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At least 1,261 records · Page 70Linked to original sources
USGS2013

Controls on the deposition and preservation of the Cretaceous Mowry Shale and Frontier Formation and equivalents, Rocky Mountain region, Colorado, Utah, and Wyoming

Regional variations in thickness and facies of clastic sediments are controlled by geographic location within a foreland basin. Preservation of facies is dependent on the original accommodation space available during deposition and ultimately by tectonic modification of the foreland in its postthrusting stages. The preservation of facies within the foreland basin and during the modification stage affects the kinds of hydrocarbon reservoirs that are present. This is the case for the Cretaceous Mowry Shale and Frontier Formation and equivalent strata in the Rocky Mountain region of Colorado, Utah, and Wyoming. Biostratigraphically constrained isopach maps of three intervals within these formations provide a control on eustatic variations in sea level, which allow depositional patterns across dip and along strike to be interpreted in terms of relationship to thrust progression and depositional topography. The most highly subsiding parts of the Rocky Mountain foreland basin, near the fold and thrust belt to the west, typically contain a low number of coarse-grained sandstone channels but limited sandstone reservoirs. However, where subsidence is greater than sediment supply, the foredeep contains stacked deltaic sandstones, coal, and preserved transgressive marine shales in mainly conformable successions. The main exploration play in this area is currently coalbed gas, but the enhanced coal thickness combined with a Mowry marine shale source rock indicates that a low-permeability, basin-centered play may exist somewhere along strike in a deep part of the basin. In the slower subsiding parts of the foreland basin, marginal marine and fluvial sandstones are amalgamated and compartmentalized by unconformities, providing conditions for the development of stratigraphic and combination traps, especially in areas of repeated reactivation. Areas of medium accommodation in the most distal parts of the foreland contain isolated marginal marine shoreface and deltaic sandstones that were deposited at or near sea level lowstand and were reworked landward by ravinement and longshore currents by storms creating stratigraphic or combination traps enclosed with marine shale seals. Paleogeographic reconstructions are used to show exploration fairways of the different play types present in the Laramide-modified, Cretaceous foreland basin. Existing oil and gas fields from these plays show a relatively consistent volume of hydrocarbons, which results from the partitioning of facies within the different parts of the foreland basin.

Colorado;Utah;Wyoming↗
USGS2001

Upper Cretaceous Ferron Sandstone: Major coalbed methane play in central Utah

Recent drilling for coalbed gas in the Upper Cretaceous Ferron Sandstone Member of central Utah has resulted in one of the most successful plays of this kind. Exploration to date has resulted in three fields and a potential fairway 6-10 mi (10-16 km) wide and 20-60 mi (32-96 km) long, corresponding to shallow coal occurrence at depths of about 1800-3500 ft (545-1060 m) in the Ferron, a sequence of interbedded fluvial-deltaic sandstone, shale, and coal in the lower part of the Cretaceous Mancos Shale. Coalbed methane (CBM) reservoirs in this interval consist of thin to moderately thick (3-10 ft [1-3 m]) coal beds of relatively low rank (high-volatile B bituminous) and variable gas content, ranging from 100 scf/ton or less in the south to as high as 500-600 scf/ton in the north. Productive wells have averaged more than 500 mcf/day and, after several years, continue to typically show negative production declines. In the major productive area, Drunkards Wash unit, the first 33 producers averaged 974 mcf and 85 bbl of water per day after five years of continuous production. Estimated ultimate recoverable reserves for individual wells in this unit range from 1.5 to 4 bcf. Based on several criteria, including gas content, thermal maturity, and chronostratigraphy, the play is divided into northern and southern parts. The northern part is characterized by coals that have the following characteristics: (1) high gas contents; (2) moderate thermal maturity (e.g., vitrinite reflectance [R o ] values of 0.6-0.8%); (3) good permeabilities (5-20 md); (4) lack of exposure; and (5) overpressuring, due to artesian conditions. Southern coals have much lower average gas contents (<100 scf/ton) and lower thermal maturity (R o = 0.4-0.6%), and they are exposed along an extensive, 35 mi (56 km) outcrop belt that may have allowed a degree of flushing. These coals, however, are also thicker and more extensive than those to the north and thus may retain significant potential. Northern coals appear to contain a mixture of gas from three sources: in-situ thermogenic methane, migrated thermogenic methane from more mature sources, and late-stage biogenic gas. Current development is focused on the northern part of the stated fairway, where well control and an existing infrastructure are present. Indications are that CBM exploration in the Ferron will expand considerably in the near future.

