Tephra layers in the Siple Dome and Taylor Dome Ice Cores, Antarctica: Sources and Correlations
Nelia W. Dunbar1, Gregory A. Zielinksi2, Daniel T. Voisins3
1. New Mexico Institute of Mining and Technology, Socorro, NM, 87801 2. Institute for Quaternary and Climate Studies, University of Maine, Orono, ME 04469-5790 3. Climate Change Research Center, University of New Hampshire, University of New Hampshire Durham, NH 03824-3525
Volcanic ash, or tephra layers, are found in the Taylor Dome, Siple Dome A and Siple Dome B ice cores. Significant shard concentrations in visible layers are found at a number of depths in all three cores. The geochemical composition of most layers is basaltic, basanitic or trachytic, and the geochemical signatures of the layers suggest derivation from the Pleiades volcanic center, Mt. Melbourne volcano or small mafic centers, probably in the Royal Society Range area. Presence of tephra layers suggests an episode of previously unrecognized Antarctic volcanic activity between 1776 and 1805 AD, from at least two volcanic centers. A strong geochemical correlation (D = 3.49 and 3.97 with a value of 4 considered identical) is observed between tephra layers at depth of 79.2 meters in the Taylor Dome ice core, and layers between 97.2 and 97.7 meters depth in the Siple B core. This correlation, and the highly accurate depth-age scale of the Siple B core suggests that the age of this horizon in the Taylor Dome ice core presented by Steig et al., (1998a, 2000) should be revised downwards, to the younger age of 675±25 years before 1995 suggested by Hawley et al., (in press).