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Ilek Formation

{{Short description|Geologic formation in Western Siberia, Russia}}

{{Infobox rockunit

| name = Ilek Formation

| image = Shestakovsky Yar.jpg

| caption = Shestakovo 1 locality

| type = Geological formation

| age = Lower Cretaceous,
Barremian–Aptian

| period = Early Cretaceous

| prilithology = Clay, siltstone

| otherlithology = Marl, sandstone

| namedfor =

| namedby = L. A. Ragozin

| year_ts = 1935

| region = Western Siberia

| country = Russia

| coordinates = {{coord|55.9|N|88.0|E|display=inline,title}}

| paleocoordinates = {{coord|54.2|N|84.6|E|display=inline}}

| unitof = Kiya River Basin

| subunits =

| underlies = Kiya Formation

| overlies = Tyazhin Formation

| thickness = Up to {{Convert|746|m|ft|-1}}

| extent = Kemerovo Oblast

| area =

| map = {{Location map+ | Russia#Russia Kemerovo Oblast

| relief = 1

| width = 250

| float = center

| places =

{{Location map~ | Russia#Russia Kemerovo Oblast

| lat_deg = 55.9

| lon_deg = 88.0

| mark = Green pog.svg

| marksize = 10

}}

}}

| map_caption =

}}

The Ilek Formation is a Lower Cretaceous geologic formation 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 marls. Age of the formation, according to a crude 1962 estimate, is Valanginian(?) - Hauterivian - Barremian. Its thickness varies greatly, reaching 746 m in Teguldet borehole. A more recent 2024 estimate based on invertebrate and vertebrate fossils placed the age of the formation at Barremian–Aptian.

Age

File:Шестаково-3.jpg

The Ilek Formation conformably overlies the Upper Jurassic Tyazhin Formation. Gastropods and bivalves of Valanginian age have been recovered from the lower part of the formation, and gastropods and bivalves of Hauterivian to Barremian age have been found in the upper part, as well as Barremian ostracods. The age of the Shestakovo 1 locality is poorly constrained.

Palynological samples from the Shestakovo 3 locality are characteristic of the Aptian. No angiosperm pollen has been found at this locality, indicating that it is older than the Albian. The upper layers of the formation do contain angiosperm pollen, indicating that part of the formation may extend into the Albian. The overlying Kiya Formation is upper Albian based on plant biostratigraphy.

Fauna

= Amphibians =

class="wikitable" align="center"

|+Amphibians reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

Kiyatriton

|K. leshchinskiyi{{Cite journal |last=Skutschas |first=P. P. |date=2014 |title=Kiyatriton leshchinskiyi Averianov et Voronkevich, 2001, a crown-group salamander from the Lower Cretaceous of Western Siberia, Russia |url=https://www.sciencedirect.com/science/article/pii/S0195667114001062 |journal=Cretaceous Research |volume=51 |pages=88–94 |doi=10.1016/j.cretres.2014.05.014 |bibcode=2014CrRes..51...88S |issn=0195-6671}}

|

  • {{nobr|Shestakovo 1}}

|Atlas, trunk vertebrae, fragmentary dentaries, femora, humerus, and nearly complete ilium

|A crown-group salamander

|

Kuzbassia

|K. sola{{Cite journal|last1=Skutschas |first1=P. |last2=Kolchanov |first2=V. |last3=Anpilogova |first3=E. |last4=Parakhin |first4=I. |last5=Averianov |first5=A. |last6=Jones |first6=M. |year=2023 |title=The last of them? A new relic karaurid stem salamander from the Lower Cretaceous of Western Siberia, Russia |journal=Biological Communications |volume=68 |issue=4 |pages=219–226 |doi=10.21638/spbu03.2023.402 |doi-access=free }}

|

  • Shestakovo 1

|Two atlantal centra and a trunk vertebral centrum

|A karaurid

|

= Mammaliamorphs =

class="wikitable" align="center"

|+Mammaliamorphs reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

Acinacodus

|A. tagaricusA. V. Lopatin; E. N. Maschenko & A. O. Averianov (2010). "A new genus of triconodont mammals from the Early Cretaceous of Western Siberia". Doklady Biological Sciences. 433 (1): 282–285. doi:10.1134/S0012496610040137.

