I/Ca ratios in benthic foraminifera from the Peruvian oxygen minimum zone: analytical methodology and evaluation as a proxy for redox conditions

[摘要] In this study,we explore the correlation of I/Ca ratios in three calcitic and onearagonitic foraminiferal species. I/Ca ratios are evaluated as possibleproxies for changes in ambient redox conditions across the Peruvian oxygenminimum zone to the ambient oxygen concentrations in the habitat of theforaminiferal species studied. Cleaning and measurement methods for thedetermination of I/Ca ratios are tested. All species show a positivetrend in their I/Ca ratios as a function of higher oxygenconcentrations. The most promising species appears to be Uvigerinastriata, which shows a highly statistically significant correlation betweenI/Ca ratios and bottom water (BW) oxygenation(I/Ca = 0.032(±0.004) × [O₂]_BW +0.29(±0.03), R² = 0.61, F = 75, P < 0.0001). Only forthe aragonitic species Hoeglundina elegans is this relationship notsignificant. The iodine volatility in acidic solutions, the speciesdependency of I/Ca–[O₂]_BW correlations, and theindividual variability of single tests, need to be accounted for whenapplying the I/Ca ratio as a proxy for redox conditions.

[学科分类] 地球化学与岩石