MODEL-DETERMINED SEDIMENT AGES FROM PB-210 PROFILES IN UN-MIXED SEDIMENTS

Radioisotope geochronology is one of the procedures employed to assess sediment accumulation rates in marine and freshwater environments. A new modeling method has been developed to analyze complex depth profil es of radioisotope activity in non-mixed sediments that eliminates man y of the restrictions of previous methods. The new approach uses inver se numerical techniques to disentangle components of variations in rad ioisotope activity with sediment depth caused by variations in sedimen t accumulation, from those components caused by variations in radioiso tope flux. The method was tested using synthetic data profiles and com pared with previous methods. Analyses of synthetic data profiles demon strate that the new approach accurately reconstructs sediment burial h istories in a variety of unmixed Pb-210 Sediment profiles, some of whi ch are uninterpretable by current methods.