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At least 991 records · Page 55Linked to original sources
USGS1983

Electrical and magnetic properties of rock and soil

Field and laboratory measurements have been made to determine the electrical conductivity, dielectric constant, and magnetic permeability of rock and soil in areas of interest in studies of electromagnetic pulse propagation. Conductivity is determined by making field measurements of apparent resisitivity at very low frequencies (0-20 cps), and interpreting the true resistivity of layers at various depths by curve-matching methods. Interpreted resistivity values are converted to corresponding conductivity values which are assumed to be applicable at 10^2 cps, an assumption which is considered valid because the conductivity of rock and soil is nearly constant at frequencies below 10^2 cps. Conductivity is estimated at higher frequencies (up to 10^6 cps) by using statistical correlations of three parameters obtained from laboratory measurements of rock and soil samples: conductivity at 10^2 cps, frequency and conductivity measured over the range 10^2 to 10^6 cps. Conductivity may also be estimated in this frequency range by using field measurements of water content and correlations of laboratory sample measurements of the three parameters: water content, frequency, and conductivity measured over the range 10^2 to 10^6 cps. This method is less accurate because nonrandom variation of ion concentration in natural pore water introduces error. Dielectric constant is estimated in a similar manner from field-derived conductivity values applicable at 10^2 cps and statistical correlations of three parameters obtained from laboratory measurements of samples: conductivity measured at 10^2 cps, frequency, and dielectric constant measured over the frequency range 10^2 to 10^6 cps. Dielectric constant may also be estimated from field measurements of water content and correlations of laboratory sample measurements of the three parameters: water content, frequency, and dielectric constant measured from 10^2 to 10^6 cps, but again, this method is less accurate because of variation of ion concentration of pore water. Special laboratory procedures are used to measure conductivity and dielectric constant of rock and soil samples. Electrode polarization errors are minimized by using an electrode system that is electrochemically reversible-with ions in pore water.

Open-File Report↗
USGS1953

The use of soils and paleosols for interpreting geomorphic and climatic history of arid regions

The study of modern surface soils, and ancient weathering zones, which occur either buried or as surface relicts, has contributed materially to understanding the complex events of the glacial and post-glacial period both in glaciated areas and in regions not influenced by glaciation. Most work of this kind in the United States has been done by geologists. Numerous Pleistocene geologists have noted weathered zones between sheets of glacial drift or loess in the middle western United States. These include Condra, et al 5 ; Frye 7 ; Frye and Leonard 8 ; Kay and Pearce 13 ; Leighton and MacClintock 15 ; Leverett 16 , 17 , 18 ; Lugn 19 ; Peltier 23 ; Schultz and Stout 26 ; Schultz, et al 27 ; and Simonson 28 . Kay and Pearce 13 interpreted the weathered zones between sheets of glacial drift as profiles of ancient soils which they referred to as gumbotil. Hseung, Marshall and Krusekopf 10 have recently questioned the pedogenic character of gumbotil, but have failed to offer a satisfactory alternative explanation. Thorp, and coworkers 30 , in a general review of buried soils, apparently consider gumbotil a product of ancient soil-forming processes.

Research Council of Israel Special Publication↗
USGS2000

Isotopic studies of authigenic sulfides, silicates and carbonates, and calcite and pyrite veinlets in the Creede Formation, San Juan Mountains, Southwest Colorado

Sulfur isotope analysis of authigenic pyrite in the Creede Formation documents its precipitation by the reaction between iron in the volcaniclastic sediments and H 2 S formed through bacteriogenic reduction of sulfate added to the lake during and immediately following repeated volcanic eruptions during sedimentation. Pyrite veinlets in the underlying Snowshoe Mountain Tuff were formed by the percolation of H 2 S-bearing pore waters into fractures in the tuff. Conventional analyses of bulk samples of authigenic pyrite range from -20.4% to 34.5% essentially equivalent to the range of -30% to 40% determined using SHRIMP microprobe techniques. Conventional analyses of bulk samples of pyrite from veinlets in the Snowshow Mountain Tiff range from -3.5% to 17.6% much more limited than the ranges of -23% to 111% and -15.6% to 67.0% determined by SHRIMP and laser ablation microbeam techniques, respectively. The extreme range of δ 34 S for the veinlets is interpreted to be the result of continued fractionation of the already 34 S-depleted pore water. Oxygen isotope analysis of authigenic smectite, kaolinite, and K-feldspar together with fluid-inclusion temperatures and oxygen isotope analysis of calcite coexisting with kaolinite indicate that the smectites formed early during burial diagenesis, in accord with petrographic observations. The 40 Ar/ 39 Ar dating of K-feldspar, concorfance of K-feldspar, kaolinite, and calcite δ 18 O values, and fluid-inclusion temperatures in calcite, indicate that the sediments at core hole CCM-1 were subjected to a hydrothermal event at 17.6 Ma. The minerals formed oxygen-shifted meteoric waters with δ 18 O values of ~-9% Smecities at CCM-1 at least partially exchanged with these waters. Carbon and oxygen isotope analysis of authigenic calcites in the Creede Formation show that they formed over a wide range of temperatures from fluids having a wide range of isotopic composition, presumably over an extended period time. Some of the cements apparently formed very late from unexchanged meteoric water. Concretions and possibly some cements at CCM-1 appear to have exchanged with the 17.6 Ma oxygen-shifted hydrothermal fluids. Such exchange is consistent with evidence that lacustrine carbonates at CCM-1 exchanged with low 18 O waters, whereas those at CCM-2 underwent little, if any, exchange. The δ 13 C-δ 18 O values for calcite veinlets in the Creede Formation are similar to those for authegenic calcites. Fluid-inclusion temperatures and δ 18 O indicate that some were deposited during the 17.6 Ma hydrothermal event and others from unexchanged meteoric water at a later date. The isotope studies confirm that part of the model of Rye et al., proposing that the barites in the southern end of the Creede Mining District were formed by mixing of the Creede hydrotermal system with Lake Creede pore of lake waters. The silicate and carbonate isotope data indicate that the pores of the Creede Formation were occupied by at least three isotopically distinct water since the time of deposition. The original pore fluids were probably shifted to lower δ 18 O values during burial diagensis as a result of the hydrolysis of the volcanic glass to for smectites and other hydrous silicates. During or prior to a 17.6 Ma hydrothermal event in the vicinity of CCM-1, the Creede Formation was flushed with oxygen-shifted meteoric water, possibly related to the breaching of the east side of the caldera wall sometime between 20 and 22 Ma. Later, the Creede Formation was again flushed, this time with unexchanged meteoric water with δD-δ 18 O values of present-day waters, possibly during the incision of the Rio Grande drainage during uplifting of the southern Rocky Mountains beginning about 5 Ma.

