TheEemian Interglacial and the succession of glaciationsduring the Last Ice Age (Weichselian)in SouthernNorway Jan Mangerud
Our main informationabout the EemianInterglacial and the Bergenis situatedfar west of the present-day(and Holocene) ciimaticvariations during the LastGlaciation comes from areas geographicallimit of spruce.In sample I Picea constitutes outsideScandinavia. Sediments with a more or lesscomplete 43'/, of all treepollen.Bearing in mind that spruceproduces stratigraphyhave been found in peripherialareas of the lesspollen than Pinus(pine). it must be assumedthat spruce ice-sheetand in areasnot coveredby ice. The presentpaper, wasthe dominating tree in the forestsaround Fjosanger at that however,reviews finds in Norway of assumedEemian age, as tlme. well as(Weichselian) interstadial sediments where datings have The denseforest, the presenceof Quercus(oak) and Corylus beenpossible. (hazel),and especiallythe presenceof llex (holly) show that the climatecould only havebeen slightly iess favourable than present, Eemian Interglacial at andcould possibly have been warmer As the pollen spectratally very well with pollendiagrams Very few pre-Holocenedeposits in Norway showevidence of from the Late Eemianin Denmark(4). it is assumedthat the sufficientlywarm conditionsto excludethe possibilityof an Fjosangervegetation dates from that period.I shouldalso like interstadialage, nor does the evidencesuggest a definitely to point out the abundanceof acidhumus plants at Fjosanger interglacialorigin. In the followingpages two localitieswill be (Picea, Ericales, Sphagnum,Ilex), which accordingto S.T. discussed,namely Fjosangernear Bergen(20) and Kroken in Andersen(5) is characteristicfor the Late Eemianin Denmark. Sogn(30). This is, however,only an ecologicalsimilarity, and cannotbe At Fjosangerseismic investigations indicate a sediment usedfor a time correlation. thicknessof at least 10 m. However,only the upper 2-3 The marine fossils have only undergone preliminary metresare exposed in a section.The sedimentsare primarily of investigations.Several well-preserved bones of sealand a large marineorigin, but weredisturbed and intermixed by iceduring number of yet-unidentifiedfragments of shellswere found. the Last Glaciation.The fossilsoccurring in the sedimentsare, Severalspecies of Foraminiferahave been identified(20. p. however,both terrestrialand marine. 176) in the samesample from which pollen-sample3 was The most importantof the terrestrialfossils are pollen and taken.The foraminifera-faunabelongs to the neriticfacies, and spores(Fig.2). The three pollen spectraso far obtainedall accordingto Ostmo-Sater(pers. comm.) it is very different show the presenceof dense forests.The compositionol from the presentfauna in the adjacentRauneford. tree-pollenhowever, is slightlydifferent in the threesamples. From investigationsat Kroken, Inner Sogn, Vorren (30) Of specialinterest is the largeamount of Picea-pollen,since describesthin layersof rebeddedinterglacial peat in Weichse-
I Interglacral(Eemran) sedrments
Seormelts corlari le- mailne X 165srls(Crq daied). a Mammoth rema ns
a Mammoth remarns, Cr!-dated
\%oo o Wood (C''-dated).
O Musk-ox vertebrae
)laI'teo cay,stl ano 5an0 - betow tltl.
\ El Mammoth remarns found rn: o 'eta's {oJnd ' ,' v,amroth o a -- C dated.
Fig. l. Sediments and fossils of sup- posed pre-Late Weichselian age in southern Norway.
The Norwegian SeaRegion 39 AP TOTAL NAP S PORE5
0 l0% 2a1, 301, 1D1, AP NAP Sp 0 t0% 0 r0%
CyAr"r*, I
Ltcopodtum.-
1423 r02 95) E.t.otes Ft I i..s
6€%
Ptceo Ctp sph Pnus !-----J-i- def 1500 34 r84) Ftl
L 70'L 11. 261, c'. i- I 1o -
5ph Ftrr: Fig. 2. Pollen diagram from inter- 8c( glacial sediments at Fjiisanger, ll? t25 54) Ett. Ft I after Ath Mangerud (20, Fig. 8). Calculation 634. 251, Car basis is sum AP for the AP-diagram, Ou and sum AP-NAP+Sp for the other 1!ex i (06) l diagrams.
