Late Pliocene and Pleistocene Biostratigraphy of the Nordic Atlantic Region

Newsletters on Stratigraphy © Gebrüder Borntraeger 2008 Vol. 43/1: 33–48, June 2008

Late Pliocene and Pleistocene biostratigraphy of the Nordic Atlantic region

Erik D. Anthonissen1

With 3 figures and 1 appendix

Abstract. The lack of primary and secondary GSSP correlative markers in Plio-Pleistocene deposits of the North Sea, Nordic seas and northern North Atlantic creates a challenge for the biostratigrapher. This study highlights the closest biostratigraphic approximations in this region to the standard chronostratigraphic boundaries of the Gelasian Stage and Lower, Middle and Upper Pleistocene. Via correlations to key Ocean Drilling studies and unambiguous magnetostratigraphies in the region, the age of shallower deposits of the North Sea has been better constrained. The closest biostratigraphic approximations to these chronostratigraphic boundaries in the region are presented, together with a framework of calibrated events according to sub-basin. The best approximating boundary events at any given location in this region depends upon both the paleoceanographic and paleobathymetric settings. In the Nordic Atlantic region only three GSSP correlative marker events have been identified in the 15 Ocean Drilling Program sites discussed. At lower neritic to bathyal water depths, the first common occurrence of Neogloboquadrina pachyderma (sinistrally-coiled morphotype) allows for direct correlation with the base Pleistocene GSSP in Italy. The occurrence of the benthic foraminifer Cibicides grossus appears to have been bathymetrically controlled, with a youngest stratigraphic occurrence at upper bathyal depths. At lower neritic depths in the central and northern North Sea the last occurrence of C. grossus coincides with the base of the Pleistocene. Diachroneity of a number of Nordic high-latitude bioevents may be primarily due to differences in surface water masses and paleobathymetry.

Key words. North Sea, Norwegian Sea, Foraminifera, calibrations, Quaternary, Pliocene

1. Introduction relevant Upper Cenozoic chronostratigraphic units, i. e. Gelasian Stage, Pleistocene Series, Neogene and This study aims to improve the temporal resolution of Quaternary Systems follow Ogg et al. (in press); they the established Plio-Pleistocene biostratigraphy of the are also available from the website of the Internation- Nordic Atlantic region, through multi-fossil calibra- al Commission on Stratigraphy (ICS) at www.strati- tions to the standard geologic time scale with its Glob- graphy.org. The orbitally tuned time scale is that of al boundary Stratotype Section and Point (GSSP) def- Lourens et al. (2004), which also re-calibrated the initions in the Mediterranean. The definitions of the Berggren et al. (1995) biochronology.

Authorʼs address: 1 Erik D. Anthonissen (E-Mail: [email protected]), Natural History Museum, University of Oslo, P.O. Box 1172 Blindern, 0318 Oslo, Norway

