Theses and Dissertations at Montana State University (MSU)
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Item Sequence stratigraphic framework of the late Devonian (Frasnian) Duperow Formation in western and central Montana(Montana State University - Bozeman, College of Letters & Science, 2019) Steuer, Christopher Johann; Chairperson, Graduate Committee: David W. BowenThe Late Devonian Duperow Formation in western and central Montana and it's equivalent lower Jefferson Formation, is comprised of shallow marine carbonate strata deposited on the western margin of North America. It has produced significant volumes of oil and natural gas in the Alberta and Williston basins where the sequence stratigraphic framework of the formation is well-documented. However, in western and central Montana, the Duperow remains largely understudied. Additionally, at Kevin Dome, in northwest Montana, the Duperow hosts a large naturally occurring carbon-dioxide (CO^2) accumulation which is a potential economic resource and an analog for CO^2 sequestration over geologic time scales. The goal of this study is to determine the facies relationships and sequence stratigraphic architecture of the Late Devonian Duperow Formation in western and central Montana. This interpretation could help in exploration for oil and natural gas and provide useful information to aid in future carbon sequestration efforts. Multiple data sets are used in this study to best constrain depositional environments on the platform during Duperow deposition. Seven measured sections, three drill cores with associated well-logs, and forty-one thin sections are used to characterize facies, facies associations, parasequences, parasequence sets and sequences of the Duperow Formation and to construct the sequence stratigraphic framework within which these strata occur. Ten lithofacies comprising six lithofacies associations allow the interpretation of six depositional environments responsible for deposition of the Duperow Formation. The Duperow thins from the west and north onto the Central Montana Uplift, a paleohigh at the time, and thickens into the Central Montana Trough, a sub-basin on the platform. Two 2nd order and seven 3rd order sequences are interpreted from measured sections. Sequences are comprised of a transgressive systems tract and a highstand systems tract with no evidence for lowstand strata on the shelf. Transgression across the Central Montana Uplift did not occur until after the basal sequence boundary of the upper 2nd order sequence. Prior to this transgression, sequences lapped out before reaching the Central Montana Uplift. Overall, the Duperow in central and western Montana exhibits retrogradational stacking and thus is part of the transgressive systems tract of a lower-order megasequence.Item Carbonate preservation of dinosaur eggs in the upper Cretaceous Anacleto Formation at Auca Mahuevo, Neuquen Basin, Argentina(Montana State University - Bozeman, College of Letters & Science, 2011) Anggraini, Niswatin Wahida; Chairperson, Graduate Committee: James G. SchmittPreservation of dinosaur eggs and footprints by precipitation of calcium carbonate in the Upper Cretaceous Anacleto Formation at Auca Mahuevo, Argentina represents a relatively unusual occcurence in the fossil record. Under normal condition, eggs are readily destroyed in sediments shortly after burial by physical, chemical, and biological processes. This study attempts to determine a preservational model for carbonate eggs by characterizing their mineralogical composition and microstructures using a variety of analytical instruments including petrographic microscope, cathodoluminesce (CL) microscope, X-ray powder diffraction (XRD) and field-emission scanning electron microscope (FEM) to characterize the composition and fabric of the fossilized eggs. Several textutal features have been observed in the carbonate eggs, including membrane, embryonic skin, spherulites, ooids, peloids, Microcodium, calcified filaments, and micrite. Microbial actvity is likely responsible for the formation of these microfabric features, facilitating calcium carbonate precipitation leading to exceptional preservation of eggs. Although microbial influence in the carbonate egg preservation has not been clearly elucidated, laboratory experiments by other workers provide an argument for the role of microbes in the precipitation of calcium carbonate. The rare preservation of egg contents in the Anacleto Formation have been linked to biological-mediated processes. This preservation also provides evidence for penecontemporaneous carbonate precipitation under subaerial conditions before significant burial.