Regenberg, Marcus, Nürnberg, Dirk , Steph, Silke, Groeneveld, Jeroen, Garbe-Schönberg, C.-Dieter, Tiedemann, Ralf and Dullo, Wolf-Christian (2006) Assessing the effect of dissolution on planktonic foraminiferal Mg/Ca ratios: Evidence from Caribbean core tops. Geochemistry, Geophysics, Geosystems, 7 (7). Q07P15. DOI 10.1029/2005GC001019.

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Abstract

In order to assess the dissolution effect on foraminiferal Mg/Ca ratios, we analyzed Mg/Ca of seven planktonic foraminiferal species and four of their varieties from Caribbean core tops from ∼900–4700 m water depth. Depending on the foraminiferal species and variety, Mg/Ca start to decline linearly below Δ[CO32−] levels of ∼18–26 μmol/kg by ∼0.04–0.11 mmol/mol per 1 μmol/kg Δ[CO32−], similar to decreases of ∼0.5–0.8 mmol/mol per kilometer below ∼2500–3000 m water depth. Above these species-specific critical levels, Mg/Ca remains stable with higher intraspecific Mg/Ca variability than below. We developed routines to correct Mg/Ca from below these critical thresholds for dissolution effects, which reduce the overall intraspecific variability by ∼24–64%, and provide dissolution-corrected Mg/Ca appropriate to calculate Holocene paleotemperatures. When taking into account only dissolution-unaffected Mg/Ca from <2000 m, the systematic succession of foraminiferal species according to their Mg/Ca reflects expected calcification depths.

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