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—We report results of a detailed study of the paleomagnetic record in the sedimentary rocks of the Taseeva Group of the Yenisei Ridge in three typical sections in the lower courses of the Angara, Taseeva and Irkineeva rivers. Our results confirm that the geomagnetic field was in an anomalous state at the Precambrian–Phanerozoic boundary. It is well known that Ediacaran rocks in general have preserved several different paleomagnetic directions that do not conform to the geocentric axial dipole model. For example, Siberian sections display two equally valid groups of paleopoles that cause many debates over the geometry of the geomagnetic field and whether any of the components correspond to its dipole configuration. The paleomagnetic record we studied is unique in that the rocks of the Chistyakovka and Moshakovka formations have captured both these components, which is factual evidence of a synchronous existence of two sources. To explain these findings, we propose an original hypothesis in which the bipolar component that is widely present in the rocks and corresponds to the Madagascar group of paleomagnetic poles is associated to the field of the geocentric axial dipole. The less widespread monopolar component corresponding to the Australian–Antarctic group of poles is reflective of a stationary anomalous source. The recording of this source became possible due to the abrupt decrease in the strength of the virtual dipole moment that probably was at its lowest during the accumulation of the Chistyakovka and Moshakovka formations. The new paleomagnetic pole calculated for the bipolar component – 39.2°N, 61.1°E – plots on the apparent polar wander path for Siberia and can be considered a key determination for the age ~570 Ma.
—We report results of a detailed study of the paleomagnetic record in the sedimentary rocks of the Taseeva Group of the Yenisei Ridge in three typical sections in the lower courses of the Angara, Taseeva and Irkineeva rivers. Our results confirm that the geomagnetic field was in an anomalous state at the Precambrian–Phanerozoic boundary. It is well known that Ediacaran rocks in general have preserved several different paleomagnetic directions that do not conform to the geocentric axial dipole model. For example, Siberian sections display two equally valid groups of paleopoles that cause many debates over the geometry of the geomagnetic field and whether any of the components correspond to its dipole configuration. The paleomagnetic record we studied is unique in that the rocks of the Chistyakovka and Moshakovka formations have captured both these components, which is factual evidence of a synchronous existence of two sources. To explain these findings, we propose an original hypothesis in which the bipolar component that is widely present in the rocks and corresponds to the Madagascar group of paleomagnetic poles is associated to the field of the geocentric axial dipole. The less widespread monopolar component corresponding to the Australian–Antarctic group of poles is reflective of a stationary anomalous source. The recording of this source became possible due to the abrupt decrease in the strength of the virtual dipole moment that probably was at its lowest during the accumulation of the Chistyakovka and Moshakovka formations. The new paleomagnetic pole calculated for the bipolar component – 39.2°N, 61.1°E – plots on the apparent polar wander path for Siberia and can be considered a key determination for the age ~570 Ma.
Research subject. The author investigates sections of the Vendian stratigraphy in the West Bashkirian subzone, written for an Explanatory Note to sheet N-40 – Ufa of the State Geological Map 1000/3 of the Russian Federation, as well as the results obtained with various thematic (stratigraphic, paleontological, lithogeochemical, paleomagnetic, etc.) studies of theVendian sedimentary sequences of the indicated subzone of the Bashkirian meganticlinorium. Materials and methods. A comparison and analysis of research materials was conducted. The research materials included facts, ideas and arguments in favor of certain conclusions and ideas of various authors. Results. A suggestion was made that studies into the architecture of the Vendian deposits of the Southern Urals, apparently, had almost reached perfection. At the same time, the affiliation of different formations to the regional stages of the Vendian of the East European Platform is still interpreted differently. Studies into the Vendian macro- and microfauna on the western slope of the Southern Urals can only be considered at their nascent stage. The dating of detrital zircons from sandstones of the Asha Group should undoubtedly be continued. For the Vendian of the western slope of the Southern Urals, the first steps have been taken regarding the dating of zircons from volcanic tuffs/ashes. These works are still far from being completed. The peak of paleomagnetic studies into the sedimentary sequences of the Vendian, to a certain extent, may have been passed; nevertheless, these research works should also be continued. Finally, only preliminary steps were taken more than 20 years ago in the study of the chemical composition of heavy minerals, which made it possible to obtain fundamentally new information on the composition and evolution of the sources of clastic material for the sedimentary sequences of the Asha Group. Works of this kind also needs to be continued. Conclusion. The conducted analysis of the studies into the Vendian sedimentary sequences of the Southern Urals published in the first two decades of the 21st century made it possible to identify their strengths and weaknesses, as well as to outline directions for further work.
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