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.S.; Richard, Z.P.; Terrence, M.Q.
Marine Micropaleontology 80(3-4): 53-61
ISSN/ISBN: 0377-8398 DOI: 10.1016/j.marmicro.2011.05.001
Three years of weekly- to biweekly-resolved sediment-trap data show that almost 9% 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 ?18O 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 ?18O data. In. Research highlights: New sediment-trap data show 9% 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 measured ?18O and calculated equilibrium depth profiles show nonencrusted specimens of Gl. truncatulinoides secrete their test in the winter surfacemixed layer. Clear separation in Mg/Ca between non-encrusted and encrusted specimens of Gl. truncatulinoides, with higher values recorded in the non-encrusted form. Non-encrusted specimens of Gl. truncatulinoides can be used as a proxy for temperature variations in the winter surface-mixed layer in the northern Gulf of Mexico. Non-encrusted Gl. truncatulinoides Mg/Ca-temperature estimates from a preliminary study from a core recovered near the sediment-trap site indicate past winter surfacemixed layer temperature increased over a ~1year interval, similar to a trend observed in a proxy record of mean-annual SST from Globigerinoides ruber (white) from the same core.