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At least 649 records · Page 36Linked to original sources

USGS2017

Mislabeling of an invasive vine (Celastrus orbiculatus) as a native congener (C. scandens) in horticulture

The horticultural industry is an important source of invasive ornamental plant species, which is part of the motivation for an increased emphasis on using native alternatives. We were interested in the possibility that plants marketed in the midwestern United States as the native Celastrus scandens , or American bittersweet, were actually the difficult-to-distinguish invasive Celastrus orbiculatus (oriental bittersweet) or hybrids of the two species. We used nuclear microsatellite DNA loci to compare the genetic identities of 34 plants from 11 vendors with reference plants from wild populations of known species identity. We found that 18 samples (53%) were mislabeled, and 7 of the 11 vendors sold mislabeled plants. Mislabeled plants were more likely to be purchased through Internet or phone order shipments and were significantly less expensive than accurately labeled plants. Vendors marketed mislabeled plants under five different cultivar names, as well as unnamed strains. Additionally, the most common native cultivar, ‘Autumn Revolution,’ displays reproductive characteristics that diverge from the typical C. scandens , which could be of some concern. The lower price and abundance of mislabeled invasive plants introduces incentives for consumers to unknowingly contribute to the spread of C. orbiculatus . Revealing the potential sources of C. orbiculatus is critical for controlling further spread of the invasive vine and limiting its impact on C. scandens populations.

Invasive Plant Science and Management↗

USGS2023

Pliocene–Pleistocene hydrology and pluvial lake during Marine Isotope Stages 5a and 4, Deep Springs Valley, western Great Basin, Inyo County, California

Deep Springs Valley (DSV) is a hydrologically isolated valley between the White and Inyo mountains that is commonly excluded from regional paleohydrology and paleoclimatology. Previous studies showed that uplift of Deep Springs ridge (informal name) by the Deep Springs fault defeated streams crossing DSV and hydrologically isolated the valley sometime after eruption of the Pleistocene Bishop Tuff (0.772 Ma). Here, we present tephrochronology and clast counts that reaffirms interruption of the Pliocene–Pleistocene hydrology and formation of DSV during the Pleistocene. Paleontology and infrared stimulated luminescence (IRSL) dates indicate a freshwater lake inundated Deep Springs Valley from ca. 83–61 ka or during Late Pleistocene Marine Isotope Stages 5a (MIS 5a; ca. 82 ka peak) and 4 (MIS 4; ca. 71–57 ka). The age of pluvial Deep Springs Lake coincides with pluvial lakes in Owens Valley and Columbus Salt Marsh and documents greater effective precipitation in southwestern North America during MIS 5a and MIS 4. In addition, we hypothesize that Deep Springs Lake was a balanced-fill lake that overflowed into Eureka Valley via the Soldier Pass wind gap during MIS 5a and MIS 4. DSV hydrology has implications for dispersal and endemism of the Deep Springs black toad ( Anaxyrus exsul ).

California↗

USGS2009

I.-Subaerial Deposits of the Arid Region of North America

The subaërial deposits now accumulating in the arid portion of the United States may be divided into four classes: 1, Eolian Sands; 2, Talus Slopes; 3, Alluvial Cones; and 4, Calcareous Clays to which no specific name has been applied, but which, for reasons stated below, will be called “adobe” in this paper.

Geological Magazine↗

USGS2009

II.-Subaerial Deposits of the Arid Region of North America

A Comparison of adobe with the loess of China forms the concluding part of this paper; but as no analyses of the Chinese deposit are known to me, a few analyses of the loess of the Mississippi Valley are inserted, not with the assumption, however, that the deposits bearing the same name in these two regions are identical. A comparison of this table with the one showing the composition of adobe is instructive, as it indicates that these two yellow earths have a very similar composition. There are other respects in which they bear a close resemblance to each other; but as my acquaintance with the loess of the Mississippi Valley is limited, this comparison will not be carried further.

