Uranium 238 decay series nuclides dissolved in Antarctic ice samples were measured. Ice from the Allan Hills, Cul de Sac site, that contains a large concentration of fine volcanic glass shards, has high 226Ra, 230Th, and 234U activities but similarly low 238U activities compared to Antarctic ice samples without volcanic shards. The 226Ra, 230Th, and 234U excesses are proportional to the shard content. The 238U decay series results are consistent with the assumption that alpha decay products recoiled into the ice from the fine shards. The age of the Cul de Sac ice is (325¿75)¿103 yr from this method of uranium series dating. |