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doi:10.1016/j.qua

Quaternary Science Reviews 23 (2004) 1285–1311

Middle Pleistocene glaciations of the Russian North

Valery Astakhov*

Geological Faculty, St. Petersburg University, Universitetskaya 7/9, St. Petersburg 199034, Russia

Abstract

Geological data on the pre-Eemian glaciations of northern Russia, including the latest results by the Russian–Norwegian

PECHORA project, are synthesized in order to present evidence for comparison with other early glaciations around the Arctic. The

bulk of evidence indicates that Arctic and Subarctic regions of European Russia, of western and central Siberia during the Middle

Pleistocene were at least 4 times covered by large ice sheets, which advanced mainly from the shelf ice domes, partly from

Fennoscandia and the Putorana Plateau. Ice accumulations in the Ural Mountains were insignificant and did not form any

noticeable ice dispersal centres. Unlike the classical glaciated areas, ice sheets of northern Russia acted mainly on a soft, perennially

frozen substrate, which was heavily glacitectonised. The Middle Pleistocene ice sheets were much larger than the Weichselian ones.

The Fennoscandian ice dispersal centre was most active in northern European Russia during the penultimate glaciation (OIS 6)

when shelf-centred ice domes were relatively weaker. Larger continental ice sheets were formed in preceding ice ages, when Kara Sea

ice dispersal centre dominated. The lowland ice sheets reached their maximum extent at different stages, from Cromerian Don

glaciation in European Russia to OIS 8 in West Siberia. Therefore, the maximum ice limit is time-transgressive in northern Russia.

r 2003 Elsevier Ltd. All rights reserved.

1. Introduction

The volume and extent of Middle Pleistocene icesheets exceeded those of the Late Pleistocene by far,especially on the eastern flank of glaciated Eurasia (e.g.Ganeshin, 1973). Accordingly, their impact on thegeological structure and environments of the Arcticand Subarctic regions was more profound. However,geological research within the QUEEN frameworkhas largely been focused on the Late Pleistocenehistory of the Russian North. Only a few sections ofMiddle Pleistocene drift have been studied byQUEEN members on the Russian mainland. Hencethe bulk of data discussed below is derived from Russianliterature.

Over the last half-century various attempts have beenmade to synthesize data on Middle Pleistocene glacia-tions collected by hundreds of Russian researchers. Theonly work in which all Quaternary of the Russian Arcticand Subarctic is discussed, is the monumental volume bySachs (1953). Another outstanding contribution is astratigraphic monograph with a Quaternary map ofEuropean Russia by Yakovlev (1956). In the 1960–1970sthe huge influx of data, especially from geological

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s: [email protected] (V. Astakhov).

front matter r 2003 Elsevier Ltd. All rights reserved.

scirev.2003.12.011

surveys, led to graphical generalisations in the form ofsynthetic Quaternary maps for the entire Soviet Union(Ganeshin, 1973) and separately for each of the super-regions of northern Eurasia such as the Russian Plain,the Urals, West and Central Siberia. These maps areprincipal sources of hard data about the size of formerice sheets obtained by generations of mapping geolo-gists. Lately they were used to compile the digital map ofPleistocene ice limits as part of the INQUA project(Astakhov, 2003).

After Sachs and Yakovlev numerous articles andregional monographs were dealing with the MiddlePleistocene glacial deposits of the North in terms ofstratigraphy (Arkhipov and Matveyeva, 1964; Lazukov,1970; Zubakov, 1972; Yakhimovich et al., 1973;Kaplyanskaya and Tarnogradsky, 1974; Arkhipovet al., 1986, 1994; Velichko and Shick, 2001), lithology(Kuznetsova, 1971; Zemtsov, 1973a, b; Sukhorukovaet al., 1987; Andreicheva, 1992; Andreicheva et al.,1997), palaeogeography and geomorphology (Isayeva,1963; Troitsky, 1975; Arkhipov et al., 1976). Structuralgeological and sedimentological works are noticeablyscarcer (e.g. Zakharov, 1968; Kaplyanskaya and Tarno-gradsky, 1975; Astakhov et al., 1996). Rare attempts toreconstruct dimensions and flow patterns of the icesheets were mostly based on till lithologies (Zubakov,1972; Sukhorukova et al., 1987) and occasionally onglaciological considerations (Voronov, 1964).

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Fig. 1. Location map of glaciated northern Russia. Solid line is Early Weichselian ice limit. Broken line is the glacial drift limit in Siberia and

Moscow glaciation limit west of the Urals, dash-and-dot line is the drift limit in European Russia (Don glaciation?). Black arcs are largest ice-pushed

features. Lines A and B are geological profiles in Fig. 2, C in Fig. 7. Black circles are key sections of Middle Pleistocene interglacial formations

sandwiched between tills: 1—Lake Chusovskoye (Stepanov, 1974); 2—Rodionovo (Loseva and Duryagina, 1973); 3—Kipiyevo (Guslitser and

Isaychev, 1983); 4—Seyda (Russian–Norwegian project PECHORA, 1998); 5—Semeika (Kaplyanskaya and Tarnogradsky, 1974); 6—Belogorye

Upland (Arkhipov et al., 1978); 7—Khakhalevsky Yar (Levina, 1964; Zubakov, 1972); 8—Bakhtinsky Yar (Arkhipov and Matveyeva, 1964;

Zubakov, 1972); 9—Pupkovo (Zubakov, 1972); 10—Novorybnoye (Kind and Leonov, 1982). Open circles indicate lowland tills in the mountains:

11—clayey tills with clasts of Carboniferous limestones at 500–600 asl (Astakhov, 1974a, b; see also Fig. 4A); 12—Weichselian end moraine of

northern origin at 560m (Astakhov et al., 1999); 13—three tills with lowland erratics on flat summit 600masl (Fainer et al., 1976). Deepest buried

valleys filled with tills: 14—borehole at Lebed, 342m bsl (Arkhipov and Matveyeva, 1964; Zubakov, 1972); 15—borehole at Kosa Kamennaya,

367 bsl (Arkhipov et al., 1994). Arrows are ice flow directions inferred from ice-pushed ridges and clast indicators.

V. Astakhov / Quaternary Science Reviews 23 (2004) 1285–13111286

The volume of existing data makes a comprehensiveoverview impossible for any journal paper. Hundreds ofpapers discussing various aspects of the pre-Weichselianglacial history from different standpoints cannot bereviewed here. My task is limited to briefly describingthe most reliable geological results in pre-Weichselianglacial geology of northern Russia beyond the realm ofFennoscandian glaciations (Fig. 1) in order to presentdata for comparison and to highlight weak points thatmight be of interest for further research. A selection ofkey evidence in a diverse area ca 4.5 million km2,although it might seem arbitrary, is actually scale-dependent. It is dictated by the author’s mappingexperience, according to which superregional conclu-sions are derived mostly from examination of largegeological features, whereas small details of geologicalstructure often yield only results of local significance.

The questions of immediate concern will be (i) size andflow pattern of former ice sheets, (ii) possible correla-tions of ice advances within the QUEEN area.

2. General geological setting

Northern Russia as an area of inland glaciation isvery different from the classical glaciated regions ofnorthwestern Europe and North America. It is largelysoft-rock flatland extending offshore as sedimentarybasins of the Barents and Kara seas (Fig. 1). The weaksubstrate is responsible for the large thickness (up to300–400 m) and predominantly fine-grained composi-tion of the Quaternary cover. Only in the east looms thePutorana Plateau, up to 1600 asl, a major source ofhard-rock clasts, built of horizontally layered dolerites

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and lavas. Other smaller sources of erratics are narrowPalaeozoic ranges of the Ural and Byrranga Mountainsand low ridges of Timan, Novaya Zemlya and Pai-Hoi(Fig. 1). The rest of the area is underlain by Mezosoicand Cenozoic sand, clay, silt, opoka, diatomite andtherefore is apt to produce few visually recognisableclasts. Consequently, the traditional method of recon-structing former glaciers by mapping boulder trainswould inevitably point to the Central Siberian uplandsand the smaller salients of folded Palaeozoic rocks asthe only sources of moving ice. The seaward slopingsedimentary basins of the Pechora, West Siberianand North Siberian lowlands have generally beenviewed as an arena of marine incursions from the ArcticOcean.

The stratigraphic methods employed and conclusionsobtained are different in two natural zones: (a) theArctic with marine and glacial formations alternating,and (b) the Subarctic, where only terrestrial stratifiedsediments occur sandwiched between thick diamictons.These zones, being crossed by the Uralian Range, givefour stratoregions to be discussed separately: two inEuropean Russia and two in Siberia. In all regions 3 to 5diamict sheets up to 60 m thick each are found inborehole profiles (Arkhipov, 1971; Zubakov, 1972;Lavrushin et al., 1989). Tills of the penultimateglaciation can be locally seen in exposures of the Arcticbeneath Upper Pleistocene strata, whereas diamicticformations of preceding ice advances normally lie belowsea level. The most continuous till sheet, observed in theSubarctic zone as the second from the surface, isbelieved to form the drift limit along 60�N in WestSiberia, deviating northwards in Central Siberia andsouthwards in European Russia (Fig. 1). Older tills ofmore restricted occurrence are known just from bore-holes.

The Middle Pleistocene till sheets gradually plungenorthwards and get progressively more eroded in thehigh Arctic, especially on the sea floor (Fig. 2). Theoccurence of pre-Weichselian tills is mantle-like: theycan be found both in buried valleys at 300–350 m bsl(locations 14 and 15 in Fig. 1) and on plateaus 500–600 m asl (locations 11 and 13 in Fig. 1). The thickestaccretions of Middle Pleistocene sediments, up to 200–300 m, are known from the areas of rougher sub-Quaternary relief along the Urals and Central SiberianPlateau, whereas the flat Timan Ridge and central WestSiberian lowlands often bear a discontinuous cover ofglacial deposits less than 50 m thick. Above the ArcticCircle the Middle Pleistocene sediments are either totallyeroded or fill in deep depressions. The latter arenormally obscured by the Weichselian glacial complexwhich is often glaciotectonically stacked to attain 100 min thickness (Fig. 2). The described regional structurereflects a lowland position of principal ice dispersalcenters.

Since the 1950s many authors, based on the lowcontent of pebbles, local occurrence of marine fossilsand the old idea of montane ice dispersal centres,interpreted thick diamict sheets, partly or entirely, asglacimarine formations (Sachs, 1953; Lazukov, 1970;Zubakov, 1972). However, sedimentological analysis offine-grained Middle Pleistocene diamictons in theirstratotype sections proved beyond any reasonable doubtthat they were deposited by huge ice sheets thatadvanced southwards (Guslitser, 1973; Kaplyanskayaand Tarnogradsky, 1974, 1975). The pattern of icepushed ridges (Fig. 1) and dispersal of lowland clastsalso indicate ice streams diverging from lowlands to theadjacent highlands (Astakhov, 1974a, 1977), contrary toice flows from the mountains predicted by the glacimar-ine hypothesis. The distribution and thickness of glacialdeposits, as well as the pattern of their imbricateaccretions (Figs. 1 and 2), is in accordance with N–Sdirected ice advances from the shelf but is hardlyexplainable by ice dispersal from the highlands.

3. Size and flow pattern of ice sheets

3.1. European Russia

3.1.1. Ice sheets inferred from erratics

The ice limits in central European Russia since theXIX century have been attributed to activity ofthe Fennoscandian ice dispersal center, as suggested bythe distinct boulder trains and configuration of themarginal formations. For the last half-century threemajor Middle Pleistocene ice advances called Oka,Dnieper (the maximum glaciation) and Moscow havebeen correlated with the Elster, Saale and Wartheglaciations of Central Europe (Yakovlev, 1956; Gor-etsky et al., 1982). In northern European Russia,however, influx of glacial ice from the northeast wasacknowledged quite early (Ramsay, 1904). The con-tributions of individual ice domes were thoroughlydiscussed by Yakovlev (1956). Based on provenance oferratics in the European North, Yakovlev distinguishedthree major areas of ice sheet growth: (1) Fennoscandia,(2) Novaya Zemlya with the adjacent Barents Sea shelfand (3) the Urals.

