Theses and Dissertations - 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.
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.
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.
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.
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.
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.
Determination of ontogenetic age and paleoseasonality using shell spiral deviations and chemical proxies from fossil brachiopods
(University of Alabama Libraries, 2015) Clark, Joanna Victoria; Perez-Huerta, Alberto; University of Alabama Tuscaloosa
Brachiopods have been extensively used in paleoclimatic and paleoecological reconstructions, but their utility would greatly increase if a method were developed to determine paleoseasonality. Currently, there is no accurate and efficient method of determining seasonal seawater temperature variations from fossil brachiopods because doing so requires knowledge of specimen ontogenetic ages, which are difficult to determine. In this study, the spiral deviation methodology for determining specimen ontogenetic ages and paleoseasonality is tested using four species of fossil brachiopods, including Laqueus rubellus, Terebratula terebratula, Pseudoatrypa sp. and Platystrophia ponderosa, which range in age from the Pleistocene to the Ordovician. Specimens were analyzed for spiral deviations using R computer code developed for brachiopod shells. These shells were then analyzed for preservation using electron backscatter diffraction and scanning electron microscopy. Finally, well-preserved fossil specimens were analyzed for oxygen isotopes and Mg/Ca ratios using a mass spectrometer and laser-ablation-inductively-coupled-mass spectrometer, respectively. Chemical analyses revealed that locations of spiral deviations on shells of L. rubellus displayed a strong direct relationship with Mg concentrations, and resulting paleotemperatures were seasonal. Conversely, specimens of T. terebratula and P. ponderosa did not show a consistently strong relationship between Mg concentrations and spiral deviations, although resulting paleotemperatures from T. terebratula agreed with those from previous studies. Overall, the results from this study indicate that the spiral deviation methodology combined with chemical proxies presents great potential for utility in past seasonal seawater temperature reconstructions in pristinely preserved, biconvex fossil brachiopods.
Effects of the 1982-1983 El Niño mega event on bivalve mollusk biomineralization
(University of Alabama Libraries, 2014) Nicosia, Alexandra Rose; Perez-Huerta, Alberto; University of Alabama Tuscaloosa
Marine bivalve mollusks are valued as climate change recorders due to predictable growth rates and the recording of the ambient seawater environment into their shells (e.g., temperature, dissolved inorganic carbon (DIC)). Bivalves that endure extreme environmental perturbations also exhibit alteration of the shell microstructure in response to the stress. Numerous studies demonstrate correlations between shell isotopic values and environmental parameters, such as δ^18O and temperature, but the possibility of confounding isotopic signatures between shell layers and microstructures in a single organism, induced by environmental stress factors, has not been sufficiently studied. Two bivalve species (Trachycardium procerum and Chione subrugosa), collected from the Peruvian coast after the 1982-1983 El Niño, exhibit microstructural alterations in the shell in correlation with the sea surface temperature (SST) anomaly during the event. Common biomineral alterations include changes in the relative thickness of certain microstructural types and the loss of intercrystalline organic matrix components. δ^18O_shell and δ^13C_shell data show no significant changes in correlation with the El Niño growth scar in any shell layers of T. procerum. C. subrugosa, an intertidal species, shows δ^13C_shell and δ^18O_shell depletion in the affected area. These data indicate that biomineralization changes are not synchronized with isotopic signatures. Furthermore, bivalve biogeochemical proxies may not be sufficiently sensitive to detect rapid fluctuations in SST, but potentially useful in detecting other localized El Niño associated events, such as an increase in rainfall.
