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Supplementary information
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Sedimentological and palaeoenvironmental interpretations
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The glacial history of the Taymyr Peninsula has been studied intensely in recent years as this
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geographical area repeatedly formed the easternmost flank of waxing and waning Eurasian
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Ice Sheets and largely remained ice-free during the last glacial/interglacial cycles (Svendsen
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et al. 1999; Hjort et al. 2004; Svendsen et al. 2004; Möller et al. 2006; Möller et al. 2011).
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Contrary to the western flank of the Eurasian Ice Sheet, i.e. the Scandinavian Ice Sheet (SIS)
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that reached its maximum position at the end of the last glacial cycle during the LGM, the
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maximum position in the east was reached already in the Early Weichselian, c. 70-90 kyr BP
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(Svendsen et al. 2004; Möller et al. 2011), here with the Kara Sea sub-dome of the Eurasian
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Ice Sheet (KSIS) (Figure 1). During the LGM only a minor northern part of the present
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Taymyr Peninsula was covered by the KSIS, most probably terminating at the North Taymyr
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ice-marginal zone (Alexanderson et al. 2001; Alexanderson et al. 2002). Consequently, the
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region to the south of the Byrranga Mountains has remained a terrestrial/sub-aerial
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environment for the last ~60-80 kyr, during which time clastic and organic sediment
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sequences have accumulated through lacustrine, fluvial and aeolian deposition. A particularly
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widespread type of deposit in the Lake Taymyr basin and the adjacent region to the south, are
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the so-called Sabler-type sediments (Figure 1 and S1). These, as described in Möller et al.
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(1999), consist predominantly of weakly laminated to massive silts and fine sands, more or
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less rich in organic detritus and with frequent occurrences of mega-fauna remains (e.g. bones
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of mammoth, horse, muskox). Radiocarbon dating of Sabler-type sediments at several
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localities reveals a depositional age range of ~46 – 12.5 cal kyr BP, which is coincident with
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the timeframe for “Mammoth steppe” conditions in the region (Möller et al. 2006; Möller et
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al. 2011).
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Cape Sabler-type perennially frozen sediments were sampled from four localities around the
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western part of Lake Taymyr, namely Upper Taymyr River delta (UTRD), Baskura Peninsula
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(BAP), Cape Sabler (CS) and Fedorov Islands (FI) (Figure 1). A fifth locality is Ovrazhny
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Peninsula (OVR), situated on the northern shore of Lake Engelgarth, a lake basin along the
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north-flowing Lower Taymyr River (Figure 1). All sites have thicker sediment accumulations
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than could be investigated; the lowermost 1 - 2 meters or more above the lake shore are
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usually slumped and refrozen sediments from further upslope, and from the top of the sections
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the ground surface slopes gently to higher terrace levels with no exposed sediments. The
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sediments are exposed due to progressive shore-bluff back wasting, leaving 10 – 30 m high
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bluffs. When ice-wedge polygons are present – which is commonly the case for these type of
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sediments – the erosion takes place along the reticulate pattern of these, forming gullies both
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perpendicular and parallel to the coastline and leaving characteristic thermokarst mounds
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(baydjarakhs, see Figure S1A).
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From their internal composition and sedimentary structures (Figure 2) Sabler-type sediments
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neither resemble typical fluvial sediment, nor pure lacustrine sediment. We interpret them as
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derived predominantly from aeolian and lacustrine sources, the latter during periods of
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elevated lake level. The sediments are primarily interpreted as sub-aerial deposits, formed by
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vertical accretion of windblown silt trapped on top of the boggy surface of an active layer,
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combined with deposition of silt and fine sand during lake and river flooding events tied to
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annual snow melt and icing formation in the Taymyr River valley. At the same time there was
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syngenetic formation of ground-ice polygons (Siegert et al. 1999). Depending on local
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factors, e.g. topography, aeolian activity and/or flooding, sediment deposition could more or
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less dominate the in situ accretion of organic deposits, explaining differences in sediment
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successions between the sites.
