Formal (Van Adrichem Boogaert & Kouwe 1993). Amended (Munsterman et al. 2012).
Medium to dark brown-grey claystones, non- to slightly silty, non-calcareous, lignitic and fossiliferous (thick pelecypod shell fragments, ostracods). Some limestone beds have been encountered. Thick sand beds, characteristic for the main Friese Front Member, are absent. Along the basin margins the lithology may change into a more sandy subfacies, like in the southern Terschelling Basin.
Restricted lagoon-like conditions with washover deposits.
Definition of lower boundary
Conformable contact with the informal main Friese Front member. Upper boundary at the first variegated or grey, non-marine clay-/siltstones or thick sand bed. In the Terschelling Basin the unit may interfinger with the Friese Front Formation.
Definition of upper boundary
Generally marked by a conformable contact with massive glauconitic sands of the overlying Noordsvaarder Member in blocks F15 and F18 or the Terschelling Sandstone Member in blocks L03 and L06. This contact may locally become unconformable in the southern Central Graben (blocks L02-L05) where it is covered by the Stortemelk Member (e.g. L05-01). In parts of blocks L03 and L09 the Oyster Ground Member interfingers with the coarse-grained coastal clastics of the Terschelling Sandstone Member.
UK: Humber Group; GER: ?; BEL: -.
late Kimmeridgian - early Tithonian.
Origin of name
Named after the Oyster Ground, a fishing ground situated at approx. N 54°, E 05° in the Netherlands offshore, north of the Dutch Wadden island of Terschelling.
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..
D.K. Munsterman, R.M.C.H. Verreussel, H.F. Mijnlieff, N. Witmans, S. Kerstholt-Boegehold, Abbink, O.A. 2012. Revision and update of the Callovian-Ryazanian Stratigraphic Nomenclature in the northern Dutch Offshore, i.e. Central Graben Subgroup and Scruff Group. Netherlands Journal of Geosciences-Geologie en Mijnbouw, 91, 555-590.
TNO-GDN ([YEAR]). Oyster Ground Member. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from http://www.dinoloket.nl/en/stratigraphic-nomenclature/oyster-ground-member.