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The Plio- glaciation in eastern , , and the : evolution of thoughts

Autor(en): Milanovsky, Evgeni E.

Objekttyp: Article

Zeitschrift: Eclogae Geologicae Helvetiae

Band (Jahr): 93 (2000)

Heft 3

PDF erstellt am: 05.10.2021

Persistenter Link: http://doi.org/10.5169/seals-168829

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http://www.e-periodica.ch 0012-9402/00/030379-16 $1.50 + 0.20/0 Eclogae geol. Helv. 93 (2000) 379-394 Birkhäuser Verlag. Basel. 2000

The Plio-Pleistocene glaciation in , Siberia, and the Caucasus: Evolution of thoughts

(Paper presented at the meeting of the International Commission on the Historv of Geological Sciences (1NHIGEO), Neuchâtel, Sept. 9-11. 1998)

EVGF.NI E. MlLANOVSKY

Kev words: 1 listorv ol Russian glacial research, paleoclimate and glaciation, neolectonics and glaciation, permafrost, alternating volcanic and glacial deposits, glacial historv of the Caucasus

ABSTRACT ZUSAMMENFASSUNG

Ihe most convincing concepì of Ihe great Pleistocene glaciation in northern Der schwedische Geologe O. Torell und der russische Geograph und Geologe was developed in the 1870s by the Swedish geologist O Torell and the P. A. Kropotkin entwickelten in den 1870er Jahren ein höchst uber/eugendes Russian geographer and geologist P. A. Kropotkin. who had discovered traces Konzept der grossen pleistozänen Vereisung im nördlichen Eurasien. Kropotkin of an extensive glaciation in eastern Siberia and Finland, published in the hatle Spuren einer ausgedehnten Vereisung in Oslsibirien und Finnland fundamental book "Researches on Ihe " (1876. in Russian). Our entdeckt, publiziert in dem fundamentalen Werk ..Untersuchungen über die paper describes Ihe complex history ol glacial research in northern Eurasia by- Eiszeit» (1876. auf russisch). Unsere Veröffentlichung beschreibt die komplexe Russian geologists. Unlike Kropotkin, most ol them regogm/ed the existence Geschichte der Erforschung der Eiszeit im nördlichen Eurasien durch of several glaciations separated by interglacial epochs. The mam centers of russische Geologen. Abweichend von Kropotkin nahmen die meisten von ihnen glaciation were distinguished. The most important glaciation developed under das Vorhandensein von mehreren Vereisungen an. getrennt durch Interglazi- ihe humid climates of and western Siberia. In the relatively alzeiten. Die Hauptzentren der Vereisung wurden unterschieden Die stärkste dry of eastern Siberia ice sheets were of more limited extent and thickness, Vereisung entwickelte sich unter den leuchten Klimalen Nordeuropas und but there, permafrost reached depths up to 1-1.5 km. Westsibiriens. In den trockeneren Regionen Ostsibiriens waren die Eiskappen First observations on the Pleistocene and Recent glaciation of the Great von geringerer Ausdehnung und Dicke, aber der Permafrost erreichte Caucasus and the Armenian Highland (especially ol the Elbrus and Araral dort Tiefen von bis zu 1-1.5 km. volcanoes) were made by G. Ahich in 1844-1850. In the first half of the 20lh G. Abich machie 1844-5(1 ersle Beobachtungen einer pleistozänen und century the Russian geologists A. P. Gcrasimov, A. L. Reinhard. V. P. rezenten Vereisung des Grossen Kaukasus und des Armenischen Hochlandes Rengarten and others established a history of Caucasian glaciations comparable (besonders der Vulkane des Elbrus und des Araral). In den ersten Hallte des wilh that developed by Penck and Brückner, even though disagreements about 2(1. Jahrhunderts entwickelten die russischen Geologen A. P. Gerasimov. A. L. the correlations subsisted. In the central part of the Great Caucasus young Reinhard. V. P. Rengarten und andere eine chronologische Einteilung der volcanic rocks alternate with glacial deposits. The modern chronology of the kaukasischen Vereisungen, vergleichbar mit der von Penck und Bruckner, Great Caucasus glaciations developed by the author and A V. Ko/hevnikov obwohl manche Korrelationen umstritten blieben. Im Zentrum des Grossen distinguishes: 1 a Late Pliocene Elbrus Glaciation (analogue of the Danubian Kaukasus wechsellagern junge vulkanische Gesteine mit Glazialablagerungen. Glaciation of the Alps?) - 2) an Eopleistocene Chegem Glaciation (analogous Die moderne Chronologie der Vereisungen des Kaukasus, entwickelt vom to Gun/) - 5) an Early Pleistocene Elliibu Glaciation (analogous to Mindel) - Autor und A.V. Kozhevnikov, unterscheidet: 1) eine spätpliozäne Elbrus- 4) a Middle Pleistocene Glaciation with several phases and stages Vereisung (analog der Donau-Vereisung der Alpen'.') - 2) eine eoplcistozäne (analogous in Rissi 5) a I .He Pleistocene-I arly Holocene Bezingi Glaciation Chegem-Vereisung (analog zum Günz) - 3) eine altpleistozäne Ellübü-Verei- (analogous to Wurm and Buhl of the Alps) - 6) advance and retreat of glaciers sung (analog zum Mindel) - 4) eine mittelpleistozane Terek-Vereisung mit in the 17lh lo 19,h centuries. The Late Pliocene - Eopleistocene glaciations mehreren Phasen und Stadien (analog zum Riss) - 5) eine spätpleislozän-ho- belonged lo ihe semi-sheet type. Pleistocene glaciations to the trough valley type. lozane Bezingi-Vereisung (analog zu Wurm und Buhl der Alpen) - 6) Ihe maximal advance of glaciers was in the Middle Pleistocene. In the eastern Vordringen und Ruckzug der Gletscher im 17. und 19. Jahrhundert. Die spatplio- part of Ihe Great Caucasus and in the Minor Caucasus glaciations are were zän-eopleisto/anen Vereisungen entsprachen mehr oder weniger dem limned due to a more arid climate and lesser elevations. Eiskappentypus, während sieh später im Pleistozän Talgletscher bildeten. Die maximale Ausdehnung der Gletscher wurde im Miltelplcistozän erreicht. Im ostlichen Grossen Kaukasus und im Kleinen Kaukasus waren die Vereisungen wegen des trockeneren Klimas und der geringeren Meereshöhe weniger ausgedehnt.

