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USGS2007

Spectral element modelling of fault-plane reflections arising from fluid pressure distributions

The presence of fault-plane reflections in seismic images, besides indicating the locations of faults, offers a possible source of information on the properties of these poorly understood zones. To better understand the physical mechanism giving rise to fault-plane reflections in compacting sedimentary basins, we numerically model the full elastic wavefield via the spectral element method (SEM) for several different fault models. Using well log data from the South Eugene Island field, offshore Louisiana, we derive empirical relationships between the elastic parameters (e.g. P-wave velocity and density) and the effective-stress along both normal compaction and unloading paths. These empirical relationships guide the numerical modelling and allow the investigation of how differences in fluid pressure modify the elastic wavefield. We choose to simulate the elastic wave equation via SEM since irregular model geometries can be accommodated and slip boundary conditions at an interface, such as a fault or fracture, are implemented naturally. The method we employ for including a slip interface retains the desirable qualities of SEM in that it is explicit in time and, therefore, does not require the inversion of a large matrix. We performa complete numerical study by forward modelling seismic shot gathers over a faulted earth model using SEM followed by seismic processing of the simulated data. With this procedure, we construct post-stack time-migrated images of the kind that are routinely interpreted in the seismic exploration industry. We dip filter the seismic images to highlight the fault-plane reflections prior to making amplitude maps along the fault plane. With these amplitude maps, we compare the reflectivity from the different fault models to diagnose which physical mechanism contributes most to observed fault reflectivity. To lend physical meaning to the properties of a locally weak fault zone characterized as a slip interface, we propose an equivalent-layer model under the assumption of weak scattering. This allows us to use the empirical relationships between density, velocity and effective stress from the South Eugene Island field to relate a slip interface to an amount of excess pore-pressure in a fault zone. ?? 2007 The Authors Journal compilation ?? 2007 RAS.

Geophysical Journal International↗

USGS2016

Hydrologic connectivity: Quantitative assessments of hydrologic-enforced drainage structures in an elevation model

Elevation data derived from light detection and ranging present challenges for hydrologic modeling as the elevation surface includes bridge decks and elevated road features overlaying culvert drainage structures. In reality, water is carried through these structures; however, in the elevation surface these features impede modeled overland surface flow. Thus, a hydrologically-enforced elevation surface is needed for hydrodynamic modeling. In the Delaware River Basin, hydrologic-enforcement techniques were used to modify elevations to simulate how constructed drainage structures allow overland surface flow. By calculating residuals between unfilled and filled elevation surfaces, artificially pooled depressions that formed upstream of constructed drainage structure features were defined, and elevation values were adjusted by generating transects at the location of the drainage structures. An assessment of each hydrologically-enforced drainage structure was conducted using field-surveyed culvert and bridge coordinates obtained from numerous public agencies, but it was discovered the disparate drainage structure datasets were not comprehensive enough to assess all remotely located depressions in need of hydrologic-enforcement. Alternatively, orthoimagery was interpreted to define drainage structures near each depression, and these locations were used as reference points for a quantitative hydrologic-enforcement assessment. The orthoimagery-interpreted reference points resulted in a larger corresponding sample size than the assessment between hydrologic-enforced transects and field-surveyed data. This assessment demonstrates the viability of rules-based hydrologic-enforcement that is needed to achieve hydrologic connectivity, which is valuable for hydrodynamic models in sensitive coastal regions. Hydrologic-enforced elevation data are also essential for merging with topographic/bathymetric elevation data that extend over vulnerable urbanized areas and dynamic coastal regions.

