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Department of Geological Sciences, University of Southern California, Los Angeles, CA 90089-0740, USA
Climatic oscillations forced by orbital variations left their imprint not only on Pleistocene ice regimes, as postulated by Croll (1875, Climate and Time in their Geological Relations, Appleton, New York) and by Milankovitch (1941, Belgrade, Serbian Academy of Science, 133), but also on the sedimentary record as postulated by Gilbert (1895, Journal of Geology, 93, 515–533), and not only in glacial times but also, and particularly sharply, in times of greenhouse climates. The amenable facies are those characterized by relatively continuous sedimentation, though in carbonate platforms interruptions constitute the Milankovitch signal. The recording mechanisms include variations in biogenic components and biotic activity, and direct expressions of physical and chemical sedimentation.
So far, cyclostratigraphy has largely remained a demonstration of principle. Applications to geochronology are in their beginnings. The chronological refinement promised by cyclostratigraphy demands quantities of stratigraphic data orders of magnitude beyond those of conventional stratigraphy. Progress in application will therefore depend on combining automated scanning devices (well logs, core and sample logging techniques of various sorts) capable of providing simple variation graphs of long sedimentary sequences, with detailed paleontological and magnetostratigraphic studies. The existence of the cycle hierarchy will provide some protection against chronological errors induced by cryptic gaps in the record, as will the reproduceability of results in distant sequences and different facies, and the possible finger-printing of individual cycles by magnetic character.
