The Scandinavian Ice Sheet Through the Last Interglacial/ Glacial Cycle

Reprint from: der letzten 130 000 Jahre' B. Frenzel (ed.) l99l: Klimageschichtliche Probleme (PaleoklimaforschungVolume l)' 451 pp. G. Fischer, Stuttg"tt] New York. The ScandinavianIce Sheetthrough the last interglacial/glacial cYcle

J,c,NMlNcE,nuo

Abstract later After theLast Interglacial(the Eemian) the ScandinavianIce Sheetstarted to grow slightly during than the ice sheetsin Antarctica and/or North America. A major ice sheetdeveloped stage5c (the isotopestage 5d (around I l0 000 beforepresent) but meltedaway during isotope (around 000 B'P') Brorup interstadial).Another ice sheetformed during isotopestage 5b 90 last ice sheet and disappearedduring stage5a (the Odderadeinterstadial). Apparently the areasof startedto grow aroundthe isotopestage 5/4 transition(75 000 B.P.) andthe central were ice- Scandinaviawere not deglaciateduntil around9000 B.P. However, the coastalareas Late free severaltimes between 75 000 and30 000 8.P., andthe final expansiontowards the Weichselianmaximum did not takeplace until after28 000 B'P'

Kurzfassungr

Das skandinavischeInlandeis begann etwas spdternach dem Ende des Letzten Interglazials (Eemian)anzuwachsen als das Eis in der Antarktisund/oder von Nordamerika'Eine groBere r8O-Isotopenstadiums Inlandeisdeckeentstand wdhrend des 5d [gegen 110 000 vor heute (v.h.)1, schmolzaber wdhrenddes Isotopenstadiums 5c (Brorup-Interstadial)wieder ab. Ein weiteresInlandeis bildete sich wihrend deslsotopenstadiums 5b (gegen90 000 v'h') und ver- schwanderneut im Isotopenstadium5a (Odderade-Interstadial).Das letzte Inlandeis begann of- fenbar,sich an der Grenzezwischen dem Isotopenstadium5 und 4 zu entwickeln(vor 75Ofi) Jahren).und das Zentrum Skandinaviensblieb bis etwa 9000 v. h. eisbedeckt.Demgegeniiber warenaberdieKiistengebietemehrfachzwischenT5000und30 000v.h.eisfrei,unddasletzte Anwachsendes Eiseszum maximalenStand wdhrend der JiingerenWeichselzeit erfolgte erst nach28 000 v.h.

Introduction

The most dramaticexpression of climaticchanges caused by the small perturbationso[ the Earth'sorbit (oftencalled Mrr-eNKovtrcH forcing) are the mid-latitude ice sheets(Bancen et al., 1984).Global ice volumes,as monitored by theocean oxygen isotope composition, have also been one of the most important parameters in the palaeoclimatic modelling on MrL,r,NxovrrcHwave lengths.However, to unravelthe historyof eachindividual ice sheet. even for the last interglacial/glacialcycle, is an extremelydifficult taskbecause the ice during

I Ubersetzung:B. FneNzPI- 308 . le,nMexcenuo

llrcllrst ttlaxitttuttt t'ctttttvctl ttttlst ol'llrc scdinrcntaryrcc.rd f'rr)rrroldcr cvcnts. l.htrs a rrr^j'r pr.- blemis simplyto find sedimentswithin theglaciated areas that survived the subsequent erosion. still' to reconstructthe historyof each ice sheetmust be attempted,at leastfor the last interglacial/glacialcycle, if we try to understand how theEarth's climatic system responds to or_ bitalforcing' The glacialhistory provides a fascinatingchallenge for scientistswho arewilling to searchfor an answerwhere no resultsare guaranteed. To constructthe history of an icesheet is like nrakinga threeor four dinrensionalpuzzle. Most pieces(sedimentary sequences) will fill in only a shortsegment of the time dimensionin the

24. j ,'1 60" I \ I t)I *'---/- /", ^r.,,",1",r",. "'it----

Fig. l: The Lateweichselianand YoungerDryas ice marginsof theScandinavian Ice Sheet.Localities and geographicalnamesused in the text are marked.srightry modified after ( r987). sveNosnN& MeNcnnuo The ScandinavianIce Sheetthrough the last interglacial/glacialcycle . 309

puzzle,just a point in the areal dimensions,and normally provide no information on the ice thicknessdimension (volume). In the puzzleI am constructingin this paper,most pieces are floating in this three/fourdimensional space without touchingeach other, leaving largeuncer- taintiesboth in time correlationsand in areal/volumeextent of the ice at differenttimes. Still the model representsa major improvementcompared to what we knew somefew yearsago. Paradoxicallymost of theimportant pieces are not glacial sediments, but non-glacial sediments indicatingwhen a site was ice-free. In this paperI reconstructthe Scandinavian Ice Sheetthrough the lastinterglacial/glacial cycle, basedon availablegeological observations. The information is still so sparsethat I only con- struct a simplified model with time as the one dimension, and linear ice-extent(instead of arealvolume)as the other (Fig. 5). I will emphasizewhen the proximal areaswere ice-free,and notdiscuss the timing of theLate Weichselian in theperipheral areas. I will alsodiscuss the Ear- ly Weichselian(isotope stage 5) more thoroughlythan the youngerpart of the cycle, andI have omittedthe deglaciationafter 20 000 beforepresent (B.P.). Unavoidably,discussion will in particular be concentratedupon siteswhich I know from my own field experience.

The stratigraphicframework

My opinionon the stratigraphyof NorthernEurope outside the Weichselianglaciation limits will first be presented,because this stratigraphyprovides the framework to which the more fragmentaryrecord within theglaciated areas has to becorrelated. I will alsocorrelate the Euro- pean stratigraphywith the deep seaoxygen isotopestratigraphy, partly becausethc latter representsa global framework, andpartly becausethe ages ofthe stageboundaries are relative- ly well established(MnnrtNsoN et al., 1987).In fact, sitesin WesternNorway whereamino acid age estimatesare available, can be more securelycorrelated with the deep sea isotope stratigraphythan to the Europeanstratigraphy, because no independentdatings exist fbr the Early Weichselianunits in Europe. The Eemian, with its stratotypealong the Eem River in the Netherlands(Zrcwl:N, l96l ), has for a centurybeen considered the Last Interglacialin the senseused in Northern Europe;an in- terglacialis definedby the occurrenceof mixed oak forestsin north-westernEurope, and nor- mallya transgressionalong the North Seacoasts, i.e. climatesand environments similar to pre- sentday conditions.However, Kuru (1971-),Bowe ru (197g), and won_r.nno (197g) qucs- tioned that the stratotypeEemian representsthe Last Interglacial. I considerthis problem as solvedby theamino acid correlation of Mrlr-pn & MnNcenuo (1986):The Eemianis indeed theLast Interglacialin Europe,and different sitescan in mostcases be correlatedunambiguous- ly by thecharacteristic pollen stratigraphy of theEemian. The correlationoI thc Ecmianwith thedeep sea oxygen isotope stage 5e, first proposedby SH.lcxleroN ( 1969),is now well estab_ lished(MnNcERUD et al., 1979;TunoN, l9g4). worrlnno's (1975, 1978,worr-r-,,',nn & Moox, l9g2) studyof the Grandepile in Northern France was a benchmark in European Quaternary stratigraphy, as this was the first site discoveredwith a continuouslacustrine sequence from theEemian up to thepresent. Above the 310 . JnN MlNcr,Rup

a 3

(o ChronostratigraPtrY aVl- -aYoJ- 618o (rtorrttalize(l) .l g dl uranqe ,g Es E | ruw Europe E 3* i a o F,ile I S "U': E I 0 U' d Eed = I 3

