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Quaternary Science Reviews 30 (2011) 3812e3822

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Quaternary Science Reviews

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Deglaciation history and age estimate of the Younger Dryas end morainesin the Kalevala region, NW Russia

Niko Putkinen a,*, J.P. Lunkka b, A.E.K. Ojala c, E. Kosonen c

aGeological Survey of Finland, Western Finland Office, P.O. Box 97, FIN-67101 Kokkola, Finlandb Institute of Geosciences, The University of Oulu, P.O. Box 3000, FIN-90014 University of Oulu, FinlandcGeological Survey of Finland, Southern Finland Office, P.O. Box 96, FIN-02151 Espoo, Finland

a r t i c l e i n f o

Article history:Received 28 January 2011Received in revised form23 September 2011Accepted 26 September 2011Available online 27 October 2011

Keywords:Glacial geologyYounger Dryas end morainesScandinavian Ice SheetChronologyPaleomagnetic dating

* Corresponding author.E-mail addresses: niko.putkinen@gtk.fi (N. Putkine

(J.P. Lunkka), antti.ojala@gtk.fi (A.E.K. Ojala), emilia.ko

0277-3791/$ e see front matter � 2011 Elsevier Ltd.doi:10.1016/j.quascirev.2011.09.023

a b s t r a c t

Three lake basins were cored in the Kalevala area, northwestern Russia in order to determine theWeichselian deglaciation history of the eastern flank of the Scandinavian Ice Sheet and to date theKalevala and Pääjärvi end moraines adjacent to these basins. Two of the lake basins, Ala-Kuittijärvi andKeski-Kuittijärvi, are situated on the proximal side of the Kalevala end moraine while the third lakebasin, Tuoppajärvi, is located on the distal side of the Pääjärvi end moraine. One site from each lake basinwas chosen for sedimentological and chronological study. The chronology presented in this paper isbased on palaeomagnetic measurements and counting of varved clays and the results are compared tothe Finnish palaeomagnetic master curve.

The results indicate that the deglaciation sediments in the Ala-Kuittijärvi and Keski-Kuittijärvi lakeswere deposited mainly by extra-marginal rivers, while those in Tuoppajärvi were deposited in an ice-contact setting. After the glacial meltwater input ceased, typical large lake gyttja clay/clay gyttja sedi-ment accumulated in all three basins. The palaeomagnetic record obtained from the Ala-Kuittijärvisediment sequence extends back to 10,900 cal. BP, while that of Keski-Kuittijärvi and Tuoppajärvi datesback to 9800 cal. BP. The palaeomagnetic record, together with 450 counted varves in Ala-Kuittijärvi,indicates that the basin was deglaciated at around 11,350 � 300 cal. BP. Based on palaeomagnetic results,geomorphological considerations and ice retreat rates, it is estimated that the Kalevala end moraine wasformed prior to 11,450 � 350 cal. BP, while the Pääjärvi end moraine, west of Tuoppajärvi, was formed atprior to 11,000 � 250 cal. BP.

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1. Introduction

During the local last glacial maximum (LGM: ca. 20e17 ka)northwestern Russia was covered by the Scandinavian Ice Sheet(SIS) (cf. Demidov et al., 2004; Svendsen et al., 2004; Larsen et al.,2006) (Fig. 1). The SIS retreated from its maximum extent innorthwestern Russia to the Scandinavian mountains between 17and 10 ka (cf. Lunkka et al., 2001; Svendsen et al., 2004; Larsenet al., 2006). During the course of the deglaciation prominent endmoraine chains were deposited in front of the ice margin all aroundthe SIS. These end moraines were formed during minor standstillsand advances of the SIS. The formation of the end moraines was

n), juha.pekka.lunkka@oulu.fisonen@gtk.fi (E. Kosonen).

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ultimately related to climate changes and their effect on thebehaviour of the SIS dynamics.

One of the most continuous end moraine belts in the world,which can be traced over a distance of more than 2500 km, aroundFennoscandia, Russian Karelia and the Kola Peninsula, was depos-ited at the margin of the SIS (cf. Andersen et al., 1995). On theeastern flank of the SIS, end moraines that belong to this contin-uous end moraine belt are the Salpausselkä I, II and III, togetherwith the Pielisjärvi end moraines in Finland, and the Rukajärvi,Kalevala and Pääjärvi end moraines in Russian Karelia. It is gener-ally accepted that these end moraines were deposited during theYounger Dryas Stadial (YD) (12.8e11.5 ka) (Muscheler et al., 2008).The existing chronology of the Salpausselkä and Pielinen endmoraines is based on varved clay chronology and biostratigraphicalevidence supported by radiocarbon age determination. It is onlyrecently that the surface exposure dating (SED) method and thepalaeomagnetic method, combined with radiocarbon dating onlake sediments, have been applied to date the Salpausselkä I and II

Fig. 1. Location map. Inset map shows the main end moraines in the Kalevala area (K¼ Kalevala end moraine, P¼ Pääjärvi end moraine, R ¼ Rukajärvi end moraine), on the KolaPeninsula (Keiva end moraines) and in southern Finland (SsI-III ¼ First, Second and Third Salpausselkäs, CFEM ¼ Central Finland end moraine, P¼ Pielisjärvi end moraine). LGMindicates the maximum extent of the Scandinavian Ice Sheet in its eastern flank, modified after Demidov et al. (2004). The larger map shows the coring sites (triangles) and theirrelationship to the Kalevala and Pääjärvi end moraines.

