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At least 73 records · Page 4Linked to original sources
USGS2015

Geochemical reanalysis of historical U.S. Geological Survey sediment samples from the Inmachuk, Kugruk, Kiwalik, and Koyuk River drainages, Granite Mountain, and the northern Darby Mountains, Bendeleben, Candle, Kotzebue, and Solomon quadrangles, Alaska

The State of Alaska’s Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska’s statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. As part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. The USGS is also undertaking SCM-related geologic studies in Alaska through the federally funded Alaska Critical Minerals cooperative project. DGGS and USGS share the goal of evaluating Alaska’s strategic and critical minerals potential and together created a Letter of Agreement (signed December 2012) and a supplementary Technical Assistance Agreement (#14CMTAA143458) to facilitate the two agencies’ cooperative work. Under these agreements, DGGS contracted the USGS in Denver to reanalyze historical USGS sediment samples from Alaska. For this report, DGGS funded reanalysis of 653 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from an area covering portions of the Inmachuk, Kugruk, Kiwalik, and Koyuk river drainages, Granite Mountain, and the northern Darby Mountains, located in the Bendeleben, Candle, Kotzebue, and Solomon quadrangles of eastern Seward Peninsula, Alaska (fig. 1). The USGS was responsible for sample retrieval from the National Geochemical Sample Archive (NGSA) in Denver, Colorado through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.

Alaska↗
USGS2013

Symposium 9: Rocky Mountain futures: preserving, utilizing, and sustaining Rocky Mountain ecosystems

In 2002 we published Rocky Mountain Futures, an Ecological Perspective (Island Press) to examine the cumulative ecological effects of human activity in the Rocky Mountains. We concluded that multiple local activities concerning land use, hydrologic manipulation, and resource extraction have altered ecosystems, although there were examples where the “tyranny of small decisions” worked in a positive way toward more sustainable coupled human/environment interactions. Superimposed on local change was climate change, atmospheric deposition of nitrogen and other pollutants, regional population growth, and some national management policies such as fire suppression.

Bulletin of the Ecological Society of America↗
USGS2004

Pesticides in mountain yellow-legged frogs (Rana muscosa) from the Sierra Nevada Mountains of California, USA

In 1997, pesticide concentrations were measured in mountain yellow-legged frogs (Rana muscosa) from two areas in the Sierra Nevada Mountains of California, USA. One area (Sixty Lakes Basin, Kings Canyon National Park) had large, apparently healthy populations of frogs. A second area (Tablelands, Sequoia National Park) once had large populations, but the species had been extirpated from this area by the early 1980s. The Tablelands is exposed directly to prevailing winds from agricultural regions to the west. When an experimental reintroduction of R. muscosa in 1994 to 1995 was deemed unsuccessful in 1997, the last 20 (reintroduced) frogs that could be found were collected from the Tablelands, and pesticide concentrations in both frog tissue and the water were measured at both the Tablelands and at reference sites at Sixty Lakes. In frog tissues, dichlorodiphenyldichloroethylene (DDE) concentration was one to two orders of magnitude higher than the other organochlorines (46 ?? 20 ng/g wet wt at Tablelands and 17 ?? 8 Sixty Lakes). Both ??-chlordane and trans-nonachlor were found in significantly greater concentrations in Tablelands frog tissues compared with Sixty Lakes. Organophosphate insecticides, chlorpyrifos, and diazinon were observed primarily in surface water with higher concentrations at the Tablelands sites. No contaminants were significantly higher in our Sixty Lakes samples.

Environmental Toxicology and Chemistry↗
USGS1985

Aeromagnetic map and analysis of aeromagnetic and aeroradioactivity data in the Blood Mountain, Chattahoochee, and Tray Mountain Roadless Areas, northern Georgia

The data for the aerornagnetic map of the Blood Mountain, Chattahoochee, and Tray Mountain Roadless Areas and vicinity were compiled from two separate airborne surveys {U.S. Geological Survey, 1977, 1981) produced in cooperation with the State of Georgia. These surveys were flown by fixed - wing aircraft in 1976 and 1981 at 500 ft (150 m) above mean terrain along rarallel flight lines oriented northwest-southeast. Flight-line spacing is 0.5 mi (0.8 km} for the 1981 survey, which covers the major part of the map, and l mi (1.6 km) for the 1976 survey, which covers the southeast corner of the map. The 1976 survey was adjusted to the magnetic level of the 1981 survey and recontoured where the surveys join. The International Geomagnetic Reference Field (Barraclough and Fabiano, 1975) has been removed from the data of each survey.

