Bois-la-Haut Member

The information on this page is a summary description.
The full formal description is available here: Bois-la-Haut Member

Abbreviation MyBo
Parent unit Hyon Formation
Child units
Lithological description Poorly sorted, faintly laminated, prominently glauconitic and highly bioturbated clayey fine sand occur in the reference borehole section of this unit at the Mont‐Panisel (151E0340) (Steubaut & King, 1994). A separate 3,6 m thick layer at the base of the section in the Mont‐Panisel borehole (151E0340, between 18 and 21,58m), is highly glauconitic, highly bioturbated, rather well‐sorted fine to medium sand with clayey patches in contrast to the finer and less‐sorted sand above (see section in Steurbaut and King, 1994 fig.3). The lower part is named the Bois‐la‐Haut Member and the main upper part is called the Mont‐Panisel Member. The latter contains also numerous irregularly shaped siliceous sandstone concretions and locally poorly cemented nummulite‐bearing sandstones occur (Steurbaut, 2006). Maximal thickness is 20 m. Geets et al. (2000) report that somewhat coarser glauconite‐rich sand in boreholes between Aalst and Brussels could correspond to the Bois‐la‐Haut Member. The X‐stone bed , named Hooglede Bed in this review, underlying the Pittem Member in the Ampe/Egem quarry has also been tentatively suggested to be a lateral equivalent of the Bois‐la‐Haut Member by Steurbaut (1998) although in Steurbaut (2011, fig.8 p 255) the X‐stone bed is again included in the base of the Pittem Member. Although the Bois‐la‐Haut Member is until now only clearly identified in the Mont Panisel borehole, it is ranked as a member seen its thickness of several meter, more than the normal thickness for a lithostratigraphic bed.
Area of occurrence These deposits were originally described by d’Omalius d’Halloy (1862) as ‘psammites, sables et argiles du Mont‐Panisel’ at the Mont‐Panisel near Mons. The Mont‐Panisel Member occurs in the area Gent‐Brussel‐Mons‐ Kortrijk. The Mont‐Panisel Member overlies the Aalbeke Clay in clay pits around Kortrijk (e.g. Mulier clay pit) (Steurbaut 2006). The sands correspond to the previously used unit ‘Panisel sand’ in Steurbaut & Nolf (1986) and this Member corresponds to the ‘Unnamed Sand member’ in the top of the Mouscron borehole and the Kortrijk outcrops of King (1991 p 365). It also occurs in the hills of North France. It corresponds to the term ‘Paniselien’ used by Gulinck in his profiles around Brussels ( Archives Belgian Geological Survey, MG/00/250‐329‐547; MG/53/327; MG/55/335; MG/56/176‐177‐313‐316;.MG/58/249). Whereas in the Gent (055W1020) area the Egem Member subdivisions Yd4, Yd5, Yd6 (sensu Bolle & Jacobs, 1993) can be recognised between the Egemkapel (Yd3 unit sensu Bolle & Jacobs,1993) and the Merelbeke Clay, such identification becomes difficult to the east near the boundary with the Brabant province. It seems that in this latter area and more to the east, the Mont‐Panisel Member replaces the Egem Member. Jacobs et al. (1996a p 28) have reported that the Egem Member becomes more clayey to the south. In the southeast of East Flanders and the neighbouring eastern Brabant province, about 6 to 11 m of glauconitic sand occurs containing sandstone layers and overlies the Aalbeke clay Member in Kerksken (086E0340) and Kattem (087W0479) boreholes; its description corresponds to the Mont‐ Panisel Member (Geological Service Company, 2003). The typical Mont‐ Panisel sand in the borehole is overlain by a clayey sand of about 11 m which in its turn is capped by the Merelbeke clay Member. The lithostratigraphic position of this clayey sand unit overlying the Mont‐Panisel sand is further discussed under the Kwatrecht Member. The implication of this succession is also that towards the east, the Kortemark Member and the Egemkapel Member have disappeared. Also on the map sheet 23 Mechelen, Buffel et al. (2009) note that the Kortemark Member disappears to the east and is only present in the western part of the map. More northwards in the Brabant province (east of Aalst), the Merchtem borehole (072E0229) (Buffel et al., 2009) shows above the Aalbeke Member and below the Merelbeke Member, the same twofold borehole geophysical log signature and thickness as the Kerksken – 086E0340 and Kattem – 087W0479 boreholes, with the lower part being the typical Mont‐Panisel Member below a more clayey glauconitic sand without sandstones (see Kwatrecht Member). This pattern can also be observed further west and north‐westwards in geophysical logs (Meise borehole 073W0394 in Welkenhuysen & De Ceukelaire, 2009) and in grain‐size analysis of the Zemst‐ Weerde borehole (073E0359) (Buffel et al. 2009). The presence of Merelbeke clay in the Zemst‐Weerde ‐ 073E0359 borehole was confirmed by micropaleontological data (Buffel et al., 2009). Note that in the Zemst‐ Weerde‐ 073E0359 interpretation by Buffel et al. (2009) these two units together were named Egem Member, an interpretation not followed in the present review. Also, just north of Brussels in Vilvoorde, Gulinck described in his profile MG 00/504 ‘Paniselien’ above a clay rich top of the ‘Ypresian’ and below the Brussel and Lede Formations; this ‘Paniselien’ is characterised by stone layers in its lower part. Over a short distance to the east, between Zemst‐Weerde (073E0359) and Zemst‐Hofstade (073E0397) the Mont‐Panisel sand and the overlying clayey sand have disappeared, except maybe for a very thin remnant, and it appears that the Aalbeke and the Merelbeke clay Members are almost superposed (interpretation Johan Matthijs), although this needs micropaleontological confirmation. This superposition would imply the wedging out of the Mont‐Panisel and Kwatrecht units by erosion before the deposition of the Merelbeke Member rather than their later erosion before deposition of the overlying Zenne Group as would be the case if only Aalbeke clay is present (see also Merelbeke Member). On the other hand in the Kallo wells (027E0148/014E0355), more northwestwards, the Kortemark and Egemkapel Members can be recognised and between the Egemkapel and the Merelbeke clay Members the sandy unit is often interpreted as Egem Member, although identification as Hyon Formation is probably more prudent. The same log signature of the Hyon Formation interval in the Kallo well 014E0355 is also recognised in the Rijkevorsel 007E0200 borehole.
Type locality The section between 0 and about 21.58m depth in the borehole of the Mont‐ Panisel (151E0340) (topographic map sheet 45/7‐8 Mons‐Givry, (x=122.300, y= 125.375, z= +102m). As the Mont‐Panisel borehole is located in an outlier area of the Mont‐Panisel Member, the interval 46‐54 m in the borehole Zemst‐Weerde (073E0359) can be considered a parastratotype of the Mont‐Panisel Member (verslag Zemst, FV Matthijs‐Buffel, 2000; Steurbaut et al., 2015).
Alternative names
Authors Steurbaut, E., De Ceukelaire, M., Lanckacker, T., Matthijs, J., Stassen, P., Van Baelen, H. & Vandenberghe, N.
Date 09/01/2017
Cite as Steurbaut, E., De Ceukelaire, M., Lanckacker, T., Matthijs, J., Stassen, P., Van Baelen, H. & Vandenberghe, N., 2017. The Bois-la-Haut Member, 09/01/2017. National Commission for Stratigraphy Belgium.


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