Kimmeridge Clay Formation SGKI


Premise Definition amended after Herngreen and Wong (1989) and NAM and RGD (1980) .
Derivatio nominis Name derived from the British stratigraphic nomencla-ture where it is applied to similar argillaceous deposits which are wide-spread in the general North Sea area NAM and RGD (1980) .
Type section Location map See figure (pdf)
  Well F03-03 (pdf)
  Location N 54°50’45.5
E 04°42’29.3
  Depth 1780 to 2547 m
  Length 767 m along hole
  Reference Herngreen and Wong (1989); Munsterman et al. (2012)
Definition The formation occurs in the northern part of the Dutch Central Graben and Step Graben. The lithology consists of olive-grey, generally silty claystones with thin dolomite streaks (expressed on wire-line logs with a characteristic spiky appearance). Fossil fragments are common in lenses, lignite particles occur frequently. Dolomitic interbeds increase to the north. Towards the south, the claystones may become increasingly silty to sandy and the carbonate streaks and olive hue disappear gradually.
Upper Boundary The formation is (slightly) unconformably overlain by the glauconitic Scruff Greensand Formation, or any younger unit, e.g. the new Lutine Formation.
Lower Boundary The formation conformably overlies the marginal marine barrier island sandstones of the Upper Graben Formation (F03-03), the lacustrine to coastal Middle Graben Formation (F03-01), or the delta plain Puzzle Hole Formation. The Kimmeridge Clay Formation interfingers with the Puzzle Hole Formation and the Upper and Middle Graben formations.
Distribution The occurrence of the Kimmeridge Clay Formation is restricted to the northern part of the Central Graben (blocks A11, A12, A16, B14, B18, F03, F05 and F06) and locally to the adjacent Step Graben (see Fig.). The formation shows  a transgressive character from north to south. The equivalence to the Lola, Farsund and Mandal formations of the Danish and Norwegian sectors of the Central Graben was demonstrated by Michelsen & Wong (1991) (see pdf).
Age Sequence 1 and 2 sensu Abbink et al. (2006). The age is Late Oxfordian to Middle Volgian. The Late Oxfordian J54 MFS sensu Partington et al. (1993) forms the base of the Kimmeridge Clay Formation. Characteristic dinoflagellate cysts are Cribroperidinium longicorne, Dichadogonyaulax chondrum, D. pannea, Egmontodinium polyplacophorum, Endoscrinium galeritum, E. luridum, Epiplosphaera bireticulata, Glossodinium dimorphum, Gochteodinia mutabilis, (LOD: Middle Volgian), Gonyaulacysta jurassica, Histiophora ornata, Leptodinium arcuatum/eumorphum, L. subtile, Muderongia sp. A sensu Davey  (1982;  LOD:  M. Volgian),  Occisucysta balios (LOD: Middle Volgian), Oligosphaeridium patulum (acme), Perisseiasphaeridium pannosum (acme), Scriniodinium crystallinum, S. inritibile and Stephanelytron spp. The bisaccate dominated sporomorph assemblages also typically contain Callialasporites. Micropalaeontological assemblages contain Galliaecytheridea dissimilis, G. punctata, G. dorsetensis, Macrodentina cicatricosa and Eripleura eleanorae (all ostracods).
Depositional Setting The sediments of the Kimmeridge Clay Formation were deposited in an outer shelf setting. Dolomitic beds and structureless organic matter (SOM) indicate times of decreased input of clastics and stagnant water conditions with  a stratified water column. The higher frequency of  dolomitic beds and SOM in the north reflect a slightly deeper environment in the northern realm.
Subdivision The Kimmerigde Clay Formation is not subdivided
  SG Scruff Group
  SGKI Kimmeridge Clay Formation (amended)
  The Clay Deep Member and the Schill Grund Member are part of the Kimmeridge Clay Formation in the Nomenclature of Van Adrichem Boogaert & Kouwe (1993). However, these units are separated from the Kimmeridge Clay Formation by the Scruff Greensand Formation. In addition, the main Kimmeridge Clay Member is older (Late Oxfordian-Middle Volgian) than the Clay Deep and Schill Grund members, which are dated as Late Volgian (post-anguiformis Ammonite Zone) - Ryazanian. Hence both members are given formation status; the Lutine Formation. As noted, the Kimmeridge Clay Formation is now geographically limited to the northern part of the Dutch Central Graben and adjacent basins.
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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