Baykonur Formation

Baykonur Formation
Stratigraphic range: Ediacaran
~
TypeGeological formation
Unit ofUlutau Group
UnderliesKoktal Formation Kurumsak Formation, Kurmenty Formation, Terreneuvian shale (unconformity)
OverliesKurayly Formation, Aksumbe Formation, Dzakhbolot Formation, Tonian-Cryogenian boundary (unconformity)
Thicknessup to 600 metres (1,970 ft)[2]
Lithology
PrimaryDiamictite, shale
OtherPhyllite, feldspar, dolomite, conglomerate
Location
RegionUlytau, Bolshoi Karatau, Aksu-Zhabagly, Middle Tian Shan, Kyrgyzstan-China border
CountryKazakhstan and Kyrgyzstan
Type section
Named forBaikonyr
RegionRang River, Kazakhstan

The Baykonur Formation[3] is a geological formation of Neoproterozoic (Ediacaran) age which outcrops in Kazakhstan and Kyrgyzstan.[1] It is correlated in age with the Hankalchough Formation in China where glaciation also occurred.[4]

History

The presence of diamictites was identified in the Baykonur Formation in 1924 by Dmitry Nalivkin,[4] and the Baykonur Formation was studied for the first time by Ergaliev (1965).[5] Chumakov (2009) and Chumakov (2011) standardised the stratigraphy of the Baykonur Formation and formalised the name of the formation.[2][4]

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.[1][4] It was formed during a period of heavy glaciation known as the Baykonurian glaciation which spread for at least 1,600 kilometres (990 mi),[1] and it has been posited as a contributor to the Cambrian explosion.[6] During the Ordovician and Devonian, the Baykonur Formation experienced faulting and folding during the Caledonian orogeny.[4]

The Baykonur Formation is formed of diamictite and phyllite with dropstones,[7] a shale layer and in some sections a feldspar layer and conglomerate layers increasing in abundance towards the western sections;[8] 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 comfortably underlie the Koktal, Kurumsak, and Kurmenty Formation and comfortably overlies the Kurayly, Aksumbe, and Dzakhbolot Formation.[4] It is up to 600 metres (2,000 ft) in places with localised diamictite outcrops reaching 30 metres (98 ft) in thickness.[2][9]

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)[10] and then Precambrian age by Korolev (1963).[11] This was then changed to ?Ediacaran to Early Cambrian age by Chumakov (2011).[4] Alexeiv (2025) refined the age to 556–540 Ma.[1]

Paleogeography

The Baykonur Formation constitutes margins believed to be related to the northern and eastern edges of the Syrdarya and Tarim microcontinents.[12]

References

  1. ^ a b c d e Alexeiev, D. V. (2025). "LATE EDIACARAN GLACIAL DEPOSITS OF THE BAYKONUR FORMATION, MIDDLE TIANSHAN OF EAST KYRGYZSTAN: AGE SUBSTANTIATION BASED ON DETRITAL ZIRCON U–Th–Pb (LA-ICP-MS) GEOCHRONOLOGICAL STUDY". Доклады Российской академии наук. Науки о Земле / Doklady Earth Sciences. 521 (1): 5. doi:10.7868/s3034506525030015. ISSN 3034-5065.
  2. ^ a b c Chumakov, N. M. (2009). "The Baykonurian glaciohorizon of the Late Vendian". Stratigraphy and Geological Correlation. 17 (4): 373–381. doi:10.1134/s0869593809040029. ISSN 0869-5938.
  3. ^ "Project 512 Neoproterozoic ice ages" (PDF). Russian National Committee for IGCP—Annual Report on IGCP-related Activities 2010. Russian National Committee for IGCP. 2010. p. 11. Retrieved 7 November 2016.
  4. ^ a b c d e f g Chumakov, N. M. (30 November 2011). "Chapter 26 Glacial deposits of the Baykonur Formation, Kazakhstan and Kyrgyzstan". Geological Society, London, Memoirs. 36 (1): 303–307. doi:10.1144/M36.26.
  5. ^ 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).
  6. ^ Germs, G.J.B.; Gaucher, C. (2012). "Nature and extent of a late Ediacaran (ca. 547 Ma) glacigenic erosion surface in southern Africa". South African Journal of Geology. 115 (1): 91–102. Bibcode:2012SAJG..115...91G. doi:10.2113/gssajg.115.91.
  7. ^ Korolev V. G., Maksumova R. A. (1984). Precambrian Tillites and Tilloids of Tien Shan Frunze Ilim (in Russian)
  8. ^ Kheraskova T. N. (1986). Vendian-Cambrian Rock Associations of Caledonides of Asia Moscow Nayka (in Russian)
  9. ^ "Geological Map of Khan Tengri Massif" (PDF). www.kyrgyzstan.ethz.ch. 2008.
  10. ^ Borovikov L. I. (1953). Lower Paleozoic of Dzhezkazgan-Ulutau Region of West Part of Kazakhstan 1955 Nedra, Moscow (in Russian)
  11. ^ Korolev V. G. (1963). About Cambrian boundaries in the Middle Asia (in Russian) Trudy Frunzinskogo politekhnicheskogo institute, Geologiya, Gornoe delo 1963 10 16-21
  12. ^ 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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