Last Interglacial marine environments in the White Sea region,northwestern Russia

KARI GRSFJELD, SVEND FUNDER, MARIT-SOLVEIG SEIDENKRANTZ AND CHRIS GLAISTER

BOREAS Grsfjeld, K., Funder, S., Seidenkrantz, M.-S. & Glaister, C. 2006 (August): Last Interglacial marineenvironments in the White Sea region, northwestern Russia. Boreas, Vol. 35, pp. 493520. Oslo. ISSN 0300-9483.Marine sediments from river sections in the Mezen River drainage, northwest Russia, have been analysed fordinoflagellate cysts, foraminifers and molluscs. The sediments were dated by pollen analysis and by reference tothe local sea-level history, and are Late Saalian to late Eemian (c. 133 to 119.5 kyr in age). The Late Saaliandeglaciation was characterized by Arctic conditions, but a few centuries into the Eemian the Gulf Stream systemcarried warm Atlantic water into the region. At 129.8 kyr BP there was a marked increase in the influx of Atlanticwater, and the advection of warm Atlantic water was stronger and probably penetrated further eastwards than atpresent. The molluscs, dinoflagellate cysts and foraminifers reflect conditions warmer than present and thatthe optimum temperature occurred at the time of the early Eemian global sea-level rise. Around 128 kyr BP, theeustatic sea-level rise was curbed by isostatic rebound and accompanying regression and constriction of marinepassages to the White Sea. Local, low-saline, stratified basins developed and characterized the next five to sixmillennia.

Kari Grsfjeld (e-mail: Kari.Grosfjeld@ngu.no), Geological Survey of Norway, NO-7491 Trondheim, Norway;Svend Funder, Geological Museum, University of Copenhagen, DK-ster Voldgade 57, DK-1350 Copenhagen K,Denmark; Marit-Solveig Seidenkrantz, Department of Earth Sciences, University of Aarhus, C. F. Mllers Alle 120,DK-8000 Arhus C, Denmark; Chris Glaister, Westlakes Scientific Consulting, The Princess Royal Building,Westlakes Science and Technology Park, Moor Row, Cumbria, CA24 3LN, UK; received 28th October 2005,accepted 24th March 2006.

During the Last Interglacial, the Eemian, the NorthRussian lowlands were inundated by marine waters upto 400 km inland from the present coastline, the so-called Boreal Transgression. Here we describe marineenvironments from this period based on deposits alonga 200-km-long eastwest transect along the riverPyoza, a tributary of the Mezen River, southeasternWhite Sea region (Fig. 1). The study is based onanalyses of dinoflagellate cyst (dinocyst), foraminiferand mollusc assemblages in marine sediments exposedalong the rivers. The sediments in the sections are datedby pollen analysis as well as by their altitude and theirrelation to the sea-level history (Fig. 14; Table 1).

In our study area, the first recognition of the BorealTransgression and its correlation with the Eemian wassupplied by Ramsay (1904). Later, Devyatova &Loseva (1964) logged the stratigraphy of the riversections systematically. This work was summarizedand correlated with the stratigraphy of the entireArkhangelsk region by Devyatova (1982). Our investi-gation is based on this comprehensive and detailedwork, which guided us to the various localities.Devyatova & Loseva (1964) and Devyatova (1982)also produced pollen diagrams from the marine sedi-ments at several of the localities and these were usedfor dating and correlation within the Eemian.

Our fieldwork was undertaken in 1997 and 1998, anda general survey of the localities with emphasis on theglacial history has been published by Houmark-Niel-sen et al. (2001) and Kjr et al. (2001), while Nielsen &Funder (2003) described some mollusc faunas, empha-sizing their taphonomy. The late Quaternary history ofthe entire northern Russia was reviewed by Svendsenet al. (2004). A synthesis of the EemianWeichselianstratigraphy of the area is provided by Larsen et al.(2006).

The purpose of this study was to examine thehydrographical and climatic history of the White Searegion through the Late Saalian and Eemian. Compar-ing the signals from different fossil groups in the samesections provides a detailed picture of the environ-mental conditions and climate in the area. The WhiteSea is a semi-enclosed basin receiving a considerableinput of riverine water, introducing a local effect onmarine life forms. However, there is also significantinput of oceanic water from the Murman CoastalCurrent, which is a continuation of the NorwegianCoastal Current, and a part of the Gulf Stream system.Combining information from the various fossil groups,we distinguish the effect of local signals from theregional oceanic ones and date the onset of the coastalcurrent and thereby of the North Atlantic surfacecirculation in the Eemian.

DOI 10.1080/03009480600781917 # 2006 Taylor & Francis

Present hydrography and biology

The White Sea is a semi-enclosed body of waterreceiving a large input of river runoff. It communicateswith the Barents Sea through a broad, less than 50 mdeep, channel (Zenkevitch 1963; Berger & Naumov2000; Berger et al. 2001). Compared to the Barents Sea,the climate is continental with relatively warm sum-mers and cold winters. Whereas the deep water hasyear-round temperatures of about 08C, the 10 to 40-m-thick surface water layer has temperatures duringsummer ranging from 7 to 158C. In sheltered bays,temperatures may reach even higher values. Duringwinter, the surface temperature falls to /1.68C and/1.78C in the northern and southern parts of thebasin, respectively. The salinity varies strongly in thebasin, with its highest values in the northern and

central parts of the sea; here the salinity of the surfacewater and the deep water is 2526 and 3031,respectively. Salinity is lowest in bays at the vicinity ofthe river mouths (B/1520). From November to May,drifting sea ice covers the sea and fast ice occurs in thebays near the river mouths. The mean amplitude of thetidal oscillations is c. 1 m, rising to 810 m in the bays.The nutrient content in the White Sea is low, pre-sumably related to the low nutrient content of thefluvial waters that enter the sea (Polyakova et al. 2003).The modern hydrological regime in the White Sea iscontrolled by the interplay between river runoff andwater exchange with the Barents Sea. The inflow ofnormal marine waters to the White Sea causes two-thirds of the basin water to be renewed annually. Incontrast, the southern Barents Sea is characterized bythe strong advection of relatively warm, saline Atlantic

Present coastline

Eemian coastline

>200 m Eemian water depth

water mixed with coastal water of the Murman CoastalCurrent with a salinity of c. 34 (Schauer et al. 2002;Ingvaldsen et al. 2004). Maximum inflow of Atlanticwater occurs during winter, and while summer surfacetemperatures on the Murman coast do not exceed 88Cthe winter temperatures never drop below 38C, and thecoastal area is ice-free almost as far as the entrance tothe White Sea.

The reduced salinity of the White Sea has an adverseeffect on the mollusc fauna, which in all parts isconsiderably impoverished compared to that of theadjacent Barents Sea. The lowest diversity occurs inthe shallow, low-saline Mezen Bay (Berger et al. 2001).The large temperature range, seasonally and geogra-phically, results in a mixture of zoogeographic assem-blages. At the foreshore in protected bays there aredisjunct occurrences of thermophilic species, commonto the Murman coast, while the deeper water hosts apeculiar low diversity and distinctly Arctic assemblage

(Galkina et al. 2000; Naumov & Fedyakov 2000). Thecombination of marine, Arctic species and shallow-water, low-salinity, thermophilic species is also seen inthe foraminiferal faunas. The modern foraminiferalfaunas of the White Sea consist exclusively of benthicforaminifers, in particular many agglutinated taxa, assalinities are too low to sustain planktonic forms. Inthe deeper basins of the White Sea the calcareous faunaconsists of typical Arctic species, while the fewthermophilic, low-salinity species are restricted tonear-coastal localities that are subject to summerheating (Mayer 1962, 1980). The total number ofphytoplankton taxa in the White Sea is much lowerthan in the Barents Sea (Makarevich & Larionov1992), and almost all phytoplankton species found inthe White Sea also occur in the Barents Sea. Thedinocyst assemblages are strongly dominated by cystsof autotrophic forms, particularly Operculodiniumcentrocarpum and Spiniferites ramosus (Polyakova

141

06

11

3 m a.s.l. 38 m a.s.l.56 m a.s.l. 12 m a.s.l.

4

20 m a.s.l.

12

37 m a.s.l.

8 10

30 m a.s.l. 31 m a.s.l. 49 m a.s.l.

13

24

58 m a.s.l.48 m a.s.l.

D

Peat

Sand

Gravel

Mud (laminated)

Diamicton

Till

Glaciotectonicunconformity

32

30

28

26

24

22

Thick

ness

(m a.

s.l.)

x

Deflation structureSoil

Ice wedge

Detritus gytja

Wood fragments

Plant detritus

Whole shells in life position

Shell fragmentsClasts

Cross laminatedplanar/through

Cryoturbation

Crossbedding

Sand with plant detritus

E

Fig. 1. (Continued)

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 495

et al. 2003; Golovnina 2005). Although the assem-blages contain a minor proportion of dinocysts that arecharacteristic of Arctic conditions, they are dominatedby taxa that tolerate a wide range of temperatures. Nothermophilic or north temperate dinocyst taxa havebeen recorded.

Thus, the present White Sea faunal and floralassemblages have low diversities and contain a mixtureof cold and warm species, and species that tolerate lowsalinity. In contrast, the faunas in the southern BarentsSea are diverse, and contain species requiring highsalinity. Although summer temperatures in the south-ern Barents Sea are much lower, the mollusc fauna havemore warmth-demanding boreal elements.

Methods

The preparation of dinocyst samples followed standardpalynological methods, using cold HCl and HF toremove carbonate and silicate particles (Rochon & deVernal 1994). No oxidation was used. The fractionlarger than 10 mm was examined. Glycerine jelly orElvacite was used as the mounting medium to makepermanent slides. Cyst counts of a minimum of 300specimens in each sample were attempted, but this wasnot possible for all samples owing to the high contentof organic material. Lycopodium tablets were added tocalculate concentrations (cysts/g of dry sediment;Stockmarr 1971). The dinocyst nomenclature followsRochon et al. (1999), Fensome & Williams (2004) andHead et al. (2001b). Most of the specimens could beidentified to species level, and those which are includedin Brigantedinium spp. usually represent B. simplex(Fig. 15, no. 5). The recorded dinocysts and theiroccurrence are listed in Table 2.

