Marine ice-rafted debris records constrain maximum extent of Saalian and Weichselian ice-sheets along the northern Eurasian margin

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Abstract

Ice-rafted debris (IRD) (>2 mm), input in eight sediment cores along the Eurasian continental margin (Arctic Ocean), have been studied over the last two glacial/interglacial cycles. Together with the revised chronologies and new micropaleontological data of two cores from the northern Barents Sea (PS2138) and northeastern Kara Sea (PS2741) spanning Marine Isotope Stages (MIS) 6 to 1, the IRD data give new insights into the glacial history of northern Eurasian ice-sheets over the last 150 ka. The chronologies of the cores are based on stable isotope records, AMS 14C datings, paleomagnetic and biostratigraphic data.

Extensive episodes of northern Barents Sea ice-sheet growth, probably to the shelf edge, occurred during the late Weichselian (MIS 2) and the Saalian (MIS 6). Major IRD discharge at the MIS 4/3-transition hints to another severe glaciation, probably onto the outer shelf, during MIS 4. IRD-based instabilities of the marine-based ice margin along the northern Barents Sea between MIS 4 and 2 are similar in timing with North Atlantic Heinrich events and Nordic Seas IRD events, suggesting similar atmospheric cooling over a broad region or linkage of ice-sheet fluctuations through small sea-level events.

In the relatively low-precipitation areas of eastern Eurasia, IRD peak values during Termination II and MIS 4/3-transition suggest a Kara Sea ice-sheet advance onto the outer shelf, probably to the shelf edge, during glacial MIS 6 and 4. This suggests that during the initial cooling following the interglacials MIS 5, and possibly MIS 7, the combined effect of sustained inflow of Atlantic water into the Arctic Ocean and penetration of moisture-bearing cyclones into easterly direction supported major ice build-up during Saalian (MIS 6) and Mid-Weichselian (MIS 4) glaciation. IRD peak values in MIS 5 indicate at least two advances of the Severnaya Semlya ice-sheet to the coast line during the Early Weichselian. In contrast, a distinct Kara Sea ice advance during the Late Weichselian (MIS 2) is not documented by the IRD records along the northeastern Kara Sea margin.

Introduction

Coarse terrigenous material (>500 μm) in deep-sea sediments from the Nordic Seas and the Arctic Ocean is usually assumed to be iceberg-rafted (cf. Nørgaard-Pedersen et al., 1998, Dowdeswell et al., 1998 for a recent discussion). As long as gravity flows and sea-ice transport can be ruled out, peak values of ice-rafted debris (IRD) (>500 μm) in sediment records possibly monitor glacial maxima and/or deglaciation phases of surrounding ice-sheets during the late Quaternary (e.g. Baumann et al., 1995, Mangerud et al., 1998). Particularly, large volumes of icebergs were released periodically when continental glaciers/ice-sheets reached the coastline, eventually protruded to the shelf edge and disintegrated (e.g. Elverhøi et al., 1995). Consequently, temporal variations in amount and composition of IRD provide important information on the changes in the loci of major continental glaciations, e.g. the Svalbard/Barents Sea ice-sheet (Mangerud et al., 1998).

Our approach to decipher waxing and waning of the northern Eurasian ice-sheets during the Saalian and Weichselian by marine records is based on the excellent temporal coincidence of IRD records from the western Svalbard margin with the glaciation history interpreted from the onshore sections on Svalbard (Mangerud et al., 1998). They concluded that, during the Weichselian, IRD peak values (>500 μm) occurred mainly during major deglaciation phases of the Svalbard/Barents Sea ice-sheet. However, along the northern Eurasian continental margin, detailed correlation of IRD records and onshore sections during the Weichselian or even the Saalian are hampered by relatively sparse terrestrial data sets. Nevertheless, the recent summaries by Velitchko et al., 1997a, Velitchko et al., 1997b and Svendsen et al. (1999) provide a glacial geologic framework which can be tested with IRD records along the Eurasian continental margin (cf. Knies et al., 2000, Kleiber et al., 2000). Svendsen et al. (1999) concluded that the maximum ice-sheet extent occurred prior to 50 ka, probably during MIS 4, whereas much of the Russian Arctic remained ice-free during the late Weichselian (MIS 2).

Here, we revise the current knowledge of the maximum extent of Saalian and Weichselian ice-sheets along the northern Eurasian margin recently published by Polyak et al. (1997), Landvik et al. (1998), Svendsen et al. (1999), Knies et al. (2000), and Kleiber et al. (2000). The IRD input into eight marine records recovered during several expeditions with the ice-breaking research vessel “Polarstern” (Fig. 1; Table 1), and, in particular, the revised chronologies and new micropaleontological data of the cores PS2138 and PS2741 (Matthiessen et al., 2001) may give new insights into the glacial history off Northern Eurasia.

IRD of >2 mm were studied in 1-cm intervals downcore expressed as No. >2 mm/10 cm3 to ascertain that, during major climatic changes, IRD attributed to sediment delivery from waxing and waning ice-sheets along the Eurasian continental margin is really considered. We exclude sea-ice as transport media for particles >2 mm in the study area because over 80% of debris in sea-ice is in the silt and clay fraction Pfirman et al., 1989, Nürnberg et al., 1994. IRD peak values related to gravity flow transport in some of the investigated cores (PS2445-4, PS2446-4, P2447-5) were identified by high resolution seismic profiles (Parasound, 4 kHz) (Kleiber et al., 2000).

