Report on the radiometric analysis of the Ghar Dalam fossil specimens prepared for the Ghar Dalam Museum

Abstract

Uranium is a radioactive element emitting mainly alpha rays, but its daughter elements Th and Ra are gamma ray emitters. A high resolution gamma ray spectrometry system can be used to determine gamma-emitting radionuclides with energies ranging from 1 keV to 10 MeV depending on the type of detector in a large variety of sample matrices. The simultaneous detection of several gamma radionuclide emitters in the sample material was carried out with a coaxial germanium detector of high resolution connected to a multichannel analyser. Automatic processing of the collected spectral data was controlled by a computer system with selected software. Sources of error in the technique may be caused by improper spectral identities, changes in background, errors in calibration and/or geometry, and lack of homogeneity in samples. Since the samples tested were not in a standardised geometry, some variation in the readings could be expected due to the difference in sample homogeneity. The results obtained for the various samples were standardised as a ratio of 40K, on the assumption that the high solubility of potassium salts would result in a steady equilibrium in all samples. Several fossil specimens kept in the Ghar Dalam Museum were borrowed by courtesy of Dr. G. Zammit Maempel. The specimens had unfortunately no information as to the level they were excavated from, and their providence could not be reliably confirmed.