I Holocene t2 a.\ - 2 a f O) 24 Denekamp o) Hengelo 3 o o (n '= Glindefoo, a = Oerel I a 0--- { se ? (o G) 4 o - = - z4 o,) r-78s5a St.Gernrainll B Odderade -- -/ sb Meliseyll Rederstall tl 2- 93 3 ------{ up o l0O 3 5c St.GermainI o Bror J -v (_ 10s g 4--. 5d MeliseyI Herning o J'' =__ _ .___ _ =__- 5e Eemian 130 o <--- 6 "normalized" "orbitally Fig.2: The oxygenisotope curve from MenrtNsoN et al. (1987)with their tun- ed" timescale.To the left on the curve are indicatedsome of the eventsgiven by them. The traditional EurlrnNr-SHAcKLEToNlettering of theisotope stages, which I usein thispaper, is givenwith approximate agesof theboundaries as identified from thecurve. The chronostratigraphyof theGrande Pile core is from Wollr-eRn (1978, only older units included). For north-westernEurope, the subdivision of the Weichselianinto Lower, Middle andUpper follows Mencenun etal. (1974),except that the middle/upper boundaryis movedto around25 000 yr. (MnNcERUD& BnncluNo, 1978,CHnuNe et al., 1980). The identificationand naming of theinterstadials/stadials (chronozones) follows MeNxe & TvNNt (1984) and/orBEHne & Lnnr (1986).I alsofollow MENru (1982),and MpNxE & TvNNI (1984)including the Amersfoortas the lower part of the bipartiteBrorup. The curve of environmentalchanges in Germany. The Netherlandsreflects mainly the summertemperature, and is basedon ZlcwllN ( 1975),MeNre & TyNNr (1984) and Besnn & LnoE (1986). Generallythe warmer interstadialscan be more precisely characterizedthan the cold tree-lessperiods, and I havetherefore mainly markedthe warm peaks.Note that the time scale for the older half of the curve is basedon the correlation to the isotopecurve, argued for in the text.

Eemian in Grande Pile are two warm periods that Wotr.l.ARD identified as true interglacials (St. Germain I and II) and she concluded that they stratigraphically should be placed between the Eemian and the Early Weichselian interstadials Brsrup and Odderade of Northern Europe (ANoensrN, 1961;ZAGWTJN, l96l; Avrnotecr, 1967:see review in MpNrc & TvNttt, 1984). The main reason why WoTILARD maintained St. Germain I and II not to correlate with the interstadials of Northern Europe, is that St. Germain I and II palynologically show a development to a full interglacial type of mixed oak (climax) forest suggesting that this vegetation could not The ScandinavianIce Sheetthrough the last interglacial/glacialcycle . 3l I exist contemporaneouslywith the coniferous(taiga type) forestsof the Brorup and OdiJerade in Northern Europe. WollleRo's correlationshave beenchallenged by severalauthors (e.g. Gnucnn; 1979a, b; MeNcsnuo et al.,1979; wrLreN, l98l; MrNru, 1982 MeNrB & TvNNr, 1984;Brsnr & LlDe , 1986),whoallacceptedheridentificationoftheEemian, butsuggestedthatSt. Germain I and II shouldindeed be correlatedwith the Brorup and Odderadeinterstadials, respectively (Fig. 2). The main argumentfor thiscorrelation is thesimilar stratigraphicalposition: In a large "warm-climate number of lacustrinebasins in Northern Germanythe first units" abovethe Eemianare the Brorup and the Odderade(MrnrE & TyNNl, 1984;Brsnn & Leoe, 1986).It is completelyimprobable that any warm interstadialor interglacialshould be missingbetween the Eemian and the Brsrup in so many closedbasins. Similarily St. Germain I and II were the first warm periodsafter the Eemianin GrandePile (WoTLLARD,1978), and this is confirmed in anotherbasin in France(on BnluI-tru & RuLrr, 1984).The correlationof the Brorup and Odderadewith St. GermainI andII, respectively,is supportedby theamplitude of environmen- tal/climaticchange: In bothareas these were thetwo warmestperiods after the Eemian, and in- deedthe only interstadialsthat werereally forested.Grande Pile is situatedmuch further to the souththan the interstadiallocalities mentionedin the Netherlandsand Germany, and therefore the GrandePile areaduring warm interstadialshad a forest similar to the interglacial forestsfar- ther north in Europe.The correlationof St. GermainI andII with Brsrup andOdderade implies somesteeper ecological/climatical north-south gradients in middle Europethan today, which I do not find difficult to accept. Wott-lnno (1978)and WoIILARD & Moox (1982)suggested that St. GermainI andII should be correlatedwith the deepsea oxygen isotopestages 5c and 5a, respectively,accepting that 5e correlatesto the Eemian.The correlationof St. GermainI with stage5c is also supported by pollen analysisof a marinecore with an isotopecurve (TuRoN, 1984).I find thesecorrela- tionsprobable, and thus that the Brorup andOdderade should correlate to isotopestages 5c and 5a, respectively.To some extent this correlationis a matchingof curves (Fig. 2): Both, in Europeand the deep sea, these are the first warm peaksabove the Eemian/Se,and in both cases they are the highestpeaks between the Eemianand the Holocene.The causativearguments are the following: On the wavelengthand amplitudeof changewe considerhere, the environmen- tal/climatical curve for Northern Europe (Fig. 2) has to be roughly parallel to the volume changeof the Scandinavianlce Sheet.A similar argumentcan be usedfor the major ice sheets on either sideof the North Atlantic. The discussedparallelisms are both demonstratedfor the last glacial maximum and deglaciation.Thus on this wavelengthand amplitudethe climatic curve for Northern Europe shouldapproximate a Northern Hemisphereglaciation curve, as doesthe isotopecurve. The only argumentI can seeagainst the proposedcorrelation, is that it predicts marine transgressionsin the North Sea area during the Brsrup and Odderade, becausethe eustaticsea levels during stages5a and 5c were not much lower than during 5e (Cuenrell & SHecKLEToN,1986; SnecxlrroN, 1987),but suchtransgressions are not identified. 312 ' JrN MnNcenuo

When did ice start to accumulatein Scandinaviaafter the peak of isotope stage5e?

For the Fjosanger site in Western Norway the amino acid analysesgiven by Mlr-lrn & Me,Ncnnuo(1986) have neither provided unambiguous results as to whetherit representsthe Eemian, nor an older interglacial.However, further analysesof the amino acids and other arguments(Sernur,1987),includingunpublishedTLdates(MnronHI-&MnNceRuo),strong- ly suggeststhat the Fjosangerianindeed is the Eemian,as originally suggestedby MeNcnRun et al. (1979, 1981), and this is acceptedhere without further discussion. At Fjosangersea level dropped eustatically some l0 to 25 m whenmixed oak forests,succeeded by spruceforests, surroundedthe site, both forest types indicatinga climate that excluded growth of any ice sheetin Scandinavia(MINGERUD et al.,1979,1981). This impliesthat the first part of the sea-leveldrop after the peakof 5e was due to ice accumulationoutside Scan- dinavia, probably in North America and/or Antarctica. For the NetherlandsZncwuN (1983)has constructed a much more accuratecurve, showinga drop of sea-levelof at least 32m at the Eemian/Weichselianboundary. ZncwllN's curve (Fig.3) showsthat around20 m of the drop occurredwithin the Eemian.However, during the latest part of the Eemian there were pine (Pinus) forests in the Netherlands,and this may be compatiblewith growth of ice in the Scandinavianmountains. I concludethat sea level dropped eustaticallybetween l0 and 20 m before any significantice-growth occurred in Scandinavia. However, the total drop in eustaticsea level from peak5e to the trough 5d was nearly 70 m

5m -Amersloorl l0m / / a 15m ,jSchornqanlum \- Pett"n

-Amersloorl _-lx-- 2Om 'p I Comperdurn I 25m \ \ i0m I

35n lAmslerdom

l0n Norlh Seo I I tSm -lvorlh Seo

0cPlh 1 2 3o 3u to 4u 5o 5u 6o 6u Delov Lote EorlY ,'escnl Weichselion Soolion (El Scol3|r0l ILSI Eemron (EWIol

Fig. 3: A sealevel curve(high tide levels)forthe Eemianin The Netherlands,reproduced from ZecwtrN (r983). The ScandinavianIce Sheetthrough the last interglacial/glacialcycle . 313

(CHnneet,l-& SnecKLEroN,1986), so the time-lag in inceptionof the ScandinavianIce Sheet comparedto otherswas probablynot large.As discussedbelow, certainlya major ice sheet developedduring 5d.