Journal of Coastal Research↗

USGS1985

Geophysical techniques for reconnaissance investigations of soils and surficial deposits in mountainous terrain

Two techniques were assessed for their capabilities in reconnaissance studies of soil characteristics: depth to the water table and depth to bedrock beneath surficial deposits in mountainous terrain. Ground-penetrating radar had the best near-surface resolution in the upper 2 m of the profile and provided continuous interpretable imagery of soil profiles and bedrock surfaces. Where thick colluvium blankets side slopes, the GPR could not consistently define the bedrock interface. In areas with clayey or shaley sediments, the GPR is also more limited in defining depth and is less reliable. Seismic refraction proved useful in determining the elevation of the water table and depth to bedrock, regardless of thickness of overlying material, but could not distinguish soil-profile characteristics.

Soil Science Society of America Journal↗

USGS2020

Wetlands in agricultural landscapes—Significant findings and recent advances from CEAP-Wetlands

The Wetlands Component of the USDA's Conservation Effects Assessment Project (CEAP-Wetlands) is a multi-agency effort advancing science related to quantifying and interpreting effects and effectiveness of conservation practices and programs on ecosystem services provided by wetlands in agricultural landscapes. This special section originated from a symposium held at the 73rd Soil and Water Conservation Society's International Annual Conference in Albuquerque New Mexico, July 29 to August 1, 2018. The symposium was jointly organized by the USDA Natural Resources Conservation Service and the US Geological Survey. To facilitate CEAP-Wetlands efforts, several regional assessments were conducted across the United States. These regional assessments were designed to address science gaps hindering wetland conservation and to develop tools facilitating conservation assessments. Conservation decisions affect not just agricultural wetlands, but also the services that these complex ecosystems provide to society. Papers in this special section of the Journal of Soil and Water Conservation present key findings and recent advances from several CEAP-Wetlands regional assessments and discuss the significant contributions of each assessment to an ever-increasing understanding of wetland ecosystems and their provisioning of ecosystem services. Modeling efforts using the Agricultural Policy and Environmental eXtender (APEX) and other process-based models are an integral component of CEAP-Wetlands. Results of these modeling efforts are also presented, and conservation implications are discussed.

Journal of Soil and Water Conservation↗

USGS2020

Managing plague on prairie dog colonies: Insecticides as ectoparasiticides

Human health practitioners and wildlife biologists use insecticides to manage plague by suppressing fleas (Siphonaptera), but insecticides can also kill other ectoparasites. We investigated effects of deltamethrin and fipronil on ectoparasites from black-tailed prairie dogs ( Cynomys ludovicianus , BTPDs). In late July, 2018, we treated three sites with 0.05% deltamethrin dust and 5 sites with host-fed 0.005% fipronil grain. Three non-treated sites functioned as experimental baselines. We collected ectoparasites before treatments (June-July, 2018) and after treatments (August-October, 2018, June-July, 2019). Both deltamethrin and fipronil suppressed fleas for at least 12 months. Deltamethrin had no detectable effect on mites (Arachnida). Fipronil suppressed mites for at least 12 months. Lice (Phthiraptera) were scarce on non-treated sites throughout the study, complicating interpretation. Concentrating on eight sites where all three ectoparasites where found in June-July, 2018 (before treatments), flea intensity was greatest on BTPDs carrying many lice and mites. These three ectoparasites co-occurred at high numbers, which might facilitate plague transmission in some cases. Lethal effects of insecticides on ectoparasite communities are potentially advantageous in the context of plague management.

South Dakota↗

USGS1985

Maceral distributions in Illinois coals and their paleoenvironmental implications