N. Putkinen et al. / Quaternary Science Reviews 30 (2011) 3812e3822 3813

moraines more accurately (Tschudi et al., 2000; Saarnisto andSaarinen, 2001; Rinterknecht et al., 2006). According to theseresults Salpausselkä I and II end moraines were deposited duringthe Younger Dryas Stadial between ca. 12.5e11.6 cal. BP. However,continuous end moraines that extend from Finland into RussianKarelia have not been dated. The age estimates of these moraineshave largely been based on radiocarbon ages from lake sediments,considerations of ice sheet retreat rates and the correlation of theRussian Karelian end moraines to the Salpausselkäs in Finland(Ekman and Iljin, 1991; Rainio et al., 1995; Boulton et al., 2001;Svendsen et al., 2004).

This study concentrates on the deglaciation history of theKalevala area, where two prominent end moraines, the Kalevalaand Pääjärvi end moraines, are located (Fig. 1). Three sedimentcores were studied from the lake basins that occur on the proximaland distal sides of the end moraines. This was done in order to: 1)reveal the lake basin history during and after deglaciation, 2)constrain the age of Kalevala and Pääjärvi end moraines and theircorrelation to the Younger Dryas end moraines in Finland usingpalaeomagnetic dating combined with varve counting.

Table 1Hydrological parameters for Ala-Kuittijärvi, Keski-Kuittijärvi and Tuoppajärvi(Alexandrov, 1959; Vodogredtsky, 1972).

Lake Basin Area (km2) Altitude(m a.s.l)

Averagedepth (m)

Maximumdepth (m)

Catchment(km2)

Keski-Kuittijärvi 275.7 101.3 10.8 34 9470Ala-Kuittijärvi 141.3 100 9.4 33 10,200Tuoppajärvi 986 109.5 15.2 56 3570

2. Study area and geological setting

The three lake basins occur in the Kalevala region of north-western Russia (Fig. 1). The dimensions of the lakes and theircatchment areas are listed in Table 1. Gently sloping hill topographyaround these lakes is dictated by the Archaean basement rocks ofthe Fennoscandian Shield. The latter typically comprises gneiss,granites and tholeitic basalts in the district (Koistinen et al., 2001).The highest points of the bedrock rise above 280 m a.s.l., but

generally the land surface lies between 100 and 140m a.s.l., slopingtowards theWhite Sea basin to the east. The present ground surfaceis characterised by peat land, lake basins and glacial landforms,such as drumlins, eskers and end moraines (Niemelä et al., 1993).

Two end moraines and an interlobate complex, formed at theformer ice-marginal zone, are the main glacial landforms in thestudy area (Fig. 1) (Putkinen and Lunkka, 2008). The lakes Ala-Kuittijärvi and Keski-Kuittijärvi are located on the proximal side ofthe Kalevala end moraine, while Tuoppajärvi occurs on the distalside of the Pääjärvi end moraine (Fig. 1).

3. Methods

3.1. Coring and laboratory work

The coringmethods and laboratory processing of lake sedimentsin this study were conducted following the procedures adopted bythe Geological Survey of Finland (GTK) (cf. Saarinen, 1994; Ojala,2001; Pajunen, 2004). The thickness of the lake sedimentssequence was mapped and examined prior to coring using an echo-

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sounding survey in autumn 2002. Following the analysis of theecho-sounding profiles, flat basinal areas from each lake wherea relatively thick sediment cover occurred were chosen for coring.In spring 2004, sediments were cored using an improved piston-operated gravity corer (cf. Putkinen and Saarelainen, 1998). Thecoring was carried out using 200e300 kg weights and 5- to 7.5-m-long steel tubes with inner plastic liners of inside diameter56.5 mm. At the Ala-Kuittijärvi site (64�56’43.2"N/31�46’31.7"E,water depth 20.70m) the sediment cores reaching impermeable tillobtained were 5.03 and 5.71 m long, at the Keski-Kuittijärvi site(65�07’56.0"N/31�28’14.9"E, water depth 19.70 m) 2.7, 2.95 and3.0 m long and at Tuoppajärvi site (65�47’00.1"N/31�33028.3"E,water depth 22.80 m) 6.13 and 6.65 m long. The sample tubes weremarked and cut into lengths 2 m long.

The cores were cut longitudinally for sampling in the laboratory,one half being used formagnetic susceptibility (k)measurements anddetailed sediment descriptions. The magnetic susceptibility reflectsthe ability of the material to bemagnetised after it has been exposedto aweakmagneticfield. This abilitymainly depends on themagneticminerals (for example, magnetite and hematite) in a sample, theirconcentration, grain size and impurities (cf. Thompson and Oldfield,1986). In the Ala-Kuittijärvi sequence, magnetic susceptibility wasmeasured from the fresh sediment surface at 10 mm intervals usinga Bartington MS2E1 surface scanning sensor. In the Keski-Kuittijärviand Tuoppajärvi sediment sequences, susceptibility was measuredfrom palaeomagnetic cubes using MS2B Dual Frequency Sensor at30 mm intervals.

Colour, grain-size, sedimentary structure, grading and fossilplant material were recorded. The main lithological structures,including laminations,weremarked on graph paper. After the visualdescription, samples for loss on ignition (LOI), grain size, micro-fossils and radiograph analysis were collected. Loss on ignition wasmeasured by a conventional method: 1-cm-thick subsamples weredried at 105 �C for 24h and ignited at 550 �C for 3 h (cf. Bengtson andEnell, 1986). The sediment grain-size analysis from the Tuoppajärvicore was undertaken at the laboratories of GTK using a sedigraph.

