Altena Group

Code
AT
Status
Formal (NAM & RGD 1980). Amended (Van Adrichem Boogaert & Kouwe 1994).
Lithological description

Predominantly fine-grained mudstones with occasional silt- and sandstones. Incidentally organic-carbon concentrations are substantially elevated.

Depositional setting

Neritic environment in a generally open-marine basin. Occasionally basin circulation stagnated. With periods of lower sea level and/or tectonic activity.

Definition of lower boundary

Conformably overlies the red-brown, variegated, anhydritic beds of the Keuper Formation. Locally, unconformably upon this unit, or on the underlying Muschelkalk Formation or on older units of the Upper Germanic Trias Group, locally even on Zechstein deposits.

Definition of upper boundary

Unconformably by the, generally variegated, siliciclastic deposits of the Schieland Group or the shallow-marine sediments of the Rijnland Group. In inverted parts of the West Netherlands Basin, the Roer Valley Graben, the Broad Fourteens Basin and the Central Netherlands Basin the group is often overlain unconformably by the Chalk Group, the Lower North Sea Group or the Middle North Sea Group.

Thickness indication
Extremely variable (up to 2900 m) as often eroded through inversion.
Geographical distribution
Regional correlation
UK: West Sole Group & Lias Group; GER: Dogger Group & Lias Group; BEL: Aalburg Formation.
Age
Rhaetian - early Oxfordian.
Holostratotype
Depth (thickness) AH:
1507 - 2838 m (1331 m)
Origin of name
The Altena Group is named after ‘Het Land van Altena’, the northern part of the Dutch province of Noord-Brabant, where the most complete sequence of the group has been encountered in wells.
Previous name(s)
None.
Reviewed by (date)
Sander Houben (2017).
References
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.
Cite as
TNO-GDN ([YEAR]). Altena Group. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from http://www.dinoloket.nl/en/stratigraphic-nomenclature/altena-group.