Abstract
Strontium-isotopic ratios of dated corals have been obtained from submerged reefs formed during Quaternary glacial periods off the Hawaiian islands. These data, combined with data from deep-sea sediments, tightly constrain the secular variation of marine 87 Sr 86 Sr for the past 800,000 yr. Although long-term trends are apparent, no significant (>0.02‰), rapid (<100,000 yr) excursions in 87 Sr 86 Sr were resolved nor did we observe any samples with 87 Sr 86 Sr greater than that of modern seawater. Strontium in mollusks from elevated marine terraces formed during interglacial periods on the southern California coast show resolvable and consistent variations in 87 Sr 86 Sr which, when compared to the trend of Quaternary marine 87 Sr 86 Sr , can be used to infer uplift rates and define approximate ages for the higher terraces. The Sr-isotope age estimates indicate that uplift rates vary among crustal blocks and were not necessarily constant with time. No contrast in Sr-isotopic ratios between similar-age Hawaiian and California fossils was observed, confirming that any change in marine 87 Sr 86 Sr from glacial to interglacial periods must be small. A realistic appraisal of the potential of Sr-isotope stratigraphy for chronometric applications in the Quaternary suggests that the technique will be limited to relatively coarse distinctions in age.
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