Geological Magazine↗

USGS2016

Middle Campanian ammonites and inoceramids from the Wolfe City Sand in northeastern Texas

The middle Campanian Wolfe City Sand in northeastern Texas yields a distinctive ammonite and inoceramid fauna with Patagiosites sp., Placenticeras sp., Hoplitoplacenticeras ( Hoplitoplacenticeras ) minor n. sp., Baculites mclearni Landes, 1940, Trachyscaphites spiniger (Schlüter, 1872) porchi (Adkins, 1929), Inoceramus ( Cordiceramus ) azerbaidjanensis Aliev, 1939, and I. ( Endocostea ) balticus Boehm, 1907. The last-named four species allow a direct correlation with the Baculites mclearni zone of the Western Interior of the United States. The base of this zone has been dated at 79.9 ± 3.2/79.2 ± 1.6 Ma on the basis of K/Ar determinations on biotite from a bentonite. Inoceramus azerbaidjanensis is also known from the Campanian of the U.S.S.R. in Azerbaidjan (where the species was first described), western Turkemenia, Georgia, the northern Caucasus, the Crimea, and Donbass.

Journal of Paleontology↗

USGS2016

Ichnology of an Upper Carboniferous fluvio-estuarine paleovalley: The Tonganoxie Sandstone, Buildex Quarry, Eastern Kansas, USA

Tidal rhythmites of the Tonganoxie Sandstone Member (Stranger Formation, Douglas Group) at Buildex Quarry, eastern Kansas, contain a relatively diverse ichnofauna. The assemblage includes arthropod locomotion ( Dendroidichnites irregulare, Diplichnites gouldi types A and B, Diplopodichnus biformis, Kouphichnium isp., Mirandaichnium famatinense , and Stiaria intermedia ), resting ( Tonganoxichnus buildexensis ) and feeding traces ( Stiallia pilosa, Tonganoxichnus ottawensis ); grazing traces ( Gordia indianaensis, Helminthoidichnites tenuis, Helminthopsis hieroglyphica ); feeding structures ( Circulichnis montanus, Treptichnus bifurcus, Treptichnus pollardi , irregular networks), fish traces ( Undichna britannica, Undichna simplicitas ), tetrapod trackways, and root traces. The taxonomy of some of these ichnotaxa is briefly reviewed and emended diagnoses for Gordia indianaensis and Helminthoidichnites tenuis are proposed. Additionally, the combined name Dendroidichnites irregulare is proposed for nested chevron trackways. Traces previously regarded as produced by isopods are reinterpreted as myriapod trackways ( D. gouldi type B). Trackways formerly interpreted as limulid crawling and swimming traces are assigned herein to Kouphichnium isp and Dendroidichnites irregulare , respectively.

Journal of Paleontology↗

USGS2016

Streptognathodus isolatus new species (Conodonta): Proposed index for the Carboniferous-Permian boundary

Davydov et al. (1995) recently proposed the Aidaralash Creek section in northern Kazakhstan (Figures 2 and 3) as the Global Stratotype Section and Point (GSSP) for the base of the Permian System. The proposed boundary is the level in an evolutionary sequence where Streptognathodus wabaunsensis Gunnell gives rise to a descendent with an isolated node field on the inside of the upper platform surface. This morphotype constitutes a new and distinct species for which we propose the name Streptognathodus isolatus new species.

Journal of Paleontology↗

USGS2009

A fungus disease in fishes of the Gulf of Maine

1. A fungus disease of epidemic proportions was found in the common sea herring (Clupea harengus) throughout the Gulf of Maine. 2. The fungus was also found to infect the common winter flounder (Pseudopleuronectes americanus) and the alewife (Pomobolus pseudoharengus). 3. The causative agent was found to be a species of fungus belonging to the genus Ichthyosporidium Caullery and Mesnil (1905). The specific name is tentatively accepted as hoferi Plehn and Muslow (1911). 4. The organism is believed to be a normal parasite to the herring and reaches epidemic proportions only when certain unknown factors are operative. 5. The causative organism was found in herring preserved in 1926, and it is believed that the epidemic has been increasing in severity since that time. 6. It is believed that such an epidermic,once initiated, increases in severity, reaches a peak, and subsides to a subpatent level. The peak is believed to have been reached in 1931. 7. The life history and effects of the organism in the herring and flounder are described. 8. The herring is believed to acquire the infection by the ingestion of parasites liberated from fish in the same school. 9. The flounder is believed to acquire the infection by the consumption of infected herring. 10. The alewife is believed to acquire the infection by ingestion of the parasite during its infrequent association with the herring. 11. Infection is believed to be established by way of the alimentary canal and, once established, to spread throughout the host by way of the blood stream or the lymphatics. 12. Direct cross infection from the herring to the flounder establishes the theory that the parasites in these two hosts are one and the same organism. 13. Direct cross infection experiments from the herring to the flounder eliminate the necessity of an intermediate host. 14. There is no reason to believe that this parasite is capable of infecting warm-blooded animals.

