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At least 1,171 records · Page 65Linked to original sources
USGS1991

Unified theory on power laws for flow resistance

Two general power formulas, one for hydraulically smooth flows and the other for fully rough flows, are derived in a rational way from the widely accepted logarithmic formulas for the velocity profile and the Darcy‐Weisbach friction factor. A regression analysis based on the method of least squares is used to determine the valid range of the local velocity (or normal distance from the wall) in the power formula. Some older empirical formulas, such as Lacey's, Manning's, Blasius', and Hazen‐Williams', and their valid ranges, are actually explained analytically by the results. Incomplete self‐similarity of the power law, in which the exponent and the associated coefficient vary with the similarity parameters, such as the Reynolds number and the relative roughness, is elucidated through the parametric representations of the power formulas and their counterparts based on the logarithmic law. This paper examines the concept and rationale behind the power formulation of uniform turbulent shear flows, thereby addressing some critical issues in the modeling of flow resistance based on the power law.

Journal of Hydraulic Engineering↗
USGS2016

An investigation of soil-structure interaction effects observed at the MIT Green Building

The soil-foundation impedance function of the MIT Green Building is identified from its response signals recorded during an earthquake. Estimation of foundation impedance functions from seismic response signals is a challenging task, because: (1) the foundation input motions (FIMs) are not directly measurable, (2) the as-built properties of the super-structure are only approximately known, and (3) the soil-foundation impedance functions are inherently frequency-dependent. In the present study, aforementioned difficulties are circumvented by using, in succession, a blind modal identification (BMID) method, a simplified Timoshenko beam model (TBM), and a parametric updating of transfer functions (TFs). First, the flexible-base modal properties of the building are identified from response signals using the BMID method. Then, a flexible-base TBM is updated using the identified modal data. Finally, the frequency-dependent soil-foundation impedance function is estimated by minimizing the discrepancy between TFs (of pairs instrumented floors) that are (1) obtained experimentally from earthquake data and (2) analytically from the updated TBM. Using the fully identified flexible-base TBM, the FIMs as well as building responses at locations without instruments can be predicted, as demonstrated in the present study.

Massachussets↗
USGS1980

Chemical analysis of 659 coal samples from the eastern United States

This report includes the analytical data on 659 coal samples from 8 States east of the Mississippi River. The number of samples from each State are: Pennsylvania, 132; Ohio, 101; Maryland, 25; West Virginia, 254; Virginia, 33; Indiana, 49; Massachusetts, 5; and Rhode Island, 10. The analytic data are filed in the National Coal Resource Data System of the U.S. Geological Survey. The U.S. Geological Survey has quantitatively determined 35 major, minor, and trace elements in each sample. Tests were also made for 35 other trace elements using semi-quantitative spectrographic methods. In addition, the Coal Analysis Section of the U.S. Department of Energy has determined proximate and ultimate analyses, 3cu, forms of sulfur, free-swelling indexes, and ash-fusion temperatures on 563 of the 659 samples. Comparison of the geometric means of the 644 bituminous coal samples of this report with an additional 968 bituminous coal samples of the eastern United States reported by Swanson and others in 1976 and by Zubovic and others in 1979 is shown in tables 2a-c. As shown by the means for ultimate and proximate analyses, small differences exist between the two sets of data; however, only the moisture and oxygen contents are significantly different. The forms of sulfur, ash-fusion temperature and heat of combustion are similar. The means for the major and minor oxides in ash are similar for SiO 2 , K 2 O, Fe 2 O 3 , TiO 2 , MgO, and P 2 O 5 are lower, whereas, MnO is higher in the analyses of the samples of this report. Eighteen of the means for the trace elements in the coal are about equal for the two sets of samples. Only As, Co, La, Li, and Pb are significantly higher, whereas, Ag, B, Ba, Be, Cd, Cs, F, Ge, Mo, Nb, and Nd are lower in the in the 64L,bituminous coal samples of this report.

