The Rb–Sr Age of Authigenic Glauconite and U–Pb Age of Detrital Zircons from Riphean and Vendian Deposits of the Mezen Syneclise, East European Platform (Keltmen-1 Borehole)

Abstract

The Rb–Sr age of glauconite and the U–Pb LA-ICP-MS age of detrital zircons from sandstones of the Riphean Okos Formation and the Vendian Ust-Pinega Formation were determined in the Keltmen-1 parametric borehole, drilled in the Vychegda trough of the Mezen syneclise in the northern part of European Russia. The model Rb–Sr age of glauconite (870–820 Ma) and the U–Pb age of the youngest detrital zircon (1005 ± 14 Ma) limit the time of accumulation of the Okos Formation to the first half of the Late Riphean, which is in good agreement with the biostratigraphic data available. The U–Pb age of the youngest detrital zircon from the lower part of the Ust-Pinega Formation suggests that accumulation of Late Vendian sandstones into the Mezen Basin began about 575 Ma. Thus, the duration of the stratigraphic hiatus between the Riphean and Vendian is estimated to be about 250–300 Ma. In the Late Riphean and Late Vendian, the Mezen basin was filled with terrigenous material of Archean–Late Proterozoic age (from 3.25 to 1.02 Ga), the sources of which were rocks of the Baltic Shield. In the lower part of the Ust-Pinega Formation, a population of detrital zircon of Vendian age (730–575 Ma) was discovered, a possible source of which could have been rocks of the Proto-Ural–Timan Orogen.