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Glacial deposits of the Bokson Group, East Sayan Mountains, Buryatian Republic, Russian Federation

Nickolay M. Chumakov
Nickolay M. Chumakov
Geological Institute of the Russian Academy of Sciences, Pyzhevsky per. 7, Moscow 119017, Russia (e-mail:
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January 01, 2011


The Bokson Group (Gr.) forms the platform cover in northern part of the Tuva-Mongolian Massif, south of the East Sayan Mountains. Widespread diamictites occur in the lower part of the Bokson Gr., in the Zabit Formation (Fm.). These contain erratic, faceted and striated stones along with dropstones. They have disconformable or gradual lower boundaries and conformable or transitional upper boundaries with overlying deposits. The isotopic δ13Ccrb curve records some maximum and minimum values as a background of insignificantly varying values (from –3 to 2‰). Maximum values (up to 5.5‰), are recorded in deposits underlying diamictites, whereas the overlying beds of the Zabit Formation (Fm.) yielded three peaks or minima down to −4‰. A fourth negative anomaly derived from the middle part of the Bokson Gr. in the lower part (close to base) of the Tabinzurt Fm. is as low as –5.7‰. The deposits underlying the diamictites contain Ediacaran (Vendian) microfossils. Cloudina sp. was discovered in the granule of diamictites, whereas beds just above include small shelly fossils (SSF) of the Nemakit-Daldynian type (Cambrotubulus decurvatus Miss., Anabarites trisulcatus Miss.), which is overlain by a member with abundant fossils of the Tommotian assemblage. The diamictites represent glaciomarine deposits formed in the uppermost Ediacaran or lowermost Cambrian stage (Upper Vendian).

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Geological Society, London, Memoirs

The Geological Record of Neoproterozoic Glaciations

Emmanuelle Arnaud
Emmanuelle Arnaud
University of Guelph, Canada
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Galen P. Halverson
Galen P. Halverson
McGill University, Canada
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Graham Shields-Zhou
Graham Shields-Zhou
University College London, UK
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Geological Society of London
ISBN electronic:
Publication date:
January 01, 2011




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