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USGS1986

URBAN STORMWATER-QUALITY INVESTIGATIONS BY THE USGS.

U. S. Geological Survey (USGS) urban stormwater investigations, in cooperation with local and Federal agencies, have produced significant national data bases of information and enhanced understanding of urban hydrologic processes. Studies in progress include statistical regionalization of urban stormwater quality, the effects of stormwater detention on water quality, ways of improving instrumentation for urban hydrology studies, and an evaluation and update of urban gaging networks. Studies performed by USGS since 1968, including 12 studies that were in the Environmental Protection Agency Nationwide Urban Runoff Program, are being summarized in a USGS report.

Conference Paper↗

USGS1950

Fifth special report of the Hawaiian Volcano Observatory of the Hawaiian Volcano Research Association and the U.S. Geological Survey: Abrasion hardness

After reviewing the work of sclerometry, this paper shows that yielding and relative softness are the mechanical basis of what should be called malacometry. The experiments have been made with diamond drills, ring cuts, end millers and grinding wheels. Auerbach's "limited scope of the Mohs list" is quantitatively confirmed. The wear of diamonds is examined. A program is carried out, for rotary or annular abrasion by diamond under three applications of energy, each progressively slower. A selected commercial talc is the control substance of softness value 100. The instruments used are synchronous motors, drill presses, wheel grinders, and watchmaker lathes. Some 200 minerals, woods, metals, glasses and plastics were originally measured. Hardness tables and curves are shown for comparison with volumetric abradability. For a Mohs succession the softer substances abrade relatively more under higher energy of contact friction, and any one substance shows higher relative values under lower energy of attrition; in other words, under slower scratching. An artificially cut diamond octahedron gives more consistent results than a natural crystal, under light pressures. Standard successions of relative abradability measurements do not hold good under different energies of attack. Functions of plasticity, brittleness, cleavage, powder lubricity, ductility and the like introduce various anomalies, and constancy of pressure varies with variable yielding. The supposition that rhythmic instrumental abrading will hold its mechanical constants, while the substance attacked yields in accord with its own surface molecular mobility relative to a control substance, is only approximately true. At low energies the approximation is better than at high, but at high speeds the wear of tool is less. Hence the advantage of using with slow speed a replaceable tool. Substances of different categories such as steels and woods, differ in behavior from minerals. The Mohs System has the great advantage of extending the controls from mineral to mineral up through the whole scale, and is purely qualitative. It is not numerically quantitative at all in terms of equal units. A principal result of this investigation is that 80 per cent of the Mohs Scale, Numbers 3 to 10, are by common consent within 1 per cent of a malacometric scale numbered 1 to 100. The scientists who determined this relation were the sclerometry investigators of the nineteenth century, who mistakenly thought that the wide intervals of sclerometry are between the hard minerals. They used the reciprocals of the measures of yielding. The simple scratch tester finally arrived at is quite different from the instruments of Parts II and III. It eliminates diamond drilling, retains the Mohs controls and utilizes a dental grinding wheel and a modern low speed motor. The object of this research has been to design a simple instrument for many uses, especially for the mechanic's shop. It is planned for manufacture at an early date. The author is indebted to Dr. Earl Ingerson, Chief, Geochemistry and Petrology Branch, for critical correction and approval of this paper, by authority of the Director, U. S. Geological Survey.

