Doctor of Philosophy, The Ohio State University, 2008, Geological Sciences

The latest Ordovician (444 million years ago) was a critical period in Earth history. This was a time of significant climatic global change with large-scale continental glaciation. Moreover, the end-Ordovician mass extinction is recognized as the secondmost devastating mass extinction to have affected the Earth. The anomalous Late Ordovician icehouse period has perplexed many researchers because all previous model and proxy climate evidence suggest high levels of atmospheric CO 2during the Late Ordovician glaciation. Also associated with this period is a large positive carbon isotope(a 13C) excursion (up to +7‰) that represents a global perturbation of the carbon cycle. Additionally, a large decrease (0.001) in seawater 87Sr/ 86Sr occurs several million years prior(~460 million years ago);this could reflect an increase in atmospheric CO 2uptake due to weathering of volcanic rocks involved in uplift of the early Appalachian Mountains. To address these Ordovician anomalies, well-studied, thick, and continuous Late Ordovician limestone sequences from eastern West Virginia, south-central Oklahoma, central Nevada, Quebec (Canada), Estonia, and China have been sampled. Carbon and strontium isotopic ratios have been measured on samples from these localities of which Estonian and Chinese sample sites represent separate paleocontinents (Baltica and South China) and are compared with other data sets from North America. These data test previous interpretations that the well-documented latest Ordovician carbon isotope excursion coincides with maximum glaciation. They support a hypothesis that the large positive carbonate carbon isotope excursion was coincident with a warm interglacial(high CO 2levels) period that separated two major glacial advances (with lowered CO 2levels). There are clear parallels between the Late Ordovician and the Late Cenozoic (the most recent) greenhouse to icehouse transitions, with silicate weathering providing the initiator and positive feedback on c (open full item for complete abstract)

Committee: Matthew Saltzman (Advisor) Subjects: Geochemistry; Geology

Master of Science, The Ohio State University, 2008, Geological Sciences

A high resolution Sr isotope data set is generated for the Llandovery Series from a thick, fossiliferous drill core in Estonia. Observed 87Sr/86Sr values are at a minimum in the early Llandovery Rhuddanian Stage (~0.7079 to 0.7080), and then trend to more radiogenic ratios in the beginning part of the late Llandovery Telychian Stage. An 87Sr/86Sr high near ~0.7084 is observed in the Telychian at the top of the studied section. The range of values is in general agreement with previous sample sets of brachiopods and conodonts recovered from localities in North America and Europe that record a rising trend in the 87Sr/86Sr ratio throughout the Llandovery from approximately 0.7080 to 0.7084.The major increase in the 87Sr/86Sr ratio during the late Llandovery may be due to increased riverine flux of radiogenic Sr into the oceans due to: 1) weathering of non-volcanic continental silicate rocks that were uplifted during early Silurian continent-continent collisions, and 2) weathering of exposed felsic volcanics in the Balto-Scandanavian region that formed during subduction of continental crust. The presence of felsic volcanic rocks is consistent with the occurrence of an unusually thick K-bentonite bed (Osmundsberg K-bentonite) representing a large-magnitude ash fall in the early Telychian. Furthermore, a negative δ13C excursion in marine carbonate and organic matter is quasi-synchronous with the increase in Sr at the level of resolution currently available. As atmospheric CO2 was apparently being drawn down in the preceding Aeronian Stage (positive δ13C excursion), the large amounts of ash may have been a catalyst for the ensuing Telychian glaciation, causing a major regression and further contributing to the increase in 87Sr/86Sr through increased continental weathering.

Committee: Matthew R. Saltzman PhD (Advisor); Kenneth A. Foland PhD (Committee Member); W. Berry Lyons PhD (Committee Member) Subjects: Geochemistry; Geology

Master of Science (MS), Wright State University, 2012, Earth and Environmental Sciences

