Westerbork Member KNNCW

 

Premise Definition after NAM and RGD (1980) . The lithological affix has been deleted. If the Westerbork Member cannot be distinguished from the Ruinen Member, the whole interval can be referred to as Schoonebeek Member (KNNCS), which is not defined separately here.
Derivatio nominis Named after the village of Westerbork in the province of Drente, in the north-eastern part of the Netherlands.
Type section Location map See figure (pdf)
  Well Westerbork-1 (pdf)
  Location N 52°46’08.0
E 06°36’54.1
  Depth 1091 to 1121 m
  Length 30 m along hole
  Reference NAM and RGD (1980)
Additional section Location map See figure (pdf)
  Well Sleen Dommerskanaal-1 (pdf)
  Location N 52°41’39.7
E 06°52’49.8
  Depth 1471.5 to 1544 m
  Length 72.5 m along hole
Definition Interval of dark-grey, silty to pebbly, micaceous, glauconitic claystones to marls, with open-marine fauna, often with a thin, glauconitic, argillaceous sandstone bed at its base (called ’Grenzsandstein’ in NAM and RGD (1980) ). Dispersed iron oolites are encountered. The whole member displays an overall bell shape on the SP log, which is not visible very well on other logs.
Upper Boundary The member is overlain conformably by the Gildehaus Member of the Vlieland Sandstone Formation 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
Lower Boundary The member mildly unconformably covers the Ruinen Member, or the Bentheim Sandstone Member of the Vlieland Sandstone Formation The contact with the Ruinen Member is best seen on an SP log (as a transition from funnel- to bell-shape). On GR logs it is barely visible, as a result of the glauconitic character of the marker sandstone. The transition to the Bentheim Sandstone Member is marked by a sharp increase in GR-log readings.
Correlation The main Vlieland Claystone Formation is a lateral equivalent to the north and east (basin centre). Some occurrences of Vlieland Sandstone Formation (Gildehaus Member, Friesland Member) to the west (basin fringe) are laterally equivalent.
Distribution Restricted to the southern part of the Dutch Lower Sax-ony Basin, i.e. southwestern Drente and eastern Overijssel. This member is not very widespread. Its distribution is related to the presence of the Gildehaus Member of the Vlieland Sandstone Formation, but also depends on the amount of erosion beneath the Holland Formation
Age An Early to mid-Hauterivian age is inferred from available palaeontological data: presence of Foveotriletes foveolatus, Concavissimisporites verrucosus, absence of Valanginian indicators as Ammovertella cellensis and Haplophragmium inconstans erectum.
Depositional Setting Palaeontological data and facies association suggest open-marine deposition. It is seen as the basinal equivalent of coastal-barrier systems formed towards the basin-fringe (the Gildehaus Member to the west).
Sequence Stratigraphy This member reflects the Maximum Flooding and Early Highstand of Haq (1988) ’s sequence LZB 2.4 and/or 2.5. Sequence LZB 2.3 and the base of LZB 2.4 are represent-ed by a hiatus.
References See References Upper Jurassic/ Lower Cretaceous

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