PLEISTOCENE GLACIATIONS OF THE SE ALTAI, RUSSIA, BASED ON GEOMORPHOLOGICAL DATA AND ABSOLUTE DATING OF GLACIAL DEPOSITS IN CHAGAN REFERENCE SECTION

Abstract Geomorphological evidence of at least two Pleistocene glacial epochsis noted within the Chagan-Uzun river basin, SE Altai. A review and analysis of all available absolute dates for reference Chagan section is presented. The highest correlation amongst all TL dates is observed for the lens of glacio-lacustrine sediments – the most suitable among glacial deposits for luminescence dating, and indicates its possible Middle Pleistocene age. IRSL dates obtained from feldspar indicate a Middle Pleistocene age of moraines already in the upper part of the section. The small number of obtained IRSL dates does not allow making geochronological reconstructions of the Pleistocene glaciations, but gives the possibility for further experiments with different variation of OSL (IRSL) techniques. Strong low temperature peak in TL signal and strong response to IR stimulation are specific regional quartz features, which could be explained by combination of short transportation distance and low number of depositional cycles for mineral grains. Available radiocarbon dates of carbonate concretions from this section are not related to the age of moraine sedimentation and most likely indicate the period of the Chagan river incision into the ancient glacial deposits. This study has shown that TL method is not valid for dating glacial sediments and TL dates cannot be utilized as chronostratigraphic markers. Generally, the Chagan section could hardly serve as a reference section for the Altai stratigraphy; available depositional correlation schemes for the Russian Altai and Siberia which are based on several TL dates obtained in the last century needs to be improved.</jats:p

Last ice-dammed lake in the Kuray basin, Russian Altai: New results from multidisciplinary research

Results from geomorphological, sedimentological and geochronological analyses, together with micropaleontological and mineralogical characteristics of lacustrine deposits in five locations within the Kuray intermountain depression, southeast Altai, mountains of south Siberia, support the thesis of repeated formations of ice-dammed lakes during MIS-2 and their draining by high energy floods. Our data suggest that the timing of one of the last cataclysmic draining events in the area can be estimated by an Optically-Stimulated Luminescence (OSL) age of 19.0 ± 1.1 ka for a sandy layer at the top of the diluvial (i.e. large flood) deposit, revealed in a sedimentary sequence of the 1570 m a.s.l. strandline – one of the lowest preserved strandlines in the western part of the basin. New OSL and radiocarbon ages, augmenting previously published dates, indicate that the last lake to occupy the Kuray depression occurred around 19–16 ka with a depth of at least 170 m in the central part of the basin and to a depth of no less than 220 m near the glacier dam. Lacustrine deposits are represented by two horizons of sandy clays separated by interlayers of mixed-size sands. The mineralogical data, supported by analysis of sedimentological and micropaleontological records, indicate accumulation of a lower lacustrine horizon in a deeper reservoir. Finding of Leucocythere sp.1, Leucocythere sp.2, and Leucocythere dorsotuberosa ostracod species in lacustrine deposits characterizes these reservoirs as periglacial freshwater cold and deep lakes. The presence of well-crystallized mica and chlorite in lacustrine silts and clays from the lower lacustrine horizon indicates cold, dry conditions at the time of their formation, as well as a predominance of physical weathering of rocks within the denudation area. After an abrupt dropping of the lake level around 16 ka, determined from OSL dating, the lake never recovered its former depth. The available radiocarbon ages for organic material in subaerial deposits within the study area and the new OSL ages suggest that the last ice-dammed lake in the Kuray basin was drained between ~16.7 and 9.9 ka. The presence of this lake might explain the absence of late Paleolithic surface finds within the basin that remained generally unsuitable for human habitation until its final drying. The last outburst flood passed along the Chuya and Katun river valleys, which had been already carved by older cataclysmic floods, but did not significantly affect the topography downstream of the Kuray-Chuya intermountain depressions. We numerically simulated the draining of a palaeolake in the Kuray basin with the water level 1650 m a.s.l. (maximal depth about 220 m near the dam) with different scenarios of breaching the ice dam. In contrast to a relatively gradual breach of the ice dam due to thermal erosion, an instantaneous dam break due to structural failure can cause an outburst flood with a peak discharge of around 2 × 106 m3 s−1. The high speeds of the water flow, 1.9–5.6 m s−1, with the maximum Froude numbers of 0.06–0.22, and peak Shields values of 0.03–0.25 indicate competence to mobilize gravel. Generally, the simulated flow remained subcritical, suggesting that bedforms developed under supercritical flows, such as antidunes, could not have developed, although the development of dunes cannot be precluded. Our data also contribute to the issue of correlating the low lake strandlines in the Kuray basin with the landforms associated with cataclysmic outburst floods.The study was supported by State Assignment of IGM SB RAS and partly funded by Russian Foundation for Basic Researches (grant 18-05-00998). We also benefited from the funds of the projects EX-AQUA (1623P) “Palaeohydrological Extreme Events - evidence and archives”, sustained by INQUA TERPRO. The flood modelling contribution by Bohorquez was supported by the Spanish Ministry of Science, Innovation and Universities (MICINN/FEDER, UE) under Grant SEDRETO CGL2015-70736-R

