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At least 289 records · Page 16Linked to original sources

USGS2013

Asian carp behavior in response to static water gun firing

The potential for invasion of Asian carp into the Great Lakes has ecological and socio-economic implications. If they become established, Asian carp are predicted to alter lake ecosystems and impact commercial and recreational fisheries. The Chicago Sanitary and Shipping Canal is an important biological conduit between the Mississippi River Basin, where invasive Asian carp are abundant, and the Great Lakes. Millions of dollars have been spent to erect an electric barrier defense in the canal to prevent movement of Asian carp into the Great Lakes, but the need for additional fish deterrent technologies to supplement the existing barrier is warranted. Scientists with the U.S. Geological Survey Northern Rocky Mountain Science Center are examining seismic water gun technology, formerly used in oceanic oil exploration, as a fish deterrent. The goal of the current study is to employ telemetry and sonar monitoring equipment to assess the behavioral response of Asian carp to seismic water guns and the sound energy it generates.

Illinois↗

USGS2025

The National integrated water availability assessment, water years 2010–20

Water availability is fundamentally important to human well-being, economic vitality, and ecosystem health. Because of its central importance, the U.S. Congress tasked the U.S. Geological Survey (USGS) and other Federal agencies with conducting regular, comprehensive assessments of water availability in the United States through the requirements under the SECURE Water Act. In response to this mandate, the USGS has developed the U.S. Geological Survey Integrated Water Availability Assessment—2010–20, which addresses aspects of water supply, quality, and use related to water availability in the United States. This is the first chapter of that report. The major climatic factors affecting water availability are also described. Multiple aspects of water availability are integrated to produce a more comprehensive analysis of water availability in the United States. This chapter enumerates the development, organization, and tools used in the USGS Integrated Water Availability Assessment. SECURE Water Act reports, developed by the Department of Energy Hydropower Climate Change Assessment and the Bureau of Reclamation West-Wide Climate and Hydrology Assessment, are also described. A distilled list of key findings from the overall report is also provided, serving as an introduction to each topic along with the most important high-level information.

conterminous United States↗

USGS2016

Mineral resources of the Sagebrush Focal Areas of Idaho, Montana, Nevada, Oregon, Utah, and Wyoming

Scientific Investigations Report 2016–5089 and accompanying data releases are the products of the U.S. Geological Survey (USGS) Sagebrush Mineral-Resource Assessment (SaMiRA). The assessment was done at the request of the Bureau of Land Management (BLM) to evaluate the mineral-resource potential of some 10 million acres of Federal and adjacent lands in Idaho, Montana, Nevada, Oregon, Utah, and Wyoming. The need for this assessment arose from the decision by the Secretary of the Interior to pursue the protection of large tracts of contiguous habitat for the greater sage-grouse ( Centrocercus urophasianus ) in the Western United States. One component of the Department of the Interior plan to protect the habitat areas includes withdrawing selected lands from future exploration and development of mineral and energy resources, including copper, gold, silver, rare earth elements, and other commodities used in the U.S. economy. The assessment evaluates the potential for locatable minerals such as gold, copper, and lithium and describes the nature and occurrence of leaseable and salable minerals for seven Sagebrush Focal Areas and additional lands in Nevada (“Nevada additions”) delineated by BLM. Supporting data are available in a series of USGS data releases describing mineral occurrences (the USGS Mineral Deposit Database or “USMIN”), oil and gas production and well status, previous mineral-resource assessments that covered parts of the areas studied, and a compilation of mineral-use cases based on data provided by BLM, as well as results of the locatable mineral-resource assessment in a geographic information system. The present assessment of mineral-resource potential will contribute to a better understanding of the economic and environmental trade-offs that would result from closing approximately 1 0 million acres of Federal lands to mineral entry.

