The role of pingos in the development of the Dzhangyskol lake-pingo complex, central Altai Mountains, southern Siberia

Page created by Jeffery Shelton
 
CONTINUE READING
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. Palinologiya serezhkotsvetnykh (Palynol-
   kompleksakh gornogo Altaya — fossil vegetation in terraceal               ogy of plants with male flowers in catkins). Nauka, Leningrad (in
   complex of the mountain Altai. Flora i rastitel ‘nost’ Altaya. Trudy      Russian).
   Yuzhno–Sibirskogo botanicheskogo sada. Altai State University          Kupriyanova, L.A., Aleshina, L.A., 1972. Pyltsa i spory rasteniy flory
   Press, Barnaul, pp. 129–135 (in Russian).                                 Evropeiskoy chasti SSSR (Pollen and spores of the flora of the
Blyakharchuk, T.A., Wright, H.E., Borodavko, P.S., van der Knaap, W.O.,      European part of the USSR), vol. 1. Nauka, Leningrad (in Russian).
   Ammann, B., 2004. Late-glacial and Holocene vegetational changes       Kupriyanova, L.A., Aleshina, L.A., 1978. Pyltsa dvudol'nykh rasteniy
   on the Ulagan high-mountain plateau, Altai Mountains, southern            flory Evropeiskoy chasti SSSR (Pollen of dicotyledonous plants of
   Siberia. Palaeogeography, Palaeoclimatology, Palaeoecology 209,           the European part of the USSR). Nauka, Leningrad (in Russian).
   259–279.                                                               Lavrenko, E.M., 1981. O rastitel'nosty pleistotsenovykh periglyat-
Blyakharchuk, T.A., Wright, H.E., Borodavko, P.S., van der Knaap, W.O.,      syal'nykh stepei (About vegetation of Pleistocene periglacial
   Ammann, B., 2007. Late Glacial and Holocene vegetational history of       steppes). Botanicheskiy Zhurnal 66 (3), 313–327 (in Russian).
   the Altai Mountains (southwestern Tuva Republic, Siberia). Palaeo-     Levina, T.P., Orlova, L.A., Panychev, N.A., Skabichevskaya, N.A., 1989.
   geography, Palaeoclimatology, Palaeoecology 245, 518–534.                 Paleogeographiya i radiouglerodnaya khronologiya na granitse
Bobrov, A.E., Kupriyanova, L.A., Litvintseva, M.V., Tarasevich, V.F.,        pleistotsena i golotsena predaltaiskoi ravniny (Palaeogeography
   1983. Spory paporotnikoobraznykh i pyl'tsa golosemennykh                  and radiocarbon chronology in the boundary of Pleistocene and
420                    T.A. Blyakharchuk et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 257 (2008) 404–420

    Holocene of the plain adjacent to the Altai Mountains). Kainozoi          Sibiri, Flora, 1990b. In: Peshkova, G.A., Malyshev, L.I. (Eds.),
    Sibiri i Severovostoka SSSR. Trudy Instituta Geologii i Geophysiki            Cyperaceae, vol. 3. Nauka, Novosibirsk. 279 pp.
    SO AN SSSR 668. Nauka, Novosibirsk, pp. 129–138 (in Russian).             Tarasov, P.E., Jolly, D., Kaplan, F.A., 1997. A continuous Late Glacial
Markov,, K.K. (Ed.), 1978. Razrez noveishikh otlozhenii Altaya                    and Holocene record of vegetation changes in Kazakhstan.
    (Section of the youngest deposits of the Altai Mountains). Moscow             Palaeogeography, Palaeoclimology, Palaeoecology 136, 281–292.
    University Press, Moscow. 207 pp. (in Russian).                           Tolmachev, A.I., 1954. K istorii vozniknoveniya i razvitiya temnokh-
Moore, P.D., Webb, J.A., Collinson, M.E., 1997. Pollen analysis.                  voinoi taigi (About origination and development of dark-
    Blackwell, Oxford.                                                            coniferous taiga). Akademii Nauk SSSR Press, Moscow–Lenin-
Okishev, P.A., 1982. Dinamika oledeneniya Altaya v pozdnem                        grad. 156 pp. (in Russian).
    pleistotcene i golotsene (Dynamics of glaciation of the Altai in          van Geel, B., Coope, G.R., van der Hammen, T., 1989. Palaeoecology
    the late Pleistocene and Holocene). Tomsk University Press,                   and stratigraphy of the lateglacial type section at Usselo (The
    Tomsk 208 pp. (in Russian).                                                   Netherlands). Review of Palaeobotany and Palynology 60,
Polozhii, A.V., Krapivkina, E.D., 1985. Relikty tretichnykh shirokolist-          25–129.
    vennykh lesov vo flore Sibiri (Relics of the Tertiary deciduous forests   van Geel, B., Bohncke, S.J.P., Dee, H., 1981. A palaeoecological study of
    in the flora of Siberia. Tomsk University Press, Tomsk (in Russian).          an upper late Glacial and Holocene sequence from “De Borchert”,
Rozanski, K., Araguas-Araguas, L., Gonfiantini, R., 1993. Isotopic                The Netherlands. Review of Palaeobotany and Palynology 31,
    patterns in modern global precipitation. In: Swart, P.K., Lohmann,            367–448.
    K.C., McKenzie, J., Savin, S. (Eds.), Climate change in continental       Washburn, A.L., 1979. Geocryology: A Survey of Periglacial
    isotopic records, 78. American Geophysical Union, Monograph,                  Processes and Environments. Edward Arnold Publishers Ltd.,
    pp. 1–36.                                                                     London. 406 pp.
Schulz, F., Lehmkuhl, F., 2007. Climatic change in the Russian Altai,         Westover, K.S., Fritz, S.C., Blyakharchuk, T.A., Wright, H.E., 2006.
    southern Siberia, based on palynological and geomorphological                 Diatom paleolimnological record of Holocene climatic and
    results, with implications for climatic teleconnections and human             environmental change in the Altai Mountains, Siberia. Journal of
    history since the middle Holocene. Vegetation History and                     Paleolimnology 35, 519–541.
    Archaeobotany 16, 101–118.                                                Wright, H.E., 1991. Coring tips. Journal of Paleolimnology 6, 37–49.
Sibiri, Flora, 1990a. In: Malyshev, L.I., Peshkova, G.A. (Eds.),
    Poaceae (Gramineae), vol. 2. Nauka, Novosibirsk. 361 pp.
You can also read