Tephra horizons contemporary with short early Holocene climate fluctuations: New results from the Faroe Islands

Abstract

The climate of the North Atlantic region was relatively unstable after the last Termination. At least three cold events superimposed upon a general warming took place during the earliest part of the Holocene: the Preboreal oscillation (11,300–11,100 cal. BP), the Erdalen event (10,300–10,200 cal. BP) and the 9.3 ka BP event. New results from the Faroe Islands could give the opportunity to test hypothesis regarding synchronous or non-synchronous response to climate forcing in the North Atlantic area. Seven tephra layers have been identified in a palaeo-lake core from the island of Sandoy on the Faroe Islands, dated to 11,700–9750 cal. BP. Three tephras were found below the visible Saksunarvatn Ash (ca. 10,300 cal. BP) and three above it. The rhyolitic Hässeldalen Tephra dated to ca. 11,350 cal. BP and previously only found in Sweden, a double-peaked basaltic tephra from the Veidivötn-Bárdarbunga volcanic system at the same depth and another rhyolitic tephra from the Askja volcanic system dated to ca. 10,400 cal. BP, tentatively correlated with the Askja-S/10 ka Tephra. Askja-S has earlier been found in large parts of the terrestrial North Atlantic region but not on the Faroe Islands. The three tephra layers above the Saksunarvatn Ash are all unreported tephras. A rhyolitic tephra with an age of ca. 10,200 cal. BP, that is still unidentified, one silicic layer from the Katla volcano (SILK) and a tephra correlated with the Torfajökull volcanic system, both with an estimated age of ca. 9700 cal. BP. These tephra horizons provide a unique potential to link not only the terrestrial records from NW Europe but also to correlate them to ice cores from Greenland. The findings of the Hässeldalen Tephra, the Askja-S Tephra and the new tephra correlating to Torfajökull volcanic system could become important time-markers for correlating the Preboreal Oscillation and the Erdalen event around the North Atlantic region.