The Baykonur Formation is a geological formation of Neoproterozoic (Ediacaran) age which outcrops in Kazakhstan and Kyrgyzstan. It is correlated in age with the Hankalchough Formation in China where glaciation also occurred.
History The presence of diamictites was identified in the Baykonur Formation in 1924 by Dmitry Nalivkin, and the Baykonur Formation was studied for the first time by Ergaliev (1965).Ergaliev, G.K. (1965). On stratigraphy of Vendian and Cambrian Baykonur Karatau–Dzhebagly zone. Izvestia of Academy of Sciences of Kazakh SSR. Geological series, 6: 31–43 (in Russian). Chumakov (2009) and Chumakov (2011) standardised the stratigraphy of the Baykonur Formation and formalised the name of the formation.
Geology The Baykonur Formation is an upper unit of the Ulutau Group and it outcrops in the mountains of Kazakhstan and Kyrgyzstan towards the border with China. It was formed during a period of heavy glaciation known as the Baykonurian glaciation which spread for at least , and it has been posited as a contributor to the Cambrian explosion. During the Ordovician and Devonian, the Baykonur Formation experienced faulting and folding during the Caledonian orogeny.
The Baykonur Formation is formed of diamictite and phyllite with dropstones,Korolev V. G., Maksumova R. A. (1984). Precambrian Tillites and Tilloids of Tien Shan Frunze Ilim (in Russian) a shale layer and in some sections a feldspar layer and conglomerate layers increasing in abundance towards the western sections;Kheraskova T. N. (1986). Vendian-Cambrian Rock Associations of Caledonides of Asia Moscow Nayka (in Russian) it has unconformities between its upper and lower boundaries with Terreneuvian shale and granosyenite of Tonian-Cryogenian boundary age respectively, although in places it does underlie the Koktal, Kurumsak, and Kurmenty Formation and conformably overlies the Kurayly, Aksumbe, and Dzakhbolot Formation. It is up to in places with localised diamictite outcrops reaching in thickness.
Age The age of the Baykonur Formation was initially suggested to be Late Paleozoic age in 1924 before the date was suggested to be Cambrian age by Borovikov (1953)Borovikov L. I. (1953). Lower Paleozoic of Dzhezkazgan-Ulutau Region of West Part of Kazakhstan 1955 Nedra, Moscow (in Russian) and then Precambrian age by Korolev (1963).Korolev V. G. (1963). About Cambrian boundaries in the Middle Asia (in Russian) Trudy Frunzinskogo politekhnicheskogo institute, Geologiya, Gornoe delo 1963 10 16-21 This was then changed to ?Ediacaran to Early Cambrian age by Chumakov (2011). Alexeiv (2025) refined the age to 556–540 Ma.
Paleogeography The Baykonur Formation constitutes margins believed to be related to the northern and eastern edges of the Syrdarya and Tarim microcontinents.Kiselev V. V. (2001). Analogues of the Sinian complex in the central and northern Tien Shan Geology and Geophysics 2001 42 1453-1463
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