Determination of sediment provenance at drift sites using hydrogen isotopes in lipids
Englebrecht, Amy C.
MetadataShow full item record
Paleoclimate records with sufficient length and temporal resolution to study the occurrence and causal mechanisms of abrupt climate change are exceedingly rare. Rapidly deposited ocean sediments provide the best archive for studying these events through geologic time, but such sites in the open ocean are limited to sediment drift deposits such as the Bermuda Rise in the northwest Atlantic. Using multiple climate proxies in a single core is becoming more common in high-resolution paleoclimate investigations, but a major potential concern for this approach arises from the possibility that the fine fraction of sediment (<63 μm), and the climate proxies within it, may represent conditions far from the deposition site. We hypothesize that hydrogen isotope ratios of alkenones, a class of lipids from phytoplankton, may provide insight into the source of fine fraction sediment. Because of their restricted sources, broad geographic distribution, and excellent preservation properties, alkenones are of particular interest in the emerging field of compound-specific hydrogen isotopic analysis, and the sedimentary abundances, extents of unsaturations, and isotopic compositions of alkenones provide quantitative and near-continuous records. We isolated alkenones from cultured unicellular algae (haptophyte Emiliania huxleyi), surface ocean particulate material, and open ocean sediments to determine the extent and variability of hydrogen isotopic fractionation in the di-, tri-, and tetraunsaturated C37 compounds. We then compared the δD of the alkenones in surface sediments between the Bermuda Rise and the Scotian Margin above which a large (~20%) δD gradient exists. We determined the fractionation between alkenones from suspended particulate samples and the water in which the phytoplankton lived, and examined the variability of alkenone δD during key climate transitions at the Bermuda Rise.
Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2004
Showing items related by title, author, creator and subject.
The sediments of the western Gulf of Mexico. I. The continental terrace of the western Gulf of Mexico : its surface sediments, origin, and development. II. Chemical studies of sediments of the western Gulf of Mexico Stetson, Henry C.; Trask, Parker D. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1953-05)In 1947 the Woods Hole Oceanographic Institution organized an expedition to investigate the bottom sediments and oceanography of the northwest Gulf of Mexico. The Geological Society of America contributed to the support ...
Flow and sediment properties influencing erosion of fine-grained marine sediments : sea floor and laboratory experiments Young, Robert Alexander (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1975-09)Erosion processes involving fine-grained marine sediments were studied by using an in situ flume to erode undisturbed bottom sediments on the sea floor in Buzzards Bay, a shallow marine embayment off the Massachusetts coast. ...
Modern sedimentation in the Northern Barents Sea : input, dipersal and deposition of suspended sediments from glacial meltwater Pfirman, Stephanie L. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1984-08)The modern depositional environment of the northern epicontinental Barents Sea varies from proximal to distal glaciomarine. The regional surface sediment distribution is controlled by erosion of shallow banks of the ...