Faculty of Geology. Moscow State University. Vorobiyovy Gory. Moscow- 11899,

Plio-Pleistocene glaciation in northern Eurasia 379 l <2

Vi

% ^ s i i Fig. 1. One of the first researchers of ancient glaciation on the Eastern European Fig. 2. One of the founders of doctrine on the Pleistocene glacial period, later plain academician Icdor Bogdanovich Schmidt (1832-1908). - the famous Russian revolutionary Pietr Alexeevieh Kropotkin (1842-1921

The first steps in the study ofthe Pleistocene glaciation in Russia ~^s Sajan expedition 1965 ••••• tq? Although in the Alps. I. Venetz. J. Charpentier, and L. Agassiz Otekma-Vitim /866 had found definite evidence of the Pleistocene glaciation in the expedition VitjÄ 1830s-40s (Hallam 1983), in northeastern Europe and Siberia the origin of sediments, which we now identify as glacial Boda moraine, remained unclear until the early 1870s. In the Angara At 1820s-30s. some geoscientists suggested the existence of a u* _<* former glaciation not only in the Alps, but also in the highlands (fl* MO T* and the plains of Norway (J. Esmark). Germany (R. Bernhardt cfjU K. Schimper). and Scotland (L. Agassiz. W. Buckland). However, the authority of Charles Lyell who published a popular W "drift hypothesis" explaining the dispersion of erratic <*-0**j>. • 0 boulders by floating ice (Lyell 1863). and of Roderick Murchison Ch Irft utsk K» (1845) who confirmed Lyell's ideas during his geological ShL sS -9 expedition to in 1840-41. impeded the recognition tA^wÌV.N..^. ^t.s *>-/. •*> of former glaciations in the East . Several X j'NT**, outstanding Russian geologists (Shchurovsky 1856. ^ RUSSIA N,H"TTS Z ,.r.y" 150 300km Helmersen 1869. Schmidt 1865) generally supported the drift i i Öy^^^-TNOIV-MONGOLIA)cetencajy^MHiW.^.^.-^ hypothesis. F. B. Schmidt (1832-1908, Fig. 1) described the Quaternary boulder-bearing sediments in Estonia. He used an Fig. 3. Routs of P. A. Kropotkin's expeditions in Baikalian of Eastern Estonian word for moraine He also "rikh" glacial deposits. Siberia in 1865 and 1866. indicated that clastic material was transported from north to south (from Finland and Sweden) based on the analysis of the composition of boulders and of the direction of scratches below the boulder-bearing deposits. At the same time. ologists attempted to combine the elements of drift and glacial Schmidt in Russia and some Scandinavian geologists interpreted hypotheses. Later on. following the works of Kropotkin. osar as coastal banks formed under the influence of ice Schmidt became, however, a convinced supporter of the glacial blocks floating in the cold of the Giacial Period. These ge- theory (Schmidt 1879).

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Fig. 4. The title pages of P. A. Kropotkin's book "Researches on the glacial period". On the righi page is written (in English translation): Researches on the glacial period by P. Kropotkin. I. On Ihe glacial deposits in Finland Report on the journey into Finland and Sweden in 1871 by proxy of Imperial Russian Geographic Society) II. On the foundations of hypotheses on the glacial period with the maps, sections and pictures in the separate brochure. First issue. S-Petersburg. M. Stasjulevich typography. Vassilijevsky oslrov. 2 L. 7. 1876. tin the left page (in English translation): Memories of Imperial Russian Geographic Society on the general geography (sections of mathematical and physical geography). Volume seven issued under edition of A. Kropotkin and I. V. Poljakov. wilh the maps, sections and pictures in the separate brochure. First issue. S.-Petersbourg. 1876.

The most complete and convincing justification ofthe concept rows on the hardrock surface beneath the boulder accumulations of the great Pleistocene glaciation in northern Eurasia (Fig. 3). He concluded that these boulders could only was given in the 1870s in the classic works by O. M. Torell have been transported and redeposited by a large and thick 1828-1900), who was the founder and first director of the glacier, which formerly covered the surrounding mountains Geological Survey of Sweden, and by Prince Petr Alekseevich and descended down to an altitude of 7(X) m, whereas the present Kropotkin (1842-1921). an outstanding Russian geographer glaciers in East Siberia do not reach farther down than and geologist, who later became a famous revolutionary and 3,000 m (Kropotkin 1873). theorist of anarchism (Fig. 2). Fascinated by the problem of a former continental glaciation In 1864-66. Kropotkin was a young officer of the East in Siberia. Kropotkin critically studied all European and Siberian Administration and also a military geographer. During American literature on this topic. Due to his great success, he his expeditions to the Vitim Highlands in Transbaikalia was soon awarded the membership of the Russian Geographical (East Siberia), he had found polished and scratched boulders Society (1967) and became the secretary of its physical in the river valleys. These were boulders of granites, absent in geography section (1868). In 1871. the Society sent him on an situ and therefore undoubtedly transported from adjacent official journey to Finland and Sweden to study the evidence for regions. Kropotkin also noted signs of smoothing and glacial fur¬ a former glaciation. During this very fruitful expedition.

