Quaternary International, Vol. 45/46, pp. 19-28, 1998. Pergamon Copyright © 1997 INQUA/ElsevierScience Ltd Printed in Great Britain. All rights reserved. PII: S 1040-6182(97)00003-7 1040~5182/98 $19.00

THE LAST ICE SHEET OF THE KARA SEA: TERRESTRIAL CONSTRAINTS ON ITS AGE

Valery Astakhov Institute of Remote Sensing Methods for Geology (VNIIKAM), Birzhevoy proyezd 6, St.-Petersburg 199034, Russia

The ice dispersal features on the Siberian mainland unanimously indicate that the last ice domes were positioned on the Kara Sea shelf and adjacent coastal plains. The age of the last glacial maximum evokes much controversy. The problem may be solved by sorting out the available radiocarbon dates, both statistically and using geological common sense. Over 200 finite radiocarbon dates have been analysed. 77% of the entire population represent sediments overlying the topmost till, including dating the most reliable organics such as mammoth remains. The rest of the dates (23%) have been obtained from the underlying sediments, mostly on materials readily prone to redeposition and contamination such as driftwood and shells. The last culmination of the shelf ice sheet must have occurred beyond the range of the conventional radiocarbon method and after the last warm-water sea transgression correlative to the Eemian. The Early Weichselian age for the last Kara Sea ice sheet is also supported by the lack of proglacial lacustrine sediments with finite radiocarbon dates in periglacial West Siberia. © 1997 INQUA/Elsevier Science Ltd

INTRODUCTION to the arcs of ice-pushed ridges (Fig. 1), certainly rule out any subsequent ice flow from highlands. A previous paper (1992) discussed geological evidence Nevertheless, many authors (e.g. Biryukov et al., 1988) from the West Siberian Plain that can be used for disregard this clear evidence and advocate the idea of reconstruction of the last glaciation of the Kara Sea. More Late Weichselian ice caps positioned upon the low details on ice dispersal features of this glaciated area can mountains, which presumably advanced east, west, and be found in Grosswald (1994), with whom I fully agree in north onto the Siberian lowlands and shelves. Such this respect. The major disagreement between Grosswald highland ice sheets should have left large terminal (1994) and the interpretation presented in Astakhov moraines concentric to the corresponding mountainous (1992) relates to the age of the last shelf-centered ice massifs, but they did not. Moreover, the northernmost tip sheets of Arctic Russia. In this paper I would like to of the Urals is devoid of any (even small) morainic loops, emphasise the temporal aspect of the problem by which could be ascribed to montane . The presenting more geochronological data not easily acces- available morainic ridges are transverse to the Uralian sible by the English speaking community. range and too large for any conceivable valley glaciers (Astakhov, 1979; Arkhipov et al., 1980). Since the ice directional features show ice dispersal ICE DISPERSAL PATTERN from topographic lows upslope, not vice versa, the hypothesis of highland ice domes can only be supported The last ice sheet of the Kara Sea commonly evokes by such ambiguous evidence as: (i) the occurrence of two questions: (i) whether it existed at all, and (ii) if hummock-and-lake topography mostly along the high- it did exist, when? In my opinion, the evidence of lands, (ii) the distribution of hard-rock clasts which are the Post-Eemian ice dispersal from the shelf onto more plentiful toward the mountains, and (iii) the adjacent dry lands is overwhelming (Astakhov, 1976, presumed lack of surficial tills in the Arctic lowlands. 1979; Andreyeva, 1978; Arkhipov et al., 1980; Kind The idea of a driftless area in the Arctic lowlands stems and Leonov, 1982; Grosswald, 1980, 1994). The ice from observations of the 1960s when diamictons with flow features directed upslope (south) from the Kara marine fossils and few pebbles were mistaken for glacio- Sea are in full accord with the very small size of marine sediments. This error was first revealed by morainic loops of alpine glaciers mapped along the Kaplyanskaya and Tarnogradsky (1975), and later by borders of the Urals and eastern Taimyr mountains other investigators (e.g. Astakhov, 1979, 1981; Komarov, (e.g. Gesse et al., 1963; Makeyev and Berdovskaya, 1986). As a result, a surficial till, lying on top of 1973). The well pronounced striae, flutes, grooves interglacial marine sediments and containing fossil glacial and eskers, trending across the Palaeozoic folds, are ice, is now mapped throughout the Arctic (Fig. 2). accompanied by numerous erratics transported south- The distribution of highland clasts is hardly a weighty wards from the Kara Sea coasts (Voronov, 1951; argument because northern highlands are always sur- Tarakanov, 1973; Andreyeva, 1978; Astakhov, 1979; rounded by fields of hard-rock pebbles regardless of the Grosswald, 1994, etc.). Such features, striking normally actual glacial history. Nobody has ever demonstrated that 19 20 V. Astakhov

