The Ilek Formation is a

Lower Cretaceous Lower may refer to: * Lower (surname) * Lower Township, New Jersey *Lower Receiver (firearms) * Lower Wick Gloucestershire, England See also *Nizhny Nizhny (russian: Ни́жний; masculine), Nizhnyaya (; feminine), or Nizhneye (russian: Н� ...

geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondar ...

in Western

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part ...

. Many different fossils have been recovered from the formation. It overlies the

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

Tyazhin Formation and underlies the

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0 ...

Kiya Formation. The formation was described by L. A. Ragozin in 1935. It consists of sands with

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 silicat ...

concretions, layers of

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 ...

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 pa ...

s 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 ...

s. Age of the formation, according to a crude 1962 estimate, is

Valanginian In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian Stage succeeds the Berriasian Stage of the Lower Cretace ...

(?) -

Hauterivian The Hauterivian is, in the geologic timescale, an age in the Early Cretaceous Epoch or a stage in the Lower Cretaceous Series. It spans the time between 132.9 ± 2 Ma and 129.4 ± 1.5 Ma (million years ago). The Hauterivian is preceded by th ...

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded ...

. Its thickness varies greatly, reaching 746 m in

Teguldet Teguldet (russian: Тегульдет) is a rural locality (a '' selo'') and the administrative center of Teguldetsky District, Tomsk Oblast, Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern ...

borehole.

Fauna

A fragmentary wing metatarsal nearly identical to the pterosaur '' Lonchognathosaurus'' is also known.

References

{{Reflist, refs= {{cite book , title=Геологический словарь , editor = Криштофович А. Н. , editor-link = Afrikan Nikolaevich Krishtofovich , date=1955 , volume = 1 (А-Л) , pages = 271 , chapter = Илекская свита , isbn = 9785458366533 , chapter-url=https://books.google.com/books?id=Ad_9AgAAQBAJ&q=свита&pg=PA271 {{cite book , title=Биостратиграфия мезозойских и третичных отложений Западной Сибири , editor = Лебедев И. В. , date=1962 , pages = 168–169 , url=https://books.google.com/books?id=RsybbAazcSAC&q=Илекская&pg=PA168 Geologic formations of Russia Lower Cretaceous Series of Asia Cretaceous Russia Shale formations Siltstone formations Paleontology in Russia Geology of Siberia