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

<p>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 similar to 4500-year, continuously varved lacustrine sediment record and tephrochronology from lake Hamalanlampi, 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 Oraefajokull 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. (c) 2026 The Author(s). Journal of Quaternary Science Published by John Wiley & Sons Ltd.<br></p>