A pulse of the Earth: A 27.5-Myr underlying cycle in coordinated geological events over the last 260 Myr

We performed spectral analyses on the ages of 89 well-dated major geological events of the last 260 Myr from the recent geologic literature. These events include times of marine and non-marine extinctions, major ocean-anoxic events, continental flood-basalt eruptions, sea-level fluctuations, global pulses of intraplate magmatism, and times of changes in seafloor-spreading rates and plate reorganizations. The aggregate of all 89 events shows ten clusters in the last 260 Myr, spaced at an average interval of ~ 26.9 Myr, and Fourier analysis of the data yields a spectral peak at 27.5 Myr at the ≥ 96% confidence level. A shorter period of ~ 8.9 Myr may also be significant in modulating the timing of geologic events. Our results suggest that global geologic events are generally correlated, and seem to come in pulses with an underlying ~ 27.5-Myr cycle. These cyclic pulses of tectonics and climate change may be the result of geophysical processes related to the dynamics of plate tectonics and mantle plumes, or might alternatively be paced by astronomical cycles associated with the Earth's motions in the Solar System and the Galaxy.