2. Regional setting or normal polarity/reversed polarity). This additional and biostratigraphy age control is often in the form of planktonic marker fossils that have been well-documented both spatially The “Nordic Atlantic region” is here defined as rough- and temporally (planktonic foraminifera, calcareous ly the area stretching from immediately south of the nannoplankton, dinoflagellate cysts and siliceous mi- Greenland-Scotland Ridge northwards, encompassing crofossils). Where integration of data sets from a range the North Sea and Nordic Seas (Norwegian Sea, of both abiotic and biotic proxies is possible (e. g. in Greenland Sea, Iceland Sea, West Barents Sea) to the deep-sea cores), well-constrained age models form the Arctic Ocean Gateway and the Yermak Plateau basis for a regional biostratigraphy. (Fig. 1). In this region, the Upper Cenozoic biostrati- High-resolution biostratigraphies have been con- graphy is based primarily upon foraminifers, calcare- structed from Upper Cenozoic depositional sequences ous nannoplankton and organic-walled dinoflagellate in Deep Sea Drilling Project (DSDP) and Ocean cysts. Marine diatoms and continental pollen se- Drilling Program (ODP) coreholes from the Mediter- quences (van der Vlerk and Florschütz 1953, Zagwijn ranean to the high Arctic. For the Nordic Atlantic re- 1974) add paleontological age control across discrete gion, the following planktonic foraminiferal zonation time intervals. At these high latitudes, many of the studies have been most utilised: Weaver and Clement standard ‘global’markers present in the mid- to low- (1986) and Weaver (1987) in the northern North At- latitudes (including the Mediterranean region) are ab- lantic (DSDP Leg 94) and Spiegler and Jansen (1989) in sent; these include most of the primary and secondary the Norwegian Sea (ODP Leg 104). For the North Sea correlative events defining the relevant GSSPs. Basin, dominated by shallow neritic benthic foramini - Various abiotic and biotic expressions of late Ceno- feral assemblages, the deterministic zonation by King zoic climatic change have been used for dating the onset (1983, 1989) and the probabilistic zonation by Grad- of the Quaternary and Pleistocene in the Nordic Atlantic stein and Bäckström (1996) are most widely used. Their region. Marine isotopic trends and magnetic polarity re- zonal boundaries are defined almost entirely upon last versals show near synchroneity across large geograph- occurrence events (LOs) due to downhole contami- ic regions. However, these dating methods often require nation in industrial exploration well samples. Both additional control to interpret an age, being inherently schemes are based primarily on poorly constrained limited to two outcomes (e. g. either glacial/interglacial ranges of benthic foraminifera, with age interpretations strongly dependent upon the biomagnetostratigraphy of DSDP Leg 94 in the northern North Atlantic. Calibration sites Arctic Ocean In response to high-frequency Quaternary climate A. Northern North Atlantic F. Yermak Plateau & Yermak Plateau & Labrador Sea Svalbard Margin 911 change, benthic communities would have been forced 80° DSDP Leg 94 (606-610); ODP Leg 151 (910, 911); 910 ODP Leg 105 (646, 647); ODP Leg 162 (986) ODP Leg 162 (980-984) to migrate repeatedly to more preferable environmen- G. North Sea B. Irminger Basin Statfjord C borehole; Svalbard Margin (East Greenland Margin) 34/8-1; 15/9-A-11; 2/4-C-11; tal conditions. Benthic foraminifera are sensitive to ODP Leg 152 (918, 919) BGS81/34; B10-3, 13-3, 986 B17-5, B17-6 C. Norwegian Sea & water mass and substrate properties and therefore they Iceland Plateau ODP Leg 151(907); Barents Sea ODP Leg 162 (985) Legend often exhibit sedimentary facies dependency (Mack- Greenland Sea D. Norwegian Sea ‘Nordic Atlantic region’ ensen et al. 1985). They are therefore often unreliable (Vøring Plateau) Warm ocean current 987 ODP Leg 104 (642-644) Cool ocean current Norwegian Sea Industrial well/borehole 907 markers, showing a high degree of diachroneity in their E. Greenland Sea ODP/DSDP Site 643 ODP Leg 162 (987) Greenland-ScotlandIceland RidgeSea 642 644 first and last appearances (Denne and Sen Gupta 1990). 985 Irminger Basin This is especially evident in the bathymetrically con- 918 984 Labrador Sea 919 34/8-1 trolled last occurrence of Cibicides grossus (C. lobatu- 60° 983 Statfjord C 646 15/9-A-11 Northern 982 2/4-C-11 lus var. grossa) in the North Sea (see Appendix 1). North Atlantic 981 BGS81/34 980 North Sea 647 Following ODP Leg 104, a number of new oceanic 611 610 B10-3,13-3,B-17-5/6 609 sites have been drilled as part of ODP Legs 151, 152 Pleistocene & Gelasian GSSP’s and 162 (Fig 1.). Calibration of the stratigraphy of 607 40° 606 898 90° 60° 30° 0° 30° these new sites to astronomical parameters has greatly increased Neogene temporal resolution (Lourens et al., Fig. 1. Map showing the location of calibration points used in this study, including Deep Sea Drilling Project Sites, 1996; Gradstein et al., 2004). These additional data Ocean Drilling Program Sites, and industrial wells/bore- points allow for a broader examination of the relation- holes. Locations are grouped according to region/basin and ship between the geographic distribution and the de- given a letter abbreviation. gree of synchroneity/diachroneity of important north- Late Pliocene and Pleistocene biostratigraphy of the Nordic Atlantic region 35 ern high-latitude bioevents. A better understanding and site coreholes. Where possible, the standard chronos- quantification of the time-transgressive nature of key tratigraphic boundaries of the Late Pliocene – Pleis- planktonic events from oceanic settings will help to tocene have been correlated between sites. This has fa- improve the accuracy of Quaternary biostratigraphy cilitated a biostratigraphic comparison of sites at both a and to better constrain benthic foraminiferal ranges in local level between sub-basins and at a more regional shallower shelf settings such as the North Sea. scale from temperate to polar latitudes. High-resolution integrated stratigraphic data sets are It is only via the high-resolution data sets provided rare in industrial exploration-well studies in the North through these deep-sea cores that reliable stratigraphic and Norwegian seas. Here both quality of material and relationships can be found between the Mediterranean economic constraints limit the availability of paleo- stages and the Nordic Atlantic biostratigraphy. The re- magnetic and isotopic data. Strontium isotope meas- liability of these relationships or calibrations can be urements may provide a limited degree of independent ranked according to the number of correlations neces- age control, but contamination has often rendered con- sary. First-order calibrations are those involving a di- tradictory results (e. g. Eidvin et al. 1993). For latest rect and onsite stratigraphic link between the respective Pleistocene deposits, amino-acid dating and optically bioevent and the standard Geologic Time Scale. This stimulated luminescence (OSL) dating have proved has most often been achieved via an onsite stratigraph- useful, especially in areas where paleomagnetic data is ic tie to the GPTS or to selected astronomically cali- ambiguous or unobtainable and where key planktonic brated events (Lourens et al. 2004). Second-order cali- markers are absent (e. g. Sejrup and Knudsen 1999). brations involved a correlation between the observed However, due to the strong dependency of amino-acid bioevent and another locality with a corresponding racemization rates on temperature, water concentration stratigraphic level which had a 1st order – calibrated and alkalinity, uncertainties regarding conditions of age. Third-order calibrations involve two correlations. preservation can obscure the results (Brown 1985). Updated ages have been calculated based on their relative positions between magnetosubchron and/or nannofossil zonal boundaries. For the majority of events, 3. Material and Methods: Mid- the age has been calculated for the depth originally to high-latitude correlations quoted in the respective DSDP/ODP publications and given to one decimal place only. This is intended to ac- The location of Nordic ocean drilling sites and selected count for low sample resolution, lack of continuous cor- industrial petroleum wells with a reliable Plio-Pleis- ing, and the often numerous occurrence of bracketing tocene record is shown in Fig. 1. The sites have been or- barren intervals. ganised from south to north, according to sub-basin. They have been divided into three correlation panels: 1) temperate to subpolar sites located south of the Green- 4. Results: Late Pliocene – land-Scotland Ridge (GSR) in the northeastern North Atlantic; 2) subpolar sites located north of the GSR in Pleistocene chronostrati - the Nordic Seas; 3) Arctic Sites in the Greenland Sea graphic boundaries and on the Yermak Plateau (Figs.2a–c). Most sites have at Nordic high-latitudes a reliable magnetostratigraphy, allowing for direct calibration of bioevents via the Geomagnetic Polarity A critical assessment of the biostratigraphy and corre- Time Scale (GPTS) to the standard chronostratigraphy lation of key deep-sea cores and industrial petroleum of Gradstein et al. (2004). At a few sites, a Pleistocene wells has resulted in the framework of calibrated bio- oxygen-isotope stratigraphy allows for high-resolution events for the Nordic Atlantic region presented in Ap- calibrations to the marine oxygen isotope stages. In ad- pendix 1. Selected bioevents can be used for the iden- dition, a limited number of astronomically calibrated tification of the standard chronostratigraphic bound- foraminiferal and calcareous nannoplankton bioevents aries of the Late Pliocene – Pleistocene in this region. (with ages according to Lourens et al. 2004) improve Four chronostratigraphic boundaries divide the the stratigraphic resolution. In a few cases, new events Quaternary: Base Upper Pleistocene Subseries, Base have been identified from the raw fossil occurrence data Middle Pleistocene Subseries, Base Pleistocene Se- in the respective publications. Each site record present- ries, and Base Gelasian Stage. To date, the Pleistocene ed here is a composite of the results from the individual and Gelasian GSSPs have been ratified by the Interna-

36 Erik D. Anthonissen Age (Ma) Age -

0.817 0.895 0.29 0.310 0.335 0.44

Zone

Diatom Tnid Pcur Nsem T. oestrupii T. curvirostris P. sem. N.

Stage

Marine Isotope Marine 1 5 7 9

11 13 15 17 19 21 25

(+ warm fauna) warm (+

Zone

Foraminiferal (LCO), (LCO)

N. pachyderma (s) pachyderma N. Planktonic

Ginf Gsci

Zone

Nannoplankton

Plac Pleistocene in Ehux

Calcareous Max. PF diversity diversity PF Max. NN 19 NN NN 20 NN NN 21 NN

East Greenland Margin East Greenland

Site 919 (composite) Site Polarity/ chron Polarity/ 1n 1r.1r

Greenland-Scotland Ridge Greenland-Scotland Depth (mbsf) Depth 0

10 20 30 40 50 60 70 80 90

100 110 120 130 140 Age (Ma) Age

0.29

(+ warm fauna) warm (+ Zone

Ndut (LCO) NpaD (LCO) NpaS (FCO) NatD NatS NatD NatD

Foraminiferal

N. atlantica (s) atlantica N. N. pachyderma (s) pachyderma N. Planktonic

]

N. atlantica (d) atlantica N.

Zone

Nannoplankton

in Pleistocene in

Ehux Upper

Calcareous NN 20 NN NN 21 NN Max. PF diversity diversity PF Max. Polarity/ chron Polarity/ - 1n 2n 1r.2r 1r.3r 1r.1r 2r.1r 1r.1n 2r.1n East Greenland Margin East Greenland

Site 918 (composite) Site Depth (mbsf) Depth 0

10 20 30 40 50 60 70 80 90

100 110 120 130 140 Age (Ma) Age

0.29 0.44 1.24 (~2.57)

Zone

Foraminiferal Natl

NpaS (FCO)

Planktonic

Gr. inflata / G. bulloides G. / inflata Gr. N. pachyderma (s) pachyderma N.

