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Science 3 January 1992:
Vol. 255. no. 5040, pp. 68 - 72
DOI: 10.1126/science.255.5040.68
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Articles

Strontium Isotopic Composition of Estuarine Sediments as Paleosalinity-Paleoclimate Indicator

B. L. INGRAM 1 and D. SLOAN 2

1 Department of Geology, Stanford University, Stanford, CA 94305, and Berkeley Center for Isotope Geochemistry, Department of Geology and Geophysics, University of California, Berkeley, CA 94720
2 Museum of Paleontology, University of California, Berkeley, CA 94720

The strontium isotopic composition of biogenic precipitates that occur in estuarine sediments can be used as proxy indicator of paleosalinity and for assessing precipitation and river discharge rates over thousands of years. In the San Francisco Bay estuary, river water with low 87Sr/86Sr ratio (average, 0.7065) and low Sr concentration (0.13 parts per million) mixes with seawater with a higher 87Sr/86Sr ratio (0.7092) and Sr concentration (7.9 parts per million). The predicted mixing relation between salinity and Sr isotopic composition is confirmed by measurements of modern estuarine surface waters. A paleosalinity record obtained from foraminifera for the ancestral San Francisco Bay during oxygen isotope substage 5e of the last interglacial reflects a global rise and fall of sea level, and short time-scale variations related to fluctuations in discharge rates of the Sacramento and San Joaquin rivers.

Submitted on July 19, 1991
Accepted on October 16, 1991


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
87Sr/86Sr and Sr/Ca Investigation of Jurassic mollusks from Scotland: Implications for paleosalinities and the Sr/Ca ratio of seawater.
C. Holmden and J. D. Hudson (2003)
Geological Society of America Bulletin 115, 1249-1264
   Abstract »    Full Text »    PDF »
Geochemical tracers of sediment sources to San Francisco Bay.
B. L. Ingram and J. C. Lin (2002)
Geology 30, 575-578
   Abstract »    Full Text »    PDF »
Pleistocene Dolomite from the Namibian Shelf: High 87Sr/86Sr and {delta}18O Values Indicate an Evaporative, Mixed-Water Origin.
(2001)
Journal of Sedimentary Research 71, 800-808
Himalayan Tectonics, Weathering Processes, and the Strontium Isotope Record in Marine Limestones.
J. M. Edmond and J. M. Edmond (1992)
Science 258, 1594-1597
   Abstract »    PDF »


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