Russian Altai in the Late Pleistocene and the Holocene

CONTENT

Introduction 5 Key questions related to the geomorphology of this excursion 9 Princess of Ukok 12

Part I. Upper Biya River valley and the Teletskoye Lake 16 NE Altai Regional settings and Quaternary history: General overview 16 Stop B1. Former glacial-dammed lake in the Yogach valley 23 Stop B2. Former alluvial-dammed lake in the Turachak valley 27 Stop B3. Teletskoye Lake and lacustrine terrace at Yaylyu 31 Geomorphic history of the Teletskoye Lake – Biya valley system: synthesis 35

Part II. Middle Katun River valley 39 Brief introduction 39 Stop K1. Catafluvial deposits of the high (Inya) terrace in the vicinity of the Bolshoi Yaloman River 41 Stop K2. Boulder field at km 702 51 Stop K3. High terraces of the Katun and Injushka Rivers at the Inya village 57 Stop K4. Composition and geochronology of the low (Saldzhar) terrace at the Chuya River confluence 68

Part III. Middle Chuya River valley, Kuray and Chuya Basins 73 Stop C1. Early Holocene seismic fall and dammed lake formation at the Sukhoi brook 73 Stop C2. Late Pleistocene glacial damming of Chuya at Kuektanar tributary valley 77 Stop C3. Lower Chagan-Uzun river: the Late Pleistocene maximal glacial advance 84 Stop C4. Beltir village: consequences of the year 2003 seismic hazard 87 Stop C5. Earthquake triggered giant landslides in the Taldura valley 92 Stop C6. Kuray dunes 99

3 Russian Altai in the Late Pleistocene and the Holocene

Stop C7. Kuray strandlines 102 Stop C8. Early Holocene lake in the western part of the Kuray Basin: the Baratal section 108 Stop C9. The Chuya spillway upstream from the Chibit town 112 Stop C10. Old valley of Chuya, age and mechanism of abandonement 115

References 120

Supplements 125 S1. Large boulder transport 125 S2. Problems of absolute dating of glacial deposits in Russian Altai by the example of the Chagan section 130 S3. The recurrence interval of strong prehistoric earthquakes in the SE Altai (the Kuray-Chuya active zone) based on dendroseismological approach and radiocarbon analysis 133 S4. Radiocarbon chronology of the Holocene landscape evolution within the Kuray-Chuya system of intermountain depressions 135

4 Introduction

INTRODUCTION (G. Baryshnikov, A. Panin)

The Russian Altai is one of the world's regions where evidence has been recognized of past megafloods – the largest known fresh-water floods which discharges exceeded 1 million m³/s, or 1 Sv (Baker, 2013). More than three decades ago giant current ripples were found in Altai in the valleys of Bashkaus, Chuya, Katun and in the bottom of the Kuray Basin (Butvilovskiy 1982, 1985; Okishev 1982; Rudoi 1984), as well as in the Biya River valley (Baryshnikov 1979, 1992). A number of workers hypothesize that these features are specific facies of glacial till (Borisov and Minina 1979; Okishev 1982, 2011). However the majority of scholars interpret them as evidence of catastrophic outburst floods that resulted from water flowing from big lakes formed due to blockage of river valleys by glaciers. Later other evidence of outbursts from glacial lakes were recognized, such as spillways and distant transportation of giant rocks torn from valley sides. Paleohydraulic assessments (Baker et al., 1993; Herget, 2005; Carling et al., 2010) permit the ranking of the Altai outburst floods with depth up to 400 m, flow velocity 20-25 m/s and discharge 10-20 million m³/s close in magnitude to the well-known Missoula flooding in western USA (Baker, 2009). Several local and international workers that independently studied the Late Pleistocene and Holocene geomorphic history of Altai in the last decades have collected into this author team to present their results to the attendees of the International Association of Geomorphologists (IAG) Regional Conference "Gradualism vs catastrophism in landscape evolution" (Barnaul, Russia, July 2- 4, 2015). This guide was prepared for the 7-day (July 5-11) post-conference excursion "Russian Altai in the Late Pleistocene and the Holocene: Geomorphological catastrophes and landscape rebound". The fieldtrip is scheduled as three consecutive parts (Fig. 1): (1) Upper Biya River and Teletskoye Lake, July 5-6, stops B1 – B3; (2) Middle Katun River valley, July 7-8, stops K1 – K4; (3) Lower Chuya River – Kuray Basin – Chuya Basin, July 9-10, stops C1 – C10.

General plan of the fieldtrip:

July 5 8.00 Departure from Barnaul for Gorno-Altaisk 12.00-13.00 The Republican National Museum in Gorno-Altaisk 12.30-14.30 Lunch 18.30 Arrival to Artybash, accommodation 19.30 Dinner

5 Introduction

Fig. 1. General map of the post-conference fieldtrip

July 6 8.00 Breakfast 9.00-12.30 Stops in the Biya valley tributaries (Iogach and Turachak rivers): exposures of alluvial and dammed-lake deposits . 12.30-13.30 Lunch 14.00-19.00 Cruse in the Teletskoye Lake: Korbu waterfall, lacustrine terrace and exposure at Yaylyu. 19.00 Dinner at Artybash July 7 7.00 Breakfast 8.00-16.00 Transfer Artybash – Ongudai. Packed meals. 16.00 Accomodation and meals in Ongudai 18.00 Ethnographic entertaining program 20.00 Dinner July 8 8.00 Breakfast 8.00 – 19.00 Transfer to Aktash with five stops in the Katun and Chuya valleys: exposures of catafluvial deposits composing the upper and lower terraces of Katun, petroglyphic arts. Meals in a roadside cafe.

6 Introduction

19.00 Accomodation in Aktash 20.00 Dinner July 9 8.00 Breakfast 9.00 – 19.00 Visiting the Chuya Basin: key sections of Late Pleistocene moraine and dammed lake deposits, Beltir earthquake, Taldura seismic landslide. Several stops in the Chuya valley: Kuekhtanar glacial dam, Iron Age geoarchaeology, the early Holocene dammed lake at Baratal. Packed meals. 19.00 Dinner in Aktash July 10 8.00 Breakfast 9.00 – 14.00 Visiting the Kuray Basin: strandlines of the Kuray Lake, large gravel ripples, synthesis of the long term debates on timing and mechanism of the Kuray Lake formation and sink. 14.00 Lunch in Aktash 15.00-19.00 Examination of the abandoned Chuya valley and the young Chuya canyon with key exposures illustrating the age and mechanism of the valley rebuilding. 19.00 Dinner and farewell party in Aktash.

July 11 8.00 Breakfast 9.00 – 19.00 Bus transfer from Aktash to Barnaul (600 km).

Problems of the Quaternary development of Russian Altai, especially glacial history and geomorphic and sedimentological features of river valleys have been massively studied by Russian geologists and geomorphologists since the 1950th, but most results both from early and from recent times were published in Russian, which makes them unavailable for scientific community outside the former USSR. Since the early 1990th, several international teams have been working in the region and some local researchers began to publish in English. Several dozens of papers were issued in international journals and books that contain both news results and overviews, which compensate partly the deficit of English-language publications from the region. Supplemented to this fieldtrip guide is a separate volume titled "Russian Altai: superfloods, glaciation, human occupation". The volume contains12 selected papers that give general introduction into the region, overview of key problems and some principal results from the last two decades. It permits us to skip these introductory issues and to focus on description of the fieldtrip stops. However the first part (Biya valley and Teletskoye Lake) contains a short introductory chapter because no English-language publications have still been made to cover it.

7 Introduction

It will become clear from the offered publications that noticeable progress has been achieved in understanding the Altaian superflood phenomena in recent decades. However many uncertainties still remain in interpretation of particular phenomena and their correlation through the fluvial system, including geomorphological and sedimentological features and geochronology of events and deposits. In this regard, we find it especially important to introduce a yet unpublished series of >30 OSL dates obtained in the last year from the Biya, Katun and Chuya valleys. Laboratory analysis was processed by Dr. Grzegorz Adamiec. Given the existence of a variety of views, we try in this guide to offer more facts and results so that to facilitate the fieldtrip attendees to elaborate their own opinions on the debated problems. Authors of the text that will also guide the excursion are: • Gennady BARYSHNIKOV, prof., Altai State University, Barnaul, Russia; • Anna AGATOVA, PhD, Institute of Geology and Mineralogy, Russian Academy of Sciences (Siberian Branch), Novosibirsk, Russia; • Paul CARLING, prof., University of Southampton, UK; • Juergen HERGET, prof., Bonn University, Germany; • Andrei PANIN, PhD, Lomonosov Moscow Sate University, Russia; • Grzegorz ADAMIEC, PhD, GADAM Centre of Excellence, Institute of Physics, Silesian University of Technology, Gliwice, Poland; • Roman NEPOP, PhD, Institute of Geology and Mineralogy, Russian Academy of Sciences (Siberian Branch), Novosibirsk, Russia.

8 Introduction

KEY QUESTIONS RELATED TO THE GEOMORPHOLOGY OF THIS EXCURSION (P. Carling, J. Herget)

A major key question is ‘Are the geomorphological features found in along the Katun, Chuja rivers and in the Kuray and Chuja Basins signature of catastrophic flooding? Or are they due to other geomorphological processes?’

• According to Carling, Herget and others the terraces along the river courses are giant bars deposited by a series of floods. According to Okishev they are kame terraces deposited by an extensive glacier. Can these competing hypotheses be tested?

• According to Rudoy, Carling, Herget and others the rippled ground in the Kuray and Chuja Basins and along the course of the Chuja and Katun rivers are fluvial bedforms due to catastrophic flooding. Others have suggested they are gullied alluvial fans, gullied moraine or rogen moraine. Can these competing hypotheses be tested?

• What are the key events in the Quaternary history of the region and how can these events be dated in time?

• The altitudinal range of strandlines around the Kuray and Chuja Basins indicate multiple changes in lake level. The strandlines are evidence for a lake but not evidence for catastrophic failure. Is it possible to find evidence of catastrophic failure from strandline evidence?

• Little is known with any certainty about the late glacial ice limits and the timing of deglaciation and the role of ice readvances in damming lakes. Is this a significant problem for the catastrophic flood hypothesis?

• Is it possible to consider different questions in isolation or is there merit in conjoining questions with complex answers? The latter idea requires whole system consideration including whole system modelling. Different components of geomorphological understanding have to interface and be interpretable as a whole.

Some ways forward:

Terrace morphology, depositional context, the stratigraphy and sedimentology can be used to decide if the sediments are typical of kame terraces, moraines, or catastrophic fluvial deposits. Hydraulic flood modelling can be used to see if the terrace altitudes are consistent with flood bar deposition. 9 Introduction

The morphology of rippled ground can be compared with the know structure of gullies, moraine and fluvial dunes respectively. Ground penetrating radar can be used to investigate the stratigraphy.

Strandlines can be investigated to infer depositional and erosional processes. To discover rapid lake level changes requires precise and accurate dating of multiple strandline levels.

Glacial ice dynamics can be explored using ice flow models calibrated from current knowledge. Mismatch of models and observations can be an important stimulus for improved modelling and better understanding of field data.

Whole system models can be constructed but this approach requires a thorough understanding of processes, products and timing.

Timing is an out-standing issue in the interpretation of the geomorphological history and consequently advances in robust dating techniques and adequate numbers of dated units will form a major key to future understanding.

Reading list (Key reprints will be available in field library during the trip)

1) Carling, P.A., Herget, J., Lanz, J., Richardson, K., Pacifici, A., 2009, Channel- scale erosional bedforms in bedrock and in loose granular material: character, processes and implications, pp 13-32 In: Burr, Carling, Baker (eds), Megaflooding on Earth & Mars, Cambridge University Press, 319pp. [A broad contextual review using examples from the Altai] 2) Carling, P.A., Burr, D., Johnsen, T., Brennand, T., 2009, A review of open- channel megaflood depositional landforms on Earth & Mars, pp 33- 49 In: Burr, Carling, Baker (eds), Megaflooding on Earth & Mars, Cambridge University Press, 319pp. [A broad contextual review using examples from the Altai] 3) Carling, P.A., Martini, P., Herget, J., Borodavko, P., Parnachov, S., 2009, Megaflood sedimentary valley fill: Altai Mountains, Siberia, pp 243-264 In: Burr, Carling, Baker (eds), Megaflooding on Earth & Mars, Cambridge University Press, 319pp. [Detailed report on the interpretation of giant bar stratigraphy & sedimentology] 4) Carling, P.A., Kirkbride, A.D., Parnachov, S., Borodavko, P.S. and Berger, G.B. (2002) Late-glacial catastrophic flooding in the Altai Mountains of south-central Siberia: a synoptic overview and introduction to flood deposit sedimentology. In: Flood and Megaflood Processes and Deposits: Recent and Ancient Examples. (Eds I.P. Martini, V.R. Baker and G. Garzon) Special Publication 32 of the IAS, Blackwell Science, Oxford. [General overview of the megaflood problem] 5) Herget, J. (2005) Reconstruction of Pleistocene ice-dammed lake outburst floods in Altai-Mountains, Siberia. Geological Society of America, Special Publication 386, 118 p. [Review on flood traces and their palaeohydraulic interpretation] 6) Huggenberger, P., Carling, P.A., Scotney, T., Kirkbride, A. and Parnachov, S.V. (1998) GPR as a tool to elucidate the depositional processes of giant gravel dunes

10 Introduction produced by late Pleistocene superflooding, Altai, Siberia. Proceeding of the 7th International Conference on Ground Penetrating Radar, Vol 1,pp 279-28, May 27-30 1998, University of Kansas, Lawrence, Kansas, USA, Austin, Texas. Publ by Radar Systems and Remote Sensing Lab, Univ. Kansas. ISBN: 0-936352-16-7. [Preliminary GPR survey of gravel dune stratigraphy] 7) Borhoquez, P., Carling, P.A., Herget, J., in press, Dynamic simulation of catastrophic late Pleistocene glacial lake drainage, Altai Mountains, central Asia. International Geology Review, invited contribution. [Computation model of the catastrophic drainage within the basins themselves] 8) Huang, W., Cao, Z., Carling, P.A., Pender, G., 2014, Coupled 2D Hydrodynamic and Sediment Transport Modelling for Megaflood due to Glacier Dam-break in Altai Mountains, Southern Siberia. Journal of Mountain Science, 11, 1442-1453. [1st Computational model that deals with the channel bifurcation at confluence of Chuja and Katun, and backwater effects in the Katun valley] 9) Carling, P.A., Villanueva, I., Herget, J., Wright, N., Borodavko, P. & Morvan, H. (2010) Unsteady 1-D and 2-D hydraulic models with ice-dam break for Quaternary megaflood, Altai Mountains, southern Siberia. Global and Planetary Change, 70, 24-34. [First 2D flood model downstream of the ice dam with consideration for ice dam failure mechanisms] 10) Carling, P.A., Knaapen, M., Borodavko, P., Herget, J., Koptev, I., Huggenberger, P. & Parnachev, S. 2011, Palaeoshorelines of glacial Lake Kuray--Chuja, south-central Siberia: form, sediments and process. J. Geological Society, London, 354, 111- 128 [Detailed account of shorelines including modelling of longshore gradients] 11) Carling, P.A. (1996a) Morphology, sedimentology and palaeohydraulic- interpretation of large gravel dunes: Altai Mountains, Siberia. Sedimentology, 43, 647-664. [Original interpretation of the Kuray ‘ripples’ as dunes] 12) Carling, P.A. (1996b) A preliminary palaeohydraulic model applied to Late- Quaternary gravel dunes: Altai Mountains, Siberia. In: Global Continental Changes: The Context of Palaeohydrology. J. Branson, K.J. Gregory and A. Brown (Editors) Geol. Soc. London Spec. Publ. No. 115, 165-179. [Preliminary attempt to derive hydraulic data from Kuray duneforms] 13) Carling, P.A., 2013, Freshwater megaflood sedimentation: what can we learn about generic processes? Earth-Science Reviews, 125: 87-113. [Comprehensive account of megaflood bar stratigraphy and interpretations based in part on Altai experience] 14) Reuther, A., J. Herget, S. Ivy-Ochs, P. Borodavko, P.W. Kubik & K. Heine (2006) Constraining the timing of the most recent cataclysmic flood event from ice-dammed lakes in the Russian Altay Mountains, Siberia, using cosmogenic in-situ 10Be. Geology 34- 11, 913-916. [Exposure dating of boulder deposits related to the outburst floods] 15) Herget, J., T. Euler, T. Roggenkamp & J. Zemke (2013) Obstacle marks as palaeohydraulic indicators of Pleistocene megafloods. Hydrology Research 44, 300-317. [Local scour as hydraulic indicator including examples from Altai Mountains]

11 Introduction

PRINCESS OF UKOK (Wikipedia.org)

The Republican National Museum in Gorno-Altaisk, which is to be visited on July 5 on the way to the Biya River, provides a unique opportunity for acquaintance with one of the most fascinating discoveries made in Altai and the whole Siberia in the last decades. The Siberian Ice Maiden, also known as the Princess of Ukok, the Altai Princess, Devochka and Ochy-bala, is a mummy of a woman from the 5th century BC, found in 1993 in a kurgan of the Pazyryk culture in Republic of Altai, Russia. It was among the most significant Russian archaeological findings of the late 20th century. In 2012 she was moved to a special mausoleum at the Republican National Museum in Gorno-Altaisk (Fig. 2, 3).

Introduction The remains of the “Ice Maiden,” a Scytho-Siberian woman who lived on the Eurasian Steppes in the 5th century BC, were found undisturbed in a subterranean burial chamber. Natalia Polosmak and her team discovered the Ice Maiden during the summer of 1993, when she was a senior research fellow at the Russian Institute of Archaeology and Ethnography in Novosibirsk. It was Polosmak’s fourth season working on the Ukok Plateau where the Institute was continuing its research into the early habitation of southern Siberia. Nearly two decades later, there are few English language sources available for the important discovery: Polosmak’s National Geographic article from October 1994, and a BBC documentary (1997) featuring Polosmak and members of her team are the most informative and accessible. The Ice Maiden was a representative of the Pazyryk Culture that thrived between the 6th and 2nd centuries BC in the Siberian steppe. The Ice Maiden’s tomb was found on the Ukok Plateau near the border of China, in what is now the Autonomous Republic of Altai. The plateau, part of the Eurasian Steppes, is characterized by a harsh, arid climate. The area is known by the local people as the “second layer of heaven,” one step above ordinary people and events. Present day Altai herdsmen still bring their sheep and horses to the plateau during winter because the fierce wind blows the snow off the grass and provides grazing land for the animals despite the freezing temperatures.

Discovery and excavation Polosmak and her team were guided by a border guard, Lt. Mikhail Chepanov, to a group of kurgans located in a strip of territory disputed between Russia and China. A kurgan is a burial mound filled in with smaller sediment and covered with a pile of rocks; typically, the mound covered a tomb chamber, which contained a burial inside a log coffin, with accompanying grave goods. Such burial chambers were built from notched wood logs to form a small cabin,

12 Introduction which may have resembled the semi-nomads’ winter shelters. The Ice Maiden's tomb chamber was constructed in this way, and the wood and other organic materials present have allowed her burial to be dated. A core sample from the logs of her chamber was analyzed by a dendrochronologist, and samples of organic matter from the horses’ stomachs were examined as well, indicating that the lady was buried in the spring, at some point during the 5th century BC.

Fig. 2. Corpse of the Siberian Ice Maiden

Fig. 3. Balueva's reconstruction of the Ice Maiden's face

13 Introduction

Before archaeologist Polosmak and her crew reached the Ice Maiden’s chamber, they hit upon a second later burial in the same kurgan positioned on top of the Maiden's wooden tomb chamber. The contents included a stone and wood coffin containing a skeleton, along with three horses. Polosmak believes that this secondary burial was that of an outside group, perhaps of subordinate peoples, who considered it honorable to bury their dead in Pazyryk kurgans. A shaft dug into the kurgan indicated that this later grave had been robbed, another means by which water and snow entered and seeped into the Ice Maiden’s hollow burial chamber. The water collected, froze, and formed an ice block within the chamber which never fully thawed because of the steppe climate, permafrost, and the rocks piled on top of the mound which deflected the sun’s rays. The contents of the burial remained frozen for 2400 years, until the time of Polosmak’s excavation.

Tomb chamber Inside the Maiden’s tomb chamber was her coffin, which was made of a solid larch wood tree trunk decorated with leather appliqués depicting deer figures. The chamber also contained two small wood tables with tray-shaped tops, which were used to serve food and drink. Horsemeat and mutton had been placed on the tables; the residue of a dairy product, perhaps yogurt, was found in a wooden vessel with a carved handle and stirrer; and some kind of beverage was served in a horn cup to sustain her on her journey. The Ice Maiden and her horses were oriented with their heads toward the east, as was the case in other Pazyryk burials. She was between 20 and 30 years old at the time of her death. The causes of the Ice Maiden's death was unknown until 2014, when new research suggested breast cancer, combined with injuries sustained in a fall, as likely culprits. She may have had the elevated status of a priestess in her community based upon the items found in her chamber. The Ice Maiden’s preserved skin has the mark of an animal-style deer tattoo on one of her shoulders, and another on her wrist and thumb. She was buried in a yellow silk tussah blouse, a crimson-and-white striped wool skirt with a tassel belt, thigh-high white felt leggings, with a marten fur, a small mirror made from polished metal and wood with carved deer figures, and a headdress that stood nearly three feet tall. The size of the headdress necessitated a coffin that was eight feet long. The headdress had a wooden substructure with a molded felt covering and eight carved feline figures covered in gold. There were remains of coriander seeds in a stone dish that may have been provided for the Maiden’s medicinal use.

Controversy The excavation of the Ice Maiden was carried out with great care, although in some ways it has been seen as problematic, due to the methods used to melt the ice and remove the artifacts and body from the coffin. The mummy

14 Introduction also suffered deterioration during her transport from the site to the lab, and even when she was in a refrigerated space, which resulted in her tattoos fading. A dispute developed between the Russian authorities and the local inhabitants, who lay claim to the Ice Maiden and other Pazyryk kurgans. For 19 years after her discovery, she was kept mainly at a scientific institute in Novosibirsk, but in 2012, the mummy was returned to the Altai, where she is to be kept in a special mausoleum at the Republican National Museum in the capital Gorno-Altaisk. Future excavations of the site have since been forbidden, even though it is suspected more artifacts are inside of the tomb. A reconstruction of the Ice Maiden’s face was created using her skull, in conjunction with measurements taken from the skulls, facial features, and skin thickness of present-day Altai inhabitants (Fig. 3). The artist who created the reconstruction, Tanya Balueva, was documented as saying that the Ice Maiden “is a clear-cut example of the Caucasian race with no typically Mongolian features.” Rima Eriknova, the director of the Altai Regional Museum, is not in agreement, commenting that, “They made the Ice Maiden completely European.” DNA testing confirmed that the woman was not related to the native Mongoloids in present-day Altai. Prior to the testing, she had been believed to be their ancestor. Today people of the Pazyryk culture are believed to be of Samoyedic blood, with elements of Iranian-Caucasian substratum.

15 Part I. Upper Biya River valley and the Teletskoye Lake

Part I Upper Biya River valley and the Teletskoye Lake

[Compiled from: Baryshnikov, G., Panin, A., Adamiec, G. Geochronology of the Late Pleistocene Catastrophic Biya Debris Flow and the Lake Teletskoye formation, Altai Region, Southern Siberia. Int. Geol. Rev. 2015. DOI: 10.1080/00206814.2015.1062733]

Numerous studies of megafloods in the Altai have still been focused on the outflows from ancient lakes dammed in the Chuya and Kuray Basins in SE Altai, through the Chuya and Katun river valleys (Baker et al., 1993; Rudoy, Baker, 1993; Rudoy, 2002; Herget, 2005; Carling et al., 2009; Carling, 2013; etc.; see review of publications earlier 1991 in Baryshnikov, 1992). Much less attention has been paid to the development of the other headwater of the Ob river system – the Biya river valley. Baryshnikov (1992) proposed that outburst floods in the Biya valley had different mechanism than that in the Katun-Chuya system where megafloods originated from breaks of glacial dams formed by glaciers descending from tributary valleys. In the Biya valley, glaciers occupied the main valley itself and a large lake was formed after glacier retreat due to valley damming by end moraines. Destruction of the morainic dam was followed by a huge debris flow that spread for many tens of kilometers downstream and probably extended out to the lowland section of the valley and to the Ob River. Age of this event has not been clear till the last year when an OSL dating program was completed, which results will be discussed at the fieldtrip stops. Three sites crucial for understanding the Late Quaternary history of the Teletskoye Lake – Biya Valley cascade system will be visited during the fieldtrip (see Fig. 1.1 for site locations). Taken together they characterize the variety of geomorphological conditions before and after BDF. The Yaylyu site (Stop B3) is situated 26 km upstream of the former moraine dam (at the Yogach River mouth) at the northern bank of the Teletskoye Lake, the Yogach site (Stop B1) is at the dam and the Kebezen site (Stop B2) is located in the Biya valley 21 km downstream of the former dam (the Yogach River mouth).

