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U.S. GEOLOGICAL SURVEY
Data Series 280

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Figure 3. Variation in strontium isotopic composition (⁸⁷Sr/⁸⁶Sr) of seawater during part of the Phanerozoic and Neoproterozoic based on analyses of unaltered brachiopods, belemnites, and conodonts from various locations worldwide. Dark curve represents the best-fit value for ages and ⁸⁷Sr/⁸⁶Sr values for data regressed by McArthur and others (2001) along with the 95-percent confidence level estimates (orange-shaded area). Solid vertical lines represent Period boundaries and dashed vertical lines represent Epoch boundaries based on the timescale of Young and Laurie (1996) as given in McArthur and others (2001), table 1.

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