Utah↗
USGS1995

Geologic framework of a transect of the central Brooks Range: Regional relations and an alternative to the Endicott Mountains allochthon

This paper evaluates the geologic framework and tectonic development of the central Brooks Range based on a transect through the range and Arctic foothills. A geologic cross section constructed through the transect is confirmed by comparing the retrodeformed section with the regional distribution of lithofacies in the central Brooks Range. Stratigraphic relations in the retrodeformed section are further explained by comparing them to similar stratigraphic relations in the Ikpikpuk-Umiat basin under the Arctic coastal plain. The structural framework of the central Brooks Range and Arctic foothills consists of fold nappes, thrust faults, and detached folds that sole in decollements and late-stage high-angle faults. In the central Brooks Range, shortening is by north-directed thrust faulting and folding of mostly Paleozoic rocks, and transport of any individual thrust sheet relative to underlying rocks is less than 30 km. In the middle of the range, imbricate blocks of lower Paleozoic basement are exposed in the core of the Doonerak anticline, and thrust sheets of stratigraphically higher Paleozoic rocks that overlie basement are exposed in the limbs of the anticline. In the northeast part of the anticline, the Amawk thrust emplaces Silurian and Upper Devonian rocks on a succession of Lower Mississippian an stratigraphically higher rocks that have been detached from the underlying basement along the Blarney Creek thrust. The Slatepile fault system, a system of high-angle faults in the north limb of the Doonerak anticline, drops the core and part of the north limb of the anticline down, giving the impression that the succession of Lower Mississippian and stratigraphically higher rocks that lie on basement south of the system high-angle faults extends under the Upper Devonian rocks that extensively crop out north of the high-angle faults. In the Arctic foothills, the mostly Paleozoic rocks of the north-central Brooks Range extend under Lower Cretaceous rocks of the North Slope foreland basin, and blind thrusts that sole in the Paleozoic rocks ramp up into the Lower Cretaceous and stratigraph cally higher rocks. Also in the Arctic foothills, a thrust sheet that contains the Arctic foothills assemblage overlies rocks of the north-central Brooks Range and Lower Cretaceous rocks of the North Slope foreland basin. Thrust transport of the Arctic foothills assemblage more than 40 km from south of the Doonerak anticline took place during the Early Cretaceous, but thrusting that deformed rocks of the North Slope foreland basin took place during the early Tertiary, with the vertical uplift of the Doonerak anticline being a late-formed feature. Conclusions based on the retrodeformed cross section contrast significantly with previous work in which the Upper Devonian and stratigraphically higher rocks north of the Doonerak anticline are considered part of the Endicott Mountains allochthon, a regional allochthon that extends the breadth of the Brooks Range. In these models, Upper Devonian and younger rocks in the north-central Brooks Range have been thrust-transported 90 or 200 km from south of the Doonerak anticline, and emplacement of the allochthon could reflect as much as 885 km of tectonic shortening. The Lower Mississippian and stratigraphically higher rocks together with the underlying basement in the northeast part of the anticline are considered to be in a window in the Endicott Mountains allochthon and to extend northward beneath allochthonous Upper Devonian and stratigraphically higher rocks in the north-central Brooks Range. Lithofacies patterns in rocks in the central Brooks Range are consistent with the retrodeformed cross section and imply plausible Upper Devonian and Carboniferous depositional systems. Thick Upper Devonian and Lower Mississippian(?) clastic prisms were deposited in basins north of the Doonerak anticline. Mississippian carbonate rocks that overlie these clastic prisms were deposited in differentially subsiding shelf environments that included rocks in the Doonerak anticline. Restored across the Blarney Creek thrust, the Mississippian shelf carbonate rocks that presently lie north of the Doonerak anticline are those that were deposited on basement in the anticline. A carbonate ramp at the south edge of these shelf deposits extends east-southeast across the central Brooks Range and in th retrodeformed section lies south of the Doonerak anticline where Upper and Middle(?) Devonian shaly rocks thicken to the south. Unrestored, the ramp would extend across the Doonerak anticline. Restored Late Devonian and Carboniferous lithofacies patterns in the central Brooks Range also are plausible from a regional perspective and have implications for exploration of basins under the Arctic coastal plain. The Late Devonian to Early Mississippian(?) basins in the north-central Brooks Range are part of a system of Early(?) Devonian to Early Mississippian(?) clastic basins that extend the length of the Brooks Range and include basins under the Arctic coastal plain. These basins are a template for depositional patterns in overlying rocks. Marine shelves between these basins where Mississippian strata unconformably lie on basement, such as in the northeastern Brooks Range and the Doonerak anticline, have depositional histories that are in contrast to areas that overlie the basi s. The resulting stratigraphic framework, together with the structural framework in the basement rocks that controlled the basins, has had a profound effect on the structural style of the fold belt, the salient effect being folds and thrust faults that are not orthogonal to the direction of structural transport. Stratigraphic relations exposed in the fold belt, especially the distribution of potential source rocks, likely model little-explored basins that underlie the North Slope foreland basin.

