Lower North Sea Group NL

 

NL Lower North Sea Group

Premise The group was originally defined by NAM and RGD (1980) . The new nomenclature is, as was the previous one, partly based on the Belgian nomenclature, published by Marechal and Laga (1988) . The Belgian lithostratigraphy is largely based on thorough outcrop studies, resulting in a very detailed subdivision. Such detail cannot be applied to the Dutch subsurface, where only well information is available. Therefore the lithostratigraphic units in this country are usually of a more generalized nature and consequently larger in size (see Figure I.1).
Derivatio nominis Named after the North Sea. The prefix ‘Lower’ has been added to designate the lower part of the clastic sedimentary succession lying immediately on top of the Chalk Group.
Type section Location map See figure (pdf)
  Well Dongen-1 (pdf)
  Location N 51°37'37.0
E 04°54'48.2
  Depth 691 to 1063 m
  Length 372 m along hole
  Reference NAM and RGD (1980)
Additional section Location map See figure (pdf)
  Well L02-04 (pdf)
  Location N 53°51'22.2
E 04°38'59.2
  Depth 1007 to 1583 m
  Length 576 m along hole
  Reference NAM and RGD (1980)
Definition Essentially a group of formations consisting of an alternation of grey sands and sandstones and clays. They are the result of several small- and large-scale, clastic sedimentation cycles in a marine realm along the edge of the North Sea Basin.
Upper Boundary The upper boundary is characterised by unconformably overlying deposits of the Middle North Sea Group or younger units.
Lower Boundary In large parts of the onshore area, the lower boundary is characterised by an unconformity, expressed as a sharp lithologic break marking the top of the Chalk Group. Elsewhere, the group rests with a distinct unconformity on still older deposits.
Distribution The group occurs all over the Netherlands, both on- and offshore, with the exception of an WNW-ESE trending zone in the central Netherlands (i.e. the ‘Southern Early Tertiary High’; see Introduction , 1.1), the easternmost part of the country and the extreme southernmost part of the province of Limburg.
Age Late Paleocene to Middle Eocene (Thanetian to Bartonian). This group is thought to cover the time interval characterised by nannoplankton zones NP 6-17. Large parts of the group do not contain nannofossils, and only floras characteristic of zones NP 8-16 have actually been identified. The foraminiferal assemblages are characteristic of zones FJ to FH of Doppert and Neele (1983) .
Depositional Setting Predominantly marine. An exception is the Swalmen Member, deposited in a brackish to non-marine environment.
Sequence Stratigraphy The Lower North Sea Group as a whole spans the upper part of the Thanetian to the Bartonian and corresponds to sequences TA 2.1 to TA 3.6. Most members that have been deposited in an open-marine depositional setting are correlatable over large distances.
Subdivision  
  The group has been subdivided into two formations;
  NLFF Dongen Formation
  NLLF Landen Formation
References See References Tertiary

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