Technical note: No impact of alkenone extraction on foraminiferal stable isotope, trace element and boron isotope geochemistry

[摘要] Recent advances in geochemical techniques mean thatseveral robust proxies now exist to determine the past carbonate chemistryof the oceans. Foraminiferal δ 11 B and alkenone carbon isotopesallow us to reconstruct sea-surface pH and p CO 2 , respectively, and theability to apply both proxies to the same sediment sample would givestrongly paired datasets and reduce sample waste. However, no studies todate have examined whether the solvents and extraction techniques used toprepare alkenones for analysis also impact the geochemistry of foraminiferawithin those sediments. Here we examine six species pairs of plankticforaminifera, with half being taken from non-treated sediments and halfbeing taken from sediments where alkenones have been extracted. We look forvisual signs of contrasting preservation and compare analyses of δ 18 O, δ 13 C, δ 11 B and trace elements (Li, B,Na, Mn, Mg, Sr and U / Ca ). We find no consistent geochemical offset betweenthe treatments and excellent agreement in δ 11 B measurementsbetween them. Our results show that boron isotope reconstructions of pH inforaminifera from alkenone-extracted sediments can be applied withconfidence.

[学科分类] 大气科学