A 32-million year cycle detected in sea-level fluctuations over the last 545 Myr

Spectral analyses of past relative sea-level oscillations as represented by the ages of 57 Phanerozoic (the last 545 Myr) stratigraphic sequence boundaries from the Canadian Arctic show a strong spectral peak at 32 Myr (>99.9% confidence). These findings concur with previous reports of significant cycles with periods of around 30 Myr in various records of fluctuations of sea level, and in potentially related episodes of tectonism, volcanism, climate, and biotic extinctions. Sequence boundaries commonly coincide with stage boundaries based on biostratigraphy, and are correlated with episodes of extinction and times of flood-basalt volcanism. The connection between tectonics and sea-level variations may come from changes in rates of ocean-floor spreading and subduction, intraplate stresses from plate-reorganizations, and pulsations of hotspot volcanism. These coordinated periodic fluctuations in tectonics, sea level and climate may be modulated by cyclical activity in the Earth's mantle, although some pacing by astronomical cycles is suspected.