New Paleomagnetic Data on the Permian-Triassic Sedimentary Sections of the Moscow Syneclise

Abstract

© 2020 Kazan Federal University. All rights reserved. The results of a detailed paleomagnetic study of the following five Permian-Triassic sections of the Russian Platform were discussed: Slukino (Vladimir region), Sartakovo and Prudovka (Nizhny Novgorod region), Klykovo and Gavrino (Vologda region). The study is important and intriguing due to the current lack of any representative and reliable paleomagnetic data on the Permian-Triassic age for Eurasia. These data can be helpful for testing the hypothesis about the possibility of relative movements of Eurasia’s lithospheric blocks in the post-Paleozoic time, as well as about the geocentric axial dipole in the Paleozoic and Mesozoic. In order to obtain new paleomagnetic poles, samples from five most promising and well-dated cross-sections of the Permian-Triassic red beds located on the eastern slope of the Moscow syneclise were taken. Laboratory treatment was carried out with the use of modern equipment and advanced techniques. Stepwise thermal demagnetization showed the presence of a paleomagnetic record of excellent quality in all the studied sections, thereby making it possible to obtain new paleomagnetic data of high accuracy and reliability. The resulting paleomagnetic poles demonstrate a so-called “far-side effect”, i.e., they are shifted relatively to the expected position of the mean Permian-Triassic paleomagnetic pole of the East European Platform along the paleomeridian towards the opposite side of the sampling site. Presumably, the reasons are (a) an inclination shallowing in the studied sedimentary rocks, (b) the presence of a significant contribution of non-dipole components to the main geomagnetic field about 250 million years ago, (c) local tectonics. The results of this study can be of considerable interest for clarifying the paleogeographic position of the East European Platform and testing the hypothesis of tectonic rigidity of Eurasia. Furthermore, they are an imporant factual material for analyzing the key features of the geomagnetic field at the Paleozoic-Mesozoic boundary.