NE ALTAI REGIONAL SETTINGS AND QUATERNARY HISTORY: GENERAL OVERVIEW (G. Baryshnikov, A. Panin)

The modern basin-and-range structure of Altai was developed during the Late Cenozoic orogeny, mostly during the Late Pliocene – Early Quaternary. At that time the Teletsky rift valley was formed and filled by the ancient Teletskoye Lake. Tectonic restructuring led to large-scale transformation of drainage net,

16 Part I. Upper Biya River valley and the Teletskoye Lake which is evident in the finds of alluvial gravels on watersheds far from the trunk river valleys. According to Baryshnikov (1984), in the early Middle Pleistocene the ancient Biya was a small river, which upper course did not reach the Turachak village (Fig. 1.2 A). In this manner it is distinguished from the Katun, which totally inherited its valley from initial fluvial systems. In the late Middle Pleistocene, outflow from the Teletskoye Lake began and the Biya valley reach between the Teletskoye Lake and the Turachak village was formed (Fig. 1.2 C). Therefore, the modern Biya valley is a combination of two parts with different ages. The reach downstream from the Turachak village is an ancient, probably pre-Quaternary, well-developed valley. The reach upstream the Turachak village to the Teletskoe Lake is young, late Middle Quaternary. The latter is the least developed and the narrowest section of the whole valley. The fieldtrip will be located within the latter section of the valley.

Fig. 1.1. Location map. (a) Russian Altai; (b) Teletskoye Lake region. B1 … B3 are fieldtrip stops.

17 Part I. Upper Biya River valley and the Teletskoye Lake

Fig. 1.2. Evolution of the drainage net in the North-East Altai (after Baryshnikov, 1992).

Before the last glacial advance, the lake in its northernmost latitudinal reach extended downstream of its present position. This supposition is supported by a borehole 2.7 km downstream from Artybash that reveals buried lacustrine sediments (Bublichenko, 1939). This borehole is shown in geological profile II (Fig. 1.3) along with other bore hole data within the Biya valley. The upper 20 m of the section are represented by alluvia coarsening upwards from fine sand (depth 14.8-20.8 m) to cobbles and boulders (upper 9.9 m). Below lie lacustrine deposits > 40 m thick (depth 20.8 – 62.7 m). The latter are clays and loams with abundant wood fragments intercalated with sands. The basal 6 m of the section is alluvial gravel and cobble in a sandy matrix, interlayered with clays. Bedrock is reached at the depth of 68.8 m. At the source of the Biya the described lacustrine/alluvial sequence is buried under glacial till (Fig. 1.3). An end moraine ridge is located here that marks the maximal glacier advance in the Teletskoye – Biya valley (Fig. 1.4). The glacier moved from the Korbu Ridge (Fig. 1.1) northwards through the meridional section of the Teletskoye Lake. At the latitudinal section of the lake trough the glacier split into two branches. One branch crossed the watershed at Yaylyu. The other one advanced through the lake trough. The end moraine of the latter is significantly eroded and therefore not clearly preserved in the

18 Part I. Upper Biya River valley and the Teletskoye Lake topography. Baryshnikov (1992) located the end moraine using a mineralogical technique: the moraine was indicated by the presence of scheelite, a fragile mineral that is well preserved in moraine but easily destroyed by water transport. The age of the terminal moraine and, consequently, of the maximal glacial advance, had not been clear till the OSL results were obtained in the last year, but was usually assigned to LGM by most workers based on indirect data.

Fig. 1.3. Geological profiles at the Biya River outflow from the Teletskoye Lake (after Baryshnikov, 1992). See location of profiles in Fig. 1.4.

19 Part I. Upper Biya River valley and the Teletskoye Lake

Fig. 1.4. Geomorphological map of the upper Biya valley downstream from the Teletskoye Lake (after Baryshnikov, 1992)

After the glacier retreat, valley deepening started and a staircase of terraces was formed (Fig. 1.4). The upper Biya valley terraces were studied by a number of researchers (see the review in Baryshnikov 1992). Terrace composition was considered unusual even for alpine valleys composition of terraces – with the occurrence of large (3 m diameter) well-rounded boulders within alluvial gravels. Accumulations of these boulders were often considered as a marker for glacial boundaries within the valley. Therefore in many papers terraces were related to action of a valley glacier. Baryshnikov (1976, 1992) and Baryshnikov, Panychev (1987) arrived at another conclusion on the origin of the large blocks of rocks in the upper Biya valley. These authors proposed that these blocks represent former moraine transported by a giant debris flow (termed below BDF – the Biya Debris Flow), which was formed due to the breach of end moraine that dammed the Teletskoye Lake at the sources of the Biya River. Velocities of the BDF were estimated at 7-7.5 m/s. Eroded material from the moraine dam was redeposited downstream and formed the 90-120-m terrace ("BDF terrace"), which stretches out over

20 Part I. Upper Biya River valley and the Teletskoye Lake

>10 km downstream from the former dam as far as to the Pyzha River (see location in Fig. 1.4). The terrace is composed of angular blocks and rounded boulders as large as up to 3-4 m in diameter in gravelly matrix. In reentrants in the valley sides or downstream of isolated rock remnants the terrace is composed of sandy gravels with parallel bedding. The terrace staircase formed after the dam failure consists of five terraces and a floodplain (Fig. 1.4). The relative elevation of each terrace increases in the upstream direction to the river outflow from the Teletskoye Lake (Table 1.1), which illustrates higher rates of river incision in the vicinity of the former dam and consistent decrease of river slope due to incision. The route of the BDF can be traced from local accumulations of large blocks formerly transported by the catastrophic current (Fig. 1.5). As such blocks could not be transported by normal river flow they have accumulated due to river incision and lateral migration. Now large blocks can be found at various elevations on different terraces and in the modern river channel and taken together they outline the BDF axis (Fig. 1.6). Locations where the route of the catastrophic flow is intersected by the modern river are marked by riffles composed of large boulders that were previously interpreted as terminal moraines (Schukina, 1960) or ice rafted debris (Ostroumov, 1963).

Fig. 1.5. Giant boulders on Biya terraces that mark the route of Biya Debris Flow (BDF)

21 Part I. Upper Biya River valley and the Teletskoye Lake

Table 1.1. Changing height of fluvial terraces through the Upper Biya valley (in meters above the river)

Location Terrace Dmitrievka vill. Turachak vill. Kebezen' vill. Floodplain 3 1.4 1.4 I 3-5 5-8 10-13 II 12-15 13-17 20-25 III 20-25 25-30 30 IV - 35-40 40 V - 55 60-80

Fig. 1.6. Reconstruction of the catastrophic Biya Debris Flow (BDF) caused by the failure of moraine dam and outburst of the Teletskoy Lake (after Baryshnikov, 1992)

22 Part I. Upper Biya River valley and the Teletskoye Lake

Stop B1 FORMER GLACIAL-DAMMED LAKE IN THE YOGACH VALLEY (G. Baryshnikov, A. Panin, G. Adamiec)

Results Yogach is a small 35-km long river flowing to Biya from the left at the Yogach and Artybash villages where Biya outflows from the Teletskoye Lake (see location in Fig. 1.1b). In the lower course, Yogach cuts through a terrace with a sub-horizontal surface lying 130 m above the Teletskoye Lake (565 m a.s.l.) and 80-90 m above the Yogach creek. It can be correlated to the BDF terrace of the Biya valley. This terrace stretches along the right side of the Yogach valley for a distance of 0.7-0.8 km immediately before its opening into the Biya valley. It is not recognized anywhere upstream and seems to have been completely eroded within the rest of the valley. The Yogach exposure (51.77392ºN, 87.25516ºE) is a sand pit that undercuts the described terrace at its north-western corner, immediately before the opening into the Biya valley. The exposure base was at an altitude 487 m a.s.l. (12 m above the Yogach creek, 52 m above the Teletskoye Lake). The total height of the exposure was 55 m, with the top located at altitude 537 m a.s.l. (62 m above the Yogach creek, 102 m above the Teletskoye Lake). The exposure top was 30 m below the surface of the terrace. The upper 30 m of the terrace sedimentary sequence were unexposed and therefore they were not studied. The terrace is composed of coarsening-upward horizontally bedded sequence of loams, sands, gravels that may be subdivided into three units gradually passing one into another (Fig. 1.7a). Unit Y1, depth 0 – 18 m: horizontally bedded coarse gravels with inclusion of boulders up to 50 cm in diameter, with few lenses of horizontally laminated mixed sand 0.5-1 m thick at an interval of 3-4 m (Fig. 1.7b). Unit Y2, depth 18 – 42 m: planar horizontal interbedding of sands (various size) and sandy gravels. Layers are 0.5 – 3 m thick, with second-order fine horizontal lamination. Unit Y3, depth 42 – 55 m (the base of the exposure): planar horizontal interbedding of loams, fine sands and coarse sands (Fig. 1.7c). Layers are 5 – 30 cm thick, microlaminated. From the depth 50 m upwards layers of coarse sand contain inclusions of well-rounded fine to medium gravel up to 2-3 cm in diameter. Loam layers are disturbed by loading structures. The whole sequence was interpreted as lacustrine deposits that filled a dammed lake in the Yogach valley. Sediments were transported from upstream into the valley. Two OSL dates were obtained from sand layers in the bottom and upper parts of the exposure (Table 1.2, Fig. 1.7b,c). Unit Y3 at depth ~55 m (0.5 m above the base of the exposure) were dated at 82.6±7.0 ka (GdTL-1715), Unit Y1 at depth 5 m – 50.2±3.3 ka (GdTL-1716).

23 Part I. Upper Biya River valley and the Teletskoye Lake

Fig. 1.7. The Yogach section (Yogach site): (a) general view, (b) fragment of Unit Y1, (c) fragment of Unit Y3. See Fig. 1.8 for legend. Y1 … Y3 – stratigraphic units.

24 Part I. Upper Biya River valley and the Teletskoye Lake

Table 1.2. OSL dates from the Biya valley and the Teletskoye Lake region

No. Sample WC , Age, Index D, m D , m a DR, Gy/ka ED, Gy NA index a % ka BP GdTL

Yogach site (Stop B1)

4 Iog-1 55 60 7 1.770±0.082 177±13 10/10 82.6±7.0 1715

5 Iog-2 5 20 7 1.914±0.088 112.9±6.0 13/13 50.2±3.3 1716

Turochak site (Stop B2)

6 Tur-1 14.1 7.0 15 1.933±0.081 156.3±7.9 14/14 73.1±4.7 1718

7 Tur-2 4.0 4.0 7 1.849±0.084 137±16 13/13 63.7±8.0 1719

8 Tur-3 1.1 1.1 7 1.791±0.068 76±11 10/10 37.4±5.6 1720

Yaylyu site (Stop B3)

1 Bi-1 16 5.0 15 2.280±0.092 91.9± 2.6 16/16 37.7±2.0 1712

2 Bi-2 10 5.0 18 1.849±0.072 86.2± 6.0 11/11 46.6±3.8 1713

3 Bi-3 5 5.0 19 1.868±0.073 70.2±3.3 12/12 37.5±2.3 1714

Notation: D – depth in geological section, Da – average lifetime depth used in DR calculations, WCa – average lifetime water content, DR – dose rate, ED – Equivalent dose, NA – number of aliquots measured for ED determination / used for CAM (Central Age Model) age calculation.

Interpretation The Yogach section demonstrates a continuous filling of a lake that occupied the Yogach valley. The section did not uncover the base of lacustrine sediment. Based on the OSL age of Unit Y3 one can only say that lake formation occurred and lacustrine sedimentation started before 80-85 ka BP. The most probable mechanism of lake formation was moraine damming at the valley opening into the Biya valley. It could be provided by a valley glacier that moved down the Biya valley at the end of MIS 5 (early Zyryanian, or early Wurmian, glacial epoch) or at the end of MIS 6 (Samarian, or Late Saalian, epoch). To choose between the two scenarios one must have reliable ages of alluvial-lacustrine sediments from the buried 60 m deep valley determined by boring in the vicinity of Biya outflow from the Teletskoye Lake. These lacustrine sediments are covered by glacial deposits that form the morainic dam in the Biya outflow – Yogach valley area (Fig. 1.3, 1.4), which puts a constraint to the age of maximal glacial advance and formation of the morainic dam.

25 Part I. Upper Biya River valley and the Teletskoye Lake

Abundance of organic remains in the buried valley fill supports indirectly a Kazantsevian (MIS 5e, Eemian) age of the valley. Then the morainic dam and lake formation in the Yogach valley should be constraint to the end of MIS 5 (early Zyryanian glaciation). Whatever the scenario, the glacial advance to the sources of the Biya and damming of the Yogach River and the Teletskoye Lake cannot be dated to the LGM as was considered previously (Baryshnikov, 1992). It must have occurred much earlier, and in the LGM the glacial boundary must have been far away from the latitudinal section of the Teletskoye Lake and from Biya outflow from it. The other evidence in favour of this conclusion is provided by the occurrence of alluvial and lacustrine deposits in the Yaylyu terrace dated to MIS 3 and not covered by younger glacial deposits. This interpretation supports the findings of Okishev (2011) that the largest Late Pleistocene glaciation in Altai occurred before the LGM and had retreated before the middle of MIS 3. During LGM, glaciation in Altai was not characterized by The sedimentary sequence in the Yogach section demonstrates gradual filling of a lake. The lower fine-grained Unit Y3 exhibits conditions of a deep lake and a big distance from river inflow. Unit Y2 with intercalation of fine- and coarse-grained layers represents more shallow conditions and an approaching river mouth. Unit Y1, in which coarse-grained components prevail, indicates the sedimentary environment of a semi-filled lake. No alluvial facies were documented in the section that must have been formed after the complete filling of the lake. Most probably this is because the upper part of the terrace that might contain such evidence was not exposed. A rough estimation can be made of the time by which the terrace had been aggraded to its top. Accumulation of a 50-m deposit between the two dated samples at elevations 487 and 537 m a.s.l. took roughly 33 ka, which implies an average sedimentation rate of 1.5 m/ka. As the terrace top is elevated at 560-570 m, the rest of the 30 m must have taken some 20 ka and sedimentation must have been completed not later than 30 ka BP. In fact this is an overestimation of the residual time of terrace formation because in the late stages of lake filling sedimentation rates must have increased. Therefore terrace formation must have been completed before 30 ka BP. Interruption of terrace aggradation may be considered to have resulted from the start of the Yogach River incision which has led to the formation of the present-day canyon in the valley lower course. The start of incision before 30 ka BP corresponds satisfactorily with the 35-40 ka BP age estimate for the sharp lake level drop at the Yaylyu site.

26 Part I. Upper Biya River valley and the Teletskoye Lake

Stop B2 FORMER ALLUVIAL-DAMMED LAKE IN THE TURACHAK VALLEY (G. Baryshnikov, A. Panin, G. Adamiec)

Results Kebezen is a big village at the right bank of Biya 19 km downstream from the Yogach River and the Biya outflow from the Teletskoye Lake (see location in Fig. 1.1b). It is located in the downstream edge of a valley widening occupied by the 5th (60-80 m) terrace of Biya (Fig. 1.4). No natural or artificial exposures occur on this terrace that could be examined to study the terrace composition. Further downstream the valley narrows and the river flows along the right valley side dissected by few small valleys. One of these valleys belongs to Turachak, a 3-km long creek that flows to Biya at the northern end of Kebezen. In its lower reach the valley is 400 m wide. It is occupied by the modern stream and its floodplain (50-70 m) and a 250-m wide terrace 32-40 m above Biya, which corresponds to the 4th Biya terrace (Fig. 1.4). Similar to the Yogach site, this terrace was designated only at the Turachak valley opening into the Biya valley and not found anywhere upstream. In the lower course, the terrace forms a segment at the right side of the valley 400 m long (along Turachak) and 200 m wide (across the valley). The terrace surface dips notably across the valley with altitudes of 438 m a.s.l. (42 m above Biya) at the valley side and 428 m a.s.l. (32 m above Biya) at the terrace edge that rises above the Turachak floodplain. At the same time, no significant dipping of the terrace can be recognized downstream along the Turachak valley, though the present-day creek has a steep gradient of 35 m/km. Along the 400-m terrace segment the terrace relative height measured as the terrace edge elevation above the creek increases twice from 9-10 m at the beginning of the terrace to 19-20 m at the valley end. The Turachak section (51.93103ºN, 87.08705ºE) is located in a sand pit cutting into the 4th (40 m) Biya terrace in the Turachak valley 370 m upstream from its inflow into Biya, or some 200 m from the Turachak valley end, i.e. in the middle of the 400-m terrace segment. Section is 14.5 m thick, with its base standing at 414 m a.s.l. (18 m above Biya) and top at 428.5 m a.s.l. (32.5 m above Biya). The exposure reaches the surface of the terrace. Terrace deposits were divided into two stratigraphic units (Fig. 1.8a). Unit T1, depth 0 – 3.7 m (Fig. 1.8b): planar cross-bedding of well- rounded coarse gravel (3-5 cm) and fine cobble (5-10 cm, up to 15 cm) with sandy-gravelly matrix; beds dipping at 12-15º to SE, i.e. across the terrace from the right side of the valley to the Turachak creek. Unit T2, depth 3.7 – 14.5 m: horizontally bedded sands and gravels. Four subunits were distinguished based on proportion of fine and coarse fractions: Subunit T2a, 3.7 – 6.4 m (Fig. 1.8c): horizontally laminated fine to medium sand with sub-layers of small to medium gravel (20-30 cm thick); erosive upper boundary. 27 Part I. Upper Biya River valley and the Teletskoye Lake

Fig. 1.8. The Turachak section (Kebezen site): (a) general view, (b) fragment of Unit T1. (c), fragment of the top of Unit T2, (d) fragment of the base of Unit T2. See Fig.1.7 for legend. T1 … T3 – stratigraphic units.

Subunit T2b, 6.4 – 9.9 m: interbedding of fine sands with thin horizontal lamination (layer thickness 0.5-0.6 m) and coarse sands (up to 1 m). Subunit T2c, 9.9 – 12.3 m: coarse gravel with fine gravel / sand matrix and rare cobbles (5-10 cm), with unclear thick horizontal bedding. Subunit T2d, 12.3 – 14.5 m (Fig. 1.8d): horizontally laminated sand, fine with silt layers in the lower 0.9 m and coarse with fine gravel in the upper 1.3 m; erosional boundary between the two sand sub-subunits. Three OSL dates were obtained from the section (Table 1.2; Figs 1.8b-d). Unit T2 was interpreted as lacustrine sediments filling a lake within the Turchak valley. At the base of the section (subunit T2d, depth 14.1 m) they were dated at

28 Part I. Upper Biya River valley and the Teletskoye Lake

73.1±4.7 ka (GdTL-1718), at the top of the unit (subunit T2a, depth 4.0 m) – 63.7±8.0 ka (GdTL-1719). Sandy matrix from Unit T1 at depth 1.1 m provided OSL age of 37.4±5.6 ka (GdTL-1720).

Interpretation The lower part of sedimentary sequence in the Turachak section (Unit T2) represents relatively deep-water lacustrine deposits – sedimentary filling of a lake which occupied the lower reaches of the Turachak valley. It is similar to Unit Y3 in the Yogach section. The upper, coarse-grained part of lacustrine sequence accumulated at final stages of lake filling is not exposed in the section as it has probably been eroded out by the Turachak stream when it was incising into the lacustrine terrace. The alluvial part of the section (Unit T1) represents an intermediate stage of this incision that began at higher altitudes at the right side of the valley and ceased close to the present-day elevation of the Turachak creek. During the incision the stream was shifting to the left side of the valley, which provided dipping of the terrace by about 10 m between its coupling with the valley side and its edge where the studied exposure is located. The maximum elevation of the terrace in the modern topography may not reflect the highest level of lacustrine accumulation as the terrace could have been eroded in the very beginning of incision. This former level can be roughly estimated from sedimentation rates. The two OSL ages from Unit T2 demonstrate a 10-m aggradation in a roughly 10-ka interval, which provides an aggradation rate of 1 m/ka. Aggradation rates are lower compared with that in the Yogach paleolake due to probably a smaller size of the river. If aggradation is assumed to have finished between 35-40 ka BP based on estimations for the Yaylyu and Yogach sites, then the section lacks sediments from the last 25-30 ka, or the upper 25-30 m of sediments. Given that the top of lacustrine sediments in the Turachak section lies at 425 m a.s.l., the maximal level of lacustrine sedimentation may be considered at 450-455 m a.s.l., or 60-65 m above Biya. This estimation corresponds well to the elevation of the highest level of accumulation in the Biya valley, which demonstrates clear dipping at a 20-km section of the valley from 120-130 m above the river at the source of Biya to 50- 60 m at the Sarakoksha River, which is a left-bank tributary to the Biya from two kilometres downstream from the Turachak creek. This dipping of the highest Biya terrace gives a full impression of the occurrence of a significant sediment supply at the modern source of the Biya that produced abundant sediment transported down the valley and forming an in-valley alluvial fan with maximum heights at the modern Biya sources and noticeably dipping downstream. The role of such sediment source could be played by a valley glacier, which front was located at the Yogach valley. Glacial and then morainic damming is a reliable explanation for the paleolake in the Yogach valley, but it cannot explain the lakes in tributary valleys downstream of the ice front, such as Turachak. Lakes in these valleys can be reasonably explained by damming by

29 Part I. Upper Biya River valley and the Teletskoye Lake rapid aggradation in the main valley caused by excessive sediment yield from the glacier. Large-scale bedding in alluvial Unit T1 in the Turachak section must have been formed by a rather powerful stream. Cross-beds in Unit T1 most probably represent lateral accretion of a channel point bar in a meandering or laterally shifting straight channel (Fig. 1.8a). The direction of paleochannel shift is in agreement with the general dipping of the terrace from the right side of the valley to the present-day position of the Turachak creek (from left to right in Fig. 1.8). Each bed in the cross-bedding series represents a former surface of paleochannel bottom. As each bed can be recognized from the top to the bottom of the alluvial layer (Unit T1), the paleostream must have been >4 m deep (thickness of Unit T1 around 3.7 m). Paleochannel width can be estimated from the "two-thirds rule" claiming that point bars occupy two-thirds of a channel width (Allen 1965, Ethridge and Schumm 1978). Based on the horizontal width of cross beds of ca 10 m, paleochannel width could be not less than 15 m. The former stream seems to have been several times larger than the present-day Turachak creek, which is only 2-3 m wide and 0.5 m deep. It makes the evidence, similar to that in the Chechehek section, of a considerable increase of specific runoff at the time of river incision into the lacustrine terrace, between 35-40 ka BP.

30 Part I. Upper Biya River valley and the Teletskoye Lake

Stop B3 TELETSKOYE LAKE AND LACUSTRINE TERRACE AT YAYLYU (G. Baryshnikov, A. Panin, G. Adamiec)

Results The Teletskoe Lake (level 435 m a.s.l.) is bordered mostly by high rocky banks. One of the few exceptions representing depositional environments is the terrace at the Yaylyu village (see location in Fig. 1.1). The Yaylyu terrace occupies a 1 km wide and 4 km long arcuate segment at the northern bank of the lake. It is a gently sloping (5-7º) surface that starts 0.9-1.1 km north from the lake at an elevation of 560-580 m a.s.l. (up to 150 m above the lake level), descends lakewards down to altitudes 475-480 m a.s.l. (some 40 m above the lake) and falls at angles 15-25º down to the modern lake beach. At the edge of the terrace, in elevation range 475-490 m, its surface becomes at places more gentle and is dipping at 2-3º only making a clear step, which breaks into a steep slope faced at the lake. A number of small creeks flow onto the terrace from the north, from the Torot Range. The terrace is enveloped by alluvial/lacustrine deposits. Terrace composition was studied in a natural exposure at the western edge of the Yaylyu village, near the edge of the terrace. The Chechenek section ( 51.77004ºN, 87.59908ºE) is a 50 m long natural exposure in the right side of the Chechenek valley (Fig. 1.9a). Chechenek is a small 6-km long creek flowing from the south slope of the Torot ridge through the Yaylyu terrace. The studied exposure exhibits a 21-m thick sedimentary section of the Yaylyu terrace not far from the terrace edge where the terrace slope becomes more gentle and makes a 400-500 m wide step with average slope of 2-3º. The top of the exposure at its middle part is at 471 m a.s.l., or 36 m above the Teletskoye Lake. The exposure did not include the near-surface of the terrace, which elevation above the lake is about 40 m at the site. The upper 4-5 m of the terrace deposits were not exposed and could not be cleaned, but their composition seems to be similar to the upper unit of the exposed section. The bottom of the section is at the level of the Chechenek creek (450 m a.s.l., 15 m above the Teletskoye Lake). The exposed sedimentary sequence can be sub- divided into three stratigraphic units (Fig. 1.9a). Unit Ch1: full lens with maximum thickness of 6 m a little to the right of the centre of the exposure. The unit is composed of two rhythmic pairs consisting of a mixed sand lower sub-layer (subunits Ch1b, Ch1d) and gravel- cobble (up to 15-20 cm in diameter) upper sub-layer (subunits Ch1a, Ch1c). Sandy subunits exhibit interbedding of laminated coarse sands (layers 5-10 mm) with inclusions of fine gravel (up to 1 cm), and massive fine to medium sands with unclear planar stratification at few places. Cobble subunits do not have any clear bedding. The lower pair makes a lens conformal to the whole Unit 1, with erosive lower boundary (Fig. 1.9b). Maximum thickness of sandy subunit Ch1d is 1.1 m, gravelly subunit 1c – 1.8 m. The upper pair represents a half-exposed 31 Part I. Upper Biya River valley and the Teletskoye Lake lens shifted to the right. Sandy subunit Ch1b is an inclined layer 0.5-0.6 m thick dipping upstream, i.e. in the direction opposite to the lake. The uppermost gravelly subunit Ch1a has its maximum thickness of ca 4 m at the right edge of the exposure.

Fig. 1.9. The Chechenek section (Yaylyu site): (a) general view, (b), fragment of Unit Ch1 (c) fragment of Unit Ch2, (d) fragment of Unit Ch3. See Fig.1.7 for legend. Ch1a … Ch3 – stratigraphic units.

