Thorium and uranium isotopes in seawater and sediments

Abstract

Thorium concentrations in three open Pacific Ocean water samples had values ofn ×10⁻¹⁰ grams/liter, concentrations similar to those previously measured in the Atlantic. Radioactive disequilibrium exists between the dissolved forms of ²²⁸Th and ²³²Th and the dissolved, excess unsupported ²²⁸Th apparently is introduced by the input of ²²⁸Ra from the particulate phases containing ²³²Th. The²³⁰Th/²³²Th ratios in seawater are similar to those taken from the surface sediments in the same area. Differences in the ²³⁰Th/²³²Th ratios in barite and foraminifera extracted from the same levels in sediments are suggestive of differences in the ratio between surface and deep ocean waters.