Volcanic Records in the Siple and Taylor Dome Ice Cores

(Collaborative Research UMaine and New Mexico Tech)

Gregory A. Zielinski and Nelia W. Dunbar

The volcanic records of the Siple Dome A (SDMA) and B (SDMB) ice cores together with the Taylor Dome ice core are being developed through a two-pronged approach. By using the continuous glaciochemical record being developed by individuals at UMaine (Mayewski et al.), primarily the SO4 and Cl time series, and the continuous tephrochronological record of SDMA, we have developed a new record of Antarctica volcanism. The composition of tephra found in many sections of core with high SO4 spikes matches the composition of material ejected from volcanoes in Victoria Land and the islands off its coast, such as Mt. Melbourne, The Pleaides and Buckle Island. We have found that there was a very active period of Antarctica volcanism in the late 1700s and early 1800s that was not known previously. We have found that tephra in SDMB matches a visible layer in the Taylor Dome core thus providing a distinct time-line for ice cores in West Antarctica and the Ross Sea region. These results are included in papers submitted to the Journal of Glaciology and Geology, and they were presented at the 2001 Fall AGU meeting and are part of the paper being presented at the Chapman Conference in the summer of 2002. Our work is now progressing through the Holocene and glacial sections of the record. We have analyzed several tephra layers from deeper in the core and have found glass that appears to match the composition of tephra found at Mt. Moulton in West Antarctica. For instance, the initial evaluation of the visible teprha layer found at 950.60 m in SDMA shows that it is geochemically similar to an ash layer found at Mt. Moulton stratigraphically close to a layer radiometrically dated to 119k. The initial results from the 1 mm thick visible layer at the 549.522-549.547 m interval in SDMA also appears to be chemically similar to tephra layers found at Mt. Moulton, but no direct correlation to a dated layer has yet been made. We also have found two layers of rhyolitic glass, and one derived from an eruption from a geochemically zoned magma chamber. These three layers are likely to be derived from non-local sources. These results have just been recently obtained , thus we are pursuing them in greater detail at this time, including pursuing trace element analyses of the shards in order to strenghten correlations. The glaciochemical volcanic record is now being developed for the glacial and older part of the record with some very large signals found during the mid-Holocene.