oxygen-isotope stratigraphy

( R e p r i n t c df i o n r N a r u r c .V o l . 2 7 7 . N o . 5 6 9 . 1 .p p . 1 8 9 - 1 9 2J a n u a r yl g 1 9 7 9 ) O lllacnrillan Journals Ltd., 1979

Correlation of the Eemian (interglacial) Stageand the deep-sea oxygen-isotope stratigraphy Jan Mangerud, Eivind Sonstegaard& Hans-petter Selrup D e p a r t m e n t o f G e o l o g y , A l l 6 g t . 4 1 , 5 0 1 4 B e r g e n - U n i v e r s i t e t e tN , orway

A complete interglacial sequencein coastal marine sediments in western lr[orway is correlated with the Eemian Stage by means of pollen stratigraphy, and with deep-sea coresby meansof marine fossils.The Eemian is correlated with isotopestage 5e. TUE correlation of deep-seaand continental records is one of the most important problems in Quaternary stratigraphy. Becausenearly all cores from the deep-sealloor can be correlated usingthe 'tO/toO record' t, oxygen-isotopestratigraphy is also the most valuable method of correlation with the continents. The general principles in the correlation of glacial/interglacial periods with oxygen-isotope stages are known'. However, the correlation of real stratigraphicalunits defined on land, and the oxygen-isotopestagcsremains probl e m a t i ch e y o n dt h e r a n g eo f ' t C d a t i n g . Here we correlate the Eemian Stageof North-west Europe with the oxygen-isotopestage -5eas follows: a complete interglacialsequencein coastalmarine sedimentsin westernNorway can be correlated with the Eemian by means of its pollen stratigraphy,and the marine fauna of the same section can be correlatedwith the biostratigraphyof coresfrom the Norwegian Sea3,in which the oxygen-isotopestratigraphy has also been establishedtt. Shakleton('first argued for the correlation of 5e with the Eemian, and his conclusionhasbeen acceptedby most scientists. Confirmation has, however, been lacking, and discussionof alternative correlationshas continued. Ofl the Pacificcoast of North America the correlation of 5e with the forest vegetation period of the last interglacialhas been demonstratedT.

exrstbetweenthe Eemian and the Weichselian.She carried out thorough studiesof the most completepollen sequencethrough the Upper Pleisrocenein western Europe, the Grand pile, France,and recognisedthat the Eemian was succeededbv two warm periods which she defined as interglacialsSt Germain I and II. The lower (St Germain l1 is further divided into two warm phases,with a short cooling between. St Germain I and II can bi corrclated with the Early W e i c h s e l i a ni n t e r s t a d i a l s ,t h e A m e r s f o o r t , B r g r u p ' , . ' , a n d Odderade'0T . h e a r g u m e n t sf o r t h i s c o r r e l a t i o na r e : ( 1 ) t h e i r s t r a t i g r a p h i c apl o s i t i o n si m m e d i a t e l y a b o v c t h c E c m i a n a r e i d e n t i c a l .( 2 ) T h e v e g e t a t i o nd u r i n g t h e S t G e r m a i n I a n d I I i n d i c a t e sa c o l d e r c l i m a t et h a n d o e s t h e E e m i a n v e g e t a t i o na t t h e s a m es i t e .( 3 ) C o n s i d e r i n gt h e s o u t h e r nl o c a t i o n( 4 7 . 4 4 , N ) o f t h e G r a n d P i l e ,i t i s p o s s i b l et o c o r r c l a t et h e v e g e t a t i o nd u r i n g the St Germain I and II with the velletation in North_wesi Europe during Amersfoort, Brorup and Odderade. To avoid any confusion which may arise if the above statements about the Eemian and Weichselianshould be shown to be erroneous, we have defined local chronostratigraphicalunits, which we subsequentlycorrelate with the Eemian and the W e i c h s e l i a n( F i g . 2 ) .

