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USGS2014

Latest Quaternary paleoseismology and evidence of distributed dextral shear along the Mohawk Valley fault zone, northern Walker Lane, California

The dextral-slip Mohawk Valley fault zone (MVFZ) strikes northwestward along the eastern margin of the Sierra Nevada in the northern Walker Lane. Geodetic block modeling indicates that the MVFZ may accommodate ~3 mm/yr of regional dextral strain, implying that it is the highest slip-rate strike-slip fault in the region; however, only limited geologic data are available to constrain the system’s slip rate and earthquake history. We mapped the MVFZ using airborne lidar data and field observations and identified a site near Sulphur Creek for paleoseismic investigation. At this site, oblique dextral-normal faulting on the steep valley margin has created a closed depression that floods annually during spring snowmelt to form an ephemeral pond. We excavated three fault-perpendicular trenches at the site and exposed pond sediment that interfingers with multiple colluvial packages eroded from the scarp that bounds the eastern side of the pond. We documented evidence for four surface-rupturing earthquakes on this strand of the MVFZ. OxCal modeling of radiocarbon and luminescence ages indicates that these earthquakes occurred at 14.0 ka, 12.8 ka, 5.7 ka, and 1.9 ka. The mean ~4 kyr recurrence interval is inconsistent with slip rates of ~3 mm/yr; these rates imply surface ruptures of more than 10 m per event, which is geologically implausible for the subdued geomorphic expression and 60 km length of the MVFZ. We propose that unidentified structures not yet incorporated into geodetic models may accommodate significant dextral shear across the northern Walker Lane, highlighting the role of distributed deformation in this region.

California↗

USGS2023

Conservation at the nexus of niches: Multidimensional niche modeling to improve management of Prairie Chub

Objective A central challenge in applied ecology is understanding how organisms are spatially and temporally distributed and how management might be tailored to maintain or restore species distributions. The niche concept is central to understanding species distributions, but the diversity of niche definitions requires that multiple dimensions be considered. For example, the Grinnellian niche concept focuses on environmental conditions that allow species to persist, the Eltonian niche concept stresses the influence of biotic interactions, and the fundamental niche concept considers both abiotic and biotic environmental features to define spaces that organisms could occupy. Methods We combined abiotic ( A ), biotic ( B ), and movement ( M ) information (collectively, BAM model) to map the multidimensional niche of Prairie Chub Macrhybopsis australis , a regionally endemic freshwater fish currently under review for listing under the Endangered Species Act. We estimated A using remotely sensed environmental riverscape variables, B using the spatial distribution of a hybridization zone between Prairie Chub and Shoal Chub M. hyostoma , and M using data from a mark–recapture study. Result The BAM model estimated the spatial extent of multiple niches, including the Grinnellian ( A ; extent = 944 km of river), Eltonian ( B ; 2974 km), and fundamental niche (overlap of A + B ; 645 km) niches. When A , B , and M components were combined, the estimated extent of the Prairie Chub niche was 645 km. Conclusion Our work shows that the realized, multidimensional niche of Prairie Chub includes medium to large rivers with high habitat connectivity in the upper–middle Red River basin upstream of the distribution of Shoal Chub. The current Prairie Chub distribution could be maintained by preventing further habitat fragmentation and maintaining the environmental gradient separating Prairie Chub from Shoal Chub. Expansion of the species distribution may be possible through restoration of longitudinal fluvial connectivity.

North American Journal of Fisheries Management↗

USGS2020

A hybrid approach for predictive soil property mapping using conventional soil survey data

Soil property maps are important for land management and earth systems modeling. A new hybrid point-disaggregation predictive soil property mapping strategy improved mapping in the Colorado River Basin, and can be applied to other areas with similar data (e.g. conterminous United States). This new approach increased sample size ~6-fold over past efforts. Random forests related environmental raster layers representing soil forming factors to samples to predict 15 soil properties (pH, texture fractions, rock, electrical conductivity, gypsum, CaCO3, sodium adsorption ratio, available water capacity, bulk density, erodibility, organic matter) at 7 depths, depth to restrictive layer, and surface rock size and cover. Cross-validations resulted in coefficient of determinations averaging 0.52, with a range of 0.20 to 0.76; and mean absolute errors ranged from 3% to 98% of training data averages with a mean of 41%. Uncertainty estimates were also developed by creating relative prediction intervals (RPIs) for the entire study area, which allow end users to evaluate uncertainty relative to original data distributions. Average error increased with higher RPI values (higher uncertainty), and areas with the highest RPI are consistently under-sampled, suggesting that additional sampling in these areas may improve prediction accuracy. Greater uncertainty was also observed in areas with shale parent materials and physiographic settings uncommon relative to the broader study area.

