Amino acid biogeochemistry and dating of offshore Peru/Chile phosphorites

Amino acid biogeochemical results for a suite of indurated sea-floor phosphate nodules from the Peru/Chile margin confirm the youthful nature of these deposits as previously indicated by uranium-series disequilibrium dating. Isoleucine epimerization is significant in the hydrolyzed acid soluble fraction of the nodules with a range in the D-alloisoleucine/L-isoleucine ratio from 0.06 to 0.32. Amino acid compositional patterns are uniform for all nodules and are similar to unlithified surface sediments from the region suggesting that the nodules and sediments constitute a single genetic series.