Upper Graben Formation SLCU

 

Premise The formation is included in the Schieland Group. The formation was defined by NAM & RGD in 1980 and amended by Herngreen & Wong (1989) and by Van Adrichem Boogaert & Kouwe (1993).
Derivatio nominis Named after the Central Graben.
Type section Location map See figure (pdf)
  Well F03-03 (pdf)
  Location N 54°50’45.5
E 04°42’29.3
  Depth 2547 to 2670 m
  Length 123 m along hole
  Reference NAM and RGD (1980)
Definition The formation consists of two units of greyish brown, fine-grained, carbonaceous sandstones,separated by a silty clay succession. Both sand intervals, but especially the upper sand bed, tend to display a funnel-shaped GR-log pattern.  
Upper Boundary The top is conformably overlain by the marine claystones of the Kimmeridge Clay Formation. To the north it pinches out into the Kimmeridge Clay Formation. To the south, the formation grades into the paralic Puzzle Hole Formation at the southern margin of blocks F05-F08 (Herngreen & Wong, 1989).
Lower Boundary The formation is conformably underlain by the Middle Graben Formation.
Distribution The Upper Graben Formation is developed in the northern Dutch Central Graben in blocks F02, F03 and the northern part of F05 and F06 (see pdf). The general depositional trend is N-S directed.
Age Sequence 1 sensu Abbink et al. (2006): Late Oxfordian. Diagnostic dinoflagellate forms are Ellipsoidictyum sp., Glossodinium dimorphum (FOD: M. Oxfordian) and Leptodinium arcuatum (FOD: M. Oxfordian). The top occurrence of Systematophora valensii has been recorded in this formation. Among the sporomorphs the earliest representatives of the Concavissimisporites- Impardecispora complex (FOD: Late Oxfordian) can be noted and also Varirugosisporites granituberosus (FOD: Late Oxfordian). The few ostracods found in this formation show more resemblance to assemblages from the underlying Middle Graben Formation than to those of the overlying marine sediments of the Kimmeridge Clay Formation. Three, probably endemic, species of Galliaecytheridea characterise this formation.
Depositional Setting Marginal marine barrier-island system.
References See References Upper Jurassic/ Lower Cretaceous
D.K. Munsterman, R.M.C.H. Verreussel, H.F. Mijnlieff, N. Witmans, S. Kerstholt-Boegehold & O.A, Abbink (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 (4):555-590.
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