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Field-based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: Core top results from the Aegean Sea (eastern Mediterranean)

Field-based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: Core top results from the Aegean Sea (eastern Mediterranean)
Field-based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: Core top results from the Aegean Sea (eastern Mediterranean)
Recent work across the Mediterranean Sea has illustrated the salinity and overgrowth effects on planktonic foraminiferal Mg/Ca, which potentially confound the use of this as a temperature proxy for paleoceanographic reconstructions. To test and verify these effects, we present new Aegean Sea results which reveal Mg/Ca values that were unreasonably high to be explained by temperature or salinity variations alone, confirming that foraminiferal Mg/Ca is affected by diagenesis. We have specifically targeted Globigerinoides ruber (w, sensu stricto), from a series of modern core tops spanning a strong sea surface salinity gradient and a minor sea surface temperature range, along a north?south Aegean Sea transect. Scanning Electron Microscopy analyses show that G. ruber specimens were covered by microscale euhedral crystallites of inorganic precipitates. This secondary calcite phase seems to be responsible for the anomalously high Mg/Ca ratios and likely formed near the sediment/water interface from CaCO3 supersaturated interstitial seawater. We also have clear evidence of diagenetic alteration in a north?south direction along the Aegean Sea, possibly depending on salinity and calcite saturation state gradients. These observations illustrate the necessity of alternative techniques (e.g., flow?through time resolved analysis or laser ablation inductively coupled plasma mass spectrometry) to potentially overcome these diagenetic issues and develop a more reliable and sensitive temperature proxy in similar subtropical settings characterized by high salinity, excessive evaporation, and restricted circulation.
1525-2027
Q09004
Kontakiotis, George
7682b6f0-5edb-42e6-ba07-cc8451282c38
Mortyn, P. Graham
cfb20adb-a4e5-45fd-8218-5bda08ae8651
Antonarakou, Assimina
7b7c8a30-a573-4e90-9770-da9984839dec
Martínez-Botí, Miguel A.
5d8a3d7c-bb00-467f-9fa4-1d9a6230697f
Triantaphyllou, Maria V.
2292aee7-286f-4f1e-b3f2-54b484507a40
Kontakiotis, George
7682b6f0-5edb-42e6-ba07-cc8451282c38
Mortyn, P. Graham
cfb20adb-a4e5-45fd-8218-5bda08ae8651
Antonarakou, Assimina
7b7c8a30-a573-4e90-9770-da9984839dec
Martínez-Botí, Miguel A.
5d8a3d7c-bb00-467f-9fa4-1d9a6230697f
Triantaphyllou, Maria V.
2292aee7-286f-4f1e-b3f2-54b484507a40

Kontakiotis, George, Mortyn, P. Graham, Antonarakou, Assimina, Martínez-Botí, Miguel A. and Triantaphyllou, Maria V. (2011) Field-based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: Core top results from the Aegean Sea (eastern Mediterranean). Geochemistry, Geophysics, Geosystems, 12 (9), Q09004. (doi:10.1029/2011GC003692).

Record type: Article

Abstract

Recent work across the Mediterranean Sea has illustrated the salinity and overgrowth effects on planktonic foraminiferal Mg/Ca, which potentially confound the use of this as a temperature proxy for paleoceanographic reconstructions. To test and verify these effects, we present new Aegean Sea results which reveal Mg/Ca values that were unreasonably high to be explained by temperature or salinity variations alone, confirming that foraminiferal Mg/Ca is affected by diagenesis. We have specifically targeted Globigerinoides ruber (w, sensu stricto), from a series of modern core tops spanning a strong sea surface salinity gradient and a minor sea surface temperature range, along a north?south Aegean Sea transect. Scanning Electron Microscopy analyses show that G. ruber specimens were covered by microscale euhedral crystallites of inorganic precipitates. This secondary calcite phase seems to be responsible for the anomalously high Mg/Ca ratios and likely formed near the sediment/water interface from CaCO3 supersaturated interstitial seawater. We also have clear evidence of diagenetic alteration in a north?south direction along the Aegean Sea, possibly depending on salinity and calcite saturation state gradients. These observations illustrate the necessity of alternative techniques (e.g., flow?through time resolved analysis or laser ablation inductively coupled plasma mass spectrometry) to potentially overcome these diagenetic issues and develop a more reliable and sensitive temperature proxy in similar subtropical settings characterized by high salinity, excessive evaporation, and restricted circulation.

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Published date: 9 September 2011
Organisations: Geochemistry

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Local EPrints ID: 196879
URI: http://eprints.soton.ac.uk/id/eprint/196879
ISSN: 1525-2027
PURE UUID: 25a8f338-c43d-4d5e-ba92-796ccb1b42cf

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Date deposited: 13 Sep 2011 16:13
Last modified: 14 Mar 2024 04:09

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Contributors

Author: George Kontakiotis
Author: P. Graham Mortyn
Author: Assimina Antonarakou
Author: Miguel A. Martínez-Botí
Author: Maria V. Triantaphyllou

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