Theses and Dissertations at Montana State University (MSU)
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Item Construction and modification of debris-flow alluvial fans as captured in the geomorphic and sedimentary record: examples from the western Sangre de Cristo Mountains, south-central Colorado(Montana State University - Bozeman, College of Letters & Science, 2020) Nicovich, Sylvia Rose; Chairperson, Graduate Committee: Mary S. Hubbard; James G. Schmitt (co-chair); James Schmitt was a co-author of the article, 'Deposition and modification of debris-flow alluvial fans, western rangefront of the Sangre de Cristo Mountains, south-central Colorado' submitted to the journal 'Journal of sedimentary research' which is contained within this dissertation.; Jim Schmitt, Ralph Klinger and Shannon Mahan were co-authors of the article, 'Late Pleistocene record of surface-modifying processes on the Pioneer debris-flow alluvial fan, San Luis Valley, Colorado' submitted to the journal 'Geological Society of America bulletin' which is contained within this dissertation.; James Schmitt was a co-author of the article, 'Impact of wind-blown sediment on the Pioneer debris-flow alluvial fan, south-central Colorado: concepts of fan activity' submitted to the journal 'Geosphere' which is contained within this dissertation.Alluvial fans and their deposits in the stratigraphic record are key in unraveling intricacies of landscape, tectonic, and climatic dynamics, though integrative geomorphologic and sedimentologic studies that comprehensively evaluate processes which build and modify fans are lacking. Therefore, a gap within the current body of literature exists concerning the sedimentological signature of depositional and surface-modifying processes on alluvial fans. This dissertation presents the sedimentological characteristics, both surficial and in the sedimentary record, of processes that build and modify alluvial fans while revisiting the contemporary concept of what defines an active surface. Detailed analysis of a suite of Quaternary active debris-flow alluvial fans on the western range front of the Sangre de Cristo Mountains in south-central Colorado was made using integrative sedimentological and geomorphic analysis, facies and soils mapping, along with infrared stimulated luminescence (IRSL) geochronology to document timing of fan construction and modification processes recorded in the alluvial fan deposits. Analysis of surface geomorphology, facies assemblages, and particle-size distributions of matrix from various facies of exposed alluvial fan deposits were also applied. These data show a clear distinction between sedimentary facies that represent processes of the primary depositional lobe surfaces versus those operating during periods of non-primary deposition, dominant on abandoned lobes. Primary processes on depositional lobes are debris flow and hyperconcentrated flow with minimal secondary modifying processes. Overland flow, input of eolian material, pedogenesis, and rock and mineral weathering are the main secondary modifying processes that govern abandoned lobes. Addition of wind-blown material, a secondary modifying process, plays a significant part in the sedimentary processes that operate on alluvial fan surfaces, ultimately influencing fan smoothing by mobilizing material derived from primary processes.Item Geomorphology, sedimentology and stratigraphy of small, holocene, debris-flow-dominated alluvial fans, northwest Wyoming(Montana State University - Bozeman, College of Letters & Science, 1993) Cechovic, Mark TodItem Alluvial fan and fluvial interaction in a foreland basin wedge-top depozone : Upper Cretaceous Beaverhead Group, SW Montana(Montana State University - Bozeman, College of Letters & Science, 1997) Dougherty, Susan LeslieItem Paleochannel aquifer potential at Montana State University : a test of hypotheses(Montana State University - Bozeman, College of Letters & Science, 1989) Donohue, David AllenItem Tectono-sedimentary evolution of a Late Cretaceous alluvial fan, Beaverhead Group, southwestern Montana(Montana State University - Bozeman, College of Letters & Science, 1993) Azevedo, Paul AlexItem Sediment routing system response to tectonic activity in the Argentine Precordillera : Sierra Las Penas-Las Higueras(Montana State University - Bozeman, College of Letters & Science, 2010) Abrahamson, Ingrid Syverine; Chairperson, Graduate Committee: James G. SchmittAlluvial fan deposition in the Argentine Central Precordillera is part of a sediment routing system that changes along strike of an active thrust front. This study area is partitioned into erosional and depositional sectors for analysis. The erosional sector drainage basins are analyzed using topographic data from a digital elevation model, to see how morphology changes with fault displacement. Drainage basins become shorter with more displacement. The depositional sector alluvial fans are classified using spectral characteristics from satellite imagery. The fans are classified based on thermal, near infrared, and elevation parameters. Fans close to the thrust front are interpreted to be old sheetflood deposits, with younger fans more distal from the front in the foreland. In this setting, progressive fault displacement causes shortening of the erosional sector, increasing the efficiency of sediment evacuation from the range, and causing a progradation of sheetflood fans into the foreland basin. Remote sensing analysis techniques are useful for characterizing the sediment routing system of alluvial systems where field-based information (geodetic, seismic, structural and lithologic data) is not available.Item Fault segmentation control on alluvial fan and fan drainage basin morphometry, Lemhi Range, East-Central Idaho(Montana State University - Bozeman, College of Letters & Science, 2011) Carr, Christina Grace; Chairperson, Graduate Committee: James G. SchmittAlluvial fan and fan drainage basin morphometric parameters are proposed to vary as a function of distance from closest fault segment boundary along the Lemhi fault in east-central Idaho. Large normal faults are broken into segments along strike that have unique rupture histories. Since potential earthquake magnitude is related to rupture area and therefore segment rupture length, accurate delineation of segments can have implications for earthquake hazard assessment. Alluvial fans were mapped on airphotos, and drainage basins were extracted from digital elevation models (DEMs). Morphometric parameters calculated