Asse Member

NLDOAS

Formal (NAM & RGD 1980). Amended (Van Adrichem Boogaert & Kouwe 1997).

Dark greenish-grey and blue-grey, plastic clay. Locally indications of bioturbation, and glauconitic (in particular at the base) and some micaceous. Generally, it is slightly to non calcareous. Notably the upper part of the member is sandy and free of calcium carbonate in a proximal position. In the eastern Netherlands, close to the palaeo-coastline, this part is very sandy, has a brownish colour and contains lignite fragments. The border zone of the basin comprises shells and Nummulites at the base.

Open-marine unit, possibly deposited in rather shallow water (Water depth of Oosteind, Ieper and Asse: up to 200 m).

The lower boundary is located at the transition to the Brussels Sandstone Member or Brussels Marl Member. This is generally a clear break, but it may be somewhat gradual in places.

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 Berg 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 Berg Member is absent, the Boom Member rests directly on the Asse or Engelschhoek members, complicating the definition of the upper boundary on lithological grounds. However, on wire-line logs, the Boom Member shows a somewhat higher gamma-ray response compared to the clays of the Lower North Sea Group. Biostratigraphic analysis is commonly applied to verify this transition.

Up to 375 m.

UK: ?; GER: ?; BEL: not completely equivalent to the Asse Member of the Maldegem Formation in the Belgian lithostratigraphic nomenclature (Marechal and Laga 1988). The Dutch Asse Member comprises an interval in northwestern Belgium that consists 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.

middle Eocene - late Eocene (Lutetian - Bartonian).

The name has been derived from the municipality of Asse in the Belgian province of Brabant.

None.

Geert-Jan Vis (2019).

Maréchal, R., Laga, P. (eds.) 1988. Voorstel lithostratigrafische indeling van het Paleogeen - Nationale Commissies voor Stratigrafie. Commissie: Tertiair, Belgische Geologische Dienst, Brussel, 208 p.

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.