Finally, the revised reconstruction of waxing and waning ice-sheets along the northern Eurasian continental margin during the last 145 ka is correlated with Atlantic water inflow variations based on dinoflagellate cysts fluctuations in two sediment records from the northern Barents and Kara Sea margins (Matthiessen et al., 2001). The results provide possible evidence for a direct coupling of Atlantic water inflow variations along the Eurasian continental margin and the resultant penetration of moisture-bearing cyclones into an easterly direction with the asymmetric build-up of the Barents and Kara Sea ice-sheets during the middle (MIS 4) and late Weichselian (MIS 2) glaciations (Svendsen et al., 1999).

Section snippets

Chronology

The age control points for the studied cores along the northern Eurasian margin are mainly provided by—with decreasing priority—AMS 14C datings, stable oxygen and carbon isotope stratigraphy, magnetostratigraphy, biostratigraphic events, radionuclide records (10Be, 230Th), and lithostratigraphic as well as seismostratigraphic units (cf. references in Table 1 for details). Briefly, age control for the cores along the northern Barents Sea continental margin are based on continuous stable oxygen

IRD patterns along the northern Barents Sea margin

The strongest release of icebergs from the northeastern Svalbard margin as indicated by IRD peak values in PS2138 occurred during the terminations of the Saalian (MIS 6), Mid- (MIS 4) and Late Weichselian (MIS 2) glaciations in the Svalbard/Barents Sea area (Fig. 2a). However, prominent single IRD peaks in between phases of reduced input are observed both during glacials and interglacials and indicate periodic melting events of calved glacial ice from the northeastern Svalbard margin during the

IRD pattern along the northeastern Kara Sea margin

A diamicton in PS2782 recovered in 340-m water depth is older than 44 ka and indicates a severe glaciation on Severnaya Semlya (Fig. 2b). The transition to glacimarine sediments is indicated by prominent IRD peaks intercalated in laminated sequences (Fig 2b; Weiel, 1997). Gravel is rare from the laminated sequence to the core top, although a distinct higher input of IRD is observed in the uppermost 50 cm (Fig. 2b).

During the Saalian (MIS 6) IRD is absent from the continental slope core PS2741,

Saalian–Middle Weichselian glaciations in the northern Barents Sea

The IRD pattern NE of Svalbard (PS2138) seems not to be confined to ice volume maxima at MIS 6, 5d and 5b, 4, and 2 (Fig. 3). However, when comparing the glaciation on Svalbard with the IRD pattern in PS2138, the general coincidence of major IRD peaks with deglacial phases on western Svalbard at the MIS 2/1, 4/3, and—with a slightly lower intensity—6/5 transitions, is striking (Fig. 3). The Saalian glaciation probably reached the northern Barents Sea shelf edge because enhanced bulk

Saalian–Middle Weichselian glaciations in the northeastern Kara Sea

The relatively low content of IRD in core PS2741 during the last 150 ka compared to the records from the Svalbard/Barents margin may reflect either the presence of relatively stable ice-sheets with small fluctuations of the ice margin or stable glacimarine conditions when ice-sheets had a small extent or were even absent (Fig. 6). A distinct IRD spike and peak values of coarse fraction input indicate a broad ice front in an advanced position on the outer shelf, possibly along the shelf edge, at

Correlation of IRD-based glacial history since MIS 6 with Atlantic water advection deduced from dinoflagellate cyst data

Fig. 9 summarizes the current knowledge of the glacial history since MIS 6 deduced from IRD studies on eight marine records along the northern Eurasian continental margin. Three main glacial phases are recorded along the northern Barents Sea margin; that is during MIS 6, 4 and 2. The most extensive ice-sheet in the Kara Sea existed during MIS 6 and 4 Fig. 9, Fig. 10. A major discrepancy between marine and terrestrial records exists for MIS 5 and is probably caused by the lower temporal

Conclusions

The maximum extent of the Barents and Kara Sea ice-sheets along the northern Eurasian Continental Margin has been examined based on IRD content (>2 mm) of eight dated sedimentary records. Evidence was found for a far extended ice-sheet along the northern Barents and Kara Sea margin during MIS 6 and 4 (Fig. 10). Furthermore, a far extended ice-sheet to the shelf edge along the northern Barents Sea margin including the St. Anna Trough (cf. Polyak et al., 1997) has been proven during the Last

Acknowledgements

We sincerely acknowledge the masters and crews of RV “Polarstern“ for cooperation during the Arctic expeditions in 1991, 1993, and 1995. For discussion and comments on earlier drafts of the manuscript we thank C. Hass, C. Vogt, and N. Nørgaard-Pedersen. We acknowledge the fruitful discussions with many colleagues at the 3rd QUEEN workshop in Øystese, Norway, which were all very helpful and informative. In particular, we thank C. Hjort, E. Larsen, and J. Mangerud for information about first

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