IDENTIFICATION OF PRIMARY CE-ANOMALY SIGNATURES IN FOSSIL BIOGENIC APATITE: IMPLICATION FOR THE CAMBRIAN OCEANIC ANOXIA AND PHOSPHOGENESIS

Abstract

Based on REE analyses of 105 world-wide distributed Cambrian fossil apatite samples and eight late Neoproterozoic phosphate concretions, a close relationship is established between the concentrations of MREE and Ce anomalies. Shale La/SmN ratios of 0.35 is suggested as a critical value for the discrimination of the natural Ce anomaly acquired during pre-burial/early diagenesis by biogenic apatite from an artificial Ce anomaly induced due to the calculation. Ce anomalies in apatites with flat REE distribution and La/SmN ratio >0.35 may be used as indicative of oceanic anoxia.