Idaho, Montana, Nevada, Oregon, Utah, Wyoming↗

USGS1956

Non-pegmatitic resources of beryllium in United States

During the period from 1948 to 1950 the U.S. Geological Survey conducted a program of field and laboratory research w determine the mode of occurrence of beryllium in non-pegmatitic rocks and mineral deposits as part of the Beryllium Program of the Division of Raw Materials of the U.S. Atomic Energy Commission. Approximately 23 man months were spent in the field collecting samples from 146 localities in 15 states; a total of 680 samples were collected and analyzed for beryllium. Additional samples collected by the Geological Survey. U.S. Bureau of Mines, various state Geological Surveys and other institutions. and private companies were analyzed for beryllium. In total, the beryllium content of 1,238 samples from about 600 localities in the United States is compiled in the final report which is being prepared for publication by the U.S. Geological Survey. The main topics discussed are: uses and properties of beryllium; methods of analysis and mineralogy of beryllium; occurrence of beryllium in igneous, sedimentary and metamorphic rocks, pyrometasomatic and related deposits, vein deposits, and hot spring deposits; the genesis of beryllium deposits; and a description of the deposits examined. This abstract and table 1 summarize the more pertinent economic data. Beryllium is more abundant than arsenic, gold, silver, and molybdenum in the lithosphere, but its chemical and physical properties prohibit its concentration in minerals which are common w large commercial vein and replacement deposits. There are 29 minerals in which beryllium is an essential constituent but of these only beryl, mined from granite pegmatites, is an ore of beryllium., Beryl also occurs disseminated in granites and high-temperature veins. The other 28 minerals occur as rare constituents in syenite and granite pegmatites, granites, and pyrometasomatic deposits. Beryllium, as a trace constituent, has been detected in 49 minerals but recovery of the beryllium requires metallurgical methods as yet unknown.

Trace Elements Investigations↗

USGS1999

Mapping the glacial geology of the Central Great Lakes region in three dimensions: A model for state-federal cooperation

Planners need to evaluate complex and competing public-policy options for managing water, land, and biological resources; they must ensure economic growth, meet the needs of an increasing population, assess hazards, and manage the environment in a sustainable manner. The State Geological Surveys of Illinois, Indiana, Michigan, and Ohio and the U.S. Geological Survey (USGS) receive many requests from local, State, and Federal planners and officials for geologic information. Thick and complex layers of glacial and related sediments blanket the bedrock of these States: a three-dimensional understanding of these deposits is critical to making informed resource-management and other planning decisions. At two recent forums (in Indianapolis, March 1997, and Columbus, Ohio, February 1999), more than 200 attendees from more than 60 local, State, and Federal agencies provided a clear message. They need three-dimensional geologic information to use in making decisions on the following issues: • Quality, quantity, distribution, and accessibility of surface and ground water • Aggregate sources and land-use conflicts • Energy and mineral resource management • Environmental management and mitigation of land and water contamination • Acceleration of the permitting processes of regulatory agencies • Industrial, commercial, residential, and infrastructure siting and construction • Agricultural land loss, erosion, sedimentation, and agrichemical use • Waste-disposal planning and mitigation • Habitat alteration and biodiversity • Coastal erosion, landslides, radon, floods, and earthquakes

Illinois, Indiana, Michigan, Ohio↗

USGS1973

Thermochemical approximations for sulfosalts

Most sulfosalts may be regarded as intermediate phases on joins between simple sulfide components (e.g., all lead sulfbismuthinides lie on the PbS-Bi 2 S 3 join). Many of the structures are characterized by subunits whose individual structures are similar to those of the component simple sulfides (e.g., galena-like and stibnite-like layers in the lead sulfantimonides). Therefore, as a first approximation one may estimate the properties of many sulfosalts in terms of mixtures of the simple sulfides.Recent work has shown that the free energy of reaction from the end-member sulfides, delta G m , for more than 20 sulfosalts is usually less negative than the hypothetical ideal free energy of mixing and that the standard free energy of formation, delta G degrees , per gram atom of sulfur in the formula may be represented as:delta G degrees = (N a delta G a degrees + . . . N i delta G i [degree) + (1.2 + or - 0.8)(N a RT ln N a + . . . N i RT ln N i )where N i is the mole fraction of the i-th simple sulfide component, R is the gas constant, and T is temperature in kelvins. The first term is far larger than the second. Estimates made for compounds in which the structural environment for the metals is quite different from that in the end-member sulfides, e.g., enargite, are subject to the greatest uncertainty.The estimated free energies may permit prediction of solubilities to a precision sufficient for many purposes, e.g., for H. C. Helgeson's computer-modeled hydrothermal systems. One may introduce some predictive capability into experimental design and anticipate some aspects of phase diagrams. This is especially true for redox reactions such as the behavior of proustite in the oxidized zone or the partial reduction of jamesonite to antimony + galena + pyrrhotite. However, other aspects, such as the prediction of the configuration of joins, e.g., PbS-As 2 S 3 , requires greater precision than the present rough estimates.