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From three of the sites, namely the Cape Sabler, Baskura Peninsula and Upper Taymyr River
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sites, a conspicuous decline in depositional rate is seen in the age/depth curves (Figure 3) with
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duration of some 4 to 6 kyr. The decline starts a few thousands of years before the LGM and
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continues into the same, after which the deposition rate shows a remarkable increase. It is
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tempting to tie the decline in deposition to an increasingly severe climate gradually evolving
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into extreme polar desert conditions over Taymyr at the LGM with close to zero precipitation
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(Hubberten et al. 2004). Such a climate would subdue most processes described above to be
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responsible for Sabler-type sediment formation. The increasing sedimentation rate, starting at
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the end of the LGM is suggested to be connected with an LGM ice advance, inundating the
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northwestern most part of the Taymyr Peninsula to the NTZ line (Fig. 1; Alexanderson et al.
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2001; Alexanderson et al. 2002), thus reversing the drainage direction of the Taymyr River
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and by this increase melt-water and sediment input in the Taymyr Lake basin (Hjort et al.
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2004).
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Study sites
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Upper Taymyr River delta. – At the entrance of the Upper Taymyr River into the western part
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of Taymyr Lake (Figure 1C), Sabler-type sediments are exposed in front of a first large delta
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in 7–9 metres high baydjarakh bluffs, of which ~5 m could be logged (Figure 2A). The
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succession consists of 10 - 90 cm thick beds of silt-soaked moss, interbedded with massive to
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weakly laminated, 12 - 95 cm thick silt beds. When lamination is evident it is in order of 1 - 4
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mm thick lamina. The silt beds are more or less rich in wood fragments and other plant
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detritus. Radiocarbon dating of eleven samples gives a depositional age frame between c.
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28.2 – 20.1 cal kyr BP (Table S2), of which two datings (UTRD 4:10 and 4:11) show clear
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age reversals, most probably due to resedimentation of older plant remains. A break in
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sedimentation, c. 5 kyr long, or an extremely low sedimentation rate between samples UTRD
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4:6 and 4:7 is indicated from retrieved radiocarbon ages between 26 – 22 cal kyr BP (Figure
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3A). The sampled sediment bed does not, however, indicate any hiatus, but continuous
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sedimentation.
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Baskura Peninsula. – The north-facing, more than 2 km long shore bluff of north-eastern
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Baskura Peninsula (Figure 1C) rises ~20 m above Taymyr Lake, exhibiting typical
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baydjarakhs (Figure S1A). Ten metres of sediments could be logged (Figure 2B), forming a
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stacked sequence of horizontally laminated coarse silt to sandy silt (Figure S1B). Silt laminas
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are usually 2-10 mm thick, occasionally up to 50 mm. The typical silt-soaked moss beds (for
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Sabler-type successions) are absent and the overall occurrence of organic detritus is low in the
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more sandy parts, but more frequent in the siltier parts. Radiocarbon dating of 21 samples
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gives a depositional age frame between c. 34.5 – 22.9 cal kyr BP (Table S2), but dated
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samples reveal frequent age reversals, most probably due to resedimentation of older plant
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remains. A break in sedimentation rate seems to occur at around 25 – 27 cal kyr BP (Figure
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3B).
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Cape Sabler. – Cape Sabler is a peninsula protruding southwards into Lake Taymyr (Figure
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1C), bordered by 5 – 25 m high bluffs actively eroded by the lake and at places exhibiting
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spectacular baydjarakh morphology. Sections along Cape Sabler were briefly investigated by
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Isayeva (1984) and in a more comprehensive study by Möller (1999). An approximately 26 m
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high section, of which 23 meters could be logged (Cape Sabler 1 (Möller et al. 1999)),
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showed a stacked sequence of predominantly horizontally laminated to massive silt rich in
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organic detritus (moss stems, small twigs, seeds, leaves), occasionally interbedded with thin
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fine sand beds occurring solitary or in intercalated sets. A characteristic feature is also 0.5-3
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m thick beds of massive silt with a very high content of moss (Figure S1E), often grading into
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silt-soaked moss peat (Figure S1D). In this study only sediments between 9.9 - 10.0 m a.s.l.
