The Hesbaye Group is a stratigraphic group (a set of sedimentary layers) 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 northeastern

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 ...

. This group was deposited during the early

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 ...

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

and is subdivided into two formations: the

Houthem Formation The Houthem Formation, named after the Dutch town of Houthem, is a geological formation that crops out in the south of Belgian and Dutch Limburg. It has also been found in borings in the northeastern part of the Campine Basin. The formation co ...

(lower) and the

Opglabbeek Formation The Opglabbeek Formation is a geologic formation in the subsurface of the eastern part of Belgian Limburg. The heterogeneous formation consists of clay and sand that was deposited lagoonally and fluvially during the early Selandian (Middle Pal ...

(upper). The group is named after the region of Hesbaye in the south of Limburg. The Houthem Formation consists of shallow marine

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 ...

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 ...

s of early to middle

Danian The Danian is the oldest age or lowest stage of the Paleocene Epoch or Series, of the Paleogene Period or System, and of the Cenozoic Era or Erathem. The beginning of the Danian (and the end of the preceding Maastrichtian) is at the Cretaceous� ...

age (about 65-63 million years old). It is found in the province of Limburg and the north of the province of

Antwerp Antwerp (; nl, Antwerpen ; french: Anvers ; es, Amberes) is the largest city in Belgium by area at and the capital of Antwerp Province in the Flemish Region. With a population of 520,504,

. This formation also occurs 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 ...

, where it is considered part of the

Chalk Group The Chalk Group (often just called the Chalk) is the lithostratigraphic unit (a certain number of rock strata) which contains the Upper Cretaceous limestone succession in southern and eastern England. The same or similar rock sequences occur acr ...

. The Opglabbeek Formation is an alternation of continental to lagunary clay, sand and

lignite Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

layers of early Selandian age (about 60 million years old). This formation only occurs in the north and east of the province of Limburg. Corresponding deposits in the Netherlands are divided with 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 ...

. The Hebaye Group lies stratigraphically on top of older,

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

formations, such as the

Maastricht Formation The Maastricht Formation (Dutch: ''Formatie van Maastricht''; abbreviation: MMa), named after the city of Maastricht in the Netherlands, is a geological formation in the Netherlands and Belgium whose strata date back to the Late Cretaceous, within ...

(sandy limestone). The late Paleocene

Hannut Formation The Hannut Formation (french: Formation de Hannut; nl, Formatie van Hannut; abbreviation: Hn) is a geologic formation in the subsurface of northern Belgium. The formation consists of marine clay and silt, alternating with more sandy layers. On to ...

(marine clays, sands and limestones) is normally lying stratigraphically on top of the Hesbaye Group.

References

*Laga, P.; Louwye, S. & Geets, S. (eds.); 2001: ''Paleogene and Neogene lithostratigraphic units (Belgium)'', Geologica Belgica 4(1-2), p. 135-152. Geologic groups of Europe Geologic formations of Belgium Lithostratigraphy of Belgium Paleocene Series of Europe Paleogene Belgium {{Europe-geologic-formation-stub