Globorotalia truncatulinoides (dextral) Mg/Ca as a proxy for Gulf of Mexico winter mixed-layer temperature: evidence from a sediment trap in the northern Gulf of Mexico

Jessica W. Spear; Richard Z. Poore; Terrence M. Quinn

doi:10.1016/j.marmicro.2011.05.001

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Globorotalia truncatulinoides (dextral) Mg/Ca as a proxy for Gulf of Mexico winter mixed-layer temperature: evidence from a sediment trap in the northern Gulf of Mexico

Jessica W. Spear·Richard Z. Poore·Terrence M. Quinn

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Abstract

Three years of weekly- to biweekly-resolved sediment-trap data show that almost 90% of the total flux of tests of the planktic foraminifer Globorotalia truncatulinoides to sediments in the northern Gulf of Mexico occurs in January and February. Comparison of δ 18 O from tests of non-encrusted Gl. truncatulinoides in sediment-trap samples with calculated calcification depths indicates that the non-encrusted individuals secrete their test in the winter surface-mixed layer, most likely at the bottom of the surface mixed zone. Mg/Ca-temperature estimates from non-encrusted Gl. truncatulinoides in sediment-trap samples are consistent with observed temperatures at the calcification depths inferred from the δ 18 O data. In contrast, Mg/Ca-temperature estimates from encrusted Gl. truncatulinoides in sediment-trap samples indicate the crust is formed in cooler (deeper) waters. A preliminary study in a core recovered near the sediment-trap site demonstrates that non-encrusted and encrusted forms of Gl. truncatulinoides in sediment samples show a similar offset in Mg/Ca values as observed in sediment-trap samples. A short (~ 100 years) Mg/Ca record from non-encrusted Gl. truncatulinoides indicates a warming trend that coincides with a warming trend in mean-annual sea-surface temperature recorded by Mg/Ca in Globigerinoides ruber (white) from the same core. These findings suggest Mg/Ca from non-encrusted Gl. truncatulinoides has clear potential as a proxy for past winter mixed-layer temperature.

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Marine Micropaleontology Article

Source-reported bounding extent: 20.71° to 30.4° latitude; -97.86° to -81.04° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Jessica W. Spear, Richard Z. Poore, Terrence M. Quinn. 2011. Globorotalia truncatulinoides (dextral) Mg/Ca as a proxy for Gulf of Mexico winter mixed-layer temperature: evidence from a sediment trap in the northern Gulf of Mexico. https://doi.org/10.1016/j.marmicro.2011.05.001

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