The role of pingos in the development of the Dzhangyskol lake-pingo complex, central Altai Mountains, southern Siberia
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Available online at www.sciencedirect.com Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404 – 420 www.elsevier.com/locate/palaeo The role of pingos in the development of the Dzhangyskol lake–pingo complex, central Altai Mountains, southern Siberia T.A. Blyakharchuk a,⁎, H.E. Wright b , P.S. Borodavko c,d , W.O. van der Knaap e , B. Ammann e a Laboratory of Bioinformation Technologies, Institute for Monitoring of Climatic and Ecological Systems SB RAS, Akademicheskii prospekt 10/3, 634055 Tomsk, Russia b University of Minnesota, Limnological Research Center, 220 Pillsbury Hall, 31 Pillsbury Drive S.E., Minneapolis MN 55455, USA c Laboratory of the Self-organisation, Institute for Monitoring of Climatic and Ecological Systems SB RAS, Akademicheskii prospekt 10/3, 634055 Tomsk, Russia d Problem Scientific Laboratory of Glacioclimatology, Tomsk State University, Lenina 36, 634050 Tomsk, Russia e Institute of Plant Sciences, Altenbergrain 21, CH 3013 Bern, Switzerland Received 20 April 2007; received in revised form 15 September 2007; accepted 24 September 2007 Abstract Dzhangyskol is a small lake of glacial origin in the central part of the Altai Mountains in southern Siberia. Pollen stratigraphies and chronologies of two cores record the vegetational development of the area from the Late Glacial treeless landscape to the forest and steppe of today. The modern lake is a remnant of a much larger ice-dammed lake, which was reduced in size and then temporarily drained after diversion of the inflowing mountain meltwater stream, which had low δ18O values. The dry lake floor allowed development of permafrost and small pingos (frozen mounds of lake sediments). With the onset of greater climatic humidity in the mid-Holocene, the input of local water with higher δ18O caused a rise in lake level, drowning the earlier pingos. Growth of a broad fen on the margin of the lake led to formation of a modern pingo complex. © 2007 Elsevier B.V. All rights reserved. Keywords: Altai Mountains; Holocene; Pollen data; Vegetation; Climate; Pingos; Oxygen isotopes 1. Introduction flora. Climatically they are at the crossroads of Atlantic, polar, and inner-Asian air masses. Biomes of desert, The Altai Mountains are situated near the center of steppe, mountain forest, alpine shrubland, and grassland the Eurasian continent and are well known in biogeog- reflect the climatic diversity. For Late Glacial and raphy for their high biodiversity and their central Holocene palaeoecological reconstructions the best function in the dynamics of the Eurasian mountain archives are in mountain lakes in formerly glaciated areas. Peat in fens or bogs in the Altai Mountains started to form only in the second half of the Holocene ⁎ Corresponding author. (Chernova, 1988; Schulz and Lehmkuhl, 2007). E-mail addresses: tarun5@rambler.ru (T.A. Blyakharchuk), hew@umn.edu (H.E. Wright), bor@ggf.tsu.ru (P.S. Borodavko), In the northern foothills of the mountain massif knaap@ips.unibe.ch (W.O. van der Knaap), ammann@ips.unibe.ch Severo Chuiskii and southwest of the Kurai intermon- (B. Ammann). tane depression is the lake Dzhangyskol (Fig. 1), 0031-0182/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2007.09.015
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 405 Fig. 1. Location of Dzhangyskol (1). Ulagan (2) (Blyakharchuk, 2003) and Tuva (3) (Blyakharchuk et al., 2007) areas in the Altai Mountains are marked. K = Kurai depression. bordered mostly by fen vegetation on frozen peat and on the ancient lake. Butvilovsky (1993) published a the south by a complex of small pingos, which are here generalized stratigraphy of a pingo on the south side frozen mounds of coarse-detritus organic lake sediments of the lake and obtained 10 radiocarbon dates (Table 1C) (gyttja) (Fig. 2). Earlier investigators (Okishev, 1982; covering the Late Glacial and parts of the Holocene. The Butvilovsky, 1993) concluded that the modern Dzhan- time interval between 10 and 7 14C ka BP is not gyskol is a secondary lake formed by thermokarst represented in the lacustrine sediments of his pingo. processes in the exposed sediments of an ancient lake. The present paper focuses on the following ques- More likely the primary lake was a meltwater lake tions: What was the origin of Lake Dzhangyskol? How dammed by the Kurumdu glacier around 13,000 14C yr and when did the fen and the pingos form? How do the BP (Borodavko and Akmatov, 2003). The modern lake sediments of the modern lake relate to the ancient lake Dzhangyskol is much smaller. It inherited sediments of sediments found in the pingos? Can we confirm the
406 T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 2. Site description 2.1. Topography, hydrology, climate Dzhangyskol (Lat. 50°11′N, Long. 87°44′E, ca. 1800 m asl (Fig. 1) is a lake situated in the western part of the Kurai intermontane depression in the central Altai Mountains. The Kurai depression is covered with steppe vegetation and is bounded by small hills with Pi- nus sibirica and Larix sibirica. The village Kurai is situated in the middle of the Kurai depression. The Chuya River crosses the depression from southeast to northwest. The Kurai depression is bounded on the south by the Severo Chuiskii Mountains and on the north by the Kurai Mountain massif. The climate is markedly continental. Summers are hot and short, and winters are long and very cold. Annual precipitation is 100–150 cm, with a marked maximum in summer and a thin snow cover in winter. Average annual temperature is − 7 °C at Kosh Agach east of the area. Winters are especially severe (absolute minimum temperature − 62 °C), and altitudinal temperature inver- sions cause the occurrence of discontinuous permafrost. Fig. 2 shows the complex of lake, fen, and pingos, bordered on the south by glaciofluvial fans of streams from the mountains. The mountain slopes are covered primarily by forests of Pinus sibirica. To the north are low hills with meadow-steppe on the slopes and patches of larch (Larix sibirica) forest above. Similar open vegetation covers the piedmonts to the south-southwest. Because of the small water depth (average 2–2.5 m), the lake is well warmed in the summer. The water Fig. 2. Above, Dzhangyskol–Karakol piedmont area between the temperature reaches 16–17°, favourable for growth of Severo Chuiskii Mountains and the Chuya River. Below, aerial abundant water plants. At present the Kurkurek River photograph of the area of investigation. (1) Dzhangyskol, (2) frozen fen, (3) pingo complex, (4) steppe, (5) forest of Larix sibirica on the approaches the lake from the fans on the mountain slope hills, (6) Kurumdu River, (7) thermokarst pools, (F) location of the Fen to the southwest and flows along the southern boundary of core (Fig. 6). Modern pingos are white, thermokarst pools are black. the pingo complex but does not enter the lake. Original air photo enhanced by computer by R.O. Megard. Dzhangyskol has a small outlet on the west through the pingo complex that joins the Kurkurek River. The pingos are about 3–6 m tall and are composed of frozen lacustrine early-Holocene time gap found in the data of Butvi- sediment with abundant plant fragments. Circular pools lovsky? How did the vegetation and climate change within the pingo complex mark thermokarst depressions. during development of this lake–pingo complex? Is The lake is bordered on the east by frozen fen, on which human impact on the environment recorded? circular patterns have the same scale as the thermokarst We addressed these questions by obtaining two pools of the pingo complex, as if they were part of the cores, one from the center of the lake (termed the lake pingo area that had been drowned by a rise of lake level core) and one from the edge of the adjacent fen next to and then overgrown by peat. Measurements showed that the modern pingo complex (termed the fen core). Pollen permafrost is located closer to the surface in these circular analysis and radiocarbon dating of the two cores, along patterns than in neighbouring areas, which in addition are with oxygen-isotope analysis of the lake core, reveals a wetter. Similar patterns faintly visible under the lake water complicated history of vegetational development and are interpreted as old flooded and eroded pingos. lake-level changes. Permafrost cannot survive under water bodies.