For purposes of assessing the maceral distribution of Illinois (U.S.A.) coals analyses were assembled for 326 face channel and drill core samples from 24 coal members of the Pennsylvanian System. The inertinite content of coals from the Missourian and Virgilian Series averages 16.1% (mineral free), compared to 9.4% for older coals from the Desmoinesian and older Series. This indicates there was generally a higher state of oxidation in the peat that formed the younger coals. This state probably resulted from greater exposure of these peats to weathering as the climate became drier and the water table lower than was the case for the older coals, although oxidation during allochthonous deposition of inertinite components is a genetic factor that needs further study to confirm the importance of the climate. Regional variation of the vitrinite-inertinite ratio (V-I), on a mineral- and micrinite-free basis, was observed in the Springfield (No. 5) and Herrin (No. 6) Coal Members to be related to the geographical position of paleochannel (river) deposits known to have been contemporaneous with the peats that formed these two coal strata. The V-I ratio is highest (generally 12–27) in samples from areas adjacent to the channels, and lower (5–11) some 10–20 km away. We interpret the V-I ratio to be an inverse index of the degree of oxidation to which the original peat was exposed. High V-I ratio coal located near the channels probably formed under more anoxic conditions than did the lower V-I ratio coal some distance away from the channels. The low V-I ratio coal probably formed in areas of the peat swamp where the watertable was generally lower than the channel areas.

International Journal of Coal Geology↗

USGS2024

Sulphide petrology and ore genesis of the stratabound Sheep Creek sediment-hosted Zn–Pb–Ag–Sn prospect, and U–Pb zircon constraints on the timing of magmatism in the northern Alaska Range

The Sheep Creek prospect is a stratabound Zn–Pb–Ag–Sn massive sulfide occurrence in the Bonnifield mining district, northern Alaska Range. The prospect is within a quartz–sericite–graphite–chlorite schist unit associated with Devonian carbonaceous and siliceous metasedimentary rocks. Volcanogenic massive sulfide (VMS) deposits in the district are hosted in felsic metavolcanic rocks (362 ± 2 Ma) associated with siliciclastic and carbonaceous sedimentary rocks that overlie the stratigraphic sequence hosting the Sheep Creek prospect. Felsic metaigneous rocks in underlying units are 372 ± 4 to 366 ± 4 Ma. Sheep Creek is atypical of the other sulfide deposits in the district in (1) having Sn grades up to 1.2%; (2) being contained in fine-grained, quartz-rich rocks and quartz–pebble conglomerate that likely originated as chert and chert-clast sediment, respectively; and (3) showing minimal evidence of volcanic components in the host rocks. Comparison of immobile trace-element proportions for graphitic and siliceous rocks from the Sheep Creek area with those for argillite associated with the Bonnifield VMS deposits indicates a continental volcanic-arc provenance for the former and a within-plate and passive margin provenance for the latter. In contrast to previously published interpretations, our data analysis supports a clastic-dominated (CD) rather than a VMS affinity for the Sheep Creek prospect. In our model, Zn–Pb–Ag–Sn mineralization formed by syngenetic or early diagenetic processes on or beneath the seafloor, possibly in the shallow-water environment of an outer continental shelf setting. Potential analogues are the Paleozoic CD deposits in the Canadian Selwyn Basin outboard of the Laurentian continental margin.

Alaska↗

USGS1998

Limits of retrospective power analysis

Power analysis after study completion has been suggested to interpret study results. We present 3 methods of estimating power and discuss their limitations. We use simulation studies to show that estimated power can be biased, extremely variable, and severely bounded. We endorse the practice of computing power to detect a biologically meaningful difference as a tool for study planning but suggest that calculation of confidence intervals on the parameter of interest is the appropriate way to gauge the strength and biological meaning of study results.

Journal of Wildlife Management↗

USGS2006

New insights into the history and origin of the southern Maya block, SE Mexico: U-Pb-SHRIMP zircon geochronology from metamorphic rocks of the Chiapas massif

