A COMPOSITE 87SR/86SR CURVE FOR PHANEROZOIC SEAWATER AND LOOK-UP TABLE FOR DERIVATION OF NUMERICAL AGE

Since Wickman proposed using ⁸⁷Sr/⁸⁶Sr of marine precipitates as a method of dating, numerous workers have attempted to define the way that the ⁸⁷Sr/⁸⁶Sr of marine Sr has varied through geological time. Building on this work, we present a composite curve of marine- ⁸⁷Sr/⁸⁶Sr through the Phanerozoic, based on 4119 literature data for ⁸⁷Sr/⁸⁶Sr, plotted against the latest numerical timescale of Gradstein et al. (2012). The curve is fitted to data using the LOWESS regression smoother of Cleveland (1979) and Cleveland et al. (1992). An accompanying table converts the ⁸⁷Sr/⁸⁶Sr values to numerical ages. A comparison is drawn with previous composite curves of marine ⁸⁷Sr/⁸⁶Sr through time and some of the details of the new fitted curve are discussed in terms of the way it may be reflecting geological events.

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