Terrestrial ages of meteorites from the Nullarbor region, Australia, based on 14C and 14C-10Be measurements

We have investigated the terrestrial ages, or residence times, of 78 meteorites (representing 73 discrete falls) recovered in Western Australia, and one from South Australia, using both 14C measurements and also 14C/10Be. The samples studied included two ureilites, one CK and one EL chondrite. We have included 10Be measurements from 30 meteorites, including some meteorites for which the 14C terrestrial age was previously determined. We find that the 14C/10Be terrestrial ages are more precise than 14C alone, as we can correct for shielding effects. In general, the two different age determinations age by 14C-10Be are precise to 0.5-1 ka and 14C alone within 1-2 ka. However, measurement of the 14C age alone gives good agreement with the 14C-10Be for most samples. The study of the terrestrial ages of meteorites gives us useful information concerning the storage and weathering of meteorites and the study of fall times and terrestrial age. We have compared the terrestrial ages to weathering, degree of oxidation (estimated from Mossbauer studies) and Delta 17O. In this study, we found that weathering is not well correlated with terrestrial age for Nullarbor meteorites. However, there is a good correlation between degree of oxidation and Delta 17O. The implications for the study of terrestrial ages and weathering from other desert environments will be discussed.