The boundaries of the International Chronostratigraphic Chart (ICC) are associated with the natural historical stages of the Earth's development, and their boundaries are usually determined by the palaeogeographical or palaeobiological event that is recognized in most regions of the world. Studies on the standardization of the Lower Devonian ICC stages duration have lasted more than 70 years. The first stages were Gedinnian, Siegenian and Emsian, but their duration was not accurately determined. The article shows the history of the establishment of the currently used Lochkovian, Pragian and Emsian stages. The key study method of the Lower Devonian stages deposits is biostratigraphic one, based on the use of archistratigraphic pelagic fossils, i.e. revealing of the zonal sequence over the conodonts, dacrioconarids and goniatites fossils and comparing them with the standard sequence adopted by the International Geological Congress (IGC). The article contains an analysis of the discussed problems related to the determination of the position of the global boundary stratotype section and point (GSSP) of the Lower Devonian stages. The use of the magnetostratigraphic method in comparison of the sections of the Emsian stage in Barrandian and Zarafshan range is also discussed. The Lower Devonian regional strata of the Zarafshan-Gissar and Turkestan-Altay mountain regions of the Southern Tian Shan are characterized. It is shown that the zonal sequences on conodonts and dacrioconarids presented in these regions almost completely coincide with the standard Lower Devonian sequences in the International Chronostratigraphic Chart. The characteristics of zones and volume of Bursykhirmanian, Sangitovarian, Khukarian, Kunjak, and Kitab horizons are given.

Importance of taphonomic researches of ostracod remains from the Middle Paleozoic deposits of the South Tien Shan for solution of ecological-facial and biostratigraphical problems is demonstrated. The allochthonous and subautochthonous ostracod burials of some Silurian and lower Devonian stratigraphic units from the South Tien Shan are described. Six stable pattern types of ecological-facial ostracod communities, connected with different paleoenvironments are presented. The development of communities is traced through lower Silurian and lower Devonian.

The Law of the USSR on State Enterprise states that the enterprise forms a repair fund at the expense of the cost of production (works, services), the means of which are used to carry out all types of repairs of fixed assets.

Representatives of the family Pachydomellidae were widely distributed in shallow areas of Paleozoic marine basins. Central Asian species were found in the Kitab horizon on the left bank of the Jindydarya River.

In the Devonian sections of the Southern Tien Shan, a group of ostracods was found, the shells of which have characteristic trapezoidal outlines and a significantly expanded and flattened ventral side. The study of the structure of the free edge of these shells allowed us to distinguish among them two groups, differing from each other primarily by the presence or absence of the internal calcified lamina ...

According to the scheme of structural-formation zoning of the Southern Tien Shan, the Zeravshan region belongs to the Zeravshan-Alai zone, where the sections of the Lower and Middle Paleozoic are characterized by predominantly carbonate composition. The Upper Silurian sediments of the Zeravshan Range are represented by the characteristic lithologically uniform Arg Formation composed of dolomites and dolomitic limestones with benthic fauna. The lower subformity of the Arg Formation corresponds to the Upper Wenlock-Ludlow Formation; the upper subformity corresponds to the Post-Ludlow (Prjidol) ...

Family rozhdestvenskajitidae ms gill, 1966 genus rozhdestvenskajites MS GILL, 1966 Rozhdestvenskajites zeravshanensis sp. nov.Table I, figs. 4-6Holotype - № 1/297, LMI Museum; whole shell; Obi Safit section; Upper Silurian, Formation 11; Table 1, fig. 4. Material. 114 specimens; shells and shells of larvae and adults from 13 localities.

In the eastern part of the Malguzar Mountains (northwestern spur of the Turkestan Ridge, the basin of the upper Zaamin-su River), the Silurian-Devonian boundary deposits occupy a significant area. They compose the wings of the latitudinal synclinal structure and are represented by very diverse terrigenous-carbonate rocks. The most complete section of them is known on the northern wing of the structure near the village of Myk in the upper part of the river. Myk in the upper reaches of the Yettkichu River, the left component of the Zaaminsu River. Zaaminsu River. Here, an alternation of organogenic and slam limestones, limestone conglomerates, clay shales, siltstones with lenses of sandstones, conglomerates and gravelites is exposed. The sediments contain abundant organic remains: stromatopores, corals, brachiopods, bryozoans, gastropods, pelecypods, nautiloids, and ostracods. Upper Silurian and Devonian sediments in this area were studied by V. D. Chekhovich [1965], A. I. Kim, and N. M. Larin (1960-1962). The author became acquainted with these sediments in the summer of 1968. The collected material is the basis of this article.

The author, as a member of a group of paleontologists of the Uzbek Geological Department, has been studying Silurian sediments of the Southern Tien Shan for a number of years. The ostracod forms described here were collected in the areas where stratotypes of the most important Silurian horizons and formations for the Turkestan-Nurata zone were identified: in the middle reaches of the Isfara River (Turkestan Ridge) and in the area of Mount Merishkor (North Nuratau Ridge). The stratigraphic scheme of the Silurian deposits [Kim, Larin, 1968] is based on long studied groups of fossil animals - stromatopores, corals, brachiopods, graptolites...