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Temperature calibration for high Mg-calcite planktic Foraminifera shells from the Gulf of Aqaba

Hypersaline, oligotrophic seas have been shown to accommodate planktic Foraminifera (PF) with enriched Mg/Ca in their calcareous shells, compared to other marine environments. Although Mg/Ca is a widely used proxy applied as a paleothermometer, its systematics in extreme hypersaline systems is not well understood.  

We measured element ratios using LASER ablation ICP-MS on the tests of the two abundant PF species, Globigerinoides ruber albus and Turborotalita clarkei, obtained from monthly resolved time series sediment traps at various water column depths in the northern part of the GOA.

Globigerinoides ruber albus shows a positive relationship between Mg/Ca and surface water temperatures of the surface mixed layer down to 60 m water depth. Although T. clarkei does not show the same positive relationship, it exhibits high Mg/Ca during water column mixing (March–April) possibly reflecting the movement of two water masses in the water column.

Using common calibration equations (Anand et al., 2003; Kisakürek et al., 2008; Gray et al., 2018), the high-Mg (5-25 mmol/mol) provided higher than measured in-situ (IS) ambient seawater temperatures (TMg/Ca and TIS, respectively). The high salinity at the GOA (>40) is assumed to be the main reason of the high shell-bound Mg.

Comparing surface dwelling G. ruber albus versus subsurface dwelling T. clarkei may facilitate reconstruction of the absolute and relative seasonal development temperature and surface water stratification. We suggest that species specific Mg/Ca-T calibrations for the GOA provide more accurate regional palaeoceanography and paleoclimate reconstruction of hypersaline environments.

Details

Author
Noy Levy1, Adi Torfstein2, Ralf Schiebel3, Natalie Chernihovsky2, Klaus Peter Jochum3, Ulrike Weis3, Brigitte Stoll3, Gerald H. Haug4
Institutionen
1Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany;The Fredy & Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel; 2The Fredy & Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel;Interuniversity Institute for Marine Sciences, Eilat 88103, Israel; 3Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany; 4Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, 55128 Mainz, Germany;Department of Earth Sciences, ETH Zurich, Sonneggstrasse 5, 8092 Zurich, Switzerland
Veranstaltung
GeoMinKöln 2022
Datum
2022
DOI
10.48380/34er-fc92
Geolocation
Europe