Photosynthesis, respiration, and decay of organic matter all involve the transfer of carbon among the carbon-bearing species in the systems. These biogeochemical processes also fractionate the carbon isotope composition, which results in changes to the carbon isotope composition of the dissolved inorganic carbon (DIC) pool. This thesis presents two separate, but related studies regarding the influence of biogeochemical processes on carbon isotopes in local lakes. Crystal Lake is a small but deep glacial lake (12.5 acres, 11.9 meters). The study shows that during thermal stratification, the heaviest carbon can be found in the epilimnion near the surface, where photosynthesis dominates the biogeochemical processes. At greater depths, the DIC carbon becomes lighter as 12C-enriched organic matter decomposes. In the hypolimnion, methane production in the late summer could be the process that resulted in slight increase in 13C of DIC. The second study investigated the relationship between the carbon isotope composition of DIC and the trophic status of three lakes in Southwestern Ohio; Indian Lake, Grand Lake St. Marys and Kiser Lake. All three lakes are shallow, man-made reservoirs, but each has unique biogeochemical characteristics. Among these three lakes, Grand Lake St. Marys had the heaviest carbon isotope composition in DIC, the highest phosphorus (P) concentration, and the lowest nitrate (N) concentration. It is the only lake among the three that has suffered severe toxin-producing blue-green algae (cyanobacteria) blooms in recent years. The P and N concentrations indicated nitrate was the limiting nutrient. This study shows that carbon isotope composition can be used as a proxy for trophic status in large, shallow lakes, like Indian Lake and Grand Lake St. Marys. It is concluded that carbon isotope composition of DIC is closely related to the biogeochemical processes in lakes and can provide important insight into those processes. However, a quantific (open full item for complete abstract)

Committee: Songlin Cheng PhD (Committee Chair); Rebecca Teed PhD (Committee Member); Abinash Agrawal PhD (Committee Member) Subjects: Biogeochemistry; Environmental Geology; Limnology

Master of Science in Environmental Science, Cleveland State University, 2024, College of Arts and Sciences

Despite the critical role of organic matter (OM) oxidation in depleting oxygen in the hypolimnetic waters of Lake Erie, uncertainties regarding the sources, quantity, and fate of OM continue to challenge our understanding and management of hypoxia in the lake. This study evaluates the effects of OM oxidation through the analysis of stable carbon isotopes (δ13C) of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in the central and eastern basins of Lake Erie. We disclose DIC contributions from OM oxidation and provide insight into the origins of OM in the hypolimnion. Our results reveal significant declines in δ13CDIC in hypolimnetic waters compared to surface waters, indicative of OM oxidation in the deepest portions of the lake. To further examine this process, we employed the Keeling plot method to estimate the composite isotopic signature of OM respiration (δ13CR). The good agreement between the respired source (-24.4‰) and the signature of the organic material (-24.6‰) support the idea that autochthonous material (internally produced OM) fuels OM oxidation in the central and eastern basins. Additionally, a binary mixing model was utilized to quantify the amount of DIC produced and the respective amount of oxygen required by OM oxidation. We estimate that 11.8 ± 1.6 % of DIC was produced in the central basin and 5.6 ± 1.2% in the eastern basin, which accounts, on average, for 89.3 ± 7.1 % of hypolimnetic oxygen depletion in the central basin and 99.2 ± 17.7 % in the eastern basin. This suggests OM oxidation accounts for most of the hypolimnetic oxygen depletion in the lake, however instances of hypoxia in the central basin may promote other mechanisms of oxygen depletion such as oxidation of CH4, Fe2+, and Mn2+. This study reveals a strong coupling between carbon cycling and oxygen depletion in Lake Erie. Our results underscore the applicability of δ13CDIC as a meaningful tracer to quantify the amount of oxygen-consuming OM in hypolimn (open full item for complete abstract)

Committee: Fasong Yuan (Advisor); Brice Grunert (Committee Member); Julie Wolin (Committee Member) Subjects: Biogeochemistry; Environmental Science; Limnology

Master of Science, The Ohio State University, 2015, Evolution, Ecology and Organismal Biology

