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At least 1,063 records · Page 59Linked to original sources
USGS1979

Geochemical evidence of drawdown in the Cerro Prieto geothermal field

Some wells of the Cerro Prieto geothermal field have undergone changes in the chemistry of fluids produced which reflect reservoir processes. Pressure decreases due to production in the southeastern part of the field have produced both drawdown of lower chloride fluids from an overlying aquifer and boiling in the aquifer with excess steam reaching the wells. These reservoir changes are indicated by changes in fluid chloride concentrations, Na/K ratios and measured enthalpies and by comparisons of aquifer fluid temperatures and chloride concentrations calculated from enthalpy and chemical measurements. Fluid temperatures have not been greatly affected by this drawdown because heat contained in the rock was transferred to the fluid. When this heat is exhausted, fluid temperatures may drop rapidly. ?? 1979.

Geothermics↗
USGS1997

Mud fossils

At the close of the 18th century, the haze of fantasy and mysticism that tended to obscure the true nature of the Earth was being swept away. Careful studies by scientists showed that rocks had diverse origins. Some rock layers, containing clearly identifiable fossil remains of fish and other forms of aquatic animal and plant life, originally formed in the ocean. Other layers, consisting of sand grains winnowed clean by the pounding surf, obviously formed as beach deposits that marked the shorelines of ancient seas.

General Information Product↗
USGS1992

Summary of ground-water hydrology of the Cambrian-Ordovician aquifer system in the northern Midwest, United States

The Cambrian-Ordovician aquifer system contains very productive aquifers throughout an area of about 161,000 square miles in the northern Midwest. The aquifer system is used extensively for industrial and rural water supplies and is the primary source of water for many municipalities in most of its area of occurrence, except in Indiana, central and southern Illinois, and western Iowa, where the aquifer system contains saline water. About 680 million gallons per day was withdrawn from drilled wells in the aquifer system in 1980. Rocks of Cambrian and Ordovician age, mainly marine sandstones and carbonate rocks, constitute most of the bedrock and subcrop beneath glacial drift in southeastern Minnesota, northeastern Iowa, Wisconsin, northern Illinois, and extreme northwestern Indiana. These strata dip generally to the south and east off the Transcontinental arch in Minnesota and the Wisconsin arch, which are structurally high areas of the Precambrian basement, into the structural lows of the Forest City basin of southwestern Iowa, the Illinois basin, and the Michigan basin. The Cambrian and Ordovician rocks are buried by younger rocks in the remainder of Iowa, Illinois, and Indiana and in most of northern Missouri. Silurian and Devonian carbonate rocks immediately overlie the Cambrian and Ordovician rocks in those areas and are termed the "Silurian-Devonian aquifer" in this study. The balance of the Devonian rocks and the overlying Mississippian and Pennsylvanian rocks generally are fine-grained sediment or dense carbonate rocks and collectively are considered to be a regional confining unit. Most of the area is covered by a veneer of glacial drift, which, along with Cretaceous sandstone in northwestern Iowa, is treated as a regional water-table aquifer. The Cambrian-Ordovician aquifer system is composed of six hydrogeologic units, which are, in descending order, the Maquoketa confining unit, St. Peter-Prairie du Chien-Jordan aquifer, St. Lawrence- Franconia confining unit, Ironton-Galesville aquifer, Eau Claire confining unit, and Mount Simon aquifer. The uppermost confining unit is the least permeable; it consists primarily of the Maquoketa Shale but includes the dense carbonate rocks of the Galena Dolomite and the Decorah, Platteville, and Glenwood Formations where they are overlain by the Maquoketa Shale. The presence of the Maquoketa in Iowa, eastern Wisconsin, northeastern Illinois, and Indiana effectively confines the entire aquifer system below. The aquifer system is a leaky-artesian system in which movement of ground water is controlled partly by the internal confining units. In the northern outcrop area, unconfined conditions prevail in shallow parts of the aquifer system and where the system is thin. Much of the recharge in upland areas discharges to streams through local flow systems, which are no more than a few miles in length. The remainder of the recharge moves slowly downward to deeper formations and downgradient to form or join the regional flow system. Computer simulations of regional ground-water flow improve understanding of the regional character of the Cambrian-Ordovician aquifer system. Ground-water flow in the confined part of the aquifer system is mainly horizontal, away from the structural highs in the north, toward the structural basins in the south and east. The rate of ground-water movement is very slow, and the flux along flow paths into the basins decreases because of a progressive loss of head and small but widespread upward leakage. Saline water in the basins restricts movement of freshwater into the deeper parts of the basins, thereby forcing flow upward through confining units. Principal regional discharge areas are the Mississippi and Missouri Rivers, the Illinois and Michigan structural basins, and Lake Michigan. However, the lake is not in direct hydraulic connection with the Cambrian-Ordovician aquifer system and receives flow primarily from the Silurian-Devonian aquifer, which it directly overlies. The longest regional flow paths originate in recharge areas in northwestern Iowa and extend southeastward as much as 400 miles toward the Illinois basin. Simulated predevelopment recharge and discharge for the Cambrian- Ordovician aquifer system balance at 351 million gallons per day. Development of the aquifer system began in various parts of the northern Midwest in the 1860's and 1870's with the drilling of deep, generally flowing artesian wells near Lake Michigan in eastern Wisconsin and northeastern Illinois and along the valleys of the Mississippi River and its tributaries. Initial heads of 186 and 130 feet above Lake Michigan at Milwaukee and Chicago, respectively, have been reported. Large-scale pumping has produced cones of depression in these two areas, with respective head declines of as much as 375 and 900 feet. Other major pumping centers generally have had much smaller declines. The largest withdrawals from the aquifer system were about 180 million gallons per day in each of the major metropolitan areas of Chicago and Minneapolis-St. Paul (Twin Cities). However, the total decline in head in the St. Peter-Prairie du Chien-Jordan aquifer in the Twin Cities by 1980 was only 90 feet because the aquifer is unconfined. Most of the eastern two-thirds of Iowa, where the aquifer system is tightly confined, is characterized by more than 50 feet of head decline, with 200 feet or more at Mason City and the Quad Cities. Pumpage from the Cambrian-Ordovician aquifer system throughout the study area averaged 683 million gallons per day for the period 1976-80. Results of a transient-model simulation show that recharge increased over predevelopment recharge by 447 million gallons per day. Natural discharge decreased by 99 million gallons per day, and 137 million gallons per day was released from aquifer storage. Mineralization of ground water in the aquifer system increases from slightly mineralized calcium magnesium bicarbonate water in the northern recharge areas, through more mineralized, mixed water types with increased sodium and sulfate, to highly mineralized sodium chloride brines in the deeper parts of the structural basins.

