The Landen Formation (abbreviation: LA) is a lithostratigraphic unit (a set 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 ei ...

) 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 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 ...

. This formation shares its name with the Belgian

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 ...

, but the Belgian unit is thinner and has different definitions. The Landen Formation consists of shallow marine 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 ...

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

s (mostly

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 ...

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 clay and

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

) from the 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 ...

to early

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

(between 58 and 54 million years old). Dutch stratigraphers see the Landen Formation as part of the Lower North Sea Group.

Lithology

The Landen Formation can be maximally 150 meters in thickness. It is subdivided into five only regionally recognized members: *The Swalmen Member, lagoonal clay, sometimes with small

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; *The Reusel Member, green sandy clay,

loam Loam (in geology and soil science) is soil composed mostly of sand (particle size > ), silt (particle size > ), and a smaller amount of clay (particle size < ). By weight, its mineral composition is about 40–40–20% concentration of sand–sil ...

and sand; *The Liessel Member,

mica Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...

and glauconite bearing clay, containing plant

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s; *The Orp Member, greenish grey sand; *The Gelinden Member, calcareous clay. Some of the sandy layers can have been made into

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) ...

diagenetic Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a ...

processes. The whole formation is interpreted as one

megacycle The cycle per second is a once-common English name for the unit of frequency now known as the hertz (Hz). The plural form was typically used, often written cycles per second, cycles/second, c.p.s., c/s, or, ambiguously, just cycles (Cy./Cyc.). The ...

: the lower parts (Swalmen and Orp) represent a

marine transgression A marine transgression is a geologic event during which sea level rises relative to the land and the shoreline moves toward higher ground, which results in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling ...

, while the upper parts (Reusel and Liessel) represent a

regression Regression or regressions may refer to: Science * Marine regression, coastal advance due to falling sea level, the opposite of marine transgression * Regression (medicine), a characteristic of diseases to express lighter symptoms or less extent ( ...

Stratigraphy

The Dutch Landen Formation is not totally equal with the Belgian Landen Group. In Belgium, the Orp and Gelinden Members are seen as one separate formation, the Heers Formation. The Dutch Landen Formation correlates with the Belgian Heers Formation, Hannut Formation, Tienen Formation and parts of the Opglabbeek Formation. The Landen Formation lies normally on top of a nonconformity with the Dutch

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 ...

, which is usually represented by the early Paleocene Houthem Formation. In most places the early Eocene Dongen Formation is found on top of the Landen Formation.

References

* (''eds.''); 1993: ''Stratigraphic nomenclature of the Netherlands, revision and update by RGD and NOGEPA'', Mededelingen Rijks Geologische Dienst 50, pp. 1–39

External links

* ; 2003
Formatie van Landen
TNO website () Geologic formations of the Netherlands Eocene Series of Europe Paleocene Series of Europe Paleogene Netherlands {{Europe-geologic-formation-stub