New U-Pb data on the age of rhyolite from Middle Zauralye: Evidence for change of crustal geodynamic regimes

The Turinskaya Series represented by Cenotype rocks of rhyolitebasalt composition is widely abun dant along the eastern slope of the Urals and in West Siberia filling large grabens in the pre Jurassic base ment. Formations of the Turinskaya volcanogenic series are usually distinguished as the taphrogenetic structural level together with the Chelyabinsk carbon iferous series. In the opinion of A.P. Karpinskii [5], the dislocated character of TriassicJurassic deposits in this long zone provides evidence for posthumous orog eny in the Urals during the Early Mesozoic period.V.E. Khain [10] distinguished the taphrogenetic struc tural level as the final stage in the evolution of the geo syncline orogenic system, which is supported by many researchers, in particular, V.N. Puchkov.