Zone

Nannoplankton Ehux Plac Gspp

Calcareous NN 21 NN 20 NN 19 NN

Bjorn Drift Polarity/ chron Polarity/ T A A N D O 1n 2n

1r.1r 1r.2r 1r.3r 2r.1r 2r.2r 1r.1n 2r.1n Site 984 (composite) Site (mbsf) Depth 0

10 20 30 40 50 60 70 80 90

300 240 250 260 100 110 120 130 140 150 160 170 180 190 200 210 220 230 Age (Ma) Age 0.3 0.6

0.68 0.84 1.25 1.53 1.89 1.65 0.29 0.44 1.24 1.66 Zone

Pcur Nrei Nfos Nsem Nsem Pcur Pdol Diatom

P. curvirostris T. oestrupii T. curvirostris P. seminae N. reinholdii N.

Stage

Marine Isotope Marine 1 5 7 9

11 13 15 17 19 21 23 25 27 29 31 33 35

Zone Foraminiferal

NpaS (FCO) Planktonic

N. pachyderma (s) pachyderma N.

Gardar Drift inflata Gr.

Zone

Site 983 (composite) Site Nannoplankton

Ehux Plac Gspp Cmac

Calcareous NN 19 NN NN 20 NN NN 21 NN Polarity/ chron Polarity/ T A A N D O

1n 2n

2r.1r 1r.1r 1r.2r 1r.1n Depth (mbsf) Depth 0

10 20 30 40 50 60 70 80 90

100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 Age (Ma) Age

0.18 0.41 1.23 2.09 2.30 2.65 2.81 1.83 3.17 0.29 0.44 1.66 2.54

Zone Foraminiferal

NpaS (FCO)

Ginf NatS Gpun Gcra

Planktonic N. pachyderma (s) pachyderma N. (s) atlantica N.

Zone

Nannoplankton Ehux Plac Cmac Dsur Plac

NN 19 NN 21 20 Calcareous

Rockall Plateau Polarity/ chron Polarity/ 2n 1n

1r.1r 1r.2r 2r.1r 2r.2r

1r.1n 2An.1n Site 982 (composite) Site (mbsf) Depth

20 40 60 80 Age (Ma) Age

2.14 2.35 2.39 0.29 0.44 1.66 2.54 0.34 0.55 1.67 2.66

Zone Foraminiferal

NatS Gpun

Ginf NpaS (FCO)

Planktonic

Gr. inflata N. pachyderma (s) pachyderma N. inflata Gr. bulloides G. (s) atlantica N.

Zone Nannoplankton

Plac

Ehux Cmac Dsur

Calcareous NN 16 NN 17 NN 16 NN NN 21 NN 20 NN 19 NN

Feni Drift Feni Polarity/ chron Polarity/ T A A N D O 1n 2n

2r.2r 2r.1n 1r.1r 1r.2r 1r.3r 2r.1r

1r.1n 2An.1n Site 981 (composite) Site (mbsf) Depth 0

10 20 30 40 50 60 70 80 90

100 110 120 130 140 150 160 170 180 South

Pleist. Pleistocene Pleistocene Gelasian

Lower Upper Middle Pliocene) (Upper Late Pliocene-Pleistocene correlation panel Fig. 2a. showing selected ocean drilling sites located south of the Greenland-Scotland Ridge (GSR). For taxon abbreviations see Fig.Ages in bold are according to 2c. the astronomical calibrations of Lourens et al. (2004), all other ages are based on interpolations according to Where possible, the four chronos- the studies cited. tratigraphic boundaries discussed are indicated. For Sites 981, 982, 983 & 984: magnetostratigraphy is according to Channell and Lehman (1999); calcareous nannoplankton biostratigraphy is according to Shipboard Scientific Party (1996a); planktonic foraminiferal biostratigraphy is according to Flower (1999); marine diatom nannoplankton biostratigraphy is according to Shipboard Scientific Party (1996a); planktonic foraminiferal according to Fukuma (1998); calcareous biostratigraphy and oxygen isotope stratigraphy is according to Koc et al. (1999). For Sites 918 919: magnetostratigraphy marine diatom biostratigraphy and oxy- (1998); planktonic foraminiferal biostratigraphy is according to Spezzaferri Wei nannoplankton stratigraphy is according to gen isotope stratigraphy is according to Koc and Flower (1998).

Late Pliocene and Pleistocene biostratigraphy of the Nordic Atlantic region 37 Age (Ma) Age

1.8 2.3

0.29 0.44

Zone

cyst cyst

F. filifera F.

M. minuta - B. simplex B. - minuta M. Mmin, Bsim Nlem Dinoflagellate

South

*coiling *coiling change*

Zone

Foraminiferal Ginf Ginf

NatS

NatD

(FCO) Gpun Gpun NpaS NatD, NpaD N. pachyderma (s) pachyderma N. Planktonic

‘encrusted’ N. atl. (s) atl. N. N. atlantica (d) atlantica N.

Zone Upper Nannoplankton

Ehux Plac Vøring Plateau

Calcareous NN 21 NN 20 NN 19 NN Site 644 (composite) Site chron Polarity/ 1n 2n

1r.1n 2r.1n 2An.1n Depth (mbsf) Depth 0

10 20 30 40 50 60 70 80 90

100 110 120 130 140 150 160 170 180 190 200 210 220 230 Age (Ma) Age 1.8 3.11 0.29 0.44

os-

Zone

B. simplex B. cyst cyst

Tpel, Tpel, Selo (LCO)

Mmin, Mmin, Bsim Aumb Dinoflagellate M. minuta - - minuta M. Ffil acme (upper) Ffil acme (lower) Ffil, Tpel Ffil,

Ffil, Nlem Ffil,

cording

Zone raw fos- Foraminiferal

NatS, Gbul (LCO)

NpaS

(FCO) NpaS N. pachyderma (s) pachyderma N. (s) atl. N. Planktonic

‘encrusted’

004). All oth-

Zone

Nannoplankton Ehux

Plac Vøring Plateau

NN 21 NN 20 19 NN Calcareous Site 642 (composite) Site chron Polarity/

2n 1n

1r.1n Depth (mbsf) Depth

10 20 30 40 50 60 70 Age (Ma) Age

?1.8 3.11 0.29 0.44

Zone

B. simplex B. cyst cyst

acme Aand Mmin, Mmin, Bsim Ffil Ffil Dinoflagellate F. filifera F. M. minuta - - minuta M.

top

Zone Foraminiferal

NatS

(FCO) NpaS N. pachyderma (s) pachyderma N. (s) atl. N. Planktonic

‘encrusted’

Zone

Nannoplankton Ehux Plac

Vøring Plateau

NN 19 NN 20 21 Calcareous Site 643 (composite) Site chron Polarity/ 1n

1r.1n 1r.1r

2An.1n Depth (mbsf) Depth

10 20 30 40 50 60

Age (Ma) Age

Zone

Cyst

Ffil

F. filifera F. Dinoflagellate

Zone

Foraminiferal

NpaS (FCO)

N. pac. (s) pac. N. Planktonic

Greenland Sea Greenland Polarity/ chron Polarity/ - 2n 1n 2r.1r 2r.2r 1r.2r 1r.3r 1r.1r 1r.1n 2An.1n

Site 987 (composite) Site Depth (mbsf) Depth 0

100 150 200 250 300 350 Age (Ma) Age

1.8

Zone

Foraminiferal

Planktonic NpaS (FCO) NatS

N. pachyderma (s) pachyderma N. Polarity/ chron Polarity/ Iceland Plateau Iceland 2n 1n 1r.1n 2Ar

1r.1r 1r.2r 1r.3r 2r.1r 2r.2r

2An.1n 2An.2n 2An.3n Depth (mbsf) Depth 0 10 20 30 40 50 60

Site 907 (composite) Site Age (Ma) Age

1.7

Zone

Foraminiferal

Planktonic NpaS (FCO) NatS N. pachyderma (s) pachyderma N.

