Seawater Strontium Isotopic Variations from 2.5 Million Years Ago to the Present

Science  06 Jul 1990:
Vol. 249, Issue 4964, pp. 51-55
DOI: 10.1126/science.249.4964.51


Measurements of marine carbonate samples indicate that during the past 2.5 million years the 87Sr/86Sr ratio of seawater has increased by 14 x 10-5. The high average rate of increase of 87Sr/86Sr indicates that continental weathering rates were exceptionally high. Nonuniformity in the rate of increase suggests that weathering rates fluctuated by as much as ±30 percent of present-day values. Some of the observed shifts in weathering rates are contemporaneous with climatic changes inferred from records of oxygen isotopes and carbonate preservation in deep sea sediments.