Georgia↗
USGS2003

Geologic surface effects of underground nuclear testing: Buckboard Mesa, Climax Stock, Dome Mountain, Frenchman Flat, Rainier/Aqueduct Mesa, and Shoshone Mountain: Nevada Test Site, Nevada

Surface effects maps were produced for 72 of 89 underground detonations conducted at the Frenchman Flat, Rainier Mesa and Aqueduct Mesa, Climax Stock, Shoshone Mountain, Buckboard Mesa, and Dome Mountain testing areas of the Nevada Test Site between August 10, 1957 (Saturn detonation, Area 12) and September 18, 1992 (Hunters Trophy detonation, Area 12). The ?Other Areas? Surface Effects Map Database, which was used to construct the maps shown in this report, contains digital reproductions of these original maps. The database is provided in both ArcGIS (v. 8.2) geodatabase format and ArcView (v. 3.2) shapefile format. This database contains sinks, cracks, faults, and other surface effects having a combined (cumulative) length of 136.38 km (84.74 mi). In GIS digital format, the user can view all surface effects maps simultaneously, select and view the surface effects of one or more sites of interest, or view specific surface effects by area or site. Three map layers comprise the database. They are: (1) the surface effects maps layer (oase_n27f), (2) the bar symbols layer (oase_bar_n27f), and (3) the ball symbols layer (oase_ball_n27f). Additionally, an annotation layer, named 'Ball_and_Bar_Labels,' and a polygon features layer, named 'Area12_features_poly_n27f,' are contained in the geodatabase version of the database. The annotation layer automatically labels all 295 ball-and-bar symbols shown on these maps. The polygon features layer displays areas of ground disturbances, such as rock spall and disturbed ground caused by the detonations. Shapefile versions of the polygon features layer in Nevada State Plane and Universal Transverse Mercator projections, named 'area12_features_poly_n27f.shp' and 'area12_features_poly_u83m.shp,' are also provided in the archive.

Nevada↗
USGS1979

Tertiary volcanic rocks of the Mineral Mountain and Teapot Mountain quadrangles, Pinal County, Arizona

The widespread distribution of Tertiary volcanic rocks in south-central Arizona is controlled in part by prevolcanic structures along which volcanic vents were localized. Volcanic rocks in the Mineral Mountain and Teapot Mountain quadrangles mark the site of a major northwest-trending structural hingeline. This hingeline divides an older Precambrian X terrane on the west from intensely deformed sequences of rock as young as Pennsylvanian on the east, suggesting increased westerly uplift. The volcanic rocks consist of a pile of complexly interlayered rhyolite, andesite, dacite, flows and intrusive rocks, water-laid tuffs, and very minor olivine basalt. Although the rocks erupted from several different vents, time relations, space relations, and chemistry each give strong evidence of a single source for all the rocks. Available data (by the K-Ar dating method) on hornblende and biotite separates from the volcanic rocks range from 14 to 19 m.y. and establish the pre-middle Miocene age of major dislocations along the structural hingeline. Most of the volcanic rocks contain glass, either at the base of the flows or as an envelope around the intrusive phases. One of the intrusive rhyolites, however, seems to represent one of the final eruptions. Intense vesiculation of the intrusive rhyolite suggests a large content of volatiles at the time of its eruption. Mineralization is associated with the more silicic of these middle Miocene volcanic rocks; specifically, extensive fissure quartz veins contain locally significant amounts of silver, lead, and zinc and minor amounts of gold. Many of the most productive deposits are hosted by the volcanic rocks, although others occur in the Precambrian rocks. Magnetic data correspond roughly to the geology in outlining the overall extent of the volcanic rocks as a magnetic low.