The dark-grey Novaya Zemlya till is a thick, fine-grained diamicton with strong NE–SW or N–S fabrics.It is devoid of Fennoscandian erratics but contains somefragments of Novaya Zemlya pink and black limestones(Andreicheva, 1992). Large limestone blocks trans-ported from the Kara Sea coast towards SW acrossthe Pai-Hoi Range have been known for a long time(Voronov, 1951). Many authors also noted numerousboulders of foreign rocks scattered over flat-toppedmountains of the Polar Urals up to 1000 m asl (Yakov-lev, 1956). Fragments of western Uralian rocks occur

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Fig. 2. Profiles of Quaternary formations on the Barents Sea coast (from Lavrushin et al., 1989, simplified). See Fig. 1 for location. Diamictons: 1—deep buried (pre-Holsteinian); 2—close to sea

level (Saalian); 3—surficial (Weichselian); 4—stratified silt and clay; 5—sand; 6—borehole. Till sheets are g1 to g5 and marine formations are m1 to m5 (m5 is probably a glaciotectonic repetition of

m4-V.A.); lIIlh is a lacustrine formation with Likhvin-type pollen spectra according to Lavrushin et al. (1989).

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east of the main watershed, limestone clasts from thelow western piedmont being often found atop glaciallysmoothed hills 500–600 m high (Savelyev, 1966). Ac-cording to Yakovlev (1956) ice streams directed fromNovaya Zemlya to the SSW reached the Volgacatchment area, where they coalesced with SE flowingFennoscandian ice of the Dnieper glaciation to form thelargest ice sheet of European Russia. This ice sheet wasthought to have penetrated into the southern steppes bytwo huge ice streams forming the Dnieper Lobe in theUkraine and the Don Lobe in southeastern Russia. Inthis model ice from northeastern sources coveredpractically all sedimentary basins of the Russian Plainnorth of 58�N.

The subsequent penultimate glaciation left the reddishbrown till widely observable on the surface west of thePechora. This till is unanimously correlated with theMoscow glacial complex of Central Russia. It containsnumerous western erratics, including the characteristicnepheline syenite from the Kola Peninsula, and there-fore must have been deposited by a Fennoscandian icesheet. East of the Pechora the latter coalesced with icestreams originating from Novaya Zemlya and the Urals(Yakovlev, 1956; Potapenko, 1974; Lavrov et al., 1986;Andreicheva, 1992).

Individual ice domes are not easily identified by theerratic dispersal alone on which many authors relyheavily. A straightforward interpretation of statistics onpebble composition and orientation may be controver-sial. For example, south of 64�N tills of westernprovenance have long been known on the Uralianpiedmont. Heaps of boulders of Palaeozoic sedimentaryrocks from the west occur even at the very foot of thehighest range of the Northern Urals. However, fartherto the west clasts of sedimentary rocks are mixed withcentral Uralian crystalline rocks, i.e. the percentage ofUralian clasts in the clayey basal till apparentlyincreases westwards. Varsanofieva (1933) explained thisparadox by ice of northern origin streaming along theUrals and fanning off westwards into the lowlands andeastwards into the mountains. North of 64�N, just westof the highest massif of the Peri-Polar Urals, clayey tillsare even more enriched in Uralian erratics, which led tothe idea of thick ice which presumably flowed westwardsfrom ice domes positioned over the Urals (Yakovlev,1956; Chernov, 1974). Pebble orientation and miner-alogical composition of the till matrix were also used tosuggest a separate Uralian ice dome (Kuznetsova, 1971;Andreicheva, 1992).

However, the question is not that simple. The mostcomprehensive work was done by Lavrov et al. (1986)who mapped the glacial topography and measuredpebble composition in hundreds of till samples a quarterof a cubic meter each. The generalised results unam-biguously show the persistent N–S and NE–SWdispersal of glacial clasts over the northeastern Russian

Plain during the maximum Pleistocene glaciation(Fig. 3A), west–east direction for the till of thepenultimate glaciation west of the Pechora andagain N–S ice flow east of this river (Fig. 3B). Themaps by Lavrov et al. (1986) offer no signs of a Uralianinfluence except at several locations with transversefabric (Fig. 3B) reported by Kuznetsova (1971). Thepebble content pattern and the main vector of tillfabric points directly towards the NE across Pai-Hoiand Novaya Zemlya into the Kara Sea, withoutdisturbance by ice flows from the Urals or from theBarents Sea.

3.1.2. Other evidence of ice dispersal

The signals from pebble composition and mineralogyof tills are often mixed. On the western carbonaceouspiedmont of the Northern Urals (63–61�N) Varsanofie-va (1933) found that the clayey till of westernprovenance was covered in places by a clast-supporteddiamicton full of central Uralian erratics at 20 km westof the mountain front. Based on these data shesuggested two glaciations: one in the form of a regionalice sheet which advanced along the Urals and asubsequent glaciation in the form of restricted piedmontice flows from old alpine troughs. The situation ismirrored on the Siberian slope of the Peri-Polar andNorthern Urals between 65�N and 62�N (Sirin, 1947;Ber, 1948), where a till of eastern (Siberian) provenancemantling the hills up to 500 m asl is superposed by acobbly diamicton of local (central Uralian) provenance.Sirin (1947) concurred with Varsanofieva to suggest twoglaciations on the eastern slope: a maximum ice sheetwhich advanced from the West Siberia onto the Uralsand a local glaciation centred in the Uralian axial zoneof metamorphic rocks.

Thick sequences of lowland drift later found on bothslopes of the mountain range amply confirm iceadvances onto the Northern Urals from both NW andNE but reject local ice caps. The thickest clayey till at500–600 m asl in the axial zone (Fig. 4A) containsfragments of black Carboniferous limestones pickedup in the low piedmont some 20 km to the west(Astakhov, 1974a). The clayey till is capped by the50 m high kame-like hummocks built of well-washedsand with small and roundish cobbles of central Uralianorigin but obviously deposited by the same inland icesheet, most probably of OIS 6. In contrast, youngerlocal moraines filling alpine troughs higher than 600 m(Fig. 4A) consist of only clast-supported tills derivedfrom metamorphic rocks. The Siberian slope of theNorthern Urals, where no alpine moraines have beenmapped, is in places covered by thick matrix-supportedtills of eastern provenance (Fig. 4B), containing frag-ments of soft Mesozoic rocks of the West Siberianbasin and the West Siberian mineralogical assemblage(Ryzhov, 1974).

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Fig. 3. Pebble content and ice flow indicators in Middle Pleistocene tills of northeastern European Russia: A—maximum glaciation; B—penultimate

glaciation. By Lavrov et al. (1986) with minor additions from Matveyeva (1967) and Gornostay (1990) for the Timan Ridge and from Astakhov

(1974b), Ryzhov (1974), Astakhov et al. (1999) for the Urals. Isolines show volumetric content of pebble fraction 1–5 cm in till samples about a

quarter of cubic meter each. Black wedges are long axes of pebbles. Arrows are other ice flow indicators: striae, boulder pavements, eskers, transport

paths of erratics. Hatched are Palaeozoic salients of the Timan Ridge and Urals. Note the pebble content decreasing downglacier and increasing

locally in the lee of the Timan Ridge at southwestern corner of Fig. 3A. Lowland erratics in basal tills (Fig. 4A) and esker orientation in Fig. 3B are at

odds with fabrics of surficial diamicton measured by Kuznetsova (1971) in the upper Pechora area.

Fig. 4. Lowland tills on western (A) and eastern (B) slopes of the Northern Urals. A—river Telpos catchment, N 63�500/E 59� (from Astakhov,

1974a); B—between rivers Manya and Mazapatya, N 62�150/E 59�500 (from Ryzhov, 1974, simplified). 1—laminated fine sand and silt;

2—coarse sand with pebbles; 3—clast-supported diamicton of local provenance; 4—matrix-supported diamicton with lowland clasts; 5—borehole.

Note kames of lowland glaciation undisturbed by Uralian glaciers in Fig. 4A.



In the lowlands no landforms testifying to ice flowfrom the Urals have ever been mapped (Fig. 1).Moreover, even on the western piedmont of the North-ern Urals, 200–300 m asl, eskers and striae are orientedeither N–S or even NW–SE (Astakhov, 1974b). This isquite compatible with ice flow directed towards themountains and not with a Uralian ice dispersal centre.

The 90-m thick sequence of fine-grained MiddlePleistocene glacial sediments of a kame field found inthe central metamorphic zone (Fig. 4) has evidentlynever been affected by any glaciers of montane origin.Similar kames built of fine sand are also known from theeast of the central range (Ber, 1948). According to thisauthor’s observations, in several places of the NorthernUrals well-preserved kames are mantled by thin clast-supported diamicton full of fragments of Uralianquartzites and schists. This sediment, which is betterbe interpreted as ablation till, may well belong to thesame ice advance. Thus, no second ice advance is neededto account for pebbles of Uralian provenance in thesurficial diamicts of the piedmonts. The crystallinepebbles mostly originate from mountains higher than500 m and therefore are rare in the basal till butabundant in the ablation till, which was enriched inclasts from nunataks during the lowering of the icesurface. This agrees with the fact that the percentage ofUralian crystalline rocks in diamictons of the PechoraBasin is minimal in the oldest tills of thicker ice sheets,but clearly increases upwards in the till succession(Andreicheva, 1992). This can be explained by thegrowing influence of montane sources with progressivethinning of each subsequent ice sheet, but should notbe taken as a proof of a separate ice dome over theUrals.

The above facts indicate that diamictons with west–east fabric and predominant central Uralian clasts maynot represent separate glaciations but belong to theablation subcomplex of the same ice age. Stagnating icesheets, while thinning, might acquire reverse surfacegradients forcing supraglacial boulders from Uraliannunataks to slide westwards. This could happen in theend of every ice age, thus adding to the volume ofcrystalline clasts already delivered to the lowlands bysmall alpine glaciers which probably acted prior to themain ice advances from the shelf. If the thin diamictonsof Uralian provenance had been formed subglacially bywestward ice flow, as Varsanofieva (1933), Kuznetsova(1971), Andreicheva (1992) and others suggested, thereshould have been abundant features of glacial erosionand deposition transverse to the longitudinal topogra-phy and structures of the Urals. Nothing of the kind hasever been detected by remote sensing or surfacemapping. On the contrary, all large structural andgeomorphic features suggest ice flow towards or parallelto the Urals. The NNE–SSW ice flow reflected in theclast distribution is also supported by large-scale

striations across the Palaeozoic structures of the TimanRidge (Fig. 3A).

The most reliable indicators of thick upslope flowinginland ice are large glaciotectonic disturbances which inplaces form arcuate ridges up to 250 km long (Astakhovet al., 1999). In the Pechora Basin such features areoriented in accordance with ice flow directions from NEand NW (Fig. 1). Huge rafts of soft Mesozoic rocks,including rock salt, have been incorporated into the tillof northeastern provenance. The till of the penultimateglaciation contains large basalt blocks from Timan(Guslitser, 1973). In the peri-Timan area ice flow fromthe west is also clearly indicated by surficial ice-pushedfeatures. For example, along the Arctic slope of theTiman Ridge a large allochtonous stack of westwarddipping, imbricated slices of Mesozoic and Quaternaryrocks, testifies to eastward glaciotectonic transport overa distance of some 40 km (Gornostay, 1990). Orienta-tion of small glaciotectonic structures is more scattered.

In the Arctic zone ice flow features directed fromlowlands into the mountains are abundant as well. Asand pit on Hanmei river near Labytnanghi on theeastern piedmont of the Polar Urals, examined duringthe PECHORA project expedition in 2000, displaysMiddle Pleistocene glaciofluvial gravels lying atop a veryclayey till (Fig. 9). Surprisingly, these sediments containmostly fragments of soft Mesozoic rocks from WestSiberia but no clasts of resistant ultramafic rocks fromthe nearby Rai-Iz massif. Gravelly cross-beds all diptowards the Urals. Farther northwards the LatePleistocene matrix-supported Sopkay moraines strikeW–E, i.e. transverse to the Urals, reflecting an ice flowfrom the shelf (Astakhov, 1979). Even the youngestbouldery moraines on the northwestern tip of the Uralsat 560 m asl show only ice push from the north, i.e. fromthe Kara Sea (Astakhov et al., 1999). The SE-facingarcuate ridges on the Siberian slope (Fig. 1), outlining apiedmont morainic apron south of the Arctic Circle(Astakhov, 1997), can hardly be of a Uralian origin,because they (i) occur only downglacier of old widetroughs crossing the narrow mountain range and (ii) donot have any symmetrical counterparts on the western,more humid slope. Therefore, the morainic apron of theeastern piedmont most likely originated from outletglaciers that drained a Middle Pleistocene ice sheet ofEuropean Russia via Uralian through valleys to the SE.This suggestion agrees with the boulder trains ofnorthwestern provenance traced across the Urals(Yakovlev, 1956).

