New data on fossil insects, soil and freshwater invertebrates, plant macrofossils, pollen and spores were obtained from a problematic lower unit of the reference section Bely Yar-II (Tunka Rift, Baikal Region, Russia). The invertebrates show a natural succession from a small lake to a wetland; plant macrofossils confirm the early stages of succession. Pollen and spore data reflect a wide range of environments and vegetation from moderate climate supporting regional forests to relatively cold, dry parkland. New Uranium-Thorium data (99 ± 20 ka and 101 ± 13 ka), along with environmental reconstructions, indicate that the lower unit was probably formed during one of the cold sub-stages towards the end the last inter-glaciation (MIS5).

This article presents the results of a comprehensive geochronological study of organic-rich sediments lying at the base of the sand suite in the well-known reference Belyi Yar II section on the left bank of the Irkut river (Tunka depression, Southwestern Cisbaikalia). It was found that in the 1960s, a pack of lake-marsh sediments from the lower part of the section was assigned to the upper Eopleistocene, and the overlying sands to the Samarovo period of the Middle Pleistocene. Later, based on the first 14C datings, the stratigraphy of these sediments was revised. The lower part of the sediments was attributed to the Karginsky time, and the overlying sands to the Sartanian glaciation. However, the questions concerning the genesis, age and conditions of formation of these sediments remain controversial. In particular, the individual dates of 14C differ greatly from one another; therefore, they require further verification. A renewed study of the lower part of the Belyi Yar II section discovered peat and gyttjas deposits of alluvial origin. It was shown that their numerical age is beyond the 14C dating method limits. Paleobotanical data showed that the gittya was formed in conditions of a relatively warm and humid climate, and the overlying layers accumulated in the cooling and more xerophytic condition. Evaluation of the 230Th/U isochronous age of these organogenic deposits, combined with palynological data, suggested that the bottom of the sand layer in the Belyi Yar II section was not formed during the Karginsky time (MIS 3), as was thought previously, but during MIS 5. The gittya could have formed during MIS-5c, whereas the overlying peat layers formed, possibly, at the transition to MIS-5b.

This article presents the results of a comprehensive geochronological study of gyttja deposits from a section of a terrace above a floodplain located on the right bank of the Ob River near the town of Kolpashevo. According to the 230Th/U dating, the age of the gyttja could be dated in the range of 110–95 kyr. The results of spore–pollen analysis suggest that the gyttja deposit was formed in the period of a wide distribution of middle taiga forest landscapes with the dominance of spruce; the climatic conditions were similar to modern ones. These events probably took place in the interstadial time during MIS-5c or at the end of Kazantsevo interglacial period.

Territories, which were subjected to technogenic influence, had different interruptions steppe and it was needed the various recultivations for them: from nonintervention in natural-recovery processes to full engineer-biological recultivation. For recultivation in Arctic zone condition always was necessary individual approach. Peculiarities of recultivations especially distinguished in different geographical zones and sub-zones of Arctic (arctic tundra, forest-tundra, northern taiga etc.) or these parts, which were included in Arctic zone of Russian Federation.

It was discussed a study of the morphology and genesis of relict polygonal sorted circles formations Late Pleistocene in the South-western part of the West Siberian Plain

Digital map of natural geosystems (landscape map) was made in scale 1:100 000 for the territory of Urengoy oil-gas field. The permafrost temperatures map was generated automatically basing on landscape map. Engineering-geological map is also generated in automatically using the geosystem map and concerning cryological data. Depending on level of modeling the information was generalized for landscapes, stow (urochishche) groups and stow types.

Dating of late Pleistocene sediments remains a challenge in Quaternary chronology, due to the inherent limitations of the 14C and OSL methods. The 230Th/U radioisotope method is theoretically applicable to wood remnants contained within Pleistocene sediments, but few results have been pub-lished to date and in some cases, the age data are ambiguous. This paper tests the use of 230Th/U da-ting of fossil wood remnants dated earlier by radiocarbon method. We analyzed a buried larch trunk from a well-known stump layer in the Lipovka outcrop, located on the Tobol River bank in Western Siberia. The stump layer is preserved in situ. We determined the specific activities of U and Th iso-topes in samples of both modern pine and fossil larch and proposed a model for the incorporation and distribution of U and Th in the buried wood during aging. Complications related with the recognition of geochemical closed systems with respect to U did not allow obtaining completely reliable 230Th/U age. Despite this the 230Th/U age obtained for the uppermost heartwood sample and 14C ages of the same larch trunk and other wood and vegetation remnants gave consistent results. These age data in combination with previously obtained pollen data testify the stump layer formation during the late cooling stage of the Karganian time (MIS-3, Middle Valdai).

