A tephra chronostratigraphic framework for the Frontier Mountain blue-ice field (northern Victoria land, Antartica).

Englacial tephra provide chronostratigraphic markers in the Antarctic ice sheets. Structural, mineralogical, geochemical and geochronological data on selected samples allowed the reconstruction of a chronostratigraphic framework for the Frontier Mountain blue-ice field-an important meteorite trap on the southeastern flank of Talos Dome in northern Victoria Land. The stratigraphic thickness of the blue-ice succession is similar to 1150 in. The Ar40-Ar39 age of one layer close to the stratigraphic bottom of the ice succession is 100 +/- 5 ka and constrains the maximum age of the bulk of Frontier Mountain blue ice. The 49 +/- 11 ka age of a second layer at a depth of similar to 950 m in the stratigraphic succession indicates that > 90% of the ice is younger than this value. These ages agree well with the terrestrial ages of meteorites found on the blue ice (up to 140 +/- 30ka), suggesting a mechanism of exhumation of meteorites by ablation after englacial transport. Particle size (up to several tens of microns) and the alkaline compositional character of 22 layers allow correlation with source volcanoes within the Cenozoic magmatism associated with the West Antarctic Rift System. The proximal Mount Melbourne, Mount Rittman and The Pleiades (within a radius of similar to 250 km) are the best candidate source volcanoes. The reconstructed chronostratigraphic framework thus lays the foundations for a detailed investigation of similar to 100ka of explosive volcanism in northern Victoria Land. Furthermore, in light of the ongoing ice core drilling project at Tales Dome, the Frontier Mountain ice succession may become important for establishing regional correlations, for sampling and dating key tephra layers, and for selecting ice successions for high-resolution studies of past atmospheric chemistry and fallout.