The article examines specific features of using charcoal as a material for the chronological attribution of iron-smelting furnaces in the mountainous southeastern Russian Altai. Archaeological charcoal from bloomery hearts of ancient nomad has a high potential not only for radiocarbon dating, but also for tree ring analysis. The use of radiocarbon analysis meets some difficulties associated, first of all, with the accuracy of dates, including those obtained by AMS technique. Another fundamental reason for the erroneous oldening of these monuments is the old wood effect, when the number of missing peripheral rings remains unknown. Tree ring analysis of charcoal in this context has great potential. With its annual resolution it can solve the problem of precise dating, and combining a large number of individual ring series can also minimize the old wood effect. This paper presents new radiocarbon dates for charcoal extracted from iron slag, including the results of Bayesian analysis, as well as 377 year-long tree ring chronology, being one of the longest in the world based on archaeological charcoal. Analysis of these data together with all available radiocarbon dates for box-shaped iron smelting furnaces in the Kuektanar location (highlands of Russian Altai) evidence for the functioning of Kosh-Agach type furnaces in the ancient Turkic period (late 5th − 10th centuries AD), which is also supported by few associated archaeological finds.

The Tuvinian rift trough, located in the northern part of the Central Asian orogenic belt (CAOB), arose in the Early Devonian on Late Proterozoic (?)‒Early Paleozoic terranes as a result of Altai–Sayan mantle plume activity. The sedimentary record from the Middle Paleozoic to the Middle Mesozoic, preserved in the Tuvinian trough, and the Middle Paleozoic igneous complexes confined to the trough structures, reflect the evolutionary stages of Earth’s crust in the Tuva segment necessary for understanding the geological history of the CAOB as a whole. Dating of accessory and rock-forming minerals from igneous rocks using low-temperature geochronology methods yields additional information about postmagmatic processes, making it possible to update the regional tectonic evolution model. In this study, we have reconstructed the stages of tectonic development of the Tuvinian trough in the northern part of the CAOB based on analysis of geological and new Ar‒Ar dating data on feldspars from mafic intrusions. As a result, the chronology of the previously known stages of postmagmatic processes manifested in the Tuvinian trough was refined and new stages identified according to the tectonic evolution of the CAOB. Ar‒Ar dating of feldspars from eight samples yielded four age groups: (i) Late Devonian, (ii) Middle Carboniferous, (iii) Early Permian, and (iv) Early Jurassic. Late Devonian ( 377 and 375 Ma) ages record an impulse of mafic magmatism, widely manifested in the northern segments of the CAOB ( 380‒365 Ma). Middle Carboniferous ( 320 and 319 Ma) dates may reflect closure of the Ob–Zaisan branch of the Paleo-Asian ocean as a result of the Kazakhstan–Siberian collision. Early Permian ( 290–279 Ma) ages are consistent with the formation of Late Carboniferous–Early Permian ( 305–275 Ma) large igneous provinces in connection with rifting processes in the northern segments of the CAOB. Lastly, a single Early Jurassic ( 188 Ma) age marks tectonic reorganization of the CAOB in the Late Triassic‒Early Jurassic in response to (i) closure of the Paleotethys Ocean with subsequent collision of Cimmerian blocks and the southern margin of the Eurasian continent and/or (ii) Mongolian mantle plume activity.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070164

Sedimentary sequences up to 4.71 m thick and up to 24 ka were made by drilling the bottom sediments in three lakes of the Boguty depression. This is the highest mountain (2390–2470 m a.s.l.) and longest sedimentary record for the neighboring areas of Altai, Tuva, and Mongolia, which reflects the course of natural processes in the highest and most arid part of Russian Altai from the Last Glacial Maximum until the present day. As early as in the first stage of this study, the reservoir effect for moraine-dammed Upper Boguty Lake is estimated at 290 years for the present and 1.2 and 1.3 ka for the boundaries at 5.7 and 9.6 ka, respectively. Using a complex of analytical methods, the sedimentological transition zone between the Late Pleistocene glacial–lacustrine clays and the Holocene biogenic–terrigenous silts is identified at 16–13 ka ago; the size of glaciers in MIS-2 and in the Younger Dryas, as well as the time of formation of thermokarst lakes (no later than 8.7 ka), within the upper terminal moraine complex is established. Widespread tree vegetation in the now treeless Boguty depression in the first third of the Holocene is confirmed.