0+- 1 l
l ,:
6 ?0l 19000:r?00 Toten
;l ! 24r,00I 900
!- Mrddlc Werchselran 2S000-42000 T-140 Several 34000: 3000 oarrngS Karmoy lrcm J -ren
T- 749 .. /cn^^.5000 I 7t3 48000.4000 2000 qan Fig. 3. Cta-datings from Norway, giv- ing definite ages ) 15,000 years, correlated with a diagram of tempera- ture fluctuations according to Coope , I Early W€ chsel an i, and Sands (9, Fig. 2), with some nmersrm,r, modifications from West (32, Figs. l, t-r l-l 2t.
lian interstadialsediments. The pollenspectra interpreted to On the islandof Karmoy thereoccurs a silty andclayey till be of interglacialage show a denseforest of Alnus(alder). with containing a large number of shell fragments(28). A some Corylus (hazel) and Ulntus (elm). In one sample 3 Cro-datinggave the ageof (T-140)34,00013,000 (23, p. 89), pollen-grainsof Piceowere found. Vorren (30) assumesthat a result confirmedby two new datingsgiving an agea few the peatstems from the MiddleEemian. thousandyears higher (B. G. Andersen,pers. comm.). The datingsindicate that Karmoy wasfree of ice duringa certain period in the Middle Weichselian,but as the molluscsare Ice-free periods during the Early and Nliddle mainlycoldwater forms (28, p.211) thereis no evidencefor Weichselian anice-retreat far inside the coast. PublishedCla-datings from Norwaygiving definite ages over The greatestthickness of pre-Holocenesediments in Norway i-5.000years are compiled in Fig.3. occursat Jaeren,where borings have gone down to a depthof The cited dating(T-749) from Fjosangerwas carried out on 92 m . The ageand origin of thesedeposits are very ambiguous slrellfragments (20. p. 1121.As the other fossilsindicate an and have lately been discussedby O. Holtedahl (18, pp. interglacialage for the deposit.the datingresult is probably 362 364,2,7 , 10, 11, 12).At present,regional mapping and incorrect.It is hypotheticallypossible that parts of rhe stratigraphicalinvestigations are being carriedout by B. G. depositsare of interstadialage, but I shouldlike to emphasize Andersen(pers. comm,). Ostmo (25 ) andWangen (31). that there is no evidencefor sucl.ran assumptionother than Belowa till from theWeichselian Glaciation, the sediments a the CI -dating,to whichseveral sources of errorare attributed at J:erenconsist of stratifiedsand and gravel and fossil-bearing (20.p. 173). marineclay. Large number of nrolluscs,indicative of arcticand
40 Th( Nt)rwegiott Sea Reg,,11 boreo-arcticconditions, have been found in the clay. The occasionallyoccurred in glacial sediments.Therefore Cr a- foraminifersin the claysfrom Sandneshave been investigated datingsare the only possiblemethod for correlationof these by Feyling-Hanssen( I I ), and these are dominatedby a flndswith the Weichselianstratigraphy outside Norway. In my coldwater fauna. As to the age of the clays, the most opinion thereis little doubt that the coastof Norwayhas been importantinformation consists of severalCra-datings giving freeof ice severaltimes during the Weichselian,and thereare agesbetween 28,000 and 42,000 years (B. G. Andersen,pers. strongevidences that evencentral parts of the country have conrm.).The conclusionthat must be drawn is that a great beendeglaciated during some interstadiai. There are, however, part of the clays,at least,originates from an interstadiaiduring so manyuncertainties concerning the datingand correlation of the MiddleWeichselian, as suggestedby B. G. Andersen(3, p. these ice-free periods, that no time-stratigraphycan be 113)and Feyling-Hanssen(i l, pp.35 and42). On basisof the establishedat present. C'a-datings,this ice-freeperiod may be correlatedwith the oneat Karmoymentioned above (3, p. I l3). Late Weichselian ice-front