Middle North Sea Group NM


Premise Original definition by NAM and RGD (1980) . Lower and upper boundaries amended.
Derivatio nominis 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.
Type section Location map See figure (pdf)
  Well Veldhoven-1 (pdf)
  Location N 51°26'20.8
E 05°21'37.2
  Depth 860 to 1229 m
  Length 369 m along hole
  Reference amended after NAM and RGD (1980)
Additional section Location map See figure (pdf)
  Well Asten-1 (pdf)
  Location N 51°23'47.7
E 05°47'27.3
  Depth 867 to 1410 m
  Length 543 m along hole
  Well Doornspijk-2 (pdf)
  Location N 52°24'36.2
E 05°46'15.6
  Depth 619 to 779 m
  Length 160 m along hole
  Reference NAM and RGD (1980)
Definition Group of formations consisting of sands, silts and clays of a predominantly marine origin. The sands have their main distribution along the southern margin of the North Sea Basin.
Upper Boundary The Middle North Sea Group is unconformably overlain by the Breda Formation, except possibly in the Roer Valley Graben.
Lower Boundary Over most of the Netherlands onshore area, the Middle North Sea Group rests with a distinct unconformity on the Lower North Sea Group (or older sediments). In the area of the Zuiderzee Low and the Voorne Trough (see pdf) , the lower boundary is ill-defined.
Distribution Present over most of the Netherlands on- and offshore area. Absent only locally in the (south) eastern and southwestern parts of the onshore area.
Age Priabonian (NP 19/20) to Chattian (NP 25), possibly Aquitanian (NN 1-2). In the lower part biostratigraphical control is poor and NP 18 is presumed to be absent. The foraminiferal assemblages belong to the FG-FE2 zonal interval as defined by Doppert and Neele (1983) .
Depositional Setting Predominantly marine. Lagoonal and coastal-plain sediments are restricted to the area of South Limburg.
Sequence Stratigraphy The Middle North Sea Group approximately covers the time interval represented by Haq (1988) 's sequences TA 4.2 - TB 1.5. Second-order changes in sea level are rather easily identified in the record (Figure I.7). The main part of the Rupel Clay Member was deposited during the Rupelian, a period characterised world-wide by a high sea level. The upper part of the Rupel Formation and the Voort Member of the Veldhoven Formation correspond to the Chattian, a period of a global low sea level. The main part of the clays on top of the Voort Member is thought to represent the Aquitanian, a second high sea-level period.
Subdivision Three formations are recognised:
  NM Middle North Sea Group
  NMVF Veldhoven Formation
  NMRF Rupel Formation
  NMTF Tongeren Formation
References See References Tertiary

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