A new, ~4500‐year varve record and high‐resolution tephrochronology from lake Hämälänlampi, eastern Finland, provides age constraints for the Furnas C and the Glen Garry/Askja A‐2000 eruptions

ABSTRACT The northern European distal cryptotephra framework is constantly developing both in terms of identification of new tephra horizons and improved age constraints for the already well‐established tephra marker horizons. However, many prehistoric tephra layers have only been dated by the radiocarbon method, with its inherent problems. Here, we present a new ~4500‐year, continuously varved lacustrine sediment record and tephrochronology from lake Hämälänlampi, eastern Finland. The varve chronology was established by repeated varve counts from epoxy‐impregnated sediment blocks and selected elemental maps (Si, K, Fe and Mn) produced by micro‐XRF scanning. The sediment core was investigated for the presence of cryptotephra, and the exact location of the nine identified cryptotephra horizons was pinpointed with either 0.5‐ or 1‐cm depth resolution. The volcanic glass shards were geochemically characterised and correlated to their source eruptions. As a result, we report the first findings of the Hekla 1947, Furnas C and Hekla C tephras in Finnish environmental records, and provide varve ages for the Furnas C, Hekla Y, Hekla C and Öræfajökull 3.5 ka tephras for the first time. We also suggest a new, high‐resolution varve age 128–117 BCE for the Glen Garry tephra, based on integration of varve ages from several studies.