Identification of primary Ce-anomaly signatures in fossil biogenic apatite: implication for the Cambrian oceanic anoxia and phosphogenesis

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 Cc anomalies. Shale La/Sm-N 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. Cc anomalies in apatites with fiat REE distribution and La/Sm-N ratio >0.35 may be used as indicative of oceanic anoxia. (C) 2001 Elsevier Science B.V. All rights reserved.