GSA Special Papers↗
USGS1987

Improving atlas methodology

We are studying a sample of Maryland (2 %) and New Hampshire (4 %) Atlas blocks and a small sample in Maine. These three States used different sampling methods and block sizes. We compare sampling techniques, roadside with off-road coverage, our coverage with that of the volunteers, and different methods of quantifying Atlas results. The 7 1/2' (12-km) blocks used in the Maine Atlas are satisfactory for coarse mapping, but are too large to enable changes to be detected in the future. Most states are subdividing the standard 7 1/2' maps into six 5-km blocks. The random 1/6 sample of 5-km blocks used in New Hampshire, Vermont (published 1985), and many other states has the advantage of permitting detection of some changes in the future, but the disadvantage of leaving important habitats unsampled. The Maryland system of atlasing all 1,200 5-km blocks and covering one out of each six by quarterblocks (2 1/2-km) is far superior if enough observers can be found. A good compromise, not yet attempted, would be to Atlas a 1/6 random sample of 5-km blocks and also one other carefully selected (non-random) block on the same 7 1/2' map--the block that would include the best sample of habitats or elevations not in the random block. In our sample the second block raised the percentage of birds found from 86% of the birds recorded in the 7 1/2' quadrangle to 93%. It was helpful to list the expected species in each block and to revise this list annually. We estimate that 90-100 species could be found with intensive effort in most Maryland blocks; perhaps 95-105 in New Hampshire. It was also helpful to know which species were under-sampled so we could make a special effort to search for these. A total of 75 species per block (or 75% of the expected species in blocks with very restricted habitat diversity) is considered a practical and adequate goal in these States. When fewer than 60 species are found per block, a high proportion of the rarer species are missed, as well as some of the common ones. Similarity indices based on fewer than 60 species per block reflect coverage rather than habitat affinities. Atlas blocks that are ecologically similar should have similarity indices (S) of at least 0.80 to be considered adequately covered. S = 2C/(A + B), where C is the number of species in common and A and B are species totals for each of the two blocks being compared. A series of 15 13-minutes roadside stops yielded more species than 15 off-road stops, but off-road stops always had some species not detected at the roadside stops. A series of timed stops is an excellent way to map relative abundance if the stops are standardized with respect to time of day and weather, and the counts are made by observers of comparable ability. Efforts to estimate Atlas block populations in powers of 10 (as in the French Atlas) have not gained acceptance in U.S.A. Most observers feel unqualified to make estimates. An efficient way to Atlas a block is to make at least 3 early morning visits to 15 or more specific stops. Arrive in the block early enough to check for nocturnal species on at least two days; and after completing the specific stops, search the block for other species and for confirmations.

Acta Oecologica Oecologia Generalis↗
USGS1986

The non-transferability of a Cretaceous coal model in the San Juan Basin of New Mexico and Colorado

The San Juan Basin of northwest New Mexico and southwest Colorado contains several Upper Cretaceous coal-bearing formations. The coals in these formations were deposited in environments associated with repeated transgressions and regressions of the Western Interior seaway in Late Cretaceous time. A detailed subsurface and surface study of the coal beds in one of these units, the Fruitland Formation, formed the basis for a coal-depositional model (Fassett and Hinds, 1971). This model basically shows that the thickest Fruitland coals formed landward of thickly stacked sandstone beds of the regressive-marine Pictured Cliffs Sandstone. Transferability of the Fruitland coal model was tested by comparing it to another San Juan Basin coal-bearing rock unit, the lower Menefee Formation. Lower Menefee coal deposits were formed in association with the Point Lookout Sandstone, an older regressive-marine unit. The purpose of this comparison was to see if thick lower Menefee coal beds were also concentrated adjacent to thick vertical shoreface-sandstone buildups. This comparison showed that even though thick sandstone buildups were found in the Point Lookout, no thick coal beds were found in the lower Menefee Formation adjacent to them. This test suggests that certain coal depositional models may have limited value as predictive tools and must be used with caution by coal explorationists. Even more importantly, potential coal-bearing areas should never be written off simply because they do not fit a previously described model.

