Asse Member NLFFB


Premise Originally defined by NAM and RGD (1980) . This unit is not completely equivalent to the Asse Member of the Maldegem Formation in the Belgian lithostratigraphic nomenclature Marechal and Laga (1988) . The Asse Member in the Dutch sense comprises an interval which consists in northwestern Belgium of an alternation of clay and sand units, which are accommodated as various members within the Maldegem Formation Marechal and Laga (1988) . With the exception of the southwesternmost part of the country, the equivalent sediments are predominantly argillaceous in the Netherlands and therefore the Asse Member has not been subdivided.
Derivatio nominis The name has been derived from the municipality of Asse in the Belgian province of Brabant.
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 735 m
  Length 44 m along hole
  Reference NAM and RGD (1980)
Additional section Location map See figure (pdf)
  Well Overflakkee-1 (pdf)
  Location N 51°46'3724.5"
E 04°02'13.8"
  Depth 444 to 615m
  Length 171 m along hole
  Well L02-04 (pdf)
  Location N 513°51'22.2"
E 04°38'59.2"
  Depth 1007 to 1035 m
  Length 28 m along hole
  Reference NAM and RGD (1980)
Definition The member consists of dark greenish-grey and blue-grey, plastic clays. The unit locally shows indications of bioturbation, and may be glauconitic and somewhat micaceous. Generally, it is slightly calcareous. Notably the upper part of the member is sandy and free of calcium carbonate in a proximal position. In eastern Netherlands, close to the palaeo-coastline, this part is very sandy, has a brownish colour and contains lignite fragments.
Upper Boundary Where the succession is not truncated by later erosion, the Asse Member is in most of the Netherlands on- and offshore area, unconformably overlain by the Rupel Formation. Where the latter starts with the sandy Vessem Member, as is the case in the central Netherlands, the upper boundary is well defined by the rather sharp transition to this overlying sandy unit. Where the Vessem Member is absent, the Rupel Clay Member rests directly on the Asse or Dongen Clay Members, complicating the definition of the upper boundary on lithological grounds. However, on wire-line logs, the Rupel Clay Member shows a somewhat higher gamma-ray response compared to the clays of the Lower North Sea Group. Palaeontological dating is commonly applied to assist in the determination of this boundary
Lower Boundary The lower boundary is located at the transition of the Brussels Sandstone Member or Brussels Marl Member to the more pure clays of the Asse Member. This is generally a clear break, but it may be somewhat gradual in places.
Distribution The member is present in the southwestern Netherlands and adjacent offshore area, and the northern to northeastern Netherlands (with the exception of the northern- and easternmost parts) and adjacent offshore area. Where the Brussels Marl Member has wedged out in the distal portion of the basin it can no longer be discerned as a separate member. There it merges into the Dongen Clay Member. The member is absent as a result of erosion on and around the ‘Southern Early Tertiary High‘.
Age Middle and Late Eocene (Lutetian to Bartonian). The member is thought to cover the time interval characterised by nannoplankton zones NP 16 and NP 17. Biostratigraphic control, however, is poor and only zone NP 16 has been identified positively. The main part of the member is devoid of nannofossils or yields non-diagnostic floras. The foraminiferal subzone FH1 has been found in the Asse Member.
Depositional Setting Open-marine unit, possibly deposited in rather shallow water.
Sequence Stratigraphy The Asse Member comprises Transgressive and Highstand systems tracts of cycles TA 3.4, TA 3.5 and TA 3.6.
  No functional subdivision of the Asse member can be made in the available exploration wells on the basis of the present knowledge. In the southwestern corner of the Netherlands, where well-logged and properly described, shallow boreholes have been drilled in this unit, the same subdivision as used in Belgium Marechal and Laga (1988) may be applied.
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].