The histories of the pre-Mesozoic landmasses in southern México and their connections with Laurentia, Gondwana, and among themselves are crucial for the understanding of the Late Paleozoic assembly of Pangea . The Permian igneous and metamorphic rocks from the Chiapas massif as part of the southern Maya block, México, were dated by U–Pb zircon geochronology employing the SHRIMP (sensitive high resolution ion microprobe) facility at Stanford University. The Chiapas massif is composed of deformed granitoids and orthogneisses with inliers of metasedimentary rocks. SHRIMP data from an anatectic orthogneiss demonstrate that the Chiapas massif was part of a Permian (&sim; 272 Ma) active continental margin established on the Pacific margin of Gondwana after the Ouachita orogeny. Latest Permian (252–254 Ma) medium- to high-grade metamorphism and deformation affected the entire Chiapas massif, resulting in anatexis and intrusion of syntectonic granitoids. This unique orogenic event is interpreted as the result of compression due to flat subduction and accretionary tectonics. SHRIMP data of zircon cores from a metapelite from the NE Chiapas massif yielded a single Grenvillian source for sediments. The majority of the zircon cores from a para-amphibolite from the SE part of the massif yielded either 1.0–1.2 or 1.4–1.5 Ga sources, indicating provenance from South American Sunsás and Rondonian-San Ignacio provinces.

Maya block↗

USGS1998

Multi-level slug tests in highly permeable formations: 2. Hydraulic conductivity identification, method verification, and field applications

Using the developed theory and modified Springer-Gelhar (SG) model, an identification method is proposed for estimating hydraulic conductivity from multi-level slug tests. The computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double-packer system. Field verification of the method was performed at a specially designed fully penetrating well of 0.1-m diameter with a 10-m screen in a sand and gravel alluvial aquifer (MSEA site, Shelton, Nebraska). During well installation, disturbed core samples were collected every 0.6 m using a split-spoon sampler. Vertical profiles of hydraulic conductivity were produced on the basis of grain-size analysis of the disturbed core samples. These results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi-level slug test responses using the modified SG model. The identification method was applied to interpret the response from 474 slug tests in 156 locations at the MSEA site. More than 60% of responses were oscillatory. The method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure. The proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data. Recommendations generalizing this experience to massive application of the proposed method are developed.Using the developed theory and modified Springer-Gelhar (SG) model, an identification method is proposed for estimating hydraulic conductivity from multi-level slug tests. The computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double-packer system. Field verification of the method was performed at a specially designed fully penetrating well of 0.1-m diameter with a 10-m screen in a sand and gravel alluvial aquifer (MSEA site, Shelton, Nebraska). During well installation, disturbed core samples were collected every 0.6 m using a split-spoon sampler. Vertical profiles of hydraulic conductivity were produced on the basis of grain-size analysis of the disturbed core samples. These results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi-level slug test responses using the modified SG model. The identification method was applied to interpret the response from 474 slug tests in 156 locations at the MSEA site. More than 60% of responses were oscillatory. The method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure. The proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data. Recommendations generalizing this experience to massive application of the proposed method are developed.