Report of the Hawaiian Volcano Observatory↗

USGS2003

Ground-Water Resources in the Black Hills Area, South Dakota

The availability of ground-water resources in the Black Hills area is influenced by many factors including location, local recharge and ground-water flow conditions, and structural features. Thus, the availability of ground water can be extremely variable throughout the Black Hills area, and even when water is available, it may not be suitable for various uses depending on the water quality. The major bedrock aquifers in the Black Hills area are the Deadwood, Madison, Minnelusa, Minnekahta, and Inyan Kara aquifers. Minor bedrock aquifers occur in other hydrogeologic units, including confining units, due to fracturing and interbedded permeable layers. Various information and maps are presented in this report that describe availability and quality of ground-water resources in the Black Hills area. However, there is no guarantee of obtaining usable water at any location due to the extreme potential variability in conditions that can affect the availability and quality of ground water in the area. Maps presented in this report include the distribution of hydrogeologic units; depth to the top of the five formations that contain major aquifers; thickness of the five formations that contain major aquifers; potentiometric maps for the five major aquifers; saturated thickness of the Madison and Minnelusa aquifers; water temperature in the Madison aquifer; specific conductance in the Madison, Minnelusa, and Inyan Kara aquifers; hardness in the Inyan Kara aquifer; sulfate concentrations in the Minnelusa aquifer; and radon concentrations in the Deadwood aquifer. Water quality of the major aquifers generally is very good in and near outcrop areas but deteriorates progressively with distance from the outcrops. In the Minnelusa aquifer, an abrupt increase in concentrations of dissolved sulfate occurs downgradient from outcrop areas, where a zone of active anhydrite dissolution occurs. Most limitations for the use of ground water are related to aesthetic qualities associated with hardness and high concentrations of chloride, sulfate, sodium, manganese, and iron. Very few health-related limitations exist for ground water; most limitations are for radionuclides, such as radon and uranium. In addition, high concentrations of arsenic have been measured in a few samples from the Minnelusa aquifer.

Water-Resources Investigations Report↗

USGS2010

Nutrients in the nation's streams and groundwater: National findings and implications

A comprehensive national analysis of the distribution and trends of nutrient concentrations in streams and groundwater from 1992 through 2004 is provided by the National Water-Quality Assessment (NAWQA) Program of the United States Geological Survey (USGS). Findings describe the distribution and causes of varying nutrient concentrations in streams and groundwater throughout the Nation and examine the primary sources that contribute to elevated concentrations. Results show that excessive nutrient enrichment is a widespread cause of ecological degradation in streams and that nitrate contamination of groundwater used for drinking water, particularly shallow domestic wells in agricultural areas, is a continuing human-health concern. Finally, despite major Federal, State and local nonpoint-source nutrient control efforts for streams and watersheds across the Nation, USGS trend analyses for 1993?2003 suggest limited national progress to reduce the impacts of nonpoint sources of nutrients during this period. Instead, concentrations have remained the same or increased in many streams and aquifers across the Nation, and continue to pose risks to aquatic life and human health. This Fact Sheet highlights selected national findings and their implications, and serves as a companion product to the complete analysis reported in the USGS Circular titled ?The Quality of Our Nation?s Waters?Nutrients in the Nation?s Streams and Groundwater, 1992?2004.?

Fact Sheet↗

USGS1979

Directory to Federal, State, and local OCS-related activities and contacts

This directory identifies specific Federal, state, and local agencies involved with oil and gas activities on the Outer Continental Shelf (OCS). Current agency responsibilities and the mechanisms used for interacting with OCS activities are outlined in three groupings: (a) an overview of major Federal activities (Chapter 2) and the mechanisms used for controlling, regulating, and monitoring OCS activities, (b) a review of major state government programs (Chapter 3) pertaining to the OCS, both the supportive activities in response to Federal initiatives as well as those activities for which the states have direct responsibility, and (c) a description of county and municipal participation (Chapter 4) in local and sub-state programs which can affect the OCS process. Appendix A is a bibliography and Appendix B is a telephone directory of agency contacts arranged alphabetically by state and region. The directory progresses from Federal to local information in Chapters two through four. The reader can then identify which level of interaction is of interest and obtain the appropriate government contact from the listings in Appendix B.

