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Item Stratigraphic architecture and diagenetic evolution of the late Devonian to early Mississippian strata in western Montana(Montana State University - Bozeman, College of Letters & Science, 2015) Borski, Jack Busse; Chairperson, Graduate Committee: James G. SchmittLate Devonian to early Mississippian strata have been extensively studied in geologic literature both for academic and economic purposes. Lithostratigraphic intervals spanning this time in western Montana include the Exshaw, Banff, Three Forks and Lodgepole formations. These formations are generally composed of a lower organic-rich black shale, a medial calcitic and dolomitic siltstone to sandstone, and upper organic rich shale. This siliciclastic-dominated rock package is anomalous in the carbonate-dominated Paleozoic of western North America. This study aims to address the following research question: where and what were the environments of deposition throughout the Late Devonian to Early Mississippian in western Montana and what is the diagenetic evolution of these rock packages? To answer this question, multiple datasets were utilized including core, outcrop and geophysical well logs. A lithofacies scheme comprised of eighteen lithofacies was constructed based on rock attributes to interpret and correlate lithostratigraphic intervals as well as to establish a sequence stratigraphic framework from outcrop. The stratigraphic framework constructed from outcrop was then mapped throughout the subsurface of the study area where outcrop is absent. Finally, a diagenetic analysis was conducted according to significant sequence stratigraphic surfaces and rock bodies. Lithostratigraphic and sequence stratigraphic surfaces are generally concurrent due to the low-accommodation epicontinental basinal setting of western Montana during this time. Sequence stratigraphic distribution indicates a long-term regression followed by a long term transgression that is overprinted by tectonically emergent features and third order cycles that are the primary concern of this project. Prominent structural features affecting sedimentary dispersal patterns include the Beartooth shelf, Sappington basin (that may be the incipient central Montana trough), the area near the Pendroy fault zone (possibly the incipient central Montana uplift), and western Canadian sedimentary basin.Item Control and distribution of porosity in the Red River 'C' laminated member at the Brush Lake Field(Montana State University - Bozeman, College of Letters & Science, 1985) Stimson, James RoyItem Investigation of permeability patterns and diagenetic heterogeneity along the J-2 unconformity (UT, CO, AZ)(Montana State University - Bozeman, College of Letters & Science, 2011) Bechberger, Melody Ann; Chairperson, Graduate Committee: James G. Schmitt; David W. Mogk (co-chair)It is important to understand the variation in permeability along eolian bounding surfaces in subsurface eolian reservoirs for hydrocarbon recovery, CO 2 sequestration, aquifer management, and groundwater contaminant transport. The objectives of this investigation are to identify features associated with the J-2 unconformity and measure the range of permeability for each of these features. These features include dune lithofacies contacts, lag and reworked deposits, polygonal fracture networks, interdunes and paleowater tables. Petrographic image analysis, cathodoluminescence, x-ray diffraction and energy dispersive x-ray elemental analysis are used to characterize possible depositional and diagenetic influences on the range of permeability for each feature. J-2 dune facies are the most common and have a similar range in permeability to that shown by wind ripple laminations. Polygonal fracture networks can be weak or well developed and can be poorly to well cemented. Permeability variation in polygonal fracture networks is based on the intensity of cementation and would only significantly affect horizontal communication in a reservoir. Paleowater tables are generally well cemented, much like wet interdune deposits, and act as permeability barriers to fluid flow. Lag and reworked deposits are likely the result of sediment gravity flows generated either by topographic relief or from dunes bypassing on the incipient J-2 surface. Depending on the thickness and cementation of the lag and reworked deposits, these could act as significant permeability barriers and even generate stratigraphic traps. While permeability is reduced in many of these deposits by their depositional character, samples with ~5% cement generally have permeabilities that are 150mD or less and samples with more than 10% cement generally have permeabilities less than 10mD. Samples with this intensity of cementation are intensely concretionary, interdunes, paleowater tables, polygonal fractures, or reworked deposits.