Open-File Report↗
USGS2017

At the foot of the smoking mountains: The 2014 scientific investigations in the Islands of the Four Mountains

An interdisciplinary research team conducted archaeological, geological, and biological investigations in the Islands of the Four Mountains, Alaska during the summer of 2014 as part of a three-year project to study long-term geological and ecological patterns and processes with respect to human settlement. Researchers investigated three archaeological sites on Chuginadak Island (SAM-0014, SAM-0016 and SAM-0047) and two archaeological sites on Carlisle Island (AMK-0003 and SAM-0034) as well as peat, tephra, and lava deposition on those islands. These investigations resulted in the delineation of archaeological sites, documentation of geological and cultural stratigraphy, excavation of house-pit features, visual characterization and sampling of potential lithic sources, and documentation of Unangan occupation in the Islands of the Four Mountains from roughly 3,800 years ago to Russian contact.

Arctic Anthropology↗
USGS2013

Simulated impacts of mountain pine beetle and wildfire disturbances on forest vegetation composition and carbon stocks in the Southern Rocky Mountains

Forests play an important role in sequestering carbon and offsetting anthropogenic greenhouse gas emissions, but changing disturbance regimes may compromise the capability of forests to store carbon. In the Southern Rocky Mountains, a recent outbreak of mountain pine beetle (Dendroctonus ponderosae; MPB) has caused levels of tree mortality that are unprecedented in recorded history. To evaluate the long-term impacts of both this insect outbreak and another characteristic disturbance in these forests, high-severity wildfire, we simulated potential changes in species composition and carbon stocks using the Forest Vegetation Simulator (FVS). Simulations were completed for 3 scenarios (no disturbance, actual MPB infestation, and modeled wildfire) using field data collected in 2010 at 97 plots in the lodgepole pine-dominated forests of eastern Grand County, Colorado, which were heavily impacted by MPB after 2002. Results of the simulations showed that (1) lodgepole pine remained dominant over time in all scenarios, with basal area recovering to pre-disturbance levels 70–80 yr after disturbance; (2) wildfire caused a greater magnitude of change than did MPB in both patterns of succession and distribution of carbon among biomass pools; (3) levels of standing-live carbon returned to pre-disturbance conditions after 40 vs. 50 yr following MPB vs. wildfire disturbance, respectively, but took 120 vs. 150 yr to converge with conditions in the undisturbed scenario. Lodgepole pine forests appear to be relatively resilient to both of the disturbances we modeled, although changes in climate, future disturbance regimes, and other factors may significantly affect future rates of regeneration and ecosystem response.

Biogeosciences Discussions↗
USGS2009

Integrating GIS-based geologic mapping, LiDAR-based lineament analysis and site specific rock slope data to delineate a zone of existing and potential rock slope instability located along the grandfather mountain window-Linville Falls shear zone contact, Southern Appalachian Mountains, Watauga County, North Carolina

Landslide hazard maps of Watauga County identify >2200 landslides, model debris flow susceptibility, and evaluate a 14km x 0.5km zone of existing and potential rock slope instability (ZEPRSI) near the Town of Boone. The ZEPRSI encompasses west-northwest trending (WNWT) topographic ridges where 14 active/past-active rock/weathered rock slides occur mainly in rocks of the Grandfather Mountain Window (GMW). The north side of this ridgeline is the GMW / Linville Falls Fault (LFF) contact. Sheared rocks of the Linville Falls Shear Zone (LFSZ) occur along the ridge and locally in the valley north of the contact. The valley is underlain principally by layered granitic gneiss comprising the Linville Falls/Beech Mountain/Stone Mountain Thrust Sheet. The integration of ArcGIS??? - format digital geologic and lineament mapping on a 6m LiDAR (Light Detecting and Ranging) digital elevation model (DEM) base, and kinematic analyses of site specific rock slope data (e.g., presence and degree of ductile and brittle deformation fabrics, rock type, rock weathering state) indicate: WNWT lineaments are expressions of a regionally extensive zone of fractures and faults; and ZEPRSI rock slope failures concentrate along excavated, north-facing LFF/LFSZ slopes where brittle fabrics overprint older metamorphic foliations, and other fractures create side and back release surfaces. Copyright 2009 ARMA, American Rock Mechanics Association.