Open-File Report↗

USGS2006

Geologic Map of the Upper Wolf Island Creek Watershed, Reidsville Area, Rockingham County, North Carolina

This geologic map provides a foundation for hydrogeologic investigations in the Reidsville area of Rockingham County, north-central North Carolina. The 16-mi2 area within the Southeast Eden and Reidsville 7.5-min quadrangles includes the watershed of Wolf Island Creek and its tributary, Carroll Creek, upstream of their confluence. Layered metamorphic rocks in this area of the Milton terrane, here informally named the Chinqua-Penn metamorphic suite, include a heterogeneous mica gneiss and schist unit that contains interlayers and lenses of white-mica schist, felsic gneiss, amphibolite, and ultramafic rock; a felsic gneiss that contains interlayers of amphibolite, white-mica schist, and minor ultramafic lenses; and a migmatitic biotite gneiss. Crushed stone is produced from an active quarry in the felsic gneiss. Igneous intrusive rocks include a mafic-ultramafic assemblage that may have originated as mafic intrusive bodies containing ultramafic cumulates, a foliated two-mica granite informally named the granite of Reidsville, and unmetamorphosed Jurassic diabase dikes. The newly recognized Carroll Creek shear zone strikes roughly east-west and separates heterogeneous mica gneiss and schist to the north from structurally overlying felsic gneiss to the south. Regional amphibolite-facies metamorphism accompanied polyphase ductile deformation in the metamorphic rocks. Two phases of isoclinal to tight folding and related penetrative deformation, described as D1 and D2, were followed by phases of high-strain mylonitic deformation in shear zones and late gentle to open folding. Later brittle deformation produced minor faults, steep joints, foliation-parallel parting, and sheeting joints. The metamorphic and igneous rocks are mantled by saprolite and residual soil derived from weathering of the underlying bedrock, and unconsolidated Quaternary alluvium occupies the flood plains of Wolf Island Creek and its tributaries. The geologic map delineates lithologic and structural features that may act as barriers or conduits for ground-water flow. It provides a hydrogeologic framework for the upper Wolf Island Creek drainage basin, including coreholes and ground-water monitoring wells along two transects. Collaborative hydrogeologic investigations by the North Carolina Department of Environment and Natural Resources and the U.S. Geological Survey are in progress to increase understanding of the influence of geological features on ground-water quality, availability, and transport in an area representative of large areas in the west-central Piedmont.

Scientific Investigations Map↗

USGS2022

Supporting the development and use of native plant materials for restoration on the Colorado Plateau (Fiscal Year 2021 Report)

A primary focus of the Colorado Plateau Native Plant Program (CPNPP) is to identify and develop appropriate native plant materials (NPMs) for current and future restoration projects. Multiple efforts have characterized the myriad challenges inherent in providing appropriate seed resources to enable effective, widespread restoration and have identified a broad suite of research activities to provide the information necessary to overcome those challenges (e.g., Plant Conservation Alliance 2015; Breed et al. 2018; Winkler et al. 2018; McCormick et al. 2021). Many of the most complex information needs relate to identifying the appropriate sources of plant species that can successfully establish in dryland environments, like the Colorado Plateau, where low and highly variable precipitation is standard. Providing this information requires synergistic research efforts in which results from earlier investigations inform the design of subsequent investigations. The U.S. Geological Survey (USGS) Southwest Biological Science Center’s (SBSC’s) research activities to support CPNPP in FY21 followed the FY21 Statement of Work to support a research framework that is continually adapting based on the needs of the restoration community and results from previous investigations; the long-term research framework is outlined in the 2019-2023 5-Year Research Strategy (hereafter referred to as the 5-year plan). This research framework provides support for the National Seed Strategy for Rehabilitation and Restoration (Plant Conservation Alliance 2015), Biden-Harris Administration Executive Order 14008 (Tackling the Climate Crisis at Home and Abroad), and Department of Interior Priority #4 (Working to conserve at least 30% each of our lands and waters by the year 2030). Research activities in FY21 centered on landscape genomics, implementing and monitoring a common garden experiment near Vernal, UT, conducting experimental treatments using the GRID (Germination for Restoration Information and Decision-making) framework, and initiating new genetics projects to investigate the impact of production techniques on plant materials and restoration treatments on native plant communities. These activities were supported by four biological science technicians. The SARS-CoV-2 pandemic delayed some aspects of the FY21 workplan, especially for outside laboratory services. However, goals were largely met, and the overall progress of research remains on track with respect to the 5-year plan. While Dr. Rob Massatti was the only scientist supported by the SBSC-CPNPP agreement in FY21, other scientists, including Drs. John Bradford, Seth Munson, Mike Duniway, Sasha Reed, and Daniel Winkler, spent a considerable amount of time providing expertise and support for individual projects. Work activities performed in support of each 5-year plan goal are discussed in turn. Products resulting from FY21 research activities are reported in Appendix 1.