New Mexico, Colorado, Wyoming, Utah, Nevada, Arizo↗

USGS2012

Seismic reflection/refraction mapping of faulting and regional dips in the eastern Alaska Range

We present the results of a Trans‐Alaska Crustal Transect (TACT) investigation of the upper 2–5 km of the eastern Alaska Range in the vicinity of the Denali fault based on seismic reflection/refraction data, laboratory measurements of rock velocities, and structural mapping. The Denali fault is a major dextral slip structure mappable for more than 2000 km separating the Wrangellia and adjacent terranes to the south from the Yukon‐Tanana and adjacent terranes to the north. Geologic mapping suggests over 400 km of dextral slip has occurred on the fault, yet within the upper 1.5 km of the crust along the TACT corridor, basement rocks juxtaposed along the Denali fault reveal no significant seismic velocity differences, although the fault zone itself is associated with a minor lowering of velocity. The lack of seismic velocity contrast adjacent to the fault is in agreement with laboratory measurements of elastic wave velocities of samples from terranes bordering the fault. Laboratory measurements of elastic wave velocities of the metasedimentary mica‐quartz schists comprising the Yukon‐Tanana basement are highly anisotropic because of preferred orientation of mica and predict significant variations in velocity accompanying variations in foliation dip. Although other interpretations are possible, the northward shallowing of foliation dip of basement rocks in the Yukon‐Tanana terrane combined with the strong anisotropy associated with these highly foliated rocks can explain an observed northward increase in seismic velocity within this terrane. Seismic reflections from basement rocks within the Yukon‐Tanana terrane may originate from variations in anisotropy with depth and/or changes in composition reflecting different proportions of sandstone and shale in the protolith.

Alaska↗

USGS2012

Intrusion of horizontal dikes: tectonic significance of Middle Proterozoic diabase sheets widespread in the upper crust of the southwestern United States

Initially horizontal sheet intrusions of Middle Proterozoic diabase are abundant in a region 650 by 300 km across in Arizona and California. The diabase forms discordant sheets in basement granite and gneiss and sills in overlying shelf sedimentary sequences. Massive granite is the most common basement host for the sheets, probably because it fractured more easily than foliated hosts during sheet emplacement. Steep feeder dikes are rare compared to the sheets. The diabase in many places is exposed in fault blocks that were tilted during Tertiary tectonic extension. Structure sections restored from the map patterns of upended blocks show that the sheets were intruded at levels throughout the upper crust, to depths of at least 13 km. Sheet intrusion implies a vertical orientation of the least compressive stress, so I conclude that the crust was under tectonic compression or in an isotropic state of stress at the time of diabase intrusion about 1.1 Ga. Magma overpressures, water encountered by rising magma, vertical changes in the crustal stress regime, and flotation of low-density granite all may be important factors for sheet intrusion. The stress conditions suggested by the presence of the sheets argue against an extensional tectonic regime earlier proposed for the diabase event. The diabase province contrasts structurally with similar-age provinces of basaltic magmatism elsewhere in North America that show evidence of tectonic extension, such as the midcontinent rift. The consistent orientations of the sheets commonly allow them to be used as structural markers for postdiabase deformation of basement blocks. Sheet intrusions in the geologic record may be seriously underreported. Their recognition is important for the interpretation of seismic reflection profiles of continental crust. Sheets in Arizona may be responsible for the Bagdad reflection sequence, which extends to depths of at least 15 km.

