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OSL ages in central Norway confirm a MIS 2 interstadial (25-20 ka) and a dynamic Scandinavian ice sheet
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK). (Quaternary Geology)
Geological Survey of Norway, Trondheim.
Nordic Laboratory for Luminescence Dating, Aarhus University, Risø National Laboratory.
(English)In: Quaternary Science Reviews, ISSN 0277-3791Article in journal (Other academic) Submitted
Abstract [en]

Recent work has suggested that the Scandinavian ice sheet was much more dynamic than previously believed, and its western marine-based margin can provide an analogue to the rapid-paced fluctuations and deglaciation observed at the margins of the Antarctic and Greenland ice sheets.

In this study we used a complimentary dating technique, OSL (Optically Stimulated Luminescence dating), to confirm the existence of the Trofors interstadial in central Norway; an ice-free period that existed from ~25 to 20 ka recorded at multiple sites throughout Norway (cf. Andøya interstadial) and that divides the Last Glacial Maximum (LGM) into two stadials. OSL signal component analysis was used to optimize data analysis, and internal (methodological) tests show the results to be of good quality. Both large and small aliquots gave consistent OSL ages (22.3 ±1.7 ka, n = 7) for sub-till glaciofluvial/fluvial sediments at the Langsmoen stratigraphic site, and an apparent old age (~100 ka) for a poorly bleached sample of glaciolacustrine sediment at the nearby stratigraphically-related Flora site. Eight radiocarbon ages of sediment from the Flora site gave consistent ages (20.9 ±1.6 cal. ka BP) that overlap within 1σ with OSL ages from the nearby Langsmoen site. The similarity in age within and between these stratigraphically-related sites and using different geochronological techniques strongly suggests that this area was ice-free around ~21 or 22 ka. The existence of the Trofors interstadial along with other interstadials during the Middle and Late Weichselian (MIS 3 and MIS 2) indicates that not only the western margin, but the whole western part of the Scandinavian ice sheet, from the ice divide to the ice margin was very dynamic. These large changes in the ice margin and accompanying drawdown of the ice surface would have affected the eastern part of the ice sheet as well.

Keyword [en]
Optically stimulated luminescence (OSL) dating, Scandinavian ice sheet, Trofors interstadial, MIS 2, LGM, Norway
National Category
Research subject
Quarternary Geology
URN: urn:nbn:se:su:diva-38796OAI: diva2:315344
Available from: 2010-04-30 Created: 2010-04-29 Last updated: 2010-12-29Bibliographically approved
In thesis
1. Late Quaternary ice sheet history and dynamics in central and southern Scandinavia
Open this publication in new window or tab >>Late Quaternary ice sheet history and dynamics in central and southern Scandinavia
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Recent work suggests an emerging new paradigm for the Scandinavian ice sheet (SIS); one of a dynamically fluctuating ice sheet. This doctoral research project explicitly examines the history and dynamics of the SIS at four sites within Sweden and Norway, and provides results covering different time periods of glacial history. Two relatively new dating techniques are used to constrain the ice sheet history: the optically stimulated luminescence (OSL) dating technique and the terrestrial cosmogenic nuclide (TCN) exposure dating technique.

OSL dating of interstadial sediments in central Sweden and central Norway indicate ice-free conditions during times when it was previously inferred the sites were occupied by the SIS. Specifically, the SIS was absent or restricted to the mountains for at least part of Marine Isotope Stage 3 around 52 to 36 kyr ago. Inland portions of Norway were ice-free during part of the Last Glacial Maximum around 25 to 20 kyr ago.

Consistent TCN exposure ages of boulders from the Vimmerby moraine in southern Sweden, and their compatibility with previous estimates for the timing of deglaciation based on radiocarbon dating and varve chronology, indicate that the southern margin of the SIS was at the Vimmerby moraine ~14 kyr ago.

In central Sweden, consistent TCN ages for boulders on the summit of Mt. Åreskutan and for the earlier deglaciated highest elevation moraine related to the SIS in Sweden agree with previous estimates for the timing of deglaciation around 10 ka ago. These results indicate rapid decay of the SIS during deglaciation. Unusually old radiocarbon ages of tree remains previously studied from Mt. Åreskutan are rejected on the basis of incompatibility with consistent TCN ages for deglaciation, and incompatibility with established paleoecological and paleoglaciological reconstructions.

Altogether this research conducted in different areas, covering different time periods, and using comparative geochronological methods demonstrates that the SIS was highly dynamic and sensitive to environmental change.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2010. 32 p.
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 22
Scandinavian ice sheet, ice sheet dynamics, luminescence dating, cosmogenic exposure dating, geochronology, moraine, interstadial, deglaciation, nunatak
National Category
Research subject
Quarternary Geology
urn:nbn:se:su:diva-38611 (URN)978-91-7447-068-0 (ISBN)
Public defence
2010-06-04, De Geersalensalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.Available from: 2010-05-11 Created: 2010-04-21 Last updated: 2010-12-30Bibliographically approved

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