The samples for foraminifer analyses were treated inthe laboratory following standard techniques (Feyling-Hanssen 1983; Knudsen 1998). For each sample, 100200 g of dry sediment was weighed and washed through

sieves with mesh sizes of 0.063, 0.1 and 1.0 mm. Thethree fractions were successively dried and weighed,thus giving a rough measure of sediment grain size. Theforaminifers from the 0.11.0 mm fraction were con-centrated using a heavy liquid with a specific gravity of1.8 g/cm3. The residue, after treatment with heavyliquid, was nearly barren of foraminifers and wasdisregarded in the analyses. Where possible, a mini-mum of 300 specimens of foraminifers were identified,counted and handpicked in the concentrated 0.11.0 mm fraction. With the exception of a few, veryrare, planktonic specimens, only benthic foraminiferswere present in the samples. The diversity of thebenthic foraminiferal faunas was calculated using theindex of Walton (1964). The recorded foraminifers arelisted in Table 3.

Mollusc and cirriped samples were collected fromselected levels in the sections representing varioussedimentary units. Their species composition is givenin Table 4, based, wherever conditions allowed, onidentification and counting in the field, and shown aspercentages of a sum of c. 100 shells and fragments. Inaddition, sediment samples of up to c. 100 kg weresieved in the field through a mesh of 0.7 mm and lateranalysed for species in the laboratory. The frequenciesof molluscs and cirriped shells which may be artifi-cially separated and fragmented are noted in the tableby simplified frequency groups. The table also givesthe species requirements to salinity from sourceslisted by Funder et al. (2002). A number of speciesdo not occur in the present White Sea. These arepartly Arctic species, which are widespread in theadjacent Barents Sea, and their absence can best beexplained by their low tolerance to reduced salinity inthe White Sea. The Boreal indicators form anothergroup, which now have their northern limit in theNorwegian or western Barents Sea. As discussedbelow, these species indicate warmer water or a largerinflow of Atlantic water than today. The taxonomicalnomenclature generally follows Le Renard (1997) and

Table 1. Age of pollen zones. For sources, see text.

1) Pollen zone Years into Eemian Age, kyr Sea level, m above present Locality (loc. no.)

from to from to from to

Zone 5 E6 7 000 11 000 124 119.5 B/22 to /12 B/12 Zaton (0)Zone 4 E5 3 000 7 000 128 124 /45 B/22 to /12 Zaton (0), Bychye (1),

Orlovets (11,12),Zone 3 E3b-E4 750 3 000 129.8 128 /45 /45 Zaton (0), Bychye (1),

Yolkino (13,14)Zone 2 E1-E3a 0 750 131 129.8 /62 /45 Zaton (0), Bychye (1),

Viryoga W (4), Viryuga E (6),Kalinov (8), Yatsevets (10);Burdui (24)

Zone 1 133 131 Zaton (0), Bychye (1), Viryuga W (4),Viryuga E (6), Kalinov (8),Yatsevets (10)

1) Zagwijn (1986).

496 Kari Grsfjeld et al. BOREAS 35 (2006)

Poppe & Goto (1991, 1993), who give comprehensivesynonyms.

Age, sediments and sea-level change

Dating the marine sediments at each locality wasachieved using a combination of pollen analysis andreference to sea-level history (Fig. 14; Table 1). Pollendiagrams, published by Devyatova & Loseva (1964)and Devyatova (1982) from Zaton (loc. 0) and Bychye(loc. 1), are shown in a simplified version in Figs 2, 3,10. In addition, we present a new diagram fromOrlovets (loc. 12, Fig. 10).

The long-distance-transported pollen from the de-ciduous forests c. 600 km to the south permits correla-tion with the northwest European pollen stratigraphy(Table 1). In the pollen diagrams we distinguish thefollowing zones: (1) Late Saalian: treeless vegetation,

until increase of birch and oak; (2) early Eemian: birch,pine and oak, until the arrival of Corylus; (3) earlyEemian: oak, elm and hazel, until the arrival ofCarpinus; (4) middle Eemian: Carpinus, Quercus andCorylus, until the disappearance of these species; (5)late Eemian: a return to Betula and conifers.

We propose absolute ages for the pollen zonesfollowing Funder et al. (2002) and Lambeck et al.(2006) (Table 1; Figs 2, 3). This is based on thecounting of annual varves in northern Germany(Muller 1974), and their correlation with the northwestEuropean sea-level history using the Eemian globalhighstand at 1299/1 kyr BP and c. 3000 years into theinterglacial as a reference point (Zagwijn 1983; McCul-loch & Esat 2000; Caspers et al. 2002), assuming thatdifferential isostasy was compensated by tectonicsubsidence (Lambeck et al. 2006). As noted above,Pyoza was c. 500 km to the north of the deciduousforests, and the pollen must have come by upper

Table 2. List of marine dinocyst and palynomorph taxa recorded from loc. 1, Bychye and loc. 12, Orlovets (/ indicates presence; indicatesabsence).

Loc. 1Bychye

Loc. 12Orlovets

Cysts of heterotrophic dinoflagellatesBrigantedinium simplex (Wall 1965) ex Lentin and Williams 1993 / /Brigantedinium spp. Reid 1977 ex Lentin and Williams 1993 / /Echinodinium karaense Head et al. 2001 / /Islandinium? cezare (de Vernal et al . 1989 ex de Vernal in Rochon et al. 1999) Head et al . 2001 / /Islandinium minutum (Harland and Reid in Harland et al. 1980) Head et al. 2001 / /Islandinium spp. indet. / Lejeunecysta sp.1 in Head et al. (2005) /Polykrikos schwartzii Butschli, 1873 /Polykrikos sp. morphotype 1 in Kunz-Pirrung 1998 / /Protoperidinium stellatum (Wall in Wall and Dale 1968) Head in Rochon et al. 1999Selenopemphix quanta (Bradford 1975) Matsuoka 1985 / /Trinovantedinium applanatum (Bradford 1977) Bujak and Davies 1983 /Votadinium spinosum Reid 1977 /Xandarodinium xanthum Reid 1977 /

Cysts of autotrophic dinoflagellatesBitectatodinium tepikiense Wilson 1973 / /Impagidinium pallidum Bujak 1984 / /Lingulodinium machaerophorum (Deflandre and Cookson 1955) Wall 1967 / /Nematosphaeropsis labyrinthus (Ostenfeld 1903) Reid 1974 / /Operculodinium centrocarpum sensu Wall and Dale 1966 / /Pentapharsodinium dalei Indelicato and Loeblich III 1986 / /Spiniferites elongatus Reid 1974 / /Spiniferites frigidus Harland and Reid in Harland et al. 1980 / Spiniferites membranaceus (Rossignol 1964) Sarjeant 1970 / /Spiniferites mirabilis (Rossignol 1964) Sarjeant 1970 /Spiniferites pachydermus (Rossignol) Reid 1974 /Spiniferites ramosus (Ehrenberg 1838) Mantell 1854 / /Spinifereites sp. A /Spiniferites sp. B /Spiniferites spp. / /

Pre-Quaternary cysts / /Other palynomorphs (acritarchs, green algae)

Halodinium sp. Bujak 1984 / /Radiosperma corbiferum Meunier 1910 / /Acritarch sp. A /Pediastrum spp. / /Botryococcus cf. braunii of Kunz-Pirrung 1998 / /

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 497

atmospheric transport, and therefore probably gives abroad regional signal of the arrival of trees in this partof northern Europe. This delay was probably less than500 years, as argued by Zagwijn (1996) for the northEuropean deciduous forest. The northwest EuropeanEemian therefore began at 131 kyr and ended atc. 119.5 kyr BP, with northern Russia deglaciatedc. 2 kyr before the beginning of the Eemian. The datesfor our pollen zones are: Zone 1, Late Saalian (c. 133131 kyr BP); zone 2, earliest Eemian (131129.8 kyrBP); zone 3, late early Eemian (129.8128 kyr BP),Zone 4, mid-Eemian (128124 kyr BP); zone 5, lateEemian (124119.5 kyr BP) (Table 1).

The foreshore deposits that mark the end of marineEemian sedimentation reflect sea level at the time whenthe regional regression reached each locality. Theforeshore sediments at the highest elevation (loc. 6)therefore reflect the earliest stage in the regression,while those at the lowest elevation (loc. 0) are younger.For the underlying deposits of glaciomarine mud anddiamicton that predate the regression, the sea level canbe inferred on the basis of their fauna. For example, inthe deglacial mud at Viryuga E (loc. 6) the foraminiferssuggest a water depth of no more than 50 m, indicatingthat the deglacial marine limit at this locality probablywas no higher than 100 m a.s.l. This value is slightly

Table 3. The occurrence of foraminifer taxa at the different localities (/ indicates presence; indicates absence).

Loc. 1Bychye

Loc. 6Viryuga E

Loc. 11Orlovets

Loc. 12Orlovets

Loc. 10Yatsevets

Loc. 8Kalinov

Calcareous foraminifera Amphycoryna scalaris (Batsch, 1791) / Astrononion gallowayi Loeblich Tappan, 1953 / / / / / /Astrononion stelligerum (dOrbingy, 1839) / Bolivina pseudoplicata HeronAllen & Earland, 1930 / Brizalina pseudopunctata (Hoglund, 1947) / Buccella frigida (Cushman, 1922) / / / / / /Buccella frigida calida (Cushman Cole, 1930) / / / / /Buccella hannai arctic Voloshinova 1960 / / Buccella tenerrima (Brady, 1950) / / Buliminella elegantissima dOrbigny, 1839 / / / Cassidulina reniforme Nrvang, 1945 / / / / / /Cibicides lobatulus (Walker Jacob, 1798) / / / / / /Discorbis nitida (Williamson, 1858) / Discorbis spp. / /Elphidiella groenlandica (Cushman, 1933) / /Elphidium albiumbilicatum (Weiss, 1954) / / / / / /Elphidium asklundi Brotzen, 1943 / / / / /Elphidium bartletti Cushman, 1933 / / / / / /Elphidium excavatum , forma clavata Cushman, 1930 / / / / / /Elphidium gerthi van Voorthuysen, 1957 / / / Elphidium hallandense Brotzen, 1943 / / / / / /Elphidium incertum (Williamson, 1858) / / / Elphidium magellanicum HeronAllen & Earland, 1932 / Elphidium margaritaceum (Cushman, 1930) / / / Elphidium tumidium (Gudina, 1969) / / /Elphidium ustulatum Todd, 1957 / / / / /Elphidium williamsoni Haynes, 1973 / / / Eoeponidella pulchella (Parker, 1952) / / / /Epistominella takayangii Iwasa, 1955 / / / / /Epistominella vitrea Parker, 1953 / / / Fissurina danica (Madsen, 1895) / / / Fissurina furcillifera (Buchner, 1940) / / / Fissurina laevigata Reuss, 1850 / / / / /Fissurina semimarginata (Reuss, 1870) / Fissurina sp. /Glabratella arctica Scott Vilks, 1991 / Glandulina laevigata (dOrbigny, 1826) / / Haynesina depressula (Walker Jacob, 1798) / / / / / /Haynesina germanica (Ehrenberg, 1840) / / / Haynesina nivea (Lafrenz, 1963) / / / /Haynesina orbiculare (Brady, 1881) / / / / / /Islandiella helenae FeylingHanssen Buzas, 1976 / / / / / /Islandiella islandica (Nrvang, 1945) / / / / Islandiella norcrossi (Cushman, 1933) / / / /Lagena apiopleura Loeblich & Tappan, 1953 / / /

498 Kari Grsfjeld et al. BOREAS 35 (2006)

lower than predicted by Lambeck et al. (2006),indicating that the eustasy/isostasy balance weighedmore heavily towards the eustasy side than is assumedin the model. This hypothesis is supported by evidencefor the Eemian eustatic sea-level rise recorded mostclearly at Yatsevets (loc. 10), described below.

