The use of paired elemental and stable isotopic measurements to reconstruct past changes in climate and hydrology has been growing rapidly yet for benthic foraminifera there are still many outstanding questions about its reliability. Under this award the PIs will use SIMS and SEM techniques in samples from preserved subsections of OCE205 box cores previously collected along the southern flank of Little Bahamas Bank to determine the source of their high Mg/Ca values. These cores were used to calibrate Mg/Ca temperatures higher than about 12 degrees C but there is evidence that the equations are not reproduced in nearby cores from the Florida Straits. SIMS and ICP-MS will be used to measure the variability between tests of benthic foraminiferal species and to compare live (stained) individuals with recent fossil individuals to determine the extent of early diagenesis in altering the primary Mg/Ca signal. Cleaning experiments will show how chemical treatment may affect the distribution and amount of magnesium in the foraminiferal test. This research will help to determine the soundness of this approach when applied to benthic foraminifera and studies of deep ocean hydrography. The results of this study will be presented in classes and for graduate training at WHOI and CU, undergraduate lectures at CU and Sea Education Association, international conferences and peer reviewed journals.