Unit Ch2: half-lens undercut by the terrace edge where it has its maximum thickness of 7 m, and tapering out to the centre of the exposure. The

32 Part I. Upper Biya River valley and the Teletskoye Lake uppermost subunit Ch2a is composed of coarse gravel (3-5 cm) with admixture of cobbles (5-10 cm) with no clear bedding. The lower 1.1.1.3 m of subunit Ch2a are composed of well-rounded cobbles (5-15 cm) with cross-bedding at places dipping upstream into the Chechenek valley, i.e. away from the Teletskoye Lake. A single rounded boulder 50×80 cm was found at the bed of the subunit Ch2a. Subunit Ch2b is a 50-70 cm thick mixed sand with an erosive lower boundary (Fig. 1.9c). In the lower part it contains small lenses composed of unrounded fine gravel derived from the underlying subunit Ch2c. The lowermost subunit Ch2c is an up to 1 m thick lens in the left side of the exposure composed of unsorted mostly sub-rounded fine gravel (5-10 mm). Unit Ch3: a rather uniform deposit that stretches downwards below the valley bottom (depth 21 m). Due to subsequent erosion, elevation of the upper boundary is not uniform: it rises from the depth of 13 m in the left to 8 m in the right corner of the exposure. In the most part deposits are represented by parallel interbedding of loam and silt layers 5-10 cm thick, with gradual boundaries, dipping lakewards (to SW) at an angle of 15º (Fig. 1.9a,d). Loam layers contain abundant well-rounded gravel (up to 5 cm in diameter), silts contain solitary inclusions of coarse sand (up to few millimetres in size). Few large (up to 1 m) angular and subrounded clasts lie in the upper half of the unit. OSL dates were obtained from each of the three units (Table 1.2). Unit Ch3 represents relatively deep-water lacustrine sediments with seasonal lamination: loams represent winter layers with coarse fraction transported by ice rafting, and silts are summer layers. Inclination of lamination results most probably from the initial slope of the submerged surface that was covered by sediments yielded to the lake by small rivers from coastal ridges. Sandy silts of Unit Ch3 at depth 16 m provided OSL age 37.7±2.0 ka BP (GdTL-1712) (Fig. 1.9d). Units Ch2 and Ch1 are fluvial deposits. In each unit basal sandy sub- layers were OSL dated. Subunit Ch2b (25 cm above its lower boundary) was dated at 46.6±3.8 ka (GdTL-1713) (Fig. 1.9c), subunit Ch1d – 37.5±2.3 ka (GdTL-1714) (Fig. 1.9b).

Interpretation The sedimentary sequence is evidence for evolution from a deep lake (Unit Ch3) to a terrestrial environment (Units Ch2, Ch1). Unit Ch3 provides a conclusion that in the interval 35-40 ka BP the lake had already existed and its level was much higher than today. Based on the elevation of Unit Ch3, the lake level could not be less than 465 m a.s.l., or 30 m above the present-day level. However, taking into account the facies interpretation (deep lake), one can assume that lake level was much higher, probably at or above the upper edge of the Yaylyu terrace (560-580 m a.s.l., or ~130-140 m above the modern lake). In this case the Chechenek section should have been characterized by a water depth ~100 m at a distance from the shore of about 1 km, which corresponds well to lithological features of accumulated sediments (Unit Ch3).

33 Part I. Upper Biya River valley and the Teletskoye Lake

Alluvial Units Ch2 and Ch1 may be interpreted as alluvial fills of paleochannels, probably branches of braided or anastomosed paleostreams. As the younger Unit Ch1 not only undercuts but also overlies Unit Ch2, with the thalweg of the former lying 3-4 m higher than that of the latter, the whole sequence may be regarded as having been formed by an aggrading stream. This fluvial aggradation could have not been a long-term tendency, but rather an episode within an overall fluvial incision caused by the lowering of lake level. Orientation of alluvial troughs, i.e. cross-sections of paleochannels, indicates the paleostream direction from NE to SW, along or diagonal to the lake shore. Dimensions of alluvial troughs provide an estimation of palaeochannel width of 30-40 m and depth of 5-6 m, i.e. much larger than the modern creek, which is not more than 5-6 m wide and 1.1.5 m deep in high water stage. Probably this stream collected a number of creeks flowing now into the Teletskoye Lake. However, even if this was the case the modern creeks could not yield enough water to fill the paleochannels, especially if they represent only a portion of a braided channel system. The large size of paleochannels indicates probably higher specific runoff values (more humid climate?) than today. Conformal bedding, presence of sand layers with microlamination within paleochannel infills as well as the occurrence of a succession of palaeochannels may serve as arguments for a normal, non-catastrophic formation regime of both the paleochannels and their alluvial fills. The palaeostream flowed in a rather wide alluvial plain along the lake shore, which is expressed now as a 300-400 m wide step at the edge of the Yaylyu terrace in the elevation range 475-490 m. Clearly, this alluvial plain was shortened by bank erosion form the lake side as is evident from undercutting of unit Ch2 (Fig. 1.9a). To prevent this stream from eroding to the lake, the lake level must have stayed at the same level – 470 m or so, and the present-day steep slope of the Yaylyu terrace must have not existed at that time. The terrace edge was formed due to subsequent fall of the lake level down to its modern position accompanied by retreat of the base of the slope caused by bank erosion. OSL dates are evidence that the switch to terrestrial conditions had occurred very quickly. In the series of three OSL ages the date 46.6±3.8 ka from Unit Ch2 makes an inversion. Most probably this date overestimates the age of alluvium. This supposition is supported by the data from the Yogach section where lacustrine sedimentation had still not finished at ~50 ka BP. Given that lacustrine sediments in Yogach (Unit Y1) were dated at an elevation ~70 m higher than the alluvial Unit Ch2, it looks impossible that this alluvia can have a similar age, it must be noticeably younger. These discrepancies provide the basis to reject the date 46.6 ka as overestimating the real age. The remaining two dates are surprisingly similar though being obtained from quite different facies – deep water lacustrine (Unit Ch3) and alluvial (Unit Ch1). It may be interpreted as the result of a very fast transformation from a lacustrine to a terrestrial environment within the interval 35-40 ka BP. At this time the lake level must have dropped significantly and within a short time period.

34 Part I. Upper Biya River valley and the Teletskoye Lake

GEOMORPHIC HISTORY OF THE TELETSKOYE LAKE – BIYA VALLEY SYSTEM: SYNTHESIS (A. Panin, G. Baryshnikov)

The data and their interpretation stated above give the basis to outline the following concept of the Teletskoye Lake – Biya valley system development. The last glacial advance to the end of the Teletskoye Lake was preceded by the Biya valley over-deepening by about 60 m below the present-day channel (Fig. 1.3). This large-scale valley incision occurred most probably at the end of MIS 6 after or in the course of the retreat of the Pleistocene maximal (according to Okishev, 2011) glaciation in Altai. Alluvial aggradation in the valley had been occurring in the first half of the Late Pleistocene and was accelerated by approaching of a valley glacier in the next cold epoch (middle-end of MIS 5 – MIS 4). The valley glacier occupied the whole Teletskoye Lake with its front standing at the present-day source of Biya. The glacier and its front and side moraines dammed the tributary valleys, including Yogach. The glacier provided a considerable increase of sediment production. Downstream sediment transport caused the Biya valley aggradation below the glacier front and formation of the highest and widest terrace level. This terrace, which height decreases rapidly from 120-130 m at Yogach-Artybash (source of Biya) to 50-60 m at the Sarakoksha and Turachak rivers 21-22 km downstream, may be regarded as an in-valley alluvial/glaciofluvial fan. A rapid rise of the bottom of the Biya valley caused by aggradation of this fan resulted in damming of tributary valleys, such as Turachak, and formation of valley lakes in their lower courses. Similar phenomenon of tributary valley damming may probably be recognized worldwide in similar mountainous terrains, past or present, where valley glaciers descend far into lower altitudes. Frontal parts of glaciers serve as sediment sources to produce downstream aggradation in their hosting valleys. At the same time, climate-governed regional rates of sediment production are too low to facilitate comparable rates of aggradation in tributary valleys and other parts of drainage net not occupied by glaciers. Based on OSL dating, aggradation of lacustrine deposits in the Biya tributary valleys started before 80 ka BP, was still in progress at 50-60 ka BP and may be supposed to have continued further as the uppermost parts of the alluvial/lacustrine terraces were not dated in our study. Age constraint for the termination of occurrence of valley lakes and the start of Biya and tributary valley incision is provided by a number of dates around 37.5 ka BP derived from lacustrine deposits of the Teletskoye Lake and alluvia overlying lacustrine deposits (no.1, 3, 8 in Table 1.2). Close grouping of final lacustrine and initial alluvial dates around 37.5 ka BP gives grounds to the suggestion that rapid changes of the valley development had occurred around this time and definitely within 35-40 ka BP. Before this date the latitudinal section of the modern Teletskoye Lake had apparently been

35 Part I. Upper Biya River valley and the Teletskoye Lake occupied by valley glacier, which dammed some tributary valleys including Yogach and caused the Biya valley aggradation which further resulted in damming of tributaries downstream of Yogach. Retreat of the glacier must have occurred not later than 37.5 ka BP. This age estimate derived from the local sedimentary chronology does not contradict the findings of Okishev (2011) who recognized two phases of glacial advance in Russain Altai in the Late Pleistocene and attributed the maximal advance to the first of them. This maximal phase was constrainted between 32 and 58 ka BP based on RTL dating of glacial till and lacustrine sediments of glacial-dammed lakes in the Chuya Basin in the SE Altai. Moraines of the second glacial stadial correlated to MIS 2 are found now within the post-maximal glacial complexes. Similar glacial history was detected in the mountain terrain in the Baikal Region: Krivonogov et al. (2004) dated the maximal glacial advance to the Early Zyryanian (Early Wurmian) epoch with numerical ages >39 ka BP. Okishev (2011) overviewed published data and concluded that typical for alpine regions of Eurasia in the temperate zone was the occurrence of two glacial stadials in the Late Pleistocene, of which the earlier one (pre-LGM phase) was characterized by maximal glacial advance and the second (LGM) phase was marked by both less glacial advance and less lowering of snowline. Krivonogov (2010) explains the wider extent of glaciation in the south of East Siberia in the late MIS 5 – MIS 4 compared to that in the LGM by changing atmospheric circulation over Eurasia in the Late Pleistocene. According to this worker, moisture transport into the interior of the Eurasian continent was higher in MIS 4 – MIS 5d and was reduced considerably in the LGM. Glacier retreat around 37.5 ka BP resulted in formation of the Teletskoye Lake, at least its northern latitudinal segment. We consider this date as the age of formation of the modern Teletskoye Lake. It is surprisingly close to the old suggestion by Bublichenko (1939) of the lake age of 36 ka derived from simple sedimentological reasoning. The initial post-glacial level of the lake was constrained by the elevation of the terminal moraine that constituted the dam at the Yogach – Artybash location – 570 m a.s.l. This level corresponds well to the maximal elevation of the Yaylyu terrace – 560-580 m a.s.l. Sediments of the initial stage of the Teletskoye Lake are represented by Unit Ch3 in the Chechenek section (Fig. 1.8a, d) accumulated under water depth of >100 m. Shortly after that the lake level dropped by about 100 m to the altitudes of <470 m a.s.l. Fluvial deposits formed in the vicinity of the ancient lake shoreline were dated to the same age around 37.5 ka BP as the deep water lacustrine sediments in the same location, which supports the sharp, probably momentary drop of water level. This level drop was likely caused by rapid discharge of the lake resulting from the break of the moraine dam at the present-day source of Biya. This event is the most probable candidate for the catastrophic Biya Debris Flow (BDF) established by Baryshnikov (1992, 2012). The age of BDF provided in the above is significantly older than that suggested previously (Baryshnikov

36 Part I. Upper Biya River valley and the Teletskoye Lake

1992). Assignment of BDF to the LGM was suggested in this study based on a set of radiocarbon dates from lacustrine clays in a number of tributary valleys that was considered to have resulted from damming of these valleys by the BDF. Existence of these clays dated in the range 12-16 ka BP (14C uncal) reveal a wide occurrence of lacustrine sedimentation in tributary valleys in post-LGM time that requires reassessment and reinterpretation in the light of a much younger age of this phenomena relative to the BDF. Rapid deepening of Biya downstream from the former dam after the BDF caused incision of tributary valleys and draining of residual lakes in them. Alluvial sequences formed during this rapid incision demonstrate flow dimensions much larger than do the present-day streams in the same valleys. Larger stream channels support the occurrence of runoff much higher than today not only due to glacial melt water (in Biya valley), but also due to higher atmospheric precipitation (in small tributary valleys) around 37.5 ka BP. After the rapid phase of incision, valley deepening slowed down. This inference is indicated by the dynamics of the Teletskoye Lake level. After the rapid drop around 37.5 ka BP the lake level lowering switched to much lower rates. It provided conditions for creation of the alluvial plain in the lake coastal area where streams flowed along-side the lake. Further lowering of the lake had been generating constantly increasing relief, which forced local streams to abandon the 37.5-ka alluvial plain and to turn directly to the lake. The total amplitude of lake lowering since 37.5 ka BP till the present may be assessed at 30-35 m. This value may serve also as an estimation of the Biya River incision at its outflow from the lake during the same period, which consequently occurred at average rate of 0.8-0.9 m/ka. Incision and the respective lowering of the lake continued in the Late Holocene, which may be deduced from a stepwise morphology of low terraces recognized at the Yurtok River confluence 2 km downstream from the Teletskoye Lake.

Conclusion Results obtained in the last yeas revealed a notably older age of the maximal Late Pleistocene glacial advance in the Teletskoye Lake – Biya River system and the catastrophic Biya Debris Flow (BDF) and formation of the modern Teletskoye Lake associated with the glacier retreat. In previous studies all these events were assigned to the LGM. We studied three sedimentary sections and produced luminescence dates from different sedimentary facies, namely: (1) lacustrine deposits in small valleys originated from glacially induced damming prior to BDF, (2) lacustrine deposits of the Teletskoye Lake at the initial phase of its formation shortly before the BDF, (3) alluvial deposits of post-BDF incision phase. The aggregate of data suggests that major geomorphic events occurred in a short time span within 35-40 ka BP,. Glacial retreat occurred some time before this date and permitted formation of the Teletskoye Lake dammed by terminal and side moraines. The initial lake water level stood some 130-140 m above its

37 Part I. Upper Biya River valley and the Teletskoye Lake present-day level. Breaching of the moraine dam around 37.5 ka BP caused the BDF and rapid incision of the Biya valley by ca 100 m accompanied by the equivalent drop of the lake. After that Biya incision and Teletskoye Lake lowering slowed down and have continued till now at an average rate of 0.8-0.9 m/ka producing the total lowering of 30-35 m in the last 37.5 ka. However the Biya valley is still far from its pre-glacial deepening of ca 60 m below the modern valley bottom. These results confirm the earlier published data of other workers that the maximal glacial advance in alpine Southern Siberia occurred much earlier than the global LGM – in the late MIS 4 or early MIS 3. A phenomenon was also detected of tributary valleys' damming and formation of in-valley lakes due to rapid aggradation in the trunk (Biya) valley caused by excessive sediment production in the front of the valley glacier.

38 Part II. Middle Katun River valley

Part II Middle Katun River valley

BRIEF INTRODUCTION (A. Panin)

Most data on deposits of catastrophic floods in the Katun-Chuya system was obtained at the 30 km long section of the Katun valley downstream from the Chuya confluence to the Bolshoi Ilgumen River confluence where Katun enters an inaccessible canyon. Main geomorphic and sedimentological features at this section are associated with two main river terraces – high, or Inya, terrace which is 170-180 m high at Chuya and lowers to 150-160 m at B.Ilgumen, and low, or Saldzhar, terrace, which is lowers from 80-100 m at Chuya to 40-50 m at B.Ilgumen (Fig. 2.1).

Fig. 2.1. Principal model of terraces and alluvial stratigraphy in the middle Katun valley (after Zolnikov, 2011). Legend: 1 –Early Pleistocene brownish alluvium; 2 – Inya superflood alluvia; 3 – alluvia of upper erosional terraces; 4 – Saldzhar superflood alluvia; 5 – alluvia of lower erosional terraces; 6 – cover aeolian and mass waste deposits.

Both terraces are composed of specific deposits, which are recognized by many researchers as "superflood alluvia". No agreement exists about the terrace age and mechanism of sedimentation. For both terraces the following alternatives exist in relation to the style of their accumulation proposed by different researchers: (1) accumulation during a single megaflood; (2) accumulation by a consecutive series of superfloods (up to seven events, according to Parnachev, 1999) during a relatively long time period; (3) ordinary style of sedimentation for mountainous valleys without

39 Part II. Middle Katun River valley megaflood effects. Age estimations for the Upper (Inya) Terrace vary from the end of the Middle Pleistocene to LGM, for the Lower (Saldzhar) Terrace – from the first half of the Late Pleistocene to the Late Glacial time. The four stops in the middle Katun valley (Fig.2.2) will illustrate morphology and composition of Katun terraces and present new data collected in recent years that could facilitate our understanding of the superflood phenomena.

Fig. 2.2. Space image showing location of stops K1 – K4

40 Part II. Middle Katun River valley

Stop K1 CATAFLUVIAL DEPOSITS OF THE HIGH (INYA) TERRACE IN THE VICINITY OF THE BOLSHOI YALOMAN RIVER

The roadside exposure at km 687 (upstream edge at 50.55992ºN, 86.56270ºE) called the Bolshoi Yaloman exposure, or Halt Kezek-Jala Bar by P.Carling and J.Herget, gives the impression of the composition of "catafluvial" deposits – specific alluvial deposits accumulated by megafloods.

General description and absolute geochronology of the Bolshoi Yaloman (BY) exposure (A. Panin, G. Adamiec and G. Baryshnikov)

Roadway excavation at the 687 km of Chuiskiy Tract undercuts the left-bank 150-170-m terrace of Katun (Fig. 2.3). Road is 70 m above the river, and the 400 m long exposure unravels the composition of the middle part of the terrace (Fig. 2.4). Exposure is typically 10-15 m high, except for its upstream starting section where it rises up to 35 m (however these upper parts of the exposure can be reached only with special equipment). The section may be divided into seven statigraphic units (Fig. 2.4). Units are large (>5 m in thickness) sedimentary bodies separated by erosional boundaries. Subunits were distinguished in cases of noticeable lithological changes within the units. Unit BY-1: visible thickness 5 m. Small gravel (rounded and unrounded) with parallel horizontal bedding, inclusions of medium gravel (5-7 cm) and solitary boulders (up to 50 cm). Unit BY-2: thickness 11 m. Planar horizontal interbedding of coarse sands and fine gravels with rare inclusions of small gravel (1-3 cm). Unit BY-3: thickness up to 20 m. Small to medium gravel with horizontal bedding. The layer has sharp erosional lower boundary dipping upstream at an angle of 10º. In the vicinity of the boundary, gravel layers bend slightly and follow parallel to the contact. Unit BY-4 (5 m). Fining-up sequence: concave layers of coarse gravel in the bottom replaced upwards by parallel layers of small gravel slightly inclined downstream (10º). The unit looks like a filled palaeochannel that was later undercut from the left side. Unit BY-5 (>20 m in total). The largest unit subdivided into two sub-units with gradual transition designated from changes in lithology. All subunits are composed of parallel layers and differ in grain size of material. Subunit BY-5a is the interbedding of small and large gravels dipping upstream at an angle of 15º. Subunit BY-5b is composed of layers of small gravels with inclusion of large gravels that do not make continuous layers. In the left side, layers are dipping upstream at the same angles as that of subunit BY-5a. To the right (downstream direction), dipping becomes more

41 Part II. Middle Katun River valley gentle (<5º). In the bottom-central part of the section beds are horizontal, but to the right (downstream direction) beds restore their inclination of 10º. The lower boundary is erosional. Along with general dipping in the upstream direction, the boundary shows gentle waves with an amplitude of 1.5 m and wavelength 15 m (320-350 m of the exposure). Basal layers are enriched with medium and small gravel, especially at places where underlying material is coarse (Unit BY-7). Unit BY-6 (5-7 m) demonstrates the most irregular structure of all described above. Subunit BY-6a is the layer of fine to medium sand having variable thickness, typically from 30 to 60 cm. It starts at the 330 m of the exposure and may be traced to 380 m where it rises to the upper limit of the exposure. At some places sand thins out, probably due to erosion preceded to the accumulation of the overlying unit. The lower boundary of sand is distinct and in some places cuts underlying beds, particularly in the right side, but erosion depth seems to be minimal. In the left side the sand layer dresses gentle wave-like (amplitude 1.5 m) structures of the underlying subunit that come probably from beneath (Unit BY-7). In the right, the sand layer follows parallel to the lower boundary of Unit BY-5 dipping in the upstream direction at an angle of 10º. The upper surface of the sand layer is relatively smooth, while its lower boundary is highly irregular. Subunit BY-6b (thickness up to 5 m) is the transition to the underlying unit. It is small gravel with beds enriched with medium and coarse gravel. At the bottom, most beds dip upstream at an angle of 10º and are parallel to the lower boundary of Unit BY-5. In the central-bottom part (330-350 m of the exposure), a dome-like stratification is found, which looks like being originated from enveloping of a prominence of underlying layer hindered under scree. In the upper part of the subunit material becomes less enriched with coarse gravels. Lower boundary cuts beds of the underlying unit. Unit BY-7 (>10 m). Coarse gravel and cobble dipping at 10-15º downstream in the left part and 5-10º upstream in the right part of the exposed section of the unit. Blocks up to 1 m large are found through the whole unit. At 350 m of the exposure group of large blocks forms a dome-like structure, probably a gentle sedimentary wave, which proves the inclusion of these blocks in sediment transport.

42

Fig. 2.3. Aerial view at the 160 m high terrace of Katun at km 687. View from NNW. 1 – upstream limit of the exposure shown in Fig. 2.4.

Fig. 2.4. The Bolshoi Yaloman section of the High (Inya) Terrace

Part II. Middle Katun River valley

The whole section demonstrates laterally accreted alluvial bodies formed most probably during a single flood event (units BY-3 – BY-7). In favor of this interpretation are parallel dipping upstream boundaries between stratigraphic units and subunits, presence of long and relatively thin parallel layers composing thick (tens of meters) parts of the section. In Unit BY-5, individual beds may be traced at a distance 70-100 m rising up by >10 m (Fig. 2.4). In fact the beds are probably much longer as one can see only small part of them exhibited between the lower and upper limits of the exposure. Unit BY-7 characterized by the coarsest material represents the bedload sediments. Change of dipping direction of cobble beds is probably inherited from gentle sedimentary waves (dunes) on the bottom of the flow, which are also visible in the wavy upper boundary of the unit (wavelength >50 m). Unit 6 formed probably of material transported near the flow bottom under highly variable flow velocity field due to irregular topography of the flow bed. Upper units (BY-5 – BY-3) are composed of alluvia transported in suspension. From the point of sedimentation mechanism, these may be considered as the analog of overbank deposits of ordinary floods. However the difference is that in the case of the giant flow the whole valley functioned as the channel, which banks were valley sides. Consistent dipping in the upstream direction of both lithological units and individual beds within the units, which is traced throughout the whole 400-m section, may evidence that the section exposes a proximal slope of a giant bar formed in the bottom of the cataclysmic flow. In all units large clasts up to 1 m in diameter are found, both rounded and unrounded. In all cases they are concordantly enchased into gravel layers so that to give an impression of transporting together with gravels rather than being dropped from above (ice rafting). In several cases aggregates of mixed sized boulders are found up to 1 m in size included into parallel bedding of gravels. To keep their continuity they must have been transported in a frozen state. In all cases such aggregates are composed of well-rounded clasts, which may point at their delivery from river bars frozen during severe winters. Units BY-1 and BY-2 may belong probably to another sedimentary cycle, but this is not evident because of poor exposure of the upper part of the section. However the absence of coarse bedload facies between units BY-1, 2 and 3 may be considered in favor of their association with the same flood event. In the latter case all these units must be of the same age. An attempt to establish absolute geochronology of the section was undertaken using OSL technique. Five dates were obtained in the GADAM Centre, Silesian University of Technology, Poland. The results are controversial but do give the general impression of the age of the sediments. Unit BY-1 was dated at 102.10±8.8 ka BP (Fig. 2.5). Unit BY-2 provided two statistically indistinguishable dates: 128.8±7.4 and 132±11 ka BP. In total the uppermost units provided a successive series of dates that correspond to early MIS-5. The last two dates may be associated with MIS 5e, the Kazantsevian Interglacial (Mikulinian, Eemian in Europe), which is questionable because the interglacial

45 Part II. Middle Katun River valley

Fig. 2.5. Sampling location in Unit BY-1 condition, warmer than the present-day climate, must have not been favorable for large glacial floods. However one should take into account possible inertia in decay of the late Middle Pleistocene glaciers, which was the Pleistocene maximal glaciation in Altai, according to Okishev (2011). Two samples from lower units gave inverse ages. Unit BY-5b provided the date 73.2±5.2 and sands of Unit BY-6a – 11.3±0.88 ka BP (Fig. 2.6). The latter date from the Fig. 2.6. Sampling location in BY-5b Early Holocene obviously underestimates the deposit age and must be rejected. The reason may be in improper quality of quartz – its low luminescence capacity, which provides its quick loading. The date 73.2±5.2, though demonstrating the inversion relative to the upper units, may not be

46 Part II. Middle Katun River valley rejected immediately, given what was said about possible age overestimation of Unit BY-2. It needs checking by repeated dating. In general, the set of dates demonstrates that the sedimentary succession was accumulated in the first half of the Late Pleistocene, probably in Early Pleniglacial (MIS 4 – MIS 5 d).

