Interlaboratory comparison study of Mg/Ca and Sr/Ca measurements in planktonic foraminifera for paleoceanographic research

Thirteen laboratories from the USA and Europe participated in an intercomparison study of Mg/Ca and Sr/Ca measurements in foraminifera. The study included five planktonic species from surface sediments from different geographical regions and water depths. Each of the laboratories followed their own cleaning and analytical procedures and had no specific information about the samples. Analysis of solutions of known Mg/Ca and Sr/Ca ratios showed that the intralaboratory instrumental precision is better than 0.5% for both Mg/Ca and Sr/Ca measurements, regardless whether ICP‐OES or ICP‐MS is used. The interlaboratory precision on the analysis of standard solutions was about 1.5% and 0.9% for Mg/Ca and Sr/Ca measurements, respectively. These are equivalent to Mg/Ca‐based temperature repeatability and reproducibility on the analysis of solutions of ±0.2°C and ±0.5°C, respectively. The analysis of foraminifera suggests an interlaboratory variance of about ±8% (%RSD) for Mg/Ca measurements, which translates to reproducibility of about ±2–3°C. The relatively large range in the reproducibility of foraminiferal analysis is primarily due to relatively poor intralaboratory repeatability (about ±1–2°C) and a bias (about 1°C) due to the application of different cleaning methods by different laboratories. Improving the consistency of cleaning methods among laboratories will, therefore, likely lead to better reproducibility. Even more importantly, the results of this study highlight the need for standards calibration among laboratories as a first step toward improving interlaboratory compatibility.

[1]  H. Elderfield,et al.  A study of cleaning procedures used for foraminiferal Mg/Ca paleothermometry , 2003 .

[2]  Henry Elderfield,et al.  Calibration of Mg/Ca thermometry in planktonic foraminifera from a sediment trap time series , 2003 .

[3]  A. Mix,et al.  Adaptation of a flow‐through leaching procedure for Mg/Ca paleothermometry , 2003 .

[4]  Niall C. Slowey,et al.  Benthic foraminiferal Mg/Ca-paleothermometry: a revised core-top calibration , 2002 .

[5]  D. Lea,et al.  A simple evaluation of cleaning procedures on fossil benthic foraminiferal Mg/Ca , 2002 .

[6]  G. P. Lohmann,et al.  Accurate estimation of sea surface temperatures using dissolution‐corrected calibrations for Mg/Ca paleothermometry , 2002 .

[7]  G. Klinkhammer,et al.  Development of a flow-through system for cleaning and dissolving foraminiferal tests , 2002 .

[8]  D. Lea,et al.  Core top calibration of Mg/Ca in tropical foraminifera: Refining paleotemperature estimation , 2002 .

[9]  C. Pelejero,et al.  Precision of the current methods to measure the alkenone proxy U37K′ and absolute alkenone abundance in sediments: Results of an interlaboratory comparison study , 2001 .

[10]  M. Sarnthein,et al.  Variation of foraminiferal Sr/Ca over Quaternary glacial‐interglacial cycles: Evidence for changes in mean ocean Sr/Ca? , 2000 .

[11]  D. Lea,et al.  Climate impact of late quaternary equatorial pacific sea surface temperature variations , 2000, Science.

[12]  H. Elderfield,et al.  Past temperature and δ18O of surface ocean waters inferred from foraminiferal Mg/Ca ratios , 2000, Nature.

[13]  D. Schrag,et al.  Coccolith Sr/Ca as a new indicator of coccolithophorid calcification and growth rate , 2000 .

[14]  G. P. Lohmann,et al.  Incorporation and preservation of Mg in Globigerinoides sacculifer: implications for reconstructing the temperature and 18O/16O of seawater , 2000 .

[15]  D. Schrag,et al.  Are seawater Sr/Ca variations preserved in quaternary foraminifera? , 1999 .

[16]  D. Lea,et al.  Controls on magnesium and strontium uptake in planktonic foraminifera determined by live culturing , 1999 .

[17]  D. Lea,et al.  Glacial–interglacial changes in Subantarctic sea surface temperature and δ18O-water using foraminiferal Mg , 1999 .

[18]  S. Emerson,et al.  Foraminiferal magnesium in Globeriginoides sacculifer as a paleotemperature proxy , 1998 .

[19]  T. Nilsson,et al.  Inter-Laboratory Studies for the Validation of Solid-Phase Microextraction for the Quantitative Analysis of Volatile Organic Compounds in Aqueous Samples. , 1997 .

[20]  E. Boyle,et al.  Last Glacial Maximum paleochemistry and deepwater circulation in the Southern Ocean: Evidence from foraminiferal cadmium , 1997 .

[21]  H. Elderfield,et al.  Variations in Mg/Ca and Sr/Ca ratios of planktonic foraminifera caused by postdepositional dissolution: Evidence of shallow Mg‐dependent dissolution , 1996 .

[22]  C. Hemleben,et al.  Assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures , 1996 .

[23]  S. Levitus,et al.  Interannual Variability of Temperature at a Depth of 125 Meters in the North Atlantic Ocean , 1994, Science.

[24]  Edward A. Boyle,et al.  Comparison of Atlantic and Pacific paleochemical records for the last 215,000 years : changes in deep ocean circulation and chemical inventories , 1985 .

[25]  C. Emiliani.  Mineralogical and chemical composition of the tests of certain pelagic foraminifera , 1955 .

[26]  E. Bard,et al.  Precision of the current methods to measure the alkenone proxy UK , 2001 .

[27]  Y. Rosenthal,et al.  Chemical Hydrography of the South Atlantic During the Last Glacial Maximum: Cd vs. δ13C , 1996 .

[28]  Wolfgang H Berger,et al.  The South Atlantic: Present and Past Circulation , 1996 .

[29]  E. Boyle.  LIMITS ON BENTHIC FORAMINIFERAL CHEMICAL ANALYSES AS PRECISE MEASURES OF ENVIRONMENTAL PROPERTIES , 1995 .

[30]  W. Broecker,et al.  GEOSECS Atlantic expedition , 1980 .

[31]  S. Gorshkov,et al.  World ocean atlas , 1976 .