Plio-Pleistocene glaciation in northern Eurasia 381 m

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Fig. 5. Several illustrations lo the 1 issue ol P. Kropotkin s book '"Researches on the glacial period'' |1876|. Kropotkin collected most valuable field data and studied also collections in the Swedish museums. These data and the critical analysis of world literature definitely convinced him that ISMS-sm.~^^>BS81t, the former glaciation had a very wide extension in northern Europe. Siberia, and . His lecture and preliminary report had a great success in the Russian Geographical Society (Kropotkin 1874). Later, he published his "Researches on the Glacial Period" (Kropotkin 1876). a fundamental two- volume monograph, where he reported on the results of his frai observations in and Siberia and outlined the principal problems and hypotheses concerning the glacial period. In this monograph. Kropotkin discussed in detail different aspects of morphology, structure and origin of glacial and related sediments and forms of glacial landscapes. Perhaps the most significant part of this work, which preserves its value up to the present day. is an original concept of the dynamics of a continental ice sheet as a result of slow plastic flow, induced by 1 its own weight. The flow was believed to start from the highest internal area of the ice sheet, where the ice was of the greatest thickness and might be several kilometers thick (Pavlov 1976. Fig. 6. Russian geologist academician Alexej Petrovich Pavlov (1854-1929) Shanzer 1976). On the other hand, some aspects of who for the first time (in 1888) established the plurality of Quaternary glaciations Kropotkin's glacial theory disagree with modern opinions. For on the East-European plain. instance, he believed in one unique glaciation and his interpretation of the origin of osar did not survive. Unfortunately. Kropotkin was not able to complete his Evolution of thoughts on the former glaciation in northern work. In the early 1870s he visited just after Europe and Siberia and its present status the French revolution of 1870-71. For a long time he became involved in secret revolutionary activities. In 1874 he was During the 40 years preceding the Russian October Revolution arrested and held prisoner in the Peter-and-Paul Citadel in St. in 1917. significant progress was made in research on the Petersburg. Nevertheless he continued his scientific work in glacial period. The systematic geological mapping of the European prison, completing the first volume of his monograph, part of Russia started in the 1880s. The area of the Baltic supplemented with a short summary of the contents of the second Shield and the Polar Urals were recognized as centers of the volume. An unfinished manuscript of the second volume is glaciation, and its maximal extent to the south was outlined. preserved, but was never published. The study of lithological successions of the various Quaternary The first volume contains 828 pages (Fig. 4) and a separate deposits showed the presence of several moraine and non- fascicle with graphic supplements including 100 maps, cross- glacial levels, i. e. several glacial and interglacial epochs were sections, and original drawings (Fig. 5). His brother and true recognized. The existence of two moraine horizons in one friend Alexander helped to publish a monograph in the Memoirs section was discovered in 1888 by the outstanding Russian geologist ofthe Russian Geographical Society, volume 7. which came A. P. Pavlov (1854-1929. Fig. 6) in the western part of the out in 1876 almost simultaneously with Kropotkin's escape central Volga region, and in 1890 by N. I. Krishtafovich near from the prison hospital. He was forced to live for more than Moscow. Later, Pavlov recognized at least three Quaternary 40 years in different countries of western Europe and devoted continental glaciation events on the himself almost completely to revolutionary activity. He (Pavlov 1922). However, some Russian geologists continued to continued his scientific work anonymously and only in passing recognize only one Pleistocene glaciation. because of his illegal position. He was a scientific reviewer of Even more important results in the study of glaciation of "Nature" and other magazines, where he published about 200 the East European Plain and of the plains and highlands of papers (Markin 1985). He could return to Russia only after the Siberia were achieved between the 1917 Revolution and World 1917 revolution shortly before his death in 1921. War II, and in the 1940s-80s before the breakup of the USSR In Russia. Kropotkin's fundamental work made a great in 1991. The latter event caused considerable reduction of impact. It convinced the majority of Russian scientists of the research in sciences in Russia. A. P. Pavlov (1922), G. F. glacial theory. His work showed the evolution of this theory Mirchink (1936). I. P. Gerasimov (in: Gerasimov & Markov and methods of glacial research employed in western Europe 1939). V.l. Gromov (1948), S.A. Yakovlev (1956). A.I. and America. However, this outstanding work was only Moskvitin (1967). K. K. Markov (in: Markov et al. 1965). G. I. published in Russian and remained almost unknown in western Goretsky. I. I. Krasnov and many other outstanding Russian Europe and America. geologists and paleogeographers obtained significant results in

Plio-Pleistocene glaciation in northern Eurasia 383 CS During this period, geologists definitely accepted the ç> * glacial origin of the boulder-bearing clayey sediments covering 150 c? the northern half of the East European Plain. However, even in the I940s-50s. the Ukrainian I. Pido- <&: zoo paleozoologist A. plichko (l946-1956) believed in the drift origin of boulders. W/ There are also diverging opinions about the origin of glacial boulder-bearing and pebble-bearing thin-bedded sediments in the northern part of the West Siberian and Pechora Plains. 150 One group of geologistes considers them as proper glacial sediments, whereas the other group perceives them as glacial-marine e sedimenls. including coarse clastic material transported hy icebergs and floating blocks of ice. The third group believes in a combination of two types. Now all Russian geologists recognize several Quaternary glacial and interglacial epochs. However. Gromov (1948). an authoritative researcher, believed ö that there were permanent ice sheets in the northern part of eastern Europe and West Siberia during the Pleistocene, which periodically expanded or retreated in connection with global Ci/ climate changes. Among polyglacialists there were, however, ^

384 E.E. Milanovsky BO u û

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Fig. 8. Maximal distribution of the Quaternary continental glaciations and permafrost on the territory of northern Eurasia. Compiteti bv E. E. Milanovsky.

In the Great Caucasus, on the arctic islands and the Baltic Don "tongue" and possibly also of the Dnieper "tongue" Shield (Table 1 the geologists observed and inferred Eopleistocene belong in reality to the Early Pleistocene glacial epoch glaciation events (Eopleistocene according to the Russian (Velichko 1981) and thus correspond approximately to the stratigraphie scale or Early Pleistocene according to the Krakow Glaciation in Poland or the Elster Glaciation in West-European scale), corresponding to the time interval Germany. This means that the Early Pleistocene glaciation had its between 1.8 and 0.7 Ma ago. These events are considered to be maximum not only in central but also in eastern Europe. equivalents of the and Günz Glaciations in the Alps. In this case, the Moscow Glaciation in eastern Europe, Between 0.7 and 0.375 Ma ago (Early Pleistocene of the which was originally correlated with the upper part ofthe Middle Russian scale) the continental ice sheet covered not only the Pleistocene and considered as a second phase of the Baltic Shield and the Polar Urals, but also spread to the south Dnieper Glaciation, corresponds to the entire Middle over the vast plains in the northern and central parts of central Pleistocene of the Russian scale (0.375-0.1 Ma ago). The Moscow and eastern Europe. By the end of the Early Pleistocene, it Glaciation can thus be correlated with all of the Saale Glacial expanded to the northern part of the West Siberian Plain. In the Epoch of , whereas it was only compared with 1980s, most Russian geologists believed that in contrast to central its late Warta) phase before. Europe, where the maximal glacial extent was attained in Until recently, the Valdai (last) Glaciation of eastern the Early Pleistocene Elster or Krakow), the Early Europe (Gerasimov & Markov 1939. Markov et al. 1965) which Pleistocene Oka) Glaciation in eastern Europe was considerably corresponds to the Vistula (or Weichsel) Glaciation of central smaller than the Middle Pleistocene Dnieper) Glaciation Europe, was correlated with the Late Pleistocene (0.1- whose main "tongues" expanded to the south along the 0.010 Ma ago). It consists of two phases: the first (main) Early lowlands of the present Dnieper and Don. reaching 48" N. However, Valdai (or Kalinin) phase and the second (smaller) Late Valdai recent studies have shown that the glacial deposits of the (or Ostashkov) phase (0.025-0.010 Ma ago). The most