For the interpretation of the ice sheet flow patterns itis crucial that the sedimentological evidence of lowlandglacial advance into the Urals are in accord with thepattern of ice-pushed ridges and terminal moraines inthe lowlands. Large ice-pushed ridges generally strikeparallel to the Arctic shoreline and nowhere fringe theUralian range except narrow morainic aprons along the

ARTICLE IN PRESSV. Astakhov / Quaternary Science Reviews 23 (2004) 1285–13111292

foot of the mountains south of 67�N (Astakhov, 1977,1997; Astakhov et al., 1986). Where discrepancies existbetween the lithological composition of the glacialdeposits and the pattern of ice-pushed ridges, the lattershould be taken as decisive evidence, because freshlarge-scale geomorphic features can only be produced bythe latest ice flows. The above mentioned horseshoe-shaped end moraines of the Kara ice sheet, shoved up-valley in the Polar Urals (Astakhov et al., 1999), consistof heaps of local boulders reoriented by ice push fromthe north. These and many other similar observationsare good evidence that the Urals were generally over-riden or bypassed by ice streams that originated north ofthe mountains, most likely on the western Kara shelf.The low and narrow mountain range of the Urals wasnot a major ice dispersal center either in the LatePleistocene (Astakhov et al., 1999), or in pre-Eemiantimes of greater continental ice sheets.

3.1.3. Dominant ice dispersal centre

Thus, the available data indicate that during theMiddle Pleistocene northern European Russia was therealm of a powerful inland ice that flowed from the NEupslope and eroded mostly soft Meso-Cenozoic sedi-ments to deposit unusually thick and clayey tills. Lateralerosion of the Ural Mountains by transit ice streamscontributed a small amount of central Uralian clasts tothe generally fine-grained drift. Although the main icestreams were basically directed to the south andsouthwest, inland ice also flowed laterally across theUrals, overriding their flat-topped mountains when theice was over 1 km thick. When the European ice sheetwas thinner, it could reach the Siberian slope of theUrals only in the form of outlet valley glaciers.

Karpukhin and Lavrov (1974) considered the Yakov-lev’s Novaya Zemlya ice sheet too large and preferred toexplain the NE–SW fabric in the Upper Volga area by adiverted flow of Fennoscandian ice. According to themtraces of a Novaya Zemlya glaciation and erratics of NEprovenance occur mainly east of river Severnaya Dvina.Immediately west of 50�E the drift limit turns almoststraight south in accordance with the margin ofFennoscandian ice. For comparison, Velichko et al.(1977), based on the peculiar composition of the fine-grained Don till, suggest that even the huge Don Lobeon 52�N was produced by the northeastern ice dispersalcentre!

The strong NNE–SSW orientation of various glacialfeatures, persistent over thousands of kilometers fromthe Pai-Hoi Range on 68�N to the Upper Volga on58�N, is truly amazing, especially compared to theradially diverging pattern of Fennoscandian ice flow. Itseems impossible for a small elongated ice dome over thenarrow Novaya Zemlya archipelago to produce theextensive ice streams which deflected the Fennoscandianice. The lowland ice sheets of northeastern origin, which

emanated such long strings of erratics and flow features,obviously were too thick to be obstructed by most iceadvances from Fennoscandia.

Yakovlev (1956), who saw the difficulty, suggested anadditional accumulation area on the adjacent BarentsSea shelf. However, no traces of ice flow from the NWonto the Russian mainland have been mapped for themaximum glaciation: anywhere east of 43�N all featuresare directed NE–SW or N–S. Features of W–E andNW–SE orientation and clasts of western provenancefirst appear in surficial tills of the penultimate (Vycheg-da=Moscow) glaciation, when the influence of thenortheastern ice dispersal centre decreased (Matveyeva,1967; Andreicheva, 1992; Andreicheva et al., 1997). Thisunderlines the dominant position of the Kara Sea shelfas a major source of inland ice in northern EuropeanRussia throughout the Pleistocene. Only during thepenultimate glaciation the shelf ice domes were over-powered by a Fennoscandian ice sheet which advancedacross the Timan Ridge at right angles to the ice flowfrom the Kara Sea.

3.2. Siberia

3.2.1. Signatures of ice motion

East of the Urals the thickness of inland ice and itsflow pattern are more controversial issues, especially forthe West Siberian Plain. Historically there have alwaysbeen competing hypotheses of large Middle Pleistoceneglaciers versus concepts of thinner local ice sheets thatwere assumed to reflect the drier Siberian climates. Thefirst paradigm is commonly maintained by practicinggeologists, who observe ubiquitous glacial features invarious areas and at various altitudes, whereas thesecond trend of thinking is largely motivated by generalpalaeogeographical considerations.

One of the main glaciation centres was inferred longago from the pyroxene abundance in till matrix and themafic rock fragments scattered over the Central SiberianPlateau built of Palaeozoic sedimentary formations,Triassic basalts and dolerites (Obruchev, 1931; Urvant-sev, 1931; Sachs, 1953). Three morainic belts rich indolerite boulders concentrically surround the PutoranaPlateau (Isayeva, 1963). In the east the Putorana icecoalesced with a small ice sheet of the Anabar Plateau. Itis interesting that during the penultimate glaciation theeasternmost Anabar ice sheet, similarly to the Europeansituation, was overpowered by eastward ice flow fromPutorana (Andreyeva and Isayeva, 1974). Ice flow fromthe High Arctic was inferred early basing on character-istic granite boulders transported onto the doleriteplateaus of Putorana from the Nordenskjold Archipe-lago and northern shores of the Taimyr Peninsula acrossthe c. 400m high Byrranga Mountains. The phenomen-on was first thought to result from a reverse topographicgradient of the Ice Age (Urvantsev, 1931). Today it is


seen as evidence of an ice dome thicker than 2 km on theKara Sea shelf. This Arctic ice sheet prevented thePutorana ice from flowing northwards (Andreyeva,1978; Kind and Leonov, 1982).

The difference between glacial features of CentralSiberia and West Siberia is striking. In Central SiberiaU-shaped valleys, deeply cut into bedrock and in placesbarred by boulder-rich morainic arcs, radiate from thePutorana ice dispersal centre. They are accompanied bysmoothed, striated, sometimes fluted and drumlinisedsurfaces, by occasional eskers and glaciofluvial fans(Isayeva, 1963; Arkhipov et al., 1976). There are suchtypical signatures of wet-based sliding as boulderpavements on the Yenissei (Troitsky, 1975).

On the contrary, eskers, flutes and marginal ridges aretotally absent west of the Yenissei. They are replaced bythe englacial glaciotectonic imbrications, kame fieldsand late glacial sandurs. Especially characteristics arethick fine-grained West Siberian tills with ubiquitouslocal and far-travelled blocks of soft sediments, includ-ing Quaternary and Palaeogene loose sands withoriginal lamination preserved. In many cases sedimen-tary rafts hundreds of meters long were transported overhundreds of kilometers (Shatsky, 1965; Zakharov, 1968;Kaplyanskaya and Tarnogradsky, 1974). The glaciotec-tonised structure of the glacial deposits, that is commonfor most sections of northern West Siberia, oftenprecludes visual tracing of stratigraphic contacts. Suchtills cannot have been deposited by lodgement, but mostlikely reflect the structure of dirty basal parts of hugestagnant ice sheets which slowly melted out in adegrading permafrost environment (Astakhov andIsayeva, 1988; Astakhov et al., 1996).

The wet-based versus dry-based features at the samelatitudes in Siberia clearly point out to the differencebetween the downslope sliding over rigid bedrock inCentral Siberia and slow glaciotectonic motion of theentire ice-permafrost couplet upslope in West Siberia.Especially suggestive are the huge composite imbrica-tions and the lack of any ice retreat features. In WestSiberia vast ice fields seem to have simultaneously lostmobility to decay for a very long time, being protectedfrom beneath by thick permafrost (Astakhov et al.,1996). Masses of buried glacial ice are ubiquitous in theUpper Pleistocene tills of Arctic Siberia. Fossil ice mayhave even survived from Middle Pleistocene glaciationsconserved in the West Siberian permafrost, as suggestedby very thick massive ice sometimes found in deepboreholes.

The described combination of glacial features indi-cates large ice sheets that were somewhat sluggish due tothe cold stored in the lithosphere over the entirePleistocene. This accummulated cold is evident fromnumerous boreholes in West Siberia, which find a thickperennially frozen layer at 150–200 m from the surfaceeven on 59–60�N, i.e. far south from the present-day

continuous permafrost of the Arctic. Detached blocksand drag structures in glacial drift of the region suggestthat the cold glaciers proceeded by involving intomotion a 300–400 m layer of very unstable althoughfrozen clayey substrate (Astakhov et al., 1996). This typeof inland glaciation is dynamically different from otherglaciated regions, which is also evident from the poorpreservation of interglacial formations. Inter-till palaeo-sols, common in North America, have never beenobserved in West Siberia.

The ice flow pattern is hard to recognise in the WestSiberian Plain, because the predominantly soft bedrock,consisting of Cretaceous and Palaeogene sand, silt, clay,opoka and diatomite provide neither streamlinedfeatures, nor enough clasts for statistical analysis.Before the onset of modern glacial sedimentology andglaciotectonic research in the 1970s the only ice flowindicators used for reconstructions were clasts ofUralian and Central Siberian crystalline rocks.Although already Obruchev (1931), basing on theconfiguration of the few known morainic chains,suggested a lowland ice dome on the Taz and Gydanpeninsulas, subsequent mapping failed to find itsmaterial signatures, and ensuing overviews acknowl-edged only ice dispersal paths from the Urals andCentral Siberian uplands (Sachs, 1953; Zarrina et al.,1961; Lazukov, 1970; Zubakov, 1972; Arkhipov et al.,1977). Nevertheless, Zemtsov (1973a, b), who inter-preted the composition of several thousand bouldersand mineralogical samples of till matrix, concluded thatthere was a central zone in the north of West Siberiawith no fragments of Uralian rocks or central Siberiandolerites. Tills of the central zone contained mostlymaterial of local Mesozoic and Cenozoic formationswith admixture of Taimyr rocks. Zemtsov thought thiszone to have been influenced by an additional icedispersal centre on the Taimyr Peninsula, and he did notrule out a possibility of ice flow from a hypotheticallowland ice dome by Obruchev (1931). Also Kaplyans-kaya and Tarnogradsky (1975) interpreted marinefossils found in diamictons of the Lower Yenissei areaas signatures of ice flow from the Kara Sea.

3.2.2. Puzzling erratics

Again, as in European Russia, in West Siberia adiscrepancy exists between the strong signatures ofupslope ice flow from lowland ice domes (Astakhov,1976, 1977) and the dominant petrographic and miner-alogical composition of the glacial drift, which see-mingly is evidence to the contrary. E.g. the mostcomprehensive study of till composition in West Siberia(Sukhorukova et al., 1987) reveals three major clasticprovinces roughly coinciding with the earlier conclu-sions by Zemtsov (1973a, b): Central Siberian, Uralianand West Siberian (Fig. 6). Sukhorukova et al. (1987)maintain that these provinces reflect the relative


significance of three major ice dispersal paths: from thePutorana Plateau, from the Urals and from the KaraSea shelf. First, this interpretation contradicts thepattern of ice-pushed features which everywhere onlyreflects ice flow directed upslope (Astakhov, 1977).Second, it is glaciologically impossible: there is noobstacles in the very low central West Siberian Plainthat would prevent Uralian and Central Siberian icestreams from moving farther south beyond the mappeddrift limit (Figs. 1 and 6). Especially strange is thesudden increase of Uralian clasts in the Ob tills south of64�N, which made Sukhorukova et al. (1987) suggest anice dome in the Northern Urals instead of the PolarUrals, as would follow from the general N–S icedirection of local boulder trains. In addition, the tillfabric along the Yenissei shows only ice movementtowards the south and not westwards across the valley.The suggestion by Kaplyanskaya and Tarnogradsky(1975), that upland ice divides, formed in the beginningof each ice age, afterwards might have shifted into thelowland, only partially helps.

