Emerson 9320911 This project will develop a new cleaning technique which will permit 230-Th dating of planktonic foraminifera. If successful, it would extend the range of direct chronology by an order of magnitude from the existing 1 4C-based methods. The problems heretofore have been the need for complete removal of detrital and adsorbed Th, and the difficulty of making precise measurements of low concentrations. The Pl's plan to address the first by using a series of rinses for reduction of Mn and Fe, followed by chelation to prevent reabsorbed ions. The thermal ionization mass spectrometer at Hanford will be used to achieve precision.
