Petrographic and SEM study of flu vial-deltaic sections of the Woodbine Group in the East Texas Basin indicates that authigenic mineral suites are controlled, in part, by the presence of organic-rich matrix. During early, precompaction diagenesis, organic matter supplied the metabolic fuel required by sulfate-reducing bacteria to reduce sulfate in depositional waters ultimately to pyrite. With burial the sulfate supply was ultimately exhausted, and bicarbonate activity thereafter controlled the precipitation of siderite and Fe-calcite. Matrix material supplied the components and reaction sites for the most import ant porosity-occluding reaction: kaolinite --> Fe,M g chlorite. Matrix physically inhibited the growth of quartz overgrowths, yet, through compaction and as a product of the above reaction, provided a supply of silica for quartz cementation. Dissolution of salt dome cap rock has played a minor role in the cementation of the Woodbine in the East Texas Basin. Pore-filling calcite, barite, and pyrite were observed in the Woodbine where the Woodbine is in direct hydraulic communication with salt dome cap rock. In the deep, central portion of the basin Na-Cl brine resulting from salt-dome dissolution is evolving toward a Na-Ca(Mg)-Cl brine. The evolution of the brine chemistry may be the result of cation exchange on clay minerals, albitization of plagioclase feldspars, or the dissolution of magnesium - and calcium- chloride-rich phases. The present study could not confirm any of these reactions. WATEQF was used to calculate mineral-saturation states in Woodbine waters. Program output appears to represent accurately in situ individual mineral-saturation states at measured pH, as confirmed by petrographic and SEM identification of authigenic minerals. Relative stability between mineral pairs can be tested with thermodynamically-derived activity diagrams for the mineral pairs.

Selenium (Se) is a micronutrient, yet elevated Se can be toxic to aquatic organisms. The range of Se concentrations within which Se uptake goes from insufficient to toxic is very narrow. It is thus important to understand the Se biogeochemical cycle in aquatic systems. In this thesis, the study focuses on changes in Se speciation during uptake by green algae. An optimized method was adopted to quantify and speciate Se in water using flow-injection atomic fluorescence spectroscopy coupled with high-pressure liquid chromatography. Details on the method are given here. For the uptake experiments, the uptakes of four Se species (selenite (Se-IV), selenate (Se-VI), selenocystine (Se-Cys) and selenomethionine (Se-Met)) by the green algae Chlamydomonas reinhardtii were compared. This thesis reports that the algae take up higher amounts of organic Se than inorganic Se. Selenomethionine (Se-Met) had the most rapid uptake, during which Se-Cys was produced. For all experiments, Se-IV was produced and found to sorb onto the algae cells, revealing that Se-IV is an important intermediate compound. Mass balance calculations revealed that more than 90% of Se was lost during uptake, probably to the atmosphere. This study also investigated the release of Se during algae decay to simulate the fate of Se during early-diagenesis. Selenium-rich algae cells were mixed with estuarine sediments at the sediment–water interface in a series of column incubations experiments. During the 7-week incubations, Se speciation was measured at the water–sediment interface and in pore water samples. We found that all the Se released to the pore water was in the form of Se-Cys. Although preliminary, these results highlight the key role of organic-Se species in the biogeochemical cycle of Se in the aquatic environment.

