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At least 793 records · Page 44Linked to original sources
USGS2000

Evolution of the Creede Caldera and its relation to mineralization in the Creede mining district, Colorado

At 25 Ma a major epithermal silver and base metal deposit formed in rhyolitic welded tuff near Creede, Colorado. Nearly 24000 metric tons of silver, appreciable lead, and small amounts of zinc, copper, and gold, have been produced from large, crustified veins under Bachelor and Bulldog Mountains north and northwest of Creede. Prior geologic, hydrologic, and stable-isotope studies showed that ore deposition was associated with the mixing and boiling of waters from diverse sources and suggester that a critical part of the ore-forming fluid may have originated within the ancient lake and sediments of the lacustrine Creede Formation that filled the Creede caldera. Two drill holes that sampled the heretofore hidden lower half of the Creede Formation are the focus of this book. The Creede caldera formed at 26.9 Ma within a high constructional plateau of silicic ashflows that covered and were sporadically interlayed with, intermediate lavas and lahars from large stratovolcanoes. The Creede caldera lake had an inflow evaporation balance that did not permit rapid filling to create a brim-full deep lake. Thus salts were evaporatively concentrated; but, with the exception of possible gypsum, no evaporite minerals preserved. Cool springs deposited travertine as mounds and contributed to limestone interlaminations within the sediment. The lake bottom was anoxic, and bacterial reduction of sulfate led to extreme sulfur isotopic fractionation in diagenetic pyrite. The caldera gradually resurged, converting the initial equant lake into an arcuate moat. Resurgent doming, alluvial fans, lacustrine sediments, ashfalls, and lava domes displaced water, lifted the lake so that it overlapped what later became the southern edge of the mineralized are, and eventually filled the basin. At 25.1 Ma an unseen pluton intruded beneath the northen part of the Creede district and created a convecting olume that drew in brine from the Creede caldera fill, meteotic water from highlands to the north, and possibly a fluid carrying radiogenic lead. These waters mixed and boiled as they approached the surface and moved southward, deposited a zoned epithermal deposit a few hundred meters below the paleosurface, and finally discharged into the top of the Creede Formation. The sulfide in the ores was the igneous derivation, but the sulfate was a mixture of biogenic sulfur from the Creede Formation, oxidized igneous sulfide, and thermochemically reduced and partially oxygen exchanged sulfate. The studies of the Creede caldera provide key observational and conceptual elements for the generalized model of the Creede ore deposit. The relation of the Creed ore deposit to a brine reservoir has broad significance because other brine accumulations (as in the Great Basin, the Green River Basin, or the playas of the Altiplano offer similar setting and exploration opportunities.

Colorado↗
USGS2003

Multiple stressor effects in relation to declining amphibian populations

Original research discusses the protocols and approaches to studying the effects of multiple environmental stressors on amphibian populations and gives new perspectives on this complicated subject. This new publication integrates a variety of stressors that can act in concert and may ultimately cause a decline in amphibian populations. Sixteen peer-reviewed papers cover: Toxicity Assessment examines methods, which range from long-established laboratory approaches for evaluating adverse chemical effects to amphibians, to methods that link chemicals in surface waters, sediments, and soils with adverse effects observed among amphibians in the field. Field and Laboratory Studies illustrates studies in the evaluation of multiple stressor effects that may lead to declining amphibian populations. A range of laboratory and field studies of chemicals, such as herbicides, insecticides, chlorinated organic compounds, metals, and complex mixtures are also included. Causal Analysis demonstrates the range of tools currently available for evaluating "cause-effect" relationships between environmental stressors and declining amphibian populations. Audience: This new publication is a must-have for scientists and resource management professionals from diverse fields, including ecotoxicology, chemistry, ecology, field biology, conservation biology, and natural resource management.