|

|Right dentary fragment

|An amphidontid mammal

|

Baidabatyr

|B. clivosusAlexander Averianov; Alexey Lopatin; Pavel Skutschas; Stepan Ivantsov; Elizaveta Boitsova; Ivan Kuzmin (2017). "An enigmatic multituberculate mammal from the Early Cretaceous of Siberia, Russia". Journal of Vertebrate Paleontology. 37 (2): e1293070. doi:10.1080/02724634.2017.1293070.

|

  • Bol'shoi Kemchug 3

|Upper premolar

|A multituberculate

|

rowspan = "2"|Gobiconodon

|G. borissiakiTrofimov, B. A. (1978). "The first triconodonts (Mammalia, Triconodonta) from Mongolia". Doklady Akademii Nauk SSSR. 243 (1): 213–216.

|

|21 upper and lower jaws.

|rowspan = "2"|A gobiconodont

|rowspan = "2"|

G. hoburensisMaschenko, E. N.; Lopatin, A. V. (1998). "First record of an Early Cretaceous triconodont mammal in Siberia". Bull. Inst. R. Sci. Nat. Belg. 68: 233–236.

|

|A fragmentary lower jaw.

Kemchugia

|K. magna

|

|A tooth

|An amphilestid mammal

|

''Kiyatherium

|K. cardiodensE. N. Maschenko and A. V. Lopatin. 2002. A new Early Cretaceous mammal from Western Siberia. Doklady Biological Sciences 386:475-477

|

|A maxilla

|A zhangheotheriid mammal

|

Sibirotherium

|S. rossicum{{Cite journal |last1=Lopatin |first1=A. V. |last2=Averianov |first2=A. O. |last3=Ivantsov |first3=S. V. |last4=Kuzmin |first4=I. T. |last5=Skutschas |first5=P. P. |date=2023-07-19 |title=An Upper Molar of a Docodontan (Docodonta, Mammaliaformes) from the Lower Cretaceous of Western Siberia |url=https://link.springer.com/10.1134/S1028334X23601128 |journal=Doklady Earth Sciences |volume=512 |issue=1 |pages=871–873 |language=en |doi=10.1134/S1028334X23601128 |bibcode=2023DokES.512..871L |issn=1028-334X}}

|

  • Bol'shoi Kemchug 4

|M1 tooth; mandibular fragments{{Cite journal |last1=Maschenko |first1=E. N. |last2=Lopatin |first2=A. V. |last3=Voronkevich |first3=A. V. |year=2002 |title=A new genus of the tegotheriid docodonts (Docodonta, Tegotheriidae) from the Early Cretaceous of West Siberia |url=http://zmmu.msu.ru/rjt/articles/article.php?volume=1&issue=2&pages=75-81 |journal=Russian Journal of Theriology |volume=1 |issue=2 |pages=75–81 |doi=10.15298/rusjtheriol.01.2.01 |doi-access=free}}

|A docodontan mammaliaform

|

Xenocretosuchus

|X. sibiricus{{Cite web|url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=254183|title=Fossilworks: Stereognathus|access-date=2021-12-17|archive-date=2021-12-13|archive-url=https://web.archive.org/web/20211213081447/http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=254183|url-status=live}}

|

|Dental elements

|A tritylodontid mammaliamorph

|

Yermakia

|Y. domitor

|

  • Shestakovo 1

|A mandible

|A tinodontid mammal

|

= Choristoderes =

class="wikitable" align="center"

|+ Choristoderes reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

style="white-space: nowrap;" | cf. Khurendukhosaurus

|K. cf. sp

|

  • Bol'shoi Kemchug 3

| Dorsal vertebra, sacral vertebra

| A non-neochoristodere choristodere

|

colspan="2" style="white-space: nowrap;" | "Shestakovo choristodere"

|

  • Shestakovo
  • Bol'shoi Kemchug 3
  • Bol'shaya Terekhtul' 2

| Fragmentary dentaries, several vertebrae, rib fragments

| A possible neochoristodere

|

Choristodera

|Indeterminate

|

  • Smolenskii Yar

| Cervical centrum

|May represent a taxon distinct from both Khurendukhosaurus and the "Shestakovo choristodere"

