The Ilek Formation is a Lower Cretaceous 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 secondary ...

in Western Siberia. Many different fossils have been recovered from the formation. It overlies the Late Jurassic Tyazhin Formation and underlies the Albian Kiya Formation. The formation was described by L. A. Ragozin in 1935. It consists of sands with sandstone concretions, layers of silts, clays 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 ...

s. Age of the formation, according to a crude 1962 estimate, is Valanginian(?) - Hauterivian - Barremian. Its thickness varies greatly, reaching 746 m in Teguldet 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

Fauna

See also

References