Definition and stratigraphicalposition of the Eemian The Eem interglacial is now generally acceptedas a chronostratigraphicalunit with stagerank: the Eemiari Stage" "'. The type locality is along the river Eem, near Amersfoort, Netherlandst'. The lower boundary is definedaswhere a subarcticpark landscapeat the type locality is replacedwith a closedforest and the upper boundary is placedwhere the forest at the type locality is replacedby a more open vegetation. The Eemian in North-west Europe is clearly recognisableby its typical pollen stratigraphyt'tt. This approach could create confusion if the vegetational development during two interglacialswere very similar. However, this does not seem to be a seriousproblem for the Eemian. Until recently it had been agreed that the WeichselianStage immediately followed the E,emian.As the type area for the Weichsel glaciation is in Poland, some correlations are. however, necessaryfor this interpretation. It is also clear that glaciersreachedPoland only during parts of the corresponding chronostratigraphical unit, the Weichselian Stage. If the Weichselian follows the Eemian, the type locality for the Eemian would also be the best boundary stratotype for the Eemian-WeichselianStageboundary, and it has been used as such for a considerabletime. We acceptthis definition based on the abundant evidence from North-west E,urope for this sequence.Woillard'a has suggested,however, that interglacials

F i g . 1 M a p o f t h e N o r w e g i a n S e a a n d s u r r o u n d i n g a r e a s .T h e location of Fjosanger and the cores mentioned in the rexr are i n d i c a t e d .T h e o c e a n i cs u r f a c ec u r r e n t sa r e a l s o s h o w n .

The FiOsangerInterglacial, and its correlation with the Eemian The Fjgsangerlocality is situatedalongthe shoreof a smallfiord, just outside the city of Bergen, western Norway (Fig. 1). Preliminary descriptions of the section have already been giventt'tt, and a detailed descriptionwill be publishedelsewhere.Two till horizonsare locatedat the baseof the sequence. Above thesefollows a sequenceof marinesediments(bedsN-E, Fig. 2), depositedin a fiord at depthsof between10 and 50 m duiing an interglacial and the earliest part of the following glacialperiod. The sedimentsconsistof silt, sandand gravel(Fig' sedimentshavea matrix 2). Ho*enet, eventhe coarse-grained of clay and silt, and both the benthicforaminiferaand the pollen stratigraphysupport an interpretation of continuousdeposition of thJ ctly-sillfraction throughout the marine sequence'The sectionis cappedbY a till. We (in preparation)havedefinedthe FjosangerianStagewith a lower boundaryat the baseof bed N (Fig. 2) and an upper boundary between beds I and H. The latter is also the lower

POLLEN

boundaryfor the HordalandianStage. The main criterion for the correlation of the Fjosangerian Stagewith the Eemian is the pollen stratigraphy (Fig. 2), the most significant features of which are: (1) the very distinct successionalphases. (2) Early immigration of. Quercus. (3) Development of a dense Quercus-Corylasforest, with very sparse occurrence of other QM-constituents. (4) Alnus increasedat the samelevel as Corylus.(5) Late immigration of Picea, with a peak very late in the interglacial.The only main feature of the Eemian which is lacking is the Carpinu.sphase, which is almost certainly due to the northerly latitude of the Fjosanger locality. The vegetation during the deposition of gravel I, indicatesa mean summertemperatureslightly higher than at present(Fig.2). At the type locality, the lower boundaryfor the EemianStage is placedat a horizonwhen a closedforestwasestablished''.By comparisonwith the Holocenevegetationaldevelopmentit may be assumedthat the spread of Betula woodland at Fjosanger took place slightly later than at the type locality in the Netherlands.Actually, Fjosangerwasstill coveredby ice at the Weich-

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Fig. 2 The stratigraphyof the Fjgsangersite.The lithology of the bedsis simplifiedand only the mostimportant speciesof pollen and molluscs are shown. The temperature curves indicate mean air and sea temperaturesfor the warmest months, July and August respectively.The atmospherecurve is deducedfrom pollen data, the seacurve from molluscsand benthic foraminifera.

