We consider the stratigraphy of sedimentary and volcanosedimentary complexes of Western Transbaikal, where accumulation of the Mokhey and Irenga Formations, deposited in the late Cretaceous-Eocene, was followed with the Oligocene-Lower Miocene Kularikta and Sosnovoozersk Formations and then with the Mid-Miocene through Quaternary units: Dzhilinda Formation, Khoygot Formation, its stratigraphic counterparts (Kydzhimit and China Formations) and with the younger Bereya one. From distribution of sediments and volcanic rocks, we define three time intervals of the area structural development. At the end of the Cretaceous through Eocene, the Eravna-Ingur bend of basins was formed along an axis of the Selenga-Vitim downwarp. In the Oligocene – Early Miocene, a structural reorganization took place that provided reactivation of the north-south Eravna-Kularikta band of basins. Since the early-middle Miocene boundary, the Vitim-Udokan zone of transtension in the Vitim Plateau became active. We propose that the found spatial-temporal distribution of sedimentation and volcanism in Western Transbaikal reflected first the Cretaceous-Paleogene thermal impact on the lithosphere of the primary West Transbaikalian transition layer melting anomaly, resulted in formation of the Selenga-Vitim downwarp, and afterwards the Miocene-Quaternary thermal impact on the lithosphere of the secondary Vitim upper mantle melting anomaly, provided the development of the Vitim Plateau morphostructure.

Chuvashova Irina Sergeevna, Candidate of Sciences (Geology and Mineralogy), Senior Research Scientist, Institute of the Earth's Crust SB RAS, 128, Lermontov st., Irkutsk, 664033, Russian Federation; Associate Professor, Irkutsk State University, 1, K. Marx st., Irkutsk, 664003, Russian Federation, tel.: (3952) 51-16-59, e-mail: chuvashova@crust.irk.ru

Hassan Abdulmonem, Graduate Student, Irkutsk State University, 1, K. Marks st., Irkutsk, 664003, Russian Federation, e-mail: abdulmonemhassan86@gmail.com 

Al Hamoud Adnan, Graduate Student, Irkutsk State University, 1, K. Marx st., Irkutsk, 664003, Russian Federation, e-mail: hamoudadnan04@gmail.com 

Kovalenko Sergei Nikolaevich, Candidate of Sciences (Geology and Mineralogy), Associate Professor, Irkutsk State University, 1, K. Marx st., Irkutsk, 664003, Russian Federation, tel.: (3952) 24-32-80, e-mail: igpug@mail.ru 

Rudneva Nadezhda Anatolyevna, Graduate Student, Institute of the Earth's Crust SB RAS, 128, Lermontov st., Irkutsk, 664033, Russian Federation, tel.: (3952) 51-16-59, e-mail: rudneva@crust.irk.ru 

Rasskazov Sergei Vasilyevich, Doctor of Sciences (Geology and Mineralogy), Professor, Head, Laboratory of Isotopiec and Geochronological Studies, Institute of the Earth's Crust SB RAS, 128, Lermontov st., Irkutsk, 664033, Russian Federation;  Head of Dynamic Geology Chair, Irkutsk State University, 1, K. Marx st., Irkutsk, 664003, Russian Federation, tel.: (3952) 51-16-59, e-mail: rassk@crust.irk.ru

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