Geological structure and Mesozoic-Cenozoic tectonic evolution of the Nenya-Chumysh basin (Southern Salair, southern Western Siberia)

Research subject . The Nenya-Chumysh basin is a long-term Mesozoic intracontinental sedimentary basin confined to the zone of a regional fault separating the Salair from the structures of Gorny Altai, Gornaya Shoria, and the Kuznetsk basin. Aim . To establish the geological and structural-kinematic characteristics of impulses of intracontinental orogeny that took place during the Mesozoic and Cenozoic in the territory of the northwestern part of the Altai-Sayan Folded Area. Materials and Methods . Geological maps of the area, geophysical data on the position of the base of the Paleozoic basement, satellite images and digital elevation models were used. The sedimentary filling of the basin is considered as a chronicle of tectonic movements in the NW part of the Altai-Sayan Folded Area at the intracontinental stage of development. Results . The Early Jurassic, Early Cretaceous, Late Cretaceous-Paleogene, and Neogene-Quaternary tectonic stages of the development of the Nenya-Chumysh basin were distinguished. In the Early Jurassic, the Nenya-Chumysh basin was a pull-apart basin in a left-hand strike-slip zone. This stage is associated with the accumulation of coal-bearing deposits of the Glushinskaya Formation, the thickness of which in the Nenya-Chumysh basin reaches about 1900 m. In the Early Cretaceous, as a result of changes in the stress field, the Nenya-Chumysh basin was transformed into a thrust basin, composed of terrigenous deposits of the Ilek Formation, forming a wedge-shaped sedimentary basin characteristic of foreland troughs. The neotectonic structure of the Nenya-Chumysh basin, formed in the stress field of the Indo-Eurasian collision, inherits an older structural plan in general terms, although differing in details. A non-inherited structure is the transverse neotectonic uplift of the Sary-Chumysh swell. Conclusions . The Early Jurassic stage is related with the closure of the Paleo-Tethys and the collision of a series of Cimmerian terranes with the southern margin of Eurasia, Early Cretaceous stage is caused with Mongol-Okhotsk collision, and the Cenozoic stage proceeds with the ongoing Indo-Eurasian collision. The geological evolution of continental sedimentary basins controlled by regional faults can be used as a source of information about the intensity and kinematic pattern of impulses of intracontinental orogeny in the geological past.