for each drainage basin/fan pair based on DEM-extracted data include: elongation ratio (measures basin roundness in map view), Melton ratio (relates absolute relief and basin area), fan area to drainage basin area ratio, and hypsometric integral. Hypsometric integral is the area under the hypsometric curve, which displays relative elevation as a function of relative area. Standard regressions compared variations in these parameters with distance to fault segment boundaries mapped by previous workers. Drainage basins closer to fault segment boundaries tend to have lower elongation ratios (more elongate shape), higher Melton ratios, higher fan area to drainage basin area ratios, higher hypsometric integrals, and straighter (less sinusoidal) hypsometric curves. No parameter is strongly correlated with distance to closest segment boundary, but the strongest correlation occurs with the Melton ratio. High Melton ratios have been associated with basins dominated by flows with higher sediment-to-water concentrations compared to basins with low Melton ratios. The observed along-strike morphometric variations can influence conceptual models of extensional footwall drainage development and hangingwall basin stratigraphic evolution. However, the relationships are not strong enough to inform seismic hazard or similar studies requiring a high degree of confidence and strong correlations. In agreement with previous studies, fan area and drainage basin area are directly correlated, fan slope and drainage basin area are inversely correlated, and drainage basin slope and area are also inversely correlated. This study recognizes differences between slope calculated conventionally and slope calculated using standard grid-based methodology. This observation requires future studies to consider which slope definition is most representative of gravity-driven hydrogeomorphic processes.Item Sedimentology and geomorphology of quaternary alluvial fans with implications to growth strata, Lost River Range, Idaho(Montana State University - Bozeman, College of Letters & Science, 2006) Patterson, Scott Joseph; Chairperson, Graduate Committee: James G. SchmittSmall-radius (<2 km), steep (8-17°), Holocene debris flow dominant alluvial fans are depositing on top of large-radius (~5 km), shallow (2-3°) inactive Pleistocene sheetflood dominant alluvial fans along the western flank of the Lost River Range, Idaho. Channel ways, with and without backfilling, have developed within the large sheetflood dominant alluvial fans. The sheetflood dominant alluvial fans are being dissected. Three wedge shaped gravel packages were identified by field mapping and measured sections in four alluvial fans along the active extensional Lost River fault. These alluvial fan deposits have all of the characteristics of growth strata (progressive unconformities) observed in extensional tectonic settings. The ages of the surfaces were calculated from carbonate coat thicknesses on clasts in the soil and are between 42,000 ± 18,000 yr and the present. Each of the four alluvial fans has different stratal patterns even though they are all situated on the active Mackay fault segment. This lateral variability has implications to rock record interpretations. The younger fan depositing on top of the older fan exhibits the interaction of neighboring alluvial fans, and there is a changing of the sediment transport process over time on an individual alluvial fan. Complexly interacting controls on alluvial fan development include: 1) temporal change in the locus of maximum displacement on the Mackay fault segment, and 2) changes in Pleistocene and Holocene discharge.Item The influence of growing structures on Cretaceous alluvial systems along the Cordilleran thrust belt front, Valley of Fire, Southern Nevada(Montana State University - Bozeman, College of Letters & Science, 2010) McNamara, Kelsey Caitlin; Chairperson, Graduate Committee: James G. SchmittOutstanding preservation and exposure of Cretaceous tectogenic deposits in the North Muddy Mountains of southern Nevada provide a rare opportunity to examine the influence of frontal structures on provenance and sediment dispersal to the Cordilleran foreland basin. Eastward migration of the Sevier wedge-top depozone into the contiguous foredeep depozone was facilitated by development of the Willow Tank thrust-cored fault-propagation fold. The resulting thrust-cored frontal ridge diverted pre-existing fluvial systems of the Willow Tank Formation and promoted proximal alluvial fan deposition of the Baseline Formation. The Albian Willow Tank Formation represents the earliest foreland basin sediments derived from large, integrated drainage basins of the thrust belt interior. Sandstone point counts reveal an up-section increase in quartz locally derived from erosion from the Jurassic Aztec Sandstone along the frontal anticlinal ridge in the proximal Willow Tank thrust hanging wall. Continued fold growth is documented by growth strata development in and provenance of the overlying White Member of the Baseline Formation. Conglomeratic clast counts and detailed lithofacies analyses in the Cenomanian Red Member of the Baseline Formation record sequential unroofing of the frontal anticline and interaction of adjacent alluvial fan and fluvial depositional environments, respectively. Clast counts of poorly-sorted, massive ungraded conglomerates indicate a reverse clast stratigraphy based on progressively increasing amounts of carbonate framework clasts up-section. This trend is attributed to exposure and erosion of Upper Paleozoic strata in the Willow Tank hanging-wall anticline. Evidence of interfingering depositional environments is shown by up-section trends including: 1) replacement of poorly-sorted and organized coarse-grained conglomerates by well-sorted stratified to normally-graded conglomerates, 2) an overall decrease in grain size, 3) a decrease in soft-sediment deformation and increase in bioturbation, and 4) an increase in lateral bed continuity. This upsection transformation represents a spatial and temporal transition from foldproximal debris flow-dominated fans to an integrated braided stream system that transported detritus from the same source. Facies examination, clast composition and intertonguing relationships between the Red and Overton Conglomerate Members suggest contiguous braided stream networks that tapped separate, distinct source areas. These observations, as well as structural relationships, imply out-of-sequence movement on the Muddy Mountain thrust.