It must be taken into account that the West Siberiantills are typical lowland diamictons consisting largely offine-grained material derived from the underlyingMesozoic and Palaeogene sediments. The admixture ofhard rock pebbles is very low (less than 1%) anddecreases northwards. Another interesting feature is flat-iron and wedge-shaped forms among the pebbles,noticeably more frequent than in other glaciatedregions. The ideal shape of glacial abrasion is oftenfound in the same pebble sample on very dissimilarmaterials, such as hard dolerites and soft opokas, unlikethe situation in Urals and Central Siberia, where wedge-shaped clasts mostly consist of schists and limestones.Also, up to 40% of the West Siberian glacial pebblesshow palimpsest aqueous roundness. Clasts in till arenormally found to be well sorted by their size, whichshould be characteristic of fluvial rather than glacialtransport (Sukhorukova et al., 1987). All these areunmistakable signs of very long paths of glacial andfluvial transport that involved multiple redepositionwhich certainly distorted the initial boulder trains.Therefore, the mapped ice limits, in agreement withthe flow pattern reflected in ice-pushed features, showonly the direction of the final, most powerful iceadvances from the north but not any earlier paths ofclast dispersal.

However, the progressive mixing and integration ofpebble and mineralogical composition over several iceages cannot explain the occurrence of large angularboulders from the Urals and Central Siberia, which areoccasionally found in the central West Siberian low-lands. These can probably be accounted for by the samemechanism as suggested for the Pechora Basin, i.e. bysuperglacial transport of stones from mountainousborderlands towards central lowlands caused by the

reversed ice surface gradient after the late glacialcollapse of the lowland ice domes.

3.2.3. Ice thickness and major ice dome

The mapped configuration of the glacial drift limit(Fig. 1) and large directional features are clear indica-tions of thick ice upslope moving during glacialculminations, irrespective of the predominant mechan-isms of crystalline clasts transport to the lowlands. Inthe adjacent mountains of the Urals and Central Siberiathere is ample evidence of upslope ice flow, such aslowland tills found high in the mountains (Fig. 4, loc.11,12, 13 in Fig. 1).

The crucial indication of southbound flow of thickMiddle Pleistocene ice in West Siberia is the system ofarcuate ice-shoved imbrications of intricately disturbedsoft rocks, often topographically expressed as hill–holepairs. The system of the largest ice pushed ridges runsroughly parallel to the coast of the Arctic Ocean (Fig. 1).The largest zones of thrusted and tightly foldedsediments are up to 200 km long and 20–25 km wide(Zakharov, 1968; Troitsky, 1975; Arkhipov et al., 1976;Astakhov, 1979; Astakhov et al., 1986). The distur-bances may penetrate down to 400 m below the surface,which is probably the world record. The tectonic style ofthese structures indicates their deformation in a frozenstate and is evidence of deep crumpling of soft substrateduring ice movement (Astakhov et al., 1996). Thesestructures, normally consisting of paraautochtonousslices or detached blocks of local provenance, as a rule,occur far upglacier from the ice margin. Along the icemargin they are often replaced by huge rafts of far-travelled Mesozoic, Palaeogene and Quaternary sedi-ments (the famous Yugan, Samarovo and Semeykaerratics of soft Jurassic and Paleogene rocks hundreds ofmeters long). They sometimes have been transported asfar as 600 km downglacier (Shatsky, 1965; Kaplyans-kaya and Tarnogradsky, 1974; Arkhipov et al., 1976).The above facts imply a thickness of the West Siberianice sheets in the order of kilometers, not hundreds ofmeters as was thought in the 1950–1960s (e.g. Lazukov,1970; Zubakov, 1972).

Independent evidence of very thick Middle Pleisto-cene ice in West Siberia is provided by numerous glacialvalleys with irregular bottom profiles that are buried bydrift, in places 300–400 m thick (Arkhipov and Mat-veyeva, 1964; Zubakov, 1972; Arkhipov et al., 1976,1994). These overdeepened, predominantly N–S strikingvalleys, never occur in the proglacial zone. Their glacialorigin can be readily seen in the longitudinal profile ofthe Quaternary thickness across the drift limit based onnumerous boreholes along the Ob and her left tribu-taries. In the periglacial area Pre-Quaternary bottomprofiles, gently sloping parallel to the present-day fluvialthalwegs, do not show any overdeepening (1–4 inFig. 5). Immediately north of the maximum glaciation

ARTICLE IN PRESS

Fig. 6. Clast provinces in tills of the West Siberian maximum

glaciation (from Sukhorukova et al., 1987, simplified). UR—Uralian

province of crystalline and Palaeozoic erratics; CS—province of

Central Siberian erratics: dolerites, carbonate rocks and sandstones;

WS—province of no Uralian and Central Siberian stones, with

predominating quartz, opokas, diatomites, siltstones, sandstones of

West Siberian Mesozoic and Cenozoic formations. Taimyr boulders

sporadically occur in both WS and CS provinces. Arrows are ice flow

directions inferred from fabrics and erratics. Dispersal of Central

Siberian and Uralian erratics is not conformable with configuration of

the ice limit (bold line), orientation of ice-pushed ridges (Fig. 1) and

with lowland tills deposited in the mountains (Fig. 4).

Fig. 5. Longitudinal profile of buried valleys of the Ob system (from Astakhov, 1991). Symbols: 1—present thalwegs; 2—sub-Quaternary surface;

3—glacial drift limit; 4—profile of boreholes across the valley. Circled numbers: (1) source of Turgai river flowing to the Aral Sea; (2) source of

Ubagan river; (3) mouth of Ubagan river; (4) mouth of Tobol river; (5) the Irtysh mouth; (6) the Ob mouth. Compare normal fluvial profiles of

extraglacial valleys in the left with bumpy overdeepened trough of glaciated area in the right of the figure.

V. Astakhov / Quaternary Science Reviews 23 (2004) 1285–1311 1295

limit the buried bottom of the Ob valley becomes veryirregular, plunging deep below sea level (5, 6 in Fig. 5),which cannot be explained by normal fluvial processes.

The principal ice dome over the Kara Sea shelf andadjacent lowlands only got generally (although notunanimously) accepted after remote sensing had re-vealed the pattern of ice pushed ridges and after foreignerratics found in the mountains were considered

(Astakhov, 1976, 1977, 1979). Lowland tills of Mesozoicprovenance of the West Siberian Basin (Fig. 4B) anderratic boulders found high in the Urals indicate thatabove the Arctic Circle inland ice covered summits morethan 1 km high, whereas at 62–63�N the trimline occursat c. 500 m asl. In the western part of the CentralSiberian Upland three till sheets with lowland erratics,33 m thick altogether, were described on the table-likesummit of a dolerite monadnock 618 asl at 150 km fromthe drift limit (location 13 in Fig. 1, Fainer et al., 1976).The surface of the inland ice, which brought Mesozoicmaterial from the northwest and deposited it atop theinselberg at loc. 13, Fig. 1, must have been higher than700 m asl (Fainer et al., 1976) and at least 900 mupglacier in the Yenissei valley, south of loc. 9(Fig. 1), where till of the maximum glaciation wasfound below sea level (Zubakov, 1972). These observa-tions make the West Siberian ice sheet at least 500 mthick at 64�N at 150 km from the drift limit and c.1000 m thick at 65�N, i.e. at 350 km upglacier from themargin of the maximum ice sheet (Fig. 6).

Voronov (1964), basing on empirical profiles ofAntarctic and Greenland ice sheets and the knownconfiguration of the drift limit in Siberia, calculated themaximum thickness of the West Siberian ice sheet as3.5 km on the Yamal Peninsula. Judging by the abovegeological facts, this estimate seems to be realistic. Tooverpower and divert southwards ice streams from thePutorana Plateau, as evidenced by the foreign tills east ofthe Yenissei, the lowland ice dome must have been reallythick and probably occupied the entire Kara Sea shelf.

4. Chronology of ice advances

4.1. European Russia

4.1.1. General stratigraphic framework

The modern chronological concepts of Middle Pleis-tocene glaciations in northern European Russia are

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Table 1

Correlations of pre-Weichselian glacial events of northeastern European Russia with other regions

Astakhov, this paper Guslitser et al. (1986)+Velichko and Shick (2001) Central Russia Northern Germany Isotope stages

Sula interglacial Sula interglacial Mikulino interglacial Eem 5e

Vychegda glacial Vychegda glacial Moscow glacial Warthe

Kostroma interstadial Interstadial 6

Dnieper glacial Drenthe

Interstadial 7

Rodionovo interglacial Cold stadial Wacken 8

Chekalin interglacial (D .omnitz) 9

Pechora glacial Kaluga cold stage Fuhne 10

Chirva=Rodionovo Chirva interglacial Likhvin interglacial Holstein 11

Pechora glacial Pomus glacial Oka glacial Elster 12–14

Visherka interglacial Visherka interglacial Roslavl=Muchkap interglacial 15

Maximum glacial Beryozovka glacial Don glacial Cromer 16

Kolva transgression Tumskaya interglacial Ilyinka interglacial 17

Pre-Kolva glacial Kama glacial Likovo glacial 18


heavily dependent on the official stratigraphic scale ofCentral Russia, either directly, as in the ArkhangelskRegion of prevailing Fennoscandian glaciers, or indisguise of local startigraphic labels, as in the Timan–Pechora–Vychegda Region of dominant ice advancesfrom the northeast (Guslitser et al., 1986).

The stratigraphic cornerstones of central EuropeanRussia are classical interglacial formations of biogenicand limnic sediments at the Likhvin and Mikulinostratotypes, indicating climates warmer than the present.They were traditionally correlated to the Holsteinianand Eemian. The most continuous till sheet is poorlytopographically expressed and for a long time has beenassociated with the Dnieper maximum of the Fennos-candian glaciation in the Ukraine, close to 48�N, andwith the German Saale glaciation. Another, lessextensive pre-Eemian glacial complex, mapped mainlynorth of 54�N by its distinct glacial topography, isattributed to the Moscow glaciation, presumablyequivalent to the Warthe glaciation (Yakovlev, 1956;Goretsky et al., 1982). The till underlying the Likhvinmarker horizon for a long time was thought to representthe oldest Oka (Elsterian) ice sheet of more limitedextent (Table 1).

The most problematic was the third interglacialformation (Odintsovo, or Roslavl) found between twouppermost Middle Pleistocene tills. This sequence,showing a characteristic pollen profile with two decid-uous peaks, is notably different from both Likhvin andMikulino pollen successions. In formal stratigraphicschemes and in general maps of the Quaternary it wasfor many years placed between the Moscow andmaximum Dnieper glaciations (Krasnov, 1971; Gane-shin, 1973), although there always were dissidentsinsisting on a much older age of the Roslavl strata.

This scheme with two separate Saalian glaciations wasalso applied to northern European Russia, where theNovaya Zemlya till was associated with the maximum

Dnieper ice advance and the younger till containingFennoscandian erratics—with the Moscow glaciation.The official regional stratigraphic scheme offers correla-tion units (climatostratigraphic horizons) replicatingcentral Russian climatoliths (Guslitser et al., 1986).Several glacials and interglacials were distinguishedfrom litho- and pollen stratigraphy in parallel with theold Central Russian stratigraphic scale, in which Saaliantills were separated by the very warm interglacial calledOdintsovo (Roslavl) around Moscow and Rodionovoon the Pechora.

However, in the 1970s it was discovered that the till ofthe Don Lobe was older than the Dnieper till of theUkraine (Velichko et al., 1977; Velichko and Faustova,1986). The Don till is overlain by the Muchkapinterglacial strata with two characteristic deciduousoptima and with remains of typically Tiraspol (Cromer)rodents. A similar fauna was described from thestratotype sections of the Roslavl interglacial. Thisimplied that the maximum glaciation on the Don wasseparated from the Dnieper till by at least twointerglacials: Roslavl (Muchkap) and Likhvin. Therebyan intra-Saalian interglacial had to be abandoned(Shick, 1989). The new stratigraphy was proven beyondany reasonable doubt when sediments with the Likhvin(Russian Holsteinian) floras were found atop theRoslavl sequence (Biryukov et al., 1992). In thestratigraphic scheme of Central Russia, presently usedby the Russian Geological Survey, no early Saalian tillor overlying intra-Saalian interglacial formation (OIS 8and 7) are mentioned. The only till sandwiched betweenthe Likhvin and Mikulino formations is the Moscowglacial complex correlated with OIS 6 which presumablylaterally merges with the Dnieper till of the Ukraine(Shick, 1989).