Iceland Sea Iceland Polarity/ chron Polarity/ -

1n 2n

1r.2r 1r.3r 2r.2r 1r.1n 2An.1n Depth (mbsf) Depth 0

10 20 30 40 50 60 70

Site 985 (composite) Site

Pleistocene Pleistocene Gelasian

Greenland-Scotland Ridge Greenland-Scotland Middle Pliocene) (Upper Lower Late Pliocene-Pleistocene correlation panel showing selected ocean drilling sites located north of the Greenland-Scotland Ridge sil occurrence data in the respective studies. Ages in bold are according to the astronomical calibrations of Lourens et al. (2 sil occurrence data in the respective studies. Fig. 2b. (GSR). For taxon abbreviations see Fig. 2c. Dinoflagellate cyst acme events are new interpretations according to analysis of the er ages are based on interpolations according to the studies cited. Where possible, the four chronostratigraphic boundaries discussed are Where possible, the four chronostratigraphic boundaries discussed er ages are based on interpolations according to the studies cited. indicated. For Sites 985 is & 907: magnetostratigraphy is according to Channell et al. (1999a); planktonic foraminiferal biostratigraphy according to Flower (1999). For Sites 643, 642 bios- & 644: magnetostratigraphy is according to Bleil (1989); planktonic foraminiferal di- tratigraphy is according to Spiegler and Jansen (1989); calcareous nannoplankton biostratigraphy Donnally noflagellate cyst biostratigraphy is according to Mudie (1989). For Sites 987 al. & 986: magnetostratigraphy according to Channell et (1999b); planktonic foraminiferal biostratigraphy is according to Flower (1999); calcareous nannoplankton ac to Shipboard Scientific Party (1996b); dinoflagellate cyst biostratigraphy (including seismic reflectors) is according to Smelror (1999). to Shipboard Scientific Party (1996b); dinoflagellate cyst biostratigraphy (including seismic reflectors) is according Smelror For Sites 910 ac- magnetostratigraphy is according to Shipboard Scientific Party (1995); planktonic foraminiferal biostratigraphy & 911: cording to Spiegler (1996); calcareous nannoplankton biostratigraphy according Sato and Kameo dinoflagellate cyst bi tratigraphy according to Matthiessen and Brenner (1996). 38 Erik D. Anthonissen Ffil

Ilac Spli Oisr Nrei Tjou Tnid Tpel Pdol Sdio Selo Nfos Pcur Ract Sbre Toes Cgro

Bsim Nlem Aand Ocen Mmin Nsem Aumb CODE CODE CODE Age (Ma) Age

TAXON TAXON TAXON

0.29 0.44 0.85 1.24 1.62 1.73 ‘warm’ assemblage ‘warm’ based on interpolation age from (1995) et al. Berggren (2004) et al. Lourens age from last occurrence or last occurrence (LCO) occurrence last common or first occurrence (FCO) occurrence first common or acme point occurrence ?2.78 DIATOMS

Zone

cyst cyst Ocen acme Ffil

North Dinoflagellate BENTHIC FORAMINIFERA Ffil acme (upper) Ffil acme (lower) DINOFLAGELLATE CYSTS Event Event Event

(consisent) Zone Zone

0.44 0.44 Foraminiferal

NpaS Grub NatD, (temperate) NatS (temperate) miculosphaera umbracula miculosphaera chomosphaera andalousiensis chomosphaera Ginf, Gsci Ginf,

Planktonic grossus) grossa (= C. Cibicides lobatulus var. Nitzschia fossilis Nitzschia reinholdii Nitzschia seminae curvirostrisProboscia doliolus Pseudoeunotia jouseae Thalassiosira nidulus Thalassiosira oestrupii Thalassiosira A A Brigantedinium simplex filifera Filisphaera Invertocysta lacrymosa minuta) Multispinula minuta (=Batiacasphaera Nematosphaeropsis lemniscata Operculodinium centrocarpum Operculodinium israelianum actinocoronata Reticulatosphaera Selenopemphix brevispinosa Selenopemphix dionaecysta Spiniferites elongatus pliocenicum Sumatradinium pellitum Tectatodinium Npac. (s) Npac. (s) atl. N. ]

(med.) R1 R5 R7

N. atl. (d) atl. N. Gtri

Dalt Ginf Tqui Plac Gsci

Mlim Dsur Gbul Ndut Gcra Gcar Grub NatS Ssem NatD Ehux

Rasa Gcon Goex Goce Gspp Gaeq Gpun NpaS NpaD Cmac Mmen Zone CODE CODE CODE Upper

Yermak Plateau Yermak

Nannoplankton Ehux Plac Rasa Gspp (large) Gspp (large) Gspp “A” Datum plane

NN 19 NN 20 19 NN 19 NN

Calcareous Legend Site 911 (composite) Site chron Polarity/ ? 2r 2n 1n

1r.1r 1r.2r 1r.1n

2An.1n Depth (mbsf) Depth 0 50 100 150 200 250 300 350 TAXON TAXON TAXON/EVENT MISCELLANEOUS PLANKTONIC FORAMINIFERA CALCAREOUS NANNOPLANKTON

Dentoglobigerina altispira Globigerinella aequilateralis Globigerina bulloides Globigerinoides conglobatus Globorotalia crassaformis (Globorotalia) inflata Globoconella Globigerinoides obliquus extremus (Globorotalia) puncticulata Globoconella Globigerinoides ruber Globorotalia scitula Globigerinoides trilobus limbata (Menardella) Globorotalia menardii (Menardella) Globorotalia (dex.) atlantica Neogloboquadrina (sin) Neogloboquadrina atlantica Neogloboquadrina dutertrei (dex.) Neogloboquadrina pachyderma (sin.) Neogloboquadrina pachyderma Sphaeroidinellopsis seminulina s.l. quinqueloba Turborotalita macintyreiCalcidiscus surculus Discoaster Emiliania huxleyi (Medium) caribbeanica Gephyrocapsa (Medium) oceanica Gephyrocapsa (Large) spp. Gephyrocapsa lacunosa Pseudoemiliania asanoi Reticulofenestra Datum plane "A" of Sato & Kameo (1996) Seismic reflector R1 Seismic reflector R5 Seismic reflector R7 Age (Ma) Age 3.1

3.14 0.44

? 2.78 1.67 - 1.73

Zone Foraminiferal

Dalt, Dalt, Gaeq Cgro

Gaeq

NatS Cgro (LCO)

Mlim

NpaS

Ssem, Ssem, NpaD Planktonic

N. pachyderma (s) pachyderma N. (s) atlantica N. N 21 N N 21 N

Pl3/Pl4 Pl4 dropstones

(consisent)

(temperate) Zone (subtropical) Gcar

Goce, Goce, med.)

