Schill Grund Member SGLUS


Premise The member is defined by Van Adrichem Boogaert & Kouwe (1993; Fig. 1). It was interpreted as the southern occurrence of the Clay Deep Member, but split off because of its slightly or non-bituminous character. Here the Schill Grund Member is transferred to the new Lutine Formation, Scruff Group. It was inappropriately attributed to the Kimmeridge Clay Formation sensu Van Adrichem Boogaert & Kouwe (1993), because both units were separated by other members of the Scruff Greensand Formation. Furthermore, the lithology of the Schill Grund Member differs substantially from the Kimmeridge Clay Formation; the former lacks the well developed dolomite stringers.
Derivatio nominis Named after the Schill Grund, a German name for the Scruff Bank in the North Sea.
Type section Location map See figure (pdf)
  Well F18-02 (pdf)
  Location N 54°04’25.3
E 04°43’48.5
  Depth 2042 to 2079 m
  Length 37 m along hole
Definition The member consists of olive-grey to grey-brown claystones. The claystones are non- to slightly calcareous, silty to very fine sandy, locally slightly bituminous, micaceous and pyritic.  
Upper Boundary The upper boundary coincides with the Sequence 3 / Sequence 4 transition sensu Abbink et al. (2006). It is associated with the Late Kimmerian unconformity. The member is covered (sometimes virtually conformably) by sediments of the Rijnland Group (or the Chalk or Lower North Sea Group). This boundary is shown by upwards decreasing values on the GR and the resistivity logs. The lithology changes towards argillaceous sandstone, sandy claystone/marl or limestone. The top is not always easy to pick on logs. Quite often, an intra Schill Grund ‘kick’ (Sequence 3) is mistaken for the base of the Rijnland Group (Sequence 4).
Lower Boundary The Schill Grund Member is conformably underlain by the glauconitic Scruff Greensand Formation (Stortemelk Member in the southern Central Graben and Terschelling Basin, e.g. well F18-02).
Distribution The Schill Grund Member is limited to the southern part of the Dutch Central Graben, Schill Grund Platform and Terschelling Basin, e.g. blocks F12, F15, F17, F18, G13, G16, G17, L02, L03, L05, L06, M01, M04 and M07. The member may partially be a lateral time equivalent of the Stortemelk Member (Scruff Greensand Formation) and the Zurich Formation (Delfland Subgroup) along the southern margin of the Central Graben and into the Vlieland Basin. To the north the Schill Grund Member grades into the more bituminous clays of the Clay Deep Member (see pdf).
Age Sequence 3 sensu Abbink et al. (2006): Late Ryazanian, kochi/ icenii-albidum Ammonite zones. Diagnostic dinoflagellates are Batioladinium radiculatum, Daveya boresphaera, Egmontodinium torynum (LOD Late Ryazanian, albidum Ammonite Zone) and Oligosphaeridium diluculum (FOD: icenii Ammonite Zone). Characteristic microfaunal elements are the ostracods Galliaecytheridea teres, Mandelstamia sexti and Paranotacythere speetonensis. Cytheropterina eboracica was also found in the type section and has an FOD (= First Occurrence Datum) at the Ryazanian/ Valanginian   boundary.
Depositional Setting Open-marine shelf conditions prevail. The slightly or non- bituminous nature of the sediments indicate near-normally oxygenated basin-floor circumstances.
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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