Molasse of the Belskii depression of the Cis-Uralian foredeep: Modern data about provenance

Abstract

The crystallochemical characteristics of Cr spinels and tourmalines in combination with U-Pb isotope data on detrital zircons from the Upper Permian and Lower Triassic sandstones of the Belskii Depres sion showed that the main provenances of the molasse sequence in the southern part of the Cis Uralian fore deep were Lower Paleozoic (Sakmara zone) and Precambrian (Uraltau zone) complexes. The absence of Late Paleozoic zircons in the Tatarian (Upper Permian) sandstones, as well as their small amount in the Lower Tri assic psammites together with geochemical and petrographic data, suggest that granite massifs of the Main Granitic Axis of the Urals, as Middle-Upper Paleozoic magmatic complexes of the Magnitogorsk Mega zone, were not involved in erosion. At the same time, the significant amount of Precambrian zircons is indic ative of the presence of metamorphic complexes in the provenance of the Uraltau zone.