Economic Geology↗

USGS2010

Global mineral resource assessment

Introduction In response to the growing demand for information on the global mineral-resource base, the U.S. Geological Survey (USGS) is conducting the Quantitative Global Mineral Resource Assessment Project (GMRAP), a cooperative international project, begun in 2002, to assess the world's undiscovered nonfuel mineral resources. Primary Objectives The USGS conducts national and global assessments of resources (mineral, energy, water, biologic) to provide science in support of decisionmaking. Mineral resource assessments provide a synthesis of available information about where mineral deposits are known and suspected in the Earth’s crust, what commodities may be present, and estimates of amounts of resources that may be present in undiscovered deposits. The Global Mineral Resource Assessment Project started in 2002 as a cooperative international effort to assess the world’s undiscovered nonfuel mineral resources. Primary objectives are to: Outline the regional locations and estimate the probable amounts of the world’s undiscovered resources of copper, platinum-group elements (PGE), and potash in selected types of mineral deposits to depths of 1 to 3 kilometers below the Earth’s surface. Provide the first globally consistent and comprehensive analysis of undiscovered nonfuel mineral resources to provide all nations with a regional and global context for evaluating their mineral resources, planning for new mineral exploration and anticipating the economic, environmental, and social impacts of mineral development, and making land use decisions. The project emphasizes the most important types of mineral deposits for world supply of copper, platinum-group elements (PGE) and nickel, and potash. Go to the Quantitative Global Mineral-Resource Assessments home page for more information.

Scientific Investigations Report↗

USGS2024

Shifting sands: The influence of coral reefs on shoreline erosion from short-term storm protection to long-term disequilibrium

Climate change is exacerbating shoreline erosion and flooding, posing significant risks to coastal communities. Although traditional coastal defenses such as seawalls, dykes, and breakwaters offer protection from these hazards, their high environmental and economic costs are driving interest in cost-competitive nature-based solutions. Coral reef restoration is a nature-based solution that may be particularly apt to mitigate tropical coastal flooding and shoreline erosion while providing benefits to local tourism, fisheries, and nature. However, the novelty of this field requires studies demonstrating the benefits of reefs for coastal protection. While the flood protection benefits of reefs have been well-documented, their effects on shoreline erosion are comparatively less understood. Here, we investigate the effects of coral reefs on shoreline erosion by comparing tropical beach responses at short and long timescales, as well as identifying important reef structural features influencing coastal erosion rates. Our analyses leveraged two key datasets created in this study: the first derived from a literature review on short-term shoreline erosion due to storm events, and another compiling >80 years of long-term erosion rates, bathymetry, habitat, and wave energy for the Hawaiian Islands of Kauaʻi, Oʻahu, and Maui. Our analyses reveal three key findings regarding the effects of reefs on shoreline erosion. Firstly, we find evidence for the role of reefs in mitigating shoreline erosion during storm events, with coral reef-protected beaches experiencing 97 % less beach volume loss than unprotected beaches. Secondly, a linear regression analysis demonstrates that coral reef structure and wave energy are important predictors of long-term shoreline erosion rates, explaining 34 % of the variation across the Hawaiian Islands. Consistent with prior research, we find beaches protected by coral reefs with shallow reef crests, wide reef flats, calmer offshore conditions, and positioned farther from the shore exhibit lower erosion rates than others. Finally, when comparing historical erosion rates of protected and unprotected beaches in Hawai'i, we find a seemingly incongruous pattern where coral reef-protected beaches eroded up to 2x faster than beaches without reefs. While the cause of the enhanced erosion is yet to be fully understood, a combination of coral reef structural degradation and sea-level rise is likely shifting the equilibrium profiles of reef-protected beaches inshore. These results emphasize the role of coral reefs in reducing coastal erosion during storm events while revealing contrasting erosion patterns over long timescales. Future studies would ideally broaden the scope to include various regions, utilize advanced sediment transport models, and undertake field experiments to deepen our understanding of coral reef-coupled shoreline dynamics.