variations From studies at Foss-Eikjeland,Jaren, Bergersenand Follestad(7) describefossil ice-wedges in glacifluvialsediments In the previous chapters on the Eemian and the Early and both below the clay and a.lsoseparated from the clay by a Middle Weichselianin Norway, our lack of knowledgeabout sheetof till. They concludethat (7, p.45) the formationof these periodsis quite obvious.Of coursethere are several the ice-wedgestook place in the Early Weichselian,but unsolvedproblems concerning the Late Weichselianas well, whetherthis occurredbefore the first glacialadvance or during but moreor lesscontinuous records from differentparts of the anearly interstadial is not clear. country exist for that time. The basisfor the dating and The oldestagc obtained with Cra-datingsin easternNorway correlation of different eventsis thereforefundamentally is that of a tree sturnp of sprucein glacifluvialsediments different from that of earlierperiods. In the followingpages, ,1 nnn t't 743) 48,00011'666B P 1.24,p. 2r5, 29). Thoughno the discussionwill be largelyrestricted to thevariations of the further infbrmation is available.tlie dating is interesting extentof the glaciersin the Bergenarea (2 I ). becauscwood chemicallyis very unreactiveand thereforenot The main resultsare presentedin Fig. 5. Before i3,000 so liableto post-depositionalchanges in the Cto/C'2-ratioas years B.P. the ice-frontreached the North Sea.During the shells.Wood is alsosuitable to pre-treatmentwith both NaOH Bolling Interstadialthe front retreatedfar inland,but then and Fl('I in order to remove contaminationsof younger advancedagain to the North Sea during the Older Dryas carbon.Therefore the datingshould be relativelyreliable. It is Stadial.This considerableoscillation during Bolling Older Itowever, surprisingthat spruceshould grow in Norwayduring Dryasis of greatinterest, since several researchers (8,26,27) an interstadialat thatdate. maintainthat thereis no evidenceof a climaticdeterioration 'Iwo of the mamnroth teeth from Norway have been betweenthe Bolling and Allerod phasesin the British Isles. Cra-datcd,giving the age 19,00011.200(15) lbr theone from The basisfor my conclusionshould therefore be put forward Toten, and 24,400J900(16) for the one from Kvam.The in somedetail. dating ol' teeth and bonesinrplies several problems (13) At Blomoy,littoral sedimentsare situated below Iodgement whrchshould not be discussedhere. Such datings oftcn yield till (21, p. 132).Cta-datings from thesediments gave (T-138) erroneousresults. A carctirlinterpretation of thedatings given 12,2001350and (T-139) i2,7001350 B.P. Approximately 700 is thcrefore necessaryuntil more datings are obtained, m farther north an investigationof a bog was carriedout. 4 preferably on wood.giving the same ages. including pollen analysis(2 I , PI . 1) and Cr -datings.The 'lhl tooth lronrToten was found in till (14),and thercfore sedimentsin the bog aresoft peatand gytja, and as there is no o no further information than the ('r -dating itself was sign of disturbancesby ice, the sedimentsare undoubtedly obtaincd.As pointedout by Heintz(15. p. 229)this age must situatedstratigraphically above the till. The datingsfrom the be tooyoung. bog are indicatedat Fig. 5, the oldestonc givingthc ageof The dated lootli l-ror.nKvam was found in fluvial or 12.0701180B.P. (T-672). Thereforeboth stratigraphical glacifiuvirl sedimentsbelow till (6) In this deposit 5 evidenceand Cro-datings from Blomoyindicate an ice-advance mantmotlr remainshave been found. The sediments,along betweenthe Bollingand Allerod intervals. with othcrdeposits of sirnilaroccurrence, are supposed to have Mangerud(21, p 132) has describedclay