Voort Member

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

Abbreviation VdVo
Parent unit Veldhoven Formation
Child units
Lithological description Fine-grained and clayey, green glauconitic sands, often rich in macrofossils. The Geological Survey of Belgium holds a rich collection of predominantly molluscs from the coal mine shaft digging at Voort locality (062W 0226).
Age Chattian ages established for the Veldhoven Formation in Belgium all refer to the Voort Member. No dating is available inside the Belgian Roer Valley Graben. In the Antwerp Campine the age of the deposits above the gravel layers encountered in the Weelde and Mol boreholes (or more in general between the gamma ray peaks of the Chattian S&T 06 and the Burdigalian Berchem black sand) is controversial: Chattian for Van Simaeys (2004) and De Man et al. (2010), hence assigned to the Veldhoven Formation vs Aquitanian to Burdigalian for Munsterman & Deckers (2020), hence assigned to the Berchem Formation and corresponding to the Edegem (and possibly Kiel) Member(s) of the Berchem Formation.
Thickness The Voort Member reaches a thickness of 135 m in Molenbeersel borehole in the Roer Valley Graben. In the eastern Limburg Campine its maximum observed thickness is 75 m, gradually thinning towards the erosive edges of the subcrop area. This thinning is partly due to gradually diminishing accommodation space around the strongly subsiding Roer Valley Graben, rather than to internal hiatuses, as shown by the regular occurrence of the S&T 06 marker bed.
Area of occurrence The Voort Member has the widest geographical extension of all units of the Veldhoven Formation and is the only recognizable member of the Veldhoven Formation outside the Roer Valley Graben. Current subcrop boundaries are of erosive nature, making discovery of additional outliers plausible, e.g. in the Antwerp harbour area. The Voort Member probably correlates with the Boncelles Sands on Tertiary sand outliers in the Hesbaye and Condroz areas.
Type locality Original type section of Voort Formation (now Voort Member of Veldhoven Formation): Coal mine shaft at Voort-Zolder (062W0226); reference section from -21 m to -45 m (Van Straelen, 1923; de Heinzelin & Glibert, 1957, p. 202); geological map 25/3-4 (Beringen-Houthalen). Co-ordinates: X = 217.330, Y = 192.725, Z = + 48,5 m.
Belgian parastratotype borehole Molenbeersel; GeoDoc 049W0226, ground level +33 m; Lambert coordinates x 247660, y 207752, Voort Member 840 – 975 m below ground level.
A further threefold subdivision of the Voort member can be made, based on a clayey marker horizon in the middle of the member:
Voort Member above gamma-ray peak 840-920 m S&T 07 to 09
Voort Member gamma-ray peak interval 920-940 m S&T 06
Voort Member below gamma-ray peak 940-975 m S&T 05
Lithostratigraphic subdivision of the Veldhoven Formation in the Molenbeersel borehole, with depth range and corresponding Schneider and Thiele hydrostratigraphic codes of the Lower Rhine Basin and Chattian age assignments based on correlation with type sections in the Lower
Alternative names Voort Formation, HCOVv2 hydrostratigraphic code (operated by VMM (2019)) for the Voort Member (named Voort zand 1): A0255.
Authors Dusar, M. & Vandenberghe, N.
Date 01/09/2023
Cite as Dusar, M. & Vandenberghe, N., 2023. The Voort Member, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Voort-Member
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