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Author ORCID Identifier
Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
R. Mark Leckie
Biodiversity | Evolution
There are outstanding questions as to how important currents are to dispersal, especially for the evolution of planktic foraminifera. During the Neogene Period there were significant increases in the diversity of planktic foraminifera that occurred during major tectonic gateway closures, episodes of warming and cooling, and reorganization and development of ocean gyres and currents. Relatedly, the behavior of some currents, namely western boundary currents, remains unknown through these times of global tectonic and climate events. This dissertation addresses outstanding questions related to how the Kuroshio Current Extension, the western boundary current of the northwest Pacific, responded to major tectonic and climate shifts, how the spin-up of currents contributed to plankton evolution, and how plankton species obtained a global presence during the Neogene Period. Chapters 1 and 2 lay the groundwork for understanding plankton evolutionary processes in the Kuroshio Current Extension (KCE) and northwest Pacific. Zonation schemes used in the northwest Pacific are modified from those developed for the southwest Pacific, as the northwest Pacific sites have a strong presence of subtropical species that allows for the addition of biozones. Chapter 3 uses geochemistry to reconstruct the behavior of the Kuroshio Current Extension through the Pliocene to earliest Pleistocene (5-2.5 million years ago). The data indicate the KCE was a very dynamic current throughout the study interval, which was sensitive to major tectonic, climate, and oceanographic events. Chapter 4 is a major paleobiogeographic study using the planktic foraminiferal genus Globoconella. I found that long-distance dispersal in the Pacific occurred during a major pulse of East Antarctic Ice Sheet growth (~14-11 Ma) during which upwelling intensified and equatorial thermoclines cooled. Plankton utilized these upwelling zones and cool-water thermocline regions to disperse across tropical waters, thus attaining global distributions. This is the first study to characterize this means of dispersal for the planktic foraminifera.
Lam, Adriane, "NEOGENE HISTORY OF THE KUROSHIO CURRENT EXTENSION AND PLANKTIC FORAMINIFERA EVOLUTIONARY IMPLICATIONS" (2020). Doctoral Dissertations. 1843.