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At least 253 records · Page 14Linked to original sources
USGS1990

1986 Great Lakes Seismic refraction survey (GLIMPCE): Line A - refraction mode

In the fall of 1986, the Geological Survey of Canada (GSC), the United States Geological Survey (USGS), two Canadian universities -- University of Western Ontario and University of Saskatchewan, and four American universities -- Northern Illinois University, Southern Illinois University, University of Wisconsin-Madison and University of Wisconsin-Oshkosh participated in a major deep seismic experiment in Lake Superior under the GLIMPCE (Great Lakes International Multidisciplinary Program on Crustal Evolution) umbrella. This Open-File Report presents the seismic sections for line A, which was shot specifically for refraction recording. The main target for study by this line was the Mid-Continent Rift System. All recording stations, 31 in total (26 land stations and 5 OBSs), recorded energy from shots fired every two minutes (333 m spacing) by a tuned airgun array towed by a contracted ship along line A in Lake Superior. These data are the densest such data ever recorded in the continental North America over such distances. It is also unique since coincident seismic reflection and refraction are available.

Lake Superior↗
USGS1980

Geology of a zone of metamorphic core complexes in southeastern Arizona

An elongate northwest-trending zone of batholith-size metamorphic core complexes extends some 130 km from the Rincon Mountains to the Picacho Mountains in southeastern Arizona. The complexes are characterized by undeformed to gneissic granitic intrusions, gneissic to phyllonitic xenoliths and wall rocks derived mainly from Precambrian granitic rock, shallow-dipping foliation, and remarkably uniform directions of lineation. Parts of this zone have been recognized and studied extensively for more than 30 yr, but there remains a divergence of opinion about the age, depth of emplacement, and origin of the complexes. Field relations indicate that host rocks as young as or younger than Mesozoic were involved in cataclasis. K-Ar and fission-track ages indicate that the complexes were at temperatures uniformly in excess of 400°C in the middle Tertiary (20 to 30 m.y. ago) and that the bedrock between and very near the complexes was not thermally affected. Tertiary plutons characteristically associated with the high-grade metamorphic rocks are also cataclastically deformed, and stratigraphic depths to the top of metamorphic terranes were no more than 6 km and possibly less than 3 km. These and other data suggest to some that the complexes developed during intrusion of composite batholiths at shallow depth in an anisotropic stress field during the middle Tertiary. On the other hand, Rb-Sr and U-Th-Pb techniques yielded older ages (≥44 m.y.) for some samples. These and additional data suggest to others that major development of cataclasis preceded the middle Tertiary and included regional thrusting.

Arizona↗
USGS2016

Database compilation for the geologic map of the San Francisco volcanic field, north-central Arizona

The main component of this publication is a geologic map database prepared using geographic information system (GIS) applications. The geodatabase of geologic points, lines, and polygons was produced as a compilation from five adjoining map sections originally published as printed maps in 1987 (see references in metadata). Four of the sections (U.S. Geological Survey Miscellaneous Field Studies Maps MF–1957, MF–1958, MF–1959, MF–1960) were created by scanning and geo-referencing stable base map material consisting of mylar positives. The final section (MF–1956) was compiled by hand tracing an enlargement of the available printed paper base map onto mylar using a #00 rapidograph pen, the mylar positive was then digitally scanned and geo-referenced. This method was chosen because the original basemap materials (mylar positives) for the MF–1956 section were unavailable at the time of this publication. Due to the condition of the available MF–1956 map section used as the base (which had previously been folded) the accuracy within the boundary of the MF–1956 section is presumed to be degraded in certain areas. The locations of the degraded areas and the degree of degradation within these areas is unclear. Final compilation of the database was completed using the ArcScan toolset, and the Editor toolset in ESRI ArcMap 10.1. Polygon topology was created from the lines and labels were added to the resultant geological polygons, lines, and points. Joseph A. Bard and David W. Ramsey updated and corrected the geodatabase, created the metadata and web presence, and provided the GIS-expertise to bring the geodatabase and metadata to completion. Included are links to files to view or print the original map sheets and the accompanying pamphlets. The orignial geologic maps were prepared under the Geothermal Research Program of the U.S. Geological Survey as a basis for interpreting the history of magmatic activity in the volcanic field. The San Francisco field, which is largely Pleistocene in age, is in northern Arizona, just north of the broad transition zone between the Colorado Plateau and the Basin and Range province. It is one of several dominantly basaltic volcanic fields of the late Cenozoic age situated near the margin of the Colorado Plateau. The volcanic field contains rocks ranging in composition from basalt to rhyolite—the products of eruption through Precambrian basement rocks and approximately a kilometer of overlying, nearly horizontal, Paleozoic and Mesozoic sedimentary rocks. About 500 km 3 of erupted rocks cover about 5,000 km 2 of predominantly Permian and locally preserved Triassic sedimentary rocks that form the erosionally stripped surface of the Colorado Plateau in Northern Arizona.

