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At least 1,405 records · Page 78Linked to original sources
USGS2008

Field Methods and Quality-Assurance Plan for Quality-of-Water Activities, U.S. Geological Survey, Idaho National Laboratory, Idaho

Water-quality activities conducted by the staff of the U.S. Geological Survey (USGS) Idaho National Laboratory (INL) Project Office coincide with the USGS mission of appraising the quantity and quality of the Nation's water resources. The activities are conducted in cooperation with the U.S. Department of Energy's (DOE) Idaho Operations Office. Results of the water-quality investigations are presented in various USGS publications or in refereed scientific journals. The results of the studies are highly regarded, and they are used with confidence by researchers, regulatory and managerial agencies, and interested civic groups. In its broadest sense, quality assurance refers to doing the job right the first time. It includes the functions of planning for products, review and acceptance of the products, and an audit designed to evaluate the system that produces the products. Quality control and quality assurance differ in that quality control ensures that things are done correctly given the 'state-of-the-art' technology, and quality assurance ensures that quality control is maintained within specified limits.

Open-File Report↗
USGS2020

Wetlands in agricultural landscapes—Significant findings and recent advances from CEAP-Wetlands

The Wetlands Component of the USDA's Conservation Effects Assessment Project (CEAP-Wetlands) is a multi-agency effort advancing science related to quantifying and interpreting effects and effectiveness of conservation practices and programs on ecosystem services provided by wetlands in agricultural landscapes. This special section originated from a symposium held at the 73rd Soil and Water Conservation Society's International Annual Conference in Albuquerque New Mexico, July 29 to August 1, 2018. The symposium was jointly organized by the USDA Natural Resources Conservation Service and the US Geological Survey. To facilitate CEAP-Wetlands efforts, several regional assessments were conducted across the United States. These regional assessments were designed to address science gaps hindering wetland conservation and to develop tools facilitating conservation assessments. Conservation decisions affect not just agricultural wetlands, but also the services that these complex ecosystems provide to society. Papers in this special section of the Journal of Soil and Water Conservation present key findings and recent advances from several CEAP-Wetlands regional assessments and discuss the significant contributions of each assessment to an ever-increasing understanding of wetland ecosystems and their provisioning of ecosystem services. Modeling efforts using the Agricultural Policy and Environmental eXtender (APEX) and other process-based models are an integral component of CEAP-Wetlands. Results of these modeling efforts are also presented, and conservation implications are discussed.

Journal of Soil and Water Conservation↗
USGS2016

Apatite fission-track evidence for regional exhumation in the subtropical Eocene, block faulting, and localized fluid flow in east-central Alaska

The origin and antiquity of the subdued topography of the Yukon–Tanana Upland (YTU), the physiographic province between the Denali and Tintina faults, are unresolved questions in the geologic history of interior Alaska and adjacent Yukon. We present apatite fission-track (AFT) results for 33 samples from the 2300 km2 western Fortymile district in the YTU in Alaska and propose an exhumation model that is consistent with preservation of volcanic rocks in valleys that requires base level stability of several drainages since latest Cretaceous–Paleocene time. AFT thermochronology indicates widespread cooling below ∼110 °C at ∼56–47 Ma (early Eocene) and ∼44–36 Ma (middle Eocene). Samples with ∼33–27, ∼19, and ∼10 Ma AFT ages, obtained near a major northeast-trending fault zone, apparently reflect hydrothermal fluid flow. Uplift and erosion following ∼107 Ma magmatism exposed plutonic rocks to different extents in various crustal blocks by latest Cretaceous time. We interpret the Eocene AFT ages to suggest that higher elevations were eroded during the Paleogene subtropical climate of the subarctic, while base level remained essentially stable. Tertiary basins outboard of the YTU contain sediment that may account for the required >2 km of removed overburden that was not carried to the sea by the ancestral Yukon River system. We consider a climate driven explanation for the Eocene AFT ages to be most consistent with geologic constraints in concert with block faulting related to translation on the Denali and Tintina faults resulting from oblique subduction along the southern margin of Alaska.

