| Popis: |
In the north of the Timan-Ural region, in contrast to its southern regions, there are no Lower Riphean deposits. The question of the presence of Middle Riphean stratons here remains open, since their age is accepted conditionally. In the Subpolar Urals, the Puiva Formation, which lies at the base of the Upper Precambrian section of this region, belongs to the Middle Riphean. The first U-Pb results of the LA-SF-ICP-MS dating of detrital zircons from terrigenous deposits of the Puiva Formation give reason to limit the lower age interval of their formation abroad about 900 million years ago. The obtained dating of the detrital zircons of their obviously basal terrigenous sediments for the Timan-Northern Ural Upper Precambrian, taking into account already available data on the age of the Upper Precambrian strata of this region, indicate that the lower age limit of the Timan continental margin of the Baltic is close to the boundary of the Middle and Late Riphean. |