Journal of Geophysical Research↗

USGS2008

Relative age of interior layered deposits in southwest Candor Chasma based on high-resolution structural mapping

High‐resolution topography generated from stereo HiRISE (High‐Resolution Imaging Science Experiment) imagery reveals the meter‐scale structure of interior layered deposits (ILD) in southwest Candor Chasma. This study seeks to determine the age of the local ILD relative to any normal faults that can be attributed to chasma formation. The study area is located near the contact of these ILD and the wall rock and is in an area where chasma‐forming normal faults have been proposed. We find that while normal faults are found in the study area, these faults are not sufficiently large nor appropriately located or oriented to accommodate the roughly northeast‐southwest extension that is required for normal faults that can be attributed to chasma formation. Additionally, bedding exposed in the local ILD generally dips toward the center of Candor Chasma, consistent with sediment deposition in a preexisting basin. Further, pit craters of Tithonia Catena, presumed to predate or be contemporaneous with the formation of west Candor Chasma, do not cut into the ILD within the study area. These independent lines of evidence support a postchasma age for the ILD exposed within the study area. Chasma‐related normal faults may exist within these ILD at depth but are not exposed at the surface. Approximately 2 km of conformable stratigraphy is exposed in the study area, and therefore at least several kilometers of the local ILD were deposited subsequent to any chasma‐related normal faulting that may have occurred in this part of Candor Chasma.

Journal of Geophysical Research E: Planets↗

USGS2026

Top-down targeted network analysis of critical mineral commodities applied to international geochemistry database

The global demand for critical mineral commodities is rapidly increasing, making domestic production an important factor in supporting the economy and national security. Large scale, publicly available geochemical databases allow for the application of data informatics methods to interrogate critical mineral commodities data for correlations in deposit formation and distribution, particularly for identifying enrichment of multiple critical mineral commodities at the same deposit. In this study, we applied network analysis to the Critical Minerals Mapping Initiative (CMMI) ore geochemistry (Critical Minerals in Ores, CMiO) database to identify the high concentration (defined as 10× bulk crustal abundance) co-occurrence of different critical mineral commodities across a mineral system hierarchy from deposit environments to individual deposits. Identifying patterns or unique outliers in enrichment in network communities will allow for the location of secondary critical mineral commodity resources from under-utilized deposits. We find trends in the enrichment of critical mineral commodities in network-communities between the elements praseodymium (Pr), neodymium (Nd), terbium (Tb), and dysprosium (Dy) across multiple CMiO database deposit environments and groups down to specific deposit types and sites. A separate trend in network community deposition is observed as well between iridium (Ir) and platinum (Pt) in deposit environments, groups, types, and sites. Network analysis focused on critical minerals in magmatic-hydrothermal deposits identified multiple deposit sites from different deposit types within the CMiO database with concentrations of Dy, Nd, Tb, Pr, Ir, and Pt that are at least ten times greater than the crustal average. This approach can be applied to any target element(s) or deposit(s) of interest, allowing broad investigation of co-enriched critical mineral commodities.

Journal of Geochemical Exploration↗

USGS2011

M3 spectral analysis of lunar swirls and the link between optical maturation and surface hydroxyl formation at magnetic anomalies

We examined the lunar swirls using data from the Moon Mineralogy Mapper (M 3 ). The improved spectral and spatial resolution of M 3 over previous spectral imaging data facilitates distinction of subtle spectral differences, and provides new information about the nature of these enigmatic features. We characterized spectral features of the swirls, interswirl regions (dark lanes), and surrounding terrain for each of three focus regions: Reiner Gamma, Gerasimovich, and Mare Ingenii. We used Principle Component Analysis to identify spectrally distinct surfaces at each focus region, and characterize the spectral features that distinguish them. We compared spectra from small, recent impact craters with the mature soils into which they penetrated to examine differences in maturation trends on- and off-swirl. Fresh, on-swirl crater spectra are higher albedo, exhibit a wider range in albedos and have well-preserved mafic absorption features compared with fresh off-swirl craters. Albedoand mafic absorptions are still evident in undisturbed, on-swirl surface soils, suggesting the maturation process is retarded. The spectral continuum is more concave compared with off-swirl spectra; a result of the limited spectral reddening being mostly constrained to wavelengths less than ∼1500 nm. Off-swirl spectra show very little reddening or change in continuum shape across the entire M 3 spectral range. Off-swirl spectra are dark, have attenuated absorption features, and the narrow range in off-swirl albedos suggests off-swirl regions mature rapidly. Spectral parameter maps depicting the relative OH surface abundance for each of our three swirl focus regions were created using the depth of the hydroxyl absorption feature at 2.82 μ m. For each of the studied regions, the 2.82 μ m absorption feature is significantly weaker on-swirl than off-swirl, indicating the swirls are depleted in OH relative to their surroundings. The spectral characteristics of the swirls and adjacent terrains from all three focus regions support the hypothesis that the magnetic anomalies deflect solar wind ions away from the swirls and onto off-swirl surfaces. Nanophase iron (npFe 0 ) is largely responsible for the spectral characteristics we attribute to space weathering and maturation, and is created by vaporization/deposition by micrometeorite impacts and sputtering/reduction by solar wind ions. On the swirls, the decreased proton flux slows the spectral effects of space weathering (relative to nonswirl regions) by limiting the npFe 0 production mechanism almost exclusively to micrometeoroid impact vaporization/deposition. Immediately adjacent to the swirls, maturation is accelerated by the increased flux of protons deflected from the swirls.

