Ecological controls on the shell geochemistry of pink and white Globigerinoides ruber in the northern Gulf of Mexico: Implications for paleoceanographic reconstruction

Richey, J. N.; Poore, R. Z.; Flower, B. P.; Hollander, D. J.

Abstract:

We evaluate the relationship between foraminiferal test size and shell geochemistry (?? 13C, ?? 18O, and Mg/Ca) for two of the most commonly used planktonic foraminifers for paleoceanographic reconstruction in the subtropical Atlantic Ocean: the pink and white varieties of Globigerinoides ruber. Geochemical analyses were performed on foraminifera from modern core-top samples of high-accumulation rate basins in the northern Gulf of Mexico. Mg/Ca analysis indicates a positive relationship with test size, increasing by 1.1mmol/mol (~2.5??C) from the smallest (150-212??m) to largest (>500??m) size fractions of G. ruber (pink), but with no significant relationship in G. ruber (white). In comparison, oxygen isotope data indicate a negative relationship with test size, decreasing by 0.6??? across the size range of both pink and white G. ruber. The observed increase in Mg/Ca and decrease in ?? 18O are consistent with an increase in calcification temperature of 0.7??C per 100??m increase in test size, suggesting differences in the seasonal and/or depth distribution among size fractions. Overall, these results stress the necessity for using a consistent size fraction in downcore paleoceanographic studies. In addition, we compare downcore records of ?? 18O and Mg/Ca from pink and white G. ruber in a decadal-resolution 1000-year sedimentary record from the Pigmy Basin. Based on this comparison we conclude that pink G. ruber is calcifying in warmer waters than co-occurring white G. ruber, suggesting differences in the relative seasonal distribution and depth habitat of the two varieties. ?? 2011 Elsevier B.V.

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Article

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70032554

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Richey, J. N.; Poore, R. Z.; Flower, B. P.; Hollander, D. J.

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English

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Marine Micropaleontology

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Ecological controls on the shell geochemistry of pink and white Globigerinoides ruber in the northern Gulf of Mexico: Implications for paleoceanographic reconstruction; 2012; Article; Journal; Marine Micropaleontology; Richey, J. N.; Poore, R. Z.; Flower, B. P.; Hollander, D. J.