Colorado, New Mexico↗
USGS2011

The Haleakala Argentine ant project: A synthesis of past research and prospects for the future

1. The Haleakala Argentine Ant Project is an ongoing effort to study the ecology of the invasive Argentine ant in the park, and if possible to develop a strategy to control this destructive species. 2. Past research has demonstrated that the Argentine ant causes very significant impacts on native arthropods where it invades, threatening a large portion of the park’s biodiversity in subalpine shrubland and alpine aeolian ecosystems. 3. Patterns of spread over the past 30+ years indicate that the invasion process is influenced to a substantial degree by abiotic factors such as elevation, rainfall and temperature, and that the ant has not reached its potential range. Predictions of total range in the park suggest that it has only invaded a small fraction of available suitable habitat, confirming that this species is one of most serious threats to the park’s natural resources. 4. Numerous experiments have been conducted since 1994 in an attempt to develop a method for eradicating the Argentine ant at Haleakala using pesticidal ant baits. Thirty baits have been screened for attractiveness to ants in the park, and ten of these were tested for effectiveness of control in field plots. While some of these baits have been very effective in reducing numbers of ants, none has been able to eliminate all nests in experimental plots. 5. Research into a secondary management goal of ant population containment was initiated in 1996. By treating only expanding margins of the park’s two ant populations with an ant pesticide, rates of outward spread were substantially reduced in some areas. While this strategy was implemented from 1997 to 2004, it was ultimately discontinued after 2004 because of the difficulty and insufficient effectiveness of the technique. 6. In order to achieve the types of results necessary for eradication, the project would probably need to explore the possibility of developing a specialized bait, rather than relying on a commercially produced bait. An alternative would be to pursue approval to use Xstinguish bait, a commercial bait manufactured in New Zealand and not registered for use in the US, which has yielded good results against Argentine ants. Either route would involve significant regulatory hurdles. Because the baits ultimately used would likely be liquid or paste in form, there would also be major logistical challenges in devising methods to successfully apply the baits across the two large ant populations at Haleakala.

Technical Report↗
USGS2024

2023-2024 Coastal sage scrub and chaparral community monitoring for western San Diego County

Western San Diego County is dominated by shrublands supporting biologically diverse native plant and animal communities. Widespread urbanization has led to regional habitat loss and fragmentation, and many species in these shrubland communities are rare, threatened, or endangered. Large-scale, multiple-species conservation planning has resulted in a regional preserve system that focuses on these shrubland communities. Several large-scale threats are leading to type conversion from shrub-dominated to non-native invasive annual grass-dominated vegetation. To understand the changes that are occurring to native shrublands, we have developed a vegetation monitoring program with several components at multiple spatial scales, focused on quantifying coastal sage scrub (CSS) and chaparral vegetation community characteristics. Several drivers of change associated with type conversion of native shrubland to non-native annual grassland have been identified by previous research including increasing fire frequency, nitrogen deposition from air pollution, and prolonged and intense drought associated with changing climate. Loss of ecological integrity indices have been proposed as useful measures of the threat of degradation and type conversion of shrublands in San Diego County. For this study, ecological integrity is defined as a system’s ability to maintain species’ relationships and functions comparable to natural habitat in the region. Previous studies have identified the percent cover of invasive non-native annual grasses as a proxy for overall ecological degradation (loss of integrity) that is consistent across native taxonomic groups. Increased cover of non-native grass is associated with lower integrity of the shrubland vegetation community as shrub-associated plant and animal species are replaced by species preferring grassy and disturbed habitats. The objectives of this CSS and chaparral vegetation community monitoring plan are to: 1) Determine the distribution, composition, structure, and integrity of CSS and chaparral vegetation communities on conserved lands in western San Diego County, 2) Identify whether these attributes of the vegetation communities are changing over time, and 3) Evaluate relationships of known drivers of change (threats) and environmental factors in association with changes in vegetation community attributes. The CSS and chaparral vegetation community monitoring program is divided into four components: 1) vegetation mapping, 2) GIS/remote sensing office analysis of landscape-scale data, 3) permanent field plots using Unmanned Aerial Systems (UAS) and field data collections, and 4) animal and target species surveys and rapid assessment protocols. The first component, which is not detailed in this vegetation monitoring plan, aims to map vegetation communities every 10-15 years based on a classification developed for western San Diego County. High resolution aerial imagery will be used to update the 2012 vegetation map and expand it across the entire study area. The second component uses remote sensing models to annually track ecological integrity of shrublands across the study area and will include a map of areas of change and areas of stability over several decades. These landscape-scale integrity classifications will be used to analyze ecological processes, threats, and abiotic factors relative to changes to shrubland ecological integrity over time and space. The third component includes field surveys of 100 permanent plots across areas historically mapped as shrublands. Surveys in the 1930s mapped vegetation types using plot data. By using this historical classification map, we included areas that have already type-converted from shrubland to non-native annual grassland. The plots were split between CSS (55 plots) and chaparral (45 plots) and stratified into four geographical eco-subregions to guarantee coverage over small patches of habitat along the heavily developed coast. Surveys will include the collection of UAS imagery at a very high resolution. Species-level identifications will be made from the imagery based on a plant list compiled of all species detected in the plot during a thorough field survey by botanists, combined with geo-referenced samples of plant species locations. In addition, herbaceous cover will be estimated in the field using nine 1-m diameter circles (one per subplot) to obtain ocular estimates of cover for each plant species within the circle frame. Soil samples will be collected and analyzed for important element compositions. These data will be analyzed to evaluate plot-level ecological integrity based on species composition and cover. Repeated monitoring will allow evaluation of changes in vegetation attributes over time with known drivers or threats and other environmental factors. In addition, analyses will focus on indicator species and various measures of biological diversity for the vegetation communities. Finally, animal species and rare plants will be assessed using either taxa-based rapid assessment protocols or specialized species-specific protocols for rarer species. The purpose of these assessments is to document the status, habitat, and threat covariates of specific species and confirm the species composition and diversity of animal taxonomic groups (e.g., pollinators). Diversity and abundance of animal species at vegetation plots will be used to refine measures and thresholds of ecological integrity. Rapid assessment protocols for animal taxonomic groups can include multiple detection methods such as, camera traps, cover boards, and bird point counts. Pollinators will be monitored at plots using a protocol currently being developed in conjunction with but separately from this plan. Target rare plant species will be monitored using the regional Inspect and Manage (IMG) protocol that measures the status of rare plant occurrences and habitat and threat covariates over time. Species-specific animal survey methods will be refined as these species are prioritized for future monitoring. The goal of this monitoring program is to classify CSS and chaparral vegetation community integrity, identify areas of degradation across western San Diego County, and characterize drivers, and environmental factors associated with loss of ecological integrity. A combination of vegetation mapping, landscape-scale remote sensing, and field plots will be used to address all the aspects of our research questions. Data compiled and collected will be available to conservation partners to help inform future management decisions.

