Provenance, stratigraphy and chronology of Holocene tephra from Vestfirðir, Iceland

Tephrochronology facilitates the interpretation and correlation of terrestrial and marine paleoclimate records in and around Iceland. The Holocene tephra record on the Vestfirðir peninsula has until now been poorly known. Based on detailed analysis of major element chemistry, we present a holistic tephra stratigraphy and chronology (n = 30) generated from four lakes located on northeastern Vestfirðir. Key markers are Tv-3, the 10 ka Grímsvötn tephra series along with the Hekla VF, Katla EG, Hekla T, Hekla 4 (intermediate component) and Hekla 3 (intermediate component), Snæfellsjökull-1, Landnám (basalt and rhyolite), Katla 920, Hekla 1693 and Bárðarbunga 1716 tephra layers. Notably, we also document two early Holocene intermediate tephra from the Hekla volcano, the oldest yet identified. Imperfections in the continuity of tephra records between lakes indicate gaps produced by either variable ash plume trajectories or periodic ice coverage (glacier or seasonal) of the lakes. The northernmost lake, Skorarvatn, archives three tephra layers consistent with the 10 ka Grímsvötn tephra layer series formed by eruptions in the same time frame as the well-known Saksunarvatn tephra from the Faroe Islands. Radiocarbon-dated macrofossils bounding Skorarvatn's upper and basal tephra layers from the 10 ka series indicate that they were produced by at least three large, successive eruptions from Grímsvötn over ∼240 years. The composite Vestfirðir tephra stratigraphy and chronology presented here will enable better age control and synchronization between paleoclimate records in the northern North Atlantic.