The New Data on Stratigraphy of the Riphean Stratotype in the Southern Urals, Russia

Abstract

A recent series of U-Pb age determinations of zircons (SHRIMP, IDTIMS) from volcanic flows of several levels permitted to refine stratigraphy of the Riphean of Bashkirian megaanticlinorium (Urals, Russia), and provide a better correlation of this straton with the International and Chinese scales of the Proterozoic. The Upper Proterozoic deposits of the Riphean and Vendian of the General Stratigraphic Scale of Russia (GSSR), widely exposed in the Bashkirian Megaanticlinorium BMA) of the Southern Urals, can be approxi- mately correlated with the Meso- and Neoproterozoic of the International Stratigraphic scale (ISS) (Stratigraphic schemes of the Urals; 1993, The Stratotype of the Riphean, 1983; The Geologic Time Scale, 2012), or Sinian to Changcheng succession of stratigraphic units of China. In the last years, after the International excursion to BMA, with participation of the Chinese and Korean stratigraphers (Field trip Guide…, 2006), the work of dating of volcanic rocks of the Riphean section was strongly activated owing to a considerable progress in technique of isotope research. The work was stimulated by understanding that the International Scheme of division of Meso- and Neoproterozoic into systems/periods of equal duration (200 Ma) contradicts to traditional principles of stratigraphy, with elaboration of a system of stratotypes and GSSPs in real sections, with application of methods of chemostratigraphy, event stratigraphy, micropaleontology and other approaches (Bleeker, 2004). The under- standing that the existing chronometric stratigraphic scale of the Precambrian needs an up-to-date chronostrati- graphic revision, based on global events, becomes now stronger (Geologic Time Scale…, 2012; Grazhdankin & Maslov, 2013), though the Meso- and Neoproterozoic scale in ISS is still unreformed. Volcanic eruptions are developed at three levels of the Riphean section of BMA and their dating is of a spe-