Validity of 14 C Ages of Carbonates in Sediments

This review is based on geologic surveys carried out in Australia and China as well as on more than 300 14 C dates published in Radiocarbon , Evaluated are the origins and pathways of carbonate formation, stable isotopic composition, carbonate nodule growth rates and paleo-climatic effects. The three identified δ 13 C abundance peaks are unrelated to environment and carbon source whilst 14 C ages group themselves into periods corresponding to past humid warm climate. It is concluded that the major error in caliche dating is due to incorporation of old limestone whilst error on nodule dating is related to their slow growth rate, Thus, caliche antedates and nodules postdate the times of their deposition. Delta 13 C values cannot be used to correct for limestone or atmospheric contamination effects.