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.
KeywordsPermian Cretaceous Lime Jurassic Miocene
Unable to display preview. Download preview PDF.
- Burke WH, Hetherington EA (1984) Normalized 87Sr/S6Sr by multiple collection and comparison to a standard. Chern Geol (Isot Geosci Sec) 2: 265–268Google Scholar
- Faure G, Powell JL (1972) Strontium isotope geology. Springer, Berlin Heidelberg New York, 188 ppGoogle Scholar
- Goldstein SJ, Jacobsen SB (1987) The Nd and Sr isotopic systematics of riverwater dissolved material: implications for the sources of Nd and Sr in seawater. Chern Geol 66: 245–272Google Scholar
- Harland WB, Armstrong RL, Cox A V, Craig LE, Smith AG, Smith DG (1989) A Geologic Time Scale. Univ Press, Cambridge, 262 ppGoogle Scholar
- Harland WB, Cox A V, Llewellyn PG, Pickton CAG, Smith AG, Walters R (1982) A Geologic Time Scale. Univ Press, Cambridge, 131 ppGoogle Scholar
- Lee Roark CK (1989). Williston Basin subsidence and sea level history: chronological and lithofacies constraints. PhD Thesis, Cornell Univ, 334 ppGoogle Scholar
- Otto JB, Blank WK, Dahl DA (1988) A nitrate precipitation technique for preparing strontium for isotopic analysis. Chern Geol (Isot Geosci Sec) 72: 173–179Google Scholar
- Vail PR, Mitchum RM, Todd RG, Widmier JM, Thompson S, Sangree JB, Bubb IN, Hatlelid WG (1977) Seismic stratigraphy and global changes in sea level. Am Assoc Petrol Geol Mem 26: 49–212Google Scholar