Theses and Dissertations - Department of Geological Sciences

Permanent URI for this collection

https://ir.ua.edu/handle/123456789/108

Browse

Now showing 1 - 20 of 162

δ15n in mollusk shells as a potential paleoenvironmental proxy for nitrogen loading in chesapeake bay
(University of Alabama Libraries, 2014) Black, Heather Dawn; Andrus, C. Fred T.; University of Alabama Tuscaloosa
Crassostrea virginica is one of the most common oyster species in North America and is frequently found in archaeological sites and sub-fossil deposits, especially in the eastern US. Although there have been several sclerochronological studies on δ13C and δ18O in the shells of this species, little is known about δ15N stored within the shells, which could potentially be a useful paleoenvironmental proxy to determine nitrogen loading and the subsequent anthropogenic impacts within an area. In order to potentially serve as paleoenvironmental proxies for N loading, bivalve shells' organic matter needs to remain chemically unaltered. Since ancient peoples cooked most archaeological shells before depositing them in shell middens, it is necessary to determine if prehistoric cooking methods alter either %N or δ15N stored within the shells. Twenty C. virginica oysters and twenty-two Mercenaria spp. clams were treated to five different prehistoric cooking methods: direct exposure to hardwood coals, roasting above hardwood coals, roasting in a dry oven, boiling in freshwater, or boiling in seawater. Each shell was bisected through the resilifer with one half treated with one of the five prehistoric cooking methods and the remaining half serving as a control. With the exception of roasting above the hardwood coals, prehistoric cooking methods do not significantly alter either %N or δ15N within the shells. Those shells roasted above the coals were typically enriched in both %N and δ15N , which is likely an effect of smoke coming from the hardwood coals and infiltrating pore spaces within the outer layers of the shell. Ninety archaeological C. virginica shells ranging in age from ~120 to 3,400 years old and thirty-two modern C. virginica shells were collected in Chesapeake Bay at the Smithsonian Environmental Research Center in Edgewater, Maryland. One valve from each shell was sub-sampled and the calcite powder was analyzed (without acidification pretreatment) using an EA-IRMS system equipped with a CO2 trap to determine the %N and δ15N content of the shells. Comparison of %N and δ15N in C. virginica shells from the six different time periods studied show relatively constant values from ~3,400 years ago to 1820 AD. Between 1820 and 1890, there are rapid increases in both %N and δ15N in the shells, which continue to exponentially increase in value to the modern shells. The increases in %N and δ15N are correlated with increased anthropogenic impact due to human population, sewage discharge, and urbanization in Chesapeake Bay at this time. Therefore, it is likely that C. virginica shells can be used as a paleoenvironmental proxy to measure the anthropogenic impact of a specific area over time. However, the constant, relatively low %N and δ15N values from ~3,400 years ago to 1820 AD compared to the increased N concentrations and enriched δ15N shells from the modern periods could be influenced by diagenetic alteration of the shell after burial in the midden. It is possible that the shells are losing N and preferentially losing 15N over time. More research is necessary to determine if bivalve shells are geochemically stable with regard to N over time or if diagenesis is likely to have occurred in these shells.
Anthropogenic and environmental drivers of the input and uptake of dissolved organic matter in temperate streams
(University of Alabama Libraries, 2019) Shang, Peng; Lu, Yuehan; University of Alabama Tuscaloosa
Dissolved organic matter (DOM) is a complex mixture of organic compounds and plays an essential role in regulating substrate and energy flows in aquatic ecosystems. However, environmental factors and biogeochemical mechanisms mediating the supply and uptake of DOM in streams are not well understood. The overarching goal of this dissertation is to assess the effects of the anthropogenic and natural drivers on the amount, source, composition, and fate of DOM in streams. The objective of Chapter II is to understand the effects of agricultural activities on DOM in a regional group of streams in Southeastern Alabama. The main finding is that agricultural land use increases DOC concentration and the proportions of terrestrial and microbial humic DOM compounds in streams, which suggests that agricultural activities accelerate the mobilization of organic matter from topsoils via enhancing oxidation, erosional transport, and shifting soil-to-stream flow paths. The objective of Chapter III is to identify the environmental drivers controlling the supply of terrestrial DOM in a Coastal Plain stream draining a forest-dominated watershed. The main finding is that discharge can be used to predict DOM supply across timescales, but other environmental drivers could be important at a given timescale. Specifically, the event-scale DOM supply is influenced by antecedent hydrological conditions and the duration of storms. At the diurnal scale, DOM variation is driven by physical dilution and concentration due to evapotranspiration. At the seasonal scale, DOM variation is mediated by organic matter availability from litterfall and discharge. The objective of Chapter IV is to determine the rates of natural DOM removal and identify the associated biogeochemical mechanisms in a second-order stream draining a forest-dominated watershed. The results provide the first record simultaneously measuring the uptake characters of humic-like and protein-like DOM, which demonstrates that humic-like DOM has a shorter uptake length and higher uptake velocity than protein-like DOM due to the preferential adsorption of humic-like compounds to benthic sediments. This dissertation improves our understandings of the supply and demand of DOM in subtropical streams in response to human land use and hydrological events, contributing to a greater understanding of the factors mediating the aquatic ecosystem response.
