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At least 1,063 records · Page 59Linked to original sources
USGS2007

Pygmy rabbit surveys on state lands in Oregon

The pygmy rabbit (Brachylagus idahoensis) is classified by the federal government as a species of concern (i.e., under review by the U.S. Fish and Wildlife Service for consideration as a candidate for listing as threatened or endangered under the Endangered Species Act) because of its specialized habitat requirements and evidence of declining populations. The Oregon Department of Fish and Wildlife (ODFW) lists pygmy rabbits as “sensitive-vulnerable,” meaning that protective measures are needed if sustainable populations are to be maintained over time (Oregon Natural Heritage Program, 2001). The Oregon Natural Heritage Program considers this species to be threatened with extirpation from Oregon. Pygmy rabbits also are a species of concern in all the other states where they occur (NatureServe, 2004). The Washington population, known as the Columbia Basin pygmy rabbit, was listed as endangered by the federal government in 2003. Historically, pygmy rabbits have been collected from Deschutes, Klamath, Crook, Lake, Grant, Harney, Baker, and Malheur Counties in Oregon. However, the geographic range of pygmy rabbit in Oregon may have decreased in historic times (Verts and Carraway, 1998), and boundaries of the current distribution are not known. Not all potentially suitable sites appear to be occupied, and populations are susceptible to rapid declines and local extirpation (Weiss and Verts, 1984). In order to protect and manage remaining populations on State of Oregon lands, Oregon Department of Fish and Wildlife needs to identify areas currently occupied by pygmy rabbits, as well as suitable habitats. The main objective of this survey was document to presence or absence of pygmy rabbits on state lands in Malheur, Harney, Lake, and Deschutes counties. Knowledge of the location and extent of pygmy rabbit populations can provide a foundation for the conservation and management of this species in Oregon. The pygmy rabbit is just one of a suite of species of concern associated with sagebrush habitats in the Great Basin. Because information on habitat and distribution of many species is scarce, a secondary goal of the rabbit surveys was to list all other vertebrate species encountered on surveyed sites. This information may be useful in directing future studies aimed at specific taxa.

Open-File Report↗
USGS1989

Evolution of the western part of the Coast plutonic–metamorphic complex, South-Eastern Alaska, USA: A summary

The western Cordillera of North America extends for over 6000 km from the tip of Baja California to the Alaska Range. It includes a wide variety of metamorphic and plutonic terrains, but none is more spectacular scenically or geologically than the Coast plutonic-metamorphic complex (Brew & Ford 1984) of western Canada and south-eastern Alaska. This report briefly describes the evolution of the western part of the complex, integrating information from the deformational, plutonic and metamorphic events. Most of the original studies are reported by the authors in U.S. Geological Survey Circular numbers 733, 751, 823-B, 868, 939, 945, 967 and 978, and are not cited specifically here. This summary does not contain either a comprehensive bibliography or a comparison of the metamorphic histories of south-eastern Alaska with the adjacent parts of British Columbia. The Coast plutonic-metamorphic complex is here divided into three major elements: the western metamorphic, the central granitic and the eastern metamorphic zones (Fig. 1). The western metamorphic belt is extremely long (900 km), and narrow (7–25 km). It consists of regional dynamothermally and regional thermally metamorphosed rocks with mineral assemblages ranging from prehnite-pumpellyite to upper amphibolite facies, scattered mesozonal to epizonal granitic bodies, and a few concentrically zoned mafic-ultramafic masses. The metamorphic grade and the amount of deformation increase from south-west to north-east, culminating at, or slightly to the north-east of, the ‘great tonalite sill’: a remarkable 700-km-long, 3- to 25-km-wide vertical to northeast-dipping belt of mostly syntectonic plutons of approximately the same age, composition and structural

Alaska↗
USGS2009

Endogenic carbonate sedimentation in Bear Lake, Utah and Idaho, over the last two glacial-interglacial cycles

Sediments deposited over the past 220,000 years in Bear Lake, Utah and Idaho, are predominantly calcareous silty clay, with calcite as the dominant carbonate mineral. The abundance of siliciclastic sediment indicates that the Bear River usually was connected to Bear Lake. However, three marl intervals containing more than 50% CaCO 3 were deposited during the Holocene and the last two interglacial intervals, equivalent to marine oxygen isotope stages (MIS) 5 and 7, indicating times when the Bear River was not connected to the lake. Aragonite is the dominant mineral in two of these three high-carbonate intervals. The high-carbonate, aragonitic intervals coincide with warm interglacial continental climates and warm Pacific sea-surface temperatures. Aragonite also is the dominant mineral in a carbonate-cemented microbialite mound that formed in the southwestern part of the lake over the last several thousand years. The history of carbonate sedimentation in Bear Lake is documented through the study of isotopic ratios of oxygen, carbon, and strontium, organic carbon content, CaCO 3 content, X-ray diffraction mineralogy, and HCl-leach chemistry on samples from sediment traps, gravity cores, piston cores, drill cores, and microbialites. Sediment-trap studies show that the carbonate mineral that precipitates in the surface waters of the lake today is high-Mg calcite. The lake began to precipitate high-Mg calcite sometime in the mid-twentieth century after the artificial diversion of Bear River into Bear Lake that began in 1911. This diversion drastically reduced the salinity and Mg 2+ :Ca 2+ of the lake water and changed the primary carbonate precipitate from aragonite to high-Mg calcite. However, sediment-trap and core studies show that aragonite is the dominant mineral accumulating on the lake floor today, even though it is not precipitating in surface waters. The isotopic studies show that this aragonite is derived from reworking and redistribution of shallow-water sediment that is at least 50 yr old, and probably older. Apparently, the microbialite mound also stopped forming aragonite cement sometime after Bear River diversion. Because of reworking of old aragonite, the bulk mineralogy of carbonate in bottom sediments has not changed very much since the diversion. However, the diversion is marked by very distinct changes in the chemical and isotopic composition of the bulk carbonate. After the last glacial interval (LGI), a large amount of endogenic carbonate began to precipitate in Bear Lake when the Pacific moisture that filled the large pluvial lakes of the Great Basin during the LGI diminished, and Bear River apparently abandoned Bear Lake. At first, the carbonate that formed was low-Mg calcite, but ???11,000 years ago, salinity and Mg 2+ :Ca 2+ thresholds must have been crossed because the amount of aragonite gradually increased. Aragonite is the dominant carbonate mineral that has accumulated in the lake for the past 7000 years, with the addition of high-Mg calcite after the diversion of Bear River into the lake at the beginning of the twentieth century. Copyright ?? 2009 The Geological Society of America.

