EESS Ph.D. Dissertation Defense - Justine Kimball
This talk comprises the public portion of the PhD dissertation defense from approximately 9:00 am -10:00 am
Department: Environmental Earth System Science
Graduate Student: Justine Kimball
Advisor: Robert Dunbar
Title: Isotope Geochemistry of Deep-sea Corals: Paleoenvironmental Proxy Development.
Abstract: Inhabiting areas of the ocean where paleoenvironmental records are sparse, deep-sea corals represent valuable yet largely untapped Holocene records of intermediate and deep ocean variability. These archives could give valuable insight into the natural variability of areas of the ocean that play an active role in large-scale climate dynamics. Living in near constant temperature, salinity and pH, and with the slowest calcification rates recorded, deep-sea corals can also provide valuable constraints on processes driving mineral equilibrium and disequilibrium signatures. Despite deep-sea corals having been indicated as potential proxies for some time, however, few records of paleoenvironmental conditions have been produced using deep-sea corals and none of these have been temperature records. The research covered in this dissertation further develops two methods for extracting temperatures from deep-sea corals. In the first, bulk δ18O and δ13C are explored in a group of calcitic octocorals and a new calibration for temperature extraction in proposed. Secondly, I report new data to further develop “clumped” isotopes as a paleothermometer in deep-sea corals as well as to investigate mineral-specific, taxon-specific, and growth-rate related effects. Carbonate clumped isotope thermometry is based on the abundance of the doubly-substituted isotopologue 13C18O16O2 in carbonate minerals and is a new and exciting method for extracting temperatures from biogenic carbonates. Deep-sea coral records of paleoventilation from the tropical and subtropical Pacific are also presented using paired 230Th-U and 14C measurements.