Special Technical Report↗
USGS2016

Concentration and retention of Toxoplasma gondii surrogates from seawater by red abalone (Haliotis rufescens)

Small marine snails and abalone have been identified as high- and low-risk prey items, respectively, for exposure of threatened southern sea otters to Toxoplasma gondii , a zoonotic parasite that can cause fatal encephalitis in animals and humans. While recent work has characterized snails as paratenic hosts for T. gondii , the ability of abalone to vector the parasite has not been evaluated. To further elucidate why abalone predation may be protective against T. gondii exposure, this study aimed to determine whether: (1) abalone are physiologically capable of acquiring T. gondii ; and (2) abalone and snails differ in their ability to concentrate and retain the parasite. Abalone were exposed to T. gondii surrogate microspheres for 24 h, and fecal samples were examined for 2 weeks following exposure. Concentration of surrogates was 2–3 orders of magnitude greater in abalone feces than in the spiked seawater, and excretion of surrogates continued for 14 days post-exposure. These results indicate that, physiologically, abalone and snails can equally vector T. gondii as paratenic hosts. Reduced risk of T. gondii infection in abalone-specializing otters may therefore result from abalone's high nutritional value, which implies otters must consume fewer animals to meet their caloric needs.

Parasitology↗
USGS2013

Advanced and applied remote sensing of environmental conditions

"Remote sensing” is a general term for monitoring techniques that collect information without being in physical contact with the object of study. Overhead imagery from aircraft and satellite sensors provides the most common form of remotely sensed data and records the interaction of electromagnetic energy (usually visible light) with matter, such as the Earth’s surface. Remotely sensed data are fundamental to geographic science. The U.S. Geological Survey’s (USGS) Eastern Geographic Science Center (EGSC) is currently conducting and promoting the research and development of several different aspects of remote sensing science in both the laboratory and from overhead instruments. Spectroscopy is the science of recording interactions of energy and matter and is the bench science for all remote sensing. Visible and infrared analysis in the laboratory with special instruments called spectrometers enables the transfer of this research from the laboratory to multispectral (5–15 broad bands) and hyperspectral (50–300 narrow contiguous bands) analyses from aircraft and satellite sensors. In addition, mid-wave (3–5 micrometers, µm) and long-wave (8–14 µm) infrared data analysis, such as attenuated total reflectance (ATR) spectral analysis, are also conducted. ATR is a special form of vibrational infrared spectroscopy that has many applications in chemistry and biology but has recently been shown to be especially diagnostic for vegetation analysis.

Fact Sheet↗
USGS1905

Economic geology of the Bingham mining district, Utah

The field work of which this report represents the final results was first undertaken in the summer of the year 1900. This district had long been selected by the writer as worthy of special economic investigation, as well on account of the importance of its products as because of its geological structure and the peculiar relations of its ore deposits. It was not, however, until the summer mentioned above that the means at the disposal of the Survey, both pecuniary and scientific, justified its undertaking. As originally planned, the areal or surface geology was to have been worked out by Mr. Keith, who had already spent many years in unraveling the complicated geological structure of the Appalachian province, while Mr. Boutwell, who had more recently become attached to the Survey, was to have charge of the underground geology, or a study of the ore deposits, under the immediate supervision of the writer. When the time came for actually taking the field, it was found that the pressure of other work would not permit Mr. Keith to carry out fully the part allotted to him, and in consequence a part of his field work has fallen to Mr. Boutwell. Field work was commenced by the writer and Mr. Boutwell early in July, 1900. Mr. Keith joined the party on August 10, but was obliged to leave for other duties early in September. Mr. Boutwell carried on his field work continuously from July until December, taking up underground work after the snowfall had rendered work on the surface geology impracticable. The geological structure had proved to be unexpectedly intricate and complicated, so that, on the opening of the field season of 1901, it was found necessary to make further study in the light of results already worked out, and Mr. Boutwell spent some weeks in the district in the early summer of 1901. His field work that year, partly in California and partly in Arizona, as assistant to Mr. Waldemar Lindgren, lasted through the summer and winter and well into the spring of 1902, so that but little time , was left before he was obliged to take the field again in his study of the Park City district of Utah. Mr. Keith had been too closely occupied with his Appalachian work to complete his part,' and thus the publication of this report has been unusually delayed. While the delay is a cause for regret, this regret is much tempered by the consideration that had the report been published earlier many facts brought to light during the vigorous development of the region in late years, which have an important bearing upon the structure and genesis of the ore deposits, could not have been used in its preparation.