Localities

Among the nine investigated localities, the mostcomprehensive records come from Bychye (loc. 1)and Orlovets (loc. 12), where dinoflagellate cysts,foraminifers, molluscs and pollen have been analysed.

Pollen evidence also exists from Zaton (loc. 0) andViryuga W (loc. 4), but from the remaining localitiesonly molluscs and/or foraminifer records exist. Eco-zones were established for Bychye, Orlovets andYatsevets (loc. 10) based on the lithology and informa-tion from all groups of organic remains. The descrip-tion of sediments from each section is adapted fromHoumark-Nielsen et al. (2001).

Loc. 0, Zaton (Figs 1, 2, 14; Tables 1 and 2)

This cliff on the western side of the Mezen River wasfirst discovered and described by Ramsay (1904). Itis the most extensively studied locality containing

Loc. 1Bychye

Loc. 6Viryuga E

Loc. 11Orlovets

Loc. 12Orlovets

Loc. 10Yatsevets

Loc. 8Kalinov

Lagena gracillima (Seguenza, 1862) / / / / Lagena meridorionalis Wiesner, 1931 / Lagena mollis Cushman, 1944 / Lagena semilineata Wright, 1886 / Lamarckina haliotidea (HeronAllen & Earland, 1911) / / / Laryngosigma lactea (Walker & Jacob, 1798) / / /Lenticulina gibba (dOrbigny, 1839) / / / Lenticulina sp. / / / Marginulina costata (Batsch, 1791) / / / / Melonis barleeanus (Williamson, 1858) / / Miliolinella chukchiensis Loeblich & Tappan, 1953 /Miliolinella subrotunda (Montagu, 1803) / /Nonionella auricula HeronAllen & Earland, 1930 / / Nononellina labradorica (Dawson, 1860) / / / / / /Oolina borealis Loeblich & Tappan, 1954 / / /Oolina caudigera (Wiesner, 1931) / Oolina globosa (Montagu, 1803) / / Oolina lineata (Williamson, 1848) / Oolina melo dOrbigny, 1839 / / / /Oolina squamosa (Montagu, 1803) / / / Oolina williamsoni (Alcock, 1865) / /Parafissurina lateralis (Cushman, 1913) / / /Parafissurina sp. / Pattelina corrugata Williamson, 1858 / / / /Planorbulina mediterranensis dOrbigny, 1826 / / Polymorphinidae / / / / / /Pullenia osloensis FeylingHanssen, 1954 / Pyrgo williamsoni (Silvestri, 1923) / / /Quinqueloculina agglutinata Cushman, 1917 /Quinqueloculina seminulum (Linne, 1758) / / /Quinqueloculina stalkeri Loeblich & Tappan, 1953 / /Stainforthia feylingi Knudsen & Seidenkrantz, 1994 / / /Stainforthia fusiformis (Williamson, 1858) / Stainforthia loeblichi (FeylingHanssen, 1954) / / / Trifarina angulosa (Williamson, 1858) / / /Trifarina fluens (Todd, 1947) / / / /Valvulineria arctica Green, 1960 /

Agglutinated foraminifera Deuterammina ochracea (Williamson, 1858) / / Portatrochammina bipolaris Bronnimann & Whittaker, 1980 / /Recurvoides turbinatus (Brady, 1881) /

Planktonic foraminifera Neogloboquadrina pachyderma (sinistral) (Ehrenberg, 1981) / Turborotalita quinqueloba (Natland, 1938) / / /

Table 3 (Continued)

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 499

Table 4. Molluscs and cirriped faunas from the Mezen area.

/

Sali

nit

y

dem

an

d; /

No

tp

rese

nt

in

/

Wh

ite

Sea

tod

ay

Loc. 0, Zaton Loc. 1, Bychye Loc. 4,Viryjoga W

Loc. 6, Virjoga E

Sample No./ 9

71

17

/ 97

11

6

/ 97

11

5

/ 97

12

1

/ 97

12

0

/ 97

12

2

/ 98

43

6

/ 97

11

9

/ 97

12

8

/ 97

12

7

/ 97

13

0

/ 97

12

5

/ 97

12

4

/ 98

43

2

m a.s.l. 2 7.1 9 13 14 15.3 16 19 30 49 59 60 61 62ecozone by2 by2 by3 by4 by5

GASTROPODAPuncturella noachina (Linne, 1771) /26 /Solariella obscura Couthouy, 1838 /25 /Margarites costalis Gould, 1841 /26 /Solariella varicosa Mighels & Adams, 1842 /27 1Bittium reticulatum daCosta, 1778 /25 Boreal /Littorina littorea (Linne, 1758) /10 j / 1Littorina obtusata (Linne, 1758) /10 1?Littorina saxatilis Olivi, 1792 /8 /Marsenina glabra Couthouy, 1839 /26 /Natica clausa Broderip & Sowerby, 1829 /23 j / j 1Euspira pallida Broderip & Sowerby, 1829 /23 /Amauropsis islandica (Gmelin, 1791) /20 j /Epitonium greenlandicum (Perry, 1811) /29 /Acirsa coarctata (Jeffreys, 1884) ? /Trophon truncatus (Strom, 1767) /15 1 1Nucella lapillus (Linne, 1758) /12 Boreal j 2 /Buccinum undatum Linne, 1758 /14 / ? j j / / 1Neptunea communis (Middendorff, 1849) /27 /Neptunea despecta (Linne, 1758) /25 / / / /Oenopota conoidea (Sars, 1878) /25 j jOenopota harpa (Dall, 1884) /26 /Oenopota pyramidalis (Strom, 1768) /26Oenopota nobilis (Mller, 1842) /26 1 j j /Oenopota simplex ( Middendorff, 1849) /19Oenopota sp. indet. /Aartsenia candida (Mller, 1842) /29Retusa obtusa (Montagu, 1803) /25Cylichna alba (Brown, 1827) /22

BIVALVIANuculoma tenuis (Montagu, 1808) /15 1 11Nuculana pernula (Muller, 1779) /15 / 10 / 15 j /Yoldia lenticula (Mller, 1842) /34 Arctic 14Yoldia hyperborea (Torell, 1859) /30Portlandia arctica (Gray, 1824) 3Mytilus edulis Linne, 1758 /3 / / j j 1 6 j j 3 / 1 2 j j jCrenella decussata (Montagu, 1808) /25 1 jArctinula greenlandica (Sowerby, 1842) /30 Arctic 5 1Chlamys islandica (Muller, 1776) /15 / j / 1 / /Heteranomia squamula (Linne, 1758) /25 / j jAxinopsida orbiculata (Sars, 1878) /15Thyasira flexuosa (Montagu, 1803) /25 Boreal /Mysella bidentata (Montagu, 1803) /15 BorealAstarte borealis (Schumacher, 1817) /15 j j j j / / 3 1 j jAstarte crenata (Gray, 1824) /30 Arctic j j j 7 j jAstarte elliptica (Brown, 1827) /15 j j j 1 j j 1 / j /Astarte montagui montagui Dillwyn, 1817 /15 j j 2 j j 9 1 ?/Astarte sp. juv. /15 j / j j jParvicardium elegantulum (Mller, 1842) /30 Arctic / /Parvicardium ovale (Sowerby, 1840) /25 Boreal 1Cerastoderma edule (Linne, 1758) /15 BorealCiliatocardium ciliatum (Fabricius, 1780) /15 1 j 3 j j / /Serripes groenlandicus (Bruguie`re, 1789) /15 / / / 9 1Spisula elliptica (Brown, 1827) /15 Boreal j j / 2 /Macoma balthica (Linne, 1758) /3 j / 5 / 2 j j j / j /Macoma calcarea (Gmelin, 1791) /5 j j 7 6 26 j j j 55 j j j 21 17 j j jAbra prismatica (Montagu, 1803) /30 BorealArctica islandica (Linne, 1767 ) /25 j j j / 1 j j 12 / ? j /Mya truncata Linne, 1758 /5 / 3 3 j / 1 j j j j 20 27 j j jCorbula gibba (Olivi, 1792) /15 Boreal /Hiatella arctica (Linne, 1767) /15 j 80 j j / / j j j 96 6 5 j j jPanomya arctica Spengler, 1793) /5 Boreal j j / /Zirfaea crispata (Linne, 1767) /25 Boreal / 5 /Lyonsia norvegica (Gmelin, 1791) /25 Boreal /

SCAPHOPODADentalium entalis (Linne, 1771) /25 Arctic / 1 1 j 8 1

CIRRIPEDIAVerruca stroemia (Muller, 1776) /25 17 / jBalanus balanus (Linne, 1758) /15 / 3 j j j j / 41 48 j j jBalanus crenatus (Bruguie`re, 1789) /5 j j j j 4 3 1 / / jBalanus hameri (Ascanius, 1767) /25 / / 12 / jBalanus improvisus Darwin, 1854 /1 Boreal / j j / j j j jSemibalanus balanoides (Linne, 1758) /15 / 1 j j j j j 1 / 2 j j jBalanid sp. j j j j j j

j j j j/dominant; j j j/frequent (more than 20 valves or fragments); j j/common (10 19 valves or fragments); j/scarce (4 9 valves or fragments); //rare (1 3 valves or

500 Kari Grsfjeld et al. BOREAS 35 (2006)

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31 32 35 36 37 38 40 39 41 45 50 52 52 60 60 61shoreface foreshore

