Quaternary magnetic studies have provided the conceptual framework to bridge magnetic studies into ancient systems. In cases where environmental materials have been subjected to diagenetic alteration two questions come to mind: 1) What part of the magnetic signal is preserved in the rocks; and 2) can the preserved signal be used to infer/identify magnetic patterns that are characteristic of the depositional, post-depositional, and/or diagenetic environment. Analyses of multi-parameter magnetic experiments conducted on upper Mississippian and lower Pennsylvanian continental successions reveal that distinct depositional, pedogenic, and diagenetic magnetic patterns can be separated and identified. Evidence for a primary depositional signal in several of the upper Mississippian lithofacies is identified by a detrital remanence component attributed to source-area-derived magnetite/titanomagnetite. Red and gray vertisols preserve a Mississippian pedogenic signal characterized by magnetic enrichment, depletion, and amalgamation patterns that are associated with the removal and transport of Fe-rich clays as well as vertical mixing by shrink-swell mechanisms. These well-developed vertisols are interpreted to reflect significant hiatuses in sedimentation associated with prolonged exposure on interfluve/floodplain surfaces that may correlative with incised valleys (lowstand surface of erosion). Similarly, in lower Pennsylvanian quartz arenite facies, early siderite cementation zones as well as conglomerate lags with distinctive magnetic characteristics are thought to reflect periods of prolonged exposure and to define unconformities within compound valley fills. / Master of Science

<p> Lower Cretaceous Mannville Group sandstones of Alberta were deposited in non-marine and marginal environments. A shallow sea transgressed several times over the study area and left evidence of tidal action. The proportion of rock fragments increases from Lower Mannville to Upper Mannville sandstones due to the uplifting of strata to the west. </p> <p> Observed petrographic and SEM textures indicate that authigenic pyrite, quartz and calcite cements were precipitated in that order followed by the dissolution of carbonate material and feldspar grains with the simultaneous precipitation of kaolinite and quartz. The secondary (or dissolution) porosity is the result of an influx of acidic pore waters. This secondary porosity is best developed in the Ellerslie Sandstone because its remnant intergranular porosity and permeability are superior to the porosity and permeability in the overlying sandstones. The present degree of diagenesis in the sandstones is largely controlled by the permeability of the rock. </p> / Thesis / Bachelor of Science (BSc)

Carbonate precipitates in biofilm were investigated from hot springs near Viterbo, Italy; Salt Pond, San Salvador; and Fowl Cay Reef, Abaco, Bahamas. Features shared by hot springs and salt ponds are supersaturation with CaCO3, abundant Spirulina, and clustered acicular aragonite crystals termed “fuzzy dumbbells.” TEM and FESEM microscopy show fuzzy dumbbells contain a core of amorphous organic matter and subhedral CaCO3 microcrystals arranged in linear fabrics. Micron- to millimeter-scale microenvironments are identified by localized dissolution, the occurrence of gothic calcite inter-grown with organic filaments, and the presence of calcite in biofilm where aragonite is chemically favored. Spherical CaCO3 precipitates in reefs were anticipated, but not encountered in TEM sections of reef biofilm. In conclusion, biofilm creates the microenvironment and organic matter provides substrate for fuzzy dumbbell precipitation. TEM is a novel technique for studying the relationship between organic matter and CaCO3 precipitation, and has potential medical, industrial, and academic applications.

No description available.

No description available.

No description available.

The primary objective of this study of four cores from the Lower Mississippian Price Formation was to determine the dominant controls on diagenesis and porosity as the Price sandstones are potential reservoirs for coalbed methane. Facies analyses of the cores, in combination with outcrop data from previous studies, lead to the conclusions that these rocks represent distal bar and prodelta, wave-reworked distributary mouth bar, and upper delta plain deposits. Petrographically, the sandstones typically are fine-grained lithic arenites that were derived from a low-grade metamorphic provenance with lesser sedimentary and minor plutonic influences. Diagenetically, most sandstones are dominated by siliceous cements and replacements, although some samples from the marine zones are dominated by carbonate cements. No original porosity is preserved and secondary porosity of any type is rare, but where present is usually the result of dissolution of carbonate phases. The age of the rocks and the maximum temperature of diagenesis (found to be >150°C throughout these sections) were strongly influential in diagenesis. The composition of the sediments was also very important in compaction, cementation, replacement, and dissolution. The variation in detrital mineralogy is limited, and this, in combination with temperature and age, results in diagenesis that is relatively homogeneous throughout these sections of the Price Formation. Finally, as porosity in the sandstones is extremely low, it seems highly unlikely that the Price Formation sandstones in this area could be economic producers of methane. / M.S.

