Tephrochronology of the Last Glacial/Interglacial transition in western Småland, southwestern Sweden

Abstract: Tephrochronology, or the dating and correlation of stratigraphic sediment sequences by the use of tephra, is a dating method that has been much refined in the last decade. This refinement has enabled the detection of cryptotephra, which has expanded the known distribution of different tephras. At the site Lake Mulakullegöl in the southwest of Sweden, three distinct tephra horizons have been detected, of which two have been geochemically identified. The identified tephras are the Vedde Ash (ca 12,000 cal. yrs BP) and the Hässeldalen Tephra (ca 11,500 cal. yrs BP), both of Icelandic origin. These tephras were deposited during the middle of the Younger Dryas Stadial and the Younger Dryas/Preboreal transition, respectively. The Vedde Ash is one of the most widespread tephras of Icelandic provenance, while the Hässeldalen Tephra so far only has been found at two sites in southeastern Sweden, prior to the current study. A third, unidentified, tephra was also detected. Based on the stratigraphic position, this tephra might be the Borrobol Tephra, which has been dated to ca 14,400 cal. yrs BP. This might indicate that warming had not yet occurred in this part of Sweden. The extended known distribution of especially the Hässeldalen Tephra, but also the Vedde Ash, has enabled a higher potential for correlations between different records deposited during the Last Glacial/Interglacial transition.