Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “American Geology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23Linked to original sources
USGS1987

Biogeochemical cycling of selenium in the San Joaquin Valley, California, USA

Subsurface agricultural drainage waters from western San Joaquin Valley, California, were found to contain elevated concentrations of the element selenium in the form of selenate. In 1978, these drainage waters began to replace previous input to Kesterson Reservoir, a pond system within Kesterson National Wildlife Refuge; this substitution was completed by 1982. In the 1983 nesting season, unusual rates of deformity and death in embryos and hatchlings of wild aquatic birds (up to 64% of eared grebe and American coot nests) occurred at the refuge and were attributed to selenium toxicosis. Features necessary for contamination to have taken place included geologic setting, climate, soil type, availability of imported irrigation water, type of irrigation, and the unique chemical properties of selenium. The mechanisms of biogeochemical cycling raise questions about other ecosystems and human exposure.

California↗
USGS2001

Raster images of geologic maps of Middle Proterozoic Belt strata in parts of Benewah, Bonner, Kootenai and Shoshone Counties, Idaho and Lincoln, Mineral and Sanders Counties, Montana

Geologic maps of the western part of the Belt Basin of western Montana and northern Idaho were converted into digital raster (TIFF image) format to facilitate their manipulation in geographic information systems. The 85-mile x 100-mile map area mostly contains rocks belonging to the lower and middle Belt Supergroup. The area is of interest as these Middle Proterozoic strata contain vein-type lead-zinc-silver deposits in the Coeur d?Alene Mining District in the St. Regis and Revett formations and strata-bound copper-silver deposits, such as the Troy mine, within the Revett Formation. The Prichard Formation is also prospective for strata-bound lead-zinc deposits because equivalent Belt strata in southern British Columbia, Canada host the Sullivan lead-zinc deposit. Map data converted to digital images include 13 geological maps at scales ranging from 1:48,000 to 1:12,000. Geologic map images produced from these maps by color scanning were registered to grid tick coverages in a Universal Transverse Mercator (North American Datum of 1927, zone 11) projection using ArcView Image Analysis. Geo-registering errors vary from 10 ft to 114 ft.

Idaho, Montana↗
USGS2017

Flood-inundation maps for the Meramec River at Valley Park and at Fenton, Missouri, 2017

Two sets of digital flood-inundation map libraries that spanned a combined 16.7-mile reach of the Meramec River that extends upstream from Valley Park, Missouri, to downstream from Fenton, Mo., were created by the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers, St. Louis Metropolitan Sewer District, Missouri Department of Transportation, Missouri American Water, and Federal Emergency Management Agency Region 7. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/ , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the cooperative USGS streamgages on the Meramec River at Valley Park, Mo., (USGS station number 07019130) and the Meramec River at Fenton, Mo. (USGS station number 07019210). Near-real-time stage data at these streamgages may be obtained from the USGS National Water Information System at https://waterdata.usgs.gov/nwis or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/ , which also forecasts flood hydrographs at these sites (listed as NWS sites vllm7 and fnnm7, respectively). Flood profiles were computed for the stream reaches by means of a calibrated one-dimensional step-backwater hydraulic model. The model was calibrated using a stage-discharge relation at the Meramec River near Eureka streamgage (USGS station number 07019000) and documented high-water marks from the flood of December 2015 through January 2016. The calibrated hydraulic model was used to compute two sets of water-surface profiles: one set for the streamgage at Valley Park, Mo. (USGS station number 07019130), and one set for the USGS streamgage on the Meramec River at Fenton, Mo. (USGS station number 07019210). The water-surface profiles were produced for stages at 1-foot (ft) intervals referenced to the datum from each streamgage and ranging from the NWS action stage, or near bankfull discharge, to the stage corresponding to the estimated 0.2-percent annual exceedance probability (500-year recurrence interval) flood, as determined at the Eureka streamgage (USGS station number 07019000). The simulated water-surface profiles were then combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.28-ft vertical accuracy and 3.28-ft horizontal resolution) to delineate the area flooded at each flood stage (water level). The availability of these maps, along with internet information regarding current stage from the USGS streamgages and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures and for postflood recovery efforts.

