Roubaix Member

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

Abbreviation KoRo
Parent unit Kortrijk Formation
Child units
Lithological description In contrast with the underlying (Orchies Member) and overlying (Aalbeke Member) compact heavy clays, the Roubaix Member consists of more silty to fine sandy calcareous clays. The thickness varies from about 40m in south Belgium to 60m in North Belgium. Calcareous fossils like nummulites and molluscs are present. Glauconite‐rich horizons occur. The more heterogeneous composition of the sediment is shown by layering (see e.g. Marke quarry in Steurbaut, 2006 fig. 7), also well visible in the geophysical well logs. Several of these specific layers, labeled 1 to 6 in the log examples in the compendium, can be recognised and correlated between well logs with a reasonable degree of confidence. Based on the correlation of these levels, Welkenhuysen and De Ceukelaire (2009) have selected a specific level as the boundary level between the Orchies and the Roubaix Member which corresponds approximately to the position of the Steurbaut (1988) definition. On the geophysical logs in the compendium, this level can most easily and reproducibly be picked below the base of the first marked sandy excursion on RES logs (labeled 6 in the compendium) and the corresponding sharp drop in GR.
Area of occurrence The Roubaix Member occurs over northwest France, north Hainaut, east and west Flanders. Towards the south the occurrence of sandy layers becomes more pronounced whilst to the northwest the Member becomes more clayey and hardly distinguishable from the underlying Orchies Member (Geets et al., 2000). Towards the southeast and the east the Roubaix Member evolves into a fine sandy unit, the Formation of Mons‐en‐Pévèle (see further). The later introduced Moen Member (Belgian stratotype area, Geets, 1988; Maréchal, 1993) used in the legend of the 1:50 000 mapping of Flanders, is synonymous with the Roubaix Member. Roubaix is a town in North France and was the original reference for this clay type as described by Gosselet (1874) and therefore the name Roubaix Member is retained. In the 1:40 000 mapping the Roubaix Member was mapped in the Yc unit, however in the Kortrijk area it was erroneously mapped as Yd (Steurbaut & Nolf, 1986; Geets et al., 2000). In the Stratigraphic Register of the Conseil Géologique (1929) and the Aardkundige Raad (1932), the Roubaix Member is included in the Y1a unit.
Type locality The Roubaix Member was previously exposed along the Bossuit Canal at Moen (near Kortrijk) (Steurbaut & Nolf, 1986) and in the Marke and Heestert clay pits near Kortrijk. As these outcrops are no longer accessible a reference section for the lower boundary is choosen in the Kallo well (Gulinck, 1969) at 341m depth (see further) whilst an upper boundary with the overlying stiff clays has been visible in the former Kobbe clay pit (DOV kb29d97e‐B989) at Aalbeke (x= 68.450, y= 164.300, z= 49 m) Steurbaut (1998).
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 Roubaix Member, 09/01/2017. National Commission for Stratigraphy Belgium.


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