Effect of sample pretreatment and size fraction on the δ18O and δ13C values of foraminifera in Arabian Sea sediments |
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| Authors: | A Sarkar R Ramesh SK Bhattacharya |
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| Institution: | Physical Research Laboratory, Ahmedabad 380 009, India |
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| Abstract: | Stable oxygen and carbon isotope ratios (δ18O and δ13C, respectively) of a planktonic foraminiferal species (Globigerinoides sacculifer) and marble carbonate were measured with and without a variety of pretreatments like ultrasonication, soaking in H2O2, methanol and roasting under vacuum. Additionally, organic matter - carbonate mixtures were also analysed with and without the above pretreatments. No significant difference was found in the isotope ratios of treated and untreated samples. It appears that most of the pretreatments may not be necessary when dealing with planktonic foraminifera, especially G. sacculifer. Analysis of two different size fractions (> 400 μm and 250–400 μm) of this species reveals that the smaller size fraction is enriched in 18O and depleted in 13C relative to the bigger size fraction. It is therefore necessary to choose a proper size fraction for isotopic analyses. |
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