Roadside Halt Kezek-Jala Bar (P. Carling, J. Herget)

It is obligatory to stop at this high exposure at the roadside not least as everyone gets very excited when seeing it! It is the outer margin of the Kezek- Jala bar which is deposited in a re-entrant in the valley side but also on the inside of the floodway bend. It is thus a fill within an alcove and a ‘point-bar’ type deposit. Large clinoforms at the base are terminated by an erosive unconformity capped locally by a fine sand and silt layer (Fig. 2.7). Above lie a sequence of rhythmic coarse sand and granule layers (Fig. 2.8). Examples of both ‘negative’ and ‘positive’ outsized clasts are found within the rhythmic sequences (Figs. 2.9 & 2.10).

Description The lowermost part of a giant bar is well exposed just south of the confluence of the Big Jaloman and Katun Rivers (within a large valley-side re- entrant at km 687 rather than within a tributary mouth). Here a gravelly clinostratified unit is overlain by thick, sandy-granule gravel. The transition is characterised by an erosional, channelised contact with remnants of massive to plane-bedded sand, overlain bymedium-scale undulating, to cross-bedded, sandy-granule gravel with some pebbles and cobbles along the bedding planes. The latter in turn is gradationally overlain by a thick interval of plane-bedded granule gravel unit.

Interpretation Considering the probable flood-flow paths, this location was relatively exposed to the initial flood flow, down the main valley, carrying coarse gravel such that the large-scale clinostrata are similar in style to those observed in the neighbouring terraced deposits of the Katun valley. The deposition of coarse gravel was followed by the deposition of laminated fine-grained gravels from a high-sediment concentrated to hyperconcentrated flood flow that expanded somewhat into the valley-side embayment. The limited exposure shows only one such highly concentrated megaflood event.

47 Part II. Middle Katun River valley

Fig. 2.7. Fine sand and silt bed deposited on erosive upper boundary to large- scale clinoforms, Kezek-Jala bar. Road sign is 2.7m high. Flow left to right.

Fig. 2.8. Coarsening-up sequence of 40 beds (c. 9m thickness) of coarse-sand and granules within the Kezek-Jala bar. The individual beds exhibited both coarsening and fining upward lamination which prevented any visual identification of sequence-scale inverse grading in the field. Rather, statistically significant inverse grading of the sequence was only revealed through detailed sampling to determine the average grain-size of each bed. Bed thickness data (not shown) displayed no trends.

48 Part II. Middle Katun River valley

Fig. 2.9. (A) Outsized clasts sitting in ‘comet-shaped scour (negative) hollow. Flow left to right. Laura Hayes provides scale. (B) Outsized clast sitting on bedding plane in aggradational (positive) setting. Flow left to right. Boulder has c. 1.5m b-axis.

49 Part II. Middle Katun River valley

Fig. 2.10. Large-scale, planar to slightly convex up clinoforms near the base of the Kezek-Jala bar. Laura Hayes (1.8m tall) provides scale. Flow left to right.

50 Part II. Middle Katun River valley

Stop K2 BOULDER FIELD AT KM 702 (J. Herget) [See also Supplement 1]

2 km downstream from Inja village numerous boulders are found on a higher terrace level of the broad bedload terrace about 10 m above the mean surface. The location is the only one of boulder deposits definitely belonging to the outburst flood. Figure 2.11 gives an impression of the location.

Fig. 2.11. Central part of the boulder field near Inja village In the background the giant bar between Inja and Little Jaloman village is visible. Note people for scale. Direction of flow was from left to right.

Most boulders are well rounded, but occassionally fractured due to post depositional weathering. The fractured components are not displaced, except some tilting by gravity. The boulders consist of cristalline rock. Many are streamline formed with a parallel orientation of their keel-lines. The steepness of the stoss slope varies between 20° to 30°. It is assumed, that the streamline form generated by corrasion of the transported suspension gravels, while the boulders were already deposited. Fig. 2.12 illustrates this phenomenon. 26 of the boulders are investigated for their size. Due to limited alternatives, the circumference of very symmetrical boulders was measured by tape, which allows calculation of the mean diameter. Considering the size of the boulders, their shape below the current surface cannot be considered. For the five largest boulders an average diameter of 11.3 m and a value of d50 = 11.0 m can be determined. The largest boulder of all has a diameter of dmax = 13.5 m.

51 Part II. Middle Katun River valley

Fig. 2.12. Streamlined boulder near Inja village. Direction of flow was from left to right.

Palaeohydraulic calculations The deposition of the boulders near Inja cannot be related to a specific stage of the flood. As the shape of the boulders is modified by transported suspension gravels and they are deposited on the bedload terrace level, which is assumed to be formed after the peak of the flood, their transport must have occurred sometimes on the falling limb of the hydrograph. Hence no related depth of flow can be assumed with a minimum level of reliability and hence no discharge can be calculated. A number of equations for the estimation of flow velocity are applied for the boulders near Inja. Even if occasionally, the range of particle size the empirical equations are derived from is transcended, the relation is used for comparison of the results with other attempts. The calculated mean diameter of the boulders derived from the measured circumference is assumed to be similar to the intermediate axis used for parameter of grain size in some of the equations. For d50 = 11.0 m estimated flow velocities by the application of the equations mentioned above are listed in Table 2.1.

52 Part II. Middle Katun River valley

Table 2.1. Estimated velocities of flow derived by competence calculations for the boulders near Inja village (d = 11.0 m) Equation (see Suppl.1) / character Reference Flow velocity / upper range of d 5 / (physical based) / - Bradley & Mears (1980) vcb = 14 m/s after Costa (1983) *) v = 20 m/s

7 / physical and empirical / < 0.33 m Zanke (1982) v = 37 m/s

8 / empirical / < 3.2 m Costa (1983) v = 17 m/s

9 / empirical / < 6.24 m O’Connor (1993) v = 19 m/s

10 / empirical (high resistance) / < Williams (1983) v = 48 m/s 0.5 m Williams (1983) v = 7 m/s 11 / empirical (low resistance) / < 1.5 m

12 / empirical (overturning) / - Torpen (1956) vcb = 22 m/s *) v = 31 m/s 13 / empirical (initial sliding) / - Torpen (1956) vcb = 8 m/s *) v = 11 m/s *) Calculated by the empirical relationship v = 1.4 vcb, valid for particles < ~2 m (Baker 1973, Zanke 1982, Costa 1983), comp. equation 6.

Considering the topographic conditions of the location of the boulder field near Inja village, other transport mechanism than by the current of the flood flow can be excluded. The nearest mountain slopes possible as origin of mass movement displacement or bank erosion of rock forming the boulders by corrasion of transported suspension gravel (note the streamlined shape of several boulders!) are about 1.5 km upstream. Next to the boulder is the giant bar between Inja and Little Jaloman located. Even if the boulders are not transported over a longer passage, they must have been displaced by the flow itself. A deposition as ice-rafted debris can also be excluded as the topography does not give any evidence for the descend of icebergs or icefloes. The extension of the boulder field of about 1 km along Katun valley also excludes this interpretation. As mentioned above, the boulders are not transported during the peak of the flood as they are deposited on the bedload terrace, which is definitely deposited after the peak. Hence the flow velocity indicated by the transported boulders does not represent the peak discharge, but an uncertain stage during the falling limb of the hydrograph. Based on the variety of the estimated flow velocities and uncertain additional effects acting on the boulder’s transport, no definite mean velocity can be given. Even while obvious arguments are missing, the flow velocity can

53 Part II. Middle Katun River valley be estimated to be in the magnitude of about 20 m/s as this value is indicated by the different applied equations. Considering this background of uncertainty, no further calculations based on an assumed flow velocity appear suitable, e.g. estimating the depth of flow by rearranging the Manning equation or a calculation via unit shear stress of flow (Costa 1983, 1992). However, the orientation of the keel-line of the detailed investigated boulder with a related obstacle mark (see below) indicates that the giant bar between Little Jaloman and Inja did not reach its final extension when the boulder was deposited. Hence the lateral height of the bar towards the valley of 80 m above the bedload terrace indicates the minimal depths of flow. From topographic maps a cross-section area of 150,000 m² can be estimated. For an assumed flow velocity of 20 m/s a minimum discharge during the deposition of 6 the boulders of Qmin = 3×10 m³/s can be taken as rough estimation.

Palaeohydraulic estimations using obstacle marks [Compiled from: Herget, J., T. Euler, T. Roggenkamp & J. Zemke (2013): Obstacle marks as palaeohydraulic indicators of Pleistocene megafloods. Hydrology Research 44, 300-317.]

Obstacle mark: The typical and completely developed obstacle mark became visible through an artificial ditch exposing parts of the frontal and lateral scour hole (Fig. 2.13). Even though the scour hole became filled by post-flood loess deposits, its dimensions are clearly visible by topography and changes in vegetation cover. According to the geodetic survey documented in detail in Herget (2005), the width of the scour hole extending on both sides along the boulder is 24.3 m with a frontal depth of at least 2.27 m. A gravel hump of reworked gravels from the scour hole is located approximately 5 m downstream of the boulder and reaches a height of up to 0.50 m above the surrounding surface. Its width of about 11 m is only an approximate value as the hump fades out laterally. Obstacle: The obstacle is a streamlined boulder with a width of 10.8 m, length of 13.8 m and height of 3.1 m. The mean frontal inclination is about 27°. According to a weak keel line on the boulder’s surface, Herget (2005) argued for a change of the main current direction related to the lateral extension of the giant bar downstream of the boulder (Fig. 2.13). More plausible could be a rotational component of the movement of the boulder into the frontal scour hole during peak formative flow conditions, which is obvious as the frontal part of the boulder is located deep inside the scour hole. It should be noted that the above postulated threshold for tilting (ds = 0.6 lo) may likely vary with asymmetric obstacle shapes and uneven internal weight distributions. Sediments: Analysis of the local sediments reveals values of D50 = 14 mm, σg = 2.61, while the largest clasts in the sediments surrounding the boulder have a mean diameter of about 60 mm (Herget 2005). Hydraulic boundary conditions: Unfortunately, there is no palaeostage 54 Part II. Middle Katun River valley indicator without some degree of uncertainty available for an estimation of the depth of flow during the obstacle mark’s formation. As the boulder must have been deposited before the initiation of the local scouring, maximum depth of flow (approximately 230 m) related to peak discharge is definitely an overestimation. Assuming a lower value, e.g., termination of the lateral extension of the giant bar by taking the elevation of the sharp edge of the bar as a depth indicator (approximately 45 m) is purely arbitrary. Downstream of the obstacle, fluvial gravel dunes developed at the same level as the obstacle mark. Taking this as an indicator for simultaneous formation, the characteristic range of the depth of flow for the formation of the gravel dunes according to their size of 6–12 m (Herget 2005) might also be considered for the location of the obstacle mark. Uncertainties: Even though the scour hole was later filled up by loess deposits, the contours of the obstacle mark are obvious. Closer inspection indicates that the depth of the scour is only a minimum value based on the visible thickness of the loess deposit. According to the empirical relationship of scour geometry (Fig. 2.13), the value of potential scour depth of 2.3 m indicates that steady-state conditions were reached and still are preserved for this example.

Fig. 2.13. Photograph and principal obstacle mark configuration at a boulder near Inya. The small arrow in the obstacle mark sketch illustrates the perspective of view of the photo. The black area marks the shape of the obstacle while the eroded scour hole marked by “-” is limited by an escarp signature at its border line. The principal configuration of the ridge in the wake is marked by “+” in addition to the stippled pattern. Scale for principle dimensions.

Estimated flow velocities: Based on the depth of flow of 6–12 m, a mean velocity between 2.8 m/s and 3.5 m/s and a tip velocity of 1.8 m/s can be estimated. Plausibility: For plausibility, the estimations for flow velocity might be compared with the values determined for the formation of the gravel dunes downstream. Considering the narrowing valley downstream from approximately 1,350 m for a depth of flow of 10 m at the boulder to 920 m at the gravel dunes, the higher mean flow velocity of ~7 m/s at the gravel dunes (Herget 2005) to 3.5

55 Part II. Middle Katun River valley m/s at the boulder can partly be explained. Note that the estimation of mean flow velocities for the formation of the gravel dunes is just an indicator of a plausible magnitude.

Table 2.2. Main parameters of Pleistocene obstacle marks and estimated flow velocities Parameter Boulder near Inya wo = obstacle width 10.8 m ho = obstacle height 3.1 m

D50 = median of the grain size distribution 0.014 m

σg = geometric standard deviation of the grain size 2.61 1/2 distribution ((D84/D16) ) dw = water depth 6–12 m (submerged) ds = scour depth >2.27 m ds_pot = potential scour depth* 2.3 m ws = scour width 24.3 m ls = scour length 6 m wr = width of ridge ~11 m Um = mean flow velocity 2.8–3.5 m/s

Ut = tip velocity 1.8 m/s

* Estimations of potential scour depths are based on the empirical relationships of the scour hole geometry at steady-state conditions.

56 Part II. Middle Katun River valley

Stop K3 HIGH TERRACES OF THE KATUN AND INJUSHKA RIVERS AT THE INYA VILLAGE

Inya Bar (P. Carling, J. Herget)

Description This large bar is well exposed where the Inja River cuts through it exposing a complex stratigraphy of gravel beds that contain large rounded pods of cobbles and sharp-edged intraclasts of laminated silts. The origin of pods is discussed below but they have been rarely described in the literature and so a brief description is provided here. A typical cobble pod has the appearance of an isolated rounded boulder at a distance (Fig. 2.14) but close- up it is seen to be a rounded, isolated mass of cobbles surrounded on all sides by finer gravels that are well-bedded away from the pod (Fig. 2.15). However, usually the layering within the finer gravel is disrupted close to the pod indicating the pod was a ‘solid’ obstacle in a flow that deposited the finer gravel around it.

Fig. 2.14. Upper and lower panels; Large gravel pods within horizontally bedded fine gravels of the Inja bar, in the entrance to the tributary Inja River valley near Inja village

57 Part II. Middle Katun River valley

Fig. 2.15. Thin, wavy lamination of coarse sand and granules in giant bar deposits

Behind the main bar in the tributary valley, lacustrine deposits occur ponded by the main bar close to the village of Injushka within the tributary valley. Here the depositional sequence is less thick and not as high as the main bar but shows a thick succession (c. 50m) of modified granule gravel with discontinuous single-clast thick, cobble to small-boulder lags along certain bedding planes and large fragments of conglomerate beds at the exposed base. The cobble horizons suggests some rough separation of the deposits into repetitive units composed of thick alternating with thinner bed. Repetitive sequences however are well defined with in the tributary valley behind the main Inja bar by the presence of three distinctive white-coloured lacustrine units, which are clearly interbedded with the gravel beds described immediately above (Fig. 2.16). The lake sediments consist of thinly laminated (varve-like) silt beds from 1m to 2m thick interbedded with three distinct granule and pebble gravels layers. Thus, the sequence within the Inja valley, behind the main bar, begins with a gravel unit at the base and this is followed by two further gravel units separated by two silty lacustrine units, the final gravel layer being topped by a third lacustrine unit that forms the present day land surface.

58 Part II. Middle Katun River valley

Fig. 2.16. Section of interbedded light coloured lacustrine deposits (Lac) and suspension gravels (grey colour) in Injushka valley, a tributary reaching Katun River at Inya. House and persons in front for scale.

Interpretation The main bar exposure shows flood deposits at the base that may have been partially re-eroded after initial deposition, and large bed-fragments reworked and mixed into the megaflood granule to small pebble deposits. Within these deposits, some stringers of larger clasts suggest fluctuations in flow conditions such that large clasts group as a lag on a bed surface subject to short- term erosion before being buried by an influx of finer grains, but there is no strong sedimentological or chronological evidence to determine whether these thick gravel units have been the product of a single flood, surges within a single flood or multiple floods. The evidence instead is clearer in the back-valley lacustrine deposits. There the silty laminations indicate sedimentation from silt- rich glacial meltwater flowing down the tributary valley into temporary lakes that formed behind a gravel bar after each flood episode. The sequence of three gravel units records three megafloods that overrode or broke through the main Inja bar and discharged into the back-bar area, each depositing gravel above a limnic layer. These gravel deposits then blocked the exit from the Inja valley. The tributary stream deposited fine silts in shallow lakes behind the gravel barriers after each flood episode. The lakes however were transitory and were drained as soon as the tributary could cut down through the impounding bar.

59 Part II. Middle Katun River valley

Lithology and geochronology of sedimentary sequences at the Injushka River confluence (A. Panin, G. Baryshnikov and G. Adamiec)

The Inya village is located on the right bank of Katun on the surface of the Low (Saldzhar) Terrace 770-780 m a.s.l., or 65-75 m above the river. The high terrace of Katun at the Inya village makes probably the most pronounced, well exposed and easily accessible example of this kind of geomorphic features in Katun, therefore this terrace is usually called the Inya Terrace throughout the Mid Katun valley. At the Inya village, it is up to 180 m high but is descending considerably away from Katun (Fig. 2.17), which, taken together with the uniform parallel-bedded gravelly composition of the terrace, makes the basis to consider the whole terrace as a single giant bar accumulated during a single megaflood. However a similar phenomena is characteristic for all aggrading rivers with higher altitudes of their floodplains in the vicinity of an active channel and low altitudes in the back parts of floodplains. In any case this kind of terrace topography is evidence of excessive sedimentation within the Katun valley that caused the terrace formation, independently of what sedimentation model is taken. According to different workers, accumulation of the Inya Terrace was produced (1) during a single huge event, (2) during a series of extreme events scattered over rather long time period, (3) due to normal style gradual sedimentation over long time. The Injushka River canyon at km 704 (50.45606 N, 86.63356 E) exposes the lower part of the Inya Terrace in the interval 40-80 m above the Katun River (Fig. 2.18). Parallel horizontal beds of fine gravels contain lenses enriched with coarse gravel and gravel pillows (Fig. 2.18, inset) that were transported probably in frozen state. Also inclusions of large blocks up to 5 m in diameter are scattered withing the terrace deposits (Fig. 2.19). In the right (Injushka downstream) part of the exposure, the side wall perpendicular to the Injushka valley presents a series of gravel lenses ascending from bottom to top of the exposure (Fig. 2.20). Probably they may be the key for understanding of sedimentation mechanisms of the Inya Terrace. Channel-like form, erosional lower boundaries of these lenses and evidences for fluvial reworking of underlying parallel-bedded fine gravels encourage their interpretation as channel deposits of Injushka buried within the sediments excessively coming from the Inya River. If this interpretation is correct, then the Injushka River was able to maintain its flow during the aggradation of the Inya Terrace, which would be impossible if the terrace sedimentation was caused by a several hundred meters deep flow moving in the Katun valley with velocities of few tens of meters per second. Conclusion is possible that at least at the first phases of terrace formation its aggradation was relatively gradual.

60

Fig. 2.17. Google Earth aerial view of the Injushka and Inya confluence 1 – Injushka canyon exposure (Fig. 2.18), 2 – view point, 3 – Injushka River 50 m terrace at Malaya Inya village containing lacustrine layers (Fig. 2.23), 4 – Inya pumping station pit (Fig. 2.22), 5 – location of dates from cover deposits on the top of the Inya terrace

Part II. Middle Katun River valley

Fig. 2.18. Exposure of the Inya terrace in the Injushka canyon. Rod is 3 m. Inset: gravel pillow. Scale is 0.5 m.

Fig. 2.19. Large block inclusion in the Inya terrace deposits 62 Part II. Middle Katun River valley

Fig. 2.20. The downstream side wall of the Injushka canyon exposure. Gravel lenses (arrows) were probably produced by the Injushka River channel concurrently with the aggradation of the Inya terrace. Rod is 3 m.

To establish the age of the lower part of the Inya terrace the coarse sand layer was dated that is exposed immediately above the Injushka flow 40 m upstream from the bridge across the Injushka River (Fig. 2.21). Sample was taken 0.7 m above Injushka, or 30 m above the Inya River. It provided OSL age of 125.3±8.4 ka associated with MIS 5e. One more age control was obtained from a gravel pit at the pumping station in the east-central edge of the Inya village, 50.44604 N, 86.62582 E. The base of excavation is few meters below the surface of the Low (Saldzhar) Terrace, about 70 m above the river. However the bottom of the pit is covered by scree fans and the lower boundary of the exposed wall corresponds roughly the terrace surface, 75 m above the river. Two lithological units are exposed in the pit (Fig. 2.22a). The lower unit (the lower 1.5 m) exposed in the central wall is composed of cross-bedded cobbles (dipping upstream Katun) with clear erosional upper boundary. In the right side of the central wall an angular boulder 1.5 m in diameter lies within the top of the unit.

63 Part II. Middle Katun River valley

Fig. 2.21. OSL sample at the base of the Inya terrace taken upstream from the bridge across the Injushka River. At the background lies one more giant boulder that has slipped down from within the Inya Terrace deposits.

The upper unit that represents the major part of the section is parallel bedding of coarse and small gravels with lenses of coarse sand. In the central wall of the exposure that stretches along the terrace and the Katun flow, bedding looks horizontal. However in side walls that are diagonal to the central wall, layers dip at angles up to 15º in the direction of the Katun River. At one site in the right edge of the exposure dipping angles reach 30-35º (Fig. 2.22a). Probably this is a proximal slope of an alluvial ridge that lies at the base of the terrace. Sublayer of coarse sand 3 m above the bottom of the upper unit, or around 78 m above Katun, was OSL dated to 100±13 ka (Fig. 2.22b). This is consistent with the reported above date 125.3±8.4 ka from the Injushka valley, which corresponds to the level 30 m above the river. Both the dates is evidence that the lower part of terrace sediments were accumulated in the beginning of the early Pleistocene, mid and late MIS 5, probably already after the Kazantsevian (Mikulinian, Eemian) interglacial, in the very beginning of the Zyryanian (Early Valdai, Early Vistulian) cold epoch. Probably sedimentation continued through this epoch. The key question for understanding the whole Late Pleistocene history of Katun is when this sedimentation stopped and when the major river incision occurred that created the high (>100 m) and steep (up to 30º) slope between the Inya and Saldzhar terraces (Fig. 2.17).

64

Fig. 2.22. Gravel pit at the pumping station in the centre of Inya village exposing the lower part of the Inya Terrace (a – general view, b – sampling from the Inya Terrace alluvia, c – sampling from cover silts on an erosional terrace cut into the side of the Inya terrace). Dashed lines designate boundaries between frontal and side walls of the pit.

Part II. Middle Katun River valley

To address the above question, sediments of the upper pert of the Inya Terrace should be dated. However they are represented by gravels with very low sand content that provided no material suitable for sampling. Therefore we decided to constraint the terrace final age by ages from cover deposits. First date was obtained from the brownish sandy silts with gravel inclusions – slopewash deposits that cover the top of the Inya pit. Total thickness of this cover layer was 0.6 m. It provided OSL age of 30.5±2.4 (Fig. 2.22c). Two small pits were dug on the top of the terrace 170-180 m above the river. Here several gentle closed hollows 30-50 m in diameter and 1.5-2 m deep were found that could serve effective traps for sediments moved over the terrace surface (Fig. 2.20a). In pits dug in the bottom of two such hollows the Inya Terrace gravels are covered by 0.6-0.7 m of brown silts, with inclusions of angular small gravels and sand, which content increased downwards. These silts provided OSL ages 11.4±1.2 and 12.5±1.1 ka (Fig. 2.20b,c). Given the above much older date from cover deposits in the Inya pit, these ages do not represent the finish of the Inya Terrace sedimentation. Probably the sampled hollows were periodically cleaned of sediments and effective catching of sediments started only in the beginning of the Holocene. Therefore the only date to be taken as the upper age constraint for the Inya Terrace formation is the date 30.5±2.4 from the Inya pit (cover sediments). Given that by this time the river has already cut by at least 10 m into the terrace, the start of incision must have begun well prior to this date, maybe around 40 ka BP or earlier. In the Injushka valley, the 50 m high terrace composed of gravels contains several layers of lacustrine sandy silts (Figs. 2.16, 2.23a). These layers are considered by most researchers to evidence superfloods on Katun that aggraded the Inya Terrace and dammed shortly the Injushka River. Chronology of these damming events is crucial as it represents indirectly the chronology of superflood events. Silts are highly carbonaceous due to "glacier meal" transported from alpine, formerly glaciated parts of the catchment. Three OSL dates were derived from the three lacustrine layers (Fig. 2.23b-d): • upper layer (depth 0-4 m): 15.4±0.7 ka (sample taken from depth 2.5 m); • middle layer (15-20 m): 21.1±1.2 ka (18 m); • lower layer (21-24 m): 24.0±1.6 ka (23 m). Baryshnikov (1992) reported two radiocarbon dates on carbonates in lacustrine silts (these dates are also catalogued in Rusanov, Orlova, 2013). Carbonates in the upper lacustrine layer showed 14C age of 22275±370 yrs uncal (SOAN-2240), in the middle lacustrine layer the age was 23350±400 yrs uncal (SOAN-2239). These radiocarbon dates are calibrate into calendar ages 26.6-27.5 ka BP (cal). This is some older than the reported OSL ages. Probably, 14C dates overestimate the sediment age due to contamination by old carbon derived from Palaeozoic carbonates.

66

The reported MIS-2 ages taken together with the above data on geochronology of the Inya Terrace (MIS 5 – MIS 4), provide the conclusion that repeated damming of Injushka was produced rather by formation of the lower, Saldzhar terrace. This is supported by geochronology of this terrace, which will be reported in the next stop.

Fig. 2.23. Exposure of the 50 m high terrace of the Injushka River 3.2 km upstream from the Injushka Canyon: (a) – gerenal view (man in the upper right for scale.); (b), (c), (d) – OSL ages of the upper, middle ad lower lacustrine layers respectively. Layers of lacustrine silts and sands are considered to indicate jamming of Injushka by superflood sediments of Katun that impeded Injushka's outflow for some relatively short time (several decades?) needed to cut through. The succession of lacustrine layers is therefore indicative of the succession of superfloods in Katun.