Still, there are researchers who accept the new pre-Holsteinian Don–Muchkap cycle but also insist on twoseparate glaciations (the Dnieper and Moscow) between


the Likhvin and Mikulino warm stages (e.g. Sudakovaand Faustova, 1995). Recently an attempt to fill in thegap between the Moscow till and Likhvin strata hasbeen undertaken by Velichko and Shick (2001). Theysuggest as climatochronological units 2 palaeosols and 2loess units found directly on top of the Likhvinlacustrine formation with Brasenia flora (Table 1). Inthis new scheme they place the Dnieper glaciation at thebeginning of OIS 6, implying that the maximum driftlimit in the Ukraine is somewhat older than the Moscowtill within the same ice age. The maximum glaciation ofthe eastern Russian Plain is firmly outlined by the DonLobe (probably OIS 16) reaching south to the 50thparallel.

4.1.2. Stratigraphy in the Arctic

The modern stratigraphic scheme first did not affectthe remote northern areas, where two Saalian tills(Pechora and Vychegda) were conventionally correlatedwith the Dnieper and Moscow glaciations. These tills areseparated by a warm interglacial with two climaticoptima described at Rodionovo as a counterpart of theOdintsovo/Roslavl (2 in Fig. 1) (Guslitser et al., 1986;Loseva et al., 1992; Duryagina and Konovalenko, 1993;Andreicheva et al., 1997). The situation is morecomplicated in the Arctic, where inter-till marineformations are not readily correlated with the centralRussian stratotypes, or with terrestrial interglacials ofthe Middle and Upper Pechora catchment. Drillingprojects by the Geological Survey provided a wealth ofinformation on the structure of drift in the Arctic. Twosuch borehole profiles supported by field observations(A and B in Fig. 1) reveal at least four independentdiamict sheets separated by four marine formations(Fig. 2). The topmost glaciotectonised complex withblocks of marine sand is obviously a deposit of the shelf-based Weichselian glaciation (Astakhov et al., 1999;Svendsen et al., this volume). It is separated from thethickest till body g3 by sands with an Eemian fauna (m4by Lavrushin et al., 1989). The g3 till lies above sea leveland cannot be anything but a Saalian till. Just below sealevel it is underlain by lacustrine sediments with Likhvintype pollen spectra merging seawards with marineformation m3 (Lavrushin et al., 1989). The two lower-most marine formations m1 and m2 and intervening tillsheets g1 and g2 cannot be correlated directly with anyof the southern stratotypes.

The old view of one boreal transgression separatingtwo last glacial events (Ramsay, 1904) was challenged byYakovlev (1956) and by geologists who reported the firstdrilling results in the White Sea basin (Biske andDevyatova, 1965). They maintained that two borealtransgressions with similar mollusc fauna occurred: theBoreal transgression s. stricto, an arm of the Eemian sea,and the so-called Northern transgression, which wasconventionally correlated with an intra-Saalian event.

The second shallow-water atlantic transgression waslater supported by drillings in the Pechora catchmentarea, where two sandy formations with boreal faunawere found alternating with diamictons. The upperboreal formation with Arctica islandica had been knownlong ago from many sections above sea level as acounterpart of the Eemian, whereas the lower formationwith characteristic extinct mollusc Cyrtodaria jenisseae

(angusta) was reported from beneath a thick diamictonjust below sea level (Zarkhidze, 1972).

A third marine sequence of deep-water silts, the so-called Kolva formation, found well below sea level at thebase of the Quaternary cover, contains mostly aSubarctic fauna with characteristic Propeamussium

groenlandicum (Yakhimovich et al., 1973) and probablycorresponds to unit m1 in the Lavrushin’s profiles(Fig. 2). In some boreholes it is underlain by adiamicton. From the Kolva formation Gudina (1976)described an arctoboreal foraminifera with character-istic Miliolinella pyriformis, which she correlated withthe Ob and Turukhan strata in West Siberia and withthe marine Holsteinian. The latter correlation is at oddswith palynological investigations which find Likhvin-type spectra stratigraphically higher than the Kolvaformation (Fig. 2). In one borehole a diamicton wasdiscovered at the base of the Kolva formation (Yakhi-movich et al., 1973).

4.1.3. Stratigraphy in the Subarctic

Terrestrial interglacial sediments sandwiched betweentills are known mainly from three natural exposures inthe Pechora catchment area. The best studied is theRodionovo section (2 in Fig. 1) with very compact,slated and slightly distorted peat up to 3.5 m thickcontained in clay and silt within a sandy inter-till fluvialsequence. In the arboreal pollen spectra spruce, pine andbirch are dominant with admixture of Abies and Alnus

(Loseva and Duryagina, 1973). Two climatic optimawere inferred based on a small admixture of deciduoustree pollen (Duryagina and Konovalenko, 1993), whichled the referred authors correlate this sequence with theOdintsovo/Roslavl interglacial of Central Russia.

In the Kipiyevo section (3 in Fig. 1) lacustrine stratawith a similar pollen assemblage also contain large Unio

shells, thick coniferous logs with ‘formidable growth oftree-rings’ and nuts of Ajuga reptans, which now livesonly in oak forests some 400 km to the south (Guslitserand Isaychev, 1983). The Kipiyevo interglacial strata aredissected by ice wedge-casts and overlain by sedimentscontaining a late Middle Pleistocene assemblage of teethof pied and grey lemming, similar to that found betweenthe Likhvin lacustrine strata and the overlying till southof Moscow. The evolutionary level of the Kipiyevolemmings is somewhat higher than in the Likhvinstratotype, which made Guslitser and Isaychev (1983)suggest a Moscow–Warthe age for this rather archaic

ARTICLE IN PRESS

Table 2

Middle Pleistocene glacial chronology of Siberia (after Arkhipov, 1989)

Glaciations/Interglaciations Arctic zone Subarctic zone Isotope stages

Ages of marine formations, ka Ages of terrestrial formations, ka

Kazantsevo ESR 105710.5; 120713; 121.9; 134.8 TL 130725 5e

Taz 6

Shirta ESR 170710 ESR 196.8720.6 7

TL 180740; 190736

Samarovo 8

Tobol ESR 306721 ESR 326.9; 396 9–11

TL 260756 to 390780

Late Shaitan TL 510765; 12–16

Early Shaitan 550(561)7110(140)

Talagaika TL 6607180; 7407170 17

Mansi 18


fauna. They also describe another find of similar rodentremains in the Akis section 6 km downstream of loc. 2,Fig. 1. At this site lemming teeth were collected fromcross-bedded sand overlying the same Novaya Zemlyatill as is at the base of the Kipiyevo sequence. Theevolutionary level of the Akis lemmings is only slightlyhigher than in the Lower Saalian beds of the Likhvinsection, again with no progressive Late Pleistocenemorphotypes present. Guslitser and Isaychev (1983)relate the Kipiyevo interglacial to the Saale–Wartheinterglacial (OIS 7) and the underlying till to the ‘earlySaale’.

Recent dating attempts by the Russian–NorwegianPECHORA project confirm an OIS 6 age for thesurficial till of the Subarctic zone. The dated section islocated in present-day tundra on Seyda river, formallyin the Arctic (4 in Fig. 1) but featuring only terrestrialsediments. A compact peat layer 1 m thick and 300 mlong, with forest pollen spectra even richer than inRodionovo, is contained in a thin sand sheet at the baseof the 40 m thick stacked till sequence. The peat firstyielded a finite radiocarbon date and was thought torepresent the Middle Weichselian (Lodmashchelye sec-tion by Arslanov et al., 1987).

However, more detailed sampling of this sequence byJ.I. Svendsen and M. Henriksen provided much olderages. An uninterrupted series of samples of the inter-tillpeat analysed for U/Th ratio in the laboratory of St.Petersburg University yielded ages of ca 200730 ka BPin the middle of the peat layer. Younger values obtainedfrom the top and bottom of the peat are accounted forby postdepositional influx of younger uranium (analystYu. Kuznetsov). OSL dating on quartz particles in thepeat produced ages of 180713, 185712 and191737 ka, whereas the surrounding sand was datedto c. 144 ka (three datings) and once to 173775 ka.Glaciofluvial and glaciotectonised sands in the upperpart of the overlying glacial complex sequences yieldedOSL values of 148710, 149713, 152711, 156716,

16079 and 170713 (Table 3). Thus, there are twodifferent sets of OSL dates: one is close to 150 ka andanother is close to 200 ka. The consistency of the datesand the large measured dose rates, according to A.Murray, make these dates apparently reliable. The 50 kadifference in OSL ages of the two sets of samplesprobably means that a Late Saalian glacier picked up apeat layer ca 200 ka old and deposited it as a stratiformraft together with younger glaciofluvial sand. A Saalianage of this sequence is supported by OSL dates of10978 from the top and 143712 ka from the bottom ofthe overlying aeolian sand. A Late Saalian OSL date of15279 ka was also obtained from the sand between thepeat and the upper till at Rodionovo (Table 3, sample byO. Maslenikova).

The age of the lower, ‘Novaya Zemlya’ till of thePechora basin is less certain. Its correlation depends onthe age of the Rodionovo interglacial. OIS 7 suggestedby local geologists by comparison with the centralRussian Odintsovo–Roslavl sequence (Guslitser et al.,1986) looks like a miscorrelation, because the Roslavlstrata around Moscow are certainly pre-Likhvin, or pre-Holsteinian (see above).

4.1.4. How many ice advances?

This question heavily depends on the correlation ofthe rare interglacial sequences. It is interesting tocompare the palaeontological characteristics of theRodionovo formation with the Chirva interglacial strataknown from boreholes in the south of the Subarcticzone (Vychegda catchment area) and correlated bypollen with the Likhvin interglacial (Duryagina andKonovalenko, 1993). These and other authors (Guslitseret al., 1986; Loseva et al., 1992; Andreicheva et al., 1997)presume that the Chirva predates the Rodionovo.However, both formations contain almost identicalbotanical taxa, including indicative Likhvin speciesOsmunda claytoniana and O. cinnamomea (Table 7 inDuryagina and Konovalenko, 1993). Both pollen

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Table 3

Optically stimulated luminescence dates by the PECHORA project according to A. Murray, the Nordic Laboratory for Luminescence Dating, Ris^,

Denmark

Lab. no Sample no. Location Age (ka) Dose rate (Gy/ka) Paleo dose (Gy)

002527 99-1238 Rodionovo, above peat 15279 1.2070.04 18376

002526 99-1237 Rodionovo, below peat 334729 0.9770.04 323722

992529 98-3078 Seyda 1, aeolian 10978 1.7370.09 18978

992528 98-3077 Seyda 1, aeolian 143712 0.9570.05 13678

002540 99-4226 Seyda 1 sand in till 148710 1.4970.06 220710

002539 99-4225 Seyda 1, sand in till 149713 1.3870.05 206715

002541 99-4227 Seyda 1, sand in till 152711 1.50 230713

002542 99-4228 Seyda 1, sand in till 16079 1.74 27979



992515 98-3029 Seyda 1, sand below till 144714 1.7670.09 254718

992511 98-3063 Seyda 1, sand below till 144713 1.4470.07 207714

962523 95-0070 Seyda 1, sand below tilll 145742 2.15 289

992502 98-3035 Seyda 1, sand above peat 185712 1.8270.09 33674

992501 98-3033 Seyda 1, interglacial peat 180713 1.3970.07 251710

962524 95-0071 Seyda 1, interglacial peat 191737 1.96 347

962525 95-0072 Seyda 1, sand below peat 173715 1.68 271

012584 01-0197 Sangompan, below rhythmite 8275 1.6170.07 13174




012586 01-0134 Pyak-Yaha, above rhythmite 133711 1.5970.08 211714

012585 01-0133 Pyak-Yaha, above rhythmite 13878 1.5170.07 20875

012581 01-0115 Pichuguy-Yaha, above rhythmite 125710 1.7770.08 221714

012582 01-0116 Pichuguy-Yaha above rhythmite 13779 1.6670.08 22779

012579 01-0119 Pichuguy-Yaha, below rhythmite 197715 0.9170.06 17978

012580 01-0120 Pichuguy-Yaha, below rhythmite 192716 0.7870.05 15077

012548 00-0505 Aksarka 2, coversand 17.370.8 1.7070.07 8173

012547 00-0504 Aksarka 2, loess-like silt 19.870.9 2.1370.08 8173

002550 00-0503 Aksarka 2, sand with wood 9778 1.90 18479

002549 00-0500 Aksarka 2, sand with wood 84710 1.94 168716

002545 00-0450 Sopkay, sandur 167722 1.17 192723

002546 00-0451 Sopkay, sandur 96713 1.54 148717

012544 00-0418 Yerkata, Yamal, aeolian sand above till 5874 1.8470.07 10675

012543 00-0416 Yerkata, Yamal, aeolian sand above till 6275 1.8970.08 11877

012542 00-0414 Yerkata, Yamal, lacustrine sand above till 6875 1.6970.07 11576

012541 00-0413 Yerkata, Yamal, lacustrine sand above till 5974 1.9470.07 11475


diagrams feature five zones and two climatic optimawith an admixture of deciduous trees, both, unlike theolder Visherka horizon, contain no Tertiary relicts andonly rare exotic (Balkan-Caucasus) elements such asBetula sect. Costatae, Picea sect. Omorica, P. sect.