Journal of Hydrology↗

USGS2010

The North American upper mantle: Density, composition, and evolution

The upper mantle of North America has been well studied using various seismic methods. Here we investigate the density structure of the North American (NA) upper mantle based on the integrative use of the gravity field and seismic data. The basis of our study is the removal of the gravitational effect of the crust to determine the mantle gravity anomalies. The effect of the crust is removed in three steps by subtracting the gravitational contributions of (1) topography and bathymetry, (2) low-density sedimentary accumulations, and (3) the three-dimensional density structure of the crystalline crust as determined by seismic observations. Information regarding sedimentary accumulations, including thickness and density, are taken from published maps and summaries of borehole measurements of densities; the seismic structure of the crust is based on a recent compilation, with layer densities estimated from P-wave velocities. The resultant mantle gravity anomaly map shows a pronounced negative anomaly (−50 to −400 mGal) beneath western North America and the adjacent oceanic region and positive anomalies (+50 to +350 mGal) east of the NA Cordillera. This pattern reflects the well-known division of North America into the stable eastern region and the tectonically active western region. The close correlation of large-scale features of the mantle anomaly map with those of the topographic map indicates that a significant amount of the topographic uplift in western NA is due to buoyancy in the hot upper mantle, a conclusion supported by previous investigations. To separate the contributions of mantle temperature anomalies from mantle compositional anomalies, we apply an additional correction to the mantle anomaly map for the thermal structure of the uppermost mantle. The thermal model is based on the conversion of seismic shear-wave velocities to temperature and is consistent with mantle temperatures that are independently estimated from heat flow and heat production data. The thermally corrected mantle density map reveals density anomalies that are chiefly due to compositional variations. These compositional density anomalies cause gravitational anomalies that reach ~250 mGal. A pronounced negative anomaly (−50 to −200 mGal) is found over the Canadian shield, which is consistent with chemical depletion and a corresponding low density of the lithospheric mantle, also referred to as the mantle tectosphere. The strongest positive anomaly is coincident with the Gulf of Mexico and indicates a positive density anomaly in the upper mantle, possibly an eclogite layer that has caused subsidence in the Gulf. Two linear positive anomalies are also seen south of 40°N: one with a NE-SW trend in the eastern United States, roughly coincident with the Grenville-Appalachians, and a second with a NW-SE trend beneath the states of Texas, New Mexico, and Colorado. These anomalies are interpreted as being due to (1) the presence of remnants of an oceanic slab in the upper mantle beneath the Grenville-Appalachian suture and (2) mantle thickening caused by a period of shallow, flat subduction during the Laramie orogeny, respectively. Based on these geophysical results, the evolution of the NA upper mantle is depicted in a series of maps and cartoons that display the primary processes that have formed and modified the NA crust and lithospheric upper mantle.

Journal of Geophysical Research B: Solid Earth↗

USGS1991

Facies development in the Lower Freeport coal bed, west-central Pennsylvania, U.S.A.

The Lower Freeport coal bed in west-central Pennsylvania is interpreted to have formed within a lacustrine-mire environment. Conditions of peat formation, caused by the changing chemical and physical environments, produced five coal facies and two mineral-rich parting facies within the coal bed. The coal bed facies are compositionally unique, having developed under varying conditions, and are manifested by megascopic, petrographic, palynologic and quality characteristics. The initial environment of the Lower Freeport peat resulted in a coal facies that is relatively high in ash yield and contains large amounts of lycopod miospores and moderate abundances of cryptotelinite, crypto-gelocollinite, inertinite and tree fern miospores. This initial Lower Freeport peat is interpreted to have been a topogenous body that was low lying, relatively nutrient rich (mesotrophic to eutrophic), and susceptible to ground water and to sediment influx from surface water. The next facies to form was a ubiquitous, clay-rich durain parting which is attributed to a general rise in the water table accompanied by widespread flooding. Following formation of the parting, peat accumulation resumed within an environment that inhibited clastic input. Development of doming in this facies restricted deposition of the upper shale parting to the margins of the mire and allowed low-ash peat to form in the interior of the mire. Because this environment was conducive to preservation of cellular tissue, this coal facies also contains large amounts of crypto-telinite. This facies development is interpreted to have been a transitional phase from topogenous, planar peat formation to slightly domed, oligotrophic (nutrient-poor) peat formation. As domed peat formation continued, fluctuations in the water table enabled oxidation of the peat surface and produced high inertinite concentrations toward the top of the coal bed. Tree ferns became an increasingly important peat contributor in the e upper facies, based on the palynoflora. This floral change is interpreted to have resulted from the peat surface becoming less wet or better drained, a condition that inhibited proliferation of lycopod trees. Accumulation of the peat continued until rising water levels formed a freshwater lake within which clays and silts were deposited. The development of the Lower Freeport peat from a planar mire through transitional phases toward domed peat formation may be an example of the type of peat formation of other upper Middle and Upper Pennsylvanian coal beds.