Alaska↗
USGS1988

Seismic-reflection technique used to verify shallow rebound fracture zones in the Pierre Shale of South Dakota

Shallow seismic-reflection data are presented to demonstrate their usefulness for locating and showing the continuity and lateral extent of rebound fracture zones in the Pierre Shale. Rebound fracture zones, identified in boreholes near Hayes, South Dakota, have variable depth, thickness, and character, thus making questionable the correlation of these zones between holes. Thus, the subsequent determination of dip and of continuity of the zones is somewhat tenuous, especially if the fracture characteristics change significantly between holes. Once rebound fracture zones have been identified and located by borehole geotechnical and geologic data, seismic profiles can reveal the extent and geometry of fractures in these zones, thus providing valuable preconstruction information without the cost of additional drilling.-Authors

South Dakota↗
USGS2021

Field methods, quality-assurance, and data management plan for water-quality activities and water-level measurements, Idaho National Laboratory, Idaho

Introduction Water-quality activities and water-level measurements conducted by the U.S. Geological Survey (USGS) Idaho National Laboratory (INL) Project Office coincide with the USGS mission of appraising the quantity and quality of the Nation’s water resources. The activities are conducted in cooperation with the U.S. Department of Energy’s (DOE) Idaho Operations Office. Results of water-quality and hydraulic head investigations are presented in various USGS publications or in refereed scientific journals, and the data are stored in the National Water Information System (NWIS) database. The results of the studies are used by researchers, regulatory and managerial agencies, and civic groups. In its broadest sense, “quality assurance” refers to doing the job right the first time. It includes the functions of planning for products, review and acceptance of the products, and an audit designed to evaluate the system that produces the products. Quality control and quality assurance differ in that quality control ensures that things are done correctly given the “state-of-the-art” technology, and quality assurance ensures that quality control is maintained within specified limits.

Idaho↗
USGS1990

A literature survey of information on well installation and sample collection procedures used in investigations of ground-water contamination by organic compounds

A survey of literature on well installation and water-quality sampling, particularly as they relate to investigations of ground-water contamination by organic compounds, has been conducted. Library card files and computerized data bases were searched to identify journal articles, conference proceedings, technical reports, books, and other publications. Pertinent information has been extracted from 105 references; each reference is listed in a bibliography. Material contained in the report is organized by topical categories that include drilling methods and equipment, well construction, well development, sampling materials and equipment, decontamination of equipment, and sampling techniques and procedures. Unpublished data of the U.S. Geological Survey on sample collection are briefly cited also.

Open-File Report↗
USGS2005

An evaluation of effects of groundwater exchange on nearshore habitats and water quality of western Lake Erie

Historically, the high potentiometric surface of groundwater in the Silurian/Devonian carbonate aquifer in Monroe County, MI resulted in discharge of highly mineralized, SO 4 -rich groundwater to the Lake Erie shoreline near both Erie State Game Area (ESGA) and Pointe Mouillee State Game Area (PMSGA). Recently, regional groundwater levels near PMSGA have been drawn down as much as 45 m below lake level in apparent response to quarry dewatering. From August to November of 2003, we conducted preliminary studies of groundwater flow dynamics and chemistry, shallow lake water chemistry, and fish and invertebrate communities at both sites. Consistent with regional observations, groundwater flow direction in the nearshore at ESGA was upward, or toward Lake Erie, and shallow nearshore groundwater chemistry was influenced by regional groundwater chemistry. In contrast, at PMSGA, the groundwater flow potential was downward and lake water, influenced by quarry discharge seeping downward into nearshore sediments, produced a different lake and shallow groundwater chemistry than at ESGA. Although the invertebrate and young fish community was similar at the two sites, taxonomic groups tolerant of degraded water quality were more prevalent at PMSGA. Sensitive taxa were more prevalent at ESGA. We propose a conceptual model, based on well-described models of groundwater/seawater interaction along coastal margins, to describe the interconnection among geologic, hydrologic, chemical, and biological processes in the different nearshore habitats of Lake Erie, and we identify processes that warrant further detailed study in the Great Lakes.

