V.Yu. Bragin

The Mesozoic Apparent Polar Wander Path for the Siberian Domain of the Eurasian Plate

Comparison of the apparent polar wander paths (APWP) is one of the most important tasks in recent paleomagnetic study. The reliability of such trajectories is largely determined by the quality and quantity of paleomagnetic data used for their construction and uniformity of distribution of these data along the APWP. Approximately 400 paleomagnetic determinations largely characterizing the Paleozoic are now available for East Siberia. The basic features of the present-day structure of northern Eurasia were formed by the end of the Paleozoic. This fact served as a basis for construction of the so-called synthetic APWP for the Eurasian continent, according to which the latter is considered as a single rigid block in the Mesozoic‐Cenozoic [1, 2]. Though paradoxical, Mesozoic strata of Siberia, except for the Lower Triassic, are insufficiently studied by the paleomagnetic method. The paleomagnetic study of Mesozoic rocks in Siberia were largely aimed at solution of stratigraphic problems, which do not need high accuracy in determination of paleomagnetic poles. Despite their reliability, such data are unsuitable for solution of tectonic tasks. The main weakness of available determinations is related to the lack of paleomagnetic tests and wide age ranges (sometimes >50 (!) Ma) obtained for paleomagnetic poles. Therefore, paleomagnetic data on Europe and China [1, 2] were used to calculate the latitudinal position and spatial orientation of the Siberian tectonic domain of the Eurasian Plate in the Mesozoic‐Early Cenozoic. At the same time, the analysis of the geological structure and paleomagnetic data available for Siberia, East Europe, and Central Asia indicates that such constructions are inconsistent

Geodynamics of the Barents–Kara margin in the Mesozoic inferred from paleomagnetic data on rocks from the Franz Josef Land Archipelago

New data on paleomagnetism and isotope geochronology of Jurassic and Early Cretaceous basic igneous rocks on Franz Josef Land Archipelago (FJL) represented by flows and dikes are discussed. The first paleomagnetic data obtained for these rocks offer the opportunity to suggest a model of spatial changes in the FJL block position during the Jurassic‒Cretaceous. In the Early Jurassic, the block occupied a different position relative to Europe from the modern one. It was displaced in the northeasterly direction by a distance of approximately 500 km and rotated clockwise by about 40° relative to its modern position. By the Early Cretaceous, the FJL block occupied a position close to the present-day one avoiding subsequent substantial relative displacements. The data obtained are of principal significance for reconstructing the geodynamic evolution of Arctic structures in the Mesozoic and contribute greatly to the base of paleomagnetic data for the Arctic region, development of which is now in progress.

Magnetic Polarity Stratigraphy of the Upper Cenozoic Deposits of Near-Sea Dagestan (Russia) and the Age of the Early Paleolithic Site Rubas-1

We studied magnetic polarity in four Upper Neogene (Akchagylian stage) sections of Near-Sea Dagestan. Paleomagnetic studies have shown that Shor-Dere section is the most complete section of Late Neogene—Late Quaternary in this territory. The section Rubas-1, which contains Paleolithic artifacts, corresponds to the upper part of the Shor-Dere section, while sections Ajinour and Rubas River are likely short fragments, so their correlation with the reference section is ambiguous. A composite magnetic polarity section of Near-Sea Dagestan was constructed on the base of correlation between Shor-Dere, Rubas-1 and, in part, Rubas River sections. Magnetic polarity pattern of the composite paleomagnetic section is well correlated with the polarity zonation of Akchagylian stage for the neighboring regions of the Caspian basin (Azerbaijan and Turkmenistan), the south of the European part of Russia and the Transcaucasia (the Northern Caspian and the Lower Volga region). Such correlation of the magnetic polarity with those from startotype regions of Akchagylian stage made it possible to identify magnetic polarity zones in the composite section with the magnetic polarity chrons of the Neogene and Quaternary Time Scale (2016). We suggest that the upper part of the composite section can be correlated with Matuyama Chron including Olduvai and Reunion subchrons, while the lower part attributes to Gauss Chron with Kaena subchron. The proposed correlation provides the basis for approximate age estimates for the studied strata and supposes the age of the stone industry from Rubas-1 site not later earlier than 2 million years ago.