Tree root exudation of soluble organic carbon (SOC) is often considered an important but under-assessed component of terrestrial net primary productivity that also strongly influences rhizosphere and soil biogeochemical processes. Although riparian and bottomland systems are often considered “hot spots” of biogeochemical activity that are potentially supported by root exudate SOC, in situ tree root exudation rates of SOC have not been previously reported for these systems. Additionally, there is an outstanding need to understand the δ13C signatures of root exudates in relation to not only different plant components such as leaves and roots but also different ecosystem pools of C, such as CO2 emitted from soil. In the present study we used an in situ method to collect root exudate SOC in order to assess root exudation rates in a bottomland forest for Acer saccharinum, Populus deltoides and Platanus occidentalis trees over five sampling dates ranging from mid-summer to late-autumn. Leaves from Acer negundo, Acer saccharinum, Lonicera maackii, Populus deltoides and Platanus occidentalis were also collected. δ13C values were determined for all of the root exudates, roots and leaves collected in this study. Exudation rates and δ13C values were evaluated in relation to leaf and root morphology, leaf and root C and N contents and a number of environmental parameters (e.g. vapor pressure deficit) and net ecosystem exchange (NEE). Findings indicate that exudation rates and δ13C values of leaves and roots were significantly correlated to time-lagged measurements of NEE, suggesting a strong link between exudation rates and δ13C values of leaves and roots and photosynthetic rates. Various time lagged environmental parameters (e.g., vapor pressure deficit) were correlated to the δ13C of exudates, leaves and roots—suggesting a rapid transfer of recent photosynthate from the canopy to roots and root exudates and relatively rapid turnover of C in leaves. When pooled toge (open full item for complete abstract)

Committee: James Bauer (Advisor); Brian Lower (Committee Member); Peter Curtis (Committee Member) Subjects: Biogeochemistry; Ecology; Plant Biology

Doctor of Philosophy, The Ohio State University, 2008, Geological Sciences

Tropical small mountainous rivers (SMRs) may transport up to 33% of the total carbon (C) delivered to the oceans. However, these fluxes are poorly quantified and historical records of land-ocean carbon delivery are rare. Corals have the potential to provide such records in the tropics because they are long-lived, draw on dissolved inorganic carbon (DIC) for calcification, and isotopic variations within their skeletons are useful proxies of palaeoceanographic variability. The ability to quantify riverine C inputs to the coastal ocean and understand how they have changed through time is critical to understanding global carbon budgets in the context of modern climate change. A seasonal dual isotope (13C & 14C) characterization of the three major C pools in two SMRs and their adjacent coastal waters within Puerto Rico was conducted in order to understand the isotope signature of DIC being delivered to the coastal oceans. Additionally a 56-year record of paired coral skeletal C isotopes (δ13C & Δ14C) and trace elements (Ba/Ca, Mn/Ca, Y/Ca) is presented from a coral growing ~1 km from the mouth of an SMR. Four major findings were observed: 1) Riverine DIC was more depleted in δ13C and Δ14C than seawater DIC, 2) the correlation of δ13C and Δ14C was the same in both coral skeleton and the DIC of the river and coastal waters, 3) Coral δ13C and Ba/Ca were annually coherent with river discharge, and 4) increases in coral Ba/Ca were synchronous with the timing of depletions of both δ13C and Δ14C in the coral skeleton and increases in river discharge. This study represents a first-order comprehensive C isotope analysis of major C pools being transported to the coastal ocean via tropical SMRs. The strong coherence between river discharge and coral δ13C and Ba/Ca, and the concurrent timing of increases in Ba/Ca with decreases in δ13C and Δ14C suggest that river discharge is simultaneously recorded by multiple geochemical records. Based on these findings, the development of coral-b (open full item for complete abstract)

Committee: Andrea Grottoli PhD (Advisor); James Bauer PhD (Committee Member); Anne Carey PhD (Committee Member); Yu-Ping Chin PhD (Committee Member); Matthew Saltzman PhD (Committee Member) Subjects: Biogeochemistry; Geochemistry; Geology; Oceanography

MS, University of Cincinnati, 2024, Arts and Sciences: Geology

The hydrogen isotopic composition (δ2H) of lipid biomarkers extracted from lake sediment serves as a valuable tool for tracking changes in the hydrologic cycle by reflecting changes in the δ2H of their source water. However, interpreting these changes is complicated by the mixture of terrestrial and aquatic lipids preserved in lake sediments, which present δ2H values influenced by different source waters (i.e. precipitation and lake water). Highly branched isoprenoids (HBI) produced by diatoms are suggested as a proxy for lake water hydrogen isotopic composition (δ2Hlw) that avoid terrestrial interferences. The controls on hydrogen isotope fractionation between HBI and its lake water source (ε2HHBI/lw) must be better constrained to improve the utility of HBI as a proxy for δ2Hlw. Here we measure ε2HHBI/lw across a broad study area comprising 48 lakes spanning 10 US states. We analyzed sediment, water filter, and sediment trap samples to evaluate the consistency of ε2HHBI/lw across the study area and identify factors controlling its variability. We observed a consistent and significant disparity in ε2HHBI/lw between sediment and water filter samples, suggesting that sedimentary ε2HHBI/lw values are not solely dictated by the hydrogen isotopic composition of HBI (δ2HHBI) in the water column during the sampling season (May-June). Furthermore, consistent with prior smaller-scale studies, we observed a standard deviation of ±30‰ in ε2HHBI/lw across the study area, comparable to that of widely accepted precipitation proxies such as plant waxes. These results demonstrate that δ2HHBI can be used to track changes in δ2Hlw through time. They also show that the effectiveness of δ2HHBI as a tool for reconstructing paleohydrology can be improved by developing a set of criteria to enable carful site selection that targets lakes with more consistent ε2HHBI/lw values, which are best suited for such studies.