A complete skeleton of the pike Esox cf. lucius L. from the Late Pleistocene deposits of the IshimIrtysh interfluve (village of Kotochiga, Western Siberia) is described. The specimen is morphologically close to the northern pike, which presently has a circumboreal range. A number of primitive characters in the structure and dentition of the dentary and palatine resemble some Pliocene specimens, although they are rather incomplete, precluding the estimation of the taxonomic value of such characters. The preservation of scales and bones in the pike from Western Siberian suggests immediate burial in the place of its death in a lacustrine basin. The material comes from loam, with traces of a paleocryogenic texture. The underlying sand bed contains abundant shells of freshwater mollusks, suggesting that the climate was comparable to that in the Recent or even softer. The 14C dating giving the age about 25 ka (MIS3) was obtained for the first time in the horizon of buried soil at the base of the sand bed. Previously, the interfluve deposits in question were dated within the range from the Middle Pleistocene (MIS8) to the end of MIS2 of the Late Pleistocene.

Terrestrial deposits in western Siberia, the ages of which correspond to the interval of MIS-5, have been well studied using palaeobotanical methods. However, because of the small number of isotope data, there is no possibility for identifying the palaeoclimatic events relevant to the substages within MIS-5. Therefore, the large numbers of palaeobotanical results have been underused for the purposes of climatic stratigraphy. Th-230-U dates produced during the past two decades have allowed the changes in vegetation during the first half of the Late Pleistocene to be determined. This has enabled a comparison with palaeoclimatic events reflected in the Greenland ice core, and the identification in western Siberia of the analogues of substages MIS-5a, 5b, 5c, 5d, and 5e as well as events 5e1, 5e2, 5e3, 5e4, and 5e5 within MIS-5e.

A radiochronological study of buried wood remnants was conducted to assess the capabilities and limitations of the Th-230-U method for dating. The buried wood sample was a larch stump from the reference Lipovka section located on the Tobol River bank (southwestern Western Siberia, lat 57 degrees 55' N). A buried soil occurs in the middle part of the sequence, in which the stump layer was found. Numerous larch stumps occur in life position, and therefore the redeposition of wood remnants can be discounted. It was found that the kernel acts as a near-closed geochemical system suitable for the 230Th-U dating method. The C-14 age of 36,400-37,930 cal BP obtained previously for the same larch stump is consistent with the confidence intervals of the Th-230-U ages of 39.1 +/- 5.7 and 40.3 +/- 3.9 kyr calculated for the larch kernel.

A 14C date older than 53900 yrs BP was obtained for the uppermost part of the buried peat bog in Krivosheino section (Middle Pleistocene of Western Siberia). These sediments also yielded 230Th/U dates of 195 −9.1 +10.8 ka using the leachate alone (L/L) and 204 −13 +17 ka using total sample dissolution (TSD) models. Peculiarities of 230Th/U dating are discussed. Palynological investigation of the buried peat bog together with underlying and overlaying sediments, and comparison with palynological data from Baikal and Elgygytgyn lakes revealed that the peat layer in Krivosheino section was formed at the end of Shirta Interglacial (Marine Isotopic-Oxygenous stages MIS-7), when climate conditions at all studied sites were more severe compared to the modern ones.

The revised study of stratotypes and key sections of the Karginsky regiostage in the West Siberian Plain with the use of 230Th/U dating determinations and advanced 14C dating indicated that many 14C ages obtained in the 1960–1970s were incorrect, and revealed the pre-Karginsky age of the Karginsky regional substage stratotypes adopted in the modern Pleistocene stratigraphic schemes of West Siberia. The available 230Th/U and 14C data along with the new paleobotanical record provided substantial refinement of the Late Pleistocene succession of paleoclimatic events in the West Siberian Plain. The 5e5 and 5e1 optima corresponding to climatic events of the Greenland ice core and 5e2 and 5e4 pessima are revealed in boreal West Siberia. The obtained 230Th/U dating determinations, even with their wide tolerance interval, make it possible to recognize not only the major but certain minor climatic events within the Kazantsevsky interglacial in boreal West Siberia. Beds corresponding to MIS 5c are recorded in the middle reaches of the Ob River. The preceding cooling was comparable with that of the later stages of the Zyryansky glaciation and is correlated with MIS 5d, which suggests the beginning of the Zyryansky glaciation occurred in the second half of MIS 5. The obtained records do not require elimination or reducing of the range of the Karginsky regiostage. However, the stratotypes of its regional sub-stages, chosen mainly in the 1960–1970s, appear to be invalid.

For a sample from the roof of peat (0–2 cm) located in a reference section for the Middle Neopleistocene in West Siberia near the village of Krivosheino, we obtained an exorbitant value of 14C date ≥53.9 ka B.P. (LU-6024). In the peat proper, the 230Th/U dates obtained by the isochronous method are 195.2 ± 10.8/9.1 ka B.P. for the L/L model and 204.1 ± 17/13 ka B.P. for the TSD model. The palynospectra of the peat characterize, from the bottom up, birch forests with fir and spruce participation; then spruce forests with fir; next spruce-cedar forests, similar to the middle taiga subzone. In the clay, the following palynospectra have been examined: forb-gramineous grasslands and light forests with spruce and Betula fruticosa. In the upper part of clays, the palynospectra reflect the evolution of swampy, birch, light forests with spruce participation. The conclusion is made that the studied part of the section formed at the end of the Samarovo Ice Age and in the last third of the Taz Ice Age. The break in sedimentation related to the erosion contact covers a part of the Samarovo Ice Age and the first two-thirds of the Taz Ice Age.