VOLCANIC ASH FROM ICELANDIC SIMILAR-TO-57,300 YR BP ERUPTION FOUND IN GISP2 (GREENLAND) ICE CORE

摘要

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 Thorsmork ignimbrite. The mineralogy of the ash is very similar to that of ash from the Icelandic Tindfjallajokull volcano that is also present in the Thorsmork ignimbrite and we suggest that this is the source volcano. Tindfjallajokull 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 yl 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 similar to 1950 m. This ice was originally dated at similar to 70,000 yr BP. [References: 7]