Calcium-41 has been suggested as a new tool for radiometric dating in the range of 10(5) to 10(6) years. The concentration of cosmogenic calcium-41 in natural samples of terrestrial origin has now been determined by high-sensitivity accelerator mass spectrometry after pre-enrichment in calcium-41 with an isotope separator. Ratios of calcium-41 to total calcium between 2 x 10(-14) and 3 x 10(-15) were measured for samples of contemporary bovine bone and from limestone deposits. Some prospects for the use of calcium-41 for dating Middle and Late Pleistocene bone and for other geophysical applications are discussed.

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We made preliminary AMS measurements of 41Ca/Ca ratios in bone and limestone specimens with the Argonne Tandem-Linac Accelerator System (ATLAS). We were able to avoid pre-enrichment of 41Ca used in previous experiments due to a substantial increase in Ca-beam intensity. Most of the measured ratios lie in the 10-14 range, with a few values below 10-14. In general, these values are higher than the ones observed by the AMS group at the University of Pennsylvania. We discuss possible implications of these results. We also present the current status of half-life measurements of 41Ca and discuss 41Ca production processes on earth.

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