Physical Sciences and Mathematics Commons^™

Rates, Timing, And Cyclicity Of Holocene Eolian Activity In North-Central United States: Evidence From Varved Lake Sediments, Walter E. Dean

United States Geological Survey: Staff Publications

Most of the sediment components that accumulated in Elk Lake, northwestern Minnesota, during the Holocene are autochthonous or biogenic, delivered to the sediment-water interface on a seasonal schedule, preserved in distinct annual laminae (varves). The main allochthonous component is detrital clastic material, as measured by bulk-sediment concentrations of aluminum, sodium, potassium, titanium, and quartz, that enters the lake mostly as eolian dust. The eolian clastic influx to Elk Lake was considerably greater during the mid-Holocene (8–4 ka) than it has been for the past 4000 yr, when periods of increased eolian activity correspond to the time of the Little Ice …

Three-Dimensional Upper Crustal Velocity Structure Beneath San Francisco Peninsula, California, Tom Parsons, Mary Lou Zoback

United States Geological Survey: Staff Publications

This paper presents new seismic data from, and crustal models of the San Francisco Peninsula. In much of central California the San Andreas fault juxtaposes the Cretaceous granitic Salinian terrane on its west and the Late Mesozoic/Early Tertiary Franciscan Complex on its east. On San Francisco Peninsula, however, the present-day San Andreas fault is completely within a Franciscan terrane, and the Pilarcitos fault, located southwest of the San Andreas, marks the Salinian-Franciscan boundary. This circumstance has evoked two different explanations: either the Pilarcitos is a thrust fault that has pushed Franciscan rocks over Salinian rocks or the Pilarcitos is a …

Two-Dimensional Seismic Image Of The San Andreas Fault In The Northern Gabilan Range, Central California Evidence For Fluids In The Fault Zone, C. Thurber, S. Roecker, W. Ellsworth, Y. Chen, W. Lutter, R. Sessions

United States Geological Survey: Staff Publications

A joint inversion for two-dimensional P-wave velocity (Vp), P-to-S velocity ratio (Vp/Vs), and earthquake locations along the San Andreas fault (SAF) in central California reveals a complex relationship among seismicity, fault zone structure, and the surface fault trace. A zone of low Vp andh ighV p/Vs lies beneatht he SAF surfacetr ace( SAFST), extending to a depth of about 6 km. Most of the seismic
activity along the SAF occurs at depths of 3 to 7 km in a southwest-dippingz one that roughly intersectst he SAFST, and lies near the southweset dgeo f the low Vp and high Vp/Vs zones. …

Herbicides And Their Metabolites In Rainfall: Origin, Transport, And Deposition Patterns Across The Midwestern And Northeastern United States, 1990-1991, Donald Goolsby, E. Michael Thurman, Michael Pomes, Michael Meyer, William Battaglin

United States Geological Survey: Staff Publications

Herbicides were detected in rainfall throughout the midwestern and northeastern United States during late spring and summer of 1990 and 1991. Herbicide concentrations exhibited distinct geographic and seasonal patterns. The highest concentrations occurred in midwestern cornbelt states following herbicide application to cropland. Volume-weighted concentrations of 0.2-0.4 μg/L for atrazine and alachlor were typical in this area during mid-April through mid-July, and weighted concentrations as large as 0.6- 0.9 μg/L occurred at several sites. Concentrations of 1-3 μg/L were measured in a few individual samples. Atrazine was detected most often followed by alachlor, deethylatrazine, metolachlor, cyanazine, and deisopropylatrazine. The high ratio …

Analysis Of Environmental Data With Censored Observations, Shiping Liu, Jye-Chyi Lu, Dana Kolpin, William Meeker

United States Geological Survey: Staff Publications

The potential threats to humans and to terrestrial and aquatic ecosystems from environmental contamination could depend on the sum of the concentrations of different chemicals. However, direct summation of environmental data is not generally feasible because it is common for some chemical concentrations to be recorded as being below the analytical reporting limit. This creates special problems in the analysis of the data. A new model selection procedure, named forward censored regression, is introduced for selecting an appropriate model for environmental data with censored observations. The procedure is demonstrated using concentrations of atrazine (2-chloro- 4-ethylamino-6-isopropylamino-s-triazine), deethylatrazine (DEA, 2-amino-4-chloro-6-isopropylamino-s-triazine), and deisopropylatrazine …

A Land-Use And Water-Quality History Of White Rock Lake Reservoir, Dallas, Texas, Based On Paleolimnological Analyses, J. Platt Bradbury, Peter C. Van Metre

United States Geological Survey: Staff Publications

White Rock Lake reservoir in Dallas, Texas contains a 150-cm sediment record of silty clay that documents land-use changes since its construction in 1912. Pollen analysis corroborates historical evidence that between 1912 and 1950 the watershed was primarily agricultural. Land disturbance by plowing coupled with strong and variable spring precipitation caused large amounts of sediment to enter the lake during this period. Diatoms were not preserved at this time probably because of low productivity compared to diatom dissolution by warm, alkaline water prior to burial in the sediments. After 1956, the watershed became progressively urbanized. Erosion decreased, land stabilized, and …