Utah↗
USGS1983

Oxygen and strontium isotopic studies of basaltic lavas from the Snake River plain, Idaho

The Snake Creek-Williams Canyon pluton of the southern Snake Range crops out over an area of about 30 km2, about 60 km southeast of Ely, Nev. This Jurassic intrusion displays large and systematic chemical and mineralogical zonation over a horizontal distance of 5 km. Major-element variations compare closely with Dalyls average andesite-dacite-rhyolite over an SiO2 range of 63 to 76 percent. For various reasons it was originally thought that assimilation played a dominant role in development of the Snake Creek-Williams Canyon pluton. However, based on modeling of more recently obtained trace element and isotopic data, we have concluded that the zonation is the result of in-situ fractional crystallization, with little assimilation at the level of crystallization. This report summarizes data available for each of the mineral species present in the zoned intrusion. Special attention has been paid to trends We present oxygen and strontium isotopic data for olivine tholeiites, evolved (that is, differentiated and (or) contaminated) lavas, rhyolites, and crustal- derived xenoliths from the Snake River Plain. These data show that the olivine tholeiites are fairly uniform in d80 (5.1 to 6.2) and 87Sr/86Sr (0.7056 to 0.7076) and reveal no correlation between these ratios. The tholeiites are considered representative of mantle-derived magmas that have not interacted significantly with crustal material or meteoric water. The evolved lavas display a wider range in d 80 (5.6 to 7.6) and 87Sr/86Sr (0.708 to 0.717) with positive correlations between these ratios in some suites but not in others. Crustal xenoliths have high and variable 8?Sr/86Sr (0.715 to 0.830) and d80 values that vary widely (6.7 to 9.2) and are a few permil greater than d80 values of the Snake River basalts. Thus, isotopic data for the evolved lavas are permissive of small degrees of contamination by crustal rocks similar to the most d80-depleted xenoliths. The d80 enrichments in some evolved lavas also are consistent with crystal fractionation processes and do not necessarily require bulk interaction with crustal rocks. Enrichment in d80 but not in 87Sr/86Sr in one suite of evolved lavas suggests that crustal contamination may not be essential to the petrogenesis of those lavas. Other suites of evolved lavas display large variations in 87Sr/86Sr that reflect at least some selective contamination with 87St. Bulk solid/liquid oxygen-isotope fractionation factors (a's) calculated for the evolved lavas from Craters of the Moon National Monument are comparatively large. These a's are dependent upon the nature and proportions of phases removed by crystal fractionation; basaltic lava a's differ from latitic lava a?s in accordance with different phenocryst assemblages in these rocks. Snake River Plain rhyolites are isotopically distinct from both the analyzed crustal xenoliths and olivine tholeiites. Their origin remains poorly understood, but crustal or sub-crustal sources may be viable. In the first case, they must be derived by anatexis of material distinct from the analyzed crustal xenoliths. In the second case, they must be derived from material unlike the source for tholeiites. No cogenetic relation with the tholeiites seems likely on the basis of available data. that might relate to the variation in the chemical petrology of the pluton.

