Development and Application of 40k-40 Ar and Laser Microprobe 40Ar/39Ar Dating for Arachaeometric Research

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With NSF support, Drs. Drake and Curtis have established a Berkeley Geochronology Center (BGC) at the Institute of Human Origins in Berkeley, California. The BGC focuses on K-Ar (potassium - argon) dating and can now produce about 250 conventional 40K Ar39 dates per year and 3000 single-crystal laser microprobe dates which equal about 500 sample dates a year (several subsamples from the same sample are routinely dated). Their microprobe is fully automated and, furthermore, provides the ability to date sub-milligram single volcanic crystals. This permits discrete age populations in multi-age component samples to be identified. More than half the laboratories research is focused on geochronology pertaining to hominid-hominoid (human- great ape) evolution and associated archaeology and paleontology. With three years of additional support, the laboratory will work to improve this dating technique to permit more precise and accurate dates. They will also continue their collaboration with paleoanthropologists and address a wide range of anthropologically significant site specific problems. The potassium argon technique, which allows absolute ages to be derived from volcanic materials has revolutionized the field of human origins studies because many important sites in Africa, which were previously undatable, contain multiple volcanic horizons. Fossils can only be correctly interpreted if put into a chronological framework, and many specimens which were difficult to use have taken on new importance. Dr. Drake and his colleagues have been leaders in the development and application of this technique. It is thus important to support both their laboratory and the specific research goals they are pursuing.