Thesis (PH. D.)--University of Nebraska, 1930. / Description based on print version record. Bibliography: p. 20.

Limestone dissolution in karst environments is likely due to geochemistry of the water, the actions of microbial communities, and the effect of water flow. We explored the rate of limestone dissolution and will examine here the microbial communities associated with the limestone. A conduit within the brackish cave, Double Keyhole Spring, on the coast of central west Florida was the site of the experiment. PVC pipes (5cm x 16cm) were filled with crushed limestone that was screened to a 1.9cm – 2.54cm size range. There were three treatments (5 replicates each): Control - sealed autoclaved controls with limestone and conduit water; Low Flow – sealed at one end, with a screen on the other so water contacts the limestone but cannot flow through; High Flow – screen mesh at both ends to allow the flow of conduit water over the limestone in the tube. After 9 months, the samples were retrieved. The Controls showed a loss of 0.33% ± 0.10, Low Flow samples showed a loss of 1.63% ± 0.71, and High Flow samples lost 2.28% ±0.29. Other studies in freshwater conditions found an average mass loss of 2.25% over the same time period under conditions similar to the High Flow sample in this experiment. Q-PCR and LH-PCR were used to estimate microbial density and species richness. The microbial community growing on the limestone samples were found to be significantly different from sediment or water column samples in both diversity and richness. The conclusion of this study is that the archaeal community growing on the limestone is the main biological driver of limestone dissolution in Double Keyhole Spring.

The electrochemical oxidation of methanol as applicable to low temperature fuel cell environments, has been investigated. The case for the use of methanol as a directly oxidisable fuel in alkaline electrolyte is presented. Initial work was targeted at establishing a non-noble metal electrode at which methanol could be oxidised in an aqueous alkaline electrolyte. Nickel, as an established electrode material for alkaline cells, was investigated by cyclic voltammetry and potentiostatic polarisation in both hydroxide and carbonate electrolytes, and noted features studied. The relative methanol oxidation performance of a selection of potential electrocatalysts, introduced through surface modification of porous and non-porous nickel structures, was later demonstrated.

In their comment on our publications on pervasive remagnetization of Jurassic-Paleogene carbonate rocks of the Tibetan Himalaya (Huang et al., 2017, Journal of Geophysical Research: Solid Earth, 122, doi: 10.1002/2016JB013662 and 122, doi: 10.1002/2017JB013987), Yi et al. (2017) questioned our fold tests applied to their published paleomagenetic results from the Paleogene Zongpu and latest Cretaceous Zongshan carbonate rocks (Patzelt et al., 1996, Tectonophysics, 259(4), 259-284; Yi et al., 2011, Earth and Planetary Science Letters, 309(1), 153-165). They argued that authigenic magnetite pseudomorphic after pyrite, which is the dominant magnetic carrier within these carbonate rocks as indicated by our thorough rock magnetic and petrographic investigations, was formed during early diagenesis and that the primary natural remanent magnetization (NRM) is retained by these carbonate rocks. However, their statement for the invalidity of our fold tests is based on unrealistic assumptions that these carbonate rocks carry primary NRM and that the upper Zongpu Formation was deposited on a 10 degrees primary dip. Their argument for immediate oxidization of pyrite to authigenic magnetite after carbonate deposition onto the continental passive margin ignores that sulfate-reducing conditions were prevailing during early diagenesis, it is also inconsistent with the timing of the secondary remanence acquisition in remagnetized carbonate rocks elsewhere. As previously demonstrated, and agreed upon by Yi et al. (2017), the Zongpu and Zongshan carbonate rocks in Gamba are remagnetized; here we argue that the timing of remagnetization cannot be demonstrated to shortly postdate sedimentation. These data should therefore not be used for tectonic reconstructions.