International Journal of Coal Geology↗

USGS2024

Decoding paleomire conditions of Paleogene superhigh-organic-sulfur coals

Superhigh-organic‑sulfur (SHOS) coals (coals with organic sulfur content >4 wt%) are unique coal deposits found at a few notable locations in the world. Specific peat accumulation and preservation conditions must be met to form SHOS coals. Organic sulfur is a major constituent of such coals, and it may have various sources depending on the prevailing paleomire conditions. Understanding such paleomire conditions sheds light on the formation mechanisms of SHOS coals. This investigation decodes the paleomire conditions of the Paleogene SHOS coals from Meghalaya, India, using sulfur isotopic compositions ( δ 34 S) of organic sulfur ( δ 34 S OS ) and pyritic sulfur ( δ 34 S Py ) along with organic petrography, pyrite morphology and trace element ratios. Thirty coal samples were collected from the Jaintia Hills in the east, Khasi Hills in the middle, and Garo Hills in the west of Meghalaya. The organic sulfur content in the Garo, Khasi, and Jaintia coals varies from 1.0 to 3.3 wt%, 1.4 to 13.8 wt%, and 1.0 to 7.2 wt%, respectively. Further, after separation from pyritic sulfur and sulfate sulfur phases, the organic sulfur content ranges from 54.4 to 69.2%, 63.8 to 79.9%, and 59.3 to 73.8%, in the Garo, Khasi, and Jaintia Hills, respectively, suggesting the SHOS nature of these coal samples. The δ 34 S Py varies from −29.3 ‰ to +5.7 ‰, −21.3 ‰ to +27.3 ‰, and −12.1 ‰ to −4.3 ‰, in the Jaintia, Khasi, and Garo Hills, respectively, while the δ 34 S OS fluctuates from −4.6 ‰ to +3.7 ‰, −9.3 ‰ to +7.8 ‰, and − 9.0 ‰ to −5.0 ‰, respectively. The δ 34 S values of pyrite and organic sulfur (OS) in Jaintia coals are 34 S depleted compared to seawater sulfate (+22 ‰), leading to fractionations in the range of −51.3 ‰ to −16.3 ‰ (mean − 31.6 ‰) and − 26.6 ‰ to −18.3 ‰ (mean − 23.1 ‰) for pyritic and organic sulfur (OS), respectively. Pyrite in Khasi coals show a relatively heavier δ 34 S composition averaging at −20.5 ‰, whereas organic sulfur (OS) isotope compositions range from −31.3 ‰ to −14.2 ‰ with a mean of −22.6 ‰. Pyrite and OS in the Garo coals are depleted compared to seawater sulfate. Isotope variations in the Jaintia, Khasi, and Garo coals indicate microbial sulfate reduction (MSR) of seawater sulfate. Large isotopic fractionations between Eocene seawater sulfate and pyritic sulfur ( Δ 34 S SO4Eocene – pyrite = up to −51.3 ‰; mean − 31.6 ‰) in Jaintia coals indicate their possible formation in the water column/near the sediment-seawater interface (open system) and also hint toward dissimilatory sulfate reduction pathways that prevailed under anoxic redox conditions. However, mean values of Δ 34 S SO4Eocene – pyrite (−20.5 ‰) in the Khasi coals imply pyrite formation deeper in the sediments (more closed system) under dysoxic conditions. The dominance of OS over pyritic sulfur, framboidal pyrite, and its microcrystal size distributions in Jaintia coals may suggest syngenetic pyrite formation in open water reducing/anoxic conditions under paralic environments. Elevated Sr/Ba and U/Th values in these coals further confirm the anoxic conditions. Nevertheless, the presence of euhedral pyrite with the alleviated pyrite framboids in the Khasi coals and their complete absence in the Garo coals may suggest dysoxic-suboxic and suboxic-oxic depositional conditions, respectively. The isotopic signatures of the Garo coals suggest sulfur contribution from the parent paleobiota and MSR under a freshwater-oxic environment. Insignificant fractionations between δ 34 S Py and δ 34 S OS indicate limited iron and sulfate availability for additional sulfur cycling and disproportionation reactions, typical of oxic conditions. The absence of framboidal pyrite, elevated sulfate concentration, and mean Sr/Ba and U/Th values of 0.5 and 0.3, respectively, further suggest the freshwater peat deposition in the Garo Hills under limnotelmatic to telmatic freshwater conditions. Moreover, high inertinite content (I mmf = 9.77–33.16 vol%), possibly induced by atmospheric peat exposure, supports the interpretation of suboxic-oxic paleomire conditions in Garo Hills. Gradually decreasing mineral matter content from Jaintia (mean 13.6 vol%) to Garo coals (mean 7.4 vol%) additionally projects a transition from mesotrophic brackish to freshwater limnotelmatic environment, complementing the shift in the paleomire condition from eastern (Jaintia) to western (Garo) Meghalayan Hills.