Arizona↗
USGS1979

Water resources of the Santa Rosa Indian Reservation and vicinity, Riverside County, California

The Santa Rosa Indian Reservation is a 17-square-mile area located between the Santa Rosa and San Jacinto Mountains in south-central Riverside County, Calif. The source of water in most of the study area is precipitation on the three topographic subbasins that nearly surround the reservation. Precipitation averages about 12 inches annually (18,000 acre-feet per year), with 10 inches (15,000 acre-feet per year) of it returning to the air by evapotranspiration, 1 inch (1,500 acre-feet per year) running off from the area, and 1 inch (1,500 acre-feet per year) going to ground-water recharge. Local geology and the shape of the ground-water basin, as defined by a gravity survey, indicate that the area receives no ground-water inflow from outside the study area. Production of a dry-farm crop is planned for the 800-acre area west of Vandeventer Flat on the reservation's main section. Additional water supplies are needed for crop irrigation. At present (1979), water is obtained from a supply well that taps the saturated section of the sandy material overlying the basement complex of Cretaceous age or older. Existing data indicate that the aquifer may not yield large volumes of water to individual wells. A specific capacity of about 0.4 gallon per minute per foot of drawdown was measured at the supply well. Estimates of specific yield for the material encountered during the drilling of three wells and a test hole were 5 to 10 percent. The thickest section of the aquifer in the Vandeventer Flat area was outlined by a gravity survey. Test wells should provide information on thickness of the aquifer, aquifer properties, and potential well yield. Damming of area streams could also supply irrigation water. Average runoff totals about 1,500 acre-feet per year, with greater volumes lost during periods of heavy precipitation and flooding. Peak discharge from the central and southern subbasins totaled about 160 acre-feet per hour during the January-March period of 1978. Water-quality analyses for the supply well and five major springs indicate that the ground water is suitable for irrigation everywhere except at Sulphur Spring, where the percent sodium of 97 is above recommended maximum levels, and at Bull Canyon Spring, where water of 1,300 micromhos specific conductance is considered a high salinity hazard. The sulfate concentration of 290 milligrams per liter in Bull Canyon Spring is above the recommended maximum level for drinking water.

California↗
USGS2020

Geologic map of the Bonanza caldera area, northeastern San Juan Mountains, Colorado

The San Juan Mountains in southwestern Colorado have long been known as a site of exceptionally voluminous mid-Tertiary volcanism, including at least 22 major ignimbrite sheets (each 150–5,000 km³) and associated caldera structures active at 34–23 Ma. Recent volcanologic and petrologic studies in the San Juan region have focused mainly on several ignimbrite-caldera systems: the southeastern area (Platoro complex), western calderas (Uncompahgre-Silverton-Lake City), and the central cluster (La Garita-Creede calderas). Far less studied has been the northeastern San Juan region, which occupies a transition between earlier volcanism in central Colorado and large-volume younger ignimbrite-caldera foci farther south and west. This map is based on new field coverage of volcanic rocks in thirteen 7.5' quadrangles in northeastern parts of the volcanic field, high-resolution age determinations for 130 sites, and petrologic studies involving several hundred new chemical analyses. This mapping and the accompanying lab results (1) document volcanic evolution of the deeply eroded Bonanza caldera that exposes unique features not previously described from ignimbrite calderas elsewhere, as well as the previously unstudied Marshall Pass caldera; (2) provide unique cross-sectional exposures of the steeply resurgent Bonanza caldera, from volcanic floor and underlying basement rocks through a complete 3.5-km-thick section of intracaldera ignimbrite and overlying compositionally diverse caldera-filling lavas; (3) document timing of caldera collapse concurrently with eruption of about 1,000 km 3 of ignimbrite that oscillated in composition from mafic dacite to rhyolite; (4) quantify the regional time-space-volume progression from the earlier Sawatch magmatic trend southward into the San Juan region; and (5) permit more rigorous comparison between the broad mid-Tertiary magmatic belt in the western U.S. Cordillera and the type continental-margin arc volcanism of the central Andes in South America.