60OE 80°N 90OE Barenls ,8 % 80°N 5e Kar / /

Isl. i

o10 ~ 9

ID .~IBERIAN "~B J PLAND

(,5,7. "v" Arctic ,5' /

A N d N D

I,Ill I I I I I

FIG. 1. Location map with some features of the last sheet glaciation. 1 -- ice-pushed ridges by terrestrial geological surveys, photogeological interpretation and marine seismics (from Astakhov, 1976Astakhov, 1979; Arkhipov et al., 1980; Kind and Leonov, 1982; Epstein and Gataullin, 1993); 2 -- same, inferred from bathymetric maps; 3 -- limit of the surficial till overlying the uppermost interglacial marine formation; 4 -- suggested limit of a possible ice sheet within 30-15 ka BP time span; 5 -- striae and flutes across Palaeozoic structures; 6 --radiocarbon dated sequence overlying the uppermost till (see Table 1); 7 -- same within the possible West Kara ice sheet; 8 -- profiles in Fig. 2. the Uralian and Mid-Siberian clasts were transported to amongst fields of stagnant ice, as well as by lakes and the lowlands specifically during the LGM. Such pebbles streams, as can be seen in Fig. 2. These late glacial often originate from non-glacial gravels and are always aqueous agencies led to a flatter topography. associated with more informative clasts of soft rocks Conversely, the debris-laden marginal parts of the Kara derived from topographic lows. ice sheet, affected by upslope compressive ice flow, The question of the fresh hummock-and-lake land- stagnated much farther south at higher altitudes, where scapes is more complicated, but sufficient explanations of they survived late glacial inundations to produce thick its peri-montane location are available after research tills and rough topography due to perforating activity of during the last two decades. The scarcity of hummock- glaciokarst sinking lakes. Closer to the highlands the till and-lake landscapes in the high Arctic can partly be of the last ice age may be 40--50 m thick (Kind and explained by retarded deglacifition, as a result of which Leonov, 1982; Komarov, 1986; Astakhov and Isayeva, large slabs of basal glacial ice still persist within the thick 1988). It is also significant that in the marginal parts of as constituents of 'primordially frozen tills', the former ice sheet pebbles in the till are oriented that need additional warming to produce expressive longitudinally (i.e. parallel to the mountain front; glaciokarst features (Kaplyanskaya and Tarnogradsky, Astakhov, 1979; Sukhorukova and Gaigalas, 1986), 1977; Astakhov and Isayeva, 1988). On the other hand, which is another phenomenon not explained by the the lowlands were occupied by central parts of the ice highland ice hypothesis. sheet where glacial ice was relatively poor in debris. The Thus, the most expressive surficial features such as resultant thinner tills could readily be destroyed by the push moraines, glacial striae, oriented pebbles unan- late glacial sea, penetrating into the isostatic trough imously indicate to the last ice advance from the low Kara The last ice sheet of the Kara Sea: terrestrial constraints on its age 21

A ItLt,m ~1

ao _ ~ "~ ~ ./~620± 1010(LU-711) 15190+170 (LU- 712.)

0" 17

Lz5O~O+- 1750 {LLJ-1|55) B \46000~ 18qO(I.U-|15~,) . . [ >46750 (LU-I~)]t?) -r I ~ 40"/OO.*llOO(Oll-lg46) 30010 t 21Q J.~ .. .Tt#,Z 1 I11 40

C D alt,m 70, .?0

.60

50

. t,O

- 50

20

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fl

FIG. 2. Geological profiles of Arctic West Siberia compiled by A. Lavrov and L. Potapenko (mapping report, 1983), based on photogeological survey data. For location see Fig. 1. Symbols: glI -- Middle Pleistocene till; gill -- Upper Pleistocene till (Upper Weichselian according to A. Lavrov and co-authors); mllIkz --Kazantsevo Formation with shells of boreal marine molluscs; a, llII- alluvial and limnic sediments; lg, lg2, lg3 Ill -- laminated sand, clay and -like silts (glaciolacustrine according to A. Lavrov and co- authors); alV -- Holocene alluvium; P --Palaeogene sediments. Black dots indicate radiocarbon samples, a -- possible Late Weichselian ice limit by Astakhov (1979)Astakhov (1981).

Sea coastlands upslope. Only the most prominent of them and Laurentide glacial stades. Still the data accumulated are pictured in Fig. 1, but they are sufficient to and presented below seem to be enough to at least demonstrate where the last came from. eliminate some geochronological speculations on the Judging by the subparallel (not radial) striae and flutes Post-Eemian glacial maximum. across Novaya Zemlya, Vaigach and Pai-Hoi, these The most popular idea of the Late Weichselian age of narrow Palaeozoic ranges could not be major ice dispersal the LGM in the Russian Arctic is shared by both groups centers (Grosswald, 1994). The Novaya Zemlya archipe- of scientists: by those who profess the hypothesis of lago is fringed along the northwest by a huge submerged restricted ice domes upon highlands (Biryukov et al., double ridge which is, according to Russian seismic 1988) and by those who accept the Kara shelf ice domes surveys and geotechnical drilling (Epstein and Gataullin, (Volkov et al., 1978; Arkhipov et al., 1980; Grosswald, 1993), built of diamicion more than 60 m thick. Traced 1980). There are others who notice discrepancies in the northeastward by bathymetry this ridge is 700 km long evidence presented and either leave ample room for (Fig. 1). Its spatial pattern does not support the idea of doubts (Kind and Leonov, 1982), or 'even reject the narrow ice caps positioned along the crest of Novaya Weichselian glaciation completely (Fisher et al., 1990). Zemlya (Biryukov et al., 1988), and fits with the The Late Weichselian age of the LGM is most ardently submerged hummocky terrain in the western Kara Sea advocated by Grosswald and the Siberian investigators by Dibner (1970), suggesting a rotund ice sheet spreading Arkhipov and Volkov. Three sets of arguments are used: westward over Novaya Zemlya. (i) the fresh appearance of the Arctic hummock-and-lake topography; (ii) limnic rhythmites in the central West Siberian Lowland which are perceived as sediments of a GEOCHRONOLOGICAL DATA huge proglacial lake with a level up to 120-130 m; (iii) finite radiocarbon dates from beneath the topmost till Now, we consider the most acute problem of the age of sheet. the last Kara glacier. The available evidence is probably Now that relict glacial ice in the Siberian Arctic has not sufficient to correlate its advances with Scandinavian been identified (Kaplyanskaya and Tarnogradsky, 1977; 22 V. Astakhov

