Theses and Dissertations at Montana State University (MSU)
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Item Ichnology and sedimentology of the non-marine Frontier Formation (upper Cretaceous) of southwestern Montana(Montana State University - Bozeman, College of Letters & Science, 2023) Panasci, Giulio; Chairperson, Graduate Committee: David J. Varricchio; This is a manuscript style paper that includes co-authored chapters.The Frontier Formation of southwestern Montana (USA) is comprised of rocks assigned to the early Upper Cretaceous (Cenomanian- Santonian), and has recently yielded a notable fossil record, mostly comprised of dinosaur tracks and invertebrate trace fossils. This fossil record lays within a poorly understood period of the Upper Cretaceous, also known as the middle Cretaceous, valued as critical to understand the evolution of terrestrial ecosystems in North America at the end of the Mesozoic Era. This study aims to describe and analyze preservation and distribution of the Frontier trace fossils record. Twelve stratigraphic sections are measured and sedimentology, taphonomy, and stratigraphic framework described for the main fossiliferous sites. Sixty-five dinosaur tracks and associated invertebrate traces are described. Three tracks are further analyzed by combining anatomical characters and track morphological features to infer a more specific producer. Photogrammetry, tridimensional models, and color elevation maps are generated to document significant specimens and to map two excavated track sites. A concise description and classification of a freshwater turtle is also included to enhance paleoecological and paleodepositional reconstructions. A Coniacian age is provided for the Frontier Formation, main fossiliferous sites. Sedimentology and fossil record suggest the establishment of a rich ecosystem in alluvial plains and wetlands extending between the offshoots of the uplifting Rocky Mountains to the east and the Cody Sea to the east. Facies distribution across the southwest-northeast transect suggests that fossil distribution and preservation is mainly controlled by autogenic and allogenic processes seen in foreland basin systems. Tracks and invertebrate trace fossils preservation was likely favored by high sedimentation rates and variations of the ground water table. Dinosaur track assemblage is comparable to those reported in other middle Cretaceous formations of western North America and include derived hadrosauriform ornithopods, ankylosaurians, and theropods. The integration of body fossil data would suggest the presence of a fauna that included elements (i.e. Neurankylus sp.) shared with Campanian and Maastrichtian formations, suggesting that the Coniacian ecosystems across southwestern Montana was likely undergoing a process of provincialisms as seen in North America at the end of the Cretaceous.Item Sedimentology of alpine debris-flow and talus deposits in Sacajawea cirque Bridger Range, Montana(Montana State University - Bozeman, College of Letters & Science, 1994) Werner, Amanda VroomanItem Sedimentology and taphonomy of a shell bed assemblage from the Upper Cretaceous (Maastrichtian) Hell Creek Formation of eastern Montana(Montana State University - Bozeman, College of Letters & Science, 2001) Shoup, Bentley EdwardItem Sedimentology, provenance, and tectonic setting of the Miocene Horse Camp Formation (Member 2), east-central Nevada(Montana State University - Bozeman, College of Letters & Science, 1994) Horton, Brian KeithItem Stratigraphic analysis of the Jurassic Ellis Group and paleotectonics in North-Central Montana : deciphering the historically enigmatic 'Belt Island'(Montana State University - Bozeman, College of Letters & Science, 2011) Porter, John Richard; Chairperson, Graduate Committee: David W. Bowen"Belt Island", an influential positive structure during the Jurassic, is widely represented in the geologic literature from 1948 to present. Introduced as primarily a stratigraphic anomaly in isopach maps of the Ellis Group, the inherent spatial and temporal context was loosely constrained. In subsequent literature, it is widely referenced in a structural context, though support is lacking for originating paleotectonics and stratigraphic data is minimal. Do the stratigraphy, sedimentology, and regional tectonics support the theory of a paleogeographic/paleotectonic high in north-central Montana during the Middle to Late Jurassic during the deposition of the Ellis Group? What are the tectonic explanations for such a feature if one did persist throughout said time? This project looked at outcrops and cores of the Ellis Group from around the project area. A lithofacies characterization was