The classification of the lithostratigraphical units was definedusing visual, macroscopic radiographs, LOI and magnetic suscep-tibility (k) results. The sediment varves were counted both visuallyand using a digital image analysis technique. The thickness varia-tions of the varves were studied from X-ray radiographs (cf. Ojala,2004), using Philips constant potential MG 102L X-ray equipmentwith the standard focal distance of 100 cm and focal spot size of0.4 � 0.4 m. Sediment exposure time was 2.5 min and the tubevoltage value used was 40 kV. The AGFA Strukturix D7/DW X-rayfilms were subsequently processed using a standard combinationof developer and fixer liquids, which enables adjustments oflightness and contrast of the final X-ray radiographs. Greyscaleimages were scanned at an optical resolution of 1000 dpi. Digital-ised images were stored as bitmap computer images (TIF) con-taining 256 grey shades (cf. Ojala and Saarinen, 2002; Ojala, 2004).Density variation of varves was measured from the TIF imagesusing an ImageJ freeware programme.

3.2. Age depth modelling

The second half core was used for palaeomagnetic measure-ments. Samples for this purpose were collected at 30 mm intervalsin polystyrene cubes (7 cm3), following Saarinen (1994). It shouldbe noted that the declination measurements presented here areonly relative. This is because the cores were not orientated withrespect to magnetic north during the coring process.

The inclination, declination and intensity of natural remanentmagnetisation (NRM) of all the samples were measured at the GTKusing a 2G-Enterprises SRM-755R three-axial SQUID within 48 h

after sample preparation. Following this, six samples (82 cm,176 cm, 283 cm, 328 cm, 439 cm and 533 cm from the top of thecore) from the Tuoppajärvi sequence, three samples (100 cm,183 cm and 222 cm from the top of the core) from Keski-Kuittijärviand three samples (162 cm, 289 cm and 381 cm from the top of thecore) from the Ala-Kuittijärvi sequence were selected for stepwisealternative field (AF) demagnetisation (0e120 mT peak AF) in orderto study the stability and strength of their NRM. These samplesrepresented different lithostratigraphical units of the lake sedimentsequences. The remaining samples were demagnetised along threeaxes using a 20 mT peak AF field and measured.

The Tuoppajärvi sediment contained an organic horizon in thelower, minerogenic part of the sequence. The material from thishorizon was sampled for 14C AMS-age determination (Fig. 2). Thiswas undertaken in order to date the beginning of deglaciation ofthe Tuoppajärvi basin. In other cores no suitable organic materialfor dating the start of deglaciation was present. Radiocarbon AMSdating was carried out by the Poznan Radiocarbon Laboratory,Poland, and calibrated ages were obtained using the Calib rev 5.0.2.programme (Stuiver and Reimer, 1993; Reimer et al., 2004).

3.3. Diatom analysis

A total of six diatom analyses were carried out on the lowermostpart of all the lake cores. This was done in order to define the envi-ronmental conditions (e.g. fresh/saline water) in the basins duringand after deglaciation. Samples for diatom analysis were preparedusing standard procedures (cf. Battarbee, 1986). An Olympus BX40light microscope with 1000� magnification was used for identifica-tion. The taxonomy and grouping of diatoms, according to theirecology, was based on the following sources: Mölder and Tynni(1967, 1968, 1969, 1970, 1971, 1972, 1973); Tynni (1975, 1976, 1978,1980); Krammer and Lange-Bertalot (1986, 1988, 1991a,b).

4. Results

4.1. Lithostratigraphy

4.1.1. Ala-KuittijärviFour distinct lithostratigraphical units occur above the basal

diamicton in the 4.95 m long sequence obtained from this site(Fig. 2). Unit I is 1.6 m thick and rests on the diamicton. It consists of439 upwards thinning, normal grading silt-clay couplets. Siltlaminae in the couplets have a sharp lower boundary, while the siltusually grades upwards into clay laminae. In the basal 0.4m, the silt-clay couplets range between 7.2 and 10 mm thick. In the next ca.0.4 m, they are 3.7e7.2 mm and in the uppermost 0.8 m they reach0.9e3.7 mm thick. Magnetic susceptibility values (k) vary between30and60SI� 10�5 inUnit I, and LOI values (%) increase from2 to2.6.

Unit I grades upwards within 0.04 m into a 0.2 m thick massiveclay (Unit II; Fig. 2). The top 0.08 m of Unit II consists of clay.Magnetic successibility values range from 35 to 55 SI� 10�5 andthe average LOI value is 2 in this unit. This massive clay unit is, inturn, overlain by sulphide-rich gyttja clay 2.6m thick (Unit III). Herethe magnetic susceptibility values decrease upwards from 35 to 7SI� 10�5 and the LOI increases from 1.4 to 6 in this unit. Unit IIIpasses into a 0.6 m thick sulphide-rich silt gyttja (Unit IV) withmagnetic susceptibility values ranging between 8 and 5 SI� 10�5

and LOI values between 6 and 8.0 (Fig. 2).

4.1.2. Keski-KuittijärviThree different lithostratigraphical units occur in the 2.64 m-

long sediment core from this site (Fig. 2). Unit I, immediately over-lying the diamicton, is 0.5 m thick. The basal 0.1 m consists ofindistinctively layered fine silt. Above, there are 300 normally

Fig. 2. Lithostratigraphical logs with loss on ignition (LOI %) and magnetic susceptibility (k) values from Ala-Kuittijärvi, Keski-Kuittijärvi and Tuoppajärvi. The main lithostrati-graphical units from each core (Roman numbers) are also marked and discussed in text. Symbols: 1. diamicton, 2. silt, 3. clay, 4. gyttja, 5. laminated, 6. organic layers and 7. sulphidelayers. The location and calibrated ages of 14C samples from Tuoppajärvi core are shown.