Missouri↗
USGS2019

Flood-inundation maps of the Meramec River from Eureka to Arnold, Missouri, 2018

Libraries of digital flood-inundation maps that spanned a combined 37.2-mile reach of the Meramec River that extended upstream from Eureka, Missouri, to downstream near the confluence of the Meramec and Mississippi Rivers were created by the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers, Metropolitan St. Louis Sewer District, Missouri Department of Transportation, Missouri American Water, Federal Emergency Management Agency Region 7, and the cities of Pacific, Eureka, Wildwood, and Arnold. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/ , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the cooperative USGS streamgages for the Meramec River near Eureka, Mo. (USGS station 07019000), the Meramec River at Valley Park, Mo. (USGS station 07019130), the Meramec River at Fenton, Mo. (USGS station 07019210), and the Meramec River at Arnold, Mo. (USGS station 07019300). Near-real-time stage data at these streamgages may be obtained from the USGS National Water Information System at https://doi.org/10.5066/F7P55KJN or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at https://water.weather.gov/ahps/ , which also forecasts flood hydrographs at these sites (listed as NWS sites erkm7, vllm7, fnnm7, and arnm7, respectively). Flood profiles were computed for the stream reach by means of a calibrated one-dimensional step-backwater hydraulic model. The model was calibrated using a stage-discharge relation at the Meramec River near Eureka, Mo., streamgage (USGS station 07019000) and documented high-water marks from the flood of December 2015 through January 2016. The calibrated hydraulic model was used to compute water-surface profiles: 1 set for the Meramec River near Eureka, Mo., streamgage (USGS station 07019000); 1 set for the Meramec River at Valley Park, Mo., streamgage (USGS station 07019130); 7 sets for the Meramec River at Fenton, Mo., streamgage (USGS station 07019210) for a range of Mississippi River conditions; and 8 sets for the Meramec River at Arnold, Mo., streamgage (USGS station 07019300) for a range of Mississippi River conditions. The water-surface profiles were produced for stages at 1-foot (ft) intervals referenced to the datum from each streamgage and ranging from the NWS action stage, or near bankfull discharge, to the stage corresponding to the estimated 0.2-percent annual exceedance probability (500-year recurrence interval) flood, as determined at the Meramec River near Eureka, Mo., streamgage (USGS station 07019000). The simulated water-surface profiles then were combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.28-ft vertical accuracy and 3.28-ft horizontal resolution) to delineate the area flooded at each simulated 1-ft stage increment. Previously published flood-inundation maps were updated and incorporated in the flood map libraries for USGS stations 07019130 and 07019210 to complete the map sets corresponding to eight Mississippi River conditions. The availability of these maps, along with internet information regarding current stage from the USGS streamgages and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures and for postflood recovery efforts.

Missouri↗
USGS2007

Strategic Plan for the North American Breeding Bird Survey: 2006-2010

Executive Summary The mission of the North American Breeding Bird Survey (BBS) is to provide scientifically credible measures of the status and trends of North American bird populations at continental and regional scales to inform biologically sound conservation and management actions. Determining population trends, relative abundance, and distributions of North American avifauna is critical for identifying conservation priorities, determining appropriate conservation actions, and evaluating those actions. The BBS program, jointly coordinated by the U.S. Geological Survey and Environment Canada’s Canadian Wildlife Service, provides the U.S. and Canadian Federal governments, state and provincial agencies, other conservation practitioners, and the general public with science-based avian population trend estimates and other information for regional and national species’ population assessments. Despite the demonstrated value of the BBS for furthering avian conservation across North America, its importance is often underappreciated, and it is underfunded compared with many other government-supported programs that report on status of the environment. Today, BBS resources, adjusted for inflation, are below the amount allocated in the 1970s and are still only sufficient to support two biologists. Yet the number of routes, participants, data, and data requests has quadrupled. Data and information management and delivery requirements and security concerns, non-existent in 1966, impose further demands on BBS resources. In addition, the Mexican expansion of the BBS offers new hope for a truly continental approach to avian conservation, but also brings additional challenges. Meeting the goals of this plan will take cooperation among myriad stakeholders; yet, even with collaboration, most objectives of this plan will be unattainable if BBS program support is not increased. The BBS developed this strategic plan to help set priorities and identify resources required for the program to continue to meet the evolving needs of the conservation community for information on bird population change. By setting clear goals, strategies, and measures of success, this plan provides a cohesive framework and vision for maintenance and development of the BBS. The plan identifies two major goals for the BBS, with a number of strategies and objectives to achieve these goals. Over the next 5 years, progress made in addressing each long-term goal and its associated 5-year strategies and objectives will gage the plan’s success. Specific actions, projected outcomes, and measures of success related to accomplishing these are outlined in Table 1, with a timeline in Table 2. The two main goals for the program, with a summary of the strategies to achieve them, are: Goal 1: Collect scientifically credible measures of the status and trends of North American bird populations at continental and regional scales. The North American Breeding Bird Survey will continue to support North American natural resource conservation through the collection of scientifically credible measures of the status and trends of continental bird populations. While doing this, the BBS will work to improve the science behind the program to better meet its mission and the changing needs of the avian conservation community. In partnership with collaborators, the BBS will address detection probability bias and habitat bias, improve analytical methods, and more fully assess and account for observer quality. Moreover, the BBS will improve the quality and breadth of avian population data through strategic increases in route density and the establishment of a Mexican BBS program. Goal 2: Ensure BBS data and analytical results are widely available and easily accessible for use by the avian conservation and management communities. At the heart of the BBS lies a four-million-record database containing more than 40 years of data on more than 600 bird species. These data are of no value if not well maintained, appropriately analyzed, and widely and easily accessible. The USGS has greatly improved data management and accessibility in recent years. Trend estimates were first made available via the Internet in the mid-1990s, followed closely by the raw data with baseline metadata and standard operating procedures. Nevertheless, numerous enhancements to data management and the usability of BBS results will greatly improve the ability of the BBS to serve avian conservation goals. The BBS needs to ensure that BBS data and results presented on the web site use the best data-management practices and statistical methods, with adequate documentation for users to understand them and any differences between different trend estimates. Moreover, the BBS needs to increase communication with BBS partners and stakeholders to ensure that it continues to meet the avian population status and trends needs of the conservation community and to encourage the development of new products. Working with collaborators, the BBS will develop tools for integrating environmental parameters like habitat change into the analyses, and for integrating BBS data with other avian survey results. In addition, the BBS will continue to improve data and database management through the incorporation of additional data and data fields, such as georeferenced stop locations and more complete metadata for the raw data and results, thus enhancing the uses that can be made of the data.

