160-1 ~60-Million-Year Periodicity in the Volatility of the Geological Carbon Cycle and in Climate: Links to Biodiversity History, Mass Extinctions, and Tectonics

Abstract:

During the Phanerozoic, marine animal biodiversity fluctuated with a periodicity of about 60 million years, and similar periodic fluctuations occur in Sr and S isotopes, suggesting links between biodiversity, tectonics, and ocean oxygenation. Here, we document a similar periodicity in the volatility of the geological carbon cycle over the past 500 m.y., where volatility was calculated as the standard deviation of δ13C values of marine carbonates within a moving window, subsampled to standardize sample size. Intervals of time with numerous/large carbon isotope excursions (CIEs) have high volatility, and intervals lacking major excursions have low volatility.

As noted previously, carbon cycle volatility decreased during the Mesozoic, which has been attributed to more complete ocean oxygenation. Spectral analysis of the detrended time series reveals a significant ~60-m.y. periodicity in volatility, in addition to an ~80-m.y. signal. Intervals of high carbon cycle volatility generally correspond with lower biodiversity.

CIEs are commonly attributed to major events like expansions of marine anoxia or large igneous province eruptions, and they are often associated with climate change. Thus, CIEs represent major disruptions of Earth-surface environments and biogeochemical cycles. Periodicity in carbon cycle volatility can thus be interpreted as periodicity in global environmental stability on million-year timescales. These results help explain why biodiversity is periodic even though mass extinctions themselves are less regular: most mass extinctions have tended to occur  during these extended intervals of increased biogeochemical instability and may contribute to the overall volatility but do not explain it on their own.

These results are consistent with Boulila et al.’s (2025, doi:10.1038/s43247-025-02370-6) suggestion that 60-m.y. biodiversity cycles relate to cycles in ocean oxygenation, as many CIEs are attributable to ocean anoxia and carbon burial. High temperature may contribute to the development of anoxia, and some Phanerozoic temperature data show evidence of a similar periodicity. These cycles could, in turn, be driven by cycles in tectonics and weathering, reflected in the strontium record. Links to reported periodicity in large igneous province eruptions are unclear.

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