Isotope Stratigraphy of the Permian Rocks, the Volga River Region

Abstract

In this investigation the ⁸⁷Sr/⁸⁶Sr values were considered for the Upper Kazanian regional section Pechishchi and accompanied sections of the Lower Kazanian substage and also the Lower Permian formation. The section Pechishchi is known as reference section formed within the Kazanian palaeosea. It is characterized by three modified Noinsky’s cycles of Kazanian palaeosea evolution. The highest ratio value 0.70832 was received for the Asselian rocks. In the Artinskian stage, the ⁸⁷Sr/⁸⁶Sr ratios decrease to 0.70774. In the Kazanian stage, the strontium ratio is much lower: 0.70769 in the Lower Kazanian substage and 0.70740 in the Upper Kazanian substage. The discrepancies between local and global data observed at some points can be explained by regional features of the sedimentation in the eastern part of the Russian Plate during the Permian period because of arid climate trend and increasing of region isolation from the ocean.