= Lizards =

class="wikitable" align="center"

|+Lizards reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

Paramacellodidae

|Indeterminate

|

  • Kemchug assemblage
  • Kiya assemblage

|

|

|

Platynota

| Indeterminate

|

  • Kemchug assemblage

|

|

|

Xenosauridae

| Indeterminate

|

  • Kemchug assemblage
  • Kiya assemblage

|

|A knob-scaled lizard

|

= Turtles =

class="wikitable" align="center"

|+Turtles reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

Kirgizemys

|

|

|

|A macrobaenid

|

= Crocodylomorphs =

class="wikitable" align="center"

|+Crocodylomorphs reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

Kyasuchus

| K. saeviEfimov, M. B. and Leshchinskiy, S. V. (2000). First finding of the fossil crocodile skull in Siberia [in Russian]. In: Komarov, A. V., ed., Materialy regional’noj konferencii geologov Sibiri, Dal’nego Vostoka i Severo−Vostoka Rossii. Tom II, 361–363. GalaPress, Tomsk.

|

  • Shestakovo 3

|A partial skull

|A shartegosuchid crocodyliform

|

Tagarosuchus

|T. kulemziniFiorelli, L.E.; Calvo, J.O. (2007). "The first "protosuchian" (Archosauria: Crocodyliformes) from the Cretaceous (Santonian) of Gondwana" (PDF).

|

  • Shestakovo 3

|Nearly complete skull

|A crocodyliform

|

= Pterosaurs =

class="wikitable" align="center"

|+ Pterosaurs reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Image

?Ctenochasmatidae

| Indeterminate

|

  • Bol'shoi Kemchug 3

|

|

|

Lonchognathosaurus

|L. cf. sp.{{Cite journal |last1=Averianov |first1=Alexander O. |last2=Ivantsov |first2=Stepan V. |last3=Leshchinskiy |first3=Sergey V. |last4=Skutschas |first4=Pavel P. |date=2022-09-01 |title=First pterosaur bone from the Lower Cretaceous of Siberia, Russia |url=https://www.sciencedirect.com/science/article/pii/S0195667122000945 |journal=Cretaceous Research |language=en |volume=137 |pages=105230 |doi=10.1016/j.cretres.2022.105230 |bibcode=2022CrRes.13705230A |s2cid=248136173 |issn=0195-6671}}

|

  • Novochernorechensk

| Wing metacarpal fragment

| A dsungaripterid

|

Ornithocheiridae

|Indeterminate{{Cite journal |last=Skutschas |first=P. |date=2006 |title=Mesozoic amphibians from Siberia, Russia |url=https://www.researchgate.net/publication/285315220 |journal=9th International Symposium on Mesozoic Terrestrial Ecosystems and Biota, Abstracts and Proceedings Volume |pages=123–126}}

|

  • Shestakovo 1

|

|

|

Pterodactyloidea

|Indeterminate

|

  • Bol'shoi Kemchug 3

|

|

|

= Dinosaurs =

== Sauropodomorphs ==

class="wikitable" align="center"

|+Sauropodomorphs reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

style="white-space: nowrap;" |Lithostrotia

|Indeterminate{{cite journal |author1=Alexander O. Averianov |author2=Stepan V. Ivantsov |author3=Pavel P. Skutschas |year=2020 |title=Caudal vertebrae of titanosaurian sauropod dinosaurs from the Lower Cretaceous Ilek Formation in Western Siberia, Russia |journal=Cretaceous Research |volume=107 |pages=Article 104309 |bibcode=2020CrRes.10704309A |doi=10.1016/j.cretres.2019.104309 |s2cid=210619334}}

