The internal structure of ice sheets reflects the history of flow and deformation experienced by the ice mass. Flow and deformation are controlled by processes occurring within the ice mass and at its boundaries, including surface accumulation or ablation, ice rheology, basal topography, basal sliding, and basal melting or freezing. The internal structure and basal environment of ice sheets is studied with ice-penetrating radar. Recently, radar observations in Greenland and Antarctica have imaged large englacial structures rising from near the bed that deform the overlying stratigraphy into anticlines, synclines, and overturned folds. The mechanisms that may produce these structures include basal freeze-on, travelling slippery patches at the ice base, and rheological contrasts within the ice column. In this thesis, I explore the setting and mechanisms that produce large basal stratigraphic structures inside ice sheets. First, I use radar data to map subglacial hydrologic networks that deliver meltwater uphill towards freeze-on structures in East Antarctica. Next, I use a thermomechanical flowline model to demonstrate that trains of alternating slippery and sticky patches can form underneath ice sheets and travel downstream over time. The disturbances to the ice flow field produced by these travelling patches produce stratigraphic folds resembling the observations. I then examine the overturned folds produced by a single travelling sticky patch using a kinematic flowline model. This model is used to interpret stratigraphic measurements in terms of the dynamic properties of basal slip. Finally, I use a simple local one-dimensional model to estimate the thickness of basal freeze-on that can be produced based on the supply of available meltwater, the thermal boundary conditions, ice sheet geometry, and the ice flow regime.

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Five folded charts in pocket. Includes bibliographical references (leaves 316-324). Available also in a digital version from Dissertation Abstracts.

The Yoakum Canyon is the largest of the Gulf Coast Eocene erosional gorges and is interpreted as a buried submarine channel. It can be traced for 67 miles from the Wilcox fault zone, which defines the position of the early Eocene shelf edge, nearly to present outcrop. This paper expands on previously published descriptions of the canyon using a more extensive subsurface data base. Decompaction of the canyon shale-fill reveals that original depths of the canyon exceeded 3500 ft (1067 m). Apparent canyon wall slump scarps and a peripheral chaotic zone, interpreted as an incipient slump feature, are comparable to similar features of the late Quaternary Mississippi submarine canyon. The Yoakum canyon formed within the Garwood subembayment to the west of and adjacent to the Middle Wilcox continuation of the Rockdale delta system. Quantitative mapping of facies adjacent to the Yoakum shale indicate the following sequence of events: 1) Muddy, distal deltaic and shelf facies of the lower Middle Wilcox were deposited during a retrogradation. 2) A resurgence of progradation deposited the upper Middle Wilcox deltaic sands atop the unconsolidated, lower Middle Wilcox continental margin muds creating a density inversion which initiated slump failure of the continental margin sediments. 3) Headward erosion of the canyon across the shelf occurred contemporaneously with a subsidence-induced transgression caused by a decrease in the sediment supply. The Yoakum canyon was excavated by a combination of slumping and current scour. 4) The canyon was filled with hemipelagic and prodelta muds. 5) Progradation of the Upper Wilcox (Carrizo) deltaic sands capped the sequence. / text

The research involves mapping of subsurface at a scale of 1:25,000 the top of three geological formations in the Southern Part of Sumatra – the Airbenakat Formation, the top of the Talangakar Formation, and the top of structural basement in the Jambi Trough. Isopach maps of the formations will be constructed. These maps will form the basis of a basin analysis and hydrocarbon source rock assessment of the Jambi Trough using Basin Mod basin modeling software (Rockworks Software). The studies utilize the L. Bogue Hunt Southeast Asia database housed in the Department of Geological Sciences at Ball State University. Seismic record sections, geophysical logs, cutting descriptions, and paleontological reports will provide basic geological data to enable mapping of the three horizons. Although hydrocarbon accumulations are abundant in Central and Southern Sumatra, the nature of the source rocks is only partially understood. The proposed research will map the Airbenakat and Talangakar Formations while identifying the areas of thermally mature source rock is the main goal of the research. This study will identify characteristics which will enable the identification of thermally mature rocks in other regions of Sumatra. The area of the project is located at the Southeastern part of Asia in Indonesia and mainly the Jambi trough located in Southern Sumatra. Generally, the geology and tectonics of this area (Sumatra) is controlled by the subduction of the Indian plate towards the east and beneath the Eurasia plate. / Department of Geological Sciences

