Lake Torfadalsvatn: a high resolution record of the North Atlantic ash zone I and the last glacial‐interglacial environmental changes in Iceland

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Abstract
High resolution environmental records with a refined chronology are essential to understand, reconstruct and model the climate dynamics of the last glacial‐interglacial transition. Sediments from Lake Torfadalsvatn in northern Iceland contain at least four primary volcanic tephras that belong to ash zone I in the North Atlantic deep‐sea cores. We chemically define these basaltic/rhyolitic tephras and the high resolution allows us to date them to about 10,800, 10,600, 9300 and 8900 BP. This detailed tephrostratigraphy will act as a refined dating and correlation tool in the North Atlantic region and enable calibration between different absolute chronologies. The pollen stratigraphy of the sediments suggests that by 10,400 14C years BP plant colonization of coastal north Iceland had begun. The pollen stratigraphy shows a succession of pioneer plants, from open tundra vegetation towards birch‐juniper woodland, which probably also reflects a transition from a cool climate at 10,400 BP to conditions similar to today's sub‐polar oceanic climate around 9200 BP. Diatom data largely concur with the climatic information from pollen, indicating gradually increasing productivity in the lake.