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Tephra horizons in the North Atlantic region during the Early Holocene
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Uncertainties about the rate and magnitude of future climate change have drawn attention to the climate variability following the Late Glacial-Early Holocene transition, c. 12-8 ka BP. Tephrochronology is a method that uses volcanic ash as isochrons in order to link, date and synchronise geological and palaeoclimatic records which could provide a better understanding of short rapid climate shifts but also the timing of these.

The main purpose of this thesis was to improve and refine the Late Younger Dryas-Early Holocene (c. 12-8 ka BP) tephrochronological framework with focus on dating and identification of new and previously known tephra horizons in the North Atlantic region. A special emphasis was to identify tephra horizons contemporary to short rapid climate events that occurred during the period; the Preboreal Oscillation (c. 11.3 ka BP), the Erdalen events (c. 10.0-9.8 ka BP), the 9.3 ka BP and the 8.2 ka BP events. Additional purposes have been to evaluate the potential of XRF ITRAX core-scanning to identify tephra in lake sediments but also as a tool in palaeoclimate studies.

The potential of tephrochronology for linking climate archives across the North Atlantic region is a main outcome in this thesis. Specific results include five new tephra horizons; four identified on the Faroe Islands and one in Central Norway. Two previously known tephras, the Hässeldalen and Askja-S tephras, were identified on the Faroe Islands for the first time and at new locations in Sweden which confirmed their widespread distribution in NW Europe. Several of these tephras have the potential to become marker horizons for some of the short rapid climate events which occurred during the Late Younger Dryas-Early Holocene but their importance is yet to be determined. Further results show that the XRF core scanner can be used successfully to identify high concentrations of basaltic tephra but also to identify palaeoclimatic events in lake sediments.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University , 2014. , 116 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 41
Keyword [en]
Tephrochronology, geochemical composition, Saksunarvatn Ash, Vedde Ash, Fosen Tephra, Askja-S, palaeoclimate, Younger Dryas, Early Holocene, “XRF ITRAX”, sediment geochemistry, stable isotopes, Faroe Islands, Norway, Sweden
National Category
Geology
Research subject
Quaternary Geology
Identifiers
URN: urn:nbn:se:su:diva-99634ISBN: 978-91-7447-847-1 (print)OAI: oai:DiVA.org:su-99634DiVA: diva2:688149
Public defence
2014-02-21, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 5: Manuscript.

Available from: 2014-01-30 Created: 2014-01-14 Last updated: 2014-01-22Bibliographically approved
List of papers
1. Tephra horizons contemporary with short early Holocene climate fluctuations: New results from the Faroe Islands
Open this publication in new window or tab >>Tephra horizons contemporary with short early Holocene climate fluctuations: New results from the Faroe Islands
2011 (English)In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 246, 157-167 p.Article in journal (Refereed) Published
Abstract [en]

The climate of the North Atlantic region was relatively unstable after the last Termination.At least three cold events superimposed upon a general warming took place during the earliest part of the Holocene: the Preboreal oscillation (11,300-11,100 cal. yr BP), the Erdalen event (10,300-10,200 cal. yr BP) and the 9.3 ka BP event. New results from the Faroe Islands could give the opportunity to test hypothesis regarding synchronous or non-synchronous response to climate forcing in the North Atlantic area. Seven tephra layers have been identified in a palaeo-lake core from the island of Sandoy on the Faroe Islands, dated to 11,700-9750 cal. yr BP. Three tephras were found below the visible Saksunarvatn Ash (ca. 10,300 cal. yr BP) and three above it. The rhyolitic Hässeldalen Tephra dated to ca. 11,350 cal. yr BP and previously only found in Sweden, a double-peaked basaltic tephra from the Veidivötn-Bárdarbunga volcanic system at the same depth and another rhyolitic tephra from the Askja volcanic system dated to ca. 10,400 cal. yr BP, tentatively correlated with the Askja-S/10 ka Tephra. Askja-S has earlier been found in large parts of the terrestrial North Atlantic region but not on the Faroe Islands. The three tephra layers above the Saksunarvatn Ash are all unreported tephras. A rhyolitic tephra with an age of ca. 10,200 cal. yr BP, that is still unidentified, one silicic layer from the Katla volcano (SILK) and a tephra correlated with the Torfajökull volcanic system, both with an estimated age of ca. 9700 cal. yr BP. These tephra horizons provide a unique potential to link not only the terrestrial records from NW Europe but alsotocorrelate them to ice-cores from Greenland. The findings of the Hässeldalen Tephra, the Askja-S Tephra and the new tephra correlating toTorfajökullvolcanic systemcould become important time-markers for correlating the Preboreal Oscillation and the Erdalen event around the North Atlantic region.