N. Putkinen et al. / Quaternary Science Reviews 30 (2011) 3812e3822 3815

graded silt-clay couplets. The varve thickness in these silt-claycouplets varies between 0.8 and 1.35 mm (Fig. 3). The magneticsusceptibility values increase from 80 to 130 SI� 10�5 and LOIvalues range between 2.3 and 1.95 (Fig. 2).

Unit I passes upwards into 0.35 m thick massive clay (Unit II).The magnetic susceptibility values range between 115 and 150SI� 10�5 and LOI decreases from 1.95 to 1.15. The contact betweenunits I and II is relatively sharp where transition into massive clayoccurs in a 0.02 m thick zone. Unit III is 1.80 m thick gyttja clayconformably overlying the massive clay beneath. Unit III includes1e10 mm thick organic-rich laminae throughout. In this unit themagnetic susceptibility decreases from 115 to 25 SI� 10�5 and LOIincreases from 1.15 to 5.

4.1.3. TuoppajärviSix different lithostratigraphical units can be differentiated

above the diamicton in the 6.28 m long sediment core fromTuoppajärvi (Fig. 2). The lowermost, Unit I, is 0.8 m thick andconsists of massive clay/massive gyttja clay with medium-sized,isolated sand grains that occur between 5.90 and 5.75 m.Sulphide laminae increase towards the top of this unit. Unit I gradesinto 1.2 m thick Unit II, which consists of gyttja clay (Fig. 2). Thisrhythmite unit is composed of one hundred, ca. 5 mm thick,internally laminated sets. In the middle part of this rhythmite unit,there are also some isolated grains (Fig. 3). At the top of the unitthere are eight normally graded silt-clay couplets. In these twolowermost units magnetic susceptibility and LOI values range from175 to 25 SI� 10�5 and 1.5 to 3.5 respectively (Fig. 2). Unit III isa massive gyttja clay unit, 0.14 m thick, that has a sharp lowercontact. Unit IV above is 0.9 m thick massive fine silt. However, itstarts with a 0.06 m thick laminated gyttja clay horizon, including20 thin silt-clay couplets (Fig. 3). The magnetic susceptibility values

in Units III to IV increase from 25 to 250 SI� 10�5 and LOI variesbetween 3.5 and 1.4.

Units V and VI in the Tuoppajärvi sequence consist of 2.0 m ofgyttja clay that passes upwards into 1.2 m thick clay gyttja. Units Vand VI include organic-rich strata and magnetic susceptibilityvalues decrease from 250 to 1 SI� 10�5 and LOI increases from 3.5to 16.5.

4.2. Natural remanent magnetisation (NRM) measurements

The natural remanent magnetisation (NRM) intensity rangesbetween 0 and 275 mAm�1 in Tuoppajärvi, 20e175 mAm�1 inKeski-Kuittijärvi and 75e360 mAm�1 in Ala-Kuittijärvi deposits,giving a fairly good comparison to magnetic susceptibility values(Figs. 2 and 4). The declination and inclination range approxi-mately between �50� and 55�e80�, respectively. The Ala-Kuitti-järvi NRM record is characterised by six inclination maxima andfive minima, and five declination maxima and minima. However,the declination signal is disturbed at least between 3.3 and 3.7 mand possibly also below 3.7 m (Fig. 4). Both the Keski-Kuittijärviand Tuoppajärvi NRM records are characterised by five inclinationmaxima and five minima, and five declination maxima and fourminima. The NRM signal is also disturbed in the Keski-Kuittijärvisediments below 1.7 m and likewise in the Tuoppajärvi sequencebelow 3.2 m (Fig. 4).

In order to study the magnetic carriers of the remanence, andto test the stability of the NRM, several samples from differentlithostratigraphical units were exposed to alternative field (AF)demagnetisation. All the samples measured exhibit a strong andstable primary component of the NRM direction. The mediandestructive field (MDF) of the Ala-Kuittijärvi samples variesbetween 35 and 47 mT, in the Keski-Kuittijärvi samples between

Fig. 3. X- radiographs from A) Keski-Kuittijärvi, showing distal lake annual laminationi.e. glacial varves and B) Tuoppajärvi, showing ice-contact lake multiple lamination.Note that in the Tuoppajärvi sediments there is abundant IRD material which is absentfrom the Keski-Kuittijärvi sediments.

N. Putkinen et al. / Quaternary Science Reviews 30 (2011) 3812e38223816

28 and 36 mT, and in the Tuoppajärvi samples between 28 and41 mT (Fig. 5). Fig. 5 illustrates the demagnetisation behaviour ofNRM in Ala-Kuittijärvi Unit III, Keski-Kuittijärvi Unit III andTuoppajärvi Units V and IV. The results also suggest that fine-grained single domain (SD) and/or pseudo-single domain (PSD)magnetite is most probably the dominant carrier of the NRM (cf.King et al., 1982; Thompson and Oldfield, 1986). The orthogonalZijderveld projections from Ala-Kuittijärvi samples confirm thatthe magnetic signal is controlled by a strong, stable primarycomponent. Similar results have been obtained from the Nauta-järvi (Ojala and Saarinen, 2002) and Mustalampi (Kosonen andOjala, 2011) sediments.

4.3. 14C and diatoms results

Two 14C AMS ages of 29,500 � 300 cal. BP (Poz-29259) and27,160 � 220 cal. BP (Poz-29415) were obtained from organicfragments in massive gyttja clay (Unit III) at a depth of 4.25e4.26 min the Tuoppajärvi sequence (Fig. 2). The age difference betweenthe dated samples taken from the same level, together with theirold age, suggest that the sediments contained a fraction of ancient

carbon derived from local, carbonate-bearing bedrock. Therefore, itseems likely that the dates obtained do not represent true age ofthe organic materials and the results cannot be used to providea chronology for the sediment.