Scientific Investigations Map↗
USGS2013

Streamflow statistics for unregulated and regulated conditions for selected locations on the Yellowstone, Tongue, and Powder Rivers, Montana, 1928-2002

Major floods in 1996 and 1997 on the Yellowstone River in Montana intensified public debate over the effects of human activities on the Yellowstone River. In 1999, the Yellowstone River Conservation District Council was formed to address conservation issues on the river. The Yellowstone River Conservation District Council partnered with the U.S. Army Corps of Engineers to conduct a cumulative-effects study on the main stem of the Yellowstone River. The cumulative-effects study is intended to provide a basis for future management decisions in the watershed. Streamflow statistics, such as flow-frequency and flow-duration data calculated for unregulated and regulated streamflow conditions, are a necessary component of the cumulative effects study. The U.S. Geological Survey, in cooperation with the Yellowstone River Conservation District Council and the U.S. Army Corps of Engineers, calculated streamflow statistics for unregulated and regulated conditions for the Yellowstone, Tongue, and Powder Rivers for the 1928–2002 study period. Unregulated streamflow represents flow conditions that might have occurred during the 1928–2002 study period if there had been no water-resources development in the Yellowstone River Basin. Regulated streamflow represents estimates of flow conditions during the 1928–2002 study period if the level of water-resources development existing in 2002 was in place during the entire study period. Peak-flow frequency estimates for regulated and unregulated streamflow were developed using methods described in Bulletin 17B. High-flow frequency and low-flow frequency data were developed for regulated and unregulated streamflows from the annual series of highest and lowest (respectively) mean flows for specified n-day consecutive periods within the calendar year. Flow-duration data, and monthly and annual streamflow characteristics, also were calculated for the unregulated and regulated streamflows.

Montana;North Dakota;Wyoming↗
USGS1996

Use of liquefaction-induced features for paleoseismic analysis

Liquefaction features can be used in many field settings to estimate the recurrence interval and magnitude of strong earthquakes through much of the Holocene. These features include dikes, craters, vented sand, sills, and laterally spreading landslides. The relatively high seismic shaking level required for their formation makes them particularly valuable as records of strong paleo-earthquakes. This state-of-the-art summary for using liquefaction-induced features for paleoseismic interpretation and analysis takes into account both geological and geotechnical engineering perspectives. The driving mechanism for formation of the features is primarily the increased pore-water pressure associated with liquefaction of sand-rich sediment. The role of this mechanism is often supplemented greatly by the direct action of seismic shaking at the ground surface, which strains and breaks the clay-rich cap that lies immediately above the sediment that liquefied. Discussed in the text are the processes involved in formation of the features, as well as their morphology and characteristics in field settings. Whether liquefaction occurs is controlled mainly by sediment grain size, sediment packing, depth to the water table, and strength and duration of seismic shaking. Formation of recognizable features in the field generally requires a low-permeability cap above the sediment that liquefied. Field manifestations are controlled largely by the severity of liquefaction and the thickness and properties of the low-permeability cap. Criteria are presented for determining whether observed sediment deformation in the field originated by seismically induced liquefaction. These criteria have been developed mainly by observing historic effects of liquefaction in varied field settings. The most important criterion is that a seismic liquefaction origin requires widespread, regional development of features around a core area where the effects are most severe. In addition, the features must have a morphology that is consistent with a very sudden application of a large hydraulic force. This article discusses case studies in widely separated and different geological settings: coastal South Carolina, the New Madrid seismic zone, the Wabash Valley seismic zone, and coastal Washington State. These studies encompass most of the range of settings and the types of liquefaction-induced features likely to be encountered anywhere. The case studies describe the observed features and the logic for assigning a seismic liquefaction origin to them. Also discussed are some types of sediment deformations that can be misinterpreted as having a seismic origin. Two independent methods for estimating prehistoric magnitude are discussed briefly. One method is based on determination of the maximum distance from the epicenter over which liquefaction-induced effects have formed. The other method is based on use of geotechnical engineering techniques at sites of marginal liquefaction, in order to bracket the peak accelerations as a function of epicentral distance; these accelerations can then be compared with predictions from seismological models.