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were sampled in 10 cm intervals for extraction of pollen, macrofossils and sedaDNA and the
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log in Figure 2B is an extraction between 8 - 13 m of the complete sediment succession at
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Cape Sabler. In total there are 36 radiocarbon dated samples, suggesting a depositional age
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frame between c. 39 – 19.9 cal kyr BP, but with frequently occurring age reversals within the
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succession. A best fit curve of ages plotted against depth, avoiding the most obvious age
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reversals (Figure 3C) indicate a pronounced decline in sedimentation rate approximately
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between 29 – 23 cal kyr BP, after which sedimentation speed up again.
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Federov Islands. – Federov Islands (Figure 1C) consist of two very flat sand plateaux
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reaching 22 m a.s.l., connected at lake level to each other by a tombola and located on a
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dolerite core. Only the upper part of a shore bluff could be dug out with in situ sediments,
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covering ~5 m (Figure 3D). The logged sediment consists of a stacked sequence of planar
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parallel-laminated, 2 - 10 cm thick coarse silt beds, interbedded with 5 - 15 cm thick, massive
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to vaguely laminated beds of fine sand. Most beds are rich in small wood fragments and other
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organic detritus. In total there are 8 radiocarbon dated samples, suggesting a depositional age
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frame between c. 13.4 – 12.3 cal kyr BP (Table S2) with only one old-age outlier. These
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sediments are thus the youngest recorded Sabler-type sediment succession, deposited with a
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high sedimentation rate (Figure 3D) at the very end of the Late Weichselian. Older sediment
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should be expected further down in the inaccessible bluff.
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Ovrazhny Peninsula. – Typical Cape Sabler-type sediments are exposed on the northern shore
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of Lake Engelgarth (Figure 1C), the sediments located in a depression between out-cropping
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glaciolacustrine varved sediments, OSL-dated to 52 - 60 kyr. These sediments stem from ice
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damming/blockage of the Taymyr River valley in the Middle Weichselian (Hjort et al. 2004;
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Möller et al. 2011) at the NTZ 2 ice-marginal zone (Figure 1B). Only ~4 m of Sabler-type
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sediment was accessible for logging (Fig. 2E), showing three 0.5 - 1.2 m thick beds of partly
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silt-soaked moss peat, interbedded with massive organic debris-rich silt beds, 35 - 50 cm
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thick. Sabler-type sediments continue up-slope to ~30 m a.s.l., but are not exposed in non-
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slumped sections. In total 8 samples were radiocarbon dated, giving our oldest ages for this
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type of sediment. Even though three out of the four lowermost datings are finite (~45 14C kyr
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BP), they are out of range to be calibrated into calendar years (Table S2). Upwards ages are in
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reverse order at around 45 cal kyr BP, with a remarkable age jump to 35 cal kyr BP for the
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uppermost sample (Figure 3E). There is no obvious sediment unconformity in the logged
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section, indicating this break in sedimentation and age.
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Results for sedaDNA, macrofossil and pollen analyses
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The results from the three analyses of sedaDNA, macrofossils and pollen are shown in figure
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S2, where records from each of the proxies are shown for all 18 samples analysed. Table 1
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and figure 5 is based on these results.
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Figures
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Figure S1. A. The Baskura Peninsula site (Fig. 1C). The shore bluff shows the, for ‘Cape
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Sabler-type’ sediments, typical thermokarst morphology called ‘baydjarakhs’, i.e. permafrost
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degradation along ice-wedge polygons. Note person for scale. B. Laminated silt with a low
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occurrence of organic remains (Baskura Peninsula). C. Interbedded silt and fine sand beds,
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rich in organic remains (Fedorov Islands). D. Silt-soaked moss peat (Ovrazhny Peninsula).