selian-Holocene boundary. Bearing this in mind, we have placed the lower boundary for the Eemian immediately after the deglaciation of the site, and we assumethat the error in this time correlation should not exceed some few hundred years. We have correlated the Eemian-Weichselian boundary with the Fjosangerian-Hordalandian boundary where the NAPpollen increasesfrom -5% to 30%. This clearly representsa complete deforestation of the area, and we assumethat all tree pollen types above this level, except possibly some Betula, are redeposited. The molluscs and benthic foraminifera lead to very similar conclusions,and therefore only the mollusc diagram is presented here (Fig. 2). The fauna indicatescold polar water in the lower part of the Eemian (silt M, Fig. 2) and thereafter a rapid increasein temperature due to the appearanceof the Atlantic Current. In beds I and J the fauna indicateswarmer water than along the coast today, and also species not known from Norwegian waters were (for example, Paruicardium papillosum). As someof the mulluscspecimensare only referredto bed I, and the benthic foraminifera indicatea shallowingduring the deposition of the upper part of this bed, it is dilficult to detect a possiblefall in temperatureduring the depositionof the upper part of bed I, but this must in any case have been very modest. From the depositionof bed I to that of bed H a drasticfall in temperature occurred, but the influence of the Atlantic Current is still detectable.In silt G, a polar fauna dominated, and during the deposition of this bed, glaciers were calving in the fiord. The fauna in gravel F indicatesthat the glaciershad retreated and this bed is assumed to correspond to an interstadial. Silt E represents another glaciomarine facies, above which the till follows. Whether or not a hiatus exists below the till is impossibleto determine. Three features of the FjOsanger section are of major importancefor correlationwith the NorwegianSeastratigraphy: (1) an oceaniccirculation pattern similar to that of the present was establishedin the lower part of the Eemian. (2) During most of the Eemian, coastalwaterswere as warm, or warmer, than at present. (3) A drastic cooling of the sea water occurred at the Eemian-Weichselianboundary.

In the cores from the Norwegian Sea (Fig. 3), the upper boundary of the warm pulse is very close to the 5e-5d boundary. At FjOsangerthe dramatic cooling of the seawater also occurred at the Eemian-Weichselian boundary, indicating thar the Eemian-Weichselian boundary is nearly synchronous with the 5e-5d boundary. These correlations are also supported by sea-level data from the North Sea area, for which Zagwijn2ahas given the best data. A major part of the transgressiontook place within the Eemian, indicating that the Eemian started long before the peak of the tto/tuo curve. Around the Eemian-Weichselian boundary, Zagwijn2afound a drop in sea level of 32 m, of which half took place within the Eemian. Compared with the t8O/160 sea-level curve derived by Shackletonand Opdyker, this suggeststhat the Eemian-Weichselian and the 5e-5d boundaries are synchronous. The sea-leveldata are also a very stong argument, independent of the main theme of this paper, that the Eemian should be correlatedwith 5e, and not a larger, or other part of stage 5.

The onset of the last glaciation The forests at Fjosanger during the later part of the Eemian indicate a climate which excluded the growth of any large ice-massesin Scandinavia. The drop in sea level during the Eemian thus indicates that the growth of ice sheets started earlier in North America and/or Antarctica than in Scandinavia. At Fj6sanger the glaciomarine silt G (Fig. 2) confirms that glaciersapproachedBergen early in the Weichselian.From the ",,