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 407 Table 1 Dzhangyskol 14C dates BP and calibrations Lab. no. Depth Lithology Material Age Age Age range 14 (cm) C yr BP cal yr BP cal yr BP (1Σ) A. Dzhangyskol Lake core CURL 5329 213–216 Gyttja Larix, needle 4150 ± 40 4686 4569–4826 CURL 5328 256–260 Gyttja Rumex, Larix, chenopod seeds 4830 ± 40 5549 5471–5648 AA45774 265–267 Gyttja Charcoal 7020 ± 200 7649 7546–8200 Poz-4404 274–275 Marl Wood, charcoal 8170 ± 50 9125 9010–9275 AA45773 283–285 Gyttja Carex seeds 11,360 ± 710 13,389 11,535–15,439 CURL 5974 289–296 Gyttja Larix needles, Betula fruit, charcoal 8660 ± 140 9706 9467–10,152 CURL 4012 307–308 Gyttja Carex seed, bark 10,750 ± 60 12,634 12,620–12,999 CURL 4349 329–330 Gyttja Betula fruit, charcoal 10,820 ± 190 12,846 12,295–13,193 CURL 4013 410–412 Gyttja Larix needle, charcoal 9890 ± 60 11,297 11,173–11,362 CURL 4014 425–428 Gyttja Chenopod seed, wood, charcoal 10,150 ± 60 11,778 11,548–12,154 CURL 4015 464–466 Silt Charcoal 10,450 ± 90 12447 12,049–12,822 B. Dzhangyskol Fen core CURL 4836 120–122 Silty gyttja Carex seed, charcoal 890 ± 30 816 808–911 Utc-8467 186 Gyttja Twig, root 330 ± 29 387 310–465 CURL 4837 229–231 Gyttja Carex seed, charcoal 2310 ± 30 2316 2305–2355 Utc-8355 278 Gyttja Riccia 7672 ± 46 8447 8382–8542 Utc-8468 318 Gyttja Bark, charcoal 6440 ± 120 7186 7152–7262 Utc-8469 350 Gyttja Charcoal 6262 ± 42 7349 7156–7571 CURL 4838 401–404 Gyttja Carex seed, charcoal 6030 ± 45 6862 6745–6990 CURL 4838 410–412 Gyttja cf. Ceratophyllum seed 6050 ± 45 6866 6780–7004 CURL 5067 428–429 Gyttja Charcoal, terrestrial epidermis 6780 ± 50 7269 7566–7691 Utc-8470 456 Silt Equisetum, charcoal 13,050 ± 150 15,637 14,543–16,224 C. Butvilovsky (1993), pingo 20 Peat Peat 1880 ± 60 1814 70 Gyttja + cryoturbated peat Peat 2100 ± 100 2082 105 Gyttja Gyttja 2240 ± 70 2232 195 Gyttja Gyttja 2450 ± 95 2530 250 Silty clay Plant macrofossils 3320 ± 20 3541 270 Gyttja Gyttja 3780 ± 35 4153 325 Silty clay Plant macrofossils 4765 ± 120 5482 420 Silty clay Plant detritus 10,845 ± 80 12,909 440 Silty clay Plant detritus 10,960 ± 50 13,000 585 Clay Ca. 13,000 15,592 Radiocarbon dates. Symbols for laboratories: AA, University of Arizona; CURL, University of Colorado; Poz, University of Poznań; Utc, University of Utrecht. For the pingo from Butvilovsky (1993), the depths of the radiocarbon dates are measured from his Fig. 52 assuming a total sediment depth of 6 m as mentioned in his text on page 177, whereas the total depth of 16 m shown on his Fig. 52 must be erroneous. The pollen stratigraphy in his Fig. 52 is problematic to read but seems well correlated with that of the fen site, and the above radiocarbon dates for the pingo reflect the unconformity between zones DZH-3 and DZH-5 at the fen site. 2.2. The modern vegetation slopes of the Kurai Mountains are xeric, and alpine vegetation is developed at higher elevations. Scarce trees According to Kuminova (1960) Dzhangyskol is of Picea obovata and Larix sibirica grow along the situated in the Kurai steppe, which belongs to the banks of the Tute and Akturu rivers flowing through the Chuya high-mountain steppe district of the southeastern Kurai steppe. Locally bordering Dzhangyskol on the subprovince of the Altai Mountains. On stony soils it is a north is a rich meadow-steppe vegetation, with Festuca desert-steppe, on chestnut-coloured and poor chernozem lenensis, Hordeum brevisubulatum, Hedysarum seti- soils a turf-grass steppe, and in river valleys and in wetter gerum, H. sangilense, Gentiana decumbens, Viola places are meadows and patches of kobresian tundra. On altaica, and Linaria acutiloba. On the frozen fen on the northern slopes of the Severo Chuiskii Mountains are the eastern and western margins of the lake the forests of Pinus sibirica and Larix sibirica. The summits vegetation consists mostly of sedges (Carex rostrata, are covered with alpine vegetation. The south-exposed C. diandra, C. juncella, and C. canescens).
