Lateglacial and holocene tephrostratigraphy in Denmark:volcanic ash in a palaeoenvironmental context

• Main Author: Larsen, Jeppe Joel
• Format: Book
• Language: English
• Published: Department of Geosciences and Natural Resource Management, Faculty of Science, University of Copenhagen 2013
• Subjects: Askja; Eyjafjallajökull
• Online Access: https://curis.ku.dk/portal/da/publications/lateglacial-and-holocene-tephrostratigraphy-in-denmark(7e7a0843-113e-4aeb-afe1-5805631c7782).html; https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122177810805763

Studies of Lateglacial and Holocene distal tephra horizons in Denmark have so far been very sparse. Here, distal tephra horizons from this period have been identified at multiple localities throughout Denmark. The sedimentary successions from palaeolakes and bogs presented here cover the periods from around 15–6.6 cal kyr BP and 4.5 cal kyr BP to present. Six tephra horizons have been geochemically identified (the Laacher See Tephra, Vedde Ash, Hässeldalen Tephra, Fosen Tephra, Hekla-4 and Hekla-3) and the results indicate the existence of about eight additional horizons, including the Eyjafjallajökull 2010 eruption. The observations of the Hässeldalen Tephra and Fosen Tephra expand the previously known depositional extent of these two tephra horizons. At Hallegård on Bornholm a distinct horizon of Laacher See-like tephra is registered c. 60 cm below the Laacher See Tephra. The tephra, here termed HAL-431, show no signs of downwards migration and the surrounding sediment has been dated to 13,261–13,078 cal yr BP (95.4%), with a modelled age difference to the Laacher See Tephra of 294±114 yr. At Lille Slotseng an Askja-type tephra shards are intermixed with Borrobol-like tephra in Bølling-Allerød sediments. Askja-type tephra horizon has not previously been recognized in sediments from this period. The sedimentary successions studied have been analysed for alaeoenvironmental and palaeoclimatic changes. The Preboreal Oscillation is registered at all localities where early Holocene occurs, including the Hässeldalen Tephra, which was deposited just prior to the onset of the Preboreal Oscillation. Correlation of all known localities containing the Hässeldalen Tephra show small stratigraphical variations of the Hässeldalen Tephra concentration peak and the relative degree of lake productivity-increase, after the termination of the glacial period. During the late Preboreal a fall in authigenic carbonate in the sediment at Store Slotseng is interpreted to reflect a decrease in lake productivity. This period is chronostratigraphically correlated to the Rammelbeek Phase, as defined by some.