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

Heuser, Alexander, Eisenhauer, Anton , Böhm, Florian, Wallmann, Klaus , Gussone, Nikolaus, Pearson, P. N., Nägler, T. F. and Dullo, Wolf-Christian (2005) Calcium isotope (δ44/40Ca ) variations of Neogene planktonic foraminifera. Open Access Paleoceanography, 20 . PA2013. DOI 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.

Document Type: Article
Keywords: calcium isotopes; δ44/40Ca; Neogene; planktonic foraminifera; ocean calcium inventory
Research affiliation: OceanRep > SFB 574 > C5
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
OceanRep > SFB 574
Kiel University
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1029/2004PA001048
ISSN: 0883-8305
Date Deposited: 16 Jul 2009 11:59
Last Modified: 23 Sep 2019 19:06

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