Maine, New Hampshire, Massachusetts, New Brunswick↗

USGS2016

Radiocarbon dates for lava flows and pyroclastic deposits on Sao Miguel, Azores

We report 63 new radiocarbon analyses of samples from São Miguel, the largest (ca 62 × 13km) and most populous (ca 150,000 inhabitants) island in the Azores archipelago (Fig 1). The samples are mainly carbonized tree roots and other plant material collected from beneath 20 mafic lava flows and spatter deposits and from within and beneath 42 trachytic pyroclastic flow, pyroclastic surge, mudflow, pumice-fall, and lacustrine deposits and lava flows. One calcite date is reported. The samples were collected during geologic mapping of the entire island (Moore, in press A; sample locations are shown on this map). Nine 1:25,000-scale topographic maps, published in 1983 by the Portuguese Army Cartographic Service, cover the island; samples and locations described below refer to these named sheets.

Radiocarbon↗

USGS2002

Degradation of marine ecosystems and decline of fishery resources in marine protected areas in the US Virgin Islands

The large number of marine protected areas (MPAs) in the Caribbean (over 100) gives a misleading impression of the amount of protection the reefs and other marine resources in this region are receiving. This review synthesizes information on marine resources in two of the first MPAs established in the USA, namely Virgin Islands National Park (1962) and Buck Island Reef National Monument (1961), and provides compelling evidence that greater protection is needed, based on data from some of the longest running research projects on coral reefs, reef fish assemblages, and seagrass beds for the Caribbean. Most of the stresses affecting marine resources throughout the Caribbean (e.g. damage from boats, hurricanes and coral diseases) are also causing deterioration in these MPAs. Living coral cover has decreased and macroalgal cover has increased. Seagrass densities have decreased because of storms and anchor damage. Intensive fishing in the US Virgin Islands has caused loss of spawning aggregations and decreases in mean fish size and abundance. Groupers and snappers are far less abundant and herbivorous fishes comprise a greater proportion of samples than in the 1960s. Effects of intensive fishing are evident even within MPA boundaries. Although only traditional fishing with traps of 'conventional design' is allowed, commercial trap fishing is occurring. Visual samples of fishes inside and outside Virgin Islands National 'Park showed no significant differences in number of species, biomass, or mean size of fishes. Similarly, the number of fishes per trap was statistically similar inside and outside park waters. These MPAs have not been effective because an unprecedented combination of natural and human factors is assaulting the resources, some of the greatest damage is from stresses outside the control of park managers (e.g. hurricanes), and enforcement of the few regulations has been limited. Fully functioning MPAs which prohibit fishing and other extractive uses (e.g. no-take marine reserves) could reverse some of the degradation, allowing replenishment of the fishery resources and recovery of benthic habitats.

Environmental Conservation↗

USGS2014

Change in agricultural land use constrains adaptation of national wildlife refuges to climate change

Land-use change around protected areas limits their ability to conserve biodiversity by altering ecological processes such as natural hydrologic and disturbance regimes, facilitating species invasions, and interfering with dispersal of organisms. This paper informs USA National Wildlife Refuge System conservation planning by predicting future land-use change on lands within 25 km distance of 461 refuges in the USA using an econometric model. The model contained two differing policy scenarios, namely a ‘business-as-usual’ scenario and a ‘pro-agriculture’ scenario. Regardless of scenario, by 2051, forest cover and urban land use were predicted to increase around refuges, while the extent of range and pasture was predicted to decrease; cropland use decreased under the business-as-usual scenario, but increased under the pro-agriculture scenario. Increasing agricultural land value under the pro-agriculture scenario slowed an expected increase in forest around refuges, and doubled the rate of range and pasture loss. Intensity of land-use change on lands surrounding refuges differed by regions. Regional differences among scenarios revealed that an understanding of regional and local land-use dynamics and management options was an essential requirement to effectively manage these conserved lands. Such knowledge is particularly important given the predicted need to adapt to a changing global climate.

