Graduation Year


Document Type




Degree Name

Master of Science (M.S.)

Degree Granting Department

Marine Science

Major Professor

Brad E. Rosenheim, Ph.D.

Committee Member

Julie N. Richey, Ph.D.

Committee Member

Amelia E. Shevenell, Ph.D.


Globorotalia truncatulinoides, Gulf of Mexico, Laser ablation, Mg/Ca, Planktic foraminifer, Sediment trap


Modern observations of planktic foraminifera from sediment trap studies help to constrain the regional ecology of paleoceanographically valuable species. Results from a weekly-resolved sediment trap time series (2008–2014) in the northern Gulf of Mexico demonstrate that 92% of Globorotalia truncatulinoides flux occurs in winter (January, February, and March), and that encrusted and non-encrusted individuals represent calcification in distinct depth habitats. We use individual foraminiferal analysis (IFA) of G. truncatulinoides tests to investigate differences in the elemental (Mg/Ca) and isotopic composition (18O and 13C) of the encrusted and non-encrusted ontogenetic forms of G. truncatulinoides, and to estimate their calcification depth in the northern Gulf of Mexico. We estimate that non-encrusted and encrusted G. truncatulinoides have mean calcification depths of 66 ± 9 meters and 379 ± 76 meters, respectively. We validate the Mg/Ca-calcification temperature relationship for G. truncatulinoides and demonstrate that the 18O and Mg/Ca of the non-encrusted form is a suitable proxy for winter surface mixed layer conditions in the Gulf of Mexico. Care should be taken not to combine encrusted and non-encrusted individuals of G. truncatulinoides for down core paleoceanographic studies.

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