Trends, cycles and nonstationarities in isotope signals of phanerozoic seawater

The new set of 87Sr/86Sr, δ18O and δ13C experimental data for Phanerozoic seawater, the “Bochum/Ottawa Isotope Dataset”, has been tested by wavelet, discontinuity and sliding window correlation dimension analyses for cyclicities and nonstationarities in the isotope signal. The tests indicate discontinuities in the strontium isotope signal at ∼500, 340, 288, 210, 65 and 28 Ma, while for the oxygen and carbon isotopes they are at ∼500, 385, 290, 210 and 65 Ma. These discontinuities, often coincident with major stage boundaries, reflect mostly single (likely tectonic) events that do not affect the structure of the underlying system. The two most pronounced nonstationarities in all isotope systematics are at ∼65 and 210 Ma, respectively, that is at the K/T and Norian/Rhaetian transitions. Wavelet analysis for all three isotope systems yields a long-term quasi-periodicity at ∼94–125 Ma, best developed during the Paleozoic, with superimposed intermittent 48–57 and 29–35 Ma oscillations, all likely a reflection of plate reorganizations within the Caledonian, Hercynian and Alpine tectonic cycles.