Environmental Conservation↗

USGS2013

Hanawaltite, Hg1+6Hg2+[Cl,(OH)]2O3 - A new mineral from the Clear Creek claim, San Benito County, California: Description and crystal structure

Hanawaltite, ideally Hg 1+ 6 Hg 2+ O 3 Cl 2 , is orthorhombic, Pbma (57), with unit-cell parameters refined from powder data: a =11.790(3), b =13.881(4), c =6.450(2) Å, V =1055.7(6) Å 3 , a : b : c =0.8494:1:0.4647, Z =4. The strongest six lines of the X-ray powder-diffraction pattern [ d in Å ( I )( hkl )] are: 5.25 (80)(111), 3.164 (60)(231), 3.053 (100)(041), 2.954 (70)(141), 2.681 (50)(401), and 2.411 (50)(232,341). The mineral is an extremely rare constituent in a small prospect pit near the long-abandoned Clear Creek mercury mine, New Idria district, San Benito County, California. It was found on a single-fracture surface where it is intimately associated with calomel, native mercury, cinnabar, montroydite, and quartz. Individual crystals are subhedral to anhedral, platy to somewhat bladed, and average about 50 μm in longest dimension. The largest known crystal is approximately 0.3×0.3 mm in size and is striated parallel [001]. Hanawaltite is opaque to translucent (on very thin edges), black to very dark brown–black in color, with a black to dark red–brown streak. Other physical properties include: metallic luster; cleavage {001} good; uneven fracture; brittle; nonfluorescent; H <5; calculated density (for the empirical formula) 9.51 g/cm 3 . In polished section, hanawaltite is moderately to strongly bireflectant and is pleochroic white ( R I ) to blue–white ( R 2 ). In reflected plane-polarized light, it is white with orange–red internal reflections in very thin grains and at grain margins. The anisotropy is strong with bright metallic blue rotation tints. Measured reflectance values, in air and in oil, are tabulated. Electron-microprobe analysis yielded Hg 2 O 82.46, HgO 14.27, Cl 3.33, H 2 O [0.34], sum [100.40], less O=Cl 0.75, total [99.65] wt. %, corresponding to Hg 1+ 6.00 Hg 2+ 1.00 [Cl 1.43 (OH) 0.57 ] Σ2.00 O 3.00 , based on O+Cl=5. After the crystal structure was determined, the original microprobe value for Hg 2 O, 96.2, was partitioned in a ratio of 6Hg 2 O:HgO and (OH) was calculated, such that Cl+(OH)=2. The hanawaltite structure consists of undulatory [Hg–Hg] 2+ ribbons which roughly parallel (100). The diatomic [Hg–Hg] 2+ groups have anion tails which, in turn, serve as cross linkages between dimer ribbons through [Hg 2+ O 2 Cl 2 ] planar rhombs. The structure is compared to that of other mercury oxychlorides and each is found to have its own unique structural features. This structural diversity is attributed to the inherent ability of mercury to adopt either metallic or ionic types of bonds. The mineral name honors the late Dr. J. D. (Don) Hanawalt (1903–1987), who was a pioneer in the field of X-ray powder diffraction.