Application of phosphate and surfactant-modified zeolite for remediation/attenuation of trace elements in soil and coal fly ash
(University of Alabama Libraries, 2012) Neupane, Ghanashyam; Donahoe, Rona Jean; University of Alabama Tuscaloosa
This dissertation presents results of a research work aimed at understanding and addressing trace element contamination sourced by coal fly ash and arsenic trioxide herbicide. Both alkaline and acidic fly ash samples were found to contain significant concentrations of environmentally available trace elements. The treatment of fly ash leachate with surfactant-modified zeolite (SMZ) decreased the mobility of several trace elements. In general, up to 30% of the As, Mo, and V; up to 80% of the Cr; and up to 20% of the Se and Sr were removed from the leachate after SMZ treatment. Batch experiments, surface complexation modeling, and X-ray spectroscopic tools were used to elucidate the kinetics and mechanisms of arsenate (As(V)) and phosphate (Pi) adsorption on ferric hydroxide. Both oxyanions showed similar adsorptions during single-ion adsorption experiments; however, As(V) was preferentially adsorbed during competitive adsorption experiments. Similarly, more As(V) was adsorbed when it was loaded in sequence in Pi-equilibrated system than vice versa. Both oxyanions competed for adsorption on ferric-hydroxide and each of them showed a limited capacity to desorb the other, and relatively, more pre-equilibrated Pi was desorbed by sequentially added As(V) than vice versa. The As K-edge EXAFS analysis indicated the presence mononuclear and binuclear bidentate As(V) surface complexes. The Fe coordination numbers (CN) of these complexes increased with increasing time and decreased with addition of Pi into the system. Finally, an arsenic-contaminated soil collected from an industrial site located in the southeastern United States was amended with Pi and Ca to precipitate the arsenic as As-bearing apatite-like minerals. Phosphoric acid amendment of the soil with simultaneous addition of Ca dramatically decreased the mobility of soil As to near zero at pH > 6. Characterization of precipitate separated from the Ca-Pi treated soil by X-ray diffraction indicated that a carbonate-apatite mineral was formed in the soil and likely incorporated As(V) into its structure. The low solubilities of many of the Ca-Pi-As(V) minerals suggest that Ca-Pi treatment has promise as an effective, long-term method for in situ chemical fixation of As in contaminated soils and wastewaters.
Aqueous geochemistry of a sulfurous freshwater spring: implications for sulfur cycling and resident microbial communities
(University of Alabama Libraries, 2014) Morrissey, Tacoma Nicole; Aharon, Paul; University of Alabama Tuscaloosa
Blount Springs offers a sulfide-rich environment inhabited by a diverse microbial community in which to study the sulfur redox reactions and the microbially mediated processes via the analysis of sulfur isotopes of sulfide and sulfate. The average δ34SH2S at the wellheads is +31.1 ±0.3 / (n=9) and the average δ34SSO4 in the biofilm and downstream locations is highly variable with a mean value of +16.9 ±7.5 / (n=9). Sulfur isotope fractionations from H2S to SO4 range from 7.1 to 13.9 /. Utilizing the sulfur isotope fractionations it is concluded that (i) the sulfide is most likely derived from Thermochemical Sulfate Reduction (TSR) in the subsurface; (ii) the sulfide is subsequently oxidized to sulfate via the microbially related process of chemosynthetic sulfide oxidation; and (iii) the sulfide is also likely consumed by the abiotic processes of sulfide oxidation and outgassing of H2S. The isotopic fractionations from H2S to SO4 corroborate the isotopic fractionations observed in the laboratory during chemosynthetic sulfide oxidation. The carbon isotopic composition of DIC and the concentration of DIC support the hypothesis of microbial consumption of organic matter. Visualization of the biofilm via macroscopic and microscopic imaging revealed a morphologically diverse community. Biofilm of white, pink, and orange color were observed over the course of the study. Microscopic images revealed rod-shaped, coccoid, and filamentous cells. PCR amplification confirmed the presence of bacterial DNA. Aerobic lithotrophs, such as Thioplaca and Beggiatoa are possible groups of bacteria responsible for the chemosynthetic oxidation of sulfide at Blount Springs.
Are the mantle lithosphere and lower crust preferentially thinned during continental rifting?
(University of Alabama Libraries, 2018) Tew, Kalyn J.; Goodliffe, Andrew M.; University of Alabama Tuscaloosa
Worldwide, estimates of extension in rift zones vary greatly depending on the method used to calculate the extension. This variability is the result of the discrepancy between different methodologies and may be the result of polyphase faulting, subresolution faulting, and/or depth-dependent extension. Such inconsistency between estimates has been noted in the Woodlark Basin, an active transition zone between continental rifting and seafloor spreading. Previous work in the basin, where seafloor spreading has not initiated, calculated extension by summing fault heaves, calculating subsidence, and determining plate motion from Euler pole kinematics, yielding estimates of 111 km (23) from brittle extension, 115 km (47) from subsidence, and 200 km (40) from Euler pole kinematics (Kington and Goodliffe, 2008). By incorporating polyphase and subresolution faulting into the brittle extension estimate, Kington and Goodliffe (2008) resolved the discrepancy between estimates of extension derived from brittle faulting and subsidence. The third method used to estimate extension, Euler pole kinematics, produced a large discrepancy. Kington and Goodliffe (2008) interpreted this to be the result of preferential extension of the lower crust and mantle lithosphere during the rifting phase and proposed that uniform extension would occur throughout the lithosphere after seafloor spreading initiation. The current study explores potential errors in previous work in the basin and determines if the results are applicable to other portions of the basin. In contrast to Kington and Goodliffe (2008), the current study determines extension where seafloor spreading initiated at ~0.8 Ma. Using the methods and associated errors from Kington and Goodliffe (2008), Euler pole extension estimates (~202 to 238 km) are ~2 times higher than brittle (~69 to 90 km) and subsidence (~60 to 79 km) extension estimates, consistent with the previously seen discrepancy. When taking into account other sources of error not considered by Kington and Goodliffe (2008), the current study shows the previous methods lack the constraints necessary to produce conclusive results. This would also render the results of the previous study by Kington and Goodliffe (2008) inconclusive. Therefore, it is not necessary to invoke the Kington and Goodliffe (2008) model to explain rifting in the western Woodlark Basin.
