Thesis (Ph. D.)--University of Wisconsin--Madison, 1974. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

xvi, 121 p. : ill. (some col.), maps (some col.) Also includes two large-scale maps in two separate pdf files. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Deformation across plate boundaries often occurs over broad zones with relative motions between plates typically accommodated by faults of different styles acting together in a complex system. Collision of the Yakutat microplate within the Alaskan portion of the Pacific-North America plate boundary drives deformation over 600 km away where the Denali fault divides predominantly rigid crustal block motions of southern Alaska from distributed deformation in central Alaska. Quaternary geologic mapping along the Nenana River valley and the Japan Hills of the northern foothills of the Alaska Range defines zones of Quaternary thrust faulting recorded in the progressive deformation of Pleistocene fluvial terraces. I use topographic profiles of these terraces and paleoseismic trenching of fault scarps to characterize the Quaternary activity and constrain the subsurface geometry of these faults. Radiocarbon and cosmogenic exposure dating methods provide age control on the stratigraphy in the trenches and landforms offset by these faults. These observations define a 1-1.5 mm/yr slip rate for the Gold King fault which changes laterally from a north-vergent thrust into a north and south vergent thrust wedge that uplifts the Japan Hills. Along the Nenana River valley, the progressive deformation of Pleistocene surfaces defines a north-vergent critically-tapered thrust wedge. The geometry of progressive uplift and folding requires a near planar, south-dipping basal thrust fault with two major north-dipping backthrusts. All three faults were active simultaneously on a scale of 10 4 yrs with slip rates of 0.25-1 mm/yr, until the late Pleistocene when we infer the retreat of glacial ice from the main axis of the Alaska Range caused a change in thrust wedge dynamics. I use the orientation of Quaternary deformation north of the Denali fault to show that strain is highly partitioned and establish geologic constraints on the regional horizontal stress orientation. North of the Denali fault, fault-normal principal shortening accommodates 3-5 mm/yr of strain transfer across the Denali fault system. Two appendices contain additional results of paleoseismic trenching and neotectonic investigations across 4 active faults near the Nenana River. This dissertation includes previously unpublished co-authored material. / Committee in charge: Ray Weldon, Chairperson, Geological Sciences; Joshua Roering, Member, Geological Sciences; David Schmidt, Member, Geological Sciences; Douglas Kennett, Outside Member, Anthropology

The Hines Creek fault (HCF) is a Holocene-active fault in central Alaska. Its trace has been mapped several times, but data on the history of fault displacement is scarce. As a major crustal-scale geologic boundary with uncertain Quaternary tectonic activity, it is a priority for more to be known about the activity of this fault to better understand the hazards it presents to the Denali National Park and Preserve and Alaskan infrastructure. This study characterizes the late Quaternary activity of the HCF through surficial geologic mapping and paleoseismic investigations. Mapping revealed a very steep (~84°-88° apparent dip), north dipping fault plane and measurements from offset Pleistocene outwash terraces revealed south side-down vertical offsets of up to 12 m, indicating a steeply dipping reverse fault. Three paleoseismic trenches excavated across the fault trace provided a record of seismic activity and hold evidence for at least four prehistoric earthquakes in the last 2 ka. Slip rate calculations estimate movement on the HCF to be between 0.6mm yr-1 and1.2 mm yr-1. The active trace of the HCF follows the southern margin of the tectonically active Mount Healy anticline, suggesting a kinematic linkage between the fault that underlies this anticline and the HCF.

The subarctic boreal forest biome is predicted to experience higher magnitudes of warming than other biomes due to climate change. The effects of this warming will be pronounced in areas underlain by discontinuous permafrost where melting permafrost and distinct changes in vegetation patterns are expected. To better understand rates of hillslope diffusion in the boreal forest I have used a geomorphic process modeling approach, using data from a sequence of Quaternary fluvial terraces located in the Nenana River valley of central Alaska. I hypothesized that diffusion rates here would be slower when compared to the mid-latitudes, and faster on north versus south-facing slopes. Calculated diffusion rates do support the hypothesis as they fall on the lower end of the global spectrum of documented hillslope diffusion rates. However, a significant difference in diffusion rates is not seen between the predominantly northeast and southwest facing slopes used in this study.