California↗
USGS2025

2022–2024 Status and trends of the Palila (Loxioides bailleui)

Palila (Loxioides bailleui) are critically endangered Hawaiian honeycreepers specializing on the seedpods of māmane (Sophora chrysophylla) and restricted to Mauna Kea volcano on the Island of Hawaiʻi. A previous analysis of survey data estimated an 89% population decline between 1998 and 2021. Using the most recent annual survey data from 2022, 2023, and 2024, we report updated annual population estimates and trends since 1998. The 2022 population estimate was 367–742 birds (point estimate: 545); the 2023 population estimate was 374–842 birds (point estimate: 596); and the 2024 population estimate was 412–970 birds (point estimate: 666). Our estimates for survey years prior to 2022 were within the confidence intervals of the estimates from the previous analysis. Our models likewise showed a population fluctuating between 4,000 and 6,800 birds from 1998 to 2005 (except for an unusually low estimate in 2000), and then a steep decline through 2010. For the next decade, palila abundance fluctuated between 776 and 1,346 birds, before declining again in 2021 to 679 birds. From 1998 to 2024, the population declined by >90% or 203 birds/year, with very strong statistical evidence of an overall downward trend.

Hawaii↗
USGS1979

Seismic, magnetic, and geotechnical properties of a landslide and clinker deposits, Powder River basin, Wyoming and Montana

Exploitation of vast coal and other resources in the Powder River Basin has caused recent, rapid increases in population and in commercial and residential development and has prompted land utilization studies. Two aspects of land utilization were studied for this report: (1) the seismic and geotechnical properties of a landslide and (2) the seismic, magnetic, and geotechnical properties of clinker deposits. (1) The landslide seismic survey revealed two layers in the slide area. The upper (low-velocity) layer is a relatively weak mantle of colluvium and unconsolidated and weathered bedrock that ranges in thickness from 3.0 to 7.5 m and has an average seismic velocity of about 390 m/s. It overlies high-velocity, relatively strong sedimentary bedrock that has velocities greater than about 1330 m/s. The low-velocity layer is also present at the other eight seismic refraction sites in the basin; a similar layer has also been reported in the Soviet Union in a landslide area over similar bedrock. The buried contact of the low- and high-velocity layers is relatively smooth and is nearly parallel with the restored topographic surface. There is no indication that any of the high-velocity layer (bedrock) has been displaced or removed. The seismic data also show that the shear modulus of the low-velocity layer is only about one-tenth that of the high-velocity layer and the shear strength (at failure) is only about one-thirtieth. Much of the slide failure is clearly in the shear mode, and failure is, therefore, concluded to be confined to the low-velocity layer. The major immediate factor contributing to landslide failure is apparently the addition of moisture to the low-velocity layer. The study implies that the low-velocity layer can be defined over some of the basin by seismic surveys and that they can help predict or delineate potential slides. Preventative actions that could then be taken include avoidance, dewatering, prevention of saturation, buttressing the toe, and unloading the head. The low-velocity layer is usually less than about 5 m thick and may be excavated by dozing, whereas the bedrock must be blasted. Thus, it would seem economically feasible to underpin a structure to nonweathered bedrock or, perhaps, to remove the low-velocity layer prior to construction. (2) Many coal beds in the Powder River Basin have burned along their outcrops, and the resulting intense heat has baked and fused the overlying clastic (sedimentary) rocks into clinkers. The clinkers are very magnetic and a buried edge of a single layer of burn can easily be located by magnetic prospecting methods. Location of the edge is very important in estimating unburned coal deposits, locating clinker quarries, and planning drilling of seismic reflection lines. The clinkers are very porous and highly fractured,-and seismic and geotechnical tests show that they have relatively low strength and competency. Many of the laboratory tests, however, are inherently biased because the clinkers are so highly fractured that only competent samples are selected. The laboratory tests, for example, show that clinkers must be loosened by heavy ripping tractors or blasting, whereas the field data and practical experience indicate that clinkers may be mined with light equipment. Heavy structures such as coal silos and bridge abutments may have to be sited on clinkers. However, differential settlement may occur, with failure in the shear mode, because chimneys of relatively greater strength occur among the weaker clinkers. Preliminary data indicate that the chimneys may be located by magnetic or possibly seismic surveys. Special foundation-preparation techniques could be used or, perhaps, the chimneys could be avoided altogether at a construction site.