Open-File Report↗
USGS1977

Genesis of a zoned granite stock, Seward Peninsula, Alaska

A composite epizonal stock of biotite granite has intruded a diverse assemblage of metamorphic rocks in the Serpentine Hot Springs area of north-central Seward Peninsula, Alaska. The metamorphic rocks include amphibolite-facies orthogneiss and paragneiss, greenschist-facies fine-grained siliceous and graphitic metasediments, and a variety of carbonate rocks. Lithologic units within the metamorphic terrane trend generally north-northeast and dip moderately toward the southeast. Thrust faults locally juxtapose lithologic units in the metamorphic assemblage, and normal faults displace both the metamorphic rocks and some parts of the granite stock. The gneisses and graphitic metasediments are believed to be late Precambrian in age, but the carbonate rocks are in part Paleozoic. Dating by the potassium-argon method indicates that the granite stock is Late Cretaceous. The stock has sharp discordant contacts, beyond which is a well-developed thermal aureole with rocks of hornblende hornfels facies. The average mode of the granite is 29 percent plagioclase, 31 percent quartz, 36 percent K-feldspar, and 4 percent biotite. Accessory minerals include apatite, magnetite, sphene, allanite, and zircon. Late-stage or deuteric minerals include muscovite, fluorite, tourmaline, quartz, and albite. The stock is a zoned complex containing rocks with several textural facies that are present in four partly concentric zones. Zone 1 is a discontinuous border unit, containing fine- to coarse-grained biotite granite, that grades inward into zone 2. Zone 2 consists of porphyritic biotite granite with oriented phenocrysts of pinkish-gray microcline in a coarse-grained equigranular groundmass of plagioclase, quartz, and biotite. It is in sharp, concordant to discordant contact with rocks of zone 3. Zone 3 consists of seriate-textured biotite granite that has been intruded by bodies of porphyritic biotite granite containing phenocrysts of plagioclase, K-feldspar, quartz, and biotite in an aplitic groundmass. Flow structures, pegmatite and aplite segregations, and miarolitic cavities are common in the seriate-textured granite. Zone 4, which forms the central part of the complex, consists of fine- to medium-grained biotite granite and locally developed leucogranite. Small miarolitic cavities are common within it. Eight textural facies have been defined within the complex, and mineralogic, petrographic, modal, and chemical variations are broadly systematic within the facies sequence. Study of these variations shows that the gradational facies of zones l and 2 systematically shift toward more mafic compositions inward within the complex. Seriate-textured rocks of zone 3 are similar in composition to those of zone 2, but porphyritic rocks of zone 3 and rocks of zone 4 mark shifts to more felsic compositions. These late-crystallizing felsic rocks are products of an interior residual magma system. This system was enriched in water and certain trace elements including tin, lithium, niobium, lead, and zinc. The complex as a whole has higher concentrations of these elements than many other granites. The nature of this geochemical specialization is particularly well demonstrated by the trace-element composition of biotite. The crystallization history of the pluton was complex. The available data suggest that this history could have included: (1) chilling and metasomatic alteration adjacent to the contact, (2) in-situ crystallization in several marginal facies accompanied by some transfer of residual constituents toward interior parts of the pluton, (3) slight upward displacement of magma that was subjacent to the crystallized walls, accompanied by disequilibrium crystallization and local vapor saturation, (4) upward displacement of part of the residual water-rich interior magma, accompanied by rapid loss of a separated vapor phase, and (5) displacement of the margins of the pluton by normal faults, accompanied by loss of an exsolved vapor phase from th

Open-File Report↗
USGS1973

Bird collections in the United States and Canada

This survey was initiated in 1966 as a project of a subcommittee of the A.O.U.'s Committee on Research, at that time chaired by Paul H. Baldwin. The subcommittee consisted of the authors and Ralph J. Raitt. In 1968 the project was separated from the Committee on Research and the temporary Committee on Collections was established, with the present authors as its members. This paper is the final report of the committee. In the past, many studies utilizing museum materials have been handicapped by ignorance of the existence of potentially important specimens. We hoped, by means of this survey, to enable future workers to take full advantage of all available material. The objectives of the survey were to determine the locations of collections of ornithological material with research potential, particularly skins, skeletons, fluid-preserved specimens, eggs, and nests; to assess the sizes and particular geographic or systematic strengths of the various collections; to locate former private collections; to learn what collections include holotypes, and who is responsible for the collections. These basic points are generally well-known for the larger institutions that specialize in maintaining research collections, but not for many smaller collections containing valuable material. The survey was inspired by and patterned after a series made of mammal collections (see Anderson et al. 1963, J. Mammal. 44: 471-500).