GASTROPODAPuncturella noachina (Linne, 1771) /26Solariella obscura Couthouy, 1838 /25Margarites costalis Gould, 1841 /26 jSolariella varicosa Mighels & Adams, 1842 /27Bittium reticulatum daCosta, 1778 /25 BorealLittorina littorea (Linne, 1758) /10 / / j / j jLittorina obtusata (Linne, 1758) /10Littorina saxatilis Olivi, 1792 /8Marsenina glabra Couthouy, 1839 /26Natica clausa Broderip & Sowerby, 1829 /23 /Euspira pallida Broderip & Sowerby, 1829 /23 / / / / j j j / jAmauropsis islandica (Gmelin, 1791) /20 j j j / j j jEpitonium greenlandicum (Perry, 1811) /29Acirsa coarctata (Jeffreys, 1884) ? /Trophon truncatus (Strom, 1767) /15Nucella lapillus (Linne, 1758) /12 BorealBuccinum undatum Linne, 1758 /14 / j j j j jNeptunea communis (Middendorff, 1849) /27 /Neptunea despecta (Linne, 1758) /25 /Oenopota conoidea (Sars, 1878) /25Oenopota harpa (Dall, 1884) /26Oenopota pyramidalis (Strom, 1768) /26 j j jOenopota nobilis (Mller, 1842) /26 j jOenopota simplex ( Middendorff, 1849) /19 jOenopota sp. indet. j j j / jAartsenia candida (Mller, 1842) /29 jRetusa obtusa (Montagu, 1803) /25 j jCylichna alba (Brown, 1827) /22 j j / j j

BIVALVIA j j / j j j /Nuculoma tenuis (Montagu, 1808) /15 / j j j j j j j j jNuculana pernula (Muller, 1779) /15Yoldia lenticula (Mller, 1842) /34 Arctic jYoldia hyperborea (Torell, 1859) /30 jPortlandia arctica (Gray, 1824) j j j j j j j j j j j j j jMytilus edulis Linne, 1758 /3 j j j / jCrenella decussata (Montagu, 1808) /25Arctinula greenlandica (Sowerby, 1842) /30 ArcticChlamys islandica (Muller, 1776) /15 / / jHeteranomia squamula (Linne, 1758) /25 /Axinopsida orbiculata (Sars, 1878) /15 /Thyasira flexuosa (Montagu, 1803) /25 Boreal j j j j jMysella bidentata (Montagu, 1803) /15 Boreal j j j j j j j j /Astarte borealis (Schumacher, 1817) /15 / j j j /Astarte crenata (Gray, 1824) /30 Arctic / / /Astarte elliptica (Brown, 1827) /15 jAstarte montagui montagui Dillwyn, 1817 /15Astarte sp. juv. /15Parvicardium elegantulum (Mller, 1842) /30 ArcticParvicardium ovale (Sowerby, 1840) /25 Boreal / j j j j / j j j /Cerastoderma edule (Linne, 1758) /15 Boreal / / jCiliatocardium ciliatum (Fabricius, 1780) /15 / j j /Serripes groenlandicus (Bruguie`re, 1789) /15 / / j j j j j j j j j j /Spisula elliptica (Brown, 1827) /15 Boreal j j j j j j j / j j j j j j jMacoma balthica (Linne, 1758) /3 j j j j j j / j j j j j j j j j j j j j / j j j / j j jMacoma calcarea (Gmelin, 1791) /5 / j j jAbra prismatica (Montagu, 1803) /30 Boreal j j j j j j j j j j j j j j j j j jArctica islandica (Linne, 1767 ) /25 j j / j j j j j j j j j j j j j j j j jMya truncata Linne, 1758 /5 j /Corbula gibba (Olivi, 1792) /15 Boreal j j j j j j j j j j j j j j j j j j /Hiatella arctica (Linne, 1767) /15 / /Panomya arctica Spengler, 1793) /5 Boreal / /Zirfaea crispata (Linne, 1767) /25 BorealLyonsia norvegica (Gmelin, 1791) /25 Boreal

SCAPHOPODADentalium entalis (Linne, 1771) /25 Arctic j j j j

CIRRIPEDIA j / j j jVerruca stroemia (Muller, 1776) /25 j j j j j jBalanus balanus (Linne, 1758) /15 j / /Balanus crenatus (Bruguie`re, 1789) /5 j j / j j j j /Balanus hameri (Ascanius, 1767) /25 j / / j j j j j j j j j j j /Balanus improvisus Darwin, 1854 /1 Boreal 4 j j /Semibalanus balanoides (Linne, 1758) /15 j j / j j j jBalanid sp. j / / j j j j j j j j j j j j j j

fragments). Figures % of field count.

Table 4 (Continued)

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 501

Eemian marine sediments in the region. The cliff is15 m high and c. 800 m long, and is eroded into afluvial terrace. It is mainly composed of marinesediments rich in mollusc shells (Devyatova & Loseva1964; Devyatova 1982). Miller & Mangerud (1985)analysed the shells for amino acids and Molodkov &Raukas (1988) and Molodkov & Bolikhovskaya (2002)ESR-dated the shells and reached the unlikely conclu-sion that the middle 2.5 m of the sediment represents c.40 kyr BP (82120 kyr) of continuous sedimentation.

The section at Zaton (loc. 0) shows marine clay atthe present river level, coarsening upwards into siltysand. In the upper part, gravel horizons, whichDevyatova (1982) interpreted as major discontinuities,are overlain by plane-laminated sand and silt, and theyare here interpreted as channel erosion and infillingcaused by incision during forced regression. Abovethis, low-angle, horizontally laminated sand reflects aforeshore facies. This is truncated and discordantlyoverlain by trough cross-bedded fluvial sand. Themarine sediments therefore reflect regression withevidence for forced regression in the upper part.

Devyatovas (1982) pollen diagram indicates that theearliest exposed marine sediment dates from the earlyEemian, shortly prior to the Corylus zone, with Corylusattaining continuous values from c. 0.5 m above riverlevel (Fig. 2). Continuous values for Carpinus beginc. 1.5 m higher up, and the incision phase took placeshortly before the disappearance of mixed oak forestpollen, which we correlate with the end of the Carpinuszone. In the overlying sand there is no pollen fromdeciduous trees, and we refer this level to our zone 5,late Eemian (Figs 2, 14; Table 1).

The mollusc faunas from the three marine unitsagree with the sedimentological interpretation indicat-ing decreasing water depth. The foreshore and thechannel-fill sediments, in particular, contain abundantshells. In the channel-fill they form densely packedhorizons with the shells convex up, reflecting strongcoastal, possibly tidal, currents in connection with thechannel erosion and infilling. However, in spite of thehigh specimen density, the faunas in these two unitshave low species diversity, and a bias towards thick-shelled species due to currents and waves is evident.The channel-fill is dominated by well-sized Hiatellaarctica, while the dominating mechanically resistantbarnacle plates in the foreshore sand indicate wavebattering. The most diverse fauna comes from thelower clay, where the scattered shells are commonly inlife position and, contrary to the other two faunas,represent a single habitat. In the earliest Eemian (zone2), sparse Spisula elliptica and abundant Arcticaislandica indicate that temperatures were slightly higherthan at present, and Dentalium entalis, Astarte crenataand Nucella lapillus show higher than present salinity(Table 4). However, all three mollusc faunas arecomposed mainly of widespread species and theclimate/hydrographic signal is weak. All three units

contain species that indicate higher than presenttemperature and salinity greater than 25. The singleshell of Corbula gibba from the channel-fill is probablythe northeasternmost occurrence of this species, whichis otherwise rare in the Russian faunas. Today, Corbulaoccurs in Norwegian fjords as far north as Hammerfest(Brattegard 2001). Another warm indicator, Balanusimprovisus, does not occur north of Troms. Thisspecies, like Corbula, prefers brackish water, and itsoccurrence in the youngest zone at Zaton may indicatedecreased salinity and diminished oceanic influence.

Loc. 1, Bychye (Figs 1, 3, 4, 5, 14; Tables 1 and 2)

The 500-m-long and 15-m-high section across the riverfrom Bychye village is typical of many exposures in theeroding meanders along the lower Pyoza River. TheBychye section was described by Devyatova & Loseva(1964) and Devyatova (1982). Molodkov & Bolikhovs-kaya (2002) ESR-dated molluscs from two levels. Thesection is dominated by grey, marine Eemian clay,deposited on an undulating surface of reddish Saaliantill. The till is exposed locally at river level, and is alsorepresented by clasts in the overlying marine clay. Themarine clay coarsens upwards into bioturbated clayeysilt. This is truncated by an erosional lag, which formsa distinct horizontal line through the section. Abovethis level, horizontally laminated sand and silt, togetherwith channel-incisions filled with laminated sand andsilt, indicate regression and shoreface and tidal condi-tions. This is truncated and overlain by cross-beddedfluvial sand from the Weichselian (Houmark-Nielsenet al. 2001).

Our lithological log is similar to that of Devyatova(1982), and her pollen diagram can be fitted directly toour observations, implying that the marine recordstarted in the Late Saalian (Fig. 3). Continuous valuesfor Corylus pollen begin c. 2 m above the base of themarine clay, and for Carpinus c. 1.5 m higher up. Valuesfor mixed oak forest, and the curve for Carpinus andother deciduous trees, continue upwards into theoverlying foreshore sand, suggesting that the recordends before 129 kyr, and does not continue into theWeichselian, as originally suggested by Devyatova(1982).

Although ending earlier, the sedimentary successionfollows the pattern seen at Zaton, and we interpret theerosional lag to mark a falling sea level and approach-ing wave base, and not a renewed transgression assuggested by Devyatova (1982). In our interpretation,the section thus spans between 3000 and 7000 years ofthe Eemian, but with a hiatus of unknown lengthtowards the end.

Samples for macro- and micropalaeontology werecollected in different years (1997 and 1998) and indifferent sections. Dinocyst samples cover only thelower part of the section, up to half a meter below thefirst erosional hiatus, and not the coarse-grained

502 Kari Grsfjeld et al. BOREAS 35 (2006)

sediment above this level. Mollusc faunas were ana-lysed from three levels spanning the entire marinesuccession, and samples for foraminifers were collectedfrom the entire marine interval (Fig. 3). The section hasbeen divided into five ecozones.

Ecozone By1 (1212.25 m a.s.l.). This ecozone ischaracterized by high (70%) values of the dinocystEchinodinium karaense, by the foraminifer Stainforthialoeblichi and by the relatively high frequencies of theforaminifers Elphidium asklundi and Haynesina orbicu-lare and the dinocyst Islandinium minutum (Figs 4, 5).The upper zone boundary is placed where the relativefrequencies of E. karaense and S. loeblichi decline andthe percentage of the dinocyst I. minutum increases. Nomolluscs were recorded in this zone.