Open-File Report↗
USGS2008

Temporal Differences in Flow Depth and Velocity Distributions and Hydraulic Microhabitats Near Bridges of the Lower Platte River, Nebraska, 1934-2006

As part of a collaborative study of the cumulative impacts on stream and riparian ecology of water and channel management practices in the lower Platte River, Nebraska, this report describes a study by the U.S. Geological Survey in cooperation with the Lower Platte South Natural Resources District that summarizes: (1) temporal differences in distribution of streamflow depth, velocity, and microhabitats among five discrete 11-water-year periods 1934-44, 1951-61, 1966-76, 1985-95, and 1996-2006, and (2) the effects of bridge proximity on distribution of streamflow depth, velocity, and microhabitat of the Platte River when cross sections were measured at a similar discharge. The scope of the study included the four presently (2008) active streamflow-gaging stations located near bridges over the lower Platte River at North Bend, near Leshara, near Ashland, and at Louisville, Nebraska, and the most downstream streamflow-gaging station within the central Platte River segment near Duncan, Nebraska. Generally, in cases where temporal differences in streamflow depth and velocity were evident, at least one of the water-year periods from 1934 through 1995 had deeper streamflow than the recent water-year period (1996-2006). Temporal differences in distributions of streamflow depth were not strongly associated with differences in either climatic conditions or the maximum peak flow that occurred prior to the latest discharge measurement during each period. The relative cross-sectional area of most hydraulic niches did not differ among the water-year periods. Part of this apparent uniformity likely was an artifact of the broad microhabitat classification used for this study. In cases where temporal differences in relative cross-sectional area of hydraulic niches were evidenced, the differences occurred during high- and low-flow conditions, not during median flow conditions. The temporal differences in relative cross-sectional area were found more frequently for hydraulic niches defined by moderate and fast velocities than for hydraulic niches defined by slow velocities. Generally, any significant increase or decrease in the relative cross-sectional areas of hydraulic niches during the water-year periods from 1934 through 1995 had disappeared during the most recent water-year period, 1996-2006. Deep-Swift niche was the predominant hydraulic niche for all near-bridge sites on the lower Platte River for high- and median-flow conditions. The Deep-Swift niche also was the predominant niche for the near-bridge sites near Ashland and at Louisville for low-flow conditions; for the near-bridge sites at North Bend and near Leshara, streamflow cross-sectional areas during low-flow conditions were shared among the Shallow-Moderate, Intermediate-Moderate, Intermediate-Swift, and Deep-Swift hydraulic niches. For the near-bridge site near Duncan, the site farthest downstream in the central Platte River system, the Deep-Swift hydraulic niche was predominant only during high-flow conditions; during median- and low-flow conditions the relative cross-sectional area was shared among the Shallow-Slow, Shallow-Moderate, Intermediate-Moderate, and Intermediate-Swift hydraulic niches. Significant temporal differences in the relative cross-sectional area of the Deep-Swift hydraulic niche were found for sites near the two farthest downstream bridges near Ashland and at Louisville, but only for low-flow conditions. The Deep-Swift microhabitat was of special interest because it is the preferred hydraulic habitat during the adult life of the endangered pallid sturgeon (Scaphirhynchus albus). Temporal differences in relative cross-sectional areas of the Glide low-flow geomorphic microhabitat that contained the Deep-Swift hydraulic niche also indicated that relative cross-sectional areas of the Glide during the 1951-61 and 1996-2006 water-year periods were lower than during the 1966-76 period. The temporal differences indicated that any significant temporal chang

Scientific Investigations Report↗
USGS2007

A ground penetrating radar investigation of a glacial-marine ice- contact delta, Pineo Ridge, eastern coastal Maine

In eastern coastal Maine, many flat-topped landforms, often identified as glacial-marine deltas, are cultivated for blueberry production. These agriculturally valuable features are not exploited for aggregate resources, severely limiting stratigraphic exposure. Coring is often forbidden; where permissible, coarse-grained surficial sediments make coring and sediment retrieval difficult. Ground penetrating radar (GPR) has become an invaluable tool in an ongoing study of the otherwise inaccessible subsurface morphology in this region and provides a means of detailing the large-scale sedimentary structures comprising these features. GPR studies allow us to reassess previous depositional interpretations and to develop alternative developmental models. The work presented here focuses on Pineo Ridge, a large, flat-topped ice-marginal glacial-marine delta complex with a strong linear trend and two distinct landform zones, informally termed East Pineo and West Pineo. Previous workers have described each zone separately due to local morphological variation. Our GPR work further substantiates this geomorphic differentiation. East Pineo developed as a series of deltaic lobes prograding southward from an ice-contact margin during the local marine highstand. GPR data do not suggest postdepositional modification by ice-margin re-advance. We suggest that West Pineo has a more complex, two-stage depositional history. The southern section of the feature consists of southward-prograding deltaic lobes deposited during retreat of the Laurentide ice margin, with later erosional modification during marine regression. The northern section of West Pineo formed as a series of northward-prograd- ing deltaic lobes as sediment-laden meltwater may have been diverted by the existing deposits of the southern section of West Pineo. ?? 2007 The Geological Society of America. All rights reserved.

Special Paper of the Geological Society of America↗
USGS1972

Clay deposits of the Connecticut River Valley, Connecticut: a special problem in land management

