Pristane/phytane ratio as environmental indicator - Reply

Abstract

We agree with Powell that pristane (Pr) to phytane (Ph) ratios close to unity should be interpreted with great caution and that fewer difficulties arise with extremely high (as in coals) or extremely low (as in sediment from hypersaline environments) Pr/Ph ratios. In these latter cases, the Pr/Ph ratios are probably influenced by specific sources of the organic matter and specific depositional environments, where the redox condition is only one of the factors. The main point of our paper concerns the generalizations and oversimplifications implied in the use of the Pr/Ph ratio as an indicator of the level of oxygen at the site of organic matter deposition into sediments. We made several new arguments based on novel geochemical findings to emphasize the restricted use of the Pr/Ph ratio as a palaeoenvironmental indicator. Of course, we do not object to using the Pr/Ph ratio as a correlative tool when samples of the same origin and maturation level are compared with one another (as in oil/source-rock correlation).