The information on this page is a summary description.
The full formal description is available here: Vert Galand Formation
Abbreviation
VEG
Parent unit
Child units
Bruyelle Member, Merlin Member
Lithological description
The Vert Galand Formation groups the marly facies of Turonian age, which were known as Dièves and Fortes Toises. The Vert Galand Formation (VEG) consists of two distinctive members, the Bruyelle and Merlin Members. Summary description from Hennebert & Doremus (1997a, b), from top to bottom:
VEG Fm Merlin Member: greenish-grey marls, with fine glauconite; white marl with grey siliceous concretions.
VEG Fm, Bruyelle Member: greenish-grey marl, with phosphatised gravel at the base; pale-grey marl with fine to coarse glauconite grains.
Age
Turonian
Thickness
Up to 75 m in the Mons basin, 50 m in the Tournai basin.
Area of occurrence
Mons (Haine) and Tournai basins, transgressing over the Brabant Parautochton, extending into the North of France.
Type locality
No formal stratotype defined for the formation. The 19th century quarries in Tournaisian limestone of the quartier Longuesault Barges Vert Galand southwest of Tournai allowed observations of the Cretaceous overburden. Decimal geographical coordinates for Rue du Vert Galant 50,576 3, 363; Lambert 72 coordinates 78750 – 141100.
Alternative names
Authors
Dusar, M.
Date
01/12/2017
Cite as
Dusar, M., 2017. The Vert Galand Formation, 01/12/2017. National Commission for Stratigraphy Belgium. https://ncs.naturalsciences.be/lithostratigraphy/Vert-Galand-Formation
Additional information
Sea level rise resulted in ever younger base of the Turonian transgression over the Brabant Parautochton, albeit with the same lithological succession (Marlière, 1954). However, the Turonian subcrop area in the south of West Flanders is not in a more marginal position compared to the Tournaisis area, quite on the contrary. As the Bruyelle and Merlin Members are deposited in regular succession and often are encountered in normal superposition, it seemed logical to group them in one formation. More detailed descriptions are given at the member level for the Bruyelle and Merlin members. A somewhat different approach was applied in the Flemish region. The 3D model of the subsoil in Flanders requires a complete stratigraphic subdivision for all rock units encountered (Matthijs et al., 2013). The Brabant Massif is overlain by uniform white chalks, assigned to the Nevele Formation (Dusar & Lagrou, 2007), equivalent of the white chalks, from Saint-Vaast to Nouvelles Formations in the Mons basin. South of the axial zone of the Brabant Massif, overlying the Brabant Parautochton the subcropping Cretaceous strata become more diversified and connect to the Cretaceous in the Nord and Wallonia. Indeed, the general stratigraphic framework can be applied, and more particularly the connection to the lithostratigraphic scale developed for the new geological map of Wallonia is rather obvious. However, the further subdivision is based on different criteria: observations from exposures in Wallonia, from boreholes with geophysical well logs in Flanders. Initially, because correlations at the member level are not secured, a regional set of lithostratigraphical subdivisions was applied for the 3D geological model of Flanders (Lagrou et al., 2011) by introducing the Nieuwkerke De Seule Member and Nieuwkerke Noordhoek member for the Bruyelle and Merlin members respectively. Today, the correspondence rather than discrepancies are emphasized, unifying therefore the stratigraphical schemes for the Flemish and Walloon regions.
