Geochemical signatures of tephras from Quaternary Antarctic Peninsula volcanoes

Abstract

In the northern Antarctic Peninsula area, at least 12 Late Pleistocene-Holocene volcanic centers could bepotential sources of tephra layers in the region. We present unique geochemical fingerprints for ten of these volcanoesusing major, trace, rare earth element, and isotope data from 95 samples of tephra and other eruption products. Thevolcanoes have predominantly basaltic and basaltic andesitic compositions. The Nb/Y ratio proves useful to distinguishbetween volcanic centers located on the eastern (Larsen Rift) and those situated on the western side (Bransfield Rift)of the Antarctic Peninsula. In addition, the Sr/Nb ratio (for samples with SiO2 <63 wt%), along with Sr/Y, Ba/La, Zr/Hfand Th/Nb are suitable to unequivocally characterize material erupted from every studied volcanic center. Microprobeanalyses on volcanic glass show that the samples are generally very poor in K2O, and that glass from Bransfield Riftvolcanoes is enriched in SiO2, while that of Larsen Rift volcanoes tends towards elevated alkali contents. We proposean algorithm for the identification of the source volcano of a given tephra layer using the new geochemical fingerprints.This will contribute to the development of a regional tephrochronological framework needed for future correlations oftephra in climate archives (e.g., marine, lacustrine and ice cores).