The Auk↗
USGS1979

The brightness of lights on Earth at night, digitally recorded by DMSP satellite

The U.S. Air Force has operated its Defense Meteorological Satellite Program (DMSP) for nearly a decade, and film images from the system have been openly available since 1973. Films are well suited for the study of weather, and users of such films have derived much useful data. For many potential remote sensing applications, however, a quantitative measurement of the brightness of the imaged light patterns is needed, and it cannot be extracted with adequte accuracy from the films. Such information is contained in the telemetry from the spacecraft and is retained on digital tapes, which store the images for a few days while they await filming. For practical reasons, it has not heretofore been feasible for the Air Force to provide a remote-sensing user with these digital data, and the quantitative brightness information has been lost with the erasure of tapes for re-use. For the purpose of evaluation of tapes as a means for remote sensing, the Air Force recently did provide to the author six examples containing records of nighttime DMSP imagery similar to that which has previously 1 been evaluated by SRI International in a film format. The digital data create many new applications for these images, owing to a combination of several factors, the most important of which are the preservation of photometric information and of full spatial resolution. In this evaluation, stress has been placed upon determination of the broad potential value of the data rather than the full exploitation of any one aspect of it. The effort was guided by an objective to develop handling methods for the vast body of numbers--methods which will be practical for use in a research or engineering environment where budgets are limited, and specialized capabilities and image reproduction equipment has not already been developed. We report the degree of success obtained in this effort, pointing out the relative strengths and the relative limitations, as compared to the sophisticated, weather-oriented data processing which is well suited for the Air Force requirements. Both geometric and photometric calibration methods are evaluated. An image can be considered as a 3-dimensional array, X, Y, Z, in which X and Y are the coordinates of a picture element (pixel) and Z is the brightness at that location. A method of approach to handling these parameters, particularly Y and Z, is developed in a form quite different from that which serves the operational applications. The user of digital data will need the film images which are generated by the Air Force from the same data as is provided on digital tape. In the first stages of analysis, the films provide both a convenient index and a guide to identification of large patterns in the data. Additionally, the infrared (8 to 13 0 film provides a valuable indicator of cloud cover. Two general conclusions are drawn from this study. Firstly, the digital DMSP data have great potential value but their cost, in terms of the interruption of the present operational routine, is quite high. Therefore, if a program is undertaken to provide for the open availability of an archive of digital records, great care must be exercised in selecting only those records which have unusually high value in order that the effort will be cost-effective. Secondly, it is concluded that several aspects of the program, well designed for Air Force operational purposes, are not adapted to earth-sensing needs. This is probably inevitable, since the two applications are largely different and in some ways incompatible. For example, the nighttime visual sensor saturates in the center of major cities and in moderately large fires (such as gas flares). This saturation prevents the analyst from integrating photometric parameters. For weather observation, this inability is unimportant, and acceptance of such saturation makes feasible a decrease in the data rate. Such limitations in the data will probably be overcome only through modifying the existing system or the implementation of a similar system designed specifically to serve earth-sensing needs.

Open-File Report↗
USGS1994

Faults and structure in the Pierre Shale, central south Dakota

Numerous faults observed at the surface and (or) determined by geometric and geophysical methods to be present as much as several hundred meters below the surface (near-surface faults) have been mapped in a 2,000-km 2 area west of Pierre, S. Dakota. Many of these faults surround an east-west-trending structural high that has been mapped on the lower part of the Virgin Creek Member of the Pierre Shale. Generally, the geometry and displacement of many of the faults precludes slumping from surficial erosion as a mechanism to explain the faults. Seismic-reflection data indicate that several of the faults directly overlie faults in Precambrian basement that have cumulative vertical displacements of as much as 340 m. The structural high is interpreted to have been uplifted by displacements along faults that cut Upper Cretaceous sedimentary rocks. Recent low-level seismicity and fluvial-geomorphic studies of stream patterns, gradients, and orders suggest that rejuvenation of drainages may be taking place as a result of rebound or other tectonic activity. The studies indicate that repeated uplift and subsidence may have been the cause of extensive faulting mapped in the Pierre Shale since its deposition in Cretaceous time. Surficial fault displacements that cause damage to engineered structures are thought to be the result of construction-induced rebound in the Pierre Shale, although tectonic uplift cannot be ruled out as a cause.

Special Paper of the Geological Society of America↗
USGS1995

Low-grade, M1 metamorphism of the Douglas Island Volcanics, western metamorphic belt near Juneau, Alaska

The western metamorphic belt is part of the Coast plutonic-metamorphic complex of western Canada and southeastern Alaska that developed during collision of the Alexander terrane and Gravina assemblage on the west against the Yukon Prong and Stikine terranes to the east. Deformation, metamorphism, and plutonism range from about 120 to 50 Ma. Subgreenschist to lower greenschist facies metabasalts exposed along the west end of the western metamorphic belt near Juneau, Alaska, record the earliest metamorphic event (M 1 ). The protolith of the M 1 , low-grade metamorphic mineral assemblages is mostly arc-affinity basaltic rocks of the Douglas Island Volcanics. The most common metamorphic mineral assemblages are chlorite-epidote-actinolite with or without pumpellyite and stilpnomelane. There is no systematic distribution of metamorphic mineral assemblages in the study area, and all assemblages are in the pumpellyite-actinolite facies near the transition to the lower greenschist facies. Different low variance assemblages can be attributed to minor differences in pressure ( P ), temperature ( T ), or X CO2 . Mineral chemistry and phase equilibria suggest that thermal peak metamorphism of pumpellyite-bearing assemblages occurred at about 325 °C and 2 to 4.8 kbar.