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Correlation with the deep-searecord Kelloggt'to studied cores from the Norwegian Sea. Mainly by meansof two faunal indices(Fig. 3), he hasshown that only once during the past 450,000 yr has the surface water of the Norwegian Seabeen aswarm, or warmer, than during the Holocene. t "O/ toO ratio has been measuredin two of the coresfrom The '. the Norwegian Sea,and one core from the Denmark Straighto world in the ocean used younger stages oxygen-isotope The stratigraphywere clearly recognisedin thesecores (Fig. 3). The dominant factor determining the surface temperature of the seaboth in the easternNorwegian Seaand along the coastof Norway is the Atlantic Current. From a theoretical point of view, it is clear that faunas from the Norwegian coast, and the surface of the eastern Norwegian Sea, can be correlated by meansof their temperaturerequirements.This is in accordance with knowledgeof the present-dayzoogeography,and alsowith geological correlations of the major change in the current ". pattern 10,000-13,000 yr ago'o 'warm pulse' The described by Kellogg can therefore be unambiguouslycorrelatedwith the warm-water phase at Fjosanger. The warm pulse in the Norwegian Sea appears at the same level as the oxygen-isotopestage 5e. As the warm-water phase at Fjosanger occurred within the Eemian, the Eemian Stagecan be correlatedwith the oxygen-isotopestage5e. Concerninga more precisecorrelationof the boundaries,the 6-5e boundary in the cores V 28-56 and K-11 (Fig.3) is significantly below the warm pulse. At Fjosanger there is also a cold fauna in the lower Eemian. We have deduced.however. a high sedimentationrate for this part of the stratigraphy,and thus a short time period. This would indicate that the lower boundary for the Eemian is slightly above the 6-5e boundary.

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Fig. 3 The stratigraphy of two Norwegian-Sea cores (Fig. 1): a , K - 1 1 ; b , Y 2 8 - 5 6 ; a c c o r d i n g t o K e l l o g g , D u p l e s ^ s ya n d t'O/toO S h a c k l e t o n a .T h e c u r v e s r e p r e s e n t ( f r o m t h e l e f t ) : t h e (numbers), right-coiling % the oxygen-isotope stages curve; species (warm) ol Globigerina pachyderma, and o/owarm-water foraminifera soecies.

presentday topographyand climate,one can concludethat these first glaciersdescendedfrom mountainsin the vicinity, and were not outlets from an inland-ice.These glaciersretreated at least once (bed F, Fig. 2) before Fjgsangerwas covered by ice. The vegetational successionduring the upper part of the Eemian indicates, in our opinion, a climatic deterioration. However, the drasticfall in temperatureat Fjgsangeroccurred simultaneouslyin the sea and on land at the Eemian-Weichselian boundary. There can be no doubt that the causeof the sudden cooling was a weakening of the flow of the Atlantic Current into the. Norwegian Sea. If the Atlantic Current was 'switchedo{T'the sequencedescribedwould result, whether or not this event was preceded by, or caused by, a climatic deterioration.

The radiometric age of the Eemian From the toC isotope enrichment method, the age of the early Weichselian interstadials has been estimated as 55.00070,000 yr Bp2s,and the Eemian is commonly assumedto be slightly older. Another approach is correlation with tropical coral reef terraces, dated with the U-series methods. Shackleton and Matthews26showed that the oxygen-isotopestage 5e can be correlated with the Barbados III terrace, dated to 125,000yr Bp. Accepting the correlation of 5e with the Eemian, this age should also apply to the Eemian. There is a significantdiscrepancyin the resultsfrom the two methods. At present we find the U-series agesmost probable. We thank Dr N. J. Shackletonand K. BiOrklund for helpful

criticisms and Dr B. Robins for correcting the English. The project was supported by grants from The Royal Council for Scientificand IndustrialResearchand The Norwegian Research Council for Scienceand Humanities.

Received 18 Septembe| accepted 15 Novcmber l97ii. 1. 2. 3. 4. 5. 6. 7. ll. 9. 10.

