Publication Date:
2024-02-02
Description:
We used modern epibenthic foraminifer tests of Cibicidoides mundulus and Planulina wuellerstorfi from South Atlantic core top sediments in order to establish Mg/Ca-temperature relationships for the temperature range from 0 to 15°C. We obtained the following calibrations: Mg/Ca (mmol/mol) = 0.830*exp(0.145*BWT (°C)) for P. wuellerstorfi, and Mg/Ca (mmol/mol) = 0.627*exp(0.143*BWT (°C)) for C. mundulus. However, a number of tests, especially those bathed in North Atlantic Deep Water, revealed higher Mg/Ca ratios than predicted from the calibration. Our data suggest that d[CO3 2-] of bottom water exerts a significant control on dMg/Ca (temperature-corrected) of C. mundulus (dMg/Ca = 0.017*d[CO3 2-] -0.14), while dMg/Ca of P. wuellerstorfi is more likely to be governed by TCO2 (dMg/Ca = -0.007*TCO2 + 15). Since both d[CO3 2-] and TCO2 are closely linked to [CO3 2-], it is inferred that carbonate ion acts as secondary control, after temperature, on benthic shell Mg/Ca below -4°C. A drop in [CO3 2-] by 25 ?mol/kg at 4 km water depth, as suggested for the Last Glacial Maximum, would decrease Mg/Ca by up to 0.4 mmol/mol, which leads to an underestimation of bottom water temperature by -3.5°C. Therefore our results indicate that the Mg/Ca thermometer should be used cautiously for benthic foraminifers where changes in the carbonate chemistry are present in the paleoceanographic record.
Keywords:
B_LANDER; Bottom lander; Brazil Basin; Cape Basin; Cibicidoides mundulus, Magnesium/Calcium ratio; Cibicidoides mundulus, Magnesium/Calcium ratio, standard deviation; Continental slope off Brazil; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Equatorial Atlantic; Event label; GeoB1041-1; GeoB1105-3; GeoB1113-7; GeoB1118-2; GeoB1203-2; GeoB1216-2; GeoB1217-1; GeoB1218-1; GeoB1707-2; GeoB1710-2; GeoB1711-5; GeoB1712-2; GeoB1713-6; GeoB1715-3; GeoB1719-2; GeoB1720-4; GeoB1721-5; GeoB1726-2; GeoB1728-3; GeoB1729-2; GeoB2102-1; GeoB2105-3; GeoB2106-1; GeoB2107-5; GeoB2715-1; GeoB2718-2; GeoB2727-1; GeoB3602-2; GeoB3603-1; GeoB3803-1; GeoB3804-2; GeoB3807-1; GeoB3808-7; GeoB3809-1; GeoB3810-2; GeoB3812-2; GeoB3822-1; GeoB3827-1; GeoB6202-5; GeoB6205-1; GeoB6208-1; GeoB6216-1; GeoB6222-2; GeoB6309-2; GeoB6330-1; GeoB6334-2; GeoB6336-2; GeoB8403-1; GeoB8430-2; GeoB8462-4; Giant box corer; GKG; Gravity corer (Kiel type); LA-ICP-MS Thermo Finnigan Element 2; M12/1; M20/2; M23/2; M29/1; M34/1; M34/3; M46/2; M46/3; M57/2; M6/6; M9/4; Meteor (1986); Mid Atlantic Ridge; MUC; MultiCorer; Namibia Continental Margin; Namibia continental slope; Planulina wuellerstorfi, Magnesium/Calcium ratio; Planulina wuellerstorfi, Magnesium/Calcium ratio, standard deviation; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; SL; Slope off Argentina; Southern Cape Basin; SPP1158; Vema Channel; Walvis Bay/Namibia; Walvis Ridge; western South Atlantic
Type:
Dataset
Format:
text/tab-separated-values, 246 data points
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