Special Paper of the Geological Society of America↗
USGS2013

Geophysical constraints on Rio Grande rift structure in the central San Luis Basin, Colorado and New Mexico

Interpretation of gravity, aeromagnetic, and magnetotelluric (MT) data reveals patterns of rifting, rift-sediment thicknesses, distribution of pre-rift volcanic and sedimentary rocks, and distribution of syn-rift volcanic rocks in the central San Luis Basin, one of the northernmost major basins that make up the Rio Grande rift. Rift-sediment thicknesses for the central San Luis Basin determined from a three-dimensional gravity inversion indicate that syn-rift Santa Fe Group sediments have a maximum thickness of ~2 km in the Sanchez graben near the eastern margin of the basin along the central Sangre de Cristo fault zone, and reach nearly 1 km within the Monte Vista graben near the western basin margin along the San Juan Mountains. In between, Santa Fe Group thickness is negligible under the San Luis Hills and estimated to reach ~1.1 km under the Costilla Plains (although no independent thickness constraints exist, and a range of thicknesses of 600 m to 2 km is geophysically reasonable). From combined geophysical and geologic considerations, pre-rift, dominantly sedimentary rocks appear to increase in thickness from none in the Sanchez graben on the east to perhaps 800 m under the San Luis Hills on the west. The pre-rift rocks are most likely early Tertiary in age, but the presence of Mesozoic and Paleozoic sedimentary rocks cannot be ruled out. Geophysical data provide new evidence that an isolated exposure of Proterozoic rocks on San Pedro Mesa is rooted in the Precambrian basement. This narrow, north-south–trending basement high has ~2 km of positive relief with respect to the base of the Sanchez graben, and separates the graben from the structural depression beneath the Costilla Plains. A structural high composed of pre-rift rocks, long inferred to extend from under the San Luis Hills to the Taos Plateau, is confirmed and found to be denser than previously believed, with little or no overlying Santa Fe Group sediments. Major faults in the study area are delineated by geophysical data and models; these faults include significant vertical offsets (≥1 km) of Precambrian rocks along the central and southern zones of the Sangre de Cristo fault system. Other faults with similarly large offsets of the Santa Fe Group include a fault bounding the western margin of San Pedro Mesa, and other faults that bound the Monte Vista graben in an area previously assumed to be a simple hinge zone at the western edge of the San Luis Basin. A major north-south–trending structure with expression in gravity and MT data occurs at the boundary between the Costilla Plains and the San Luis Hills structural high. Although it has been interpreted as a down-to-the-east normal fault or fault zone, our modeling suggests that it also is likely related to pre-rift tectonics. Aeromagnetic anomalies over much of the area are interpreted to mainly reflect variations of remanent magnetic polarity and burial depth of the 5.3–3.7 Ma Servilleta Basalt of the Taos Plateau volcanic field. Magnetic-source depth estimates are interpreted to indicate patterns of subsidence following eruption of the basalt, with maximum subsidence in the Sanchez graben.

Colorado, New Mexico↗
USGS2007

A framework for assessing the sustainability of monitored natural attenuation

The sustainability of monitored natural attenuation (MNA) over time depends upon (1) the presence of chemical/biochemical processes that transform wastes to innocuous byproducts, and (2) the availability of energy to drive these processes to completion. The presence or absence of contaminant-transforming chemical/biochemical processes can be determined by observing contaminant mass loss over time and space (mass balance). The energy available to drive these processes to completion can be assessed by measuring the pool of metabolizable organic carbon available in a system, and by tracing the flow of this energy to available electron acceptors (energy balance). For the special case of chlorinated ethenes in ground-water systems, for which a variety of contaminant-transforming biochemical processes exist, natural attenuation is sustainable when the pool of bioavailable organic carbon is large relative to the carbon flux needed to drive biodegradation to completion. These principles are illustrated by assessing the sustainability of MNA at a chlorinated ethene-contaminated site in Kings Bay, Georgia. Approximately 1,000 kilograms of perchloroethene (PCE) was released to a municipal landfill in the 1978-1980 timeframe, and the resulting plume of chlorinated ethenes migrated toward a nearby housing development. A numerical model, built using the sequential electron acceptor model code (SEAM3D), was used to quantify mass and energy balance in this system. The model considered the dissolution of non-aqueous phase liquid (NAPL) as the source of the PCE, and was designed to trace energy flow from dissolved organic carbon to available electron acceptors in the sequence oxygen > chlorinated ethenes > ferric iron > sulfate > carbon dioxide. The model was constrained by (1) comparing simulated and measured rates of ground-water flow, (2) reproducing the observed distribution of electron-accepting processes in the aquifer, (3) comparing observed and measured concentrations of chlorinated ethenes, and (4) reproducing the observed production and subsequent dilution of dissolved chloride, a final degradation product of chloroethene biodegradation. Simulations using the constrained model indicated that an average flux of 5 milligrams per liter per day of organic carbon (CH2O) per model cell (25 square meters) is required to support the short-term sustainability of MNA. Because this flux is small relative to the pool of renewable organic carbon (about 4.7 x 107 milligrams [mg] per model cell) present in the soil zone and non-renewable carbon (about 6.9 x 108 mg per model cell) in an organic-rich sediment layer overlying the aquifer, the long-term sustainability of MNA is similarly large. This study illustrates that the short- and long-term sustainability of MNA can be assessed by: 1. Estimating the time required for contaminants to dissolve/disperse/degrade under ambient hydrologic conditions (time of remediation). 2. Quantifying the organic carbon flux to the system needed to consume competing electron acceptors (oxygen) and direct electron flow toward chloroethene degradation (short-term sustainability). 3. Comparing the required flux of organic carbon to the pool of renewable and non-renewable organic carbon given the estimated time of remediation (long-term sustainability). These are general principles that can be used to assess the sustainability of MNA in any hydrologic system.

