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South Coast Geological Society October Meeting

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Dave & Buster's

20 City Blvd West

Orange, CA 92868

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South Coast Geological Society welcomes you to join our monthly meeting on October 2nd, 2017 to be held at Dave and Buster's in Orange (20 City Blvd West, Orange CA). We are delighted to host guest speaker, Sean Loyd, Ph.D., Associate Professor at Cal State University, Fullerton. Dr. Loyd will present his talk titled "Salt dome cap rock calcite formation by the anaerobic oxidation of methane."


Abstract:

Significant hydrocarbon deposits accumulate in traps associated with salt domes. Whereas some of this hydrocarbon is extracted for economic uses, a significant amount is degraded in the subsurface as a result of microbial processes that yield mineral precipitates as byproducts. Salt domes of the Gulf of Mexico Basin typically exhibit extensive deposits of calcite that form atop the salt structure as cap rock. Current cap rock formation models invoke salt-hosted evaporite mineral dissolution as a source of sulfate, which microbes utilize to degrade hydrocarbon. Despite model inferences, the specific natures of these microbial reactions remain largely uncharacterized. We find carbonate-associated sulfate sulfur isotope compositions (δ34SCAS) that exceed those of salt-hosted sulfate minerals, implying cap rock carbonate generation via microbial sulfate reduction under closed-system conditions. The widespread co-occurrence of low carbonate carbon isotope compositions (δ13Ccarb) and high δ34SCAS values indicate that sulfate-dependent anaerobic oxidation of methane (AOM) led to calcite formation. Therefore AOM may serve as an important, unrecognized methane sink that reduces methane emissions from the subsurface in salt dome settings.

Speaker Information:

Sean Loyd, Ph.D. received his B.Sc. in Geology at University of California, Santa Barbara in 2005. In 2010, he obtained his Ph.D. in Geological Sciences at the University of Southern California. From 2010-2013, Dr. Loyd was a UCLA postdoctoral scholar in geobiology through a fellowship funded by the Agouron Institute. Dr. Loyd is currently an Assistant Professor in the Department of Geological Sciences at CSU, Fullerton. His research primarily focuses on the geochemistry of carbonate minerals with particular emphasis on microbial mediation. To explore carbonate mineral precipitation (authigenesis) his lab utilizes a broad spectrum of analyses including sulfur phase (carbonate-associated sulfate and pyrite) and sulfur isotope compositions, trace metal contents, carbon, oxygen and clumped isotope compositions. Specific projects that he currently works on include: Paragenetic evolution and precipitation mechanisms of salt dome cap rocks; Constraining formation temperatures of cold seep carbonates and concretions through clumped isotope analyses; Identification of microbial processes that mediate mineralization of carbonate concretions and their modern analogs in marine sediments; Evaluation of the chemistry of the Neoproterozoic and Paleozoic oceans; and Drivers of hot spring and alkaline lake carbonate mineral formation.

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Date and Time

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Dave & Buster's

20 City Blvd West

Orange, CA 92868

View Map

Refund Policy

Refunds up to 1 day before event

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