Diatoms were identified in three samples from Ala-Kuittijärvi;from Unit I at 4.68 m, 3.82 m and from Unit II 3.24 m levels belowthe top. A scarce diatom flora in the lowermost varved clay samplewas dominated by small periphytic Fragilaria species (F. robusta, F.construens f. venter, F. pinnata, F. brevistriata, F. cf. polonica) withsome fragments of epipelic diatoms (Navicula spp., Pinnularia spp.,Cymbella spp., Frustulia rhomboides) and attached species (Epi-themia adnata, Eunotia bilunaris var. mucophila). In contrast, epi-pelic species (e.g., Navicula costulata, N. capitoradiata, N.schmassmannii, Amphora fogediana, Caloneis bacillum) dominatedthe scarce diatom flora of the massive clay sample at 3.24 m,together with certain Cyclotella taxa (Cyclotella ocellata, C. rossii, C.stelligera). No diatoms or their fragments were found from thevarved clay sample at 3.82 m.

Three diatom samples from levels 6.06 m, 4.56 m and 3.98 mbelow the top were also identified from the Tuoppajärvi sequence.No diatoms were found at 4.56 m and 3.98 m, but a scarce diatomflora from 6.06 m (Unit I) was dominated by Aulacoseira ambiqua,Fragilaria exiqua and fragments of Thalassiosira baltica andT. hyberborea.

5. Interpretation

5.1. Sedimentary sequences

5.1.1. Ala-Kuittijärvi and Keski-KuittijärviLake Ala-Kuittijärvi and Keski-Kuittijärvi are located on the

proximal side of the Kalevala end moraine zone (see Fig. 1). Dia-micton at the base of two cores was deposited by retreating ice,most likely as basal till. The laminated sediments in Keski-Kuitti-järvi and Ala-Kuittijärvi were most probably derived from ice-contact extra-marginal meltwater streams entering the basin.Regular variation observed between uniform silt-clay coupletsindicate that they were deposited annually between a short-termglacial melt season as quasi-continuous or slump-generateddensity underflows and settling of overflow-interflow suspensionmaterial during winter time (cf. Smith and Ashley, 1985; Ashley,1988). Upward thinning trend of laminae indicates a quasi-continuous retreat of the ice margin, which led to more distaldeposition within the basin. Varve counting shows that thermallystratified conditions existed in the glacial lake for at least 439 yearsin the Ala-Kuittijärvi basin and 300 years in the Keski-Kuittijärvibasin. In fact, the glacier-fed lake environment existed slightlylonger than calculated in Ala-Kuittijärvi, since the uppermost var-ves were too thin to identify.

In both lake sediment cores there is massive clay above thevarved clay unit (see Fig. 2). Massive clay in Ala-Kuittijärvi occurs insuccession where the upwards thinning varves pass gradually intomassive clay. This indicates that the basin was no longer in contactwith the glacier meltwater input. In Keski-Kuittijärvi, however, thevarved clay unit does not show a thinning trend towards the top ofthe varved clay sequence. Unlike in Ala-Kuittijärvi, massive clayrests with a sharp contact above the varved clays. This indicatesthat there could be a hiatus in the sequence between varvedsediments and massive clay.

Massive clays themselves represent settling of suspensionmaterial that might have originated from gravity flow caused byslumping of unstabilized sediments around the basin after degla-ciation (cf. Smith and Ashley, 1985), a water-level drop or glacioi-sostatic tilting that caused subsequent washing of finematerial intothe water column. These events might also explain the occurrence

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Fig. 5. AF demagnetisation of NRM in Tuoppajärvi, Ala-Kuittijärvi and Keski-Kuittijärvi undisturbed sections and their correlation to the Mustajärvi AF demagnetisation.MDF ¼ median destructive field. The stepwise AF demagnetisation of Ala-Kuittijärvi NRM is also presented in orthogonal Zijderveld projections and stereoplots.

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of both periphytic and epipelic diatom species found in varved claysand massive clays in Ala-Kuittijärvi, indicating redeposition. As willbe shown later, the massive clay units in Ala-Kuittijärvi and Keski-Kuittijärvi are not time-correlative and therefore the events that ledto massive clay deposition were separate.

Massive clay gyttja, gyttja clay and gyttja above massive clayunit represent normal Holocene large lake pelagic sedimentation(cf. Håkanson and Jansson, 1983). The sulphide laminae within thegyttja indicate oxygen-poor conditions in the pelagic environment(cf. Håkanson and Jansson, 1983).

5.1.2. TuoppajärviTuoppajärvi is located in the distal side of the Pääjärvi end

moraine (see Fig. 1). The diamicton found at the base of the corewas deposited by retreating ice most likely as basal till. Themassiveclay - gyttja clay unit above, with abundant sand grains and occa-sional sulphide laminae (see Figs. 2 and 3), was formed in a largelake during pelagic sedimentation (cf. Håkanson and Jansson,1983).

Multiple lamination sets and IRD material in Unit II (see Figs. 2and 3) represent waters deriving mainly from seasonally controlledsource. They certainly represent a glacier-fed “ice-contact lake”deposition by a summer single pulsating or intermittent densityunderflow events and the fine laminae were deposited fromwinteroverflow-interflow suspension (cf. Smith and Ashley, 1985; Eylesand Eyles, 1992). Massive gyttja clay, i.e. Unit III, representspelagic sedimentation including small seasonal sediment influxes.The 0.9 m thick massive fine silt (Unit IV, see Figs. 2 and 3) isthought to represent a slump deposit generated for example bydelta-front collapse in the Pääjärvi end moraine zone and/or thedrop of a water level in the basin. This type of density underflowevents forming slump deposits are commonly encountered in gla-ciolacustrine sequences (cf. Smith and Ashley, 1985; Ashley, 1988;Benn and Evans, 2003). The massive gyttja clay (Unit 5) and claygyttja (Unit 6) represent large lake pelagic sedimentation in thebasin.