|

|Caudal vertebrae

|Potentially three distinct taxa of titanosaur

|

Sibirotitan

|S. astrosacralis

|

  • Shestakovo 1
  • Shestakovo 3{{Cite journal|last1=Averianov |first1=A. |last2=Podlesnov |first2=A. |last3=Slobodin |first3=D. |last4=Skutschas |first4=P. |last5=Feofanova |first5=O. |last6=Vladimirova |first6=O. |year=2023 |title=First sauropod dinosaur remains from the Early Cretaceous Shestakovo 3 locality, Western Siberia, Russia |journal=Biological Communications |volume=68 |issue=4 |pages=236–252 |doi=10.21638/spbu03.2023.404 }}

|Vertebrae, sacrum, and pedal elements

|A somphospondylan sauropod

|File:Sibirotitan model.jpg

== Ornithischians ==

class="wikitable" align="center"

|+Ornithischians reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

Ornithischia

|Indeterminate

|

  • Shestakovo 1
  • Bol'shoi Kemchug 3

|Isolated teeth

|Originally identified as two distinct "hypsilophodontid" taxa

|

Psittacosaurus

|P. sibiricusAverianov, Alexander O.; Voronkevich, Alexei V.; Leshchinskiy, Sergei V.; Fayngertz, Alexei V. (2006). "A ceratopsian dinosaur Psittacosaurus sibiricus from the Early Cretaceous of West Siberia, Russia and its phylogenetic relationships". Journal of Systematic Palaeontology. 4 (4): 359–395. doi:10.1017/s1477201906001933.

|

  • Shestakovo

|Several skeletons

|A ceratopsian

|File:Psittacosaurus sibiricus.png

Stegosauria

|Indeterminate

|

  • Bol'shoi Kemchug 3

|Isolated teeth

|

|

== Theropods ==

class="wikitable" align="center"

|+Theropods reported from the Ilek Formation

Genus

! Species

! Locality

! Material

! Notes

! Images

Evgenavis

|E. nobilisO'Connor, JL; Averianov, AO; Zelenkov, NV (2014). "A confuciusornithiform (Aves, Pygostylia)-like tarsometatarsus from the Early Cretaceous of Siberia and a discussion of the evolution of avian hind". Journal of Vertebrate Paleontology. 34 (3): 647–656. doi:10.1080/02724634.2013.828734.

|

|A set of limb elements

|A confuciusornithiform

|File:Evgenavis tarsometatarsus.png

Kiyacursor

|K. longipes{{cite journal |last1=Averianov |first1=A. O. |last2=Skutschas |first2=P. P. |last3=Atuchin |first3=A. A. |last4=Slobodin |first4=D. A. |last5=Feofanova |first5=O. A. |last6=Vladimirova |first6=O. N. |year=2024 |title=The last ceratosaur of Asia: a new noasaurid from the Early Cretaceous Great Siberian Refugium |journal=Proceedings of the Royal Society B: Biological Sciences |volume=291 |issue=2023 |at=20240537 |doi=10.1098/rspb.2024.0537 |pmc=11285863 }}

|

  • {{nobr|Shestakovo 1}}

|Partial skeleton including cervical and caudal vertebrae, cervical and dorsal ribs, a left scapulocoracoid, humeri, and much of both hind limbs

|A noasaurid theropod

|File:Kiyacursor PM (white bg).png

Paraves

|Indeterminate

|

|Teeth

| May belong to either Microraptorinae or Troodontidae

|

Mystiornis

|M. cyriliEvgeny N. Kurochkin; Nikita V. Zelenkov; Alexandr O. Averianov; Sergei V. Leshchinskiy (2011). "A new taxon of birds (Aves) from the Early Cretaceous of Western Siberia, Russia". Journal of Systematic Palaeontology. 9 (1): 109–117. doi:10.1080/14772019.2010.522202.

|

  • {{nobr|Shestakovo 1}}

|Isolated metatarsus

|An avisaurid enantiornithean

|File:Mystiornis.png

Paraves

|Indeterminate

|

|Teeth

| May belong to either Microraptorinae or Troodontidae

|

Tyrannosauroidea

|Indeterminate

|

|Teeth

|

|

Urbacodon

|U. cf. sp.

|

| Teeth

| A troodontid with unserrated teeth

See also

References

{{Reflist|refs=

{{cite book

|title=Геологический словарь

|editor = Криштофович А. Н.