RECURRENCE INTERVAL OF STRONG EARTHQUAKES IN THE SE ALTAI, RUSSIA REVEALED BY TREE-RING ANALYSIS AND RADIOCARBON DATING

Abstract This paper presents the results of paleoseismogeological investigations including tree-ring analysis and radiocarbon dating in pleistoseist zone of the 2003 Chuya earthquake, SE Altai, Russia. Twenty-five radiocarbon dates of previously unknown evidences of prehistoric earthquakes along the fault bounders of the Chagan-Uzun massif, North Chuya and South Chuya ranges are reported. Perspectives of applying dendroseismological approach within the high mountainous seismically active southeastern part of Russian Altai are demonstrated. In addition to estimating the germination ages of trees growing on the bare surfaces of seismically triggered landslides, analysis of wood penetrating injuries in the individual tree ring series was applied for dating paleorock-falls. Analysis of distribution patterns of tree-ring anomalies and injured trees suggests a criterion of recognizing seismic origin of past rock-falls. Dendrochronologically obtained dates of abrupt intensifications of rock-falls can be considered as supposed dates of past earthquakes, which should be verified by alternative proxy data. Obtained results argue for the high regional seismicity in the second half of the Holocene. Strong earthquakes occurred here AD 1532, and 600–700, 1300–1500, 2400–2700, 3400–3700, 3800–4200 cal BP. This data clarifies the chronology of seismic events within the SE Altai. The specified recurrence interval of strong earthquakes is about 400 years during the last 4000 years.</jats:p

New Data on Iron-Smelting Sites in the Kuektanar and Turgun Valleys, Southeastern Altai

This paper presents the findings relating to iron-smelting furnaces in the Kuektanar and Turgun valleys of the Russian Altai, which were part of the Chuya-Kurai metallurgical province and are undergoing rapid erosion. On the Chuya River, downstream of the mouth of the Kuektanar, we discovered hitherto unknown (and completely eroded) remains of furnaces. Radiocarbon dating of charcoal fragments from smelting furnaces (bloomeries) at Kuektanar-1 and 2 and Turgun-1, using both scintillation and AMS techniques, suggests the use of trees that grew in 5th–10th centuries AD as a fuel for metallurgical production. Dates of charcoal relating to the same iron-smelting event differ by over 300 years, probably because various parts of adult larches (Larix sibirica Ledeb.) were used, creating an “old wood” effect. Samples of uncharred bark in bloomery 2 at Kuektanar-1 suggest that the last smelting occurred in 655–765 AD. The totality of radiocarbon dates makes it possible to conclude that the furnaces were active during the Old Turkic period. The proximity of iron ore sources and the abundance of forest vegetation account for the wide use of iron-smelting by the nomads in the region. The erosion of the river bank where the furnaces are located allowed us to assess the erosion rate since their construction to be approximately 0.5 cm per year. © 2018 A.R. Agatova, R.K. Nepop, I.Y. Slyusarenko, V.S. Panov.The study was performed under Public Contract (Project No. 0330-2016-0015); archaeological studies were supported by the Russian Science Foundation (Project No. 14-50-00036), geological and geomorphological studies, including radiocarbon dating, were supported by the Russian Foundation for Basic Research (Project No. 16-05-01035)

Specific Effects of the 1988 Earthquake on Topography and Glaciation of the Tsambagarav Ridge (Mongolian Altai) Based on Remote Sensing and Field Data

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. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The study was supported by State Assignment of IGM SB RAS and partly funded by Russian Science Foundation (grant 22-27-00447)

Potentiality of Charcoal as a Dendrochronological and Paleoclimatic Archive: Case Study of Archaeological Charcoal from Southeastern Altai, Russia

