The Hannut Formation (french: Formation de Hannut; nl, Formatie van Hannut; abbreviation: Hn) is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

in the

subsurface In geology, bedrock is solid rock that lies under loose material (regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bedro ...

of northern

Belgium Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...

. The formation consists of

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

and

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension with water. Silt usually has a floury feel when ...

, alternating with more

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

y layers. On top of this the

lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...

changes to

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

and

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

and the top of the formation is formed by a layer of glauconite bearing sand. The Hannut Formation was formed during the early to middle

Thanetian The Thanetian is, in the International Commission on Stratigraphy, ICS Geologic timescale, the latest age (geology), age or uppermost stage (stratigraphy), stratigraphic stage of the Paleocene epoch (geology), Epoch or series (stratigraphy), Serie ...

age (Late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

, about 57 million years ago). The formation is named after the town of

Hannut Hannut (; wa, Haneu; nl, Hannuit, ) is a city and municipality of Wallonia located in the province of Liège, Belgium. On January 1, 2006, Hannut had a total population of 14,291. The total area is 86.53 km² which gives a population dens ...

in the

province of Liège A province is almost always an administrative division within a country or state. The term derives from the ancient Roman ''provincia'', which was the major territorial and administrative unit of the Roman Empire's territorial possessions outs ...

Lithologies

The Hannut Formation can be about 100 meters thick in the

Campine Basin The Campine (French ) or De Kempen (Dutch ) is a natural region situated chiefly in north-eastern Belgium and parts of the south-eastern Netherlands which once consisted mainly of extensive moors, tracts of sandy heath, and wetlands. It encomp ...

and about 55 meters thick in the Mons Basin. In between these two basins the thickness varies between 40 and 20 meters. The formation is subdivided into five members: *The Chercq Member,

tuffite Tuffite is a tuff containing both pyroclastic and detrital materials, but predominantly pyroclasts. According to IUGS definition tuffite contains 75 to 25% volcanic (epiclastic) material. There are several classifications that define tuffite. ...

, clay and glauconite bearing sand layers. This member is most distinctively recognizable in the

province of Hainaut Hainaut (, also , , ; nl, Henegouwen ; wa, Hinnot; pcd, Hénau), historically also known as Heynowes in English, is a province of Wallonia and Belgium. To its south lies the French department of Nord, while within Belgium it borders (clock ...

; *The Lincent Member, a locally lithified, predominantly clayey layer. It occurs in and around the Hesbaye region; *The Halen Member, clayey silt and silty sand; *The Waterschei Member, calcareous clay and silty clay. It occurs in the northeast of Belgium; *The Grandglise Member, the upper glauconiferous sand. It is almost always present.

Stratigraphic relations

In Belgian lithostratigraphy the Hannut Formation is one of the two formations of the

Landen Group The Landen Group is a lithostratigraphic unit (a "group" of rock strata) in the Belgian subsurface. The group consists of two formations of Thanetian (late Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that ...

. The other formation is the younger

Tienen Formation The Tienen Formation ( nl, Formatie van Tienen; french: Formation de Tienen; abbreviation: Ti) is a geologic formation in the subsurface of northern Belgium. The formation crops out in the province of Hainaut and the Hesbaye region in the provinc ...

(continental and

lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...

al sands and clays from the late Thanetian age), which is normally found on top of the Hannut Formation. In the northern and eastern parts of

Flanders Flanders (, ; Dutch: ''Vlaanderen'' ) is the Flemish-speaking northern portion of Belgium and one of the communities, regions and language areas of Belgium. However, there are several overlapping definitions, including ones related to culture, ...

the Hannut Formation lies stratigraphically on top of the

Heers Formation The Heers Formation ( nl, Formatie van Heers; french: Formation de Heers; abbreviation: Hs) is a geologic formation in the subsurface of Belgium. The formation consists of sand and marl and was deposited in the shallow sea that covered Belgium durin ...

(middle Paleocene sands and marls). The Hannut Formation correlates with parts of the

Landen Formation The Landen Formation (abbreviation: LA) is a lithostratigraphic unit (a set of rock strata) in the subsurface of the Netherlands. This formation shares its name with the Belgian Landen Group, but the Belgian unit is thinner and has different defin ...

in the

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

References

* (eds.); 2001: ''Paleogene and Neogene lithostratigraphic units (Belgium)'', Geologica Belgica 4(1-2), p. 135-152 Geologic formations of Belgium Paleocene Series of Europe Paleogene Belgium Thanetian Stage Hannut {{Europe-geologic-formation-stub