Calcite saturation, foraminiferal test mass, and Mg/Ca‐based temperatures dissolution corrected using XDX—A 150 ka record from the western Indian Ocean

Abstract

A record of deep-sea calcite saturation ðD½CO 22 3 Þ, derived from X-ray computed tomographybased foraminifer dissolution index, XDX, was constructed for the past 150 ka for a core from the deep (4157 m) tropical western Indian Ocean. G. sacculifer and N. dutertrei recorded a similar dissolution history, consistent with the process of calcite compensation. Peaks in calcite saturation ($15 mmol/kg higher than the present-day value) occurred during deglaciations and early in MIS 3. Dissolution maxima coincided with transitions to colder stages. The mass record of G. sacculifer better indicated preservation than did that of N. dutertrei or G. ruber. Dissolution-corrected Mg/Ca-derived SST records, like other SST records from marginal Indian Ocean sites, showed coolest temperatures of the last 150 ka in early MIS 3, when mixed layer temperatures were $4 C lower than present SST. Temperatures recorded by N. dutertrei showed the thermocline to be $4 C colder in MIS 3 compared to the Holocene (8 ka B.P.).

Effect of preservation state of planktonic foraminifera tests on the decrease in Mg/Ca due to reductive cleaning and on sample loss during cleaning

“…Correlation between Δ[CO3 2-] and analytical yield (Table 3) confirms anecdotal evidence that analytical yield tends to be lower for poorly preserved samples ( Figure 6, Table 3) In order to further test the utility of the relationship between yield and test preservation, we compared analytical yield of (Mg-cleaned) G. sacculifer to a record of preservation for a down core record for which Mg/Ca has been published [Kiefer et al, 2006, Johnstone et al, 2014. Sediment core WIND 28K [McCave, 2001] et al, 2008].…”

“…(1) There was no difference in the slope of regression between Δ[CO3 [Kiefer et al, 2006]. Red line is dissolution index XDX [Johnstone et al, 2014] Table 2. Analytical yield and Mg/Ca, Mn/Ca, Al/Ca, Fe/Ca for four species of planktic foraminifera cleaned using Mg-cleaning and Cd-cleaning methods.…”

Integrating palaeoclimate time series with rich metadata for uncertainty modelling: strategy and documentation of the PalMod 130k marine palaeoclimate data synthesis

“…Whereas benthic foraminifera live in a generally stable environment, the near-sea-surface habitat of planktonic foraminifera shows large seasonal and vertical gradients. Species-specific seasonal and/or depth habitat preferences may therefore leave a considerable imprint on the proxy signal contained in their shells (Jonkers and Kučera, 2017;Mix, 1987). For all proxies based on foraminifera, it is relevant to record the species as well as the number of individuals that were pooled for geochemical analysis.…”