Provenance in the lower Belt-Purcell Supergroup is constrained based on geochemical systematics and chemical monazite ages of argillites and sandstones. Rare earth element (REE), Cr-Ni, and Th/Sc-Sc systematics is equivalent for both facies and consistent with a dominantly post-Archean source area. Detrital monazite chemical ages restrict major provenance for the Appekunny and Grinnell sandstones and argillites to Paleoproterozoic terranes at ~1800-1600 Ma, minor contributions at ~1600-1500 Ma, and marginal contributions from Archean terranes at ~2600, likely in Laurentia. Similar detrital age spectra for monazites of argillites and sandstones of the Appekunny Formation are consistent with a common provenance for the two facies.</p> <p>The Belt-Purcell sequence records three major diagenetic stages displayed in argillites and sandstones: (1) K-addition and rare earth element post-Archean upper continental crust (PA-UCC)-like pattern; (2) a stage characterized by heavy REE enrichment relative to light REE and HFSE fractionation, and U and Ce mobility; and (3) local dolomitization with REE and high field strenght elements (HFSE) mobility. REE and HFSE mobility are interpreted as the result of oxidized alkaline brines developed by dissolution of evaporites. Monazites from the Appekunny and Grinnell formations differ compositionally and texturally in two groups. Rounded or inclusions with ages >~1400 Ma, interpreted as detrital, have higher Th2O, Y2O3 and lower LREE/HREE contents than euhedral individual monazite grains with chemical ages <~1400 Ma that posses opposed compositional characteristics, and viewed as diagenetic. Monazites that span <~1400 to 300 Ma could be the result of basinal brine activity during stages (2) and (3). </p> <p>Chemical index of alteration (CIA) for argillites and sandstones, corrected for a diagenetic K-addition average 73 and 66 respectively. These results, coupled with correlation of CIA with Eu/Eu*, low K/Cs ratios, and low Sr, Ca, and Na relative to PA-UCC, could be interpreted as the result of an moderate weathered provenance in a hot, wet climate being drained by a large-scale river system. Presence of minor pristine feldspars lowers the CIA values, and may signify minor contributions from proximal source with short-river transport under the arid to semi-arid climate in the depositional setting. Moderate to intense weathering of the larger provenance may be associated with elevated levels of atmospheric CO2 degassed from a mantle plume implicated in the rifting of the supercontinent Columbia at ~1500 Ma.

CLAY MINERALOGY AND DIAGENESIS OF K-BENTONITES OCCURRING IN THE DEVONIAN YILANLI FORMATION FROM NORTH WESTERN ANATOLIA (BARTIN-ZONGULDAK) &Uuml / nl&uuml / ce, &Ouml / zge M. Sc., Department of Geological Engineering Supervisor: Prof. Dr. Asuman G&uuml / nal T&uuml / rkmenoglu January 2013, 80 pages Yellowish brown and gray-green colored K-bentonite horizons revealing thicknesses up to 60 cm are exposed within the limestone-dolomitic limestone successions (Middle Devonian-Lower Carboniferous Yilanli formation) deposited on a shallow marine carbonate platform at Zonguldak and Bartin area in the western Black Sea region. In this study, bentonite samples collected from two different locations / Gavurpinari quarry and Yilanli Burnu quarry are investigated by means of optical microscopy, X-ray powder diffraction analyses (XRD), both scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis, high resolution transmission electron microscopy (HR-TEM) and inductively coupled plasma mass spectrometry (ICP-MS) in order to reveal their mineralogicalgeochemical characteristics and understand their origin and evolution. Illite is determined as the major phyllosilicate mineral in K-bentonites. Additionally, kaolinite and illite-smectite mixed-layer clay minerals are also detected in some samples. As non-clay minerals calcite, dolomite, quartz, gypsum, feldspar, pyrite and zircon are present in these K-bentonites. Crystal-chemical characteristics (K&uuml / bler index-KI, intensity ratios (Ir), illite polytypes (%2M1), (d060) of illite minerals from the two different sampling locations were investigated. Their KI values (for Yilanli Burnu sampling location varying between 0.47-0.93 (with an average of 0.71 &Delta / &deg / 2&theta / ) / for Gavurpinari quarry sampling location varying between 0.69-0.77 (with an average of 0.72 &Delta / &deg / 2&theta / )) / % of swelling component (smectite-max 5%) and crystallite thickness (N=10-20 nm) indicate that these illites were affected by high-grade diagenetic conditions. Similarly, illite polytype ratios (%2M1/(2M1+1Md)) range between 20-50% (with an average of 36%) for the Yilanli Burnu quarry samples, whereas, these ratios are between 25-45% (with an average of 37%) for the Gavurpinari limestone quarry samples. Illite polytpe data also supports a high-grade diagenetic origin possibility of K-bentonites. Illite d060 values ranges between 1.491-1.503 &Aring / , (with an average of 1.499 &Aring / ) which reflect the octahedral Mg+Fe compositions are varying between 0.27-0.51 and thus approach the ideal muscovite-phengite values close to dioctahedral muscovite composition. Based on the data obtained from this study, volcanic ash was firstly transformed into a smectitic I/S mineral in early stages of sedimentation and burial diagenesis. This initial smectite was then be transformed into a highly illitic I/S, and finally illite by diffusion of elements into and out of the bed, during Devonian. Mineralogical-petrographical data points out that these K-bentonites evolved in a high-grade diagenetic environment (approximately 100-150 &deg / C) from the products of volcanic eruptions having yet unknown source and distance during Middle-Late Devonian time.

