Syrdarya Gr

Along the Syrdarya River. N.P. Vasilkovsky, 1935 (128, p.22), as a phase of denudation; G.F. Tetyukhin, 1961 (469a, pp. 386-388) as a complex. Kh.A. Toychiev, M.V. Mikulin

Synonym: Syrdarya Complex, Сырдарьинский компл.

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To the Sydraya Gr in the high mountains are attributed glacial deposits of the Akbulak moraine, alluvial terrace bodies, colluvial deposits of landslides and collapses, and polygenetic formations; in the mid-mountain, foothill, and plain areas, the S. complex includes alluvial deposits of the riverbed, floodplain I and II above-floodplain terraces, proluvial cones of outwash, subaerial deposits of the upper part of the Suyok Fm and deposits of other polygenetic types. Thickness from 2-5 to 50 m.

N.P. Vasilkovsky (128) identified the S. complex as undivided, and in subsequent works of geological surveyors (419a; 469a) and in specialized studies (Mikulin et al., 1982f., Safarov et al., 1999f.) it was subdivided into:

Lower Syrdarya terrace subcomplex, which forms the lower part of the modern link, including the deposits of the II above-floodplain terrace of the Abay (Khodzhikent) Valley. The Abay terrace is identified by the eponymous village near the city of Tashkent. In the stratotype, at the base of the subcomplex, alluvial pebbles lie. Thickness 9-10 m, in the Chirchik Valley up to 15 m. Thickness of upper parts up to 2-3 m, in depressions up to 5 m and more. Maximum thickness along valleys 30-36 m, in depressions up to 50 m.

Middle Syrdarya terrace subcomplex - middle part of the modern link, includes deposits of the I floodplain terrace of the Iskander. Stratotype in the valley of the Chirchik River near the village of Iskander, Prishchekent district. Distributed in the middle and foothill zones. Composed of boulders and pebbles of poor and good roundness with sandy-gravelly, sandy-loamy filler, sometimes with a thin layer of sand and loam on the surface of the terrace. M. usually 2-5, sometimes up to 15 m.

Upper Syrdarya terrace subcomplex - upper part of the modern link, includes deposits of the high floodplain, floodplain, and channel of large watercourses of the Prishchekent district, Fergana Valley, Hungry Steppe, basin of the Kashkadar River. Distributed only in the middle mountains and foothills (Zakharovich et al., 1971). Composed of poorly rounded boulders, boulders, large pebbles with sandy-gravelly filler in the middle mountains and gravelly-sandy and loamy - in the foothills. M. usually up to 2, sometimes up to 6-10 m. In the plain zone, floodplain, high floodplain, and I floodplain terrace deposits are distinguished by some researchers (Heifetz, 1970, 1972, 1974) jointly in the upper Syrdarya subcomplex, and by others (Mikulin, 1982, Safarov, 1999) as the middle-upper Syrdarya subcomplex undivided.

In the deposits of the floodplain, I and II above-floodplain terraces, bone remains of modern mammalian fauna were found - Marmota bobac Miill., Muridae, Canidae, Alactaga, Meriones meridianus Pall., Capreolus capreolus pygargus Pallas, Equus caballus L., Bovidae (Bos.), Ovis cf. arcal., O. sp., Capra sp., Garella subguturosa Guld. and others (218); rodents, plant remains of currently existing species, as well as artifacts of human economic activity, kurgans, and fortresses from the Neolithic to the present day. The rodent complex most often indicates steppe and semi-steppe conditions of their habitat, and the bones of animals by their specific weight during calcination give a modern dating of no more than 10 thousand years.

In terms of paleomagnetism, the deposits of the S. complex as a whole are magnetized with normal polarity, but in the deposits of the early Syrdarya terrace, a short-term reverse episode of the geomagnetic field has been established, the age of which is dated by the TL method at 7800 years; in the deposits of the I floodplain terrace and in the upper part of the II floodplain terrace, another episode of reverse polarity has been recorded, the age of which is dated by the TL method at 5600 years; in modern floodplains, a reverse episode of magnetic polarity with an age of 1600 years has been established. These episodes of the magnetic field divide the deposits of the complex into three independents.