Conference Paper↗
USGS2014

Mountain pine beetle-caused mortality over eight years in two pine hosts in mixed conifer stands of the southern Rocky Mountains

Eruptive mountain pine beetle ( Dendroctonus ponderosae , MPB) populations have caused widespread mortality of pines throughout western North America since the late 1990s. Early work by A.D. Hopkins suggested that when alternate host species are available, MPB will prefer to breed in the host to which it has become adapted. In Colorado, epidemic MPB populations that originated in lodgepole pine expanded into mixed-conifer stands containing ponderosa pine, a related host. We evaluated the susceptibility of both hosts to successful MPB colonization in a survey of 19 sites in pine-dominated mixed-conifer stands spanning 140 km of the Front Range, CO, USA. In each of three 0.2-ha plots at each site, we (1) assessed trees in the annual flights of 2008–2011 to compare MPB-caused mortality between lodgepole and ponderosa pine; (2) recorded previous MPB-caused tree mortality from 2004–2007 to establish baseline mortality levels; and (3) measured characteristics of the stands (e.g. tree basal area) and sites (e.g. elevation, aspect) that might be correlated with MPB colonization. Uninfested average live basal area of lodgepole and ponderosa pine was 74% of total basal area before 2004. We found that for both species, annual percent basal area of attacked trees was greatest in one year (2009), and was lower in all other years (2004–2007, 2008, 2010, and 2011). Both pine species had similar average total mortality of 38–39% by 2011. Significant predictors of ponderosa pine mortality in a given year were basal area of uninfested ponderosa pine and the previous year’s mortality levels in both ponderosa and lodgepole pine. Lodgepole pine mortality was predicted by uninfested basal areas of both lodgepole and ponderosa pine, and the previous year’s lodgepole pine mortality. These results indicate host selection by MPB from lodgepole pine natal hosts into ponderosa pine the following year, but not the reverse. In both species, diameters of attacked trees within each year were similar, and were progressively smaller the last four years of the study period. Our results suggest that, in contrast to previous reports, ponderosa and lodgepole pine were equally susceptible to MPB infestation in the CO Front Range during our study period. This suggests that forest managers may anticipate similar impacts in both hosts during similar environmental conditions when epidemic-level MPB populations are active in mixed-pine stands.

Colorado↗
USGS2009

Rocky Mountain evolution: Tying Continental Dynamics of the Rocky Mountains and Deep Probe seismic experiments with receiver functions

In this study, we have determined the crustal structure using three different receiver function methods using data collected from the northern transect of the Continental Dynamics of the Rocky Mountains (CD-ROM) experiment. The resulting migrated image and crustal thickness determinations confirm and refine prior crustal thickness measurements based on the CD-ROM and Deep Probe experiment data sets. The new results show a very distinct and thick lower crustal layer beneath the Archean Wyoming province. In addition, we are able to show its termination at 42??N latitude, which provides a seismic tie between the CD-ROM and Deep Probe seismic experiments and thus completes a continuous north-south transect extending from New Mexico into Alberta, Canada. This new tie is particularly important because it occurs close to a major tectonic boundary, the Cheyenne belt, between an Archean craton and a Proterozoic terrane. We used two different stacking techniques, based on a similar concept but using two different ways to estimate uncertainties. Furthermore, we used receiver function migration and common conversion point (CCP) stacking techniques. The combined interpretation of all our results shows (1) crustal thinning in southern Wyoming, (2) strong northward crustal thickening beginning in central Wyoming, (3) the presence of an unusually thick and high-velocity lower crust beneath the Wyoming province, and (4) the abrupt termination of this lower crustal layer north of the Cheyenne belt at 42??N latitude. Copyright 2009 by the American Geophysical Union.

Journal of Geophysical Research B: Solid Earth↗
USGS2005

Estimating ground-water recharge from streamflow hydrographs for a small mountain watershed in a temperate humid climate, New Hampshire, USA