Alaska↗
USGS2000

Schaben field, Kansas: Improving performance in a Mississippian shallow-shelf carbonate

Schaben field (Kansas), located along the northeastern shelf of the Hugoton embayment, produces from Mississippian carbonates in erosional highs immediately beneath a regional unconformity. Production comes from depths of around 4400 ft (1342 m) in partially dolomitized shelf deposits. A detailed reservoir characterization/simulation study, recently performed as part of a Department of Energy Reservoir Class Oil Field Demonstration Project, has led to important revision in explanations for observed patterns of production. Cores recovered from three new data wells identify three main facies: Spicule-rich wackestone-packstone, echinoderm wackestone/packstone/grainstone, and dolomitic mudstone-wackestone. Reservoir quality is highest in spicule-rich wackestone/packstones but is subject to a very high degree of vertical heterogeneity due to facies interbedding, silification, and variable natural fracturing. The oil reservoir is underlain by an active aquifer, which helps maintain reservoir pressure but supports significant water production. Reservoir simulation, using public-domain, PC-based software, suggests that infill drilling is an efficient approach to enhanced recovery. Recent drilling directed by simulation results has shown considerable success in improving field production rates. Results from the Schaben field demonstration project are likely to have wide application for independent oil and exploration companies in western Kansas.Schaben field (Kansas), located along the northeastern shelf of the Hugoton embayment, produces from Mississippian carbonates in erosional highs immediately beneath a regional unconformity. Production comes from depths of around 4400 ft (1342 m) in partially dolomitized shelf deposits. A detailed reservoir characterization/simulation study, recently performed as part of a Department of Energy Reservoir Class Oil Field Demonstration Project, has led to important revision in explanations for observed patterns of production. Cores recovered from three new data wells identify three main facies: spicule-rich wackestone-packstone, echinoderm wackestone/packstone/grainstone, and dolomitic mudstone-wackestone. Reservoir quality is highest in spicule-rich wackestone/packstones but is subject to a very high degree of vertical heterogeneity due to facies interbedding, silification, and variable natural fracturing. The oil reservoir is underlain by an active aquifer, which helps maintain reservoir pressure but supports significant water production. Reservoir simulation, using public-domain, PC-based software, suggests that infill drilling is an efficient approach to enhanced recovery. Recent drilling directed by simulation results has shown considerable success in improving field production rates. Results from the Schaben field demonstration project are likely to have wide application for independent oil and exploration companies in western Kansas.

Kansas↗
USGS1977

Lisburne Group (Mississippian and Pennsylvanian), potential major hydrocarbon objective of Arctic Slope, Alaska