Committee: Aaron Diefendorf Ph.D. (Committee Chair); Dylan Ward Ph.D. (Committee Member); Thomas Lowell Ph.D. (Committee Member) Subjects: Geology

MS, University of Cincinnati, 2023, Arts and Sciences: Geology

During the Miocene, North America's Great Plains were a broad mosaic of savanna-woodlands that were carpeted by grasses, herbs, and shrubs. Tree cover was sparse, although there were heterogenous clusters of dense vegetation and wetlands. A diverse ungulate fauna inhabited this landscape, including one of the most successful and ubiquitous megaherbivores, Teleoceras. This genus of large, short-legged, barrel-chested rhinoceroses is generally accepted to have foraged in open habitats on grasses and other vegetation. However, other aspects of Teleoceras paleoecology remain uncertain, including the degree to which it used aquatic habitats (e.g., rivers, ponds, marshes, or mud wallows), and formed large social groups. We investigated the paleoecology of Teleoceras major from Ashfall Fossil Beds State Historical Park (henceforth “Ashfall”) in north-central Nebraska using carbon (δ13C), oxygen (δ18O), and strontium (87Sr/86Sr) isotopes. This mid-Miocene (ca. 12 Ma) site preserves a watering-hole filled by volcanic ash that entombed over a hundred, mostly complete, articulated skeletons of T. major and other co-occurring ungulates. We analyzed bulk enamel samples from seven total taxa: T. major (N = 13); three horse species (Cormohipparion occidentale, Pliohippus pernix, and Pseudhipparion gratum; N = 3 each); two camels (Procamelus grandis and Protolabis heterodontus; N = 1 each); and one musk deer (Longirostromeryx wellsi; N = 3). We further investigated the relative importance of seasonality, ontogeny, and sex-specific behaviors on T. major foraging ecology through bulk and serial sampling of second and third lower molars (M2 and M3, respectively). Carbon isotope data indicate that all seven taxa foraged in open habitats dominated by C3 plants (ca. -10‰ to -7‰ VPDB). Taxa reconstructed to have consumed a greater proportion of browse (L. wellsi and camels) had slightly, but insignificantly, lower δ13C values than those that consumed more grasses (T. major and horses). Th (open full item for complete abstract)

Committee: Brooke Crowley Ph.D. (Committee Chair); Ross Secord Ph.D. (Committee Member); Joshua Miller Ph.D. (Committee Member) Subjects: Paleoecology

Doctor of Philosophy, The Ohio State University, 2023, Earth Sciences

Our understanding of the Earth's multimillion-year carbon cycle, with primary implications for the evolution of life, depends on our ability to decipher information encoded in chemical signals of shallow marine sediments. This dissertation attempts to develop our knowledge of two main topics: (1) the causes of multimillion-year global climate change in terms of changes in the sources and sinks of atmospheric carbon dioxide (CO2), and (2) the causes and meaning of post-depositional alteration of shallow marine sediments with respect to chemical proxy records of the evolution of global (and/or local) Earth processes. To this end, this work applies radiogenic strontium and neodymium (87Sr/86Sr, εNd(t)) and stable calcium (δ44/40Ca) isotopic records in bulk carbonate rocks and conodont apatite from Middle–Late Ordovician (Darriwilian–Katian stages; ~470–450 million years ago, abbrev. Ma) sections in the Antelope Range, central Nevada; Clear Spring, Maryland; and the Fjacka and Kargarde sections of the Siljan district, Dalarna province, central Sweden. Bulk rock samples from the tropical Middle–Late Ordovician setting of the Antelope Range, Nevada were analyzed for proxy records of regional and global continental weathering source lithology (87Sr/86Sr and εNd(t)) which were paired with published paleotemperature proxy measurements (δ18O) of conodont apatite from the same section. This paired suite of proxy records is used to test the hypothesis that low-latitude island arc accretion during the Middle–Late Ordovician Taconic Orogeny enhanced the weatherability of Earth's crust, increasing the rate of CO2 removal by the weathering of mafic silicate minerals and producing the global cooling observed in the Middle–Late Ordovician paleotemperature record. These records show coeval inflections in 87Sr/86Sr and εNd(t) values at ~463 Ma that reveal the influence of tectonic uplift and enhanced weathering of mafic ophiolite provinces on the Taconic margin. This change in weather (open full item for complete abstract)