The Weichselian glaciation(s) west of the Scandinavian mountains

The mountainsin Scandinaviaare like a major asymmetricalbackbone running from southto north. The westernside is steep,with deepfiords, and receiveslarge amounts of precipitation with thewesterly winds. The eastern side is gentle,and is in therain shadow. Further to theeast thereare largeplains (Finland, Estonia,etc.), andthe broad depressionof the Baltic Sea.The Scandinavianmountains are actually not very high, the highestsummit today being 2469 m a.s.l., but theyare situatedat a high latitude,from 58o to more than7l oN. From thedescribed topographyone might expectthat the glacial developmentwas different on each side of the mountainchain, so I will first discussthe west side, and subsequentlythe eastside. Earlierversions of theglaciation curve for thewest side are given in MnNcsnuo ( l98l , 1983), wherean extensivereview of earlierliterature is alsoprovided. In the following I will concen- trate on sitesthat give key informationsfor dating the glacial advances.

Fjosanger Bo, Karmoy m Skjonghelleren,Sunnmore lo

Block B = Holocene Diam.G = Alesund intersl Haugesund Diamiclon E 10 GravelF=Fana Block K interst Bo Sand

-_Silly gravel H Karmoy 5 Diamicton josangerian F - (=Eemian) TorvastadSand Avaldsnes Block M Paradis Till Sand (Eemian) "r""oYrXho,, 0 . "r"yo3ha; "o**r,

-t^ -a Fig. 4: Simplified lithostratigraphyfor some sites in western Norway. Fjosanger modified from MnNcenuo et al. (1981).Bo, Karmoy modifiedfrom ANoERSENet al. (1983);in this figurethe names for the lithostratigraphicalunits are usedalso for stadials(Haugesund and Karmoy), interstadials(Bo and Torvastad),and the Avaldsnesinterglacial. Skjonghelleren cave, modified from LnRsENet al. (1987); note that block/diamicton beds in this casewere depositedduring ice free periods, the clay bedsduring glaciations. 314 ' JnN M,rNcenuo

Fjosanger

Above the Eemian beds at Fjosanger is a thick glaciomarine silt (G on Fig. a) which demonstratesthat glaciers at that time were calving somefew km from the site(MnrucrnuD et al., 1981).All observations(lithostratigraphy, pollen, foraminifers, amino acids) suggest that thereis no major unconformitybetween the Eemianbeds and the glaciomarinesilt: thusthis

6 o a c) o

I o 6 o 0) o I Coast Mounl ain ; c Mounl ains Denmark Finland o E east U) F wesl/nor th

YoungerDryas

^:--rl.- !, i '..4 UdrslUV

o 6 N Swcdert O. Dosebacka r Torvastad*

tt-

o; f,

Fana Fornes o Perepoh iola o E o I Tepsankumpuand Hovden t2 Avatdsnes@ olher Finnishsiles @Fiosangerian Leveiniemi

@ Faunasuggesting climale as today,ot warmer. * Faunawith Allanlic Curent'guide lossils.' Fig 5: Schematicglaciation curves for the last interglacial/glacialcycle in Fennoscandia.The left curve is for the west sideof the mountains,the right curve for the eastside in the mountain-proximalareas (N. Swedenand Finland) andtowards south(Denmark) in the distal parts.The horizontal scalesare somewhat "projected" arbitrarybecause sites scattered over a hugearea are into a theoreticallinear cross-section. Ages for isotopestage boundaries from MnnrrNsoN et al. (1987), comparewith Fig. 2. The ScandinavianIce Sheerthrough the last interglacial/glacialcycle 3 I 5

glaciationis undoubtcdlyof isotopcstage -5d or Hcrningstadial age (Fig. 5). It (lcmonstrarcs that in this areathe glacierswere nearlyas largeduring 5d as they wereduring the younger Dryas. Ifthe correlationis correct,there must have been a considerableglacio-isostatic depres- sion to keep the site below sealevel, as eustaticsea level droppednearly 70 m from the peak 5e to thetrough 5d (Cuernrll & SHecrl-EroN,1986). Thus the Scandinavian Ice Sheetmust have beencorrespondingly large. Above the glaciomarinesilt is a gravel depositedduring a milder period, the Fana interstadial (Fig. a). Amino acid analysisstrongly suggeststhat the Fanashould be correlatedwith isotope stage5c (Mrllrn et al., 1983;Selnup, 1987),and thusthe Brorup (Fig. 5). originally we (Mance nun etal. , 1981)suggested that Fana is older than Brorup, because the fauna suggested colderclimate than we expectedfor theBrorup. If we now acceptthe age, the unexpected cool fauna can be explainedin two ways: l) The warmestpart of the interstadialis missing.2) The differencein summertemperature between the presentand the Brorup was larger in Western Norway than further eastin Europe.This latteris supportedby temperaturegradients deduced from pollen sequencesin Europe, and I assumeit is at leasta part of the explanation. Three observationshave led us to concludethat there is no unconformitybetween silt E and the Bsnes (Fig. Till a)' andthus that the Bsnes Till is of isotopestage 5b or Rederstallstadial ase (Fig.5): l) Inthreeoutoffourexcavationsthetillconformablyoverliesthe0.5mthicksiltE. Itwould be most surprisingif glacialerosion had stoppedat severaldifferent placesjust at this stratigraphicalleve.. 2) Upglacier, in the deeperpart of the fiord, the glacier erodedmarine sedimentsthat it overrode, and thereforethe till is full of transportedfossils. These fossils may all be correlated with the Eemianand Early Weichselianbeds at Fjosanger;there are no hints of younger fossils. 3) A large number of amino acid analysesof shell fragmentsin the till gave only ratios cor- respondingto the bedsat Fjosanger,suggesting that the glacier did not erodeany younger beds.

Godoya

At Godoya,Sunnmsre (Fig. l), LnNovlx & Mencenun (1985)described a sandurthat they, andalso LANnvtx & Hn Msonc( 1987),interpreted to beof MiddleWeichselian age. However, severalthermoluminescence dates now suggestit is of isotopestage 5d age (JuNcNenet al., 1989). I will not discussthe reliabilityof thesedates here, just statethat if they arecorrect the ice reachedmuch further west during stage5d than during the Younger Dryas in this area.

Karmoy

Excavations in the Bo claypitat Karmoy (Fig. l) reachedbeds (the Avaldsnes Sand, Fig. 4) wherepollen-, mollusc-,foraminifera-, and amino acid stratigraphy all suggestan Eemianage (ANoenstlNetal., 1983;Sclnup,t987). Directlyontopof thcintcrglacial bcclslicsthcTgr- 316 .leNMANcERUD vastad(interstadial) Sand, where the marine fossils suggest conditions comparable to thenorth- ernmosttip of Norwaytoday (SEJRUT, 1987). The pollenassemblage indicates an open vegetation with somebirch, but it is difficult to interpretit becauseof the largeamount of redeposited pollenin thesemarine sediments (ANoanseN et al., 1983).Amino acidracemization suggests anage of theTorvastad interstadial of 78000 + 7000B. P. (Mlr-lrn etal., 1983),and thus a correlationwith theisotope stage 5a and the Odderade interstadial in Europe(Fig. 5). Thissuggests a major hiatusbetween the Avaldsnesand the TorvastadSands. Abovethe Torvastad interstadial is a basaltill (theKarmoy Diamicton, Fig. a) showingthat rhe site was overridden by a glacier reaching the open sea. Between this till and the Late Weichseliantill (the HaugesundDiamicton) is the Bs Sand, demonstratinganother ice-free (Bo) interstadial.Several radiocarbon dates gave finite ages around 40 000B.P. (ANornsENet al., 1983)for thisinterstadial, an agesupported by aminoacid analyses of molluscs,whereas amino acidson foraminiferasuggested an agearound 60 000 B. P. (Mrr-len et al., 1983).Even thoughneither the agenor the durationcan be fixed exactly,the sitedemonstrates a Middle Weichselianinterstadial, certainly predating c. 40 000B.P., with seasurface temperatures like in northernmostNorway today(Sr-rnup, 1987). From the ages given above for the Torvastadand Bs interstadials,the glacial advance demonstratedby the Karmoy Diamicton can most reasonablybe correlatedwith isotopestage a (Fig. 5), eventhough this is a correlationwith weekconstraints.

