Gissar-Alai

a mountain system located in Middle Asia south of the Fergana Valley and the eastern part of the Kyzylkum Desert. It is bordered on the south by the Karsh Steppes, the Tadzhik Depression, and the Alai Valley. Its eastern part is in the Kirghiz SSR, its central part is in Tadzhikistan, and its western part is in Uzbekistan. The Gissar-Alai system forms a laterally sloping arc bulging to the south. It extends approximately 900 km from west to east and is up to 150 km wide in the west and up to 80 km wide in the east.

Relief. The main mountain ranges extend latitudinally and sublatitudinally. The Turkestan, Zeravshan, and Gissar ranges with their spurs make up the western and central parts of the Gissar-Alai. The Alai Range with its northern foothills (for example, the Kichik-Alai) forms the eastern part. In the western part in an extension of the Turkestan Range and its spur, the Mal’guzar Range, are located the medium-elevation chains Nuratau and Aktau (on the right bank of the Zeravshan) and a series of low-mountain massifs in an extension of the Zeravshan Range called the Zirabulak-Ziaetdin Mountains (on the left bank of the Zeravshan). There are many ranges that exceed an elevation of 5,000 m. In the region of the Matchin plexus of mountains at the eastern edge of the Turkestan Range the elevation is 5,621 m and at the junction of the Zeravshan and Alai ranges (Igla Peak), 5,301 m. Farther east is the highest point in the Alai chain, 5,539 m, and in the central part of the Zeravshan Range, the highest elevation is 5,489 m (Mount Chimtarga).

The main peaks of the Turkestan, Zeravshan, Gissar, and Alai ranges and several of their higher foothills (for example, Kichik-Alai) have typical alpine topography. In the northern foothills of the Alai and Turkestan ranges, in the western part of the Turkestan Range and its spurs, in the Nuratau Range and other ranges, there are well-preserved examples of flat, leveled surfaces that were caused between the Neocene and Pleistocene periods by tectonic deformations in the form of longitudinal, anticlinal buckling. These plateau-like surfaces on the peaks and slopes are cut by gorges formed by erosion. To the north at the foot of the Alai and Turkestan ranges and the Kichuk-Alai foothills there are rugged, forest-covered loess foothills (adyry). In the limestone of the Zeravshan Range and the northern foothills of the Alai and Turkestan ranges karst is widespread.

Geologic structure and mineral resources. In tectonic terms, the Gissar-Alai is a symmetrical folded structure of the Her-cynian age, made up of Paleozoic (from Cambrian to Lower Permian) geosynclinal formations. The central part of the Gissar-Alai—the Zeravshan Valley and the southern slope of the Turkestan Range—is made up chiefly of thick, dislocated series of Silurian shales. The northern slopes of the Turkestan and Alai ranges, the Zeravshan Range, and the northern slope of the Gissar Range are formed of thick series of limestones and shales of the Silurian and Devonian periods and limestone of the Lower and Middle Carboniferous periods. Upper Paleozoic (from Middle Carboniferous to Lower Permian) conglomerates, sandstones, and effusive rocks are found along deep faults in the Zeravshan Valley and on the northern slopes of the Turkestan Range. More strata of the Upper Paleozoic are found in the deep faults of the southern Fergana Valley and of the southern slopes of the Gissar Range. The magmatic rocks of the Gissar-Alai—granite, grano-diorite, and alkaline rocks—form the main bodies in the axial part of the Turkestan and Alai ranges. They are also present in the Zeravshan Range, but in the Gissar Range they form a large batholith. On the northern slopes of the Turkestan Range ultrabasic serpentine intrusions of the Middle Paleozoic age have been observed. The Paleozoic geosynclinal development in the Gissar-Alai gave way to the Meso-zoic-Paleocene platform development, and at the end of the Paleocene Period a new epoch of activity occurred, which led to the formation of the present-day topography. Mesozoic and Paleocene deposits have a platform-like appearance and were preserved in the mountains as narrow strips squeezed by deep faults, except in the southern Fergana Valley and the southwestern spurs of the Gissar Range, where they form wide fields. These deposits are characterized by continental coal-bearing Jurassic formations and reddish Lower Cretaceous and marine multicolored Upper Cretaceous and Paleocene formations gathered in simple folds. The Oligocene-Miocene, Pliocene, and early Anthropocene deposits form an orogenic complex of continental molasse, which filled in foothill and intermontane depressions.

Deposits of wolfram, molybdenum, arsenic, and gold are found with the late Paleozoic granitoid rocks. The mercury-antimony deposits of the northern slopes of the Turkestan and Alai ranges (for example Khaidarken, Chauvai, and Kadamdzhai) and the antimony deposits of Tadzhikistan, including Shing-Magian and Dzhizhikrut, are extremely valuable. Coal is restricted to Jurassic strata (Suliukta, Shurab, Kizyl-Kiia, Fan-Iagnob, and the fields of the southern slopes of the Gissar Range). The sulfur deposits at Shorsu are found in the Paleocene strata in the northern foothills of the Turkestan Range. The oil deposits of the southern Fergana (for example, the Kim, Chimion, and Andizhan deposits) are found in the Cretaceous and Paleocene strata.

Climate. Extreme variations in temperature and irregular distribution of precipitation and humidity due to altitudes are characteristic in the Gissar-Alai. In the basins and valleys along the perimeters of the mountains there is an average temperature of 24.3° C in the warmest month (July) at Osh and 28.2° C (at Dushanbe). In the coldest months the average temperatures at the same places are -3.0° C and 1.4° C. The annual totals of the temperatures higher than 10° C at Osh and Dushanbe are 3853° C and 4880° C, respectively. At an elevation of approximately 3,600 m (near Anzob Pass in the Gissar Range) the average temperatures in the warmest and coldest months and the total of temperatures above 10° C are 11° C, -13.2° C, and 484° C, respectively. On the windward slopes of the mountains facing south and west, the annual precipitation reaches 1,000-2,000 mm. (On the southern slopes exposure to the sun’s rays and evaporation are very great.) However, on the leeward slopes, even in the mid mountain region, there are places that receive less than 200 mm of rainfall. The maximum precipitation in the foothill regions occurs in the spring; higher up it occurs during spring and summer.

Rivers and lakes. Rivers have mixed sources of water, primarily from the melting of snow and glaciers. At the upper reaches of the Zeravshan River (Matcha) melting glaciers provide an especially great supply of water. The mountain lakes Iskanderkul’ and Marguzoz (in the Zeravshan Basin) are known for their beauty. Many high peaks are covered by permanent snow and glaciers. The largest glacier is the Zeravshan (about 25 km long), which is located in the upper reaches of the Zeravshan River.

Types of landscape. There are five elevation zones and belts along the slopes of the mountains from bottom to top: (1) a semidesert zone of foothill plains and adyry with ephemeral and ephemeral wormwood vegetation; (2) a subtropical steppe zone consisting of loess foothills and mid mountain regions covered with belts of mixed grass and scrubwood steppes; (3) a mid mountain zone of juniper woods, sparse forests, steppes, and mixed wooded and meadow steppes; (4) an alpine meadow zone with subalpine meadows and meadow steppes, alpine mixed grass meadows, and a subnivean belt covered with high alpine soil and plant life alternating with bare rock and talus; (5) a glacial zone of permanent snow, glaciers, and rocks.