Circular↗
USGS1977

Population ecology of the mallard: IV. A review of duck hunting regulations, activity, and success, with special reference to the mallard

This, the fourth in a series of reports on the mallard, ( Anas platyrhynchos ), deals at length with the harvest of mallards by waterfowl hunters. Long-term summaries of duck hunting regulations (1948- 1974), Migratory Bird Hunting Stamp sales (1934-1974), Hunter Questionnaire (1952-1974), Duck Wing Collection (1960-1974), and Hunter Performance (1965-1972) Survey data for the United States are presented and discussed. Similar data from Canada are also summarized. Mallard harvest figures for 1961-1974 are presented by Mallard Harvest Area, of which 100 are defined for the United States and 14 for Canada, as well as by State or Province and flyway. During the 23-year period beginning in 1952, an average of 1.6 million adult and 0.2 million junior waterfowl hunters accumulated almost 12.3 million hunter-days of recreation and a harvest of 11.2 million ducks each year. Hunter reports indicate that mallards made up about 43% (5.5 million annually) of the ducks taken before 1960, when mallard regulations were less restrictive; the Duck Wing Survey indicates that mallards have made up 33% of the harvest (3.6 million annually) since 1960. The age and sex compositions and the chronological distribution of the mallard harvest are examined in detail. Among the patterns noted are peak harvests during the first few days of the season in many States, alternately increasing and decreasing annual age ratios, and sex ratios that suggest differential migration of adult drakes and hunter selectivity for males. It is estimated that almost 19% of the ducks shot down are not retrieved. Relationships between duck hunting regulations and hunter behavior are examined briefly. Hunter compliance with mallard bag limits, hunter selectivity of mallards by sex, and, to a lesser extent, the size of the unretrieved kill are all sensitive to the particular bag limit regulations in effect. Survey data are also examined for relationships between harvest and various hunting regulations: starting time and day of the week for opening day, opening date, season length, split seasons, daily shooting hours, and daily bag limits. Tables are presented relating changes in duck and mallard harvests to season length and bag limit, and examples of what effects changes in other regulations have on harvest are also given. The evaluation of bag limit regulations, one of the most important tools used in managing harvest, is carried a step further with the development of a procedure for calculating expected hunter success under a wide variety of bag limit regulations. This method appears promising for evaluating point-limit as well as fixed-limit regulations. In addition, it may provide useful measurements of the degree of hunter selectivity induced by various types of bag limit regulations, an increasingly important aspect of harvest management. Finally, this study clearly demonstrates that the effects of a particular regulation can differ dramatically from area to area, so it is usually necessary to evaluate each proposal on a State-by-State basis.

Resource Publication↗
USGS2011

The story of the Hawaiian Volcano Observatory -- A remarkable first 100 years of tracking eruptions and earthquakes

The year 2012 marks the centennial of the Hawaiian Volcano Observatory (HVO). With the support and cooperation of visionaries, financiers, scientists, and other individuals and organizations, HVO has successfully achieved 100 years of continuous monitoring of Hawaiian volcanoes. As we celebrate this milestone anniversary, we express our sincere mahalo—thanks—to the people who have contributed to and participated in HVO’s mission during this past century. First and foremost, we owe a debt of gratitude to the late Thomas A. Jaggar, Jr., the geologist whose vision and efforts led to the founding of HVO. We also acknowledge the pioneering contributions of the late Frank A. Perret, who began the continuous monitoring of Kīlauea in 1911, setting the stage for Jaggar, who took over the work in 1912. Initial support for HVO was provided by the Massachusetts Institute of Technology (MIT) and the Carnegie Geophysical Laboratory, which financed the initial cache of volcano monitoring instruments and Perret’s work in 1911. The Hawaiian Volcano Research Association, a group of Honolulu businessmen organized by Lorrin A. Thurston, also provided essential funding for HVO’s daily operations starting in mid-1912 and continuing for several decades. Since HVO’s beginning, the University of Hawaiʻi (UH), called the College of Hawaii until 1920, has been an advocate of HVO’s scientific studies. We have benefited from collaborations with UH scientists at both the Hilo and Mänoa campuses and look forward to future cooperative efforts to better understand how Hawaiian volcanoes work. The U.S. Geological Survey (USGS) has operated HVO continuously since 1947. Before then, HVO was under the administration of various Federal agencies—the U.S. Weather Bureau, at the time part of the Department of Agriculture, from 1919 to 1924; the USGS, which first managed HVO from 1924 to 1935; and the National Park Service from 1935 to 1947. For 76 of its first 100 years, HVO has been part of the USGS, the Nation’s premier Earth science agency. It currently operates under the direction of the USGS Volcano Science Center, which now supports five volcano observatories covering six U.S. areas—Hawaiʻi (HVO), Alaska and the Northern Mariana Islands (Alaska Volcano Observatory), Washington and Oregon (Cascades Volcano Observatory), California (California Volcano Observatory), and the Yellowstone region (Yellowstone Volcano Observatory). Although the National Park Service (NPS) managed HVO for only 12 years, HVO has enjoyed a close working relationship with Hawaiʻi Volcanoes National Park (named Hawaii National Park until 1961) since the park’s founding in 1916. Today, as in past years, the USGS and NPS work together to ensure the safety and education of park visitors. We are grateful to all park employees, particularly Superintendent Cindy Orlando and Chief Ranger Talmadge Magno and their predecessors, for their continuing support of HVO’s mission. HVO also works closely with the Hawaiʻi County Civil Defense. During volcanic and earthquake crises, we have appreciated the support of civil defense staff, especially that of Harry Kim and Quince Mento, who administered the agency during highly stressful episodes of Kīlauea's ongoing eruption. Our work in remote areas on Hawaiʻi’s active volcanoes is possible only with the able assistance of Hawaiʻi County and private pilots who have safely flown HVO staff to eruption sites through the decades. A special mahalo goes to David Okita, who has been HVO’s principal helicopter pilot for more than two decades. Many commercial and Civil Air Patrol pilots have also assisted HVO by reporting their observations during various eruptive events. Hawaiʻi’s news media—print, television, radio, and online sources—do an excellent job of distributing volcano and earthquake information to the public. Their assistance is invaluable to HVO, especially during times of crisis. HVO’s efforts to provide timely and accurate scientific information about Hawaiian volcanoes and earthquakes succeed only because of you, our receptive and keenly aware public. By following the activity of Hawaiʻi’s active volcanoes through our daily eruption updates posted on the HVO website, viewing HVO webcam images, reading our weekly “Volcano Watch” articles, and attending our public lectures, you help us to ensure that you can live safely with Hawaiʻi’s dynamic volcanoes. To everyone who has shared in HVO’s reaching this milestone—100 years of continuous volcano monitoring—we extend our deepest gratitude. Mahalo nui loa!

