Thesis (M.S.)--Mississippi State University. Department of Geosciences. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 174-185). Also available in electronic version. Access restricted to campus users.

The Hickory Sandstone Member of the Riley Formation is dominantly quartz sandstone up to 167 m thick which crops out in the Llano Uplift region of central Texas and dips away in all directions. It lies unconformably upon the irregular surface of the Precambrian Texas craton. The association of isopach thicks and thins over cratonic lows and highs demonstrates topographic control of Hickory deposition. Regional subsurface studies delineate the extent of the overlying Cap Mountain Limestone. Beyond the limits of the Cap Mountain, the Hickory grades into the Lion Mountain Sandstone laterally and vertically so that correlations are difficult. The six lithofacies of the Hickory Sandstone were deposited as nonbarred tidally-influenced or estuarine-related equivalents to deposits of Holocene environments. Outer estuarine tidal channel-shoal deposits display abundant channel fills of large-scale foresets, parallel bedded sandstone, and minor siltstone. Trilobite trackways (Cruziana) and resting traces (Rusophycus) occur in these deposits, associated with U-shape burrows (Diplocraterion and Corophioides). Deposits of open coast sandy tidal flats display upward-fining character, medium-to large-scale festoon crossbedding, abundant small-scale ripple bedforms of all types, and mudcracks. These deposits include the U-shape burrows, Corophiodes, and the trackway, Climactichnites. Deposits of inner estuarine tidal channels and tidal flats display upward-fining character, wavy-lenticular bedding, bimodal paleocurrent patterns, and the resting trace, Pelecypodichnus. All of these deposits prograded as a unit until sea level rise shut off sediment supply. Progradation of tidal channel and shoal sediments was renewed. These deposits are festoon crossbedded hematitic sandstone with wavy-lenticular bedding and abundant fossil debris. Storm energy funneled through tidal channels deposited crossbedded sandstone onto the nearshore inlet-influenced shelf. Final Hickory deposits and initial Cap Mountain deposits were storm-dominated, burrowed and laminated calcitic shelf sands. / text

The Indian Creek subdistrict is the northernmost mineralized area in the Southeast Missouri district and is unique because ore-grade concentrations of sulfides occur within the Lamotte Sandstone. The Lamotte Sandstone-hosted Goose Creek mine is located on the northern end and the Bonneterre Dolomite-hosted Indian Creek mine on the northwestern side of a N30°E-trending, Precambrian rhyolite ridge. A saddle on the northern end of the ridge separates the Indian Creek subdistrict from another probable high along the same trend to the north. Lamotte deposition was influenced by pre-Lamotte basement topography, and local thickness ranges from 0 where it pinches out against the ridge to over 100 ft toward the basin. It is comprised of a thin, discontinuous basal cobble conglomerate overlain by a medium-grained, moderately to poorly sorted, well-rounded quanzarenite. Fourteen authigenic minerals, plus hydrocarbons cement the Lamotte Sandstone at Goose Creek in the following paragenetic sequence: dolomite - framboidal pyrite - marcasite - cuboctahedral pyrite - bravoite - bladed marcasite - pyrite - quartz dissolution - brecciation - siegenite - marcasite - dolomite - brecciation - chalcopyrite - quartz dissolution - sphalerite - galena (cuboctahedral) - quartz - galena (cubic) - dolomite - gypsum - hydrocarbon - kaolinite - illite - calcite - hydrocarbon. Primary and secondary porosity in the Lamotte vary between 1 and 20 volume percent and authigenic cements account for up to 35 volume percent of the sandstone. Quartz overgrowths are the most common cement in the Lamotte Sandstone at Goose Creek, comprising from 1 to 11 volume percent of the rock. Galena is the most abundant sulfide and commonly occurs in 1 to 3 mm blebs, averaging 3-4 volume percent. Chalcopyrite averages 0.5 volume percent, but high grade concentrations reach 8-10 volume percent locally. Sulfides in the Lamotte Sandstone in the Indian Creek subdistrict commonly occur within 40 ft of the Bonneterre-Lamotte contact, with the highest concentrations within 20 ft or less of the contact. Structure maps of the lead- and copper- bearing-zones mimic the basement topography, suggesting that the Precambrian basement was the major controlling factor on ore deposition in the Indian Creek subdistrict. Vertical tubes of sulfides, which cross-cut bedding near the Lamotte pinchout in the Goose Creek mine, suggest that the ore-bearing fluids moved through the sandstone aquifer until the pinchout forced them into the overlying Bonneterre. There the fluids were channeled through the grainstone-algal reef complex along the N30°E-trending Precambrian ridge. Limited fluid inclusion data for Bonneterre-hosted sphalerite indicate that the mineralizing fluid was a Na-Ca-Cl brine with temperatures between 105 and 120° C. / text

