Volcanic ash from Icelandic ∼57,300 yr BP eruption found in GISP2 (Greenland) ice core

We have found volcanic ash in Wisconsinan ice from the GISP2 ice core retrieved from the Summit location in Central Greenland. The ash consists, predominantly, of large rhyolitic glass shards similar to the ones found in Wisconsinan Dye 3 ice from Southern Greenland. We give the results of our analysis of the ash and present evidence that correlates this ash with the Z2 ash layer found in Atlantic sediment cores, with the Dye 3 ash, with ash recently found in the GRIP ice core from Central Greenland and with ash associated with the Icelandic Thorsmörk ignimbrite. The mineralogy of the ash is very similar to that of ash from the Icelandic Tindfjallajökull volcano that is also present in the Thorsmörk ignimbrite and we suggest that this is the source volcano. Tindfjallajökull has also been suggested as the source of the Z2 ash. Based on the excellent dating of the GISP2 ice core, we determined that the eruptions that produced the GISP2 ash occured 57,300 ± 1,700 yr BP which agrees extremely well with the most recent dating of 57,500 ± 1,300 yr BP of the Z2 ash based on the SPECMAP chronology. This provides us with a reliable revision of the Dye 3 ice core dating at a depth of ∼1950 m. This ice was originally dated at ∼70,000 yr BP.