Assessment of the petroleum generation potential of the Neal Shale in the Black Warrior Basin, Alabama
(University of Alabama Libraries, 2014) Legg, Joel Arthur; Donahoe, Rona Jean; University of Alabama Tuscaloosa
The Neal shale, the organic-rich interval of the Floyd Shale located in the Black Warrior Basin of Alabama and Mississippi, has attracted recent attention as a potential economic source of hydrocarbons. X-ray diffraction (XRD) and X-ray fluorescence (XRF) spectroscopic analysis of 54 Neal shale samples indicate the formation is clay-rich and quartz-poor, with the clay content averaging 47.2 wt% and the quartz content averaging 25.2 wt%. Total organic carbon (TOC) values averaged 2.27 wt%, based on the correlation of XRF trace element concentrations to pyrolysis data. Nine samples of the Neal shale, representing 3 different levels of thermal maturity, were analyzed by FIB-FESEM to determine if organic porosity increases with thermal maturation. Based on this analysis, Neal shale porosity is a mixture of fissure, organophillic, and interparticle porosity. However, no increase in organic matter porosity was observed with increasing thermal maturation. Instead, the organophillic porosity development was found to be linked to bitumen migration/maturation. This suggests organic porosity development was significantly affected by the organic matter composition, rather than by thermal maturity alone (Figure 8). Kinetic porosity modeling indicates the formation developed as much as 4.82% kerogen porosity. However, kinetic porosity models like the one used in this study may not be valid because they do not account for the chemical composition of the organic matter (i.e., kerogen vs. bitumen). Basin modeling indicates that the Neal shale has a large resource potential, with an adsorbed gas estimate of 460 Tcf and recoverable free gas estimates ranging from 227-4,943 Bcf. Uniaxial strength tests indicate Neal shale samples have an average unconfined axial strength of 3.42 MPa, and the underlying Lewis Limestone samples have an average unconfined diametral strength of 22.22 MPa. This suggests that the underlying Lewis Limestone should serve as an active barrier to hydraulic fracturing efforts within the Neal shale. Although the Neal shale has retained a large volume of natural gas, mapping of the limestone fracture barriers and additional testing of hydraulic fracturing mechanics on clay-rich formations will be necessary before the potential development of the Neal shale as an unconventional petroleum reservoir can be fully evaluated.
Biogeochemical analysis of late cretaceous vertebrate fossils of western Alabama, USA
(University of Alabama Libraries, 2016) Harrell, Terry Lynn; Perez-Huerta, Alberto; University of Alabama Tuscaloosa
In the past, vertebrate paleontologists in Alabama focused primarily on classical methods of investigation, for example, by examining the gross anatomy of fossilized skeletal elements. More recently, new methods were developed that enable paleontologists to examine the molecular composition of fossilized bones and teeth, so that they may be used as proxies for determining past environmental and biological conditions. The analyses presented here examine vertebrate fossils from the Late Cretaceous aged marine formations of Alabama, which represent one of the warmest time periods in Earth’s history. The first analysis examines the rare earth element (REE) content of biophosphates to determine fossil provenance and relative paleobathymetry of the marine strata in which the fossils were deposited. The second analysis examines the strontium isotope ratios present in fossil shark tooth enameloid to determine numerical ages of the containing geologic formations. The final analysis examines the oxygen isotope content of biophosphates for ambient temperature determination of seawater present during the Late Cretaceous and the body temperatures of a variety of vertebrate organisms including mosasaurs and birds. The data obtained by this study on the greenhouse climate present during the Late Cretaceous may possibly be used to better enhance computer modelling of future climate change, given the current state of global warming, and the biological response to this warming trend.
