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An extensive database of ⁸⁷Sr/⁸⁶Sr measurements on marine carbonate, evaporite, and phosphate samples compiled at Mobil and elsewhere has permitted construction of a ⁸⁷Sr/⁸⁶Sr “curve” for the Phanerozoic (see illustration below). During intervals when the ⁸⁷Sr/⁸⁶Sr curve is relatively linear and steep with respect to time (e.g., during the Permian, Jurassic, Late Cretaceous, and several intervals within the Late Eocene to Holocene), the strontium curve can be used as a chronometer because any given ratio along the line can be associated with a unique numerical age. The accuracy of the resulting age estimates approaches ±1.0 m.y for the Cenozoic intervals.

An extensive database of ⁸⁷Sr/⁸⁶Sr measurements on marine carbonate, evaporite, and phosphate samples compiled at Mobil and elsewhere has permitted construction of a ⁸⁷Sr/⁸⁶Sr “curve” for the Phanerozoic (see illustration below). During intervals when the ⁸⁷Sr/⁸⁶Sr curve is relatively linear and steep with respect to time (e.g., during the Permian, Jurassic, Late Cretaceous, and several intervals within the Late Eocene to Holocene), the strontium curve can be used as a chronometer because any given ratio along the line can be associated with a unique numerical age. The accuracy of the resulting age estimates approaches ±1.0 m.y for the [[Cenozoic]] intervals.

[[:file:applied-paleontology_fig17-31.png|Figure 3]] shows evolution of the ⁸⁷Sr/⁸⁶Sr ratio in seawater through the Phanerozoic.

[[:file:applied-paleontology_fig17-31.png|Figure 3]] shows evolution of the ⁸⁷Sr/⁸⁶Sr ratio in seawater through the Phanerozoic.