Arizona, Colorado, New Mexico, Utah↗

USGS1984

Chemical analyses of soils and other surficial materials, Alaska

Introduction: The favorable response to the reports on the geochemistry of unconsolidated surficial materials of the conterminous United States (informally called the '50-mile geochemical survey,' Shacklette and others, 1971a, 1971b, 1973, and 1974) led us, in 1975, to initiate a somewhat similar survey of Alaska. The principal objective of studies of this type is to establish estimates of the abundance of elements in soils and other surficial materials. Such information is useful in the evaluation of geochemical data for (1) mineral resources, (2) environmental appraisals, and (3) the definition of broad-scale geochemical patterns. For about six years this effort progressed slowly on a non-funded, time-available basis. During fiscal years 1982 and 1983, however, some funds were made available through the USGS Energy Lands and Alaska Mineral Surveys programs which allowed for the completion of the field-work phase of the project. The sampling plan was kept simple because, as with the 50-mile study, the acquisition of samples depended on the voluntary cooperation of field personnel (only about 40 percent of the total number of samples was obtained by the authors).

Open-File Report↗

USGS2007

Precambrian Time - The Story of the Early Earth

The Precambrian is the least-understood part of Earth history, yet it is arguably the most important. Precambrian time spans almost nine-tenths of Earth history, from the formation of the Earth to the dawn of the Cambrian Period. It represents time so vast and long ago that it challenges all comprehension. The Precambrian is the time of big questions. How old is the Earth? How old are the oldest rocks and continents? What was the early Earth like? What was the early atmosphere like? When did life appear, and what did it look like? And, how do we know this? In recent years, remarkable progress has been made in understanding the early evolution of the Earth and life itself. Yet, the scientific story of the early Earth is still a work in progress, humankind's latest attempt to understand the planet. Like previous attempts, it too will change as we learn more about the Earth. Read on to discover what we know now, in the early 21st century.

Fact Sheet↗

USGS2021

Patterns of bubble bursting and weak explosive activity in an active lava lake—Halema‘uma‘u, Kīlauea, 2015

The rise of the Halemaʻumaʻu lava lake in 2013–2018 to depths commonly 40 meters or less below the rim of the vent was an excellent opportunity to study outgassing and the link to associated eruptive activity. We use videography to investigate the rise and bursting of bubbles through the free surface of the lake in 2015. We focus on low-energy explosive activity (spattering) in which the ascent and bursting of meter-sized, mechanically decoupled bubbles trigger the ejection of fluidal bombs to tens of meters above the free surface. A decay in initial pyroclast velocity with time follows the same functional form as that observed for ejecta at Stromboli (Italy), suggesting a similar bubble-burst mechanism. We also find that the upward velocity of the bubble crust as it bursts is around 2.5 times higher than the velocity of the bubble as it rises through the lake surface, indicating that the bubbles are over-pressurized. Prior to bursting, bubbles emerge at velocities of 4 to 14 meters per second, suggesting rise from depths of at least tens of meters but unaffected by the deeper circulation of the lava lake. We identify three styles of bubble bursting: (1) isolated, widely spaced, single bursts, (2) recurring clusters of discrete bubbles, and (3) prolonged episodes of overlapping bubble bursts along elongate narrow sources typically parallel to the margins of the lava lake. We call these styles of bursting isolated events, clusters, and prolonged episodes, respectively. The frequency of bubble bursting and the mass fluxes of gas and pyroclasts increase from styles 1 to 3. The intensity (mass eruption rate) for single bubble bursts ranges from 280 to 3,500 kilograms per second. The total erupted mass of pyroclasts for a single burst is <4,000 kilograms (kg) and for a single well-constrained prolonged episode is about 10 7 kg. These numbers place the observed spattering at the lowest end of basaltic explosivity in terms of erupted mass (that is, magnitude). Most ejecta fell back into the crater; only strands of Pele’s hair rose to heights where they could be advected downwind from the vent. Collectively, the explosive activity accompanying the three styles of bubble bursting spans from impulsive, transient eruptive behaviors to sustained discharge; this shift represents progressively higher frequency and intensity of bubble bursting.