Plio-Pleistocene glaciation in northern Eurasia 385 Tabic ]. Chronological correlation of the Pliocene and Quaternary glaciations in Eastern Europe, Great Caucasus and Siberia with Central Europe and the Alps t ompiled by FE Milanovsky. 1998 abs geolog ago age West - Middle th Western - Russian Alps Central Europe Eastern Europe Great Caucasus St bona Allaj mountains y European scale scale 10 HokxxTwQ, W mi 2 qUiidiion \%l-.lulrt gluuallon Lata Wolilai (Ostashk>v) glac !'--.-i-H'.l 2 l.l.: lull- Ii 2>nan - 2 i^-utnni qlii iation Mtkem g> V) LATE w rm- 1 glaciation S/th.-Ciil mol epodi Early Walrlai cool .¦poi h Bezmgl - l qî«' iation Z\rtdti 1 (|l.i lali.in Chibil gla. 100 PLEISTOCENE R W inturgidì idi Li-m inii'UjIcK idi Riss- 2 ' jl

400 PLEISTO Mindel glaciation EIsUt (Cr.ikowl glaciation Ok., [Berezina) glaciation Ell b — 2 glaciation Sbaitan glaciation Lat.- K.ilun gla< CENE E\RLY

500 VNTH- PLEISTOCENE G- M irtterglacial Kromer inU'fglacial Belovivhti Intergla«rial ROPO- 600 CENE

1 1 v Oi ¦ ¦-! -r h glac |f 1 Don |Dzuki| glaciation Earty Katun gla<

700 O Ell jb. 1 glaciation

800 V, nz glaciation Menapiitri roui epoch Olonets glaciation 1?) 2 eo pleistocene Bdshkdtau gioì glaciation? EARLY EOPLEISTOCENE

1000 Oeo PLEISTOCENE D-c; interglacial Vaal warm epoch Scypbian wami epoch

1000 |\pshe l-KXI roman stage) Danub IDoitau) Eburoii cool epoch Domashkino cool epoch I.mpleulocene JM' Irli -1. glaciation 7

1600 B-D Intarglacial Teyelffi warm epoch

1800 LATE

2000 PLIOCENE PUO- Akchagyl glaciation Pre - TegeJen epoch Chogem glaciation 2500 30XXI « ENE sia go Elbniv gldi iation n3 3500 hi mmenan 4000 EARLY (Balakhan) PLIOCENE stagv 4500 5000 N7' 5500 Lato Miocene

recent study showed that the cooling of the first half of the The less important Taz Glaciation took place in the Middle Late Pleistocene was not significant enough to cause a considerable Pleistocene. The relatively limited Zyrian (early Zyrian) and glaciation on the East European Plain and that the only Sartan (or late Zyrian) Glaciations in Siberia are of late undisputable Late Pleistocene Ostashkov. or proper Valdai Pleistocene age. Glaciation, which spread from the Baltic Shield to the northern The glacial sheets in West Siberia spread southeastward part of the East European Plain, occurred at the end of from the Polar Urals and southwestward from the Putorana the Late Pleistocene between 25.000 and 10.000 years ago and Highlands in the northwestern part of the East Siberian completely disappeared in the first half of the Holocene Plateau. They completely (or almost completely) joined each (Velichkol981). other in the central part ofthe West Siberian Plain. These The interglacial epochs of the Pleistocene and the glaciers formed temporary glacial and moraine barriers which postglacial Holocene Epoch correlate with considerable glacio- dammed the main West Siberian rivers Tobol. Irtysh. . and eustatic rises of the ocean level and consequently with Enisei. flowing to the north. This created great lakes and a transgressions of the marginal seas of the . huge West-Siberian Lake to the south of this glacial barrier. and in the Holocene. They also correlate with the During such epochs, water partly leaked to the southwest into marine ingression in the river valleys of Severnaya Dvina. the basins of the Aral and Caspian Lakes. Some geologists, Pechora, and Enisei. In contrast, transgressions and ingressions however, believe that a considerable part of "glacial" of the isolated coincided with the termination of sediments in the northern part of West Siberia is in fact of marine- the glacial epochs and the beginning of interglacial epochs. glacial or even marine origin. On the West Siberian Plain, the first (Shaitan) Glaciation In East Siberia, where Quaternary climatic conditions were occurs only at the end of the Early Pleistocene, later than the the coldest and driest compared to West Siberia and eastern- first glaciation on the East European Plain. The most significant Europe, the epochs of global cooling intensified the process of Samarovo Glaciation spread southward to 60°N-62°N. freezing in the upper part of the EartfTs crust. Glacial sheets in

