Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that...
In the face of dramatic declines in groundfish populations and a lack of sufficient stock assessment information, a need has arisen for new methods of assessing groundfish populations. We describe the integration of seafloor transect data gathered by a manned submersible with high-resolution sonar imagery to produce a habitat- based...
One of the most persistent questions regarding the phase equilibria of mid-ocean ridge basalts (MORB) pertains to the petrogenesis of the anorthitic plagioclase phenocrysts (>An₉₀) that are characteristic of the more primitive members of such suites. Anorthitic phenocrysts are present in many if not most MORB suites in spite of...
Debris flows have typically been viewed as two-phase mixtures of sediment and water, but in forested mountain landscapes, wood can represent a sizable fraction of total flow volume. The effects of this third phase on flow behavior are poorly understood. To evaluate whether wood can have a significant effect on...
Steepland valleys subject to debris flows incise bedrock even as episodic deposition typically covers valley bottoms. This paper’s hypothesis is that, while continual fluvial processes evacuate deposits, storage of episodic deposition drives valley widening and, thereby, creation of accommodation space for sediment storage on the valley floor. Data from three...
The magnitude, seasonality, and duration of peak discharge responses to forest removal and regrowth and roads in 10 pairs of experimental basins in the western Cascade Range of Oregon are consistent with fundamental water balance and routing concepts in hydrology. Hypothesized effects of forestry treatments on evapotranspiration, cloud water interception,...
This study examined daily streamflow response over up to four decades in northwest conifer forest and eastern deciduous forest sites in the United States. We used novel methods to analyze daily observations of climate and streamflow spanning more than 900 basin years of record at 14 treated/control basin pairs where...
The modeling of fluvial systems is constrained by a lack of spatial information about the continuity and structure of streambed sediments. There are few methods for noninvasive characterization of streambeds. Invasive methods using wells and cores fail to provide detailed spatial information on the prevailing architecture and its continuity. Geophysical...
We propose the experimental use of resazurin (Raz) and develop a metabolically active transient storage (MATS) model to include processes that may provide additional information on transient storage from a biogeochemical perspective in stream ecosystems. Raz is a phenoxazine compound that reduces irreversibly to resorufin (Rru) in the presence of...
We have reconstructed chronology for the disturbed bottom parts of the GRIP and GISP2 ice cores using the combined paleoatmospheric records of CH₄ concentration and δ¹⁸O[subscript atm] in the trapped gases. Our reconstructed ages for basal ice samples are based on comparison of published measurements of CH₄ and δ¹⁸O[subscript atm]...
Using new and existing ice core CO₂ data from 65 ∼ 30 ka a new chronology for CO₂ is established and synchronized with Greenland ice core records to study how high latitude climate change and the carbon cycle were linked during the last glacial period. Atmospheric CO₂ rose several thousand...
The origin of the Pacific Decadal Oscillation (PDO), the leading mode of sea surface temperature variability for the North Pacific, is a matter of considerable debate. One paradigm views the PDO as an independent mode centered in the North Pacific, while another regards it as a largely reddened response to...
The High Lava Plains province (HLP) is a late Cenozoic bimodal volcanic field at the northern margin of the Basin and Range province in southeastern Oregon that hosts a westward younging trend of silicic volcanism that crudely mirrors northeastward migration of silicic volcanism along the Yellowstone–Snake River Plain (YSRP) trend....
The collapse of the Laurentide Ice Sheet over Hudson Bay ∼8.47 ka allowed the rapid drainage of glacial Lake Agassiz into the Labrador Sea, an event identified as causing a reduction in Atlantic meridional overturning circulation (AMOC) and the 8.2 ka cold event. Atmosphere‐ocean models simulations based on this forcing,...
Coral reef ecosystems are the most diverse on earth, and their subsistence is being threatened by natural and adverse anthropogenic patterns and processes. In an effort to understand and protect these marine environments, several programs have outlined strategies and initiatives. For example, the United States Coral Reef Task Force’s Mapping...
New seafloor mapping and sampling demonstrates that the eruption of the high-Ca boninites is clearly associated with rifting of the northern Tonga ridge and the northern Lau Basin at the northern termination of the Tonga Trench. There is very strong evidence for OIB plume related mantle sources involved in the...
The Mount Fubilan Intrusion is part of a geologically young hypabyssal stock in the Star Mountains of Papua New Guinea. This stock was mapped as the Ok Tedi Intrusive Complex and divided into four separate bodies: the Mount Fubilan, Sydney Intrusion, Kalgoorlie, and Ningi Intrusions. Hydrothermal fluids caused alteration of...
A model for the spatial and temporal evolution of the gray sericitic (GS) and sericite with remnant biotite (SBr) hydrothermal alteration selvages within the Butte Quartz Monzonite (BQM) of the porphyry copper deposit at Butte, Montana, is presented. The model provides a mathematical description for the location and advance of...
This thesis presents a hydrogeologic study of the Parrett Mountain Region,
located approximately 20 miles south of Portland, Oregon. The aim of the study was
to investigate the impacts of Columbia River Basalt on the regional groundwater
system, to expand our understanding of flow through fractured basalt, to improve
management...
Glacial deposits on San Francisco Mountain, Arizona, were mapped in order to provide constraints on ice extents in separate valleys for late Pleistocene glacial events. Qualitative and semi-quantitative relative dating methods were employed in order to correlate moraines between drainages and to provide a basis for distinguishing between separate glacial...