World-class outcrops of an outermost erg-margin can be observed within the Middle Jurassic Entrada Sandstone near Capitol Reef National Park, Utah. These erg-margin deposits contain isolated reservoir quality sandstone bodies that transition into a muddy tidal flat facies. These high quality reservoirs are dominated by eolian-influenced facies interbedded with sandy interdune facies. They are sealed vertically by muddy and silty facies of associated tidal flat deposits that act as excellent stratigraphic traps in the subsurface. A variety of approaches were used to characterize these Entrada erg-margin reservoirs including: annotated panoramas of outcrops, measured sections, scintillometer measurements of field sections, facies analysis, 2D high-resolution shallow seismic surveys, porosity and permeability analysis, and sedimentary petrography. Logs from the North Hill Creek/Flat Rock gas field were analyzed and correlated to the outcrop study. Eolian dune facies, along with an upper ripple laminated facies representing interdune deposits, display the highest porosities and permeabilities and are volumetrically the most important facies of the reservoir quality sandstones. Baffles and possible barriers within the sandstone bodies are limited to quartz filled fractures, deformation bands, silty and muddy interdune facies, and first order bounding surfaces. Many of the sandstone bodies within the outcrop belt are genetically related and in communication with each other. This relationship results from dune complex migration to the south and up section over time. Stratigraphic climb can potentially be imaged seismically and may serve as a key indicator of eolian dune complexes in the subsurface. The volumetric size of one of these complexes is estimated around 470 million cubic feet. Smaller outcrop sandstone bodies were often found to be isolated from the large dune complexes and ranged down to 1 million cubic feet in size.

The cyclic wetting and drying of a rock is considered to be one of a number of physical weathering processes that have an effect on the weathering of rock. While the presence of moisture is known to be of critical importance for the activation and enhancement of a number of other known weathering processes, such as cryogenic weathering, salt weathering and slaking it is possible that the mere cyclic application and removal of moisture over time may also have an effect on the physical structure of a rock. The precise nature of the process is not well understood, however. This document begins by investigating the studies that have previously been undertaken to determine how the wetting and drying weathering process is defined and to ascertain the current state of knowledge regarding this process. After an establishment of background context, a physical experiment is carried out on Clarens Formation sandstone and Marion Island basalt to note the relationship between cyclic wetting and drying and the changing physical properties of the rocks. The rocks were subjected to 105 wetting and drying cycles over a period of 21 weeks. At the beginning of the experiment, physical rock properties were measured by way of the method laid out by Cooke (1979) and again at the end of the experiment. Since the experiment was carried out under static environmental conditions, the comparison of physical rock properties gives a good indication of how the rocks have altered their structure over the experimental time period. The results obtained in this experiment show that different rock types will change in different ways when exposed to a common weathering process. The basalt samples experienced no mass loss at, while the sandstones did. The sandstones, which are rocks that are of common lithology and of very similar physical and chemical structure reacted to the wetting and drying weathering process in ways that could not be predicted without experimentation. The data does show a clear causal link between the application of external stimuli and rock property change, however. Changes in physical rock properties are not always straightforward and linear, but evolve dynamically over time, often yielding results that appear to oppose those intuitively predicted. A number of questions are asked regarding the philosophical approach that is taken to process isolation studies, with emphasis given to the careful consideration of the place that such studies have in the realm of process geomorphology. While process isolation studies may give an excellent indication of what a particular weathering process may be capable of under certain conditions and on certain rock types, they should not be regarded as indicative of what is occurring in the field. Additionally, it has become clear that it is not possible to predict how a specific rock type may respond to a specific weathering process without physical experimentation since the number of variables present in a typical weathering system are simply too vast to easily categorise. / Dissertation (MSc)--University of Pretoria, 2010. / Geography, Geoinformatics and Meteorology / MSc / Unrestricted