Indiana, Maryland, Massachusetts, Ohio, Pennsylvan↗
USGS2008

Development of a standard reference material for Cr(vi) in contaminated soil

Over the last several decades, considerable contamination by hexavalent chromium has resulted from the land disposal of Chromite Ore Processing Residue (COPR). COPR contains a number of hexavalent chromium-bearing compounds that were produced in high temperature industrial processes. Concern over the carcinogenic potential of this chromium species, and its environmental mobility, has resulted in efforts to remediate these waste sites. To provide support to analytical measurements of hexavalent chromium, a candidate National Institute of Standards and Technology (NIST) Standard Reference Material?? (SRM 2701), having a hexavalent chromium content of approximately 500 mg kg -1, has been developed using material collected from a waste site in Hudson County, New Jersey, USA. The collection, processing, preparation and preliminary physico-chemical characterization of the material are discussed. A two-phase multi-laboratory testing study was carried out to provide data on material homogeneity and to assess the stability of the material over the duration of the study. The study was designed to incorporate several United States Environmental Protection Agency (USEPA) determinative methods for hexavalent chromium, including Method 6800 which is based on speciated isotope dilution mass spectrometry (SIDMS), an approach which can account for chromium species inter-conversion during the extraction and measurement sequence. This journal is ?? The Royal Society of Chemistry 2008.

Journal of Analytical Atomic Spectrometry↗
USGS1951

Determination of molybenum in soils and rocks: A geochemical semimicro field method

Reconnaissance work in geochemical prospecting requires a simple, rapid, and moderately accurate method for the determination of small amounts of molybdenum in soils and rocks. The useful range of the suggested procedure is from 1 to 32 p.p.m. of molybdenum, but the upper limit can be extended. Duplicate determinations on eight soil samples containing less than 10 p.p.m. of molybdenum agree within 1 p.p.m., and a comparison of field results with those obtained by a conventional laboratory procedure shows that the method is sufficiently accurate for use in geochemical prospecting. The time required for analysis and the quantities of reagents needed have been decreased to provide essentially a "test tube" method for the determination of molybdenum in soils and rocks. With a minimum amount of skill, one analyst can make 30 molybdenum determinations in an 8-hour day.

Analytical Chemistry↗
USGS1982

Near-station terrain corrections for gravity data by a surface-integral technique

A new method of computing gravity terrain corrections by use of a digitizer and digital computer can result in substantial savings in the time and manual labor required to perform such corrections by conventional manual ring-chart techniques. The method is typically applied to estimate terrain effects for topography near the station, for example within 3 km of the station, although it has been used successfully to a radius of 15 km to estimate corrections in areas where topographic mapping is poor. Points (about 20) that define topographic maxima, minima, and changes in the slope gradient are picked on the topographic map, within the desired radius of correction about the station. Particular attention must be paid to the area immediately surrounding the station to ensure a good topographic representation. The horizontal and vertical coordinates of these points are entered into the computer, usually by means of a digitizer. The computer then fits a multiquadric surface to the input points to form an analytic representation of the surface. By means of the divergence theorem, the gravity effect of an interior closed solid can be expressed as a surface integral, and the terrain correction is calculated by numerical evaluation of the integral over the surfaces of a cylinder, The vertical sides of which are at the correction radius about the station, the flat bottom surface at the topographic minimum, and the upper surface given by the multiquadric equation. The method has been tested with favorable results against models for which an exact result is available and against manually computed field-station locations in areas of rugged topography. By increasing the number of points defining the topographic surface, any desired degree of accuracy can be obtained. The method is more objective than manual ring-chart techniques because no average compartment elevations need be estimated ?

Open-File Report↗
USGS2019

Quantitative guidance for efficient vertical flow measurements at the sediment-water interface using temperature-depth profiles

Upward discharge to surface water bodies can be quantified using analytical models based on temperature-depth (T-z) profiles. The use of sediment T-z profiles is attractive as discharge estimates can be obtained using point-in-time data that are collected inexpensively and rapidly. Previous studies have identified that T-z methods can only be applied at times of the year when there is significant difference between the streambed-water interface and deeper sediment temperatures (e.g., winter and summer). However, surface water temperatures also vary diurnally, and the influence of these variations on discharge estimates from T-z methods is poorly understood. For this study, synthetic T-z profiles were generated numerically using measured streambed interface temperature data to assess the influence of diurnal temperature variations on discharge estimation and provide insight into the suitable application of T-z methods. Results show that the time of day of data collection can have a substantial influence on vertical flux estimates using T-z methods. For low groundwater discharge fluxes (e.g. 0.1 m d-1), daily transience in streambed temperatures led to relatively large errors in estimated flow magnitude and direction. For higher discharge fluxes (1.5 m d-1), the influence of transient streambed temperatures on discharge estimates was strongly reduced. Discharge estimates from point-in-time T-z profiles were most accurate when the uppermost point in the T-z profile was near the bed interface daily mean (two time periods daily). Where temperature time series data are available, daily averaged T-z profiles can produce accurate discharge estimates across a wide range of discharge rates. Seasonality in shallow groundwater temperature generally had a negligible influence on vertical flow estimates. These findings can be used to plan field campaigns and provide guidance on the optimal application of T-z methods to quantify vertical groundwater discharge to surface water bodies.