Bottom sediment from a 750-square-mile area offshore from the mouth of the Brazos River, Texas, has been analyzed statistically to determine the pattern and processes of sedimentation of the neritic environment and of a modern delta. The Brazos delta is characterized by topset beds of poorly sorted laminated sand, silt, and clay, foreset beds dipping at approximately 1° composed of fine sand grading downward (seaward) into clay, and poorly developed bottomset beds representing slow deposition of clay from the Brazos combined with reworking of material from a submerged Pleistocene deltaic plain. Interpretation of the sediment on the basis of its modal characteristics indicates that effective sorting by waves develops a unique uniform distribution of sediment types from the beach to a depth of 60 feet. Farther offshore from this depth exotic agents such as hurricanes and uncharted bottom currents are predominant and act to bring "obstacles" (topographic irregularities) into a marine profile of equilibrium. Maps of sediment types, mean size, inclusive standard deviation, inclusive skewness, and kurtosis precisely describe the geologic history of the surface sediments. Individual and bivariant plots of the statistical parameters are shown to be useful in determining direction to the shoreline as well as completely defining the modality of the sediment, which in effect defines the environment of deposition. Fluctuations in source area are reflected by the relation of mean size and depth. Heavy mineral distribution shows that the suite of durable minerals carried by the present Brazos River is diluting an existing widespread suite of less durable minerals characteristic of the Colorado River drainage area. Variation in clay mineral composition results from differential sedimentation and reflects source area, providing no evidence of alteration of the clay minerals during deposition by diagenesis. / text

The petrologic study of cave sediments is a new field whose history dates back only about 30 years. Most previous work has been done in Europe, with very little in North America. This is the first petrologic study of sediments of Texas caves. Sediments from the 11 Central Texas caves investigated provide information on the diagenetic sequence of authigenic calcite and collophane, and add to the knowledge of the occurrence and distribution of red clays and dolomite silts. The sediments from Fyllan Cave in Travis County place a maximum date of mid-Pleistocene on the existing Colorado River terraces. X-ray analysis of clays in sediments from three caves indicates a decline in kaolinite content, confirming a drying tendency for the last 8000 years. / text

Macroscopic transport properties of porous media depend on textural rock parameters such as porosity, grain size and grain shape distributions, surface-to-volume ratios, and spatial distributions of cement. Although porosity is routinely measured in the laboratory, direct measurements of other textural rock properties can be tedious, time-consuming, or impossible to obtain without special methods such as X-ray microtomography and scanning electron microscopy. However, by using digital three-dimensional pore-scale rock models and physics-based algorithms researchers can calculate both geometrical and transport properties of porous media. Therefore, pore-scale modeling techniques provide a unique opportunity to explore explicit relationships between pore-scale geometry and fluid and electric flow properties. The primary objective of this dissertation is to investigate at the pore-scale level the effects of grain shapes and spatial cement distribution on macroscopic rock properties for improved understanding of various petrophysical correlations. Deposition and compaction of grains having arbitrary angular shapes and various sizes is modeled using novel sedimentation and cementation pore-scale algorithms. Additionally, the algorithms implement numerical quartz precipitation to describe preferential cement growth in pore-throats, pore-bodies, or uniform layers. Subsequently, petrophysical properties such as geometrical pore-size distribution, primary drainage capillary pressure, absolute permeability, streamline-based throat size distribution, and apparent electrical formation factor are calculated for several digital rock models to evaluate petrophysical correlations. Furthermore, two geometrical approximation methods are introduced to model irreducible (connate) water saturation at the pore scale. Consolidated grain packs having comparable porosities and grain size distributions but various grain shapes indicate that realistic angular grain shape distribution gives the best agreement of petrophysical properties with experimental measurements. Cement volume and its spatial distribution significantly affect pore-space geometry and connectivity, and subsequently, macroscopic petrophysical properties of the porous media. For example, low-porosity rocks having similar grain structure but different cement spatial distribution could differ in absolute permeability by two orders of magnitude and in capillary trapped water saturation by a factor of three. For clastic rocks with porosity much higher than percolation threshold porosity, pore-scale modeling results confirm that surface-to-volume ratio and porosity provide sufficient rock-structure character to describe absolute permeability correlations. In comparison to surface-to-volume ratio, capillary trapped (irreducible) water saturation exhibits better correlation with absolute permeability due to weak pore space connectivity in low-porosity samples near the percolation threshold. Furthermore, in grain packs with fine laminations and permeability anisotropy, pore-scale analysis reveals anisotropy in directional drainage capillary- pressure curves and corresponding amounts of capillary-trapped wetting fluid. Finally, results presented in this dissertation indicate that pore-scale modeling methods can competently capture the effects of porous media geometry on macroscopic rock properties. Pore-scale two- and three-phase transport calculations with fast computers can predict petrophysical properties and provide sensitivity analysis of petrophysical properties for accurate reservoir characterization and subsequent field development planning. / text

