Lower Coevorden Member SKCFL

 

Premise Definition extended after NAM and RGD (1980) , originally Lower Coevorden Clay Member The lithological affix has been deleted. Equivalent to the lower B├╝ckeberg Folge of Kemper (1973).
Derivatio nominis Named after the town of Coevorden in the southeastern part of the Dutch province of Drente.
Type section Location map See figure (pdf)
  Well Schoonebeek-197 (pdf)
  Location N 52°38’58.0
E 07°02’34.2
  Depth 1126 to 1230 m
  Length 104 m along hole
  Reference NAM and RGD (1980)
Additional section Location map See figure (pdf)
  Well Ruinen-1 (pdf)
  Location N 52°44’09.8
E 06°27’12.8
  Depth 1010 to 1046 m
  Length 36 m along hole
  Well Exloo Odoorn-2 (pdf)
  Location N 52°54’20.7
E 06°51’57.8
  Depth 1679 to 1697 m
  Length 18 m along hole
  Well De Bente-1 (pdf)
  Location N 52°41’37.8
E 06°46’15.7
  Depth 1130 to 1174 m
  Length 44 m along hole
  Well Oldenzaal-2 (pdf)
  Location N 52°17’18.8
E 06°56’23.8
  Depth 162 to 295 m
  Length 133 m along hole
Definition Section of grey, calcareous, occasionally sandy claystones. Limestone beds occur frequently in the basal parts, but disappear upwards, where the clays are less calcareous t Hart (1969) . In type well Schoonebeek-197 some halite beds occur in the base.
Upper Boundary The upper contact, with the Middle Coevorden Member, is marked by a fairly sharp increase in carbonate content. This generally coincides with the base of a funnel-shaped zone of increased resistivity-log readings. If the Middle Coevorden Member has been truncated, the Rijnland Group or younger deposits can overlay this member.
Lower Boundary The basal contact with the Serpulite Member of the Weiteveen Formation is marked by a clear claystone break, which is seen prominently on resistivity and sonic logs. In some salt-dome-related occurrences the Weiteveen Formation is absent, and the Coevorden Formation is in unconformable contact with the Altena Group or older deposits.
Distribution Restricted to the Lower Saxony Basin, part of which covers the easternmost parts of the Dutch provinces of Groningen, Drente and Overijssel.
Age Ryazanian. In the local ostracod zonation the member covers Wealden 1 - 2 or 3 (Wolburg (1949) ; Sung (1955) ). Numerous Cypridea species (ostracods) are found in this member, among which Cypridea fasciculata, C. buxtorfi, C. lata, C. alta, C. bispinosa bimammata, C. dolabrata angulata, C. dolabrata dolabrata and C. setina are most important. Also present is Bisulcocypris striata.
Depositional Setting Marginal- to open-lacustrine setting with rare brackish influence. Fines settled from suspension. The carbonates (microcoquina shell beds) are interpreted as storm layers or periods of low sediment input (hardgrounds). Some fine sand was imported by small-scale fluvial/deltaic systems.
Sequence Stratigraphy The member reflects the full sequence LZB 1.5b and the Lowstand and early Transgressive systems tract of sequence LZB 1.6.
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.
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