408 T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 Human influence on the vegetation of the Kurai steppe shrubby Betula in the Altai Mountains (B. nana and in modern time is connected with grazing of sheep and B. humilis). horses on steppe areas and meadows. Dark-coniferous A total of 300–500 pollen grains of trees plus all forests with Pinus sibirica, Abies sibirica, and Picea other pollen and spore taxa were counted at each obovata cover large areas of the Altai Mountains a few analyzed level. Percentages of all taxa were calculated hundred kilometers southwest and northeast of the Kurai on the basis of a pollen sum including all pollen and intermontane depression. Southeast of the Kurai steppe spore types of vascular plants except those of water upstream along the Chuya River is the wide Chuya plants, wetland plants, and minor types redeposited or of intermontane depression, covered by drier desert-steppe. long-distance transport. Pollen taxa were grouped in the Both intermontane depressions are influenced by arid categories Trees, Shrubs, High-elevation plants, Dry- continental air masses penetrating from the southeast from soil herbs, Ruderals, Mesophilous herbs, Wetland Mongolia along the Chuya and Katun' valleys. But the plants, Aquatics, and Long-distance and Redeposited. Kurai intermontane depression is closer to the central Altai These groups are not absolute, because some pollen Mountains and is influenced also by precipitation brought types can represent plants of different ecological groups. by Atlantic cyclones from the west, mostly in the summer. High-elevation plants, for example, grow most abun- As a result it is covered not by desert-steppe but by real dantly but not exclusively at high elevation. steppe and meadow-steppe. Increasing continentality from Pollen diagrams were constructed with the PC west to east across the Altai Mountains promotes the programs TILIA and TILIA-Graph (Grimm, 1991). The spread of Larix forest with admixture of Pinus sibirica on depth scale for the lake core is referenced to the water the slopes of the central Altai Mountains, contrasting with surface (water depth 120 cm). The scale for the fen core is the dark-coniferous forests on the western slopes, which referenced to the peat surface, which is 10 cm above the far to the west grade into Pinus sylvestris forests and lake. The peat itself is 130 cm thick and overlies lake finally to forests of Betula pendula on the western sediment. piedmonts of the Altai Mountains. The latter extend to The pollen-percentage diagrams for the lake and fen the steppes of Western Siberia and Kazakhstan. cores are divided into six Local Pollen Assemblage Zones (LPAZ) according to dominant and diagnostic pollen 3. Materials and methods types. The prefix DZH is used to designate the site. For measurement of ratios of stable isotopes of carbon In summer 1998 two cores were obtained with a and oxygen 15 samples from the lake core were analyzed square-rod piston corer (Wright, 1991). The top meter of in the laboratory of Emi Ito at the University of the lake core was taken with a transparent plastic tube Minnesota. The fen core had insufficient carbonate for fitted with a piston. It overlapped the long core at 65 cm measurement. and was subsampled in the field while vertical. The fen Terrestrial-plant macrofossils were dated by the core came from the narrow thawed margin of the fen AMS-radiocarbon technique at the R.J. van de Graaff near the outlet stream on the west side of the lake. laboratory in Utrecht (The Netherlands), the University For pollen analysis 1-ml samples were prepared. of Colorado (USA), the University of Arizona (USA), Pollen analysis was carried out by the first author in the and the University of Poznań, Poland. All original Institute of Biology and Biophysics in Tomsk (Russia) radiocarbon dates were calibrated to calendar years under 400× magnification. Throughout the cores the referenced to year AD 1950 with CALIB 4.4 (http:// pollen concentrations were sufficient for analysis, and depts.washington.edu/qil/dloadcalib/). 14C dates and preservation was good. For identification of pollen and uncalibrated ages from the literature were also calibrated spore taxa the works of Kupriyanova (1965), Kupriya- in order to correlate events with the record from the nova and Aleshina (1972, 1978), Bobrov et al. (1983), Ulagan Plateau and the Tuva Republic in the Altai and Moore et al. (1997) were used. Nomenclature of Mountains (Blyakharchuk et al., 2004, 2007) and from pollen and spore types follows the conventions of the other sites. EPD (European Pollen Database, Arles, France). The type “Bryales/Algae” is an informal name corresponding 4. Results to types 403, 227, and 234 of van Geel et al. (1981, 1989), and also to some types of Bryales spores (Katz 4.1. The depth–age relations (Fig. 3, Table 1) et al., 1977). Pollen of Betula species was identified according to the descriptions of Kupriyanova (1965), in For estimation of the absolute age of the palaeogeo- which Betula nana-type pollen includes pollen of all graphic events, 21 AMS-radiocarbon dates were used
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 409 for the two investigated cores (11 for the lake core and 4.3. The pollen record (Figs. 4 and 5) 10 for the fen core; Table 1A, B). In addition 10 dates measured by decay counting are available from a pingo 4.3.1. DZH-1: Picea–Abies LPAZ (Lake 495–440 cm; (Butvilovsky, 1993) (Table 1C). Fen, not present) The depth/age relations for both cores are plotted on This pollen zone was found only in the basal silt of the the same graph (Fig. 3). The curve for the lake core has a lake core. It is characterized by relatively high percent- middle nearly horizontal segment marking an unconfor- ages of conifers (Picea obovata, Pinus sylvestris, mity between DZH-4 and DZH-6. For the fen core a P. sibirica, Abies sibirica) together with tree Betula, horizontal segment at 440 cm marks a related unconfor- B. nana, and Cyperaceae. Pollen of various temperate mity at the base of DZH-5. The fen core has a middle trees must be reworked from older deposits eroded by the vertical segment (C group) that marks a brief interval of glacier (Tsuga, Quercus, Corylus, Juglans, Carya, Pter- rapid deposition of more than 1.5 m of sediment in a few ocarya, Podocarpus). Aquatic macrophytes are lacking hundred years or less. The three old dates for the lake core except for single finds of Potamogeton. (B group) are rejected, as they are probably reworked from older sediments, as explained in the discussion. The 4.3.2. DZH-2: Chenopodiaceae LPAZ (Lake 440– date at 278 cm of 8447 cal yr BP for the fen core is rejected 425 cm; Fen, not present) because it was made on the remains of a submerged This pollen zone is also found only in the lake core, aquatic plant and is therefore subject to reservoir effects. where it occurs in the upper part of the silt. The marked decrease of tree pollen at the base of the zone is matched 4.2. Lithology by a clear maximum of Chenopodiaceae (60%). Most of the other dry-soil types continue. Reworked pollen is The lake core consists of 65 cm of silt overlain by still found but in lower numbers. 