Journal of Geophysical Research E: Planets↗

USGS2026

Hyperspectral narrowband imaging spectroscopy: A new paradigm for Earth observation

This editorial introduces the Special Issue entitled “Hyperspectral Narrowband Imaging Spectroscopy: A New Paradigm for Earth Observation” in the August 2026 issue of Photogrammetric Engineering & Remote Sensing (PE&RS), the flagship journal of the American Society for Photogrammetry and Remote Sensing (ASPRS). This volume represents the fourth dedicated hyperspectral special issue published in PE&RS, following earlier contributions by Thenkabail et al. (2025, 2024a, 2024b), and continues ASPRS’s commitment to advancing cutting‑edge imaging spectroscopy research and its applications across Earth system science. Remote sensing is undergoing one of the most profound transformations in its history. The emergence of hyperspectral narrowband (HNB) imaging spectroscopy data, capable of acquiring hundreds of contiguous, narrow spectral bands, has shifted the discipline from observing Earth in a handful of broad spectral windows to capturing continuous spectral signatures of the Planet. This transition marks a decisive break from the multispectral paradigm that has dominated satellite remote sensing for nearly five decades, driven by the advent of new orbital imaging spectrometers such as EnMAP, PRISMA, and NASA’s EMIT, and by the forthcoming Surface Biology and Geology (SBG) mission ((Pires Silva et al., 2026; Bourriz et al., 2025; Thenkabail et al., 2025; Chabrillat et al., 2024; Aneece et al., 2024; Dave et al., 2024; Thenkabail et al., 2024a; Thenkabail et al., 2024b; Thenkabail, 2024a; Thenkabail, 2024b; Thompson et al., 2022; Kokaly et al., 2022; Aneece & Thenkabail, 2022; Cawse Nicholson et al., 2021; Guanter et al., 2021; Vangi et al., 2021; Thenkabail et al., 2021). These missions (e.g., Table 1) deliver unprecedented spectral fidelity, improved signal to noise ratios, and global coverage capabilities, enabling a new era of quantitative, spectroscopy based Earth observation. Where multispectral broadbands (MBBs) provide only a few discrete measurements along the electromagnetic spectrum, HNB systems deliver rich, diagnostic information that enables scientists to characterize Earth’s surface with unprecedented biochemical, biophysical, and structural detail (Figure 1a, 1b). The implications for environmental monitoring, agriculture, water resources, and mineral exploration are profound. Several overarching themes emerge: • Spectral fidelity matters. The ability to preserve subtle absorption features is essential for mineral mapping, vegetation trait retrieval, and biochemical modeling. • AI and deep learning are indispensable. From destriping to classification, modern analytics must be scalable, label‑efficient, and capable of exploiting the full spectral–spatial richness of HNB data. • Physics‑based and data‑driven approaches must converge. Radiative transfer models such as PROSAIL, enhanced with localized soil parameterizations, remain foundational for biophysical retrievals and model‑based inference. • Dimensionality reduction and feature extraction are critical. Techniques such as L1‑ISOMAP demonstrate that intelligent manifold learning can unlock the structure of fused, high‑dimensional datasets. • Next‑generation architectures must be interactive and multimodal. ICTNet exemplifies the future of hyperspectral classification: hybrid, synergistic, and capable of modeling both local textures and global spectral dependencies.