67 Part II. Middle Katun River valley

Stop K4 COMPOSITION AND GEOCHRONOLOGY OF THE LOW (SALDZHAR) TERRACE AT THE CHUYA RIVER CONFLUENCE (A. Panin, G. Baryshnikov)

River Chuya tributes to Katun at km 712 km of Chuiskiy Tract. Here a goof viewpoint is located on a rock remnant that offers a perspective view downstream and upstream the Katun and upstream the Chuya valleys (Fig. 2.24). Adjacent to the viewpoint a big gully cuts the Saldzhar Terrace of Katun and provides a full stratigraphy of this terrace, which elevation above the river exceeds 100 m (Fig. 2.25). Terrace aggradation here was shadowed by the rock promontory at the confluence, which explains relatively small size of material composing the terrace. Horizontal interbedding of rather well rounded varying-sized gravels contains layers of mixed-sized sand and is interrupted by two thick lenses of fine sands and silts that are considered to have lacustrine origin. Mean features of the exposure can be observed from the viewpoint. Those attendees who feel themselves capable of a walk with altitude range of ~100 m may follow a walk path along the left edge of the gully, then descend over the gully left side to he gully bottom having examined the Upper Lacustrine Unit (ULU) by the way. Having got to the gully bottom, one can follow to the Katun River: this is the only chance to touch the Katun's water during the trip as the river flows mostly in the inaccessible bottom of steep canyon. Further walking path is optional: either ascending by the right side of the gully with examination of the Lower Lacustrine Unit (LLU), or walking upstream the gully over its bottom and watching over composition of the Saldzhar Terrace exposed in gully walls. The final destination of both paths is the roadside cut at the Chuiskiy Tract, on the current side of the road, opposite to the gravel pit on the other side. Below we present a short description of the Saldzhar Terrace section exposed in the gully. At the Chuiskiy Tract road the back side of the Saldzhar Terrace is 110 m above the Katun River (830 m a.s.l.). On the other side of the road the slope of the Inya terrace starts with a gravel pit having cut its base. This pit was not sampled because of a problematic interpretation of the undercut deposits: they may be rather fan alluvia of a gully that cuts the above slope than the Inya Terrace alluvia. The riverside roadcut exposes the uppermost part of the Saldzhar Terrace, which is a horizontal interbedding of different-sized gravel containing 10-15-cm thick layers of fine sand. One of the sand layers at a depth of 1.7 m was OSL-dated to 12.91±0.73 ka (Fig. 2.25b).

68

Fig. 2.24. Aerial view at the Chuya River confluence. Arrow indicates the location of the view point. Dashed line shows thalweg of the gully that exposures the Saldzhar terrace (Fig. 2.25).

Part II. Middle Katun River valley

Fig. 2.25. Exposure of the Saldzhar Terrace at the Chuya confluence: (a) – general view with indication of sampling points; (b) – roadside cut (sample depth 1.7 m below the terrace surface); (c) – silt sublayer in the middle part of the terrace (depth 4.5 m); (d) – view at the left side of the gully showing upstream thinning of the Upper Lacustrine Unit (ULU, Unit 4; indicated by the climber); (e) – ULU at the river-faced facet of the gully system; (f) – OSL sample from Unit 5 below ULU; (g) – the right side of the gully at its lower course exposing the Lower Lacustrine Units (LLU1, LLU2). 70 Part II. Middle Katun River valley

The terrace descends riverward by ~30 m at a distance of 200 m. The terrace edge stands 80 m above the river (800 m a.s.l.). In the middle part of the terrace where the gully has depth of 32 m, the terrace stratigraphy is the following. The surface is covered by massive light-brown silts with thickness of up to 1.1 m. This is probably an aeolian or slopewash cover (Unit 1). Below lies an 11-m thick Unit 2 composed of fine to medium well-rounded gravels bedded parallel to the slightly inclined terrace surface, with several sublayers of silt up to 15-20 cm thick. Silt sublayer found at depth 4.5 m rises in the direction of he valley side, parallel to the terrace surface (2.5 m per 30 m). It was OSL dated at 12.26±0.61 ka (Fig. 2.25c). Unit 3 (depth 11.5-15.0 m) is horizontal interbedding of fine gravel and gravelly sand. Unit 4 (15.0-18.0 m) is what was designated in the above as the "Upper Lacustrine Unit" (ULU). It is intercalation of grey fine sands and light yellow silts. This layer thins out from the river (upstream the gully), which is evident in Fig. 2.25d, and thickens to the river so that its base dips at a steeper angle than its roof. ULU is not found in the section exposed by the right side of the gully, which provides the deduction on a local character of the former lake. The deepest part of the lake was located at the present-day river-faced wall of the exposure, where ULU is 6 m thick (Fig. 2.25e). Here microlaminated silts form massive sublayers 30-50 cm thick, and finely laminated fine sands with admixture of medium and coarse sands form sublayers of varied thickness in the range 5-50 cm, most frequently 10-15 cm. Sand-silt couples may be interpreted as annual varves. If this is correct, the whole ULU must have been aggraded in 20-25 years. Evidence of complete lake filling is appearance of gravel sublayers in the upper half-meter of the Unit. Sample from a fine sand sublayer 1 m below the top of ULU provided unreliable (understated) OSL age of 7.83±0.54. ULU has sharp lower boundary, which probably is evidence of occurrence of erosion prior to the start of lacustrine sedimentation. Unit 5 (visible depth 18.0-23.5 m) is horizontally bedded fine and medium gravel in sandy matrix, with sublayers of sand and silt. Sample taken from sand sublayer at depth 19.3 m (Fig. 2.25f) showed a big scatter of apparent OSL ages between different aliquots (19.5 to 89.0 ka), which results probably from high admixture of only partially zeroed and non-zeroed old sand particles. Below 23.5 m the gully side is hidden under scree. Stratigraphically below Unit 5, two steeply dipping lenses of light-brownish silts 2.5-4 m thick separated by 6 m of gravels are exposed in the right side in the lower course of the gully (Units 6-8) (Fig. 2.25g). Silts were interpreted as

71 Part II. Middle Katun River valley lacustrine sediments (Lower Lacustrine Units 1 and 2: LLU1, LLU2). Both silts and separated gravels are parallel bedded with dipping angle of 35º. Obviously, they envelope a side of a palaeovalley that periodically was being dammed and filled by lakes. Lake depth was >15 m. Unit 6 (LLU1) was OSL dated to 14.1±1.4 ka. Sample from Unit 8 (LLU2) provided big scatter between individual aliquots (31 to 130 ka) most probably due to admixture of non-zeroed old particles. The lower age limit of 130 ka gives ground for supposition that at the initial phases of the Saldzhar Terrace formation its aggradation occurred to a large part due to erosion and redeposition of material from the Inya Terrace. The lowermost deposits exposed in the gully are coarse gravels (Unit 9) with visible thickness of 7-8 m. The base of the Saldzhar Terrace deposits is located probably below Katun.

Summary The Chuya confluence section indicates that aggradation of the Saldzhar Terrace have occurring rather gradually (in general) than due to one catastrophic event. It lasted few thousands of years, from > 14 ka BP till ~12 ka BP. Extreme event took part in the sedimentation process producing periodical incision (the palaeovalley enveloped by LLU layers). Formation of local lakes could also be the consequence of extreme floods due to both in situ scouring effects and damming from large masses of accumulated material elsewhere down stream. Chronology of the section is in general close to the timing of the same terrace at the left bank of Katun downstream from Injushka confluence (Stop K2) where (Reuter et al., 2006) established surface exposure ages of giant boulders on terrace surface at 15.8±1.8 ka. Probably it was the same (glacial outburst?) flood that was responsible for the scour at the Chuya confluence with subsequent lake formation (palaeovalley filled by units 6-9) and for aggradation downstream from Injushka.

72 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Part III Middle Chuya River valley, Kuray and Chuya Basins

Stop C1 EARLY HOLOCENE SEISMIC FALL AND DAMMED LAKE FORMATION AT THE SUKHOI BROOK (A. Agatova, R. Nepop)

Stop C1 (50º15´12.34´´, 87 º42´27.33´´) is located at the right bank of the Chuya river between the Kurai and Chuya intermountain depressions (Fig. 3.1). The Chuya valley in this location is a graben separating the Kurai range (2600- 3200 m a.s.l.) and Chagan-Uzun massif (2300- 2900 m a.s.l.). The high regional seismicity is evidenced by numerous landslides and large talus fans located throughout both river banks. The ancient shorelines can be traced along both valley slopes and mark former lake levels up to about 2100 m a.s.l. This argues for the existence of the conjoined Chuya–Kurai lake at some phases of the Pleistocene hydrological system evolution. Terraces clearly expressed in topography are ones of the main features of this part of the Chuya valley. These are lake terraces - wave-cut and accumulative, and river terraces - erosional and erosion-accumulative ones. All these landforms were formed as a result of the development and draining of the Neopleistocene giant ice-dammed lakes and further fluvial activity. Conglomeration of large boulders of different petrographic composition on the surface of the medium terraces indicates flowing of the high energetic floods, which could be connected with lake drying or abrupt lowering of its water level. The river incision into ancient lacustrine sediments near the outlet of Chuya graben into the Kurai depression is about 170 m with the water edge 1582 m a.s.l. here. In the mouth of the Sukhoi river in the outcrop of the low 15-m terrace on the right Chuya river bank 5-m layer of large boulders is exposed (Fig. 3.2). This layer is interpreted as deposits of cataclysmic outburst floods (Butvilovsky, 1993). It is covered by lacustrine sands. One of the numerous earthquake induced paleolandslides on the left Chuya valley slope downstream the Sukhoi mouth dammed the river which caused the local lake formation. Regarding the chronology of hydrological system transformation within this part of the Chuya river valley it could be stated that cataclysmic outburst floods occurred before the Holocene. It is evidenced by the age of peat layers at the bottom of lacustrine deposits on the left Chuya river bank - 9717±177 and 8308±110 cal. years BP (8700±65 (SOAN 2378), 7530±60 (SOAN 2379)) (Butvilovsky, 1993). Draining of the landslide-dammed lake took place no later

73

Fig. 3.1. Chuya Canyon between the Kurai and Chuya Basins: aerial view Chuya Basin is in the upper right corner.

Part III. Middle Chuya River valley, Kuray and Chuya Basins than 3000-3300 cal. years BP, which is evidenced by the age of the lowest fossil soils on the both left and right Chuya river banks (Fig. 3.3) - 3324±68 cal. years BP (3110±30 (SOAN 2380)) (Butvilovsky, 1993) and 2966±174 cal. years BP (2835±55 (SOAN 9100)) (Agatova et al., 2014) respectively. The age of the middle fossil soil layer from the outcrop near the Sukhoi mouth is 1178±96 cal. years BP (1250±30 (SOAN 9098)) and correlates with the prosperity of Turk nomads in SE Altai (Agatova et al., 2014).

Fig. 3.2. Deposits of cataclysmic outburst flood. The flood came from Chuya intermountain depression along the Chuya valley no later than 10 000 cal. years BP. 9717±177 cal. years BP (Butvilovsky, 1993) the layer with large boulders was covered by deposits of the landslide-dammed lake.

As for this 15-m terrace (1633 m a.s.l.) during the last three thousand years it was not flooded - soils do not express any traces of aquatic influence. Perhaps only occasionally during the strong floods the flow duct appeared in the proximal part of the terrace. At the same time the good preservation of numerous nomadic burial grounds and ritual structures associated with the Pazyryk culture and Turk epoch, including elite Pazyryk tombs, on the surface of the next 25-m terrace (1665-1670 m a.s.l.) (Fig. 3.4) indicate the non- cataclysmic character of these floods. Nowadays intensive river incision and both river banks’ erosion are going on.

75

Fig. 3.3. Subaerial complex - buried soils and eolian sands, overlying deposits of the landslide-dammed lake near the Sukhoi mouth on the surface of the lower 15- m terrace.

Fig. 3.4. Pazyryk tombs and Turk burial grounds and ritual structures on the surface of the 25-m terrace evidence the absence of cataclysmic floods here from the Scythians times. The site is 200-800 m away from the Chuya river.

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C2 LATE PLEISTOCENE GLACIAL DAMMING OF CHUYA AT KUEKTANAR TRIBUTARY VALLEY (A. Agatova, R. Nepop)

Kuektanar is the right Chuya River’s tributary. The place of confluence is located between the Kurai and Chuya depressions (Figs 3.1, 3.5). The Chuya valley here is a graben separating the Kurai range and Chagan-Uzun massif. This is one of key locations for understanding and reconstructing the Neopleistocene/Holocene hydrological system evolution in the region. This place, where the second dam within the Chuya-Kurai lake system was formed, is one of the most highly debatable objects of geomorphological researches. Near the mouth of the Kuektanar River the Chuya valley widens up to 3.5 km (at the isoline 1,800 m a.s.l.). Nevertheless, it is here that the terminal moraine complex of the Kuektanar glacier and landslide sediments of the multievent Sukor paleodislocation form the dam. However there are different views on each issue of the paleogeographical reconstructions: dam genesis, lakes size and the time of their formation as well as parameters of their draining. Since this place is truly a Mecca for researchers of the Altai’s Quaternary history, the number of reconstructions is almost the same as the number of researchers who worked in this area. The dam genesis is considered by different authors as glacier, moraine, landslide or mixed origin. Glacier went down into the Chuya valley from its right Keuktanar tributary and giant Sukor landslide was triggered on the left slope of the graben (Fig. 3.6). According to some authors (Okishev, 1982; Novikov and Parnachev, 2000; Okishev and Borodavko, 2001; Rusanov, 2010) there was a large lake which occupy the Chuya depression upstream the Chuya valley. In contrast, others (Butvilovsky, 1993; Rogozhin and Platonova, 2002; Zol’nikov and Mistrukov, 2008) suggest quite moderate size of this lake which was located only within the graben of the Chuya valley. There are much more significant differences in the assessment of the time of lake formation and parameters of its draining. The gradual lake draining in the end of the late Neopleistocene is supposed by (Sheinkman, 1990; Okishev and Borodavko, 2001) in contrast to practically recent cataclysmic draining as a result of washing the dam caused by seismically induced landslide no later than 1000 years ago (Rusanov, 2010) or even during the 1761 Great Mongol earthquake (Rogozhin and Platonova, 2002).

77

Fig. 3.5a. Geomorphological map and cross-section of the Chuya valley near the mouth of the Kuektanar river. Numbers indicate studied sections (Fig.3.6). Above - panoramic view of the Chuya valley near the mouth of the Kuektanar river. Below – photo of the Sukor paleodislocation.

Fig. 3.5b. Sections studied in the Chuya valley near the mouth of the Kuektanar river. Section 2a shown after (Butvilovsky, 1993).

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.6. Moraine of the Kuektanar glacier near the place of the Chuya riverbed incision. Cirque of the Sukor paleodislocation is on the background.

Obviously, available geochronological data - thermoluminescence (Sheinkman, 1990; Carling et al., 2002) and radiocarbon (Butvilovsky, 1993; Rogozhin, Platonov, 2002) ages of sediments of various origins, do not allow estimating the time formation of moraine and landslide deposits as well as overlying lacustrine sediments. At the same time radiocarbon date of the lowest fossil soil within the loess-soil cover indicates the “upper possible time” of moraine-landslide dam functioning - 8223±181 cal. BP (7440±95 (SOAN 8903) (Agatova et al., 2014).

Stop C2a (50º09´35.96´´, 88 º17´46.51´´) The first stop will be done near the mouth of the Kuektanar river downstream the Chuya valley. It is located at the brow of 25-m scarp of the river terrace leaning against the proximal moraine rampart. The river crosses the moraine dam in a deep steep-sided gorge, which is a single erosion incision

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Part III. Middle Chuya River valley, Kuray and Chuya Basins into the dam. About 6-10 m of this height is the incision into the bedrock. Neogene(?) sediments interbedded with brown coal covered by moraine sediments of different ages, lacustrine sands and loams, with the loess and soils complex on top are exhumed in an outcrop along the steep right riverbank at 1,730 m a.s.l. (Fig.3.5, section 3 shows upper part of outcrop). The oldest fossil soils in an area were found here (Fig. 3.7). From this point palaeolake shorelines on the surface of the washed sediments of giant Sukor seismodislocation are visible under certain lighting. These shorelines could be traced up to 1800 m a.s.l. The same lake level is clearly expressed in topography downstream the Chuya valley. All these argue for the landslide-moraine dam formation and its partial washing (down to 1750- 1760 m a.s.l.) before the final draining of the last lake with the water edge no lower 1800 m a.s.l. Most likely it was the common lake for both Chuya and Kurai depressions which was impounded near the mouth of the Maashey river. After the final draining of this conjoined lake before the Holocene time (the age of the fossil soil near the Baratal mouth) and no later 8223±181 cal. BP (the oldest soil near the Kuektanar mouth) “the Kuektanar dam” was able to impound the lake in Chuya depression only with the level no upper than 1750- 1760 m a.s.l. (altitudes of the highest moraine ramparts). Most likely the lake level was even lower because the incision into the moraine dam had been already existed although it was not as deep as it is now.

Fig. 3.7. The oldest fossil soil within the Chuya valley is located near the mouth of the Kuektanar river

81 Part III. Middle Chuya River valley, Kuray and Chuya Basins

By 8223±181 cal. BP soil has been formed at 1730 m a.s.l. on the surface of lacustrine sediments above moraine of Kuektanar glacier. Thus only local lakes with the water edge lower than 1730 m a.s.l. could occupy this part of the Chuya valley at that times (the floor of the Chuya depression is located above this level). At the same time the final draining of this local lake occurred before constructing the coal smelting furnaces near the mouth of the Kuektanar river (VI-X centuries AD). Radiocarbon age of char coals from these furnaces (1696±122 cal. BP (1775±35 (SOAN 5040) (Gutak and Rusanov, 2013)) and 1152±143 cal. BP (1250±65 (SOAN 9091) (Agatova et al., 2014))) indicate the draining of this lake long before the 1760 Great Mongolian earthquake. After that the fluvial system remained highly mobile, which is evidenced by the high rate of riverbank retreat and Chuya river channel migration.

Stop 2 (50º08´59.70´´, 88º18´22.18´´) The second stop is near the archaeological site Kuektonor I, which represents the stone blocks – remnants of coal smelting furnaces (VI-X centuries AD) on the steep right Chuya River bank (Fig. 3.8). This location is famous for its archaeological sites of various epochs. Few late Paleolithic stone tools (35-10 ka (Derevjanko and Markin, 1987)) and artifacts of Kyrgys culture of the Middle Ages (second half of the IX-XI centuries (Khudjakov, 1990)) were found among the sand dunes - deflated lacustrine sediments with horizons of buried soils. The Holocene age of fossil soils and evidences of intensive fluvial activity during the last third of the Holocene (Fig. 3.9, Fig. 3.5 sections 5a, 5b) argue for the redeposition of all late Paleolithic surface finds (Agatova et al., 2014). Partly covered by sand small stone mounds of uncertain cultural identity as well as coal smelting furnaces (dated by VI-X centuries AD on the basis of their typological features (Zinjakov, 1978)) on the steep river banks and terraces are the only archaeological sites located “in situ”. Now, only part of the back walls and small fragments of the side walls of two coal smelting furnaces are still preserved. Modern gullies are quickly developing the location of four other furnaces. Under the back wall of the upper coal smelting furnace, the fragments of larch bark, charcoal pieces, and slag was collected. The charcoal age obtained by radiocarbon method is 1174±121 cal. BP (SOAN 9091) (Agatova et al., 2014). Data on the typical design of the SE Altai coal smelting furnaces of this time (lengths of working chamber 1.0–1.2 m; channel for slag removing 0.4–1.3m; working space before the furnace ~5.6m (Zinjakov 1988)) allow the late Holocene rate of riverbank retreat to be estimated – (5.4–7.7)·10-3 ma−1. The sandy area on the right Chuya river bank is clearly visible from this point. Lacustrine sands with the loess-soil complex included up to three soil layers on top partly cover moraine sediments up to 1,735– 1,740 m a.s.l. Today only single larches and willows settled an area in contrast to earlier more wide

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Part III. Middle Chuya River valley, Kuray and Chuya Basins distribution of forest vegetation, which is evidenced by ancient fire places and furnaces. Most likely intensive timber cutting was made for metal production. “Kuektanar” means “put on chain armour” in Turk language.

Fig. 3.8. Preserved fragment of the side walls of the coal smelting furnace A) located on the edge of the steep riverbank near the mouth of the Kuektanar river B) and extracted pieces of slag C).

Fig. 3.9. Section of altering fine and coarse grain sands upstream the mouth of the Kuektanar river. Number 5 on the Fig. 3.5 demonstrates fluvial activity and possible migration of the Chuya river.

83 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C3 LOWER CHAGAN-UZUN RIVER: THE LATE PLEISTOCENE MAXIMAL GLACIAL ADVANCE (Compiled from Okishev, 2011)

In the Late Pleistocene, the Juzhno-Chuysky Ridge hosted numerous valley glaciers that moved into the Chuya Basin and joined into vast ice fields occupying the bottom of the basin (Fig. 3.10). Ice fronts reached altitudes from 2130 m (Elangash glacier) to 1840 m (Chagan-Uzun glacier). The Chagan-Uzun glacier was the largest and most complicated as it combined a number of big ice flows from the Juzhno-Chuysky and Severo-Chuyski Ridges. The lower courses of Chagan-Uzun and Kyzylchin valleys (Fig. 3.11) host unique in their preservation deposits of the ancient Chuya Lake. Excellent preservation of these highly erodible sediments results from their geomorphological position: due to deep valley incision the limnic sediments were well-protected from destructive impacts of waves and currents in the palaeolake.

Fig. 3.10. Map of the Late Pleistocene glaciation over the north side of the Juzhno-Chuysky Ridge and SW part of the Chuya Basin (from Okishev, 2011). Legend: 1 – glaciers of the 1st Late Pleistocene glacial megastadial, 2 – glaciers of the 2nd Late Pleistocene glacial megastadial; 3 – alpine crests with present-day glaciation; 4 – low ridges without present-day glaciers. River Chagan-Uzun in the lower course (stop C3) is in the top centre of the map. 84

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.11. Aerial view at the western Chuya Basin and bordering ridges (stops C3 – C5). White arrow points at the exposure of the older limnic unit to be visited on the way to Beltir.

Exposures of glacio-limnic deposits are located at the highest elevation within the valley widening 2 km downstream from the Beltir village (Fig. 3.11, 3.12). These exposures will be examined on the way to stop C4. Further downstream the limnic deposits may be found within the valley to the confluence with the Kyzylchin River. Both in the valley widening and in the downstream gorge two limnic units (LU) are found. Upstream from the gorge, the younger LU is enclosed into the older one, i.e. it fills an erosion cut incised into the older LU. Due to the valley incision that had occurred after accumulation of the older LU, the latter was destroyed within the most part of the valley. The older LU was preserved at valley edges in the right bank upstream from the cross-elevation in the valley and in both valley sides between the cross-elevation and the gorge. During the inter-limnic erosion phase, the bottom of the valley was covered by alluvial gravels 1-3 m thick (Fig. 3.12). It thins and becomes finer downstream from the upstream edge of the lacustrine deposits to the cross-ridge. The younger LU lies on these gravels. The gravel unit is buried by the younger LU, which top forms a distinct geomorphic surface (lacustrine terrace) with elevation 10-15 m lower than that of the older unit.

85 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.12. Synthesized cross-section of the lower Chagan-Uzun valley (from Okishev, 2011). Legend: 1 – glacial till, 2 – glacio-fluvial gravels, 3 – varved deposits of the older limnic unit (LU), 4 – varved deposits of the younger LU, 5 – slope deposits, 6 – alluvial gravel, 7 – rocks

No gravel layer was found downstream from the valley cross-elevation, but the two LUs can be clearly recognized by some indirect features. They still differ in the elevation of top surfaces. No gravels is found on the younger (lower) lacustrine terrace, which provide evidence that it was not destroyed by posterior erosion. In contrast, the surface of the older (upper) lacustrine terrace is characterized by occurring of thin gravel covers and scattered gravels (Fig. 3.12). The two LU differ also in the evidences of post-sedimentation freezing. The older LU demonstrates the characteristic frost-generated micro- plate structure in the upper 1.5-2 m compared to that 2-3 times less in the younger LU. This difference is caused probably by different duration of freeze- thaw action indicating different age of the two LUs. In the downstream part of the gorge, the inter-LU gravel layer restores. It follows from the above that the varved limnic deposits are found not only within the moraine of the Late Pleistocene glacier that ended at the beginning of the Chagan-Uzun gorge, but also beyond the frontal moraines. This is the ground for the conclusion that the palaeolake was not a local water body dammed by moraine within the Chagan-Uzun valley. It was a small bay of the large Chuya Palaeolake, which occupied the whole Chuya Basin (see map of shoreline disposition in the description of Stop C7). Most probably, the Chuya and Kuray basins were occypied by the single Chuya-Kuray Palaeolake. Geomorphic traces of its Kuray part will be observed at Stop C7. In the Kuray Basin, lacustrine terraces cut by the Artalyk brook at 1860 m a.s.l. were dated to 32190±260 BP (Beta-137035). Therefore the beginning of the rapid rise of the Chuya-Kuray Palaeolake may be associated with the final stage of the 1st Late Pleistocene glacial megastadial dated in (Svitoch, 1978) by RTL technique to 32 ka BP. 86

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C4 BELTIR VILLAGE: CONSEQUENCES OF THE YEAR 2003 SEISMIC HAZARD (G. Baryshnikov)

The 2003 Altai earthquake, or 2003 Chuya earthquake, occurred on September 27, 2003, at 18:33 local time (11:33 UTC). The epicenter was put at 49.954ºN, 87.832ºE, 25 km west from the Beltir village, the settlement closest to the epicenter. The magnitude was put at Mw 7.3 and the depth 18 km. Intensity of the seismic shock was IX-X degree, according to the MSK-64 12-degree scale (similar to the Modified Mercalli (MM) scale used in the United States). It was the strongest earthquake in this region since an estimated 7.7 earthquake on December 20, 1761. It was felt in a wide range of southern Siberia, and the intensity was MM V in Novosibirsk. More than 1800 houses were damages in the Gorny Altai Repunclick, 300 houses destroyed. Totally destroyed was the Beltir village (Fig. 3.13). This earthquake occurred in a segmented fault zone which had not been previously recognized (Fig. 3.14) and had both right-lateral strike-slip and reverse movements. Most pronounced lithogenic effects of the shock were seismogravitational movements and ruptures. The former will be observed in Stop C5. Examples of the latter are demonstrated in Fig. 3.15. Lithogenic effects were accompanied by various hydrogenic phenomena. At the initial stage of the Chuya seismic hazard sudden explosions of ground water and mud were detected (Fig. 3.16). Usually mud eruptions operated as groups along linear zones. Water disappeared rapidly through the same canals it had been exploded. The mechanism of mud explosions was probably formation of cracks in surficial deposits and occurrence of unfrozen water within them. Passing of seismic waves caused liquefaction of clayey deposits and their explosion. The estimated volume of underground water exploded in Beltir is 1000 m³. In some cases funnels formed up to 1.0-1.5 m deep and up to 1.5 m in diameter that exploded liquefied clay masses and warm water in the day of the earthquake and in the next day. Formation of mud micro- volcanoes (not higher than 60 cm) was followed by their collapse and sink of mud, which resulted in formation of rounded micro-depressions 50-70 cm in diameter.