310 cm of silty gyttja. The fen core consists of 330 cm of silty gyttja. Results of LOI are shown in Figs. 4 and 5. 4.3.3. DZH-3: Artemisia LPAZ (Lake 425–382 cm; The overlying 130 cm of peat was not collected because Fen 457–440 cm) of deeply rooted sedges, and because the youngest time This pollen zone occurs in the lake core as the first interval was more reliably covered by the lake core. LPAZ in gyttja, but in the fen core it is poorly devel- oped in silt. It is characterized in both cores by high values of Artemisia and by other taxa of open areas, but the diversity is less than in DZH-2 and DZH-1. Tree pollen is at a minimum except for Larix, which shows a slight maximum. Reworked pollen is absent. Among water plants Potamogeton increases, Myriophyllum appears, and Bryales/Algae shows a maximum in the lake core. 4.3.4. DZH-4: Pinus–Abies–Artemisia LPAZ (Lake 382–273 cm; Fen, not present) This zone shows lower values of Artemisia and higher of Pinus sibirica, P. sylvestris, Picea obovata, and Abies sibirica. Pollen of Abies sibirica has a maximum only in this LPAZ. Indicators of open treeless areas are still common (Artemisia, Chenopodiaceae, Ephedra, Hor- deum, Thalictrum, Rosaceae, and Poaceae). Among water plants, macrophytes such as Potamogeton and Myr- iophyllum (two species) as well as Bryales/Algae show relatively high frequencies. 4.3.5. DZH-5: Pinus sibirica–Cyperaceae LPAZ (Lake, Fig. 3. Depth-age relation for the lake core and the fen core. Groups of 14 C dates designated by letters are explained in the text. Depth-age not present; Fen 440–280 cm) model for the lake core shows pollen samples as small circles, for the DZH-5 is present only in the fen core, for in the lake fen core as small rectangles. core an unconformity cuts it out except for one dated
410 T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 Fig. 4. Pollen diagram for the lake core. Vertical scale is depth below lake surface. Water depth is 120 cm.
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 411 Fig. 5. Pollen diagram for the fen core. Vertical scale is depth below peat surface.
412 T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 level, and DZH-4 there is overlain directly by DZH-6, 5. Discussion thus separating the early Holocene from the late Holocene without the intermediate middle Holocene. The radiocarbon dates indicate that the two cores The dominance of tree pollen involves mainly cover different time intervals and have unconformities at Pinus sibirica but also P. sylvestris. Indicators for open different levels, implying a complicated history for the vegetation decline slightly, but their diversity increases. lake. The presence of the large area of pingos south of Cyperaceae is conspicuously higher than below, under- the lake and the image of the drowned pingos beneath standable because the expanding fen was approaching the lake (Fig. 2) add unusual features to the history of the coring site. Otherwise the composition of DZH-5 lake development. The isotope stratigraphy is yet differs little from that of DZH-4, but the radiocarbon another factor that requires integration in the recon- dates place DZH-4 in the early Holocene (11–9 ka cal struction. In the discussion that follows, the vegetation BP) and DZH-5 in the mid-Holocene (8–7 ka cal BP). phases as shown on the pollen diagrams are considered first, and then speculations are offered to explain the 4.3.6. DZH-6: Pinus sibirica LPAZ (Lake 280–120 cm; lake-level changes and development of pingos, as Fen 280–130 cm) illustrated by Fig. 6 and Table 2. In the lake core this zone extends to the surface of the sediment beneath 120 cm of water. It includes the short 5.1. Vegetation history core of the uppermost soft sediment. At the fen site the peat at the top (0–130 cm) was not collected. In the 5.1.1. Late Glacial (DZH-1 and DZH-2; 13.0–11.7 cal lake core some indicators of human impact are present, ka BP) such as Triticum and Secale, as well as increasing The lowest pollen-zone DZH-1, found only in the charcoal and signs of lake eutrophication (Bryales/ lake core, contains a special combination of NAP and Algae, Potamogeton, Myriophyllum verticillatum, AP. The NAP reflects periglacial tundra-steppe with M. alterniflorum). predominance of sedges, along with some Artemisia and grasses and a relatively high diversity of other herb 4.4. Stable isotopes types. An open landscape prevailed, with incipient soils and patches of vegetation consisting of turf-sedges, The stable-isotope analyses of samples from the lake grasses, and pioneer species of Cruciferae and Compo- core (Fig. 4) show a striking increase in the values for sitae. Much of the area was bare, promoting accumu- δ18O from about − 17 to − 9 per mil at 260 cm, close to lation of gray silt in the lake. The climate was cold and the unconformable pollen-zone boundary DZH-4/DZH- dry. This reconstruction conforms to the opinion of 6. The higher level continues upwards, with values Lavrenko (1981) that the cold periglacial steppes were similar to those at the nearest stations that monitor the largely covered with sedges and grasses. Remnants of isotopic values of modern precipitation (Rozanski et al., such vegetation still exist in the modern Kurai steppe, 1993). A very low δ18O value of − 17 is usually found with turf-plants such as Kobresia myosuroides, Carex only in high mountains or at very high latitudes. Here it sabynensis, C. duriuscula, C. supina, Luzula confusa, represents meltwater from mountain glaciers to the south Koeleria cristata, Festuca kryloviana, and F. lenensis. of the area. The unconformity in the lake core between The first two of these species have disjunct areas in the DZH-4 and DZH-6 marks the time of low lake level Siberian arctic and in the mountains of southern Siberia when the mid-lake site was exposed to erosion before (Flora Sibiri vol. 2–3, 1990a,b). being flooded again in the late Holocene — this time by AP may have different sources. The exotic tree pollen water of local nonglacial origin rather than by mountain (Tsuga, Tilia, Quercus, Pterocarya, etc.) had poor water, and thus it has higher values of δ18O. The preservation and must be reworked from much older proportional increase of local water input to Dzhangys- sediments dating from a time when temperate-zone kol could have been caused by a regional increase of forest existed, suggesting that some of the major conifer precipitation, for the increase in forest cover occurred pollen may also be reworked, although the good about the same time, which is the time of the uncon- preservation of the conifer pollen does not support this formity (9–6.5 ka cal BP). This time is consistent with possibility. Local presence of conifers cannot be the expansion of forest patches in previously more demonstrated, for macrofossils and stomata were not widespread steppe vegetation at 9.5–8.5 ka cal BP in the found. Because of the low local pollen production of the Ulagan area, which is 30 km to the north (Blyakharchuk herbaceous vegetation the high pollen percentages of et al., 2004). major conifers (Picea, Pinus sibirica, P. sylvestris-type,