Photogrammetric Engineering and Remote Sensing (PE↗

USGS1974

Paleozoic tectonics in the Edna Mountain quadrangle, Nevada

Geologic mapping at scale 1:24,000 of the Edna Mountain 15-minute quadrangle, Humboldt County, Nev., revealed two episodes of pre-Mesozoic deformation that are difficult to reconcile with either the Antler or the Sonoma orogeny. We believe that the older episode predated the Antler orogeny and may be as old as Late Cambrian. The younger episode may have been more localized, predated the Sonoma orogeny, and was probably Late Pennsylvanian to Permian in age. Deformation related to Antler and Sonoma orogenies also occurred. These four episodes suggest that cycles of uplift, folding, faulting, and erosion began early in the development of the southern Cordillera and continued intermittently throughout Paleozoic time. West of the continental shelf was a broad subsiding basin marked by narrow troughs and elongate structural highs which emerged, matured, and diminished at different times. Waxing and waning deformation in various parts of the geosyncline acting upon local "highs" and troughs can explain the seemingly erratic distribution in north-central Nevada of different fades of time-correlative stratigraphic units and structural blocks of Paleozoic age. Telescoping of facies by thrust faulting certainly took place, but large displacements within brief periods are not essential to the validity of the explanation.

Nevada↗

USGS2020

High-resolution mapping of the freshwater-brine interface using deterministic and Bayesian inversion of airborne electromagnetic data at Paradox Valley, USA

Salt loads in the Colorado River Basin are a primary water quality concern. Natural groundwater brine discharge to the Dolores River where it passes through the collapsed salt anticline of the Paradox Valley in western Colorado is a significant source of salt to the Colorado River. An airborne electromagnetic survey of Paradox Valley has provided insights into the 3D distribution of brine in the surficial aquifer. A combination of stochastic and deterministic resistivity inversions were used to interpret the top of the freshwater-brine interface and to qualitatively describe the vertical salinity gradients across the interface. Low-resistivity regions indicative of brine occur near the land surface where brine discharges to the Dolores River and increase in depth several kilometers up-gradient along the axis of the valley. The most conductive parts of the brine plume are found in the areas below and adjacent to the river, suggesting that the brine becomes shallower and more concentrated as it reaches its natural discharge location. A significant freshwater lens overlying the brine west of the Dolores River is spatially correlated to the intermittent West Paradox Creek and agricultural irrigation. Below this lens, the transition from freshwater to brine appears to occur abruptly over a few meters and correlates to available well information. However, away from these regions and particularly with distance from the river, the freshwater-brine interface appears to be more diffuse.

Colorado↗

USGS2019

Shear velocity structure from ambient noise and teleseismic surface wave tomography in the Cascades around Mount St. Helens

Mount St. Helens (MSH) lies in the forearc of the Cascades where conditions should be too cold for volcanism. To better understand thermal conditions and magma pathways beneath MSH, data from a dense broadband array are used to produce high‐resolution tomographic images of the crust and upper mantle. Rayleigh‐wave phase‐velocity maps and three‐dimensional images of shear velocity ( Vs ), generated from ambient noise and earthquake surface waves, show that west of MSH the middle‐lower crust is anomalously fast (3.95 ± 0.1 km/s), overlying an anomalously slow uppermost mantle (4.0–4.2 km/s). This combination renders the forearc Moho weak to invisible, with crustal velocity variations being a primary cause; fast crust is necessary to explain the absent Moho. Comparison with predicted rock velocities indicates that the fast crust likely consists of gabbros and basalts of the Siletzia terrane, an accreted oceanic plateau. East of MSH where magmatism is abundant, middle‐lower crust Vs is low (3.45–3.6 km/s), consistent with hot and potentially partly molten crust of more intermediate to felsic composition. This crust overlies mantle with more typical wave speeds, producing a strong Moho. The sharp boundary in crust and mantle Vs within a few kilometers of the MSH edifice correlates with a sharp boundary from low heat flow in the forearc to high arc heat flow and demonstrates that the crustal terrane boundary here couples with thermal structure to focus lateral melt transport from the lower crust westward to arc volcanoes.

