The Scythian plate southern boundary in the system of block divisibility consolidated crust of the Greater Caucasus Central and Eastern segments

Abstract

Relevance. In regional terms, the boundary of the crystalline crust of the approaching plates determines the style of the collision process and the features of its evolution. Most of the proposed collision models for the formation of the Greater Caucasus structure assume that the Scythian plate is a stop-block for the northward shifting Arabian plate. The boundary of the Scythian plate and the Transcaucasian microplate also largely determined the regional tectonics of the Greater Caucasus Central and Eastern segments. In this regard, the establishment of the Scythian plate southern boundary at the level of the crystalline base is an urgent problem. Aim. The purpose of this work is to estimate the position of the deep southern boundary of the Scythian plate, overlain by sedimentary rocks of the Central and Eastern segments of the Greater Caucasus megaanticlinorium, by analyzing the block structure of the consolidated crust. Methods. In order to assess the southern deep boundary of the Scythian plate, an interpretation of geological and geophysical materials was carried out in the area tectonically corresponding to the Central, Eastern and South-Eastern segments, framing their of the foothill troughs of Scythian plate and structures in the north, and in the southern part ‒ the Transcaucasian system of depressions and median arrays. The methods and methodology of the work consisted in the complex interpretation of materials (gravimetric, seismic studies on the DSS and MMS profiles, generalization of data on the tectonic structure). Results: It is shown that the consolidated crust of the Greater Caucasus Central and Eastern segments belongs to the Black Sea-Caspian geoblock, divided by the longitudinal Svaneto-Alazani fault into Tyrnyauz-Kubachi and Java-Shirak megablocks, characterizing the southern flank of the Scythian plate and the northern flank of the Transcaucasian microplate, respectively. Most of the Mesozoic-Cenozoic sedimentary complex of the Central and Eastern segments is confined to the southern flank of the Scythian Plate. The southern boundary of the Scythian plate at the level of the consolidated crust within the Central and Eastern segments of the Greater Caucasus is expressed by the Svaneto-Alazani fragment of the Bolshekavkazsky interplate fault, which delimits the Scythian plate from the Eastern Blackseas and Transcaucasian microplates.