Place, publisher, year, edition, pages
Elsevier: , 2011
Keyword
tephra, Faroe Islands, early Holocene, Hässeldalen Tephra, Askja-S, Torfajökull
National Category
Earth and Related Environmental Sciences
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-62887 (URN)10.1016/j.quaint.2011.05.014 (DOI)000298270600015 ()
Available from: 2011-10-03 Created: 2011-10-03 Last updated: 2017-12-08Bibliographically approved
2. Recommendations for using XRF core scanning as a tool in tephrochronology
Open this publication in new window or tab >>Recommendations for using XRF core scanning as a tool in tephrochronology
2012 (English)In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 22, no 3, 371-375 p.Article in journal (Refereed) Published
Abstract [en]

X-ray fluorescence (XRF) core scanning is a relatively new arrangement of a classic analytical technique which allows for non-destructive, in situ XRF analysis of sediment cores from submillimetre resolution upwards. In this contribution we explore the use of XRF core scanning for tephrochronology based on the analysis of three gyttja-rich sediment cores from the Faroe Islands. Using a combination of optical and radiographic images, analytical parameters and elemental profiles (Si, K, Ca, Ti, Mn, Fe, Sr and Zr), higher concentration basaltic tephra layers (>1000 shards/cm3) were positively identified. The XRF core scanning did not capture the lower concentration (<850 shards/cm3) rhyolitic layers found in the core. The elemental data generated for the detected tephra layers using XRF core scanning was not comparable to individual shard analysis by electron microprobe. We recommend using XRF core scanning for tephra screening in order to localize depths for high-resolution subsampling and to avoid depths where sediment mixing has caused tailing/mixing of the tephra signal. At the studied site the basaltic Saksunarvatn ash as well as a tephra belonging to the Askja-S/10 ka eruption were identified.

Place, publisher, year, edition, pages
Sage, 2012
Keyword
elemental data, Faroe Islands, gyttja, lake sediment, tephra, XRF core scanning
National Category
Earth and Related Environmental Sciences
Research subject
Quarternary Geology
Identifiers
urn:nbn:se:su:diva-62889 (URN)10.1177/0959683611423688 (DOI)000300436200010 ()
Note
4Available from: 2011-10-03 Created: 2011-10-03 Last updated: 2017-12-08Bibliographically approved
3. A Lateglacial-early Holocene tephrochronology for SW Sweden
Open this publication in new window or tab >>A Lateglacial-early Holocene tephrochronology for SW Sweden
2013 (English)In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 42, no 3, 544-554 p.Article in journal (Refereed) Published
Abstract [en]

Four cores from southwestern Sweden are presented together with their tephra geochemistry. Two cryptotephra horizons were confirmed geochemically in the cores, the Vedde Ash and the Hässeldalen Tephra. The Lateglacial Hässeldalen Tephra (11 360–11 300 cal. a BP) offers great potential as a regional isochrone to add a new degree of certainty to the deglaciation chronology of southern Sweden, including the extent of glacial Lake Bolmen. In addition, the geographical distribution of the Hässeldalen Tephra has recently been extended outside of Sweden, making it an important time-marker horizon in northern Europe. There are potential difficulties, however. Proper identification of the actual isochrone is complicated by the vertical pattern of shard distribution, which could be the result of several eruptive events, as well as by the fact that shards from the 10-ka Askja horizon (10 500–10 350 cal. a BP) were found in close stratigraphical proximity. The geochemical data presented are the result of improved EPMA methodology, which significantly reduces sodium mobilization. The results therefore have slightly altered values, which has consequences for classifying new finds when they are compared with previous data for geochemically similar tephras. Finally, potential indications of the Borrobol/Penifiler horizon are presented, although the existence of the horizon could not be confirmed geochemically. This highlights the need to retrieve cores from different locations within a basin based on an analysis of basin morphology if horizons are to be located.

