Útdráttur:

The Saksunarvatn Ash, originating from the Grímsvötn volcanic system in Iceland, is a prominent and widespread tephra layer in the North Atlantic. However, due to Grímsvötn’s frequent Early Holocene eruptions with consistent geochemical composition, both the number of the contributing eruptions and the age of the Saksunarvatn Ash has been debated. Recently, the characteristically thick basaltic ash layer has been suggested to reflect seven phases of eruption, spanning 500 years, between 10,400 and 9,900 cal. yr BP. West of Iceland, ash with Grímsvötn affinity has been identified (visible and crypto) in four of the Greenlandic ice cores (GRIP, GISP2, NGRIP and NEEM) and is associated with a single prolonged volcanic sulphate peak. Age estimates range from 10,297 ± 89 yrs. BP (GICC05 NGRIP/GRIP) to 10,180 ± 60 yrs. BP (GRIP). East of Iceland, in western Norway (Kråkenes Lake), an age of 10,176 ± 49 cal. yr BP is suggested for the tephra, using a well-constrained Bayesian statistical age-depth. In this study we review and quality assess previously published age constraints on the Saksunarvatn Ash derived from marine, lacustrine and soil archives from the North Atlantic. Furthermore, we introduce a handful of new well dated proximal locations (distributed around Iceland), where age depth models are used to constrain the lower and upper bounds of the distinct tephra. We place these age constraints in hand with ice core data and ultimately suggest a refined age for the marker layer. Accurately dated tephra is a fundamental component of a marker layer.

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