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. © 2023 by the authors.Russian Science Foundation, RSFThe study was supported by grant 22-27-00454 from the Russian Science Foundation

Archaeological sites as markers of Neopleistocene-Holocene hydrological system transformation in the Kurai and Chuya basins, Southeastern Altai: Results of geomorphological and geoarchaeological studies

Multidisciplinary studies using geomorphological, geoarchaeological, and geochronological approaches indicate contrasting environmental changes in Southeastern Altai, beginning in the Late Pleistocene. 29 new radiocarbon dates from the subaerial complex overlying Late Neopleistocene sediments in the high-altitude Kurai and Chuya basins confirm the degradation of a single ice-dammed reservoir in that area before the Early Holocene. In the first half of the Holocene, those basins were filled with isolated lakes. At the mouth of the Baratal River in the western Kurai basin, a reservoir with a water-level of at least 1480 m a.s.l. emerged ca 10–6.5 ka cal BP; whereas in the Chuya depression, numerous residual lakes existed at least 8 ka cal BP. Landslide- and moraine-dammed lakes between the depressions in the Chuya River valley existed until 7–3 ka cal BP, when they drained away. The state of preservation of in situ archaeological sites, their cultural affiliation, and their locations within the depressions and along the main Chuya valley attest to spatial and temporal changes in the hydrological system. This evolution in the second half of the Holocene did not entail major consequences for humans. All cataclysmic flood events took place (occurred) before 10–8 ka cal BP. © 2016 A.R. Agatova, R.K. Nepop, I.Y. Slyusarenko, V.S. Myglan, V.V. Barinov.Geomorphological studies, including radiocarbon dating, were supported by the Russian Foundation for Basic Research (Projects No. 15-05-06028 and 16-05-01035); archaeological and dendrochronological studies were supported by the Russian Science Foundation (Projects No. 14-50-00036 and 15-14-30011 respectively)

Археологические памятники как маркер перестройки неоплейстоцен-голоценовой гидросети Курайской и Чуйской впадин (Юго-Восточный Алтай): результаты геолого-геоморфологических и геоархеологических исследований

Multidisciplinary studies using geomorphological, geoarchaeological, and geochronological approaches indicate contrasting environmental changes in southeastern Altai beginning from the Late Pleistocene. Twenty-eight new radiocarbon dates from the subaerial complex overlying Late Neopleistocene sediments in the high-altitude Kurai and Chuya basins confi rm the degradation of a single ice-dammed reservoir in that area during the Early Holocene. In the first half of the Holocene, those basins were filled with isolated lakes. At the Baratal River mouth in the western Kurai basin, a reservoir with a water level of at least 1480 m a.s.l. emerged ca 10-6.5 ka BP, whereas in the Chuya depression, numerous residual lakes had existed at least 8 ka BP. Landslide- and morainedammed lakes between the depressions in the Chuya valley had existed until 7-3 ka BP, when they drained away. The preservation state of in situ archaeological sites, their cultural affiliation, and their location within the depressions and along the main Chuya valley attest to spatial and temporal changes of the hydrological system. This evolution occurred in the second half of the Holocene and did not entail major consequences for humans. © 2016 Siberian Branch of the Russian Academy of Sciences.Geomorphological studies, including radiocarbon dating, were supported by the Russian Foundation for Basic Research (Projects No. 15-05-06028 and 16-05-01035); archaeological and dendrochronological studies were supported by the Russian Science Foundation (Projects No. 14-50-00036 and 15-14-30011 respectively)

Влияние землетрясения 1988 г. на оледенение и рельеф массива Цамбагарав (Западная Монголия)

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 № 15 simultaneously lost 0.1 km2 of its tongue (10.4% of total area), as the whole in 1988–2015 it lost 56% of its area, whereas neighboring glaciers № 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 avalanchehazardous 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.Ледник № 15 (по [3]), потерявший в результате Цамбагаравского землетрясения 1988 г. магнитудой М = 6,4 фрагмент языка (10,4% всей площади) и часть объёма в области аккумуляции, в период 1988–2015 гг. сократился на 56%, что больше сокращения соседних ледников (15–35%). Погребённый лёд в отложениях ледово-каменной лавины, заполнивших долину р. Зуслан на протяжении 5 км, частично сохранялся и в 2004 г.; полностью он растаял к 2019 г. Обломочный материал лавины повторяет рельеф подстилающих плейстоценовых морен, что может осложнить реконструкцию ледниковых событий в регионе. Уточнены факторы, определившие возникновение лавины на «воздушной подушке»