Strobus. The slightly richer floristic compostion of theChirva strata is easily explained by the more southerlyposition of the studied site. As mentioned above, therodent assemblages above the Kipiyevo (Rodionovo)strata are very similar to those found on top of theLikhvin type sequence. The only OSL date availablefrom the base of the Rodionovo peat gave a fairly oldvalue 334729 ka, more appropriate for OIS 9 or 11 thanfor OIS 7 (sample by O. Maslenikova, Table 3).

The most important is the stratigraphic position ofthe interglacial formations in borehole profiles of theArctic zone (A, B and C in Fig. 1). Loseva et al. (1992)relate the pollen spectra of the terrestrial inter-till

sequence in boreholes 8-y, 5-y, 3-y and 71 (Fig. 7) tothe Chirva interglacial, but the marine formation at thesame level in the SE boreholes 754 and 755 is correlatedwith the younger Rodionovo interglacial. Consequently,the overlying till in the NW boreholes is thought to bethe Pechora till (OIS 8 in their correlation), but itslateral counterpart in the SE is referred to the youngerVychegda till (OIS 6) (Fig. 7). Neither the lithologicalcomposition of the tills, nor the landscape featuressupport such a differentiation. In the profile describedby Lavrushin et al. (1989) slightly farther to the east (Ain Fig. 1) the lateral change from the Likhvin lacustrineformation to the marine formation m3 (Fig. 2),suggested by the authors, seems more logical.

The Chirva and Rodionovo interglacials have neverbeen found in superposition (Figs. 2 and 8). Therefore, itappears that the uppermost Middle Pleistocene inter-glacial, the Rodionovo on the Pechora, is identical with

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Fig. 7. Middle Pleistocene formations in boreholes of profile C (Fig. 1) (from Loseva et al., 1992, simplified). Letters indicate correlation with

regional climatostratigraphic horizons assumed by Loseva et al. (1992): v—Visherka interglacial, pm—Pomus glacial, W—Chirva interglacial; pW—

Pechora glacial; r—Rodionovo interglacial, vW—Vychegda glacial. Broken lines is alternative correlation suggested by this author.


the Chirva interglacial of the Vychegda catchment area.Many interglacial sequences covered by the upper till inthe Subarctic zone, and lying just below sea level in theArctic, probably belong to the same interglacial interval,most likely represented by the marine formation withCyrtodaria angusta. The Cyrtodaria strata are in placesfound up to 70 m asl (Zarkhidze, 1972), which gives arough idea of the large isostatic depression caused by thethick preceding ice sheet.

In the compromise scheme by Velichko and Shick(2001), accepting the different Chirva and Rodionovointerglacials, the Pechora glaciation is not correlatedanymore with the Dnieper or other maximum iceadvance of Central Russia. Instead it is shifted down-wards to OIS 10, probably in order to accommodate atOIS 12 another glaciation called the Pomus by Guslitseret al. (1986) (Table 1). This results in the correlation ofthe mighty Pechora glaciation of NE provenance withthe thin Kaluga loess on top of the Likhvin stratotypesequence. However, the Pechora till, widely observed inmany Subarctic sections and covered by the distinctlyinterglacial Rodionovo formation, is still the mostsalient feature of the northern drift. Therefore, it bettercorrelates with a central Russian till covered by theLikhvin strata, the Oka till, which has been always

thought as Elsterian in age. There is no lithostrati-graphic evidence of a laterally consistent Pomus glacialcomplex.

Whether the Chirva/Rodionovo interglacial corre-sponds to OIS 9 or to OIS 11 is uncertain, but itsstratigraphic postion makes it the best candidate forcorrelation with the Russian Holsteinian, i.e. theLikhvin s. stricto. The preceding Visherka interglacialsequence, containing Tertiary relics such as Liquidambar

and Pterocarya plus exotic Tsuga and Ilex, not knownfrom younger interglacials, consequently would bettercorrespond to the Roslavl/Muchkap strata overlying theDon till of the maximum glaciation, as suggested byVelichko and Shick (2001) (Table 1).

In this respect sections close to the glacial drift limitare of particular interest. The best picture of thegeological structure of the Pechora–Volga interfluvearea is given by the geotechnical drilling data describedby Stepanov (1974, 1976). Two of his profiles crossingeach other at right angles are presented in Fig. 8. Thesurficial till g3 correlated by Stepanov with the Dnieperglaciation is covered by only one interglacial alluvialformation of the modern valleys with fresh-watermolluscs, rich diatom flora and chracteristic Mikulinopollen spectra. A modern area of concentration of the

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Fig. 8. Borehole profiles of Middle Pleistocene tills at Lake-Chusovskoye, Pechora–Kama interfluve, N 61� (from Stepanov, 1974, simplified).

1—diamicton; 2—gravel; 3—sand; 4 laminated silt and clay; 5—loess-like silt; 6—bedrock; 7—borehole. Broken line shows intersection

of two perpendicular profiles. Till units are numbered upwards in the succession g1, g2, g3 irrespectively of their possible age.


fossil flora can be found in southern Germany andPoland. The same is true of the Mikulino type flora ofcentral Russia.

The interglacial formation between g3 and theunderlying g2 till (Fig. 8) contains a flora similar tothe Likhvin assemblage with indicator plants such asOsmunda claytoniana, Pinus sect. Strobus, Picea sect.

Omorica, Tilia tomentosa which have a modern area ofconcentration in the western foothills of the Alps,according to L. Tyurina. The plant macrofossilsidentified by P.I. Dorofeyev are typical for the Singilfloras of the Russian ‘Mindel-Riss’ (Stepanov, 1976). Asingle find of forest elephant Palaeoloxodon sp. is knownfrom a similar sequence on Kolva river, tributary to the

Kama river (Yakhimovich et al., 1973). The overlying g3till should be the Uralian counterpart of the Vychegdatill. The underlying dark-grey till g2, low in Uralianboulders, contains mostly clasts of sedimentaryrocks and in this respect is not different from thePechora till.

The lower inter-till formation (between g2 and g1)shows pollen spectra of mixed forests with very fewpollen of Carpinus, Corylus and exotic trees. The highpercentage of pyrite grains is typical for the oldestinterglacial of the eastern Russian Plain (Stepanov,1974). If the lower interglacial sequence, locally labeledthe Solikamsk formation, can be correlated withthe Roslavl/Muchkap strata, then the underlying


overconsolidated g1 till (the Kama till of Stepanov)should be a counterpart of the Don till of southernRussia.

The alternative interpretation puts the Solikamskinterglacial into OIS 17–19 and the Kama till into OIS20 (Zubakov, 1992), which makes the Kama tillcontemporaneous to the Mansi till of West Siberiapresently attributed to the Matuyama chron (Volkovaand Babushkin, 2000). If the latter interpretation iscorrect, then the maximum glaciation of northeasternRussia is represented by g2 till of Stepanov’s profile(Fig. 8). The limit of this maximum glaciation shown inthe left lower corner of Fig. 1 was for many yearsattributed to the Dnieper (early Saalian) glaciation(Krasnov, 1971; Ganeshin, 1973) which later proved tobe wrong (Velichko et al., 1977; Shick, 1989).

The correlation between the Arctic region of marinetransgressions and the Upper Pechora–Vychegda catch-ments remains problematic. A formal comparison saysthat the three main glacial complexes underlying theUpper Pleistocene of the Arctic (Fig. 2) probablycorrespond to the three tills of the Pechora–Kamainterfluve (Fig. 8). However, g1, g2 and g3 in bothprofiles are just diamict units numbered by this authorand cannot be viewed as synchronous with similarlydesignated tills in the Arctic profiles. Actually, it is noteasy to find in the Arctic Pleistocene counterparts to allwarm intervals of the southern record. Two borealtransgressions are more or less satisfactorily reflected inthe warm Mikulino and Likhvin floras of the south,whereas there is no evidence to synchronise the coolKolva marine strata with the Visherka or Solikamskinterglacial formations with their exotic plant remains.It is possible that the Kolva interglacial is missing in theterrestrial record of the Subarctic zone. This questionwill stay open until more reliable means of long-distancecorrelation are found.

The above brief analysis of the available stratigraphicdata allows to conclude that there are at least threereadily recognisable glacial complexes and major pre-Weichselian ice advances in northeastern EuropeanRussia, which certainly does not preclude their subdivi-sion into minor glacial stages. The fourth ice advancepreceding the Kolva transgression in the Arctic mighttentatively be correlated with the Kama till of thePechora–Volga intefluve.

4.2. Siberia

4.2.1. General stratigraphic situation

The Siberian glacial chronology is more arbitrary dueto the formidable size of the country and poorapplicability of pollen analysis. Unfortunately thedominant boreal forests have a monotonous composi-tion with practically no deciduous trees presentlygrowing, except sparse lime in southwestern West

Siberia. Therefore, in distinguishing interglacials onehas to rely on N–S shifts of very broad biogeographicalzones, which would demand hundreds of meticulouslystudied sections. In literature one can usually seegeneralisations of a continental scale based on a handfulof sites and, which is even worse, with European labelsattached to totally unrelated objects, i.e. atlantic termsapplied to a non-atlantic environment. This certainlyhinders development of an independent Siberian Pleis-tocene startigraphy. Many geologists, exasperated bythe difficulties encountered in Siberia, took to elaborat-ing local stratigraphic scales by exclusively chronometricmethods which normally should only be used for long-distance correlation. This poor practice, exemplified bythe popular misuse of radiocarbon dating, led tocorruption of the traditional stratigraphic nomencla-ture, which is not reliable anymore, being permanentlyreshuffled after each laboratory ‘discovery’ (Astakhov,2001). To lesser degree the same happens with theMiddle Pleistocene, although the limited number ofavailable chronometric methods helps to keep the oldstratigraphic terminology in a better shape.

Two stratigraphic markers, identified in key sectionsof the West Siberian basin, over several decades havebeen the cornerstones of glacial history and Quaternarymapping. These are the interglacial formations of theKazantsevo transgression in the Arctic and the Tobolalluvium in central and southern West Siberia. TheKazantsevo formation consists mostly of shallow-waterfacies containing rich arctoboreal mollusc fauna withcharacteristic boreal species such as Arctica islandica

indicating water temperatures 4–8�C above the present-day Kara Sea temperature (Sachs, 1953; Troitsky, 1975).This formation is conventionally correlated with theEemian strata of the Boreal transgression in EuropeanRussia. This correlation seems to be confirmed inYenissei Siberia by several ESR dates on marine shellsin the range 108–134 ka (Sukhorukova, 1999). The maindrawback of this marker horizon is its being limited tothe Arctic, where it is overlain by till and often badlyglaciotectonised.

The marker significance of the Kazantsevo formationis somewhat diluted by the fact, that, as in EuropeanRussia, there are distinct traces of another borealtransgression. First, boreal mollusc shells and foramini-fera have been locally found in Middle Pleistocenediamictons (Arkhipov and Matveyeva, 1964; Kaplyans-kaya and Tarnogradsky, 1975). Second, there are inter-till strata with rare boreal molluscs (Zubakov, 1972).Third, some Kazantsevo marine sequences containshells of extinct species Cyrtodaria jenisseae (angusta)

(Sachs, 1953; Kind and Leonov, 1982, see also discus-sion on Taimyr in Svendsen et al., this volume) andprobably belong to earlier interglacials.

