Morphostructure of the Rybinsk Unit of the Central Russian dislocation zone as a reflection of the latest intra-platform geodynamics

The problem of decoding the geodynamic features of the manifestation of the latest local horizontal intraplatform mobility of the earth’s crust is poorly studied. It is revealed by the example of the junction of the Baltic shield and the Russian plate. The study is based on the previously proposed by M.G. Leonov possibility that hard crystalline rocks are subject to quasi-plastic deformations. Morphostructural analysis, which compares the geological structure and features of the relief, is used as a methodological approach. Large massifs are distinguished in the crystalline basement of the EEP. Under the influence of regional geodynamic processes, in recent times the Karelian massif of the Baltic Shield has been experiencing horizontal deformations of small amplitude, leading to its compression in the center and extension in the form of ledges on the outskirts. From the southwest, the massif is limited by the Rybinsk fault, which displaces the Central Russian aulacogen by 100 km to the southeast, as a result of which the Rybinsk morphostructural node is formed. The node is a postglacial depression with two straight sides, located above the faults in the basement. According to these the morphostructure can be defined as the neotectonic graben. Graben is located on the continuation of the narrowing edge of the Karelian massif hidden under the sediment cover. It can be associated with the removal of this edge during the general deformation of the massif, which was summarized with the movement of the shield to the plate, occurs due to tectonic processes that reveal the North Atlantic. Thus, the Rybinsk structural unit is an indicator of both the intraplate geodynamics of the Karelian massif and the impact of a wider geodynamic system associated with the disclosure of the North Atlantic and the removal of the shield.

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