The Lisburne Group, a thick carbonate-rock unit of Mississippian and Pennsylvanian age, is one of the most widespread potential reservoir-rock units in northern Alaska. A comprehensive review of the Lisburne in the subsurface of the eastern Arctic Slope indicates attractive reservoir characteristics in a favorable source and migration setting where numerous trapping mechanisms appear to be available. Evaluation of this group as a potential exploration objective is particularly timely because of impending offshore sales in the Beaufort Sea and current exploration programs under way in the Prudhoe Bay area and the Naval Petroleum Reserve. Dolomite and sandstone have been identified as reservoir rocks. Oolitic grainstone is a common rock type, but observations indicate little reservoir potential owing to complete void filling by calcite cement. The most important reservoir rock as judged by thickness, areal extent, and predictability is microsucrosic (10 to 30μ) dolomite of intertidal to supratidal origin. It is present throughout the Lisburne and is most abundant near the middle of the sequence. Northward it decreases in thickness from 1,000 ft (300 m) to less than 100 ft (30 m). Porosity of the dolomite as determined in selected wells averages between 10 and 15% and attains a maximum of slightly more than 25%. Net thickness of reservoir rocks (i.e., rocks with greater than 5% porosity) ranges in these wells from 140 to 390 ft (40 to 120 m). Oil shows are common, and drill-stem tests have yielded as much as 1,600 bbl/day of oil and 22 MMcf/day of gas in the Lisburne pool of the Prudhoe Bay field and as much as 2,057 bbl/day of salt water outside the field area. The occurrence of dolomite over such a large area makes its presence in the offshore Beaufort Sea and adjacent Naval Petroleum Reserve 4 fairly certain. The presence of sandstone as thick as 140 ft (40 m) in the middle and upper part of the Lisburne in two coastal wells suggests that larger areas of sandstone may be found on the north in offshore areas. Shows of oil and gas and a saltwater flow of 1,470 bbl/day have been recorded from this sandstone facies. Shales of Permian and Cretaceous ages unconformably overlie the Lisburne, providing adequate sealing beds above potential reservoirs. Impermeable limestone (completely cemented grainstone) and thin beds of shale may serve as seals within the Lisburne, but the possibility of fractures in these units may negate their sealing capability. The most favorable source rock for Lisburne hydrocarbons appears to be Cretaceous shale that unconformably overlies the Lisburne east of Prudhoe Bay. This shale is reported to be a rich source rock and is the most likely source for the entire Prudhoe Bay field. A source within the Lisburne or within the underlying Kayak Shale is postulated for oil shows in the southernmost Lisburne wells. This postulated source may be in a more basinal facies of the Lisburne and may be similar to dark shale in the upper Lisburne in thrust slices to dark shale in the upper Lisburne in thrust slices in the Brooks Range. Coal in the underlying Endicott Group is a possible source for dry gas. At present, much of this coal probably is in a gas-generating regime downdip from the Prudhoe Bay field. Stratigraphic traps involving the Lisburne Group may have resulted from widespread Permian and Cretaceous unconformities. Structural traps related to normal faulting may be present along the trend of the Barrow arch, and faulted anticlines are numerous in the foothills of the Brooks Range. Combination traps are possible along the trend of the Barrow arch.

Alaska↗
USGS2004

Chronostratigraphic and depositional sequences of the Fort Union formation (Paleocene), Williston Basin, North Dakota, South Dakota, and Montana

The Fort Union Formation in the Williston Basin of North Dakota, South Dakota, and Montana comprises chronostratigraphic and depositional sequences of Paleocene age. Individual chronostratigraphic sequences are defined by palynostratigraphic (pollen and spore) biozones and radiometric ( 40 Ar/ 39 Ar) ages obtained from tonsteins or volcanic ash layers. Analyses of depositional sequences are based on lithofacies constrained by the radiometric ages and biozones. The lower Paleocene (biozones P1-P3) contains three marine parasequences (landward stepping) in southwestern North Dakota that sequentially onlapped westward between 65 and 61 Ma (lower Ludlow and Cannonball Members). Maximum flooding (transgressive systems tract) occurred during an approximate 1-m.y. interval from 65 to 64 Ma, which regionally is correlated biostratigraphically to a tidally influenced, distributary-shoreface, and fluvial-channel complex in the Cave Hills, northwestern South Dakota, and to channel-dominated fluvial (low-stand incised paleovalley systems) and tidally influenced, flood-plain-deltaic transition facies in the Ekalaka area of southeastern Montana. The progradational parasequences in the Cannonball Member consist of shore-face sandstone beds (with ravinement lag deposits) deposited by strand-plain barrier systems. Landward of the barrier systems, tidal-estuarine and mire deposits included thick but laterally discontinuous peat accumulations (e.g., Beta and Yule coal beds in the Ludlow Member, southwestern North Dakota). However, landward of the coastal deposits, the laterally equivalent T-Cross-Big Dirty coal zone (dated 64.78 Ma) in southeastern Montana formed as thick, laterally extensive peat accumulations in mires in a fluvial setting. In the flood-plain-deltaic, tidal transition zone near Ekalaka, Montana, the Ludlow Member consists of flood-plain facies, discontinuous coal beds, and rooted and burrowed horizons that contain the marine or brackish trace fossil Skolithos. The flood-plain-deltaic tidal transition zone facies are incised by a massive, agglomerated channel sandstone complex (paleovalley fill) that is exposed along the modern Snow Creek drainage south of Mill Iron, Montana. The flood-plain-tidal transition zone was reworked during the maximum sea level highstand during the early Paleocene. This event was followed by a fall of sea level and deposition of the paleovalley fill. Sea level fall during the mid-Paleocene (biozones P3 and P4) produced a regressive shallow-marine and lower deltaic tidal system (seaward stepping) that deposited strata that thin toward the east. These strata are overlain by a widespread paleosol (Rhame bed) and, in turn, a lignite-bearing fluvial facies (Tongue River Member) containing the laterally persistent Harmon-Hanson coal zone (61.23 Ma). Upper Paleocene biozone P5 is represented by fluvial, coal-bearing strata that contain several economically minable coal beds (HT Butte, Hagel, and Beulah-Zap zones, Sentinel Butte Member). The Fort Union Formation of the Williston Basin contains significant coal resources. These coal deposits are now being explored for their potential coal-bed gas resources. A better understanding of the depositional setting for these deposits can lead to improved exploration and exploitation practices and a better understanding of regional paleogeography and paleoclimate during the Paleocene.

