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2.6.1. Hannut Formation - Hn

Author: De Geyter (1988a).

Description: this marine unit consists of clay, sandy clay and silt, siliceous limestone, siltstone and sandstone, mostly covered by glauconitic, fine sand.

Stratotype: stratotypes have only been designated for the members.

Area: the formation extends almost over the whole northern part of Belgium. The outcrops are mainly situated in the Hesbaye area and in Hainaut.

Thickness: the formation thickens to the northeast and reaches more than 100 m in the Campine (Mol borehole). In the Mons Basin the maximum thickness is about 55 m. In East- and West-Flanders the thickness mostly varies between 20 and 40 m, but mark-edly decreases in the north of West-Flanders (Knokke borehole).

Members: the formation is subdivided into the Chercq Mbr (Hainaut), the Lincent Mbr (Hesbaye area), the Halen Mbr and the Waterschei Mbr (northeast Belgium), and the Grandglise Mbr (almost the whole northern part of Belgium).

Age: Early and Middle Thanetian.

Remarks: the formation is also discussed by Baudet (1939), Cornet (1899), De Geyter (1980, 1981), D'Omalius d'Halloy (1939, 1842), Gullentops et al. (1995), Gulinck (1948), Gulinck & Hacquart (1954), Kaaschieter (1961), Lyell (1852a), Macar et al. (1947), Maréchal (1993), Moorkens (1972b, 1982), Nijs & De Geyter (1985), Steur-baut (1998) and Vincent & Rutot (1879).