Brussels Sand Member NLFFS

 

Premise Originally defined by NAM and RGD (1980) , with the intention to follow the Belgian nomenclature. Unfortunately, it was later discovered that the Dutch Brussels Sand Member was not the equivalent of the Belgian Brussel Formation Marechal and Laga (1988) , but covers a much larger stratigraphic interval (see Figures I.1 and I.5). However, for the sake of continuity of the Dutch nomenclature, it is suggested here to retain the name ‘Brussels Sand Member’.
Derivatio nominis The name refers to the capital of Belgium, Brussels, and to the prevailing lithology.
Type section Location map See figure (pdf)
  Well Dongen-1 (pdf)
  Location N 51°37'37.0
E 04°54'48.2
  Depth 735 to 844 m
  Length 109 m along hole
  Reference NAM and RGD (1980)
Definition Succession of green-grey, glauconitic, very fine-grained sand with, mainly in the upper part, a number of hard, calcareous sandstone layers of some decimetres thickness (leading to high-resistivity peaks). Towards the base of the unit the clay content increases, and the calcium carbonate content and amount of glauconite decreases. A minor amount of mica occurs. Farther from the palaeo-coastline the member becomes silty and marly. The upper part with the cemented, calcareous sandstone layers is very rich in fossil fragments, especially in the Achterhoek and Twente: abundant Nummulites, shells (including Pecten) and Echinodermata, indicating a near-shore environment. Near the palaeo-coastline and on palaeo-highs the lower part of the member may be missing because of non-deposition and/or erosion.
Upper Boundary The upper boundary with the overlying Asse Member is formed by the clear transition from sands to clays. Over large areas, the Brussels Sand Member has been eroded and is overlain by younger deposits.
Lower Boundary The lower boundary to the Ieper Member is variable in nature. Regionally it is an unambiguous boundary between the clays of the Ieper Member and the overlying sands. However, in many places the boundary is gradual and complex in nature, because different parts of the succession are missing locally as a result of several phases of erosion and/or non-deposition.
Distribution The Brussels Sand Member is present in the southwestern Netherlands and adjacent offshore area, the northern to northeastern Netherlands (with the exception of the northern- and easternmost parts). It is missing as a result of erosion on the ‘Southern Early Tertiary High’. Towards the distal part of the basin, the Brussels Sand Member grades into the Brussels Marl Member.
Age Early and Middle Eocene (Ypresian to Lutetian). The nannoplankton zones NP13 to NP 15 are represented in this member. The member comprises the foraminiferal subzones FH1 and FH2. The age of this member can vary rather drastically from one area to the next, because parts of the succession may be absent. On some palaeo-highs only the youngest part of the unit is present, represented by the NP 15; the NP 13 and 14 are missing there.
Depositional Setting Marine unit, deposited in inner-neritic to near-shore environment. In general, the water depth appears to be shallowing upwards, with a possible exception for the uppermost part of the unit.
Sequence Stratigraphy The Brussels Sand Member comprises the interval covered by the Highstand systems tract of cycle TA 2.7 and the Transgressive systems tract of cycle TA 3.4.
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].