Montana, North Dakota, South Dakota↗
USGS2017

A validation of 11 body-condition indices in a giant snake species that exhibits positive allometry

Body condition is a gauge of the energy stores of an animal, and though it has important implications for fitness, survival, competition, and disease, it is difficult to measure directly. Instead, body condition is frequently estimated as a body condition index (BCI) using length and mass measurements. A desirable BCI should accurately reflect true body condition and be unbiased with respect to size (i.e., mean BCI estimates should not change across different length or mass ranges), and choosing the most-appropriate BCI is not straightforward. We evaluated 11 different BCIs in 248 Burmese pythons ( Python bivittatus ), organisms that, like other snakes, exhibit simple body plans well characterized by length and mass. We found that the length-mass relationship in Burmese pythons is positively allometric, where mass increases rapidly with respect to length, and this allowed us to explore the effects of allometry on BCI verification. We employed three alternative measures of ‘true’ body condition: percent fat, scaled fat, and residual fat. The latter two measures mostly accommodated allometry in true body condition, but percent fat did not. Our inferences of the best-performing BCIs depended heavily on our measure of true body condition, with most BCIs falling into one of two groups. The first group contained most BCIs based on ratios, and these were associated with percent fat and body length (i.e., were biased). The second group contained the scaled mass index and most of the BCIs based on linear regressions, and these were associated with both scaled and residual fat but not body length (i.e., were unbiased). Our results show that potential differences in measures of true body condition should be explored in BCI verification studies, particularly in organisms undergoing allometric growth. Furthermore, the caveats of each BCI and similarities to other BCIs are important to consider when determining which BCI is appropriate for any particular taxon.

PLoS ONE↗
USGS2017

Translating statistical species-habitat models to interactive decision support tools

Understanding species-habitat relationships is vital to successful conservation, but the tools used to communicate species-habitat relationships are often poorly suited to the information needs of conservation practitioners. Here we present a novel method for translating a statistical species-habitat model, a regression analysis relating ring-necked pheasant abundance to landcover, into an interactive online tool. The Pheasant Habitat Simulator combines the analytical power of the R programming environment with the user-friendly Shiny web interface to create an online platform in which wildlife professionals can explore the effects of variation in local landcover on relative pheasant habitat suitability within spatial scales relevant to individual wildlife managers. Our tool allows users to virtually manipulate the landcover composition of a simulated space to explore how changes in landcover may affect pheasant relative habitat suitability, and guides users through the economic tradeoffs of landscape changes. We offer suggestions for development of similar interactive applications and demonstrate their potential as innovative science delivery tools for diverse professional and public audiences.

PLoS ONE↗
USGS2024

Does daily activity overlap of seven mesocarnivores vary based on human development?