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070115

An Erratum to this paper has been published: https://doi.org/10.1134/S1028334X23070164

Charcoal is a common material for radiocarbon dating. Meanwhile, it is underestimated as an object of dendrochronological analysis used to date natural and historical–archaeological events with an accuracy of up to a year. The new approach to charcoal sample preparation developed by the authors makes it possible to remove previous restrictions on this fragile material imposed in the dendrochronological studies and to use it as an efficient information source in paleoecology, paleoclimatology, paleogeography, and archaeology. This new method has been applied to construct a 377-year tree-ring chronology using archaeological charcoals from ancient iron-smelting furnaces in the Chuya–Kurai ferrous metallurgy province of the Russian Altai. This tree-ring chronology of charcoal is the first in Russia and the longest in dendrochronological practice throughout the world. Further analysis will provide new information on the nature and archaeological events of the high-mountain region located in the center of Eurasia.

Geochemical study of volcaniclastic material and radiocarbon dating of charred plant debris from Holocene deposits of the Guram site, which is located in vicinity of Vetrovoi Isthmus on Iturup Island, demonstrate that an explosive eruption (VEI 4-5) occurred there about 2000 years ago. The geochemical and age similarity with the tephra of marker layer CKr that was distinguished on Iturup, Urup, Simushir, Rasshua, and Matua islands of the Kuril Island Arc led to the conclusion that this eruption is possibly a source of this tephra. The data presented are proposed as a motivation for revision of the volcanic hazard on Iturup Island.

Archaeological charcoal from ancient nomad iron-smelting furnaces collected in the highland southeastern Russian Altai has great potential as a material for tree ring analysis. Dendrochronological dating was applied to 355 viable samples (>80% of the 448 collected ones), prepared using a new protocol. Individual tree ring series of 155 (~43%) samples were used to construct nine floating chronologies from 76 to 290 rings long. The archaeological and radiocarbon data on charcoal that fueled the hearths of the Kosh-Agach type bracket the floating tree ring chronologies between the second and tenth centuries AD. The results demonstrate that long tree ring “steppe” chronologies can be obtained for intermontane basins in the arid zone of Southern Siberia, using the analysis of charcoal samples. A strong climate signal imprinted in the annual growth of trees allowed for crossdating samples with relatively few rings. The revealed common climate signal for larches from different locations indicates similar paleoclimate conditions of their growth despite the strong modern southeastward aridization trend in the region, which was not so pronounced ca. 1.5 ka ago. The further matching of these chronologies to the calendar timeline will provide reference for the precise comparison of climatic conditions in the floors of intermontane basins and in the flanking mountains.

The glacier recession of the North-Chuya ridge, Altai, after the maximum of the Little Ice Age (LIA) is estimated based on remote sensing and in situ studies of the Bolshoi Maashei glacier. The glacier area decreased from 304.9 ± 23.49 km2 at the LIA maximum to 140.24 ± 16.19 km2 in 2000 and 120.02 ± 16.19 km2 in 2021. The average equilibrium-line altitude (ELA) rise after the LIA was 207 m. The reduction of glaciers was caused by the warming trend, most rapid in the 1990s, and by the decrease in precipitation after the mid-1980s. The volume of glaciers decreased from approximately 16.5 km3 in the LIA maximum to 5.6–5.8 km3 by 2021. From the LIA maximum to 2022, the Bolshoi Maashei glacier decreased from 17.49 km2 to 6.25 km2, and the lower point rose from 2160 m to 2225 m. After the LIA, the glacial snout retreat was about 1 km. The fastest retreat of the glacier terminus was estimated in 2010–2022 as 14.0 m a−1 on average. The glacier mass balance index was calculated, with the results showing a strong negative trend from the mid-1980s until now. Strong melt rates caused the increase in the area of the Maashei lake, which could lead to the weakening of its dam, and prepared for its failure in 2012. The current climatic tendencies are unfavorable for the glaciers.

In recent years, dendrochronological analysis in archaeology has undergone a substantial transformation, offering an opportunity to use samples of wood that were previously considered uninformative. One striking example is the analysis of charcoal excavated from archaeological sites. We have studied 448 samples of charcoal collected from metallurgical (iron smelting) furnaces in the Kurai and Chuya basins of the Russian Altai Mountains. Earlier methods of preparing such samples were slow and inefficient. Our approach guarantees fast, simple, and high-quality preparation of a large number of samples of virtually any size and shape. Its advantages include low cost of apparatus, high quality measurement of annual rings, the possibility of efficient remote measurement, no need for verification, and a wider range of measured parameters of the annual ring. Hopefully, the new approach will help to solve the critical problem relating to the construction of a tree-ring chronology in the arid zone of Southern Siberia. Such a c hronology will be highly prospective for assessing the age of wood from numerous mounds in the intermountain depressions of the AltaiSayan region, and year-by-year reconstructions of the humidity regime; and for revealing extreme droughts and other climatic phenomena in this territory.