Experimental simulation of arsenite leaching on soils and mechanism of arsenite oxidation
(University of Alabama Libraries, 2012) Yue, Ziming; Donahoe, Rona Jean; University of Alabama Tuscaloosa
Arsenic trioxide was widely applied to soils in North America as an herbicide during the 1950-60s. These herbicide applications led to soil arsenic contamination at numerous sites. Decades after the herbicide application, the contaminated soil served as a secondary source for long-term leaching of arsenic into the groundwater system. To understand the history of arsenic contamination at these sites, column experiments were conducted to simulate the herbicide application and subsequent arsenic leaching processes. The experimental data showed that the effluent solution arsenic became dominantly As(V) after 180 pore volumes (equivalent to ~60 years of natural leaching, assuming a 50% recharge rate) of leaching, which represented an abnormally rapid arsenite oxidation rate (up to 60 mg/L/6.5 hours As(V)) (Yue and Donahoe, 2009). During peak arsenic release, the arsenite oxidation rate doubled (120 mg/mL/6.5 hours). Homogeneous As(III) oxidation cannot be responsible for the observed oxidation rate because the half life of As(III) in air can be up to one year (Eary and Schramke, 1990). Incubation experiments were designed, where sterilized and inoculated serum bottles with added aqueous As(III) and soil were compared for their aqueous total arsenic and As(V) concentrations. The aqueous As(V) in the innoculated series increased with time but remained below detection in the sterile series. This indicated that the As(III) oxidation observed in the column experiments was caused by the microbes in the soil. Bacterium strains A4 and A12 were isolated from the column soil and were tested to be the efficient arsenite oxidizers in the column experiments. Strain A12 shared 100% 16S rDNA sequence with Burkholderia. fungorum LMG 16225^T, while strain A4 shared 99.1%, 97.3% and 96.7% 16S rDNA sequences with strains Burkholderia. zhejiangensis CCTCC AB 2010354^T, B. glathei DSM 50014^T and B. sordidicola KCTC 12081^T, respectively. A polyphasic characterization, including phenotypic and biochemical characterization, 16S rDNA sequence analysis, DNA-DNA hybridization, and fatty acid analysis, was conducted on strain A4 to determine its taxonomic position. The results showed that strain A4 represented a novel species in the genus Burkhoderia, for which the name Burkholderia arsenicoxydans sp. nov. is proposed. The type strain is A4^T (=ATCC BAA-2404^T=CCTCC AB 2012027^T).
Geochronology and pressure-temperature conditions of mid-to-lower crustal processes in a Cretaceous magmatic arc, Fiordland, New Zealand
(University of Alabama Libraries, 2010) Parker, Karen Ann; Stowell, Harold Hilton; University of Alabama Tuscaloosa
Exposures of mid-to lower-crust in Fiordland contain evidence of high temperature and pressure processes occurring beneath magmatic arcs. This thesis presents new U-Pb zircon ages that constrain emplacement of the Malaspina Pluton, Western Fiordland Orthogneiss (WFO) to 116-114 Ma and new Sm-Nd garnet ages of 115-110 Ma for partial melting of the Malaspina near the Doubtful Sound Shear Zone (DSSZ), central Fiordland. U-Pb igneous zircon ages, from west to east across Doubtful Sound (DS), are 114.2 ± 2.2, 115.4 ± 2.2, and 116.1 ± 2.4 Ma. This compares to a contact metamorphic zircon rim age of 114.8 ± 2.4 Ma for the 119.8 ± 2.9 Ma Misty Pluton. From west to east across DS, Sm-Nd garnet ages are 113.6 ± 2.5, 113.2 ± 2.8, 115.6 ± 2.6, 111.6 ± 3.1, 110.6 ± 1.9, 113.3 ± 2.6, and 111.9 ± 3.0 Ma. Hence partial melting and garnet granulite-facies metamorphism lasted ≥ 5 m.y. in DS and occurred within 5.5 m.y. of pluton emplacement. These ages compare to Sm-Nd garnet ages for garnet granulite of 126-109 Ma in northern Fiordland (Pembroke) and ca. 110 Ma in southern Fiordland (Resolution Island). Mineral assemblages in DS migmatite include Amp + Cpx + Grt + Qtz + Pl ± Bt + Rt + Ilm ± relict OPx ± relict Czo. Euhedral, peritectic garnet occurring in leucocratic veins and reaction zones, has little zoning in composition and ranges from Alm_53 Prp_27 Sps_3 Grs_17 in the west to Alm_44 Prp_36 Sps_1.5 Grs_18.5 in the east. Ilmenite with exsolved rutile and oriented exsolution needles of rutile in garnet indicate re-equilibration after high T and P. Phase diagram sections for melted WFO and thermobarometry using garnet, clinopyroxene, and plagioclase compositions indicate 700-840°C and 10.6-14.2 kbar for metamorphism on DS. Similar methods for Pembroke Granulite of >750°C at 12-16 kbar indicate diachronous widespread high P metamorphism and partial melting for this ca. 4,375 km^2 section of mid-to lower-crust with these processes occurring early in the north and later in the south (126-105) Ma.