When man first settled the United States, two natural features favored settlement; flat land that was easy to build on and to farm, and a nearby river that could act as a source of water, transportation, and power. The Connecticut River Valley from Middletown, Ct. north past the Connecticut-Massachusetts state line satisfied these two needs, and was favored by many early Americans in New England. This area remains an area of rapid urbanization, partly because of the broad flat lowlands. The subdued topography of this area is due in large part to deposition of fine-grained materials into glacial Lake Hitchcock. This lake was formed during the Wisconsinan age when southward drainage in the Triassic valley of Connecticut was dammed by glacial drift in the area of Rocky Hill, Connecticut. Lake Hitchcock grew to and beyond St. Johnsbury, Vt. with much of the lake being filled with cyclical lake-bottom deposits during the 2,290 to 2,350 years of its life. Aside from the relative flatness inherent in the deposition of fine-grained lake-bottom deposits, these deposits present very few characteristics that are favorable for urbanization. Favorable characteristics are possible sources of clay for manufacturing and possible sources for waste storage sites. Unfavorable characteristics include low water yields resulting in poor urban water-supply sources, and very low flows in streams during dry periods; low percolation rates resulting In drainage and septic problems; and low or uneven bearing strength which create problems in construction. Fine-grained lake-bottom deposits have been mapped for six quadrangles in the Connecticut Valley lowlands; the quadrangles of Windsor Locks, Broad Brook, Hartford North, Manchester, Hartford South, and Glastonbury (all located in Connecticut). All the maps were prepared from existing information including well and test hole data on file at the Water Resources Division in Hartford, surficial geologic quadrangle maps, and bedrock contour maps. The maps also reflect geologic interpretations of the history of glacial Lake Hitchcock. The Hartford North maps were prepared as test maps to determine if the project was feasible. They were prepared using the previously described information plus additional subsurface data obtained from engineering firms and the State Highway Department. During preparation of the maps, an arcuate-shaped, ice-contact deposit composed of coarse sand and gravel was delineated in the Broad Brook and Windsor Locks quadrangles. This feature marks the location of a zone of stagnant ice In front of and marginal to active ice to the north. Two types of maps were prepared for the area in study; Thickness of the Principal Clay Deposit, and Thickness of Material Overlying the Principal Clay Deposit. The term "principal clay deposit" refers to the fine-grained lake-bottom deposits of Glacial Lake Hitchcock. These maps define the distribution of the deposit, and show the thickness of the deposit in 50 foot intervals and the thickness of the material overlying the deposit In 20 foot intervals. The maps indicate that much of the area is underlain with substantial thicknesses of finegrained lake-bottom deposits (50 feet thick or greater), and that much of the deposit is within 20 feet of the surface. The maps included in this report can be used for land-use planning. Uses include location of favorable sites for specific uses such as landfills, utility corridors, heavy construction, etc; location of problem areas for specific land uses; identification of possible problems for specific areas; design and construction cost estimates; and prospecting for exploitable clay deposits. It Is suggested that, for effective planning, these maps be used together or in conjunction with other maps such as maps showing surface materials, depth to bedrock, depth to water table, and flood prone areas.

Connecticut↗
USGS2007

Pygmy rabbit surveys on state lands in Oregon

The pygmy rabbit (Brachylagus idahoensis) is classified by the federal government as a species of concern (i.e., under review by the U.S. Fish and Wildlife Service for consideration as a candidate for listing as threatened or endangered under the Endangered Species Act) because of its specialized habitat requirements and evidence of declining populations. The Oregon Department of Fish and Wildlife (ODFW) lists pygmy rabbits as “sensitive-vulnerable,” meaning that protective measures are needed if sustainable populations are to be maintained over time (Oregon Natural Heritage Program, 2001). The Oregon Natural Heritage Program considers this species to be threatened with extirpation from Oregon. Pygmy rabbits also are a species of concern in all the other states where they occur (NatureServe, 2004). The Washington population, known as the Columbia Basin pygmy rabbit, was listed as endangered by the federal government in 2003. Historically, pygmy rabbits have been collected from Deschutes, Klamath, Crook, Lake, Grant, Harney, Baker, and Malheur Counties in Oregon. However, the geographic range of pygmy rabbit in Oregon may have decreased in historic times (Verts and Carraway, 1998), and boundaries of the current distribution are not known. Not all potentially suitable sites appear to be occupied, and populations are susceptible to rapid declines and local extirpation (Weiss and Verts, 1984). In order to protect and manage remaining populations on State of Oregon lands, Oregon Department of Fish and Wildlife needs to identify areas currently occupied by pygmy rabbits, as well as suitable habitats. The main objective of this survey was document to presence or absence of pygmy rabbits on state lands in Malheur, Harney, Lake, and Deschutes counties. Knowledge of the location and extent of pygmy rabbit populations can provide a foundation for the conservation and management of this species in Oregon. The pygmy rabbit is just one of a suite of species of concern associated with sagebrush habitats in the Great Basin. Because information on habitat and distribution of many species is scarce, a secondary goal of the rabbit surveys was to list all other vertebrate species encountered on surveyed sites. This information may be useful in directing future studies aimed at specific taxa.

Open-File Report↗
USGS1989

Evolution of the western part of the Coast plutonic–metamorphic complex, South-Eastern Alaska, USA: A summary

The western Cordillera of North America extends for over 6000 km from the tip of Baja California to the Alaska Range. It includes a wide variety of metamorphic and plutonic terrains, but none is more spectacular scenically or geologically than the Coast plutonic-metamorphic complex (Brew & Ford 1984) of western Canada and south-eastern Alaska. This report briefly describes the evolution of the western part of the complex, integrating information from the deformational, plutonic and metamorphic events. Most of the original studies are reported by the authors in U.S. Geological Survey Circular numbers 733, 751, 823-B, 868, 939, 945, 967 and 978, and are not cited specifically here. This summary does not contain either a comprehensive bibliography or a comparison of the metamorphic histories of south-eastern Alaska with the adjacent parts of British Columbia. The Coast plutonic-metamorphic complex is here divided into three major elements: the western metamorphic, the central granitic and the eastern metamorphic zones (Fig. 1). The western metamorphic belt is extremely long (900 km), and narrow (7–25 km). It consists of regional dynamothermally and regional thermally metamorphosed rocks with mineral assemblages ranging from prehnite-pumpellyite to upper amphibolite facies, scattered mesozonal to epizonal granitic bodies, and a few concentrically zoned mafic-ultramafic masses. The metamorphic grade and the amount of deformation increase from south-west to north-east, culminating at, or slightly to the north-east of, the ‘great tonalite sill’: a remarkable 700-km-long, 3- to 25-km-wide vertical to northeast-dipping belt of mostly syntectonic plutons of approximately the same age, composition and structural

