Department of Geological Sciences

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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.
Abundance and morphology of charcoal in sediments provide no evidence of massive slash-and-burn agriculture during the Neolithic Kuahuqiao culture, China
(PLOS, 2020) Hu, YuanFeng; Zhou, Bin; Lu, YueHan; Zhang, JianPing; Min, SiYu; Dai, MingZhe; Xu, SiYu; Yang, Qing; Zheng, HongBo; Nanjing University; University of Alabama Tuscaloosa; Chinese Academy of Sciences; Institute of Geology & Geophysics, CAS; Yunnan University
It remains debatable whether slash-and-burn practices were adopted in rice cultivation by the Neolithic Kuahuqiao culture in the Ningshao Plain, one of the birthplaces of rice farming. Here, we established charcoal-based indices to reconstruct the history of fire and vegetation in the Ningshao Plain since the last glacial period. We collected representative modern vegetation and conducted combustion and fragmentation experiments to simulate fire and depositional processes, respectively. Charcoals from modern vegetation show clear morphological differences between herbaceous and woody plants. In particular, the length to width ratios (L/W) of herbaceous charcoals were systematically higher than those of woody charcoals, and the associated end-member values were 4.50 and 1.94, respectively. These values were then applied to sediment cores (KHQ-14/15) collected in proximity to the Kuahuqiao archaeological site. Results show that the amount of combusted herbaceous plants increased sharply after the Holocene, and the most remarkable rise occurred around 8550 yr B.P. This observation may reflect local environment (sedimentary and/or climatic) changes or small-scale early human activities. During the Kuahuqiao cultural period (8250-7450 yr B.P.), the relative abundance of woody charcoals increased, but the overall fire intensity decreased. This finding suggests that the Kuahuqiao farming was restricted to a small geographic area and large-scale slash-and-burn farming activities were not adopted.
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.
An approach to quantifying the efficiency of a Bayesian filter
(American Geophysical Union, 2013-04-26) Nearing, Grey S.; Gupta, Hoshin V.; Crow, Wade T.; Gong, Wei; University of Arizona; United States Department of Agriculture (USDA); Beijing Normal University; University of Alabama Tuscaloosa
Data assimilation is the Bayesian conditioning of uncertain model simulations on observations to reduce uncertainty about model states. In practice, it is common to make simplifying assumptions about the prior and posterior state distributions, and to employ approximations of the likelihood function, which can reduce the efficiency of the filter. We propose metrics that quantify how much of the uncertainty in a Bayesian posterior state distribution is due to (i) the observation operator, (ii) observation error, and (iii) approximations of Bayes' Law. Our approach uses discrete Shannon entropy to quantify uncertainty, and we define the utility of an observation (for reducing uncertainty about a model state) as the ratio of the mutual information between the state and observation to the entropy of the state prior. These metrics make it possible to analyze the efficiency of a proposed observation system and data assimilation strategy, and provide a way to examine the propagation of information through the dynamic system model. We demonstrate the procedure on the problem of estimating profile soil moisture from observations at the surface (top 5 cm). The results show that when synthetic observations of 5 cm soil moisture are assimilated into a three-layer model of soil hydrology, the ensemble Kalman filter does not use all of the information available in observations.
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.
Archaeological climate proxies and the complexities of reconstructing Holocene El Nino in coastal Peru
(National Academy of the Sciences, 2020) Sandweiss, Daniel H.; Andrus, C. Fred T.; Kelley, Alice R.; Maasch, Kirk A.; Reitz, Elizabeth J.; Roscoe, Paul B.; University of Maine Orono; University of Alabama Tuscaloosa; University of Georgia
Archaeological evidence plays a key role in longitudinal studies of humans and climate. Climate proxy data from Peruvian archaeological sites provide a case study through insight into the history of the "flavors" or varieties of El Nino (EN) events after similar to 11 ka: eastern Pacific EN, La Nina, coastal EN (COA), and central Pacific or Modoki EN (CP). Archaeological proxies are important to the coastal Peruvian case because more commonly used paleoclimate proxies are unavailable or equivocal. Previously, multiproxy evidence from the Peruvian coast and elsewhere suggested that EN frequency varied over the Holocene: 1) present in the Early Holocene; 2) absent or very low frequency during the Middle Holocene (similar to 9 to 6 ka); 3) low after similar to 6 ka; and 4) rapidly increasing frequency after 3 ka. Despite skepticism about the reliability of archaeological proxies, nonarchaeological proxies seemed to confirm this archaeological EN reconstruction. Although there is consensus that EN frequency varied over this period, some nonarchaeological and archaeological proxies call parts of this reconstruction into question. Here we review Holocene EN frequency reconstructions for the Peruvian coast, point to complexities introduced by apparent contradictions in a range of proxy records, consider the impact of CP and COA phenomena, and assess the merits of archaeological proxies in EN reconstructions. Reconciling Peruvian coastal paleoclimate data is critical for testing models of future EN behavior under climate variability.
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.
Assimilating remote sensing observations of leaf area index and soil moisture for wheat yield estimates: An observing system simulation experiment
(American Geophysical Union, 2012-05-17) Nearing, G. S.; Crow, W. T.; Thorp, K. R.; Moran, M. S.; Reichle, R. H.; Gupta, H. V.; University of Arizona; United States Department of Agriculture (USDA); National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; University of Alabama Tuscaloosa
Observing system simulation experiments were used to investigate ensemble Bayesian state-updating data assimilation of observations of leaf area index (LAI) and soil moisture (theta) for the purpose of improving single-season wheat yield estimates with the Decision Support System for Agrotechnology Transfer (DSSAT) CropSim-Ceres model. Assimilation was conducted in an energy-limited environment and a water-limited environment. Modeling uncertainty was prescribed to weather inputs, soil parameters and initial conditions, and cultivar parameters and through perturbations to model state transition equations. The ensemble Kalman filter and the sequential importance resampling filter were tested for the ability to attenuate effects of these types of uncertainty on yield estimates. LAI and theta observations were synthesized according to characteristics of existing remote sensing data, and effects of observation error were tested. Results indicate that the potential for assimilation to improve end-of-season yield estimates is low. Limitations are due to a lack of root zone soil moisture information, error in LAI observations, and a lack of correlation between leaf and grain growth.
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.
Biogeochemical fingerprinting of magnetotactic bacterial magnetite
(National Academy of the Sciences, 2022) Perez-Huerta, Alberto; Cappelli, Chiara; Jabalera, Ylenia; Prozorov, Tanya; Jimenez-Lopez, Concepcion; Bazylinski, Dennis A.; University of Alabama Tuscaloosa; University of Granada; United States Department of Energy (DOE); Ames National Laboratory; University of Nevada Las Vegas
Biominerals are important archives of the presence of life and environmental processes in the geological record. However, ascribing a clear biogenic nature to minerals with nanometer-sized dimensions has proven challenging. Identifying hallmark features of biologically controlled mineralization is particularly important for the case of magnetite crystals, resembling those produced by magnetotactic bacteria (MTB), which have been used as evidence of early prokaryotic life on Earth and in meteorites. We show here that magnetite produced by MTB displays a clear coupled C-N signal that is absent in abiogenic and/or biomimetic (protein-mediated) nanometer-sized magnetite. We attribute the presence of this signal to intracrystalline organic components associated with proteins involved in magnetosome formation by MTB. These results demonstrate that we can assign a biogenic origin to nanometer-sized magnetite crystals, and potentially other biominerals of similar dimensions, using unique geochemical signatures directly measured at the nanoscale. This finding is significant for searching for the earliest presence of life in the Earth's geological record and prokaryotic life on other planets.
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.

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