Ash layers from Iceland in the Greenland GRIP ice core correlated with oceanic and land sediments

Four previously known ash layers (Ash Zones I and II, Saksunarvatn and the Settlement layer) all originating in Iceland, have been identified in the Central Greenland ice core GRIP. This correlation of the ash between the different environments is achieved by comparison of the chemical composition of glass shards from the ash. This establishes and confirms detailed correlations between the different types of depositional records and the absolute dating of the younger part of the ice core by counting annual layers dates the eruptions accurately. A precise connection with dates obtained by 14C beyond the range of dendrochronology is established which provides an excellent confirmation of 230Th- 234U dates from corals. Four additional Icelandic ash layers have also been identified in the core but not yet correlated with known ash deposits.