Committee: Matthew Saltzman (Advisor); Audrey Sawyer (Committee Member); Elizabeth Griffith (Committee Member); William Ausich (Committee Member) Subjects: Chemistry; Earth; Geochemistry; Geology

Master of Arts (MA), Bowling Green State University, 1962, Biological Sciences

Committee: Jacob Verduin (Advisor) Subjects: Biology

Master of Arts (MA), Bowling Green State University, 1959, Biological Sciences

Committee: Jacob Verduin (Advisor) Subjects: Biology

Master of Arts (MA), Bowling Green State University, 1959, Biological Sciences

Committee: Jacob Verduin (Advisor) Subjects: Biology

PhD, University of Cincinnati, 2020, Arts and Sciences: Geology

Plant biomarkers are primarily derived from leaf waxes, the protective waxy coating that covers the cuticular layer of a leaf. These biomarkers and their carbon isotope compositions are important paleoclimate and paleovegetation tools for investigating how landscapes, climate, and the carbon cycle have changed in the Earth's past and provide a mechanism to understand how climate change may affect vegetation dynamics and ecosystems in the future. This dissertation addresses several key gaps in knowledge about plant-derived d13C values including the effect of paleo pCO2, paleovegetation signals contributing to leaf carbon isotopes (d13Cleaf) in the sedimentary record, and the carbon isotopic composition of integrated vegetation communities, such as forests and grasslands. The first study (Chapter 2) investigates the relationship between ?leaf and pCO2, and the efficacy of this relationship to reconstruct pCO2 through geologic time. We utilize the geologic record as a natural laboratory operating on timescales over which plants evolve (millions of years). We measure d13C values from sediment-derived leaf wax n-C29 alkanes, primarily from angiosperms, to calculate leaf carbon isotope fractionation (?leaf) across North American paleoflora sites. These sites represent 40 million years from the Late Cretaceous into the Oligocene and capture a wide range of pCO2 values (200 to 900 pmmV; Foster et al., 2017). Using the fossil leaves at each site, we account for age, floral composition, mean annual precipitation (MAP), and mean annual temperature (MAT), thereby providing a means to test the sensitivity of ?leaf to pCO2 independent of confounding biotic and abiotic effects on geologic timescales. The second study (Chapter 3) examines a possible strategy to infer the major taxon sources of sediment n-alkanes using paleobotanical sites in North America from the Paleogene that capture a range of forest types, with high, mixed, and low conifer abundance. We utilize d13C val (open full item for complete abstract)

Committee: Aaron Diefendorf Ph.D. (Committee Chair); Brooke Crowley Ph.D. (Committee Member); Thomas Lowell Ph.D. (Committee Member); Kevin Mueller Ph.D. (Committee Member); Dylan Ward Ph.D. (Committee Member) Subjects: Geology

Doctor of Philosophy, The Ohio State University, 2019, Food, Agricultural and Biological Engineering