Biomineralization of giant clam shells (tridacna gigas): implications for paleoclimate applications
(University of Alabama Libraries, 2016) Gannon, Michelle E.; Perez-Huerta, Alberto; Aharon, Paul; University of Alabama Tuscaloosa
The giant clam, Tridacna gigas, is an important faunal component of Indo-Pacific reef ecosystems, for which its shell is often used as an environmental archive for modern and past climates. This thesis is a study of the shell microstructure of modern specimens from Palm Island, Great Barrier Reef (GBR), Australia and Huon Peninsula, Papua-New Guinea (PNG), using a combination of petrography, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and Raman spectroscopy, as well as a microstructural comparison of fossil T. gigas through 200 ka from PNG. Daily growth increments are recognizable in all specimens through ontogeny within the internal layer. For modern T. gigas from PNG, increments are composed of pairs of organized aragonitic needles and compact, oblong crystals, whereas modern specimens from GBR are composed of shield-like crystals. The combination of nutrient availability and rainfall are likely the most significant factors controlling shell growth and it may explain the observed differences in microstructure. The external layers are composed of a dendritic microfabric, significantly enriched in 13C compared to the internal layer, suggesting a different metabolic control on layer secretion. The internal and external layers are likely mineralized independent from each other, associated with the activity of a specific mantle organ. Furthermore, needles similar to those of modern T. gigas from PNG, are observed and the widths are measured in the set of fossil T. gigas. An exception includes two mid-Holocene-aged individuals, composed of elongated crystals, oblique to the outside of the shell. The results show that widths follows a cyclic pattern, similar to those of solar radiation variability, suggesting there is a relationship between solar activity and the width of aragonitic needles. Differences between modern and mid-Holocene T. gigas, are likely associated with fundamental environmental differences. The results of this study, pointing to locality and environmental dependence, layer specific mantle biomineralization, and co-variation between needle width and solar modulation, advance the potential of giant clam shells to assist in the reconstruction of many climate parameters that were previously limited to chemical analyses. Microstructural results are additionally applicable in engineering and medical research fields.
Biostratigraphy of the Bluffport Marl Member of the Demopolis Chalk, Cretaceous of Alabama
(University of Alabama Libraries, 1969) Newman, Harry Ellsworth, III.; University of Alabama Tuscaloosa
The Bluffport Marl Member of the Demopolis Chalk was sampled to find what lithologic and paleontologic variations occur along the strike of this unit. The Bluffport Marl Member has been traced in Alabama from Sumter County eastward into the western edge of Lowndes County, somewhat farther east than reported in earlier publications. Insolubles increase upward in the section and along strike towards the eastern extent of the Bluffport Member, implying an eastern source of clastics. The abundant invertebrate faunal assemblage of the Bluffport decreases upward in the section and to the east in direct relation to the increase in clastics. Although the Bluffport species vary in abundance at different localities, the total number of species found is nearly consistent from location to location in the lower part of the section. Morphologically, there is very little difference in the western and eastern Bluffport fauna, although there is a significant decrease in size of these assemblages toward the upper part of the section. Based on faunal changes, this increase in clastics reflects environmental conditions that were below those optimum conditions that existed in the lower and more western Bluffport section and in which these reef assemblages thrived.
Biostratigraphy, paleogeography, and paleoenvironments of the Upper Cretaceous (Campanian) northern Mississippi Embayment
(University of Alabama Libraries, 2010) Ebersole, Sandy; Stock, Carl W.; University of Alabama Tuscaloosa
Most paleogeographic and paleoenvironmental reconstructions of the northern Mississippi Embayment during the Late Campanian (Late Cretaceous) illustrate a generalized gulf between central Mississippi and Arkansas stretching northward into southern Illinois. The most detailed reconstruction shows a large river flowing from the Appalachians to the northeastern edge of the gulf with a river delta covering most of the northern embayment and stretching from southern Illinois to west-central Alabama. Lack of age constraints, incorrect stratigraphic correlations, paucity of detailed geologic maps and subsurface data, and misunderstanding of the basin geometry have led to inaccurate or vague paleogeographic interpretations of the Upper Cretaceous northern Mississippi Embayment. This project correlates the marine and nonmarine biostratigraphy, identifies the upper Campanian lithofacies, interprets the paleoenvironment of each lithofacies, and maps these interpretations to create a paleogeographic model of the northern Mississippi Embayment during the Late Campanian. Biostratigraphic indicators used in this project include foraminifera, calcareous nannoplankton, palynomorphs, ammonites, and other mollusks. Uppermost Campanian units correlated in this project include the uppermost Demopolis Chalk and lowermost Ripley Formation in Alabama and Mississippi; a basal volcaniclastic deposit of the subsurface Demopolis Chalk in Mississippi; the Coon Creek Formation lower facies in Tennessee; the Coffee Sand in northern Tennessee, Kentucky, Illinois, and Missouri; the smectite clays (proposed name of Glenallen Clay) in Missouri; the lower Nacatoch Sand and upper Saratoga Chalk in Arkansas; and the Saratoga and Demopolis Chalks undifferentiated calcareous clay in the central embayment subsurface. Paleoenvironments identified in the study area include molluscan-rich clastic shelf; barrier bar complex; carbonate shelf; estuaries and tidal flats; depression marshes and lakes; and volcanoes with clastic and carbonate rims.