386 EE. Milanovsky similar to that of the Alps, where the bygone great Pleistocene glaciation was already convincingly established. In 1844-50. the German Wilhelm Abich (1806-1886) A (Fig. 9), a pioneer of Caucasian geology, collected first scientific data on present and former glaciations in the Greater Caucasus I and the . In particular, he visited the \ highest volcanic mountains of Elbrus (5.642 m) and Ararat (5.165 m). At the southern foot of the Elbrus, near the source m of the Baksan River, he found and described the signs of the ^âsf very recent advance of glaciers sliding down from this biggest volcano (Abich 1849. 1852. 1871). One tongue of the Elbrus ^ glacier "intruded" into a pine at the bottom of the Azau Trough. Today, 150 years after Abich's observation, the termination of the Azau Glacier has retreated by several kilometers, ft which is typical for many Caucasian glaciers. In the second half of the 19lh century, glaciologists discovered terminal moraines in some trough valleys in the central /¦i f part of the Greater Caucasus. They correspond to different ' "7 /\ stages of the still continuing late Pleistocene-Holocene glaciation. : Ml, On the slopes of the valleys, remains of older stacked //"TT troughs produced by valley-type glaciers during preceding glacial epochs were found, but these ancient glacial forms 'MM /wuMMcc remained poorly studied. l-ig. 9. Hie German Wilhelm Abich 1806-1886) - "lather of Caucasian In the first half and in the middle of the 19,h century, geology", the tirsi researcher of the modern and recent glaciation of Caucasus. outstanding Russian geologists worked in the Caucasus: A. P. Member of Sl.-Petersbure Acad Sci. Gerasimov (1911), A. L. Reinhard (1936. 1947). V. P. Ren- garten (1932). L. A. Vardanyants (1932. 1948). N. V. Dumi- trashko (1949. 1977). P.V. Kovalev (I960). S.L. Kushev (1964). G. K. Tushinsky (1949. 1958). L. I. Maruashvili (1956. 1971). I.N. Safronov (1959). A.V. Kozhevnikov and many East Siberia periodically appeared on the highlands of others had elaborated a detailed scale of the Caucasian glaciations. Putorana, Anabar. Taimyr. Transbaikalia and Anadyr and also It was similar to the scale proposed for the Alps in in the high mountain ridges of Altai. Western and Eastern 1901-09 by A. Penck and E. Brückner (Günz Mindel Riss Sayan. Stanovoy. Verkhoyansk. Chersky. Koryak, and - - - Würm). but the detailed correlation between the two scales . remained uncertain. At first, it was suggested that the ancient Extensive and thick glacial sheets probably survived the glaciers on the northern slope of the Central Caucasus expanded whole Quaternary time until present on the archipelagos and to the Ciscaucasian Foredeep Plain during their maximum large islands of the Arctic Ocean on Svalbaard. Franz-Josef- advance, because in some places moraine-like accumulations Land. Novaya Zemlya. Severnaya Zemlya. Novaya Sibir. etc. were found, consisting of large boulders and blocks from the According to M.G. Grosswald (1983) vast, but thin shelf internal part of the Caucasus (Shvetsov 1928). However, in the glacial sheets of the present type in Antarctica 195()s-6()s. it was shown that these coarse clastic accumulations formed during glacial epochs in the shallow shelf seas of the were transported and deposited by mud flows in sudden Arctic Ocean (Barents. Kara. Laptev. East Siberian Seas etc.). catastrophic inflows from the mountains into the foredeep plains. These seas reveal glacioeustatic falls of ocean level in such In fact, in contrast to the Alps, even during the coldest stages epochs. of the Pleistocene the glaciers on both slopes of the Greater Caucasus did not expand to the foothill plains but stayed in the trough valleys. In the Caucasus, both present and former Evolution of thoughts on the former glaciation in the reached their maximum in the central Caucasus glaciations highest segment of the Greater Caucasus, where many summits are as The geological and glaciological research in the Caucasian high as 4.000-5.000 m and even exceed 5.600 m on the Elbrus mountainous region began after its conquest by Russia in the volcano. The eastern segment of the Greater Caucasus is also I850s-60s, i. e. later than in the Alps. From the very beginning, very high (up to 4.(X)() m and more), but its climate is dry. The the Russian scientists believed in a significant former glaciation present and former glaciations are much more limited there in the Greater Caucasus, because these mountains are than in the central segment. In the and in the much higher than the Alps. The size of glaciers in this region is Armenian Volcanic Highlands the altitudes do not exceed

Plio-Pleistocene glaciation in northern Eurasia 387 M", V ^

%& r. Cri ss ss \« CS Pere <*,

.lMces.,1 Middle - LatePliocer I moraine deposits ol Middle Pleistocene I Elbrus 1 glaciation f2li - min \ I &/a-l0\ Terek glaciation deposits ol Late Pliocene M *- [moraine I ^s. limits of Great Caucasus mountain region af Ichegem glaciation I7.V8 - 2 min v.t

|,7"'7""7. Ilk. Eopleistocene lim loglacial nnd IUI'.Ulli Imudstone flow deposits (17 - 0 7 min \ i moraine deposits ol Early Pleistocene Rg. 10. Distribution ol traces ol the ancient (pie- 1 EltüMi .il..nailon |650 400 Ih l - \ Late Pleistocene) glaciations on ihe northern /-.'. ol I slope of Central Caucasus. Compiled bs E. Mi- "TT-llragimiiLs Ihroughs ol Middle Pleistocene yi, greatest extinct volcanoes -^f [Terek glaciation 1230 - 150 Ih v I | ->f<- lanovskv11966].

3,000-4,000 m except for the Ararat volcano. The local climate sediments. The volcanic rocks underlie and overlie the oldest is even more arid. The ancient glaciation was insignificant, and moraines, widely distributed on the northern slope of the Central now only small glaciers exist on the Ararat (5.000 m) and Aragats Caucasus and in the Elbrus volcanic area. They extend (4.000 m) volcanoes. from the Elbrus volcano in the west to the Verkhniy Chegem In most Eurasian mountainous systems the in situ pre- Highlands in the southeast and to the Nizhniy Chegem Highlands Würm and pre-Riss moraines were denudated. However, in in the northeast. The isotopie age of these ignimbrites is many places of the central high mountains of the Greater 2.8 Ma according to very precise recent data (Lipman et al. Caucasus and especially on its northern slope, moraines were 1993). preserved under young lavas, ignimbrites and tuffs, erupted during On the eastern slope of the Elbrus volcano. Milanovsky & several volcanic phases in the Elbrus and Kazbek volcanic Koronovsky (I960. 1961) found the oldest moraine deposits in areas from the late Pliocene to the Holocene. The stratigraphie the Caucasus (the Elbrus Glaciation). This 20 m thick moraine and geomorphological correlation of glacial deposits and occurs at an altitude of 3.700 m. It overlies a weathered crust of young volcanic rocks provides a unique opportunity to date the Paleozoic basement, whereas layered ignimbrites glacial deposits "protected" under a volcanic armour (Fig. 10). unconformably overly its top. The ignimbrites are unconformably In the 1950s-6()s the author and his colleagues from the overlain by the Holocene moraine of the modern Elbrus glacial Moscow University (A. V. Kozhevnikov. N. N. Koronovsky) sheet (Fig. 11). The moraine deposits of the ancient Elbrus analyzed relationships between late Cenozoic glacial and Glaciation are evidently older than 2.8 Ma. Taking into account volcanic complexes by geological mapping and special research in the unconformable contact of the overlying ignimbrites. the the central part of the Greater Caucasus. We proposed a moraine might be as old as 3-3.5 Ma. It would thus correspond chronostratigraphic scale ofthe late Pliocene-Holocene glaciations to the beginning of the late Pliocene and coincide with the first in the Caucasus (Milanovsky 1966) on the basis of the glaciation in Iceland. This means that the axial zone of the central universally-adopted stratigraphie scheme of the Caucasus Greater Caucasus, situated at 42°^13° N. experienced a (Kozhevnikov et al. 1977. Dumitrashko & Milanovsky 1977. neotectonic uplift which attained a considerable altitude, at least Kozhevnikov & Milanovsky 1984). The study of the late 2,000-3,000 m. which are necessary to produce a mountain Pliocene rhyolite-dacite ignimbrites was very important for the glaciation. It has to be taken into account that the Elbrus age determination of late Pliocene and Eopleistocene glacial volcano was very active and formed a considerable caldera during

