Geologicheskii Vestnik

The article gives a detailed description of the most complete and well-exposed sections of the Zigan Formation of the Asha Group of the Vendian: along the Zigan river (stratotype) and in the inter uve of Kukrauk and Zigan in the technogenic excavations of the Sterlitamak – Verkhniy Avzyan highway in the section Makarovo village – Kulgunino village, which is proposed as the hypostratotype of the Zigan Formation. The characteristic facies lateral variability of the Zigan sediments was clearly manifested even in closely spaced sections: along the Zigan river, Kukrauk stream and in their inter uve, which makes it possible to make a judgment about the features of individual sections of the sedimentary basin in the Zigan time. For the rst time in the south of the Alatau anticlinorium, in the section of the Zigan Formation between the Kukrauk stream and Zigan river, several tuff interlayers have been exposed. Tuffs are of considerable interest as an object of dating by modern isotope methods (based on clay minerals and zircon) and as a material for paleogeographic reconstructions of the region at the Vendian-Paleozoic boundary. The presence of tuff interlayers at the base and top of the Zigan Formation makes it possible to determine the age of the formation, its lower boundary and the Precambrian / Cambrian boundary.

Vendian, Zigan Formation, Asha Series, tuff, stratotype, Alatau anticlinorium, Southern Urals

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