Washington↗

USGS1999

Distinguishing Grenvillian basement from pre-Taconian cover rocks in the Northern Appalachians

Distinguishing Grenvillian basement rocks from pre-Taconian cover sequences in the Appalachians is a first-order problem essential for accurate structural interpretations. The Cavendish Formation in southeastern Vermont presents a classic example of this problem. Doll and others (1961) showed the Cavendish Formation as younger than the Middle Proterozoic Mount Holly Complex but older than the lithologically similar Cambrian Tyson and Hoosac Formations. More recently, the name Cavendish Formation has been informally abandoned, and its metasedimentary units have been mapped as the Tyson and Hoosac Formations of Late Proterozoic to Cambrian age. In a radical departure from these interpretations, Ratcliffe and others (1997) reassigned metasedimentary rocks of the Cavendish Formation to the Mount Holly Complex based on an inferred intrusive relationship between them and a 1.42 Ga tonalite. This new age assignment, if correct, requires a completely new structural interpretation of the region. SHRIMP and Pb evaporation ages of detrital zircons extracted from a quartzite layer from Cavendish Gorge near the proposed intrusive contact with the tonalite constrain the time of deposition of the Cavendish Formation. Grain shapes of the zircons vary from euhedral to nearly spherical. Virtually all the grains have pitted surfaces and show at least some rounding of edges and terminations; grains exhibit oscillatory zoning typical of zircons that crystallized from a magma. Single-grain Pb evaporation analyses of ten zircons and SHRIMP analyses of 15 zircons all yield ages less than 1.42 Ga. Seven of the grains are consistent with derivation from the Bull Hill Gneiss that postdates the Grenville orogenic cycle and predates deposition of the Cavendish Formation. Thus, the metasedimentary units of the Cavendish Formation should not be assigned to the Mount Holly Complex.

northern Appalachians↗

USGS2017

The study of fresh-water lake ice using multiplexed imaging radar

The study of ice in the upper Great Lakes, both from the operational and the scientific points of view, is receiving continued attention. Quantitative and qualitative field work is being conducted to provide the needed background for accurate interpretation of remotely sensed data. The data under discussion in this paper were obtained by a side-looking multiplexed airborne radar (SLAR) supplemented with ground-truth data. Because of its ability to penetrate adverse weather, radar is an especially important instrument for monitoring ice in the upper Great Lakes. It has previously been shown that imaging radars can provide maps of ice cover in these areas. However, questions concerning both the nature of the surfaces reflecting radar energy and the interpretation of the radar imagery continually arise. Our analysis of ice in Whitefish Bay (Lake Superior) indicates that the combination of the ice/water interlace and the ice/air interface is the major contributor to the radar backscatter as seen on the imagery At these frequencies the ice has a very low relative dielectric permittivity (< 3.0) and a low loss tangent Thus, this ice is somewhat transparent to the energy used by the imaging SLAR system. The ice types studied include newly formed black ice, pancake ice, and frozen and consolidated pack and brash ice. Although ice thickness cannot be measured directly from the received signals, it is suspected that by combining the information pertaining to radar backscatter with data on the meteorological and sea-state history of the area, together with some basic ground truth, better estimates of the ice thickness may be provided. In addition, certain ice features (e.g. ridges, ice-foot formation, areas of brash ice) may be identified with reasonable confidence. There is a continued need for additional ground work to verify the validity of imaging radars for these types of interpretations.

Upper Great Lakes↗

USGS2007

Regional assessment of NLEAP NO 3- N leaching indices

Nonpoint source ground water contamination by nitrate nitrogen (NO 3 -N) leached from agricultural lands can be substantial and increase health risks to humans and animals. Accurate and rapid methods are needed to identify and map localities that have a high potential for contamination of shallow aquifers with NO 3 -N leached from agriculture. Evaluation of Nitrate Leaching and Economic Analysis Package (NLEAP) indices and input variables across an irrigated agricultural area on an alluvial aquifer in Colorado indicated that all leaching indices tested were more strongly correlated with aquifer NO 3 -N concentration than with aquifer N mass. Of the indices and variables tested, the NO 3 -N Leached (NL) index was the NLEAP index most strongly associated with groundwater NO 3 -N concentration (r 2 values from 0.37 to 0.39). NO 3 -N concentration of the leachate was less well correlated with ground water NO 3 -N concentration (r 2 values from 0.21 to 0.22). Stepwise regression analysis indicated that, although inorganic and organic/inorganic fertilizer scenarios had similar r 2 values, the Feedlot Indicator (proximity) variable was significant over and above the NO 3 -N Leached index for the inorganic scenario. The analysis also showed that combination of either Movement Risk Index (MIRI) or NO 3 -N concentration of the leachate with the NO 3 -N Leached index leads to an improved regression, which provides insight into area-wide associations between agricultural activities and ground water NO 3 -N concentration.