Nature-Based Solutions↗

USGS2014

Site fidelity and condition metrics suggest sequential habitat use by early juvenile snook

The common snook Centropomus undecimalis is an estuarine-dependent fish that relies on landward wetlands as nursery habitat. Despite its economic importance, portions of the snook's early life history are poorly understood. We compared habitat use of young-of-the-year (YOY) snook in 2 geomorphic mesohabitats (tidal pond and tidal creek) along an estuarine gradient (upstream vs. downstream) within a single wetland during fall recruitment. We used abundance, length, condition indices, and stable isotopes to assess ontogenetic mesohabitat use and site fidelity. We found that (1) YOY snook were more abundant within the upstream creek and ponds; (2) the smallest snook were found only in ponds; (3) snook from ponds had lower condition (Fulton's K and hepatosomatic index); (4) snook began moving from ponds to the creek at ~40 mm standard length; and (5) snook from the 2 mesohabitats were isotopically distinct, indicating high site fidelity at rather small spatial scales. Collectively, these data identified sequential use of mesohabitats, wherein seaward-spawned YOY snook moved landward and recruited to pond habitats, where they dedicated energy to growth (as length) before making an ontogenetic habitat shift to the creek. Once in the creek, YOY snook condition improved as they approached maturity and started the downstream return towards seaward locations. The wetland network that was previously viewed as generalized nursery habitat instead consists of mesohabitats that support different life stages in sequence. This represents ontogenetic habitat complementation, in which lower availability of a required mesohabitat type may limit the entire wetland's contribution to the adult population.

Marine Ecology Progress Series↗

USGS2016

Manganese nodules

The existence of manganese (Mn) nodules (Figure 1) has been known since the late 1800s when they were collected during the Challenger expedition of 1873–1876. However, it was not until after WWII that nodules were further studied in detail for their ability to adsorb metals from seawater. Many of the early studies did not distinguish Mn nodules from Mn crusts. Economic interest in Mn nodules began in the late 1950s and early 1960s when John Mero finished his Ph.D. thesis on this subject, which was published in the journal Economic Geology (Mero, 1962) and later as a book (Mero, 1965). By the mid-1970s, large consortia had formed to search for and mine Mn nodules that occur between the Clarion and Clipperton fracture zones (CCZ) in the NE Pacific (Figure 2). This is still the area considered of greatest economic potential in the global ocean because of high nickel (Ni), copper (Cu), and Mn contents and the dense distribution of nodules in the area. While the mining of nodules was fully expected to begin in the late 1970s or early 1980s, this never occurred due to a downturn in the price of metals on the global market. Since then, many research cruises have been undertaken to study the CCZ nodules, and now 15 contracts for exploration sites have been given or are pending by the International Seabed Authority (ISA). Many books and science journal articles have been published summarizing the early work (e.g., Baturin, 1988; Halbach et al., 1988), and research has continued to the present day (e.g., ISA, 1999; ISA, 2010). Although the initial attraction for nodules was their high Ni, Cu, and Mn contents, subsequent work has shown that nodules host large quantities of other critical metals needed for high-tech, green-tech, and energy applications (Hein et al., 2013; Hein and Koschinsky, 2014).

Book chapter↗

USGS2017

Coupling ecological and social network models to assess “transmission” and “contagion” of an aquatic invasive species

Network analysis is used to address diverse ecological, social, economic, and epidemiological questions, but few efforts have been made to combine these field-specific analyses into interdisciplinary approaches that effectively address how complex systems are interdependent and connected to one another. Identifying and understanding these cross-boundary connections improves natural resource management and promotes proactive, rather than reactive, decisions. This research had two main objectives; first, adapt the framework and approach of infectious disease network modeling so that it may be applied to the socio-ecological problem of spreading aquatic invasive species, and second, use this new coupled model to simulate the spread of the invasive Chinese mystery snail ( Bellamya chinensis ) in a reservoir network in Southeastern Nebraska, USA. The coupled model integrates an existing social network model of how anglers move on the landscape with new reservoir-specific ecological network models. This approach allowed us to identify 1) how angler movement among reservoirs aids in the spread of B . chinensis , 2) how B . chinensis alters energy flows within individual-reservoir food webs, and 3) a new method for assessing the spread of any number of non-native or invasive species within complex, social-ecological systems.

