Field-based validation of a diagenetic effect on G. ruber Mg/Ca paleothermometry: Core top results from the Aegean Sea (eastern Mediterranean)
Kontakiotis, George (Panepistēmio Athēnōn. Department of Historical Geology and Paleontology)
Mortyn, P. Graham (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Antonarakou, Assimina (Panepistēmio Athēnōn. Department of Historical Geology and Paleontology)
Martínez Botí, M. A. (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Triantaphyllou, Maria V. (Panepistēmio Athēnōn. Department of Historical Geology and Paleontology)

Data:	2011
Resum:	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.
Ajuts:	Ministerio de Ciencia e Innovación CTM2006-11936
Drets:	Tots els drets reservats.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	G. ruber (w, sensu stricto) ; Mg/Ca paleothermometry ; Calcite saturation state ; Eastern Mediterranean ; High-Mgcalcite diagenetic overgrowths ; Palaeoceanography
Publicat a:	Geochemistry, geophysics, geosystems, Vol. 12, Issue 9 (Sept. 2011) , p. 1-14, ISSN 1525-2027

DOI: 10.1029/2011GC003692

14 p, 1006.0 KB

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