Terschelling Sandstone Member SGSKT


Premise The Terschelling Sandstone Member is defined by Van Adrichem Boogaert & Kouwe (1993). The member is included in the Skylge Formation, Scruff Group.
Derivatio nominis Named after the Terschelling Basin (see pdf) , where this member is typically developed.
Type section Location map See figure (pdf)
  Well L06-02 (pdf)
  Location N 53°48’53.7
E 04°59’19.97
  Depth 2463 to 2500 m
  Length 37 m along hole
Additional section Location map See figure (pdf)
  Well L03-01 (pdf)
  Location N 53°56’55.4
E 04°40’22.0
  Depth 2399 to 2482 m
  Length 83 m along hole
Definition Fine- to medium-grained sandstone (occasionally up to coarse sand and gravel), well to poorly sorted. Carbonate cement, glauconite and lignite are common. The sandstones predominantly show fining but locally coarsening upward trends. Deposition mainly in the form of sheets and channels, separated by thin intervals of claystones. Note that the Terschelling Sandstone Member in the former type well L09-02 (interval 3028-3054 m) is not the most representative section. In this well the Terschelling Sandstone Member is unconformably underlain by the Aalburg Formation. It was selected due to the lack of public wells in the early nineties. A more appropriate type section is L06-02 (interval 2463-2500 m), although the true vertical thickness of this member may be reduced by faulting.
Upper Boundary The member is conformably overlain by the shallow marine calcareous claystones of the Lies Member. The top of the Terschelling Sandstone is diachronous. The youngest (latest Kimmeridgian) successions occur in the southern Terschelling Basin, blocks L06 and M04.
Lower Boundary The conformable basal contact with the Oyster Ground Member is characterised by a sharp downhole change to finer-grained deposits (base of the sandstone bed), the appearance of restricted-marine (lagoonal) fossils, a change towards higher GR log readings and a more serrated sonic log pattern. In the type section well L06-02, the member unconformably rests on the Altena Group. In the deepest part of the Terschelling Basin, in well L03-01, interfingering is shown with the Oyster Ground Member. The Terschelling barrier sands in well L03-01 alternate with fine-grained lagoonal sands.
Distribution The Terschelling Sandstone is deposited in the southeastern Dutch Central Graben and the Terschelling Basin, blocks L02, L03, L05, L06, L09, M01, M04 and M07 (see pdf).
Age equence 2 sensu Abbink et al. (2006): Early-Middle Volgian. The top of the member is diachronous. In general the top coincides with the Early Volgian J66 MFS sensu Partington et al. (1993), but in the southern Terschelling Basin (blocks L06 and M04) the top is associated with the Middle Volgian J71 MFS sensu Partington et al. (1993). The Middle Volgian is characterised by the presence (FOD) of Muderongia sp. A sensu Davey (1982).
Depositional Setting In most cases, e.g. in wells L06-02, L06-03 and M01-01, the sediments of this member are interpreted to be deposited as a barrier island complex, including shoreface to foreshore and washover fans environments, protecting the restricted marine (lagoonal) setting of the Oyster Ground.
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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