Engineering Geology↗
USGS2018

Water-table and potentiometric-surface altitudes in the upper glacial, Magothy, and Lloyd aquifers of Long Island, New York, April–May 2016

The U.S. Geological Survey, in cooperation with State and local agencies, systematically collects groundwater data at varying measurement frequencies to monitor the hydrologic conditions on Long Island, New York. Each year during April and May, the U.S. Geological Survey completes a synoptic survey of water levels to define the spatial distribution of the water table and potentiometric surfaces within the three main water-bearing units underlying Long Island—the upper glacial, Magothy, and Lloyd aquifers—and the hydraulically connected Jameco and North Shore aquifers. These data and the maps constructed from them are commonly used in studies of the hydrology of Long Island and are used by water managers and suppliers for aquifer management and planning purposes. Water-level measurements made in 424 monitoring wells (observation and supply wells), 13 streamgages, and 2 lake gages across Long Island during April–May 2016 were used to prepare the maps in this report. Groundwater measurements were made by the wetted-tape or electric-tape method to the nearest hundredth of a foot. Contours of water-table and potentiometric-surface altitudes were created using the groundwater measurements. The water-table contours were interpreted using water-level data collected from 275 observation wells and 1 supply well screened in the upper glacial aquifer and the shallow Magothy aquifer and 13 streamgages and 2 lake gages. The potentiometric-surface contours of the Magothy aquifer were interpreted from measurements at 88 wells (61 observation wells and 27 supply wells) screened in the middle to deep Magothy aquifer and the contiguous and hydraulically connected Jameco aquifer. The potentiometric-surface contours of the Lloyd aquifer were interpreted from measurements at 60 wells (55 observation wells and 5 supply wells) screened in the Lloyd aquifer and the contiguous and hydraulically connected North Shore aquifer. Many of the supply wells are in continuous operation and, therefore, were turned off for a minimum of 24 hours before measurements were made to allow the water levels in the wells to recover to ambient (nonpumping) conditions. Full recovery time at some of these supply wells can exceed 24 hours; therefore, water levels measured at these wells are assumed to be less accurate than those measured at observation wells, which are not pumped. In addition to pumping stresses, density differences (saline water) also lower the water levels measured in certain wells. Recent water-quality data are lacking in these wells; therefore, a conversion to freshwater head could not be performed accurately and was not attempted. In this report, all water-level altitudes are referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29). The land surface altitude, or topography, was obtained from the National Oceanic and Atmospheric Administration. The data were collected using light detection and ranging (lidar) and were used to produce a three-dimensional digital elevation model. The lidar data have a horizontal accuracy of 1.38 feet and a vertical accuracy of 0.40 foot at a 95-percent confidence level for the “open terrain” land-cover category. The digital elevation model was developed jointly by the National Oceanic and Atmospheric Administration and the U.S. Geological Survey as part of the Disaster Relief Appropriations Act of 2013. Land surface altitude is referenced to the North American Vertical Datum of 1988 (NAVD 88). On Long Island, NAVD 88 is approximately 1 foot higher than NGVD 29. Hydrographs are included on these maps for selected wells that have continuous digital recording equipment, and each hydrograph includes the water level measured during the synoptic survey. These hydrographs are representative of the 2016 water year and show the changes throughout that period; a water year is the 12-month period from October 1 to September 30 and is designated by the year in which it ends.

New York↗
USGS2003

Associations among land-use, habitat characteristics, and invertebrate community structure in nine streams on the island of Oahu, Hawaii

The island of Oahu is one of 51 study units established as part of the U.S. Geological Surveys National Water-Quality Assessment (NAWQA) program to assess the status and trends of the Nations surface and ground-water resources, and to link status and trends with an understanding of the natural and human factors that affect water quality. As part of the NAWQA program, benthic invertebrate communities were surveyed at ten sites in nine streams representing the three main types of land use on Oahu: urban, agriculture, and forested. At each sampling site, habitat characteristics were determined at a range of spatial scales including drainage basin, segment, reach, transect, and point. Associations among land use, habitat characteristics, and benthic invertebrate community structure were examined. The rapid population growth and increasing urbanization on Oahu has resulted in substantial stream habitat alteration. Instream habitat characteristics at the urban and mixed (urban and agriculture) land-use sites were markedly different from those at the forested sites. Urban and mixed land-use sites, most of which were channelized, tended to have less riparian vegetation, higher water temperatures, smaller substrate, and higher levels of embeddedness and siltation than sites in forested watersheds. The majority of invertebrate taxa identified during this study were non-native. Invertebrate abundance was lower at urban and mixed land-use sites than at forested sites, while species richness (the number of different species) showed the opposite pattern. Multivariate analyses indicated that invertebrate species composition was similar at sites with similar land use. Aquatic insects of the orders Diptera and Trichoptera were the most common insects in all samples. The ratio of Diptera to Trichoptera abundance varied with urbanization. Forested sites were dominated by Trichoptera, and urban and mixed land-use sites were dominated by Diptera. Molluscs typically occurred in channelized urban streams although no native molluscs were collected during this study. The most abundant molluscs were pan-tropical thiarid snails, the introduced clam Corbicula fluminea, and the limpet Ferrissia sharpi. Two native and four introduced species of Crustacea were collected at the sampling sites. To effectively manage Hawaiian watersheds for native species and the communities they form, the ways in which these species respond to human-induced changes needs to be understood. This report provides important information describing the usefulness of invertebrates as indicators of stream quality conditions and how an integrated assessment of stream quality will allow for the development of appropriate monitoring and management strategies.