Karst caves,Nordland

Speleothemsin karstcaves can only beprecipitated when the cave is notcovered by anice sheet, becausebeneath the ice the cave would be filledwith water,or alternativelyit wouldbe frozen. LeuRlrzrN (1984,1986, oral communications1988) has performed uranium series dating of morethan 90 speleothemsfrom cavesalong the valleys and in themountains west of thewater- shedin Nordland(Fig. l). The distributionof thedates shows major peaks around the ages of isotopestages I (the Holocene)and 5e (the Eemian),but alsoenough dates from the restof isotopestage 5 to demonstratethat these mountains were also ice-free after 5e, probablyduring both 5a and 5c. In factLeururznn hasdiscovered three speleothems which he assumes grew continuously from around130000 to 95000 B.P.. If correct,this will contradictthe extensiveglaciation I have concludedfor isotopestage 5d (Fig. 5). Alternativelyone could postulatcdiffcrent glacial historiesfor the different areas.To someextent that is certainly right, but that can not explain the referred contradiction.

Skjonghelleren, Sunnmere

Skjonghellerenis a 100m long wave-cutcave with a uniqueon-off signalof glaciations (LnnsENet al., 1987):When it wasoverridden by glaciersan ice-dammedlake was formed, and laminatedclay deposited(beds L, J-I, andF, Fig. 4); whenit was ice-freestones fell from the roof, and animalslived in the cave. The ScandinavianIce Sheetthrough rhe last interglacial/glacialcycle 3 | 7

The last ice-freeperiod (the Alesundinterstadial, letter G on Figs. 4 and 5) is well datedto around 30000 B.P. by radiocarbondates on bonesand U-seriesdates on speleothems.The fossilsshow marine conditionsso warm that a branchof the North Atlantic current must have enteredthe Norwegian Sea at that time. The clay F from the last glacial overriding has a characteristicpalaeomagnetic signature correlated with the Lake Mungo excursion,dated to around28 000 B.P. (LensENet al., 1987;LsvrtE & SaNoNes,1987). Below the Alesund interstadialis a sequenceshowing two more glaciationsand two ice-free periods.These are not as well datedas the last cycle, but palaeomagneticcorrelations suggest thatthe lastof theseglaciations (letters I andJ, Fig. 4) occurredbetween 36 000 and42 000 B.P. ago.

The extent of the Late Weichselian maximum

I shallnot discussthis topic here,just mentionsome recent results. On the basisof extensive field studiesRvs et al. (1987)and Nrstr et al. (1987)concluded that summitsin Sunnmsre (Fig. l) and areassouth and east of Sunnmsre,in WesternNorway remainedice-free nunataks throughoutthe Late Weichselian,a topic discussedfor a century. This provides strong con- straintson thethickness of theice. Srrnup et al. ( 1987)demonstrated that the Scandinavianand the British ice sheetsprobably did not meetin the North Sea.VoRneN et al. (1988)showed that Andoya(Fig. l) wasice-free around 20 000 B.P., andafter a shortglacial overrun during the Late Weichselianmaximum, finally deglaciatedaround l8 500 B.P.

Discussionand conclusionsfor the westernflank of the ice sheet

A coupleof decadesago, the view wasthat most of Scandinaviawas continuously glaciated during theentire last ice age.This view is now completelychanged, but a logicalapproach is still to assumethat it was ice-coveredduring all thoseperiods where we cannotdemonstrate ice-free conditions.One reasonfor this approachis that the ageand durationof ice-freeperiods can be shown by fossil-bearingsediments, whereas basal tills cannotbe dated.An exceptionfor this is the Skjonghellerencave discussedabove, and hopefully other similar caves,where glacial periods are recordedby laminatedclays which in fortunatestratigraphic positions might be datedby palaeomagneticcorrelations. The approachdescribed here leadsto a history with a minimumnumber of events.New localitiesprobably will showa largernumber of glacialad- vancesand ice-free periods than shown on Fig. 5. If duringsome periods there was a high fre- quencyforcing of climate,as e.g. suggestedby DlNscr,r.no (1987)for partsof the Middle Weichselian,the Younger Dryas may providean exampleof theglacial response: In Western Norway therewas during the Younger Dryas a major re-advanceof the ice sheetthat lastedfor somefew hundredsof yearsonly (Mnncrnun, 1987). The glaciationcurve (Fig. 5) is a conceptualcurve that ideallyshould show glacial advances and retreatsfrom themountains in theeast to thecoast in thewest. However, the sitesare spread out alongthe coastfrom north to south,and the configurationof the ice-front wascertainly dif- 318 ' leN MeNcenuo ferent at different times. Here I have followed the same approachas I have done earlier (MlNcrnuo, l98l); the coastalsites (Fjosanger, Karmoy, Sunnmore)are plottedrelative to their distanceto the Younger Dryas end moraines. However, the main pattern of the curve would not changewith a different way of plotting. I will point out that both the Karmoy and Sunnmsresites are closeto the opensea, so when the glacieroverrode the sitesit locally ended in the openocean. The curve is drawn after different rulesbefore and after 50 000 B. P. For the older part I have simply placedthe advancesand retreatsat thetime of the isotopestage boundaries , eventhough thatcorrelation is strictly demonstratedonly for the5el5d boundary. For theyounger part I have followedthe datings. I considerthe main patternthrough the isotopestages 5e-5d-5c asestablished, because we could demonstratethat the first glaciationat Fjosangerfollowed soonafter the Eemian. The nearlycomplete deglaciation of Scandinaviaduring the Brorup (5c) is documentedby several sitesdiscussed in the nextchapter, and the Fsrnessite (VonntN & Ronloser, 1977)located in thewestern mountains. Therefore, the glacial/deglacial cycle of stages5d/5c is demonstrated evenif theFana interstadial should be olderthan the Brorup, as assumed in theearlier version of thecurve(MnNcenuo,198 l). However,theconsequencefortheisotopestage5bglaciation mightbe moreimportant; if theFana is olderthan stage 5c, theBsnes tilt shouldalso be older, and no recordof a 5b glaciationis known. A basaltill betweenthe Torvastad and Bs interstadialsdemonstrate unambiguously that there wasat leastone glaciationin thattime interval.I haveplotted that glaciation to isotopestage 4, basedon aminoacid ratios, but theprecision of theseage assignments are too poorto really demonstratethat this was a stage4 glaciation.Also thecorrelation of clay L in Skjonghelleren "counting to thediscussed glaciation (Fig. 5), is mainly by from the top". I havedrawn a more extensivedeglaciation for isotopestages 5c and 5a than for the younger interstadials,because for the two former a deglaciationof CentralScandinavia is demonstrated (see below). Inland sites with reliable finite radiocarbondates are not demonstratedyet. However,the fauna in bothBs andAlesund interstadials suggests warmer conditions than the faunain Fana, andas warm a climateas in Torvastad.In both Bs and Alesundthe faunascom- paretotheAllerodfauna(MANGERUD,1977),forwhichweassumethatabranchoftheAtlantic Currententered the Norwegian Sea. During Allersd there was still a considerableice sheet over Scandinavia,even though it certainlywould have shrunk much more in theeasterly areas if the mild climatehad lasted longer. ANnrnsrN et al. (1981)inferred a short-lived,large glaciation close to 40000 B.P. at Jeren. A glaciationof thatage is also postulated from Skjonghelleren(LansrN et al., 1987).However, in neithercase is theglaciation reliably dated. The timingof the lastadvance is betterknown: The glacier front passedSkjonghelleren close to 29000 B.P. on its way towardsthe Late Weichselianmaximum position at theedge of thecontinental shelf. The Scandinavian lce Sheetthrough the last interglaciar/glaciarcycre 3 l9 The Weichselian glaciations in the central areasand on the east side of the Scandinavian mountains

