper boundary
Conformably overlain by the Gildehaus Sandstone Member. The boundary is placed at the base of the first massive sandstone or conglomerate. Because of the prograding character of this sandstone unit, the contact will be somewhat diachronous. In salt-dome-margin areas the member can be covered unconformably by the Holland Formation.
UK: Valhall Formation; GER: ~Minden-Braunschweig-Gruppe; BEL: -.
early - middle Hauterivian.
Origin of name
Named after the village of Westerbork in the province of Drenthe.
NAM & RGD 1980. Stratigraphic nomenclature of The Netherlands. Verhandelingen van het Koninklijk Nederlands Geologisch Mijnbouwkundig Genootschap 32, 77 p.
Van Adrichem Boogaert, H.A. & Kouwe, W.F.P. 1993. Stratigraphic nomenclature of The Netherlands; revision and update by RGD and NOGEPA, Section G, Upper Jurassic and Lower Cretaceous. Mededelingen Rijks Geologische Dienst, 50, 1-80..
TNO-GDN ([YEAR]). Westerbork Member. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from https://www.dinoloket.nl/en/stratigraphic-nomenclature/westerbork-member.