The Tobol strata are much better preserved in thearea of their classic occurrence along the transverse Ob


and lower Irtysh, mostly between 62�N and 56�N, i.e.just within the drift limit and in the periglacial area.They are washed, diagonally bedded quartz sands withthick lenses of green-bluish clayey silts, partly coveredby till of the maximum glaciation. Literature on theTobol strata is extensive, especially regarding palaeon-tological questions. A comprehensive overview ofgeological data is given in a collection of papers editedby Arkhipov (1975), and also in numerous works bypalaeobotanists.

Pollen spectra, as always in Siberia, are not verycharacteristic. Sequences in the present taiga zonemainly show a predominance of arboreal Betula andrich herb assemblages with a minor coniferous compo-nent, which is common for the Siberian forest-steppe.Some successions reveal two coniferous peaks below andabove the main forest-steppe phase. The interglacialnature of the formation is clear from abundant fresh-water molluscs, especially Corbicula fluminalis (tibeten-

sis) presently living only in Central Asia. However, arather cool and relatively humid climate is indicated bythe rich macrofossil flora with exotic aquatic fernsAzolla interglacialica, Selaginella selaginoides, Salvinia

natans, etc. This assemblage, known as the ‘Flora of theDiagonal Sands’, is similar to the Singil flora of theRussian Plain and has for several decades been the mainindicator of the so-called ‘Siberian Mindel-Riss’ and anargument for its correlation with the Likhvin andterrestrial Holsteinian. Later Azolla remains were alsofound in Upper Pleistocene sediments of the Lower Ob(Arkhipov et al., 1977).

The mammal fauna is the most controversial issue,probably due to the all-pervading redeposition ofosteological material by the huge laterally migratingrivers. More frequent are finds of bones of the Tiraspol(Cromer) mammals. There is only one known site withforest fauna of the Singil type represented by Palaeolox-

odon, Megaloceros, Bison, Eolagurus, Arvicola, etc. Inmany places the ‘diagonal sands’ contain mammalspecies ranging from pre-Tiraspol to typical LatePleistocene lemming faunas. The explanation is thatthe ‘diagonal sands’ may be deposited at the sametopographic level by slow meandering rivers duringdifferent interglacials. The Tobol formation proper,according to Arkhipov (1975), chronologically rangesfrom the second half of Mindel to the Mindel-Rissinterval, i.e. belongs to two interglacials.

This interpretation was supported by a wedge ofglaciolacustrine varves (the Semeika formation) foundin the middle of the Tobol formation on the Irtysh,where it is also overlain by till of the maximumSamarovo glaciation. The lower alluvial sequence, calledthe Talagaika formation, is thought to represent a pre-Holsteinian interglacial (Kaplyanskaya and Tarno-gradsky, 1974). In the present stratigraphic scheme onlythe Corbicula sands between the Samarovo till and the

Semeika varves are related to the Tobol climatostrati-graphic horizon s.stricto (Volkova and Babushkin,2000). Correlation of the Tobol horizon with theHolsteinian is apparently supported by TL dates of300775 and 313780 ka and ESR date 306720 ka on aCorbicula shell. However, in the periglacial zoneCorbicula shells yielded ESR ages 285, 219 and 174 ka(Arkhipov, 1989). Later the palaeomagnetic excursionBiwa-II-Semeika along with the ESR date of 396 kawere reported from the basal part of the Tobol alluviumwith Corbicula shells (Volkova and Babushkin, 2000).

Anyway, there are two independent interglacialmarkers, one of marine and another of terrestrial originthat can be seen in West Siberian exposures. The Arcticmarker, if identified correctly, should provide the upperboundary of the Middle Pleistocene tills. The Subarcticmarker separates surficial Middle Pleistocene tills frompre-Holsteinian glacial events known only from glacialdeposits of buried valleys.

4.2.2. Stratigraphy in the Arctic

The till overlying the Kazantsevo strata in most casescan be safely correlated with the Weichselian, theunderlying till being related to OIS 6 (Svendsen et al.,this volume). These ice advances are distinguished bytheir geographic distribution, because the post-Kazant-sevo glaciation is limited to the Arctic, whereas the pre-Kazantsevo ice advance reached far beyond the ArcticCircle. The main problem is that in many cases eithermarine strata with a boreal fauna are older than theKazantsevo s. stricto, or the Eemian interglacial isrepresented by non-marine facies. The first case isknown from the Pupkovo section in the Yenissei valley(loc. 9 in Fig. 1), where marine strata with interglacialpollen spectra and rare finds of a boreal fauna, includingArctica islandica, are sandwiched between two tills wellbeyond the limit of Late Pleistocene glaciation (Zuba-kov, 1972). Troitsky (1975), who insisted on the Eemianage of this marine formation, had therefore to extendthe Weichselian ice limit along the Yenissei as far southas 64�N, which is refuted by periglacial evidence(Astakhov et al., 1986). A similar situation is in thecentral part of the West Siberian basin close to theArctic Circle, but well beyond the currently acceptedWeichselian ice limit (Svendsen et al., this volume). Inthe Samburg borehole a thick marine formation with anarctoboreal fauna was found beneath a Middle Pleisto-cene till (Zubakov, 1972).

Non-marine Eemian is found on the Lower Ob, wheretwo main stratigraphic concepts have been competing.The classical concept relates most of surficial diamictonsand varved sequences to glacial or glaciomarine forma-tions of the Middle Pleistocene (Lazukov, 1970;Zubakov, 1972). According to Zubakov, this interpreta-tion is based on pollen spectra characteristic of southerntaiga found in sand infills incised into the thick varved

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Fig. 9. Principal profile across the Ob valley on the Arctic Circle south of Early Weichselian Sopkay moraines (not to horizontal scale). Russian–

Norwegian PECHORA project. 1—loess-like silt; 2—diamicton; 3—silt/clay rhythmite changing into varves; 4—glacifluvial sand and fine gravel; 5—

laminated sand with peat lenses. Open dots are OSL (optically stimulated luminescence) datings, blackened dots are radiocarbon dates; age values are

indicated in kiloyears BP. Note on southern bank non-finite radiocarbon dates and four OSL ages 125–138ka from interglacial sand overlying

rhythmite of mid-Weichselian age by Arkhipov et al. (1977).


rhythmite at the Pyak-Yaha section of the southernbank of the Ob in the present forest-tundra (Fig. 9).Only thin lenses of diamict and gravel materials whichsometimes occur on the surface suggest a LatePleistocene glaciation (Lazukov, 1970). In contrast, theconcept of the ‘young stratigraphy’, based mostly onsparse radiocarbon dates obtained in different sections,ascribes a Late Pleistocene age to all units of stratifiedand non-stratified drift observed in natural sections. Inthe latter scheme the Kazantsevo marker is representedby sand with boreal foraminifera identified in boreholesjust below sea level (Arkhipov et al., 1977). This conceptis currently accepted in the official stratigraphic scheme(Volkova and Babushkin, 2000).

Arkhipov et al. (1994), applying their radiocarbon-based ‘young stratigraphy’ to the entire Arctic Pleisto-cene, suggest a Holsteinian age for another interglacialformation at 100–200 m bsl, the so-called ‘Ob marinestrata’. This older interglacial formation, underlain by

only one till, contains an assemblage of arctoborealforaminifera of ‘Miliolinella pyriformis zone’. The thickdiamictic sequence positioned between the two inter-glacial marine formations in this scheme belongs to OIS6–8. Arkhipov et al. (1994) offer TL-dates on coresamples of 153715 ka for their ‘Kazantsevo formation’and 246723, 306726, 366731, 370731 ka for the ‘Obstrata’.

The latest results from the Russian–NorwegianPECHORA project clearly refute the ‘young stratigra-phy’. Weichselian tills and related glaciolacustrinesediments are found only on the northern bank of theOb river (Fig. 9). The fluvial or deltaic sands with forestpollen spectra incised into the thick varved sequence ofthe southern bank yielded four OSL dates of 125 to138 ka (samples 115, 116, 133 and 134, Pyak-Yaha, inTable 3), together with non-finite radiocarbon datessupporting an Eemian age of these sands. Glaciofluvialsands beneath the varved sequence, as well as on high


interfluves of the Uralian piedmont, are OSL dated to c.200 ka (samples 119 and 120 Pichuguy-Yaha in Table 3),which is consistent with a Middle Pleistocene age of thelast ice advance on the Arctic Circle (Fig. 9). Theunderlying Middle Pleistocene till and terrestrial sandwith peat are stratigraphically above the Arkhipov’s‘Kazantsevo’ with TL-date of 153 ka, which means thatthe TL method underestimates the age, as compared toOSL dating. The better reliability of OSL datings hasbeen independently confirmed by U/Th dating of theSeyda peat and by the above pollen data. Therefore, thesand with boreal foraminifera below sea level, Eemianby Arkhipov et al. (1977), is most likely MiddlePleistocene, probably Holsteinian.

Consequently, the deep lying Ob interglacial forma-tion must be pre-Holsteinian, similar to the Kolvaformation of the Pechora Basin with the same for-aminifera assemblage (Gudina, 1976). This implies thatthe thickest (more than 100 m) till sequence, sandwichedbetween two interglacial marine formations, is notSaalian but older. Another important implication isthat, accepting the traditional correlation of the Obstrata with the Tobol alluvium, the latter must be pre-Holsteinian. However, it is possible that the Tobolalluvium corresponds in the Arctic to the first marineformation with boreal foraminifera lying just bsl, i.e. tothe ‘Kazantsevo strata’ by Arkhipov et al. (1977, 1994).In this case the lower marine formation, the Ob strata,may correlate with the Talagaika or even olderinterglacial deposits of the south (see below).

Middle Pleistocene tills of the eastern glaciated Arcticare poorly studied. The thick fine-grained diamictonsdirectly underlying the Kazantsevo marine strata withboreal fauna were related to the marine or glaciomarineSanchugovka formation with a sparse, predominantlyArctic fauna (Sachs, 1953; Lazukov, 1970; Zubakov,1972) until Kaplyanskaya and Tarnogradsky (1975)thoroughly investigated the type section and found thatthe formation consisted of basal tills with rafts of marinesediments. The diamictons contain not only an Arcticfauna, but also shells of boreal and Cretaceous molluscs.The Sanchugovka till is believed to represent OIS 6,although Arkhipov (1989) thinks that below sea levelthere are real marine strata with Arctic foraminifera ofOIS 7 underlain by tills of OIS 8.

One of the rare sections in which two interglacialmarine formation are separated by the Murukta till canbe seen is Novorybnoye at the mouth of Khatanga river(10 in Fig. 1). The upper marine unit, which is notcovered by till, is commonly interpreted as a deposit ofthe Eemian transgression, whereas the lower marineformation, containing foraminifera of the Miliolinella

pyriformis zone, and in another section farther to thewest also Cyrtodaria angusta, is thought to represent theSiberian equivalent of the Holsteinian. The alternativestratigraphic model suggests an Eemian age for the

lower marine unit and a mid-Weichselian age for theupper marine formation (Kind and Leonov, 1982). Thelatter interpretation is not only palaeontologicallydubious, it is also at odds with the latest results of theQUEEN program which do not support a LatePleistocene glaciation that far east (Svendsen et al.,2004). The traditional interpretation of this sequence inwhich the earlier transgression is thought to beHolsteinian (e.g. Gudina, 1976) suggests a Saalian agefor the Murukta till, which agrees well with itswidespread occurrence in Central Siberia.

4.2.3. Stratigraphy in the Subarctic

Best identifiable in this zone is the Samarovo till of themaximum glaciation named after the settlement close tothe Irtysh mouth, where the famous thick sequence ofstacked tills and Palaeogene opoka rafts has long beenknown (Shatsky, 1965). The additional diamicton uniton top of the Samarovo till north of the Irtysh mouth isthought to represent the penultimate Taz glaciation. TheSamarovo till, resting on the Tobol alluvium, is gettingthinner upstream and disappears south of the Semeikavillage (5 in Fig. 1). North of this point a couple ofadditional tills beneath the Tobol formation are knownfrom boreholes. The lowermost interglacial formation(the Talagaika alluvium) north of 63�N is overlain by adouble diamict formation up to 70 m thick called theShaitan till which is thought to correspond to theSemeika glaciolacustrine clay on the Irtysh (Volkovaand Babushkin, 2000). The lowermost till (the Mansitill) is found beneath the Talagaika interglacial at thebottom of a drill well north of the drift limit on theIrtysh (Arkhipov, 1989).