Bioretention is an increasingly prevalent green infrastructure practice for urban and suburban stormwater management. While research has shown the ability of this technology to reduce stormwater volume and improve stormwater quality, there is a gap in knowledge regarding long term performance. Additionally, hydrocarbons are an important but understudied stormwater pollutant. Column studies indicate bioretention is an effective treatment technology for reducing hydrocarbons in stormwater flows, but there is limited research confirming this performance in field settings. To address both of these concerns, simultaneous studies were performed evaluating the hydrological performance and hydrocarbon removal of a bioretention cell six years post installation. Nine simulated storms (3.5 mm equivalent storm) were conducted, with eight of those sampled for hydrocarbon concentrations. Despite an apparent increase in preferential flow as indicated by rapid bromide tracer breakthrough and accelerated water table response rates, there was no significant difference in volume reduction between 2011 (average 53%) measurements and those done in this study (2015-2016: average 69%), after accounting for runoff volume differences. These results indicate continued effective operation of this facility, at least during small events. The effective operation was possibly due to location (suburban neighborhood) and maintenance (~monthly sediment removal). Hydrocarbon mass reductions in bioretention tests (83%), measured as total petroleum hydrocarbons, were similar to other studies while concentration reductions were lower (53%), possibly due to low input concentrations (0.58 mg/L). Hydrocarbon concentrations in the soil were higher in the upslope cell, indicating historical accumulations. However, within each cell, concentrations did not vary significantly over the year of study, indicating steady state conditions iv and no accumulation during the period of study. Comparisons of hydrocarb (open full item for complete abstract)

Committee: Jay Martin PhD (Advisor); Winston Ryan PhD (Committee Member); Kalcic Margaret PhD (Committee Member); Gabor Rachel PhD (Committee Member) Subjects: Biogeochemistry; Environmental Engineering; Sustainability

Master of Science, The Ohio State University, 2019, Earth Sciences

A step-change in atmospheric oxygen (O2) levels in the Ordovician has been attributed to the emergence of land plants. This phenomenon is tied to a major baseline shift in the stable carbon isotope (δ13C) curve consistent with an increase in nutrient delivery and enhanced primary productivity in the ocean and land, leading to high organic carbon burial. The timing and magnitude of this baseline shift, however, is still elusive in part because of the lack of high resolution δ13C data from this period. Much of the existing Ordovician 13C literature is focused on isotopic excursions with less emphasis on identifying long term shifts in baseline (pre- and post-excursion) values. This study presents new 13C curves from stratigraphic sections at Germany Valley (West Virginia) and Union Furnace (Pennsylvania) in the Central Appalachian Basin. These sections span the Upper Ordovician Sandbian Stage (~ 458.4 to 453.0 Ma) and cross into the Lower Katian Stage. The curves from both sections are characterized by relative stability and light (< 0‰) carbon isotope values in the Early Sandbian, followed by a shift toward positive values (> 0‰) in the Late Sandbian. I propose that the positive shift represents a long-term global shift in the δ13C baseline. A temporal relationship between this positive shift and diversification of liverworts clade and a clade that letter became mosses, hornworts, and vascular plants from their common ancestor in terrestrial plants suggests an organic carbon burial (net release of oxygen) mechanism for the stepwise oxygenation of the atmosphere in the Late Ordovician.

Committee: Matthew Saltzman (Advisor); Elizabeth Griffith (Committee Member); Thomas Darrah (Committee Member) Subjects: Earth; Geology; Sedimentary Geology

MS, University of Cincinnati, 2016, Arts and Sciences: Geology

Studies of Precambrian life on Earth have been dominated by those of shallow marine deposits, and in order to gain a more complete picture of life's early evolution it is important to consider a wider range of inhabited environments, including deep marine and terrestrial ecosystems. Evidence for early microbial life comes primarily from fossil microorganisms (microfossils), microbial sedimentary structures (e.g., stromatolites), and sedimentary organic matter (e.g., kerogen). The diversity and preservation of these different forms of fossil evidence introduces several challenges to their interpretation, requiring thorough analysis for accurately determining their biological origins. Investigating the paleobiology, organic geochemistry, and thermal maturity of such deposits provides a holistic approach to exploring the Precambrian biosphere in unfamiliar paleoenvironments. This thesis presents two studies of unique Precambrian ecosystems: a diverse microfossil assemblage from a 2.52-billion-year-old (Ga) deep marine deposit, and thermally altered stromatolites from a 1.4-billion-year-old evaporitic lacustrine deposit. Black cherts from the upper Gamohaan Formation (2.52 Ga) contain a consortium of organic-walled large and small coccoids, tubular filaments, and mat-like biofilm structures. Geochemical analyses of stromatolitic chert-carbonate from the Middlebrun Bay Member (1.4 Ga) in contact with a mafic sill show a trend in organic carbon isotopes relative to thermal maturity that is contrary to theoretical predictions. Findings from these studies reveal, for the first time, microfossil evidence of a diverse microbial community in the open Archean ocean prior to the Great Oxidation Event (GOE) ~2.4 billion years ago, and provide insight on the relationship between thermal maturity and organic carbon isotopes within a set of terrestrial stromatolites. Together, these studies help capture the enigmatic nature of the Precambrian fossil record and expand our full unders (open full item for complete abstract)

