A sequence of volcanic, volcaniclastic, and epiclastic deposits from Oligocene to Recent age are exposed in the region from Lake
Simtustus to Madras in central Oregon. The epiclastic sediments of the Oligocene John Day Formation are unconformably overlain by two flows of the middle Miocene Columbia River Basalt Group. The...
The goal of dissertation research was to use geochemical, statistical and geological methods to constrain and understand climate variability over several different time scales. Specifically, I have addressed three questions regarding past climate change: (1) how does the record of Irish cirque glaciers constrain the dimensions of the Irish Ice...
This dissertation explores one overarching question relevant to the
paleoclimate of the latest Pleistocene glacial cycle (approximately the last
130,000 years): “How did spatial and temporal evolution of ocean
temperature, both at the surface and interior, relate to other parts of the
climate system in the late Pleistocene?” Results from...
Elevated groundwater nitrate (NO3
-) concentrations in the Southern Willamette
Valley (SWV) caused the Oregon Department of Environmental Quality (ODEQ) to
declare a Groundwater Management Area (GWMA) in Spring, 2004. To better
understand direction of groundwater flow, groundwater age, and nitrate transport
pathways of the SWV we developed a steady-state...
This dissertation presents the results of statistical analyses of large climate datasets from two time intervals – the 20th century instrumental record and the proxy record of the last deglaciation – in order to understand the forcings and mechanisms of past climate variability.
A longstanding question in climate dynamics concerns...
This dissertation presents results from three studies that address major scientific questions in glacial geology and paleoclimatology for the late Pleistocene and Holocene using relatively new geochemical and statistical techniques. Each of the studies attempts to answer a longstanding question in the respective field using geochemical or statistical methods that...
Reconstructing the sensitivity of past climate to forcings, and of ancient glaciers and ice sheets to this climate, can allow us to better understand the range of climate and cryosphere behavior we may see in the coming centuries. The Arctic is a region of particular importance due to its well-documented...
The goals of this dissertation are centered on understanding changes in Earth surface and climate systems through the use of geologic proxies as records of past changes in these systems. Specifically, this dissertation (1) establishes a new chronology for retreat of the Ross Sea sector of the West Antarctic Ice...
This dissertation presents the results of three studies that assessed climate variability on short and long timescales in western United States. The growth of carbonate formations in caves (speleothems) is used to infer the timing and amplitude of past climate variability. We first assess the controls on speleothem growth for...
Numerous investigations demonstrate that mantle convective processes such as upwelling affect the surface topography of the overriding plate. The surface expression of mantle flow has been coined ‘transient topography’. Transient topography in the North American plate is thought to result from a mantle thermal anomaly beneath the Yellowstone volcanic center,...