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Defining the Permian-Triassic boundary at Quinn River Crossing, northwest Nevada, and the Hogup Mountains, northwestern Utah
Sperling, Erik2004.Online Search ProQuest Dissertations & Theses. Not all titles available.
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A REDOX-FOCUSED GEOCHEMICAL SURVEY OF PHANEROZOICSOURCE ROCK-RESERVOIR SHALES FROM NORTH AMERICA
Ritzer, SamanthaDecember 12, 2022Source rock-reservoirs (SRR) are continuous-type hydrocarbon systems characterized by fine-grained facies that contain adequate organic matter (OM; typically >2 wt%) to generate and retain significant hydrocarbon¬ accumulations. It is clear from modern analogue studies that O2-deficient conditions favor preservation of qualitatively- and quantitatively-enhanced OM, with appreciable productivity and OM flux to the sediment required to establish and maintain these conditions. However, debates regarding controls on source rock quality have mainly focused on oxic versus anoxic conditions, and the implications of different anoxic redox states for exploration and production remain unexplored. Here, we present detailed multi-proxy sedimentary geochemical studies of major Paleozoic and Mesozoic North American SRRs to elucidate their depositional redox conditions. This is the first study focused on SRR geochemistry to use Fe-speciation – presently the only proxy able to independently distinguish anoxic conditions as ferruginous (H2¬S-limited) or euxinic (H2S-replete, Fe-limited) – coupled with total organic carbon (TOC) and redox-sensitive trace element proxies. These analyses demonstrate that SRRs were almost exclusively deposited under anoxic bottom waters, but that there is wide variance in the prevalence of euxinic versus ferruginous conditions. Specifically, in contrast to most modern analogue systems, many SRRs were deposited under dominantly ferruginous or oscillatory conditions. TOC is significantly higher under euxinic bottom waters, although sediments deposited under both redox states have economically appreciable levels. Differences in initial redox condition likely impact organic matter quantity and quality, the presence of carbonate and clay cements, and the abundance of authigenic phases (pyrite and toxic metals) that can cause environmental or engineering issues during production. Increased emphasis on how initial depositional conditions affect the properties of the sediment, and the downstream implications of these differences, will ultimately lead to better sweet spot targeting and higher resource extraction efficiencies than a ‘one-size-fits-all’ model.
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Using the Metabolic Index to Elucidate the Relative Predictive Capacities of Environmental Indicators on Marine Invertebrate Biogeography in the Southern California Bight
Matsumoto, KendallJune 2, 2022Under a changing climate, the marine life in the global ocean is facing a variety of stressors. Hypoxia (low oxygen conditions), warming, and acidification are of particular concern. While studies have examined the effects of these various stressors, little research has explored synergistic effects of multiple stressors and the role of physiological parameters on invertebrate biogeography. Here, I calculate the metabolic index, an ecophsyiological framework that incorporates both temperature and oxygen in order to understand how an organism’s environment affects its phenology and biogeography. Employing machine learning techniques, naïve Bayes and full Bayes models, I investigate the relative capacity of various environmental parameters–temperature, oxygen, metabolic index (phi), salinity, and pH–for predicting the occurrence of Kellet’s whelk (Kelletia kelletii) and white urchin (Lytechinus pictus) in the Southern California Bight. Although Kellet’s whelk occurrence data was too sparse for machine learning techniques to produce viable results, Bayesian models did indeed produce predictive results for white urchin analysis. I ultimately find that although there seems to be no single environmental parameter that wholly accounts for marine invertebrate occurrence, full Bayes models indicate that oxygen leads as the dominant parameter with the highest predictive power for white urchin in the study area. This finding agrees with existing literature on the importance of oxygen in predicting biogeographic distribution in marine environments. Ultimately, these results contribute to a growing body of research indicating hypoxia is a major threat to marine ecosystems and highlight the need for expanded policy efforts to mitigate greenhouse gas emissions driving oxygen depletion in global oceans.
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