HOLOCENE RECORD OF ICELANDIC VOLCANIC ERUPTIONS on THE SE GREENLAND SHELF

The Holocene record of Icelandic volcanic events stored in marine sediments off SE Greenland provide evidence for the frequency and timing of atmospheric dispersal of eruption plumes from Iceland towards Greenland in post-glacial time. Core MD99-2322 was analysed. This well-dated, 26 m-long core extends from c. 190-11,780 cal. yrs BP. The age model was developed through paleomagnetic secular variation (PSV) depth correlation with core MD99-2269, North Iceland shelf, and subsequent commingling of radiocarbon dates from both cores (44 ¹⁴C control points) (Stoner et al., 2007). Counting of glass shards in the 106 to 1000 micron sediment fraction of sediments identified 14 distinct micro-tephra peaks; four containing dark-colored vescicular shards, seven characterized by pumice and colorless platy bubblewall shards, and three containing both dark and colorless shards. Geochemical analyses from six of the micro-tephra peaks indicate Icelandic volcanoes as the source. A peaks at 334-335cm (3.1 ka) is characterized by shards of silicic and intermediate composition. It exhibits mixed provenance and may represent two or more silicic tephras from the Katla and Askja volcanoes. Four of the analysed micro-tephras are basaltic. One, with an age in the range of 6.5-7 ka, has a composition consistent with source at the Katla volcano. The remaining three basaltic peaks, which fall in the age bracket of 10-10.4 ka, exhibit composition indicating Grimsvotn volcano as the source. Moreover, their major element composition is indistinguishable from that of the well-known ~10.2 ka Saksunarvatn tephra, which has been used as an isochron in lacustrine, marine, ice core, and peat climate archives across the North Atlantic region. Multiple Grimsvotn tephra layers with westward dispersal and composition identical to the Saksunarvatn tephra have been identified in Icelandic lake records (Johannsdottir, 2007), a finding that is now corroborated by the discoveries reported on here from MD99-2322 on the East Greenland shelf.