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Calcium isotope (δ44/40Ca) variations of Neogene planktonic foraminifera

Heuser, Alexander, Eisenhauer, Anton, Böhm, Florian, Wallmann, Klaus, Gussone, Nikolaus, Pearson, Paul Nicholas, Nägler, Thomas F. and Dullo, Wolf-Christian 2005. Calcium isotope (δ44/40Ca) variations of Neogene planktonic foraminifera. Paleoceanography 20 (2) , PA2013. 10.1029/2004PA001048

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Measurements of the calcium isotopic composition (δ44/40Ca) of planktonic foraminifera from the western equatorial Pacific and the Indian sector of the Southern Ocean show variations of about 0.6‰ over the past 24 Myr. The stacked δ44/40Ca record of Globigerinoides trilobus and Globigerina bulloides indicates a minimum in δ44/40Casw (seawater calcium) at 15 to 16 Ma and a subsequent general increase toward the present, interrupted by a second minimum at 3 to 5 Ma. Applying a coupled calcium/carbon cycle model, we find two scenarios that can explain a large portion of the observed δ44/40Casw variations. In both cases, variations in the Ca input flux to the ocean without proportional changes in the carbonate flux are invoked. The first scenario increases the riverine calcium input to the ocean without a proportional increase of the carbonate flux. The second scenario generates an additional calcium flux from the exchange of Ca by Mg during dolomitization. In both cases the calcium flux variations lead to drastic changes in the seawater Ca concentrations on million year timescales. Our δ44/40Casw record therefore indicates that the global calcium cycle may be much more dynamic than previously assumed.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Additional Information: Pdf uploaded in accordance with publisher's policy at (accessed 20/02/2014).
Publisher: American Geophysical Union
ISSN: 0883-8305
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 03:00

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