Alaska↗
USGS1966

Birds and Aircraft on Midway Islands, 1959-63 Investigations

At Midway Naval Station, 1.100 miles west-northwest of Honolulu, military aircraft collide with flying albatrosses at the rate of about 300 to 400 per year. One aircraft out of every five that hits an albatross on takeoff either aborts (stops before it is airborne), or dumps fuel and returns for appraisal of damage. About 70,000 pairs of Laysan albatrosses and 7,000 pairs of blackfooted albatrosses nest at Midway in any given year. The population is declining. Two-thirds or more of the birds of breeding age nest each year. The minimum breeding age recorded is 5 years (each species), but many individuals do not nest until at least 7 years of age. Young birds begin to return to Midway at 3 years of age and are found more frequently as breeding age approaches. They come ashore more frequently in March and April (the high bird strike months) than in midwinter. Even in midwinter the number of 'walkers' (birds not on nests) may comprise more than 40 percent of the albatrosses present on Sand Island, Midway. Maximum longevity of the Laysan albatross is believed to exceed 40 years; 6 out of 99 birds banded as breeding adults (7+ years old) were still alive 24 years after banding. Control methods tested experimentally include disturbance, gunfire, other sounds, radar beams, smoke, odors, destruction of nests, eggs, chicks, and adults, moving of birds, eggs, and chicks, erection of obstacles to flight, and habitat management. Habitat management (leveling and hardsurfacing of shoulders of runways) has been the most effective. Albatrosses were counted over the runways at 10 locations in 1957, 1958, and 1960 to determine the effects of wind direction, wind speed, and topography on the numbers of flying birds. Birds were most concentrated in areas where rising air currents were created as winds blew against dunes or tall trees. Soaring and strike rate both increased with greater wind speeds. There was a highly significant correlation between strike frequency and wind direction. Soaring and strike rate were greatest over runway 6-24 when winds were from a northerly quadrant, and greatest over runway 15-33 when winds were east to southeast. Counts (nearly 7,000 observations) before and after the leveling of dunes along part of the south side of the principal runway, 6-24, showed a 61 percent decrease in soaring over the principal runway as compared with a 4 percent increase over runway 15-33 where no major habitat management had been done. Studies of population dynamics of Laysan and black-footed albatrosses in 4 study plots (totaling 14 1/2 acres) are yielding information on nesting density, changes in nesting population from year to year, frequency of nesting of individual birds, closeness of return, reproductive success, rate of nest loss, age at which young birds begin nesting, age composition of the population, and life expectancy of adults. Recommendations are made for reducing the bird hazard and for protecting birds that are not involved in the hazard.

Special Scientific Report - Wildlife↗
USGS2022

The Pacific as the world’s greatest theater of bird migration: Extreme flights spark questions about physiological capabilities, behavior, and the evolution of migratory pathways

The Pacific Basin, by virtue of its vastness and its complex aeroscape, provides unique opportunities to address questions about the behavioral and physiological capabilities and mechanisms through which birds can complete spectacular flights. No longer is the Pacific seen just as a formidable barrier between terrestrial habitats in the north and the south, but rather as a gateway for specialized species, such as shorebirds, to make a living on hemispherically distributed seasonal resources. This recent change in perspective is dramatic, and the research that underpins it has presented new opportunities to learn about phenomena that often challenge a sense of normal. Ancient Polynesians were aware of the seasonal passage of shorebirds and other landbirds over the Pacific Ocean, incorporating these observations into their navigational “tool kit” as they explored and colonized the Pacific. Some ten centuries later, systematic visual observations and tracking technology have revealed much about movement of these shorebirds, especially the enormity of their individual nonstop flights. This invites a broad suite of questions, often requiring comparative studies with bird migration across other ocean basins, or across continents. For example, how do birds manage many days of nonstop exercise apparently without sleep? What mechanisms explain birds acting as if they possess a Global Positioning System? How do such extreme migrations evolve? Through advances in both theory and tracking technology, biologists are poised to greatly expand the horizons of movement ecology as we know it. In this integrative review, we present a series of intriguing questions about trans-Pacific migrant shorebirds and summarize recent advances in knowledge about migratory behavior operating at temporal scales ranging from immediate decisions during a single flight, to adaptive learning throughout a lifetime, to evolutionary development of migratory pathways. Recent advances in this realm should stimulate future research across the globe and across a broad array of disciplines.

