CYCLOCHRONOLOGY OF THE ALBIAN STAGE

Sedimentary cyclicity developed in response to orbital forcing provides a potential means of testing and refining radiometric chronologies. Herbert et al. (1995), used the 95-ka cyclicity in the pelagic Albian Fucoid Marls of Italy to arrive at a length of 11.9 Ma for the stage, compared to radiometric estimate of 13.3 ma (Gradstein et al., 1995). Reanalysis of the core by means of a gray-scale scan of a digitized and image-processed “photolog” reveals both the 95- and 406-ka cyclicities. The combination of both cycle series provides firmer ground for chronology. It yields a duration of 13.2 ma, and pin-points the sites at which the eight 95-ka cycles went unrecorded.