Scruff Spiculite Member SGGSP


Premise The Scruff Spiculite Member is defined by Van Adrichem Boogaert & Kouwe (1993). The member is included in the Scruff Greensand Formation, Scruff Group.
Derivatio nominis Named after the offshore Upper Scruff Bank near well F03-03.
Type section Location map See figure (pdf)
  Well F15-02-S1 (pdf)
  Location N 54°14’18.5
E 04°50’44.9
  Depth 3041 to 3065 m
  Length 24 m along hole
Additional section Location map See figure (pdf)
  Well F18-01 (pdf)
  Location N 54°05’54.5
E 04°44’32.1
  Depth 2193 to 2230 m
  Length 37 m along hole
Definition The member consists of light green-grey, fine-grained, glauconitic and slightly argillaceous intensely bioturbated sand- stones. Primary sedimentary structures are absent. The name of the unit refers to the abundance of spicules in the sediment. Spicules are the skeletal remains of sponges. The sponge spicules may make up the bulk of the framework forming a bioclastic sandstone.
Upper Boundary The member is mildly unconformably overlain by the Stortemelk Member. The boundary is placed at the transition of a cylinder- or funnel-shaped GR-log pattern (Scruff Spiculite Member) to a bell-shaped pattern (Stortemelk Member). This level is nearly always marked by a clear GR-log peak, belonging to the Stortemelk  Member.
Lower Boundary The lower boundary with the Noordvaarder and the Lies members is marked by an increase in GR-log readings, resulting from the downward increasing clay content. The boundary coincides with the Sequence 2 / Sequence 3 boundary sensu Abbink et al. (2006). Sequences 2 and 3 are relatively thick in the Terschelling Basin as compared to the Central Graben. A hiatus occurs in the Central Graben, but deposition was continuous in the depocentre of the Terschelling Basin (Abbink et al., 2006). The abundant occurrence of the sponge spiculae or its moulds may be taken as an additional criterion.
Distribution The Scruff Spiculite Member is developed in the southern Dutch Central Graben and in the Terschelling Basin, blocks F11 (p.p.), F12, F15, F18, L02 (p.p.), L03, L05 (p.p.), L06 (p.p.), M01, M04 and M07 (see pdf).
Age Sequence 3 sensu Abbink et al. (2006): latest Middle Volgian - Early Ryazanian, oppressus-base kochi Ammonite Zone. The base of the member is characterised by the acme of the dinocyst Cribroperidinium hansenii (oppressus-primitivus Ammonites zones). The LOD (= runctoni Ammonite Zone) of Gochteodinia virgula is recorded in this unit. The transition from the Spiculite to the Stortemelk member coincides with the Early Ryazanian kochi climate shift.
Depositional Setting The sediments of this formation were deposited in a (offshore to) shoreface environment. Facies change laterally from relatively clean ‘bioclastic’ sandstone to an argillaceous sandstone reflecting the position of the depositional area on the basin floor topography (Abbink et al., 2006). A semi-enclosed shallow marine environment is envisaged.
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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