International Journal of Coal Geology↗

USGS2013

Combined ESR/U-series chronology of Acheulian hominid-bearing layers at Trinchera Galería site, Atapuerca, Spain

The Sierra de Atapuerca, northern Spain, is known from many prehistoric and palaeontological sites documenting human prehistory in Europe. Three major sites, Gran Dolina, Galería and Sima del Elefante, range in age from the oldest hominin of Western Europe dated to 1.1 to 1.3 Ma (millions of years ago) at Sima del Elefante to c.a. 0.2 Ma on the top of the Galería archaeological sequence. Recently, a chronology based on luminescence methods (Thermoluminescence [TL] and Infrared Stimulated Luminescence [IRSL]) applied to cave sediments was published for the Gran Dolina and Galería sites. The authors proposed for Galería an age of 450 ka (thousands of years ago) for the units lower GIII and GII, suggesting that the human occupation there is younger than the hominid remains of Sima de los Huesos (>530 ka) around 1 km away. In this paper, we present new results obtained by combined Electron Spin Resonance/Uranium-series (ESR/U-series) dating on 20 herbivorous teeth from different levels at the Galería site. They are in agreement with the TL results for the upper part of the stratigraphic sequence (GIV and GIIIb), in the range of between 200 and 250 ka. But for the GIIIa to GIIb levels, the TL ages become abruptly older by 200 ka while ESR ages remain relatively constant. Finally, the TL and ESR data agree in the lowest part of the section (GIIa); both fall in the range of around 350–450 ka. Our results suggest a different interpretation for the GII, GIII and GIV units of Galería and the upper part of Gran Dolina (TD10 and TD11) than obtained by TL. The ESR/U-series results are supported by a Bayesian analysis, which allows a better integration between stratigraphic information and radiometric data.

Atapuerca Mountains↗

USGS1996

Detection and monitoring of H2O and CO2 ice clouds on Mars

We have developed an observational scheme for the detection and discrimination of Mars atmospheric H 2 O and CO 2 clouds using ground-based instruments in the near infrared. We report the results of our cloud detection and characterization study using Mars near IR images obtained during the 1990 and 1993 oppositions. We focused on specific wavelengths that have the potential, based on previous laboratory studies of H 2 O and CO 2 ices, of yielding the greatest degree of cloud detectability and compositional discriminability. We have detected and mapped absorption features at some of these wavelengths in both the northern and southern polar regions of Mars. Compositional information on the nature of these absorption features was derived from comparisons with laboratory ice spectra and with a simplified radiative transfer model of a CO 2 ice cloud overlying a bright surface. Our results indicate that both H 2 O and CO 2 ices can be detected and distinguished in the polar hood clouds. The region near 3.00 μm is most useful for the detection of water ice clouds because there is a strong H 2 O ice absorption at this wavelength but only a weak CO 2 ice band. The region near 3.33 μm is most useful for the detection of CO 2 ice clouds because there is a strong, relatively narrow CO 2 ice band at this wavelength but only broad “continuum” H 2 O ice absorption. Weaker features near 2.30 μm could arise from CO 2 ice at coarse grain sizes, or surface/dust minerals. Narrow features near 2.00 μm, which could potentially be very diagnostic of CO 2 ice clouds, suffer from contamination by Mars atmospheric CO 2 absorptions and are difficult to interpret because of the rather poor knowledge of surface elevation at high latitudes. These results indicate that future ground-based, Earth-orbital, and spacecraft studies over a more extended span of the seasonal cycle should yield substantial information on the style and timing of volatile transport on Mars, as well as a more detailed understanding of the role of CO 2 condensation in the polar heat budget.