Journal of the American Water Resources Associatio↗

USGS2003

Temporal and spatial stability of red-tailed hawk territories in the Luquillo Experimental Forest, Puerto Rico

We mapped Red-tailed Hawk (Buteo jamaicensis) territories in the Luquillo Experimental Forest (LEF) of Puerto Rico in 1998. We combined our 1998 data with that collected during previous studies of Red-tailed Hawks in the LEF to examine population numbers and spatial stability of territorial boundaries over a 26-yr period. We also investigated potential relationships between Red-tailed Hawk territory sizes and topographic and climatic factors. Mean size of 16 defended territories during 1998 was 124.3 ?? 12.0 ha, which was not significantly different from our calculations of mean territory sizes derived from data collected in 1974 and 1984. Aspect and slope influenced territory size with the smallest territories having high slope and easterly aspects. Territory size was small compared to that reported for other parts of the species' range. In addition, there was remarkably little temporal change in the spatial distribution, area, and boundaries of Red-tailed Hawk territories among the study periods. Further, there was substantial boundary overlap (21-27%) between defended territories among the different study periods. The temporal stability of the spatial distribution of Red-tailed Hawk territories in the study area leads us to believe the area might be at or near saturation.

Journal of Raptor Research↗

USGS2018

Structural evolution of a gold-bearing transtensional zone within the Archean Porcupine-Destor deformation zone, southern Abitibi greenstone belt, eastern Ontario, Canada

The Garrison camp comprises four structurally distinct orogenic gold deposits that formed in different host lithologies during progressive deformation. Detailed field mapping, drill core logging, and geochronological constraints suggest that the 2678 ± 2 Ma Garrison granitic stock played a fundamental rheological role in the location of the four deposits. Initial local shear movement occurred along the southwestern margin of the stock leading to the development of the NW-trending sinistral NE-side-up Buffonta shear zone, which hosts the Buffonta deposit. Subsequently, a transtensional zone formed between the NE-trending sinistral Porcupine-Destor and Munro deformation zones, which host the 903 and Jonpol deposits, respectively. Finally, a local change in shortening orientation from NE to NNW caused westerly directed extension resulting in the formation of the younger gold-bearing veins composing the Garrcon deposit. In situ U-Pb laser ablation-inductively coupled plasma-mass spectrometry performed on monazite grains formed within the shear fabric of the Munro deformation zone indicates that transtension occurred at 2657 ± 15 Ma. Therefore, at least three of the four deposits formed subsequent to crystallization of the Garrison granitic stock. The reported U-Pb dates represent the first direct age constraints on the movement along a gold-bearing deformation zone in the southern Abitibi greenstone belt.

Ontario↗

USGS2007

Near-infrared spectral mapping of Titan's mountains and channels

We investigate the spectral reflectance properties of channels and mountain ranges on Titan using data from Cassini's Visual and Infrared Mapping Spectrometer (VIMS) obtained during the T9 encounter (26 December 2005). We identify the location of channels and mountains using synthetic aperture radar maps obtained from Cassini's RADAR instrument during the T13 (30 April 2006) flyby. Channels are evident even in VIMS imaging with spatial resolution coarser than the channel size. The channels share spectral characteristics with Titan's dark blue terrain (e.g., the Huygens landing site) that is consistent with an enhancement in water ice content relative to the rest of Titan. We use this fact to measure widths of ???1 km for the largest channels. Comparison of the data sets shows that in our study area within the equatorial bright spectral unit east of Xanadu, mountains are darker and bluer than surrounding smooth terrain. These results are consistent with the equatorial bright terrain possessing a veneer of material that is thinner in the regions where there are mountains and streambeds that have likely undergone more recent and extensive erosion. We suggest a model for the geographic relationship of the dark blue, dark brown, and equatorial bright spectral units based on our findings.

Journal of Geophysical Research E: Planets↗