The Landen Group is a

lithostratigraphic 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 ...

unit (a "

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic iden ...

" of

rock strata In geology and related fields, a stratum (: strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ...

) in the

Belgian Belgian may refer to: * Something of, or related to, Belgium * Belgians, people from Belgium or of Belgian descent * Languages of Belgium, languages spoken in Belgium, such as Dutch, French, and German *Ancient Belgian language, an extinct language ...

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 ...

. The group consists of two formations of

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 ...

(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), ...

) to

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

(early

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

) age. The Landen Group is named after the town of

Landen Landen () is a Municipalities of Belgium, municipality and City status in Belgium, city located in the Belgium, Belgian province of Flemish Brabant. The municipality comprises the city of Landen proper and the villages of Attenhoven, Eliksem, Eze ...

Flemish Brabant Flemish Brabant ( ; ) is a province of Flanders, one of the three regions of Belgium. It borders on (clockwise from the North) the Belgian provinces of Antwerp, Limburg, Liège, Walloon Brabant, Hainaut and East Flanders. Flemish Brabant also ...

Subdivision

The Landen Group is subdivided into two formations: * The

Hannut Formation The Hannut Formation (; ; 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 top of this the lithology changes to limestone, sil ...

, an alternation 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 ...

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 ...

s and

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) ...

s; * The

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 ...

, a

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-

continent A continent is any of several large geographical regions. Continents are generally identified by convention (norm), convention rather than any strict criteria. A continent could be a single large landmass, a part of a very large landmass, as ...

al alternation of clay, sand and

lignite Lignite (derived from Latin ''lignum'' meaning 'wood'), 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 ...

. This formation is known for its fossils. Both formations can be found in the subsurface of all northern Belgium. They crop out 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 ...

Stratigraphy

The Landen Group is stratigraphically on top of the Bertaimont Formation or Heers Formation (marine

marl Marl is an earthy material rich in carbonate minerals, Clay minerals, clays, and silt. When Lithification, hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae. M ...

s, sands and clays of

Selandian The Selandian is a stage in the Paleocene. It spans the time between . It is preceded by the Danian and followed by the Thanetian. Sometimes the Paleocene is subdivided in subepochs, in which the Selandian forms the "middle Paleocene". Stratig ...

to Thanetian age). In the Belgian lithostratigraphy, the Landen Group is overlain by the

Ieper Group The Ieper Group (; ) is a group (stratigraphy), group of stratum, rock strata in the Subsurface (geology), subsurface of northwest Belgium. The group is subdivided into three marine (ocean), marine formation (stratigraphy), formations, all formed ...

, marine clays and sands of Ypresian age. The Landen Group shares its name 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 def ...

in the lithostratigraphy of 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 ...

. However, this Dutch formation contains not only the equivalents of the Belgian Landen Group but also strata that

correlate In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics ...

with the Belgian Opglabbeek Formation and Heers Formation.

References

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