Geomorphological relationships through the use of 2-D seismic reflection data, Lidar, and aerial imagery
(University of Alabama Libraries, 2014) Alesce, Meghan Elizabeth; Goodliffe, Andrew M.; University of Alabama Tuscaloosa
Barrier Islands are crucial in protecting coastal environments. This study focuses on Dauphin Island, Alabama, located within the Northern Gulf of Mexico (NGOM) Barrier Island complex. It is one of many islands serving as natural protection for NGOM ecosystems and coastal cities. The NGOM barrier islands formed at 4 kya in response to a decrease in rate of sea level rise. The morphology of these islands changes with hurricanes, anthropogenic activity, and tidal and wave action. This study focuses on ancient incised valleys and and the impact on island morphology on hurricane breaches. Using high frequency 2-D seismic reflection data four horizons, including the present seafloor, were interpreted. Subaerial portions of Dauphin Island were imaged using Lidar data and aerial imagery over a ten-year time span, as well as historical maps. Historical shorelines of Dauphin Island were extracted from aerial imagery and historical maps, and were compared to the location of incised valleys seen within the 2-D seismic reflection data. Erosion and deposition volumes of Dauphin Island from 1998 to 2010 (the time span covering hurricanes Ivan and Katrina) in the vicinity of Katrina Cut and Pelican Island were quantified using Lidar data. For the time period prior to Hurricane Ivan an erosional volume of 46,382,552 m3 and depositional volume of 16,113.6 m3 were quantified from Lidar data. The effects of Hurricane Ivan produced a total erosion volume of 4,076,041.5 m3. The erosional and depositional volumes of Katrina Cut being were 7,562,068.5 m3 and 510,936.7 m3, respectively. More volume change was found within Pelican Pass. For the period between hurricanes Ivan and Katrina the erosion volume was 595,713.8 m3. This was mostly located within Katrina Cut. Total deposition for the same period, including in Pelican Pass, was 15,353,961 m3. Hurricane breaches were compared to ancient incised valleys seen within the 2-D seismic reflection results. Breaches from hurricanes from 1849, 1916, and 2005 all correlated with incised valley. Interpretations from horizons A and P correlated well with the 1849 shoreline, while Horizon B correlated best with the 1916 and 2005 hurricane breaches. The correlation of incised valleys and breaches provides a probable causation of breach locations. With further investigations, determination of the impacts of these relict valleys can be validated and established. Preferential subsidence within the relict incised valleys would account for the lower elevations on the island surface. Very fine to fine grained sediment deposits from the Mobile Bay would contribute to preferential subsidence. The lower elevations are more likely to erode from overwash and surges during strong storm systems.
High resolution, U/Th dated (32,000 to 11,000 years), oxygen and carbon isotope proxy climate records from a stalagmite in Desoto Caverns, Alabama, USA
(University of Alabama Libraries, 2010) Lambert, William Joseph; Aharon, Paul; University of Alabama Tuscaloosa
This study addresses the question whether speleothems from DeSoto Caverns (Childersburg, AL) can serve as archives of paleoclimate conditions for the Southeast, USA. The focus of the study involves determining present-day controls of cave water δ^18 O and δ^13 C followed by interpretation of stalagmite δ^18 O and δ^13 C variability in comparison to climate events of the past. The monitoring program involved a 3-year study of cave waters and local rainfall (Tuscaloosa, AL) during years characterized by a significant trend from wet to dry conditions. Decreasing recharge of the cave aquifer was expressed as an interannual trend of declining drip flow rates, which was punctuated by seasonal oscillations due to varying rates of evapotranspiration. Amount-weighted mean monthly rainwater δ^18 O range from -1.5 to -8.3 /, show a mean seasonal amplitude of ~4 /, and exhibit an interannual trend toward ^18 O-enrichment that I interpret as being governed by global atmospheric circulation patterns. The cave's aquifer attenuates seasonal δ^18 O variability, records 20% of rainfall's interannual ^18 O-enrichment, and is biased toward winter rainfall δ^18 O. Cave waters display strong seasonal variability in dissolved inorganic carbon (DIC) and δ^13 C, which range from 0.2 to 6.0 mM and 2.7 to -12.9 / (VPDB), respectively. The data suggest the strongest seasonal controls are cave air ventilation/stagnation and varying CO_2 fluxes through the soil horizon and epikarst. δ^13 C of active speleothems imply the precipitating aragonite captures the seasonality observed in source dripwaters and time-series δ^13 C records of stalagmites carry the imprints of drip annual means entailing climate-driven δ^13 C seasonal biases. A fossil stalagmite provided a high-resolution proxy record of rainfall variability between 31.9 and 11.3 ka. I propose a more southerly polar jet stream (PJS) promoted increased winter rainfall amounts during cold phase events while warm phases result in a higher PJS position and decreased winter rainfall. The Younger Dryas was characterized by a dramatic change in the PJS path as warm air from the Gulf of Mexico infiltrated deep into the continent's interior and substantially decreased winter rainfall. Establishment of near modern climate conditions greatly enhanced deposition rates before changes in flow paths through the epikarst prevented stalagmite deposition since 11.3 ka.
