GROWING PROCESSES OF AN INLAND ANTARCTIC ICE WEDGE, MESA RANGE, NORTHERN VICTORIA LAND

During the XVI Italian Antarctic Expedition (2000-2001) the geomorphologic survey of permafrost-related polygons has been carried out in the northern sector of Mesa Range - Pain Mesa - located in the upper part of Rennick Glacier. An ice wedge was found in a volcanic regolith at an elevation of about 2200 m a.s.l.. This altitude is below the trimline that in this sector of Mesa Range is at 2380 m a.s.l.. Samples of ice were taken using a 14 mm internal diameter ice screw that was inserted into the ice wedge in vertical sequences. A co-isotopic study was performed, measuring both oxygen (?18O) and hydrogen (?D) isotope compositions. Tritium activity measurements were carried out on the same samples as well as chemical determinations of both major cations and anions. The ?18O and ?D obtained showed a strong divergence from the expected snowfalls occurring at this elevation, with extremely negative d excess values. Melting-refreezing and/or sublimation processes were taken into account to define the origin of the ice forming the wedge. The tritium data obtained suggest that the growth process of the ice wedge might be active still today. High values of non-sea salt sulphate concentrations, obtained for all samples, showed a strong contribution from a terrestrial source for sulphate which is probably associated with calcium.