Astakhov and Isayeva, 1988) it is clear that basal parts of contrary, the hypothesis of the Late Weichselian ice former ice sheets, fused together with thick permafrost, advance has to explain why in the flat lowland the great can survive close to the surface through minor climatic north-flowing rivers failed to flood all country and arrest fluctuations until the permafrost is completely destroyed the development of permafrost features, soils and large by a major warming. In the Kara Sea catchment area such mammals. a warming occurred only in the span of 9-3 ka BP, when The thick sediment fill of the Turgai Valley with the south of the Arctic Circle the permafrost table dropped dates ca. 19 and 29 ka BP (in Grosswald, 1983) cannot be well below the level of seasonal freezing. Yet north of the taken as reliable evidence of a Late Weichselian spillway 68th parallel the Pleistocene continuous permafrost directed to the Aral Sea because they are mostly survived even the Mid-Holocene warming (Baulin et lacustrine clay, loess, aeolian sand and mass-movement al., 1984). The present fossil glacial ice could have been diamicts. Only a thin gravel over the bedrock bottom left by any Weichselian glaciation. Deep sinking lakes are relates to a south-directed overflow of proglacial water. It developing these days on buried glaciers regardless of the occurs at altitudes of ca. 40 m, suggesting not the 120 m age of the corresponding ice advance. The resultant but much lower level of the overflow and not necessarily glaciokarst landscapes are most conspicuous in the during the Late Weichselian (Astakhov, 1992). southern Arctic, between 68 and 66°N, where permafrost Finally, we should consider the glaciated area itself. became discontinuous in the course of the Holocene The thick and diverse sedimentary succession overlying warming (Kaplyanskaya and Tarnogradsky, 1977; Asta- the topmost till includes glaciomarine and varved clays, khov and Isayeva, 1988). outwash sand, multi-staged sink-hole rhythmites and The question of the existence of a Late Weichselian frozen loess-like silts with long syngenetic ice wedges proglacial lake has been discussed elsewhere (Astakhov, (Astakhov, 1992). The classical concept viewed the 1989, 1992). Special research has revealed no real numerous mammoth remains scattered in the Arctic as signatures of an extensive fresh-water lake, but only evidence of a relatively old age of the last glaciation of sporadic lenses of sink-hole limnic sediments incorpo- West Siberia as compared to the European one (Sachs, rated into a discontinuous mantle of loess-like silts with 1953). Modem authors consider radiocarbon dates as far ice-wedge casts, palaeosols and mammal bones. The more important evidence. Grosswald in particular has lenses of limnic rhythmites make numerous oval and quoted 23 finite dates ranging from 26 to 52 ka BP doughnut-shaped knolls at all altitudes from 40 to recovered from sediments underlying the topmost till of 150 m, irrespective of underlying surface. Local hor- the Kara Sea catchment area (Grosswald, 1980, 1983; izons of ice-wedge casts and sometimes buried Grosswald and Goncharov, 1991). He disregards much soils are suspended within these shallow-pond fine more numerous 'old' radiocarbon dates obtained from sand-silty sediments up to 10-15 m thick (Astakhov, sediments postdating the latest till. The idea is that such 1989, 1992). Hummock-and-bog landscapes built of dates, being derived from redeposited organics, indicate the loess-like and stratified silts are widespread in only maximum ages (Grosswald and Goncharov, 1991). central-southern West Siberia, far south from the drift This idea, although not groundless, has led its authors limit, and often perceived as glaciokarst forms by too far. In the work mentioned they had to push the Late investigators unfamiliar with permafrost processes. Ac- Weichselian ice limit 500 km south, as compared to Fig. 1 tually these knolls are not glaciokarst, but typical of this paper, based on several finite dates from under the features, the difference being the signifi- Yenissei till. If such dates are only taken into account, cantly lower content of the parental ice which originated one could draw the limit even farther south in the subterraneously (see Fig. 3). Glaciokarst develops on periglacial zone, because there are also finite radiocarbon thick relatively clean subaerial ice where sinking and dates from beneath a till at 61°N (Arkhipov et al., 1980). lateral shifting of deep thaw lakes are not impeded The error stems from underestimating the contamination by surrounding mineral matter. Thermokarst ponds, by younger carbon which happens very frequently, evolving normally along polygonal ice wedges, are especially in areas where ground waters were very active more shallow and restricted in their development by during the degradation of the Pleistocene permafrost. L.D. ground massifs with low ice content and by thickness Sulerzhitsky, a radiocarbon expert, quotes a number of of the permafrost. That is why inverted thermokarst finite dates from Eemian sediments. In his opinion most knolls, unlike kames, are normally flatter, often clus- dates on shells and even logs are too young. According to tered in polygonal patterns, and commonly have, due many years of his dating experience in the Arctic, more to isotropic thermoerosion of frozen soil, a fairly regular stable results are received from bones. The experimental oval or circular form in plan. Fig. 3 illustrates the origin dating of driftwood from the same formation has shown a of the West Siberian landscapes south of the LGM limit rapid decrease of radiocarbon content in logs recently as understood by this author, the principal idea being released from permafrost, which is explained by bacterial borrowed from works by Boitsov (1961) and Kaplyans- activity (in Kind and Leonov, 1982). kaya (in Mikhankov, 1973). Taking into account all these complications, no single Thus, south of the suggested limit of the last glaciation radiocarbon date can be referred to as completely reliable. (Fig. 1) there are no geological phenomena that would We do not have any other option than to consider the demand a high-level impoundment of an extensive lake to whole collection of available dates in searchfor age explain the Late Weichselian palaeogeography. On the indications. A typical spectrum of radiocarbon dates in The last ice sheet of the Kara Sea: terrestrial constraints on its age 23

aeolian ~ust with ice wodgen thaw lakes A except at Malaya Heta section with five finite dates (Kind, 1974). But in the latter case there is no sedimentological proof that the overlying diamicton is not flowtill, which is very likely judging by the well studied sequence in the Yenissei river valley (Astakhov f r o s t h e a v e and Isayeva, 1988). h e a ~ $ n g B On the contrary, the dates from above the surficial till commonly occur in series of 3-12 successive ages (Tables 1 and 2) and mostly originate from mammal remains, local herbs, shrubs, peat and plant detritus. It is noteworthy that all dated mammoth remains, including obviously in situ frozen carcasses, have been found in sediments overlying the uppermost till. The entire population of the radiocarbon dates should be sorted out to get a more clear indication of the age of R I ~ m C sink-hole r, hythmites . .. the surficial till. Table 1 presents 92 dates of which 76 are / ~ lOeSs-like silt8 17 ka and older, all from sediments indisputably postdat- ing the last glaciation. The location of the dated sequences is shown in Fig. 1. To make the selection of ,,'~"~ 'p, e rm ~f-Ur~'~-~t~ ' radiocarbon dates in Table 1 less arbitrary the following FIG. 3. Origin of the loess-limnic formation of central negative criteria have been used: (i) no dates on shells; West Siberia in the course of thermokarst inversion of (ii) no isolated dates (except remains of mammals and Weichselian periglacial landscapes. A -- solid Weich- selian permafrost; B -- initial climatic amelioration with large logs from perennially frozen sediments); (iii) no silt and sand accumulating in sinking lakes; C -- present sections with significant age inversions. state after the sagging of perennially frozen terrains. R Some comments on the list of dates selected for Table 1 -- reference plane. can be made. Most of the dates are not likely to yield maximum but rather minimum age estimates. This is N 40- especially obvious in the case of frozen mammoth carcasses which cannot be transported far. The compar-