Lake Erie↗
USGS2009

Hydrologic support of carbon dioxide flux revealed by whole-lake carbon budgets

Freshwater lakes are an important component of the global carbon cycle through both organic carbon (OC) sequestration and carbon dioxide (CO 2 ) emission. Most lakes have a net annual loss of CO 2 to the atmosphere and substantial current evidence suggests that biologic mineralization of allochthonous OC maintains this flux. Because net CO 2 flux to the atmosphere implies net mineralization of OC within the lake ecosystem, it is also commonly assumed that net annual CO 2 emission indicates negative net ecosystem production (NEP). We explored the relationship between atmospheric CO 2 emission and NEP in two lakes known to have contrasting hydrologie characteristics and net CO 2 emission. We calculated NEP for calendar year 2004 using whole-lake OC and inorganic carbon (IC) budgets, NEP oc and NEP IC , respectively, and compared the resulting values to measured annual CO 2 flux from the lakes. In both lakes, NEP Ic and NEP Ic were positive, indicating net autotrophy. Therefore CO 2 emission from these lakes was apparently not supported by mineralization of allochthonous organic material. In both lakes, hydrologie CO 2 inputs, as well as CO 2 evolved from netcalcite precipitation, could account for the net CO 2 emission. NEP calculated from diel CO 2 measurements was also affected by hydrologie inputs of CO 2 . These results indicate that CO 2 emission and positive NEP may coincide in lakes, especially in carbonate terrain, and that all potential geologic, biogeochemical, and hydrologie sources of CO 2 need to be accounted for when using CO 2 concentrations to infer lake NEP. Copyright 2009 by the American Geophysical Union.

Journal of Geophysical Research G: Biogeosciences↗
USGS1983

Mechanical and chemical compaction in fine-grained shallow-water limestones

Artificial compaction of in-situ cores of sediments resulted in: 1) reduction of sediment thickness by 50 percent and more; 2) reduction of initial porosities of 65 to 75 percent to 35 to 45 percent; 3) creation of megascopic textures almost identical to many ancient lime mud- and wackestone; 4) creation of organic, wispy "stylolite-like" layers; 5) chemical compaction, evidenced by thin sections showing quartz grains piercing mollusc shells without causing fractures and SEM evidence of solutional interfitting of 1 to 4-mu m-size aragonitic carbonate grains; 6) obliteration of pellets and birdseye or fenestral voids in those sediments where early cementation was lacking; obliteration of identifiable marine grasses and vertical "root" tube voids; 8) mashing of sediment-filled circular burrows to produce ellipsoidal structures. Significant mechanical compaction resulted from pressures simulating less than 1,000 ft of burial. Increasing loads to more than 10,000 ft did not significantly increase compaction. Chemical compaction was detected only in cores compacted to pressures greater than 10,000 ft of burial. These experiments suggest that chemical compaction would begin at much shallower depths given geologic time. Experiments that caused chemical compaction lend support to the hypothesis that cement required to produce a low-porosity/low-permeability fine-grained limestone is derived internally. Dissolution, ion diffusion, and reprecipitation are the most likely processes for creating significant thicknesses of dense limestones. Continuation of chemical compaction after significant porosity reduction necessitates expulsion of connate fluids, possibly including hydrocarbons.--Modified journal abstract.

Journal of Sedimentary Petrology↗
USGS2014

Field methods and quality-assurance plan for water-quality activities and water-level measurements, U.S. Geological Survey, Idaho National Laboratory, Idaho

Water-quality activities and water-level measurements by the personnel of the U.S. Geological Survey (USGS) Idaho National Laboratory (INL) Project Office coincide with the USGS mission of appraising the quantity and quality of the Nation’s water resources. The activities are carried out in cooperation with the U.S. Department of Energy (DOE) Idaho Operations Office. Results of the water-quality and hydraulic head investigations are presented in various USGS publications or in refereed scientific journals and the data are stored in the National Water Information System (NWIS) database. The results of the studies are used by researchers, regulatory and managerial agencies, and interested civic groups. In the broadest sense, quality assurance refers to doing the job right the first time. It includes the functions of planning for products, review and acceptance of the products, and an audit designed to evaluate the system that produces the products. Quality control and quality assurance differ in that quality control ensures that things are done correctly given the “state-of-the-art” technology, and quality assurance ensures that quality control is maintained within specified limits.

