Trends, cycles and nonstationarities in isotope signals of Phanerozoic seawater

The new set of Sr-87/Sr-86, delta(18)O and delta(13)C experimental data for Phanerozoic seawater, the "Bochum/Ottawa Isotope Dataset", has been tested by wavelet, discontinuity and sliding window correlation dimension analyse s for cyclicities and nonstationarities in the isotope signal. The tests in dicate discontinuities in the strontium isotope signal at similar to 500, 3 40, 288, 210, 65 and 28 Ma, while for the oxygen and carbon isotopes they a re at similar to 500, 385, 290, 210 and 65 Ma. These discontinuities, often coincident with major stage boundaries, reflect mostly single (likely tect onic) events that do not affect the structure of the underlying system. The two most pronounced nonstationarities in all isotope systematics are at si milar to 65 and 210 Ma, respectively, that is at the K/T and Norian/Rhaetia n transitions. Wavelet analysis for all three isotope systems yields a long -term quasi-periodicity at similar to 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, Her cynian and Alpine tectonic cycles. (C) 1999 Elsevier Science B.V. All right s reserved.