10Be in manganese nodules

10Be (t/sub 1/2) = 1.5 MY) is(formed in the upper atmosphere by cosmic ray spallation on nitrogen and oxygen. It is transported to the earth's surface via precipitation. In the oceans it is eventually associated with solid phases depositing on the ocean floor such as manganese nodules and deep-sea sediments. One of the assumptions that is normally made in analysis of such processes is that 10Be has been produced at a relatively uniform rate over the pat several million years. If we assume, in addition, that the initial specific concentration of 10Be as it precipitates with a solid phase is invariant with time, then we would expect that the decrease of the 10Be concentration as a function of depth in a deep-sea core or in a manganese nodule would provide a record of sediment accumulation rate in the former and of growth rate in the latter. The possibility of using cosmic-ray produced 10Be for the dating of marine deposits had been proposed 25 years ago by Arnold and Goel et al. The method of analysis used by these investigators, and those subsequently pursuing the problem, was low-level β counting. Though the potential of using 10Be for dating manganese nodules was explored more than a decade ago, only a few measurements of 10Be in nodules exist in date. This is largely because of the 10Be measurements in environmental samples have gained considerable momentum during the past 3 to 4 years, after the development of accelerator mass spectrometry for its determination