The present study contributes to a better understanding of early dissolution mechanisms for syngenetic karst development and provides constraints on the timing of formation of the Rattlesnake Canyon paleokarst system in the Guadalupe Mountains, New Mexico, U.S.A. Paleozoic paleokarsts commonly undergo burial and collapse, which reduces significantly the preservation of early fracture networks and geometries of dissolution. Rattlesnake Canyon constitutes a magnificent scenario for the study of global controls on Upper Permian karsting since early fracture networks and dissolution geometries are extremely well preserved and lack major tectonic deformation. This thesis sheds light on the scientific knowledge of paleokarsts and can be of interest to the oil industry since paleokarsts are common targets of exploration. As the evolution of the reservoir properties is often diagenetically controlled, the diagenetic study was particularly useful in determining the degree of sealing following hydrocarbon charge. 1) Aims This thesis seeks to improve our understanding of the relationship between early syndepositional fracture networks that are typically found in platform margins and syngenetic karst development. The thesis includes multidisciplinary carbonate studies aimed at understanding the multiscale paleokarst heterogeneity by means of (i) the development of a conceptual model for the karst evolution, (ii) the construction of a 3D paleokarst model, (iii) the determination of the diagenetic history of the paleokarst system and (iv) the paleokarst reservoir characterization. 2) Thesis Structure The thesis consists of 9 chapters and 2 appendices. Chapter 1 sets out the rationale for this thesis. Chapter 2 provides an introduction to the most basic aspects of karst science and to the hydrogeological model of Carbonate Island as well as an overview of the state-of-the-art paleokarst studies. The geological setting and the study area is detailed in Chapter 3. The results of the thesis are contained in Chapters 4 to 7. Because of the multidisciplinary nature of this thesis, each of these chapters is dedicated to one discipline. Chapter 4 focuses on the analysis of field data to obtain a conceptual model for the evolution of the paleokarst system. Chapter 5 discusses the methodology to implement the 3D paleokarst model and provides data to assess the dimensions of the system in subsurface. Chapter 6 focuses on the diagenetic stages that affected and controlled the karst development. Finally, Chapter 6 offers a paleokarst reservoir characterization. A comprehensive approach and discussion of the results obtained in each of these chapters are included in Chapter 8. General and specific conclusions are presented in Chapter 9. Appendix One contains a representative image compendium of the petrographic features observed in the paleokarst filling sequence of Fault N. Appendix Two sets out the raw data from the geochemical analysis. The paleokarst analysis using different disciplines provides a complete characterization of paleokarst heterogeneity and enables us to elucidate the controls of the system. / Aquesta tesi contribueix al coneixement dels mecanismes de dissolució que controlen el desenvolupament dels karsts singenètics i proporciona les claus per establir la seqüència de formació del sistema paleokàrstic de Rattlesnake Canyon, Guadalupe Mountains, New Mexico, EEUU. Degut al potencial com a reservori que tenen aquest tipus de sistemes, aquesta tesi no solament concorre al coneixement científic en relació als paleokarsts sinó que també pot ésser d’interès per la indústria del petroli. a) Objectius Aquest estudi cerca contribuir en el coneixement de les relacions entre les falles i fractures sindeposicionals i les estructures de dissolució a Rattlesnake Canyon, així com en el coneixement dels controls globals per la formació de karsts singenètics costaners. La tesi inclou estudis multidisciplinaris dirigits a la determinació de la heterogeneïtat multi-escala del paleokarst de Rattlesnake Canyon mitjançant els següents objectius concrets: a) l’acompliment d’un model conceptual d’evolució del sistema kàrstic, b) la construcció d’un model 3D del sistema kàrstic, c) la determinació de la història diagenètica del paleokarst i d) la caracterització de les propietats de reservori del sistema.

