Radiometric ages of phosphorites from the west coast of India

Abstract

Four algal carbonate nodules with approx 1 mm thick phosphorite coatings were dated, by the 230Th/234U and three of the carbonates by 14C methods. All ages (5.8-13.9 k.y) are in satisfactory agreement indicating that phosphorite deposition started soon after the carbonate nodule formation. The U, Th concentrations and isotopic ratios as well as the U/P weight ratios of the phosphorite coatings are in good agreement with those from other regions of the world