Circular↗
USGS2019

The effects of management practices on grassland birds

Since the mid-1960s, populations of grassland birds have been declining more precipitously than any other group of birds in North America. These long-term declines highlight the need to better understand the habitat requirements of grassland birds and how management practices affect individual species and their habitats. Although resource managers have long recognized that every management approach contains inherent advantages and disadvantages, depending on the species in question, they are often faced with making critical management decisions armed with little or no information. The need for information on management and its effects on grassland birds was identified by the U.S. Prairie Pothole Joint Venture, a part of the North American Waterfowl Management Plan, in support of its objective to stabilize or increase populations of declining grassland- and wetland-associated wildlife species in the Prairie Pothole Region. In 1996, scientists from the U.S. Geological Survey’s Northern Prairie Wildlife Research Center began a long-term, collaborative effort to review and synthesize literature on the effects of management practices on grassland bird species. Major funding for this effort was provided by the Prairie Pothole Joint Venture, U.S. Fish and Wildlife Service, and the U.S. Geological Survey; additional funding was provided by the U.S. Forest Service, The Nature Conservancy, and the Plains and Potholes Landscape Conservation Cooperative. This compendium on “The Effects of Management Practices on Grassland Birds” is a culmination of that work. More than 6,000 published and unpublished publications have been consulted and several thousand publications have been incorporated and synthesized in species accounts for 40 North American grassland bird species. The 40 species represent a taxonomically diverse group that includes grouse, shorebirds, owls, diurnal raptors, and many songbirds. The focus of this effort is on management of breeding habitat, with an emphasis on the Great Plains. The accounts provide land managers with a summary of information on the effects of specific management practices on grassland birds and help to identify the most critical research gaps in our understanding of grassland bird ecology, habitat needs, and responses to management practices. This compendium is organized into three primary sections: an introduction, species accounts, and a concluding chapter. The introduction provides an overview of grasslands, the processes under which grasslands formed, the influence of anthropogenic changes to grasslands, the effects of those changes on grassland bird populations, and the management tools available to land managers. The bulk of this compendium is the individual species accounts, covering 40 species of North American grassland birds arranged in taxonomic order. Each species account includes information on species range, suitable breeding habitat, area requirements and landscape associations, breeding-season phenology, species’ response to management, and management recommendations. Information on rates of brood parasitism by the Brown-headed Cowbird ( Molothrus ater ) in grassland bird nests is summarized in a chapter at the end of this report. The final chapter includes concluding remarks concerning habitat requirements and management effects on grassland birds.

Professional Paper↗
USGS2011

Improving stream studies with a small-footprint green lidar

Technology is changing how scientists and natural resource managers describe and study streams and rivers. A new generation of airborne aquatic-terrestrial lidars is being developed that can penetrate water and map the submerged topography inside a stream as well as the adjacent subaerial terrain and vegetation in one integrated mission. A leading example of these new cross-environment instruments is the Experimental Advanced Airborne Research Lidar (EAARL), a NASAbuilt sensor now operated by the U.S. Geological Survey (USGS) [Wright and Brock, 2002].