Bulk chemical composition and mineral effects on grain conductivity and ice nucleation affinity of volcanic ash
(University of Alabama Libraries, 2017) Cloer, Shelby; Genareau, Kimberly D.; University of Alabama Tuscaloosa
Volcanic lightning is a common phenomenon during explosive eruptions, occurring as vent discharges, near-vent discharges, and plume lightning. Plume lightning is most similar to thunderstorm lightning, where volcanic ash may act as ice nuclei, leading to charging from ice-ice or ice-particle collisions. Volcanic ash samples were used to evaluate the role of ash mineralogy and bulk composition in the intrinsic electrical behavior and ice nucleation efficiency of ash. Samples from 8 volcanoes were used: Augustine, Crater Peak, Katmai, Okmok, Redoubt (Alaska, U.S.A.), Lathrop Well (Nevada, U.S.A.), Taupo (New Zealand), and Valles Caldera (New Mexico, U.S.A.). Five to nine resistance measurements were performed on all ash samples using an Electro-Tech Systems Model 828/863 current amplifier and resistance meter in a controlled environment. Depositional and immersion-mode ice nucleation experiments were performed using a Nicolet Almega XR Dispersive Raman spectrometer, following the methods of Schill et al. (2015). Depositional nucleation experiments were conducted from 225-235 K, and immersion-mode nucleation experiments were conducted from 233-278 K. A JEOL JSM 6010 Plus/LA scanning electron microscope (SEM) and Image-J freeware were used to quantify the number density of mineral phases in backscattered electron images. An x-ray diffractometer (XRD) was used to determine bulk mineralogy and an x-ray fluorescence (XRF) spectrometer was used to determine bulk ash composition. Resistance measurements with SEM analyses reveal that bulk ash composition and mineralogy do not control ash grain electrical conductivity. However, bulk composition and mineralogy do control the frozen fractions generated in immersion-mode ice nucleation experiments, with amounts of MnO, TiO2, and percentage of Fe-oxide phases showing a negative correlation with the frozen fraction. This study adds to our knowledge base on volcanic lightning dynamics and adds new implications for global climate models, which currently only address effects of mineral dust as ice nuclei and overlook the potential role of volcanic ash.
Carbonation of flue gas desulfurization gypsum for CO2 sequestration
(University of Alabama Libraries, 2021) Riddle, Jonathan B.; Donahoe, Rona J.; University of Alabama Tuscaloosa
The IPCC asserts that to prevent a 2°C global temperature increase by the year 2050, CO2 must be removed from the atmosphere by sequestration. The goal of this study was to use FGD gypsum for CO2 mineralization and experimentally explore to find the optimal conditions for the highest conversation rates at ambient temperature while eliminating ammonia usage. While maintaining an alkaline solution using NaOH, a stirred reactor was utilized to study the effects of PCO2 (0.69, 2.07, 4.14, 6.89, and 17.24 bar), solution pH (12, 13, 13.5 and 14), solid-to-solution ratio (1:100, 1:80, 1:40, 1:100), and reaction time (10, 15, 30, and 120+ min) variation on the rate of conversion. The CaCO3 produced was calculated by Rietveld refinement of XRD patterns to determine the impact of each experimental variable.Experimental results showed solution pH was a primary control on mineralization, with nearly 100% conversion of FGD gypsum to CaCO3 occurring at initial pH = 13.5 and 14, for PCO2 > 2 bar and S:L = 1:100. At initial pH of 12, no gypsum conversion occurred. Reaction time also affected the amount of gypsum conversion to CaCO3. At initial pH = 13, S:L = 1:100 and PCO2 = 2.07 bar, 15 min was the optimum reaction time, achieving 75% conversion. However, with the same conditions at 360 min, a 61% conversion occurred, due to final pH’s below 7. Increasing S:L ratio resulted in increased gypsum-to-carbonate conversion. The optimal conditions for conversion of gypsum into calcite occurred at short reaction times of 15 min, low pressures at around PCO2 = 2.07 bar, and low solution ratios of S:L = 1:100, achieving 75% conversion. In contract, a reaction time of 360 min produced a result of only 61% conversion at the same PCO2 and S:L ratio, due to the pH dropping below 7. The results of this study demonstrate that FGD gypsum is a viable feedstock for CO2 mineralization, potentially offering a cheap and rapid method for carbon sequestration.
Cave air and dripwater variability in Cathedral Caverns, Alabama
(University of Alabama Libraries, 2016) McKay, Kathleen Kingry; Lambert, William J.; Andrus, C. Fred T.; University of Alabama Tuscaloosa
Monthly monitoring of dripwater (δ18O, δD, [DIC], δ13CDIC, and pH) and air (pCO2 and δ13CCO2) chemistry from within Cathedral Caverns (Grant, AL) was conducted for 12 months (January 2015-December 2015) to better characterize the factors influencing deposition and δ18O chemistry of speleothems within the cave. Cave dripwater (δ18O and δD) isotope values for the Southeast, US are thought to be consistent with a yearly average. Cave monitoring of Cathedral Caverns, however, indicates that dripwater values are biased towards the winter season. This winter signal is emphasized through the study of the cave air pCO2, which shows a maximum during the month of October (7691 ppmV) and minimums during the colder, winter months. The max pCO2 value indicates that less CO2 is degassing from the dripwater during the hot summer months while during the colder winter months, more CO2 is degassed leaving less [DIC] to remain in the dripwater and more potential calcite deposition onto the stalagmite. The [DIC] and δ13CDIC which range from 0.6 to 6.0 mM and -4.7 to -14.7‰, respectively, show that [DIC] is at a maximum and δ13CDIC is 13C-depleted during summer months. These results indicate that the paleoclimate record in Cathedral Cavern’s speleothems and possibly most SE U.S. caves is biased towards a winter climatic signal. This conclusion is supported by: (i) a strong coupling between the timing of karst aquifer recharge (winter) and increased dripwater flow rates, (ii) cave dripwater δ18O (-5.7‰ (±0.2)) and δD (-32.1‰ (±2.6)) being similar to winter rainwater (-5.1‰ (±1.4) for δ18O and -27.8‰ (±15.1) for δD) collected at nearby Tuscaloosa, AL, and (iii) more favorable chemical conditions for calcite deposition to occur during winter months. These data illustrate that seasonal cave air exchange with the outside atmosphere is an important control on cave-specific periods of enhanced calcite deposition as well as the effect on the chemistry of dissolved inorganic carbon within the dripwater. This work demonstrates the utility of monitoring dripwater chemistry before conducting on paleoclimate reconstructions and furthermore, serves as a precursor for paleoclimate reconstruction of δ18O in speleothems from Cathedral Caverns.
