Ghosts of Oceans Past: Analysis of Microfossils from Deep Sea Sediments

This research focuses on the analysis of microfossils from deep-sea sediments. I am investigating a series of deep-sea sediment cores from the South Pacific. The cores are a vertical timeline of sedimentation, with each centimeter layer representing approximately 1,000 to 5,000 years of deposition. I subsampled each core by removing 10cc of sediment every 150 cm. Each subsample spans 2cm. After recording the mass of each sample, I washed and agitated each in purified water and sodium metaphosphate (disaggregant) solution to break up any clays adhering to the fragile fossil material. After rinsing over a 63m sieve, the samples were dried, and then transferred to a storage vial. Each sample was examined under a low-power binocular microscope to identify and quantify the assemblage of microfossils. I also analyzed the microfossil specimens using the scanning electron microscope to aid in identification and capture images of the important specimens. Results document changes in the composition of microfossil shells and faunal assemblages through time. In general, the dominant sediment lithology is red clay. However, several cores contain evidence of significant sediment variability through time. Typically, South Pacific deep waters are corrosive to calcium carbonate, so the preservation of carbonate fossils in the sediments reflects intervals of anomalous ocean chemistry that in turn may reflect changes in atmospheric CO inventories. These results show that over a relatively short geologic period, the ocean level at the coring site fluctuated between shallower nutrient rich waters and deeper carbonate rich waters. Future work, in collaboration with colleagues at the University of Michigan and Boise State University, will focus on more precise determinations of the sediment layer ages and geochemical analyses of the microfossils to determine ancient oceanic and atmospheric circulation patterns