Open-File Report↗
USGS1993

Oblique synoptic images, produced from digital data, display strong evidence of a "new" caldera in southwestern Guatemala

The synoptic view of broad regions of the Earth's surface as displayed in Landsat and other satellite images has greatly aided in the recognition of calderas, ignimbrite plateaus and other geologic landforms. Remote-sensing images that include visual representation of depth are an even more powerful tool for geologic interpretation of landscapes, but their use has been largely restricted to the exploration of planets other than Earth. By combining Landsat images with digitized topography, we have generated regional oblique views that display compelling evidence for a previously undocumented late-Cenozoic caldera within the active volcanic zone of southwestern Guatemala. This "new" caldera, herein called Xela, is a depression about 30 km wide and 400-600 m deep, which includes the Quezaltenango basin. The caldera depression is breached only by a single river canyon. The caldera outline is broadly circular, but a locally scalloped form suggests the occurrence of multiple caldera-collapse events, or local slumping of steep caldera walls, or both. Within its northern part, Xela caldera contains a toreva block, about 500 m high and 2 km long, that may be incompletely foundered pre-caldera bedrock. Xela contains several post-caldera volcanoes, some of which are active. A Bouguer gravity low, tens of milligals in amplitude, is approximately co-located with the proposed caldera. The oblique images also display an extensive plateau that dips about 2?? away from the north margin of Xela caldera. We interpret this landform to be underlain by pyroclastic outflow from Xela and nearby Atitla??n calderas. Field mapping by others has documented a voluminous rhyolitic pumiceous fallout deposit immediately east of Xela caldera. We speculate that Xela caldera was the source of this deposit. If so, the age of at least part of the caldera is between about 84 ka and 126 ka, the ages of deposits that stratigraphically bracket this fallout. Most of the floor of Xela caldera is covered with Los Chocoyos pyroclastics, 84-ka deposits erupted from Atitla??n caldera. Oblique images produced from digital data are unique tools that can greatly facilitate initial geologic interpretation of morphologically young volcanic (and other) terrains where field access is limited, especially because conventional visual representations commonly lack depth perspective and may cover only part of the region of interest. ?? 1993.

Journal of Volcanology and Geothermal Research↗
USGS2003

Reinterpretation of the stratigraphy and structure of the Rancho Las Norias area, central Sonora, Mexico

New geologic mapping and fossil data in the vicinity of Rancho Las Norias, 30 km east of Hermosillo, Sonora, Mexico, show that rocks previously mapped as Precambrian instead are Paleozoic. Previous geologic maps of the Rancho Las Norias area show northeast-directed, southwest-dipping reverse or thrust faults deforming both Precambrian and Paleozoic rocks. The revised stratigraphy requires reinterpretation of some of these faults as high-angle normal or oblique-slip faults and the elimination of other faults. We agree with earlier geologic map interpretations that compressional structures have affected the Paleozoic rocks in the area, but our mapping suggests that the direction of compression is from southeast to northwest. Published by Elsevier Ltd.