30- = ison of dates on outer and inner layers of mammoth tusks is needed to assess how carefully young humic acids were

20- removed in laboratory (Makeyev etal., 1979). An additional proof of reliability of the mammoth dates is provided by the very similar ages obtained on fossil plants either from the stomach of the beast (site 5) or from the o enclosing sediments (site 8). 15 17 21 25 29 33 ~ 7 49 1 k8 BP The dated tooth of a woolly rhinoceros (site 11) was FIG. 4. Distribution of finite radiocarbon dates in the Kara Sea catchment area covered by Weichselian tills extracted from the lower jaw with a full set of teeth (within limit 3 in Fig. 1). Solid line -- total number of preserved. The jaw was found in 1974 in a sandy Yenissei dates in 4 ka intervals (N=208); broken line -- number terrace at the mouth of P. Tunguska river (Fig. 1). of dates from sediments underlying the uppermost till (n=48). Black dots represent dates obtained on mam- According to Grosswald and Goncharov (1991) this moth remains (all from sediments overlying the till), terrace at 80 m a.s.1, must be very young because they circles -- dates obtained on shells from sediments ascribe the Late Weichselian maximum (ca 20 ka BP) to underlying the topmost till. the higher terraces at 120 and 160 m a.s.l., presumably left by the proglacial lake. This date of ca. 21.5 ka BP the West Siberian Arctic can be seen in Fig. 2. One can obtained on the intact jaw of the terrestrial beast strongly see a variety of radiocarbon ages in sediments overlying supports the alternative view. according to which the the uppermost till and occasional finite dates in the Middle-Late Weichsetian of the proglacial area is underlying strata. recorded in this low alluvial terrace descending to the The general distribution of the finite radiocarbon dates north along the Yenissei valley (Laukhin, 1981). older than 15 ka for the Kara Sea catchment within the The remarkable succession of radiocarbon dates limit of the last glaciation is presented in Fig. 4. The bulk ranging from 12 to 35 ka BP at site 13 (Cape Sabler in of them (160) is derived from sediments not covered by Lake Taimyr) was obtained from undisturbed surficial till, and only 48 dates (23%), including all shell samples, limnic silts and sands with seams of local plant remains originate from beneath the topmost till. Most of the sub- (Kind and Leonov, 1982). The non-finite date on a frozen till dates have been obtained on materials notoriously mammoth (site 6) comes from the area glaciated during prone to redeposition and contamination such as mollusc the Late Weichselian according to Grosswald and shells, driftwood and plant detritus. Almost all such dates Goncharov (1991), but the site is likely to remain beyond are singular in a studied section: no successive series of the limit of Weichselian glaciations (Fig. 1). The radiocarbon ages being known in the sub-till position successions of dates at locations 23, 24 and 26 quoted 24 V. Astakhov TABLE 1. Radiocarbon dates from sediments overlyingthe topmost till of the Kara Sea catchment area

Site Date, years BP Dated material Reference A. Mammals and related plants

1 19,6404-330 (LU-654A) mammoth tusk, outer part Makeyev et al., 1979 19,2704-130 (LU-654B) mammoth tusk, inner part ibid. 2 19,9704-110 (LU-688) mammoth tooth ibid. 3 24,910+200 (LU-749A) mammoth bone ibid. 24,960±210 (LU-749C) same ibid. 4 11,5004-60 (LU-610) mammoth tusk ibid. 5 11,4504-250 (T-297) mammoth flesh Heintz and Garutt, 1964 11,7004-300 (MO-3) accompanying plants ibid. 6 >53,170 (LU-1057) mammoth flesh Arslanov et al., 1980 7 36,0004-4300 (T-169) same Heintz and Garutt, 1964 33,5004-1000 (T-298) same ibid. 8 30,1004-300 (GIN-3742) mammoth bone find by Kaplyanskaya in Asta- khov, 1992 29,700±270 (GIN-3743) accompanying plants ibid. 25,400+300 (GIN-2210) mammoth bone Avdalovich and Bidzhiyev, 1984 32,6004-1300 (GIN-2026) underlying peat ibid. 34,5004-1000 (GIN-2027) same ibid. 10 25,4004-300 (GIN-2210) mammoth bone ibid. 11 21,4454-145 (TUa-675) tooth of woolly rhinoceros find by Astakhov B. Plant remains

12 35,800±500 (Gin-1498) stump Kind et al., 1981 35,800-4-1000 (GIN-1497) plant detritus ibid. >46,000 (GIN-1500) plant detritus ibid. >48,600 (GIN-1499) stump ibid. 13 12,1000-100 (GIN-1528) detritus, depth 1 m Kind and Leonov, 1982 11,600-4-200 (GIN-1527) same, depth 4 m ibid. 12,000-4-150 (GIN-1289) same, depth 5 m ibid. 17,7504-300 (GIN-1290) same, depth 7 m ibid. 18,400±1000 (GIN-1526) same, depth 8 m ibid. 2!,4004-1100 (GIN-1525) same, depth 11 m ibid. 24,9000-700 (GIN-1291) peat, depth 15.5 m ibid. 24,200-4-800 (GIN- 1524) detritus, depth 17 m ibid. 30,300±400 (GIN- 1521) detritus, base of section ibid. 29,600±1000 (GIN-1522) same ibid. 30,4004-600 (GIN-1523) same ibid. 34,500-4-2000 (GIN-1292) same ibid. 14 29,600-4-1100 (GIN-3818) peat Fisher et al., 1990 29,900-4-1200 (GIN-3819) same ibid. 40,600-4-900 (GIN-3803) plant detritus ibid. 43,800-4-1500 (GIN-3825) same ibid.