The Arumbera Sandstone forms distinctive strike ridges with dark reddish slopes and orange-white cliffs throughout most of the northeastern Amadeus Basin. It is divisible into four readily mappable informal units. The ridge-forming units, 2 and 4, are divided into three and two subunits, respectively. Unit 1, Subunit 2b, Unit 3 and Subunit 4b are generally comprised of recessive, pale-red to grayish-red, medium- to thin-bedded, fineto medium-grained arkose with major proportions of siltstone and mudshale. These sedimentary bodies are interpreted as a complex system of coastal to nearshore-marine environments including tidal flats, tidal channels, estuaries and beaches. Evidence includes: (1) predominance of alpha-, beta, and cross-stratification with common herringbone laminae, truncated wave-ripple laminae, and flaser bedding; (2) bimodal paleocurrents; (3) records of intermittent, subaerial exposure (desiccation mudcracks, raindrop prints, and casts of gypsum and halite crystals); and (4) rare to abundant trace fossils of probable marine origin. Subunits 2a and 4a are comprised of cliff-forming, white to pinkish-gray, thick-bedded, fine- to medium-grained lithic arkose and arkose. Subunit 2c is also resistant, and is comprised of "maroon" to moderate-red, thick-bedded conglomerate and conglomeratic sandstone with pebbles and small cobbles of chert, quartzite, and vein quartz. These three subunits are interpreted as fluvial sheet sandstones on the basis of: (1) predominance of pi-, omikron-, and lambda cross-stratification; (2) thick bedding and paucity of mudrocks; (3) unimodal, northeastward-oriented paleocurrents with a crude radiating pattern; (4) abundant shale pebbles and wedging channelsand bodies; (5) absence or rarity of trace fossils in the subunits; and (6) sheet-like geometry. The Arumbera Sandstone was probably deposited in a coastal environment perhaps analogous to the delta of modern Godavari River of India. Evidence includes: (1) a pronounced depocenter for the unit in the central part of the study area (1123 m relative to 216 m in the southwest); (2) unidirectional paleocurrents from fluvial sheet sands that radiate to the N, NE, E, and SE; (3) fluvial and coastal deposits in vertical, cyclic succession; and (4) east- and northeast-trending zones of thicker deposits within fluvial sheet sands, which may be distributary lobes. The Arumbera is considered part of the molasse sequence associated with the Late Proterozoic and Early Cambrian Petermann Ranges orogeny. The uplifted Petermann Ranges shed sediment from sedimentary, metamorphic, and plutonic rocks. Terrigenous material was probably transported to the coastal environment of the northeastern Amadeus Basin by braided streams in an environment devoid of vascular terrestrial vegetation. Grain mineralogy and weathering characteristics suggest a hot, semiarid to humid climate throughout this region. Detailed petrographic study of ten thin sections demonstrates the following average sandstone composition: quartz (54%), orthoclase (25%), chert (6%), plagioclase (5%), lithics (4%), microcline (2%), and minor zircon, tourmaline, rutile, magnetite, muscovite, and biotite. Common cementing agents are syntaxial quartz and feldspar overgrowths, chert, hematite, kaolinite, and carbonate. The inferred diagentic sequence is : Eogenetic: (1) mechanical compaction and (2) formation of "dust rims"; Mesogenetic: (3) syntaxial feldspar overgrowths, (4) syntaxial quartz overgrowths, (5) calcite cement, (6) organic maturation(?) and creation of secondary porosity, and (7) pyrite crystals; T elogenetic: (8) kaolinite, and (9) chert. The Arumbera is regarded as of possible Late Proterozoic and probable Early Cambrian age based on the presence of the trace fossils Rangea cf. longea and Phycodes antecedens in Unit 1, Arumberia banksi in Subunit 2b, and Bergauria, Diplichnites, Laevicyclus, Phycodes pedum, Plagiogmus, Psammichnites, Rusophycus and Skolithos in Units 3 and 4. The Arumbera is a potential petroleum reservoir. Suitable source rocks, sealing mechanisms, reservoir porosity and permeability, and stratigraphic and structural traps are present in the northeastern Amadeus Basin. The close association of organic maturation with generation of secondary porosity and tectonic fracturing, both in time and space, also favors the accumulation of petroleum in the Arumbera.

A review of the history of the nomenclature of the Medina Formation and of the previous studies of its members, particularly those studies dealing with the source of the Whirlpool sandstone. This is an attempt to show the direction of origin of the detrital materials of the Whirlpool sandstone by a study of the lateral variation of its grain size along the Niagara Escarpment. It is illustrated with maps and with photographs taken by the writer. / Thesis / Master of Science (MSc)

<p> 101 samples of Thorold sandstone were collected from 12 geographically distinct regions along the Niagara Escarpment. The average number of vertical worm tubes in each region was determined as was clay content, organic matter, burrow diameter, interburrow distance, mean grain size, sorting, quartz proportion, distance from shore, porosity, and the sandstone/shale ratio. Stepwise linear regression and principal component analysis were used to investigate relationships between the variables. The number of worm tubes can be predicted by clay content, organic matter, distance from the shore, and porosity, a model which explains 62% of the observed variation. All 11 variables accounted for 99. 9% of the variation. Distance from shore can be predicted by organic matter, burrow diameter, mean grain size, and the sandstone/shale ratio, a model which explains 94% of the variation. All 11 variables accounted for 99.9% of the variation. Organisms living in the Thorold evidently reacted to environmental parameters in a similar fashion to modern tidal flat organisms.</p> / Thesis / Bachelor of Science (BSc)

No description available.

