Cyclic patterns in the Paleozoic and Mesozoic: Implications for time scale calibrations


  • Ulf Bayer,

  • George R. McGhee Jr.


The analysis of both physical and biological data from the Devonian strata of New York State reveals the existence of two robust cyclic patterns: one cycle with a duration of 4.5–5.7 m.y. and a larger cycle of approximately twice this wavelength at 11.3–13.6 m.y. depending upon the absolute time scale used in the wavelength calculation. The analysis of sedimentation rates from the Jurassic likewise reveals a cycle with a temporal spacing of 4 to 6 m.y., a cycle with a periodicity virtually identical to the shorter cycle detected in the Devonian. The data further suggest the existence of cycles at 2.3 m.y. and 30 m.y. intervals, though these periodicities approach the lower and upper limits of resolution of the data base. The potential correlation of cyclic patterns has considerable implication for the development of new chronological time scales and global chronostratigraphic resolution. Current radiometric time scales have a resolution which is still above the stage level for most of the pre-Cenozoic. In estimating the ages of stage boundaries, most time scales are based on either the assumption of equal stage durations or the assumption of equal biostratigraphic zone durations, and the subsequent linear interpolations between control tie-points. Operating under the working hypothesis that a regular periodic signal exists in the data, the above listed Devonian cycles are brought into a more uniform periodicity by transforming the time scale itself, yielding an alternatively calibrated timescale which is neither equal stage nor equal zone in structure.