Variation in 87Sr /86Sr of Permian Seawater: An Overview
The strontium isotope ratio (87Sr/S6Sr) of seawater has changed significantly through time in response to variations in the input of Sr to the oceans from various crust and upper mantle sources with differing 87Sr /86Sr values. An important aspect of this temporal variation is the empirical finding that, while the 87Sr /86Sr of seawater may vary through time, at any given time the Sr isotope ratio of the oceans is everywhere the same. Isotopic uniformity is achieved because the marine residence time of Sr (~ 4 X 106 yr) is long (e.g., Veizer 1989) compared to the oceanic circulation time (~ 103 yr). The oceans, therefore, are well mixed with respect to both Sr and Sr isotope ratio, and all coeval, marine-derived, carbonates, sulfates, and phosphates will possess the same initial 87Sr/S6Sr value. Consequently, the temporal changes in the 87Sr/S6Sr of seawater can be used to correlate and date marine strata and can provide insight into the global processes that have shaped our world.
KeywordsChem Geol Strontium Isotope Marine Stratum Strontium Isotopic Composition Delaware Basin
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