Rubidium isotope ratios change in marine sediments from South Asia with Age.

Abstract

Rb isotopes undergo isotopic fractionation, where adsorption to clay minerals results in a lighter solid phase. Marine sediments are heavier than the crustal average and are affected by the Rb isotopic ratio of the liquid phase (delta⁸⁷Rb), which is heavier due to adsorption of clay minerals in rivers. Measurements of the age variation of delta⁸⁷Rb in marine sediments showed that the isotopic ratio tended to be lighter in warmer and wetter conditions. This may be due to the influence of lighter particulate Rb isotopic ratios due to adsorption of Rb on clay minerals in river water. On the other hand, the significantly heavier delta⁸⁷Rb at 17 Ma suggests the influence of weathering of the Columbia River Basalt.