Discovery of tephra in a Late-glacial and early Holocene organic sediment sequence in Schünsmoor (Niedersachsen, Germany)

Investigation of an in-filled lake basin in Schünsmoor, Ldkr. Rotenburg (Wümme), northern Germany, reveals the discovery of ‘cryptotephra’ (non-visible volcanic ash) in biogenic sediments dating to the Late-glacial and early Holocene periods (c.15.4 - 7.5 ka cal BP). Major element geochemistry of glass shards shows the tephra originates in Iceland from the Katla volcanic system. However, uncertainties in the bio-stratigraphic position and dating of the tephra in Schünsmoor mean it is not clear if more than a single tephra is present nor is it possible to correlate confidently to previously documented eruptions. Three potentially relevant correlates are identified: the Vedde Ash (c.12.1 ka cal BP), an eruption documented from many regions of Europe that dates from the Younger Dryas sub-stage; the Abernethy Forest AF555 tephra, previously identified in Scotland with a age of 11.79 - 11.20 ka cal BP; and the c. 8.0 ka cal BP Suðuroy Tephra, first observed in the Faroe Isles. Future tephrostratigraphic investigations may ultimately resolve the ambiguities identified in Schünsmoor, thereby allowing the tephra record to be placed in a wider European context.