388 E.E. Milanovsky ^ot/g Km Liparite peak 3750« r. ^,Kum-Tyube mt. Chegem k Sarynsu 12 415 m jgff^ 7!f>(. &§&. + + m m £P2_ NN «sa i- + sg/tsa z-z =-V Mode Elb rus ac er the oi^g^und) =^T &-,y + + 8 ^ycv^ Present glacier ol Elbrus (on the Ime Ol crossection) Moraine deposits of Q32 - Q4 Bezengi glaciation Its moraine ol 19-20 century Andésite lavas and eroded volcanoes ol the Uppermost part ol Pliocene f^r-y- and Eopleistocene Upper Pliocene (2.8 min y stnped rhyolite and rhyo-dacite ignimbntes similar to the same ol Upper Chegem volcanic highland IIH» Moraine deposits ot Late Pliocene Chegem glaciation (2.8-2 min y /irjKj£ Coarse clastic non-sratilied moraine-like deposits consisting of big _____t__ boulders and angular fragments itiamly of Palaeozoic granites L.._and Dacite tuffs of the Upper part of rhyodacite ignimbnte senes gneisses Jurassic argillites and massive rhyo-dacite lavas in the sandi- gravel cement Rhyo-dacite and rhyolite ignimbnte senes of Late Pliocene age (2,8 min y filling Upper Chegem caldera tarty-Middle Pliocene weathering crust consisting of products of Upper Jurassic limestone senes mechanical and chemical weathering ol Upper Palaeozoic grey granites and migmatites i^a Lower-Middle Jurassic terngenous senes + + + Non-weathered Upper Palaeozoic grey granites and migmatites 5ü? r^i Upper Palaeozoic granites and metamorphic rocks I ig. 11. Traces of Middle Late Pliocene Elbrus glaciation on the eastern slope of Elbrus volcano under the "Liparite peak" between Irik-chal and Jtka- Rg. 12. Latitudinal cross-section ol Upper Chegem volcanic highland showing Uchen-Kez glaciers. The geographic position of this section is shown in the the stratigraphical and geomorphological position of the Upper Pliocene- right corner. Compiled bv E. /-.. Milanovsky and N. V. Koronovsky | W611. moraine deposits of Chegem glaciation. Compiled by E. E. Milanovsky.

the late Pliocene and the Quaternary. The moraine deposits of east, on the waterdivide between the left tributaries of the the Elbrus Glaciation occur inside the eastern slope of this Terek River (Chegem. Nalchik. Cherek Bezengiysky, and caldera and were involved in its relative subsidence. Cherek Balkarsky) at 2.500-3.500 m altitude, more than In the Verkhniy Chegem Volcanic Highlands, at an 1.000 m above the present beds of these rivers (Milanovsky altitude of 3.500 m. up to 2,000-3,000 m thick rhyolite-dacite I960. 1964. 1966). The fluvioglacial sediments of the Elbrus ignimbrites are conformably overlain (but with a hiatus) by 50 m and Chegem Glaciations are found within the Upper thick typical moraine deposits ofthe Chegem Glaciation. This Pliocene-Eopleistocene molasse deposits in the Terek Foredeep moraine includes large boulders of Paleozoic granites and Depression. Geomorphological observations suggest that metamorphic rocks (Fig. 12) and is covered by andesitic lava the Chegem Glaciation was of sheet or half-sheet type and flows, with a hiatus, but without unconformity. This lava erupted developed when the internal parts of the rapidly rising mountain in centers on the Verkhniy Chegem Plateau, where ridge of the Greater Caucasus was not yet dissected by deep moraine deposits are preserved. It represents a last post-caldera river valleys. phase of the volcanic cycle in the Verkhniy Chegem Volcanic In contrast, the following Quaternary glaciations of the Area, which began with a grandiose explosion of ignimbrites Greater and the Lesser Caucasus were of mountain-valley (Milanovsky I960.1%4. 1966. Milanovsky et al. 1962). The age type. Glaciers were localized in glacial cirques and trough-like of the Chegem Glaciation, which took place between these U-shaped valleys. The valleys were successively deepened by two volcanic phases, does not significantly differ from that of exaration and erosion during several glacial and interglacial the underlying rhyodacite ignimbrites and that ofthe overlying epochs, taking place during an arch-like uplift of the Greater andésite lavas. Unfortunately, the andésite volcanics overlying Caucasus. The amplitude of the uplift was more than 1.000 m. the moraines of the Chegem Glaciation are not studied iso- Detailed geological and geomorphological studies of the topically. The Chegem Glaciation may correspond to the interval successive Quaternary glaciations on the northern slope of the of 2.8-2.5 Ma. but in any case it occurred earlier than 2 Ma central Caucasus, in the trough valleys of the major rivers ago: The moraines and the overlying andésite lava are located (Kuban. Terek und their tributaries Malka. Baksan. Chegem. on the horizontal surface of the 3.500 m high volcanic plateau, Cherek. and Urukh) provide a basis for the chronostratigraphic which v\as formed before the onset of the erosion of the correlation of the Quaternary glaciations in the Caucasus Chegem River gorge, whose bed is now at 1.500 m. 2.000 m (Milanovsky 1966). This chronostratigraphic scale consists of below the moraine of the Chegem Glaciation. three main glacial and interglacial epochs subdivided into Other fragments of the Chegem moraine occur farther phases and stages, corresponding to the Early Pleistocene, the

