Valletta, Rachel Don

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  • Publication
    Novel Applications Of Meteoric- And In Situ-Produced Beryllium-10 In The East Antarctic
    (2017-01-01) Valletta, Rachel Don
    This work comprises three novel applications of in situ- and meteoric-produced beryllium-10 (Be-10) in East Antarctica. Sampled deposits cover a wide spatiotemporal transect through the Dry Valleys, from an inland, middle elevation location of Quaternary age, to a mid-valley, high elevation location of Miocene age, and finally to an offshore, submarine location of Pliocene age. Each research chapter we present is a unique project unto itself, but all chapters utilize the cosmogenic radionuclide Be-10. In the first application, we present ``Difference Dating,'' a new approach to date glacial moraines in regions where traditional exposure age dating is fraught with complications. Difference Dating allows for the construction of deglaciation chronologies in regions where they are frequently precluded by inheritance issues. We use Difference Dating to constrain the ages of Quaternary moraines in an alpine glacial cirque, Wright Valley, Dry Valleys. The second and third applications use meteoric-produced Be-10 in two different depositional settings. In marine sediments, we recast the Be-10/Be-9 ratio as a proxy for East Antarctic Ice Sheet freshwater discharge during mid-Pliocene interglacials. Using this record, we suggest that zones of deep water formation may be significant in funneling Be into the global thermohaline circulation belt. We also apply the meteoric-produced Be-10 system to paleolake sediments, where extremely low concentrations are used to construct an age model extending to 14-17.5 Ma. This range is commensurate with lake sediment deposition during the Middle Miocene Climatic Optimum, a rare Antarctic terrestrial deposit of this globally significant warming event.