Water-Resources Investigations Report↗
USGS2001

Geologic map and map database of the Spreckels 7.5-minute Quadrangle, Monterey County, California

Introduction The Spreckels quadrangle lies at the north end of the Sierra de Salinas and extends from the Salinas Valley on the northeast across Los Laurelles Ridge south to Carmel Valley, an intermontane valley that separates the Santa Lucia Range from the Sierra de Salinas (fig. 1). The Toro Regional Park occupies the east-central part of the quadrangle, whereas the former Fort Ord Military Reservation covers the northwestern part of the area and is the probable locus of future development. Subdivisions largely occupy the older floodplain of Toro Creek and the adjacent foothills, with less dense development along the narrower canyons of Corral de Tierra and San Benancio Gulch to the south. The foothills southwest of the Salinas River are the site of active residential development. Geologically, the study area has a crystalline basement of Upper Cretaceous granitic rocks of the Salinian block and older metasedimentary rocks of the schist of the Sierra de Salinas of probable Cretaceous age. Resting nonconformably upon these basement rocks is a sedimentary section that ranges in age from middle Miocene to Holocene and has a composite thickness of as much as 1,200 m. One of the purposes of the present study was to investigate the apparent lateral variation of the middle to upper Miocene sections from the typical porcelaneous and diatomaceous Monterey Formation of the Monterey and Seaside quadrangles to the west (Clark and others, 1997) to a thick marine sandstone section in the eastern part of the Spreckels quadrangle. Liquefaction, which seriously affected the Spreckels area in the 1906 San Francisco earthquake (Lawson, 1908), and landsliding are the two major geological hazards of the area. The landslides consist mainly of older large slides in the southern and younger debris flows in the northern part of the quadrangle. This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (skmf.txt, skmf.pdf, or skmf.ps), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:24,000 or smaller.

Miscellaneous Field Studies Map↗
USGS2020

Planetary science decadal survey planetary mission concept study report: Ceres: Exploration of Ceres’ habitability

Dwarf planet Ceres is a compelling target as an evolved ocean world with, at least, regional brine reservoirs and potentially ongoing geological activity. As the most water-rich body in the inner solar system (in relative abundance), it is a representative of the population of planetesimals that brought volatiles and organics to the inner solar system. Situated in the Main Belt of asteroids, Ceres is accessible enough for a sample return with the resources of a typical medium-class (New Frontiers) NASA mission. Under the Discovery program, Dawn explored Ceres from 2015 to 2018. The extensive dataset revealed the presence of liquid, brine-driven activity, organic matter, and a rich salt chemistry. With this evidence, the overarching goals of the mission concept presented herein are to quantify Ceres’ current habitability potential and origin.

Cooperator Report↗
USGS1979

Petrographic and trace-element data on rocks from the Yemen Arab Republic

Petrographic descriptions are given for rocks in the Yemen Arab Republic (YAR), including mainly Precambrian igneous and metamorphic rocks from the southeastern part of the country, which previously was geologically undescribed. Also included are descriptions of Cretaceous and/or Tertiary lavas of the Yemen Volcanics, Miocene(?) alkali granite, Pliocene caprock of the Guma salt dome, and late Pleistocene and Holocene basalts of the Aden Volcanic Series (?). The petrographic studies permitted the selection of 11 samples of rock for future use in obtaining isotopic analyses for age determinations. Analyses of these rock specimens for trace amounts of gold, indium, mercury, selenium, and thallium completed the geochemical studies. Results of these analyses are interpreted to show that regional geochemical exploration should be undertaken for base and precious metals near Jibal Hufash, the Manakhah area, the region around Al Bayda, the Sa'dah-Majadh area, and the Wadi Jawf area. Additional studies of trace elements in commercial salt deposits of the YAR should be made to evaluate the amounts of mercury and selenium in this industrial raw material.