The sedimentary sequence in Tuoppajärvi indicates a succes-sion in an ice-contact glaciolacustrine setting. Basal sedimentsshow typical proximal glaciolacustrine sedimentation with abun-dant sand grains representing ice rafted detritus (IRD). A drasticchange in the basin evolution took place when the rhythmite

Fig. 6. Chronological comparison of the earth’s magnetic field (NRM) secular variation from tmaster curve (Ojala and Saarinen, 2002), North Karelian stack (Haltia-Hovi et al., 2010) and

sedimentation stopped. It is suggested here that roughly at thattime the Pääjärvi end moraine, next to this basin, was formed.Subsequently ice retreated from the Pääjärvi end moraine zone tothe west and meltwater input into the basin ceased. This event ismarked by the deposition of massive gyttja clay (Unit III). Slumpdeposits (Unit IV) above are possibly related to a marked loweringof the water level in the basin due to glacioisostatic uplift and theopening of a new outflow route. After this event, normal large lakesedimentation started to operate, depositing units V and VI. Thescarce amount of diatom species found in Tuoppajärvi sedimentsare most likely redeposited (cf. Vos and Wolf, 1993; Saarnisto et al.,1995).

5.2. Age depth modelling of sediment sequences

Holocene sediment inclination and declination of NRM vari-ability in the lake sediments studied correlates relatively well withthe Nautajärvi Finnish master curve (Ojala and Saarinen, 2002), theNorth Karelian PSV stack (Haltia-Hovi et al., 2010), the MustalampiNRM record (Kosonen and Ojala, 2011) (Fig. 6) and also with resultsof other recent NRM studies in Fennoscandia (cf. Saarnisto andSaarinen, 2001; Snowball and Sandgren, 2002; Snowball et al.,2007).

NRM records extend to approximately 10,900 cal. BP in Ala-Kuittijärvi, 9800 cal. BP in Keski-Kuittijärvi and 9800 cal. BP inTuoppajärvi (Fig. 6). There are difficulties in interpreting thepalaeomagnetic signal in massive and laminated clay/silt units inthe sections studied (see Fig. 4). As pointed out e.g. by Saarinen(1994) and Bakhmutov et al. (2006), the palaeosignal measuredfrom clay minerals does not necessarily indicate the Earth’smagnetic field direction, since the signal may be disturbed e.g. bycurrent activity, compaction, bioturbation or post-depositionalreworking of sediments.

However, the Ala-Kuittijärvi sediment sequence is the mostcomplete, covering the longest time span of all cores studied here(Fig. 6). This interpretation is based on comparison of the Lake Ala-Kuittijärvi palaeomagnetic results with 1) the Lake Nautajärvi PSVmaster curve (declination feature j and inclination feature m), 2) theLake Mustalampi palaeomagnetic curve and the Mustalampi AMS14C date of 10,900 � 150, and 3) counting of 439 varves between4.95 and 3.36 m depth of the Lake Ala-Kuittijärvi core (Table 2).

he Ala-Kuittijärvi, Keski-Kuittijärvi and Tuoppajärvi profiles with the Nautajärvi FinnishMustalampi profile (Kosonen and Ojala, 2011) for the past 11,000 years.

Table 2The sediment sequences age depth correlation.

Varve age (cal. BP) Regional PSV features Depth in study lakes (m) 14C cal. BP age

Nautajärvi reference curve Relative declination Inclination Ala-Kuittijärvi Keski-Kuittijärvi Tuoppajärvi Mustalampi

1000 d 0.25 0.31900 d 0.4 0.44 0.452570 e 0.53 0.552600 e0 0.58 0.6 0.552800 f 0.63 0.644800 q 1 1.03 1.435300 i 1.15 1.08 1.655500 g0 1.2 1.156300 k 1.3 1.2 1.96750 h 1.45 1.257900e8400 l 1.7 1.4 2.558500e8900 i 1.9 1.479000 m 2.13 1.6 2.99500 j 2.3 1.659500 n 2.3 1.68

3.1 10, 900 cal. BP

N. Putkinen et al. / Quaternary Science Reviews 30 (2011) 3812e3822 3819

We conclude that the varve sedimentation in Ala-Kuittijärvistarted at around 11,350� 300 cal. BP, indicating that the basin nextto the proximal side of the Kalevala end moraine was ice-free atthat time. This age was obtained by adding 439 varves to the Ala-Kuittijärvi NMR record that extends to ca. 10,900 years cal. BP. Thisage contains uncertainties due to errors in the Nautajärvi PSVchronology (�2%) (Ojala and Saarinen, 2002) and inherent accuracyproblems with Mustalampi radiocarbon age (9500 yr BP � 50calibration as a result of radiocarbon plateau (Becker and Kramer,1991; Lotter et al., 1992).

6. Discussion

6.1. Age of the Kuittijärvi and Pääjärvi end moraines

Continuous end moraine belts around Fennoscandia, RussianKarelia and the Kola Peninsula were deposited during the YoungerDryas Stadial (cf. Andersen et al., 1995). The Younger Dryas age endmoraines are therefore very important landforms for the recon-struction of the deglaciation history of Fennoscandia and north-western Russia. However, the precise age of these moraines hasbeen difficult to define. The reason for this is that only the surfaceexposure dating and luminescence dating methods can be used todate the end moraine sediments proper, but both of these methodshave a poor resolution order of 500e700 years at best. There arealso several problems related to the use of the radiocarbon datingmethod in dating these end moraines. First, there is very seldom insitu datable material in or adjacent to the end moraines. However,the main difficulties of using the radiocarbonmethod for dating theYounger Dryas end moraines are the radiocarbon plateau, lack ofreliable calibration scale to calendar years through the YoungerDryas period and the difficulties of defining marine reservoir age(Mangerud, 2004). The most promising methods for the highresolution dating of the Younger Dryas moraines are obtained byusing a combination of different dating methods, such as palae-omagnetic dating, varve counts and radiocarbon dating (cf.Saarnisto and Saarinen, 2001), the methods applied in the presentinvestigation.