assembled based on rock properties. Utilizing previous work on lithostratigraphy, biostratigraphy, and regional unconformities and integrating these data with the lithofacies characterization a sequence stratigraphic framework was assembled. This sequence stratigraphic framework was applied to an extensive subsurface well database to generate a geologic framework over the project area. The distributions of lithofacies do support the theory of a large feature in the project area during the deposition of the Ellis Group. The stratigraphic architecture as well supports this theory, and additionally adds a spatial and temporal constraint to the feature. With the integrated sequence stratigraphic framework, it is apparent there was regional syntectonic activity influencing deposition. With the ability to put a temporal and spatial constraint on the paleotectonic feature it is possible to understand through time how this feature behaved. This allows the research to state that the feature originally known as "Belt Island" was the paleogeographic area of non-deposition and erosion of a larger peripheral bulge. This lithospheric flexure would have been the reaction to the crustal loading to the west during the Western North America Cordilleran Orogeny.Item Sedimentology and stratigraphy of a deepwater transient fan on the continental slope : the Late Miocene Isongo Formation, equatorial West Africa(Montana State University - Bozeman, College of Letters & Science, 2011) Wolak, Jeannette Marie; Chairperson, Graduate Committee: Michael H. Gardner; Michael H. Gardner was a co-author of the article, 'A hierarchical approach to understanding reservoir property distribution (porosity and permeability) in the Isongo Formation, equatorial West Africa' in the journal 'Sedimentology' which is contained within this thesis.; Michael H. Gardner and W. Sebastian Bayer were co-authors of the article, 'Incipient structural growth and transient fan development in the Late Miocene Isongo Formation, Southeastern Niger Delta' in the journal 'AAPG bulletin' which is contained within this thesis.Deepwater clastic deposits of the Late Miocene Isongo Formation, located 50 km northwest of Bioko Island, characterize a sand-rich transient fan system developed in response to incipient structural growth on the continental slope. Approximately 1200 ft (366 m) of conventional core, 21 wells, 3-D seismic (maximum 40-60 Hz), biostratigraphy, chemostratigraphy and dynamic production data from the 100 km 2 study area are used to: (1) Define process-based sedimentological facies within the Isongo Fan; (2) Characterize porosity and permeability trends at three temporal and spatial scales; (3) Identify sedimentary bodies throughout cored and uncored intervals; and (4) Correlate stratigraphic sequences within a framework of adjustment, initiation, growth and retreat (AIGR). While the former two objectives capture small-scale geologic heterogeneities developed at the time of deposition, the latter two describe changes in fan geomorphology during coeval uplift and sedimentation. Fifteen core-defined sedimentological facies reflect subaqueous depositional processes including turbidity currents, debris flows and pelagic settling. Pore space generated during deposition is correlated to grain size; pore connectivity is correlated to sorting. Sedimentation units and facies assemblages, which characterize depositional processes operating during a single sedimentation event, show patterns of accumulative flow in the confined, narrow portion of the Isongo Fan; depletive flow in the unconfined, southwestern portion. Erosional slope channel-levee systems in the northeast demonstrate very large sedimentation events, likely due to eruptive activity and uplift of Mount Cameroon 50 km updip. Partly confined to unconfined distributary channel-lobe systems in the southwest characterize a change in fan geomorphology off the flank of a growing structure. Core-calibrated petrophysical facies and wireline log thicknesses allow identification of sedimentary bodies in uncored intervals throughout the Isongo Fan, a 2.3 million year episode of sand-rich deposition (3rd order sequence). High frequency 4th and 5th order sequences are used to describe changes in fan morphology over time relative to the growing anticline. A surface of adjustment marks the onset of syn-sedimentary growth, followed by 4th order phases of initial deposition that onlap the structure. Sandrich fan growth, however, is greatest during a period of minimal uplift, followed by retreat of the Isongo depocenter to the north. Post-Isongo deposits suggest that renewed anticline growth resulted in avulsion of the system to the northwest after 8.2 Ma.