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2200 Colorado Avenue, Boulder, CO 80309

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Andreas Teske
U. North Carolina - Chapel Hill

Topic: From magma to microbe: the deep hot biosphere of Guaymas Basin.

Academic host: Julio Sepulveda

Abstract: The Guaymas Basin in the Gulf of California is a young marginal rift basin characterized by active seafloor spreading and hydrothermal venting. High plankton production in surface waters and terrigenous sedimentation from the Sonoran mainland combine to rapidly deposit organic‐rich sediments, which are permeated by extensive thermal and geochemical gradients. Deeply emplaced hot volcanic sills extend across the basin and alter the surrounding sediments by transforming buried sedimentary carbon into hydrocarbons, especially methane. The rapid mobilization and re-injection of these hydrocarbons into the biosphere impact the carbon cycle of the basin and provide a model system that illuminates climate perturbations. Subsurface microbial populations potentially intercept and process these hydrothermally generated and mobilized carbon sources, but their depth extent and cell numbers are expected to be controlled by the steep geothermal gradients that are characteristic of Guaymas Basin. Here I will provide an overview on this fascinating hydrothermal geo-ecosystem, and introduce IODP drilling expedition 385 to Guaymas Basin (Sept. 16 to Nov. 16, 2019) with JOIDES Resolution.  The expedition scientists and drilling crew recovered 4 km of sediment core and >350 m of sill core from eight drilling sites across Guaymas Basin, measured geothermal gradients in diverse settings ranging from recently emplaced hot sills to cold seep sites, and probed the highly diverse biogeochemistry and microbiology of the Guaymas Basin subsurface sills and sediments. Naturally I am not entirely unbiased, but the expedition has come upon many surprising and unexpected findings that will sustain many years of follow-up research. Highlights will be presented as appropriate for ongoing investigations.

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