Fracture Permeability And Its Relationship To In-Situ Stress In The Dixie Valley, Nevada, Geothermal Reservoir, Colleen A. Barton, Stephen Hickman, Roger H. Morin, Mark D. Zoback, Thomas Finkbeiner, John Sass, Dick Benoit

United States Geological Survey: Staff Publications

An extensive suite of spinner flowmeter, high-resolution temperature and borehole televiewer logs were acquired in a 2.7-km-deep well drilled into a fault-hosted geothermal reservoir at Dixie Valley, Nevada. Localized perturbations to wellbore temperature and flow were used to identify hydraulically conductive fractures. Comparison of these data with fracture orientations from the borehole televiewer logs indicates that hydraulically conductive fractures in crystalline rocks within and adjacent to the producing fault zone have an orientation distinct from the overall fracture population. In conjunction with in-situ stress measurements from this well, Coulomb analysis indicates that these permeable fractures are critically stressed, potentially active …

Correlation Of Late-Pleistocene Lake-Level Oscillations In Mono Lake, California, With North Atlantic Climate Events, Larry Benson, Steve P. Lund, James W. Burdett, Michaele Kashgarian, Timothy P. Rose, Joseph P. Smoot, Martha Schwartz

United States Geological Survey: Staff Publications

Oxygen-18 (¹⁸O) values of sediment from the Wilson Creek Formation, Mono Basin, California, indicate three scales of temporal variation (Dansgaard-Oeschger, Heinrich, and Milankovitch) in the hydrologic balance of Mono Lake between 35,400 and 12,900 ¹⁴C yr B.P. During this interval, Mono Lake experienced four lowstands each lasting from 1000 to 2000 yr. The youngest low stand, which occurred between 15,500 and 14,000 ¹⁴C yr B.P., was nearly synchronous with a desiccation of Owens Lake, California. Paleomagnetic secular variation (PSV) data indicate that three of four persistent low stands occurred at the same times as Heinrich events …

First Record Of Common Moorhen Nesting In South Dakota, William A. Meeks, Kenneth F. Higgins

United States Geological Survey: Staff Publications

The common moorhen (Gallinula chloropus) is widespread in North America, but is not very abundant throughout its range (Greij 1994, Common Moorhen, Pages 145-157 in Tacha and Braun [eds.] Migratory Shore and Upland Game Bird Management in North America, Allen Press, Lawrence). In North Dakota its status is accidental (Konrad 1983, Prairie Nat. 15:144); in South Dakota it is considered a casual visitor and a probable breeding species (South Dakota Ornithologists' Union 1991, The Birds of South Dakota, Northern State University Press, Aberdeen; Peterson 1995, The Breeding Bird Atlas of South Dakota, Northern State University Press, Aberdeen).

Fractured-Aquifer Hydrogeology From Geophysical Logs; The Passaic Formation, New Jersey, Roger H. Morin, Glen B. Carleton, Stephane Poirier

United States Geological Survey: Staff Publications

The Passaic Formation consists of gradational sequences of mudstone, siltstone, and sandstone, and is a principal aquifer in central New Jersey. Ground-water flow is primarily controlled by fractures interspersed throughout these sedimentary rocks and characterizing these fractures in terms of type, orientation, spatial distribution, frequency, and transmissivity is fundamental towards understanding local fluid-transport processes. To obtain this information, a comprehensive suite of geophysical logs was collected in 10 wells roughly 46 m in depth and located within a .05 km² area in Hopewell Township, New Jersey. A seemingly complex, heterogeneous network of fractures identified with an acoustic televiewer was …

Statistical Modeling Of Agricultural Chemical Occurrence In Midwestern Rivers, William A. Battaglin, Donald A. Goolsby

United States Geological Survey: Staff Publications

Agricultural chemicals in surface water may constitute a human health risk or have adverse effects on aquatic life. Recent research on unregulated rivers in the midwestern USA documents that elevated concentrations of herbicides occur for 1–4 months following application in late spring and early summer. In contrast, nitrate concentrations in unregulated rivers are elevated during fall, winter, and spring months. Natural and anthropogenic variables of river drainage basins, such as soil permeability, amount of agricultural chemicals applied, or percentage of land planted in corn, affect agricultural chemical concentration and mass transport in rivers.

Presented is an analysis of selected data …

Hands-On Geology For Navajo Nation Teachers, Russell Frank Dubiel, Stephen Tom Hasiotis, Steven Christian Semken

United States Geological Survey: Staff Publications

The Navajo Nation comprises the largest land area and the largest population of any Native American community in the United States, and it hosts some of earth's most spectacular geology.

Nearly Synchronous Climate Change In The Northern Hemisphere During The Last Glacial Termination, Larry V. Benson, James Burdett, Steve Lund, Michaele Kashgarian, Scott Mensing

United States Geological Survey: Staff Publications

The climate of the North Atlantic region underwent a series of abrupt cold/warm oscillations when the ice sheets of the Northern Hemisphere retreated during the last glacial termination (17,700–11,500 years ago). Evidence for these oscillations, which are recorded in European terrestrial sediments as the Oldest Dryas/Bølling/ Older Dryas/Allerød/Younger Dryas vegetational sequence, has been found in Greenland ice cores. The geographical extent of many of these oscillations is not well known, but the last major cold event (the Younger Dryas) seems to have been global in extent. Here we present evidence of four major oscillations in the hydrological balance of the …