Regional study of the Silurian Amabel and Guelph (including the Eramosa Member) formations in the subsurface on the Bruce Peninsula provides petrographic details of these pervasively dolomitized rocks, defines lithofacies changes within each formation, and demonstrates the use of ground-penetrating radar as a tool for shallow subsurface stratigraphic mapping. Detailed stratigraphic logging of core provides insight on the complex depositional history of the pervasively dolomitized Amabel and Guelph formations by highlighting lateral facies changes that are not readily observable in outcrop. <br /><br /> The Lions Head and Colpoy Bay members of the Amabel Formation are continuous in core across the Bruce Peninsula. These members contain characteristic dark grey mottles which are the result of increased porous zones and pyrite, and/or concentrations of undifferentiated organics. Chert nodules and the abundance of silica is most abundant in the upper Lions Head Member where silica-replaced fossils are recognized within the surrounding dolomite. Typical Wiarton Member crinoidal lithofacies from the upper Amabel Formation are more common in the southern half of the Peninsula. The Eramosa Member is more laterally continuous on the Bruce Peninsula than previously assumed. Although there is a lack of bituminous argillaceous Eramosa lithofacies within core, the laminated Eramosa Member is thick near Wiarton which suggests that a large restricted less-oxygenated area existed in that vicinity during the Silurian. Thick accumulations of tan-brown fossiliferous undifferentiated Guelph Formation dolostones occur at both the northern and southern ends of the Peninsula. <br /><br /> Petrographic analyses reveal that the Amabel and Guelph formations are dolomitized with no precursor limestone observed. Four types of dolomite were observed within these formations and differentiated based on crystal size. These dolomites are characterized by a uniform dull red luminescence, and range from inclusion-rich anhedral very finely (< 5 µm) crystalline dolomite to clearer euhedral coarsely (> 250 µm) crystalline dolomite. Petrographic analyses also revealed secondary minerals such as pyrite, calcite (and dedolomite), silica, sphalerite, fluorite, and glauconite. <br /><br /> Ground-penetrating radar surveys provided high-resolution data, which combined with detailed geologic observations of accessible quarry outcrops and borehole logs, support the conclusion that GPR is a useful tool for locating karstic features, vuggy porosity, and lateral and vertical facies changes in carbonate rocks. Radar profiles may have important implications for the aggregate and building-stone industries as a tool to locate carbonate units of exploration interest or to avoid zones with high impurities.