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 413 Abies) may be a result of mostly of long-distance relatively warm summers allowed aquatic micro- and transport, although the 20% Picea pollen far exceeds the macrophytes to increase in the lake. Tarasov et al. (1997) minimum of 5% taken to indicate local occurrence also reconstructed for the early Holocene a dry continental (Huntley and Birks, 1983), and Abies (5%) is a poor climate for a site near Semipalatinsk just to the west of the disperser of pollen. Even if presence of local trees Altai Mountains in the Kazakhstan plains, attributing the cannot be demonstrated, extensive regional forests can lack of trees to the low winter temperatures related to the be inferred at lower elevation in the Altai Mountains to insolation cycle. provide all the conifer pollen for distant transport. Ideas about refuges for trees and temperate herbs in 5.1.3. Early- and middle-Holocene forest development the Altai and Kuznetskii Alatau Mountains have been (DZH-4; 11.0–9.0 cal ka BP and DZH-5; discussed in the literature (Krylov, 1898; Tolmachev, 9.0–6.0 cal ka BP) 1954; Kuminova, 1957; Khlonov,1965; Razrez The long transition period from steppe to forest noveishikh otlozhenii Altaya, 1978; Polozhii and Kra- started in the early Holocene, as recorded in DZH-4 in pivkina, 1985; Levina et al., 1989; Baryshnikov, 1996). the lake core. The implied higher effective moisture Such a reconstruction of regional forests for DZH-1 reflects more precipitation rather than less evapotrans- implies warmer climatic conditions than in the following piration, for the still high values of Abies and of aquatic DZH-2, which is marked by 70% Chenopodiaceae pollen plants point to rather warm conditions. and only 15% AP. The dominance of Chenopodiaceae Forest belts probably developed first on mountain pollen in DZH-2 (to 70%) may reflect widespread pioneer slopes, where orographic rain provided more humidity. vegetation on the surface of the drained southern portion Steppe vegetation became restricted to intermontane of the basin. Modern investigations of the primary plant basins and to slopes exposed to the south. Comparison succession on the surface of coal-spoil hillocks in the may be made with the Ulagan high-mountain plateau of Kuzbass area about 400 km north show that Chenopo- the central Altai Mountains 30 km to the north diaceae species are the most abundant among pioneers (Blyakharchuk et al., 2004), where dense forests began (verbal information from Yu. A. Manakov, Kuzbass to spread after 9.5 cal ka PB in the Kurai intermontane Botanical Garden). On the other hand, chenopod maxima depression and on surrounding mountain slopes, but in are a widespread feature of cold and dry conditions for the lower-lying intermontane depressions the role of steppe Younger Dryas interval throughout Eurasia. Scarcity of vegetation was still considerable until 6.5 cal ka BP. aquatic plants suggests low water temperatures. During this period in shallow gorges and valleys of the If DZH-2 is correlated with the Younger Dryas, then Altai Mountains Pinus sibirica and Abies sibirica DZH-1 with its high AP pollen may represent the occurred together with Picea obovata. In steppes of preceding Bølling–Allerød warm phase. The radiocar- Kazakhstan west of the Altai Mountains Pinus sylvestris bon dates give some support for these correlations. forests expanded in this period because of increase in average winter temperatures (Tarasov et al., 1997). 5.1.2. The earliest Holocene Artemisia steppe (DZH-3; The early-Holocene DZH-4 is confined to the lake 11.7–11.0 cal ka BP) core, and it is overlain unconformably by the late- This pollen zone is found in both cores. The upland Holocene DZH-6. Although DZH-4 is missing from the vegetation was an Artemisia steppe with Ephedra and fen core, the forest assemblage recorded in DZH-4 of the other indicators of dry open landscapes. The reduction in lake core is continued in the mid-Holocene by DZH-5 of Chenopodiaceae from its dominance in zone DZH-2 to the fen core, although the latter is marked by a greater Artemisia dominance in zone DZH-3 indicates the diversity of NAP. Also, the two dates in DZH-4 are older inception of less arid conditions in the early Holocene. than 9 ka cal BP, whereas DZH-5 has five radiocarbon The end of the silt and beginning of gyttja deposition at dates in the range of 6.9 to 7.3 ka cal BP. Because of the the transition DZH-2/DZH-3 in the lake core imply difference in dates the two sequences are given different increased aquatic productivity, pedogenesis in the catch- labels, thus facilitating discussion of the lake-level history ment, less erosion of minerogenic matter, decrease of (see below). unvegetated surfaces, and increase of steppe communi- ties, which replaced the cold desert-steppe. Diatoms were 5.1.4. The late-Holocene forest phase with Pinus found for the first time, coincident with the increase in sibirica and P. sylvestris (DZH-6; 6.0–0 cal ka BP) organic matter (Westover et al., 2006). AP values are At the fen site DZH-6 shows continued forest lower than in the early Late Glacial. The inferred dry development from DZH-5 into the late Holocene. At the conditions prevented expansion of forest, although lake site the change is more conspicuous, because at the