Iowa, Illinois, Indiana, Michigan, Minnesota, Miss↗
USGS1930

Geologic history of the Yosemite Valley

The problem of the origin of the Yosemite Valley inherently demands a solution in quantitative terms. Its essence is, To what extent is the valley a product of glacial action, to what extent a product of stream erosion? The principal result of the investigations upon which this report is based is the determination within narrow limits of the preglacial depth of the Yosemite Valley and of other facts concerning its preglacial development which permit fairly definite estimates of the proportionate shares of work performed by stream and by glacier. The investigations comprise a detailed survey of the glacial and geomorphologic features of the Yosemite region and an equally intensive study of its rock formations, supplemented by reconnaissance work of both kinds in adjoining parts of the Sierra Nevada. The petrologic studies were made by Frank C. Calkins; the glacial and geomorphologic survey by Francois E. Matthes. Detailed mapping of the morainal system of the ancient Yosemite Glacier has served not only to determine the farthest limits reached by that glacier but to throw new light on the significance of the hanging valleys of the Yosemite region. It is reasonably certain that the glacier never extended more than about a mile beyond the site of El Portal. The hanging side valleys of the Merced Canyon below El Portal, therefore, hang not because of any glacial deepening suffered by that canyon. The explanation is offered that they hang because their streamlets have been unable to trench as rapidly as the Merced River since the rejuvenation of the Merced by the last uptilting of the Sierra Nevada. The streamlets were handicapped not only by their comparatively small volume but also by the fact that their courses trend northwestward and southeastward, substantially at right angles to the direction of the tilting, and therefore have remained essentially unsteepened, whereas the Merced's course trends southwestward, directly down the slope of the Sierra block, and therefore has been appreciably steepened. Projection of the longitudinal profiles of these hanging valleys forward to the axis of the Merced Canyon shows that they are closely accordant in height. Their profiles indicate a series of points on a former profile of the Merced with respect to which the side streams had graded their courses prior to the last uplift. This old profile can be extended upward into the glaciated part of the Merced Canyon above El Portal and even into the profoundly glaciated Yosemite Valley, accordant points being furnished by a number of hanging side valleys (due allowance being made for glacial erosion suffered by those valleys). However, not all the hanging valleys of the Yosemite region are accordant with this set. Several of them, including the upland valley of Yosemite Creek, constitute a separate set indicating another old profile of the Merced at a level 600 to 1,000 feet higher than the first. Others, including the hanging gulch of lower Bridalveil Creek, point to an old profile of the Merced about 1,200 feet lower than the first. There are thus three distinct sets of hanging valleys produced in three cycles of stream erosion. The valleys of the upper set, like those of the middle set, were left hanging as a result of rapid trenching by the Merced induced by an uplift of the range, there having been two such uplifts. Only the valleys of the lower set hang because of glacial deepening and widening of the Yosemite Valley, the cycle in which they were cut having been interrupted by the advent of the Pleistocene glaciers. They consequently indicate the preglacial depth of the Yosemite Valley. That depth, measured from the brow of El Capitan, was about 2,400 feet; measured from the rim at Glacier Point it was about 2,000 feet.

California↗
USGS2017

Graphite

Graphite is a form of pure carbon that normally occurs as black crystal flakes and masses. It has important properties, such as chemical inertness, thermal stability, high electrical conductivity, and lubricity (slipperiness) that make it suitable for many industrial applications, including electronics, lubricants, metallurgy, and steelmaking. For some of these uses, no suitable substitutes are available. Steelmaking and refractory applications in metallurgy use the largest amount of produced graphite; however, emerging technology uses in large-scale fuel cell, battery, and lightweight high-strength composite applications could substantially increase world demand for graphite. Graphite ores are classified as “amorphous” (microcrystalline), and “crystalline” (“flake” or “lump or chip”) based on the ore’s crystallinity, grain-size, and morphology. All graphite deposits mined today formed from metamorphism of carbonaceous sedimentary rocks, and the ore type is determined by the geologic setting. Thermally metamorphosed coal is the usual source of amorphous graphite. Disseminated crystalline flake graphite is mined from carbonaceous metamorphic rocks, and lump or chip graphite is mined from veins in high-grade metamorphic regions. Because graphite is chemically inert and nontoxic, the main environmental concerns associated with graphite mining are inhalation of fine-grained dusts, including silicate and sulfide mineral particles, and hydrocarbon vapors produced during the mining and processing of ore. Synthetic graphite is manufactured from hydrocarbon sources using high-temperature heat treatment, and it is more expensive to produce than natural graphite. Production of natural graphite is dominated by China, India, and Brazil, which export graphite worldwide. China provides approximately 67 percent of worldwide output of natural graphite, and, as the dominant exporter, has the ability to set world prices. China has significant graphite reserves, and China’s graphite production is expected to increase, although rising labor costs and some mine production problems are developing. China is expected to continue to be the dominant exporter for the near future. Mexico and Canada export graphite mainly to the United States, which has not had domestic production of natural graphite since the 1950s. Most graphite deposits in the United States are too small, low-grade, or remote to be of commercial value in the near future, and the likelihood of discovering larger, higher-grade, or favorably located domestic deposits is unlikely. The United States is a major producer of synthetic graphite.

Professional Paper↗
USGS2022

Enhanced bioremediation of RDX and co-contaminants perchlorate and nitrate using an anaerobic dehalogenating consortium in a fractured rock aquifer

The potential neurotoxic and carcinogenic effects of the explosives compound RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) on human health requires groundwater remediation strategies to meet low cleanup goals. Bioremediation of RDX is feasible through biostimulation of native microbes with an organic carbon donor but may be less efficient, or not occur at all, in the presence of the common co-contaminants perchlorate and nitrate. Laboratory tests compared biostimulation with bioaugmentation to achieve anaerobic degradation of RDX, perchlorate, and nitrate; a field pilot test was then conducted in a fractured rock aquifer with the selected bioaugmentation approach. Insignificant reduction of RDX, perchlorate, or nitrate was observed by the native microbes in microcosms, with or without biostimulation by addition of lactate. Tests of the RDX-degrading ability of the microbial consortium WBC-2, originally developed for dehalogenation of chlorinated volatile organic compounds, showed first-order biodegradation rate constants ranging from 0.57 to 0.90 per day (half-lives 1.2 to 0.80 days). WBC-2 sustained degradation without daughter product accumulation when repeatedly amended with RDX and lactate for a year. In microcosms with groundwater containing perchlorate and nitrate, RDX degradation began without delay when bioaugmented with 10% WBC-2. Slower RDX degradation occurred with 3% or 5% WBC-2 amendment, indicating a direct relation with cell density. Transient RDX daughter compounds included methylene dinitramine, MNX, and DNX. With WBC-2 amendment, nitrate concentrations immediately decreased to near or below detection, and perchlorate degradation occurred with half-lives of 25 to 34 days. Single-well injection tests with WBC-2 and lactate showed that the onset of RDX degradation coincided with the onset of sulfide production, which was affected by the initial perchlorate concentration. Bioegradation rates in the pilot injection tests agreed well with those measured in the microcosms. These results support bioaugmentation with an anaerobic culture as a remedial strategy for sites contaminated with RDX, nitrate, and perchlorate.

New Mexico↗
USGS2018

Estimating the pressure-limited CO2 injection and storage capacity of the United States saline formations: Effect of the presence of hydrocarbon reservoirs

The U.S. Geological Survey (USGS) national assessment of carbon dioxide (CO 2 ) storage capacity evaluated 192 saline Storage Assessment Units (SAUs) in 33 U.S. onshore sedimentary basins that may be utilized for CO 2 storage (see USGS Circular 1386). Similar to many other available models, volumetric analysis was utilized to estimate the initial CO 2 injection and storage capacity of these SAUs based on aquifer characteristics and buoyant and residual trapping. The factor being almost always overlooked in most CO 2 storage capacity models is that many of the evaluated SAUs contain large numbers of both conventional and unconventional discovered and undiscovered oil and gas reservoirs. The hydrocarbon production and pressure distribution of the resident oil and gas reservoirs may be negatively influenced by the propagated CO 2 plume and pressure front resulting from a CO 2 injection and storage operation in the surrounding SAU. To have a more realistic and accurate estimation of CO 2 injection and storage capacity in saline formations, a model was previously developed that considers the CO 2 injectivity of a given formation, underground pressure build-up limitations imposed by the rock fracturing pressure and the presence of hydrocarbon reservoirs within these aquifers. The developed method estimates the pre–brine extraction, pressure-limited CO 2 injection and storage capacity of a saline formation by applying 3D numerical simulation only on the effective injection area (A eff ) surrounding each CO 2 injection well utilizing TOUGH2-ECO2N simulation software.

Sligo and Hosston Formations↗
USGS1984

Mineralogic evidence for an impact event at the Cretaceous-Tertiary boundary

A thin claystone layer found in nonmarine rocks at the palynological Cretaceous-Tertiary boundary in eastern Montana contains an anomalously high value of iridium. The nonclay fraction is mostly quartz with minor feldspar, and some of these grains display planar features. These planar features are related to specific crystallographic directions in the quartz lattice. The shocked quartz grains also exhibit asterism and have lowered refractive indices. All these mineralogical features are characteristic of shock metamorphism and are compelling evidence that the shocked grains are the product of a high velocity impact between a large extraterrestrial body and the earth. The shocked minerals represent silicic target material injected into the stratosphere by the impact of the projectile.

Science↗
USGS2024

Black shale - Its deposition and diagenesis.

Black shale is a dark-colored mudrock containing organic matter that may have generated hydrocarbons in the subsurface or that may yield hydrocarbons by pyrolysis. Many black shale units are enriched in metals severalfold above expected amounts in ordinary shale. Some black shale units have served as host rocks for syngenetic metal deposits. Black shales have formed throughout the Earth's history and in all parts of the world. This suggests that geologic processes and not geologic settings are the controlling factors in the accumulation of black shale. Geologic processes are those of deposition by which the raw materials of black shale are accumulated and those of diagenesis in response to increasing depth of burial. Depositional processes involve a range of relationships among such factors as organic productivity, clastic sedimentation rate, and the intensity of oxidation by which organic matter is destroyed. If enough organic material is present to exhaust the oxygen in the environment, black shale results. Diagenetic processes involve chemical reactions controlled by the nature of the components and by the pressure and temperature regimens that continuing burial imposes. For a thickness of a few meters beneath the surface, sulfate is reduced and sulfide minerals may be deposited. Fermentation reactions in the next several hundred meters result in biogenic methane, followed successively at greater depths by decarboxylation reactions and thermal maturation that form additional hydrocarbons. Suites of newly formed minerals are characteristic for each of the zones of diagenesis.

Clays and Clay Minerals↗
USGS2009

Ground-Water Quality in the Upper Hudson River Basin, New York, 2007

Water samples were collected from 25 production and domestic wells in the Upper Hudson River Basin (north of the Federal Dam at Troy, N.Y.) from August through November 2007 to characterize the ground-water quality. The Upper Hudson River Basin covers 4,600 square miles in upstate New York, Vermont, and Massachusetts; the study area encompasses the 4,000 square miles that lie within New York. The basin is underlain by crystalline and sedimentary bedrock, including gneiss, shale, and slate; some sandstone and carbonate rocks are present locally. The bedrock in some areas is overlain by surficial deposits of saturated sand and gravel. Of the 25 wells sampled, 13 were finished in sand and gravel deposits, and 12 were finished in bedrock. The samples were collected and processed by standard U.S. Geological Survey procedures and were analyzed for 225 physical properties and constituents, including major ions, nutrients, trace elements, radon-222, pesticides, volatile organic compounds (VOCs), and indicator bacteria. Water quality in the study area is generally good, but concentrations of some constituents exceeded current or proposed Federal or New York State drinking-water standards; these were: color (1 sample), pH (2 samples), sodium (5 samples), nitrate plus nitrite (2 samples), aluminum (3 samples), iron (1 sample), manganese (7 samples), radon-222 (11 samples), and bacteria (1 sample). Dissolved-oxygen concentrations in samples from wells finished in sand and gravel [median 5.4 milligrams per liter (mg/L)] were greater than those from wells finished in bedrock (median 0.4 mg/L). The pH of all samples was typically neutral or slightly basic (median 7.6); the median water temperature was 9.7 deg C. The ions with the highest concentrations were bicarbonate (median 123 mg/L) and calcium (median 33.9 mg/L). Ground water in the basin is generally soft to moderately hard (less than or equal to 120 mg/L as CaCO3) (median hardness 110 mg/L as CaCO3). Concentrations of nitrate plus nitrite in samples from sand and gravel wells (median concentration 0.47 mg/L as nitrogen) were generally higher than those in samples from bedrock wells (median estimated 0.05 mg/L as nitrogen), and concentrations in two samples exceeded established drinking-water standards for nitrate (10 mg/L as nitrogen). The trace elements with the highest concentrations were strontium [median 217 micrograms per liter (ug/L)] and iron (median 39 ug/L). The highest radon-222 activities were in samples from bedrock wells [maximum 2,930 picocuries per liter (pCi/L)] and 44 percent of all samples exceeded a proposed U.S. Environmental Protection Agency (USEPA) drinking-water standard of 300 pCi/L. Ten pesticides and pesticide degradates were detected among 11 samples at concentrations of 1.47 ug/L or less; most were herbicides or their degradates. Six VOCs were detected among 10 samples at concentrations of 4.2 ug/L or less; these included three trihalomethanes and methyl tert-butyl ether, tetrachloroethene, and toluene. Most detections were in samples from sand and gravel wells and none exceeded drinking-water standards. Total coliform bacteria were detected in only one sample, and fecal coliform bacteria, including Escherichia coli, were not detected in any sample.

Open-File Report↗
USGS2003

Ground-water resources of Saipan, Commonwealth of the Northern Mariana Islands

Saipan has an area of 48 mi 2 and is the largest of the 14 islands in the Commonwealth of the Northern Mariana Islands (CNMI). The island is formed by volcanic rocks overlain by younger limestones. The island is situated in the western Pacific Ocean at latitude 15 o 12'N and longitude 145 o 45'E, about 3,740 mi west-southwest of Honolulu and midway between Japan and New Guinea (fig. 1). The climate on Saipan is classified as tropical marine with an average temperature of 80 o F. The natural beauty of the island and surrounding waters are the basis for a growing tourist-based economy. The resulting rapid development and increases in resident and tourist populations have added stresses to the island's limited water supplies. Freshwater resources on Saipan are not readily observable because, aside from the abundant rainfall, most freshwater occurs as ground water. Fresh ground water is found in aquifers composed mainly of fragmental limestones. About 90 percent of the municipal water supply comes from 140 shallow wells that withdraw about 11 Mgal/d. The chloride concentration of water withdrawn from production wells ranges from less than 100 mg/L for wells in the Akgak and Capital Hill well fields, to over 2,000 mg/L from wells in the Puerto Rico, Maui IV, and Marpi Quarry well fields. The chloride concentrations and rates of ground-water production are not currently adequate for providing island residents with a potable 24-hour water supply and future demands are expected to be higher. To better understand the ground-water resources of the island, and water resources on tropical islands in general, the U.S. Geological Survey (USGS) entered into a cooperative program with the Commonwealth Utilities Corporation (CUC). The objective of the program, initiated in 1989, is to assess the ground-water resources of Saipan and to make hydrologic information available to the CUC in support of their ongoing efforts to improve the quality and quantity of the municipal water supply. This report presents some of the results of the program including descriptions of (1) the geography and geology, (2) the occurrence of fresh ground water in permeable limestones that extend to some distance below sea level where water-level elevation is affected by ocean tides (coastal aquifers) and in limestones that overlie volcanic basement rocks above sea level (high-level aquifers), (3) the water-table configuration and directions of ground-water flow, and (4) the rainfall, ground-water withdrawal, and chloride concentrations in well water. Also described is the relation of the changes in water-table elevations to changes in sea level, rainfall, and ground-water withdrawal.

Saipan↗
USGS2017

Rare-earth elements

The rare-earth elements (REEs) are 15 elements that range in atomic number from 57 (lanthanum) to 71 (lutetium); they are commonly referred to as the “lanthanides.” Yttrium (atomic number 39) is also commonly regarded as an REE because it shares chemical and physical similarities and has affinities with the lanthanides. Although REEs are not rare in terms of average crustal abundance, the concentrated deposits of REEs are limited in number. Because of their unusual physical and chemical properties, the REEs have diverse defense, energy, industrial, and military technology applications. The glass industry is the leading consumer of REE raw materials, which are used for glass polishing and as additives that provide color and special optical properties to the glass. Lanthanum-based catalysts are used in petroleum refining, and cerium-based catalysts are used in automotive catalytic converters. The use of REEs in magnets is a rapidly increasing application. Neodymium-iron-boron magnets, which are the strongest known type of magnets, are used when space and weight are restrictions. Nickel-metal hydride batteries use anodes made of a lanthanum-based alloys. China, which has led the world production of REEs for decades, accounted for more than 90 percent of global production and supply, on average, during the past decade. Citing a need to retain its limited REE resources to meet domestic requirements as well as concerns about the environmental effects of mining, China began placing restrictions on the supply of REEs in 2010 through the imposition of quotas, licenses, and taxes. As a result, the global rare-earth industry has increased its stockpiling of REEs; explored for deposits outside of China; and promoted new efforts to conserve, recycle, and substitute for REEs. New mine production began at Mount Weld in Western Australia, and numerous other exploration and development projects noted in this chapter are ongoing throughout the world. The REE-bearing minerals are diverse and often complex in composition. At least 245 individual REE-bearing minerals are recognized; they are mainly carbonates, fluorocarbonates, and hydroxylcarbonates (n = 42); oxides (n = 59); silicates (n = 85); and phosphates (n = 26). Many of the world’s significant REE deposits occur in carbonatites, which are carbonate igneous rocks. The REEs also have a strong genetic association with alkaline magmatism. The systematic geologic and chemical processes that explain these observations are not well understood. Economic or potentially economic REE deposits have been found in (a) carbonatites, (b) peralkaline igneous systems, (c) magmatic magnetite-hematite bodies, (d) iron oxide-copper-gold (IOCG) deposits, (e) xenotime-monazite accumulations in mafic gneiss, (f) ion-absorption clay deposits, and (g) monazite-xenotime-bearing placer deposits. Carbonatites have been the world’s main source for the light REEs since the 1960s. Ion-adsorption clay deposits in southern China are the world’s primary source of the heavy REEs. Monazite-bearing placer deposits were important sources of REEs before the mid-1960s and may be again in the future. In recent years, REEs have been produced from large carbonatite bodies mined at the Mountain Pass deposit in California and, in China, at the Bayan Obo deposit in Nei Mongol Autonomous Region, the Maoniuping deposit in Sichuan Province, the Daluxiang deposit in Sichuan Province, and the Weishan deposit in Anhui Province. Alkaline igneous complexes have recently been targeted for exploration because of their enrichments in the heavy REEs. Information relevant to the environmental aspects of REE mining is limited. Little is known about the aquatic toxicity of REEs. The United States lacks drinking water standards for REEs. The concentrations of REEs in environmental media are influenced by their low abundances in crustal rocks and their limited solubility in most groundwaters and surface waters. The scarcity of sulfide minerals, including pyrite, minimizes or eliminates concerns about acid-mine drainage for carbonatite-hosted deposits and alkaline-intrusion-related REE deposits. For now, insights into environmental responses of REE mine wastes must rely on predictive models.

Professional Paper↗
USGS1998

Characteristics of discrete and basin-centered parts of the Lower Silurian regional oil and gas accumulation, Appalachian basin: Preliminary results from a data set of 25 oil and gas fields

Oil and gas trapped in Lower Silurian "Clinton" sands and Medina Group sandstone constitute a regional hydrocarbon accumulation that extends 425 mi in length from Ontario, Canada to northeastern Kentucky. The 125-mi width of the accumulation extends from central Ohio eastward to western Pennsylvania and west-central New York. Lenticular and intertonguing reservoirs, a gradual eastward decrease in reservoir porosity and permeability, and poorly segregated gas, oil, and water in the reservoirs make it very difficult to recognize clear-cut geologic- and production-based subdivisions in the accumulation that are relevant to resource assessment. However, subtle variations are recognizable that permit the regional accumulation to be subdivided into three tentative parts: a western gas-bearing part having more or less discrete fields; an eastern gas-bearing part having many characteristics of a basin-centered accumulation; and a central oil- and gas-bearing part with "hybrid" fields that share characteristics of both discrete and basin-centered accumulation. A data set of 25 oil and gas fields is used in the report to compare selected attributes of the three parts of the regional accumulation. A fourth part of the regional accumulation, not discussed here, is an eastern extension of basin-centered accumulation having local commercial gas in the Tuscarora Sandstone, a proximal facies of the Lower Silurian depositional system. A basin-centered gas accumulation is a regionally extensive and commonly very thick zone of gas saturation that occurs in low-permeability rocks in the central, deeper part of a sedimentary basin. Another commonly used term for this type of accumulation is deep-basin gas accumulation. Basin-centered accumulation is a variety of continuous-type accumulation. The "Clinton" sands and Medina Group sandstone part of the basin-centered gas accumulation is characterized by: a) reservoir porosity ranging from about 5 to 10 percent; b) reservoir permeability equal to or less than 0.1 mD; c) low reservoir water saturation and an average water yield per well less than about 9 to 13 BW/MMCFG; d) a broadly defined updip water-block trap; e) underpressured reservoirs with a gradient ranging from 0.25 to 0.35 psi/ft; and f) reservoir temperature of at least 125° F (52° C). Other than for historical and location purposes, the term field has little or no meaning as an assessment unit for the regional accumulation. In practice, each designated field represents a production sweet spot having relatively high EURs per well that in turn merges with surrounding gas-productive regions that are generally larger in area but have lower EURs per well. This important feature of the Lower Silurian regional accumulation, whereby most wells drilled into it are gas productive, must be considered when assessing its potential for remaining recoverable gas resources. Most of the remaining gas resources reside in "Clinton" sands and Medina Group sandstone in the basin-centered part of the accumulation where as much as several tens of TCF of natural gas may be technically recoverable. The Tuscarora Sandstone in the eastern extension of the basin-centered part of the accumulation underlies a very large area and, although commonly characterized by very low porosity and permeability and low-Btu gas, probably contains additional gas resources. Remaining undiscovered recoverable gas and oil resources in the discrete and hybrid parts of the accumulation are primarily located beneath Lake Erie.

Maryland, New York, Ohio, Ontario, Pennsylvania, V↗
USGS2022

Foraging habitat selection of shrubland bird community in tropical dry forest

Habitat loss due to increasing anthropogenic disturbance is the major driver for bird population declines across the globe. Within the Eastern Ghats of India, shrubland bird communities are threatened by shrinking of suitable habitats due to increased anthropogenic disturbance and climate change. The development of an effective habitat management strategy is hampered by the absence of data for this bird community. To address this knowledge gap, we examined foraging sites for 14 shrubland bird species, including three declining species, in three study areas representing the shrubland type of forest community in the Eastern Ghats. We recorded microhabitat features within an 11 m radius of observed foraging points and compared these data with similar data from random plots. We used chi-square to test the association between plant species and bird species for sites where they were observed foraging. We observed significant differences between foraging sites of all the study species and random plots, thus indicating selection for foraging habitat. Using linear discriminant analysis, we found that the microhabitat features important for the bird species were shrub density, vegetational height, vertical foliage stratification, grass height, and percent rock cover. Our results show that diet guild and foraging strata influence the foraging microhabitat selection of a species (e.g., ground-foraging species differed significantly from other species). Except for two species, all focal birds were associated with at least one plant species. The plant-bird association was based on foraging, structural, or behavioral preferences. Several key factors affecting foraging habitat such as shrub density can be actively managed at the local scale. Strategic and selective harvesting of forest products and a spatially and temporally controlled livestock grazing regime may allow regeneration of scrubland and create conditions favorable to birds.

Andhra Pradesh↗
USGS2009

Mesozoic magmatism in an upper- to middle-crustal section through the Cordilleran continental margin arc, eastern Transverse Ranges, California

The eastern Transverse Ranges provide essentially continuous exposure for >100 km across the strike of the Mesozoic Cordilleran orogen. Thermobarometric calculations based on hornblende and plagioclase compositions in Mesozoic plutonic rocks show that the fi rst-order distribution of rock units resulted from differential Laramide exhumation. Mesozoic supracrustal rocks are preserved in the relatively little exhumed eastern part of the eastern Transverse Ranges and south-central Mojave Desert, and progressively greater rock uplift and exhumation toward the west exposed rocks originating at mid-crustal depths. The eastern Transverse Ranges thus constitute a tilted, nearly continuously exposed crustal section of the Mesozoic magmatic arc and framework rocks from subvolcanic levels to paleodepths as great as ??22 km. The base of this tilted arc section is a moderately east-dipping sheeted magmatic complex >10 km in width by 70 km in length, constructed structurally beneath, yet synchronous with Late Jurassic and Cretaceous upper-crustal plutons. Geochronology and regional structural relations thus suggest that arc magmas generated in the lower crust of this continental arc interacted in a complex mid-crustal zone of crystallization and mixing; products of this zone were parental magmas that formed relatively homogeneous upper crustal felsic plutons and fed lavas and voluminous ignimbrites. ?? 2009 The Geological Society of America.

Special Paper of the Geological Society of America↗
USGS2011

Fire in Chile

The mediterranean-type climate (MTC) in Chile (Fig. 6.1) is distributed from La Serena (30° S; Región IV, see Appendix 6.1) in the north to Concepción (37° S; Región X) in the south. It is constrained to the west side of the Andean mountain range, although as the height of this range decreases in the south, a MTC is observed at least as far eastward as Bariloche, Argentina. Although a pattern of winter rains and summer droughts extends northward into the Atacama Desert, this area falls outside our definition of MTC because winter evaporation exceeds rainfall in these areas of extremely low precipitation. The northern border of the MTC region is the transition from desert communities to shrubby matorral, while the southern border corresponds to the point of transition from sclerophyll woodlands to Valdivian evergreen forests (Gajardo 1994; Amigo & Ramirez 1998; Rundel et al . 2007). The landforms of central Chile can be divided into three north–south trending geomorphic zones (Fig. 6.1): the Coastal Cordillera, the Central Valley, and the high Andean Cordillera (Armesto et al . 2007). The Coastal Cordillera rises relatively sharply from the coast, with little extent of coastal terraces, and reaches elevations as high as 2222 m at Cerro Roble and 1880 m at Cerro Campana, which lie between Valparaíso (Región V) on the coast and Santiago (Región Metropolitana) at the base of the Andes. The Central Valley is a structural basin filled to great depth by sediments from the surrounding mountains. North of Santiago, spurs from the Andes extend west across the valley and connect with the Coastal Cordillera, separating individual river basins such as that of the Río Aconcagua (Región V). From Santiago to the south, however, the valley extends uninterrupted for a distance of 900 km to Puerto Montt (Región X), with typical elevations of 400–700 m. The Andean Cordillera marks the eastern boundary of the MTC zone of central Chile. It is the product of complex tectonic activity beginning in the Cretaceous (see Fig. 9.1), but with major uplift in the late Tertiary. Paleobotanical evidence suggests that the central Andes had not attained more than half their current elevation by 10 Ma (Gregory-Wodzicki 2000), but was close to the present height by the end of the Miocene (Reynolds et al . 1990). Elevations reach from 4000 m to nearly 7000 m. To the north of Santiago the Andes are largely composed of metamorphosed sedimentary rock, but a major volcanic zone extends from south of Santiago through the Lake District (Los Lagos Región X).

Book chapter↗
USGS1989

Earthquakes triggered by fluid extraction

Seismicity is correlated in space and time with production from some oil and gas fields where pore pressures have declined by several tens of megapascals. Reverse faulting has occurred both above and below petroleum reservoirs, and normal faulting has occurred on the flanks of at least one reservoir. The theory of poroelasticity requires that fluid extraction locally alter the state of stress. Calculations with simple geometries predict stress perturbations that are consistent with observed earthquake locations and focal mechanisms. Measurements of surface displacement and strain, pore pressure, stress, and poroelastic rock properties in such areas could be used to test theoretical predictions and improve our understanding of earthquake mechanics.

Geology↗
USGS2009

Climatic and limnologic setting of Bear Lake, Utah and Idaho

Bear Lake is a large alkaline lake on a high plateau on the Utah-Idaho border. The Bear River was partly diverted into the lake in the early twentieth century so that Bear Lake could serve as a reservoir to supply water for hydropower and irrigation downstream, which continues today. The northern Rocky Mountain region is within the belt of the strongest of the westerly winds that transport moisture during the winter and spring over coastal mountain ranges and into the Great Basin and Rocky Mountains. As a result of this dominant winter precipitation pattern, most of the water entering the lake is from snowmelt, but with net evaporation. The dominant solutes in the lake water are Ca 2+ , Mg 2+ , and HCO 3 2- , derived from Paleozoic carbonate rocks in the Bear River Range west of the lake. The lake is saturated with calcite, aragonite, and dolomite at all depths, and produces vast amounts of carbonate minerals. The chemistry of the lake has changed considerably over the past 100 years as a result of the diversion of Bear River. The net effect of the diversion was to dilute the lake water, especially the Mg 2+ concentration. Bear Lake is oligotrophic and coprecipitation of phosphate with CaCO 3 helps to keep productivity low. However, algal growth is colimited by nitrogen availability. Phytoplankton densities are low, with a mean summer chlorophyll a concentration of 0.4 mg L -1 . Phytoplankton are dominated by diatoms, but they have not been studied extensively (but see Moser and Kimball, this volume). Zooplankton densities usually are low (<10 L -1 ) and highly seasonal, dominated by calanoid copepods and cladocera. Benthic invertebrate densities are extremely low; chironomid larvae are dominant at depths <30 m, and are partially replaced with ostracodes and oligochaetes in deeper water. The ostracode species in water depths >10 m are all endemic. Bear Lake has 13 species of fi sh, four of which are endemic. Copyright ?? 2009 The Geological Society of America.

Special Paper of the Geological Society of America↗