Age of the Cuddapahs, India

Abstract

Russell and Slawson have clearly brought out, presumably for the first time, the significance of the pressure-scattering correction which may change the lead-207/lead-204 ratio by about 3 per cent when low resolution mass-spectrometers are used for the isotopic analysis of lead. This correction, coupled with differences in the mode of measurement of peak heights, is responsible for the discrepancies in lead isotope ratios given by Russell and Slawson and those given by me1. It is possible that the correction may improve the accuracy of the lead isotope ratios, but this requires to be corroborated. The objective of this communication is to discuss the conclusions that flow from the revised model age of the Zangamrajupalle galena.