Plio-Pleistocene glaciation in northern Eurasia 389 SW Middle Pleistocene, and the Late Pleistocene-Holocene. The Relative highs NE glacial epochs of the Eltiibii. Terek, and Bezingi Glaciations m800- g{Q,(without Lam Soulder-s) ¦tìOfi are chronological equivalents of the Mindel. Riss, and Wiirm- BuKa-Bashi Mt. in I J550m n Biihl glacial epochs the Alps (see Table _Q>vel of Ui 600- 9C0. 600 During the Quaternary, the rivers gradually deepened and "Soutder's) Y\ troughtötW* narrowed their valleys against the background of 1.000 m tee- 7-/77/7>^ ^oc Ihe slopes. 400-700 m above the river bed. In some places, Tegenexli ir tage mouth Adyl-su ir o/ especially in the Chegem Valley near the Eltiibii Village and in the the Baksan the Quaternary Relative upper part of Valley, remnants of highs^~SOOm' m500Ts y*vè>^-- 9fQ: -500 moraine are preserved on their shoulders (Fig. 13). The Fgea relatively narrow and deep troughs of the Middle Pleistocene -tOÜ WO m Lever 3BOm '7 00 lerek Glaciation occur inside the Farlv Pleistocene F.ltubu 9ea troug-hiottom troughs. As a rule, fragments of their bottoms can be traced at Lc4glQ iL,) 300 270 _it"Q 180-350 m above the beds of the valleys. Even narrower Level trou present dottom and the Glaciation 200 deeper troughs of Talc Pleistocene Bezengi ;>H0 occur inside the troughs of the Terek Glaciation 14). gl'i} Level (Fig. rough doti In there moraine the 100 100 some places, are deposits on bottom of 70rr\_ the Middle Pleistocene troughs. In the upper part ofthe Baksan geo FglQ and Terek valleys, this moraine is covered by Middle Pleistocene lava, thus proving that it belongs to the Terek Glaciation. Chegem r W The bottom of troughs formed by the I.ale Pleistocene- Relative highs Holocene Bezengi Glaciation are usually near the bed of the m 1000 -1000 «Meo present rivers. Most of them belong to the late Bezengi Phase BOOm which started about 25.000 its 800- gtM -800 years ago. reached maximum T N- bottom 700m Level of mrauçh 15,000-20,000 years ago and is still continuing. But in some valleys, 600 BOO the bottom of the Late Pleistocene troughs is under the 500m Level trough_. river bed. For instance, in the upper part of the Baksan Valley, tiöttom 400 y-400 it is KK) m below its bed. in the upper part of the Kuban Valley \V level "tO trough 200 m. and in the the Terek dottom upper part of Valley 3IXM50 m Ì00 at 100 Drilling revealed very thick glacial, fluvioglacial and glaciolacustrine sediments (Fig. 13A. 13C). The glacial deposits of Y< od pliam of Te.ere/c r. Je" -0 the Bezengi Glaciation, formed during its second phase and YQ eu several stages of retreat, and the features of the glacial 200- glQ --200 accumulative and exarational topography are very well preserved ôuried exarative eolioboti and exposed. In several trough valleys, lacustrine sediments M00 of Q, trough valley of Ter-eK '(00 accumulated in glacial lakes during different phases and stages of the Bezengi Glaciation. These temporary lakes formed Fig 13. Conditions of occurrence and interrelations of glacial and other types between the termination of valley glaciers and dams of moraine, of and Eopleistocene Pleistocene continenlal deposits and torms of relief in landslide or avalanche origin. the trough valleys on the Northern slope of Central Caucasus. Compiled b\ E.E. Milanovsky (1966). A. Crossection of Ihe trough valley of Baksan river near its source between Conclusion Tegenekli village and the mouth of Advl-su river. B. Crossection of the trough valley of Chegem river Elliibu near village. A chronological scheme of the Pliocene-Quaternary glacia-__ C. Crossection of of Terek river Ihe trough valley to soulh from Kazbegi tions in different settlement. regions of northern Eurasia, resulting from 150-years of research is shown in Table 1. Distribution and development of glaciations depend on geographic position, climatic conditions, topography and neotectonic movements in the regions where the glaciations occurred.

390 E.L. Milanovskv v< KO r. eü Ont

Rc On ''C lï SfcSÎ> maximal ad va, h„ment v.iiu-v _j—-i „| glaciers during Ih present glaciers — j '"s' plMso '-I UU- Pleistocene Bezengi glaciation |„ _ Lati- Pleistocene near glacier dam lakes """K I dreal Caucasus |-<^j mountain region '¦.as,n,„l ddwix.vnK.nl .,1 valley glaciers ih. r——. during rr 1 questa* \yy^\ M,t'""d ph" ' U''" '^'"'sloci-n.- Bezengi glaciation [StXJ 14. Distribution of the Late Pleistocene mor.niii hk< mud >ne Laic PleLMoce Fig. axes ol ridges deposte Bezengi glaciation on the northern slope of Central Caucasus. Compiled bv ICE. Milanovsky S s gn-atesl Quaternary volcano, (l%2).

This correlation scheme shows that in the time span decrease of glaciation intensity and in a gradual delay of 3-3.5 Ma there was repeated alternation of cold and the beginning of the first and of the maximal glaciation. For relatively warmer climates in northern Eurasia in particular, instance, in Scandinavia and on the plains of central and and on the whole Earth's surface. Glaciations periodically eastern Europe glaciation started in the Eopleistocene. occurred on vast plains, plateaus and in mountainous reaching its maximum in the Early Pleistocene, whereas on regions of Eurasia, whereas during warmer epochs the glacial the West Siberian Plain the first glaciation took place at sheets considerably diminished or completely disappeared. the end of the Early Pleistocene, reaching its maximum in First evidence of the Cenozoic global-scale cooling is the first half of the Middle Pleistocene: its extent was recorded in Antarctica, where glaciation started in the considerably smaller than the Early Pleistocene glaciation in Oligocene, whereas in parts of northern Eurasia. , central and eastern Europe. In East Siberia, the first glaciation and North America the first glaciation was only took place at the end of the Early Pleistocene, with a Pliocene. In general, the glaciation in the western part of maximum in the Middle Pleistocene, but it was even more northern Eurasia reached its maximum between 0.7 and restricted than in West Siberia, occurring only on the 0.4 Ma ago. i. e. in the Early Pleistocene according to the plateaus, highlands and mountains, where precipitations were Russian Chronostratigraphic Scale, whereas in the eastern much more abundant than in the lowlands and plains. part of northern Eurasia it happened about 0.2 Ma ago. i. e. At the same time, the dominant arid climate in the East led by the end of the Middle Pleistocene, and then significantly to an extensive development of permafrost: in eastern diminished in size in the Late Pleistocene. Europe ( and Pechora Lowlands) permafrost is The regional extent of glaciations, the maximum thickness limited to the North of the (67 N). to 60°N in and volume of glacial sheets in different parts of northern West Siberia, whereas in the northern part of the West Eurasia depend on climatic factors such as average annual Siberian Lowlands and to the East of the Enisei River, temperature, relative humidity and therefore on precipitation permafrost exists practically everywhere to the North of in the form of snow. During the Pliocene and the 48°-50°N: near the southern border of Russia, in North Quaternary the average annual temperature and precipitations Mongolia and North China (Fig. 8). In many places of East decreased considerably towards the East of northern Eurasia. Siberia the depth of permafrost attains 1.000 m or even This eastward increase in ariditv manifested itself in a 1.500 m.

