The structures of the Alai and Kichi-Karakol depressions and the latest deformations in their mountainous surroundings (Southern Tien Shan)

Abstract

Research subject. A series of research studies was conducted in the Alai Range area, at the junction of the folded Tien Shan and Pamir provinces with the purpose of investigating the morphological structure of alpine deformations in the Paleozoic basement and Mesozoic–Cenozoic sediment cover.Materials and Methods. Structural and geological observations were carried out in the Alai and Kichi-Karakol inter-mountain depressions and their mountainous surroundings. These investigations included an analysis of the morphology and orientation of the deformation structures of the sedimentary cover and structural inconsistencies based on detailed geological mapping; measurements of the orientations of tectonic slickenlines and slickensides in the zones of active faults; processing the entire complex of data in terms of kinematic strain indicators using proven methods and calculation programs in order to determine the main parameters of the stress-strain state of the upper crustal rock complexes.Results. The age intervals and kinematic conditions of the main phases of structural transformation of the Southern Tien Shan at the Alpine stage of tectogenesis were determined based new structural and geological data, as well as materials published in previous works. It was demonstrated that, in the territory of Alai, the most significant deformations and activation of the Paleozoic basement faults occurred at the Neogene-Quarter boundary. Conclusions. At the present stage, the area under study constitutes a relatively stable block, which does not experience significant deformations associated with the encroachment of the upper crustal rock complexes of the Northern Pamir from the south.