Alaska↗
USGS2009

Endogenic carbonate sedimentation in Bear Lake, Utah and Idaho, over the last two glacial-interglacial cycles

Sediments deposited over the past 220,000 years in Bear Lake, Utah and Idaho, are predominantly calcareous silty clay, with calcite as the dominant carbonate mineral. The abundance of siliciclastic sediment indicates that the Bear River usually was connected to Bear Lake. However, three marl intervals containing more than 50% CaCO 3 were deposited during the Holocene and the last two interglacial intervals, equivalent to marine oxygen isotope stages (MIS) 5 and 7, indicating times when the Bear River was not connected to the lake. Aragonite is the dominant mineral in two of these three high-carbonate intervals. The high-carbonate, aragonitic intervals coincide with warm interglacial continental climates and warm Pacific sea-surface temperatures. Aragonite also is the dominant mineral in a carbonate-cemented microbialite mound that formed in the southwestern part of the lake over the last several thousand years. The history of carbonate sedimentation in Bear Lake is documented through the study of isotopic ratios of oxygen, carbon, and strontium, organic carbon content, CaCO 3 content, X-ray diffraction mineralogy, and HCl-leach chemistry on samples from sediment traps, gravity cores, piston cores, drill cores, and microbialites. Sediment-trap studies show that the carbonate mineral that precipitates in the surface waters of the lake today is high-Mg calcite. The lake began to precipitate high-Mg calcite sometime in the mid-twentieth century after the artificial diversion of Bear River into Bear Lake that began in 1911. This diversion drastically reduced the salinity and Mg 2+ :Ca 2+ of the lake water and changed the primary carbonate precipitate from aragonite to high-Mg calcite. However, sediment-trap and core studies show that aragonite is the dominant mineral accumulating on the lake floor today, even though it is not precipitating in surface waters. The isotopic studies show that this aragonite is derived from reworking and redistribution of shallow-water sediment that is at least 50 yr old, and probably older. Apparently, the microbialite mound also stopped forming aragonite cement sometime after Bear River diversion. Because of reworking of old aragonite, the bulk mineralogy of carbonate in bottom sediments has not changed very much since the diversion. However, the diversion is marked by very distinct changes in the chemical and isotopic composition of the bulk carbonate. After the last glacial interval (LGI), a large amount of endogenic carbonate began to precipitate in Bear Lake when the Pacific moisture that filled the large pluvial lakes of the Great Basin during the LGI diminished, and Bear River apparently abandoned Bear Lake. At first, the carbonate that formed was low-Mg calcite, but ???11,000 years ago, salinity and Mg 2+ :Ca 2+ thresholds must have been crossed because the amount of aragonite gradually increased. Aragonite is the dominant carbonate mineral that has accumulated in the lake for the past 7000 years, with the addition of high-Mg calcite after the diversion of Bear River into the lake at the beginning of the twentieth century. Copyright ?? 2009 The Geological Society of America.

Special Paper of the Geological Society of America↗
USGS2013

Geophysical constraints on Rio Grande rift structure in the central San Luis Basin, Colorado and New Mexico

Interpretation of gravity, aeromagnetic, and magnetotelluric (MT) data reveals patterns of rifting, rift-sediment thicknesses, distribution of pre-rift volcanic and sedimentary rocks, and distribution of syn-rift volcanic rocks in the central San Luis Basin, one of the northernmost major basins that make up the Rio Grande rift. Rift-sediment thicknesses for the central San Luis Basin determined from a three-dimensional gravity inversion indicate that syn-rift Santa Fe Group sediments have a maximum thickness of ~2 km in the Sanchez graben near the eastern margin of the basin along the central Sangre de Cristo fault zone, and reach nearly 1 km within the Monte Vista graben near the western basin margin along the San Juan Mountains. In between, Santa Fe Group thickness is negligible under the San Luis Hills and estimated to reach ~1.1 km under the Costilla Plains (although no independent thickness constraints exist, and a range of thicknesses of 600 m to 2 km is geophysically reasonable). From combined geophysical and geologic considerations, pre-rift, dominantly sedimentary rocks appear to increase in thickness from none in the Sanchez graben on the east to perhaps 800 m under the San Luis Hills on the west. The pre-rift rocks are most likely early Tertiary in age, but the presence of Mesozoic and Paleozoic sedimentary rocks cannot be ruled out. Geophysical data provide new evidence that an isolated exposure of Proterozoic rocks on San Pedro Mesa is rooted in the Precambrian basement. This narrow, north-south–trending basement high has ~2 km of positive relief with respect to the base of the Sanchez graben, and separates the graben from the structural depression beneath the Costilla Plains. A structural high composed of pre-rift rocks, long inferred to extend from under the San Luis Hills to the Taos Plateau, is confirmed and found to be denser than previously believed, with little or no overlying Santa Fe Group sediments. Major faults in the study area are delineated by geophysical data and models; these faults include significant vertical offsets (≥1 km) of Precambrian rocks along the central and southern zones of the Sangre de Cristo fault system. Other faults with similarly large offsets of the Santa Fe Group include a fault bounding the western margin of San Pedro Mesa, and other faults that bound the Monte Vista graben in an area previously assumed to be a simple hinge zone at the western edge of the San Luis Basin. A major north-south–trending structure with expression in gravity and MT data occurs at the boundary between the Costilla Plains and the San Luis Hills structural high. Although it has been interpreted as a down-to-the-east normal fault or fault zone, our modeling suggests that it also is likely related to pre-rift tectonics. Aeromagnetic anomalies over much of the area are interpreted to mainly reflect variations of remanent magnetic polarity and burial depth of the 5.3–3.7 Ma Servilleta Basalt of the Taos Plateau volcanic field. Magnetic-source depth estimates are interpreted to indicate patterns of subsidence following eruption of the basalt, with maximum subsidence in the Sanchez graben.