Hawai'i↗
USGS2002

Dinosaurs that did not die: Evidence for Paleocene dinosaurs in the Ojo Alamo Sandstone, San Juan Basin, New Mexico

Palynologic and paleomagnetic data confirm a Paleocene age for the Ojo Alamo Sandstone (and its contained dinosaurs) throughout the San Juan Basin of New Mexico. The recently reported discovery of 34 skeletal elements from a single hadrosaur in the Ojo Alamo provides unequivocal evidence that these bones were not reworked from underlying Cretaceous strata. Geochemical studies of samples from several single-dinosaur-bone specimens from the Paleocene Ojo Alamo Sandstone and the underlying Late Cretaceous (Campanian) Kirtland Formation show that mineralized bones from these two rock units contain distinctly different abundances of uranium and rare-earth elements and demonstrate that Cretaceous and Paleocene bones were mineralized at different times when mineralizing fluids had distinctly different chemical compositions. These findings indicate that the dinosaur bone from the Paleocene Ojo Alamo is indigenous and not reworked. These data show that a relatively diverse assemblage of dinosaurs survived the end-Cretaceous asteroid-impact extinction event of 65.5 Ma. The San Juan Basin’s Paleocene dinosaur fauna is herein named the Alamoan fauna. Magnetic-polarity chronology shows that these survivors lived for about one million years into the Paleocene and then became extinct around 64.5 Ma. We suggest that a plausible survival mechanism for this Lazarus fauna may have been the large numbers of buried dinosaur eggs, laid just before the asteroid impact occurred. These buried eggs would have provided a safe haven for developing dinosaur embryos for the first one to two years after the impact, thereby making it possible for them to survive the worst of the impact’s early devastation.

Colorado, New Mexico↗
USGS1996

Deep-sea ostracode shell chemistry (Mg:Ca ratios) and late Quaternary Arctic Ocean history

The magnesium:calcium (Mg:Ca) and strontium:calcium (Sr:Ca) ratios were investigated in shells of the benthic ostracode genus Krithe obtained from 64 core-tops from water depths of 73 to 4411 m in the Arctic Ocean and Nordic seas to determine the potential of ostracode shell chemistry for palaeoceanographic study. Shells from the Polar Surface Water (−1 to −1.5°C) had Mg:Ca molar ratios of about 0.006–0.008; shells from Arctic Intermediate Water (+0.3 to +2.0°C) ranged from 0.09 to 0.013. Shells from the abyssal plain and ridges of the Nansen, Amundsen and Makarov basins and the Norwegian and Greenland seas had a wide scatter of Mg:Ca ratios ranging from 0.007 to 0.012 that may signify post-mortem chemical alteration of the shells from Arctic deep-sea environments below about 1000 m water depth. There is a positive correlation ( r 2 = 0.59) between Mg:Ca ratios and bottom-water temperature in Krithe shells from Arctic and Nordic seas from water depths <900 m. Late Quaternary Krithe Mg:Ca ratios were analysed downcore using material from the Gakkel Ridge (water depths 3047 and 3899 m), the Lomonosov Ridge (water depth 1051 m) and the Amundsen Basin (water depth 4226 m) to test the core-top Mg:Ca temperature calibration. Cores from the Gakkel and Lomonosov ridges display a decrease in Mg:Ca ratios during the interval spanning the last glacial/deglacial transition and the Holocene, perhaps related to a decrease in bottom water temperatures or other changes in benthic environments.

Geological Society Special Publication↗
USGS1996

Late Holocene alluvial geomorphology of the Virgin River in the Zion National Park area, southwest Utah