Open-File Report↗
USGS1981

Stratigraphy, sedimentology, and paleomagnetism of the Coral Ridge sand body, eastern Taylor Valley, Victoria Land, Antarctica

A body of moderately well sorted and well stratified ice-cemented sand, here informally called the Coral Ridge sand body, was deposited across eastern Taylor Valley before the deposition of a veneer of glaciogenic deposits related to late Pleistocene incursions of the Ross Sea ice sheet. The Coral Ridge sand body is more than 50 m thick where preserved in a north-south trending ridge that is transverse to the long axis of the valley. The ridge forms a drainage divide that stands 100 m above sea level and separates the basin of Lake Fryxell on the west from the seacoast to the east. An erosion surface having about 35 m of abrupt local relief was apparently developed on the sand body before the latest incursions of Ross Sea ice. The Coral Ridge sand body accumulated in a fluviatile or possibly fluviomarine deltaic environment following deposition of coarse diamictons and interbedded layers of sand in a fjord that once occupied the site of Taylor Valley. From its sedimentary characteristics and topographic distribution, the sand was deposited across the valley following filling of the fjord. The 1) comparatively high degree of sorting, 2) general lack of clay and silt, and of very coarse detritus, and 3) common fluviatile cross-stratification, argue for stream transport and for accumulation principally above sea level. Coarse glacial detritus, which must have existed in the source area, was not transported to the area of sand deposition. Very fine glacial detritus that presumably was transported with the sand was deposited some place beyond the area of sand deposition. Evidence bearing on the direction of transport, and thus the source area, has not yet been developed. The source could have been a grounded ice sheet in the Ross Sea to the east, or alternatively, the source could have lay to the west in the area of the Lake Fryxell basin at a time when the basin was occupied by a more extensive Taylor Glacier. Evidence bearing on the age of the Coral Ridge sand body also is not fully developed. West of the Coral Ridge divide, the upper 2-3 m of a 14-mthick section of Coral Ridge sand near the top of hole DVDP-11 is reversely polarized. All other beds of the ice-cemented sand have been found to be normally polarized. Two possibilities exist: 1) the Coral Ridge sand body was deposited during late Pliocene time, mainly during a time of normal polarity of the Gauss polarity epoch, or 2) the sand body is much younger and was deposited during the Bruhnes normal polarity epoch of Pleistocene time, less than 730,000 years ago (in which case, the reversely polarized strata are anomalous). Additional subsurface and surface geological and paleomagnetic study is required to resolve the problems of age and source, critical to deciphering the late Cenozoic glacial and structural history of Taylor Valley and environs.

Victoria Land↗
USGS2021

Assessment of streamflow and water quality in the Upper Yampa River Basin, Colorado, 1992–2018