The dinocysts E. karaense, I. minutum and Islandi-nium? cezare are commonly abundant in regions withseveral months of sea-ice cover and a very shortproductive season (Vernal et al. 1997, 2001; Headet al. 2001; Marret & Zonneveld 2003). The relativeabundances of these species are likely controlled by theavailability of preferred prey for their heterotrophicplanktonic stages. E. karaense is presently living in theKara and Laptev Seas (Head et al. 2001b; Kunz-Pirrung 2001), being abundant in river-proximal areas.The strong dominance of cysts of Echinodinium kar-aense (Fig. 15 nos. 1 and 2) is interpreted as reflectinghigh levels of nutrients in the water column. High levelsof nutrients may originate within the seasonal runofffrom the hinterland via the river systems. The high levelof nutrients is supported by the foraminifers Elphidiumexcavatum, forma clavata, Stainforthia loeblichi andIslandiella helenae (Figs 4, 5, 14; Steinsund et al. 1994;Polyak et al. 2002). The foraminifers Elphidium ask-lundi and Haynesina orbiculare are also known fromriver-proximal areas in the Kara and Laptev seas (Bude1997; Polyak et al. 2002). Bottom-water salinity nolower than 30 is indicated by the foraminifersCassidulina reniforme and Stainforthia loeblichi (Stein-sund et al. 1994; Korsun & Hald 1998).

Dinocysts and foraminifers therefore suggest highlevels of nutrients, low water temperatures, presumablyseasonal sea-ice cover, proximity to the coast and anopen connection to a cold ocean (Fig. 14). In agree-ment with Devyatovas (1982) pollen diagram, we referthis zone to the Late Saalian, our pollen zone 1.

Ecozone By2 (12.2513.75 m a.s.l.). At the base ofthe zone there is a drop in the relative proportion ofEchinodinium karaense and the dinocyst assemblagebecomes dominated by Islandinium minutum (Fig. 4). Itis not easy to explain the change from the E. karaensedominated assemblages to the I. minutum dominatedassemblages on the basis of the present knowledgeabout the distribution of these two species. It isobviously due to a change in the source of nutrients.I. minutum is characteristic of polar/subpolar areas. It

has been observed within a broad range of tempera-tures, salinities (down to 17), nutrient concentrationsand the duration of sea-ice cover (de Vernal et al. 1997;Marret & Zonneveld 2003). Several diatom species areassociated with sea ice during parts of their life cycle,living in or in close relationship to the sea ice. Afterbeing washed away from icefloes, they continue to growin the surface layer of the seawaters, between themelting block of sea ice and in polynyas (Polyakovaet al. 2003). Sea-ice diatoms may be the preferredsource of nutrients for the dinoflagellates of I. minu-tum. High primary productivity in the water issupported by abundant Islandiella helenae (foramini-fer), which also favours summer ice-edge productivityin areas of seasonal ice cover (Korsun & Polyak 1989;Steinsund et al. 1994). The high percentages of I.minutum reflect a short productive season with nutrientrich waters and possibly summer sea-ice and low watertemperatures.

The upwards decline of the river-proximal benthicforaminifers Elphidium asklundi and Haynesina orbicu-lare (Figs 4, 5; Polyak et al. 2002) likely reflectsincreasing salinity and a shift from a river-proximalto a more offshore setting. This environmental changemay explain the change from the E. karaense domi-nated to the I. minutum dominated assemblages. Thetemperature signal from the molluscs is weak withYoldiella lenticula indicating cold offshore conditions,

2

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lus

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Fig. 2. Locality 0 (Zaton) lithology and stratigraphy. The positionof the mollusc samples is shown on the left. The curves of selectedpollen taxa are modified after Devjatovas (1982) pollen diagram.Details on the ages of the pollen zones are indicated in Table 1.

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 503

while the sparse Parvicardium ovale, which at presenthas its northeastern limit on the Murman coast(Galkin 1998), suggests that temperature and salinitywere approaching those of the present southwesternBarents Sea (Table 4).

Towards the top of the zone, Islandinium minutumdeclines and the dinocyst and foraminifer faunabecome more diverse. A small bloom of the foraminiferElphidium bartletti, followed by a minor influx ofMiliolina and Epistominella spp. as well as the presenceof the molluscs Astarte crenata and Yoldiella lenticula,marks an upward transition to more oceanic and saline(salinity /34) water.

Operculodinium centrocarpum (9%), Pentapharsodi-nium dalei (7%) and Spiniferites ramosus (1%) appear inthe top of the zone, although two single specimens ofO. centrocarpum were recorded in zone By1. S. ramosusis a species that occurs within a broad range oftemperatures and salinities and in areas with up to 12months of sea-ice cover (Marret & Zonneweld 2003).However, because it occurs abundantly, together withO. centrocarpum, in the samples from the White Sea,which is strongly influenced by normal marine waters(Polyakova et al. 2003), its occurrence is probablyrelated to inflow of oceanic waters. Among the moderndinoflagellate cyst species, O. centrocarpum belongs tothose that tolerate the widest range of temperaturesand salinities. In contrast to many other species, itsurvives abrupt environmental changes (Wall et al.

1977). Nevertheless, it appears that its present distribu-tion in the Atlantic Ocean is associated with the NorthAtlantic Current, and that it is a good indicator formodern, North Atlantic water masses (Rochon et al.1999). Pentapharsodinium dalei occurs in a variety ofenvironments (Marret & Zonneweld 2003), but appearsto be abundant in stratified waters. It is particularlyprevalent as part of the spring bloom within fjordsystems (Dale 1977; Harland et al. 2004a, b). It appearsto thrive on the spring rise in temperature with theaccompanying rise in nutrients following the winterand equinoxal storms that mix the waters of the fjords(Harland et al. 2004a, b). Although there appears to bea pulse of encystment in the spring, the species hasbeen found in the water from March through toSeptember (Lewis et al. 1984). The species is oftenpresent in water with high numbers of diatoms thatalso follow a similar life strategy, but P. dalei is anautotrophic species that does not feed on othermembers of the plankton. P. dalei occurs in polarand subpolar shelf environments, influenced by NorthAtlantic waters with summer temperatures above 48C(Rochon et al. 1999; Voronina et al. 2001). Therefore,the significant occurrence of the dinocysts O. centro-carpum and P. dalei in the top of zone By2 probablyindicates the point in time when the Gulf StreamCurrent system started to influence the region, initiat-ing a surface water warming.

Fig. 3. Locality 1 (Bychye) lithology and stratigraphy. Thepositions of the molluscs, dinocyst andforaminifer samples are shown on theleft-hand and right-hand side, respectively.The curves of selected pollen taxa aremodified after Devjatovas (1982)pollen diagram. The ages of thepollen zones are indicated in Table 1.

504 Kari Grsfjeld et al. BOREAS 35 (2006)

The faunas in ecozone By2 thus reflect a graduallyincreasing inflow of Atlantic water and rising sea level.That the inflow of oceanic water was higher thanpresent is suggested by the high-salinity demandingforaminifer and mollusc species. In agreement withthe pollen analysis of Devyatova (1982), we refer thiszone to the earliest Eemian, our pollen zone 2 (Fig. 3).The faunas therefore show the onset and deep penetra-tion of the North Atlantic Drift already less than 750years into the Eemian.

Ecozone By3 (13.7516.75 m a.s.l.). The start of thiszone is characterized by the abrupt reduction of thedinocyst Islandinium minutum from 74% to 13%, theincrease of cysts of Pentapharsodinium dalei from 7% to74%, introduction of higher salinity demanding for-aminifers and by increased dinocyst and foraminiferspecies diversity.

The abrupt reduction of I. minutum and the domina-tion of P. dalei (4074%) in the lower part of this zonereflect increased length of the productivity season,increased temperature and increased advection of

Atlantic water into the region. This interpretation isbased on the occurrence of P. dalei in polar andsubpolar shelf environments, influenced by relativelywarm North Atlantic waters, as described above (By3).Increased influence of Atlantic water upward in thezone is also indicated by the increasing cyst speciesdiversity (Dale 1996) and the increasing relativeabundance of dinocysts produced by autotrophicdinoflagellates. Although the ratio of cysts of hetero-trophic dinoflagellates to cysts of autotrophic dino-flagellates (here referred to as the H/A ratio) isfrequently used in the literature as a proxy of upwelling(Dale 1996), it also appears to be a useful proxy for thedegree of influence of oceanic currents on the Arcticshelf. The heterotrophic dinoflagellates occur abun-dantly in areas where the nutrient level is high. Suchconditions exist not just in upwelling areas but also inareas which are strongly influenced by the riverineregime. At present, the regions of the Arctic shelf thatare the least influenced by Atlantic waters, i.e. the Karaand Laptev seas, have the highest proportion of cysts ofheterotrophic dinoflagellates (Head et al. 2001b; Kunz-

Fig. 4. Locality 1 (Bychye) dinoflagellate cysts. Relative frequencies and concentrations (no of cysts/g of dry sediment) of selected dinocysttaxa and total dinocyst concentration. Ecozones are indicated to the left. One of the samples in ecozone 2 is almost barren of dinocysts,containing a single specimen of Islandinium minutum , whereas up to 1230 specimens of I. minutum per gram of sediment were calculated in theother two samples in the zone.

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 505

Pirrung 2001). In the present White Sea, the H/A ratioincreases landwards. Cysts of autotrophic dinoflagel-lates in ecozone By3 are Opeculodinium centrocarpum,Spiniferites membranaceus, Spiniferites ramosus, Bitec-tatodinium tepikiense and Nematosphaeropsis labyrin-tus. B. tepikiense is characteristic of fully marineconditions in cold/temperate regions, and is rare inregions with sea-ice cover exceeding 4 months/year(Marret & Zonneveld 2003). According to Dale (1996)there is strong evidence from recent cyst distributionsthat even a few specimens of Nematosphaeropsis cystsmay be used as a definite signal of oceanic waterinfluence. However, this disagrees with Marret &Zonneveld (2003), who refer to several previous recordsof N. labyrintus from a range of salinity values down to108C and duration of sea-ice cover up to 12 months/year (Kuntz Pirrung 2001) in coastal shelf environ-ments. S. membranaceus is mainly found in coastalsediments with summer sea surface temperatures above128C and salinities not below 28.9 (Marret & Zonne-veld 2003). The benthic foraminifers Astrononiongallowayi, Islandiella norcrossi and Melonis barleeanusare also commonly associated with normal marine,oceanic waters (Figs 4, 5). Salinities around 3335are indicated by both foraminifers (Astrononiongallowayi and Miliolina) and molluscs (Astarte crenata,Dentalium entalis), suggesting that the advection ofoceanic Atlantic waters into the region during the

Eemian was greater than that at present (Fig. 5;Table 4).