Hydrographs of stream discharge were analyzed to determine ground-water recharge for two small basins draining into Mirror Lake, New Hampshire. Two methods of hydrograph analysis developed for determining ground-water recharge were evaluated, the instantaneous recharge method and the constant recharge method. For the instantaneous recharge method, recharge is assumed to be instantaneous and uniform over the basin. For the constant recharge method, recharge is assumed to be constant and uniform over the basin for a period of weeks to months. Both methods require that a ground-water recession slope be determined. The recession slope is used directly in the calculation for the instantaneous recharge method, and it is used as a base of reference for fitting a type curve in the constant recharge method. Results of the study indicated that the estimates of ground-water recharge for both methods agree to within about 10 percent. Two approaches to the instantaneous recharge method, manual and automated, were also evaluated, and the results were statistically similar. The baseflow component of streamflow commonly is assumed to be equivalent to ground-water recharge; therefore, two methods developed for determining the baseflow component of streamflow, graphical partitioning and digital filtering, were evaluated also. Baseflow values determined by graphical partitioning of hydrographs were about 25 percent less than the ground-water recharge values. Baseflow values determined by two different approaches to the mathematical digital filtering method were generally less than baseflow determined by graphical partitioning. However, one of the approaches to digital filtering agreed reasonably well with graphical partitioning if an appropriate filter constant was used. The other approach to digital filtering resulted in baseflow values that were much less than the other baseflow values and was therefore deemed inappropriate for use on these small mountain watersheds.

Groundwater↗
USGS2002

Rocky Mountain snowpack chemistry network: History, methods, and the importance of monitoring mountain ecosystems

Because regional-scale atmospheric deposition data in the Rocky Mountains are sparse, a program was designed by the U.S. Geological Survey to more thoroughly determine the quality of precipitation and to identify sources of atmospherically deposited pollution in a network of high-elevation sites. Depth-integrated samples of seasonal snowpacks at 52 sampling sites, in a network from New Mexico to Montana, were collected and analyzed each year since 1993. The results of the first 5 years (1993–97) of the program are discussed in this report. Spatial patterns in regional data have emerged from the geographically distributed chemical concentrations of ammonium, nitrate, and sulfate that clearly indicate that concentrations of these acid precursors in less developed areas of the region are lower than concentrations in the heavily developed areas. Snowpacks in northern Colorado that lie adjacent to both the highly developed Denver metropolitan area to the east and coal-fired powerplants to the west had the highest overall concentrations of nitrate and sulfate in the network. Ammonium concentrations were highest in northwestern Wyoming and southern Montana.

Rocky Mountains↗
USGS1995

Geology of the Blue Mountains region of Oregon, Idaho, and Washington: Petrology and tectonic evolution of pre-Tertiary rocks of the Blue Mountains region

This Professional Paper contains 14 chapters on the Blue Mountains region of Oregon, Idaho, and Washington. The authors discuss petrology and tectonic evolution of an island arc that formed in the ancestral Pacific Ocean during the Permian to Cretaceous interval. The island arc was accreted to cratonal North America in the Early Cretaceous and thereby became one of the several exotic terranes in western North America.

Idaho, Oregon, Washington↗
USGS2002

Persistence of an unusual pelagic zooplankton assemblage in a clear, mountain lake

The planktonic zooplankton assemblage in Mowich Lake, Mount Rainier National Park (MORA), was composed almost entirely of rotifers in 1966 and 1967. Adult pelagic crustacean taxa were rare. Their paucity was attributed to predation by kokanee salmon (Oncorhynchus nerka), which had been stocked in 1961. During a park-wide survey of 24 lakes in 1988, Mowich Lake was the only one that did not contain at least one planktonic crustacean species. Given the apparent persistence of the unusual pelagic zooplankton assemblage in Mowich Lake, the first objective of this study was to document the interannual variation in the taxonomic structure of the zooplankton assemblages in the lake from 1988 through 1999. A second objective was to determine if it was possible to predict the taxonomic composition of the pelagic crustacean zooplankton assemblage in Mowich Lake prior to the stocking of kokanee salmon. The Mowich Lake zooplankton assemblages in 1988-1999 were consistent with those in 1966 and 1967. Crustacean taxa were extremely rare, but they included most of the primary taxa collected from 23 MORA lakes surveyed in 1988. Nonetheless, the 1988 collections showed that the September rotifer assemblage in Mowich Lake was similar to 10 of the 24 lakes sampled. Seven of the 10 lakes were dominated by cladocerans, primarily Daphnia rosea and Holopedium gibberum. Therefore, it appeared that either one or both of these species may have numerically dominated the crustacean zooplankton assemblage in the lake prior to 1961.

Hydrobiologia↗