Hydrological Processes↗
USGS2018

The multiple-comparison trap and the Raven’s paradox—perils of using null hypothesis testing in environmental assessment

Detecting and quantifying environmental thresholds is frequently an important step in understanding ecological responses to environmental stressors. We discuss two statistical issues often encountered in threshold detection and quantification when statistical null hypothesis testing is used as a main analytical tool.The hidden multiple-comparison trap (leading to a much higher risk of a false detection) and Raven’s paradox(rendering a "detection" meaningless) are often obscured when statistical hypothesis testing is used as part of a more elaborate model, especially models based on computer-intensive methods. Using two examples, we show that the hidden multiple-comparison trap can be exposed using computer simulation to estimate the probability of making a false detection; Raven’s paradox can be avoided by clearly stating the null and alternative hypotheses using scientific terms to substantiate that the rejection of the null is equivalent to proving that the alternative of interest is true. The hidden multiple-comparison trap implies that a null hypothesis testing based on a computer-intensive method should be used with caution. The implication of Raven’s paradox re-quires that we focus on providing evidence supporting the proposed hypothesis or model, rather than seeking evidence against the frequently irrelevant null hypothesis. These two problems, and many others related to null hypothesis testing, suggest that statistical hypothesis testing should be used only as a component of the body of evidence, perhaps, as the devil’s advocate.

Environmental Monitoring and Assessment↗
USGS2002

Ultraviolet spectrophotometric determination of tantalum with pyrogallol

In a search for a more rapid method for the determination of tantalum in rocks and minerals, an intensive study was made of the tantalum-pyrogallol reaction recommended by Platanov and Krivoshlikov, and a better modified spectrophotometric procedure is given. The improved method consists in measuring the absorbancy of the tantalum-pyrogallol complex at 325 m μ in 4 N hydrochloric acid and a fixed concentration (0.0175 M ) of ammonium oxalate. Beer's law is followed for the concentration range up to 40 γ per ml. Sensitivity in terms of molar absorbancy index is 4775. Most interferences are additive in character and readily correctable. Separations or major corrections are required in the presence of significant amounts of molybdenum, tungsten, antimony, and uranium. The method has been successfully applied to three ores previously analyzed by gravimetric techniques. The method affords greater speed, sensitivity, and reproducibility in the determination of tantalum in rocks and minerals. A more reliable technique for preparing standard solutions of tantalum has been developed.

Analytical Chemistry↗
USGS2021

Characterizing physical properties of streambed interface sediments using in situ complex electrical conductivity measurements

Streambed sediment physical properties such as surface area, are difficult to quantify in situ but exert a high‐level control on a wide range of biogeochemical processes and sorption of contaminants. We introduce the use of complex electrical conductivity (CC) methods (also known as spectral induced polarization (SIP)) that measure both real and imaginary conductivity to non‐invasively and efficiently characterize shallow streambed sediments. We explore the method through synthetic modeling, laboratory, and field measurements to demonstrate the sensitivity of imaginary conductivity to sediment surface area, controlled in part by fine‐grained iron oxides produced by anoxic groundwater discharge. Laboratory measurements verify expected relationships between CC parameters and sediment properties. Synthetic modeling using a 1D analytical model illustrates the influence of water layer depth and conductivity on the field CC measurements made at the streambed‐stream water interface. Specifically, the inverted sediment imaginary conductivity is less impacted by uncertainty in the water layer depth and conductivity relative to the real conductivity and phase shift. Field CC measurements along a landfill‐impacted river reveal discrete streambed zones with enhanced bulk surface area generally corresponding to anoxic groundwater discharges zones with high concentrations of fine‐grained iron oxide precipitates.