Journal of South American Earth Sciences↗
USGS2013

Merapi 2010 eruption—Chronology and extrusion rates monitored with satellite radar and used in eruption forecasting

Despite dense cloud cover, satellite-borne commercial Synthetic Aperture Radar (SAR) enabled frequent monitoring of Merapi volcano's 2010 eruption. Near-real-time interpretation of images derived from the amplitude of the SAR signals and timely delivery of these interpretations to those responsible for warnings, allowed satellite remote sensing for the first time to play an equal role with in situ seismic, geodetic and gas monitoring in guiding life-saving decisions during a major volcanic crisis. Our remotely sensed data provide an observational chronology for the main phase of the 2010 eruption, which lasted 12 days (26 October–7 November, 2010). Unlike the prolonged low-rate and relatively low explosivity dome-forming and collapse eruptions of recent decades at Merapi, the eruption began with an explosive eruption that produced a new summit crater on 26 October and was accompanied by an ash column and pyroclastic flows that extended 8 km down the flanks. This initial explosive event was followed by smaller explosive eruptions on 29 October–1 November, then by a period of rapid dome growth on 1–4 November, which produced a summit lava dome with a volume of ~ 5 × 10 6 m 3 . A paroxysmal VEI 4 magmatic eruption (with ash column to 17 km altitude) destroyed this dome, greatly enlarged the new summit crater and produced extensive pyroclastic flows (to ~ 16 km radial distance in the Gendol drainage) and surges during the night of 4–5 November. The paroxysmal eruption was followed by a period of jetting of gas and tephra and by a second short period (12 h) of rapid dome growth on 6 November. The eruption ended with low-level ash and steam emissions that buried the 6 November dome with tephra and continued at low levels until seismicity decreased to background levels by about 23 November. Our near-real-time commercial SAR documented the explosive events on 26 October and 4–5 November and high rates of dome growth (> 25 m 3 s − 1 ). An event tree analysis for the previous 2006 Merapi eruption indicated that for lava dome extrusion rates > 1.2 m 3 s − 1 , the probability of a large (1872-scale) eruption was ~ 10%. Consequently, the order-of-magnitude greater rates in 2010, along with the explosive start of the eruption on 26 October, the large volume of lava accumulating at the summit by 4 November, and the rapid and large increases in seismic energy release, deformation and gas emissions were the basis for warnings of an unusually large eruption by the Indonesian Geological Agency's Center for Volcanology and Geologic Hazard Mitigation (CVGHM) and their Volcano Research and Technology Development Center (BPPTK) in Yogyakarta — warnings that saved thousands of lives.

Merapi Volcano↗
USGS2000

Standardizing the nomenclature of Martian impact crater ejecta morphologies

The Mars Crater Morphology Consortium recommends the use of a standardized nomenclature system when discussing Martian impact crater ejecta morphologies. The system utilizes nongenetic descriptors to identify the various ejecta morphologies seen on Mars. This system is designed to facilitate communication and collaboration between researchers. Crater morphology databases will be archived through the U.S. Geological Survey in Flagstaff, where a comprehensive catalog of Martian crater morphologic information will be maintained.

Journal of Geophysical Research E: Planets↗
USGS2007

Olivine friction at the base of oceanic seismogenic zones

We investigate the strength and frictional behavior of olivine aggregates at temperatures and effective confining pressures similar to those at the base of the seismogenic zone on a typical ridge transform fault. Triaxial compression tests were conducted on dry olivine powder (grain size ???60 ??m) at effective confining pressures between 50 and 300 MPa (using Argon as a pore fluid), temperatures between 600??C and 1000??C, and axial displacement rates from 0.06 to 60 ??m/s (axial strain rates from 3 ?? 10-6 to 3 ?? 10-3 s-1). Yielding shows a negative pressure dependence, consistent with predictions for shear enhanced compaction and with the observation that samples exhibit compaction during the initial stages of the experiments. A combination of mechanical data and microstructural observations demonstrate that deformation was accommodated by frictional processes. Sample strengths were pressure-dependent and nearly independent of temperature. Localized shear zones formed in initially homogeneous aggregates early in the experiments. The frictional response to changes in loading rate is well described by rate and state constitutive laws, with a transition from velocity-weakening to velocity-strengthening at 1000??C. Microstructural observations and physical models indicate that plastic yielding of asperities at high temperatures and low axial strain rates stabilizes frictional sliding. Extrapolation of our experimental data to geologic strain rates indicates that a transition from velocity weakening to velocity strengthening occurs at approximately 600??C, consistent with the focal depths of earthquakes in the oceanic lithosphere. Copyright 2007 by the American Geophysical Union.

