This award supports the study of a series of Arctic lake-sediment cores in a program to ascertain the best methods of obtaining reliable C-14 dates on such material. The paleoclimate record in lake sediments gives a very complete record of climatic change; these samples, therefore, are critical for the study of changes which have occurred over the last millennium, and tens of millennia. Earlier studies have demonstrated that radiocarbon dating of lake sediments can be problematic, due to the incorporation of fossil and reworked carbon, and uptake of dissolved carbonate by aquatic plants and organisms. This project is a coordinated effort combining the expertise of the INSTAAR group at the University of Colorado with that of the AMS radiocarbon dating laboratory at University Arizona. This research program would focus on extracting C-14 information from a variety of physical and chemical separates of sediment as a function of depth in a series of lake cores showing both "reliable" and "problematic" dates. This project will allow the development of procedures to produce more reliable dates for the expected increase in the study of Arctic lake sediment.
