Banjaard Group OB

 

Premise Only a few wells in the southern Netherlands have reached the Pre-Carboniferous. The limited data do not allow a formal lithostratigraphical description of the strata encountered. The Dinantian carbonates of the Zeeland Formation are underlain by shaly mudstones , interbedded claystones, sandstones and carbonates (Kastanjelaan-2) or by more massive sandstones (e.g. Booischot borehole: Legrand (1964) ; Wachtendonk 1: Elberskirch (1962) ; see also Bless ( 1976) . Placid’s O18-01 well penetrated 37 m of shaly and sandy deposits underneath the Dinantian carbonates, presumably of Middle to Upper Devonian age, and bottomed in the before-mentioned Upper Silurian turbidites. In well Kastanjelaan-2 (see pdf) the shaly/sandy sequence below the Zeeland Formation could be adequately dated as ranging in age from Upper Famennian to early Tournaisian.
  The Devonian strata discussed in this chapter are marine deposits, in contrast with the continental deposits of the Old Red Group. The former are provisionally placed in the informal Banjaard group. The scanty knowledge of this unit does not allow the reliable assignment of a type section.
Derivatio nominis Named after a shoal off the coast of the island of Schouwen-Duiveland.
Definition A group of marine mudstones, claystones and sandstones and subordinate carbonates.
Upper Boundary The upper boundary is marked by a conformable or mildly unconformable contact with the overlying, massive carbonates of the Carboniferous Limestone Group.
Lower Boundary The lower boundary of the Banjaard group has not been documented by wells in the Netherlands. Most likely it is formed by the contact of Devonian clastics unconformably overlying the Caledonian basement.
Distribution The group occurs north of the London-Brabant Massif in the Dutch and Belgian subsurface. Details of its distribution are unknown. The limited amount of data available indicate the presence of the formation in the Elbow Spit High area and part of the Mid North Sea High. It is also known from the central North Sea Cameron (1993a) .
Age Devonian to earliest Carboniferous.
Depositional Setting The formation was deposited in a fluvial setting. The sandstones are stacked channel deposits of a predominantly braided river system.
Subdivision The group can be divided into two formations, that are considered informal units because of the limited amount of data available in the Netherlands:
  OBBS Bosscheveld Formation
  OBGC Bollen claystone Formation
References See References Devonian and Lower Carboniferous

Van Adrichem Boogaert, H.A. & Kouwe, W.F.P., 1993-1997. [Stratigraphic unit]. In: Stratigraphic Nomenclature of the Netherlands.
Retrieved [Datum] from [url].