A high-resolution hydroclimate record of the last three millennia from a cored stalagmite at Desoto Caverns (Alabama, USA)
(University of Alabama Libraries, 2010) Dhungana, Rajesh; Aharon, Paul; University of Alabama Tuscaloosa
Late Holocene climate changes in the Southeast USA are poorly documented due to the paucity of high-resolution paleo-records. This study provides high-resolution records of rapid hydroclimate changes in the Southeast over the last three millennia. The records are based on stable isotope rainfall proxies whose time series are constrained by precise U/Th dates from a stalagmite sampled at DeSoto Caverns. The average growth rate of the stalagmite was 149 µm/yr prior to 1400 years and it has been growing with an average growth rate of 42 µm/yr in the last 1400 years. During the past three thousand years stable isotope time series document six wet episodes (at ~ 2950, 2450, 1675, 1200, 700 and 70 years ago) alternating with six drier periods (at ~ 3100, 2800, 1900, 1500, 800 and 300 years ago). The biannually resolved 18O record agrees well with the contemporaneous SST record from the Sargasso Sea cores suggesting that changes in moisture availability in the Southeast are likely linked to subtropical North Atlantic SST variability. Power spectra analysis of the stalagmite-based oxygen isotope record reveals statistically significant periodicities at 24±1 and 36±1 year that are consistent with those observed in the contemporaneous atmospheric 14C production record. The 24 years periodicity is also consistent with the 24-year NAO Index periodicity. On the basis of our analysis we propose that the hydroclimate in the Southeast USA over the last three millennia was intimately linked to NAO variability powered by solar activity fluctuations.
Hydroclimate time-series archived in a 4300 year old stalagmite from Desoto Caverns (Alabama, USA)
(University of Alabama Libraries, 2014) Aldridge, David Edward; Aharon, Paul; University of Alabama Tuscaloosa
Recently published climate studies have implicated the Atlantic Multidecadal Oscillation (AMO) as the dominant factor modulating the precipitation in the regions adjacent to the Atlantic Ocean and the Gulf of Mexico but long range, land-based paleoclimate proxies, are notably lacking. Here I report the results of a new stalagmite- derived ä18O and ä13C ( / VPDB) time series and petrographic study from DeSoto Caverns, Alabama, spanning the interval from recent to 4025 years BP. The new data document AMO as having a pervasive controlling influence on the Southeastern USA region's hydroclimate during the Late Holocene. Ten precise 230Th/234U age determinations, from an 11.3 cm section of stalagmite, spanning the interval from 1883 to 4025 years BP, were used to construct an age model for the stable isotopes time-series containing 882 determinations. Analysis of the stalagmite's ä18O time-series in the frequency domain exhibits dominant periodicities of 30.8 ± 1.4 years and 27.4 ± 0.8 years at the Chi Squared 95% confidence interval that match the instrument-derived AMO half cycle periodicity of approximately 30 years. At the Chi Squared 90% confidence interval, the stalagmite's ä18O time-series frequency analysis reveal a periodicity of 58.0 ± 2.7 years, matching the instrument derived AMO full cycle of approximately 60 years. Starting about 1883 years BP a series of anomalous black laminations appear in the stalagmite and continue, with short interruptions, until a return to normal deposition at approximately 49 years BP. Petrographic investigations reveal that the section of the stalagmite that contains the black laminations also features intense dissolutional unconformities that are predominately composed of detrital material. Both the detrital material and dissolutional unconformities, likely resulted from intense landscape modifications by the pre-Columbian Native American and European societies inhabiting the region during the time.
