The Willamette Silt is a surficial geologic unit composed of successive Missoula Flood Deposits that underlies 3100 km2 (1200 mil) of arable land in the Willamette Valley of Oregon. The Willamette Silt protects the underlying regionally important Willamette
Aquifer from agricultural contamination while acting as a semi-confining unit and a...
This dissertation focuses on the role of ice sheets in the transition during the middle Pleistocene (-1.2 Ma) from 41-kyr glacial cycles to 100-kyr glacial cycles. This research evaluates the hypothesis that the middle Pleistocene transition (MPT) was related to the glacial erosion of a regolith mantle and the subsequent...
Three broadly interrelated problems of critical significance to the proper interpretation of melt inclusion (MI) data are addressed in this thesis. The first issue, the petrogenesis of anorthitic plagioclase phenocrysts in MORB lavas, has relevance due to the presence of numerous MI in many high-An feldspars. This problem was addressed...
This project explores mechanisms governing the invasion of fluvial systems by two
contrasting exotic species in stream networks of steep, relatively remote forested landscapes
of western Oregon. This research addresses hypotheses relating limitations of seed source
locations, seed transport processes, and sink availability to the distributions of scotch broom
(Cytisus...
Feeder dikes to the Columbia River Basalt Group (CRBG) large igneous province provide a rare opportunity to examine magma transport through the shallow crust during flood basalt eruptions. Over 70% of the CRBG erupted from the Chief Joseph dike swarm, which is exposed across southeastern Washington, eastern Oregon, and western...
Geomorphic change along the lower Clackamas River is occurring at
a millennial scale due to climate change; a decadal scale as a result River
Mill Dam operation; and at an annual scale since 1996 due to a meander
cutoff. Channel response to these three mechanisms is incision.
Holocene strath terraces,...
Concentration of carbon dioxide (CO₂) in the atmosphere has increased over the past 150 years. Because CO₂ is one of a number of radiatively active gases, there is concern that global temperatures will rise and climatic conditions will change. Recent research indicates northern hemisphere forests may currently be accumulating carbon...
This dissertation concentrates on the controlling factors on the instability of the Laurentide Ice Sheet (LIS) and their effects on abrupt climate change. Northern Hemisphere climate fluctuated abruptly during the last deglaciation possibly related to variability in Atlantic meridional overturning circulation (AMOC) and reduced aerial extent of the LIS. Reductions...
The Tobin Range of central Nevada lies in the Basin and Range extensional province near the transition between more extended terrane (>50%) to the south and east, and generally less extended terrane to the north and west. Geologic mapping, 40Ar/39Ar dating and whole-rock geochemical analysis were employed to establish the...
Dam removal is increasingly viewed as a river restoration tool because dams affect so many aspects of river hydrology, geomorphology, and ecology; but removal also has impacts. When a dam is removed, sediment accumulated over a dam’s lifetime may be transported downstream; and the timing, fate and consequences of this...
This thesis presents a detailed seismotectonic investigation of the Himalayan region and the Tibetan plateau as part of project HiCLIMB to explore the state of stress and the kinematics of the world’s largest continental collision zone. Using full regional waveforms for moment tensor inversion, source parameters for 107 earthquakes were...
In steep headwater basins of the Oregon Coast Range (OCR), debris flows episodically deliver material from low-order tributary basins to larger catchments. Much of this material is stored in valleys and gradually removed by fluvial processes. Quantifying the transfer of material from hillslopes to mainstem channels is essential in understanding...
The northwestern corner of the Basin and Range Province (NWBR) lies in southeast Oregon where extensive Late Miocene, mafic to bimodal basalt-rhyolite volcanism and extensional faults dominate a stark and arid landscape. Near Lake Abert, the Late Miocene volcanic section abuts Early Miocene, dominantly intermediate composition volcanoes at the Coleman...
Accurate estimation of live and dead biomass in forested ecosystems is important for
studies of carbon dynamics, biodiversity, and wildfire behavior, and for forest management.
Lidar remote sensing has been used successfully to estimate live biomass, but studies focusing
on dead biomass are rare. We used lidar data, in conjunction...
Oregon’s High Lava Plains Province (HLP) has strongly bimodal basalt and rhyolitic volcanism. The Province caps the northern margin of the Basin and Range Province and serves as a transitional region between westward extension of the Basin and Range Province and unextended crust to the north . The High Lava...
An integral component to understanding lithospheric rheology, fault mechanics, and geodynamic processes is knowledge of the subsurface thermal regime. This study presents thermal data from 26 new borehole sites drilled during the installation of borehole strain meters as part of the Plate Boundary Observatory (PBO). These data extends existing coverage...
Bar-pool morphology in rivers can provide vital habitat to aquatic species, notably salmonids, which require gravel riffles to bury eggs and pools for hydraulic and cold-water refuge. In some cases, the erosion and subsequent deposition of coarse sediment downstream of a dam removal can modify habitat by inundating bar-pool structure,...
Since 2003, 39 small earthquakes have been detected offshore central Oregon in the nominally locked part of the Cascadia subduction zone, where very little seis- mic activity has been recorded in spite of a paleo-seismic record of great subduction events. Although the regional earthquake bulletin reports depths of 29 and...
In this dissertation the interactions between hydrodynamics, sediment suspension and transport, and morphological evolution in the surf zone was investigated with a large-scale laboratory experiment data, CROss-Shore Sediment Transport Experiment (CROSSTEX). The data set included comprehensive measurements of water surface elevation, fluid velocity, sediment concentration, and morphology for irregular waves...
Numerous flights of Quaternary marine terraces are present around the island of Cyprus, in the Eastern Mediterranean. These terraces are a result of the global eustatic sea-level curve and local tectonism. Marine Isotope Stage (MIS) 5 through MIS 13 terraces are identified, mapped and dated. Palaeoshoreline elevation, an excellent indicator...