by Astakhov (1992) have been obtained from thick loess- permafrost. The pre-Late Weichselian dates from sites 19 like silts with very long syngenetic ice wedges that were and 20 are of interest because they originate from loess- developing through the depositional history of this like sediments overlying the 'Late Weichselian till' by postglacial formation (Vasilchuk et al., 1984; Bolikhovs- Grosswald and Goncharov (1991). ky, 1987). The dates younger than 17 ka BP are included in A date at site 19, from alluvium at the mouth of Table 1 only if they belong either to the successive series Kureika river, has been obtained on small shrubs with of older ages, or to the western sector (Fig. 1) where a bark intact (Astakhov and Isayeva, 1988), supporting Late Weichselian age for the uppermost till is plausible. another date from the same Second Terrace on plant Any randomly chosen date from this list may prove to be detritus (Kind, 1974). A nearby section 18 in the town of wrong, but the whole constellation unambiguously points Igarka contains perennially frozen logs and stumps in in one direction: the uppermost till east of 70°E must have sink-hole silts which have never melted out since been deposited prior to 40-50,000 radiocarbon years BP deposition, and was discovered in an observation pit in most likely beyond the range of the radiocarbon method. The last ice sheet of the Kara Sea: terrestrial constraints on its age 25

TABLE 2.

Site Date, years BP Dated material Reference 15 25,7004-400 (GIN-3480) plant detritus ibid. 32,0704-300 (GIN-3494) peat ibid. 32,5004-400 (GIN-3479) same ibid. 38,0004-700 (GIN-3838) peat ibid. 44,4004-800 (GIN-3839) plant detritus ibid. 16 16,7804-80 (GIN-3939) same ibid. 25,7004-400 (GIN-3934) same ibid. 32,7104-400 (GIN-3940) same ibid. 17 28,4904-450 (MGU-687) peat Danilov and Parunin, 1982 35,0504-600 (MGU-686) peat ibid. 32,000-4-1600 (GIN-2876) plant detritus Sulerzhitsky et al., 1984 18 35,4004-300 (GIN-140) !og Kind, 1974 35,8004-600 (GIN-76) plant detritus ibid. 39,0004-460 (GIN-328) log ibid. >50,000 (GIN-327) log ibid. 19 31,1004-800 (GIN-3674) twigs with bark Astakhov and Isayeva, 1988 32,5004-400 (GIN-99) plant detritus Kind, 1974 20 42,7804-1135 (SOAN-2519) peat Sukhorukova et al., 1991 39,3404-750 (SOAN-2518) same ibid. 45,5204-1270 (SOAN-2517) same ibid. 21 34,2004-1000 (GIN-2872a) plant detritus Astakhov et al., 1986 35,200±1500 (GIN-2872b) wood ibid. 22 32,700±1500 (GIN-2189) peat Avdalovich and Bidzhiyev, 1984 38,0004-500 (GIN-2190) same ibid. 23 21,9004-900 (GIN-2469) peat Vasilchuk et al., 1984 25,1004-220 (GIN-247 l) same ibid. 28,6004-800 (GIN-2638b) same ibid. 30,2004-800 (GIN-2470) same ibid. 24 17,1004-600 plant detritus Bolikhovsky, 1987 16,8304-670 same ibid. 16,6804-500 (MGU- 1047) same ibid. 16,5204-550 same ibid. 18,3804-700 same ibid. 25 38,6004-100 (GIN-1926) peat Avdalovich and Bidzhiyev, 1984 37,1004-400 (GIN- 1928) same ibid. 39,0004-1500 (GIN-1927) same ibid. 38,900-t- 1200 (GIN- 1929) same ibid. 38,8004-600 (GIN-1930) same ibid. 26 22,7004-300 (GIN-2473) peat seam Vasilchuk et al., 1984 22,6004-600 (GIN-2475) same ibid. 23,5004-400 (GIN-2474) same ibid. 24,3004-300 (GIN-2476) same ibid. 39,1004-1500 (GIN-2477) same ibid. 27 35,3204-1570 (LU-1137) frozen log Astakhov, 1992 C. Dates from the western sector

28 14,590±300 (Ri-285) peat seam Gataullin, 1988 29 13,830-t-260 (Tin-1059) fossil weeds ibid. 13,970±140 (Tin-1026) same ibid. 13,3404-200 (GIN-5196) fossil moss Bolikhovskaya and Bolikhovsky, 1992 13,280±150 (GIN-5197) same ibid. 30 15,310-4-650 (LU-1188) peat seam Malyasova, 1989 31 8210+90 (LU- 1462) peat seam ibid. 10,5504-160 (LU-1466) basal peat ibid. 9230-t-100 (LU-1464) peat seam Krasnozhon et al., 1982 15,120+120 (LU-1446) basal peat ibid. See Fig. 2 for more radiocarbon dates, and Fig. 1 for location of dated sequences, to the figures of "The last ice sheet of the Kara Sea: terrestrial constraints on its age" by Astakhov. 26 V. Astakhov

