Possibilities and limitations of isotopic chemostratigraphy

Postsedimentary transformations of rocks impede the use of isotopic methods for the paleoecological reconstruction and correlation of geological events. This fact was demonstrated previously based on the study of Neoproterozoic-Cambrian rocks (Vinogradov, 2008). Detailed analysis of literature material shows that the younger (Paleozoic) rocks were also subjected to alterations of composition and initial isotope ratios. As compared to Precambrian rocks, Paleozoic rocks are characterized by a much narrower scatter in isotope ratios of cyclical elements. This situation significantly complicates the interpretation of isotopic variations, and correlation of geological events is difficult or even impossible. Thus, isotopic methods can apparently be used adequately for the chemostratigraphic analysis only since Mesozoic.