Slochteren Formation ROSL

 

Premise This unit was originally described as a member of the Upper Rotliegend Formation by Stäuble and Milius (1970) . van Adrichem Boogaert (1976) raised it to formation status, which was adopted by NAM and RGD (1980) .
   
Derivatio nominis Named after the municipality of Slochteren, where the well Slochteren-1 discovered gas in the Upper Rotliegend Group in 1959, and consequently, the Groningen field.
Type section Location map See figure (pdf)
  Well Slochteren-4 (pdf)
  Location N 53°11’33.2
E 06°45’14.9
  Depth 2709 to 2856 m
  Length 147 m along hole
  Reference NAM and RGD (1980)
Additional section Location map See figure (pdf)
  Well Uithuizermeeden-1 (pdf)
  Location N 53°26’58.9
E 06°48’29.2
  Depth 2949 to 3041 m
  Length 92 m along hole
  Depth 3058 to 3167 m
  Length 109 m along hole
  Reference NAM and RGD (1980)
Definition Sequence of usually pink to pale red-brown, occasionally yellow or grey, sandstones and conglomerates with subordinate amounts of intercalated dark red, red-brown or green-grey silty claystones. The sandstones show a wide range of grain sizes, textures and sedimentary structures. The uppermost tens of metres, immediately below the contact with the Zechstein Group, may show a massive, fluidised or brecciated, intensely cemented character.
Upper Boundary The unit is overlain by either red-brown claystones of the Silverpit Formation or black bituminous shales of the Coppershale Member of the Z 1 (Werra) Formation.
Lower Boundary The formation unconformably overlies the Limburg Group (or locally volcanics of the Lower Rotliegend Group). In the area of Ameland and Terschelling it conformably overlies a tongue of the Silverpit Formation (Hollum Member or Buren Member).
Correlation Towards the basin centre, the Slochteren Formation interfingers with and grades into the Silverpit Formation. At the basin fringe, younger deposits of the Zechstein Group rest upon the Slochteren Formation.
Distribution The formation is encountered almost across the entire Dutch sector of the Southern Permian Basin, although in the centre of the basin it is generally restricted to a very thin basal sandstone bed. The maximum thickness is found in the Off Holland Low.
Age Saxonian. According to recent studies Menning (1994) , this middle-European age most likely belongs to the Late Permian (Tatarian). Initially, deposition was restricted to the centre of the basin, subsequently the southern flank of the basin was progressively incorporated in this depositional realm. This is reflected in onlap of the Slochteren Formation from north to south. At the same time the facies belt of the Slochteren Formation was replaced progressively from the north by the depositional environment of the Silverpit Formation.
Depositional Setting Using textural parameters and sedimentary structures, the Slochteren Formation can be subdivided into deposits laid down by wind and those laid down by water. The aeolian deposits can be differentiated further into dunes and sand flats (dry, damp and wet). The water-laid sandy deposits can be subdivided into fluvial channel fills (low- and high-sinuous, highly ephemeral to perennial) and sheet floods. The associated fine-grained deposits have been attributed to lakes, interdune ponds and sabkha mudflats. For decriptions of these lithofacies the reader is referred to Glennie (1972) and Glennie (1990) , Reijers et al (1993) . The local occurrence of intensely cemented, fluidised or brecciated sandstones in the top of the formation has been explained as an effect of ‘instantaneous’ flooding during the Late Permian Zechstein transgression.
Subdivision The Slochteren Formation can be subdivided into two members. Locally, in central Friesland and northeastern Drenthe, a grey sandstone tongue of the Slochteren Formation occurs wedged between the Ten Boer Member and the base of the Zechstein Group. It has informally been called the Akkrum Sandstone member (ROSLA) (RGD (1993) .
  ROSLU Upper Slochteren Member
  ROSL Lower Slochteren Member
References See References Permian

Van Adrichem Boogaert, H.A. & Kouwe, W.F.P., 1993-1997. [Stratigraphic unit]. In: Stratigraphic Nomenclature of the Netherlands.
Retrieved [Datum] from [url].