National Category
Geology Physical Geography
Identifiers
urn:nbn:se:su:diva-90103 (URN)10.1111/j.1502-3885.2012.00296.x (DOI)000320782800005 ()
Available from: 2013-05-22 Created: 2013-05-22 Last updated: 2017-12-06Bibliographically approved
4. A Late Younger Dryas-Early Holocene tephrostratigraphy for Fosen, Central Norway
Open this publication in new window or tab >>A Late Younger Dryas-Early Holocene tephrostratigraphy for Fosen, Central Norway
2013 (English)In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 28, no 8, 803-811 p.Article in journal (Refereed) Published
Abstract [en]

A number of rapid climate oscillations occur during the Lateglacial-Early Holocene, 15-8 ka BP period and a well-developed tephrostratigraphy in association with these oscillations increases the possibilities to correlate climate archives around the North Atlantic. This paper presents a tephrostratigraphy for Fosen peninsula, Central Norway. Both the Vedde Ash ca.12.1 ka BP and the Saksunarvatn Ash approximate to 10.3 ka BP are important isochrones for correlations of Late Quaternary palaeoenvironmental records in the North Atlantic region and have been assigned ages in GICC05. Beside these tephras we have also identified a new tephra, the Fosen Tephra, with a Borrobol-type geochemistry that occurs above both the Vedde Ash and the Saksunarvatn Ash with an age approximate to 10.2 ka BP. Several tephras with Borrobol-type geochemistry have been identified around the North Atlantic. One group is the Borrobol/Penifiler tephras dated to Greenland Interstadial-1 and another group is dated to the Early Holocene. We suggest that some of the Early Holocene Borrobol-type tephras and the Fosen Tephra may actually be the same layer. If so, the Fosen Tephra is spread over a large area of the North Atlantic and has the potential to become an important marker for short-term climate variability in Scandinavia and in the northern hemisphere.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2013
Keyword
Fosen Tephra, Norway, Saksunarvatn Ash, Tephra, Vedde Ash
National Category
Physical Geography
Identifiers
urn:nbn:se:su:diva-99143 (URN)10.1002/jqs.2676 (DOI)000328348500006 ()
Note

AuthorCount:3;

Funding Agency:

SSAG (the Swedish Society for Anthropology and Geography); Swedish Research Council 

Available from: 2014-01-13 Created: 2014-01-12 Last updated: 2017-12-06Bibliographically approved
5. Lacustrine response to short rapid climate shifts during Late Younger Dryas-Early Holocene in Central Norway, registred by XRF and stable isotopes
Open this publication in new window or tab >>Lacustrine response to short rapid climate shifts during Late Younger Dryas-Early Holocene in Central Norway, registred by XRF and stable isotopes
(English)Manuscript (preprint) (Other academic)
Abstract [en]

There is relatively good knowledge about the climate and the deglaciation pattern during the Late Glacial-Early Holocene transitionin Norway. The origin and mechanisms behind the short, rapid climate shifts that occurred during this period are however notwell known. In this context climate studies in this region can contribute to our understanding of climate patterns. Our specificobjectives in this study were to compare the geochemical response of lake sediments during Late Younger Dryas-Early Holoceneto the general picture of deglaciation in Central Norway and also to evaluate if the Preboreal oscillation (PBO), the Erdalen events,the 9.3 and 8.2 ka cal BP could be detected, superimposed on the general Late Glacial-Early Holocene climate. To address this; highresolutionXRF fluorescence core-scanning, Total organic carbon (TOC), carbon/nitrogen (C/N), stable isotopes of carbon andnitrogen (δ13C, δ15N) and total nitrogen (TN) were made on a palaeolake core from Grønlia fen situated on the Fosen peninsula,Central Norway. The reconstructed Late Younger Dryas-Early Holocene climate from the Grønlia record was noteworthily similarto other reconstructions from the region. The Younger Dryas-Preboreal transition was dated to c. 11 420 cal a BP and five climateshifts were identified in the Early Holocene; c. 11 190 cal a BP, 10 500 cal a BP, 10 200 cal a BP, 9900 cal a BP and 9250 cal a BP.

Keyword
Palaeoclimate, XRF, stable isotopes of C and N, tephra
National Category
Climate Research
Research subject
Quaternary Geology
Identifiers
urn:nbn:se:su:diva-99631 (URN)
Available from: 2014-01-14 Created: 2014-01-14 Last updated: 2014-01-16Bibliographically approved

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Citation style
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  • ieee
  • modern-language-association-8th-edition
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  • Other style
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  • Other locale
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Output format
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  • text
  • asciidoc
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