Dolostone as a reliable tracer of seawater lithium isotope composition
Xiaofeng Liu, Xiaoming Liu, Xi-Kai Wang, Shikui Zhai, Xi-Kai Wang, Shikui Zhai, Xiaofeng Liu, Xiaofeng Liu
Abstract
Abstract The lithium isotope composition (δ 7 Li) of seawater records important information on the evolution of the carbon and silicon cycles over geologic time. Here we report δ 7 Li values in a suite of Neogene dolostones (23–3.4 Ma, n = 39) from the South China Sea. Over the Neogene, dolostone δ 7 Li values have increased from 24.9‰ to 30.1‰, overlapping previously published foraminifera records and documenting seawater δ 7 Li without applying any isotopic fractionation factor correction. Our results suggest that fabric-retentive dolostones are good proxies for providing seawater δ 7 Li records even after early diagenesis. Importantly, these results provide a high-resolution dolostone record rather than a foraminifera record to confirm the observed ~5‰ increase in Neogene seawater δ 7 Li. We predict that early marine diagenetic dolostones with fabric textures abundant in the Proterozoic may record changes in seawater δ 7 Li and continental weathering, providing great insights into the Precambrian global carbon cycle.