This study traces the geomorphic development of the alluvial valley of the Virgin River in the Zion National Park region of southwest Utah. The purpose is to identify, date, and interpret the patterns of erosion and deposition that formed the alluvial valley over the past 1,000 years. This information is a basis for understanding how the geomorphology of the alluvial valley changes under essentially natural flow conditions. Sediment in the alluvial valley is classified as mainstem or tributary in origin. Mainstem alluvium is the largest volumetrically; it is mainly light-colored sand derived from upstream sources that accumulated on now abandoned flood plains (or terraces) by overbank deposition. Tributary sediment is typically dark colored, coarse-grained sand or gravel transported to the alluvial valley by streamflow or debris flow. Tributary and mainstem sediment are interbedded near the margin of the valley, and the older deposits are truncated parallel to the river, suggesting that in time the river removes both its own deposits and those of tributaries. In the natural flow regimen, the river probably maintains a balance between erosion and deposition of mainstem and tributary deposits. Four terraces and the active channel and flood plain are widespread along the Virgin River; from oldest to youngest these are the prehistoric, settlement, historic, and modern terraces. Dating was done by archeologic context, tree-ring methods, historic documents, relocation of early photographs, and correlation with other streams on the southern Colorado Plateau. Results indicate that prehistoric deposition ended by about A.D. 1100–1200, deposition of the settlement alluvium was from about A.D. 1400–1880, development of the historic terrace was from after 1883 until 1926, deposition of the modern alluvium was from 1940–1980, and development of the active channel and flood plain was after about 1980. The principal deposits (prehistoric, settlement, and modern alluviums) are separated by two periods of stream entrenchment and channel widening referred to as the prehistoric and historic arroyo cutting, respectively. Erosional activity of roughly similar age occurred in most southern Colorado Plateau streams. The early erosion is not well dated in the study area, although regional relations suggest A.D. 1200–1400, if not somewhat earlier. Historic arroyo cutting began after 1883 in the study area and continued until around 1940 when deposition of the modern alluvium began. Both erosions affected the human population of the region. Although the dating is imprecise, the Anasazi probably abandoned the region during prehistoric arroyo cutting, partly because of adverse environmental conditions. Likewise, historic arroyo cutting caused major losses of property and economic hardship among Anglo settlers. Erosion and deposition were largely contemporaneous with variations in streamflow. Long-term streamflow of the Virgin River was estimated from calibration of annual tree growth with measured streamflow. Results indicate that erosion was during periods of unusually high streamflow and that deposition was during periods of relatively low streamflow. These relations are best illustrated by historic arroyo cutting and subsequent deposition of the modern alluvium. Precipitation and runoff immediately before and during historic arroyo cutting were the most unusual of the past 300 years; they varied from the driest immediately preceding erosion to the wettest during erosion. Deposition of the modern alluvium was during relatively low runoff after 1940. High runoff destabilizes the channel, enhancing flood erosion. Conversely, relatively low runoff increases channel stability, reducing the erosional effect of floods and enhancing flood plain deposition. Adjustments in the width and depth of the channel are frequent, even after relatively small, short-term variations of streamflow.

Utah↗
USGS1960

Geology and ground-water resources of the lower Little Bighorn River Valley, Big Horn County, Montana, with special reference to the drainage of waterlogged lands

The lower Little Bighorn River valley, Montana, is in the unglaciated part of the Missouri Plateau section of the Great Plains physiographic province. The river and its principal tributaries rise in the Bighorn Mountains, and the confluence of this northward-flowing stream with the Bighorn River is near the east edge of Hardin, Mont. The normal annual precipitation ranges from about 12 inches in the northern part of the area to 15 inches in the southern part. The economy of the area is founded principally on farming, much of the low-lying land adjacent to the river being irrigated. The irrigated land is within the Crow Indian Reservation, although a part is privately owned. The bedrock formations exposed in the area are of Cretaceous age and include the Parkman sandstone, Claggett shale, Eagle sandstone, Telegraph Creek shale, and Cody shale. The Cloverly formation, Tensleep sandstone, and Madison limestone, which underlie but are not exposed in the area, and the Parkman sandstone in the southern half of the area appear to be the principal bedrock aquifers. All except the Parkman lie at depths ranging from a few feet to several thousand feet, and all appear to be capable of yielding water in commercial quantities. Some of the other formations arc capable of yielding enough water for domestic and stock needs. The river alluvium of Recent age and the Pleistocene terrace deposits are the principal unconsolidated formations in the area with respect to water supply and drainage. Wells yielding as much as 100 gallons per minute may be developed in favorable areas. Pumping tests reveal that the transmissibility of the coarser unconsolidated materials probably ranges from about 15,000 to 30,000 gallons per day per foot. Two tests of the Parkman sandstone showed transmissibilities of 6,000 and 20,000 gallons per day per foot. Although a test of the Cloverly formation showed a transmissibility of only 3,000 gallons per day per foot, the high artesian pressure--80 pounds per square inch at the land surface--in the Cloverly caused the tested well to yield about 200 gallons per minute by natural flow; this is greater than the yield of any other single well in the area. Textural properties were compared with the hydraulic properties determined by laboratory tests to show the relation between different types of waterbearing materials. Materials classified as heavy soils-normally somewhat dense and impervious-had an average permeability of 7.2 gallons per day per square foot, which was more than expected. One sample of very coarse alluvial material had a permeability of 6,000 gallons per day per square foot. The depth to water beneath irrigation units was mapped, thus showing the waterlogged areas. Waterlogging is not a serious problem where the water table is more than 6 feet below the land surface. For the drainage studies the unconsolidated deposits are classified in two zones-coarse-grained sediments resting on the relatively impermeable bedrock floor and overlying fine-grained sediments which extend to the land surface. The transmissibility of the coarse-sediment zone generally is many times greater than that of the fine-sediment zone. Because in many places drains could not be economically dug deep enough to enter the coarse zone, the study of the effectiveness of drainage completed in the fine zone received much attention. The studies showed that, despite a considerable thickness of fine-grained sediments between the bottom of the drain and the top of the coarse zone, drainage ditches frequently were effective in relieving waterlogging of fields nearby. Pilot relief wells installed in existing drains showed that the effectiveness of some drains could be increased appreciably by installing a series of relief wells. Records of fluctuations of water levels in 196 observation wells and water-level contour maps were studied to show the principal areas of recharge and discharge in the irrigable areas.