Water Resources Research↗
USGS1976

Numerical modeling of subsurface radioactive solute transport from waste seepage ponds at the Idaho National Engineering Laboratory

Aqueous chemical and low-level radioactive effluents have been disposed to seepage ponds since 1952 at the Idaho National Engineering Laboratory. The solutions percolate toward the Snake River Plain aquifer (135 m below) through interlayered basalts and unconsolidated sediments and an extensive zone of ground water perched on a sedimentary layer about 40 m beneath the ponds. A three-segment numerical model was developed to simulate the system, including effects of convection, hydrodynamic dispersion, radioactive decay, and adsorption. The first segment uses an analytical solution to simulate transport from the ponds to the 25-m thick perched-water lens, assuming steady vertical flow through a 15-m long saturated homogeneous column. The second segment simulates two-dimensional horizontal transport in the perched-water body using finite-difference methods, assuming complete vertical mixing with vertical leakage from the bottom. The third segment of the model simulates vertical solute transport from the perched-water body toward the aquifer, by assuming unsaturated but steady water flow in a series of contiguous, nonhomogeneous independent vertical columns. The transport equation is solved by a "hop-scotch" finite-difference scheme for each column. Simulated hydraulics and solute migration patterns for all segments agree adequately with the available field data. The model can be used to project subsurface distributions of waste solutes under a variety of assumed conditions for the future. Although chloride and tritium reached the aquifer several years ago, the model analysis suggests that the more easily sorbed solutes, such as cesium-137 and strontium-90, would not reach the aquifer in detectable concentrations within 150 years for the conditions assumed. However, a change in chemistry or hydraulic conditions could increase the mobility of adsorbed waste solutes. Such changes might result from changes in waste disposal practices and effluent chemistry, flooding from the Big Lost River, or future irrigation activity.

Idaho↗
USGS1985

Field guidelines for collection, treatment, and analysis of water samples, Montana district

This manual provides a set of standardized guidelines and quality-control procedures for the collection and preservation of water samples and defines procedures for field analyses of unstable constituents or properties. Seldom is the water being samples of such uniformity that a single grab sample is representative of the whole. For this reason a variety of sampler types and sampling methods have been devised. Descriptions and procedures for field use are given for a number of sampler types. Several methods of sampling are described for which these samplers can be used. Sample-processing devices such as sample splitters and filtration apparatus are discussed along with methods of cleaning. Depending on the type of analysis to be performed in the laboratory, samples may need to be preserved shortly after collection. Various types of preservation are described in detail. Analyses for unstable constituents or properties are of necessity accomplished in the field. This manual addresses analytical techniques and quality assurance for: (1) Water temperature, (2) specific conductance, (3) pH, (4) alkalinity, (5) dissolved oxygen, and (6) bacteria. Examples of field report forms are given as attachments. Information pertinent to certain field calculations is also presented. (USGS)

Open-File Report↗
USGS2020

Stratigraphic units of shallow unconsolidated deposits in Deadwood, South Dakota, delineated by real-time kinematic surveys

The City of Deadwood, South Dakota, has been working on a new archeological investigation in preparation for economic growth and expansion within the city limits, through the Deadwood Historic Preservation Office. During the excavation process, buried artifacts and historical features from the late 1800s have been uncovered. The stratigraphy of shallow unconsolidated deposits in the city of Deadwood, S. Dak., was surveyed on January 29, 2020, using real-time kinematic survey methods and described to identify variations in geologic material, thickness, and depth from the land surface in support of archeological studies by the city. The findings of the study will provide city managers and the public with reliable and impartial information for their use by advancing field or analytical methodology and understanding of hydrologic processes in the study area. The primary excavation site was surveyed, and stratigraphic units were delineated from changes in material properties or depositional environment. The primary excavation site consisted of nine stratigraphic units; however, some units were not consistent along the length of the excavation and pinched out along the cross section. Survey data points also were collected for artifacts and other sites of interest. The shallow surficial geology in the study area was affected by human construction, fires, and flooding.

