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Browsing by Subject "Green River Formation"

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    Proteins in Geobiology: New Approaches for Enzyme Field Detection and Biomarker Visualization
    (2021-01) Medina Ferrer, Fernando
    Proteins are the biomolecules that carry out most functions of the cells, yet their impacts and potentials to understand current and past Earth-life interactions are understudied. Here, I attempt to exploit the use of proteins—in the form of antibodies and enzymes—to answer fundamental questions in geobiology through two different approaches: (1) Using field assays to identify enzyme activity in the field that promotes calcium carbonate precipitation in modern environments, and (2) using antibodies to visualize lipid biomarkers in the fossil record. The first objective explores in-field analysis of urease and carbonic anhydrase (CA) activity, two enzymes known to promote carbonate precipitation. Microbes are attributed to drive environmental changes that explain geological phenomena, yet the mechanisms underlying these transformations are poorly studied. Simple, fast, and economical field tests were developed to identify on-site CA and urease in biofilms. The tests were used in microbial samples from calcareous fens, ferruginous springs, and an alkaline lake (Salt Lake) in Minnesota, along with carbonate tufa biofilms from an alkaline lake (Big Soda Lake) in Nevada. Relatively high in situ microbial urease activity in lake samples also promoted carbonate precipitation in microcosm incubation experiments. Active enzymes in tufas, together with community characterization by 16S rRNA gene sequencing and shotgun metagenomics, provided a plausible new mechanism to understand tufa biogenicity and its rapid growth. The second objective explores immunological techniques—antibody-based methods used in life sciences—here used to detect lipid biomarkers in the rock record. A previously known antibody that binds squalane was used to detect biomarkers in crude oil samples and to identify in situ micro-scale signatures in organic-rich rocks and potentially in fish fossil remains from the Eocene Green River Formation. A novel chromatographic method developed to separate and immunodetect hydrocarbon fingerprints showed that the antibodies also bind other soluble hydrocarbons in Green River Formation rocks, likely acyclic isoprenoids. The use of antibodies proved useful for identifying biomarker distributions in the sedimentary fabric that are otherwise difficult to study by current techniques. Future methods aimed at investigating the role of microbial proteins in the environment and their value as detection tools will benefit our understanding of the past and current biosphere and its interactions with the geosphere.
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    Updated Magnetostratigraphy for The Eocene Green River Formation, Wyoming
    (2022-05) Schneider, Emma
    The Green River Formation (GRF) is one of the best-preserved continuous Eocene terrestrial records in the world, allowing researchers to track phenomena in high resolution related to climate, vegetation, tectonics, and geomorphology. The preservation of the early Eocene in the GRF is particularly important as it records the Early Eocene Climatic Optimum (EECO), an analog for current greenhouse gas-driven global warming. Here we provide an updated magnetostratigraphy for the Wilkins Peak Member (WPM) of the GRF integrated with recent 238U-206Pb and 40Ar/39Ar results that more confidently identifies the geomagnetic reversals preserved in the sediments (C22n, C22r, C23n.1n, C23n1.1r, C23n.2n, and C23r) and refines their radioisotopic ages. Earlier GRF magnetostratigraphic studies were challenged by the presence of pervasive authigenic pyrrhotite in sediments of the Wilkins Peak member (Sheriff and Shive, 1982), which are confirmed in non-tuff lithologies in this study. Here, we build on the work of Tsukui and Clyde (2012) by focusing paleomagnetic sampling on ash-fall tuffs, which are more resistant to the formation of authigenic sulfides and can be dated directly using 238U-206Pb and 40Ar/39Ar techniques. The tuffs were deposited in a closed-lake basin setting and are sufficient in number to refine the stratigraphic position of geomagnetic reversals. Most tuffs show minimal post-depositional alteration and act as reliable paleomagnetic recorders. Tuffs of both normal and reversed polarity were identified using alternating field and thermal demagnetization protocols. The magnetic mineral carriers are magnetite, hematite, and their Ti-substituted equivalents and were characterized using hysteresis loops, backfield curves, and magnetic susceptibility. Fe- sulfides are present in some samples and produce secondary magnetic minerals during thermal demagnetization at temperatures >450°C. This updated terrestrial magnetostratigraphy provides an important bridge for correlating to marine records deposited across the EECO, and ongoing cyclostratigraphic work promises an even higher resolution view of the natural history preserved within the GRF.