414 T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 unconformity the early-Holocene values of AP are intermontane depressions and on the south slopes of succeeded by the stronger late-Holocene values, espe- riverbanks. Since that time P. sibirica and Larix sibirica cially in the case of Picea obovata. Accumulation of forests occupied larger areas in the central Altai gyttja took place in DZH-6 both at the lake site and in the Mountains than dark-coniferous forests of Picea and fen and pingo areas. This presumes that the lake level rose Abies because of increased continentality. The cooler and occupied again the full area of the lake–fen–pingo winters caused the spread of discontinuous permafrost complex, covering the eroded early pingos near both the after 2100 cal yr BP, and pingo formation increased. lake site and the fen site. As a result the sediments of the new Dzhangyskol in DZH-6 accumulated on the surface 5.2. Holocene lakes and pingos (DZH-3/DZH-6; of the dried DZH-4 at the lake site, producing the 11.7–0 cal ka BP) unconformity between DZH-4 and DZH-6, whereas the deposition at the fen site continued from DZH-5. Because The large Late Glacial lake of DZH-1 and DZH-2 the mountain stream had been diverted (see below), δ18O (Fig. 6, Stage A) received mostly clastic deposits because values of the carbonates (−9 per mil) at this stage reflect of the sparse vegetation cover. The early-Holocene DZH- local water and precipitation (Fig. 4). The diatom 4 in the lake core (Fig. 6, Stage B) is marked by three stratigraphy of the lake core prepared by Westover et al. anomalously old macrofossil AMS dates (13,389, 12,634, (2006) shows no response of diatoms at the level of and 12,846 cal yr BP; group B in Fig. 3). When the lake change in source water at the DZH-4/DZH-6 unconfor- level lowered in the early Holocene as a result of removal mity. Presumably the mountain water prior to the change of the ice dam that bounded the primary proglacial lake, had been warmed in the lake enough so that the diatom the Late Glacial sediments of DZH-1 and DZH-2 became populations were not affected by the change to local exposed at the shore and were eroded and redeposited in water. Thus the diatoms reflected the local climate as DZH-4 along with their old macrofossils (Fig. 6, stage B). determined by elevation, and the isotopes reflected the At this time the lake was fed by mountain streams with water source. meltwater marked by low δ18O values (−17‰). The major expansion of the forest in the Dzhangyskol At the end of DZH-4 time the lake became drained. It area is approximately dated to 6.5 cal ka BP. The main is postulated that the inflowing Kurkurek mountain component of the forest was Pinus sibirica, with stream, which had been delivering mountain water to the admixture of Betula pendula. Forests of P. sylvestris lake, shifted its course to the west on its alluvial fan. It probably developed west of Dzhangyskol in the joined the Kurumdu River, which flowed eastward along piedmont of the Altai Mountains and contributed pollen the toe of the fan, thus by-passing the lake, just as it does by distant transport. Two other conifers (Picea obovata today. Perhaps this course was aided by the growth of fen and Abies sibirica) decreased, whereas Larix sibirica along the southern lake margin. It is further postulated increased. This shift can be interpreted as an indication of that down-cutting of the Kurumdu River allowed a stronger continentality or cooling, i.e. more permafrost, tributary from the drained lake floor to work back which is tolerated by Larix but not by Abies. High values headward into the area near the fen site as well as at the of aquatic plants at the beginning of DZH-6 may reflect pingo of Butvilovsky (1993), thereby removing DZH-4 warm summers. in those areas. The radiocarbon dates in both cases After 6.5 cal ka BP in DZH-6 Pinus sibirica forests indicate the absence of the early-Holocene sediment of expanded on large areas of the mountains. Steppe DZH-4 (Table 1B and C). DZH-4 was thus at the fen site vegetation decreased and was concentrated only in the completely removed down to the top of DZH-3 at 440 cm Fig. 6. Sequential sketches illustrating the development of the pollen-assemblage zones of the Dzhangyskol lake–fen–pingo complex, as recorded by the pollen stratigraphy and radiocarbon dating of cores from the lake core, fen core, and the section in a pingo reported by Butvilovsky (1993). The heavy dotted line indicates a dry land surface or (if buried) an unconformity. Although the pingos are indicated diagrammatically by a single extrusion, in reality they may consist of clusters. Table 2 summarizes the phases of development. Read from bottom up. A. Late Glacial proglacial lake. B. Early Holocene lower lake level, exposing marginal Late Glacial sediments and resulting in their erosion and the redeposition of their macrofossils in DZH-4, as suggested by the arrow. C. Early mid-Holocene. The inflowing mountain stream was diverted by early pingos on the exposed and frozen lake-shore area. Pingo formation may have been facilitated by hydrostatic pressure from mountains (suggested by arrows). A depression was then eroded in the drained lake floor in the area of the fen core. Other early pingos formed in the area of the lake core. D. Later mid- Holocene. Flooding of the depression in the area of the fen core. The upper arrows suggest that erosion of DZH-4 and the early pingos caused the rapid deposition of DZH-5. E. Further increase in lake level, causing flooding of the early pingos and deposition of DZH-6 at both core sites and in the area of the modern pingos. F. Formation of the modern pingos. Development of the modern fen on the east and west sides of the lake.
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 415 (Fig. 6, stage C). The top of DZH-4 had been at 270 cm pingos at Dzhangyskol are much smaller than those on the below datum, as is the case with the lake core. Thus Mackenzie River delta of Canada and other arctic 170 cm of DZH-4 was removed during this excavation. locations, but the open-system type of formation described The drained lake was subject to the development of by Washburn (1979) provides a plausible mechanism for permafrost, which cannot form under lakes because of the the Dzhangyskol mini-pingos. In this application sub- heat retained in the water. Pingos could form as well. The surface water on the mountain fan was under hydrostatic
416 T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 Fig. 6 (continued ). (artesian) pressure moved under thin permafrost of the dry Early pingo development in the fen area south of the lake floor. There it froze and bowed up weak spots in the present lake could have dammed up the basin and allowed permafrost, producing small pingos. Repeated injections the lake to form again, not with mountain water but with could result in clusters of ice-filled mounds. local runoff, as indicated by the isotope data. At first the