Cave air C O_2 and drip-water geochemical variability at Desoto Caverns: implications for speleothem-based paleoclimate studies
(University of Alabama Libraries, 2017) Dhungana, Rajesh; Aharon, Paul; University of Alabama Tuscaloosa
This study has addresses the question whether speleothems from DeSoto Caverns (Childersburg, AL) can be used as paleoclimate archives for the Southeast USA. The monitoring program encompassed determination of cave air CO2, cave ambient conditions (i.e., air temperature, humidity), drip-water geochemistry and local rainfall amount, and stable isotopes of oxygen and hydrogen (Tuscaloosa, AL). The substantial attenuation of drip water isotope ranges (-3.1 to – 5.3 ‰ V-SMOW) relative to rainwater (-1.2 to -6.4 ‰ V- SMOW) is likely caused by mixing of freshwater with residual evaporated water in the epikarst zone. The cave drip water δ18O shows an interannual negative trend from the warm/dry year (2012) to the relatively cool/wet year (2013) suggesting that evapotranspiration above the cave plays an important role in drip water δ18O variability. Drip water Ca, Mg and Sr and Mg/Ca and Sr/Ca ratios exhibit lower values and higher ratios, respectively, during the warm/dry relative to the cool/wet year. The interannual rainfall amount variability likely exerts a dominant control on the elemental concentrations and elemental ratios of the drips. Cave air pCO2 varies seasonally with high values (up to 5.0 atm ×103) during summer when cave air flow is in stagnation mode and low values (down to 0.48 atm ×103) during winter when cave air flow is in ventilation mode. The data suggest that seasonal variations in the concentration of cave air CO2 affect the δ13C of drip water and by extension that of speleothem δ13C values. The documented abrupt hydroclimate changes at ~5 ka in a DeSoto stalagmite is synchronous with the reduction of the North Atlantic Deep Water (NADW) production suggesting the latter being the likely controlling factor. The periodic (68 ± 4 yrs periodicity) switches of seasonal rainfall amount dominance from winter to summer and back are a prominent feature of the mid-to-late Holocene δ18O time series of the speleothem. The observed 68 ± 4 yrs periodicity in stalagmite 18O agrees well with the ~ 70 yrs periodicity of the Atlantic Multidecadal Oscillation (AMO) suggesting the latter played a dominant role in the hydroclimate changes in the southeastern US during the late Holocene.
Cenozoic landscape evolution of a post-compressional orogenic wedge: intermontane basin development and sediment dispersal patterns, Renova Formation, southwest Montana
(University of Alabama Libraries, 2010) Rothfuss, Jennifer L.; Weislogel, Amy L.; University of Alabama Tuscaloosa
Sediment pathways and landscape evolution are useful proxies for refining the current understanding of crustal and surficial processes that initiated Paleogene post-compressional demise of the Cordilleran orogenic wedge in southwest Montana. Basin-fill deposits of Cenozoic intermontane basins that lie along the leading edge of the Sevier fold thrust belt provide a relatively complete sedimentary record by which to evaluate surficial and crustal processes that regulate landscape evolution of a deconstructional orogen. The Paleogene Renova Formation records initial post-Laramide sediment accumulation in the intermontane basins, marking the transition from fluvial incision to sediment backfilling. Facies assemblages reflect dominance by high-energy fluvial systems and alluvial fans that record radiating dispersal from basin-bounding uplifts including as the Boulder batholith-Highland Range and Pioneer Mountains. Paleogene fluvial systems were marked by rapid fluvial aggradation, and coeval basin margin deposits preserve rapid alluvial fan progradation. Progradational and aggradational stacking patterns reflect a rapidly subsiding environment in which the rate of accommodation space generation either outpaced or was equal to the rate of sediment influx. Syndepositional volcanism coupled with rapid denudation of Sevier-Laramide highlands, some of which were bounded by normally-reactivated reverse faults, provided abundant detritus into the depositional systems during the Paleogene. Paleogene paleodrainage reconstructions are strikingly similar to Cretaceous paleodrainage reconstructions for the Kootenai, Blackleaf, and Frontier Formations (Schwartz and DeCelles, 1988), and the Beaverhead Group (Sears and Ryan, 2003), suggesting that relict Late Cretaceous paleotopography coupled with regional Sevier-Laramide structural grain, exhibited strong infrastructural control on post-Laramide drainage evolution. Two distinct Paleogene paleodrainage networks have been identified in the study area based on detrital zircon age populations and paleoflow indicators, and likely reveal the presence of two distinct and separate Paleogene fluvial systems. Altogether, data presented suggest that rugged paleotopography characterized the Southwest Montana Re-entrant of the Sevier fold thrust belt during the Paleogene. Normal-sense reactivation of Sevier thrust faults coupled with erosion by high energy fluvial and alluvial systems rapidly dissected the Cordilleran orogenic wedge.