A glaciationcurve for the eastside is developedby LuNoqursr (1974, l9gl, 19g3, 19g6), LrrunNrn(1984), LtNotlsn et al. (1984),and Manr.ran(1969,lggl). The main modifications I havemade to LuNnQutsr's curveis to stretchthe time scalefor theolder part by correlating the Brorup and odderade to isotopestages 5c and 5a, respectively,and to accepttwo Early weichselianice-free periods. Similar interpretationsof the time scaleand correlationshave earlierbeen presented by Fonssrnou (1984), but he usedthe oxygen isotope curve more direct- ly as a glaciationcurve for Scandinavia. In Northern Germany the Brorup and Odderadeinterstadials were the last forestedperiods before the Late weichselian glacial maximum (MrNxe & TvNNr, l9g4; BEHnE& Lnoe, 1986),and therefore I considerthese interstadials as also the last periodsthat forestspossibly could have existed in Fennoscandia.Accepting the correlation to the deep sea-isotope stratigraphy,this means thatforested sires have a minimumage of 75 000 B.p. (Fig. 2). Boih finite and infinite radiocarbon dateshave been obtained for suchsites. with the assumptionsI have madehere, apparent radiocarbonages (finite or infinite) cannotbe usedfor correlations of siteswhere the existenceof forestsis demonstrated.

The stratigraphy of Northern Finland

NorthernFinland (Laplandand periipohjola regions,Fig. r) is for two reasonsa key area (reviews in Hrnveset al., lggl andHrnvns & NENoNEN,l9g7); l) More interglacialand interstadial sites(more than 100, Hrnvns & NrNoNsN, l9g7) are known from this areathan from any other areawithin the bordersofthe ScandinavianIce Sheet. 2) The areais a lowland plain, so that till bedscan be mappedover large areas. Interglacialsare defined by a pollen-florasimilar to, or in factslightly more warrn-clernanding thanthe Holocene, e.g. with pin pjc us,Betura, and some ea, andArnus(Hlnvas & KurlNsuu, 198I ) ' An interglacialage on thatbasis is unquestionable,and most of thesrtes are assumed to be Eemian(Hlnvns, 1983).

--I-1 tl - l*l t*b"d\\-'-H -i"lJPontottf'...... ''...] - - - riilbedil Fig..6: Sketch showing the principle l\l for constructing the _tl stratigraphyin Finland: Till beds, especiallythe direction of ice-flow that depositedthem, areused for lateralcorrelations; Eemian organic(and other non-glacial)beds are usedlor ..clatinc... 320 leNMexcrnuo

Ahovethc youngcstintcrglacial hcds f

. CENTRAL CHRONO LAPL AND €g hrrvo3 STRAT I GRAPHY el ot 1977

LATE ANO MIDDLE -/SANO<.. aNO WEIC HSE LIAN \--_!RAvEL rtrr ard---_

PERA POHJO LA INTERSTAOIAL INTERSTADIALPEAT GYTIJA, SILT,E TC I JAMTLAND. 8R9RUP )

EARLY WEICHSELIAN t LA5T IN IE RGL AC IAL €EH INTERGL AC I A L PEA] 6YT]JA INIERGLACIAI ETC GYT TJA {EEM,LEVEA NIEMI,MIKULINO)

rILL 8ED L OWESI tr I ILL A€O SAALIAN

SILT SAND l_'-

rILL8EO

{::^J'"0 i r { L ht ;r(l I Fig' 7: Correlation of the stratigraphy of Northern Finland. Note that the given sequencefbr eacharea is a synthesisof many sites; two organicbeds do not occur aboveeach other at any singlelocality. Repro- ducedfrom Hrnvrs & NeNoNrN (l997). The ScandinavianIce Sheetthrough the last interglacial/glacialcycle . 32 I mappedby SurrNeNrepresent the limit of thepre_perripohjola glaciation (: glaciation). isotopestage 5d At many sitesorganic and other non-glacial sedimentsare foundon tills identified III. as till bed The pollenflora in thesesediments is always dominatedby Beturaandherbs (Fig. 7), sug_ gestinga birch forest,and thus cooler conditions thanduring the Holocene. All these referred sitesare to the Perdpohjolainterstadial, first defined by Ko-nrer-a (1969). and generallycor- relatedwith theBrorup (HInvns et al. 1981). ' As discussedabove, the only alternativeperiod within the weichselianthat could allow a birch forestto thrive thereis the odderade. Theconclusion by Htnvnset al. (1981),Hlnves & NrNoNrN(19g7), and many earlier authors citedby them' is thatduring the weichselian therewere in NorthernFinland two glaciations, separated by one single ice-freeperiod, the Periipohjola interstadial,correlated with rhc Brorup' Thestrength of thismodel is that it apparentlyexplains all observations.I will especial- ly point out that if sites from two differeni ice-free periods were grouped together Periipohjola in the interstadial,this shouldhave led to differenttill fabricsLelowand/or above the bedsfrom the differentinterstadiats (Fig. 6), and suchsites are not found. I will briefly mentionthe interesting siteof oulainen(Fig. l) furthersouth in pinu.s Finland.which has up to90% poilen.Fonssrnou (19g2, 19g4,l9g5) assumedan inrerglaciaragc, whereasDoNNen (19g3),HvvAnrNEN (19g5),and Fonssrnauet ar.(19g7) Periipohjola assumeda (Brorup)interstadial age, Iater supported by manyTL dates(JuNcNe n, l9g7). If the latterconclusion is correct,it would mean thatthe northernboundary of pine forestswas bctwcenoulainen and{hc classical Pcrripohjolasitcs. This is surprisinglyI'ar to northc.nrparcd thevegetation in middleand Northern Euiope (MENrr & TyNNl, | 9g4),and wourd require a lowertemperature gradient between Germany andFinland during the Brorup than at present. if theclimatic pattern was similar. However,during the Brarup there possibly tinental wasa morecon- climatewith steepersummer temperature gradients towardsthe coolerwest coast. If oulainen is of Brorup age' someother sites earlier assumedto be Brorup probably represent other ice-freeperiods, e.g. the Odderade.

The central area of Sweden and Norway Many siteswith sub-tillsediments, most of them withonry minerogenic sediments, are kn.wn from areasclose to the watershed of the Scandinavianmountai; (e.g. LuNoqulsr, BencrnseN r967, & GnnNes,198 l). when thesesites were ice-free,nearly all glacierice in Scan- dinaviamust have been gone. A recentreview is givenby LuNnqursr (19g6),who assumed thatall sitesare from one single ice-freeperiod, the Brorup interstadial(fbr which he assumed a much lower agethan in this paper). Two key sitesare Brumunddar(Helle et al., pirgrimstad lggr) and (LuNogursr, 1967), becausethey containorganic sediments that offered tne posiiuitity of constructing diagrams' pollen At Brumunddal(Helu et al., l98l) the lithostratigraphy(till/pear/riil) and the pollen stratigraphyshow a full environmentalor climatic cycle: Glaciation/tundra/birch forest/tundra/glaciation, where the ice-free period did not ,each the temperatureof an in- 322 ' lxr'tM,rxcenuo terglacial.The frequentoccurence of lnrix and alsothe occurenceof Picea, within the Betula forestsuggests a correlationto the Brorup, eventhough both treesalso occurred during theOd- deradein Northern Europe.The underlyingtill suggestsa glaciationbetween the preceding interglacialand the Brumunddal interstadial. The pollendiagram from Pilgrimstad(LuNnqursr, 1967)is very similar to the one from Brumunddal,except that lnrix is missing,and probably correlatesto the sameinterstadial.