|editor-link = Afrikan Nikolaevich Krishtofovich

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|volume = 1 (А-Л)

|pages = 271

|chapter = Илекская свита

|publisher = Рипол Классик

|isbn = 9785458366533

|chapter-url=https://books.google.com/books?id=Ad_9AgAAQBAJ&q=свита&pg=PA271

}}

{{cite journal |last1=Averianov |first1=A. O. |last2=Leshchinskiy |first2=S. V. |last3=Skutschas |first3=P. P. |last4=Fayngertz |first4=A. V. |last5=Rezvyi |first5=A. S. |date=2004 |title=Dinosaurs from the Early Cretaceous Ilek Formation in West Siberia, Russia |url=https://www.researchgate.net/publication/235807189 |journal=Second European Association of Vertebrate Paleontologists Meeting. Abstracts of Papers |volume=6 |issue= |pages=6 |doi=}}

{{cite journal |last1=Averianov |first1=A. O. |last2=Skutschas |first2=P. P. |last3=Lopatin |first3=A. V. |last4=Leshchinskiy |first4=S. V. |last5=Rezvyi |first5=A. S. |last6=Fayngerts |first6=A. V. |title=Early Cretaceous mammals from Bol'shoi Kemchug 3 locality in West Siberia, Russia |journal=Russian Journal of Theriology |date=2005 |volume=4 |issue=1 |pages=1–12 |doi=10.15298/rusjtheriol.04.1.01 |url=https://www.researchgate.net/publication/235806746|doi-access=free }}

{{Cite journal| doi = 10.1016/j.geobios.2017.12.004| issn = 0016-6995| volume = 51| issue = 1| pages = 1–14| last1 = Averianov| first1 = Alexander| last2 = Ivantsov| first2 = Stepan| last3 = Skutschas| first3 = Pavel| last4 = Faingertz| first4 = Alexey| last5 = Leshchinskiy| first5 = Sergey| title = A new sauropod dinosaur from the Lower Cretaceous Ilek Formation, Western Siberia, Russia| journal = Geobios| date = 2018| bibcode = 2018Geobi..51....1A}}

{{Cite journal|last1=Averianov|first1=A.O.|last2=Ivantsov|first2=S.V.|last3=Skutschas|first3=P.P.|date=2019-06-25|title=Theropod teeth from the Lower Cretaceous Ilek Formation of Western Siberia, Russia|journal=Proceedings of the Zoological Institute of the Russian Academy of Sciences|language=ru|volume=323|issue=2|pages=65–84|doi=10.31610/trudyzin/2019.323.2.65|issn=0206-0477|doi-access=free}}

{{Cite conference| conference = Fifth International Symposium of International Geoscience Programme| pages = 31–34| last1 = Bugdaeva| first1 = E V| last2 = Markevich| first2 = V S| last3 = Volynets| first3 = E B| title = Palaeoenvironmental and palaeoclimatic reconstruction of the Early Cretaceous psittacosaur localities, Asia| book-title = Proceedings and Field Guidebook for the Fifth International Symposium of International Geoscience Programme IGCP Project 608| location = Jeju Island, Korea| date = 2017}}

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{{cite book

|title=Биостратиграфия мезозойских и третичных отложений Западной Сибири

|editor = Лебедев И. В.

|date=1962

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{{cite journal |last1=Ivantsov |first1=S. V. |last2=Fayngerts |first2=A. V. |last3=Feofanova |first3=O. A. |last4=Vladimirova |first4=O. N. |last5=Slobodin |first5=D. A. |date=2024 |title=Early Cretaceous continental sedimentatary environments, palaeogeography and biota of southeastern Western Siberia |url= |journal=Geological Society, London, Special Publications |volume=545 |issue= |pages= |doi=10.1144/SP545-2023-62}}

}}

Category:Geologic formations of Russia

Category:Lower Cretaceous Series of Asia

Category:Cretaceous Russia

Category:Shale formations

Category:Siltstone formations

Category:Paleontology in Russia

Category:Geology of Siberia

Category:Marl formations