Journal of Environmental Management↗

USGS1973

Solid solutions in the system Cu-Fe-S, part I: The Cu-S and CuFe-S joins

T he data of Rau (1967) on the H 2 S/H 2 ratios of gas in equilibrium with high digenite solid solutions permit the calculation of the activity of Cu 2 S as a function of temperature and composition. The activity of Cu 2 S falls to 0.5 when the mole fraction (in the system Cu 2 S-S) drops only to 0.87. These calculations also permit the estimation of the activity of S 2 -temperature curve for the hexagonal chalcocite-high digenite reaction and a revised standard free energy for covellite.New data on the variation of the activity of S 2 in equilibrium with various metal/sulfur ratios for Cu = Fe in the intermediate solid solution permit the calculation of the activity of CuFeS 2 and show that it may drop as low as 0.2 at a mole fraction of 0.90 (system CuFeS 2 -Cu 2 Fe 2 S 2 ). The behavior of the copper-bearing solid solutions closely parallels that of pyrrhotite (Toulmin and Barton, 1964) in which the activity of FeS falls to 0.4 at a mole fraction of 0.9. A phase diagram is given for the CuFe-S join between 400 degrees and 700 degrees C.

Economic Geology↗

USGS2014

Stitching the western Piedmont of Virginia: Early Paleozoic tectonic history of the Ellisville Pluton and the Potomac and Chopawamsic Terranes

The theme of the 2014 Virginia Geological Field Conference is the tectonic development, economic geology, and seismicity of the western Piedmont of Louisa County, Virginia. It is timely for the conference to turn its attention here, for during the past decade these aspects of western Piedmont geology have garnered the renewed attention of researchers. In terms of regional tectonics, it has been hypothesized that the major structure in the region, the Chopawamsic fault system, represents the most significant boundary in the Appalachian orogen, the main Iapetan suture (Hibbard et al., 2014). Economically, recent elevated market values of metals— particularly that of gold—has spurred reconsideration of the economic geology of the western Piedmont. Finally, the August 23, 2011, M5.8 earthquake, with its epicenter in our field area, startled the North American east coast and has revived awareness of the seismic potential of the region. This renewed interest in the geology of the western Piedmont of north-central Virginia has led to new detailed bedrock mapping, detailed surficial mapping, high-resolution UPb TIMS zircon geochronology, U-Pb LA-ICPMS detrital zircon geochronology, radiogenic isotope geochemistry, major/minor/REE geochemistry, and geophysical studies (e.g. Bailey et al., 2005, 2008; Bailey and Owens, 2012: Berti et al., 2012; Burton et al., 2014; Burton, in progress; Harrison, 2012; Horton et al., 2010, in press; Hughes, 2010, 2014; Hughes et al., 2013a, 2013b, 2014, in press a, in press b; Malenda, in progress; Owens et al., 2013; Spears and Gilmer 2012; Spears et al. 2013, Terblanche, 2013; Terblanche and Nance, 2012). A host of institutions have taken part in the research, including North Carolina State University, the Virginia Department of Mines, Minerals, and Energy, the U.S. Geological Survey, Virginia Tech, Lehigh University, and the College of William and Mary. Many of these investigations remain active. The majority of the data presented herein is the product of research conducted from 2010 to 2014 by geologists at North Carolina State University. This field trip guide is intended to complement a Geological Society of America field guide (Hughes et al., 2014) that covers the western Piedmont geology along strike to the northeast in the vicinity of Fredericksburg. Geologic mapping and geochronologic and geochemical sampling were coordinated between these two areas as part of a study funded in part by the National Science Foundation and the USGS EDMAP program. Some of the stops in this guide have previously been written up in past field guides (Hughes, 2010; Burton et al., 2014) and are reused here because of their ease of access for large groups and because of new data that update the context and our understanding of the outcrops.