Glacial geomorphological features in Russian Karelia have beendescribed in numerous maps and papers during recent decades(cf. Kurimo, 1982; Punkari, 1985; Ekman and Iljin, 1991; Niemeläet al., 1993; Rainio et al., 1995; Kleman et al., 1997; Boultonet al., 2001; Putkinen and Lunkka, 2008; Pasanen et al., 2010).The most prominent end moraines in the western part of RussianKarelia are the Rukajärvi, Kalevala and Pääjärvi end moraines

(Fig. 1). These moraines form part of an end moraine belt thatextends around Fennoscandia, Russian Karelia and the KolaPeninsula (cf. Andersen et al., 1995). It is thought that the Kalevalaand Rukajärvi end moraines were laid down in front of the SISduring the Younger Dryas Stadial (ca. 12.8e11.5 ka), althoughgeochronological age determinations are lacking.

The NRM data and varve-counting results from the Ala-Kuitti-järvi and Keski-Kuittijärvi sequences suggest that the ice hadalready retreated from the Kuittijärvi basins by 11,350� 300 cal. BP,including the uncertainties due to the dating methods used(paleomagnetic dating, �2%, varve chronology � 1%, and 14C-dating). At that time a glacier-fed lake was formed. Since thewestern margin of Ala-Kuittijärvi is situated ca. 25 km inside theKalevala end moraine, the end moraine itself must be older than11,350 � 300 cal. BP. If it is considered that the ice retreat rate innorthwestern Russian Karelia was 350 � 50 m/year during degla-ciation, as suggested by Boulton et al. (2001) for example, then theminimum age for the formation of the Kalevala end moraine wouldbe 11,450 � 350 cal. BP. Therefore, the Kalevala end moraine wasdeposited slightly prior to 11,450 � 350 cal. BP, most probablyduring the latter part of the Younger Dryas Stadial.

Age determinations of the Salpausselkä I and II end moraines inFinland, adjacent to the Russian Karelian Kalevala and Pääjärvi endmoraines discussed here, indicate that the Salpausselkäs weredeposited during the Younger Dryas Stadial (cf. Tschudi et al.,2000; Saarnisto and Saarinen, 2001; Rinterknecht et al., 2004).According to Rinterknecht et al. (2004), Salpausselkä I was formedca. 12,500 � 700 cal. BP. Saarnisto and Saarinen (2001) dated thebeginning of the Salpausselkä I formation at 12,250 cal. BP andthey concluded that the Salpausselkä II was deposited prior to11,590 cal. BP.

According to the results presented here, the Kalevala endmoraine may have formed slightly later than the Salpausselkä IIend moraine (Fig. 1). This conclusion is also supported by thegeomorphological evidence, since the Kalevala end morainecontinues to the Pielisjärvi and Jaamankangas end moraines inFinnish northern Karelia, which are located north of the Sal-pausselkä II end moraine (cf. Andersen et al., 1995; Rainio et al.,1995).

The NRM data from Tuoppajärvi, situated immediately on thedistal side of the Pääjärvi end moraine, extends only to 9800 yearsago. As discussed above, high energy ice-contact glaciolacustrinesedimentation produced a sediment sequence unsuitable for thepreservation of a NRM signal. Therefore this age can only beregarded as a minimum age for the formation of the Pääjärvi end

N. Putkinen et al. / Quaternary Science Reviews 30 (2011) 3812e38223820

moraine. Based on radiocarbon AMS dates, Putkinen and Lunkka(2008) have already shown that the distal side of the Pääjärviend moraine had became ice free by ca. 10,800 cal. BP and theyconcluded that that the Pääjärvi endmorainewas formed at aroundca. 10,900 cal. BP.

Since the Pääjärvi end moraine is situated some 80 km west ofthe Kalevala end moraine, and was formed at the margin ofa different ice lobe than the Kalevala end moraine (Fig. 1), thePääjärvi end moraine must therefore have been deposited laterthan the Kalevala formation. The age estimate of 11,000 � 250 cal.BP presented here is close to the age of 10,900 cal. BP previouslyassumed by Putkinen and Lunkka (2008), if one assumes an iceretreat rate for Karelia of 350� 50 m/year over a distance of 80 km.

6.2. Palaeoenvironmental setting and deglaciation history

The lower part of the sediment sequence in Tuoppajärvi repre-sents deposition into a typical glacier-fed ice-contact lake (cf. Smithand Ashley, 1985; Eyles and Eyles, 1992). Features indicating theice-contact setting in Tuoppajärvi sediments include the frequentoccurrence of IRD material, multiple lamination and massive slumpdeposits. However, the Keski-Kuittijärvi and Ala-Kuittijärvi sequen-ces represent deposition in a classical glacially fed distal lake whereextra-marginal rivers carried meltwater and sediment into thethermally stratified basin. The sediments observed represent annu-ally deposited varves consisting of clay-silt couplets (cf. Sauramo,1923; Smith and Ashley, 1985). There is no IRD material in varvedclays and the couplet thickness decreases upwards. As discussedabove, massive clays in these sequences indicate water-level drop inthe basins (cf. Smith and Ashley, 1985). Holocene gyttja that occursabove the massive sediments represents large lake pelagic sedi-mentation. The calculated sedimentation rate for this material is

Fig. 7. Reconstruction of the main palaeoenvironmental events of the Kuittij

2e3 mm/year, which is comparable to that of boreal lakes in Finland(Pajunen, 2004).