87 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.13. Seismic destructions in Beltir (school, mud-house) Photo: G. Baryshnikov

88

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.14. Position of the strongest seismic shocks on structural geology map of SE Russian Altai. 1 – Intermountain depression (K.B. – Kuray Basin, C.B. – Chuya Basin); 2-5 – structural formational zones: 2 – hercynian zones, 3 – caledonian- hercynian zones, 4 – upper proterozoic carbonaceous zones, 5 – proterozoic crystalline schist zones; 6 – major faults (K – Kuraisky, C – Chokraksky, C-T – Charyshsko-Terektinsky); 7 – area of the highest concentration of epicenters; 8-9 – epicenters of earthquakes with magnitudes: 8 – more than 6, 9 – more than 5; 10 – settlements (A – Aktash, B – Beltir, K – Kuray, K.-A. – Kosh- Agach, O – Ortolyk, U-U – Ust-Ulagan, C-U – Chagan-Uzun)

89 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.15. Ruptures in alluvial deposits in the Beltir village Photo: G. Baryshnikov

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.16. Ejection of liquid clay masses and collapse sink-holes within erupted clay masses Photo: G. Baryshnikov

91 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C5 EARTHQUAKE TRIGGERED GIANT LANDSLIDES IN THE TALDURA VALLEY (A. Agatov, R. Nepop, G. Baryshnikov)

The strong Chuya earthquake (МS=7.3) stroke the SE Altai in September 27, 2003. It was accompanied by numerous aftershocks two of which (occurred on September 27 and October 1) were the strongest ones with the magnitudes МS=6.6 and МS=6.9 accordingly. This seismic excitation was the strongest historical seismic event within the Russian Altai. It caused a complex system of primary seismotectonic dislocations, including a NW trending pivotal rupture about 70 km in extent, which is a right-lateral strike-slip fault with a horizontal offset of up to 2 m, and auxiliary splays of reverse and right-lateral strike-slip kinematics (Rogozhin et al., 2008). The 2003 Chuya earthquake also triggered a lot of rock-falls and landslides. The giant landslide in the Taldura river valley (N 49.9551º, E 88.0746º) is the most impressive among them (Fig.3.17). This landslide is located on the right slope of the Taldura valley about 10 km upstream from the confluence with the Chagan river, 9 km WSW from village Beltir and 17 km east from the recognized epicenter of the earthquake. Together with other numerous large landslides and rock falls (Fig. 3.18) it marks active fault boundaries of Chagan-Uzun neotectonic block separated Kurai and Chuya intermountain depressions (Fig.3.19). The total landslide area is about 0.66 km2, the volume of displaced material is about 0.027 km³, and the length of the detachment wall is 1.1 km with its height up to 150 m.

Fig. 3.17. Giant earthquake-induced landslide in the Taldura river valley

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

The landslide displaced glacial till dated by P.A.Okishev (2011) to the late Middle - Upper Pleistocene. The morains are composed of cemented loams and silts with abundant gravels and boulders, with massive ice matrix with lenses of pure ice. All deposits were permanently frozen except for the upper 2.0-2.5 m of the active layer, which still had not get frozen by the end of September. Probably, it was the frozen state of deposits and presence of rock juts under them that governed the formation of this landslide, which resembled rockfall in its dynamic: in its frontal part frozen deposits were thrown up to 30 m. The total volume of displaced masses was ~3.5 million m³. The general structure of the landslide resembles "broken plate" with vertical displacement between adjacent blocks of up to 45-44 m. However this seismogravitational displacement is not an epicentral phenomenon, but rather it is located at the periphery of the epicentral zone. Such a prominent geomorphic effect results from amplification of seismic impact due to local geological and geomorphological settings. Hydrogeological effects of the seismic shock are shown in Fig. 3.20.

Fig. 3.18. Modern (2003) and prehistoric (numbers 1 and 2 in circles) earthquake triggered landslides in the epicentral zone of the 2003 Chuya earthquake

93 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.19. Large landslides and rock falls are associated with active fault boundaries of Chagan-Uzun massif which separates Kurai and Chuya intermountain depressions (after Agatova et al., 2014). Square marks the landslide body in the epicenter of the 2003 Chuya earthquake.

Evidences of strong prehistoric earthquakes are presented in the deposits of this giant landslide which is looks like broken plate (Fig. 3.21). Several sections were studied within the landslide. Buried peat, paleosols, charcoals and wood fragments included in seismically deformed deposits give opportunity to clarify the chronology of ancient earthquakes within SE Altai.

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.20. Seismically induced hydrological effects: (a) ephemeral explosions of water in the body of the seismic landslide, (b) disappearance of a small lake in the riverhead of Kuskunnur River. Photo: G. Batyshnikov

The ages of seismically cut or deformed fossil soils with wood/charcoal fragments return the low possible date of seismic event while overlaid undistorted layers give information about its upper possible date. Radiocarbon ages of buried soils in the proximal part of the landslide (Fig. 3.22) marks the time bounders of strong earthquake. The precise date (AD 1532) of this strong medieval earthquake was reconstructed applying dendrochronological techniques. 95 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.21. Inner structure of the giant landslide triggered by the 2003 Chuya earthquake

Fig. 3.22. Seismically cut fossil soil and peat overlaid undistorted paleosol

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

The age of buried peat layers as well as organic material in lacustrine deposits returns the upper possible date of earthquakes that coursed peat bog or lake formation in the proximal part of landslide about 600-700, 900 and 4000 cal. years BP (SOAN 8658, 8673, 8664, 8672, 8671)). Figure 3.23 presents the section of lacustrine sediments with seismic convolutions. Seismically cut buried peat layer covers these lacustrine sediments and underlie deposits of younger lake. Marking the period of tectonic repose and peat bog formation the age of peat (about 2000 cal. years BP (SOAN 8416)) also returns the low possible date of prehistoric earthquake. Newly arisen outcrop in other scarp of the giant landslide triggered by the 2003 Chuya earthquake in the Taldura valley indicates a complicated slope sedimentation patterns. A section of redeposited slope material with broken and deformed thin soil layers stuffed with charcoals overlays brownish sandy loams above moraines. Radiocarbon dating of organic material from this section evidences two periods (about 1400 and 2600 cal. years BP) of abrupt intensification of slope activity which can be related to seismic excitations. Fossil soils buried by colluvium sediments at the steep slopes mark periods of tectonic repose and soil formation which were later altered by intensive slope mass movements (Fig. 3.24). Several such time intervals could be revealed by radiocarbon dates of fossil soils in newly formed ruptures within this landslide. Newly obtained radiocarbon dates and their paleoseismological interpretation within this location support previously published data on high regional seismicity (Rogozhin and Platonova 2002; Rogozhin et al. 2007; Nepop and Agatova, 2008) and argue for the repeated activization of the same focal zones during the Holocene. These data clarify the chronology of seismic events within the SE Altai allow specifying the recurrence interval of strong earthquakes in the SE Altai as about 400 years for the last 4000 years.

Fig. 3.23. Seismic convolutions in lacustrine sediments

97 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.24. Periods of tectonic repose and soil formation altered by intensive slope mass movements

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stops C6 and C7 will be located in the Kuray Basin (Fig. 3.25). First a rock remnant in the NW part of the basin will be visited, which provides an excellent viewpoint over the famous Kuray dunes. After that the group will descend to the dunefield (Stop C6) and then go up to the NW side of the basin to observe palaeoshorelines of an ancient lake that filled the Kuray basin (Stop C7).

Fig. 3.25. Satellite image of NE Kuray basin showing the visiting points: 1 – viewpoint on an rock remnant, 2 – dunefield (Stop C6), 3 – strandlines (Stop C7). The eastward termination of the Kuray dunefield is visible top centre.

Stop C6 KURAY DUNES (P. Carling, J. Herget)

The Kuray dunefield has been described in detail by Carling (1996a) and estimated local flow parameters were calculated using dune morphology and grain size data (Carling 1996b, Herget 2005). Recently the entire drainage of the Kuray Basin has been modelled and data abstracted from the model that pertain to the flow in the area of the Kuray dunes (Bohorquez et al., in press 2015). This latter model demonstrates that the Kuray dunefield formed during a short period of time, near the end of the drainage event, when the lake water was forced to flow to the east by a local ridge rather than flow directly towards the ice-dam breach near Aktash.

99 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Arguments occasionally have been made that the Kuray field (Fig. 3.26) is not a dunefield, but could be gullied outwash, rogen moraine or gullied moraine. Ground-penetrating radar profiles (Fig. 3.27) have shown conclusively that the radar stratigraphy is that due to water flow from the east to the west. Gravel foresets are clearly evident as is the presence of two reactivation surfaces. Reactivation surfaces occur when a dune that has stopped moving for a significant period of time begins to move again. The presence of two reactivation surfaces demonstrates that the dunes moved on up to four occasions; firstly before the first reactivation surface and with two subsequent movements. The simplest explanation is that dunes formed when the lake first drained and were reactivated at two subsequent occasions when the lake had refilled and drained again. This evidence for three major floods is in accord with the evidence for three floods recorded by limnic/flood gravel sequences in the giant bar at Inja.

Fig. 3.26. Panoramic views of gravel dunes in Kuray Basin. Flow was right to left.

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.27. GPR profile through a large gravel dune in the Kuray Basin. As well as well-defined foresets (e.g. blue labels) the radar stratigraphy shows reactivation surfaces (red labels) as well as the interface with the underlying gravel deposits. Flow right to left.

Fig. 3.28. Within Kuray dune field with trees growing in the troughs only. Flow towards direction of view. Arrow marks one level of multiple shorelines on the slope in the background.

101 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C7 KURAY STRANDLINES (P. Carling, J. Herget)

Strandlines occur at many locations around the Kuray Basin but are often very feint (Fig. 3.28). However, well-developed strandlines occur on the southern side of the Kuray Basin (Fig. 3.25 & 3.29). The nature of strandlines in the Kuray and Chuja Basin have been detailed by Carling et al. (2011). Glacial lake Kuray-Chuja occupied the Kuray and Chuja Basins during the Quaternary Period (Marine Isotope Stages 2 and 3) left distinct shoreline features around the basin margins. At the greatest extent the lake had a surface area of 2951km² with wind fetches up to 70 km. Wind waves constructed erosional, erosional- accumulative and accumulative strandlines; the latter including spits, tombolos, barrier beaches and offshore bars but these latter features are not evident at the site visited during the fieldtrip. Strandlines range in altitude between c. 1600 m and 2100 m; the range in altitudes demonstrating lake level variations through time. Kuray Basin strandline sediments consist of angular to sub-rounded fine to very coarse pebbles (mode -3 to -5 phi) occasionally having small cobble units or isolated cobble clasts present. Lenses, a few centimetres thick, of sand (2 to 3 phi) and coarse silt occur locally but only rarely form units of significant thicknesses (i.e. > 100mm). Chuja Basin strandlines sediments can be coarser, including angular small boulders. The few shallow pits opened in the Chuja Basin have similar stratigraphy as described below for the Kuray Basin. Sections within erosional-accumulative shorelines in the south-east of the Kuray Basin at elevations between 1600 and 1700 m (Fig. 3.29) are presented in Fig. 3.30. Section 1 (Fig. 3.30a) is cut into moraine by waves emanating from the west and northwest. The surface layer 1 consists of a well-sorted coarse- granule soil horizon. Layer 2 is water-washed medium sorted sandy-gravels, locally demonstrating graded bedding dipping offshore. Layer 3 is gravelly but rich in quartz-feldspar sands and silty-sands which can be attributed to calm- weather deposition as usually these deposits are not preserved as thick units due to later erosion by storm waves. Well-sorted, coarse to fine sequences with relatively extensive bedding, exhibiting low dips, can be interpreted as individual shore-building swash/back- swash dominated units termed ‘selection pavements’ by Bluck (1999). In Fig. 3.30 an only two major units of this kind can be identified: layers 8 to 7 fine upwards and layers 6 and 5 likewise. Layer 4 contains abundant organic detritus in silty-sand and might be interpreted as a jetsam depositional unit during raised summertime lake level regimen due to the annual melt cycle. Layers 3 and 2 are not typical of selection pavements, rather they contain lenses of fine gravel or of sand and outward dipping bedding with an abundance of poorly-rounded and angular gravel. These units might represent locally derived colluvium, little reworked by wave action. Although it is probable that water levels were 102

Part III. Middle Chuya River valley, Kuray and Chuya Basins sustained for some time at this elevation, the coarseness of the gravels and the limited accumulation ensures that little if any evidence of individual storm events or local fluctuations in water level are recorded. Section 2 is cut into moraine (Fig. 3.30b) and has better defined bedding than the strandlines described above (Fig. 3.30a). Several distinct selection pavements might be distinguished. Event 1: layers 10 and 9; event 2: layers 8, 7 and 6; event 3: layers 5 and 4; event 4: layer 3 and event 5: the inset layer 2. Layer 4 contains in situ rootlet traces and represent a temporary fall in water level during which colonisation of the foreshore by herbs occurred. Section 3 (Fig. 3.30c) is similar to Section 2 but is less-well developed. Three shore- building events are recorded. Event 1: layer 5; Event 2: layers 4 and 3; Event 3: layer 2. Layer 2 consists of distinctly less rounded gravel than the rest of the sequence and must reflect a short period less-energetic depositional condition with short pebble transport distances. The cross-shore gravel-rich stratigraphy of an accumulative strandline at 1600m altitude on the northern slopes of the Kuray Basin is presented in Fig. 3.31. Although the location in respect of the prevailing palaeowind differs, otherwise the setting is not dissimilar to that of the strandlines in Figure 3.30. The surface of the 30 m wide tread (Fig. 3.31) dips offshore. The upper edge of the tread is marked by an indistinct riser with a surface accumulation of larger well-rounded clasts, mixed with angular colluvial gravel particles. The tread at this point is incised into the sediments of the next strandline upslope. Distinct, steep, lake-facing unconformities reflect reactivation surfaces due to wave cutting, with lakeward accretion characterised by cross-stratified gravels lying above unconformities.

Fig. 3.29. Simplified scheme of shoreline disposition in the Kuray-Chuja Basins 103 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.30. Sketches of small sections cut in Kuray Basin strandlines on the southern shore. Numbering refers to distinctive layers picked-out primarily by differences in grain-size (see text for detail). 104

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.31. Sketches of small sections cut in Kuray Basin strandlines on the northern shore. Distinctive layers are picked-out primarily by differences in grain-size and style of bedding (see text for detail) (redrawn from Butvilovsky, 1993, his fig. 22).

Fig. 3.32. Oblique view of the low elevation shorelines in eastern Kuray Basin as seen in the vertical view of Fig. 3.25.

Although offshore dipping strata represent wave-break swash action cutting the outer margins, no distinct water level is evident from the strata packages and the preserved strata packages must represent only a small proportion of the layers that would have been deposited and eroded repeatedly during the growth of the beach height. The presence of the coarse-gravel/fine- gravel layering represents energetic wave conditions probably during storms whilst sandy lenses represent calm weather transport with sorting and deposition of fine grains by small waves traversing stable gravel layers. Each of these described beach accumulations are no more than several metres thick, and as such they represent relatively stable lake levels; the beach thickness indicating the limited range of the water level fluctuations. As wave-cut ravinement surfaces are noted at some locations cut into the basement it is clear that water levels were stable for considerable periods of time.

105 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Kuray strandlines - supplement (A. Panin, G. Baryshnikov, G. Adamiec)

In July 2012 during the field excursion organized by prof. A.V.Pozdnyakov (Tomsk university) we sampled deposits of one of the strandlines in order to derive their luminescence age. A pit was shoveled in central part of a 30 m wide terrace at elevation of 1650 m, 100-120 m above the dunefield in the bottom of the basin visited at Stop C6 (Fig. 3.33). Terrace surface dips from the edge to the back of the terrace, which is quite typical for all strandlines. The pit revealed the following composition: • Unit 1, 0-0.9 m: brownish cover silt reworked by soil processes in the upper 0.6 m, with abundant inclusion of fine gravel, mostly poorly rounded, in the intervals 0.25-0.5 and 0.7-0.9 m. • Unit 2, 0.9 – 1.0 m: fine sand with inclusions of fine gravel; sharp lower boundary. • Unit 3, 1.0 – 1.4 m (visual): mixed-sized sand with abundant fine gravel. Sample from depth 1.25 m (Fig. 3.33) produced an OSL age of 18.2±1.1 ka, close to LGM, which may be considered as rough estimation of the age of the lake.

Fig. 3.33 Lacustrine terrace at 1650 m a.s.l. 106

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Considerable width of the terraces, their cross profiles typical for wave- generated coastal bars, and sedimentary composition of the studied terrace – all this make ground for the conclusion that each terrace was subject for a long- lasting wave action under a stable water level of the lake, probably an average annual level. The whole set of lacustrine terraces (strandlines) facilitates the conclusion that the style of the lake draining was rather gradual lowering that lasted several decades than a momentary outburst. The almost LGM date from the lacustrine terrace shows that emptying of this particular lake probably was not the driver of extreme events in the Katun valley dated around 14-16 ka BP, though it must be admitted that accuracy of dating is not too high and only one direct age determination has been done still for the Kuray Lake. Another argument against the catastrophic drowning of the lake is the absence of any traces of this catastrophic flow in the Chuya old valley at Aktash (will be discussed at Stop C10) and preservation of the late MIS 4 lacustrine silts in the new Chuya canyon (Stop C9). If the lake had not drowned catastrophically, what was the driver of the Kuray gravel dunes formation? This is the question for which we can not suggest an answer yet. If the dunes are older than the lake, their surface must be covered by deposits of the lake that created the lacustrine terraces, which is not the case. If dunes are younger, where are any traces of the extreme flow that had generated them and why this flow had not destroyed the ancient shorelines? It still makes a challenge for us.

107 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C8 EARLY HOLOCENE LAKE IN THE WESTERN PART OF THE KURAY BASIN: THE BARATAL SECTION (A. Agatova, R. Nepop)

The stop (50.2534ºN, 87.7076ºE) is located at the foot of the Kuray range about 3.5 km upstream the Chuya River from the mouth of its left tributary Maashey (Fig.3.34; see also Fig.3.38). During the Neopleistocene exactly near the mouth of the Maashey river mountain glaciers from the Kuray and North Chuya ranges repeatedly blocked the Chuya valley. The ice dam impounded the vast lake in Chuya-Kuray system of intermountain depressions. In its western part particularly near the dam the lake had the largest depth – up to 600-750 m (there are different estimates of the largest lake size from different authors). The chronology of the late Pleistocene lake evolution is still highly debatable due to the lack of the absolute age determinations of lacustrine sediments. Among available dating material there are mainly fragments of char coals and other organic substrate, and the probability of its redeposition is quite high. That is the reason why dating of the Neopleistocene subaerial complex, especially including peats and soils “in situ”, overlying lacustrine deposits is very important for dating the last giant lake formation and draining. Studying such objects in places of dam location where depression’s outlet were plugged near the Kuektanar and Maashey mouths gives an indication of the possible existence of separate lakes in Kuray and Chuya depressions during the last stage of lakes formation.

Fig. 3.34. Chuya valley near the mouth of the Baratal river. Black arrows show location of the ice dam near the mouth of the Maashey river. Strips indicate the late Pleistocene (?) lacustrine sediments clearly preserved in topography near the bedrock remnants (the right part of the mandible Marmota baibacina was found in the lacustrine sands. The late Pleistocene age could be assumed on the basis of the state of its preservation (paleontological identification was made by A.V. Shpansky, Tomsk Federal University)). White strip line with arrows shows the riverbed location and flow direction of the pra-Chuya River (or its distributary). Ovals indicate the location of Pazyryk tombs (Borotal-I, II burial ground).

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

Near the Baratal mouth the most ancient fossil soils within the Kuray- Chuya system of intermountain depressions were studied (Fig. 3.35) - 9861±324 cal. BP (Agatova et al., 2014). It was developed on the surface of the talus fan which covered lacustrine sediments near the right slope of the Kuray depression. This date indicates that draining of the last late Neopleistocene ice-dammed lake occurred before the beginning of the Holocene (taking into account the time of talus fan formation and soil development). However another interesting and unexpected fact is that ancient colluvium sediments with paleosoil on the surface are covered by 10-m layer of slope material which was accumulated in aquatic conditions. Gently inclined lamination and evidences of washing of underlying fossil soil with redeposited humus between the colluvium layers indicate the lake existence which was most likely the low flow lake. Radiocarbon dates of fossil soils in the roof of this 10- m layer of slope material indicate that lake with the water level no less than 1480 m a.s.l. was developed in the western part of the Kuray depression during the time period 10000 - 6500 cal. years BP (Agatova et al., 2014). This lake could not be dammed by glaciers. The significant degradation of mountain glaciers within the SE Altai and adjusted Tuva region by the beginning if the Holocene is evidenced by numerous finds of palaeotrees of 10000-11000 cal. years old within several hundred meters above the modern upper timber limit in the heads of troughs (Nazarov et al., 2012). No later than 7000 cal. years BP glaciers within mountain framing of Kuray and Chuya depressions did not exceed the size of modern ones and possibly could be completely degraded (Nazarov et al., 2012; Agatova et al., 2012).

Fig. 3.35. The most ancient fossil soil studied within the Kuray-Chuya system of intermountain depressions. The soil is sandwiched between colluvium and slope sediments which were accumulated under aquatic conditions at the foot of the Kuray range. Taking into consideration the time of talus fan formation and soil development the last large lake within the Kuray depression was dried by the beginning of the Holocene.

109 Part III. Middle Chuya River valley, Kuray and Chuya Basins

After this lake draining and before building of Scythian tombs associated with the Pazyryk culture on the surface of the right bank river terrace (Kubarev and Shulga, 2007) the river bed occupied close to its current position - closer to the center of the valley, while earlier it most likely was located near the foot of the Kuray range (Fig.3.34). Archaeological site “Borotal-I burial ground” is located within the flooding zone of the planned hydropower Chuya plant. It includes more than one hundred tombs of different shape and size. Six of these tombs were excavated by V.D. Kubarev in 1974-1975. Larch log cabins were discovered in most of tombs. The burial mounds included also remnants of dead horses (up to seven horses in the largest tomb). A lot of tombs were robbed in ancient times. Construction of the hydropower Chuya plant started in 1961 for supplying Aktash mercury mine. It was mainly conducted by student teams. Today the remnants of hydropower constructions could be observed near the mouth of the Maashey river. In 1972 when construction works were practically completed (it was necessary just to dam of the river and to install the delivered equipment) it turned out that the quality of construction works was unacceptably low and finishing of these works was inappropriate. It is interesting that partial removal of the Chuya runoff was planned to be sent into her ancient riverbed. Today this ancient part of the pra-Chuya River valley is occupied simultaneously by two rivers – Menka and Chibitka.

Fig. 3.36. Large stone debris that broke soil horizon suggests the strong earthquake occurred about 5000 cal. years BP.

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Part III. Middle Chuya River valley, Kuray and Chuya Basins

1 km southwest from paleosoil location (50º15´13´´, 87 º41´32´´) lacustrine clays, loams, sands, and embedded fluvial deposits - rhythmically interbedded sands and clays, are exposed within the prolonged river bank outcrop (height of about 13 -5 m( (Fig. 3.37). This complex is covered by subaerial complex of aeolian sands and buried soils (up to three horizons) which was developed during the last third of the Holocene, i.e. after the final draining of the Holocene reservoirs. By the beginning of settlement of this territory by Scythians associated with the Pazyryk culture lower soil horizon has been already formed.

Fig. 3.37. Beyond the talus fan the Holocene lacustrine offshore sediments covers the Neopleistocene lacustrine sands.