Virginia↗

USGS2015

Biogeochemical aspects of uranium mineralization, mining, milling, and remediation

Natural uranium (U) occurs as a mixture of three radioactive isotopes: 238 U, 235 U, and 234 U. Only 235 U is fissionable and makes up about 0.7% of natural U, while 238 U is overwhelmingly the most abundant at greater than 99% of the total mass of U. Prior to the 1940s, U was predominantly used as a coloring agent, and U-bearing ores were mined mainly for their radium (Ra) and/or vanadium (V) content; the bulk of the U was discarded with the tailings (Finch et al., 1972). Once nuclear fission was discovered, the economic importance of U increased greatly. The mining and milling of U-bearing ores is the first step in the nuclear fuel cycle, and the contact of residual waste with natural water is a potential source of contamination of U and associated elements to the environment. Uranium is mined by three basic methods: surface (open pit), underground, and solution mining (in situ leaching or in situ recovery), depending on the deposit grade, size, location, geology and economic considerations (Abdelouas, 2006). Solid wastes at U mill tailings (UMT) sites can include both standard tailings (i.e., leached ore rock residues) and solids generated on site by waste treatment processes. The latter can include sludge or “mud” from neutralization of acidic mine/mill effluents, containing Fe and a range of coprecipitated constituents, or barium sulfate precipitates that selectively remove Ra (e.g., Carvalho et al., 2007). In this chapter, we review the hydrometallurgical processes by which U is extracted from ore, the biogeochemical processes that can affect the fate and transport of U and associated elements in the environment, and possible remediation strategies for site closure and aquifer restoration. This paper represents the fourth in a series of review papers from the U.S. Geological Survey (USGS) on geochemical aspects of UMT management that span more than three decades. The first paper (Landa, 1980) in this series is a primer on the nature of tailings and radionuclide mobilization from them. The second paper (Landa, 1999) includes coverage of research carried out under the U.S. Department of Energy’s Uranium Mill Tailings Remedial Action Program (UMTRA). The third paper (Landa, 2004) reflects the increased focus of researchers on biotic effects in UMT environs. This paper expands the focus to U mining, milling, and remedial actions, and includes extensive coverage of the increasingly important alkaline in situ recovery and groundwater restoration.

Applied Geochemistry↗

USGS2019

Rare earth element mineral deposits in the United States

Because of their unique special chemical properties, many of the metals in the group of rare earth elements (REEs) have essential applications in 21st century technologies. Examples of products that use REEs are cell phones, computers, fluorescent and light-emitting-diode lights, flat-screen television and computer monitors, and in high-strength magnets used by clean energy technologies such as the generators of wind turbines and batteries of hybrid and electric vehicles. REEs are used in many defense applications, such as in components of jet engines, missile guidance systems, antimissile defense systems, satellites, and communication systems. The rare earth elements have become vital to manufacturing numerous high-tech products, which has been accompanied by a large increase in their demand. At the same time, there has been concern by the United States and many other Nations about the near-monopoly of mining, processing, and supply of REEs from one Nation, China. Between 2011 and 2017, China produced approximately 84 percent of the world’s REEs, and during this time the United States only produced REEs between 2012 and 2015. The U.S. production came entirely from the Mountain Pass mine in California, providing only about 4 percent of the world REE supply. Because REEs are essential for technological applications and are primarily supplied by one Nation, there has been an increased concern in identifying new sources of REEs, including economic REE deposits. In response to these concerns, since 2009, the U.S. Geological Survey (USGS) has conducted numerous studies focused on the distribution, geology, and potential resources for the REE-bearing mineral deposits in the United States. The basic characteristics of mineral deposit types that host REE enrichments in the United Sates are summarized in this report, with selected examples. Several types of REE-enriched mineral deposits are reviewed, including deposits in carbonatites, alkaline igneous rocks, sedimentary phosphate-rich rocks (phosphorite), regions containing REE-rich veins, iron oxide deposits containing REE-bearing apatite, monazite-xenotime-bearing placer deposits (heavy-mineral sands), and ion-adsorption clay deposits (REE in granite-derived regolith). A better understanding of these mineral deposits will assist in identifying domestic resources to help alleviate the dependence on imported REEs. The economic development of REE mineral deposits is affected by many factors beyond mining, such as commodity prices and mineral processing costs. Most of the REEs are hosted by minerals that have complex chemical formulas; this presents more challenges to process and extract the REEs. Continued advancements and refinements in mineral processing techniques may allow REE deposits with complex mineralogy to be economically developed in the future.