Clams and climate: implications for measuring seasonality in the marine bivalve, saxidomus gigantea
(University of Alabama Libraries, 2016) Bassett, Christine Nicole; Andrus, C. Fred T.; University of Alabama Tuscaloosa
Sclerochronological and sclerochemical analysis of shellfish remains from archaeological sites afford the opportunity to understand environmental change and its impacts on human populations through time. During the Late Holocene in the Gulf of Alaska, the paleoenvironmental record reflects fluctuating marine conditions throughout the region. The effects of changes in regional climate patterns, as well as human responses to such change, however, can exhibit great variability locally. In the Kodiak archipelago in the Gulf of Alaska, changing environmental conditions, population growth, technological transitions, and contact with other communities likely promoted the transition from needs based maritime hunting and gathering to surplus-based, semi-permanent villages. The precise role of climate in this transition is understudied. Few paleoclimate reconstructions are available for the Kodiak archipelago and while climate reconstructions for the Gulf of Alaska are not uncommon, regional climate reconstructions are often insufficient for archaeological research. Many climate reconstructions lack sub-annual resolution and cannot produce a detailed understanding of seasonal behaviors in human populations. Sclerochronological and sclerochemical analysis of shellfish remains from archaeological sites in the archipelago may provide additional paleoenvironmental information. Measuring and comparing the length of seasonal shell growth in select species of bivalves may complement stable oxygen isotope analysis, together providing a more precise paleoclimate reconstruction. This research utilizes the growth of Saxidomus gigantea, abundant both on modern and ancient coastlines to provide information about the length of its growing seasons. To measure seasonality, a total of 25 modern samples were collected from Alaska and British Columbia and the number of circalunidian growth lines were counted between annual winter growth lines confirmed by oxygen isotope analysis. Clams collected from Alaska grew a total of 143±34 days while the Canadian clams grew 273±14 days. Additionally, oxygen isotope values were more positive from annual winter growth lines from Alaskan samples than Canadian samples. This method was then applied to three archaeological samples collected from the Rice Ridge site (KOD-363), the Uyak site (KOD-145), and the Settlement Point site (AFG-105), which grew an average of 166±22, to confirm that these methods can be applied to archaeological samples through time to detect spatial and temporal changes in seasonality. These results suggest that changes in sea surface conditions and seasonality are detectable both spatially and temporally through detailed sclerochronological and sclerochemical analysis of shellfish remains from archaeological sites and offer the potential to reconstruct marine environmental conditions throughout the Holocene.
Comparing the magnitude and mechanisms of submarine groundwater discharge (SGD) and associated nutrient fluxes in estuaries and coastal karst systems: the examples of mobile bay (usa) and maro-cerro gordo (spain)
(University of Alabama Libraries, 2018) Montiel Martin, Daniel Agustin; Dimova, Natasha T.; University of Alabama Tuscaloosa
Submarine groundwater discharge (SGD) is an important source of natural and anthropogenic nutrients and contaminants in coastal waters. Nutrient inputs from SGD can cause or exacerbate eutrophication, hypoxia, seagrass beds degradation, and harmful algal blooms (HABs), among other ecological impacts. Coastal karst systems and estuaries are among the most complex coastal areas, where the assessment of SGD and derived nutrient fluxes is particularly challenging. Their typically heterogeneous hydrogeology combined with temporal fluctuations of marine and terrestrial forcing result in large variations of SGD in both systems. In this dissertation I evaluated the magnitude and mechanisms driving SGD and its importance as a source of water and nutrients to Maro-Cerro Gordo (a coastal karst system in southern Spain) and Mobile Bay (an estuary of the northern Gulf of Mexico). In Maro-Cerro Gordo I found that SGD accounted for an important part of the water budget of the coastal karst aquifer, the only source of freshwater for nearby population and agricultural activities. Additionally, SGD served as a vector for NO3- fertilizers contamination to the sea, putting at risk the endangered species of the coastal ecosystem. In Mobile Bay I found that 1/4 of the nutrient budget is delivered by SGD during the dry season as NH4+ (56% of the total) and DON (15% of the total), mostly on the east shore, where Jubilees occur. I demonstrated that these SGD-derived nutrient inputs, in contrast to previous hypotheses, are originated naturally from organic matter mineralization in a peat layer found only on the east shore of the bay. In comparison, groundwater discharge in Maro-Cerro Gordo was primarily controlled by the terrestrially driven hydraulic gradient of the karst aquifer, while in Mobile Bay SGD was mainly marine-driven by sea level fluctuations (tidal pumping). Furthermore, the extremely fast groundwater flow of the karst aquifer in Maro-Cerro Gordo always created oxic conditions, allowing the NO3- contamination to reach the sea. In contrast, in the shallow coastal aquifer of Mobile Bay I found that, while the main form of nitrogen in inland fresh groundwater was NO3-, the SGD-derived nitrogen inputs to the bay was almost entirely in the form of NH4+. These large fluxes of NH4+ were produced by two main processes: organic matter mineralization and dissimilatory nitrate reduction to ammonium (DNRA).
