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]
Ilek Formation | |
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Stratigraphic range: Lower Cretaceous, Barremian–Aptian | |
Type | Geological formation |
Unit of | Kiya River Basin |
Underlies | Kiya Formation |
Overlies | Tyazhin Formation |
Thickness | Up to 746 metres (2,450 ft) |
Lithology | |
Primary | Clay, siltstone |
Other | Marl, sandstone |
Location | |
Coordinates | 55°54′N 88°00′E / 55.9°N 88.0°E |
Approximate paleocoordinates | 54°12′N 84°36′E / 54.2°N 84.6°E |
Region | Western Siberia |
Country | Russia |
Extent | Kemerovo Oblast |
Type section | |
Named by | L. A. Ragozin |
Year defined | 1935 |
Ilek Formation (Russia) Ilek Formation (Kemerovo Oblast) |
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] A more recent 2024 estimate based on invertebrate and vertebrate fossils placed the age of the formation at Barremian–Aptian.[4]
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.[5]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.[6] 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]
Taxon | Locality | Material | Notes | Images |
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Kiyatriton leshchinskiyi[7] |
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Atlas, trunk vertebrae, fragmentary dentaries, femora, humerus, and nearly complete ilium | A crown-group salamander | |
Kuzbassia sola[8] |
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Two atlantal centra and a trunk vertebral centrum | A karaurid |
Taxon | Locality | Material | Notes | Images |
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Acinacodus tagaricus[9] | Right dentary fragment | An amphidontid mammal | ||
Baidabatyr clivosus[10] |
|
Upper premolar | A multituberculate | |
Gobiconodon hoburensis[11] | 21 upper and lower jaws. | A gobiconodont | ||
Gobiconodon borissiaki[12] | A fragmentary lower jaw | A gobiconodont | ||
Kemchugia magna[13] | A tooth | An amphilestid mammal | ||
Kiyatherium cardiodens[14] | A maxilla | A zhangheotheriid mammal | ||
Xenocretosuchus sibiricus[15] | Dental elements | A tritylodontid mammaliamorph | ||
Yermakia domitor[13] |
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A mandible | A tinodontid mammal | |
Sibirotherium rossicum[16] |
|
M1 tooth;[16] mandibular fragments[17] | A docodontan mammaliaform |
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
cf. Khurendukhosaurus[18] |
|
Dorsal vertebra, sacral vertebra | A non-neochoristodere choristodere | |
"Shestakovo choristodere"[18] |
|
Fragmentary dentaries, several vertebrae, rib fragments | A possible neochoristodere | |
Choristodera indet.[18] |
|
Cervical centrum | May represent a taxon distinct from both Khurendukhosaurus and the Shestakovo choristodere |
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Paramacellodidae indet.[4] |
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Platynota indet.[4] |
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Xenosauridae indet.[4] |
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A knob-scaled lizard |
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Kirgizemys | A macrobaenid |
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Kyasuchus saevi[19] |
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A partial skull | A shartegosuchid crocodyliform | |
Tagarosuchus kulemzini[20] |
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Nearly complete skull | A crocodyliform |
Taxon | Locality | Material | Notes | Image |
---|---|---|---|---|
?Ctenochasmatidae indet.[13] |
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cf. Lonchognathosaurus sp.[21] |
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Wing metacarpal fragment | A dsungaripterid | |
Ornithocheiridae indet.[22] |
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Pterodactyloidea indet.[13] |
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Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Evgenavis nobilis[23] | A set of limb elements | A confuciusornithiform | ||
Mystiornis cyrili[24] |
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Isolated metatarsus | An avisaurid enantiornithean | |
Paraves indet.[25] | Teeth | May belong to either Microraptorinae or Troodontidae | ||
Theropoda indet.[26] |
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Partial cervical vertebra | A long-necked theropod, possibly similar to basal therizinosauroids like Falcarius | |
Tyrannosauroidea indet.[25] | Teeth | |||
cf. Urbacodon sp.[25] | Teeth | A troodontid with unserrated teeth |
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Lithostrotia indet.[27] | Caudal vertebrae | Potentially three distinct taxa of titanosaur | ||
Sibirotitan astrosacralis[5] |
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Vertebrae, sacrum, and pedal elements | A somphospondylan sauropod |
Taxon | Locality | Material | Notes | Images |
---|---|---|---|---|
Ornithischia indet.[4] |
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Isolated teeth | Originally identified as two distinct "hypsilophodontid" taxa[29] | |
Psittacosaurus sibiricus[30] |
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Several skeletons | A ceratopsian | |
Stegosauria indet.[13] |
|
Isolated teeth[29] |