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.

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.

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, ¹⁴C) 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, ¹⁴С 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.

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 paper discusses landscape evolution in a broad transitional zone between the Western Sayan and Altai mountain structures in the context of cataclysmic and gradual geomorphological processes. This region hosts a global watershed between Arctic Ocean and Mongolian inland drainage basin. The distribution of glacial landforms and deposits there indicates vast late Pleistocene glaciation included large ice sheet at the Shapshal Range, ice cap on the Mongun-Taiga massif and valley glaciers in the Chikhachev Range. The ranges are separated by Dzhulukul depression, Kargy and Mogen-Buren River valleys which show different scenarios of deglaciation and further evolution of post glacial landscapes. Gradual non-cataclysmic deglaciation and transformation of the fluvial system was inherent to the Kargy River basin. The neighboring Mogen-Buren River basin exposes landscape affected by cataclysmic outburst floods from ice-dammed lakes. Another specific deglaciation feature is redirection of the water runoff from the Dzhulukul depression from the south to north. The early-middle Holocene landscapes of the region developed under more humid and warm climate conditions. Various proxy data: lacustrine sedimentation patterns, chironomid and vegetation change records, paleosoil archives indicate abrupt climatic changes in the second half of the Holocene towards colder conditions and intensified aridity, which is especially pronounced for the last 2–1.5 ka. Despite scattered single Paleolithic finds of loose time constraints, this severe land became regularly populated since the Bronze Age.