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A new mid-Holocene tephra in central Sweden
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2009 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 131, no 4, 293-297 p.Article in journal (Refereed) Published
Abstract [en]

A mid Holocene tephra, LBA-2 has been found in a peat bog in central Sweden. Geochemical analyses suggest an origin in an evolved volcanic centre, most likely the Snæfellsnes volcanic centre in western Iceland. The geochemistry of the LBA-2 tephra is similar to the youngest of three silicic tephra layers from Snæfellsjökull, Sn-1 dated to 1780 cal yr BP. However, wiggle-match dating indicates an age of 3550-3650 cal yr BP, close in age to the Hekla-S/Kebister tephra (3720 cal yr BP), previously found in several sites in Scandinavia. Detailed geochemical analyses and dating is lacking for the mid Holocene Sn-2 tephra in Iceland but it is likely that the geochemical composition is similar as the Sn-1 tephra. The LBA-2 tephra is tentatively correlated with the Sn-2 tephra and we also suggest that the ‘x’ tephra layer (ca 3500 BP) found in the Dyngjufjöll area, central Iceland (Sigvaldason et al. 1992) can be correlated with the Sn-2 tephra.

Place, publisher, year, edition, pages
London: Taylor & Francis , 2009. Vol. 131, no 4, 293-297 p.
National Category
Geology
Identifiers
URN: urn:nbn:se:su:diva-32910DOI: 10.1080/11035890903452662ISI: 000272850400003OAI: oai:DiVA.org:su-32910DiVA: diva2:281927
Available from: 2009-12-17 Created: 2009-12-17 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Late Holocene humidity variability in central Sweden
Open this publication in new window or tab >>Late Holocene humidity variability in central Sweden
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The aim of this thesis was to reconstruct humidity variability in central Sweden during the late Holocene. A multi-proxy approach was used to infer humidity changes as recorded in a lake and a mire. Age-models were constructed based on radiocarbon dating and the Askja-1875 tephra. Stable isotopes (δ18O and δ13C) on Chara spp encrustations and Pisidium spp mollusc shells and carbon content were analysed in the lake record, whereas peat stratigraphy, humification, testate amoebae assemblages, C/N ratio and stable isotopes (δ13C and δ15N) were analysed in the mire record. Stable isotopes (δ2H and δ18O) on lake water showed that Lake Blektjärnen responded to changes in the balance between evaporation and input water (E/I ratio). A high E/I ratio results from a dry and probably warmer climate during which evaporation and atmospheric equilibration likely enrich lake water in 18O and 13C, respectively, and vice versa for a low E/I ratio. The relatively high Chara δ18O and δ13C values between ca 4400 and 4000 cal yr BP thus suggest relatively dry and likely warm conditions, whereas depleted values suggest wetter and probably cooler conditions between ca 4000 and 3000 cal yr BP. Again, drier and probably warmer conditions were inferred from the relatively enriched δ18O values between ca 2500 and 1000 cal yr BP, and depleted δ18O values were recorded between ca 1000 and 50 cal yr BP indicating wetter and likely cooler conditions. The results from the mire mainly indicated vegetation succession, however, the changes inferred at ca 2600 and 1000 cal yr BP could have been triggered by climate change. This study shows that the proxies responded sensitively to humidity changes in the investigated archives allowing for reconstruction of climate change in central Sweden during late Holocene.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2010. 60 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 20
Keyword
humidity change, stable isotopes, Chara spp, Pisidium spp, testate amoebae assemblages, humification, C/N ratio, late Holocene, central Sweden
National Category
Geology
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-36884 (URN)978-91-7155-929-6 (ISBN)
Public defence
2010-03-05, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
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Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 3: Accepted. Paper 5: In progress.Available from: 2010-02-11 Created: 2010-01-28 Last updated: 2010-10-07Bibliographically approved

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