Hawaii↗

USGS1981

North Atlantic summary report: Outer Continental Shelf oil and gas activities in the North Atlantic and their onshore impacts: A summary report, July 1981

The leasing process for oil and gas exploration on the North Atlantic Outer Continental Shelf (OCS) began in June 1975. The first lease sale in the region (Lease Sale 42) was scheduled for January 31, 1978, by the Department of the Interior. However, the sale was delayed for 23 months by litigation before it was finally held on December 18, 1979. Of the 116 tracts offered, 63 tracts comprising 358,671 acres were leased as a result of the sale. Eight exploration plans have been submitted by five oil companies since Lease Sale 42. The plans call for exploratory drilling on 11 separate tracts in the lease sale area. The plans and the required Federal drilling permits for two blocks, Exxon's block 133 and Shell's block 410, have been approved. Exploratory drilling on these two blocks began on July 24, 1981. The review process to approve the other plans and the required OCS drilling permits is in progress. Onshore impacts resulting from OCS exploration in the North Atlantic are expected to be minimal. The same support base at Davisville, Rhode Island, used for drilling operations in the Mid-Atlantic Region is servicing North Atlantic activities. This facility has more than enough capacity and berthing space to service the level of activity expected during exploratory drilling. Moreover, support requirements for the North Atlantic are expected to supplement the declining level of support activity that has occurred for the Mid-Atlantic Region.

North Atlantic Region↗

USGS2004

Optimization of limestone drains for long- term treatment of acidic mine drainage, Swatara Creek Basin, Schuylkill County, PA

Limestone drains were constructed in 1995, 1997, and 2000 to treat acidic mine drainage (AMD) from the Orchard, Buck Mtn., and Hegins discharges, respectively, in the Swatara Creek Basin, Southern Anthracite Coalfield, east-central Pennsylvania. This report summarizes the construction characteristics and performance of each of the limestone drains on the basis of influent and effluent quality and laboratory tests of variables affecting limestone dissolution rates. Data for influent and effluent indicate substantial alkalinity production by the Orchard and Buck Mtn. limestone drains and only marginal benefits from the Hegins drain. Nevertheless, the annual alkalinity loading rates have progressively declined with age of all three systems. Collapsible-container (cubitainer) testing was conducted to evaluate current scenarios and possible options for reconstruction and maintenance of the limestone drains to optimize their long-term performance. The cubitainer tests indicated dissolution rates for the current configurations that were in agreement with field flux data (net loading) for alkalinity and dissolved calcium. The dissolution rates in cubitainers were larger for closed conditions than open conditions, but the rates were comparable for coated and uncoated limestone for a given condition. Models developed on the basis of the cubitainer testing indicate (1) exponential declines in limestone mass and corresponding alkalinity loading rates with increased age of limestone drains and (2) potential for improved performance with enlargement, complete burial, and/or regular flushing of the systems.

Pennsylvania↗

USGS1980

Conflict resolution in railroad right-of-way disputes; Columbia, Missouri, and Douglas County, Nebraska

The environmental mediation process has been used to avoid potential disputes and to resolve conflicts once an impasse has been reached. One successful case of dispute avoidance was in the conversion of an abandoned railroad right-of-way to a linear park in Columbia, Missouri. The potential disputes in this case were twofold: the first centered on the question of ownership of the right-of-way where the railroad holds easements; the second was the issue of how the right-of-way would be developed. This second issue was addressed through the use of third party assistance. A member of the American Arbitration Association and a member of the Heritage Conservation and Recreation Service acted as an outside third party to facilitate negotiations between the city and adjacent landowners. The result of these negotiations is that the proposal to convert the right-of-way to a linear park has met with acceptance and the project to acquire the land is progressing. In a similar case in Douglas County, Nebraska, third party assistance was not employed and an impasse resulted. Plans to convert the railroad right-of-way have been terminated.