The assemblage of old radiocarbon dates overlying the certain. Submerged hummocky relief in this part of the uppermost till in Table 1 even numerically leaves sea was mapped long ago (Dibner, 1970). The available Grosswald's statistics far behind, not even considering ice directional features and erratics on the adjacent the reliability of the ages obtained. It is not accidental that uplands indicate that there was a recent ice advance from among the dates cited by Grosswald and other advocates the western Kara Sea to the south and west (Arkhipov et of the Late Weichselian ice sheet no measurements are al., 1980; Grosswald, 1994) and also to the east onto the mentioned on undisputably in situ materials such as Yamal Peninsula (Astakhov, 1979; Gataullin, 1988). The remains of large mammalia. If the aforementioned huge morainic ridges on the adjacent Barents Sea shelf negative criteria of selecting are applied to sub-till finite (Fig. 1) tell the same story. dates, only the five values in the span 3544 ka BP from Several finite radiocarbon dates are known from Malaya Heta section (Kind, 1974) should be taken into sediments underlying the upper till of this area, but their account to offset more than 70 dates obtained from above validity might be the same as elsewhere in the Kara Sea the till. These five dates being in discrepancy with the rest basin. The lack of old radiocarbon dates from sediments of the radiocarbon evidence, obviously call for a overlying the till seems to be more important (Figures 1 reinvestigation of the site, especially of the overlying and 2, and Table 1). The available dates at least limit the diamicton, which might be a flowtill deposited well after active ice phase for the western sector to earlier than the ice sheet stagnation. 15 ka BP. Especially intriguing are 15 ka BP dates from peats of Novaya Zemlya. Peat seams of this archipelago are also dated to 10.5, 8.2 and 6.4 ka BP. Presently, peat DISCUSSION accumulation occurs only on the mainland, not farther north than 68 ° N (Krasnozhon et al., 1982; Malyasova, The above data can serve as constraints on speculations 1989). This implies that several episodes with climate about the last ice sheet centered on the Kara Sea shelf. warmer than the present one have occurred since the last The size of ice-pushed ridges and position of the ice advance. The western Kara till cannot be very young, maximum ice limit (3 in Fig. 1) permit a suggestion that which follows from the overlying loess-like silts up to thicker inland ice was occupying not only present 5 m thick that contain syngenetic ice wedges and t3- shallows between Severnaya Zemlya and northern Yamal, 14 ka BP dates (site 29) on the western coast of Yamal but the western Kara Sea along with the Eastern Novaya Peninsula (Gataullin, 1988; Bolikhovskaya and Boli- Zemlya Trough up to 400 m deep as well. The southern khovsky, 1992). The Younger Dryas age for this ice margin then was distanced from the ice divide glaciation can be safely eliminated, but a Late or Middle suggested in Grosswald (1980) by 500 to 1000 km (as Weichselian ice advance from the western Kara Sea is in Scandinavia), but not as far south as in later models by still possible, although the configuration of this younger Grosswald and Goncharov (1991) and Grosswald (1994). ice sheet (4 in Fig. 1), inferred from the available The maximum ice thickness, which may have varied evidence (Fig. 2) looks rather artificial at its southeastern from 2 to 3 km, is difficult to estimate more precisely margin. More evidence is needed to decide whether the until we know more about the marine geology of the Kara West Kara glacier was just a part of the large Early Sea. On one hand, judging by the thick Pleistocene Weichselian ice sheet or represented a second Weichse- permafrost containing fossil glacial ice, the glacier must lian activation of shelf inland ice. Such evidence is have been very cold, which implies thicker ice. On the probably obtainable from Arctic European Russia. other hand the very soft clayey substrate, consisting of The most significant inference from the data on Cretaceous, Palaeogene and Quaternary sediments, may Novaya Zemlya and adjacent areas is the constraint on have flattened the ice dome. The striated and polished the age of the last glacial maximum of the Barents Sea. surfaces on the northern tip of the Urals and on the right Even if a Late Weichselian of the last ice sheet is bank of the Yenissei show that the ice sheet may have eventually proven, it would apply only to shelf areas reached 400-500 m in thickness even very close to its directly east and west of Novaya Zemlya, the huge margin (Arkhipov et al., 1980), which is more consistent marginal ridges (1 in Fig. 1) included. A more extensive with the thicker ice model. In any case the observed ice cover of the Barents Sea shelf would inevitably signatures of cold and thick upslope moving ice are demand a more or less symmetrical ice flow in the incompatible with the idea of mountainous ice dispersal opposite direction, of which no signs exist in West Siberia centers. It is even difficult to imagine theoretically how east of 70°E. The major part of the Barents shelf must such an ice cap could reside upon a rugged range 1 km have been glaciated earlier: otherwise the fresh ice flow high of the size of the Polar Urals which is only 50- features on the adjacent dry land, especially across 80 km wide. Novaya Zemlya (Grosswald, 1994), would have been The available geological evidence from both glaciated directed eastwards. The narrow strip of Novaya Zemlya and proglacial areas (Astakhov, 1992) along with the highlands, likewise the Urals, could never accomodate an radiocarbon data presented above do not permit any ice extensive ice dome responsible for such large terminal advances from the Kara shelf onto the Siberian landmass features as pictured in Fig. 1. within the range of the radiocarbon dating. However, the The geological and geochronological evidence for an age of the last ice sheet in the deepest western part of the early culmination of the last Kara ice sheet raises the Kara Sea between Yamal and Novaya Zemlya is less issue of the maximum time limit for this glaciation. The last ice sheet of the Kara Sea: terrestrial constraints on its age 27