The mollusc assemblages, with such boreal species asPanomya arctica, Spisula elliptica and Parvicardiumelegantulum, indicate significantly warmer and moreoceanic conditions than at present, possibly compar-able to present-day conditions in the southwesternBarents Sea, with summer and winter sea-surfacetemperatures at 8 and 38C, respectively, and little, ifany, sea ice.

Upward from the middle of the zone, the coarse-grained fraction of the sediment increases, accompa-nied by an increase in shallow-water foraminifers(Elphidium hallandense and Elphidium tumidum). Thisshows that the sea-level rise had come to an end andwater depth was decreasing. This is also seen in theappearance of shallow-water bivalves (Astarte borealis,Arctica islandica and Spisula elliptica). In addition, thebenthic foraminifer Astrononion gallowayi indicates anincreased energy level (Steinsund et al. 1994; Jenningset al. 2004). The peak occurrences of the foraminifersEpistominella spp. and Nonionellina labradorica mayindicate the increased primary production around thepycnocline (cf. Rytter et al. 2002; Jennings et al. 2004).

In summary, ecozone By3 details the developmenttowards warmer, saltier, shallower and more oceanicconditions with little or no sea ice. All the fossil groupsindicate that salinity and temperature increasedthroughout the zone. A higher than present inflow of

Fig. 5. Locality 1 (Bychye) foraminifers. Relative frequencies of selected species, species diversity (Walton 1964) and total foraminiferconcentration. Ecozones and pollen stratigraphy are shown to the left.

506 Kari Grsfjeld et al. BOREAS 35 (2006)

Atlantic water is indicated by the molluscs and thebenthic foraminifers.

Ecozone By4 (16.7518.75 m a.s.l.). The develop-ment observed in Ecozone 3 continues into Ecozone 4.The zone boundary is determined on the basis of anoticeable change in the hydrography, involving asignificant shallowing to B/2030 m.

The dinoflagellates of the Brigantedinium spp. ap-pear to bloom where there are abundant nutrients andwhere salinities are reduced (de Vernal et al. 2001). Thedistribution of Brigantedinium spp. in the shelf sedi-ments of the Arctic seas coincides with the distributionof the diatom species of the Chaetoceros genus(Polyakova et al. 2003). The highest abundance ofBrigantedinium spp. occurs where this genus predomi-nates in the plankton. The interpreted high levels ofnutrients may originate within the seasonal runoff fromthe hinterland via river systems. Therefore, a moreriver-influenced environment may explain the gradualincrease and strong dominance of Brigantedinium spp.(Fig. 15, no. 5) in this ecozone. This is supported byseveral thermophilic foraminifer taxa tolerating re-duced salinities. A high food supply is also inferredby the foraminifers Trifarina fluens and Buccella spp.(e.g. Steinsund et al. 1994; Rytter et al. 2002) andpossibly also the low but significant percentage (2%) ofthe dinocyst Lingulodinium machaerophorum (Dale1996) (Fig. 15, no. 6). Although L. machaerophorumhas been recorded from a wide range of salinities, itseems to favour reduced but changing salinity and astratified water column (Reid 1975; Gundersen 1988;Dale 1996; Grsfjeld & Harland 2001).

In the dinocyst assemblages, increasing length of theproductivity season and increasing water temperatureare reflected by the further decrease of the dinocystIslandinium minutum and the occurrence of Lingulodi-nium machaerophorum (Lewis & Hallet 1997; Dale1996, 2000). In the foraminifer assemblages, this isreflected by the decrease in the Arctic species Elphidiumexcavatum, f. clavata and Cassidulina reniforme, thedisappearance of the Arctic sea-ice indicator Islandiellahelenae (Fig. 5) and the appearance of the thermophilicTrifarina angulosa, Elphidium margaritaceum, Elphi-dium williamsoni, Elphidium gerthi, Haynesina germa-nica and Haynesina depressula. The further reductionin Arctic foraminifers in the middle and upper parts ofthe zone suggests that the warming trend was enhancedin these parts. The occurrence of the foraminiferTrifarina angulosa and the dinocyst Lingulodiniummachaerophorum may be taken as a signal of warmerthan present conditions in the water (Mayer 1962,1980; Gudina & Evzerov 1973). Trifarina angulosa hasits northern limit in the southwestern Barents Sea,whereas L. machaerophorum has not been found northof Trondheimsfjorden, central Norway (Digas 1969;Gudina & Evzerov 1973; Steinsund et al. 1994; Dale1996). L. machaerophorum bloomed in sheltered,

nearshore environments during late summer/autumn.The temperatures in the euphotic zone likely exceededthe lower temperature limit of 128C of this species(Lewis & Hallet 1997). Islandinium minutum likelybloomed during spring, when sea ice still existed orafter melting had started. Therefore the co-occurrenceof the dinocysts L. machaerophorum and the stillsignificant percentage of I. minutum reflect a strongseasonality. Many of the foraminifer species listedabove tolerate low salinities. However, the presence ofMiliolina as well as H. depressula and E. margarita-ceum indicates that the salinity did not drop below 25(Penney 1984).

Mollusc faunas include both thermophilic and highsaline species but less frequently than in the underlyingzone (Table 4).

Ecozone By5 (20.0022.00 m a.s.l.). This zonecomprises a foreshore sand deposit lying on a sig-

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Fig. 6. Locality 4 (Viryuga W) lithology and stratigraphy. Thepositions of the mollusc samples are shown on the left. The pollenzonation is inferred from correlation with the pollen-dated localitiesbased on locality altitude and sea-level history. Pollen zone ages areindicated in Table 1.

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 507

nificant erosion surface that defines the base of thezone. The sand indicates regression and the end of themarine interval at this locality (Fig. 3). The upperboundary is an erosive contact towards overlyingfluvial sand.

The record from this zone includes only benthicforaminifers and molluscs (Fig. 3). The shallow-water, Arctic foraminifers Elphidium hallandense andHaynesina orbiculare increase, while the warm-water Elphidium margaritaceum, Elphidium williamsoni,Elphidium gerthi, Haynesina germanica and Haynesinadepressula decrease (Fig. 5). The mollusc fauna has alow diversity, being dominated by Macoma calcareaand supplemented by the widespread Buccinum unda-tum, Mytilus edulis, Macoma balthica, Balanus hameriand Dentalium entalis (Table 4).

The significant decrease in the thermophilic forami-nifers and the concurrent increase in Arctic speciesindicate that, in addition to shallowing and greaterfresh-water input, cooling was taking place. However,subarctic species such as Buccinum undatum, Mytilusedulis, Macoma balthica and Balanus hameri indicatethat temperatures were similar to those at present andnot any cooler. Sparse Dentalium entalis indicates thatin the proximity salinity was higher than now.

Loc. 4, Viryuga W (Figs 1, 6; Tables 1 and 2)

This is a 500-m-long and 35-m-high exposure along ameander on the northern side of Pyoza (Figs 1, 6). It isthe only exposure along the river showing two shell-

bearing beds separated by a till. Devyatova & Loseva(1964, loc. 53) considered the lower shell-bearing bed, ac. 10-m-thick stratified sand with scattered reworkedshells, as glaciofluvial. The upper shell-bearing bed, ac. 10 m thick clayey diamicton with frequent shells, wasinterpreted as Weichselian marine sediment. In con-trast, Houmark-Nielsen et al. (2001) considered thelower bed as tidal-marine Eemian, whereas the upperbed was also interpreted as Weichselian glaciolacus-trine with reworked shells.

The differing interpretations reflect the complexityof the succession in relation to other sections along theriver, and we venture here to offer a third interpreta-tion. Based mainly on the shells modes of occurrencewe suggest that both shell-bearing beds are marinedeposits. The lower bed contains an element of heavilyworn and hardly identifiable reworked fragments ofmolluscs and barnacles, but also an element of well-preserved Macoma balthica (Nielsen & Funder 2003).At present, this species totally dominates tidal estuariesin the region, and in agreement with Houmark-Nielsenet al. (2001) we consider this sediment as marine-tidal.However, contrary to Houmark-Nielsen et al. (2001),we suggest that the OSL dates obtained from thissediment, with ages between 194 and 237 kyr BP, aremore or less correct and place this marine episodewithin an ice-free interval in the Saalian. The uppershell-bearing diamicton between 46 and 49 m a.s.l. isquite rich in well-preserved shells, some paired, butoverall the fauna has low diversity and is mainlycomposed of the widespread species Mya truncata

510 30 100 30 305 30 10 103

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Fig. 7. Locality 6 (Viryoga E) lithology, stratigraphy and foraminifers. Percentage occurrence of selected foraminifers, species diversity(Walton 1964) and total foraminifer concentration. The positions of the mollusc and foraminifer samples are shown on the left and right,respectively. The pollen zonation is inferred from correlation to the pollen-dated localities based on locality altitude and sea-level history.Pollen zones are indicated in Table 1.

508 Kari Grsfjeld et al. BOREAS 35 (2006)

and Macoma calcarea. Pebbles with attached barnaclesindicate that the shells are not reworked. We suggestthat this diamicton correlates with the high-lyingmarine sediment at nearby Viryuga E (Fig. 7). How-ever, the sediments at Viryuga W contain such sub-arctic species as Mytilus edulis, Macoma balthica andSemibalanus balanoides, which shows that the environ-ment was not glacial but only slightly colder than atpresent (Table 4). We suggest that this marine sedimentis earliest Eemian (Figs 6, 14), which concurs with thepollen analysis presented by Devyatova & Loseva(1964) showing decreasing herbs and increasing bushesand trees.

Loc. 6, Viryuga E (Figs 1, 7; Tables 1, 2)

The marine Eemian sediments at this locality arenotable for their high elevation, up to 63 m above sealevel and among the highest in the region. Further-more, they apparently date to the Late Saaliandeglaciation of the area. The locality was first de-scribed by Devyatova & Loseva (1964, loc. 54). Somenotes were provided by Houmark-Nielsen et al. (2001)and Nielsen & Funder (2003). The locality comprisesthe partly overgrown headwall of a small landslide atthe southern side of the Pyoza River, c. 65 km upstream

from its mouth. The exposed sediments have a thick-ness of c. 10 m and consist of a top unit of large-scale,cross-bedded sand, gravel and clay with beds ofreworked mollusc shells, especially in the lower part(Fig. 7). We interpret this unit as the flank of a coastalspit eroded into horizontally laminated shoreface sandand silt, which again overlies a glaciomarine diamictonwith an erosional contact, locally developed as aconglomerate. The glaciomarine diamicton overlies atill with a deglacial flooding contact signifying the finalcollapse of an ice barrier and the immediate attainmentof sea-level highstand. It is therefore the earliest LateSaalian/early Eemian sediment in the region.