Ornithology↗
USGS2016

Distributions of small nongame fishes in the lower Yellowstone River

The Yellowstone River is the longest unimpounded river in the conterminous United States. It has a relatively natural flow regime, which helps maintain diverse habitats and fish assemblages uncommon in large rivers elsewhere. The lower Yellowstone River was thought to support a diverse nongame fish assemblage including several species of special concern. However, comprehensive data on the small nongame fish assemblage of the lower Yellowstone River is lacking. Therefore, we sampled the Yellowstone River downstream of its confluence with the Clark’s Fork using fyke nets and otter trawls to assess distributions and abundances of small nongame fishes. We captured 42 species (24 native and 18 nonnative) in the lower Yellowstone River with fyke nets. Native species constituted over 99% of the catch. Emerald shiners Notropis atherinoides , western silvery minnows Hybognathus argyritis , flathead chubs Platygobio gracilis , sand shiners Notropis stramineus , and longnose dace Rhinichthys cataractae composed nearly 94% of fyke net catch and were caught in every segment of the study area. We captured 24 species by otter trawling downstream of the Tongue River. Sturgeon chubs Macrhybopsis gelida , channel catfish Ictalurus punctatus , flathead chubs, stonecats Noturus flavus , and sicklefin chubs Macrhybopsis meeki composed 89% of the otter trawl catch. The upstream distributional limit of sturgeon chubs in the Yellowstone River was the Tongue River; few sicklefin chubs were captured above Intake Diversion Dam. This study not only provides biologists with baseline data for future monitoring efforts on the Yellowstone River but serves as a benchmark for management and conservation efforts in large rivers elsewhere as the Yellowstone River represents one of the best references for a naturally functioning Great Plains river.

Montana↗
USGS2015

Fire effects on aquatic ecosystems: An assessment of the current state of the science

Fire is a prevalent feature of many landscapes and has numerous and complex effects on geological, hydrological, ecological, and economic systems. In some regions, the frequency and intensity of wildfire have increased in recent years and are projected to escalate with predicted climatic and landuse changes. In addition, prescribed burns continue to be used in many parts of the world to clear vegetation for development projects, encourage desired vegetation, and reduce fuel loads. Given the prevalence of fire on the landscape, authors of papers in this special series examine the complexities of fire as a disturbance shaping freshwater ecosystems and highlight the state of the science. These papers cover key aspects of fire effects that range from vegetation loss and recovery in watersheds to effects on hydrology and water quality with consequences for communities (from algae to fish), food webs, and ecosystem processes (e.g., organic matter subsidies, nutrient cycling) across a range of scales. The results presented in this special series of articles expand our knowledge of fire effects in different biomes, water bodies, and geographic regions, encompassing aquatic population, community, and ecosystem responses. In this overview, we summarize each paper and emphasize its contributions to knowledge on fire ecology and freshwater ecosystems. This overview concludes with a list of 7 research foci that are needed to further our knowledge of fire effects on aquatic ecosystems, including research on: 1) additional biomes and geographic regions; 2) additional habitats, including wetlands and lacustrine ecosystems; 3) different fire severities, sizes, and spatial configurations; and 4) additional response variables (e.g., ecosystem processes) 5) over long (>5 y) time scales 6) with more rigorous study designs and data analyses, and 7) consideration of the effects of fire management practices and policies on aquatic ecosystems.

