Ilek Formation
Stratigraphic range: Lower Cretaceous
Shestakovo-3 locality
TypeGeological formation
Unit ofKiya River Basin
UnderliesKiya Formation
OverliesTyazhin Formation
ThicknessUp to 746 metres (2,450 ft)
Lithology
PrimaryClay, siltstone
OtherMarl, sandstone
Location
Coordinates55°54′N 88°00′E / 55.9°N 88.0°E / 55.9; 88.0
Approximate paleocoordinates54°12′N 84°36′E / 54.2°N 84.6°E / 54.2; 84.6
RegionWestern Siberia
Country Russia
Extent Kemerovo Oblast
Type section
Named byL. A. Ragozin
Year defined1935
Ilek Formation is located in Russia
Ilek Formation
Ilek Formation (Russia)
Ilek Formation is located in Kemerovo Oblast
Ilek Formation
Ilek Formation (Kemerovo Oblast)

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.[1]

The formation was described by L. A. Ragozin in 1935. It consists of sands with sandstone concretions, layers of silts, clays and marls.[2] Age of the formation, according to a crude 1962 estimate, is Valanginian(?) - Hauterivian - Barremian. Its thickness varies greatly, reaching 746 m in Teguldet borehole.[3]

Age

The Ilek Formation conformably overlies the Upper Jurassic Tyazhin Formation.[1] 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.[4] 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.[5] 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.[1]

Fauna

Amphibians reported from the Ilek Formation
Taxon Locality Material Notes Images
Kiyatriton leshchinskiyi A set of vertebrae A salamander
Mammaliamorphs reported from the Ilek Formation
Taxon Locality Material Notes Images
Acinacodus tagaricus[6] Right dentary fragment An amphidontid mammal
Baidabatyr clivosus[7]
  • Bol'shoi Kemchug 3
 Upper premolar A multituberculate
Gobiconodon hoburensis[8] 21 upper and lower jaws. A gobiconodont
Gobiconodon borissiaki[9] A fragmentary lower jaw A gobiconodont
Kemchugia magna[10] A tooth An amphilestid mammal
Kiyatherium cardiodens[11] A maxilla A zhangheotheriid mammal
Xenocretosuchus sibiricus[12] Dental elements A tritylodontid mammaliamorph
Yermakia domitor[10]
  • Shestakovo-1
 A mandible A tinodontid mammal
Sibirotherium rossicum[13]
  • Bol'shoi Kemchug 4
 M1 tooth;[13] mandibular fragments[14] A docodontan mammaliaform
Choristoderes reported from the Ilek Formation
Taxon Locality Material Notes Images
cf. Khurendukhosaurus
  • Bol'shoi Kemchug 3
 Dorsal vertebra, sacral vertebra[15] A non-neochoristodere choristodere
"Shestakovo choristodere"
  • Shestakovo
  • Bol'shoi Kemchug 3
  • Bol'shaya Terekhtul' 2
 Fragmentary dentaries, several vertebrae, rib fragments[15] A possible neochoristodere[15]
Choristodera indet.
  • Smolenskii Yar
 Cervical centrum May represent a taxon distinct from both Khurendukhosaurus and the Shestakovo choristodere[15]
Lizards reported from the Ilek Formation
Taxon Locality Material Notes Images
Ilekia sibirica[16]
  • Bol'shoi Kemchug 3
 A member of Paramacellodidae
Shestakovia voronkevichi
  • Bol'shoi Kemchug 3
 A knob-scaled lizard
Turtles reported from the Ilek Formation
Taxon Locality Material Notes Images
Kirgizemys A macrobaenid
Crocodylomorphs reported from the Ilek Formation
Taxon Locality Material Notes Images
Kyasuchus saevi[17] A partial skull A shartegosuchid crocodyliform
Tagarosuchus kulemzini[18]
  • Shestakovo
 Nearly complete skull A crocodyliform
Pterosaurs reported from the Ilek Formation
Taxon Locality Material Notes Image
cf. Lonchognathosaurus sp.
  • Novochernorechensk
 Wing metacarpal fragment[19] A dsungaripterid
Dinosaurs reported from the Ilek Formation
Taxon Locality Material Notes Images
Evgenavis nobilis[20] A set of limb elements A confuciusornithiform
Mystiornis cyrili[21]
  • Shestakovo-1
 Isolated metatarsus An avisaurid enantiornithean
Psittacosaurus sibiricus[22]
  • Shestakovo
 Several skeletons A ceratopsian
Lithostrotia indet. Caudal vertebrae Potentially three distinct taxa of titanosaur[23]
Sibirotitan astrosacralis[4]
  • Shestakovo-1
 Vertebrae, sacrum, and pedal elements A somphospondylan sauropod
Paraves indet. Teeth May belong to either Microraptorinae or Troodontidae[24]
Theropoda indet.[25]
  • Shestakovo 1
 Partial cervical vertebra A long-necked theropod, possibly similar to basal therizinosauroids like Falcarius
Tyrannosauroidea indet.[24] Teeth
cf. Urbacodon sp.[24] Teeth A troodontid with unserrated teeth

