A Holocene tephrochronological framework for Finland

Abstract

<p>Regional tephrochronological frameworks serve as dating and correlating tools that enable critical assessment of the validity of single cryptotephra findings. In this study, our aim was to construct an outline for a Finnish Holocene tephra framework by investigating 12 peatlands and one lake site for presence of cryptotephra. As a result, glass shards from 19 individual tephras were geochemically characterized and correlated to their source volcanoes in Iceland and Alaska. Fifteen of these tephras were identified in Finland for the first time. The oldest identified cryptotephra in the Finnish environmental records is the 7 ka Hekla 5 tephra, and the youngest one is the Askja 1875. The identification of two Alaskan tephras (White River Ash eastern lobe and Aniakchak tephra) in Finland demonstrates an opportunity for intercontinental tephra correlations. The first Finnish Holocene tephrochronology presented here reveals a great potential for using tephrochronology as a dating method in Finland and is expected to aid in future cryptotephra research in the region. Additionally, the cryptotephra findings in this study help to refine the dispersal areas of several Holocene tephras. </p>