There are two main problems with the till count inthis zone. The first is connected with the Taz glaciationwhich is thought to predate the Eemian and deposit a tillof limited distribution on top of the Samarovo glacialcomplex. Originally the Taz till was mapped in the upperreaches of river Taz, where it is separated from theunderlying Samarovo strata by sands with ambiguouspalaeontological characteristics. Later such a till wasdistinguished all over West Siberia. Although nointerglacial formation with abundant organics has everbeen found between the Samarovo and Taz till, thealleged Shirta interglacial, called ‘interstadial’ by morecautious geologists, persists in the regional stratigraphicschemes (Volkova and Babushkin, 2000). Interglacialorganics are in general rare in Siberian inter-tillformations. This led Lazukov (1970) to suggest that alltill sheets along the Ob river are deposited by themaximum Samarovo glaciation, whereas (Arkhipov1989; Arkhipov et al., 1978) tried to subdivide thissequence by means of thermoluminescence dating (A inFig. 10).

According to Arkhipov the upper sand and silt inKormuzhikhantka section on the Belogorye Upland

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Fig. 10. Key sections of Middle Pleistocene tills of West Siberia. A—Kormuzhikhantka section at locality 6 in Fig. 1 (from Arkhipov, 1989;

Arkhipov et al., 1978, simplified), B—Bakhtinsky Yar section at locality 8 in Fig. 1 (Arkhipov and Matveyeva, 1964), C—Khakhalevsky Yar section

supplemented by a borehole at locality 7 in Fig. 1 (Levina, 1964). 1—loess-like silt; 2—soft diamicton; 3—compact diamicton; 4—varved clay;

5—laminated silt; 6—sand; 7—peat and gyttja; 8—cryoturbations; 9—fresh-water mollusks; 10—TL samples.


(loc. 6 in Fig. 1) is Eemian, and the overlying softdiamicton is therefore an Early Weichselian till (Fig.10A). The till below the Eemian TL values belongs tothe Taz glaciation of OIS 6, and the till next down-wards—to the Samarovo glaciation of OIS 8. Thelowermost till in this sequence is related to the LateShaitan glaciation of OIS 10–12 (Arkhipov, 1989). Thiscorrelation does not contradict the latest PECHORAresults in the Arctic Ob area. However, taking intoaccount the too young TL dates in the Arctic zone, thislowermost till might be even older. As to the uppermostKormuzhikhantka till, this soft, mantle-like diamicton,very low on pebbles, without structures of ice flow orshear planes at the base, is neither traceable regionally,nor associated with other glacigenic sediments. There-fore, it should be better viewed as a solifluction bed, or aflowtill derived from residual Middle Pleistocene ice, butnot as a signature of a Late Pleistocene ice advance(Zolnikov, 1990). The latter interpretation fits thePECHORA data indicating no Late Pleistocene glacia-tion on the Ob along the Arcticle Circle (Fig. 9).

Another problem is the correlation of the Ob-Irtyshice advances with the Central Siberian events. As waspointed out, south of the Late Pleistocene ice limit onthe Yenissei there are two tills separated by a marine

formation with rare boreal shells (loc. 9 in Fig. 1).Zubakov (1972) relates the upper till to the last MiddlePleistocene glacial event called the Yenissei glaciation,OIS 6. This event is supposed to be identical with theTaz glaciation of West Siberia. Isayeva (1963) acknowl-edged this till as a counterpart of her second (NizhnyayaTunguska) belt of end moraines running around thePutorana Plateau between the drift limit and the LatePleistocene Onyoka moraines. The Nizhnyaya Tungus-ka moraines in the northeast merge with the Muruktamoraines, which in the stratigraphic scheme of CentralSiberia are positioned above the Eemian level (Isayevaet al., 1986). This seems to be a miscorrelation because,according to the QUEEN results, the Early Weichselianmaximum is represented by the youngest belt of theOnyoka moraines sensu Isayeva (1963) (see Taimyrdiscussion in Svendsen et al., this volume). Therefore,both Yenissei and Murukta tills should belong to OIS 6.

The till underlying the Pupkovo marine strata (loc. 9in Fig. 1) is traditionally correlated with the Samarovoglaciation of OIS 8, which is thought to have reached thedrift limit also on the Yenissei (Zubakov, 1972).However, it is more likely that the earlier borealtransgression, as on the Pechora and Ob, relates to theHolsteinian or OIS 11, thus making the lower till in the


Yenissei bluffs Elsterian in age. The official stratigraphicscheme keeps all these strata in the Bakhta superhorizon(Volkova and Babushkin, 2000) exemplified by theBakhtinsky Yar section (B in Fig. 10, loc. 8 in Fig. 1).There is no indications of warm palaeoclimates in theinter-till sediments traditionally correlated with the‘Shirta interglacial’ (or interstadial) (Arkhipov andMatveyeva, 1964). This sequence is a rare case of thelower till overlying interglacial alluvium with a bone ofAlces latifrons. The latter is characteristic of the Tiraspol(Cromer) mammalian complex (Arkhipov and Matveye-va, 1964; Arkhipov, 1975), which implies that the lowertill in the Yenissei sections might well be Elsterian.Upstream of Bakhtinsky Yar a thicker till formationwas found below the Bakhta strata in a boreholereaching 342 bsl. This so-called Lebed till is the lower-most member of the official stratigraphic scheme ofCentral Siberia (Isayeva et al., 1986).

Another key section is Khakhalevsky Yar close to thedrift limit (C in Fig. 10, loc. 7 in Fig. 1). It represents theTurukhan alluvium (Arkhipov and Matveyeva, 1964),or Panteleyeva formation (Zubakov, 1972), sandwichedbetween two tills. The coarse channel alluvium overlyingthe lower till grades upwards into floodplain silts withgyttja and peat lenses, changing farther upwards intoproglacial varves distorted by the maximum ice advance.The succession is capped by till and glaciofluvial sand.Pollen spectra of the channel alluvium show an upwardincrease of pollen of coniferous forests with predomi-nance of Picea and Pinus sibirica. In the floodplain siltsthey are gradually replaced by Betula dominated park-lands with abundant herbs, Ericaceae and Selaginella

selaginoides (Levina, 1964). By these and other similarspectra the Turukhan alluvium is correlated with theTobol alluvium of the Ob and Irtysh (Arkhipov, 1975).However, pollen spectra of the preceding Talagaikainterglacial are not much different. Therefore, it cannotbe excluded that the maximum glaciation on theYenissei correlates not with OIS 8, as suggested byArkhipov for the Samarovo glaciation, but with thepreceding cold stages OIS 10 or 12.

The latter option is even more likely for the CentralSiberian Upland, where the poorly preserved tills of themaximum glaciation are in a stark contrast with theinner belt of topographically expressive NizhnyayaTunguska moraines (Isayeva, 1963). There are authorswho correlate the maximum glaciation limit of theeastern Central Siberia with the thick sequence ofdiamictons and stratified drift found by boreholes at240 m bsl and lower on the bottom of the overdeepenedYenissei valley at Lebed (loc. 14 in Fig. 1). By itsposition under the sedimentary complex of the max-imum Yenissei glaciation the Lebed double till sequenceis similar to the Shaitan tills on the Ob (Volkova andBabushkin, 2000). However, the Lebed tills might evenbe pre-Elsterian in age.

4.2.4. How many ice advances?

The most pressing stratigraphic problem concerns theage of the two surficial tills—the Taz and Samarovo—overlying the Tobol horizon. They are traditionallyrelated to OIS 6 and 8 correspondingly (Table 2). Thealternative that both belong to OIS 6 is unlikely, becauseglacial landforms are not known atop of the Samarovotill covered by loess-like silts up to 15 thick. If the Tobolhorizon proves to be pre-Holsteinian, and real inter-glacial organics are found between the Taz andSamarovo tills, then the Taz till may relate to theSaalian (OIS 6) and the Samarovo till to the Elsterian.

The latter option was considered by Arkhipov basedon TL and ESR datings. He concluded that the Tobolformation s. stricto might be pre-Holsteinian andtherefore the Samarovo glaciation might be Elsterian.However, this alternative would upset the traditionalcorrelation pattern and therefore not desirable for thetime being (Arkhipov, 1989). Anyway, the great thick-ness of the tills underlying the penultimate interglacial inall major buried valleys suggests that Elsterian or earlierice sheets of West Siberia were very large. It is quitepossible that several ice advances are still hidden in the70–100 m thick diamict sequences of the buried valleys,where no good interglacial formations have beendistinguished so far. The latest results of deep coringin Arctic West Siberia show that assemblages ofarctoboreal foraminifera (previously perceived as theHolsteinian ‘zone of Miliolinella pyriformis’) occur atthree different stratigraphic levels (Volkova and Ba-bushkin, 2000). This makes correlation of the Arctic tillswith the terrestrial record in the south even moredifficult.

The above data allow to infer four major pre-Eemianice advances in the Siberian record (Table 2). The oldestMansi till reflects a more restricted ice sheet. In thepresent official stratigraphic scheme of West Siberia(Volkova and Babushkin, 2000) this ice advance isrelated to the Matuyama chron of reverse polarity, i.e. isthought to be older than 700 ka, although Arkhipov(1989) preferred to place it at OIS 18. The thickestShaitan tills separated by stratified drift with Arcticforaminifera are certainly pre-Holsteinian but within theBruhnes chron, their more precise correlation with theEuropean record being premature. The correlation withOIS 12–16 suggested by Arkhipov (Table 2) is onlybased on very old and therefore hardly reliable TLdates. The maximum glaciation (OIS 8, or 10, or 12)probably produced the thickest (up to 3.5 km) ice sheetthat grew over the Kara Sea shelf and eventuallyoverrode nearby mountain ranges up to an altitude of1 km. The last Middle Pleistocene ice sheet called theTaz (or Yenissei, or Murukta), judging by the freshglacial landscapes, was formed in OIS 6. It was thickenough to cover almost the same area as the maximumglaciation and flow southwards over the low mountains.


5. Conclusions

(1)
The huge ice sheets, much larger than the Weichse-lian ones, at least 4 times covered the Russianmainland and adjacent shelves prior to the Eemian.
(2)
The main centre of ice accumulation was the KaraSea shelf, additional sources of inland ice beingFennoscandia and the Barents Sea shelf in Eur-opean Russia, and the Putorana Plateau in Siberia.The Ural Mountains played mostly the passive roleof an orographic barrier in the ice flow pattern.
(3)
The extent and geological work of the coalesced icesheets imply an Antarctic type of glaciation with icethickness up to 3.5 km. Unlike Antarctic and mostof North Atlantic ice sheets, North Russiancontinental glaciers acted on predominantly softand perennially frozen substrate, which was deeplyaffected by pervading glaciotectonism.
(4)
The thickest tills are found beneath interglacialformations similar to the Holsteinian, suggestingthat the most extensive ice sheets are pre-Saaliannot only in European Russia, but probably also inSiberia.
(5)
During the maximum (Cromerian) glaciation andsubsequent ice ages (OIS 16 to 10) the influence ofthe Fennoscandian ice dome was limited in north-ern European Russia. The Fennoscandian ice sheet,however, culminated during the penultimate glacia-tion (OIS 6), when shelf sources of inland ice wereless powerful than in pre-Holsteinian times.
(6)
The drift limit in Northern Russia is time-trans-gressive, being certainly pre-Holsteinian in north-eastern Europe, probably OIS 8 in West Siberia andgetting older east of the Yenissei.
(7)
There are several unsolved questions concerningcorrelation of the marine transgressions withterrestrial interglacial events. The reliability of thecorrelation of Russian pre-Eemian interglacialswith their western European counterparts notice-ably decreases northwards and eastwards partlybecause of the insufficient data available, and alsodue to the fading biotic signal of the climaticfluctuations.
Acknowledgements

This work is part of the current Russian–NorwegianPECHORA project supported mostly by the NorwegianResearch Council. It is also a contribution to theEuropean Science Foundation program QUEEN. OSLdating was performed by A. Murray at the NordicLaboratory for Luminescence Dating, Ris^, Denmark.Radiocarbon and U/Th dates have been obtained in theGeochronological Laboratory of St. Petersburg Uni-versity, Russia, under the guidance of Kh. Arslanov.

Editing efforts by J. Ehlers, A. Raukas and ananonymous referee have considerably improved thetext. The author offers his sincere thanks to thementioned persons and institutions.

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