Many species of wildlife alter their daily activity patterns in response to co-occurring species as well as the surrounding environment. Often smaller or subordinate species alter their activity patterns to avoid being active at the same time as larger, dominant species to avoid agonistic interactions. Human development can complicate interspecies interactions, as not all wildlife respond to human activity in the same manner. While some species may change the timing of their activity to avoid being active when humans are, others may be unaffected or may benefit from being active at the same time as humans to reduce predation risk or competition. To further explore these patterns, we used data from a coordinated national camera-trapping program (Snapshot USA) to explore how the activity patterns and temporal activity overlap of a suite of seven widely co-occurring mammalian mesocarnivores varied along a gradient of human development. Our focal species ranged in size from the large and often dominant coyote ( Canis latrans ) to the much smaller and subordinate Virginia opossum ( Didelphis virginiana ). Some species changed their activity based on surrounding human development. Coyotes were most active at night in areas of high and medium human development. Red fox ( Vulpes vulpes ) were more active at dusk in areas of high development relative to areas of low or medium development. However, because most species were primarily nocturnal regardless of human development, temporal activity overlap was high between all species. Only opossum and raccoon ( Procyon lotor ) showed changes in activity overlap with high overlap in areas of low development compared to areas of moderate development. Although we found that coyotes and red fox altered their activity patterns in response to human development, our results showed that competitive and predatory pressures between these seven widespread generalist species were insufficient to cause them to substantially alter their activity patterns.

PLoS ONE↗
USGS2025

New technology for an ancient fish: A lamprey life cycle modeling tool with an R Shiny application

Lampreys (Petromyzontiformes) are an ancient group of fishes with complex life histories. We created a life cycle model that includes an R Shiny interactive web application interface to simulate abundance by life stage. This will allow scientists and managers to connect available demographic information in a framework that can be applied to questions regarding lamprey biology and conservation. We used Pacific lamprey ( Entosphenus tridentatus ) as a case study to highlight the utility of this model. We applied a global sensitivity analysis to explore the importance of individual life stage parameters to overall population size, and to better understand the implications of existing gaps in knowledge. We also provided example analyses of selected management scenarios (dam passage, fish translocations, and hatchery additions) influencing Pacific lamprey in fresh water. These applications illustrate how the model can be applied to inform conservation efforts. This tool will provide new capabilities for users to explore their own questions about lamprey biology and conservation. Simulations can hone hypotheses and predictions, which can then be empirically tested in the real world.

PLoS ONE↗
USGS2005

Conclusion

This book has presented what is known about the extent and causes of amphibian population declines in the United States and what can be done about them. It has also examined life history and natural history features needed to manage for amphibians, with a current assessment of their distribution. In assembling the literature for this project, and with a quick look at the species accounts, what is immediately noticeable is that a few species are well known and have a large literature, some species are better known and have a modest literature, and many species are almost unknown. An existing scientific literature creates a future scientific literature and results in a species bias. Workers are strongly encouraged to explore species that are not well known and to seek questions from field observations. Scientists must also explore creative new techniques for observing and monitoring inconvenient animals.

Book chapter↗
USGS2010

Trace elements have limited utility for studying migratory connectivity in shorebirds that winter in Argentina

Trace-element analysis has been suggested as a tool for the study of migratory connectivity because (1) trace-element abundance varies spatially in the environment, (2) trace elements are assimilated into animals' tissues through the diet, and (3) current technology permits the analysis of multiple trace elements in a small tissue sample, allowing the simultaneous exploration of several elements. We explored the potential of trace elements (B, Na, Mg, Al, Si, P, S, K, Ca, Ti, Cr, Mn, Ni, Cu, Zn, As, Sr, Cs, Hg, Tl, Pb, Bi, Th, and U) to clarify the migratory connectivity of shorebirds that breed in North America and winter in southern South America. We collected 66 recently replaced secondary feathers from Red Knots (Calidris canutus) at three sites in Patagonia and 76 from White-rumped Sandpipers (C. fuscicollis) at nine sites across Argentina. There were significant differences in trace-element abundance in shorebird feathers grown at different nonbreeding sites, and annual variability within a site was small compared to variability among sites. Across Argentina, there was no large-scale gradient in trace elements. The lack of such a gradient restricts the application of this technique to questions concerning the origin of shorebirds to a small number of discrete sites. Furthermore, our results including three additional species, the Pectoral Sandpiper (C. melanotos), Wilson's Phalarope (Phalaropus tricolor), and Collared Plover (Charadrius collaris), suggest that trace-element profiles change as feathers age. Temporal instability of trace-element values could undermine their application to the study of migratory connectivity in shorebirds. ?? The Cooper Ornithological Society 2010.

