Formal (NAM & RGD 1980). Amended (Van Adrichem Boogaert & Kouwe 1994).
Sequence of grey, fossiliferous, claystones, overlain by brown, locally sandy claystones (often containing a considerable quantity of megaspores).
Shallow, open-marine environment. Organic-rich intervals are likely deposited under stagnant water conditions.
Definition of lower boundary
On top of the reddish anhydritic mudstone beds of the Keuper Formation (Upper Germanic Trias Group). In the eastern part of the Netherlands the formation locally rests unconformably upon older members of the Keuper Formation or the light-greenish/grey carbonates and marls of the Muschelkalk Formation or Röt Formation.
Definition of upper boundary
Covered by the argillaceous limestone of the Aalburg Formation.
Generally less than 80 m, but up to 156 m in F18-05.
UK: Penarth Group; GER: Lias Group; BEL: Sleen Formation.
Origin of name
Named after the municipality of Sleen, which is situated in the southeastern part of the Dutch province of Drenthe.
NAM & RGD 1980. Stratigraphic nomenclature of The Netherlands. Verhandelingen van het Koninklijk Nederlands Geologisch Mijnbouwkundig Genootschap 32, 77 p.
Van Adrichem Boogaert, H.A. & Kouwe, W.F.P. 1994. Stratigraphic nomenclature of The Netherlands; revision and update by RGD and NOGEPA, Section F, Lower and Middle Jurassic. Mededelingen Rijks Geologische Dienst, 50, 1-20.
TNO-GDN ([YEAR]). Sleen Formation. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from https://www.dinoloket.nl/en/stratigraphic-nomenclature/sleen-formation.