Generally it is predetermined by the occurrence of the Astakhov, V.I. (1979). New data on the latest activity of Kara shelf glaciers in West Siberia. IGGR Project 73/1/24. Quaternary uppermost till on top of the Kazantsevo interglacial glaciations in the Northern Hemisphere, Rpt. 5, Prague, 22-31. sediments (Fig. 2). This marine formation is convention- Astakhov, VT (1981). Tills in the Northern Yamal. Doklady Acad. Sci. ally correlated with the Eemian because it contains USSR, 260(1), 149-152 (in Russian). numerous shells of boreal molluscs such as Arctica Astakhov, V.I. (1989). Late Pleistocene sedimentary environments in West Siberia. Trudy Inst. Geol. and Geophys., Siberian Branch Acad islandica (Sachs, 1953) which presently can survive only Sci. USSR, Nauka, Novosibirsk, 118-126 (in Russian). west of the White Sea. There are also other works Astakhov, V.I. (1992). The last glaciation in West Siberia. Sveriges describing another (Karginsky) marine formation with Geologiska Undersiikning, Ser. Ca, 81, 21-30. Astakhov, VT and Isayeva, L.L. (1988). The 'Ice Hill': an example of boreal fauna. Many authors, taking into account finite 'retarded deglaciation' in Siberia. Quaternary Science Reviews, 7, radiocarbon dates from marine sediments, suggest a 29-40. second transgression in the span of 50 to 26 ka BP, i.e. Astakhov, V.I., Isayeva, L.L., Kind, N.V. and Komarov, V.V. (1986). correlative to Isotope Stage 3 (Kind and Leonov, 1982). On geologic and geomorphic criteria for timing the glacial history of the Yenissei North. In: Velichko, A.A. and Isayeva, L.L. (eds), Sulerzhitsky, however, is sure that all such dates are Chetvertichnye oledeneniya Srednei Sibiri, pp. 18-28. Nauka, obtained from the Eemian organics (Fisher et al., 1990). Moscow (in Russian). On the other hand, in European Russia the last boreal Avdalovich, S.A. and Bidzhiyev, R.A. (1984). The Karginsky marine transgression is reliably correlated with the Eemian, and terraces in northern West Siberia and problem of the Sartan glaciation, lzvestia Acad. Sci. USSR, ser. geogr., 1, 89-100 (in the previous one is often referred to as intra-Saalian Russian). (Yakovlev, 1956). Zubakov (1986), who thinks that the Baulin, V.V., Belopukhova, Ye.B. and Danilova, N.S. (1984). Holocene finite radiocarbon dates are not evidence for a Weichse- Permafrost in the USSR. In: Velichko, A.A. (ed.), Late Quaternary lian warm-water sea, has suggested a similar framework Environments of the Soviet Union, pp. 87-91. University of Minnesota Press. for West Siberia, placing the Kazantsevo formation at Biryukov, V.Y., Faustova, M.A., Kaplin, P.A., Pavlidis, Y.A., 230-170 ka BP (Isotope Stage 7) and Karginsky forma- Romanova, E.A. and Velichko, A.A. (1988). The palaeogeography tion with finite dates on shells -- at 130-110ka BP of Arctic shelf and coastal zone of Eurasia at the time of the last (Stage 5). If the latter correlation is correct, then the last glaciation (18,000 yr BP). Palaeogeography. Palaeoclimatology, Palaeoecology, 68, 117-125. glaciation of the Kara Sea could even belong to Stage 6. Bolikhovsky, V.F. (1987). The sediments of West Siberia. In: This option is difficult geologically. The uppermost till Novye dannye po geokhronologii chetvertichnogo perioda, pp. 128- contains large fields of fossil glacial ice (Astakhov and 136. Nauka, Moscow (in Russian). Boitsov, M.N. (1961). On development of topography in the conditions Isayeva, 1988; Astakhov, 1992) which in the latter case of subterraneous glaciation. Trudy VSEGEI, ser. nov., 64, 27-36 (in would had to survive through the very warm Eemian Russian). transgression. Bolikhovskaya, N.S. and Bolikhovsky, V.F. (1992). The radiocarbon In the view of this important fact and data described chronology and palynostratigraphy of the Yedoma sediments of West Siberia. In: Geokhronologia chetvertichnogo perioda, pp. t02-111. elsewhere in this paper the only reasonable solution is to Nauka, Moscow (in Russian). place the last ice sheet of the Kara shelf and adjacent Danilov. I.D. and Parunin, O.B. (1982). The comparative results of Siberia in the span of 110 to 50 ka BP, probably within radiocarbon dating carbonate concretions and plant remains from the Isotope Stage 4. This, of course, refers only to the live ice Upper Pleistocene sediments of the Karginsky terrace on the lower Yenissei. Doklady Acad. Sci. USSR, 262(2), 402-404 (in Russian). phase because large isolated masses of dead ice are still Dibner, V.D. (1970). Geomorphology. In: Sovietskaya Arktika, pp. 59- buried in the drift. 64. Nauka, Moscow (in Russian). Epstein, O.G. and Gataullin, V.N. (1993). The lithology and sedimentary environments of the Quaternary in the eastern Barents Sea. Litologia i ACKNOWLEDGEMENTS poleznye iskopayemye, 1, 110-124 (in Russian). In RussianFisher, E.L., Leonov, B.N., Nikolskaya, M.Z., Petrov, O.M., My sincere thanks are due to Dr. Alexander Lavrov, Aerogeologia, Ratsko, A.P., Sulerzhitsky, L.D. and Cherkasova, M.N. (1990). The Moscow, for the permission to use his unpublished geological profiles Late Pleistocene of the central North-Siberian Lowland. Izvestia and to Dr. John lnge Svendsen, University of Bergen, for helping to date Acad. Sci. USSR, ser. geogr., 6, 109-118. the rhinoceros tooth. Gataullin, V.N. (1988). The Upper Quaternary sediments of the western coast of the Yamal Peninsula. Ph.D. thesis, VSEGEI, Leningrad (in Russian). Gesse, V.N., Granovicb, I.B. and Savelyev, A.A. (1963). On the mode of glaciation of the Polar Urals in the Late Pleistocene and Holocene. In: REFERENCES Popov, A.1. and Afanasyev, B.L. (eds), Kainozoisky pokrov Bolshezemelskoi tundry, pp. 105-110. Moscow University (in Andreyeva, S.M. (1978). The Zyryanka glaciation in northern Mid- Russian). Siberia. lzvestiya Acad. Sci. USSR, ser. geogr., 5, 72-79 (in Russian). Grosswald, M.G. (1980). Late Weichselian ice sheet of Northern Arkhipov, S.A., Astakhov, VT, Volkov, I.A., Volkova, V.S. and Eurasia. Quaternary Research, 13, 1-32. Panychev, V.A. (1980). Paleogeografia Zapadno-Sibirskoi ravniny v Grosswald, M.G. (1983). Pokrovnye ledniki kontinentalnykh shelfov (Ice maksimum pozdnezyryanskogo oledeneniya (Palaeogeography of the sheets of continental shelves). Nauka, Moscow, 216 pp. (in Russian). West Siberian Plain at the Late Zyryanka glaciation maximum). Grosswald, M.G. (1994). The drumlin fields of the Novaya Zemlya- Nauka, Novosibirsk, 109 pp. (in Russian). Arslanov, Kh.A., Vereshchagin, N.K., Lyadov, V.V. and Ukraintseva, Urals region and their relation to the Kara ice dispersal center. V.V. (1980). On the chronology of the Karginsky interglacial and Geomorfologia, 1, 40-53 (in Russian). reconstruction of the Siberian environments by carcasses of Grosswald, M.G. and Goncharov, S.V. (1991). On the southern limit of mammoths and their 'associates'. In: Ivanova, I.K. and Kind, N.V. the last Kara ice dome. Materialy glatsiologicheskikh issledovaniy (eds), Geokhronologia chetvertichnogo perioda, pp. 208-213. Nauka, Inst. Geogr. of Russian Acad. Sci., 71, 154-159 (in Russian). Moscow (in Russian). Heintz, A.E. and Garutt, V.Ye. (1964). Determinations of absolute age Astakhov, VT (1976). Geological evidence of the Pleistocene ice of fossil mammoth and woolly rhinoceros remains from Siberian dispersal center on the Kara Shelf. Doklady Acad. Sci. USSR, 231(5), permafrost by radiocarbon. Doklady Acad. Sei, USSR, 154(6), 1367- 1178-1181 (in Russian). 1370 (in Russian). 28 V. Astakhov