Based on the data presented here, it can be concluded that tillbeneath the base of the lake sediment was deposited as subglacialtill at the time when ice was covering the study area. According tothe age estimates presented here, the ice retreated from theKalevala end moraine 11,450 � 350 cal. BP (Fig. 7a). As Pasanenet al. (2010) show, the SIS terminated in a glacial lake that occu-pied theWhite Sea Basin area. Subsequently the ice front retreatedfrom the Kalevala end moraine to the west of the Kuittijärvi basin(Fig. 7b). During the ice retreat glaciolacustrine conditions wereestablished in the Kuittijärvi basin separated from the White Seaby the Kalevala end moraine. Varved sediments were deposited inthis glaciolacustrine setting for ca. 450 years between11,350e10,900 cal. BP (Fig. 7b). During this time the Pääjärvi endmoraine was formed at or slightly prior to ca. 11,000 � 250 cal. BPas the ice front stagnated in that area and terminated into theWhite Sea ice lake (Fig. 7d). This event is represented by a massiveclay - gyttja clay unit with IRD material and couplets of multiplelamination structures in the Tuoppajärvi sediments. The Tuoppa-järvi basin must have been isolated from the White Sea relativelyshortly after 11,000 cal. BP as a consequence of rapid isostaticuplift following deglaciation (Fig. 7e).

Massive silts in the Kuittijärvi basin most probably indicate twoseparate events related to water-level drop/gravity flow events inthe basin. The massive clay unit in the Ala-Kuittijärvi sequence isrelated to a water-level fall in the basin at around 10,900 cal. BP.This water-level drop probably resulted from the drainage of theice-lake waters via the Jyskyjärvi threshold to the proto-VienanKemi River towards the east resulting from glacioisostatic tiltingof the Kuittijärvi basin (Fig. 7c). However, the origin of the massiveclay in the Keski-Kuittijärvi deposits, dated to ca. 9800 cal. BP, is not

ärvi and Tuoppajärvi basins during deglaciation. See text for discussion.

N. Putkinen et al. / Quaternary Science Reviews 30 (2011) 3812e3822 3821

known but was presumably caused by suspension sedimentationdue to gravity flow events. After these events normal Holocenelarge lake gyttja clay and clay gyttja was deposited in the basins. InTuoppajärvi, large lake gyttja clay deposition began at ca. 9800 cal.BP ago after a possible water-level fall indicated by a massive 0.9 mthick silt (Fig. 7f).

7. Conclusions

Based on the results presented here on the deglaciation chro-nology of the SIS in the Kalevala region, northwestern Russia, thefollowing conclusions can be reached:

Two prominent end moraines, the Kalevala and Pääjärvi endmoraines, in the western part of Russian Karelia, were depositedat the margin of the SIS at or slightly prior to 11,450 � 350 cal. BPand 11,000 � 250 cal. BP ago, respectively. These moraines arenot time-correlative to the Salpausselkä I and II moraines inFinland. The Kalevala end moraine is a time-correlative to thePielisjärvi moraine in Finnish Karelia and it is possibly alsoa time equivalent of the Salpausselkä III end moraine in south-western Finland.

After the ice retreat from the Kalevala end moraine, a glaciallyfed lake formed in the Kuittijärvi basin which was not connected tothe White Sea basin in the east. This lake received meltwater viaextra-marginal rivers between 11,350 to 10,900 cal. BP, after whichthe lake was connected to the White Sea via the proto Vienan KemiRiver.

In contrast to the Kuittijärvi basin, the Tuoppajärvi basin was anice-contact lake connected to the White Sea basin when the icemargin stood at the Pääjärvi end moraine at or slightly prior to11,000 cal. BP. A marked lowering of the water level in Tuoppajärvioccurred 9800 cal. BP agowhen a new outlet of the already isolatedlarge lake opened.

Large lake sedimentation of gyttja clay and clay gyttja began inthe Kuittijärvi basin at 10,900 cal. BP and in Tuoppajärvi at 9800 cal.BP. However, the latter age estimate is only a minimum age becauseof the presence of a hiatus in the sediment sequence.

The three cores drilled in these basins indicate that eventhough the sediment coring sites were carefully selected afterthe examination of echo-sounding profiles, only the Ala-Kuitti-järvi sequence has a continuous sediment record. Therefore, itseems to be the case that sedimentation in these relatively largelakes, with water depths exceeding 20 m, was affected by massmovements and water-level drops resulting from opening ofnew drainage routes, e.g. as a consequence of glacioisostatictilting.

Acknowledgements

This study was funded by the Jenny and Antti Wihuri Foun-dation (N.P.), and the University of Oulu Thule Institute PACE-project (J.P.L) and the Finnish Academy Project no 210909 (J.P.L.)We thank Prof Matti Saarnisto for fruitful discussions and initi-ating the coring campaign and assistance in the field and labo-ratory. We also thank Prof. Jussi Pekka Taavitsainen forassistance in the field and Seppo Putkinen for assistance in theecho soundings and coring expeditions. We would also like tothank Erna Mäkeläinen for diatom sample preparation, Dr.Tommi Kauppila for diatom analyses, and several people whoassisted us during the work. Dr. Phil Gibbard is thanked forfruitful discussion on the topic and checking the language. Wealso thank V. Rinterknecht and two anonymous reviewers forconstructive comments and suggestions to the earlier version ofthe manuscript.

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