Journal of Geophysical Research E: Planets↗

USGS2017

Enhancing the interpretation of stated choice analysis through the application of a verbal protocol assessment

A stated choice survey was employed to evaluate the relative importance of resource, social, and management attributes by asking visitors to select preferred configurations of these attributes. A verbal protocol assessment was added to consider how respondents interpret and respond to stated choice questions applied to hikers of a popular trail at Acadia National Park. Results suggest that visitors are sensitive to changes in public access to the trail and its ecological conditions, with level of encounters least important. Verbal protocol results identified considerations made by respondents that provide insight to their evaluations of alternative recreation setting configurations. These insights help clarify issues important to visitors that stated choice results on their own do not provide.

Maine↗

USGS2008

Controls on mineralisation in the Sierra Foothills gold province, central California, USA: A GIS-based reconnaissance prospectivity analysis

The assessment of spatial relationships between the location, abundance and size of orogenic-gold deposits in the highly endowed Sierra Foothills gold province in California, via the combination of field studies and a GIS-based analysis, illustrates the power of such an approach to the characterisation of important parameters of mineral systems, and the prediction of districts likely to host economic mineralisation. Regional- to deposit-scale reconnaissance mapping suggests that deposition of gold-bearing quartz veins occurred in second- and third-order, east-over-west thrusts during regional east - west compression and right-lateral transpression. At the district-scale, significant zones of mineralisation correspond with such transpressional reactivation zones and dilational jogs that developed during the Late Jurassic - Early Cretaceous along the misaligned segments of first-order faults throughout the Sierra Nevada Foothills Metamorphic Belt. Field-based observations and interpretation of GIS data (including solid geology, structural elements, deposit locations, magnetics, gravity) also highlight the importance of structural permeability contrasts, rheological gradients, and variations in fault orientation for localising mineralisation. Although this approach confirms empirical findings and produces promising results at the province scale, enhanced geological, structural, geophysical and geochronological data density is required to generate regionally consistent, high-quality input layers that improve predictive targeting at the goldfield to deposit-scale.

Australian Journal of Earth Sciences↗

USGS2025

Leveraging high-frequency sensor data and U.S. National Water Model output to forecast turbidity in a drinking water supply basin

As high-frequency sensor networks increasingly enhance data-driven models of water quality, process-based models like the U.S. National Water Model (NWM) are generating accessible forecasts of streamflow at increasingly dense scales. There is now an opportunity to combine these products to construct actionable water quality forecasts. To that end, we couple streamflow forecasts from the NWM to a gradient-boosted decision tree algorithm (LightGBM) trained on 5+ years of high-frequency monitoring data to forecast in-stream turbidity levels in the Catskill Mountains, NY, USA. Results indicate LightGBM models are capable of relatively skillful predictions, which enable robust forecasts for 1–3 days lead times. LightGBM models offer improvements over a simplified linear model across the entire forecast horizon, and more spatially complex models are more resilient to error at shorter lead times (1–3 days). Moreover, interpretation of model features emphasizes high flows as a driver of turbidity in the region. Results suggest that interpretable, flexible, and efficient machine learning algorithms can produce capable water quality forecasts from streamflow forecasts and expand understanding of process dynamics. The use case illustrated here—to our knowledge the first NWM-based water quality forecast—underscores the potential to employ the NWM to expand national water quality forecasting capacity and can overall serve as a guide for similar efforts in basins across the country.

New York↗