Missouri, Nebraska↗

USGS2020

Simulation of groundwater-level changes from projected groundwater withdrawals in the Truxton basin, northwestern Arizona

A three-dimensional, numerical groundwater flow model of the Hualapai Plateau and Truxton basin was developed to assist water-resource managers in understanding the potential effects of projected groundwater withdrawals on groundwater levels and storage in the basin. The Truxton Basin Hydrologic Model (TBHM) is a transient model that simulates the hydrologic system for the years 1976 through 2139, including hypothetical low-, medium-, and high-groundwater withdrawal scenarios beginning in 2020. The simulated effects of these withdrawal scenarios are presented as groundwater-level changes from the year 2020 to 2070, and from 2020 to 2140. Hydrologic properties in the TBHM are derived from calibration of a steady-state model of the predevelopment (before 1976) groundwater system. The future pumping scenarios are each simulated with three different interpretations of basin depth supported by geophysical data. For each of the resulting nine transient models, a Monte Carlo approach is used to produce a range of possible and probable groundwater-level changes at points throughout the basin given probabilistic ranges of hydrologically reasonable aquifer property values supported by the model calibration results. The ensemble of models that simulate the future pumping scenarios include pumping from the existing well field (three wells) plus additional pumping from a proposed new well. Simulated high future pumping increases progressively to 1,840 acre-feet per year in 2120 and produces a range of drawdowns between 20 and 39 feet (ft) near the pumping center, with a median drawdown of 28 ft. The low future pumping scenario, which increases progressively to 650 acre-ft per year in 2120, produces a range of drawdowns between 5 and 15 ft, with a median drawdown of 10 ft at the same location over the same period of time.

Arizona↗

USGS1989

The significance of sediment transport in arroyo development

Arroyo widening dominates postincisional arroyo development, and the manner of widening is dependent on the grain size of bed material transported by the channel. When bed material is predominantly gravel, subaqueous bars that alternate from one side of the channel to the other form during high flows in initially narrow, often straight, arroyos. These alternate bars grow and become coarse-grained point bars. Moderate and low flows cannot rework these coarse bars, and the channel meanders around them. Arroyo walls opposite the bars are undercut and eroded. With progressive arroyo widening by erosion of cut banks, high-flow channel width increases, and depth decreases, reducing channel competence. Gravel is deposited in midchannel bars, point bars are reworked, and the channel becomes braided. As braiding becomes dominant, both arroyo walls are eroded. This conceptual model of coarse-grained arroyo development is based on observations of arroyo development through time using physical models and interpretation of the channel and arroyo morphology and sedimentology during a short period along the San Simon, San Pedro, and Santa Cruz Rivers in southeast Arizona. When bed material is predominantly sand, the channel pattern within initial arroyos is typically braided, and both arroyo walls are actively eroded. Alternate bars may form within single-thread, high-flow channels, but they are reworked during recessional flows, and the .low-flow channel is again braided. With progressive arroyo widening, fine sand, silt, and clay carried in suspension are deposited across a flood plain within the wide arroyo, causing the channel to meander. This fine-grained arroyo development model is based on observations of arroyo development through time using physical models and interpretation of the channel and arroyo morphology and sedimentology during a short period along the Rio Puerco, New Mexico. Experimental investigations using physical models in which incised channels were monitored through time indicate that the rate of arroyo widening is dependent on the amount of bedload transported through a reach. This is documented by the relations between the rate of arroyo erosion and the observed sediment transport, the channel slope, the channel width and the channel width-to-depth ratio. When a small amount of bed material is being transported, arroyos do not widen whether they are narrow (arroyo width-to-depth ratios between 1.5 and 3.1), intermediate (between 2.5 and 4.8), or wide (greater than 4.9). Arroyo widening resumes when a larger supply of bed material is introduced. Arroyo widening decreases through time because with progressive increases of arroyo width, the frequency with which unstable channels within the arroyo impinge upon arroyo walls decreases. Arroyos become wider in a downstream direction in response to the cumulative effect of upstream sediment production.

