Regional Magnetostratigraphic Scale for the Permian-Triassic Boundary of the East European Platform

The construction of a geomagnetic polarity timescale is one of the most crucial issues in modern stratigraphy. Compiling such a scale for the Permian-Triassic transition is possible by studying sections of sedimentary and volcanic rocks. Although the GSSP for the Permian-Triassic boundary is defined in marine rocks at Meishan, China (Yin et al., 2001), the widespread occurrence of continental rocks of this age requires the precise development of local magnetostratigraphic scales and their correlation with marine rocks. Magnetostratigraphic division of Permian-Triassic continental rocks of the East European Platform can significantly advance the establishment of a magnetic polarity scale through the good quality of paleomagnetic data and the high degree of characterization of sections by biostratigraphic data. The latest version of the regional magnetostratigraphic scale of the Permian-Triassic boundary (Hounslow, Balabanov, 2018) requires specification due to both advances in the biostratigraphic division of sections and the inconsistency of previously obtained data with modern reliability criteria of paleomagnetic determinations. Over the past eight years, our team has been conducting paleomagnetic and rock magnetic studies of Permian-Triassic terrestrial sections of the Russian Plate, as well as re-examining some key sections (Fetisova et al., 2018a,b, 2020, 2022, 2023a-c, 2024). The work was carried out in the European part of Russia in the Volga and Northern Dvina river basins. We have also recently studied the Bolshoe Bogdo section in the Caspian Depression. The latter is a unique object as it is one of the few locations where both continental and marine sedimentary rocks are presented. This fact greatly facilitates comparison with the global time scale (Gradstein et al., 2022). The sections we studied cover the interval from the Upper Vyatkian Substage (Bykovian regional stage) to the Upper Olenekian Substage and are represented mainly by red-colored and varicolored terrigenous rocks: sandstones, siltstones, and clays. Our findings have allowed us to significantly specify and detail the existing regional magnetostratigraphic scale of the Permian-Triassic boundary deposits in accordance with modern requirements for paleomagnetic data (Fetisova et al., 2023, 2024). We have identified eight orthozones in the above-mentioned time interval. One of the most significant results of the study is the establishment of an interval with anomalous paleomagnetic record directly below the Permian-Triassic boundary in several outcrops of the Russian Plate, which can act as a stratigraphic marker for regional correlations and, potentially, for the global ones. As shown in the latest review of magnetostratigraphic data on the Permian-Triassic boundary (Zhang et al., 2025), the magnetostratigraphic scales of the East European Platform and China (Meishan section) show high convergence in the Induan interval of the scale, but vary greatly below the Permian-Triassic boundary. We hope that further research will specify the regional scale and make progress in solving the problem of high-precision correlation of marine and terrestrial rocks in these regions. The research was supported by the state research programs of the IPE RAS FMWU-2025-0033.