Colorado, New Mexico↗
USGS2007

A framework for assessing the sustainability of monitored natural attenuation

The sustainability of monitored natural attenuation (MNA) over time depends upon (1) the presence of chemical/biochemical processes that transform wastes to innocuous byproducts, and (2) the availability of energy to drive these processes to completion. The presence or absence of contaminant-transforming chemical/biochemical processes can be determined by observing contaminant mass loss over time and space (mass balance). The energy available to drive these processes to completion can be assessed by measuring the pool of metabolizable organic carbon available in a system, and by tracing the flow of this energy to available electron acceptors (energy balance). For the special case of chlorinated ethenes in ground-water systems, for which a variety of contaminant-transforming biochemical processes exist, natural attenuation is sustainable when the pool of bioavailable organic carbon is large relative to the carbon flux needed to drive biodegradation to completion. These principles are illustrated by assessing the sustainability of MNA at a chlorinated ethene-contaminated site in Kings Bay, Georgia. Approximately 1,000 kilograms of perchloroethene (PCE) was released to a municipal landfill in the 1978-1980 timeframe, and the resulting plume of chlorinated ethenes migrated toward a nearby housing development. A numerical model, built using the sequential electron acceptor model code (SEAM3D), was used to quantify mass and energy balance in this system. The model considered the dissolution of non-aqueous phase liquid (NAPL) as the source of the PCE, and was designed to trace energy flow from dissolved organic carbon to available electron acceptors in the sequence oxygen > chlorinated ethenes > ferric iron > sulfate > carbon dioxide. The model was constrained by (1) comparing simulated and measured rates of ground-water flow, (2) reproducing the observed distribution of electron-accepting processes in the aquifer, (3) comparing observed and measured concentrations of chlorinated ethenes, and (4) reproducing the observed production and subsequent dilution of dissolved chloride, a final degradation product of chloroethene biodegradation. Simulations using the constrained model indicated that an average flux of 5 milligrams per liter per day of organic carbon (CH2O) per model cell (25 square meters) is required to support the short-term sustainability of MNA. Because this flux is small relative to the pool of renewable organic carbon (about 4.7 x 107 milligrams [mg] per model cell) present in the soil zone and non-renewable carbon (about 6.9 x 108 mg per model cell) in an organic-rich sediment layer overlying the aquifer, the long-term sustainability of MNA is similarly large. This study illustrates that the short- and long-term sustainability of MNA can be assessed by: 1. Estimating the time required for contaminants to dissolve/disperse/degrade under ambient hydrologic conditions (time of remediation). 2. Quantifying the organic carbon flux to the system needed to consume competing electron acceptors (oxygen) and direct electron flow toward chloroethene degradation (short-term sustainability). 3. Comparing the required flux of organic carbon to the pool of renewable and non-renewable organic carbon given the estimated time of remediation (long-term sustainability). These are general principles that can be used to assess the sustainability of MNA in any hydrologic system.

Circular↗
USGS1977

Population ecology of the mallard: IV. A review of duck hunting regulations, activity, and success, with special reference to the mallard

This, the fourth in a series of reports on the mallard, ( Anas platyrhynchos ), deals at length with the harvest of mallards by waterfowl hunters. Long-term summaries of duck hunting regulations (1948- 1974), Migratory Bird Hunting Stamp sales (1934-1974), Hunter Questionnaire (1952-1974), Duck Wing Collection (1960-1974), and Hunter Performance (1965-1972) Survey data for the United States are presented and discussed. Similar data from Canada are also summarized. Mallard harvest figures for 1961-1974 are presented by Mallard Harvest Area, of which 100 are defined for the United States and 14 for Canada, as well as by State or Province and flyway. During the 23-year period beginning in 1952, an average of 1.6 million adult and 0.2 million junior waterfowl hunters accumulated almost 12.3 million hunter-days of recreation and a harvest of 11.2 million ducks each year. Hunter reports indicate that mallards made up about 43% (5.5 million annually) of the ducks taken before 1960, when mallard regulations were less restrictive; the Duck Wing Survey indicates that mallards have made up 33% of the harvest (3.6 million annually) since 1960. The age and sex compositions and the chronological distribution of the mallard harvest are examined in detail. Among the patterns noted are peak harvests during the first few days of the season in many States, alternately increasing and decreasing annual age ratios, and sex ratios that suggest differential migration of adult drakes and hunter selectivity for males. It is estimated that almost 19% of the ducks shot down are not retrieved. Relationships between duck hunting regulations and hunter behavior are examined briefly. Hunter compliance with mallard bag limits, hunter selectivity of mallards by sex, and, to a lesser extent, the size of the unretrieved kill are all sensitive to the particular bag limit regulations in effect. Survey data are also examined for relationships between harvest and various hunting regulations: starting time and day of the week for opening day, opening date, season length, split seasons, daily shooting hours, and daily bag limits. Tables are presented relating changes in duck and mallard harvests to season length and bag limit, and examples of what effects changes in other regulations have on harvest are also given. The evaluation of bag limit regulations, one of the most important tools used in managing harvest, is carried a step further with the development of a procedure for calculating expected hunter success under a wide variety of bag limit regulations. This method appears promising for evaluating point-limit as well as fixed-limit regulations. In addition, it may provide useful measurements of the degree of hunter selectivity induced by various types of bag limit regulations, an increasingly important aspect of harvest management. Finally, this study clearly demonstrates that the effects of a particular regulation can differ dramatically from area to area, so it is usually necessary to evaluate each proposal on a State-by-State basis.

Resource Publication↗