USE OF TEPHROCHRONOLOGY IN THE EVALUATION OF ACCUMULATION RATES ON NELSON ICE CAP, SOUTH SHETLAND ISLANDS, ANTARCTICA (SCI)

A volcanic ash layer was observed in the 3 ice cores on the Nelson Ice Cap,Antarctica.A comparison of major elemental composition of glass shards from the 3 tephra layers with average whole-rock compositions of 1967-1970 eruptions on the Deception Island and of glass shards from other suspected De- ception Island eruptions collected from Antarctic ice and firn indicate that the most reasonable source for the tephra in the Nelson Ice Cap cores is the 1970 eruption on the Deception Island.From the depth of the vol- canic ash layer and measured density profile of the cores,the net accumulation rate at the summit,Core GW,is 1200 g·cm~(-2)·a~(-1) during the past 20 years,and the net accumulation rates are 700 g·cm~(-2)·a~(-1) and 6 g·cm~(-2)·a~(-1) at sites N30 and N50,respectively.In the eastern part of the Nelson Ice Cap,the accu- mulation rate may be higher than that in the northern part,because no volcanic ash in ice cores was observed at similar depths collected from this region.

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