English
 
Privacy Policy Disclaimer
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT
  Sodium incorporation in foraminiferal calcite: An evaluation of the Na/Ca salinity proxy and evidence for multiple Na-bearing phases

Gray, W. R., Evans, D., Henehan, M., Weldeab, S., Lea, D. W., Müller, W., Rosenthal, Y. (2023): Sodium incorporation in foraminiferal calcite: An evaluation of the Na/Ca salinity proxy and evidence for multiple Na-bearing phases. - Geochimica et Cosmochimica Acta, 348, 152-164.
https://doi.org/10.1016/j.gca.2023.03.011

Item is

Files

show Files

Locators

show

Creators

show
hide
 Creators:
Gray, William R1, Author
Evans, David1, Author
Henehan, Michael2, Author              
Weldeab, Syee1, Author
Lea, David W1, Author
Müller, Wolfgang1, Author
Rosenthal, Yair1, Author
Affiliations:
1External Organizations, ou_persistent22              
23.3 Earth Surface Geochemistry, 3.0 Geochemistry, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum, ou_146037              

Content

show
hide
Free keywords: -
 Abstract: The ratio of sodium to calcium (Na/Ca) in foraminiferal calcite has been proposed as a proxy for salinity, yet relatively little is known about the incorporation of sodium into the shells of foraminifera. Ongoing debates include the location of Na in the calcite crystal lattice, the possibility that at least some Na might be complexed with organics, and the influence of spines/spine bases. We present new Na/Ca measurements, determined using both solution and laser ablation ICP-MS, of the planktonic foraminifera Globigerinoides ruber (white) from plankton tows and sediment traps spanning a wide salinity range (32.5–40.7 salinity units), laboratory cultures under varying carbonate chemistry, and globally-distributed core-top samples. Our results show that Na/Ca in recently living foraminifera measured by laser ablation ICP-MS is elevated by up to 5 mmol/mol (∼85%) relative to the same samples measured by solution ICP-MS (the same comparison for Mg/Ca shows excellent agreement between the techniques). Na/Ca in recently living foraminifera measured by laser ablation ICP-MS displays a significant relationship with salinity above ∼36 salinity units with a slope of ∼0.7 mmol/mol/salinity unit; however, only a weak relationship is observed between salinity and Na/Ca measured by solution ICP-MS. We propose that Na is incorporated in at least two discrete phases; a primary phase within the CaCO3 mineral, and a (or likely multiple) secondary phase(s). Possibilities for these secondary phases include residual metastable CaCO3, fluid inclusions, high Na/Ca spine bases, and organics. These secondary phases contribute to spatially-resolved analyses (i.e. laser ablation ICP-MS) of recently living foraminifera but are removed by crushing/oxidative cleaning for solution ICP-MS, and during early diagenesis, as evidenced by the agreement between laser analysis of coretop samples and Na/Ca measured by solution. The amount of one of these secondary phases, or the amount of Na within this phase, appears to vary as a function of salinity, and is likely the principal driver of the previously observed steep Na/Ca-salinity relationship in recently living foraminifera analysed by laser ablation. Overall, we find salinity, temperature, carbonate chemistry, and bottom water saturation state (Ωcalcite) all have a significant but relatively weak effect on Na/Ca in the primary calcite phase. As such, Na/Ca in planktonic foraminifera recovered from sediment cores is unlikely to find widespread utility as a salinity proxy.

Details

show
hide
Language(s):
 Dates: 20232023
 Publication Status: Finally published
 Pages: -
 Publishing info: -
 Table of Contents: -
 Rev. Type: -
 Identifiers: DOI: 10.1016/j.gca.2023.03.011
GFZPOF: p4 T5 Future Landscapes
 Degree: -

Event

show

Legal Case

show

Project information

show

Source 1

show
hide
Title: Geochimica et Cosmochimica Acta
Source Genre: Journal, SCI, Scopus
 Creator(s):
Affiliations:
Publ. Info: -
Pages: - Volume / Issue: 348 Sequence Number: - Start / End Page: 152 - 164 Identifier: CoNE: https://gfzpublic.gfz-potsdam.de/cone/journals/resource/journals161
Publisher: Elsevier