Late-Holocene ultra-distal cryptotephra discoveries in varved sediments of Lake Żabińskie, NE Poland

Abstract

Varved (annually laminated) lake sediments provide valuable archives for ultra-distal tephra preservation and at the same time allow the precise dating of volcanic eruptive events. We used a high-precision varve chronology from Lake Żabińskie in NE Poland and EPMA glass chemical data to identify cryptotephra from three large-scale, late Holocene eruptions from European and Northern American volcanoes: the White River Ash eastern lobe (WRAe) eruption from Mount Churchill, Alaska (833–850 CE); a tentative finding of the Glen Garry eruption of the Askja volcano, Iceland (1966–2210 cal a BP); and an yet undefined eruption from Furnas volcano, Azores. The varve age of 863–903 CE of the Alaskan WRAe cryptotephra in Lake Żabińskie is slightly younger than the proximal radiocarbon date and the annual layer estimate of the distal AD860B correlative in the Greenland NGRIP ice core but is within 14C dating uncertainties of distal tephra findings in the Irish peat record. The varve ages of the Glen Garry and Furnas tephras in Lake Żabińskie provide a minimum age at 1991 cal a BP (41 BCE). All three cryptotephra findings represent their easternmost occurrences from the volcanic source and hence considerably extend existing tephra dispersal maps.