with molluscs been depositedduling a period named Guldbrandsdalen belowtwo bedsof till at Sandvikenin Bergen.At thislocality Interstadial(6, p. 106),in whichGuldbrandsdalen was free of the assumptionof a Bollingage for the clayis supportedsolely ice.Basing their conclusions on the two datingsof rnammoth by the Cra-datings, and cannot be proved from the teeth and on correlationswith other areas.Bergersen and stratigraphy.Three datings are obtained, the first givingan age Ciarnesassume that the ageof thc interstadialshould be rvithin of 12,470t150B.P. (T-750) (21). This was a dating of 24.000 30.000years B.P. well-preservedmolluscs of the speciesChlantys islandicus, Severallocalities with sedimentsor fossilsof pre-Late where the outer l0 7, of the shellswere removedwith HCl. a Weichselianage, but whereno Cr -datingshave been obtained. and the datingis thereforebelieved to be reliable.In the clay a areknown in SouthernNorway. These are marked on the map, large number of pebblesoccurred that were coveredby Fig. I, and are summarizedby Mangerud(20, pp. 178 ll9), carbonate,probably a1gae. The bedrockon the siteis granite, with later additionsby Mangerudand Skreden(22) and and pebblesof this rock werechosen; therefore no contami- Bergersenand Garnes(6). Severallocalities on the Swedish nationof old carbonshould be possible. It wouldbe more likely sideof the border,described by J. Lundqvist(19) shouldalso that datingsof the carbonate-cover(stromatolith) would give bementioned here. ages that are too young, as the surface area is large and Thereare severalsources of errorsconcerning Cra-datings. exchangeof young carbonfrom percolatingground-water is These errors are of greaterimportance when considering thereforeprobable. Two measurementsof the carbonatecover datingsgiving ages above 20,000 years.However, in all cases gave(T-10244) 12,4801180 and (T-10248) I1,970ti60 B.P. discussedabove, the stratigraphyis very incomplete or The arithmeticmean of the threedatings is 12,3l0 B.P.,and completelylacking. The datingswere performed on fossilsthat consideringthe discussionof errorsabove. I suggestthe clay to
The Norwegian SaaRegittn 4l Fig. 4. Map of the Bergen area, with key map of southern Norway. Contour intervals of 200 m for both land and sea. The end moraines from Younger Dryas are shown as solid lines, stipled in places where the position is uncer- tain. From Mangerud(21, Fie. l).
OSCILTATONSOF THE POS]TIONOF THE GLACIER FRONT \oF q s.oMo dLPOu sEA ot {1 ; ro zo
HOLOCENE
YOUNGER Fig. 5. Oscillations of the position of DRYAS !05.! ! r.l glacier the Late Weich- STAD AL the front during Ira?eo! fo] selian in the Bergen area. The curve indicates the position of the ice-front at various times. The profiles run in ir?so: i rol the direction of movement of the ice, !r.Dc,r roj a little to the north of Bergen - [f5cor 3oo] through Herdla-BIom 42 The l,,lorwegianSea Region Fig. 6. Palaeogeographicmap of southernNorway during the tater part of the Younger Dryas Stadial.From Mangerud(21, Fie. l0). Conclusions history is far more complex. The coast of Norway has probably been ice-free severaltimes during the Weichselian, Our knowledge about the Eemian Interglacial in Norway is and there is a possibility that the entire country, with the very scanty. We do not know hqw_ the flora and fauna exception of high mountain areas,was ice-freeduring one or developed,nor do we know what changestook placeduring severalinterstadials. Climatic variations at the end of the the climatic deterioration before the Last Glaciation. However, Weichselianhave also resulted in considerableoscillations of the finds at the locality of Fj The lr/orwegian Sea Region