The Hannut Formation (; ; 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, officially the Kingdom of Belgium, is a country in Northwestern Europe. Situated in a coastal lowland region known as the Low Countries, it is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeas ...

. The formation consists of marine

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

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 (chemistry), suspension with water. Silt usually ...

, alternating with more

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

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 is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

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. Although its permeabil ...

and

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

and the top of the formation is formed by a layer of

glauconite Glauconite is an iron potassium phyllosilicate ( mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek ...

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), ...

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

Hannut Hannut (; ; ) is a municipality and city 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 density of 165 inhabitants ...

in the province of Liège.

Lithologies

The Hannut Formation can be about 100 meters thick in the

Campine Basin The Campine () or Kempen () 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 encompasses a large n ...

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 Member may refer to: * Military jury, referred to as "Members" in military jargon * Element (mathematics), an object that belongs to a mathematical set * In object-oriented programming, a member of a class ** Field (computer science), entries in ...

: *The Chercq Member,

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

, clay and

bearing sand layers. This member is most distinctively recognizable in the

province of Hainaut A province is an administrative division within a country or state. The term derives from the ancient Roman , which was the major territorial and administrative unit of the Roman Empire's territorial possessions outside Italy. The term ''provin ...

; *The Lincent Member, a locally

lithified Lithification (from the Ancient Greek word ''lithos'' meaning 'rock' and the Latin-derived suffix ''-ific'') is the process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially, lithificati ...

, 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 Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneous ...

the Hannut Formation is one of the two formations of the Landen Group. The other formation is the younger

Tienen Formation The Tienen Formation (; ; 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 province of Limburg. It has a late Thanetian (Paleocene) t ...

(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'') an ...

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 ( or ; ) is the Dutch language, Dutch-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, la ...

the Hannut Formation lies stratigraphically on top of the Heers Formation (middle Paleocene sands and marls). The Hannut Formation correlates with parts of the Landen Formation in the

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

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