California↗

USGS2021

Approach for quantifying rare Earth elements at low keV

The challenges of analyzing bastnaesite (REECO3F) and hydroxylbastnaesite (REECO3OH) include beam sensitivity, quantification of light elements in a heavy element matrix, the presence of elements that cannot be analyzed with EPMA (H), and the use of x-ray lines whose physical constants are not well known. To overcome some of these challenges, Ca, La, Ce, Pr, Nd, and Sm were analyzed at 15 keV accelerating voltage and the light elements (C, O, F) were analyzed at 7 keV accelerating voltage. This approach is ideal for samples that are homogeneous within the volume analyzed. However, for the bastnaesite of interest, this solution is unsatisfactory as backscattered electron imaging reveals chemical variations at scales of less than 1 m (fig. 1). Monte Carlo simulations and wavescans of the REE M family of x-rays were evaluated to determine the best analytical approach. Monte Carlo simulations using Casino v2.42 were ran on a substrate of CeCO3F with a density of 5.00 g/cm3 at 15 keV and 7 kCV accelerating voltage. Depth distribution curves, φ(ρz), reveal x-ray generation at 15 keV for the Ce L shell x-rays approaches 1.0 m whereas the depth of Ce M shell x-ray generation at 7 keV is less than 0.4 m. Similarly, the K shell x-ray generation depth for C, O, and F at 7 keV is also less than 0.4 m. These simulations demonstrate an accelerating voltage of 7 keV or less and use of the REE M x-rays is necessary to acquire chemical information from the same volume of material for the light and heavy elements. Bastnaesite contains all REE and therefore one must consider the energy of the highest x-ray line of interest, namely the Lu M at 1.83 kV, to achieve an overvoltage (Eo/Ec) of over 2. Bastnaesite is also an insulator and requires a conductive coating, therefore 7 keV was used to avoid contributions of the coating material to the analysis given the above constraints. The USNM REE phosphate standards, Edinburgh REE glasses, CeO2, LaB6, and the metals of Sm, Dy, Gd, Er, and Yb were selected to evaluate the peak overlaps of the M family x-ray lines. The materials were coated with ~ 5nm iridium with a Leica ACE600 prior to analysis. Full spectrometer wavescans were collected at 7 keV accelerating voltage, 50 nA beam current, and 20 um beam diameter on a JEOL 8530F Plus using TAP and TAPL crystals. The step size was 0.109 mm along the length of the spectrometer with a dwell of 3 seconds at each step. M and M lines are broad and not individually resolved for the light REE but become more separated and sharper with increasing atomic number. M and M lines for each REE are also present across the spectrometer range further complicating peak interference corrections. The peak positions and overall shape for the Ce M and M lines vary with the coordination of the element. Significant shifts in position and shape were not observed when comparing the Ce M peaks of CeO2 and CePO4. Similar results were seen when comparing the available REE metal to the phosphate (Sm, Dy, Gd, Er, Yb). These wavescans suggest the use of the M or M lines if matrix matched standards are not available.

Microscopy and Microanalysis↗

USGS2022

Gas hydrate saturation estimates, gas hydrate occurrence, and reservoir characteristics based on well log data from the hydrate-01 stratigraphic test well, Alaska North Slope

The Hydrate-01 Stratigraphic Test Well was drilled at the Kuparuk 7-11-12 site on the Alaska North Slope in December 2018. Sonic log data provide compressional (P) and shear (S) slowness from which we determine gas hydrate saturation ( S gh ) estimates using effective medium theory. The sonic S gh estimates compare favorably with S gh estimated from resistivity and nuclear magnetic resonance (NMR) logs, showing that gas hydrate occupies up to approximately 90% of the pore space in the target reservoir sands. The informally named B1 sand (2294 feet below mean sea level) shows lower V P / V S ratios than the D1 sand (2770 feet below mean sea level), with the lower part of the B1 sand showing lower V P / V S ratios than the upper part of the B1 sand. This corresponds to a stiffer, or more “cemented”, behavior for the lower B1 sand and less cemented behavior for the D1 sand. This trend could be due to differences in the reservoirs themselves or in the gas hydrate morphology or to both factors. We observe that the presence of gas hydrate in the upper B1 sand has greater impact on hydraulic permeability (measurements suggest a greater difference between intrinsic and effective permeability) than in the D1 sand, possibly related to gas hydrate morphology but more likely due simply to higher gas hydrate saturations in the upper B1 sand. Analyses of S gh relative to porosity, shale fraction, and intrinsic permeability show that reservoir quality (as represented by these three metrics) exerts control on gas hydrate saturation. Grain size and mineralogy data show somewhat smaller grains and better sorting in the D1 reservoir relative to the upper B1 reservoir and smaller grains and greater clay fraction in the lower B1 reservoir relative to the other two reservoir zones. Together, these data suggest that reservoir characteristics play a role in the observed V P / V S patterns, but gas hydrate morphology (possibly varying with saturation) must also be considered.

Alaska↗

USGS2010

A role for analytical chemistry in advancing our understanding of the occurrence, fate, and effects of Corexit Oil Dispersants

