Open AccessCalcite saturation, foraminiferal test mass, and Mg/Ca‐based temperatures dissolution corrected using XDX—A 150 ka record from the western Indian Ocean
Author(s) -
Johnstone Heather J. H.,
Kiefer Thorsten,
Elderfield Henry,
Schulz Michael
Publication year - 2014
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2013gc004994
Subject(s) - calcite , geology , dissolution , thermocline , saturation (graph theory) , holocene , mineralogy , water mass , oceanography , geochemistry , chemistry , mathematics , combinatorics
A record of deep‐sea calcite saturation ( Δ [ CO 3 2 − ] ) , derived from X‐ray computed tomography‐based 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 µmol/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.).