The Use of Percentage Cover Measurements in Lichenometric Dating

Abstract

The percentage cover technique is a lichenometric method that has been proposed as a means of obtaining both absolute and relative dates of deposits. The technique is subjective, and the results obtained by different observers are not reproducible. Errors are not randomly distributed: some observers obtain consistently high estimates of cover whereas others are consistently low. There are substantial variations in the cover on individual moraines, with the least heterogeneity occurring at the bases of moraines. The percentage cover appears to be more sensitive to environmental variations than the diameters of the largest lichens and substantial anomalies in the cover-age relationship may occur as a result. The technique appears to be relatively unreliable, although it has considerable potential for the relative dating of small deposits which may not be datable by conventional lichenometric techniques.