Mont Héribu Member

The information on this page is a summary description.
The full formal description is available here: Mont Héribu Member

Abbreviation KoMh
Parent unit Kortrijk Formation
Child units
Lithological description Alternating horizontal laminae of glauconite bearing clayey sand or sandy clays with compact silty clays or clayey silts. Locally burrows are present. The base of the unit consists of cemented clayey sand and lenses of just sand. The unit occurs at the very base of the Ieper Group, except where the Zoute Mbr is present. The definition of the Mont‐Héribu is limited to the sandy base of the Ieper Group. This sandy base is 6 m in the Mons Basin, maximal 10 m southwest of Brussels but in most boreholes it is limited to 1 to 2m and rarely noticed i most boreholes (see for example sections in Gulinck, 1967). Therefore the interpretation of the extension of the Mont‐Héribu Member in the 1:50 000 mapping of Flanders is exaggerated and comprises for a large part the overlying Orchies Member. The definition refers to a grain‐size distribution with only a limited clay fraction and a coarser fraction that gradually evolves upward over a short distance to the larger clay content of the Orchies Member. This short pattern of rapidly fining upwards is the typical signature on GR and RES logs (see borehole logs ON‐Kallo‐1 014E0355, Rijkevorsel 007E0200).
Area of occurrence The unit was first reported as ‘Argile de l’ Eribus’ (Cornet, 1874, p 567) at the locality Eribus (‘Mont de l’Heribu’, south of Mons) which geology was studied by Ortlieb & Chelloneix (1870, p 168). In the Mons Basin the unit can reach up to 6m and; its maximum thickness is reported from Bierghes (southwest of Brussels) where it reaches 10m (Geets, 1991, including grain‐size data). In many borehole descriptions this unit is not formally recognised as an individual unit, or supposed to be reduced to just a few cm thickness; King (1991) interprets the occurrence of the Mont‐Héribu Member in central West Flanders and not in the Knokke well 011E0138. What is mapped as Yb on the Geological maps 1:40 000 logically corresponds to the Mont‐Héribu Member. In the Stratigraphic Register by the Conseil Géologique (1929) and translated by the Aardkundige Raad (1932), it is included in the Lower Ypresian Y1a.
Type locality Sand pit at the Mont de l’Héribu south of Mons between +57.5 en +51.4 m topographic height on the geological map 151 Mons‐Givry (topographic map 45/7). Coordinates: X = 119.750, Y = 124.510, Z = + 57,5 m.
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 Mont Héribu Member, 09/01/2017. National Commission for Stratigraphy Belgium.


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