Water Supply Paper↗

USGS2025

Foundational uncertainties in terminal Ediacaran chronostratigraphy revealed by high-precision zircon U-Pb geochronology of the Nama Group, Namibia

The Nama Group of southern Namibia and northwestern South Africa hosts the best-dated mixed carbonate-siliciclastic foreland basin succession of the terminal Ediacaran [ca. 551 million years (Ma) ago to <538 Ma] and is key for resolving the chronology of early metazoan evolution. Numerous silicified volcanic tuff interbeds are present, but differing interpretations regarding the fidelity of their ages lead to different regional stratigraphic correlations, especially for the Urusis Formation of the Schwarzrand Subgroup. An expanded record of the Urusis Formation is found in the Swartpunt area of southern Namibia, which has yielded an important metazoan biota. But the succession in this area is preserved as a series of thrusts at the leading edge of the Gariep orogenic belt and zircon U-Pb data show systematic age repetition. We use regional stratigraphic and structural mapping, integrated with carbonate carbon isotope (δ 13 C carb ) chemostratigraphy and high-precision radioisotope U-Pb zircon geochronology from outcrop and recently acquired drill core to develop a temporally calibrated basin-wide depositional model. This integrated dataset either reflects complex zircon reworking, inheritance, or potential analytical biases (Scenario 1) or the presence of a Gariep-related cryptic décollement within the Spitskop Member that has resulted in stratigraphic repetition (Scenario 2). We investigate the evidence for and against both scenarios and consider their implications for stratigraphic and δ 13 C carb correlations between the Swartpunt area and coeval exposures along the Orange River border with South Africa. Given that these issues are in an area that hosts numerous silicified ash beds and extensive exposure, an inability to confidently discount either scenario highlights a level of compounding uncertainty in zircon U-Pb geochronology that must be considered when attempting to build global chronostratigraphic frameworks. Scenario 1 implies that some of the weighted mean ages and Bayesian eruption ages from the Swartpunt area may be >1 Myr older than the depositional age of their respective ash beds when assuming existing stratigraphic correlations. If this scenario is preferred, then a cautious approach would be to consider all weighted mean zircon U-Pb ages from ash beds to reflect maximum depositional ages. Both scenarios support deposition of the Huns Member >540 Ma in the Swartpunt area if the oldest weighted mean age reported here represents a near-depositional age, which has significant implications for the temporal calibration of important terminal Ediacaran ichnofossil assemblages and future cyclostratigraphic studies. Stratigraphic correlations common to both scenarios allow us to temporally calibrate a basin evolution model for the Nama Group. Temporal trends in initial hafnium isotope (εHf) compositions of zircon grains from ash beds throughout the succession may support progressive crustal thickening associated with underplating of the Damara orogenic belt along the northern periphery of the Kalahari craton from ca. 547 Ma to ca. 538 Ma. The compilation of new and published zircon U-Pb ages may also imply that the locus of carbonate platform development migrated from north to south (present co-ordinates), tracking the migration of foredeep subsidence.