Impact of elevated dissolved CO_2 on aquifer water quality
(University of Alabama Libraries, 2015) Pugh, John David; Donahoe, Rona Jean; University of Alabama Tuscaloosa
Carbon capture and storage (CCS), specifically by means of geologic sequestration (GS), is a developing technology to reduce CO2 emissions to the atmosphere. This technology involves separating CO2 from flue gas and transporting the CO2 to underground storage locations that are isolated from the atmosphere. These storage locations are typically permeable and porous geologic formations that are not useful for any other purpose, such as drinking water. Geologic carbon sequestration operated at full-scale will require extensive performance monitoring, including potable groundwater monitoring. However, researchers and regulators do not fully understand what impact elevated CO2 levels would have on groundwater quality in the event that CO2 should leak into an overlying aquifer. The focus of the current study was to thoroughly characterize the properties of a typical Gulf Coast potable aquifer for purposes of performing a controlled CO2 release experiment and to construct coupled geochemical and transport models capable of predicting impacts from CO2 migration into a drinking water aquifer. The aquifer is a methanogenic environment composed primarily of quartz and feldspars, with minor or trace amounts of pyrite, mica, illite, smectite, and kaolinite. The formation water is dominantly Na-HCO3, consistent with the theory and PHREEQC modeling results that suggest aquifer freshening and ion exchange have played dominant roles in determining the present-day dissolved major ion composition. This study also presents the design and implementation of a closed loop pumping and injection system designed to simulate CO2 leakage into a test site aquifer. Process monitoring results indicated that the test was performed with minimal variation in key process parameters, including temperature, pressure and injectate pH. In situ instrumentation deployed in monitoring wells allowed continuous readings of groundwater pH and conductivity, which were critical parameters for evaluating the aquifer response to carbonation and acidification. Successful modeling simulation of the pH response using results from the aquifer testing program suggested that the test was implemented and monitored appropriately and that that future data interpretations and modeling of the field experiment were not compromised by test design. Test results showed that no constituent was mobilized in excess of US EPA maximum contaminant levels, but that many constituents (primarily major and minor cations) were released in a pulse-like response at levels above their baseline concentrations. Dissolution of trace carbonate and pyrite in the aquifer are hypothesized to have triggered cation exchange reactions, a dominant geochemical process affecting major and minor cation behavior in the aquifer. Overall, the test has shown that the migration of carbon dioxide into a drinking water aquifer can mobilize ions into solution, but at levels that may not exceed EPA MCLs under the field conditions tested for this specific system. Data presented here are potentially applicable to assessments across the Gulf Coast, where the potential for deep geologic carbon sequestration and continued reliance upon groundwater resources are high.
Investigating the presence and distribution of organic components in bacterial magnetite
(University of Alabama Libraries, 2013) Spry, Jacob; Perez-Huerta, Alberto; University of Alabama Tuscaloosa
The formation of magnetites within magnetosomes is subjected to highly controlled biomineralization processes by bacteria. Similar biominerals have been observed to contain occluded ("intra-crystalline") organics, revealing significant information about such processes. The size of magnetite particles produced by bacteria (< 100 nm) and limitations in analytical instrumentation have hindered a better understanding of whether organics are located within these nanoparticles. In this study, bright field TEM images, STEM images, and EDS chemical data have been collected for magnetite particles produced by Magnetospirillum gryphiswaldense in order to investigate the potential presence and distribution of organic components. Results reveal low atomic number features in STEM images, suggesting presence of an organic matrix near the edges of nanoparticles. Additionally, STEM-EDS analysis indicates presence of phosphorous within the magnetosome nanoparticles. The mean P/Fe ratio for the outer half of the magnetsome nanoparticles was significantly higher than the mean ratio for the inner "core", suggesting that phosphorus is present with greater magnitude in the "rim" in a co-location with STEM features. Phosphorus is not accounted for in any known mineral constituent of the samples and it is a vital organic element, present in certain types of lipids, which have been associated to the formation of magnetosomes. Overall results contribute to a better knowledge of these highly controlled biomagnetite particles, with significant implications for the recognition of biomarkers and their potential applications in nanotechnology and medicine.