Committee: Andrew Czaja Ph.D. (Committee Chair); Julie K. Bartley Ph.D. (Committee Member); Carlton Brett Ph.D. (Committee Member); Aaron Diefendorf Ph.D. (Committee Member) Subjects: Planetology

MA, University of Cincinnati, 2016, Arts and Sciences: Anthropology

In order to better understand agricultural practices and land use strategies on the Greek mainland over the course of the Bronze Age, I analyzed stable carbon isotope ratios for 50 samples of charred seeds from the Final Neolithic to Late Bronze Age archaeological site of Tsoungiza in southern Greece. These seed samples were comprised of four economically important taxa barley (Hordeum vulgare), einkorn wheat (Triticum monococcum), emmer wheat (Triticum dicoccum), and lentils (Lens culinaris). Contexts from which seeds in this analysis were recovered included archaeological pits, cisterns, fill and floor deposits. Having controlled for other variables, such as tissues type and source CO2, carbon isotopic data (the ratio of ¹³C/¹²C) in the form of carbon isotope discrimination (?¹³C values) reflect crop water availability in water limiting environments, such as those hypothesized for southern Greece during the Bronze Age (3,300-1,060 BC). I utilized Mann-Whitney non-parametric statistical tests to determine whether statistically significant differences existed between samples of barley from phases of the Early Helladic period (3,300-2,000 BC) and Early Mycenaean period (Late Middle Helladic to Late Helladic II; 1,750-1,580 BC), as well as between samples of einkorn from Early Helladic periods. The data for einkorn and barley from Tsoungiza indicate that growing conditions varied by species during the Early Helladic period, but were largely stable for barley throughout the Early Helladic. Results document a significant decline in carbon isotope discrimination for barley from the early Mycenaean period as compared to periods of the Early Helladic. I interpret that these data suggest increasing cultivar specialization or species-specific cultivation strategies used during the Bronze Age, including a substantial decline in water availability for barley from the Early Helladic to the early Mycenaean period. Through stable isotope biogeochemistry, I identify agricultural p (open full item for complete abstract)

Committee: Susan Allen Ph.D. (Committee Chair); Brooke Crowley Ph.D. (Committee Member) Subjects: Archaeology

MS, University of Cincinnati, 2015, Arts and Sciences: Geology

Fog is recognized as a highly important source of moisture in cloud forests, yet the degree to which increased relative humidity from fog versus soil moisture from canopy drip affect plant water use efficiency has not been investigated. The oceanic island of Tenerife, Canary Islands presents an ideal cloud forest biome to investigate how fog induced moisture affects plant water use efficiency. The high altitude of Tenerife's peak, Mount Teide (3,718 m asl) combined with the orographic uplift of moisture-laden northeastern trade winds creates a humid cloud forest on the northern slope of the island. To evaluate the manner in which fog impacts water use efficiency for plants living in Tenerife's subtropical montane cloud forest, I analyzed carbon isotope discrimination (Δleaf) and nitrogen isotope (δ15N) values in vegetation from Tenerife's five diverse biomes (coastal scrub, thermophilous forest, cloud forest, pine forest, and subalpine scrub). These isotopes are strongly affected by water use efficiency and soil moisture respectively, which allows them to distinguish the degree to which fog-derived relative humidity versus soil moisture affect plant water use efficiency in cloud forests. Carbon discrimination values are highest in the cloud forest, reflecting a decrease in water use efficiency and poorly regulated stomatal conductance among plants in this biome. Nitrogen isotope values suggest that soil moisture does not substantially impact cloud forest vegetation. Therefore, increased relative humidity from fog is likely driving the high Δleaf values. An improved understanding of how stomatal conductance, and therefore water use efficiency, in cloud forest vegetation is affected by fog will provide insights on cloud forest microclimates and the environment that sustains them. The combination of Δleaf and δ15N values may provide a tool for observing changes in cloud forest vegetation over time and predicting the impacts of impending climate change on cloud forest b (open full item for complete abstract)

Committee: Brooke Crowley Ph.D. (Committee Chair); Yurena Yanes Ph.D. (Committee Member); Aaron Diefendorf Ph.D. (Committee Member) Subjects: Biogeochemistry

