Code
NM
Status
Formal (NAM & RGD 1980). Amended (Van Adrichem Boogaert & Kouwe 1997). The NU-Group, NM-Group and NL-Group can be taken together as North Sea Supergroup (code N).
Lithological description
Sands, silts and clays of a predominantly marine origin. The sands have their main distribution along the southern margin of the North Sea Basin.
Depositional setting
Predominantly marine. Lagoonal and coastal-plain environments only found in the area of South Limburg.
Definition of lower boundary
Rests with a distinct unconformity on the Lower North Sea Group (or older sediments) over most of the Netherlands onshore area. In the area of the Zuiderzee Low and the Voorne Trough, the lower boundary is poorly defined.
Definition of upper boundary
Unconformably overlain by the Breda Formation, except possibly in the Roer Valley Graben.
Thickness indication
Up to ~550 m.
Geographical distribution
Regional correlation
UK: ~Westray Group; GER: no equivalent group; BEL: Tongeren Group & Rupel Group.
Age
Priabonian - Chattian, possibly Aquitanian.
Holostratotype
Well:
Depth (thickness) AH:
860 - 1229 m (369 m)
Parastratotype
Well:
Depth (thickness) AH:
619 - 779 m (160 m)
Hypostratotype
Well:
Depth (thickness) AH:
867 - 1410 m (543 m)
Origin of name
Named after the North Sea. The prefix ‘Middle’ has been added to designate the middle (approximately Oligocene) part of the clastic sequence on top of the Chalk Group.
Previous name(s)
None.
Reviewed by (date)
Dirk Munsterman (2018).
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. 1997. Stratigraphic nomenclature of The Netherlands, revision and update by RGD and NOGEPA, Section I, Tertiary. Mededelingen Rijks Geologische Dienst, 50, 1-39.
Cite as
TNO-GDN ([YEAR]). Middle North Sea Group. In: Stratigraphic Nomenclature of the Netherlands, TNO – Geological Survey of the Netherlands. Accessed on [DATE] from https://www.dinoloket.nl/en/stratigraphic-nomenclature/middle-north-sea-group.