Freshwater Science↗
USGS2002

Vertebrate biostratigraphy of the Hell Creek Formation in southwestern North Dakota and northwestern South Dakota

Field surveys of the Upper Cretaceous Hell Creek Formation in southwestern North Dakota since 1986 have produced a total of 10124 specimens from 42 vertebrate microsites and an additional 41 dinosaur skulls or partial skeletons or skulls from separate sites representing 61 taxa of vertebrates dominated by fish, dinosaurs, turtles, and crocodilians. Common elements of this diverse fauna occur to within 2.37 m of the Cretaceous-Tertiary (K-T) boundary. The stratigraphically highest fossil in the study is a partial ceratopsian skeleton 1.77 m below the K-T boundary in the basal Fort Union Formation . All dinosaurs that occur at more than two sites also occur at the highest level that yielded more than 500 specimens (8.40 m below the K-T boundary). The fine-grained uppermost 2 m of the Hell Creek is nearly devoid of all fossils, including taxa known to occur in the overlying formation . The absence of channel deposits in this part of the formation may be the reason for the absence of fossil localities. The presence of marine-tolerant taxa suggests that the study area may have been adjacent to a previously unidentified seaway of latest Cretaceous age. Rarefaction analysis indicates no evidence for a decline in vertebrate diversity through the formation or dinosaurian diversity in the 3 m below the K-T boundary. Our results are not compatible with gradual vertebrate extinction at the end of the Cretaceous.

North Dakota↗
USGS2011

Evaluation of the genetic distinctiveness of Greater Sage-grouse in the Bi-State Planning Area

The purpose of this study was to further characterize a distinct population of Greater Sage-grouse: the population located along the border between Nevada and California (Bi-State Planning Area) and centered around the Mono Basin. This population was previously determined to be genetically distinct from other Greater Sage-grouse populations across their range. Previous genetic work focused on characterizing genetic variation across the species' range and thereby used a coarse sampling approach for species characterization. The goal of this study was to investigate this population further by obtaining samples from breeding locations within the population and analyzing those samples with the same mitochondrial and microsatellite loci used in previous studies. Blood samples were collected in six locations within the Bi-State Planning Area. Genetic data from subpopulations were then compared with each other and also with two populations outside of the Bi-State Planning Area. Particular attention was paid to subpopulation boundaries and internal dynamics by drawing comparisons among particular regions within the Bi-State Planning Area and regions proximal to it. All newly sampled subpopulations contained mitochondrial haplotypes and allele frequencies that were consistent with the genetically unique Bi-State (Mono Basin) Greater Sage-grouse described previously. This reinforces the fact that this group of Greater Sage-grouse is genetically unique and warrants special attention. Maintaining the genetic integrity of this population could protect the evolutionary potential of this population of Greater Sage-grouse. Additionally, the White Mountains subpopulation was found to be significantly distinct from all other Bi-State subpopulations.

Open-File Report↗
USGS2001

Hydrogeologic framework and potentiometric surface of the Williamson Creek Aquifer "B" sand in the Fort Polk area, Vernon Parish, Louisiana, March 1997

The Fort Polk Military Reservation(hereinafter referred to as the Reservation) in Vernon Parish, Louisiana, occupies 107,024 acres of lands; 66,998 acres are owned by the U.S. Army, and 40,026 acres are owned by the U.S. Forest Service (Dan Nance, Fort Polk Public Affairs office, written commun., 1998). Some areas of the Reservation, such as an artillery impact area, live-firm areas, and special purpose training areas, are restricted to military personnel. The Williamson Creek and Carnahan Bayou aquifers are major sources of freshwater for the Reservation. IN 1996, the Reservation's total water pumpage from the Williamson Creek aquifer for public supply was approxiamately 2.4 million gallons per day (Edward Ducote, Water and Wastewater Branch, Directorate of Public Works, Fort Polk, written commun., 1998). In 1997, the water withdrawl rate for public supply was approzimately 1.88 million gallons per day from 11 wells completed in the Williamson Creek aquifer. Almost all of the water was withdrawn from the "B" sand, which is the predominant sand layer of the Williamson Creek aquifer in the study area. In 1997, nearby Leesville, the seat of Vernon Parish, withdrew all its water for public supply from the deeper Carnahan Bayou aquifer.

Louisiana↗