No abstract provided. / Thesis / Bachelor of Science (BSc)

Understanding unconventional petroleum reservoirs and HALO plays, areas outside existing production zones which are made up of thin-bedded or heterolithic intervals, has gained in importance in recent years with the continual demand for energy and the increased development of such prospects. Heterolithic units within deltaic successions host vast quantities of oil and gas that often go unexploited due to a lack of understanding of the sandstone shape, morphology and continuity within such reservoirs. The purpose of this work is to examine the thin-bedded units within the Late Cretaceous prodelta successions of the Gallup Sandstone in the Shiprock area of New Mexico in order to quantify the fundamental processes responsible for the deposition of these sands and to perform a correlation for such heterolithic deposits. Rock Ridge and Sanostee show heterolithic deposits, within parasequences 5a and 7a of the Gallup sandstone, and were analyzed, using measured sections and photomosaics, near the Shiprock area in order to compare the heterolithics in different stratigraphic settings. Five measured sections were collected at the centimeter scale in order to observe every facies change at a high resolution. Facies associations, such as tempestites, turbidites, and hyperpycnites, were used to identify dominant processes of deposition. Corresponding net-to-gross calculations yielded the sandstone percentage of each section with the result that storm-dominated beds present at Sanostee yielded the highest percentage of sand content. Two high resolution gigapan photomosaics of each heterolithic exposure were collected in order to perform a correlation of all the sandstones observed within the measured sections, across the entire exposure. Results show that dominant process of deposition varies along strike. Towards Sanostee, in the south, storm-waves are dominant while farther north rivers exert greater influence. However, the presence of large scale storm-deposited gutter casts at Sanostee has significant implications for lateral and vertical continuity of sandstones in comparison to the more tabular sandstone facies found at Rock Ridge. These guttered facies have a major impact on net-to-gross and vertical conductivity due to their high degree of amalgamation and therefore may signify important areas for prospecting in such heterolithic reservoirs. Furthermore, the presence of large scale gutters beneath a sharp-based shoreface is indicative of a Falling Stage Systems Tract, leading to the conclusion that Parasequence 7a-6d were affected by forced regression. / Thesis / Master of Science (MSc)

Velocity tomography is a noninvasive technique that can image the interior of a rock structure. To apply tomography to rock specimens, a propagation wave, which acts as a probe, is used. The propagation wave propagates from a source until it reaches a sensor on the surface of the rock specimen. Tomograms can then be generated from the velocity distribution within the rock structure. Areas of higher velocity are typically representative of higher stress concentrations, whereas areas of low velocity can be areas of fracturing. The variation of velocity tomography described in this thesis uses acoustic emissions as sources for the propagation wave. Acoustic emission sources provide advantages over mechanical sources, since the acoustic emission source is generated by the rock as a result of deformation and fracturing. Velocity tomography of rock structures in the field has numerous applications and advantages. Velocity tomography can be used to monitor rock structures surrounding tunnels and underground openings such as mines. To monitor the rock structure, velocity tomography is used to determine areas of higher stress concentration that may be precursors to rock failure. However, velocity tomography must first be used in a laboratory environment to determine failure in rock samples before being applied to the field. The research presented includes the unconfined compression strength testing of 19 Berea sandstone samples. These samples were loaded to failure and during the experiment the acoustic emission events within the samples were monitored using a commercial acquisition system manufactured by Engineering Seismology Group (ESG) Canada. Source location software, also produced by ESG, was used for the location of the acoustic emission events. Ray inversions were performed on the data from the experiments to generate tomograms. The tomograms generated display the p-wave velocity distribution imaged within the Berea sandstone samples with the ultimate goal of being able to predict rock failure. Based on the experiments discussed in this thesis it can be inferred that velocity tomography is a useful tool for imaging the inside of the Berea sandstone samples. Precursors of rock failure could not be determined in this early stage of research. However, the tomograms do image the p-wave velocity distribution and do show a gradual progression of the p-wave velocity from the initial velocity model to higher velocities. Results of these 19 experiments do provide reasonable confidence in the method and warrant pursuit of further research to refine and improve this method of monitoring velocity tomography. / Master of Science

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