Application of geological geomorphological and geochronological (14C, OSL) methods allowed to establish that the bordering mountains of the Chuya basin (Russian Altai) were affected by glaciation already in the Middle Pleistocene – about 160–180 ka ago (MIS 6). However, the maximal ice-dammed lake with the highest (up to 2100 m a.s.l.) strandlines both in the Chuya and Kurai basins existed later than 90–80 ka ago, in the Late Pleistocene. This chronological benchmark limits the influence of the cataclysmic outburst floods from the largest ice-dammed lakes on the accumulation of the Inya formation in the Chuya and Katun river valleys. It is confirmed that a large ice-dammed lake existed and had a water level of at least 1730 m a.s.l. in MIS 2 in the Kurai basin. It was drained no later than 16 ka ago. Synchronously (about 17–16 ka ago) the accumulation of diluvial-lacustrine cyclites began in the Inya mouth. The Saldzhar formation had been depositing as a result of not only flood events, but also gradual hydrological processes in the Katun river valley between the mouths of the Chuya and Sema rivers during the entire MIS 2. It is necessary to revise the concept adopted by SibRISC in 2018. This concept assumes i) absence of ice-dammed lakes in intermountain basins of the Russian Altai in MIS 2 and ii) accumulation of the Inya and Saldzhar formations deposited by glacial megafloods in the valleys of the Chuya and Katun rivers before 90 ka ago.

Strong earthquakes could serve as a trigger for glacier detachment and associated ice–rock avalanches. The 1988 Tsambagarav earthquake (M = 6.4) initiated collapse of part of the glacier tongue and a further ice–rock avalanche with an abnormal 5 km long path in Zuslan valley, Tsambagarav ridge (Mongolian Altai). Early documentation of surface effects in 1988, remote sensing and field data gathered 16 and 30 years after this event allowed for the assessment of the seismic impact on a reduction of “damaged” glacier under conditions of global warming as well as estimating topography changes in this arid and seismically active area. Because of the earthquake, the glacier immediately lost 10.4 % of its area (0.1 km2 of tongue surface). Additionally, 56% of its area was lost during 1988–2015, shrinking much faster than neighboring glaciers of similar size and exposition. Collapse of snow–ice cornice in the accumulation zone could play a key role in rapid acceleration of the detached ice block and abnormally long path of the ice–rock avalanche. A large amount of debris material provided more than 16 years of ice melting. Downstream, the valley avalanche debris cover repeats the topography of underlying Pleistocene moraines, which should be considered in regional paleogeographical reconstructions.

The upcoming edition of new stratigraphic scheme of Quaternary deposits of the Altai–Sayan mountain province is based on the concept of cataclysmic draining of the Pleistocene ice-dammed lakes that occurred prior to 90 ka (MIS-5 and earlier). Our geochronological (OSL, 14 C) and paleontological data argue against excluding the Sartansky cryochron (MIS-2) from the epochs of the Altai glaciogenic fluvial catastrophes. The last cataclysmically drained ice-dammed lake in the Chuya Depression existed after 37 ka. The Kurai Depression during MIS-2 was filled with water already by 25 ka and was drained at ~19–16 ka. Draining of the last ice-dammed lake in the Kurai Basin correlates with the onset of the formation of the section of catafluvial-lacustrine cyclites in the Inya River valley (a right tributary of the Katun River) at 17–16 ka (MIS-2). Previously, this section was suggested as a parastratotype of the Saldzhar catafluvial deposits accumulated during MIS-5 in the new edition of the Altai–Sayan stratigraphic scheme. OSL dates (16–12 ka) were obtained for deposits at the margin of the 70-m “Saldzhar” terrace of the Katun River upstream of the mouth of the Chuya River. The paleontological findings of lacustrine fauna in situ allow us to reconsider the concept of the exclusively catafluvial genesis of the Saldzhar deposits of the 60-m terrace of the Katun River, near the mouth of its left tributary, the Sema River. The OSL date (32 ka) of deposits at the base of this terrace indicates the onset of its formation not earlier than the end of MIS-3. The section proposed as the stratotype of the post-Saldzhar Maly Yaloman alluvium with the age 90 ka does not meet the requirements of the Stratigraphic Code, because the contact with the Saldzhar deposits has not been revealed here and genesis of deposits is controversial. At present, 14 С and OSL dates of the Saldzhar sequence and post-Saldzhar alluvium form two non-overlapping clusters, older than 90 and 35–12 ka, which can be connected both with methodological features of age dating and with insufficient geological knowledge. Only one of the eight IRSL and OSL dates obtained for Inya sequence deposits, which compose high (up to 300 m) bars in the Chuya and Katun river valleys, falls within the MIS-6 time, which is insufficient to establish its age as MIS-6 and older. To make correct stratigraphic reconstructions, it is necessary not only to expand a dataset obtained by different geochronological methods but also to study the dated deposits using a complex of geological methods.