The diagenesis of rocks during burial occurs in response to changing temperature, pressure, and solution composition. Due to their geologic abundance, high surface area, and reactivity clay minerals are important participants in the diagenesis of clastic rocks. The kinetic and thermodynamic stability of clays is in general poorly understood. This dissertation research measured the rate of transformation of kaolinite to muscovite/illite and developed a method to estimate clay mineral thermodynamic stability. Clastic rock diagenesis is controlled by the rates of silicate mineral growth and transformation. Marine mudstones commonly contain large proportions of kaolinite which reacts during diagenesis to form muscovite/illite and/or chlorite. Batch reactor experiments were used to measure the reaction rate of 1.5 kaolinite + K⁺ = muscovite + H⁺ + 1.5 H₂O using the initial rate method and a fitted form of the integrated rate equation. Experiments were performed at temperatures ranging from 250° to 307°C with solutions of 0.5 - 2.0 m KCl. These results can then be extrapolated to diagenetic temperatures using the Arrhenius equation. ln addition, a technique was developed to estimate the ΔG_f0 and ∆H_f0 of silicate minerals. Silicate minerals have been shown to act as a combination of basic polyhedral units (Hazen 1985 and 1988). This work showed that their thermodynamic properties could be modeled as the sum of polyhedral contributions. A multiple linear regression model was used to find the contribution of the oxide and hydroxide components (gᵢ and hᵢ) to the ΔG_f0 and ∆H_f0 of a selected group of aluminosilicate minerals at 298 K. The ΔG_f0 and ∆H_f0 of other silicate minerals can be estimated from a weighted sum of the contribution of each oxide and hydroxide component (gᵢ and hᵢ). These results can be also used to estimate the ΔG_f0 of silicate minerals at higher temperatures (up to =600 K) by using the equation, gᵢ(T)= hᵢ(298) - T((hᵢ(298)-gᵢ(298))/298) / Ph. D.

Yes / Archaeological burial contexts may include a variety of white substances, but few analyses have been published. This study reports on the physico‐chemical characterization of such residues from seven archaeological sites. It is often assumed that white materials from burial contexts are lime. Our findings demonstrate that they can be gypsum, calcite (chalk), aragonite, brushite, degraded metal, natural (gum) resins or synthetic polymer–based products. These may be present as the result of diagenetic processes, funerary practices or modern contamination. This paper provides an analytical approach for the holistic investigation of white materials encountered in burial contexts. / Investments for the future’ (IdEx Bordeaux ANR‐10‐IDEX‐03‐02). Grant Number: ANR‐10‐IDEX‐03‐02; Collaborative Projects of the France‐Stanford Center for Interdisciplinary Studies; Collaborative Projects of the France–Stanford Center; French State. Grant Number: IdEx Bordeaux ANR‐10‐IDEX‐03‐02; Northern Archaeological Associates Ltd; PACEA; Wessex Archaeology; INRAP; Mersea Island Museum Trust; Vatican's Pontifical Commission for Sacred Archaeology; University of Reading; IRAMAT-CRP2A; University of Bradford; CEREGE

Reactive Transport Models (RTMs) provide quantitative tools to analyze the interaction between transport and biogeochemical processes in subsurface environments such as aquatic sediments and groundwater flow. A tremendous amount of research has shown the role and impact of scaling behavior of the reactive systems which stems from geologic heterogeneity. Depending on the kinetics of the reactions, different types of formulations have been proposed to describe reactions in RTMs. We introduce a novel quantitative criteria on the range of validity of local equilibrium assumption (LEA) in aquatic sediments with irreversible heterogeneous sorption reactions. Then we present a one-dimensional (1-D) early diagenetic module, MATSEDLAB, developed in MATLAB. The module provides templates for representing the reaction network, boundary conditions and transport regime, which the user can modify to fit the particular early diagenetic model configuration of interest. We describe the theoretical background of the model and introduce the MATLAB pdepe solver, followed by calibration and validation of the model by a number of theoretical and empirical applications. Finally, we introduce a new pore-scale model using lattice Boltzmann (LB) approach. It uses an iterative scheme for the chemical transport-reaction part and recent advances in the development of optimal advection-diffusion solvers within the lattice Boltzmann method framework. We present results for the dissolution and precipitation of a porous medium under different dynamical conditions, varying reaction rates and the ratio of advective to diffusive transport (Pe, Peclet number) for linear reactions. The final set of calculations considers sorption reactions on a heterogeneous porous medium. We use our model to investigate the effect of heterogeneity on the pore-scale distribution of sorption sites and the competition between three different sorption reactions.