Benthic foraminifers are limited to the glaciomarinediamicton, as no specimens were found in the shorefacedeposits (Fig. 7). The foraminifer faunas in theglaciomarine sediments belong to the Arctic shallow-water community (Elphidium excavatum, formaclavata, Haynesina orbiculare, Elphidium albiumbilica-tum, Elphidium asklundi). Their presence and the nearabsence of Cassidulina reniforme, indicate salinitiesbelow 30, possibly due to a large meltwater outflow.Cold, low-saline water is also indicated by the low-diversity mollusc fauna, which is dominated by in situHiatella arctica and occasional cold-water species(Portlandia arctica, Arctinula greenlandica). The up-

Fig. 8. Locality 8 (Kalinov) lithology, stratigraphy and foraminifers. Percentage occurrence of selected foraminifers, species diversity(Walton 1964) and total foraminifer concentration. The position of the foraminifer samples is indicated. The pollen zonation is inferred fromcorrelation to the pollen-dated localities based on locality altitude and sea-level history. Pollen zone ages are indicated in Table 1.

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 509

ward increase of the foraminifer Elphidium bartlettiindicates slightly increasing salinity possibly due to amore distal environment or less meltwater runoff.

The mollusc faunas in the overlying sand and gravelare warmth demanding with characteristic Eemianboreal species. These sediments were deposited duringforced regression, punctuated by the two erosionalhiata. The wave-tossed and habitat-mixed molluscfaunas in the upper shoreface sand and gravel arerich, but biased towards large, robust shells (Nielsen &Funder 2003). The boreal Zirfaea crispata, sitting in itsburrows, forms festoon-like horizons in the lower sand,showing that temperatures were higher than at present.This is emphasized by a single find of Bittiumreticulatum, the northernmost known occurrence ofthis small gastropod, which also indicates that thesalinity was below 30. The faunas in the sand andgravel reflect decreasing water depths, with the littoralMytilus edulis occurring at the top. Their high elevationshows that they belong to an early phase in theregression, and we refer them to the earliest Eemian.

Hence, the record from this locality shows twodistinctly different facies separated by a hiatus. Thelower glaciomarine diamicton belongs to the LateSaalian deglaciation with cold and low saline water.The fauna in the overlying shoreface sand and gravelindicate higher than present temperatures, but re-

stricted water mass exchange with the ocean. Amongour localities, the shoreface sand and gravel occupiesthe highest position above sea level, and we refer theseto the earliest Eemian (pollen zone 2).

Loc. 8, Kalinov (Figs 1, 8; Tables 1, 2, 3)

At this site, located 10 km upstream from loc. 6(Viryuga E), marine clay with sandy interbeds isexposed from the river level to 8 m (Fig. 8). It iserosively overlain at 39 m a.s.l. by fluvial sand (Hou-mark-Nielsen et al. 2001). The sediment is interpretedas lower shoreface mud with storm-generated sandlayers (Fig. 8).

The foraminifer faunas show few changes throughthe section (Fig. 8). The concentration of foraminifersis low (520 specimens/gram sediment) and the faunais dominated by Elphidium excavatum, forma clavatawith frequent Cassidulina reniforme, Haynesina orbicu-lare, Elphidium asklundi and Elphidium bartletti. Thisindicates Arctic shallow water with a salinity of not lessthan 30, reflecting estuarine conditions and moresubstantial inflow of oceanic water than at present.This is in agreement with the low diverse mollusc faunadescribed by Nielsen & Funder (2003), dominated bywidespread Arctic species (Table 4). From their eleva-tion the sediments can be referred to the Late Saalianor early Eemian, and the fauna indicate correlation

Fig. 9. Locality 10 (Yatsevets) lithology, stratigraphy and foraminifers. Relative frequency of selected foraminifer species, species diversity(Walton 1964) and total foraminifer concentration. The pollen zonation is inferred from correlation to the pollen-dated localities based onlocality altitude and sea-level history. Pollen zone ages are indicated in Table 1.

510 Kari Grsfjeld et al. BOREAS 35 (2006)

with the Late Saalian (pollen zone 1) sediments at loc.6 (Fig. 14).

Loc. 10 Yatsevets (Figs 1, 9; Tables 1, 2)

At loc. 10, located 20 km further upstream along theriver from loc. 8, a 4-m layer of thick marine clayoverlies a till. The clay bed is erosively overlain byproglacial fluvial gravel at 38 m a.s.l. (Houmark-Nielsen et al. 2001; Nielsen & Funder 2003). Thesection was sampled for foraminifers and molluscs. Theforaminifer assemblage shows a general developmentfrom Arctic, shallow-water conditions with salinitiesbelow 30, to a cold, deeper water setting withsalinities/33 (Figs 9, 14). Zone Ya-1 is characterizedby Haynesina orbiculare, Elphidium asklundi and El-phidium albiumbilicatum, all of which are common inArctic environments with salinity B/30 (Polyak et al.2002). The diversity increases upwards with the pre-sence of Elphidium bartletti and later also Epistominellaspp., Astrononion gallowayi and Cassidulina reniformein Zone Ya-2, indicating gradually increasing salinitiesto more than 33 and an ample food supply. The topof the section, Zone Ya-3, is characterized by a low-diversity fauna, dominated by Elphidium excavatum, f.clavata, indicating conditions with reduced oxygen atthe sea floor.

The faunal development illustrates a graduallyincreasing water depth, from Zone Ya-1 deposited in

shallow, low-saline water above the pycnocline. TheArctic assemblage is devoid of thermophilic species,indicating that this part of the section was deposited inthe Late Saalian (Fig. 9). Buccella frigida, Epistomi-nella spp., Polymorphinidae and Islandiella helenaemay indicate high-productivity (Gooday 1993;Steinsund et al. 1994; Wollenburg 1998; Polyak et al.2002), and their peak occurrences in Zone Ya-2 may berelated to high-productivity around the pycnocline.Zone Ya-3 was probably deposited in the deep, coldwater below the pycnocline. The section contains nospecies indicating influx of oceanic water. The mollus-can assemblages are of low diversity and are composedof widespread species. A single shell of Panomyanorvegica shows that warmer than present conditionsexisted somewhere in the area.

This locality therefore reflects the development of alocal, possibly threshold-controlled basin with re-stricted water-mass exchange, spanning the intervalfrom the Late Saalian deglaciation and into the earlyEemian.

Locs 11 and 12, Orlovets (Figs 1, 10, 11, 12, 13;Tables 1, 2)

Two 20-m-high sections on the same bank of Pyoza,west of the mouth of the tributary Orlovets, showsimilar sedimentary successions and are treated to-gether here. Coarsening-upward, laminated marine silts

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Fig. 10. Locality 12 (Orlovets) lithology, stratigraphy and pollen. The positions of mollusc, dinocyst and foraminifer samples are indicated.Pollen zone ages are indicated in Table 1.

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 511

and sands with abundant shells are exposed from theriver level and up to 6 m. At the top, the sequence istruncated and overlain either by fluvial sand (loc. 12)or by foreshore sand and gravel (loc. 11). Devyatova &Loseva (1964, loc. 30, 29) published sketch-pollendiagrams from both sections. Houmark-Nielsen et al.(2001) presented sedimentary logs and descriptionswith emphasis on the overlying glacigenic sediments,whereas Nielsen & Funder (2003) gave a detaileddescription of the mollusc assemblages.

The fine-grained sediments were sampled for dino-cysts, foraminifers and pollen (Fig. 10). In addition,loc. 11 was sampled for molluscs and the upper coarse-grained sediment also for foraminifers (Fig. 13).

The fine-grained marine sediment contains largequantities of wood and fresh-water algae (Pediastrumand Botryococcus), showing that the sediment wasdeposited in a sheltered area close to the coast. Thereare several reworked dinocysts and acritarchs. Speci-mens of Acritarch A were particularly abundant (Fig.15, no. 13). Both dinocysts and foraminifers occur inmuch higher concentrations than at other localities.The pollen diagram shows little variation, and constantvalues for deciduous trees indicate rapid sedimentation(Fig. 10). This is in agreement with the dinocyst and

foraminifer data (Figs 11, 12), which mainly show arecord of regression and shallowing. The section isdivided into a shoreface and a foreshore faciesseparated by an erosion horizon.

Shoreface facies Orlovets (loc. 12). The microfossilassemblages indicate nutrient-rich waters and cooltemperatures (dinocysts Islandinium minutum, Islandi-nium? cezare, Echinodinium karaense, Polykrikos Arc-tic morphotype; foraminifers Elphidium excavatumforma clavata, Buccella frigida, Cassidulina reniformeand Islandiella helenae). The bivalves indicate cool,saline bottom water (Macoma calcarea, Nuculomatenuis, Nuculana pernula, Yoldia hyperborea, Figs 11,12; Table 4). However, both bivalves (Cerastodermaedule and Mysella bidentata) and foraminifers (Elphi-dium margaritaceum, Elphidium gerthi, Elphidiumwilliamsoni) display an upward shallowing (Fig. 12;Table 4). The presence of the foraminifer Elphidiummargaritaceum indicates that salinities did not dropbelow 20 (Fig. 14; Penney 1984). The highestrecorded abundance of dinocysts of Islandinium?cezare occurs in the parts of the sequences at bothOrlovets and at Bychye (loc. 1, Fig. 4), which had theshallowest water depths. This indicates that the

Fig. 11. Locality 12 (Orlovets) dinoflagellate cysts. Relative frequency and concentration (cysts/g of dry sediment) of selected dinocyst taxaand total cyst concentration.

512 Kari Grsfjeld et al. BOREAS 35 (2006)

plankton stage of this dinocyst preys on a nutrientsource associated with river outlets.

The dinocyst assemblages comprise several thermo-philic species (Lingulodinium machaerophorum, Spini-ferites pachydermus, Xandarodinium xanthum (Fig. 15,nos. 6, 7, 8, 9)) which are more abundant in warmerwaters at lower latitudes (Fig. 11; Rubino et al. 2000)and have not been recorded from the area today(Polyakova et al. 2003). Spiniferites sp. A and B(Fig. 15) are known from Eemian sediments in theBaltic Sea (Head et al. 2004).

Foreshore facies (loc. 11). The rich and diversemollusc fauna, concentrated by waves at the foreshore,represent a number of habitats. Both mollusc andforaminifer faunas are rich in boreal species (bivalvesSpisula elliptica, Arctica islandica, Mysella bidentata,Cerastoderma edule, Zirfaea crispata and Balanusimprovisus; foraminifers Haynesina germanica, Elphi-dium williamsoni, Elphidium gerthi; Fig. 13, Table 4).The molluscs suggest that the salinity was 25 orhigher (Margarites costalis, Oenopota harpa, O. nobilisand Aartsenia candida).