Evidences of more than one Lower weichselian ice-free interstadial

As discussedabove, the stratigraphyin Northern Finland indicatesthat there was only one Lower Weichselianice-free interstadial, the Periipohjola.Lulroeursr (1986) also concluded thatthere was only one ice-freeinterstadial in the centralareas of Swedenand Norwav. which

oor$ 9:>;i - 6 ,*,t*:EsF-f; r c5!c ;EffiTtr3si5 5,"3g5E Upper lill

Till witi or9anic mallar

--.ot- Alnus

+ Pinus ----*- picea Fig' 8: Pollen diagram from Permantokoski,Perdpohjola, the type areafor the periipohjolainterstadial. Reproduced from Konpell (1969); the original Germanrext is translated.Note ttuiin tf,. total diagram the amount of herb pollen (NAP) is given relative to 100 tree pollen (AP), so that throughout the peal bed Betula Sirch) pollen constitutes more than 70 to j5% of the total amount of pollen. The ScandinavianIce Sheetthrough the last interglacial/glacialcycle . 323 he correlatedwith the Periipohjolaand the Brorup. However, in NorthernGermany the Brorup wasonly slightly wanner thanthe Odderade(MeNxr & TyNNr, 1984;Brnnr & Lene. 1986). Furthermore, if the correlation in Fig. 2 is correct, the duration of the Odderade(isotope stage 5a) andthe Brorup (5c) shouldbe similar, andindeed approximately as long asthe Eemian(5e) and the Holocene(stage 1), all periods having a duration between l0 000 and 13 000 years. Theseconsiderations lead me to examineif thereis evidenceof more than one ice-freeperiod in central areascovered by the ScandinavianIce Sheet. First I will simply statethat a reliablemutual correlationof the many individual sitescorrelated ''Brorup" with the Jiimtland,Gudbrandsdalen, Brumunddalen and other interstadialsin Swe- denand Norway is impossible.Theoretically, different sitesmay stemfrom many different interstadials,and evendifferent glacials(MeNcenuo, l98l). When they all were groupedinto one single interstadial(e.g. LuNnqutsr, 1986), it was partly becausethis was the simplest model which explainedall observations.Up to now this model has not beencontradicted. The most obvious evidencefor more ice-freeinterstadials is presentedby LncrnnAcx, who from Northern Sweden(around Junosuando, Fig. l) reportedthree siteswith two interstadial beds separatedby a till (LacrnnAcr, 1986; HrrrlnoRc et al., 1986). Basedon till fabric and pollen stratigraphyLncensAcx & RonrnrssoN (1988)correlate the lower interstadialwith the Periipohjola.Also the upper, namedthe Tirendci interstadial,has an infinite radiocarbonage, and is tentativelycorrelated with the odderade (LncrnnAcr & Ronenrssor.r,1988). LuNnquIsr(1967)describedsub-tillclayandsiltatVilbacken,nearPilgrimstadonFig.l,and includedthese sediments in theJiimtland interstadial. ManNrn ( I 981) found that the Vilbacken sedimenthas a palaeomagneticsignal similar to the signal of event F in St. Germain II in the GrandePile, and different from the signal in St. Germain I. The correlationsgiven in Fig. 2 reflect ihat Vilbacken is of Odderade age.

Ice-free periods with finite radiocarbon ages?

Many finite radiocarbon dateswith agesabove 20 000 B. P. have beenobtained from the central partsofScandinavia(seeLuNoqursr, 198 l, 1986;Hrnvlsetal., 1981,MaNcBnuo, lggl for further references).Many of them canbe demonstratedto be minimum agesonly, e.g. because they dateforested periods. In my opinion no finite datefrom Central Scandinavia,e.g. the area proximal to the Younger Dryas endmoraines,can at presentbe convincinglyargued to be correct. This may be changed in the future, but with Fig. 5 I have assumedthat the central areas were coveredby ice from 500m to 12000 B.P.. BrncensrN & THonnseN(oral communication1988) recently obtaineda TL date of 37 000 B.P. for windblown sedimentsfrom Gudbrandsdalen(Fig. l). LeunnznN (oral communica- tionl988)obtainedU-seriesdatesaround30000B.P.onspeleothemsfromNordland(Fig.l). Both thesecases have to be re-tested,and I haveconservatively not includedthem in thediagram (Fig. 5). Still they openexciting ways of datingice-free periods to cold, or to short, for organic production. If they are correct, eachof them would demonstratethat central areasindeed were ice-free. 324 . ttn Mrxcrnuo

Discussionand conclusionsfor the eastern flank of the ice sheet

It seemsquite clear that there was a glaciationin the centralareas during the Herning stadial "mild" (isotopestage 5d): All interglacialbeds are directlyoverlain by a till (andnot a interstadial),and all interstadialbeds are found on till (andnot on an interglacial). A mainproblem in mapping the geographicalextent of that glaciationis that interglacialand interstadialsites hardlyexist between the centralarea and the marginalzone of the Weichselianglacial maximum. The mostproximal site with Eemianand Brorup sediments not separatedby a till is Stenberget (Fig. l) in SouthernSweden (Bencrurun & Lncr,nr-uNn,l98l). If thedating of thetill III in Finlanclis correct, Laplandand PerZipohjoladistricts were glaciated,whereas Osterbotten (aroundthe siteOulainen, Fig. l) remainedice-free during stage 5d. The Brumunddalsite in Norway(Fig. l) (Hrlle et al., l98l) suggestsa glacier with a minimumextension of nearly the YoungerDryas size. Mainly basedon TL dates,Morsxt (1980,1985), GaloN (1982). Lrr.roNen( 1984), and LINnNE n etal. ( 1984)concluded that the lowest Weichselian till bedalong thelower Vistula valley in Polandis of pre-Brorupage, which would suggesta stage5d glacia- tionconsiderably larger than the Younger Dryas, and incompatible with theconclusions drawn from Finland.However, this age is notproven by overlyingBrorup sediments, and Kozensrt ( 1980),for example,postulates a Late Weichselianage for that till. The patternof glaciationduring the Herning and the Late Weichselian maximum was quite different. During the Herningthe ice-shedremained in the mountainsto the west (Hrnve,s& Ne,NoNeN,1987; Hlnvls et al., 1986)whereas during the Late Weichselianit was far to the east.Based on thegiven observations, I conclude that the size of theHerning time glacierwas of the sameorder of magnitudeas the Younger Dryas glacier west of themountains, and probably somewhatsmaller on the eastside. I also concludethat therewere two (or possiblymore) interstadials,of agesbeyond the range of radiocarbondating, when areas close to themountains were ice-free. The older of thesecor- relateswith thePeriipoh.jola (LlceneAcx & RoerRrssoN,1988), or at leastwith someof the localitiesgrouped together as Periipohjola, and probably with the Brorup. The logical assump- tion will then be that the youngerTdrendri interstadial correlates with the Odderade.The correlation,or ratherthe splitting,of the other Swedishand Norwegiansites into the two in- terstadialsis difficult, simplybecause most of themlack any criteriafor both relativeand ab- soluteages. The most promising techniquesfor solving this problem are TL dating and palaeomagneticcorrelations with areasoutside the Wcichselianglaciation. The scaleof the glaciationbetween the two interstadials(that should be Rederstallstadial : isotopestage 5b) is unknown.LecsnsAcx (writtencommunication 1988) assumes that it had a considerableextent in NorthernSweden and Finland, even though a till bedof thisage is not reportedfrom Northern Finland. Theextension of theisotope stage4 glaciation is unknown,too. Bothfor this,and for theearlier advances.Poland may be the key area.Dnozoowsxl (1980),Dnozoowsxr & Feoonowrcz ( 1987).Molsxt (1980,1985), LtNonrn (1984),and LtNoNrn ct al. (1984)conclude, rnainly The Scandinavianlce Sheetthrough the lastinterglacial/glacial cycle 325

on thebasis ofTL dates,that the ScandinavianIce Sheettransgressed Poland around this time, and that the ice front approachedthe limit of the Late Weichselianmaximum. However. this is not yet generallyaccepted (Koznnsxl, 1980). The Dssebackasite, near Gotenburgin south-westernSweden has severaltill beds, too, separatedfrom oneanother by horizonssuggesting ice-free conditions, mostly as wind abraded surfaceswithsomeorganicmatter(Htlr-enons,1974,1986).Thedatingisproblematictyetthe stratigraphysuggests that the ice overrode this area several times during the Weichselian. A TL dategave about 50 000B. P. for aninterstadial bed (Hrllrrons, 1986);if correctit maysuggest that the underlying till is of isotopestage 4 age. PrrrnsnN (1984)assumed that a till at Holmstrup(correlated with theoldest Weichselian till in RistingeKlint) in Denmark wasdeposited by a glacier flowing from the Baltic at a time that may correlate with isotopestage 4. If he is right. the ice sheetmust also have transgressed Poland,and thushis conclusionis indeedcompatible with the similarconclusion for poland givenabove. However, HoutraRx-NTELSEN ( 1987) postulated the same till to beof pre-Eemian age.LlcenluNn (1987)concluded that the first Weichselianice advanceover southernmost Sweden,and thus Denmark, postdate the Gdrdslsv beds (Mrr-lrn , 1977)from which thereare severalradiocarbon dates in the range2l 000 to 30 000 B. P. I still considerthe time of the first Weichselianice advanceto Denmark as unsolved.