Montana↗
USGS2013

Proceedings of a workshop on American Eel passage technologies

Recent concerns regarding a decline in recruitment of American eels ( Anguilla rostrata ) have prompted efforts to restore this species to historic habitats by providing passage for both upstream migrant juveniles and downstream migrant adults at riverine barriers, including low-head and hydroelectric dams (Castonguay et al. 1994, Haro et al. 2000). These efforts include development of management plans and stock assessment reviews in both the US and Canada (COSEWIC 2006, Canadian Eel Working Group 2009, DFO 2010, MacGregor et al. 2010, ASMFC 2000, ASMFC 2006, ASMFC 2008, Williams and Threader 2007), which target improvement of upstream and downstream passage for eels, as well as identification and prioritization of research needs for development of new and more effective passage technologies for American eels. Traditional upstream fish passage structures, such as fishways and fish lifts, are often ineffective passing juvenile eels, and specialized passage structures for this species are needed. Although designs for such passage structures are available and diverse (Knights and White 1998, Porcher 2002, FAO/DVWK 2002, Solomon and Beach 2004a,b, Environment Agency UK 2011), many biologists, managers, and engineers are unfamiliar with eel pass design and operation, or unaware of the technical options available for upstream eel passage, Better coordination is needed to account for eel passage requirements during restoration efforts for other diadromous fish species. Also, appropriately siting eel passes at hydropower projects is critical, and siting can be difficult and complex due to physical restrictions in access to points of natural concentrations of eels, dynamic hydraulics of tailrace areas, and presence of significant competing flows from turbine outfalls or spill. As a result, some constructed eel passes are sited poorly and may pass only a fraction of the number of eels attempting to pass the barrier. When sited and constructed appropriately, however, eel passes can effectively pass thousands of individuals in a season (Appendix D). technologies for preventing impingement and entrainment mortality and injury of downstream migrant eels at hydropower projects are not well developed. Traditional downstream fish passage mitigative techniques originally developed for salmonids and other species are frequently ineffective passing eels (Richkus and Dixon 2003, EPRI 2001, Bruijs and Durif 2009). Large hydropower projects, with high project flows or intake openings that cannot be fitted with racks or screens with openings small enough to exclude eels, pose significant passage problems for this species, and turbine impingement and entrainment mortality of eels can be as high as 100%. Spill mortality and injury may also be significant for eels, given their tendency to move during high flow events when projects typically spill large amounts of flow. Delays in migration of eels that have difficulty locating and utilizing bypass entrances can also be significant. Therefore, downstream passage technologies are at a much more nebulous state of development than upstream passage technologies, and require further evaluation and improvement before rigorous design guidelines can be established. There have been few studies conducted to evaluate effectiveness of current mitigative measures for both upstream and downstream passage of eels. Research is needed to determine eel migratory timing, behavior, and appropriate mitigation technologies for specific sites and eel life history stages. Both upstream and downstream eel passage structures can be difficult to evaluate in terms of performance, and examples of how evaluation and monitoring can be accomplished were reviewed at the workshop.

Report↗
USGS2015

Preface

This book grew out of a topical session on “Central Virginia Earthquakes of 2011: Geology, Geophysics, and Significance for Seismic Hazards in Eastern North America” at the 2012 The Geological Society of America (GSA) Annual Meeting in Charlotte, North Carolina (USA). It also benefitted from related sessions at other meetings. The goal of this volume, The 2011 Mineral, Virginia, Earthquake, and Its Significance for Seismic Hazards in Eastern North America , is to bring together as much information as possible on lessons learned from this rare event. Chapters encompass a wide range of geoscience, engineering, and related studies of this earthquake and its effects from the epicentral area in central Virginia to Washington, D.C., and beyond. The intended audience is a broad spectrum of geoscientists, engineers, and decision makers interested in understanding earthquakes and seismic hazards in eastern North America and other intraplate settings. Chapters by Berti et al. (21), Chapman (2), Costain (8), Davenport et al. (15), Green et al. (9), Heller and Carter (10), Horton et al. (14), Hughes et al. (19), Powars et al. (23), Pratt et al. (16), Roeloffs et al. (7), Shah et al. (17), Stephenson et al. (3), Walsh et al. (18), and Wells et al. (12) are expansions of presentations at the 2012 GSA meeting. The volume also contains chapters from recent studies that were not presented at the GSA meeting, including those by Bobyarchick (22), Burton et al. (20), Dreiling and Mooney (5), Li et al. (11), McNamara et al. (4), Pollitz and Mooney (6), and Shahidi et al. (13). Following an overview and synthesis by the volume editors (1), chapters are arranged under the topical headings “Seismology and Regional Effects,” “Earthquake Damage, Geotechnical, and Engineering Investigations,” “Aftershocks, Geophysical Imaging, and Modeling,” “Geologic Investigations—Epicentral Area,” and “Geologic Investigations— Central Virginia Seismic Zone and Nearby Faults.” We thank the authors for their contributions and the many scientists and engineers who contributed time and expertise in reviewing manuscripts to substantially improve the quality of the volume. These reviewers include Gail Atkinson, Christopher Bailey, Richard Berquist, Kimberly Blisniuk, Paul Bodin, Aaron Bradshaw, Clive Collins, Ariel Conn, Randy Cox, Haitham Dawood, James Dewey, John Ebel, David Fenster, Alexander Gates, Kathleen Haller, Gregory Hancock, Robert Hatcher, William Henika, Paul Hsieh, Steven Jaumé, Jeffrey Kimball, Charles Langston, Jongwon Lee, Andrea Llenos, John McBride, Scott Olson, Michael Oskin, Brent Owens, Gilles Peltzer, Mark Quigley, Dhananjay Ravat, David Saftner, Arthur Snoke, Jamison Steidl, Kevin Stewart, Alice Stieve, Danielle Sumy, Ertugrul Taciroglu, Roy Van Arsdale, Mason Walters, Chiyuen Wang, Yang Wang, Richard Whittecar, Lorraine Wolf, Clint Wood, Liam Wotherspoon, and some anonymous reviewers.