The Dona and Roberts Bay watershed comprises one of the five major watersheds in Sarasota County, Florida. It is connected to the Gulf of Mexico via Venice Inlet. Like many estuaries in the Florida, significant modifications have been made to the drainage basins, principally to the main tributaries. The system has undergone several anthropogenic modifications to enhance water management efforts. Creeks that comprise fresh water input into the system have been dammed in order to inhibit the upstream flow of salt water during the dry season. They are also deepened or lengthened to allow for better drainage. In addition, biogenic activity has also had morphological effects on the system. There are numerous oyster bars, and mangrove forests that impose obstruction to the tidal and river flows. This has resulted in a highly complicated estuary system in terms of flow velocities and sedimentation patterns. The objectives of this study are to quantify the sediment characteristics and deposition-erosion trends and their relationship to flow patterns and other natural and anthropogenic factors within the system. A detailed sedimentary analysis was conducted based on 149 surface sediment samples and 29 drill cores. Spatial distribution of the sediment properties is quite complex, controlled by several interactive factors including; local sediment supply, intensity of the hydrodynamic processes, distribution of oyster bars and mangrove islands, and artificial structures. Sedimentation and erosion is significantly influenced by flood events. In some locations, such as the mouth of the fluvial channels, or the confluence of two creeks, the core data suggest that rapid sedimentation, driven by flood events, is responsible for the development of some of the large shoals. A 2-D depth-averaged circulation model was established for the study area. Many of the natural structures and artificial modifications to the watershed system are incorporated into the model. A close relationship between the flow intensity and sediment characteristics, and therefore, sedimentation-erosion tendency is identified. Remotely sensed data is also incorporated into the study in order to gain an understanding of the development of the estuary system over a ten-year period. Data suggests that the maturation of biogenic organisms that inhabit the system coincides with the development of complex sedimentation patterns.

Allochthonous, seaward-dipping deposits that flank reef-rimmed carbonate platforms (reef-rimmed carbonate foreslopes) display a spectrum of deposit types, seismic-scale stratal architecture, and bed-scale heterogeneity due to diverse sediment sources and resedimentation processes. This variability has resulted in a lack of consistent characterization approaches, and has made the development of predictive models that link carbonate foreslope deposit types to stratal architecture challenging. This study uses data from outcrops, including the Upper Devonian of the Canning Basin, Western Australia and the Upper Permian of the Delaware Basin, West Texas, and examples from literature to provide 1) an approach for characterizing reef-rimmed carbonate foreslopes in terms of deposit types and architecture, 2) conceptual models that outline the variations that exist, and 3) discussion of the intrinsic and extrinsic factors that control the observed variations. The primary depositional elements that construct reef-rimmed carbonate foreslopes can be categorized as 1) debris elements (breccias and blocks) from brittle reef failure, 2) grain-dominated elements (grainstones and rudstones) from offbank transport of sand and gravel, and 3) mud-dominated elements (mud-dominated fabrics) that record relative foreslope quiescence and fine-grained periplatform shedding. The fundamental stratal geometries observed are 1) accretionary margins, characterized by margin-toforeslope interfingering and clinoforms, and 2) escarpment margins, characterized by aggrading-retrograding margin architecture and foreslope onlap. The combinations of element proportions, element distribution, stratal geometry, bed- to bedset-scale architecture, and depositional profile scale that exist in carbonate foreslopes range widely, warranting multiple depositional models. The deposit type and architectural variations observed in detail from Upper Devonian and Upper Permian outcrops of the Canning Basin, Western Australia, and the Delaware Basin, West Texas, respectively, are linked to differing scales of superimposed accommodation change and reef faunal assemblage. Observations from other outcrops and extensive literature review display further controlling factors that affect carbonate foreslope development, such as platform morphology, oceanographic conditions, slope height, tectonic setting, and siliciclastic input, suggesting a multi-variable interplay of controls. These controls dictate the productivity and resedimentation of the contributing sediment factories, and/or influence the development of the carbonate platform system as a whole. Knowledge and classification of carbonate foreslope deposit types, architecture, and controls not only improve understanding of these complex systems, but also allow for the development of predictive relationships for economic purposes. / text

No description available.