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High-elevation cosmogenic nuclide dating of the last deglaciation in the central Swedish mountains: implications for the timing of tree establishment
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK). (Quaternary Geology)
University of Glasgow, Department of Geographical and Earth Sciences.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We use cosmogenic exposure ages to determine the timing of deglaciation of the Scandinavian ice sheet (SIS) at summit elevation in the central Swedish mountains. Mean exposure ages for boulders on the summit of Mt. Åreskutan (10.6 ±0.6 ka, n = 3, 1420 m a.s.l.) and from the highest-elevation moraine related to SIS deglaciation in Sweden (12.0 ±0.6 ka, n = 3, 1135 m a.s.l.) are consistent with previous lower-elevation radiocarbon age estimates for the timing of deglaciation. Summit areas in this region deglaciated ~12.0-10.6 ka, coinciding approximately with the termination of the Younger Dryas cold interval (11.7 ka). Unusually old radiocarbon ages of tree remains previously studied from the summit-area of Mt. Åreskutan are rejected on the basis of incompatibility with consistent TCN ages for deglaciation, and incompatibility with established paleoecological and paleoglaciological reconstructions. Analysis of the new exposure ages against radiocarbon ages from lower elevation indicates that the SIS decayed rapidly during final deglaciation.

Keyword [en]
cosmogenic exposure dating, radiocarbon dating, moraine, deglaciation, nunatak
National Category
Geology
Research subject
Quarternary Geology
Identifiers
URN: urn:nbn:se:su:diva-38797OAI: oai:DiVA.org:su-38797DiVA: diva2:315350
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.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 22
Keyword
Scandinavian ice sheet, ice sheet dynamics, luminescence dating, cosmogenic exposure dating, geochronology, moraine, interstadial, deglaciation, nunatak
National Category
Geology
Research subject
Quarternary Geology
Identifiers
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)
Opponent
Supervisors
Note
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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