Gentbrugge Formation

Gentbrugge Formation
Stratigraphic range: Ypresian ~
Type	Geological formation
Unit of	Ieper Group
Sub-units	Egemkapel & Kortemark Members
Underlies	Aalter & Brussel Formations
Overlies	Mons-en-Pévèle Formation
Thickness	up to 50 m (160 ft)
Lithology
Primary	Sandstone, siltstone
Other	Claystone
Location
Region	West Flanders, East Flanders, & Antwerp
Country	Belgium
Extent	Campine Basin
Type section
Named for	Gentbrugge
Region	East Flanders

The Gentbrugge Formation (Dutch: Formatie van Gentbrugge, abbreviation: Ge; named after the town of Gentbrugge in East Flanders) is a geologic formation in the west of Belgium. The formation crops out in East Flanders and West Flanders and also occurs in the subsurface of the Province of Antwerp. It consists of marine clay, silt and sand, deposited in the shallow sea that covered northern Belgium during the Ypresian age (around 50 million years ago, part of the early Eocene).

Description

The Gentbrugge Formation reaches its greatest thickness in the north of Belgium, where it can be maximally 50 metres (160 ft) thick. It is subdivided into three members. The base of the formation is formed by silty clay and clayey silt (Merelbeke Member). On top of this are laminae of silt (Pittem Member) and beds of very fine sand, disturbed by bioturbation (Vlierzele Member). The sands can have horizontal bedding as well as cross bedding, and are often lithified into sandstone.

Stratigraphy

The Gentbrugge Formation is part of the Ieper Group and is stratigraphically on top of the older Mons-en-Pévèle Formation (micaceous sandstone), another formation of the same group. On top of the Gentbrugge Formation are deposits of the Lutetian Zenne Group. In the north of Belgium this is often the Aalter Formation (marine clays and sands). In the south the Aalter Formation often lacks and the younger Brussel Formation (marine sand and marl) and Lede Formation (marine calcareous sand) can be found directly on top of the Gentbrugge Formation.

See also

• List of fossiliferous stratigraphic units in Belgium
• Ypresian formations
  • Fur Formation of Denmark
  • London Clay Formation of England
  • Silveirinha Formation of Portugal
• Wasatchian formations
  • Nanjemoy Formation of the eastern United States
  • Wasatch Formation of the western United States
• Itaboraian formations
  • Itaboraí Formation of Brazil
  • Laguna del Hunco Formation of Argentina

References

Bibliography

• Steurbaut, Etienne; De Ceukelaire, Marleen; Lanckacker, Tim; Matthijs, Johan; Stassen, Peter; Van Baelen, Hervé; Vandenberghe, Noël (2017), An update of the lithostratigraphy of the Ieper Group (PDF), National Commission for the Stratigraphy of Belgium, pp. 1–79, retrieved 2020-09-07
• Steurbaut, Etienne (2006), "Ypresian", Geologica Belgica, 9: 73–93, retrieved 2020-09-07
• Laga, P.; Louwye, S.; Geets, S. (2001), "Paleogene and Neogene lithostratigraphic units (Belgium)", Geologica Belgica, 4 (1–2): 135–152, doi:10.20341/gb.2014.050, retrieved 2020-09-07