Circular↗

USGS2014

Correlation chart of Pennsylvanian rocks in Alabama, Tennessee, Kentucky, Virginia, West Virginia, Ohio, Maryland, and Pennsylvania showing approximate position of coal beds, coal zones, and key stratigraphic units

The Appalachian basin, one of the largest Pennsylvanian bituminous coal-producing regions in the world, currently contains nearly one-half of the top 15 coal-producing States in the United States (Energy Information Agency, 2006). Anthracite of Pennsylvanian age occurs in synclinal basins in eastern Pennsylvania, but production is minimal. A simplified correlation chart was compiled from published and unpublished sources as a means of visualizing currently accepted stratigraphic relations between the rock formations, coal beds, coal zones, and key stratigraphic units in Alabama, Tennessee, Kentucky, Virginia, West Virginia, Ohio, Maryland, and Pennsylvania. The thickness of each column is based on chronostratigraphic divisions (Lower, Middle, and Upper Pennsylvanian), not the thickness of strata. Researchers of Pennsylvanian strata in the Appalachian basin also use biostratigraphic markers and other relative and absolute geologic age associations between the rocks to better understand the spatial relations of the strata. Thus, the stratigraphic correlation data in this chart should be considered provisional and will be updated as coal-bearing rocks within the Appalachian coal regions continue to be evaluated. Most geologic formations are identified and defined by the distinctive lithologic features they contain. However, formations of Pennsylvanian age in the Appalachian basin and the Pennsylvania Anthracite region have traditionally been described and named to reflect the presence or absence of economic coal beds and coarse-grained sandstone units, most of which have since been proven to be locally or regionally discontinuous (Ruppert and Rice, 2001). Many of the stratigraphic names and boundaries used for the coals and other geologic units in the Pennsylvanian rocks differ between States or regions (fig. 1). Because local and regional stratigraphic complexities occur within some States, a multiplicity of State-specific names is introduced that may be confusing to those conducting regional geologic assessments in the basin. Nonetheless, many of these stratigraphic names and boundaries have some elements that allow for regional stratigraphic correlation. For instance, many coals in the northern Appalachian basin coal region are easier to trace over greater distances than coals in the central and southern Appalachian basin coal regions (fig. 2). The Upper Pennsylvanian Pittsburgh coal bed (fig. 1) of the northern Appalachian basin coal region, for example, occurs as a synchronogenic bed deposited on a laterally continuous surface of sediments (Cross, 1954; Tewalt and others, 2001). The base of the Pittsburgh coal bed is designated as the contact between the Conemaugh Group (Upper Pennsylvanian) and the overlying Monongahela Group in western Pennsylvania, western Maryland, Ohio, and West Virginia (fig. 1). Therefore, in areas where the Pittsburgh coal bed is present, there is little controversy over its position or the placement of the boundary between the Conemaugh and Monongahela Groups. In other regions of the basin, group and formation boundaries are more difficult to identify over extensive areas. One example is the placement of the contact between the New River Formation and the overlying Kanawha Formation—a boundary that is not easily defined beyond the area where these units were first defined in West Virginia. At the type section of the Kanawha Formation, the base of the Lower Douglas coal zone (fig. 1) defines the contact between the Kanawha Formation and the underlying New River Formation (Rice and others, 1994b). However, subsequent mapping has demonstrated that the Lower Douglas coal zone is regionally discontinuous and in many parts of West Virginia is absent (Blake and others, 2002). Where absent, the Nuttall Sandstone Member of the underlying New River Formation sometimes occurs in the stratigraphic position of the Lower Douglas coal zone. Yet, even the Nuttall Sandstone Member has been found to be regionally discontinuous and of varying thickness throughout its extent, features that hinder its use as a regional stratigraphic marker bed in the Appalachian basin. Because of the many names used to identify individual coal beds and coal zones in the historic Appalachian basin coal-mining districts, coal bed designations may differ even more than stratigraphic nomenclature. In eastern Kentucky, northwest of the Pine Mountain thrust fault on the Cumberland overthrust sheet, for example, coal beds or coal zones equivalent to the Lower Elkhorn coal zone (within the Pikeville Formation) are identified also as the Eagle coal zone, Pond Creek coal zone, and Blue Gem coal bed (fig. 1). Southeast of the Pine Mountain thrust fault, yet still in Kentucky, equivalent coals in this same interval are known as the Imboden and Rich Mountain. Moreover, this same interval of coal is identified as the Blue Gem coal in Tennessee, the Imboden coal bed or Campbell Creek or Pond Creek coal zones in Virginia, and the Eagle coal zone in West Virginia.