Journal of Geophysical Research B: Solid Earth↗
USGS2012

Intrusion of horizontal dikes: tectonic significance of Middle Proterozoic diabase sheets widespread in the upper crust of the southwestern United States

Initially horizontal sheet intrusions of Middle Proterozoic diabase are abundant in a region 650 by 300 km across in Arizona and California. The diabase forms discordant sheets in basement granite and gneiss and sills in overlying shelf sedimentary sequences. Massive granite is the most common basement host for the sheets, probably because it fractured more easily than foliated hosts during sheet emplacement. Steep feeder dikes are rare compared to the sheets. The diabase in many places is exposed in fault blocks that were tilted during Tertiary tectonic extension. Structure sections restored from the map patterns of upended blocks show that the sheets were intruded at levels throughout the upper crust, to depths of at least 13 km. Sheet intrusion implies a vertical orientation of the least compressive stress, so I conclude that the crust was under tectonic compression or in an isotropic state of stress at the time of diabase intrusion about 1.1 Ga. Magma overpressures, water encountered by rising magma, vertical changes in the crustal stress regime, and flotation of low-density granite all may be important factors for sheet intrusion. The stress conditions suggested by the presence of the sheets argue against an extensional tectonic regime earlier proposed for the diabase event. The diabase province contrasts structurally with similar-age provinces of basaltic magmatism elsewhere in North America that show evidence of tectonic extension, such as the midcontinent rift. The consistent orientations of the sheets commonly allow them to be used as structural markers for postdiabase deformation of basement blocks. Sheet intrusions in the geologic record may be seriously underreported. Their recognition is important for the interpretation of seismic reflection profiles of continental crust. Sheets in Arizona may be responsible for the Bagdad reflection sequence, which extends to depths of at least 15 km.

Journal of Geophysical Research↗
USGS2004

Landsat yesterday and today: An American vision and an old challenge

Since the late 1960s, the United States government has invested more than $1 billion in designing, launching, and operating the Landsat (land satellite) series of Earth-observing satellites. Global change researchers, geologists, and environmental scientists have used images gathered by the satellites for purposes ranging from human health research, energy exploration, and pollution detection to agricultural assessments, urban growth monitoring, and earthquake lineament studies. The earliest data were captured on a digital medium called wide-band video tape (WBVT). However, two decades of unsound media storage conditions and a poorly maintained processing system have left the physically deteriorating WBVTs with no mechanism for interpretation. A national treasure was in jeopardy. With seed money from the National Aeronautics and Space Administration (NASA), the U.S. Geological Survey (USGS) began a project to rescue the data. More than 21,000 tapes from the 1970s have been transcribed to stable, archival media, preserving the data for future studies in Earth System Science.

Journal of Map & Geography Libraries↗
USGS2006

High-resolution stratigraphy of a Mississippi subdelta-lobe progradation in the Barataria Bight, north-central Gulf of Mexico

The coastal zone of southeastern Louisiana is the product of numerous cycles of progradation, abandonment, and marine transgression of the Mississippi River delta. Currently, the shoreline in the Barataria Bight is undergoing significant erosion and retreat, and understanding its evolution is crucial in stabilization efforts. This study uses an extensive collection of geophysical and sediment core data from Barataria Bay and offshore to develop a geologic model of the shallow (< 10 m) subsurface. The purpose of the model is twofold: (1) establish the stratigraphic architecture of a subdelta lobe of the Bayou des Families delta, deposited by the Mississippi River approximately 4000 years before present; and (2) provide a high-resolution description of the geologic framework in a context that can be applied to coastal management issues in similar fluvially dominated coastal environments worldwide. The results of the study demonstrate how high-quality geologic data from the coastal environment can be used not only to further our understanding of shoreline evolution but also to provide pertinent information for coastal management needs.

Louisiana↗