111 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C9 THE CHUYA SPILLWAY UPSTREAM FROM THE CHIBIT TOWN (A.Panin, G.Baryshnikov)

Few kilometers the Baratal section (Stop C8) Chuya makes a 90º left turn to leave its old valley and to enter the young 20 km long and 600 m deep canyon (Fig. 3.38). Chuya flows at 1449 m a.s.l. at the entrance to the canyon and leaves it at 1135 m a.s.l. (confluence of the Chibitka River at the western margin of the Chibit town), which provides total dipping of 314 m, or 15.7 m/km. In the downstream 70 km long reach to the discharge to Katun, Chuya dips by 413 m (722 m a.s.l. at the confluence), or 5.9 m/km. The 28 km long upstream reach from the Kurai Basin (1515 m at the bridge across Chuya east from Kyzyl-Tash village) to the entrance to the canyon is characterized by dipping of 66 m and slope 2.4 m/km only. Consequently, the valley slope in the young canyon is extraordinary high, which reflects the canyon youth. Numerical ages of valley transformation (old valley abandonement and incision of the young canyon) has not been established yet. In Stops C9 and C10 we will present new data that permit age estimations and provide ground for conclusions about drivers of this event. In the downstream reach of the canyon, a 0.5 km wide and 100-120 m high terrace goes on the right bank of the river. Shallow pits and road undercuts show that the terrace is composed presumably of non-rounded local rocks with some admixture of well-rounded exotics. This is glacial till accumulated by the Maashey glacier, which repeatedly occupied the Katun valley (see location of the Maashey valley in Fig. 3.38). Upstream, the moraine terrace narrows to 100- 200 m and new terrace level appears probably of alluvial origin at an elevation of 40-50 m above the river. 4.5 km upstream from the Chibitka R. mouth (3.5 km from the outlet of the canyon) the moraine terrace is undercut by a large meander circus. Roadcut at 50,2909ºN, 87.5125ºE, 65 m above the river on the slope of the 120 m morain terrace exposes alternating beds of microlaminated silts/fine sands (up to 1.2 m thick) and subrounded clasts in silty matrix (0.6-0.7 m thick) (Fig. 3.39). They were interpreted as limnic and mass waste deposits respectively. Limnic layers reflect valley damming by a downstream glacier, probably that from the Chibitka valley (see Fig. 3.38). Presence of slope deposits is in accordance with the position of the section at the base of a steep and high valley side. Sample from the upper limnic layer provided OSL age of 62.5±6.8 ka. This age makes ground for three conclusions. (1) Tthe canyon had already existed by the end of MIS 4. (2) This time was characterized by notable glacial advance that resulted in damming of the trunk valley by valley glaciers descended through tributaries. (3) As limnic deposits cover the slope of the 120 m morain terrace, both this terrace and the whole canyon are significantly older than 60 ka.

112

Fig. 3.38. Oblique downstream view at the Chuya abandoned valley and young canyon (Stops C9 and C10) White arrow indicates the 3.5 km long reach of the Maashey valley used by Chuya as a part of the young canyon.

Part III. Middle Chuya River valley, Kuray and Chuya Basins

The earth road goes upstream along the right bank of Chuya ~10 km from the dated section to the mouth of the Maashey River. The upper course of the valley is occupied by the Maashey glacier, which is considered as one of the glaciers to have formed ice dams in the Chuya valley in the past. Now the front of the glacier (Fig. 3.40) stands 16 km upstream forn river mouth at an altitude of 2240 m a.s.l., >800 m above Chuya.

Fig. 3.39. Lacustrine silts covering the slope of the 120-m terrace in the young Chuya canyon

Fig. 3.*. Fig. 3.40. Front of the Maashey glacier in 1968 (from Okishev, 2011). A – Bedding formed due to movement of ice plates along chip planes (darker strips with abundant mineral material), and plastic deformations in the base of ice. B – steep bedding in the left edge of the glacier, recognized also in ice cracks upstream the same glacier. 114

Part III. Middle Chuya River valley, Kuray and Chuya Basins

Stop C10 OLD VALLEY OF CHUYA: ITS AGE AND MECHANISM OF ABANDONEMENT (A. Panin, G. Baryshnikov)

To consider the reasons and time constraints of the Chuya old valley abandonement, one should examine the headwater part of this ancient valley where two distinct geomorphic features may be found. The headwaters of the old Chuya valley are plugged by a 100 m high ridge that has glacial origin and complex structure (Fig. 3.41). Probably it was the glacial damming that forced Chuya to abandon this valley and cut a spillway – the present-day canyon that was visited at Stop C9. Valley glaciers that filled the old valley and formed the end-morain/glacio-fluvial cross-ridge originated probably from the Chibitka valley (see Fig. 3.38). Two phases of development may be designated in the morphology of the morain/glacio-fluvial ridge (Fig. 3.41). The major phase, during which the general outlines of the ridge were developed, is represented by the dome-like terrace with the top at 1540-1560 m a.s.l. and slopes extending downstream and upstream the valley (distal and proximal slopes). This first generation of morphological complex was cut through (note the hollow which is used by Chuiskiy Tract in Fig. 3.41) and partly reworked at its proximal side during the second formation phase (see the younger morphological generation in Fig. 3.41). Structure of both geomorphic generations may be examined in two pits in the area of the unfinished Mena Hydropower Station, part of the Chuya Hydropower Plant (see Stop C8 for historical description). Okishev (2011) reports that in the foundation pit 15 m deep excavated in 1960s the so called Mena moraine was exposed in the northern (proximal) edge – solid gravely loam with beds dipping downstream the valley (Fig. 3.42a). In the opposite (southern) edge the Mena moraine was covered by glacio-fluvial gravels and sands dipping upstream the old valley, towards the present-day Chuya River (Fig. 3.42b). Okishev (2011) dated this moraine/glacio-fluvial complex to the Late Pleistocene, which has been supported by the latest results of numerical dating (see below). The present-day lower pit exposes the following deposits (50.2801ºN, 87º6713E; Fig. 3.43), from bottom to top. Unit 1: fine sand with horizontal layers of coarse sand and fine gravel. Unit 2: gravels to cobbles (up to 30 cm in diameter), horizontally bedded, without fine-grained matrix. Unit 3: fine to medium gravel in silty sand matrix, with gently dipping bedding. Unit 4: fine gravel with admixture of medium gravel, in coarse sand matrix, parallel bedding inclined at 20º downstream the olds valley and to its left side.

115 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Fig. 3.41. Oblique view at the upstream part of the old valley of Chuya. Elements of the morain/glacio-fluvial ridge plugging the old valley: 1 – top of the initial ridge; 1a, 1b – its proximal and distal sides; younger morphological generation: 2 – reworked initial ridge; 2a –steep (undercut?) proximal side. Pits in the Mena HPS area: A – lower pit excavated on top of the second generation; B – pit within the proximal side of the first generation. Valley glaciers moved from the front of the scene. The present-day Chuya River at its entrance to the spillway (young canyon) is at the background.

Fig. 3.42. Exposure in the Mena HPS foundation pit (excavated in 1960s): (a) – inclined Mena morain in the northern (proximal) part, (b) – glacio- fluvial gravels and sands in the southern (distal) part.

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Fig. 3.43. General scheme of the gravel pit on the lower terrace at Mena hydropower station

Unit 5: intercalation of greenish-grey mixed-sized sands and fine unrounded gravels; the unit is broken by reverse micro-faults gently dipping downstream the valley with amplitude of shift up to 30 cm, probably of seismic origin; OSL date from the level 5.7 m above the pit bottom: 53.6±4.8 ka. Unit 6: lens with complex structure including three subunits, mainly massive small gravel in coarse sand matrix (subunit 6c); the unit undercuts Unit 5; subunits 6a and 6b are transitional deposits formed probably in connection with the erosion contact –fine gravels and sands bedded parallel to the contact. Unit 7: lens cutting Unit 6; mixed sized material from cobbles to sands, organized in diffuse concave layers concordant to the lower boundary of the lens.

117 Part III. Middle Chuya River valley, Kuray and Chuya Basins

Unit 8: part of a lens filling palaeochannel, slightly concave parallel layers of fine and coarse sands and gravels; in the interval 1.5 – 4.8 m above the base reverse microfaults are found with an amplitude of shift ~10 cm, direction of shift – towards the left side of the valley. Unit was OSL dated at 0.5 m above the bottom at 81.3±6.1 ka and at 4.2 m above the bottom (0.4 m below the top of the unit) – to 51.3±5.4 ka. According to stratigraphy, the lower date looks appropriate and the upper date probably depicts subsequent reworking of deposits. Unit 9: fine to medium gravels with lenses of sand, containing big consolidated fragments of material from Unit 3 (probably transported in frozen state). Units 10-12 – slope cover deposits. In a pit below the main bottom gravel-cobble is found similar to Unit 2 (designated as Unit -1). Under it lie fine to medium horizontally bedded sands (Unit -2). Unit -2 was OSL dated to 98.8±7.3 ka. The upper terrace that represents the proximal side of the older generation of the initial end-morain/glacio-fluvial complex is exposed in the upper pit (50.2801ºN, 87º6713E; Fig. 3.44). Bottom of this pit is 40 m above the bottom of the lower pit. Total height of the exposure is ~30 m. Upper edge of the pit is at 1500 m a.s.l. The exposure exhibits nearly horizontal beds of cobbles, gravel and sands that are cut by the slightly dipping surface of the terrace and its steep slope. The thickest layer of sand is at 3-5 m above the pit bottom. Sample from this layer taken at the level of 4 m was OSL dated at 93.9±7.6 ka (Fig. 3.44).

Interpretation According to the dates from the older generation of the moraine/glacio- fluvial ridge, the ridge may be interpreted as the end-morain complex formed by valley glacier that arrived from the Chibitka tributary valley (see Fig. 3.38) around 80-100 ka BP, i.e. during the late MIS 5. The glacier filled the valley, dammed Chuya and forced it to cut a spillway west from the old valley. The Maashey valley had entered Chuya at the present-day division of old and young valleys. Chuya used the lower course of the Maashey valley as the first section of the young canyon (see Fig. 3.38). Consequently, the Maashey glacier did not descended to the very end of the valley at this time, which favored usage of this valley by Chuya. The other prominent event in development of the old valley was reworking of the end-moraine ridge. According to the few obtained OSL dates, it took place around 50-60 ka BP (late MIS 4 – early MIS 3). This reworking was probably related to a new glacial advance. Alternative scenarios can be suggested to explain details of the data. In both cases the driver of change was the Chibitka glacier. First scenario is glacier advance upstream the old Chuya valley to the old end-moraine ridge. Melt waters from the glacial front could cut through the ridge and produce the valley enclosed into it. This scenario explains well the very fresh outlines of the proximal slope where the Mena hydropower station

118

Part III. Middle Chuya River valley, Kuray and Chuya Basins stands. However it is not clear why the reworked part of the ridge preserved its dipping downstream the old valley (see Fig. 3.41).

Fig. 3.44. Gravel pit exposing the proximal side of the oldest generation of glacio-fluvial ridge at Mena hydropower station

Second scenario is glacier advance downstream the old Chuya valley and damming of Chuya in its new valley. Waters of the dammed lake could overflow the plugging end-moraine ridge, incise into it and partly rework its proximal side. This hypothesis fits well the presence of the 60-ka old lacustrine deposits within the young Chuya canyon and the occurrence of relatively fresh moraine (large angular boulders) at the town of Chibit. The only shortage of this explanation is the undisturbed condition of the steep proximal slope at Mena Station. However it can be explained by passing of overflowed waters at the other side of the valley. During LGM and the Late Glacial, no significant geomorphic change is detected in the old valley, which contradicts to the hypothesis of the catastrophic outburst from the Kurai Lake at that time. In case of a flow several hundred meters deep it must have blown into the old valley, but no geomorphic or sedimentological evidence exist of such impact. Also, lacustrine sands on the side of the young canyon (Stop C9) would have not survived also.

119 References

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Agatova AR, Nazarov AN, Nepop RK, Rodnight H 2012. Holocene glacier fluctuations and climate changes in the southeastern part of the Russian Altai (South Siberia) based on a radiocarbon chronology. Quat Sci Rev 43: 74– 93 Agatova AR, Nepop RK, Bronnikova MA, Slyusarenko IYu, Orlova LA 2014. Human occupation of South Eastern Altai highlands (Russia) in the context of environmental changes. Archaeological and Anthropological Sciences. DOI 10.1007/s12520-014-0202-7 Baker, V.R. 2009. Megafloods and global paleoenvironmental change on Mars and Earth. In: Chapman, M.G., and Kesthelyi, L., eds, Preservation of Random Mega-scale Events on Mars and Earth: Influence on Geologic History: Geological Society of America Special Paper 453, p. 25-36. Baker, V.R., Benito, G., and Rudoy, A.N. 1993. Paleohydrology of Late Pleistocene superflooding, Altai Mountains, Siberia: Science, v. 259, p. 348– 350. Baker,V.R. 2013. Global late Quaternary fluvial paleohydrology: with special emphasis on paleofloods and megafloods. In: Shroder, J. (Editor in Chief), Wohl, E. (Ed.), Treatise on Geomorphology. Academic Press, San Diego, CA, v. 9, Fluvial Geomorphology, p. 511–527. Baryshnikov, G.Y. 1976. Morphology and deposits of the Biya valley. In: Problems of Geomorphology of Altai Krai. Leningrad, LGU, p. 14–17 (in Russian). Baryshnikov, G.Y. 1984. Aeolian sediments in the Altai foothills and their links with paleoclimates. In: Contemporary Geomorphological Processes in the Altai Krai. Biysk, Pedagogical Institute Press, p. 6–9 (in Russian). Baryshnikov, G.Y. 1992. Landscape Development in Transitional Zones of Orogens in the Cenozoic: Tomsk, Tomsk University Press, 181 p. (in Russian). Baryshnikov, G.Y. 2012. Landscapes of Transitional Zones of Orogens: Barnaul, Altai University Press, 498 p. (in Russian). Baryshnikov, G., Panin, A., Adamiec, G. 2015. Geochronology of the Late Pleistocene Catastrophic Biya Debris Flow and the Lake Teletskoye formation, Altai Region, Southern Siberia. International Geology Review. DOI: 10.1080/00206814.2015.1062733 Baryshnikov, G.Y., Panychev, V.A. 1987. Formation of terrace assemblages in the upper Biya valley: Questions of Geography in Siberia, v. 17, p.41–52 (in Russian). Borhoquez, P., Carling, P.A., Herget, J., in press, Dynamic simulation of catastrophic late Pleistocene glacial lake drainage, Altai Mountains, central Asia. International Geology Review, invited contribution.

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Carling, P.A., Knaapen, M., Borodavko, P., Herget, J., Koptev, I., Huggenberger, P. & Parnachev, S. 2011. Palaeoshorelines of glacial Lake Kuray--Chuja, south-central Siberia: form, sediments and process. J. Geological Society, London, 354, 111-128 Carling, P.A., Martini, P., Herget, J., Borodavko, P., Parnachov, S. 2009. Megaflood sedimentary valley fill: Altai Mountains, Siberia, pp 243-264 In: Burr, Carling, Baker (eds), Megaflooding on Earth & Mars, Cambridge University Press, 319pp. Carling, P.A., Martini, P., Herget, J., Parnachov, S., Borodavko, P. and Roberts, B. 2009. Megaflood sedimentary valley fill – Altai Mountains, Siberia. In: Burr, D., P. Carling and V. Baker (eds.): Megaflooding on Earth and Mars. Cambridge (Cambridge University Press), p. 243-264. Carling, P.A., Villanueva, I., Herget, J., Wright, N., Borodavko, P. & Morvan, H. 2010. Unsteady 1-D and 2-D hydraulic models with ice-dam break for Quaternary megaflood, Altai Mountains, southern Siberia. Global and Planetary Change, 70, 24-34. Derevyanko AP, Markin SV 1987. Paleolit of the Chuya depression: Gorny Altai [Paleolit Chujskoy kotloviny: Gorny Altai]. Nauka Publishers, Novosibirsk (in Russian) Gutak YM, Rusanov GG 2013. About the age of iron smelting furnaces in the Kuyakhtanar valley (Gorny Altai) [O vozraste zhelezoplavil’nyh pechej urochischa Kuyahtanar (Gorny Altai)]. Bull Sib State Ind Univ [Vestnik Sibirskogo Gosudarstvennogo Industrial’nogo Universiteta] 2(4):18–21 (in Russian) Herget, J., 2005. Reconstruction of Pleistocene Ice-Dammed Lake Outburst Floods in the Altai Mountains, Siberia: Geological Society of America Special Paper, v. 386, 118 p. Herget, J., T. Euler, T. Roggenkamp & J. Zemke 2013. Obstacle marks as palaeohydraulic indicators of Pleistocene megafloods. Hydrology Research 44, 300-317. Huang, W., Cao, Z., Carling, P.A., Pender, G. 2014. Coupled 2D Hydrodynamic and Sediment Transport Modelling for Megaflood due to Glacier Dam-break in Altai Mountains, Southern Siberia. Journal of Mountain Science, 11, 1442-1453. Huggenberger, P., Carling, P.A., Scotney, T., Kirkbride, A. and Parnachov, S.V. 1998. GPR as a tool to elucidate the depositional processes of giant gravel dunes produced by late Pleistocene superflooding, Altai, Siberia. Proceeding of the 7th International Conference on Ground Penetrating Radar, Vol 1,pp 279-28, May 27-30 1998, University of Kansas, Lawrence, Kansas, USA, Austin, Texas. Publ by Radar Systems and Remote Sensing Lab, Univ. Kansas. ISBN: 0-936352-16-7. Khudjakov YS 1990. Kyrgyz in Gogny Altai [Kyrgyzy v Gornom Altae]. In: Surazakov AS (ed) Problems of studying the ancient and midevial history of

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Rogozhin EA, Ovsyuchenko AN, Marakhanov AV, Ushanova EA 2007. Tectonic setting and geological manifestations of the 2003 Altai earthquake. Geotectonics 41(2):87-104. Rogozhin EA, Platonova SG 2002. Source areas of Holocene large earthquakes in Gorny Altai [Ochagovye zony siljnyh zemletrjasenij Gornogo Altaya v golocene]. IFZ RAN, Moscow (in Russian) Rudoy, A.N. 1984. Giant current ripples – evidence for catastrophic outbursts from glacial lakes in Altai. In: Contemporary Geomorphological Processes in the Altai Krai. Biysk, Pedagogical Institute Press, p. 60–64 (in Russian). Rudoy, A.N. 2002. Glacier-Dammed Lakes and geological work of glacial superfloods in the Late Pleistocene, Southern Siberia, Altai Mountains: Quaternary International, v. 87, no. 1, p. 119–140. Rudoy, A.N., Baker, V.R. 1993. Sedimentary Effects of cataclysmic Late Pleistocene glacial flooding, Altai Mountains, Siberia: Sedimentary Geology, v. 85, no. 1–4, p. 53–62. Rusanov GG 2010. The Holocene climate changes in Chuya depression (Gorny Altai) on the basis of ostracod fauna analysis [Izmenenija klimata Chujskoj kotloviny Gornogo Altaja v golocene po faune ostracod]. Prog Mod Nat Sci [Uspehi sovremennogo estestvoznanija] 10:20–25 (in Russian) Rusanov, G.G., Orlova, L.A. 2013. Radiocarbon Dates (SOAN) from the Altai mountains and Predaltaiskaya Plain: AGAO, Biysk, 291 p. (in Russian with English summary). Schukina, E.N. 1960. Spatial distribution and stratigraphy of Quaternary deposits in Altai: Proceedings of the Geological Institute USSR Ac. Sci., v. 26, p. 127–164 (in Russian). Sheinkman VS 1990. Pleistocene glaciations of mountains of Siberia: analysis and new data [Pleistocenovoe oledenenie gor Sibiri: analiz i novye dannye]. Materials of Glaciological Investigations (Materialy gljaciologicheskih issledovanij) 69, 78-85. (in Russian). Vandenberghe, D., 2004. Investigation of the optically stimulated luminescence dating method for application to young geological sediments. Unpublished PhD Thesis. University of Gent, 298 p. Zinjakov NM. 1988. History of the ferrous metallurgy and blacksmith's work of the ancient Altai [Istorija chernojmetallurgii I kuznechnogo remesla drevnego Altaja]. Tomsk University Press, Tomsk (in Russian) Zolnikov ID, Mistrukov AA (2008) Quaternary deposits and relief of the Chuya and Katun valleys [Chetvertichnye otlozhenija i rel’ef dolin Chui i Katuni]. Parallel, Novosibirsk (in Russian) Zolnikov, I.D. 2011. Role of glaciations and glacial superfloods in formation of sedimentary complexes of the Upper Neopleistocene in Altai and the foreland Predaltaiskaya Plain. Unpubl. thesis of habilitation dissertation. Novosibirsk, 33 p. (in Russian).

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Supplements

Supplement 1

LARGE BOULDER TRANSPORT (J. Herget) [Text from: Herget, J. (2005): Reconstruction of Pleistocene ice-dammed lake outburst floods in the Altai Mountains, Siberia. Geological Society of America Spec. Pap. 386, 96-104]

The attempt to derive information about a flood from the transported sediments is a proximate idea. The correlation of transported grain size with the magnitude of flow expressing the competence of flow is obvious and can be expressed by correlation with different hydraulic parameters like flow velocity v, shear stress τ, unit stream power ω, discharge Q or even depth of flow y (Costa 1983). In many cases, the competence of flow is expressed as minimal velocity for the erosion of particles of a given size (e.g. Zepp 2002, 141). By a closer look, this might be characterized as threshold flow, while competence can be expressed as the maximum particle size transportable by a flow (Richards 1982, 79). This previously recognized difference of definition (Baker & Ritter 1975) could become important, if coarse material of a given grain size might not be erodable in a specific reach, but the drag force of the flow is strong enough to keep it in transport. The relationship between competence and grain size of the sediment depends on various factors of the flow and the sediment, which have to be in balance. As this strength of flow depends on characteristics of the sediments like density, grain size distribution, geometry of particle, exposure of grain, compaction and cohesion respectively, envelope curves of threshold values for minimum values of initial movement are frequently determined. As not all factors of influence on the initial movement of particles can be quantified in applied studies, the degree of empirical elements in equations to calculate necessary flow conditions varies. Hence the range of validity of estimated equations must be considered carefully, as no final universal formula is found yet, that can be expressed in a applicable style (comp. Raudkivi 1982, 12). The correlation can be carried out by physical based equations with minor empirical elements (e.g. Bradley & Malde 1980, Carling 1983, Zanke 1982) or purely empirical relations like the well-known diagram by Hjulström (1935) or the equations derived from studies e.g. by Costa (1983) or Williams (1983) (comp. e.g. Graf (1971) and Novak (1973) for additional references).

Hydraulic background

According to the DuBoys equation, the shear stress τ0 acting on a particle at initial movement depends on the specific weight of water γf, depth of flow that can be expressed as hydraulic radius R and the slope of the channel S (Knighton 1998): τ0 = γf R S (eq. 1)

If this threshold value of the shear stress is reached, the drag and lift forces of the flow equal the gravitational and frictional forces acting on the particle. The lift force results from the difference in flow velocity between the top and bottom of a particle, which sets up a pressure gradient that tends to move the particle vertically upwards. Turbulent eddying in the wake of the particle, which act directly upwards close to the bed, supports the uplift force (Fig. S1).

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Fig. S1. Forces acting on a submerged particle (modified after Knighton 1998, Fig. 4.4B)

By investigations of palaeoflow velocities needed to transport boulders, Bradley & Mears (1980) developed a physical based equation for sliding, where all forces acting on a boulder (Fig. S1) are balanced to determine the threshold velocity of initial movement. The drag force FD is expressed as

FD = CD’ An (γf vcb² / 2) (eq. 2)

where An cross-section area of boulder vcb velocity at channel perpendicular to flow bottom CD’ adjusted drag coefficient γf specific weight of fluid

The lift force FL is FL = CL Ap (γs vcb² / 2) (eq. 3)

where Ap cross-section area of boulder vcb velocity at channel parallel to flow bottom CL lift coefficient γs specific weight of particle

The resisting forces FR consist of the submerged weight of the boulder considering a static friction coefficient minus the component of submerged weight acting down the channel slope:

FR = (γs - γf) Vb g (Csf cos S – sin S) (eq. 4)

where γs specific weight of particle γf specific weight of fluid

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Vb boulder volume Csf static friction coefficient S slope of channel

It is found that even slopes of 100 ‰ are of negligible influence compared to drag and lift forces of the flow, hence can be dropped from the equation. The balance of forces can be expressed as FD + FL = FR. In a modified form, derived by Costa (1983) by consideration of values for the coefficients from various sources, the equation of the critical velocity for boulder movement at the channel bed vcb can be solved from equations 2-4 as

2 (γ s − γ f ) d g Csf vcb = (eq. 5) γ f (CL + CD' )

where CD’ adjusted drag coefficient g gravity constant (= 9.81 m/s²) (= 1.05 for a shape factor of 0.60) γf specific weight of fluid (= 9,800 CL lift coefficient (= 0.178) N/m²) Csf static friction coefficient (= 0.7) γs specific weight of particle d boulder diameter in m (= 25,970 N/m²)

In this modification, the shape of the boulders is modelled to be that of a cube. Even if this simplification appears crude, it is useful to calculate the volume and area of a boulder which are of influence on the drag force and the drag force coefficient CD. The channel bottom velocity vcb represents the velocity of flow about 1/3 boulder diameter above the mean bed level, for which the lift coefficient is CL = 0.178. The mean velocity of flow v within a channel can be estimated as

v = 1.4 vcb (eq. 6)

This estimation is based on a value given by Baker (1973, 26), who assumes an underestimation for very deep flows. The factor is confirmed by Zanke (1982, 170), while Costa (1983) mentions a factor of 1.2 and Bradley & Mears (1980) of 1.3. The equations 2-6 illustrate the complexity of the physical background of particle movement in fluvial channels. Within this brief review of the hydraulic background, a focus is laid on aspects of relevance for boulders. The subject is explained on a more general level and higher degree of complexity e.g. by Chanson (1999), Graf (1971), Graf & Altinakar (1998), Hoffmans & Verheij (1997), Richards (1982) or Zanke (1982). Another equation for the threshold velocity of initial particle movement is developed by Zanke (1982, 170). As several hydraulic parameters are left as variables, the influence of empirical elements is less than in other equations. For the mean velocity of flow in a channel and non-cohesive sediments his equation can be written as υ v = 2.8 ρ' g d + 14.7 (eq. 7) d where ρ’ relative density (= 1.65) d particle diameter (cm) g gravity constant (= 981 cm/s2) υ kinematic viscosity (= 0.01519 cm²/s)

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Zanke (1982) found a sufficient correlation with the curve of the diagram by Hjulström (1935), which indicates a validity mainly for fine sediments up to gravels. A good correlation of sediments up to 33 cm with the Hjulström curve is found by Helley (after Graf in Zanke (1982)). This equation is chosen from numerous other attempts (comp. Graf 1971) only for comparison with equation 5 as it is frequently applied in Germany. Numerous empirical relations between competence of a flow and different hydraulic parameters are developed, but are limited to smaller sediments up to gravels. For example, Novak (1973) illustrates the failure of empirical relations to estimate river competence for coarse sediments by the example of the modified Hjulström-type curve from Sundborg (1967). Unfortunately, Novak (1973) erred by drawing the Sundborg (1967)-curve and shifted the curve of “critical erosion velocity” (upper one) and “cessation of movement” (lower one) one magnitude of flow velocity below the values originally given by Sundborg (1967, Fig. 1). Hence the interpretation by Novak (1973, 23), that this curve “… fails to adequately predict coarse sediment competency…” is still right, but if it is extrapolated to coarser sediments it over- instead of underestimates competence flow velocities. On the other hand, the scatter of data points increases considerably for particles of d > 1000 mm (Fig. S-2).