Doctor of Philosophy, The Ohio State University, 2014, Geological Sciences

This chemostratigraphic study uses new carbon (d13C) and sulfur (d34S) isotope data measured from Lower–Middle Ordovician carbonate rocks from the Great Basin region, USA. The Pogonip Group was sampled at meter-scale from Shingle Pass (east-central Nevada) and the Ibex area (western Utah) to integrate the stable isotope stratigraphy with a well-studied conodont biostratigraphic framework. The Pogonip Group is a succession of mixed carbonate and siliciclastic rocks that accumulated on a carbonate ramp under normal marine conditions during the Late Cambrian to Middle Ordovician. The d13C trend has four distinct characteristics recognized in both Great Basin sections: 1) a drop in d13C from +1‰ at the base of the Ordovician (Tremadocian) to -0.7‰, 2) a 1–2‰ positive d13C shift during the late Tremadocian, 3) a gradual d13C increase from -2‰ to ca. 0‰ during the end of the Early Ordovician (Floian), and 4) a steady d13C decrease from 0‰ to -4 to -5‰ during Middle Ordovician (Dapingian–Darriwilian). The d34S trend measured from carbonate-associated sulfate (CAS) at Shingle Pass has an overall decrease from +35‰ during the Tremadocian to +20 to +25‰ during the Floian. A 15‰ negative excursion is present near the Dapingian-Darriwilian boundary before d34S values increase up to +35‰ at the top of the section. Corresponding d34S measured from sedimentary pyrite shows an overall similar drop in the Lower Ordovician but pyrite d34S values are more variable. During the early Tremadocian Stage pyrite d34S varies between 0 to +20‰ but makes a major drop of 20‰ during the late Tremadocian to values between -10–0‰ throughout the Floian and Dapingian Stages. Pyrite d34S increases gradually near the Dapingian-Darriwilian boundary to values between +10 to +20‰ at the top of the section. The Lower–Middle Ordovician d13C and d34S trends reported here from the Great Basin are not consistent with a causal mechanism involving sea level change and subsequent migration of isoto (open full item for complete abstract)

Committee: Matthew Saltzman (Advisor); William Ausich (Committee Member); Stig Bergström (Committee Member); Lawrence Krissek (Committee Member) Subjects: Geochemistry; Geology

Doctor of Philosophy, The Ohio State University, 2012, Geological Sciences

Coral reefs are declining globally due to a combination of direct and indirect human impacts. Much of this decline can be attributed to prolonged exposure to elevated sea surface temperatures which induces coral bleaching – a process whereby corals lose their endosymbionts and/or their endosymbiotic pigments resulting in corals that appear pale or white. Corals have extremely different responses to bleaching events: some corals bleach and die, others bleach and recover, and some do not visibly bleach at all. In the absence of abundant photosynthetically fixed C, corals may rely on one or more of the following strategies to sustain themselves and promote recovery: (1) catabolize stored energy reserves, including lipids, carbohydrates, and/or proteins, (2) reduce respiration rates, (3) decrease skeletal growth, (4) increase heterotrophy or (5) shuffle or change their endosymbiont type(s). Although mounding species of coral have been shown to survive bleaching events in greater abundance than branching species, the underlying mechanism(s) for mounding coral resilience is unknown. Furthermore, controlled bleaching and recovery experiments coupled with detailed carbon budgets that incorporate autotrophy and multiple heterotrophic sources (i.e. zooplankton and dissolved organic carbon) do not exist for Caribbean corals. Therefore, two controlled tank experiments, one in Hawaii and the other in Puerto Morelos, Mexico were conducted to understand the bleaching and recovery responses in the Hawaiian coral Porites lobata and the three Caribbean corals Montastraea faveolata, Porites astreoides, and Porites divaricata. Four major findings were observed: 1) Bleaching resilience in the mounding coral P. lobata is due to it harboring a thermally tolerant endosymbiont type combined with an ability to actively metabolize zooplankton acquired C and utilize DOC as a significant fixed C source, 2) Bleached P. astreoides were capable of meeting greater than 100% of metabolic demand by i (open full item for complete abstract)

Committee: Andrea Grottoli Dr (Advisor); James Bauer Dr (Committee Member); Yo Chin Dr (Committee Member); Ozeas Costa Dr (Committee Member); Meg Daly Dr (Committee Member) Subjects: Biological Oceanography