ASSESSMENT OF PB-210 DATA FROM CANADIAN LAKES USING THE CIC AND CRS MODELS

Much discussion has centered around which Pb-210 dating method should be used, the constant initial concentration (CIC) model or the constan t rate of supply (CRS) model. In this study, the activity data from 22 lacustrine sediment cores from the Canadian prairies were used to com pare the determination of sediment accumulation using the two models. Other relative and absolute dating techniques have been used to calibr ate the methodology. For half of the core sites examined, the mass sed imentation rate was constant, and thus both the CIC and CRS models wer e found to be valid. For the other half, variability was observed in t he CRS mass accumulation rate trend. The validity of the CIC model for these cores was dependent on the degree of variability of the mass se dimentation rate. Where the variability is moderate to high, the CRS m odel may be more satisfactory. Caution should be exercised when using chronological data determined with the CRS model, however, as the accu racy of chronology in the lower reaches of a profile is questionable.