S h a c k l t o n ,N . J . & O p d y k e , N . D . O e d r . R € r . 3 , 3 9 5 5 ( 1 9 7 - i l . S h a c k l e t o n ,N . J . & O p d y k e . \ . D . G e o l . S o ( . A m . M e n . 1 4 5 , , 1 , 1 9 , 4 6 j I 1 9 7 6 ) . K e l l o g g ,T . L ] . G e o l . s o c .A m . M e m . 1 i 1 5 . 7 7 I l 0 ( 1 9 7 6 ) . K e l l o g g ,T . B . , D u p l e s s y ,J . C l .& S h a c k l e r r n ,N . J . B o l e d r 7 , 6 l 7 3 ( 1 9 7 8 ) . D u p l e s s y ,J . C . , C h e n o v a r d ,t - . & V i l a , F . S c i e n c e1 8 8 , 1 2 0 8 1 2 0 9 I 1 9 7 5 ) . Shacklcton, N. J. Proc. R. Soc. B 174. 135-154 ( 1969). Shackleton, N. J. & Heusser, L. Abstt. X INQUA Congr. Birmingham t 977, 116 | l9'7'l ). Andersen, S. T., Vries, H. de & Z-agwijn, W. H. Geol. Miinh.39,3i1 42 d960) M a n g e r u d , J . , A n d e r s e n . S . T . . B e r g l u n d , B . E . & D o n n e r , J . J . B o r e o s 3 , l 019Z ' l t l 9 ' / 1 ) . Zagwijn,W.H.&Staaldvinen,C.J.yanToelithtinghijG?ologischeoterzichrskaartencan N e d e r l a n d( R i j k s G e o l . D i e n s t . ,H a r l e m , 1 9 7 5 ) . 1 L Zagwijn, W. H. Med. geol. Sticht., nietwe Ser. 14, 1 5-.15 ( 196 I ). 1 2 . A n d e r s e n ,S . T . B a l / . g e o l . S o c .D e n m a r k 1 9 , 9 0 1 0 9 ( 1 9 6 9 ) . 13. Menke, B. & Behre, K. E. EiszeitaLrerGegenw.23121,251-261 \19'/3). 1 . 1 U i ) i l l a f d . G . M . A c f u r g @ { . L o t d n i e n i al ; l , 1 l 6 l i ( l 9 7 t r : e u r i l Rtt 9. I llrlgTNr l - 5 . A n d e r s e n .S . - l ' . D a n m . G e o l . U n d e r s - ,I I . R a e k k e 7 2 \ ) 9 6 t t . 16. Averdieck, F.-R. in Frilhe Menschheit und Umwelt 1I (eds Gripp, K.. Schrlrrumpf, R. & S c w a b e d i s s e nH, . ) l 1 ) 1 - 1 2 5 t K o l n c r a z , 1 9 6 7 1 . 17. Mangerud, J.. Sonslegaard,E. & Scjrup. H. t,. Abrrr XIi\:QtiA Citngr. Birninghon 1977. 286 (.19'7'7). 18. Haldorsen, S.. Mangerud. J.. Sejrup, H.-P. & Sgnstegaard,E. Dept Geol. Agricuh. Llnit. Nor||ay, Rep.7, I-39 ( 1978). 19. Kellogg, T. B. Mar. MicropaL.2, 235-219 1197't). 2 0 . R u d d i m a n , W . F . & M c l n t y r e , , 4 , .Q u a r R e s . 3 , 1 1 7 1 3 0 ( 1 9 7 1 ) . 21. Ruddiman, W. F., Sancctta, C. D. & Mclntyre. A. Phil. Trans. R. Soc. a 280, I 19 1,12 119'7'7). 22. Mangerud, J. Nor. Geol. Tidsskr.57,23-51 \19'/7t. 23. Vorren, T. Ouar. Res. (in rhc pressl. 24. Zagw rjn, W. H. Abs.r X I NQ U A Con gr. B i rmi nsham | 9 7 7, 5tJ9\ 19j j ). 2 5 . G r o o t e s , P . M . t h e s i s .G r o n i n g e n U n i v . ( 1 9 7 7 ) ; S c i e n c e2 O O ,l l l 5 ( 1 9 7 8 1 . 26. Shackleton, N. J. & Matthews. R. K Ndretu, 268. 6 I 8-620 { I 977 l

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