The Upper Cretaceous (Maastrichtian) Belqa Group in Jordan consists predominantly of organic-rich carbonate mudrocks that represent excellent source rocks but are still immature to just entering the oil window. Therefore, they offer a unique opportunity to study lithology, source rock composition, and geochemistry prior to the onset of maturation and expulsion of hydrocarbons. Our study examines the lithological and geochemical characteristics of these high-quality source rocks. To define the lithofacies and analyze the heterogeneities, 23 samples were investigated for their composition and texture using optical microscopy, SEM/EDS, XRD, and XRF). Geochemistry analyses were based on total organic carbon (TOC), Rock-Eval pyrolysis, and vitrinite reflectance. Four lithofacies were defined in this study: Strongly bioturbated calcareous mudstone (LF1), Slightly laminated calcareous mudstone (LF2), Parallel laminated calcareous mudstone to wackestone (LF3), Fine to coarse silicified wackestone to packstone (LF4), all containing significant organic content (TOC varies from 6 to 20 wt.%) and Sulphur contents (1.3-4.7 wt.%). Kerogen types are predominantly II-S with high HI (Hydrogen Index) values of >700 mg HC/g TOC. XRD results show that the rocks are mainly composed of calcite (75% on average) and quartz (10% on average). Minor amounts of clay (< 7%), pyrite (up to 6%), gypsum (up to 4%), and dolomite (up to 3%) also exist. Our results evidenced the high heterogeneity in the lithofacies of the MCM formation samples. Despite the traditional interpretation of low-energy suspension settling, we demonstrated the presence of bottom currents during the deposition of the Upper Cretaceous source rocks in Jordan (ripples, rip-up mud, reworking material, and fossil-rich lenses) and insight into the bottom water conditions (anoxic and oxic). The integration of the data obtained through the different techniques used in this study, together with the unique characteristics of these source rocks, allowed the characterization of the geological and geochemical properties of the defined lithofacies associations in these immature, Upper Cretaceous source rocks. This, in turn, helped to better evaluate the occurrence and distribution of the different litho- and organic facies and estimate hydrocarbon source potential.

In the past, oceans have strongly influenced atmospheric CO2 levels through organic and inorganic carbon cycling. The inorganic carbon pump relies on the formation of calcium carbonate which releases CO2 into the surface ocean and traps alkalinity in solid form which sinks to deeper ocean layers and sediments. After sinking, calcium carbonate can either then become trapped in the sediments or dissolve increasing the alkalinity of deeper ocean layers. The net effect is of acidifying surface oceans and encouraging release of CO2 to the atmosphere. The present thesis focuses on marine teleost (bony) fish in temperate areas as previously poorly understood but potentially major producers of calcium carbonate in the ocean. Fish in temperate areas may be contributing to carbonate sediment production and as such the inorganic carbon pump. Prior to this thesis only tropical fish have been investigated as major piscine sediment producers. The present thesis describes the composition and morphology of carbonates produced by many different species of temperate fish providing a basis for the understanding the fate of these carbonates in the environments and their potential contribution to sediment production and the inorganic carbon cycle. Characteristics of carbonates produced by fish in the wild were fairly consistent within a species upon examination of carbonates produced by poor cod (Trisopterus minutus) over the course of a year. However, despite the likely consistent and distinct characteristics of fish carbonates, little evidence of them was found in temperate shallow sediments beneath pens of farmed Atlantic salmon (Salmo salar) where there theoretically should be very high production rates. Reduced salinity, often a feature of temperate areas compared to tropical areas, was found to reduce production rates of carbonate from fish compared to higher salinities. However, salinity reductions below the ocean average of 35 psu (practical salinity units) had less impact on production rates than increases above 35 psu. As such it is argued that production rates in temperate environments should still be relatively high considering high fish biomasses in some temperate regions and could still mean fish in temperate areas are an important source of carbonate production and potential sediment production.

Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

The Bahamas Island archipelago grows by the precipitation and secretion of calcium carbonate. A majority of this growth is by lateral accretion of shoreline sedimentary deposits. Previous research is not clear on whether the growth is largely due to eustasy, sediment input from catastrophic events, or a combination of both. The Bahamas is an ideal location for studying Holocene carbonate generation and deposition, but there is limited research on the analysis of strandlines in relation to lateral accretion. Carbonate strandline deposits are commonly classified as low-energy beach ridge deposits. Previous researchers have primarily focused on ooid shoals and subtidal regions. Understanding the mechanisms of platform and shoreline growth in the Bahamas is important for creating petroleum reservoir analogs for exploration. We use ground penetrating radar (GPR) to image and interpret the internal fine-scale stratigraphy of Bahamian carbonate strand plains and thereby constrain our understanding of the processes by which the islands grow. Although GPR has been used extensively to analyze the interior of clastic strandline deposits across the world, tropical carbonate settings have received little attention. We are the first to utilize GPR to study strand plains in Crooked Islands, The Bahamas, our primary location for 2D GPR data acquisition. We integrate our interpretation of these data with a 3D GPR data volume collected on Pleistocene eolianites on San Salvador Island, The Bahamas. We used a GSSI (Geophysical Survey Systems, Inc.) bistatic 400-MHz antenna with a field frequency filter of 100"“800 MHz for all datasets. GPR allowed visualization of the interior of the strand plains down to a depth of about 2 m with high resolution. Data processing was performed using state-of-the-art petroleum industry techniques (e.g., gain control, deconvolution, migration, seismic attribute computation) to better visualize the reflectivity. Our data constrains a model that the lateral accretion of carbonate sediment preserved in strandline was deposited in a combination of storm processes and gradual sediment progradation, rather than one or the other. Our conclusions help determine that The Bahamas is ideal for GPR imaging of strandlines due to being assessable, high data quality, no clastic influence, and a dry environment during parts of the world

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