Correlation and cyclicity of stratigraphic sequence boundaries and chronostratigraphic stage boundaries of the last 253 My: Synchrony of tectonism, sea level, climate and biotic change

Chronostratigraphic stage boundaries (based primarily on biostratigraphy and radio-isotopic dating) and stratigraphic sequence boundaries (based on changes in global sea level and tectonism) are two major ways of subdividing the Phanerozoic geologic record. We find a close correlation between the ages of 28 sequence boundaries of the last 253 My and the ages of 28 dated chronostratigraphic stage boundaries established for the same time interval. For the maximum mismatch in the two datasets (∼4 My), the probability of 28 matches is between 0.01 and 0.001. For the average mismatch of 0.7 My, there are 18 matches with a very small probability of 10⁻⁵. Using the binomial cumulative-distribution function, we find that 28 matches of the ages of sequence boundaries out of a total of 47 stage boundaries (60 %) in the last 253 My gives a very high confidence level, indicating that the correlations are clearly not accidental, and suggesting that unconformities at sequence boundaries were commonly utilized to help define stage boundaries. Independent spectral analyses of the 28 sequence boundaries and 28 correlative stage boundaries show a common strong spectral peak at 31 My (> 99.9 % confidence). These findings support a relationship between global sea-level lows (indicated by stratigraphic sequence boundaries) and the changes in marine fauna that have been used to define the chronostratigraphic stages (GSSPs). Similar ∼26 to 36 My cycles have been reported in various forms of tectonism, intra-plate volcanism, climatic change, ocean anoxia, biodiversity and mass-extinction events, which implies causal linkages among these phenomena. Internal Earth processes are likely to be involved in these cyclical events, although essentially identical cycles have been reported in the amplitude modulations of the Earth's 2.4-My and 9-My long orbital eccentricity cycles. This suggests that changes in the Earth's orbital parameters might provide a pacemaker for multi-million-year changes in climate, tectonism and sea levels.