Regional study of the Silurian Amabel and Guelph (including the Eramosa Member) formations in the subsurface on the Bruce Peninsula provides petrographic details of these pervasively dolomitized rocks, defines lithofacies changes within each formation, and demonstrates the use of ground-penetrating radar as a tool for shallow subsurface stratigraphic mapping. Detailed stratigraphic logging of core provides insight on the complex depositional history of the pervasively dolomitized Amabel and Guelph formations by highlighting lateral facies changes that are not readily observable in outcrop. <br /><br /> The Lions Head and Colpoy Bay members of the Amabel Formation are continuous in core across the Bruce Peninsula. These members contain characteristic dark grey mottles which are the result of increased porous zones and pyrite, and/or concentrations of undifferentiated organics. Chert nodules and the abundance of silica is most abundant in the upper Lions Head Member where silica-replaced fossils are recognized within the surrounding dolomite. Typical Wiarton Member crinoidal lithofacies from the upper Amabel Formation are more common in the southern half of the Peninsula. The Eramosa Member is more laterally continuous on the Bruce Peninsula than previously assumed. Although there is a lack of bituminous argillaceous Eramosa lithofacies within core, the laminated Eramosa Member is thick near Wiarton which suggests that a large restricted less-oxygenated area existed in that vicinity during the Silurian. Thick accumulations of tan-brown fossiliferous undifferentiated Guelph Formation dolostones occur at both the northern and southern ends of the Peninsula. <br /><br /> Petrographic analyses reveal that the Amabel and Guelph formations are dolomitized with no precursor limestone observed. Four types of dolomite were observed within these formations and differentiated based on crystal size. These dolomites are characterized by a uniform dull red luminescence, and range from inclusion-rich anhedral very finely (< 5 µm) crystalline dolomite to clearer euhedral coarsely (> 250 µm) crystalline dolomite. Petrographic analyses also revealed secondary minerals such as pyrite, calcite (and dedolomite), silica, sphalerite, fluorite, and glauconite. <br /><br /> Ground-penetrating radar surveys provided high-resolution data, which combined with detailed geologic observations of accessible quarry outcrops and borehole logs, support the conclusion that GPR is a useful tool for locating karstic features, vuggy porosity, and lateral and vertical facies changes in carbonate rocks. Radar profiles may have important implications for the aggregate and building-stone industries as a tool to locate carbonate units of exploration interest or to avoid zones with high impurities.

Provenance in the lower Belt-Purcell Supergroup is constrained based on geochemical systematics and chemical monazite ages of argillites and sandstones. Rare earth element (REE), Cr-Ni, and Th/Sc-Sc systematics is equivalent for both facies and consistent with a dominantly post-Archean source area. Detrital monazite chemical ages restrict major provenance for the Appekunny and Grinnell sandstones and argillites to Paleoproterozoic terranes at ~1800-1600 Ma, minor contributions at ~1600-1500 Ma, and marginal contributions from Archean terranes at ~2600, likely in Laurentia. Similar detrital age spectra for monazites of argillites and sandstones of the Appekunny Formation are consistent with a common provenance for the two facies.</p> <p>The Belt-Purcell sequence records three major diagenetic stages displayed in argillites and sandstones: (1) K-addition and rare earth element post-Archean upper continental crust (PA-UCC)-like pattern; (2) a stage characterized by heavy REE enrichment relative to light REE and HFSE fractionation, and U and Ce mobility; and (3) local dolomitization with REE and high field strenght elements (HFSE) mobility. REE and HFSE mobility are interpreted as the result of oxidized alkaline brines developed by dissolution of evaporites. Monazites from the Appekunny and Grinnell formations differ compositionally and texturally in two groups. Rounded or inclusions with ages >~1400 Ma, interpreted as detrital, have higher Th2O, Y2O3 and lower LREE/HREE contents than euhedral individual monazite grains with chemical ages <~1400 Ma that posses opposed compositional characteristics, and viewed as diagenetic. Monazites that span <~1400 to 300 Ma could be the result of basinal brine activity during stages (2) and (3). </p> <p>Chemical index of alteration (CIA) for argillites and sandstones, corrected for a diagenetic K-addition average 73 and 66 respectively. These results, coupled with correlation of CIA with Eu/Eu*, low K/Cs ratios, and low Sr, Ca, and Na relative to PA-UCC, could be interpreted as the result of an moderate weathered provenance in a hot, wet climate being drained by a large-scale river system. Presence of minor pristine feldspars lowers the CIA values, and may signify minor contributions from proximal source with short-river transport under the arid to semi-arid climate in the depositional setting. Moderate to intense weathering of the larger provenance may be associated with elevated levels of atmospheric CO2 degassed from a mantle plume implicated in the rifting of the supercontinent Columbia at ~1500 Ma.