Earth-Science Reviews↗

USGS2012

Impacts of climate change on biodiversity, ecosystems, and ecosystem services: technical input to the 2013 National Climate Assessment

Ecosystems, and the biodiversity and services they support, are intrinsically dependent on climate. During the twentieth century, climate change has had documented impacts on ecological systems, and impacts are expected to increase as climate change continues and perhaps even accelerates. This technical input to the National Climate Assessment synthesizes our scientific understanding of the way climate change is affecting biodiversity, ecosystems, ecosystem services, and what strategies might be employed to decrease current and future risks. Building on past assessments of how climate change and other stressors are affecting ecosystems in the United States and around the world, we approach the subject from several different perspectives. First, we review the observed and projected impacts on biodiversity, with a focus on genes, species, and assemblages of species. Next, we examine how climate change is affecting ecosystem structural elements—such as biomass, architecture, and heterogeneity—and functions—specifically, as related to the fluxes of energy and matter. People experience climate change impacts on biodiversity and ecosystems as changes in ecosystem services; people depend on ecosystems for resources that are harvested, their role in regulating the movement of materials and disturbances, and their recreational, cultural, and aesthetic value. Thus, we review newly emerging research to determine how human activities and a changing climate are likely to alter the delivery of these ecosystem services. This technical input also examines two cross-cutting topics. First, we recognize that climate change is happening against the backdrop of a wide range of other environmental and anthropogenic stressors, many of which have caused dramatic ecosystem degradation already. This broader range of stressors interacts with climate change, and complicates our abilities to predict and manage the impacts on biodiversity, ecosystems, and the services they support. The second cross-cutting topic is the rapidly advancing field of climate adaptation, where there has been significant progress in developing the conceptual framework, planning approaches, and strategies for safeguarding biodiversity and other ecological resources. At the same time, ecosystem-based adaptation is becoming more prominent as a way to utilize ecosystem services to help human systems adapt to climate change. In this summary, we present key findings of the technical input, focusing on themes that can be found throughout the report. Thus, this summary takes a more integrated look at the question of how climate change is affecting our ecological resources, the implications for humans, and possible response strategies. This integrated approach better reflects the impacts of climate in the real world, where changes in ecosystem structure or function will alter the viability of different species and the efficacy of ecosystem services. Likewise, adaptation to climate change will simultaneously address a range of conservation goals. Case studies are used to illustrate this complete picture throughout the report; a snapshot of one case study, 2011 Las Conchas, New Mexico Fire , is included in this summary.

Report↗

USGS2002

Digital mapping techniques '02, workshop proceedings : May 19-22, 2002, Salt Lake City, Utah

The Digital Mapping Techniques '02 (DMT'02) workshop was attended by 101 technical experts from 43 agencies, universities, and private companies, including representatives from 25 state geological surveys (see Appendix A). This workshop was similar in nature to the previous five meetings, held in Lawrence, Kansas (Soller, 1997), in Champaign, Illinois (Soller, 1998a), in Madison, Wisconsin (Soller, 1999), in Lexington, Kentucky (Soller, 2000), and in Tuscaloosa, Alabama (Soller, 2001). This year's meeting was hosted by the Utah Geological Survey, from May 19 to 22, 2002, on the University of Utah campus in Salt Lake City. As in the previous meetings, the objective was to foster informal discussion and exchange of technical information. When an attendee adopts or modifies a newly learned technique on the basis of discussions at the workshop, the workshop clearly has met that objective. Evidence of learning and cooperation among participating agencies continued to be a highlight of the DMT workshops (see example in Soller, 1998b, and various papers in this volume). All the DMT workshops have been coordinated by the Association of American State Geologists (AASG) and the U.S. Geological Survey (USGS) Data Capture Working Group, which was formed in August 1996 to support the AASG and the USGS in their effort to build a National Geologic Map Database (see Soller and Berg, this volume, and http://ncgmp.usgs.gov/ngmdbproject/standards/datacapt/ ). The Working Group was formed because increased production efficiencies, standardization, and quality of digital map products were needed for the database--and the State and Federal geological surveys--to provide more high-quality digital maps to the public. At the 2002 meeting, oral and poster presentations and special discussion sessions emphasized (1) methods for creating and publishing map products (here, "publishing" includes Web-based release); (2) techniques for scanning already published maps and managing and delivering them on the Web; (3) continued development of the National Geologic Map Database; and (4) progress toward building a standard geologic map data model. In addition, special presentations were provided on building a statewide GIS council, incorporating geology as a NSDI Framework layer, and resolving the roles of surveyors and GIS professionals.

Open-File Report↗