HR: 0800h
AN: PP31B-0420    [Abstracts]
TI: Mg/Ca in Different Size Classes of Planktonic Foraminifera
AU: * Richey, J N
EM: jrichey@marine.usf.edu
AF: University of South Florida, College of Marine Science, 140 Seventh Ave South, St. Petersburg, FL 33701, United States
AU: Poore, R Z
EM: rpoore@usgs.gov
AF: University of South Florida, College of Marine Science, 140 Seventh Ave South, St. Petersburg, FL 33701, United States
AU: Flower, B P
EM: bflower@marine.usf.edu
AF: U.S. Geological Survey, 600 Fourth St. South, St. Petersburg, FL 33701, United States
AU: Hollander, D J
EM: davidh@marine.usf.edu
AF: University of South Florida, College of Marine Science, 140 Seventh Ave South, St. Petersburg, FL 33701, United States
AB: The ratio of Mg/Ca in the tests of planktonic foraminifers is widely used to reconstruct past sea-surface temperature. However little is known about the effects of biological factors on foraminiferal Mg/Ca. In this study we consider the relationship between test size and Mg/Ca in the planktonic foraminifers Globigerinoides ruber (pink and white), Neogloboquadrina dutertrei and Globorotalia menardii. Foraminifera were picked from modern core-top samples from the Pigmy and Garrison Basins in the northern Gulf of Mexico. Results indicate a positive correlation between Mg/Ca and test size, with a range of 1.0 mmol/mol (2.5°C) from the smallest (150-212μm) to largest (500-600μm) size fractions of G. ruber (pink). N. dutertrei exhibits a negative correlation between Mg/Ca and test size, while G. ruber (white) shows no apparent relationship between test size and Mg/Ca. Changes in depth habitat during the life cycle of some species of planktonic foraminifera may account for the relationship between Mg/Ca and test size observed. This hypothesis is supported by the relationship of oxygen isotope ratios with test size. Given that the range of Mg/Ca values between the smallest and largest size classes within some species exceeds the amplitude of Mg/Ca variability observed in many climate records, it is imperative that Mg/Ca analyses be performed on a narrow size fraction of foraminifera.
DE: 4924 Geochemical tracers
DE: 4944 Micropaleontology (0459, 3030)
DE: 4954 Sea surface temperature
DE: 4994 Instruments and techniques
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting