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At least 271 records · Page 15Linked to original sources
USGS2000

Heavy minerals and sedimentary organic matter in Pleistocene and Cretaceous sediments on Long Island, New York, with emphasis on pyrite and marcasite in the Magothy aquifer

Abundance and distribution of iron-bearing and other heavy minerals in sediments of Long Island, N.Y., were examined to identify sources and sinks of dissolved iron and other ground-water constituents along a deep flow path from the ground-water divide to the southern shore along the Nassau-Suffolk County border. The occurrence and reactivity of many iron-bearing minerals in the aquifer system are affected by terminal electron-accepting processes, which are a function of depth below land surface, distance from the ground-water divide, and organic-matter content of the sediment. The lateral distribution of heavy minerals within lithologic sediments is not uniform throughout Long Island, or even along the 30-kilometer study section at the Nassau-Suffolk County border. Mineralogy and mineral abundance in Pleistocene units differ from those in Cretaceous sediments, and some of the trends vary with depth as well as from north to south. Major heavy minerals in the Cretaceous sediments at the study sites include pyrite, marcasite, muscovite, leucoxene, ilmenite, rutile, staurolite, chloritoid, and aluminosilicates (Al2SiO5); those in the overlying Pleistocene deposits at one site include iron oxides, leucoxene, zircon, garnet, ilmenite, aluminosilicates, and hornblende. Pyrite, marcasite, garnet, hornblende, and tourmaline were found locally in the Cretaceous sediments. Pyrite and marcasite were detected less frequently in borehole samples from near the ground-water divide, where the ground water is generally oxic, than in those from near the southern shore of Long Island, but were found in sulfate- reducing zones throughout the Magothy aquifer. Glauconite was present in Cretaceous and Pleistocene deposits, but only in the marine or transitional units. The most abundant and potentially reactive of the iron-bearing minerals found were iron (hydr)oxides, leucoxene, glauconite, chlorite, pyrite, and marcasite. The presence and morphology of pyrite and marcasite can be indicative of the microbial and geochemical environments. Pyrite generally was found in association with lignite or as interstitial cement. Marcasite was found as interstitial cement and is associated with the oxidation of iron-sulfide minerals upgradient. Pyrite crystals were octahedral, cubic, cubo-octahedral, and framboidal, and many samples showed more than one generation of crystal growth. Marcasite cement, which consisted of platey crystals in most samples, probably forms only under nonmarine conditions.

Water-Resources Investigations Report↗
USGS2001

Differential rates of feldspar weathering in granitic regoliths

Differential rates of plagioclase and K-feldspar weathering commonly observed in bedrock and soil environments are examined in terms of chemical kinetic and solubility controls and hydrologic permeability. For the Panola regolith, in the Georgia Piedmont Province of southeastern United States, petrographic observations, coupled with elemental balances and 87Sr/86Sr ratios, indicate that plagioclase is being converted to kaolinite at depths > 6 m in the granitic bedrock. K-feldspar remains pristine in the bedrock but subsequently weathers to kaolinite at the overlying saprolite. In contrast, both plagioclase and K-feldspar remain stable in granitic bedrocks elsewhere in Piedmont Province, such as Davis Run, Virginia, where feldspars weather concurrently in an overlying thick saprolite sequence. Kinetic rate constants, mineral surface areas, and secondary hydraulic conductivities are fitted to feldspar losses with depth in the Panola and Davis Run regoliths using a time-depth computer spreadsheet model. The primary hydraulic conductivities, describing the rates of meteoric water penetration into the pristine granites, are assumed to be equal to the propagation rates of weathering fronts, which, based on cosmogenic isotope dating, are 7 m/106 yr for the Panola regolith and 4 m/106 yr for the Davis Run regolith. Best fits in the calculations indicate that the kinetic rate constants for plagioclase in both regoliths are factors of two to three times faster than K-feldspar, which is in agreement with experimental findings. However, the range for plagioclase and K-feldspar rates (kr = 1.5 x 10-17 to 2.8 x 10-16 mol m-2 s-1) is three to four orders of magnitude lower than for that for experimental feldspar dissolution rates and are among the slowest yet recorded for natural feldspar weathering. Such slow rates are attributed to the relatively old geomorphic ages of the Panola and Davis Run regoliths, implying that mineral surface reactivity decreases significantly with time. Differential feldspar weathering in the low-permeability Panola bedrock environment is more dependent on relative feldspar solubilities than on differences in kinetic reaction rates. Such weathering is very sensitive to primary and secondary hydraulic conductivities (qp and qs), which control both the fluid volumes passing through the regolith and the thermodynamic saturation of the feldspars. Bedrock permeability is primarily intragranular and is created by internal weathering of networks of interconnected plagioclase phenocrysts. Saprolite permeability is principally intergranular and is the result of dissolution of silicate phases during isovolumetric weathering. A secondary to primary hydraulic conductivity ratio of qs/qp = 150 in the Panola bedrock results in kinetically controlled plagioclase dissolution but thermodynamically inhibited K-feldspar reaction. This result is in accord with calculated chemical saturation states for groundwater sampled in the Panola Granite. In contrast, greater secondary conductivities in the Davis Run saprolite, qs/qp = 800, produces both kinetically controlled plagioclase and K-feldspar dissolution. Faster plagioclase reaction, leading to bedrock weathering in the Panola Granite but not at Davis Run, is attributed to a higher anorthite component of the plagioclase and a wetter and warmer climate. In addition, the Panola Granite has an abnormally high content of disseminated calcite, the dissolution of which precedes the plagioclase weathering front, thus creating additional secondary permeability. Copyright ?? 2001 Elsevier Science Ltd.

Geochimica et Cosmochimica Acta↗
USGS1990

Mechanisms controlling Cu, Fe, Mn, and Co profiles in peat of the Filson Creek Fen, northeastern Minnesota

Filson Creek Fen, located in northeastern Minnesota, overlies a Cu-Ni sulfide deposit. A site in the fen was studied to evaluate the hydrogeochemical mechanisms governing the development of Fe, Mn, Co, and Cu profiles in the peat. At the study site, surface peat approximately 1 m thick is separated from the underlying mineralized bedrock by a 6–12 m thickness of lake and glaciofluvial sediments and till. Concentrations of Fe, Mn, Co, and Cu in peat and major elements in pore water delineate a shallow, relatively oxidized, Cu-rich zone overlying a deeper, reduced, Fe-, Mn-, and Co-rich zone within the peat. Sequential metal extractions from peat samples reveal that 40–55% of the Cu in the shallow zone is associated with organic material, whereas the remaining Cu is distributed between iron-oxide, sulfide, and residual fractions. Sixty to seventy percent of the Fe, Mn, and Co concentrated in the deeper zone occur in the residual phase. The metal profiles and associations probably result from non-steady-state input of metals and detritus into the fen during formation of the peat column. The enrichment of organic-associated Cu in the upper, oxidized zone represents a combination of Cu transported into the fen with detrital plant fragments and soluble Cu, derived from weathering of outcrop and subcrop of the mineral deposit, transported into the fen, and fixed onto organic matter in the peat. The variable stratigraphy of the peat indicates that weathering processes and surface vegetation have changed through time in the fen. The Fe, Mn, and Co maxima at the base of the peat are associated with a maximum in detrital matter content of the peat resulting from a transition between the underlying inorganic sedimentary environment to an organic sedimentary environment. The chemistry of sediments and ground water collected beneath the peat indicate that mobilization of metals from sulfide minerals in the buried mineral deposit or glacial deposits is minimal. Therefore, the primary source of Cu to the peat at the study site is outcrops and shallow subcrops of the mineral deposit adjacent to the fen.

Geochimica et Cosmochimica Acta↗
USGS1997

The chemical evolution and paragenesis of uranium minerals from the ruggles and palermo granitic pegmatites, New Hampshire

A study of the chemical evolution and paragenesis of the uranium minerals at the Palermo No. 1 and Ruggles granitic pegmatites, Grafton County, New Hampshire, revealed four stages of secondary mineralization. A total of eight uranium minerals were identified in the four stages. The first stage is a mixture of uranyl oxide hydroxide-hydrates represented by mineral "A", which surrounds and replaces a uraninite core. The second stage is a carbonate stage found only at the Palermo No. 1 pegmatite, and is represented by rutherfordine. The third stage is represented by uranyl silicates. At the Palermo No. 1 pegmatite, this stage consists of ??-uranophane, and at the Ruggles pegmatite, it consists of soddyite and ??-uranophane. A final fourth stage is a phosphate stage represented by phosphuranylite and meta-autunite I. The first three stages of mineralization developed from hydrothermal and meteoric processes. With dropping temperatures, hydrothermal fluids reached meteoric temperatures and acquired the characteristics of meteoric water. The pH shifted from acidic (pH less than about 6 at 100??C) to alkaline (pH > 7 at 25??C). Since mineral "A" contains hydroxyl and a low amount of molecular water, it probably formed at a temperature greater than 100??C in the acidic environment. After the first stage, the hydrothermal fluids likely reached the temperatures of meteoric water. The initial pH of the meteoric water was acidic (pH less than about 6 at 25??C) and then slowly shifted to alkaline. The mineralizing fluids became oversaturated in CO3, Ca, K, and Si. Uraninite and mineral "A" became unstable and were replaced by rutherfordine and uranyl silicates. The fourth or phosphate stage developed from the introduction of groundwater. The uranyl phosphate minerals precipitated from an acidic fluid (pH < 7 at 25??C) that was oversaturated with Ca, K, U, and P.

Canadian Mineralogist↗
USGS1954

Sedimentary facies of iron-formation

The sedimentary iron -formations of Precambrian age in the Lake Superior region can be divided on the basis of the dominant original iron mineral into four principal facies : sulfide, carbonate, oxide, and silicate. As chemical sediments, these rocks reflect certain aspects of the chemistry of the depositional environments. The major control, at least for the sulfide, carbonate, and oxide types, probably was the oxidation potential. The evidence indicates that deposition took place in restricted basins, which were separated from the open sea by thresholds that inhibited free circulation and permitted development of abnormalities in oxidation potential and water composition. The sporadic distribution of metamorphism and of later oxidation permits description of the primary facies on the basis of unoxidized, essentially unmetamorphosed material. The sulfide facies is represented by black slates in which pyrite may make up as much as 40 percent of the rock. The free-carbon content of these rocks typically ranges from 5 to 15 percent, indicating that ultra-stagnant conditions prevailed during deposition. Locally, the pyritic rocks contain layers of iron -rich carbonate. The carbonate facies consists, in its purer form, of interbedded iron -rich carbonate and chert. It is a product of an environment in which oxygen concentration was sufficiently high to destroy most of the organic material but not high enough to permit formation of ferric compounds. The oxide facies is found as two principal types, one characterized by magnetite and the other by hematite. Both minerals appear to be of primary origin. The magnetite-banded rock is one of the dominant lithologies in the region; it consists typically of magnetite interlayered with chert, carbonate, or iron silicate, or combinations of the three. Its mineralogy and association suggest origin under weakly oxidizing to moderately reducing conditions, but the mode of precipitation of magnetite is not clearly understood. The hematite-banded rocks consist of finely crystalline hematite interlayered with chert or jasper. Oolitic structure is common. This facies doubtless accumulated in a strongly oxidizing, probably near-shore, environment similar to that in which younger hema-titic ironstones such as the Clinton oolite were deposited. The silicate facies contains one or more of the hydrous ferrous silicates (greenalite, minnesotaite, stilpnomelane, chlorite) as a major constituent. Granule structure, similar to that of glauconite, is typical of some varieties; others are nongranular and finely laminated. The most common association of the silicate rocks is with either carbonate- or magnetite-bearing rocks, which suggests that the optimum conditions for deposition ranged from slightly oxidizing to slightly reducing. The relationship between the iron -rich rocks and volcanism, stressed by many authors, is considered by the writer to be structural, not chemical: in the Lake Superior region both iron -deposition and volcanism are believed to be related to geosynclinal development during Huronian time. In Michigan, the lower Huronian rocks are iron -poor quartzite and dolomite-typical "stable-shelf" deposits; much of the upper Huronian consists of iron -poor graywacke and slate with associated volcanic rocks -a typical "geosynclinal" assemblage. Thus the iron -rich beds of the middle Huronian and lower part of the upper Huronian were deposited during a transitional stage in structural history. The major environmental requirement for deposition of iron - formation is the closed or restricted basin; this requirement coincides in time with what would be a normal stage in evolution of the geosyncline: namely, structural development of offshore buckles or swells that subsequently develop into island arcs characterized by volcanism.

Lake Superior↗
USGS2006

Uranyl adsorption and surface speciation at the imogolite-water interface: Self-consistent spectroscopic and surface complexation models

Macro- and molecular-scale knowledge of uranyl (U(VI)) partitioning reactions with soil/sediment mineral components is important in predicting U(VI) transport processes in the vadose zone and aquifers. In this study, U(VI) reactivity and surface speciation on a poorly crystalline aluminosilicate mineral, synthetic imogolite, were investigated using batch adsorption experiments, X-ray absorption spectroscopy (XAS), and surface complexation modeling. U(VI) uptake on imogolite surfaces was greatest at pH ∼7–8 ( I = 0.1 M NaNO 3 solution, suspension density = 0.4 g/L [U(VI)] i = 0.01–30 μM, equilibration with air). Uranyl uptake decreased with increasing sodium nitrate concentration in the range from 0.02 to 0.5 M. XAS analyses show that two U(VI) inner-sphere (bidentate mononuclear coordination on outer-wall aluminol groups) and one outer-sphere surface species are present on the imogolite surface, and the distribution of the surface species is pH dependent. At pH 8.8, bis-carbonato inner-sphere and tris-carbonato outer-sphere surface species are present. At pH 7, bis- and non-carbonato inner-sphere surface species co-exist, and the fraction of bis-carbonato species increases slightly with increasing I (0.1–0.5 M). At pH 5.3, U(VI) non-carbonato bidentate mononuclear surface species predominate (69%). A triple layer surface complexation model was developed with surface species that are consistent with the XAS analyses and macroscopic adsorption data. The proton stoichiometry of surface reactions was determined from both the pH dependence of U(VI) adsorption data in pH regions of surface species predominance and from bond-valence calculations. The bis-carbonato species required a distribution of surface charge between the surface and β charge planes in order to be consistent with both the spectroscopic and macroscopic adsorption data. This research indicates that U(VI)-carbonato ternary species on poorly crystalline aluminosilicate mineral surfaces may be important in controlling U(VI) mobility in low-temperature geochemical environments over a wide pH range (∼5–9), even at the partial pressure of carbon dioxide of ambient air ( p CO2 = 10 −3.45 atm).

Geochimica et Cosmochimica Acta↗
USGS2010

Hydrated mineral stratigraphy of Ius Chasma, Valles Marineris

New high-resolution spectral and morphologic imaging of deposits on walls and floor of Ius Chasma extend previous geomorphic mapping, and permit a new interpretation of aqueous processes that occurred during the development of Valles Marineris. We identify hydrated mineralogy based on visible-near infrared (VNIR) absorptions. We map the extents of these units with CRISM spectral data as well as morphologies in CTX and HiRISE imagery. Three cross-sections across Ius Chasma illustrate the interpreted mineral stratigraphy. Multiple episodes formed and transported hydrated minerals within Ius Chasma. Polyhydrated sulfate and kieserite are found within a closed basin at the lowest elevations in the chasma. They may have been precipitates in a closed basin or diagenetically altered after deposition. Fluvial or aeolian processes then deposited layered Fe/Mg smectite and hydrated silicate on the chasma floor, postdating the sulfates. The smectite apparently was weathered out of Noachian-age wallrock and transported to the depositional sites. The overlying hydrated silicate is interpreted to be an acid-leached phyllosilicate transformed from the underlying smectite unit, or a smectite/jarosite mixture. The finely layered smectite and massive hydrated silicate units have an erosional unconformity between them, that marks a change in surface water chemistry. Landslides transported large blocks of wallrock, some altered to contain Fe/Mg smectite, to the chasma floor. After the last episode of normal faulting and subsequent landslides, opal was transported short distances into the chasma from a few m-thick light-toned layer near the top of the wallrock, by sapping channels in Louros Valles. Alternatively, the material was transported into the chasma and then altered to opal. The superposition of different types of hydrated minerals and the different fluvial morphologies of the units containing them indicate sequential, distinct aqueous environments, characterized by alkaline, then circum-neutral, and finally very acidic surface or groundwater chemistry. ?? 2009 Elsevier Inc. All rights reserved.

Icarus↗
USGS2001

Crocoite: An unusual mode of occurrence for lead in coal

What is believed to be a very unusual mode of occurrence for lead in coal has been identified as crocoite (PbCrO4). As part of a larger study on trace elements and mineralogy in the Cretaceous Main Seam in New Zealand, crocoite was found in raw coal samples within the lower part of the coal seam. X-ray diffraction (XRD) and bulk chemical data from a SEM equipped with an energy dispersive X-ray analyser (EDXA) have confirmed the identity of this mineral. This is apparently the first time that crocoite has been reported in coal. Crocoite usually occurs only in the oxidised zone of lead mineral deposits. The occurrence of this mineral in the Main Seam coal implies that the deposit was exposed to an oxidising environment at some stage, most likely after coalification. Published by Elsevier Science B.V.

International Journal of Coal Geology↗
USGS1971

Ore fluids in the porphyry copper deposit at Copper Canyon, Nevada

The large, low-grade copper and gold deposit at Copper Canyon, Lander County, Nevada, formed in the contact metasomatic environment adjacent to a shallow Tertiary intrusion. Vein and disseminated chalcopyrite-pyrite-pyrrhotite-arsenopyrite mineralization, with lesser amounts of gold, galena, sphalerite, marcasite, and siderite occur in the Upper Cambrian Harmony and Middle Pennsylvanian Battle Formations. Studies of fluid inclusions in stages of vein quartz and in healed fractures through quartz phenocrysts and pebbles reveal the presence of very saline, sometimes CO 2 -rich fluids in the early and middle stages of mineralization. Ore fluid salinities during the base metal mineralization were approximately 40 wt percent, and temperatures were near 375 degrees C. Circulation of this hot brine was apparently restricted to an elongate highly fractured zone within 3,000 feet laterally of the intrusive. Later fluids in this central zone were somewhat cooler, near 300 degrees C, and had significantly lower salinities in the range 12 to 1.2 wt percent. Smaller lode deposits approximately 1 to 5 miles from the intrusion appear to have formed from low to moderate salinity fluids at temperatures generally in the range 250 to 335 degrees C. Geologic and fluid considerations suggest formation at approximately 6,000 feet in depth.

Nevada↗
USGS2017

Central Plains Water Science Center bookmark

The U.S. Geological Survey Central Plains Water Science Center, serving the states of Kansas and Nebraska, has collected and interpreted hydrologic information for more than a century. Data collected include streamflow and gage height, reservoir content, water quality and water quantity, suspended sediment, and groundwater levels. Interpretative hydrologic studies are completed on national, regional, statewide, and local levels and cooperatively funded through partnerships with these agencies. The U.S. Geological Survey provides impartial scientific information to describe and understand the health of our ecosystems and environment; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life. These collected data are in the National Water Information System (Kansas: https://dashboard.waterdata.usgs.gov/app/nwd/en/ and Nebraska: https://dashboard.waterdata.usgs.gov/app/nwd/en/ ), and all results are documented in reports that also are online (Kansas: https://www.usgs.gov/centers/kswsc and Nebraska: https://www.usgs.gov/centers/nebraska-water-science-center/publications ).

General Information Product↗
USGS2017

Science programs in Kansas

The U.S. Geological Survey (USGS) is a non-regulatory Earth science agency within the Department of the Interior that provides impartial scientific information to describe and understand the health of our ecosystems and environment; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life. The USGS cooperates with Federal, State, tribal, and local agencies in Kansas to deliver long-term data in real-time and interpretive reports describing what those data mean to the public and resource management agencies. USGS science programs in Kansas provide real-time groundwater monitoring at more than 19 locations; streamflow monitoring at more than 216 locations; water-quality and trends in the Little Arkansas and Kansas Rivers; inflows and outflows of sediment to/from reservoirs and in streams; harmful algal bloom research in the Kansas River, Milford Lake, and Cheney Reservoir; water-quantity and water-quality effects of artificial groundwater recharge for the Equus Beds Aquifer Storage and Recovery project near Wichita, Kansas; compilation of Kansas municipal and irrigation water-use data statewide; the occurrence, effects, and movement of environmental pesticides, antibiotics, algal toxins, and taste-and-odor compounds; and funding to the Kansas Water Resources Research Institute to further research and education through Kansas universities.

Kansas↗
USGS1978

U.S. Geological Survey offshore program of resource and geo-environmental studies and topical investigations, Pacific-Arctic region

The Geological Survey's marine geology investigations in the Pacific-Arctic area are presented in this report in the context of the underlying socio-economic problem of expanding the domestic production of oil and gas and other mineral and hard- and soft-rock resources while maintaining acceptable standards in the marine environment. The primary mission of the Survey 's Pacific-Arctic Branch of Marine Geology is to provide scientifically interpreted information about the (1) resource potential, (2) geo-environmental setting, and (3) overall geologic characteristics of the continental margins (that is, the continental shelf, slope and rise) and adjacent deeper water and shallower coastal areas off California, Oregon, Washington, Alaska and Hawaii and also, where it is of interest to the U.S. Government, more remote deep-sea areas of the Pacific-Arctic realm.

Open-File Report↗
USGS2011

Proceedings of the third USGS modeling conference, June 7-11, 2010, Broomfield, Colorado-Understanding and predicting for a changing world

The Third USGS Modeling Conference was held June 7th-11, 2010, in Broomfield, Colorado. The conference focused on the development and application of analytical and theoretical models and data availability that support managing the Nation's resources and help protect lives and property. Participants at the conference included scientists and managers from Department of the Interior (DOI) Bureaus; national and international Federal, State, and local agencies; academic institutions; and nongovernmental organizations. The conference was organized according to DOI priorities and the strategic directions of the USGS Science Strategy; the following themes were emphasized: (1) Understanding Ecosystems and Restoring America's Treasured Landscapes; (2) Climate Change and Impact; (3) New Energy Frontier and Minerals for America; (4) A National Hazards, Risk, and Resilience Assessment Program; (5) Role of Environment and Wildlife in Human Health; (6) A Water Census of the United States; and (7) New Methods of Investigation and Discovery. The conference theme-"Understanding and Predicting for a Changing World"-focused on the following goals: advance development and application of models; provide tools that address management issues; present state-of-the-art models ranging from individual phenomena to integrated systems; and foster a working community among scientists and managers.

Scientific Investigations Report↗
USGS2004

Global environmental databases from CEOS agencies

The Committee on Earth Observation Satellites (CEOS) is an international organization charged with coordinating international civil spaceborne missions designed to observe and study planet Earth. Comprising 44 space agencies and other national and international organizations, CEOS is recognized as the major international forum for the coordination of Earth observation satellite programs and for the interaction of these programs with users of satellite data worldwide. CEOS was created in 1984 in response to a recommendation from the Economic Summit of Industrialized Nations Working Group on Growth, Technology, and Employment’s Panel of Experts on Satellite Remote Sensing. This group recognized the multidisciplinary nature of satellite Earth observation and the value of coordination across all proposed missions. The CEOS members collect, maintain, apply, and make available data from space missions that encompass the atmospheric, terrestrial, and oceanographic fields. Collectively, these members possess petabytes of Earth observation data critical to understanding the Earth environment. Uses include monitoring oil slicks, evaluating human-induced changes to the atmosphere, determining mineral exploration areas, assessing the environmental effects of volcanic eruptions, measuring the growth of urban areas, determining where landscapes have changed because of urban growth trends, improving the efficiency of fishing as a world food stock, monitoring pest infestation, managing crop production, predicting climate and weather, and numerous other applications vital to industry, national infrastructures, and the world as a whole. The vast amount of satellite obtained, environmental data the CEOS members possess represents a fertile resource for researchers worldwide to exploit.

Conference Paper↗
USGS1984

Geologic and hydrologic characterization and evaluation of the Basin and Range Province relative to the disposal of high-level radioactive waste: Part I, Introduction and guidelines

The U.S. Geological Survey's program for geologic and hydrologic evaluation of physiographic provinces to identify areas potentially suitable for locating repository sites for disposal of high-level nuclear wastes was announced to the Governors of the eight States in the Basin and Range Province on May 5, 1981. Representatives of Arizona, California, Idaho, New Mexico, Nevada, Oregon, Texas, and Utah, were invited to cooperate with the Federal Government in the evaluation process. Each Governor was requested to nominate an Earth scientist to represent the State in a province working group composed of State and U.S. Geological Survey representatives. This report, Part I of a three-part report, provides the background, introduction and scope of the study. This part also includes a discussion of geologic and hydrologic guidelines that will be used in the evaluation process and illustrates geohydrologic environments and the effect of individual factors in providing multiple natural barriers to radionuclide migration. Part II is a reconnaissance characterization of the geologic and hydrologic factors to be used in the initial screening of the Basin and Range Province. Part III will be the initial evaluation of the Province and will identify regions that appear suitable for further study. The plan for study of the Province includes a stepwise screening process by which successively smaller land units are considered in increasing detail. Each step involves characterization of the geology and hydrology and selection of subunits for more intensive characterization. Selection of subunits for further study is by evaluation of geologic and hydrologic conditions following a set of guidelines. By representation on the Province Working Group, the States participate in a consultation and review role in: (1) Establishing geologic and hydrologic guidelines, and (2) characterizing and evaluating the Province. The States also participate in compilation of geologic and hydrologic data used in characterizing the Province. The current (1983) needs for a high-level radioactive waste repository include: (1) Disposal in a mined repository; (2) retrievability of the waste for as much as 50 years; and (3) confidence of isolation of the waste from the accessible environment. Isolation of the waste needs to be assured using geologic and hydrologic conditions that: (1) Minimize risk of inadvertent future intrusions by man; (2) minimize the possibility of disturbance by processes that would expose the waste or increase its mobility; and (3) provide a system of natural barriers to the migration of waste by ground water. The guidelines adopted by the Province Working Group are designed to provide a standard with which these conditions can be compared. The guidelines can be grouped into four principal categories: (1) Potential host media, (2) ground-water conditions, (3) tectonic conditions, and. (4) occurrence of natural resources. Ideally the host medium constitutes the first natural barrier to migration of radionculides. The host medium ideally should be a rock type that prevents or retards dissolution and transport of radionuclides. Rocks in both the saturated and unsaturated zones may have desirable characteristics for host media. Rocks-other than the host-in the ground-water flow path from the repository ideally should be major barriers to radionuclide migration. Confining beds of low permeability might be present to retard the rate of flow between more permeable beds. Additionally, sorption of radionuclides by materials such as clays and zeolites in the flow path can further retard the flow of radionuclides by several orders of magnitude. Tectonic conditions in an area should not present a probable cause for exhumation or increased mobility of radioactive waste. Natural resources are a factor for consideration because of the problem of future human intrusion and exposure to radioactivity in the quest for minerals, oil, gas, water, and geothermal resources. The ultimate evaluation of the suitability of a geohydrologic environment for developing a mined repository needs to assess all geologic and hydrologic characteristics and their interaction in providing confidence that a geohydrologic environment will effectively isolate radionuclides from human access. Several hypothetical settings with typical geohydrologic conditions in the Basin and Range Province are used to illustrate the effect of multiple barriers in the isolation of radionuclides.

Arizona, California, Idaho, Nevada, New Mexico, Or↗
USGS2019

Insect herbivores on urban native oak trees

Oak trees host an amazing diversity of insects, many of which specialize on Quercus species. Oak species and genotypes are commonly planted far from where an acorn was produced. Urban plantings, restoration sites, and plantings anticipating climate change each cause this to happen. What evidence exists that provenance of oak plantings affects herbivores such as galls and leaf miners? And what other factors, such as weather, predators, urban forestry, and geographic isolation affect the populations of these insects? I present evidence from studies of oaks conducted at different scales. Provenance matters to herbivores - but predominantly at large genetic scales. Aspects of the urban environment can help some herbivores of oak trees but hurt others. Predators are of key importance to populations of gall wasps and leaf miners, and isolated trees can maintain a great diversity of galls and miners. Creating habitat for oak herbivores (at least the ones that do not kill trees) can be a great benefit of planting native oaks, and many of those insects are nearly as charismatic as their host trees!

International Oaks↗
USGS2026

Tectonic controls on volcanism and associated hydrothermal activity in a sediment-dominated mid-ocean ridge; Escanaba Trough

Mid-ocean ridges, the Earth's most extensive volcanic system, exhibit unique characteristics in sediment-dominant environments. Thick sediment cover insulates the crust and channels fluid along pathways that can lead to the formation of distinct crustal alteration patterns, exceptionally large mineral deposits, and specialized chemosynthetic ecosystems. This study presents an interdisciplinary investigation into the tectonics of the Escanaba Trough, a heavily sedimented axial valley at the southern Gorda Ridge in the Northeast Pacific Ocean. A primary challenge in such environments is overcoming the masking effect of thick sediments on basement structures that control magmatic and hydrothermal activity. We address this by employing three-dimensional (3D) magnetic modeling of high-resolution near-seafloor magnetic data collected by an autonomous underwater vehicle (AUV). The 2022 surveys with AUV Sentry provided data for 3D magnetic susceptibility models, refining our understanding of the geometry of sub-sediment laccoliths/saucer-shaped sills and hydrothermal alteration. In conjunction with a new 1:100,000 scale lithostratigraphic map, we outline the tectonic controls on the emplacement of Escanaba Trough's three main volcanic centers, characterize the geometry of its spreading segments, and provide volumetric data on the distribution of sub-sediment volcanism in the southern Gorda Ridge.

Escanaba Trough, Pacific Ocean↗
USGS2011

Measurement of net nitrogen and phosphorus mineralization in wetland soils using a modification of the resin-core technique

A modification of the resin-core method was developed and tested for measuring in situ soil N and P net mineralization rates in wetland soils where temporal variation in bidirectional vertical water movement and saturation can complicate measurement. The modified design includes three mixed-bed ion-exchange resin bags located above and three resin bags located below soil incubating inside a core tube. The two inner resin bags adjacent to the soil capture NH 4 + , NO 3 - , and soluble reactive phosphorus (SRP) transported out of the soil during incubation; the two outer resin bags remove inorganic nutrients transported into the modified resin core; and the two middle resin bags serve as quality-control checks on the function of the inner and outer resin bags. Modified resin cores were incubated monthly for a year along the hydrogeomorphic gradient through a floodplain wetland. Only small amounts of NH 4 + , NO 3 - , and SRP were found in the two middle resin bags, indicating that the modified resin-core design was effective. Soil moisture and pH inside the modified resin cores typically tracked changes in the surrounding soil abiotic environment. In contrast, use of the closed polyethylene bag method provided substantially different net P and N mineralization rates than modified resin cores and did not track changes in soil moisture or pH. Net ammonification, nitrifi cation, N mineralization, and P mineralization rates measured using modified resin cores varied through space and time associated with hydrologic, geomorphic, and climatic gradients in the floodplain wetland. The modified resin-core technique successfully characterized spatiotemporal variation of net mineralization fluxes in situ and is a viable technique for assessing soil nutrient availability and developing ecosystem budgets.

Biogeochemistry↗