Towardsclimatic and glaciologicalmodels for the Weichselianglaciations

Glaciologicalmodels for the Weichselianhave been developed by, for example,DeNroN & Hucnes (1981);BoulroN etal. (1985),and LAcsnLuNn (1987). Such models are extremely importantto improve the understandingboth of the climatic role of the ice sheets,and fbr severalother geological problems. A crucialboundary condition in all suchmodels is thetype of observationsdiscussed in thispaper: Field data on thesize of theice sheetat differenttimes. I shallnot discussthe modelshere, but only presentsome thoughts originating in the geological observationspresented here. The Weichselianwas not onesimple glacial cycle from an interglacialto a glacialmaximum. In fact ice sheetsdeveloped (at least) three times, each time from virtually no glacier ice. However, only the first of thesestarted from a full interglacialclimate, with an oceanto the west aswarm asat present.In contrast,the last major expansion to the LateWeichselian maximunt (around started 30000 B.P.) from an ice sheetthat already was relativelylarge. There are all reasonsto believethat the different starting points and different climates during thc cycles caused quitedifferent types of developmentof the geometryof the ice shcetsmentioned. Allobservationssuggest that the first glaciation (stage 5d) remaineda mountaincentcre6 glaciation, with the ice-shedremaining in the mountainsthroughout the glaciation. This contrasts stronglywith the Last Glaciation,when the ice-shedmoved far eastand southof the watershed in Swedenand Norway (LuNoqutsr, 1974,BancenseN & GnnNBs,1983). Whether this was a slow movementduring severalthousand years, or whetherit hadhappened rapidly aroundthe time of themaximum glaciation, is unknown.Further north Hrnves et al. (l98l) and Hrnvns 326 . sexMeNcsnuo

& NTNoNEN(1987) did not find anyfabric in thetill suggestingthat this Last Glaciation started in the westernmountains, and their observationswould ratherlead to a modelof instantaneous glacierizationof large areasof Northern Finland.

Acknowledgements

A draft of this manuscriptwas widely distributed to Nordic colleaguesearly February l9gg, and I receiveda large number of written and orar comments,noruuiy from J. J. DoNNen, M. EnoNeN,L. FonssrRdu, H. HrRv,rrs,and K. NTNoNENfrom Finiand;R. LecrnnAcx, E. LAcERr-uNn,J. Lunoqursr, andA. M. RosrnrssoNfrom sweden;M. Hourrllnr_NlErspN andK' S. Perrnsrhr,Denmark; B. G. ANoe nsEN,o. F. Bnnornsrp, J. LaNnvrx, E. LlnssN, s' E' LnunrrzrN, A. Nrs*, H. p. Sarnup, and M. THoREsnN,Norway. MrcHneLTnlsor correctedthe Englishlanguage. To all these friendsI offer my sincerethanks. The projectwas financially supported by the Norwegian Researchcouncil for Science and Humanities (NAVF).

References

ANoEnsEN'B.G., Nvonr-,R., wnnceN, o. p.&osrr,.ro, s. R.(r9gl): weichserianbefore B.P. at r5 00oyears Jaren-Karmoyin southwesternNorway. Boreas 10, 2g:'_314. -, Sr'rnup,H. p. & KrnrHus, 6. (r9g3):Eemian and weichselian a.pnrit, at Bo way:A preliminary onKarmoy, SW Nor_ . report.Norges geologiske undersskerse 3g0, ig9-20r. ANornsrN's' T' (1961): vegetationand its-environment in Denmark in the (lastglacial). Eartyweichselian Glacial DanmarksGeologiske Undersskelse. II Rekke 75, r_r75. AVERDIECK,F' R. (1967):Die vegetationsentwicklung 4., n..-int..gi"ri.r, undder Frtihwiirm-ln- tersradialevon Odderade/Schleswig_Holstein. Fundamenta2, l0t _ i2S. BrnuLtEu,J' L' nr & Rrlue, M. A pleistocene 1t9441: longUpper pollenrecord from Les Echets, Lyon,France. Boreas f-i, lll_132. near BeHnn'K' E' & Le'pe,u' {1986):Eine Folge von Eem und 4 weichsel-lnterstadialen sachsenund ihr Vegetarionsablauf. in oerel/Nieder- * EiszJitalteru. Gegenwart 36, ll-36. Bencrn,A., Irrrsn|E, J.,Hevs, J., Kuxle, G. & SAirzrueN,B. (eds.)(19g4): NATO Milankovitchand climare. ASI Series126 (2 volumes),D. Reidel,Dordrecht. BsncensEN' o' F' & GrnNss,K. (1981):weichselian in centralSouth Norway: The Gudbrandsdal In- terstadialand the following glaciation. Boreas 10, - - 315-322. & (1983):Glacial deposits in theculmination zoneofthe Scandinavian ice sheet. In: EslEns, (ed'):Glacial deposits in north-wesr J. - Europe,zg-40. A. A. Batkemo,noii.roor. BencluNo'B' E' & LecBnLuNo, E. (1981j:Eemian and weichselian stratigraphy Boreas10, 323-362. in southSweden. BoulroN' G' s', Srrrrrn,G. D., JoNrs,A. s. & Nrwsorrlr,J. (19g5): of thelast Glacialgeorogy and graciorogy mid-latitudeice sheets. J. Geol.Soc. London 142,44i474. BownN,D. (197g): e. euaternaryGeology. p".garnon press, Oxford. tt:il? MEYER.x."o. *sE')' Report i;;i?l:;Jrlfi ontrre sfmposium Visturian srrarigraphy, cHrppcLt-,J'&sH,c,cxl-sroN,N.J...(1986):oxygenisotopesandsealevel.Nature 324, 137-.140. De*screno,w' (1987):Ice core evidence of abruit climaticchanges.l;,;;";.*, w. H. & Lensynrr, L' D. (eds.):Abrupt crimatic change, NATO A'sISeries c. 216,223_234.D. Reider,Dordrecht. The ScandinavianIce Sheetthrough the lastinterglacial/ glacial cycle . 327

