Litho- and biostratigraphic analysis of a number of Ordovician reference sections has been completed in five different blocks of Salair, including West-Berd' (Medvedkovo), East-Berd', Krasnoe, Gurievsk and Eltsovka. Modern data on nine mainly terrigenous and, less often, carbonate-terrigenous sections bearing fossils and composed of carbonate units and volcanic rocks including lavas, as well as tuff and tuff sandstones have been presented. The Ordovician terrigenous sedimentation in the study area was complicated by stages of volcanic sedimentation. Volcanic-sedimentary sequences were documented at four biostratigraphically dated stages in Salair: 1) the Tremadocian, 2) the late Floian, 3) the middle - late Darriwilian, 4) the late Katian - Hirnantian.

--New and revised previous data based on detailed description of sections have provided better constraints on fauna taxonomy, lithology, and stratigraphy, as well as on biostratigraphic ages of sediments. The lithology and stratigraphy of several key Upper Ordovician sections in the northern Gorny Altai area show that the local units of Sandbian and Katian Savelieva and Bulukhta formations can be used as reference for the regional Ordovician division. It is suggested to include a newly distinguished Bulukhta facies zone, an area of Late Ordovician coarse clastic deposition, into the mapped Ordovician deposits of Gorny Altai. According to paleogeographic reconstructions, the deposition occurred in a large sea gulf surrounded with elevated landmasses exposed to erosion.

New paleontological and biostratigraphic data were obtained for a series of Middle Ordovician sections in the Charysh-Inya and Uimen’-Lebed’ structural-facial zones (SFZ) of the Gorny Altai. Regional stratigraphic stages, namely, the Kuibyshevo and Kostinsky horizons, are discussed in detail. By graptolites, the complete stratigraphic volume of the Kuibyshevo regional unit is defined as following zonal succession: (1) sinodentatus/Cardiograptus/Oncograptus, sinodentatus, (2) austrodentatus, (3) dentatus; and the Kostinsky regional unit within the lentus/balhaschensis/kirgisicus Zone. Beds with conodonts Eoplacognathus pseudoplanus were distinguished in the Batun Section of the Kostinsky Horizon; the same-age beds with conodonts Semiacontiodus asymmetricus–Parapanderodus striatus were distinguished in the Baraniy-1 Section. For the first time in the Voskresenka Formation, in the stratotype of the Kuibyshevo Horizon (Maralikha Section), a brachiopod assemblage was found and identified.

The paper presents data on the classification, structure, and biota of reef complexes from the Late Ordovician-early Silurian Altai Basin. The early Paleozoic history of the Altai Basin included the early-middle Katian, late Katian, early Hirnantian, late Telychian, and middle-late Sheinwoodian events of large-scale reef formation which produced framework reefs, mud mounds, and coral meadows. The early Paleozoic reefs of the area formed at rates of 40 to similar to 12 cm per thousand years. The late Telychian reef system, which formed in 0.51-1.0 Myr, occupied the largest area of the basin. The lateral extent of reef systems in the Late Ordovician-early Silurian basin of Altai depended more on the rates of vertical and lateral growth, as well as on the previous sea bottom topography and clastic inputs, than on the duration of reef formation. Carbonate deposition in the Altai basins of that time can be simulated with a general model implying formation of distal barrier reefs.

New brachiopod species Eoanastrophia tozodoviensis sp. nov. is described from the Tozodov Body, Upper Ordovician of the Teletskoe Lakeside facies zone, Altai Mountains. Amendments are suggested to the diagnosis of Eoanastrophia Nikiforova et Sapelnikov.

During the Late Precambrian-Palaeozoic the southern Siberian continent bordered on the Palaeopacific and Palaeoasian Ocean tectonic plates. Their interactions led to the formation of the complex Central Asian folded (orogenic) belt containing the Silurian Tuvaella and Retziella brachiopod fauna. The subduction of the Palaeopacific plate under the Siberian continent led to the formation of the Late Precambrian-Palaeozoic accretionary orogen. The subduction of the Palaeoasian Ocean plate, including Gondwana-derived continental blocks, under the Siberian continent, created in the Late Precambrian-Ordovician a composite Kazakhstan-Baikal continent (collisional orogen). The Late Precambrian-Early Palaeozoic Ob'-Zaisan ocean basin was located between the Kazakhstan-Baikal and the Siberian continents. On site of the Ob'-Zaisan ocean basin the amalgamation and collision of these two continents resulted in the formation of the Early Palaeozoic Ol'khon suture-shear zone in the Baikal region, the Middle Palaeozoic Charysh-Terekta-Ulagan-Sayan suture-shear zones in the Altai-Sayan region, accretional and island arcs in Junggar and East Kazakhstan. The Silurian Tuvaella brachiopod fauna inhabited the Ob'-Zaysan ocean basin coastal outskirts, the epicontinental sea and active margins of the Kazakhstan-Baikal continent in subtropical-temperate latitudes. To this continent, the Gondwana-derived continental blocks with the Silurian Retziella brachiopods fauna have been accreting since the Late Palaeozoic. The Silurian Retziella brachiopod fauna inhabited shallow epicontinental marine areas of the continental blocks (Tarim, North China, South China, Australia and New Zealand) during the rifting of Gondwana separated from the Siberian continent by the Mongol-Okhotsk Ocean.