Nannoplankton Plac

NN 19 NN 19 NN NN 20 NN Datum plane “A” Calcareous Yermak Plateau Yermak

( Gspp Polarity/ chron Polarity/ T A A N D O

Site 910 (composite) Site Depth (mbsf) Depth 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230

base Pleistocene in Channel et al. (1999b) in Channel et al. base Pleistocene base Pleistocene in Flower (1999) in Flower base Pleistocene Age (Ma) Age

0.2 - 0.44 ~1.0 ~2.3 ?0.44 Zone

Ffil Ffil

Spli cyst cyst Oisr Selo Tpel Ocen acme Sdio Sbre

acme Aumb Aand Dinoflagellate Ffil acme (upper) Ffil acme (lower)

Ract, Ilac Ract,

Zone

Foraminiferal

(LCO) NatS, NatS,

(FCO)

NpaS N. pachyderma (s) pachyderma N. (s) atl. N. Planktonic R5 seismic reflector R7 seismic reflector R1 seismic reflector

Gbull

Zone

Svalbard Margin Svalbard Nannoplankton

Plac

NN 20 NN 19 NN

Calcareous Site 986 (composite) Site chron Polarity/ ? ? ? T ? ? A A N D O

1n 2n

1r.1r 1r.1n 1r.2n 2r.1r 1r.xx Depth (mbsf) Depth 0 50

100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950

South

Pleistocene Pleistocene Gelasian

Middle Lower Pliocene) (Upper Late Pliocene-Pleistocene correlation panel showing selected ocean drilling sites located in the Fig. 2c. Dinoflagellate cyst acme events are new interpretations according to analysis of the raw fos- Arctic region. Ages in bold are according to the astronomical calibrations of sil occurrence data in the respective studies. Where pos- All other ages are based on interpolations according to the studies cited. Lourens et al. (2004). sible, the four chronostratigraphic boundaries discussed are indicated. For Site 986: magnetostratigraphy according to Channell et al. (1999b); planktonic foraminiferal biostratigraphy is according Flower (1999); calcareous nannoplannkton biostratigraphy is according to Shipboard Scientific Party (1996b); dinoflagellate cyst biostratigraphy (including seismic reflectors) is according to Smelror (1999). For Sites 910 & 911: magnetostratigraphy is according to Shipboard Scientific Party (1995); planktonic foraminiferal biostratigraphy according to Spiegler (1996); calcareous nannoplankton biostratigraphy Sato and Kameo graphy according to Matthiessen and Brenner (1996). -strati (1996); dinoflagellate cyst bio Late Pliocene and Pleistocene biostratigraphy of the Nordic Atlantic region 39 tional Commission on Stratigraphy as formal global the Upper Pleistocene occurs at a level approximating boundaries (Ogg et al. in press). The Base Upper Pleis- to the middle of Calcareous Nannoplankton Zone tocene Subseries is provisionally placed at the base of NN21. The same is true for ODP Site 919 on the East the Eemian Interglacial in Marine Isotope Stage (MIS) Greenland margin (Koç and Flower 1998) and ODP 5. The Base Middle Pleistocene Subseries is provi- Site 643 on the Vøring Plateau (Jansen et al. 1989). sionally placed at the Brunhes-Matuyama magnetic reversal (Gibbard 2003). The identification of these Diatoms chronostratigraphic boundaries outside of the Mediter- Based on the oxygen isotope studies at ODP Sites 983 ranean type area is possible via first-order principal and 919, the boundary should be placed within the and secondary correlative events associated with the Thalassiosira oestrupii Zone of Koc et al. (1999). It GSSPs (Aguirre and Pasini 1985, Rio et al. 1998). In can be identified more precisely as the base of the sec- the Nordic Atlantic region, only two secondary correl- ond and largest acme of T. oestrupii, as counted either ative marker events for the base Pleistocene GSSP at uphole or downhole. Vrica have been identified. These are the calcareous nannofossil last occurrence of Calcidiscus macintyrei (northern North Atlantic) and the first occurrence of 4.2 Base Middle Pleistocene (0.781 Ma) medium Gephyrocapsa spp. (Yermak Plateau). For direct correlation to the base Gelasian GSSP, the last oc- Planktonic foraminifera currence of Discoaster surculus was the only primary At ODP Site 919, on the East Greenland margin in the correlative event observed in the northern North northern North Atlantic, the top of MIS 19 (warm stage) Atlantic (Fig.3). In addition to these relatively rare corresponds to the last common occurrence (LCO) of observations, the following microfossil markers best the ‘warm-temperate’ species Globorotalia scitula and approximate the four main chronostratigraphic bound- Globorotalia inflata (new event identified in Flower aries dividing the Late Pliocene – Pleistocene interval 1998 and Spezzaferri 1998). Similarly, at neighbouring in this region (see Appendix 1 for details): ODP Site 918 the last common occurrence of the ‘cool-temperate’ (‘warm-subpolar’) Neo globoquadrina pachyderma (dextral) and the slightly later LCO 4.1 Base Upper Pleistocene (0.126 Ma) N. dutertrei occur close to the Brunhes-Matuyama Planktonic foraminifera boundary. This level is also marked by a maximum in At all ODP sites in the Nordic Atlantic region where Pleistocene planktonic foraminiferal species diversity MIS 5e was identified, this level occurred within the at both East Greenland Margin ODP Sites 918 and 919 Neogloboquadrina pachyderma (sinistral) Zone. In (Spezzaferri 1998), consistent with the top of the MIS addition, it marks the base of a warm temperate plank- 19 warm stage (Fig. 2a). North of the Greenland-Scot- tonic foraminiferal assemblage at ODP Sites 918 and land Ridge, this ‘cool-temperate’ assemblage appears 919 (Spezzaferri 1998), consistent with the Eemian In- to be absent at this level with the LCO (consistent) terglacial. N. pachyderma (dextral) occurring older, close to the Pliocene-Pleistocene boundary (Spiegler and Jansen Benthic foraminifera 1989; Spiegler 1996). On the Yermak Plateau, the LCO This level coincides with a high-productivity benthic (consistent) N. pachyderma (dextral) does, however, foraminiferal assemblage rich in Bulimina marginata, occur together with the last occurrence of a cool-tem- Cassidulina laevigata and Bolivina spp. in the North perate assemblage close to the Pliocene-Pleistocene Sea (Knudsen and Sejrup 1988). It may coincide with boundary (Spiegler 1996). The lack of a clearly identi- the last common occurrence of Elphidium ustulatum in fiable younger LCO N. pachyderma (dextral) and other neritic deposits (see Appendix 1). “warmer species” at most sites north of the GSR may be attributed to a reduced impact of warmer interglacial Calcareous nannoplankton surface currents at these higher latitudes. At ODP Site 983, on the Gardar Drift in the northern North Atlantic, the base of MIS 5 occurs approximate- Benthic foraminifera ly 15 metres below the seafloor (Koç et al. 1999), and At shallow neritic paleo-water depths in the North Sea, ca. 10 metres above the first occurrence of Emiliania the base of the Middle Pleistocene corresponds to the huxleyi (0.29 Ma in Lourens et al. 2004). The base of top of a warm assemblage of abundant Bulimina mar- 40 Erik D. Anthonissen