Condor↗
USGS2014

The persistent problem of lead poisoning in birds from ammunition and fishing tackle

Lead (Pb) is a metabolic poison that can negatively influence biological processes, leading to illness and mortality across a large spectrum of North American avifauna (>120 species) and other organisms. Pb poisoning can result from numerous sources, including ingestion of bullet fragments and shot pellets left in animal carcasses, spent ammunition left in the field, lost fishing tackle, Pb-based paints, large-scale mining, and Pb smelting activities. Although Pb shot has been banned for waterfowl hunting in the United States (since 1991) and Canada (since 1999), Pb exposure remains a problem for many avian species. Despite a large body of scientific literature on exposure to Pb and its toxicological effects on birds, controversy still exists regarding its impacts at a population level. We explore these issues and highlight areas in need of investigation: (1) variation in sensitivity to Pb exposure among bird species; (2) spatial extent and sources of Pb contamination in habitats in relation to bird exposure in those same locations; and (3) interactions between avian Pb exposure and other landscape-level stressors that synergistically affect bird demography. We explore multiple paths taken to reduce Pb exposure in birds that (1) recognize common ground among a range of affected interests; (2) have been applied at local to national scales; and (3) engage governmental agencies, interest groups, and professional societies to communicate the impacts of Pb ammunition and fishing tackle, and to describe approaches for reducing their availability to birds. As they have in previous times, users of fish and wildlife will play a key role in resolving the Pb poisoning issue.

The Condor↗
USGS2018

A new high-resolution map of world mountains and an online tool for visualizing and comparing characterizations of global mountain distributions

Answers to the seemingly straightforward questions “what is a mountain?” and “where are the mountains of the world?” are in fact quite complex, and there have been few attempts to map the mountains of the earth in a consistent and rigorous fashion. However, knowing exactly where mountain ecosystems are distributed on the planet is a precursor to conserving them, as called for in Sustainable Development Goals 6 and 15 of the United Nations 2030 Agenda for Sustainable Development. In this article we first compare 3 characterizations of global mountain distributions, including a new, high-resolution (250 m) map of global mountains derived from terrain characteristics. We show how differences in conceptual definition, methodology, and spatial resolution of source data can result in differences in the extent and location of lands classed as mountains. For example, the new 250-m resource documents a larger global mountain extent than previous characterizations, although it excludes plateaus, hilly forelands, and other landforms that are often considered part of mountain areas. We then introduce the Global Mountain Explorer, a new web-based application specifically developed for exploration, visualization, and comparison of these maps. This new open-access tool is an intuitive and versatile resource suitable for a broad range of users and applications.

Mountain Research and Development↗
USGS2011

Epistemic uncertainty in California-wide synthetic seismicity simulations

The generation of seismicity catalogs on synthetic fault networks holds the promise of providing key inputs into probabilistic seismic-hazard analysis, for example, the coefficient of variation, mean recurrence time as a function of magnitude, the probability of fault-to-fault ruptures, and conditional probabilities for foreshock–mainshock triggering. I employ a seismicity simulator that includes the following ingredients: static stress transfer, viscoelastic relaxation of the lower crust and mantle, and vertical stratification of elastic and viscoelastic material properties. A cascade mechanism combined with a simple Coulomb failure criterion is used to determine the initiation, propagation, and termination of synthetic ruptures. It is employed on a 3D fault network provided by Steve Ward (unpublished data, 2009) for the Southern California Earthquake Center (SCEC) Earthquake Simulators Group. This all-California fault network, initially consisting of 8000 patches, each of ∼12 square kilometers in size, has been rediscretized into Graphic patches, each of ∼1 square kilometer in size, in order to simulate the evolution of California seismicity and crustal stress at magnitude M∼5–8. Resulting synthetic seismicity catalogs spanning 30,000 yr and about one-half million events are evaluated with magnitude-frequency and magnitude-area statistics. For a priori choices of fault-slip rates and mean stress drops, I explore the sensitivity of various constructs on input parameters, particularly mantle viscosity. Slip maps obtained for the southern San Andreas fault show that the ability of segment boundaries to inhibit slip across the boundaries (e.g., to prevent multisegment ruptures) is systematically affected by mantle viscosity.

