MESOZOIC-CENOZOIC INTRAMOUNTAIN BASINS OF THE TIEN SHAN AND WESTERN TRANSBAIKALIA: COMPARATIVE CHARACTERISTICS AND CORRELATION OF EVENTS ARTICLE 1. QUESTION FORMULATION. INTRAMOUNTAIN BASINS OF THE GISSAR-ALAI AND CENTRAL TIEN SHAN

Negative structures of the Earth’s crust, including intermountain and intramountain basins, are key sources of information on the formation of the continental crust through plate tectonic and orogenic cycles. The aim of the work is to give a comparative description of the Mesozoic-Cenozoic basins of the Eurasian intracontinental orogen and to identify regional features of the geodynamic development of its various segments. The object of the study is the Mesozoic-Cenozoic intramountain basins of the Gissar-Alai mountain system (Western Tien Shan), Central Tien Shan, and Western Transbaikalia. The research methodology included comparative geological analysis, structural and tectonic research, geomapping of key areas, description of lithological sections, experimental tectonophysics, magnetotelluric sounding, etc. The first article of the series shows that the Mesozoic and Cenozoic territory of the Western and Central Tien Shan was a zone of dispersed shear flow. These were the conditions in which a system of intramountain depressions and their separating uplifts was formed and evolved. It has been found that the movements of rock masses in the "depres­sion/uplift" system were caused by the redistribution of rock masses during their rheid deformation under conditions of vertical and lateral rheological heterogeneity of the crust. The second article of the series will present a description of the depressions in Western Transbaikalia, discuss the material, and formulate conclusions on the research problem.