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 417 Table 2 Postulated sequence of events represented by sketches in Fig. 6 cal BP Fen core Lake core Postulated event Cause Pingo activity F Fen peat Fen growth Stable lake level Modern Present pingos F DZH-6 DZH-6 Higher lake level, with higher δ18O of Further increase in Modern pingos, 6 ka local water. Part of early pingos of D precipitation and and drowning and E are drowned forest cover of early pingos E Unconformity Pingo formation throughout area Exposed lake floor More early pingos D DZH-5 Exposed Rapid filling of blocked depression in lake Blocking of tributary Early pingos 7 ka DZH-4 floor with sediment eroded from exposed outlet by early pingos DZH-4. Increased forest cover implies increase in precipitation and runoff C Unconformity Exposed Kurkurek River on fan shifts westward, Erosion by Kurumdu 8 ka DZH-4 diverting meltwater from lake. River works headward Kurumdu River along toe of fan downcuts, up tributary and its tributary from north drains the lake and excavates a depression in the dry lake floor B Unconformity DZH-4 Lower lake level to produce smaller Holocene lake. Failure of ice dam on 9 ka Inflow of mountain meltwater with low δ18O. Kurkurek River Erosion of exposed Late Glacial lake sediments, and redeposition of their macrofossils in DZH-4 A DZH-3 DZH-1 to -3 High level of primary Late Glacial lake Dam of Kurkurek River by 11.3 ka Kurumdu glacier Read from bottom up. The reconstructions are based on the following relations, supported by radiocarbon dates: 1. DZH-4 (early Holocene) is found only in the Lake core, and an unconformity exists between DZH-4 and -6 (late Holocene). δ18O increases abruptly at the unconformity from − 17‰ (from mountain meltwater) to −9‰ (local rainwater). 2. DZH-5 (middle Holocene) is found only in the Fen core, and an unconformity exists between DZH-3 (earliest Holocene) and DZH-5. 3. Permafrost and pingos cannot form under water bodies, so they imply a dry lake floor or a peat surface. Drowned pingos imply a rise in lake level. filling occurred only in the area of the fen site, where the Encroachment of the surface of DZH-5 by fen lake floor had been excavated (Fig. 6, stage D). The DZH- produced the dry surface that made possible the growth 4 sediment on the adjacent still-dry lake floor was eroded there of pingos (Fig. 6, stage E), producing the forms that and rapidly redeposited in the previously excavated and were later drowned by the late-Holocene lake-level rise now dammed area, thus accounting for the 150 cm and the deposition of DZH-6 there as well as at the lake sediment of DZH-5 deposited in only a few hundred site (Fig. 6, stage F). The drowned pingos are visible on years. The basal sediments in DZH-5 are silty, recording the air photograph of the lake and on the fen adjacent to the first deposition above the unconformity as the lake the east (Fig. 2). At the lake site the isotope values for level rose. The five radiocarbon dates for DZH-5 are not DZH-6 indicate that the water was derived from local strictly in stratigraphic order but are all in the range of sources, whereas for the unconformably underlying 6.8–7.3 cal ka BP (Table 1). Possibly the dated early-Holocene DZH-4 the water had been supplied by macrofossils all were derived from the vegetation that the mountain stream. The pollen diagram for the lake had colonized the dried lake floor. The top of DZH-5 in core shows a major change from NAP dominance in the the fen core is at 290 cm below datum, or about the same early-Holocene DZH-4 to AP dominance in the late- as the top of DZH-4 (270 cm) in the lake core, indicating Holocene DZH-6, and the radiocarbon dates indicate that that the excavated area on the old lake floor was filled up the mid-Holocene record (DZH-5) is missing at the by DZH-5 nearly flush with the level of the old DZH-4 dry unconformity. In the fen core the carbonate content was lake floor. insufficient for isotope analysis, but the pollen diagram
418 T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 indicates that the increase in AP and thus in precipitation DZH-4. Local erosional removal of this sediment in the had occurred already in the mid-Holocene while the area of the fen core was followed by damming of the excavated area was being filled by DZH-5. eroded area by early pingo formation and a consequent The modern pingos examined by Butvilovsky (1993) rise of the lake level, leading to the rapid filling of the contain sediments correlated with DZH-6, unconformably depression with DZH-5 in the mid-Holocene. Increased overlying the Late Glacial sediments of DZH-2, according precipitation implied by the transition from steppe to to the radiocarbon dates (Table 1C) and the pollen forest further increased the lake level in the late Holocene sequence. DZH-6 here is of limnic origin but contains (DZH-6), inundating the entire area of the present lake numerous plant fragments eroded from the encroaching and drowning pingos that had previously formed. As fen fen margin, resulting in the rapid deposition implied by encroached on the south side of the lake, the modern the three uppermost dates in the fen core (Fig. 3). pingos developed there. The modern pingos then formed Apparently the earlier DZH-6 sediments (Table 1C) in the south of the lake, and fen developed especially on the modern pingo area had become overgrown with peat, east and south sides. The modern pingo field is pock- providing a dry setting for permafrost and pingo marked with thermokarst pools. formation in the fen area. In any case the youngest date Even with all the evidence of proxy data the above- in the modern pingo, 1814 cal yr BP in DZH-6 (Table 1C), reconstructed picture of development of Dzhangyskol implies that artesian pressure of the open-system of pingo since the Late Glacial is admittedly speculative, but the formation is probably still the mechanism of pingo cyclic development of pingo–thermokarst systems in the formation. area of discontinuous permafrost has been observed also in the north of the West Siberian Plain (Kirpotin et al., 6. Summary and conclusions 2003). The aridity of the climate before about 9.5 cal ka BP as The complex palaeogeographic investigations (geo- revealed in the Ulagan area of the Central Altai Mountains morphic, palynologic, isotopic, and chronologic) of the (Blyakharchuk et al., 2004) is consistent with the pollen Dzhangyskol lake–pingo complex in the Kurai inter- data from Dzhangyskol, where the period of absolute montane depression (central Altai Mountains) revealed a minimum of tree pollen and predominance of Chenopo- complicated history of development, recorded by pollen diaceae and Artemisia pollen is marked in the Late Glacial analysis and radiocarbon dating of two cores of lake and continues in the early Holocene. A similar pattern is sediment, one near the center of the lake (“lake core”), apparent to the west in Kazakhstan (Tarasov et al., 1997). and the other at the edge of the bounding fen (“fen core”). The subsequent transition from steppe to forest vegetation Dzhangyskol is one of the oldest extant lakes in the in the Dzhangyskol area prevailed until about 6.5 cal ka Central Altai Mountains. It originated as a primary BP, longer than at the Ulagan sites, where it ended about glacial meltwater