AUTORADIOGRAPHY FOR U, TH, AND ISOTOPIC DISEQUILIBRIUM STUDY OF SIWALIK FOSSIL BONES

The relation between the concentration of uranium and thorium atoms in geological samples and the alpha-track production rate in the plastic track detector, LR-115 type II, was used for the analysis of fossil b ones collected from the Siwalik Himalayas of India. The alpha-track me asurements from the samples under secular equilibrium define the total uranium and thorium concentrations, while fission track measurements yield uranium concentration alone. By combining the results of both me asurements, uranium and thorium concentrations can be determined. The results of uranium and thorium concentration determined by alpha-autor adiography are distinctly different from those of fission track analys is, indicating the existence of radioactive disequilibrium in Siwalik fossil bones. (C) 1996 Elsevier Science Ltd.