A record of lead isotopes from 237 ky to 409ky BP in the Vostok ice core, antarctica

Abstract

Thermal ionization mass spectrometry has been used to measure Lead (Pb), Barium (Ba) and Pb isotopes in ice dating from 237 ky to 409 ky BP, drilled at Vostok, Antarctica. Significant changes occurred in the Pb and Ba concentrations and the 206Pb/207Pb isotopic ratios in these samples. Higher metal concentrations were found during the colder periods, and this was accompanied by lower 206Pb/207Pb ratios. This suggests that the isotopic composition of Pb present in the atmosphere in Antarctica during colder colder periods is diluted by Pb in terrestrial dust which is present at high concentrations during these periods, particularly near the glacial maxima.