According to the Ade observation (Ade, W., pers. Comm.) “95% of all commercial oil fields in the Sumatra region occur within 17 km of seismically mappable structural grabens in the producing basins”. The Ade observation proposes a link between the subsidence of the source rocks (the Talang Akar Formation) in the grabens and the maturity of the organic material. To test the validity of the Ade observation, subsurface mapping of the region was carried out using geophysical logs. Using the well log information, the basement and the formation tops have been mapped with a special emphasis on Talang Akar and Air Benakat Formations. The isopach maps of these formations show that most of the producing wells on the Sunda shelf are in fact located in and around the major structural basins. Trends in the occurrence of the oil fields have also been observed which are analogous to the orientation of the grabens. Structural mapping of the basins have identified several wrench faults. These are of particular interest as wrench faults provide good structural traps for oil in the Los Angeles and the North Sumatra Basins and may prove to be very important for future exploration in southern Sumatra and northwest Java. In South Sumatra Basin, 77.78% of the potential oil fields are located in the 17 km margin from the grabens. For Sunda/Asri Basins and the Ardjuna Basin, it is 100 and 92 respectively. Identifying the source rocks in this 17 km window will enhance the success rate of oil exploration in the Sundaland Basins. / Department of Geological Sciences

This is an analysis of fractures occurring within the Paloezoic sedimentary rocks in a portion of southeastern Indiana. Fifteen hundred seventy-two fractures were used in analysis of distribution, orientation, pervasiveness, persistence, and intensity. The data collected is representative of eight counties and seventeen different collection sites.All fracture data were given an associated numerical value identifying each variable used for analysis and recorded into computer data files. A computer program was used for statistical analysis and construction of equal area nets which graphically displayed the distribution of variables. The compilation of the fracture data allowed for close interpretative analyses of variables and correlation of the orientation and distribution of the fractures within the study area.This study revealed that two orthogonal fracture systems exist in southeastern Indiana. The fracture set containing the largest percentage of those measured is oriented N11W with its compliment oriented N73W. The orientation of the second largest fracture set is N8E with its compliment oriented N82°W.The effects of the tectonic history as well as contemporary stress on the area are discussed relative to their effects on the overall distribution of fracture sets.Evidence is presented to substantiate a reactivation of the Cincinnati Arch as indicated in the Devonian-Mississippian lithologic units from data collected in the southeastern portion of the study area. Fracture data correlating to these units displays a rotation of the major fracture set maxima 90w. This data is supported by radiometric dates from the Belfast member of the Brassfield Limestone in which Laskouski, et.al., correlated a reactivation of the arch.Also within this study are lithologic descriptions of all the Paleozoic formations used for data collection. These descriptions were developed over a three year period from extensive field observation.A map of the study area is presented displaying the distribution and orientation of the fractures recorded at each data collection site. / Department of Geology

The uppermost Cambrian-Lower Ordovician Kamouraska Formation in the external Humber Zone of the Quebec Appalachians consists of dominant thick massive to graded quartz arenite beds, subordinate pebble conglomerate and intercalated thin shale and siltstone beds. It was deposited by hyperconcentrated to concentrated density flows in a meandering submarine canyon on the continental slope bordering the Iapetus Ocean. Turbidity currents deposited beds with turbidite structure divisions. The sandstones consist of well sorted, well rounded quartz sand with frosted grains. Scanning electron microscopy reveals the presence of textures supporting eolian transport before redeposition in the deep sea. The Kamouraska quartz arenites are considered an ancient equivalent of Pleistocene eolian-sand turbidites on an abyssal plain off West Africa consisting of Sahara sand. Sand provenance is attributed to eolian equivalents of the Cairnside Formation of the Potsdam Group. The quartz arenites of the Kamouraska Formation provide a variant to tectonic sandstone provenance proposed in the scheme of Dickinson and Suczek (1979).

Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xiv, 225 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 113-116).