See also

References

  1. 1 2 3 Golovneva, L. B.; Shchepetov, S. V. (April 2010). "Phytostratigraphy of Albian-Cenomanian sediments in the Kiya River basin (the Chulym-Yenisei area of the west Siberian lowland)". Stratigraphy and Geological Correlation. 18 (2): 153–165. Bibcode:2010SGC....18..153G. doi:10.1134/s0869593810020048. ISSN 0869-5938. S2CID 140540821.
  2. ↑ Криштофович А. Н., ed. (1955). "Илекская свита". Геологический словарь. Vol. 1 (А-Л). p. 271. ISBN 9785458366533.
  3. ↑ Лебедев И. В., ed. (1962). Биостратиграфия мезозойских и третичных отложений Западной Сибири. pp. 168–169.
  4. 1 2 Averianov, Alexander; Ivantsov, Stepan; Skutschas, Pavel; Faingertz, Alexey; Leshchinskiy, Sergey (2018). "A new sauropod dinosaur from the Lower Cretaceous Ilek Formation, Western Siberia, Russia". Geobios. 51 (1): 1–14. Bibcode:2018Geobi..51....1A. doi:10.1016/j.geobios.2017.12.004. ISSN 0016-6995.
  5. ↑ Bugdaeva, E V; Markevich, V S; Volynets, E B (2017). "Palaeoenvironmental and palaeoclimatic reconstruction of the Early Cretaceous psittacosaur localities, Asia". Proceedings and Field Guidebook for the Fifth International Symposium of International Geoscience Programme IGCP Project 608. Fifth International Symposium of International Geoscience Programme. Jeju Island, Korea. pp. 31–34.
  6. ↑ A. 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.
  7. ↑ Alexander 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.
  8. ↑ Trofimov, B. A. (1978). "The first triconodonts (Mammalia, Triconodonta) from Mongolia". Doklady Akademii Nauk SSSR. 243 (1): 213–216.
  9. ↑ Maschenko, 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.
  10. 1 2 A. V. Lopatin, E. N. Maschenko, A. O. Averianov, A. S. Rezvyi, P. P. Skutschas and S. V. Leschinskiy. 2005. Early Cretaceous Mammals from Western Siberia: 1. Tinodontidae. Paleontological Journal 39(5):523-534
  11. ↑ E. N. Maschenko and A. V. Lopatin. 2002. A new Early Cretaceous mammal from Western Siberia. Doklady Biological Sciences 386:475-477
  12. ↑ "Fossilworks: Stereognathus".
  13. 1 2 Lopatin, A. V.; Averianov, A. O.; Ivantsov, S. V.; Kuzmin, I. T.; Skutschas, P. P. (2023-07-19). "An Upper Molar of a Docodontan (Docodonta, Mammaliaformes) from the Lower Cretaceous of Western Siberia". Doklady Earth Sciences. doi:10.1134/S1028334X23601128. ISSN 1028-334X.
  14. ↑ Maschenko, E. N.; Lopatin, A. V.; Voronkevich, A. V. (2002). "A new genus of the tegotheriid docodonts (Docodonta, Tegotheriidae) from the Early Cretaceous of West Siberia". Russian Journal of Theriology. 1 (2): 75–81. doi:10.15298/rusjtheriol.01.2.01.
  15. 1 2 3 4 Skutschas, Pavel P.; Vitenko, Dmitriy D. (2017-05-04). "Early Cretaceous choristoderes (Diapsida, Choristodera) from Siberia, Russia". Cretaceous Research. 77: 79–92. Bibcode:2017CrRes..77...79S. doi:10.1016/j.cretres.2017.05.004. ISSN 0195-6671.
  16. ↑ A. O. Averianov, P. P. Skutschas, A. V. Lopatin, S. V. Leschinskiy, A. S. Rezvyi and A. V. Fayngerts. 2005. Early Cretaceous mammals from Bol'shoi Kemchug 3 locality in West Siberia, Russia. Russian Journal of Theriology 4(1):1-12
  17. ↑ Efimov, 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.
  18. ↑ Fiorelli, L.E.; Calvo, J.O. (2007). "The first "protosuchian" (Archosauria: Crocodyliformes) from the Cretaceous (Santonian) of Gondwana" (PDF).
  19. ↑ Averianov, Alexander O.; Ivantsov, Stepan V.; Leshchinskiy, Sergey V.; Skutschas, Pavel P. (2022-09-01). "First pterosaur bone from the Lower Cretaceous of Siberia, Russia". Cretaceous Research. 137: 105230. Bibcode:2022CrRes.13705230A. doi:10.1016/j.cretres.2022.105230. ISSN 0195-6671. S2CID 248136173.
  20. ↑ O'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.
  21. ↑ Evgeny 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.
  22. ↑ Averianov, 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.
  23. ↑ Alexander O. Averianov; Stepan V. Ivantsov; Pavel P. Skutschas (2020). "Caudal vertebrae of titanosaurian sauropod dinosaurs from the Lower Cretaceous Ilek Formation in Western Siberia, Russia". Cretaceous Research. 107: Article 104309. Bibcode:2020CrRes.10704309A. doi:10.1016/j.cretres.2019.104309. S2CID 210619334.
  24. 1 2 3 Averianov, A.O.; Ivantsov, S.V.; Skutschas, P.P. (2019-06-25). "Theropod teeth from the Lower Cretaceous Ilek Formation of Western Siberia, Russia". Proceedings of the Zoological Institute of the Russian Academy of Sciences (in Russian). 323 (2): 65–84. doi:10.31610/trudyzin/2019.323.2.65. ISSN 0206-0477.
  25. ↑ Averianov, Alexander O.; Lopatin, Alexey V. (2023-07-10). "A long-necked theropod from the Lower Cretaceous of Western Siberia, Russia". Journal of Vertebrate Paleontology. doi:10.1080/02724634.2023.2216761. ISSN 0272-4634.
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