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E. Massive to vaguely laminated silt rich in moss (Cape Sabler).
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Figure S2. Diagram showing results from the DNA, macrofossil and pollen analyses from all
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samples/localities sorted according to radiocarbon age (calibrated). Numbers indicate the
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method the taxa were detected by. D: DNA (green); M: macrofossils (blue); P: pollen (red);
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DM: DNA & Macrofossils; DP: DNA & Pollen; MP: Macrofossils & Pollen; and “ALL” for
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all proxies.
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Table S1. Lithofacies codes as used in sediment logs.
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Table S2. 14C dates from investigated sites. All are AMS dates, LuA numbers from the
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Radiocarbon Dating Laboratory at Lund University, Sweden and the Poz numbers from the
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Poznan Radiocarbon Laboratory in Poland. Positions of samples analyzed for
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pollen/macrofossils/sedDNA are marked in grey.
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References
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Alexanderson H, Adrielsson L, Hjort C et al. (2002). Depositional History of the North
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Taymyr Ice-Marginal Zone, Siberia - a Landsystem Approach. Journal of Quaternary Science
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17, 361-382.
175
176
Alexanderson H, Hjort C, Möller P, Antonov O, Pavlov M (2001). The North Taymyr Ice-
177
Marginal Zone, Arctic Siberia - Preliminary Overview and Dating. Global and Planetary
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Change 31, 427-445.
179
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Hjort C, Möller P, Alexanderson H (2004). Weichselian Glaciation of the Taymyr Peninsula,
181
Siberia. In: Quaternary Glaciations - Extent and Chronology, Part 1: Europe (eds. J Ehlers
182
and PL. Gibbard). Developements in Quaternary Science 2A, 359-367. Elsevier.
183
184
Hubberten HW, Andreev A, Astakhov VI et al. (2004). The Periglacial Climate and
185
Environment in Northern Eurasia During the Last Glaciation. Quaternary Science Reviews
186
23, 1333-1357.
187
188
Isayeva LL (1984). Late Pleistocene glaciation of North-Central Siberia. In: Late Quaternary
189
Environments of the Soviet Union (ed. AA Velichko), 21-30. University Minnesota Press,
190
Minneapolis.
191
Möller P, Bolshiyanov DY, Bergsten H (1999). Weichselian Geology and
192
Palaeoenvironmental History of the Central Taymyr Peninsula, Siberia, Indicating No
193
Glaciation During the Last Global Glacial Maximum. Boreas 28, 92-114.
194
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195
Möller P, Hjort C, Alexanderson H, Sallaba F (2011). Glaciation History of the Taymyr
196
Peninsula and the Severnaya Zemlya Archipelago, Arctic Russia. In: Quaternary Glaciations -
197
Extent and Chronology - a closer look (eds. J Ehlers and PL Gibbard). Developements in
198
Quaternary Science 15, 375-386. Elsevier.
199
200
Möller P, Lubinski DJ, Ingolfsson O et al. (2006). Severnaya Zemlya, Arctic Russia: A
201
Nucleation Area for Kara Sea Ice Sheets During the Middle to Late Quaternary. Quaternary
202
Science Reviews 25, 2894-2936.
203
204
Siegert C, Derevyagin AY, Shilova GN, Hermichen WD, Hiller A (1999). Paleoclimatic
205
Evidences from Permafrost Sequences in the Eastern Taymyr Lowland. " Land-Ocean
206
Systems in the Siberian Arctic." L. A. Timokhov.
207
208
Svendsen JI, Alexanderson H, Astakhov VI et al. (2004). Late Quaternary Ice Sheet History
209
of Northern Eurasia. Quaternary Science Reviews 23, 1229-1271.
210
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Svendsen JI, Astakhov VI, Bolshiyanov DY et al. (1999). Maximum Extent of the Eurasian
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Ice Sheets in the Barents and Kara Sea Region During the Weichselian. Boreas 28, 234-242.
213
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