California↗
USGS2019

Ensembles of ETAS models provide optimal operational earthquake forecasting during swarms: Insights from the 2015 San Ramon, California swarm

Earthquake swarms, typically modeled as time-varying changes in background seismicity that are driven by external processes such as fluid flow or aseismic creep, present challenges for operational earthquake forecasting. While the time decay of aftershock sequences can be estimated with the modified Omori law, it is difficult to forecast the temporal behavior of seismicity rates during a swarm. To explore these issues, we apply the Epidemic-Type Aftershock Sequence (ETAS) model (Ogata, JASA, 1988) to the 2015 San Ramon, California swarm, which lasted several weeks and had almost 100 2≤M≤3.6 earthquakes. We develop 3-day forecasts during the swarm based on an ETAS model fit to all prior seismicity in the region as well as an ETAS model fit only to previous swarms in the region, which is better at capturing the higher background rate during the swarm. We also explore forecasts where the background rate is updated periodically during the swarm using data over different lookback windows and find that generally these models perform better than the models where the background rate is fixed. Finally, we construct ensemble forecasts by combining the different models weighted according to their performance. The ensemble forecasts outperform all of the individual models and allow us to avoid making arbitrary choices at the outset of a swarm as to which single model will perform the best.

California↗
USGS2022

Active‐source interferometry in marine and terrestrial environments: Importance of directionality and stationary phase

We utilize active‐source seismic interferometry with dense seismic arrays both offshore and onland to explore the utility of this method to create virtual sources and reveal body‐wave reflections in these two different environments. We first utilize data from an ocean‐bottom cable (OBC) array in the Gulf of Mexico with equal numbers of sources (160 airgun shots) and receivers (160 ocean‐bottom four‐component sensors). We next use data from a geophone array across the Bighorn Mountains of Wyoming with many receivers (1300 vertical‐component geophones) but a small number of sources (14 borehole active‐source shots). We find that the OBC virtual source results, which produce strong reflections from sub‐seafloor structures, are far superior to the onland results which lack usable reflections, and we explore reasons for these differences through a set of selective stacking approaches. We present techniques to account for the direction the seismic waves travel (directionality) and stationary phase and show that improvements can be made when incorporating these corrections. Although interferometric methods are based on assumptions of large numbers of widely distributed actual sources, we find that selective exclusion of potentially problematic source–receiver pairs can yield improved results. These geometric adjustments to active‐source interferometry methods have utility for dense‐nodal‐array surveys that are now common in academic studies, but that often suffer from sparse source geometry.

Bulletin of the Seismological Society of America↗
USGS2022

An efficient, analytic solution using order statistics for probabilistic seismic‐hazard assessment without the Poisson assumption

Standard approaches to probabilistic seismic‐hazard assessment (PSHA) assume that earthquakes are random, independent events that follow a Poisson distribution of occurrences in a given time period ( Cornell, 1968 ). To overcome the limitations of the Poisson assumption, such as ignoring earthquake clustering, we introduce an analytic method for PSHA that uses order statistics to allow for arbitrary distributions of earthquake occurrence. Cornell (1968) used the Poisson assumption to achieve a computationally efficient method that enables users to explore the impact of parameters used in earthquake occurrence and ground‐motion models. We apply our order statistics method to the highly clustered seismicity associated with caldera collapses at Kīlauea and explore the general implications of non‐Poisson behavior for PSHA. We find that non‐Poisson behavior has the greatest impact for high probabilities of exceedance, low‐mean rates of occurrence, and multiple exceedances. Those conditions can be important for applications such as operating standards for buildings and infrastructure engineering, standards for temporary structures and during construction, the insurance industry, the design of earthquake early warning, and to assess hazards due to clustered processes such as aftershock sequences and earthquake swarms. The commonly used rate of exceedance hides the difference between the hazard due to a non‐Poisson distribution and a Poisson distribution with the same mean rate of earthquakes. Thus, including non‐Poisson behavior in PSHA means that we must plot and discuss PSHA results as the probability and not the rate of exceedance.

Bulletin of the Seismological Society of America↗