|Premise||The Central Graben was defined as a group by NAM & RGD (1980) and down-graded in status to a subgroup by Van Adrichem Boogaert & Kouwe (1993). The subgroup contains all formations of the Schieland Group that have been deposited in the Dutch Central Graben and Terschelling Basin.|
|Derivatio nominis||Named after the Central Graben in the northern Dutch offshore.|
|Type section||Location map||See figure (pdf)|
|Depth||2547 to 3652 m|
|Length||1105 m along hole|
|Reference||Herngreen and Wong (1989); Munsterman et al. (2012)|
|Additional section||Location map||See figure (pdf)|
|Depth||2422 to 2686 m|
|Length||264 m along hole|
|Reference||Munsterman et al. (2012)|
|Definition||Subgroup of mainly non-marine sediments consisting of variegated claystones, silty to clayey sandstones and distinct coal layers or calcareous intercalations are locally present.
|Upper Boundary||Usually the Central Graben Subgroup is conformably overlain by the marine Scruff Group. In the centre of the Dutch Central Graben however, the Rijnland Group or younger groups unconformably rests on this group, if a prominent Late Kimmerian II unconformity is developed.|
|Lower Boundary||The Central Graben Subgroup rests unconformable on the marine claystones of the Lower to Middle Jurassic Altena Group, or even on older Lower and Upper Germanic Trias and Zechstein groups.|
|Distribution||The subgroup is mainly developed in the Dutch Central Graben. In addition to the southernmost Central Graben, the youngest part of the Subgroup, i.e. the late occurrences of the Friese Front Formation, are also present in the Terschelling Basin (see pdf)|
|Age||In the Dutch Central Graben the subgroup is dated as Sequence 1 sensu Abbink et al. (2006): Middle Callovian- Oxfordian. In the southernmost Central Graben the early Sequence 2 is also reached: Kimmeridgian. In the Terschelling Basin the age is limited to the earliest Sequence 2: late Early Kimmeridgian- Early Volgian, mutabilis-hudlestoni Ammonite zones.|
|Depositional Setting||Mostly non-marine coastal to delta plain deposits, with intermittent marine sediments, deposited during transgressions.|
|Subdivision||The Central Graben Subgroup is differentiated into five formations:|
|SLCF||Friese Front||Formation (amended)|
|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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