On April 24, 2010, the sinking of the Deepwater Horizon oil rig resulted in the release of oil into the Gulf of Mexico. As of July 19, 2010, the federal government's Deepwater Horizon Incident Joint Information Center estimates the cumulative range of oil released is 3,067,000 to 5,258,000 barrels, with a relief well to be completed in early August. By comparison, the Exxon Valdez oil spill released a total of 260,000 barrels of crude oil into the environment. As of June 9, BP has used over 1 million gallons of Corexit oil dispersants to solubilize oil and help prevent the development of a surface oil slick. Oil dispersants are mixtures containing solvents and surfactants that can exhibit toxicity toward aquatic life and may enhance the toxicity of components of weathered crude oil. Detailed knowledge of the composition of both Corexit formulations and other dispersants applied in the Gulf will facilitate comprehensive monitoring programs for determining the occurrence, fate, and biological effects of the dispersant chemicals. The lack of information on the potential impacts of oil dispersants has caught industry, federal, and state officials off guard. Until compositions of Corexit 9500 and 9527 were released by the U.S. Environmental Protection Agency online, the only information available consisted of Material Safety Data Sheets (MSDS), patent documentation, and a National Research Council report on oil dispersants. Several trade and common names are used for the components of the Corexits. For example, Tween 80 and Tween 85 are oligomeric mixtures.

Environmental Science & Technology↗

USGS1997

Analysis of environmental data with censored observations

The potential threats to humans and to terrestrial and aquatic ecosystems from environmental contamination could depend on the sum of the concentrations of different chemicals. However, direct summation of environmental data is not generally feasible because it is common for some chemical concentrations to be recorded as being below the analytical reporting limit. This creates special problems in the analysis of the data. A new model selection procedure, named forward censored regression, is introduced for selecting an appropriate model for environmental data with censored observations. The procedure is demonstrated using concentrations of atrazine (2-chloro-4-ethylamino-6-isopropylamino- s -triazine), deethylatrazine (DEA, 2-amino-4-chloro-6-isopropylamino- s -triazine), and deisopropylatrazine (DIA, 2-amino-4-chloro-6-ethylamino- s -triazine) in groundwater in the midwestern United States by using the data derived from a previous study conducted by the U.S. Geological Survey. More than 80% of the observations for each compound for this study were left censored at 0.05 μg/L. The values for censored observations of atrazine, DEA, and DIA are imputed with the selected models. The summation of atrazine residue (atrazine + DEA + DIA) can then be calculated using the combination of observed and imputed values to generate a pseudo-complete data set. The all-subsets regression procedure is applied to the pseudo-complete data to select the final model for atrazine residue. The methodology presented can be used to analyze similar cases of environmental contamination involving censored data.

Environmental Science & Technology↗

USGS2002

Molecular structure of the decamolybdodicobaltate(III) ion

When solutions of cobalt(II) ion and heptamolybdate ion (Mo₇O₂₄⁶⁻) are mixed in the presence of an oxidizing agent (such as bromine), Kurnakov, Hall, and others found that an emerald green complex is formed as the main product, namely, the heteropoly complex ion hexamolybdocobaltate(III), which forms salts such as (NH₄)₃[H₆CoMo₆O₂₄]·12H₂O. Friedheim and Keller showed that at the same time a small amount of another complex is also formed, having a Co:Mo ratio of 1:5. Tsigdinos, et al., found that if a hot solution of the hexamolybdocobaltate complex ion is treated with activated charcoal or Raney nickel the 1:6 complex is converted almost entirely to the 1:5 complex. These workers proved the latter to be a dimer, and formulated the ammonium salt (earlier prepared by Friedheim and Keller) as (NH₄)₆[Co₂Mo₁₀O₃₆]·10H₂O. We have now completed a crystal structure analysis of this interesting compound, which shows the proper formula to be (NH₄)₆[H₄Co₃Mo₁₀O₃₈]·7H₂O.

Journal of the American Chemical Society↗

USGS2005

Direct measurement of methane hydrate composition along the hydrate equilibrium boundary

The composition of methane hydrate, namely n w for CH 4 · n w H 2 O, was directly measured along the hydrate equilibrium boundary under conditions of excess methane gas. Pressure and temperature conditions ranged from 1.9 to 9.7 MPa and 263 to 285 K. Within experimental error, there is no change in hydrate composition with increasing pressure along the equilibrium boundary, but n w may show a slight systematic decrease away from this boundary. A hydrate stoichiometry of n w = 5.81−6.10 H 2 O describes the entire range of measured values, with an average composition of CH 4 ·5.99(±0.07)H 2 O along the equilibrium boundary. These results, consistent with previously measured values, are discussed with respect to the widely ranging values obtained by thermodynamic analysis. The relatively constant composition of methane hydrate over the geologically relevant pressure and temperature range investigated suggests that in situ methane hydrate compositions may be estimated with some confidence.

Journal of Physical Chemistry B↗