Standard Chrono- Calcareous Nannoplankton Planktonic Foraminifera Selected Age Calibrated Nordic Markers stratigraphy

Selected (Sub-)Tropical Bioevents Selected (Sub-)Tropical Bioevents

Geomagnetic according to Lourens et al. (2004) according to Lourens et al. (2004) See Appendix 1 for calibrations Epoch Stage Age (Ma) Polarity Time Scale Polarity Time (Bold = GSSP correlative events) (Bold = GSSP correlative events) (Bold = GSSP correlative events)

0 L.Pl. NN21 Emiliania huxleyi base 2nd acme (up/downhole) of Hol. 0.13 0.29 0.13 (DT) Thallassiosira oestrupii (A,B) 0.29 0.44 0.29 (CN) Emiliania huxleyi (A-D,F) NN20 Pseudoemiliania lacunosa 0.3 (DT) Proboscia curvirostris (A,B) 0.44 0.44 (CN) Pseudoemiliania lacunosa (A,B,D,F) Gephyrocapsa sp.3 0.61 Globorotalia tosaensis 0.61 M. Pleist. (BF) top acme B. marginata-C. teretis-T. fluens (G) 0.78 0.78 0.78 Pt1 1.3 Globigerinoides obliquus (DT) Nitzschia seminae (A) 0.84 Reticulofenestra asanoi 0.99 C1 0.91 (BF) Cibicides grossus L. Neritic-U. Bathyal (F, G) N22 0.9 1 1.17 1.02 (DC) Filisphaera filifera and/or small Gephyrocapsa spp. dominance 1.19 Neogloboquadrina acostaensis (DC) Nematosphaeropsis lemniscata (B,F,G) 1.0 NN19 1.24 1.58 (CN) large Gephyrocapsa spp. (A,F) 1.24 large Gephyrocapsa spp. Globoturborotalita apertura Pleistocene 1.64 (CN) medium (CN) Calcidiscus macintyrei (A) 1.6 E. Pleist. Gs. fistulosus Calcidiscus macintyrei 1.77 Gephyrocapsa spp. (F) 1.73 Neogloboquadrina spp.(s) common [Med.] 1.73 (BF) Cibicides grossus M. Neritic (G) 1.6 1.77 1.8 1.81 1.78 1.79 F. filifera medium Gephyrocapsa spp. 1.7-1.8 (PF) N. pachyderma (s) (DC) top of Upper 1.8 1.98 acme (D,F) 1.95 1.93 Globigerinoides extremus common (A,C,D,F) 1.93 2.0 2.0 Discoaster brouweri Gr. truncatulinoides (PF) Neogloboquadrina 2 PL6 1.7-1.9 2.13 Discoaster triradiatus 1.95 2.1 (PF) Globorotalia inflata (A,G) NN18 Globorotalia limbata atlantica (d) (B,D,F) 2.15 2.24 C2 2.49 2.3 (CN) Discoaster surculus (A) 2.39 Globoturborotalita woodi

Gelasian 2.39 Discoaster pentaradiatus 2.39 (BF) Monspeliensina pseudotepida U-M. Neritic (G) 2.5-2.6 Gr. miocenica [Atl.] 2.39 NN17 (PF) N. atlantica (s) consistently common (A,G) 2.6 2.59 2.59 2.49 Discoaster surculus 2.49 PL5 2.41 Gr. puncticulata + (DC) base of Lower Filisphaera filifera 2.4-2.6 Neogloboquadrina atlantica (s) [Med.] acme (D,F) N20 Discoaster tamalis 2.8 /N21 Dentoglobigerina altispira 3.13 3 3.03 NN16 3.13 Legend 3.12 PL4 Sphaeroidinellopsis seminulina 3.14 3.21 C2A 3.14 (PF) Foraminifera (A) Northern Atlantic 3.23 3.33 3.24 Gr. inflata Globoquadrina (CN) Nannoplankton (B) Irminger Basin (E) Greenland Sea Pliocene PL3 (DC) Dinoflagellates (C) Iceland Plateau (F) Yermak Plateau

