Stortemelk Member SGGSS


Premise The member is defined by Van Adrichem Boogaert & Kouwe (1993). It is the uppermost member of the Scruff Greensand Formation, Scruff Group. The second additional reference section, well Vlieland Oost-01, interval 2330-2393 m (in Van Adrichem Boogaert & Kouwe, 1993) is rejected. The purely continental sporomorph assemblages with minor amounts of near-coastal elements do not support the assignment to this unit (Herngreen et al., 2000). Marine influence such as acritarchs and dinoflagellate cysts has not been recorded. Attribution to the overlying Zurich Formation is more likely (see Annex G-24 in Van Adrichem Boogaert & Kouwe, 1993).
Derivatio nominis Named after the Stortemelk, a channel of the outer tidal delta between the Wadden Islands of Vlieland and Terschelling.
Type section Location map See figure (pdf)
  Well F18-02 (pdf)
  Location N 54°04’25.3
E 04°43’48.5
  Depth 2079 to 2105 m
  Length 26 m along hole
Additional section Location map See figure (pdf)
  Well F15-02-S1 (pdf)
  Location N 54°14’18.5
E 04°50’44.9
  Depth 3021 to 3041 m
  Length 20 m along hole
Definition Section of fine- to very fine-grained, argillaceous sandstones with intense bioturbation. The sands are often slightly calcareous, glauconitic, with thin streaks of lignite. Cores show some intercalations of up to coarse, glauconitic and sometimes argillaceous sandstone.
Upper Boundary The Stortemelk Member is conformably overlain by the Lutine Formation, Schill Grund Member. This upper contact is marked by a general rise in GR-log readings. In the southern Dutch Central Graben an unconformable upper contact with the Vlieland Claystone Formation (Rijnland Group) may be possible locally.
Lower Boundary In the Terschelling Basin the lower boundary of this member is characterised by a mild unconformity with underlying Scruff Spiculite Member or undifferentiated Scruff Greensand Formation. The boundary is placed at the discontinuity (consistent basal peak) of the GR-log. The GR-log shows lower values in the Spiculite Member, due to a decreasing argillaceous content. The Stortemelk Member has a distinct bell-shaped GR-log pattern. In the case of a contact with the Spiculite Member, a downhole increase in the sponge spiculae content may be taken as an additional criterion. In the southern Central Graben the base of the Stortemelk Member may be unconformably underlain by the Skylge or Friese Front Formation, due to the development of a prominent Late Kimmerian II unconformity. A diagnostic log kick on the gamma log at the base suggests a cemented horizon.
Distribution The Stortemelk Member is developed in the southern Dutch Central Graben and Terschelling Basin, blocks F15, F17, F18, L02, L03, L06, L09 and M01. In the L12 and L15 blocks this member interfingers with the paralic Zurich Formation, into which it shales out. To the north it shales out into the Schill Grund Member (see pdf).
Age Sequence 3 sensu Abbink et al. (2006): late Early - earliest Late Ryazanian, kochi-icenii Ammonite zones. The base of the Stortemelk Member is associated with the Early Ryazanian kochi climate shift. Chronostratigraphic important dinoflagellate cysts are: Batioladinium radiculatum (FOD: E. Ryazanian, runctoni Ammonite Zone), Daveya boresphaera (kochi-stenomphalus Ammonite zones) and Systematophora daveyi (LOD: Early Ryazanian, kochi Ammonite Zone).
Depositional Setting Shoreface to offshore setting.
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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