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We present the results of measurements of 26 Al and 10 Be produced in situ in 12 samples of Libyan Desert Glass by cosmic rays during the last ten million years. Based on the variability of the concentrations of 10 Be and of the 26 Al/ 10 Be ratios we measured, we conclude that individual fragments of glass have experienced different exposure histories, implying several major redistributions of the glass within the past 10 6 years. The 26 Al and 10 Be concentrations are inconsistent with the theoretical estimates of the rates of in situ production. We estimate minimum production rates of 70 atoms g -1 yr -1 and 10 atoms g -1 yr -1 for 26 Al and 10 Be, respectively, produced in quartz at sea level between 60–90° latitude. Despite the present uncertainty in the rates of production, we feel that these results show clearly the effectiveness of in situ produced 26 Al and 10 Be in studying earth-surface processes.
Klein et al. (1986) studied this question.