Virginia↗
USGS2001

Species and population variation to salinity stress in Panicum hemitomon, Spartina patens, and Spartina alterniflora: Morphological and physiological constraints

Panicum hemitomon, Spartina patens, and Spartina alterniflora are wide-spread dominant grasses of fresh, brackish, and salt marsh plant communities, respectively. Our previous research identified significant intraspecific variation in salt tolerance and morphology among populations within each species. In this study our objectives were to determine shorter-term physiological/biochemical responses to salinity stress and identify potential indicators of salt tolerance, with the ultimate goal of discerning similarities and differences in the mechanisms of salinity stress resistance. We subjected a subset of six populations within each species, ranging from high to low salt tolerance, to sublethal salinity levels (4, 20, and 30 ppt, respectively, for species) and monitored physiological and growth responses after 1 week (early harvest) and 5 weeks (late harvest). In all three species sublethal salinity levels generally resulted in significantly reduced net CO2 assimilation, leaf expansion, midday leaf xylem pressure, water use efficiency, and live and total biomass; and significantly increased leaf Na+/K+ ratio, leaf proline, leaf glycine betaine, leaf sucrose, root-to-shoot ratio, and dead:total aboveground biomass ratio. All three species displayed significant population (intraspecific) variation in net CO2 assimilation, leaf expansion, water use efficiency, midday leaf xylem pressure, leaf proline, leaf glycine betaine (except Panicum, where it could not be accurately determined), leaf Na+/K+ ratio, leaf sucrose, total plant biomass, dead:total aboveground biomass ratio, and root-to-shoot ratio. General indicators of salt tolerance (regardless of species) included high net CO2 assimilation rates and water use efficiencies, and low ratios of root-to-shoot and dead:total aboveground biomass. Factor analysis and a-priori linear contrasts revealed some unique differences between species in terms of the relative importance of morphology and physiology in explaining intraspecific variation in salt tolerance. Plant morphology (size attributes) were strongly associated with salt tolerance in P. hemitomon, weakly associated with salt tolerance in S. patens, and not associated with salt tolerance in S. alterniflora. Highly salt-tolerant populations of Spartina alterniflora displayed the greatest ion selectivity (lower leaf Na+/K+ ratios), which was not displayed by the other two species. These results suggest that plant size attributes can be very important in explaining population differences in salt tolerance in glycophytes, but may be independent of salt tolerance in halophytes, which have specialized physiological (and/or anatomical) adaptations that can confer salinity stress resistance through mechanisms such as selective ion exclusion and secretion. ?? 2001 Elsevier Science B.V. All rights reserved.

Conference Paper↗
USGS2013

Tectonic evolution and Cretaceous gold metallogenesis of southwestern Alaska

Cretaceous gold metallogenesis in southwestern Alaska comprises three distinct episodes related to the accretionary evolution of northwestern North America. The oldest mineralizing event is characterized by 112 Ma Cu-Au-Bi-Te porphyry-type(?) veining in the zoned Bonanza and adjacent plutons that intruded rocks of the Nyac terrane. Tectonic reconstructions and limited geological and geochemical data suggest that Cu-Au mineralization in the Nyac district may be related to terminal subduction during accretion of the Togiak-Koyukuk arc. The subsequent 100 to 89 Ma metallogenic event is a product of subduction-related magmatism immediately following accretion of the Peninsular-Alexander-Wrangellia superterrane and includes formation of the giant Pebble porphyry Cu-Au-Mo deposit. Pebble underwent a complex history of highly oxidized magmatism that is isotopically linked to enriched lithosphere or metasomatized mantle sources. Pebble and other porphyryrelated plutons were emplaced as a consequence of changes in plate motion and onset of dextral transpression along the continental margin to the southeast of their present-day locations. The final 75 to 65 Ma metallogenic event is regionally the most extensive. It followed a ~15-m.y.-long magmatic lull and is related to enigmatic subduction-related magmatism in the western part of the Alaska Range and the Kuskokwim basin. This event resulted in the formation of porphyry, reduced pluton-related, orogenic, and possible epithermal Au deposits. In the better-studied relatively low-relief areas of the Kuskokwim basin, many of the mineralized systems are spatially associated with ilmenite-series monzonite to quartz monzonite composite plutons that have isotopic signatures consistent with derivation from crustally contaminated mantle sources. These pluton-hosted Au deposits comprise low-sulfide stockworks, sheeted veins, and/or breccias in the cupolas of moderately differentiated intrusions that contain high Au; anomalous As, Bi, Sb, and/or Te; and have variable, but not uneconomic, Cu concentrations. In addition, Au, Sb, and/or Hg deposits hosted by competent NE-trending granite porphyry dike-sill complexes or along faults in flysch are widespread in the Kuskokwim basin. These deposits, including the giant Donlin Creek Au deposit, formed at shallow crustal levels and are classified here as epizonal orogenic Au deposits and related Hg and Sb lodes. Mesozonal orogenic Au deposits were formed along the margins of the uplifting Willow Creek pluton that is now exposed along the southern side of the Talkeetna Mountains batholith. Recent discoveries in the rugged Alaska Range comprise less well-studied porphyry Au-Cu (Whistler, Island Mountain), epithermal(?) Au (Terra), and reduced pluton-hosted Au deposits (Estelle). The cause of the broad latest Cretaceous magmatism associated with the final metallogenic event is enigmatic, but indicates widespread high heat flow possibly related to flat-slab subduction, lithospheric mantle delamination, or escape tectonics. Plutonism postdated regional folding and coincided with periods of movement along regional faults and formation of the NE-trending structural fabric. Magmatism resulted from initiation of transpressional faulting in more landward positions during oblique subduction of the Kula plate. Crustal contamination of mantle melts, either near their source or during ascent through the thick flysch of the Kuskokwim basin, produced low oxidation state magmas and controlled much of the metallogeny, particularly for those deposits that display similarities to both reduced porphyry Au-Cu deposits and, to a lesser degree, reduced intrusion-related Au systems. High heat flow also induced crustal melting and metamorphic devolatilization to form orogenic Au deposits. A transition to extension at ~60 Ma recorded elsewhere in Alaska temporally corresponds to termination of gold deposit formation in southwestern Alaska. The multiple periods of gold metallogenesis in southwestern Alaska offer a wide variety of targets for exploration within discrete parts of the region.