Jurassic limestone-marl sequences in northern spain: detecting diagenetic signals using rare earth and trace elements
(University of Alabama Libraries, 2012) Hollon, Brittany Elise; Perez-Huerta, Alberto; University of Alabama Tuscaloosa
Mesozoic rhythmically bedded limestone and marl sequences have been traditionally interpreted to be the result of eustatic sea-level changes related to Milankovitch cycles. An alternative interpretation supports the idea that these calcareous alternations are a product of diagenetic bedding. Stratigraphic analysis is typically used to determine the extent of diagenesis and detect any primary depositional signal in these limestone-marl rhythmites. Rare earth and trace element geochemistry is an overlooked method to distinguish the presence of a primary signal from a diagenetic one. The main objective of this study was to test the validity of using rare earth and trace elements as a method for determining diagenesis in calcareous rhythmites that are part of the Rodiles Formation (Pliensbachian, Lower Jurassic) from coastal outcrops in NW Spain. Data from the application of this geochemical approach, in conjunction with stratigraphic analysis, provides insight into the distribution of elements that are facies-controlled, chemically-controlled, and elements that are independent of both. Results presented here for the use of rare earth elements as a test for a primary signal are inconclusive. Problems with using rare earth elements in this study include the possibility of unrealized REE mobility and signal interference from strontium, which many rare earth elements commonly substitute for. Thorium and strontium presented primary signals that are independent of facies and diagenesis. Of the two, thorium is the best element for use in the detection of a primary, externally controlled signal. Using thorium as a geochemical proxy, it may be concluded that despite diagenesis, diagenetic bedding is not the mechanism behind the formation of these carbonate rhythmites. Therefore, it can be concluded that the Rodiles Formation is the result of eustatic sea-level changes. Furthermore, thorium could be an ideal element for chemostratigraphy of Jurassic and Cretaceous deposits within the same paleogeographic setting as the Rodiles Formation.
Mineralogy and seasonal growth of South Pacific mussel valves
(University of Alabama Libraries, 2010) Jones, Christie Ann; Andrus, C. Fred T.; University of Alabama Tuscaloosa
Choromytilus chorus and Aulacomya ater are among the most common mussel species in the South Pacific. However, little sclerochronological analysis has been conducted on them, even though they are found in both archaeological sites and sub-fossil deposits and could potentially be useful paleoclimate proxies. One valve from each species was analyzed via x-ray diffraction (XRD) and Raman spectroscopy to determine the shell's mineralogy. C. chorus is mostly calcite with aragonite in some zones, while A. ater is mostly aragonite with less calcite. There are abrupt and continuous boundaries between the two calcite layers and across the aragonite-calcite interface of C. chorus. All of the boundaries in C. chorus can be seen in cross section under reflected or transmitted light along the longest growth axis. The boundaries between mineralogical and structural variations in A. ater are not as visually distinct, and thus may render the species problematic for oxygen isotope analysis. Comparison of C. chorus oxygen isotope profiles to regional temperature records and local water δ18O suggest the sampled shells' lifespan was between one and two years of age. Analyses of the oxygen isotope profiles indicate nearly continuous shell growth throughout the first year of life, with a marked decrease or periods of cessation in shell growth in the second year in the larger specimens analyzed. This growth pattern may make the valves useful as proxies for at least one year of paleoclimatic/paleoenvironmental data. Three out of the four specimens of C. chorus analyzed for oxygen isotopes display a prominent growth break on the outer surface of their valves and each appear roughly contemporaneous. Oxygen isotope analysis indicates that the prominent growth breaks in each of the three valves were formed just before the peak SST of January of 2006 occurred. Qualitative seasonal variations are recorded in the δ18O profiles of the four shells, and median annual δ18O values are in general agreement between individuals. However, the full range of the winter to summer seasonal shift in SST was not recorded by all C. chorus valves. Therefore, caution should be exercised when utilizing C. chorus valves to interpret changes in seasonality.

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Browsing Theses and Dissertations - Department of Geological Sciences by Author "Andrus, C. Fred T."

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