Kaplyanskaya, F.A. and Tarnogradsky, V.D. (1975). Origin of the Malyasova, Ye.S. (1989). The palynology of Novaya Zemlya. In: Sanchugovka Formation and the problem of interrelation of Kotlyakov, V.M. (ed.), Moreny -- istochnik glatsiologicheskoi glaciations and marine transgressions in the north of West Siberia. informatsii, pp. 182-200. Nauka, Moscow (in Russian). In: Zubakov, V.A. (ed.), Kolebaniya urovnya Mirovogo Okeana v Mikhankov, Yu.M. (1973). Metodicheskiye ukazania po geologicheskoi pleistotsene, pp. 53-95. Geogr. Soc. USSR, Leningrad (in Russian). syomke masshtaba 1:50000, 6 (Manual for geological mapping of Kaplyanskaya, F.A. and Tarnogradsky, V.D. (1977). On the problem of 1:50 000 scale, issue 6), Nedra, Leningrad, 240 pp. (in Russian). formation of the relict glacial ice deposits and preservation of the Sachs, V.N. (1953). Chetvertichny period v Sovietskoi Arktike (The primordially frozen tills. Izvestiya Geogr. Soc. USSR, 109(4), 314-- Quaternary Period in the Soviet Arctic). Trudy Inst. Geol. of the Arctic, 77, 627 pp. (in Russian). 319 (in Russian). Sukhorukova, S.S. and Gaigalas, A.T. (1986). The fabric and Kind, N.V. (1974). Geokhronologia pozdniego antropogena po izotop- petrographic composition of the Yenissei tills. In: Chetvertichnye nym dannym (Late Quaternary geochronology according to isotopes oledeneniya Srednei Sibiri, pp. 65-73. Nauka, Moscow (in Russian). data). Trans. Geol. Inst. Acad. Sci. USSR, 257, 255 pp. (in Russian). Sukhorukova, S.S., Shevko, A.Ya., Krivonogov, S.K., Bakhareva, V.A., Kind, N.V. and Leonov, B.N. (eds) (1982). Antropogen Taimyra (The Panychev, V,A. and Orlova, L.A. (1991). New data to the Anthropogene of Taimyr Peninsula). Nauka, Moscow, 184 pp. (in stratigraphy of the cover sediments of the right-bank Middle Yenissei Russian). as related to the problem of age of glaciations. Bull. Komissii po Kind, N.V., Sulerzhitsky, L.D., Vinogradova, S.N. and Ryabinin, A.L. izucheniyu chetvertichnogo perioda Acad. Sci. USSR, 60, 116-122 (in (1981). The radiocarbon dates by Geological Institute of Acad. Sci. Russian). USSR. Communication X. Bull Komissii po izucheniyu chetver- Sulerzhitsky, L.D., Vinogradova, S.N., Ryabinin, A.L. and Zaichuk, G.I. tichnogo perioda, 51, 184-189. Nauka, Moscow (in Russian). (1984). The radiocarbon dates by Geological Institute of Acad. Sci. Komarov, V.V. (1986). The diamicton of Potapovo settlement vicinity USSR. Communication XI. Bull. Komissii po izucheniyu chetvertich- (Lower Yenissei). In: Generalov, p.P. (ed.), Stratigrafia neogena i nogo perioda Acad. Sci. USSR, 60, 163-168 (in Russian). pleistotsena severa Zapadnoi Sibiri, pp. 114-117. ZapSibN1GNI, Tarakanov, L.V. (1973). On the question of the Vaigach Island relief. Tyumen (in Russian). Geomorfologia, 4, 85-91 (in Russian). Krasnozhon, A.S., Baranovskaya, O.F., Zarkhidze, V.S., Malyasova, Vasilchuk, Yu.K., Serova, A.K. and Trofimov, V.T. (1984). New data on Ye.S. and Lev, O.M. (1982). The Upper Quaternary of the Southern the sedimentary environments of the Karginsky Formation in the Island of Novaya Zemlya. In: Stratigrafia i paleogeografia pozdniego north of West Siberia. Bull. Komissii po izucheniyu chetvertichnogo kainozoya Arktiki, pp. 40-52. Sevmorgeologia, Leningrad (in perioda Acad. Sci. USSR, 53, 28-35. Nauka, Moscow (in Russian). Volkov, I.A., Grosswald, M.G. and Troitsky, S.L. (1978). On the Russian). proglacial drainage during the last glaciation in West Siberia. Laukhin, S.A. (1981). To the palaeogeography of the West Siberian lzvestiya Acad. Sci. USSR, ser. geogr., 4, 25-35 (in Russian). lowland at the time of the last Late Pleistocene glaciation, lzvestiya Voronov, P.S. (1951). New data on glaciations and Quaternary deposits Acad. Sci. USSR, ser. geogr., 6, 101-113 (in Russian). of the Central Pai-Khoi. Sbornik statei po geologii Arktiki, 2, Makeyev, V.M., Arslanov, H.A. and Garutt, V.Ye. (1979). The age of Glavsermorput, 84-92 (in Russian). the mammoths from Severnaya Zemlya and some questions of the Yakovlev, S.A. (1956). Osnovy geologii chetvertichnykh otlozheniy Late Pleistocene palaeogeography. Doklady Acad. Sci. USSR, 245(2), Russkoi ravniny (The fundamentals of the Quaternary geology of the 421-424 (in Russian). Russian Plain). Trudy VSEGEI, 17, 314 pp. Moscow (in Russian). Makeyev, V.M. and Berdovskaya, G.M. (1973). The stratigraphy of the Zubakov, V.A. (1986). Disputable problems of geological history of the Middle-Upper Quaternary sediments of Pronchishchev Coast and West Siberian North. In: Generalov, P.P. (ed.), Stratigrafia neogena i adjacent part of the Byrranga Mountains. Trudy of Arctic and pleistotsena severa Zapadnoi Sibiri, pp. 38--44. ZapSibNIGNI, Antarctic Institute, 318, 114-139. Leningrad (in Russian). Tyumen (in Russian).