Society of Economic Geologists Special Publication↗
USGS2006

Diagenetic alteration of impact spherules in the Neoarchean Monteville layer, South Africa

Intercontinental correlation of distal Archean impact ejecta layers can be used to help create a global time-stratigraphic framework for early Earth events. For example, an impact spherule layer in the Neoarchean Monteville Formation (Griqualand West Basin, South Africa) may be correlated with layers in one or more formations in Western Australia. To help assess the degree to which diagenetic alteration would hinder such correlations, we performed a petrographic study of spherules in the Monteville layer. Most of the spherules in the Monteville layer have botryoidal rims composed of radial-fibrous K-feldspar, but compaction and replacement have greatly altered their appearance and mineralogy. Moreover, the Monteville spherule layer consists of three main subunits, and spherule compaction varies between subunits as well as across the Griqualand West region. Compaction is about three times greater in a medial spherulerich subunit as compared to a basal subunit rich in large intraclasts, resulting in better preservation of the shapes of melt particles in the latter. However, spherule rims have omparable numbers of fractures in both subunits, indicating the melt particles were fractured prior to compaction. Some spherules contain mica ribbons with a septarian geometry. Fracturing via rapid thermal quenching could help explain all of these features. f hot spherules possessing crystalline rims were thermally shocked when they hit the ocean, fractures would have the observed geometries and provide pathways for fluid infiltration and local replacement of glass by mica. Although heavily distorted, impact spherules in the Monteville layer are very similar to those in the Hesta occurrence of the Neoarchean Jeerinah spherule layer of the Hamersley Basin, even showing similar diagenetic histories. In this instance, diagenetic alteration may actually help rather than hinder intercontinental correlation of impact spherule layers. ??2006 Geological Society of America.

Special Paper of the Geological Society of America↗
USGS2008

Molt and aging criteria for four North American grassland passerines

Prairie and grassland habitats in central and western North America have declined substantially since settlement by Europeans (Knopf 1994) and many of the birds and other organisms that inhabit North American grasslands have experienced steep declines (Peterjohn and Sauer 1999; Johnson and Igl 1997; Sauer, Hines, and Fallon 2007). The species addressed here, Sprague’s Pipit (Anthus spragueii), Grasshopper (Ammodramus savannarum) and Baird’s (A. bairdii) sparrows, and Chestnut-collared Longspurs (Calcarius ornatus), are grassland birds that are of special conservation concern throughout their ranges due to declining populations and the loss of the specific grassland habitats required on both their breeding and wintering ranges (Knopf 1994, Davis and Sealy 1998, Davis 2003, Davis 2004, Jones and Dieni 2007). Population-trend data on grassland birds, while clearly showing declines, provides no information on the causes of population declines. Without demographic information (i.e., productivity and survivorship), there are no means to determine when in their life cycle the problems that are creating these declines are occurring, or to determine to what extent population trends are driven by factors that affect birth rates, death rates, or both (DeSante 1995). For migratory birds, population declines may be driven by factors on breeding grounds, during migration, and/or on wintering grounds. Lack of data on productivity and survivorship thus impedes the formulation of effective management and conservation strategies to reverse population declines (DeSante 1992). Furthermore, if deficiencies in survivorship are revealed, management strategies may need to address habitats on both breeding and non-breeding grounds, as well as along migratory pathways. One technique that helps inform management strategies is the biochemical analysis of isotopes and genetic markers, from the sampling of individual feathers from live birds (Smith et al. 2003, Pérez and Hobson 2006; Appendix). Determining demographic parameters and effectively sampling feathers to reveal connectivity between breeding and wintering grounds requires detailed knowledge of molt patterns and age determination criteria for the target species, in the hand. For example, productivity, survivorship, and territory acquisition may all be age-dependent, with first-year birds showing different patterns and responses than older birds. In many cases it may be possible to sample both a feather grown on the breeding grounds and one grown on the wintering grounds from a single individual, but knowledge of age-specific molt patterns, as well as an ability to recognize different feather generations, is needed to accomplish such a task. While some information on molt and aging criteria exists for grassland passerine species (Pyle 1997a), these species have been rarely captured during mark-recapture studies (Jones et al. 2007) and this information thus needs refining. There is a need for additional resources to assist field workers in determining molt patterns and age in captured individuals. Our objective is to describe molt and aging criteria for four grassland passerine species with the aid of digital photographs taken in the field. We hope that this document will be useful for researchers studying grassland species through capture and banding of live individuals on either the breeding or the wintering grounds. We present a general section on molt and aging techniques, followed by specific accounts for the four species treated: Sprague’s Pipits, Grasshopper and Baird sparrows, and Chestnut-collared Longspur. We also provide a brief protocol on collecting feather samples (Appendix).

Biological Technical Publication↗
USGS2015

Association of anatase (TiO2) and microbes: unusual fossilization effect or a potential biosignature?

We combined microbial paleontology and molecular biology methods to study the Eyreville B drill core from the 35.3-Ma-old Chesapeake Bay impact structure,Virginia, USA. The investigated sample is a pyrite vein collected from the 1353.81-1353.89 m depth interval, located within a section of biotite granite. The granite is a pre-impact rock that was disrupted by the impact event. A search for inorganic (mineral) biosignatures revealed the presence of micron-size rod morphologies of anatase (TiO2) embedded in chlorite coatings on pyrite grains. Neither the Acridine Orange microbial probe nor deoxyribonucleic acid (DNA) extraction followed by polymerase chain reaction (PCR) amplifi cation showed the presence of DNA or ribonucleic acid (RNA) at the location of anatase rods, implying the absence of viable cells in the investigated area. A Nile Red microbial probe revealed the presence of lipids in the rods. Because most of the lipids are resistant over geologic time spans, they are good biomarkers, and they are an indicator of biogenicity for these possibly 35-Ma-old microbial fossils. The mineral assemblage suggests that rod morphologies are associated with low-temperature (<100 &deg;C) hydrothermal alteration that involved aqueous fl uids. The temporal constraints on the anatase fossils are still uncertain because pre-impact alteration of the granite and postimpact heating may have provided identical conditions for anatase precipitation and microbial preservation.

Geological Society of America Bulletin↗