Formal (Van Adrichem Boogaert & Kouwe 1993).
Massive sequence of fine- to medium-grained, locally coarse-grained sandstones, generally light-grey, well-sorted with sub-angular to rounded grains, moderately cemented, both bioturbated and stratified. The sandstones locally contain streaks of heavy mineral sand, coal laminae and pyrite particles.
The sandstones were deposited as barrier sands.
Definition of lower boundary
Stratigraphically rests slightly unconformably on the Breeveertien Formation, which also forms its lateral equivalent to the south and east.
Definition of upper boundary
In the north-west, conformably overlain by the Vlieland Claystone Formation.
UK: Valhall Formation; GER: ~Minden-Braunschweig-Gruppe; BEL: -.
latest Berriasian - middle Valanginian.
Origin of name
Named after the Kotter oil field, located in the Broad Fourteens Basin (block K18a).
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]). Kotter Member. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from https://www.dinoloket.nl/en/stratigraphic-nomenclature/kotter-member.