The foraminifer faunas indicate shallowing fromthe shoreface facies with accompanying decreasingsalinity (Fig. 13). The foraminifer fauna is dominated

by Elphidium excavatum, forma clavata, but consistsof a mixture of species with different temperaturerequirements (the subarctic species Islandiella helenae,Buccella spp. and Trifarina fluens, the thermophilicHaynesina germanica and the cosmopolitan Bulimi-nella elegantissima and Elphidium albiumbilicatum).This assemblage reflects strong annual variation inthe surface waters with months of warm surface waterand high food availability, together with monthsof temperatures around freezing and low food avail-ability.

In summary, the Orlovets section reflects a sheltered,near-coast environment where deposition occurredwithin a short time period of the early Eemian, duringpollen zone 4. Restricted oceanic circulation is indi-cated by low salinity (c. 25) and water-mass stratifi-cation with cold bottom water and warming of thesurface water during summer. The area is comparableto the present sheltered and warm embayments in thesouthern White Sea.

Locs 13 (9801A) and 14 (9801B), Yolkino

At Yolkino, 30 km upstream from Orlovets, a 20-m-high exposure shows a thick sequence of glacial andglaciofluvial sediments underlain at river level by 3

Fig. 12. Locality 12 (Orlovets) foraminifers. Relative frequency of selected foraminifer species, species diversity (Walton 1964) and totalforaminifer concentration. The pollen zonation is shown to the left.

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 513

4 m of thick marine foreshore sand and gravel up to52 m a.s.l. This important locality was described byDevyatova & Loseva (1964) and the glacial sedimentsby Houmark-Nielsen et al. (2001).

The rich, habitat-mixed mollusc assemblages containabundant boreal species (Cerastoderma edule, Spisulaelliptica, Abra prismatica, Panomya norvegica, Balanusimprovisus). This indicates that sea-surface tempera-tures were higher than at present, sea-ice was absent orof short duration and salinities were higher than 30(Astarte crenata, previously identified as A. sulcata byNielsen & Funder 2003). From their elevation, theforeshore sediments are younger than those at ViryogaE and Burdui, and we refer them to pollen zone 3.

Loc. 24 (9811), Burdui

This small exposure, 180 km east of the mouth ofPyoza, is the easternmost and most remote occurrenceof marine sediments in this region (Fig. 1). It consistsof 2-m-thick foreshore sand and gravel overlain by tillat 62 m a.s.l. (Houmark-Nielsen et al. 2001). Nielsen &Funder (2003) gave a detailed description of themollusc fauna. The habitat-mixed mollusc assemblagescontain such boreal indicators as Spisula elliptica andCerastoderma edule. Higher than present salinity(/30) is suggested by the frequent occurrence ofAstarte crenata (previously identified as A. sulcata byNielsen & Funder 2003). This shows that warmAtlantic water penetrated into the most remote part

of the region. We assign the deposits from this highelevation to zone 2; however, a younger age cannot beexcluded (Fig. 14).

Hydrographical and oceanographicaldevelopment

Pollen zone 1 (Late Saalian, c. 133131 kyr BP)

Marine invasion into the area followed immediately ondeglaciation. This is seen from the deglacial floodingcontacts and deposition of offshore glaciomarinediamicton at Bychye (loc. 1, ecozone 1); Viryuga E(loc. 6); linov (loc. 8) and Yatsevets (loc. 10, ya12).Initially, the marine environment was characterized bycold, low-salinity marine water. At Yatsevets (loc. 10),low diversity foraminifer faunas reflect transition fromshallow and low salinity environments to faunasindicative of deeper water and more saline environ-ments. This change is interpreted as reflecting sea-levelrise, probably through a threshold-controlled localbasin, and shows that in Late Saalian times eustaticsea-level rise could exceed isostatic effects. At Bychye(loc. 1), the more regional dinoflagellate and forami-nifer records reflect open connection to a cold ocean,but also significant influence from local river runoff. Ingeneral, salinities were low, although they locallyreached 33 at the end of the zone, indicating a higherthan present inflow of oceanic water.

Fig. 13. Locality 11 (Orlovets) lithology, stratigraphy and foraminifers, percentage occurrence of selected foraminifers, species diversity(Walton 1964) and the total foraminifer concentration. The position of the foraminifer samples is indicated.

514 Kari Grsfjeld et al. BOREAS 35 (2006)

Pollen zone 2 (earliest Eemian, c. 131129.8 kyr BP)

This interval is represented by pollen-analysed, lowershoreface sediments at Zaton (loc. 0) and offshore mudat Bychye (loc. 1, ecozone 2), and by sea-level datedshoreface and foreshore sediments at Yatsevets (loc. 10,Ya-3) and Burdui (loc. 24). At Viryuga W (loc. 4), theupper offshore mud probably dates from the pollenzone 12 transition.

The records from different localities show consider-able variation. At Zaton (loc. 0), the locality that isclosest to the present White Sea shore, the first borealand saline molluscs are recorded, showing that warmAtlantic water had arrived in the area at this time. Thesame type of evidence is also found in the less well-dated foreshore and shoreface sediments at Viryuga E(loc. 6) and the most remote locality Burdui (loc. 24).In contrast to this, the detailed record from Bychye(loc. 1) shows Arctic conditions during the initial phaseof the Eemian, with considerably lower water tempera-tures than in the present White Sea (Polyakova et al.2003). At Yatsevets, the offshore facies sediments alsoshow cold Arctic conditions (loc. 10).

In zone 2, therefore, warm Atlantic water reachedthe area. The Pyoza valley formed a series of isolatedbasins, some with pools of cold, saline bottom water,but rising sea level brought an increasing inflow ofAtlantic water upwards through the zone.

Pollen zone 3 (early Eemian, 129.8128 kyr BP)

This zone is represented by pollen-dated shorefacesediments from Bychye (loc. 1, lower ecozone 3) andsea-level dated foreshore sediments at Yolkino (locs.13, 14). The foreshore sand and gravel at Yolkinocontain the areas richest mollusc fauna with abundantboreal species.

The molluscs indicate saline waters and temperatureshigher than at present, and, in particular, that theinfluence of Atlantic water was more extensive thantoday. The foraminiferal faunas support the interpreta-tion of greater salinity. The dinocyst assemblagesclearly record the transition from the earliest andcoldest part of the Eemian (pollen zone 2), withpredominantly heterotrophic species, to the signifi-cantly warmer period of pollen zone 3, which is

DEGLACIATION

?

?

By

chye

(1)

Viry

uga

W (4

)

Viry

uga

E (6)

Kalin

ov (8

)

Burd

ui (2

4)

Yolk

ino

(13,14

)

Orlo

vets

(11,1

2)

Yats

evets

(10)

Zato

n (0)

Burd

ui (2

4)

B

ych

ye (1

)

Viry

uga

W (4

)

Viry

uga

E (6)

Kalin

ov (8

)

Yolk

ino

(13,14

)

Orlo

vets

(11,1

2)

Yats

evets

(10)

Zato

n (0)

Bych

ye (1)

131

130

128

133

124

126

122

1

2

3

4

5

Polle

n zo

ne

DEGLACIATION SAALIAN

EEM

IAN

Age, kyr

WEICH-SELIAN

1 2 3

1 Molluscs2 Dinocysts3 Benthic foraminifers

1 2 3

1 2 31 2 3

1 2 3 1 2 3

Temperature

1 2 3

1 2 3

?

No data

Values related to the White Sea at present

below

above

Erosional boundary

1 2 31 2 3

1 2 3

1 2 3

1 2 31 2 3 1 2 3

1 2 3

1 2 3

? ?

?

Salinity

?

1 2 3

Fig. 14. The relative age of the investigated sections within the Late Saalian/Eemian and the temperature and salinity conditions during thisperiod, indicated by the various proxies. The conditions refer to those in the White Sea at present, which has surface water temperatures andsalinities up to 208C and around 24, respectively, and bottom water temperatures and salinities of 08C and 29, respectively, and around 6months of seasonal sea ice.

BOREAS 35 (2006) Last Interglacial marine environments, NW Russia 515

516 Kari Grsfjeld et al. BOREAS 35 (2006)

dominated by autotrophic forms. A high abundance ofautotrophic forms reflects the influence of salineoceanic. However, comparison of our dinocyst datawith those from areas influenced by warm oceanicwater, e.g. the present White Sea (Polyakova et al. 2003;Golovnina 2005) and the southeastern Barents Sea(Voronina et al. 2001) and Eemian assemblages in asediment core from the northern Barents Sea margin(Matthiessen & Knies 2001), suggests that the surfacewaters in the White Sea area during the last interglacialwere, comparatively speaking, more influenced by thelocal environment.

In summary, at Bychye, molluscs, dinocysts andforaminifers show that conditions became warmer(winter temperatures /38C), more saline (3335)and more oceanic during the early Eemian. Theduration of sea ice, if any, was considerably reduced.This shows that the advection of warm Atlantic watercontinued to increase through pollen zone 3. From themiddle part of the zone, both lithology and palaeontol-ogy show a facies change from transgression to regres-sion and a return to more diversified environments.

Pollen zone 4 (mid-Eemian, 128124 kyr BP)

Now regression had set in and the local basins withstratified water columns seen in zones 1 and 2reappeared. Cold, saline bottom water was overlainby comparatively warmer, low-saline surface waterwith summer temperatures that may have exceededthose in the present White Sea. None of our sectionscover the entire period. Upper shoreface and foreshoresediments are exposed in the pollen-dated sectionsZaton (loc. 0), Bychye (loc. 1, upper ecozone By3,ecozones By4, By5) and Orlovets (locs. 11, 12).

As the regression progressed, the local basins becamegradually more enclosed and the summer warming ofthe surface waters continued. The warming is shown byall fossil groups, but is seen most clearly in the benthicforaminifer fauna of ecozone By4 at Bychye (Figs 3, 4,5). Arctic foraminifer taxa decrease, whereas thermo-philic, low saline (5/25) taxa appear. In the molluscfaunas, both thermophilic and high saline species areless frequent than in the preceding zone (Table 4). Inthe dinocyst record the trend is best seen in the furtherdecrease in Islandinium minutum and in the increase inBrigantedinium spp. The dinocyst assemblages fromthis part of the Eemian are strongly dominated byheterotrophic dinoflagellates. In this respect, theyresemble the assemblages from the earliest part of theinterglacial (ecozone By1 and By2). The dinocystassemblages from both time intervals reflect possible

abundant nutrients. However, the species that dominateare different and provide various climatic sig