Fig. S2 Data of competence of flow for coarse particles (modified on the base of Novak 1973, Fig. 6) Data for streams, Pleistocene floods, recent floods and engineering works from various sources are compared with the curve of flow competence by Sundborg (1967) with d for mean particle size in mm and v for velocity of flow in cm/s. Unfortunately, the curves by Sundborg (1967) are drawn one magnitude below the values originally given, hence if extrapolated, this curves over- instead of underestimate flow competence for coarse particles. Four groups of empirical equations, purely based on statistical analysis are considered here, as they are focused on coarse sediments. Equation 8 (Costa 1983, 991) is recommended for steep channels and grain sizes 50 mm < d < 3200 mm, and is derived from previously developed equations as arithmetic average. The mean velocity of flow given in m/s can be estimated as v = 0.18 d 0.487 (eq. 8)

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where the diameter d is expressed as intermediate axis of the particle given in mm. This equation considers the widest range of particle’s diameters of all empirical equations found in the literature. O’Connor (1993, 56) correlates data of mean velocity estimated by step-backwater calculations with intermediate axis of boulders transported by Pleistocene Lake Bonneville Flood. The considered boulders with intermediate axis varying from 10 to 624 cm, while the largest measured long diameter of a transported boulder was 1120 cm. He found a correlation of r² = 0.52 for the 75 considered boulders in the form of

v = 0.29 d 0.60 (eq. 9)

with v given in m/s and d in cm. Williams (1983) determined approximated envelope lines for transported particles in a range of 10 mm < d < 1500 mm in log-log scale diagrams of intermediate particle diameters (mm) versus mean velocity of flow (m/s) from various references. For the upper envelope line of initial particle movement he found

v = 0.46 d 0.50 for 15 < d < 500 mm (eq. 10)

and for the lower limiting line of particle movement he estimates

v = 0.065 d 0.50 for 10 < d < 1500 mm (eq. 11)

His upper envelope line can be interpreted as maximum velocity of flow for initial particle movement under uncertain factors of a high resisting force FR, while the lower line is empirical estimated for more favourable conditions to initial movement. Torpen (1956, Fig. 5) summarizes experiences with the dimension of riprap for channel bank protection. As interpolation from various sources he finds

d = 0.08 vcb² (eq. 12)

for the bottom velocity of overturning of coarse particles (v in ft/s and d in inches) and

d = 0.6 vcb² (eq. 13)

for the bottom velocity for initial sliding of coarse particles (units like above). Originally, the equations are determined by regarding the weight of stones and were modified by Novak (1973) by the assumption of spheres for the shape of particles. The use of competence as palaeohydraulic indicator is complicated by the possible influence of macroturbulence (Matthes 1947, Jackson 1976). This secondary circulation phenomenon occurs in deep, high gradient flows and creates a upward vortex that increases lift force on particles on a channel considerably. It is assumed to be caused by flow separation and is compared to tornadoes in the atmosphere. Large amounts of sediments are observed to be moved by the vortex, even concrete slabs of boulder size, that are far beyond the shear stress energy of tractive flow (after Tiffany from Jackson 1976, 555). Due to limited knowledge about the phenomenon, its influence cannot be quantified, but is considered occasionally (Scott & Gravlee 1968, Baker 1973 a/b). An overview of the fluid mechanics is given by Jackson (1976). Baker (1978 a, 77) considered this effect by the limitation to “smaller scabland boulders” up to about 2 m in mean diameter during the estimation of a regression equation for shear stress versus particle size (comp. Baker & Ritter 1975). This threshold value is also mentioned by Costa (1983, 1000).

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Supplement 2

PROBLEMS OF ABSOLUTE DATING OF GLACIAL DEPOSITS IN RUSSIAN ALTAI BY THE EXAMPLE OF THE CHAGAN SECTION

Nepop R.K.1, Agatova A.R.1, Rodnight H.2 1 Institute of Geology and Mineralogy, Russia, [email protected] 2 Institute for Geology and Palaeontology, Austria, [email protected]

Reconstruction of the patterns of Pleistocene glaciations in the mountains of Southern Siberia, as well as correlating the sediments within mountains of Central Asia mountain belt and platform areas of Siberia, is not possible without absolute dating of glacial deposits, but these types of continental sediments are very complex to date absolutely. Insufficient bleaching of glacial sediments is a common problem for making adequate luminescence dating. Deposits associated with proglacial, glaciofluvial, and glaciolacustrine sediments have a higher potential to be bleached than subglacial and englacial ones, but the risk of insufficient bleaching is still considerable. Essentially, the effectiveness of luminescence signal zeroing is directly controlled by the geomorphic processes responsible for the sediment production and reworking. At the present the Quaternary of the Russian Altai is still poorly understood with the number of glacial cycles unknown and the proposed extent of glaciation varying widely between different authors. The Chagan section, located in the southeastern part of the Russian Altai (SE Altai) is one of the most representative sections of the Altai Pleistocene glacial deposits. A comprehensive study of it was carried out in the 1970’s and included TL dating [1]. Eight TL ages, three of which characterize the glacial and associated sediments in the upper part of the section, form the basis of depositional correlation schemes for the Russian Altai and Siberia.

Fig. 1. Schematic drawing of the Chagan section showing samples locations and available absolute dates.

This study presents 1 radiocarbon, 20 TL, 3 IRSL dates and discussed all previously published ones (3 radiocarbon and 10 TL dates) for the upper part of the Chagan section which is presented by glacial sediments of various types (Fig. 1). Analysis of all available

130 Supplements dates demonstrates the considerable complexity of absolute dating of these sediments and cast doubt on available depositional correlation schemes for the Russian Altai and Siberia which are based on several TL dates obtained in the last century. As a part of this study detailed geomorphological investigations of the Chaga-Uzun river basin were carried out in order to determine the number, patterns of and evolution of the Pleistocene glaciations in the region. These investigations included mapping of the glacial landforms and sediments. Selected exposures were studied to examine the deposits and landform associations and to analyze the sedimentology of moraines in different states of preservation. The material for luminescence dating was derived from glaciofluvial, glaciolacustrine and englacial meltwater sediments to estimate the age of moraine formation equal to the age of glaciations. Preference was given to deposits containing finely grained fractions. A single radiocarbon date of carbonate concretes was obtained from the bottom of the glacial complex. TL method was used prior to the development of the optically stimulated luminescence (OSL) and infra-red stimulated luminescence (IRSL) methods. Previously, the applicability of TL dating has been demonstrated for various sedimentary environments [2 and references therein], mainly focused on those that have experienced sufficient exposure to daylight enabling a complete resetting of the luminescence signal. Luminescence dating of glacial and associated sediments applying this technique is difficult, mainly due to insufficient bleaching during transportation and deposition of the sediments. In addition to the problem of zeroing of the luminescence signal, there is also a great regional diversity in physical properties of quartz grains. Quartz properties, with regards to their luminescence signal, are mainly determined by the content and composition of microimpurities which form electron traps in the crystal structure of the mineral. This leads to variations in the suitability of a quartz or alternative silicate minerals (such as feldspar) as a geochronometer for luminescence dating. Generally 38 samples were collected from deposits containing sands and sandy loams within the Chagan section and finally 14 TL dates were obtained in the RTL dating Laboratory, Buryatia Geological Institute SB RAS (BurGIN) applying naturally saturated etalon and 9 ones - in the Laboratory of dosimetry, radioactivity and RTL dating, Moscow State University (MGU) using artificially saturated standard. It is noteworthy that in the samples analyzed at BurGIN, from the 24 successfully prepared samples a TL signal was measured only from 14 samples, including the 3 saturated ones. Quartz extracted from the remaining 10 samples gave strong low temperature peak and therefore was unsuitable for measurements. A similar proportion of undated samples was shown in MGU data. This fact emphasizes the importance of the discussion about choosing the mineral-paleodosimeter (quartz versus feldspar) for regional luminescence dating. Generally it could be stated that mineral material from the Chagan section is very hard for luminescence dating. Physical properties of mineral grains most likely are affected by a short transportation distance and low number of depositional cycles which is also problematic for luminescence dating techniques. Our study reveals a big difference (sometimes an order of magnitude) in the values of TL ages obtained in different laboratories. The dates of both laboratories also agree poorly with the stratigraphic position of the sample in the section. Thus, we concluded that the TL method is unsuitable for dating glacial sediments [3, 4] and should only cautiously be used for making any reconstructions and correlations. The OSL method is expected to be more suitable for dating glacial sediments, mainly due to the significantly shorter time (several seconds) of daylight exposure needed for complete bleaching the sample. In 2008 we made a first attempt to apply this technique for dating deposits of glacial origin from the Chagan section. A number of samples were taken from the glaciofluvial and glaciolacustrine layers. It was discovered that quartz in these samples showed a strong response to IR stimulation, thought to be resulting from feldspar present as 131 Supplements inclusions, and therefore feldspar had to be used for analysis although it is only present in very low quantities. 3 IRSL dates were obtained in Institute for Geology and Palaeontology, University of Innsbruck, Austria. The Middle Pleistocene age of the glacio-fluvial sandy layer in the upper part of the section at 2250 m a.s.l. was obtained. It is older age than all previously published dates for the upper part of the section. Geochemical analysis reveals a significant difference in content of petrogenic oxides between this layer and other glacial stratums, suggesting a possible change the source area and pattern of sedimentation in the upper part of the section. The small number of IRSL dates obtained does not allow assessment of the appropriateness of using this method for age estimation of glacial sediments, which remain one of the most difficult types of continental deposits for dating. We can also assume a relatively low number of depositional cycles for the grains in this section and a short transport which also complicate luminescence dating. Radiocarbon dates of carbonate concretes from the bottom and the middle part of the glacial complex in the Chagan section generally correlate to each other but poorly agree with the stratigraphic position and return the ages of another order of magnitude in comparison with the luminescence dates. Some difficulties of applying radiocarbon method for dating such type of material were discussed in [5]. The problems of radiocarbon age measurement for lacustrine carbonate samples from the Pleistocene Lake Lahontan, Nevada, USA are presented by Lin and coauthors [6]. They reported systematically younger ages and explain it with the problems of contamination with secondary calcite and the local reservoir age correction. We consider all obtained radiocarbon dates for the Chagan section as invalid. Thus, the age of Pleistocene glacial sediments and landforms within the Russian Altai remains a mainly relative determination. The large spread in ages of deposits in reference sections within the Russian Altai and the weak provision of some of them with absolute dates do not allow the correlation of glaciations between different oroclimatical zones of Russian Altai, or further comparison with the other mountain systems of Central Asia and Siberia. The adopted scheme of correlation between Altai and Siberia glaciations, based on the first TL dates of Chagan section, needs to be improved.

The study was partly funded by the Russian Foundation for Basic Researches (grants 13- 05-00555; 15-05-06028).

REFERENCES 1. Svitoch A.A., Boyarskaya T.D., Voskresenskaya T.N., Glushankova I.I., Evseev A.V., Kursalova V.I., Paramonova N.N., Faustov S.S., Khorev V.S. 1978. The sections of the latest deposits of Altai. MSU Publisher, Moscow, 208 p. (In Russian). 2. Wagner, G.A. 1998. Age Determination of Young Rocks and Artefacts, Heidelberg, Berlin and New York: Springer-Verlag, 466 p. 3. Agatova, A.R., Devyatkin, E.V., Vysotsky, E.M., Skobelitcin, G.A., Nepop, R.K. 2004. Results of using TL method for dating glacial sediments of the Chagan section (SE Altai). Proceed. 38Plenum of Geomorphological commission , Novosibirsk, 7-9. (In Russian) 4. Agatova, A.R., Nepop, R.K., Rodnight, H. 2014. On the problems of correlating the Pleistocene glacial deposits in Russian Altai with Siberian stratigraphic scales. In: STRATI 2013 First International Congress on Stratigraphy At the Cutting Edge of Stratigraphy. Rocha R., Pais J., Kullberg J.C., Finney S., (Eds.) 2014. Springer, 903-907. 5. Aitken, M.J., 1990. Science-Based Dating in Archaeology, London: Longman, 274 p. 6. Lin, J.C., Broecker, W.S., Anderson, R.F., Hemming, S., Rubenstone, J.L., Bonan, G. 1996. New 230Th/U and 14C ages from Lake Lahontan carbonates, Nevada, USA, and a discussion of the origin of initial thorium, Geochimica et Cosmochimica Acta, 60(15), 2817-2832.

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Supplement 3

THE RECURRENCE INTERVAL OF STRONG PREHISTORIC EARTHQUAKES IN THE SE ALTAI (THE KURAY-CHUYA ACTIVE ZONE) BASED ON DENDROSEISMOLOGICAL APPROACH AND RADIOCARBON ANALYSIS

Nepop R.K.1, Agatova A.R.1, Myglan V.S.2, Nazarov A.N.2, Barinov V.V.2 1 Institute of Geology and Mineralogy, Russia, [email protected] 2 Siberian Federal University, Russia, [email protected]

The evolution of paleoseismogeological studies clearly demonstrates that in order to properly understand the seismic potential of a region, and to assess the associated seismic hazard, extensive studies are necessary to take full advantage from the geological evidence of past earthquakes. The period of instrumental seismological observations is insignificant in comparison with the recurrence interval of strong earthquakes. Thus to achieve these goals the historical data are being involved. Paleoseismogeology supplements historical and instrumental records of seismicity by characterizing strong prehistoric earthquakes. It is focused on studying ground effects (both primary - ruptures, and secondary - gravitational deformations) from past earthquakes preserved in the geologic and geomorphic environment. We present the results of our paleoseismogeological investigations of the high mountain, seismically active southeastern part of the Russian Altai (Fig.1), which reveal a previously unknown complex of earthquake induced landslides in the Arydjan valley. Using dendrochronological analysis of the wood penetrating injuries of trees (both dead and living ones) caused by seismically induced rockfalls allowed establishing the date of previously unknown strong medieval earthquake (Fig.1 A). This date was also verified by radiocarbon dating of seismically cut fossil soil overlapped by undistorted one (Fig.1 B) [1]. The presented study was focused mainly at the epicenter zone of the 2003 Chuya earthquake. Fault bounders of the Chagan-Uzun massif were reactivated during this the largest historical seismic event. Newly arisen and renewed scarps and ruptures gave a unique opportunity to study previously unknown evidences of strong prehistoric earthquakes. A lot of suitable material was collected in the Taldura river valley (southern fault bounder of the Chagan-Uzun massif) where the giant landslide was triggered (Fig. 2).

Fig. 1. Southeastern part of Russian Altai. Study sites A) in the Arydjan valley and results of dendrochronological analysis; B) in the Taldura valley and results of radiocarbon dating.

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To reconstruct the regional chronology of strong earthquakes the radiocarbon dating of various types of available organic material was applied. The ages of seismically cut or deformed fossil soils with wood/charcoal fragments return the low possible date of seismic event while overlaid undistorted layers give information about its upper possible date. Fossil soils buried by colluvium sediments at the foot of the steep slopes mark periods of tectonic repose and soil formation which were later altered by intensive slope mass movements. The age of buried peat layers as well as organic material in lacustrine deposits returns the upper possible date of earthquakes that coursed peat bog or lake formation in the proximal part of landslide (Fig.3).

Fig. 2. Giant landslide triggered by the 2003 Chuya earthquake in the Taldura valley: A) inner structure and B) frontal part.

Fig. 3. Seismic convolutions in paleolacustrine sediments exhumed in outcrop of seismically triggered landslide within the epicenter zone of the 2003 Chuya earthquake, which evidence for repeated reactivation of the same focal zones within the SE Altai during the Holocene.

25 new radiocarbon dates of previously unknown evidences of prehistoric earthquakes along the fault bounders of the Chagan-Uzun massif argue for the high regional seismicity in the second half of the Holocene. Strong earthquakes occurred here about 600-700, 1300-1500, 2400-2700 and 3800-4200 cal. years BP. Together with the previously published radiocarbon dates [2, 3] this data clarify the chronology of seismic events within the SE Altai. The specified recurrence interval of strong (M≥7) earthquakes for the SE Altai is about 400 years during the last 4 000 years. This data argues for the high Holocene seismicity of the SE Altai and defines the Chagan-Uzun massif as one of the major regional seismogenerating structures. The study was partly funded by the Russian Foundation for Basic Researches (grants 13- 05-00555; 15-05-06028). REFERENCES 1. Agatova, A.R., Nepop, R.K., Barinov, V.V., Nazarov, A.N., Myglan, V.S. 2014. The first dating of strong Holocene earthquakes in Gorny Altai using long-term tree-ring chronologies, Russian Geology and Geophysics, 55, 1065–1073. 2. Rogozhin, E.A., Platonova, S.G. 2002. Source Areas of Holocene Large Earthquakes in Gorny Altai [Ochagovye zony siljnyh zemletrjasenij Gornogo Altaya v golocene], Moscow: IFZ RAN, 130 p. (in Russian). 3. Rogozhin, E.A., Ovsyuchenko, A.N., Marakhanov, A.V., Ushanova, E.A. 2007. Tectonic setting and geological manifestations of the 2003 Altai earthquake, Geotectonics, 41(2), 87-104.

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Supplement 4

RADIOCARBON CHRONOLOGY OF THE HOLOCENE LANDSCAPE EVOLUTION WITHIN THE KURAY-CHUYA SYSTEM OF INTERMOUNTAIN DEPRESSIONS

Nazarov A.N.1, Agatova A.R.2, Nepop R.K.2, Bronnikova M.A.3 1 Siberian Federal University, Russia, [email protected] 2 Institute of Geology and Mineralogy, Russia, [email protected] 3 Institute of Geography, Russia, [email protected]

Reconstruction of intricate Pleistocene-Holocene evolution of mountain landscapes requires accurate genetic typification of deposits and chronological data of each relief- forming process. Time is a fundamental parameter in such historically oriented disciplines, such as geology, geography, and geomorphology. Imprinted in landscape and in sediments events are not informative and factual unless they are not organized in the chronological order. Only after the ordering in time the cause-and-effect relationships between them could be studied. During the last decade we obtained a numerous dataset of more than 150 radiocarbon dates which characterize various Holocene nature events within the Kuray-Chuya system of intermountain depressions and framing ridges [1, 2, 3, 4]. This area is famous worldwide for cataclysmic glacial outburst floods which were released from ice-dammed lakes. During the Pleistocene glaciations, glaciers extended repeatedly from the high ranges into the major valleys and impounded extensive lakes in intermountain depressions. Subsequent ice-dam failures led to outburst floods ranked within the largest known terrestrial discharges of fresh water. But the chronology of glacier advances as well as ice-dam outburst floods is still debated mainly due to the problem of absolute dating of glacial deposits and contradictory dates obtained by different techniques [5]. The Holocene hydrological system transformation was closely related and influenced by the draining of these Pleistocene lakes. The last common for both depressions ice-dammed reservoir was disintegrated by the beginning of the Holocene. In the first half of the Holocene there was just a system of separate lakes which were connected by Chuya River. All cataclysmic flood events related to the hydrological changes occurred before 8 -10 ka BP but during the whole Holocene fluvial system remained highly mobile. Recent glacier retreats and ice melting in moraines has led to exhumation of organic material allowing the possibility of radiocarbon dating. We report more than 50 new radiocarbon dates from wood remains buried by moraines and from proglacial forefields, from peat layers and lacustrine sediments that cover moraines, from dead trees at the upper tree limit, and from rock glaciers on trough slopes from the heads of glacial valleys in the North, South Chuya and Chikhachev ranges [1, 4]. Such a numerous dataset for the vast but unified in neotectonic and climatic conditions area is presented for the first time in the history of research in the Russian Altai. Together with the previously published radiocarbon ages, mainly of fossil soils and peat layers in the foot of the ranges in SE Altai, they form the basis for understanding the relative magnitudes and timing of the most important glacial and climatic events of SE Altai. The significantly extended radiocarbon data set of previously unknown evidences of prehistoric earthquakes in the SE Altai argue for the high regional seismicity here in the second half of the Holocene. Strong paleoearthquakes led to significant landscape changes including surface rupturing, landsliding and forming of landslide-dammed lakes in the major river valleys. Together with the previously published radiocarbon dates our data clarify the chronology of seismic events imprinted in landforms and sediments within the SE Altai [2, 3].

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To specify the recurrence interval of strong earthquakes we have also calibrated all previously published radiocarbon dates. Several radiocarbon dates were obtained for archaeological sites and provide valuable information for understanding paleolandscape characteristics and dating geomorphic processes and landforms [4]. Evolution of residual lakes in both depressions, high mobility of fluvial system, periodical glaciers advances in the mountain valleys of framing ridges, fluctuation of the upper timber limit, soils formations, aeolian activity, vast forest-fires – were determined by contrasting climate changes. The general trend of these changes is climate cooling and aridity intensification in the second half of the Holocene in this part of Central Asia. It should be emphasized that interpretation of dating results often varies, regardless of dating technique. Thus the age of dead tree, which was melted out from moraine, could be interpreted as the time of glacier advance (i.e. the period of climate deterioration) or the time tree growing in the head of troughs in a modern glacial zone (i.e. the period of climate conditions favorable for forest vegetation and location of the ancient upper tree limit above the modern one). Both interpretations are acceptable [1, 6] and should be verified by other proxi data (such as, for example, ages of paleosoils and paleopeat in the mountain valleys). At the same time the problems of absolute dating and age interpretations of paleosoils are well known. Due to gravitation and openness of the soil system, the radiocarbon dates of paleosoils are usually interpreted as “minimal ages of their burning”, when the process of soil formation can take several thousands years. Therefore in spite of impressive set of obtained radiocarbon dates the available information could not be considered as exhaustive. It is necessary to expand the dataset of chronometric dates which characterize the whole complex of surface processes and allow specifying paleogeographical and paleoclimate reconstructions. The study was partly funded by the Russian Foundation for Basic Researches (grants 13- 05-00555; 15-05-06028).

REFERENCES 1. Agatova, A.R., Nazarov, A.N., Nepop, R.K., Rodnight, H. 2012. Holocene glacier fluctuations and climate changes in the southeastern part of the Russian Altai (South Siberia) based on a radiocarbon chronology, Quaternary Science Review, 43, 74–93. 2. Agatova, A.R., Nepop, R.K., Slyusarenko, I.Yu., Myglan, V.S., Nazarov, A.N., Barinov, V.V. 2014. Glacier dynamics, palaeohydrological changes and seismicity in southeastern Altai (Russia) and their influence on human occupation during the last 3000 years, Quaternary International, 324, 6-19. 3. Agatova, A.R., Nepop, R.K., Barinov, V.V., Nazarov, A.N., Myglan, V.S. 2014. The first dating of strong Holocene earthquakes in Gorny Altai using long-term tree-ring chronologies, Russian Geology and Geophysics, 55, 1065–1073. 4. Agatova, A.R., Nepop, R.K., Bronnikova M.A., Slyusarenko, I.Yu., Orlova, L.A. 2014. Human occupation of South Eastern Altai highlands (Russia) in the context of environmental changes, Archaeological and Anthropological Sciences. DOI 10.1007/s12520-014-0202-7 5. Agatova, A.R., Nepop, R.K., Rodnight, H. 2014. On the problems of correlating the Pleistocene glacial deposits in Russian Altai with Siberian stratigraphic scales. In: STRATI 2013 First International Congress on Stratigraphy At the Cutting Edge of Stratigraphy. Rocha R., Pais J., Kullberg J.C., Finney S., (Eds.) 2014. Springer, 903-907. 6. Nazarov, A.N., Agatova, A.N., 2008. Glacier dynamics in the North Chuya range, Central Altai, during the second half of the Holocene (Dinamika lednikov Severo-Chujskogo hrebta na Central’nom Altae vo vtoroj polovine golocena), Materials of Glaciological Investigations (Materialy gljaciologicheskih issledovanij), 105, 73-86 (in Russian).

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