ABSTRACT The available paleosol and paleowood data from the head of the Akkol trough valley, South Chuya range, indicates a climatically driven glacier dynamic in the Russian Altai. Radiocarbon dating of paleosols and paleotree fragments help determine the beginning of the Neoglacial in this high mountain region in the middle of the Holocene. New data limit the advance of the Sofiysky glacier at that time by the front of the Historical moraine. Less so than during the Historical stage (2.3–1.7 cal kBP), glacial activity 5–4 cal kBP is also supported by rapid reforestation. The Akkem moraine in trough valleys of the Russian Altai accumulated prior to the Holocene. The limitations and difficulties of radiocarbon dating of paleosols should be considered when interpreting the dating results.

Early documentation of the consequences of the Tsambagarav earthquake happened on July 23, 1988 (M = 6.4) compiled by Soviet and Mongolian specialists allowed the authors, using the example of Tsambagarav (Mongolian Altai), to assess the impact of the seismic process on the reduction of mountain glaciation and topography of the trough valleys in the arid region of Central Asia. In 1988, in upper part of the Zuslan river valley, 13 days after the earthquake, the release of a fragment of one of the glaciers gave rise to an ice-rock avalanche << on an air cushion >>. Its deposits with a thickness of up to 30 m blocked the valley over a distance of 5 km. Analysis of space images taken in different time together with field researches revealed that as a result of the earthquake the glacier N degrees 15 simultaneously lost 0.1 km(2) of its tongue (10.4% of total area), as the whole in 1988-2015 it lost 56% of its area, whereas neighboring glaciers N degrees 16 and 17, similar in size and the same exposure, lost significantly less - 35 and 15% of the area, respectively. Rapid shrinking of not only the glacier tongue, but also of its accumulation zone; the established deficit of ice volume in the broken off ice fragment (in comparison with initial assessment), and the abnormally long path of the avalanche made it possible to clarify the factors and mechanism of its initiation: the fall of the ice-snow ledge from the accumulation zone could lead to the rapid release of the broken ice fragment in the tongue part of the glacier. In 2004, 16 years after the avalanche, the buried ice in its deposits was still partially preserved, having completely degraded by 2019. The long time of the ice degradation process was caused by the high content (about half of the volume) of debris that armored the surface of avalanche sediments. The debris material of the avalanche repeats the relief of the underlying Pleistocene moraines, which may complicate the reconstruction of the number, scale and age of glacial events in avalanche hazardous areas. The relatively high rate of leveling of the avalanche traces and, as a consequence, the difficulties of their subsequent identification in the relief allow us to assume a greater number of avalanche releases, including seismic ones, in the recent geological past than it can be established at present in the Altai ridges.

A 48 km long zone of surface deformation produced by the Ms = 7.3 intracontinental earthquake of 2003 in Gorny Altai is studied in its five segments between the Aktru and Irbistu rivers, where ruptures show the greatest offsets and distinct structural patterns. A total of 554 coseismic ruptures of five slip geometry types are analyzed in terms of length, orientation, and relative percentage. The rupture patterns are discussed with reference to previously published evidence and compared with other strike-slip zones worldwide.

Analysis of new chronological data, including 55 radiocarbon, 1 OSL, and 8 dendrochronological dates, obtained in the upper reaches of trough valleys within the Katun, North Chuya, South Chuya, and Chikhachev ranges, together with the 55 previously published ones, specifies climatically driven glacier dynamic in the Russian Altai. Available data refute the traditional concept of the Russian Altai Holocene glaciations as a consecutive retreat of the Late Pleistocene glaciation. Considerable and prolonged warming in the Early Holocene started no later than 11.3–11.4 cal kBP. It caused significant shrinking or even complete degradation of alpine glaciers and regeneration of forest vegetation 300–400 m above the modern upper timber limit. Stadial advances occurred in the middle of the Holocene (4.9–4.2 cal kBP), during the Historical (2.3–1.7 cal kBP), and the Aktru (LIA thirteenth–nineteenth century) stages. New radiocarbon ages of fossil soils limited glaciers expansion in the Middle Holocene by the size of the Historical moraine. Lesser glacial activity between 5 and 4 cal kBP is also supported by rapid reforestation in the heads of trough valleys. Glaciers advance within the Russian Altai, accompanied by accumulation of the Akkem moraine, could have occurred at the end of the Late Pleistocene.