The Upper Yampa River Basin drains approximately 2,100 square miles west of the Continental Divide in north-western Colorado. There is a growing need to understand potential changes in the quantity and quality of water resources as the basin is undergoing increasing land and water development to support growing municipal, industrial, and recreational needs. The U.S. Geological Survey, in cooperation with stakeholders in the Upper Yampa River Basin water community, began a study to characterize and identify changes in streamflow and selected water-quality constituents, including suspended sediment, Kjeldahl nitrogen, total nitrogen, total phosphorus, and orthophosphate, in the basin. This study used streamflow and water-quality data from selected U.S. Geological Survey sites to provide a better understanding of how major factors, including land use, climate change, and geological features, may influence streamflow and water quality. Analysis of long-term (1910–2018) and short-term (1992–2018) records of streamflow at main-stem Yampa River and tributary sites indicate downward trends in one or more streamflow statistics, including 1-day maximum, mean, and 7-day minimum. Long-term downward trends in daily mean streamflow in April (22 percent overall) at Yampa River at Steamboat Springs, Colorado, correspond to observed changes in streamflow documented across western North America and the Colorado River Basin that are predominately associated with changes in snowmelt runoff and temperatures. During the short-term period of analysis, decreases in streamflow at main-stem Yampa River and some tributary sites are likely related to changes in consumptive use and reservoir management or, at sites with no upstream flow impoundments, changes in irrigation diversions and climate. Concentrations of water-quality constituents were typically highest in spring (March, April, and May) during the early snowmelt runoff period as material that is washed off the land surface drains into streams. Highest concentrations occurred slightly later, in May, June, and July, at Yampa River above Stagecoach Reservoir, Colo., and slightly earlier, in February and March at Yampa River at Milner, Colo., indicating that these sites may have different or additional sources of phosphorus from upstream inputs. Yampa River at Milner, Colo., and Yampa River above Elkhead Creek, Colo., had the highest net yields of suspended sediment, Kjeldahl nitrogen, and total phosphorus, and are likely influenced by land use and erosion as the basins of both of these sites are underlain by highly erodible Cretaceous shales. Upward trends in estimated Kjeldahl nitrogen and total phosphorus concentrations and loads were found at Yampa River at Steamboat Springs, Colo. From 1999 to 2018, the Kjeldahl nitrogen concentration increased by 10 percent or 0.035 milligram per liter, and load increased by 22 percent or 26 tons. Total phosphorus concentration increased by 20 percent or 0.0081 milligram per liter, and loads increased by 41 percent or 6.2 tons. Decreases in streamflow and changes in land use may contribute to these trends. During multiple summer sampling events at Stagecoach Reservoir, the physical and chemical factors indicated conditions conducive to cyanobacterial blooms, including surface-water temperatures greater than 20 degrees Celsius and total phosphorus and total nitrogen concentrations in exceedance of Colorado Department of Public Health and Environment interim concentrations for water-quality standards. Local geological features (predominately sandstones and shales) and additional inputs from upstream land use likely contribute to the elevated nutrient conditions in Stagecoach Reservoir.

Colorado↗
USGS2021

Two-event genesis of Butte lode veins: Geologic and geochronologic evidence from ore veins, dikes, and host plutons

The long-standing ore-genesis model for world-class deposits of the Butte mining district, Montana, is of deep pre-Main Stage porphyry Cu-Mo and overlying Main Stage Ag-Zn-Cu-zoned lode veinsformed from discrete hydrothermal systems related to rhyolite dikes. The lode-specific model describes metals zones that formed in the lode veins as hydrothermal processes diminished in intensity (changing temperature and chemical characteristics) outward from the district center. New geologic and multi-method geochronologic studies pro- vide new timing constraints on the lode veins and reevaluation of geologic relations (Lund and others, 2018), leading to a new model for formation of the lode veins and their relations to stockwork Cu-Mo deposits and igneous events.

Montana↗
USGS2001

Biology and conservation of the common murre in California, Oregon, Washington, and British Columbia: Vol. 1, Natural history and population trends

Over the past 30 years, the common murre ( Uria aalge californica ) has been recognized as a prominent indicator of marine conservation issues in California, Oregon, Washington, and British Columbia, especially regarding oil pollution, certain fisheries, and human disturbance. To assist the effective management of the common murre and the marine environments in which they live, this summary of available information on the biology and regional status of the common murre has been sponsored by the U.S. Fish and Wildlife Service (Division of Migratory Bird Management). In Volume 1 (Chapter 1), the natural history of the common murre is summarized, drawing heavily on breeding studies from the South Farallon Islands, California, plus a host of detailed breeding studies from the North Atlantic Ocean. Population trends of the common murre are summarized in Volume 1 (Chapter 2), focusing on changes in whole-colony counts determined from aerial photographs between the late 1970s and 1995 in California, Oregon and Washington. Historical data and human impacts to murre colonies since the early nineteenth century are also summarized. Volume 2 will summarize population threats, conservation, and management. Information presented in Volume 1 has been obtained and recorded by a large number of researchers and natural historians over two centuries. From the 1960s to 1995, most work in California, Oregon, and Washington was sponsored by the U.S. Fish and Wildlife Service, Minerals Management Service, and California Department of Fish and Game. Important breeding biology studies were conducted at the South Farallon Islands (Farallon National Wildlife Refuge) by the Point Reyes Bird Observatory, in coordination with the U.S. Fish and Wildlife Service (San Francisco Bay National Wildlife Refuge). Colony surveys in California were conducted mainly by the U.S. Fish and Wildlife Service (San Francisco Bay National Wildlife Refuge), U.S. Geological Survey (Western Ecological Research Center, Dixon Field Station), Humboldt State University, and University of California (Santa Cruz). Colony surveys in Oregon and Washington were conducted mainly by the U.S. Fish and Wildlife Service (Oregon Coast National Wildlife Refuge and Washington Maritime National Wildlife Refuges). In British Columbia, most work from the 1960s to 1995 was sponsored and conducted by the Canadian Wildlife Service and Royal British Columbia Museum.