Appalachian basin↗

USGS2020

Carrying capacity of a population diffusing in a heterogeneous environment

The carrying capacity of the environment for a population is one of the key concepts in ecology and it is incorporated in the growth term of reaction-diffusion equations describing populations in space. Analysis of reaction-diffusion models of populations in heterogeneous space have shown that, when the maximum growth rate and carrying capacity in a logistic growth function vary in space, conditions exist for which the total population size at equilibrium (i) exceeds the total population that which would occur in the absence of diffusion and (ii) exceeds that which would occur if the system were homogeneous and the total carrying capacity, computed as the integral over the local carrying capacities, was the same in the heterogeneous and homogeneous cases. We review here work over the past few years that has explained these apparently counter-intuitive results in terms of the way input of energy or another limiting resource (e.g., a nutrient) varies across the system. We report on both mathematical analysis and laboratory experiments confirming that total population size in a heterogeneous system with diffusion can exceed that in the system without diffusion. We further report, however, that when the resource of the population in question is explicitly modeled as a coupled variable, as in a reaction-diffusion chemostat model rather than a model with logistic growth, the total population in the heterogeneous system with diffusion cannot exceed the total population size in the corresponding homogeneous system in which the total carrying capacities are the same.

Mathematics and Computers in Modern Science - Acou↗

USGS2017

Using CO 2 Prophet to estimate recovery factors for carbon dioxide enhanced oil recovery

Introduction The Oil and Gas Journal’s enhanced oil recovery (EOR) survey for 2014 (Koottungal, 2014) showed that gas injection is the most frequently applied method of EOR in the United States and that carbon dioxide (CO 2 ) is the most commonly used injection fluid for miscible operations. The CO 2 -EOR process typically follows primary and secondary (waterflood) phases of oil reservoir development. The common objective of implementing a CO 2 -EOR program is to produce oil that remains after the economic limit of waterflood recovery is reached. Under conditions of miscibility or multicontact miscibility, the injected CO 2 partitions between the gas and liquid CO2 phases, swells the oil, and reduces the viscosity of the residual oil so that the lighter fractions of the oil vaporize and mix with the CO 2 gas phase (Teletzke and others, 2005). Miscibility occurs when the reservoir pressure is at least at the minimum miscibility pressure (MMP). The MMP depends, in turn, on oil composition, impurities of the CO 2 injection stream, and reservoir temperature. At pressures below the MMP, component partitioning, oil swelling, and viscosity reduction occur, but the efficiency is increasingly reduced as the pressure falls farther below the MMP. CO 2 -EOR processes are applied at the reservoir level, where a reservoir is defined as an underground formation containing an individual and separate pool of producible hydrocarbons that is confined by impermeable rock or water barriers and is characterized by a single natural pressure system. A field may consist of a single reservoir or multiple reservoirs that are not in communication but which may be associated with or related to a single structural or stratigraphic feature (U.S. Energy Information Administration [EIA], 2000). The purpose of modeling the CO 2 -EOR process is discussed along with the potential CO 2 -EOR predictive models. The data demands of models and the scope of the assessments require tradeoffs between reservoir-specific data that can be assembled and simplifying assumptions that allow assignment of default values for some reservoir parameters. These issues are discussed in the context of the CO 2 Prophet EOR model, and their resolution is demonstrated with the computation of recovery-factor estimates for CO 2 -EOR of 143 reservoirs in the Powder River Basin Province in southeastern Montana and northeastern Wyoming.

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