South Dakota↗
USGS2018

In situ LA-ICPMS U–Pb dating of cassiterite without a known-age matrix-matched reference material: Examples from worldwide tin deposits spanning the Proterozoic to the Tertiary

Cassiterite (SnO 2 ), a main ore mineral in tin deposits, is suitable for U–Pb isotopic dating because of its relatively high U/Pb ratios and typically low common Pb. We report a LA-ICPMS analytical procedure for U–Pb dating of this mineral with no need for an independently dated matrix-matched cassiterite standard. LA-ICPMS U-Th-Pb data were acquired while using NIST 612 glass as a primary non-matrix-matched standard. Raw data are reduced using a combination of Iolite™ and other off-line data reduction methods. Cassiterite is extremely difficult to digest, so traditional approaches in LA-ICPMS U-Pb geochronology that utilize well-characterized matrix-matched reference materials (e.g., age values determined by ID-TIMS) cannot be easily implemented. We propose a new approach for in situ LA-ICPMS dating of cassiterite, which benefits from the unique chemistry of cassiterite with extremely low Th concentrations (Th/U ratio of 10 −4 or lower) in some cassiterite samples. Accordingly, it is assumed that 208 Pb measured in cassiterite is mostly of non-radiogenic origin—it was initially incorporated in cassiterite during mineral formation, and can be used as a proxy for common Pb. Using 208 Pb as a common Pb proxy instead of 204 Pb is preferred as 204 Pb is much less abundant and is also compromised by 204 Hg interference during the LA-ICPMS analyses. Our procedure relies on 208 Pb/ 206 Pb vs 207 Pb/ 206 Pb (Pb-Pb) and Tera-Wasserburg 207 Pb/ 206 Pb vs 238 U/ 206 Pb (U-Pb) isochron dates that are calculated for a ~1.54 Ga low-Th cassiterite reference material with varying amounts of common Pb that we assume remained a closed U-Pb system. The difference between the NIST 612 glass normalized biased U-Pb date and the Pb-Pb age of the reference material is used to calculate a correction factor (F) for instrumental U-Pb fractionation. The correction factor (F) is then applied to measured U/Pb ratios and Tera-Wasserburg isochron dates are obtained for the unknown cassiterite analyzed in the same analytical session. This allows for U-Pb dating of cassiterite of any age with no need for an independently dated matrix-matched reference material, nor assumptions about the isotopic composition o f common Pb. Results for cassiterite from tin deposits in Bolivia, Brazil, China, Russia, Saudi Arabia, South Africa, Spain, and the United Kingdom, with ages ranging from ~20 Ma to ~2060 Ma, demonstrate the applicability of this approach across a broad range of geologic time. These ages are in good agreement with published geochronology of the host rocks assoc iated with the tin deposits and with previously published U-Pb ages of some cassiterites from the same deposits. Thus, our in situ LA-ICPMS methodology verifies the use of cassiterite as a reliable U-Pb mineral-geochronometer with the advantages of fast and relatively low cost in situ analyses with moderate spatial resolution.

Chemical Geology↗
USGS2007

Isotopic analysis of N and O in nitrite and nitrate by sequential selective bacterial reduction to N2O

Nitrite is an important intermediate species in the biogeochemical cycling of nitrogen, but its role in natural aquatic systems is poorly understood. Isotopic data can be used to study the sources and transformations of NO 2 - in the environment, but methods for independent isotopic analyses of NO 2 - in the presence of other N species are still new and evolving. This study demonstrates that isotopic analyses of N and O in NO 2 - can be done by treating whole freshwater or saltwater samples with the denitrifying bacterium Stenotrophomonas nitritireducens , which selectively reduces NO 2 - to N 2 O for isotope ratio mass spectrometry. When calibrated with solutions containing NO 2 - with known isotopic compositions determined independently, reproducible δ 15 N and δ 18 O values were obtained at both natural-abundance levels (±0.2−0.5‰ for δ 15 N and ±0.4−1.0‰ for δ 18 O) and moderately enriched 15 N tracer levels (±20−50‰ for δ 15 N near 5000‰) for 5−20 nmol of NO 2 - (1−20 μmol/L in 1−5 mL aliquots). This method is highly selective for NO 2 - and was used for mixed samples containing both NO 2 - and NO 3 - with little or no measurable cross-contamination. In addition, mixed samples that were analyzed with S. nitritireducens were treated subsequently with Pseudomonas aureofaciens to reduce the NO 3 - in the absence of NO 2 - , providing isotopic analyses of NO 2 - and NO 3 - separately in the same aliquot. Sequential bacterial reduction methods like this one should be useful for a variety of isotopic studies aimed at understanding nitrogen cycling in aquatic environments. A test of these methods in an agricultural watershed in Indiana provides isotopic evidence for both nitrification and denitrification as sources of NO 2 - in a small stream.

