14C Chronostratigraphic Techniques in Paleolimnology

Abstract

Down-core paleolimnological investigations of lake-sediment sequences require sufficient age control to enable comparisons and correlations on local, regional and global scales. Provided that the sediments are annually laminated, age control may be achieved through counting of annual layers or varves (see Lamoureaux, this volume). However, since only sediments deposited under certain conditions will allow obtaining an annual time resolution, other dating techniques based on, for example, the radioactive decay of certain elements will have to be applied. Among these, radiocarbon dating (14C) is the most widely used and also the earliest radiometric method available. The method was ‘invented’ in 1951 by Libby (1955), who subsequently introduced and applied it to date the recent geological past. The background and principles of radiocarbon dating have been outlined and discussed in detail in numerous textbooks, journals and articles (see e.g., Lowe & Walker, 1997; Lowe, 1991a; Smart & Frances, 1991; Olsson, 1991; 1986), as well as in specific volumes of the journal Radiocarbon and will, therefore, only shortly be summarised here.