The main structures of the Chui Basin and its mountainous framing were formed by Baikal and Caledonian orogenies. The oldest (Archean - early Proterozoic) crystalline basement is exposed in the eastern mountain framing of the basin called Aktyuz-Bordin; in the northern framing of the basin, the gneissic basement lies at a depth of 2-3 km, plunging to 12 km to the south, and in the axial part of the Kyrgyz Range - to a depth of up to 5 km.
Outcrops of carbonaceous marbles, marbleized limestones, and quartzites in the river basins of Kegety and Issyk-Ata testify to the Baikal structural level.
The Caledonides with erosion lie on the Precambrian structures, and in plan, they repeat the orientation of the Baikal structures or bypass the central massifs that settled in the Precambrian.
Mountain formation was accompanied by the formation of a large fault, the intrusion of granite intrusions, and the metamorphosis of sedimentary deposits. As a result of powerful uplift, the Kyrgyz Range becomes an area of erosion, while the Chui Basin becomes an area of accumulation. The formation of depressions occurred from the mid-Devonian on the central massifs or at the junctions of folded zones controlled by faults. One of these epicaledonian depressions was located in the area of the present Chui Basin.
The Hercynian folding, accompanied by intrusions, completed the Paleozoic stage of development of this geological zone. As a result, the Chui Valley and the mountainous framing formed a single massif with a similar tectonic regime, generally close to platform-like (as part of a vast epigercynian platform).
Tectonic activity sharply intensified only at the end of the Neogene. The platform regime (peneplain) was replaced by sharp differentiated movements of large amplitude, which continued into the Quaternary period.
The Kyrgyz Ala-Too, as a mountain range, was formed during the Alpine folding. According to L.I. Turbin (1966), the most powerful folding and block movements of the Alpine era occurred during the Naryn tectonic phase, manifested at the boundary of the Neogene and Quaternary periods. Vertical displacements of ridges relative to basins reached 3.0 - 3.5 km at that time. In fact, it is from this moment that the history of the formation of the Kyrgyz Range as a mountain structure begins.
Regarding the nature of the latest tectonic movements within the Kyrgyz Range, there is no complete consensus. According to some authors (Geology of the Cenozoic of the Chui Basin, 1976), maximum uplift rates (up to 6 mm/year) are characteristic of the most elevated central part of the range. The authors conclude that during the last segment of the Quaternary (QIII2 - QIII), the contrast of movements along the main faults increased by 2-3 times, and the maxima of relative speeds shifted westward.
Significant contributions to the study of modern tectonics of the Tien Shan Mountains (Northern Tien Shan - Chui Basin) were made by B.A. Fedorovich (1931), S.S. Shultz (1948, 1970, 1979), and others.
Recent tectonic movements within the Chui Basin continue to this day, as evidenced by the high seismicity of the territory. According to the seismic zoning map of the Kyrgyz Republic (Zhanuzakov et al., 1979) and the microseismic zoning of Bishkek (Turdukulov et al., 1995), the Chui Basin is located in the northern Tien Shan seismic zone, within which earthquakes with intensities of 8-9 points and more are possible. The following earthquakes have been registered directly in the Kyrgyz Range or in adjacent areas: Belovodskoye (1865), Kemin (1911, 1999), Tokmok (1976), and others. Most earthquakes are concentrated in the zone of junction of the Kyrgyz Range with the Chui Basin, expressed in the relief by low foothills (transition zone). Here, the four most seismically dangerous points are: the extreme east of the range (Baibichsorin seismic node), the Chui Basin in the area of Tokmok (Tokmok seismic node), the Chui Basin in the area of Belovodskoye (Aksuyskiy seismic node), and the Chui Basin in the area of Merke. The extreme eastern periphery of the Kyrgyz Range is particularly characterized by high seismicity. In the rest of the range, the epicenters of the strongest earthquakes are shifted into the limits of the Chui Basin.
Overall, the very complex and diverse petrographic composition of the rocks, forming the substrate of the landscape, significantly influences a number of features of natural components and geosystems. In particular, the widespread development of granite and granodiorite, gneiss intrusions and their decomposition products account for the relatively low carbon content of the soils in the Chui Valley.