Indiana↗
USGS2006

Estimation of elastic moduli in a compressible Gibson half-space by inverting Rayleigh-wave phase velocity

A Gibson half-space model (a non-layered Earth model) has the shear modulus varying linearly with depth in an inhomogeneous elastic half-space. In a half-space of sedimentary granular soil under a geostatic state of initial stress, the density and the Poisson's ratio do not vary considerably with depth. In such an Earth body, the dynamic shear modulus is the parameter that mainly affects the dispersion of propagating waves. We have estimated shear-wave velocities in the compressible Gibson half-space by inverting Rayleigh-wave phase velocities. An analytical dispersion law of Rayleigh-type waves in a compressible Gibson half-space is given in an algebraic form, which makes our inversion process extremely simple and fast. The convergence of the weighted damping solution is guaranteed through selection of the damping factor using the Levenberg-Marquardt method. Calculation efficiency is achieved by reconstructing a weighted damping solution using singular value decomposition techniques. The main advantage of this algorithm is that only three parameters define the compressible Gibson half-space model. Theoretically, to determine the model by the inversion, only three Rayleigh-wave phase velocities at different frequencies are required. This is useful in practice where Rayleigh-wave energy is only developed in a limited frequency range or at certain frequencies as data acquired at manmade structures such as dams and levees. Two real examples are presented and verified by borehole S-wave velocity measurements. The results of these real examples are also compared with the results of the layered-Earth model. ?? Springer 2006.

Surveys in Geophysics↗
USGS2001

Some simple guides to finding useful information in exploration geochemical data

Most regional geochemistry data reflect processes that can produce superfluous bits of noise and, perhaps, information about the mineralization process of interest. There are two end-member approaches to finding patterns in geochemical data—unsupervised learning and supervised learning. In unsupervised learning, data are processed and the geochemist is given the task of interpreting and identifying possible sources of any patterns. In supervised learning, data from known subgroups such as rock type, mineralized and nonmineralized, and types of mineralization are used to train the system which then is given unknown samples to classify into these subgroups. To locate patterns of interest, it is helpful to transform the data and to remove unwanted masking patterns. With trace elements use of a logarithmic transformation is recommended. In many situations, missing censored data can be estimated using multiple regression of other uncensored variables on the variable with censored values. In unsupervised learning, transformed values can be standardized, or normalized, to a Z-score by subtracting the subset's mean and dividing by its standard deviation. Subsets include any source of differences that might be related to processes unrelated to the target sought such as different laboratories, regional alteration, analytical procedures, or rock types. Normalization removes effects of different means and measurement scales as well as facilitates comparison of spatial patterns of elements. These adjustments remove effects of different subgroups and hopefully leave on the map the simple and uncluttered pattern(s) related to the mineralization only. Supervised learning methods, such as discriminant analysis and neural networks, offer the promise of consistent and, in certain situations, unbiased estimates of where mineralization might exist. These methods critically rely on being trained with data that encompasses all populations fairly and that can possibly fall into only the identified populations.

Natural Resources Research↗
USGS2020

Interpreting and reporting 40Ar/39Ar geochronologic data

The 40 Ar/ 39 Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40 Ar/ 39 Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide range of geologic and extraterrestrial processes. Analyses of increasingly smaller subsamples have revealed age dispersion in many materials, including some minerals used as neutron fluence monitors. Accordingly, interpretive strategies are evolving to address observed dispersion in dates from a single sample. Moreover, inferring a geologically meaningful “age” from a measured “date” or set of dates is dependent on the geological problem being addressed and the salient assumptions associated with each set of data. We highlight requirements for collateral information that will better constrain the interpretation of 40 Ar/ 39 Ar data sets, including those associated with single-crystal fusion analyses, incremental heating experiments, and in situ analyses of microsampled domains. To ensure the utility and viability of published results, we emphasize previous recommendations for reporting 40 Ar/ 39 Ar data and the related essential metadata, with the amendment that data conform to evolving standards of being findable, accessible, interoperable, and reusable (FAIR) by both humans and computers. Our examples provide guidance for the presentation and interpretation of 40 Ar/ 39 Ar dates to maximize their interdisciplinary usage, reproducibility, and longevity.

GSA Bulletin↗