DexroN,G.H.&Hucsps,T.J.(eds.)(1981):Thelastgreaticesheets.JohnWiley&Sons,NewYork. DonNEn,J. (1983):The identificationof Eemianinterglacial and Weichselianinterstadial deposits in Finland. Annales AcademiaeScientiarum Fennica. Series A 136, l-38. Dnozoowsrt, E. (1980): Chronostratigraphyof the Vistulian glaciation on the lower Vistula valley. Quatern. Studiesin Poland2, 13-20. - & FBponowlcz, S. (1987): Stratigraphyof Vistulian glaciogenicdeposits and correspondingther- moluminescencedates in the lower Vistula region. Boreas16, 139-153. Fonssrnou, L. (1982): The Oulaineninterglacial in Ostrobothnia,western Finland. Acta Universitatis Oufuensis.Series A 136, l-125. - (1984):Eemian and Weichseliancorrelation problems in Finland.Boreas 13, 301-318. - (1985): Further observationson Weichselianand Eemian correlationsin Finland: A reply to Hannu Hyvdrinen. Boreas14, 2&-266. -, EnoNrr,M.&GnONluNo,T.(1987):OnmarinephasesandshorelevelsoftheEemianlnterglacial and Weichselianinterstadials on the coastof Ostrobothnia,Finland. Geological Survey of Finland. SpecialPaper 2,3742. Grt-oN, R. (1982): On the stratigraphyand chronology of the last glaciation (Vistulian) in Poland. Quatern. Studiesin Poland3,3'748. Gnucrn, E. (1979a): Die Seeablagerungenvon Samerberg/Obb.und ihre Stellungim Jungpleistoziin. Eiszeitalteru. Gegenwart29, 23-34. - (1979b):Commenton"GrandePilepeatbog:Acontinuouspollenrecordforthelastl40000years" by G. M. WorLLnno.Quatern. Res. 12, 152-153. Hlr',rsonc,M., Hrnvns, H., Le,cBnsAcK,R., MAKTNEN,K., NeNoxen, K., OrsrN, L., RoHoe, L., SurtNeN,R. &THonrsBN, M. (1986):MapofQuaternarygeology, sheet4: Quaternary stratigraphy, Northern Fennoscandia,1: I mill., GeologicalSurveys of Finland, Norway and Sweden. Her-ls, M., SoNsrrcelno,8., coopB, R. G. & Rve, N. (1981):Early weichselianpeat at Brumund- dal, southeasternNorway. Boreas.10, 369-379. Hlllrrons, A. (tSU+):The stratigraphyand genesis of the Drisebackaand Ellesbodrumlins. A contribu- tion to the knowledgeof the Weichsel-glacialhistory in westernSweden. Geologiska Foreningens i StockholmForhandlingar 96, 355-37 4. - (1986): The Dtisebackainterstadials, 17. Nordiska geologmotet,Helsingfors Universitet, 54. Htnve,s,H. (1983): Correlationproblems of interglacialdeposits in Finnish Lapland.Quaternary Glacia- tions in the Northern Hemisphere,IGCP project 24, Report 9, 129-139, paris. -, Konpele, K. & Kul,c'Nsuu,R. (1981): Weichselianin Finlandbefore 15 000 B.P. Boreas10, 42343t. - & KurnNsuu,R. (1981):Quaternary stratigraphy and chronology in northernFinland. In: Gon- BUNov, G. I. (ed.): Glacial depositsand glacial history in easternFennoscandia, Kola branch of the USSRAcademy of Sciences,Aparity, 5-15. -, LlcBngAcK,R., MAKINEN,K., MrNer_1,H., NnnonpN,K., OrseN,L., RoHor, L., Surrr.reN,R. & TsonesBN, M. (1986): Map of Quaternarygeology, sheet5: Ice flow directions, Northern Fen- noscandia.Geological Surveys ofFinland, Norway and Sweden. - & NnNoneN, K. (1987): The till stratigraphyof Finland. GeologicalSurvey of FintandSpecial paper 3,49-63. Houturnx-NtersEN, M. (1987): Pleistocenestratigraphy and glacial history of the central part of Den- mark. Bull. Ceol. Soc. Denmark-i6, l-189. HvvAntNEN,H. (1985):Weichselian and Eemiancorrelations in Finland: A discussion.Boreas 14, 262-263. JuNcxen, H. (1987): Thermoluminescencedating of sedimentsfrom Oulainenand Vimpeli, Ostrabothnia,Finland. Boreas 16, 231-236. -, LeNovIx,J. & MnNcenuo,J. (1989):Thermoluminescencedatesof Weichselian sediments in western Norway.Boreas ,18, 23-29. 328 lnN MnNcenuo

Konpnle, K. (1969): Die Weichsel-Eiszeitund ihr Interstadialin Perdpohjola(n

Mo'rsxt'J' E' (1980):Vistulian stratigraphy in theglaciated polish '7i areaof the lowlands. Studies in Poland2 , -99. euarern. - (1985):Quaternary' Part 3b of Geologyof Poland.Publishing House wydawnicrwa Geologiczne, Warsaw,248 p. MonNen' N' A' (1969):The Late Quaternaryhistory of the KattegatSea and the Sveriges Swedishwesr coast. GeologiskaUndersokning Serie C 640, l_4g:.. - (1981): weichserianchronostratigraphy and correrations.Boreas ./0, 463_470. NEsrr,A', ANon, E., RvE,N., LrBN,i.,-Hor-r, p. A. & Blrxnn, L. H. (lgg7):The verticarexrenr of ,:;\i;::;\iselian icesheet in theNordfor d-Msrearea,western Norway. Norsk geotogisktidsskrift PerrnsrN, K. S. (1984):Stratigraphical positions of weichselian tills in Denmark.Striae 20,75- 7g. Rvp' N' ' Nasre'A'. LrrN, R. & ANoe, g. (tssz): TheLate weichselian ice sheer in theNordfiord-Sunn- oeglaciationchronology for Nordford, westernNor*uy. N;;l geografisk ry:Tuuno tidsskrift4t , SE:nup'H' P' (1987):Molluscan and foraminiferal biostratigraphy- of anEemian-Early weichselian tion on sec- Karmsy, southwesternNorway. Boreas16, 2j42. -, AnRserH,I., Elr-rNcspN,K. L., Rrrrsrn, E., JeNsEN,E., Lov'*, R., BeNr, A., BnrcHeu- GnprrE, J', Le'nsEN,E. & sroxpn, M. (1987): euaternaryrr;tigrr;l; oi ,t. ntua.n area, North Sea:A multidisciplinary cenrral study.J. euatern.Science 2, 35_5g. SHrcxt-s-roN,N' J' (1969): The last interglacialin the marine andterrestrial records. proceedings Royal SocietyLondon B 174, 135_154. - (1987): isotopes,ice vorume lx1sen and searevel. euatern. Science Rev. 6, lg3_r90. SvpNossN'J' I' & MlNce nuo, (1987): J. Late weichselianand Holocene sea-level section hisroryfor a cross- of western Norway. J. euatern. Science2, l13_132. SurlNeN' R' (1984): on the glacial stratigraphyin Pudzijarviarea, periipohjola. (ed.): In: KoNrcssoN, L.-K. Ten yearsof Nordic till research.Siriae 20, gl-.94. TunoN'J L' (1984):Directland/seacorrelationsinthelastinrerglacial complex.Nature j0g, 6.73--676. 330 ' :eN MeNcrnuo

VonnrN, T. O. & RoeLnser, E. (1977):Stratigraphy and lithologyof Late Pleistocenesediments at Mosvatn, Hardangervidda,south Norway. Boreas6, 53-69. - VonnsN,K.D.,Ar-r'l,T.,Gur-LrrssN,S.,&Lovr-rp,R.(1988):Thelastdeglaciation(20000to I I 000) on Andoya, northern Norway. Boreas1Z 4l-77. WEI-rrN, M. ( l98l ): Verdriingungund Vernichtungder anspruchsvollenGeholze am Beginnder letzten Eiszeit und die Korrelation der Friihwiirm-lnterstadialein Mittel- und Nordeuropa. Eiszeitalteru. Gegenwart3l , 187-202. WotLLeno,G. ( 1975):Recherches palynologiques sur le Pl6istocdnedans I'est de la Bdlgiqueet dansles VosgesLorraines. Acta GeographicaLovaniensia 14, l-118. WoIlLlno, G. M. (1978): GrandePile peatbog: A continuouspollen record for the last 140 000 years. Quatern.Res. 9, 1-2L - & Moox, W. G. (1982): Carbon-14dates at GrandePile: Correlationof land and seachronologies. Science215 , 159-161. ZrcwtrN, W. H. (1961):Vegetation, climate and radiocarbondatings in the Late Pleistoceneof the Netherlands.Part I: Eemian and Early Weichselian. Mededelingenvan de GeologischeStichting NieuweSerie 14, l5-45. - (1975):Indeling van het Kwartair op grondvan veranderingen in vegetatieen klimaat.In: Zncwr:r.r, W. H. & AstenLourNEN, C. J. (eds.): Geologischeoverzichtskaarten van Nederland,Rijks GeologischeDienst, Haarlem, 109-l 13. - (1983): Sea-levelchanges in the Netherlandsduring the Eemian. Geologieen Mijnbouw 62, 437-450.

Received,March 25, 1988 Author'saddress: Prof.Dr. JeNMnNcrnuo, university of Bergen,Department of Geology,Section B, Allegt.41, N-5007Bergen