Abstract

The relative abundance of phosphorite as a function of age was estimated for the southeastern United States using 87Sr/86Sr derived ages. The Sr-derived ages define seven phosphogenic episodes on the northeast Florida platform. Phosphorus burial rate estimates for the southeastern United States margin range from 2 to 12 × 109 mol ṁ P ṁ yr−1, and phosphorus accumulation rates range from 1 to 3 µmol ṁ cm−2 ṁ yr−1, similar to modern phosphogenic margins. The estimated amount of organic carbon burial ranges from 1 to 12 × 1016 mol C; sufficient to shift the ocean δ13C by 0.1‰ to 0.6‰. On long time scales (>1 m.y.) phosphogenesis in the southeastern United States corresponds to increased organic carbon burial (positive δ13C shifts) and rising sea level (negative δ18O shifts). On shorter time scales (<1 m.y.), the correlation of phosphogenesis to positive δ13C and δ18O shifts suggests a different relation between phosphogenesis, organic carbon burial, eustasy, and climate transitions during the Miocene.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not currently have access to this article.