Reconstructing seawater δ88/86Sr response to climate-induced sea level fluctuations and neritic carbonate burial using novel pore fluid archive

Abstract

The seawater stable strontium isotope (δ^88/86Sr) proxy is an emerging geochemical tool for reconstructing carbon cycle processes like global shelf carbonate burial and recrystallization. Application of this proxy to glacial/interglacial cycles promises new insight to continuing questions about the links between climate and the carbon cycle, including Berger’s (1982) “coral reef hypothesis” which predicts a role for shelf carbonate burial in glacial/interglacial pCO₂ fluctuations. A unique pore fluid archive of glacial seawater chemistry discovered by IODP Expedition 359 in the Maldives Inner Sea (Blättler et al., 2019) provides an opportunity to directly measure the δ^88/86Sr of the glacial ocean. I propose to measure δ^88/86Sr and ⁸⁷Sr/⁸⁶Sr in pore fluids and carbonates from Site U1466 and U1468, using ⁸⁷Sr/⁸⁶Sr to constrain the contribution of carbonate diagenesis to pore fluid strontium and thus determine the δ^88/86Sr of glacial seawater. These results will test the hypothesis that glacial seawater δ^88/86Sr differed from modern, reflecting a sea level-driven shift in shelf carbonate burial and recrystallization. Complementary analyses of pore fluid δ^88/86Sr from two pelagic carbonate-poor sites will provide key context for the interpretation of δ^88/86Sr profiles from the Maldives shallow carbonate platform and for future application of the δ^88/86Sr proxy in both carbonates and pore fluids.

Biography

I grew up in the Northeast Kingdom of Vermont in a rural, dairy-farming town with a population just shy of five hundred. My parents, a middle school science teacher and a forester, fostered in me a curiosity for the natural world and sense of environmental responsibility that guided my interest in science throughout middle and high school. With little formal exposure to the geosciences as a field of study, I started college at the University of New Hampshire with a major in chemical engineering. I was introduced to paleoclimatology and geochemistry during a Fulbright UK Summer Institute on global climate change at the University of Exeter and found the perfect blend of natural science to fit my interests in chemistry and the Earth. After changing my major, I earned a B.S. in Earth Sciences and completed a senior thesis on seasonal shifts in mercury cycling in coastal New Hampshire wetlands. Now I am pursuing my PhD at the University of California, Santa Cruz, where I reconstruct the stable strontium isotopic composition of seawater to investigate carbon cycle changes during periods of climate change. My dissertation is focused on understanding how carbonate burial in the shallow ocean responded to sea level fluctuations during Late Quaternary glacial/interglacial cycles and the Eocene-Oligocene Transition.