Piacenzian baroemoenensis (DT) Diatoms (D) Vøring Plateau (G) North Sea 4.19

Fig. 3. Comparison of the low-latitude standard biozonations and important calibrated Nordic region bioevents. The geographic distribution of calibration points for each Nordic bioevent is indicated by the letters following its name (see Legend). ginata, Trifarina fluens and Cassidulina teretis (Sejrup South Atlantic and Eastern Mediterranean to 0.9 Ma in et al. 1987). This may coincide with the first common Lourens et al. (2004). This is the only nannofossil occurrence of the cold-indicator Elphidium asklundi marker for the base Middle Pleistocene in the Nordic (Knudsen and Asbjørnsdottir 1991). At Lower Neritic Atlantic region and was only identified at this high- to Upper Bathyal depths the last occurrence of Cibi- Arctic location. It is believed to have entered the Arc- cides grossus approximates the boundary (King 1989; tic through the Bering Strait. Osterman 1996). At Lower Bathyal depths the Mid- Pleistocene saw the extinction of deep-sea benthic Diatoms foraminifera with elongate, cylindrical tests and high- South of the Greenland-Scotland Ridge, the best bio- ly specialised apertures. The ‘Stilostomella Extinction’ stratigraphic approximation to the base of the Middle has been documented globally as occurring around the Pleistocene is the last occurrence of the diatom Brunhes-Matuyama boundary. This includes ODP Nitzschia seminae. This event was dated to 0.84 Ma Sites 980 and 982 in the northern North Atlantic, (MIS 21) at the northern North Atlantic ODP Site 983 where the event was seen to culminate at ~ 0.694 Ma (Koç et al. 1999) and 0.817–0.895 Ma (MIS 22–24) at at Lower Bathyal water depths (Kawagata et al. 2005). ODP Site 919 on the East Greenland Margin (Koç and Flower 1998). Calcareous nannoplankton At ODP Site 911, on the Yermak Plateau, Sato and Dinoflagellate cysts Kameo (1996) found the last occurrence of Retic- In the Norwegian Sea, Smelror (pers. comm.) placed ulofenestra asanoi at 0.85 Ma. This species had its last the last occurrence of Filisphaera filifera at 1.4 Ma. common occurrence calibrated astronomically in the This age is according to correlations with the nanno- Late Pliocene and Pleistocene biostratigraphy of the Nordic Atlantic region 41 plankton stratigraphies of ODP Leg 151 (Poulsen et al. Vøring Basin, and 918 in the Irminger Basin. This 1996). Mudie et al. (1990) placed the last occurrence event can also be described as the last occurrence of of F.filifera in the Norwegian Sea and North Atlantic N. atlantica as a species including both coiling mor- at slightly older than the base of the Middle Pleis- photypes. This was the case in the original range chart tocene (ca. 1 Ma). The dinoflagellate cyst stratigra- published by Aguirre and Pasini (1985) where they ob- phies for Norwegian Sea ODP Sites 643 and 642 place served the last occurrence of N. atlantica just above this event slightly older than the base of the Middle the boundary at Vrica. It may sometimes occur togeth- Pleistocene. At Arctic ODP Site 911 this event occurs er with the LCO N. pachyderma (dextral). at a level similar to the Norwegian Sea occurrence. At the Svalbard Margin ODP Site 986, it is significantly Benthic foraminifera younger, occurring in the Upper Pleistocene (between At upper neritic depths in the southern North Sea, the 0.2 and 0.44 Ma). Whether this is due to reworking or last common occurrence of the benthic foraminifer true extinction events is not known. The last occur- Elphidiella hannai occurs close to the Pliocene-Pleis- rence of F.filifera, according to these data, appears to tocene boundary within the Olduvai Subchron (Kuhl- be a rough approximation to the base of the Middle mann 2004). At deeper lower neritic depths in the Pleistocene in the Norwegian Sea and possibly further central and northern North Sea, the last occurrence of south. Cibicides grossus is a better approximation to the boundary (see Appendix 1). 4.3 Base Pleistocene (1.806 Ma) Dinoflagellate cysts Planktonic foraminifera The dinoflagellate cyst stratigraphy of Kuhlmann None of the base Pleistocene primary or secondary (2004) for the southern North Sea describes a first GSSP markers are present in the Nordic deep-sea cores and second ‘Filisphera/Habicysta/Bitectatodinium (with the exception of a rare occurrence of Globigeri- acme’ during the Olduvai normal event. A second or noides obliquus extremus in discontinuous Upper Plio- “upper F.filifera acme” is also evident in the raw fos- cene sediments of ODP Site 910), which usually offer sil occurrence data of ODP Site 642 (see Mudie most precise dating via direct correlation to the Geo- 1989) on the Vøring Plateau, and at ODP Site magnetic Polarity Time Scale. However, examination 911(see Matthiessen and Brenner, 1996) on the Yer- of the microfossil data in the original definition of the mak Plateau. At both sites this upper acme corre- Vrica GSSP (Aguirre and Pasini 1985) shows, in addi- sponds closely to the top of the Olduvai Subchron. tion to the secondary markers mentioned, the first oc- On the Svalbard Margin, at ODP Site 986, this same currence of Neogloboquadrina pachyderma (sinistral) acme event can be identified (see Smelror 1999), occurring just above the boundary. In a later study of however, the ambiguous magnetostratigraphy in the Vrica Section, Lourens et al. (1996) astronomical- these samples obscures a reliable age estimate. It ly calibrated the first common occurrence of N. pachy- therefore appears that the upper F.filifera acme is the derma (s) to 1.799 Ma. The first common occurrence most reliable palynological marker for a level that is (FCO) of this species has also been recorded in ocean slightly younger than the base Pleistocene through- drilling cores throughout the Nordic Atlantic region as out much of the Nordic Atlantic region. corresponding approximately to the top of the Olduvai Subchron: North Atlantic DSDP Sites 609, 610, 611 Calcareous nannoplankton (Weaver and Clement 1986 recorded as a first occur- The calcareous nannoplankton stratigraphy of north- rence of the “encrusted” morphotype); Northern North ern North Atlantic ODP Sites 981, 982 and 983 ap- Atlantic ODP Site 985 (Flower 1999), Norwegian Sea pears to be the most reliable biostratigraphy for this ODP Sites 642, 643, 644 (Spiegler and Jansen 1989); time interval, at least south of the GSR. At all three Iceland Plateau Site 907 and Svalbard Margin ODP sites the last occurrence of Calcidiscus macintyrei Site 986 (Flower 1999). occurs at the same level, above the Olduvai Sub- An additional planktonic foraminiferal event mark- chron in C1r.3r. This datum was astronomically cal- ing the boundary is the last occurrence of Neoglobo- ibrated to 1.66 Ma according to Lourens et al. (2004) quadrina atlantica (dextral), or the top of the Upper and occurs approximately 10 metres above the first N. atlantica (dextral) Zone of Spiegler and Jansen common occurrence of N. pachyderma (s) at all three (1989). It has been noted at ODP Sites 644 on the sites. 42 Erik D. Anthonissen