Plio-Pleistocene glaciation in northern Eurasia 391 Wò u ö o o ù> Q^ tf c o 2* ><^

^ m m Kam« \ Vo Q' <~-i Cb y ^r* a- TT i. O Vj i?.Cr*

shown territory shown boundary of *. territory shown terntory rp on the tig. 3 on the fig 7 on"the fig former USSR H3 Y/y// /A 10.1I4

Fig. 15. Map indicating Ihe trames of territories represented on the fig. 3. 4. 10 and 14.

3. The orographic factor played also an important role. The ous regions of Siberia compared with the Caucasus on the decrease of the average annual temperature is in direct other hand, reflect a general eastward increase of aridity in correlation with the altitude, so that precipitations are in the northern Eurasia. form of snow during the winter. In the high mountains The neotectonic factors, such as the intensity, extent and between 40 N and 52UN. such as the Alps, the Greater Caucasus, time of orogenic uplift played also a very important role in the Altay. the first glaciation started in the late the development of the late Cenozoic glaciation. The first Pliocene (Alps. Caucasus) or in the Eopleistocene (Altay). significant glaciation in the center of the Great Caucasus whereas farther north in the plains of Eurasia glaciation and in the Alps took place in the first half of the late began only at the end of the Eopleistocene in Europe or in Pliocene (2.5-3 Ma ago), i. e. much earlier than the first the Early Pleistocene in Siberia. glaciation on the plains of eastern and central Europe. It Although the elevations of the Greater Caucasus are higher was almost synchronous with the first glaciation in Iceland, than those of the Alps, the ancient and present glaciation near the Arctic Circle. This shows that the axial zones of are much more important in the Alps. During the the alpine orogenic systems were already uplifted to the Wiirm glacial epoch, almost the whole Alps, except small altitudes which were necessary to produce glacial sheets. waterdivide peaks, were covered by a thick (up to Markov et al. (1965) estimated that the mountains were 1,000-2,000 m) glacial sheet, which spread out onto the 2,000-3,000 m or even 3,000-4,000 m high. The present northern plains in some places (van Husen 1987). altitudes are of 4.000-5.000 m in the Greater Caucasus However, in the Greater Caucasus the glaciers of the Late (5.600 m on the Elbrus volcano) and 3.000-4.800 m in the_ Pleistocene (Bezengi) glaciation remained in glacial Alps. The amplitude of neotectonic uplift after the first cirques and trough valleys as 50-60 km long ice tongues, glaciation, i. e. during the last 2.5 Ma. was at least covering only about 12 % of the whole area. Their thickness 1.000-2.000 m in the axial zones of the central Greater did not exceed some hundred meters. These differences Caucasus and 500-1.500 m in the Alps. Erosion produced between the Alps and the Greater Caucasus on the very deep river valleys on the slopes of the Greater Caucasus. one hand, and between the Tien-Shan and high mointain- In the process of intensive uplift, the late Pliocene and

392 E.E. Milanovsky Eopleistocene sheet-type glaciers were gradually replaced 1X76: Research on the Glacial Period. - Mem. Ross. Geograf. Obsc. Obshch. 7/1 (with a booklet of cross-sections and by mountain-valley or trough-type glaciers during the Geograf.. separate maps, drawings) (in Russian). Pleistocene. Kl SHEV. S. L. 1964: Ihe Bezengi Glaciation of the Central Caucasus - Trudy 5. In contrast to the glaciated mountainous regions of Eura¬ Me/hd. Konf. Oleden. Kavka/.i (111. p. 1X4-202). - Mosk. Univ. (in sia, the central part of the Greater Caucasus reveals a close Russian) 1 IPMAN. P. W., BOGATIKOV. O. A., el al. 1993: 2.8 Ma Ash Flow Caldera al interaction of glacial and volcanic processes with volcano- the Chegem Ri\cr in the Northern (Russia). tectonic deformations of the Earth's crust (in particular Contemporaneous Granites and Associated Ore Deposits. - Journ. Volcanol formation of Calderas). The alternation of glacial epochs Geotherm. Res.. 37.85-124. and phases of volcanic activity led to the formation of a I YELL. C. 1X63: The Geological Evidences ol the Antiquitv of Man. - London. relatively hard volcanic "armour" protecting moraines from \l\RkiN. V.A. 1985: Petr Alexeevich Kropotkin (1842-1921). - Nauka. Moscow (in Russian). total denudation in the Caucasus. For instance, in the Markov K. K.. Lasi kov. G. I. & Nikoi ai v. V. A. 1965: The Quaternary in Verkhniy upper) Chegem Highlands and the Elbrus Period: the Glacial and the Anthropogene Periods (1 & II) - Mosk. Univ. volcanic massif, the late Pliocene glacial deposits were (m Russian). preserved inside calderas. Glaciation might there be synchronous M \ri vsiivii i. L. I. 1956: Expediency of Revision ofthe Existing Thoughts on the Palaeogeographic Conditions of Ihc Glacial Period in Ille Caucasus. with subglacial volcanic eruptions, which represent a - Akad. Nauk Gru/. SSR. (in Russian). in Iceland. widespread phenomenon 1971: Glacial and Ancient Glacial Forms of the Quaternary Period (Post- Kimmerian). In: Geomorphology of . - Tbilisi (in Russian). Mu VNOVSKY. E. E. I960: Aboul Traces ofthe Late Pliocene Glaciation in the High Mountainous Part of the Central Caucasus. - Dokl. Akad. Nauk Rl 11 RINOS SSSR. 130/4. 158-161 (in Russian). 1964: Aboul the Upper Pliocene Glaciation of the Central Caucasus Auk ii. G. W. 1849: ('her die Schneegrenze und die Gegenwart im Kaukasus - (Selected Works Int. Geophys. Year. 10. p. 9-43) - Mosk. Univ. (in Russian). Bull. Acad. Imp. Sci Sl -Petersburg. XXIV/2. 1966: Principal Problems of ihe Ancient Glaciation History of Ihe Central lcS52: Explanation ofthe Geological Sequences on the Northern Slope of Caucasus. In: Problems of Geology and Palaeogeography of the Anthropogene the Caucasus from Elbrus to Beshtau. - In: Kavka/skiy Kalendar 1853. (p. 5—19) - Mosk. Univ. (in Russian). Iilhs. Pan 4. 440-471 (in Russian). 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