In this study we investigated the effect of tidal forcing on iron cycling in intertidal saltmarsh sediments (ISS). Historically, sulfate has been considered the major terminal electron acceptor involved in organic carbon remineralization in ISS. Although sulfate is a more efficient electron acceptor for organic matter degradation in anoxic ISS, irons rapid recycling at the surface of ISS may allow it also to be an important electron acceptor for the remineralization of organic matter. Bioturbation, macrophyte-mediated irrigation, and semidiurnal tidal forcing in this environment may increase the abundance of O2 in the top few cm of the sediment, rapidly oxidizing iron and inhibiting sulfate reduction. To determine if the cycling of iron may be faster than previously thought in these sediments, we combined sediment core chemical profiles of reduced and oxidized insoluble iron with in-situ electrochemical profiles of O2, Fe2+, soluble organic-Fe3+ complexes, FeS(aq), and hydrogen sulfide in the top few centimeters of unvegetated creek bank sediments over several tidal cycles. We also installed monitoring wells in the tidal creek bank to quantify tidal forcing and to investigate tidal direction in the sediments. We built a transient, reactive transport model to simulate measured geochemical profiles and test our understanding of diagenetic processes. Additional tests were run on the model to investigate the importance of bioirrigation compared to tidally-induced porewater advection. Results indicate that tidal action is a more dominant transport process. It affects the cycling of iron in ISS by flushing reduced species out of the sediment during flood tide, and allowing oxygen and oxidized species deeper into the sediment during ebb tide. As a result, amorphous iron oxides are replenished at the sediment surface, and microbial iron reduction may be the main respiratory process in the first tens of centimeters of creek bank saltmarsh sediments subjected to intense tidal forcing.

Seagrass productivity is largely limited by nutrient and light availability. However, increasing evidence suggests that sedimentary geochemical processes may play an essential role in seagrass productivity/health. Much of this work has been largely phenomenalistic and has not clearly identified the spatio-temporal behavior of the major geochemical parameters involved in diagenesis of seagrass sediments. In this study, a much broader range of both dissolved and solid phase chemical parameters in eelgrass vegetated sediments was investigated. Parallel measurements were made on adjacent unvegetated sediments (<10 m) to more clearly refine the specific influences of seagrass (Zostera marina) on chemical gradients in associated sediments. Previous studies have pointed strongly toward diurnal ??ventilation?? of sediments vegetated with seagrass by the exudation of photosynthetically produced oxygen. However, strong lateral variability of sediment geochemical parameters among and between seagrass vegetated and unvegetated sediments made the observation of diurnal effects sufficiently difficult. Changes resulting from temporal variability were difficult to discern within the spatial variability. A critical question that is often not dealt with in the study of the early diagenesis of sediments is what spatial and temporal sampling intervals are required to account for the dominant source of variability. The auto-covariance function (ACF) was used to determine the optimum scaling length for sample intervals (?x) of ?H2S and Fe2+. Characteristic scale lengths obtained for sediments from seagrass environments are not significantly different from those observed for unvegetated sediments and averaged 13.7?? 2.2 mm. Lateral variations in our scales analyses showed that scale length approximated our sampling interval and that lateral sampling intervals were smaller than the vertical sampling intervals. Our results indicate that macrofauna dwelling in the sediment, the seagrass root/rhizomes, and aggregations of bacteria, microalgae, and meiofauna may be responsible for the vertical and lateral variability. Model calibrations and sensitivity analyses from a sediment-seagrass diagenetic model revealed that changes in physical parameters of the sediments (irrigation, advection, and porosity, for example) had the greatest effect on organic carbon and total dissolved sulfides. This study revealed that sedimentary geochemical parameters that are both vertically and laterally heterogeneous may also affect seagrass productivity.