A comparison of continental extension estimates across the margins of the Woodlark Basin, Papua New Guinea
(University of Alabama Libraries, 2017) Nazlim, Berg; Goodliffe, Andrew M.; University of Alabama Tuscaloosa
Previous studies have shown that depth dependent extension is common across rifted margins. A discrepancy exists between the estimates of extension made through whole lithosphere/crust vs fault heave calculations (for example, northwest Australia, South China Sea, Galicia). Although this discrepancy is also observed in the Woodlark Basin (~111 (23) from brittle extension and ~115 (47) from subsidence [Kington and Goodliffe, 2008]), the location of this study, including sub-seismic resolution and poly-phase faulting reduces this mismatch. What makes the Woodlark Basin unique is that a third measure of continental extension is available, Euler pole kinematics. Previous studies show that this predicts almost double (~220 km) the extension calculated from subsidence and brittle extension [Kington and Goodliffe, 2008]. Extension in the Woodlark Basin began at ~8.4 Ma and transitioned to sea-floor spreading in the east at ~6 Ma [Kington and Goodliffe, 2008]. The basin is an ideal place to study the extension discrepancy because of its young age and thin sediments. Seismic reflection data provide good images of basement and fault structures. High-resolution bathymetry permits tracing of major faults on the seafloor. A previous study focused on the extension discrepancy at the rifting to spreading transition. This study will focus on the discrepancy further east where seafloor spreading began at ~1.8 Ma and opening rates are faster. Using high resolution bathymetry, magnetics, gravity, and low-fold 2-D seismic reflection data allowed me to estimate the amount of extension through brittle extension and subsidence. Euler pole derived extension rates from previous studies were used for comparison. The results of this study show that the amount of extension increases towards the east as is expected from having a Euler pole to the west. Subsidence derived extension estimates yielded 95.6 (38) km at 153.0E with a maximum stretching factor of 1.8. This increased to 145.3 (52) km with a maximum stretching factor of 1.89 to the east. Brittle extension estimates yielded between 107.1 (26.8) and 143.1 (35.8) km of extension between 153.0E and 154.0E. Both estimates of extension are far lower than the ~235 km of extension predicted by Euler Pole kinematics for the same area. As in the Kington and Goodliffe [2008] study, brittle faulting and subsidence derived extension estimates match (within the error limits).
Comparison of crude oils found in carboniferous reservoir rock and potential source rocks in the Black Warrior Sasin, Southeastern United States
(University of Alabama Libraries, 2017) Drago, Leonard William; Robinson, D. M.; University of Alabama Tuscaloosa
The Black Warrior basin in northwestern Alabama achieved maximum burial, maturation, and subsequent cessation of hydrocarbon generation during Late Permian time. The Chattanooga and Floyd/Neal Shales are viable potential source rocks for the Carboniferous sandstone reservoirs in the Black Warrior basin. To determine which source rock produced the crude oil in the Carboniferous-aged North Blowhorn Creek and Chicken Swamp Branch Oil Fields, this study uses Rock-Eval Pyrolysis and biomarker analyses. This study establishes total organic content (TOC) values ranging from 2.92 to 6.25% (4.29% average) in the Chattanooga Shale, and 0.62 to 3.16% (1.86% average) in the Floyd/Neal Shale. These values, in tandem with Rock-Eval Pyrolysis data, display previous expulsion and potential future expulsion of hydrocarbons from both potential source rocks by showing established maturation levels based on Tmax values and ample amounts of organics necessary to expel hydrocarbons. Gas Chromatography-Mass Spectrometry results show that the C27-29 sterane levels and pristane/phytane ratios are similar in the Carter sandstone crude oils, the Pottsville A sand crude oils and the Floyd/Neal Shale samples. No discernible similarities or patterns between the crude oils and shale samples could be identified from the biomarker results with the exception of the sterane and pristane/phytane results. The Floyd/Neal Shale samples have a pristane/phytane average of 1.23, while the Chattanooga Shale samples have an average of 0.34. The Carter sandstone and Pottsville A sand crude oils have averages of 1.46 and 1.53, respectively. A positive correlation was noted between thickness and %TOC levels of the Floyd/Neal Shale. The evidence suggests the Floyd/Neal Shale as the likely source rock of the crude oils in the North Blowhorn Creek and Chicken Swamp Branch oilfields in the Black Warrior basin of western Alabama.
A comparison of pre-treatment methods for δ^15 N analysis in mollusk shells
(University of Alabama Libraries, 2011) Hansen, Jestina Anne; Andrus, C. Fred T.; University of Alabama Tuscaloosa
Two sample preparation methods, acid pretreatment and no pretreatment, for δ^15 N analysis in mollusk shells were compared on sample splits from three common Gulf of Mexico and North Atlantic mollusks (Mercenaria spp., Crassostrea virginica, and Mytilus edulis). In all but one sample, no statistically significant difference (2σ) in δ^15 N values was measured between these two preparation techniques. However, sample splits that were not acid pretreated produced lighter δ^15 N values than their acidified counterparts in 82% of samples studied, and lower N content in small samples correlated with greater differences in method results. In addition, shell biomineralogy directly affected the %N of the samples; calcitic shell material contained greater %N, and produced data with higher analytical precision than aragonitic shell in the analyzed taxa. These data suggest that shell N content controls analytical data precision and that biomineralogy controls shell %N and N content. Within a singe species, N shell content varied as much as 30μg in C. virginica and 24μg in Mercenaria spp., likely as a result of differences in available food supply and N sources to grow-out locations. Because %N can vary greatly among and within species, preliminary analyses are recommended to determine the expected N content in samples and to establish whether omitting acid pretreatment of samples will result in sufficient analytical data precision. N content should also be reported along with analytical error to demonstrate that results are robust.

UA cloudflare authentication

Browse

Browsing Theses and Dissertations - Department of Geological Sciences by Title

Results Per Page

Sort Options