| Ilek Formation | |
|---|---|
| Stratigraphic range: Lower Cretaceous, Barremian–Aptian | |
 Shestakovo 1 locality | |
| 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 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] A more recent 2024 estimate based on invertebrate and vertebrate fossils placed the age of the formation at Barremian–Aptian.[4]
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