lake before about 15.6 cal ka BP due to 8.2 cal ka BP. The predominant steppe then changed to damming of the mountain streams by the advance of the forest-steppe, with Picea, Abies, and Pinus sibirica on Kurumdu glacier (Okishev, 1982; Butvilovsky, 1993). the upper slopes of the mountains. Islands of steppe were Blue–gray slightly laminated silts of this ancient lake surrounded by P. sibirica and P. sylvestris forest on the accumulated in the primary basin. This ancient lake was lower mountain slopes. With enhanced continentality much larger than the modern Dzhangyskol (Borodavko Abies and Picea decreased and Pinus sibirica–Larix and Akmatov, 2003), and it was surrounded by barren sibirica forests became dominant. areas with localized primary vegetation of pioneer plants So after the last deglaciation of the Dzhangyskol area and turf-sedges and grasses. in the Central Altai Mountains at about 15 cal ka BP, Warming and drying of the climate in the early numerous developments occurred, including changes of Holocene caused destruction of the glacial dam and lake area, vegetation cover, drainage relations, and pingo reduced the size of the meltwater lake to close to its formation. These changes were caused both by local modern dimensions. Chenopodiaceae first propagated geomorphic processes and by regional climatic changes on the partially exposed lake bottom (DZH-2), and then in the Altai Mountains. During this period the lake– at the beginning of the Holocene vegetation dominated pingo complex was very sensitive to climatic changes. by Artemisia covered the adjacent hill slopes, stabilizing Our investigations revealed a dry period in the history of the soils and leading to deposition of gyttja in the lake the lake during the early Holocene, when the area rather than silt (DZH-3). As the early Holocene covered by a lake was minimal. Two periods of maximal progressed, diversion of the inflowing mountain stream lake expansion occurred in the area, first during the time caused drainage of the entire lake and the exposure of of the ancient Late Glacial meltwater lake, and then in the
T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420 419 late Holocene during the maximal expansion of boreal rastenii flory Evropeiskoy chasti SSSR (Spores of Pteridophyta forests in the Altai Mountains. and pollen of Gymnospermae and Monocotyledonae of the flora of the European part of the USSR). Nauka, Leningrad (in Russian). The question about human influence on lake develop- Borodavko, P.S., Akhmatov, S.V., 2003. K geografii ozer Yugo- ment is not very clear. Possibly a marked maximum of vostochnogo Altaya (About geography of lakes of Southeast aquatic algae together with the pollen of aquatic macro- Altai). Vestnik Tomskogo Gosudarstvennogo Universiteta: Probl- phytes, findings of Triticum pollen, and a slightly increased emy geologii i geografii Sibiri, vol. 3(5). Tomsk University Press, Tomsk, pp. 31–35 (in Russian). amount of charcoal at a depth of 180–200 cm in the Butvilovsky, V.V., 1993. Paleogeografiya poslednego oledeneniya i Dzhangyskol lake pollen diagram may be related to cattle golotsena Altaya: sobytiino-katastroficheskaya model' (Palaeogeo- grazing and human settlement near the lake. This phase has graphy of the last glaciation and Holocene of Altai: event-catastrophic no radiocarbon dates so its dating is uncertain, but possibly model). Tomsk University Press, Tomsk 252 pp. (in Russian). these signs are connected with the development of the Chernova, G.M., 1988. Rezul'taty palinologicheskogo izucheniya ancient Scythian culture in the Altai Mountains 2.3–2.5 cal golotsenovykh otlozhenii Verkhnekarakabinskoi vpadiny, yugo- zapadny Altai (Results of palynological investigation of Holocene ka BP (Grach, 1980). The upper maximum of charcoal deposits of the Verkhnekarakabinskaya depression, south-western reflects the latest human influence. Altai). Vestnik Leningradskogo Gosudarstvennogo Universiteta 7(3) (21), 101–105 (in Russian). Acknowledgements Grach, A.D., 1980. Drevnije kochevniki v tsentre Asii (Ancient nomads in the center of Asia). Nauka, Moscow (in Russian). Grimm, E., 1991. Tilia 1.12, Tilia⁎Graph 1.18. Illinois State Museum, The investigation of Dzhangyskol was carried out Research and Collection Center, Springfield, Illinois. with support of grants to H.E. Wright from the National Huntley, B., Birks, H.J.B., 1983. An atlas of past and present maps for Geographic Society for summer fieldwork in 1998 and Europe: 0–13,000 years ago. Cambridge University Press, Cambridge. from the U.S. National Science Foundation for subse- Katz, N.Ya., Katz, S.V., Skobeeva, E.I., 1977. Atlas rastitel'nykh quent pollen studies and radiocarbon dating. We ostatkov v torfakh (Atlas of plant remnants in peat). Nedra Press, Moscow (in Russian). acknowledge Reed McEwan and Emi Ito for isotope Khlonov, Yu.P., 1965. Lipy i lipnyaki Zapadnoi Sibiri (Linden and analysis. We are grateful to Pavel Blyakharchuk, who linden forests in Western Siberia). SO ANSSSR Press, Novosibirsk did a lot for the success of the expedition, to the student 154 pp. (in Russian). Yevgenii Perevodchikov from Tomsk State University, Kirpotin, S.N., Blyakharchuk, T.A., Vorob'ev, S.N., 2003. Dinamika who helped in the field work, to Jacqueline van subarkticheskikh ploskobugristykh bolot Zapadno–Sibirskoi rav- niny kak indikator globalnykh klimaticheskikh nzmenenii (Dy- Leeuwen, who aided in the pollen-analytical investiga- namics of subarctic flat palsa mires of the West Siberian plain as an tions, to Florencia Oberli (Bern, Switzerland) and Jan indicator of global climatic changes), 7. Vestnik Tomskogo van Tongeren (Utrecht, The Netherlands), who helped in Gosudarstvennogo Universiteta, Tomsk, pp. 122–134 (in Russian). the laboratory preparations of pollen samples, to Ivanka Krylov, P.N., 1898. Taiga s estestvenno istoricheskoi tochki zreniya (Taiga from the natural–historical point of view). Public lecture Stefanova, who constructed the sequential sketches organised by Tomsk Department of IMPERATOR Moscow illustrating the environmental history, and to Petra Society of Agriculture, autumn 1897. Nauchnye ocherki Toms- Kaltenrieder and Lucia Wick, who extracted and kogo i Eniseiskogo kraya, Tomsk, pp. 1–15 (in Russian). identified the material for several radiocarbon dates. Kuminova, A.V., 1957. Teletski refugium tretichnoi rastitel'nosti (Teletski refuge of the Tertiary vegetation). Izvestiya vostochnykh Filialov Akademii Nauk SSSR 2, 104–108 (in Russian). References Kuminova, A.V., 1960. Rastitel'nyi pokrov Altaya (Vegetation cover of Altai). SO AN SSR Press, Novosibirsk 450 pp. (in Russian). Baryshnikov, G.Ya., 1996. Iskopaemaya rastitel ‘nost’ v terrasovykh Kupriyanova, L.A., 1965. 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