Possible evidence for a large decrease in seawater strontium/calcium ratios and strontium concentrations during the Cenozoic

Tripati, A. K. and Allmon, W. D. and Sampson, D. E. (2009) Possible evidence for a large decrease in seawater strontium/calcium ratios and strontium concentrations during the Cenozoic. Earth and Planetary Science Letters, 282 (1-4). pp. 122-130. DOI 10.1016/j.epsl.2009.03.020

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Abstract

Few constraints exist on the major element chemistry of ancient oceans. Turritellid marine snails precipitate aragonitic shells and are abundant in the Cenozoic fossil record, and therefore may be ideal for reconstructing past seawater chemistry. Here we report strontium to calcium (Sr/Ca) ratios of modern and early Cenozoic turritellid shells that still retain an aragonitic mineralogy. By applying partition coefficients determined from modern specimens to data for Paleocene and Eocene shells, we calculate paleo-seawater Sr/Ca values. The high Sr/Ca values recorded in fossil shells may imply that seawater Sr/Ca ratios varied from at least 9.5-15.2 mmol/mol, much higher than modern average seawater values (8.6 mmol/mol). High paleo-seawater Sr/Ca ratios may indicate that substantial changes in the biogeochemical cycling of Sr have occurred over the past ~ 37 million years. A decrease in seawater strontium concentrations could have arisen from an increase in the proportion of weathered radiogenic silicate rocks relative to carbonates, reducing the riverine flux of strontium to the oceans, or changes in the exposure and erosion of aragonitic carbonates on tropical shelves due to variations in sea level.

Item Type: Article
Uncontrolled Keywords: 08AREP; IA57;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 282
Page Range: pp. 122-130
Identification Number: 10.1016/j.epsl.2009.03.020
Depositing User: Sarah Humbert
Date Deposited: 29 May 2009 16:09
Last Modified: 23 Jul 2013 09:55
URI: http://eprints.esc.cam.ac.uk/id/eprint/1028

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