British Columbia, California, Oregon, Washington↗
USGS2021

Effects of hydrologic variability and remedial actions on first flush and metal loading from streams draining the Silverton caldera, 1992–2014

This study examined water quality in the upper Animas River watershed, a mined watershed that gained notoriety following the 2015 Gold King mine release of acid mine drainage to downstream communities. Water-quality data were used to evaluate trends in metal concentrations and loads over a two-decade period. Selected sites included three sites on tributary streams and one main-stem site on the Animas River downstream from the tributary confluences. During the study period, metal concentrations and loads varied seasonally and annually because of hydrologic variability and remedial actions designed to ameliorate the effects of acid mine drainage. Water-quality data were divided into two periods based on the timing of remedial activities in the watershed. The first period includes active water treatment, surface reclamation and installation of bulkheads in adits; the second period includes the decade following these activities. Water-quality data were used to estimate annual and monthly zinc loads using the Adjusted Maximum Likelihood Method (using LOADEST software) and U.S. Geological Survey streamflow data. This study presents one of the first applications of LOADEST focused on metal loads. Monthly flow-weighted concentrations were analysed using a Mann-Kendall trend test to determine the direction, magnitude, and significance of temporal trends in zinc loading in any given month and using t -test comparisons between the two periods. Zinc loads estimated for the Animas River below the tributaries indicate decreased zinc loading during the rising limb of the hydrograph in the second period, perhaps reflecting a reduction of snowmelt-derived zinc load following surface reclamation activities. In contrast, base-flow zinc loading increased at the main-stem site, perhaps because of the cessation of water treatment in tributary streams. Flow weighting of monthly load estimates yielded increased statistical significance and enabled more nuanced differentiation between the effects of hydrologic variability and remedial activities on zinc loading.

Colorado↗
USGS2004

Structural geology of the proposed site area for a high-level radioactive waste repository, Yucca Mountain, Nevada

Geologic mapping and fracture studies have documented the fundamental patterns of joints and faults in the thick sequence of rhyolite tuffs at Yucca Mountain, Nevada, the proposed site of an underground repository for high-level radioactive waste. The largest structures are north-striking, block-bounding normal faults (with a subordinate left-lateral component) that divide the mountain into numerous 1-4-km-wide panels of gently east-dipping strata. Block-bounding faults, which underwent Quaternary movement as well as earlier Neogene movement, are linked by dominantly northwest-striking relay faults, especially in the more extended southern part of Yucca Mountain. Intrablock faults are commonly short and discontinuous, except those on the more intensely deformed margins of the blocks. Lithologic properties of the local tuff stratigraphy strongly control the mesoscale fracture network, and locally the fracture network has a strong influence on the nature of intrablock faulting. The least faulted part of Yucca Mountain is the north-central part, the site of the proposed repository. Although bounded by complex normal-fault systems, the 4-km-wide central block contains only sparse intrablock faults. Locally intense jointing appears to be strata-bound. The complexity of deformation and the magnitude of extension increase in all directions away from the proposed repository volume, especially in the southern part of the mountain where the intensity of deformation and the amount of vertical-axis rotation increase markedly. Block-bounding faults were active at Yucca Mountain during and after eruption of the 12.8-12.7 Ma Paintbrush Group, and significant motion on these faults postdated the 11.6 Ma Rainier Mesa Tuff. Diminished fault activity continued into Quaternary time. Roughly half of the stratal tilting in the site area occurred after 11.6 Ma, probably synchronous with the main pulse of vertical-axis rotation, which occurred between 11.6 and 11.45 Ma. Studies of sequential formation of tectonic joints, in the context of regional paleostress studies, indicate that north- and northwest-striking joint sets formed coevally with the main faulting episode during regional east-northeast-west-southwest extension and that a prominent northeast-striking joint set formed later, probably after 9 Ma. These structural analyses contribute to the understanding of several important issues at Yucca Mountain, including potential hydrologic pathways, seismic hazards, and fault-displacement hazards. ?? 2004 Geological Society of America.

Geological Society of America Bulletin↗