Publications

Hydrothermal systems currently are active near some gold deposits in northwestern Nevada. Possible links of these modern systems to gold mineralization were evaluated by chemically and isotopically analyzing water samples from the Brady, Dixie Valley, Humboldt House, San Emidio-Empire, Soda Lake, and Wabuska geothermal areas. In addition, quartz veins from Humboldt House and the adjacent...

The Lake Pillsbury area lies in the eastern part of the northern California Coast Ranges, along the east side of the transform boundary between the Pacific and North American plates (fig. 1). The Bartlett Springs Fault Zone is a northwest-trending zone of faulting associated with this eastern part of the transform boundary. It is presently active, based on surface creep (Svarc and others...

Understanding the movement of water through thick vadose zones, especially on time scales encompassing long-term climate change, is increasingly important as societies utilize semi-arid environments for both water resources and sites viewed as favorable for long-term disposal or storage of hazardous waste. Hydrologic responses to Pleistocene climate change within a deep vadose zone in...

It is reasonably clear that disequilibrium or “far-from equilibrium” conditions lead to the formation of silica colloids and their deposition in many epithermal deposits. This implies ore-forming solutions had elevated concentrations of dissolved silica, well in excess of amorphous silica saturation. We have previously demonstrated that such colloidal silica particles were deposited in...

The Lake Mead fault system is a northeast-striking, 130-km-long zone of left-slip in the southeast Great Basin, active from before 16 Ma to Quaternary time. The northeast end of the Lake Mead fault system in the Virgin Mountains of southeast Nevada and northwest Arizona forms a partitioned strain field comprising kinematically linked northeast-striking left-lateral faults, north-striking...

Rock uplift rates can be difficult to measure over 103–105 yr time scales. If, however, a landscape approaches steady state, where hillslope erosion and rock uplift rates are steady and locally similar, then it should be possible to quantify rock uplift rates from hillslope erosion rates. Here, we test this prediction by comparing channel steepness index values and 10Be catchment...

In vitro bioaccessibility (IVBA) studies were carried out on samples of mercury (Hg) mine-waste calcine (roasted Hg ore) by leaching with simulated human body fluids. The objective was to estimate potential human exposure to Hg due to inhalation of airborne calcine particulates and hand-to-mouth ingestion of Hg-bearing calcines. Mine waste calcines collected from Hg mines at Almadén...

Dissolution has removed large volumes of rock at low-angle normal faults, i.e., detachment faults, in the Mormon Mountains and the Tule Springs Hills in the eastern Basin and Range Province, southeastern Nevada. Evidence for major dissolution includes widespread solution-collapse breccias, meter-scale stylolite structures, and high-angle accommodation faults that terminate at or merge...

Proxy evidence at decadal resolution from Late Holocene sediments from Pickerel Lake, northeastern South Dakota, shows distinct centennial cycles (400-700 years) in magnetic susceptibility; contents of carbonate, organic carbon, and major elements; abundance in ostracodes; and delta18O and delta13C values in calcite. Proxies indicate cyclic changes in eolian input, productivity, and...

A snapshot of the thermal state of permafrost in northern North America during the International Polar Year (IPY) was developed using ground temperature data collected from 350 boreholes. More than half these were established during IPY to enhance the network in sparsely monitored regions. The measurement sites span a diverse range of ecoclimatic and geological conditions across the...

New optically stimulated and radiocarbon ages for alluvial fan and lake deposits in the Mojave Desert are presented, which greatly improves the temporal resolution of surface processes. The new Mojave Desert climate-landscape record is particularly detailed for the late Holocene. Evidence from ephemeral lake deposits and landforms indicates times of sustained stream flow during a wet...

Combined petrographic and geochemical methods are used to investigate the microfabrics present in thin sections prepared from representative organic carbon-rich mudstones collected from three successions (the Kimmeridge Clay Formation, the Jet Rock Member of the Whitby Mudstone Formation, and the pebble shale and Hue Shale). This study was initiated to determine how organic carbon-rich...