The biostratigraphic data on the ammonoid, brachiopod, conodont, and ostracod assemblages of the Mamontovo and Zarechnoe horizons of the Salair were revised and analyzed. The stratigraphic succession of the Middle Devonian deposits of the Salair is clarified, and the new Zarechnoe Horizon, including the Akarachkino, Safonovo, and Kerlegesh beds, is proposed. The upper Eifelian ammonoid assemblage of the Agoniatites Zone, established in the upper part of the Akarachkino Beds, is the biostratigraphic level for global correlations. The upper Eifelian and lower Givetian brachiopod assemblage (Indospirifer padaukpinensis (=I. pseudowilliamsi)) characterizes the Safonovo Beds. Two middle Givetian brachiopod zones were recognized in the Kerlegesh Beds: Rhynchospirifer hians (=Ilmenia subhians) and Subrensselandia? salairica (=“Chascothyris” salairica). The conodont assemblage of the Akarachkino Beds characterizes the upper Eifelian. The middle Givetian conodont assemblage, including Icriodus difficilis Ziegler et Klapper, Polygnathus linguiformisklapperi Clausen, Leuteritz et Ziegler, Po. parawebbi Chatterton beta morphotype, Po. ovatinodosus Ziegler et Klapper, and Po. pseudofoliatus Wittekind, was found in the upper part of the Safonovo Beds. No conodont assemblage was found in the Kerlegesh Beds.

Study of the Ordovician sedimentary sequences of Gorny Altai and Salair has revealed lithological and paleontological features correlating with global sedimentary events: (1) The Acerocare Regressive Event (an initial event in the Early Tremadocian); (2) Black Mountain Transgressive Event (Early Tremadocian); (3) Peltocare Regressive Event (Tremadocian); (4) Kelly Creek Regressive Event (Late Tremadocian); (5) Ceratopyge Regressive Event (Late Tremadocian); (6) Billingen Transgressive Event (Early Floian); (7) Stein Lowstand Event (Middle Darriwilian); (8) Vollen Lowstand Event (Sandbian); (9) Arestad Drowning Event (Middle Sandbian); (10) Frognerkilen Lowstand Event (Early Katian); (11) Linearis Drowning Events 1 and 2 (Middle Katian); (12) Terminal Husbergoya Lowstand Event (Hirnantian); and (13) Hirnantian Lowstand Event (HICE) (Late Ordovician). The chronostratigraphic levels with traces of the global sedimentary events in the Uymen-Lebed structural-facies zone (SFZ) (Gorny Altai) differ from those in the Charysh-Inya and Anui-Chuya SFZ (Altai). In the Ordovician, the Altai basin located in the Charysh-Inya and Anui-Chuya SFZ was a marine area separated from both the Uymen-Lebed basin and the coeval Salair basin. The traces of the global sedimentary and/or biotic events in the Altai and Salair sections can be used as a precise basis for direct correlation of the local stratigraphic units with the units of the International Stratigraphic Chart.

The age of the Paleozoic sedimentary successions of the Yuryung-Tumus Peninsula in the Khatanga Gulf is determined as Middle Devonian, late Eifelian, and the beginning of the early Givetian on the basis of the study of brachiopods, ammonoids, nautiloids, bactritoids, gastropods, and conodonts, and in the terminology of the standard conodont succession, these deposits are not older than the late Eifelian Tortodus kockelianus Zone, but include the terminal Eifelian Polygnathus ensensis Zone and the first Givetian Polygnathus hemiansatus Zone and are no younger than the beginning of the early Givetian Polygnathus varcus Zone. The Middle Devonian sedimentary successions of the Yuryung-Tumus Peninsula show the level of the global sedimentary Kačak Event. The areas of distribution of the Devonian sedimentary deposits in the Yuryung-Tumus Peninsula in the Khatanga Gulf should be considered as one of the fragments of the regional geological structures of a remote (isolated?) region of the Taymyr Fold System rather than a component of the structures of the northern Siberian Platform.

New data on the structure, diversity and longevity of Late Ordovician, Silurian and Devonian reef structures in the Gorny Altai, Salair and Rudny Altai are presented.

Brachiopods, ostracods and conodonts from the stratotype section for the Izyly and Vassino horizons were investigated. Biostratigraphic analysis of faunal associations specified age of Izyly Horizon to be early Frasnian.