4.4 Base Gelasian (2.588 Ma) 5. Discussion: Synchroneity/ diachroneity of selected Planktonic foraminifera In the northern North Atlantic (DSDP Sites 609, 610, planktonic foraminiferal datums 611), Weaver and Clement (1986) and Weaver (1987) found the last occurrence (LO) Neogloboquadrina at- The age of the last occurrence of Neogloboquadrina lantica (sinistral) between the Gauss/Matuyama mag- atlantica (sinistral) in the Nordic Atlantic region has a netic polarity boundary and the Olduvai Subchron. In history of conflicting interpretation. North Sea zona- the southern North Sea core study by Kuhlmann tions have most often referred it to an age of 2.3 Ma, (2004), the last common occurrence (LCO) of N. at- based on the temperate northern North Atlantic bio- lantica was found just above the Gauss/Matuyama magnetostratigraphy of DSDP Leg 94 (Weaver and boundary. There may be exceptions to this age inter- Clement 1986). This study shows this bioevent to be pretation (see Discussion). clearly time-transgressive across the region, but with three age clusters recorded at ca. 1.8 Ma, ca. 2.3 Ma Benthic foraminifera and ca. 3.1 Ma (Appendix 1). The benthic foraminiferal extinction of Monspeliensi- The oldest age assignment for the LO N. atlantica (s) na pseudotepida in the Lower Neritic North Sea and of ca. 3.1 Ma was recorded at sites that show evidence offshore Mid-Norway corresponds approximately to of a significant Mid-Pliocene warm-water influx: the base of the Gelasian Stage (Kuhlmann 2004). This Vøring Plateau ODP Sites 642 & 643 (?C2r.1r) and event was used by King (1989) to define his NSB Yermak Plateau ODP Site 910 (slightly older than the 14/15 zonal boundary in the North Sea, which he standard Pl3/Pl4 planktonic foraminiferal zonal bound- placed close to the LO of N. atlantica (s) at 2.3 Ma ary of Berggren et al. 1995). The ‘Mid-Pliocene global (age according to Weaver and Clement 1986). The LO warmth’ is evident here in the warm-temperate to sub- Monspeliensina pseudotepida also occurrs at a level tropical planktonic foraminiferal assemblage at ODP with a strontium isotope date of 2.5–4.5 Ma in the Site 910 (including Dentoglobigerina altispira and central North Sea well 2/4-C-11 (Eidvin and Riis Globorotalia (Menardella) limbata), and the acmes of 1995). Globigerina bulloides and the dinocyst Achomo- sphaera andalousiensis on the Vøring Pla teau. Knies Dinoflagellate cysts et al. (2002) identified a seasonally ice-free period in In the southern North Sea, Kuhlmann (2004) found a the eastern Arctic, contemporaneous with the ‘Mid- first and a second acme of Filisphera/Habicysta/Bi- Pliocene global warmth’. tectatodinium. The base of the first (or lower) acme The ca. 2.3 Ma age assignment for the LO N. at- corresponds closely to the Gauss-Matuyama magnetic lantica (s) applies to the northern North Atlantic sites reversal and therefore to the base of the Gelasian currently overlain by the warm surface waters of the Stage. An analysis of the raw fossil occurrence data for North Atlantic Drift (ODP Sites 981, 982,?984) and for ODP Sites 642 (Vøring Plateau), 986 (Svalbard Mar- the Vøring Plateau ODP Site 644, currently overlain gin) and 911 (Yermak Plateau) reveals both an upper by the warm Norwegian Coastal Current. At these lo- and a lower F.filifera acme. On the Vøring Plateau, the cations the LO N. atlantica (s) occurs within the pale- base of this acme approximately coincides with the omagnetic Subchron C2r.2r. Gauss/Matuyama boundary (see Mudie 1989). On the The youngest age assignment for the LO N. atlanti- Svalbard Margin, it occurs slightly below the “R7 seis- ca (s) of ca. 1.8 Ma (straddling the Pliocene-Pleis- mic reflector” (Smelror 1999), with a correlated age of tocene boundary) was recorded at sites currently over- ca. 2.3 Ma according to Faleide et al. (1996). While lain by cold to mixed surface currents: Irminger Basin this suggests agreement with the Norwegian Sea age, ODP Site 918 (upper C2n), Iceland Sea ODP Sites 985 this is not the case for the Yermak Plateau ODP Site (?C1r.3r) and 907 (mid C2n), Svalbard Margin ODP 911, where the acme occurs much higher in the se- Site 986 (?C1r.3r) and Yermak Plateau ODP Site 911 quence. Further study is needed to ascertain the relia- (mid C2n). The complete absence of this bioevent and bility of these acme events as regional markers. poor preservation encountered at Greenland Sea ODP A comparison between the key Nordic region bio- Site 987 is probably due to dissolution as a result of the events and the standard (sub)tropical zonations is giv- overlying cold East Greenland Current. The presence en in Fig 3. of this bioevent at the more northerly sites could be Late Pliocene and Pleistocene biostratigraphy of the Nordic Atlantic region 43 due to the contemporaneous inception of the warm gional scale and on a more local scale between sub- Proto-Norwegian Current at ca. 1.9 Ma (Henrich et al. basins. 2002). Poore and Berggren (1974) observed this event Possible explanations for the diachronous record of in the Labrador Sea at Deep Sea Drilling Project Site the last occurrence Neogloboquadrina atlantica (sinis- 113 as a very rare occurrence at the same level as the tral) in the Nordic Atlantic region are: calcite dissolu- LO Discoaster brouweri (1.9 Ma astronomically cali- tion under cold ocean currents (results in a depressed brated age in Lourens et al. 2004). At other Labrador range); ice-rafting or other reworking (results in an ar- Sea sites, the event occurred lower in the Upper tificially extended range); sites located under warm Pliocene, also possibly due to dissolution by the cold surface water from the Gulf Stream/North Atlantic Labrador Current. Drift might have experienced unfavourable environ- The age of the first common occurrence of Neo - mental conditions for this apparently cold-adapted, globoquadrina pachyderma (sinistral) appears to be sinistrally-coiled N. atlantica morphotype (results in a largely synchronous across the region, ranging from depressed range). At locations dominated by cold or 1.7–1.9 Ma (mid C2n to lower C1r.3r) in the majority mixed ocean currents, the last occurrence of Neo - of the sites investigated. The only exceptions to this globoquadrina atlantica (s) occurs together with the record are the anomalously young ages of 1.0–1.1 Ma first common occurrence of N. pachyderma (s). recorded at East Greenland ODP Site 918 (upper The first common occurrence of N. pachyderma (s) C1r.2r) and Greenland Sea ODP Site 987 (mid C1r.1r). is a largely synchronous datum in the region, and a Both sites are presently overlain by the cold East good biostratigraphic approximation for the base of Greenland Current, which may have resulted in calcite the Pleistocene. The exception occurs at locations dissolution of the lower parts of the N. pachyderma (s) dominated by cold ocean currents such as the East acme. The inception of the warm Proto-Norwegian Greenland Current, where only the uppermost part of Current at ca. 1.9 Ma might have been responsible for the acme is present. The earlier onset of this acme this sudden acme event. Since these warmer-water in- event in the southern and eastern parts of the region cursions are believed to have been confined to the east- may be related to the inception of the warm Proto-Nor- ern and southern Nordic Seas, the Greenland Sea wegian Current (Henrich et al. 2002). would not have experienced the same ameliorated sur- The continuing efforts of the Integrated Ocean Dril - face-water conditions (Henrich et al. 2002). The ano- ling Program (IODP) and further advances in amino- malously younger age does, however, coincide with acid dating, OSL and isotope dating methods may im- the globally synchronous first occurrence of the larger prove linking these high-latitude microfossil records modern N. pachyderma (s) morphotype (Kucera and to the standard Neogene chronostratigraphic defini- Kennett, 2002). tions of the Mediterranean.

6. Conclusions Acknowledgements. This study, under the supervision of Felix M. Gradstein, is part of an ongoing project at the Natural History Museum in Oslo (Norway) to calibrate The correlation of deep-sea cores in the Nordic At- Nordic Upper Cenozoic biozones relative to the standard lantic region highlights the geographical extent and global time scale. Support comes from the Natural History stratigraphic range of a number of high-latitude mar- Museum, University of Oslo and the Norwegian Interactive ker species. This has resulted in the identification of Lithostratigraphic Lexicon (NORLEX Project). synchronous and diachronous bioevents, together with the best biostratigraphic approximations to the standard chronostratigraphic boundaries of this time peri- 7. References od. Although many of these taxa have been know to show diachronous local ranges, this regional correla- Aguirre, E., Pasini, G., 1985. The Pliocene-Pleistocene 8 tion allows for a better quantification of the degree of boundary. Episodes (2), 116–120. Aksu, A. E., Kaminski, M. A., 1989. Neogene planktonic this diachroneity. This has resulted in identification of foraminiferal biostratigraphy and biochronology in Baf- the best biostratigraphic approximations to the stand - fin Bay and the Labrador Sea. In: Srivastava, S. P., Arthur, ard Late Pliocene – Pleistocene chronostratigraphic M., Clement, B., et al. (Eds.), Proceedings of the Ocean boundaries at these high latitudes. In addition, this Drilling Program, Scientific Results 105, Ocean Drilling study highlights biostratigraphic trends on both a re- Program, College Station, p. 287–304. 44 Erik D. Anthonissen

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Anthonissen Calibrations of key microfossil bioevents in the Nordic Atlantic region. Each calibrated age is organised according to the region/basin where the calibrati- according to the region/basin Atlantic region. Each calibrated age is organised Calibrations of key microfossil bioevents in the Nordic Appendix 1. the average of these calibrated ages has been ascribed to a diachronous bioevent. Where nessecary, on was made.