Eos, Transactions, American Geophysical Union↗
USGS1994

Meteoroid mayhem in Ole Virginny: Source of the North American tektite strewn field

New seismic reflection data from Chesapeake Bay reveal a buried, 85-km-wide, 1.5-2.0-km-deep, peak-ring impact crater, carved through upper Eocene to Lower Cretaceous sedimentary strata and into underlying pre-Mesozoic crystalline basement rocks. A polymictic, late Eocene impact breccia, composed mainly of locally derived sedimentary debris (determined from four continuous cores), surrounds and partly fills the crater. Structural and sedimentary characteristics of the Chesapeake Bay crater closely resemble those of the Miocene Ries peakring crater in southern Germany. We speculate that the Chesapeake Bay crater is the source of the North American tektite strewn field.

Geology↗
USGS2011

To reactivate or not to reactivate: nature and varied behavior of structural inheritance in the Proterozoic basement of the Eastern Colorado mineral belt over 1.7 billion years of earth history

The eastern central Front Range of the Rocky Mountains in Colorado has long been a region of geologic interest because of Laramide-age hydrothermal polymetallic vein-related ores. The region is characterized by a well-exposed array of geologic structures associated with ductile and brittle deformation, which record crustal strain over 1.7 billion years of continental growth and evolution. The mineralized areas lie along a broad linear zone termed the Colorado Mineral Belt. This lineament has commonly been interpreted as following a fundamental boundary, such as a suture zone, in the North American Proterozoic crust that acted as a persistent zone of weakness localizing the emplacement of magmas and associated hydrothermal fluid flow. However, the details on the controls of the location, orientation, kinematics, density, permeability, and relative strength of various geological structures and their specific relationships to mineral deposit formation are not related to Proterozoic ancestry in a simple manner. The objectives of this field trip are to show key localities typical of the various types of structures present, show recently compiled and new data, offer alternative conceptual models, and foster dialogue. Topics to be discussed include: (1) structural history of the eastern Front Range; (2) characteristics, kinematics, orientations, and age of ductile and brittle structures and how they may or may not relate to one another and mineral deposit permeability; and (3) characteristics, localization, and evolution of the metal and non–metal-bearing hydrothermal systems in the eastern Colorado Mineral Belt.

Colorado↗
USGS2017

Coastal circulation and water-column properties in the National Park of American Samoa, February–July 2015

There is little information on the oceanography in the National Park of American Samoa (NPSA). The transport pathways for potentially harmful constituents of land-derived runoff, as well as larvae and other planktonic organisms, are driven by nearshore circulation patterns. To evaluate the processes affecting coral reef ecosystem health, it is first necessary to understand the oceanographic processes driving nearshore circulation, residence times, exposure rates, and transport pathways. Information on how the NPSA’s natural resources may be affected by anthropogenic sources of pollution, sediment runoff, larval transport, or modifications to the marine protected areas is critical to NPSA resource managers for understanding and ultimately managing coastal and marine resources. To address this need, U.S. Geological Survey and U.S. National Park Service researchers conducted a collaborative study in 2015 to determine coastal circulation patterns and water-column properties along north-central Tutuila, American Samoa, in an area focused on NPSA’s Tutuila Unit and its coral reef ecosystem. The continuous measurements of waves, currents, tides, and water-column properties from these instrument deployments over 150 days, coupled with available meteorological measurements of wind and rainfall, provide information on nearshore circulation and the variability in these hydrodynamic properties for NPSA’s Tutuila Unit. In general, circulation was strongly driven by regional winds at longer (greater than day) timescales and by tides at shorter (less than day) timescales. Flows were primarily directed along shore, with current speeds faster offshore to the north and slower closer to shore, especially in embayments. Water-column properties exhibit strong seasonality coupled to the shift from non-trade wind season to trade wind season. During the non-trade wind season that was characterized by variable winds and larger waves in the NPSA, waters were warmer, slightly more saline, relatively less optically clear, and more stratified. When winds shifted to a more consistent trade wind pattern in the austral fall, the waters cooled and became less stratified because of decreased insolation. There are consistent spatial patterns in water column characteristics—Waters were warmer and less saline near the surface and closer to shore, especially in embayments, which tended to be more turbid, less clear, and characterized by higher chlorophyll than waters offshore. Water residence times were shorter farther offshore and longer closer to shore and in embayments, but varied spatially because of different forcing. Warmer, lower salinity, higher chlorophyll, and more turbid waters in embayments tend to reside in those locations for much greater durations, resulting in greater exposure of embayment ecosystems to those waters. This is in contrast with waters farther offshore, where the combination of shorter residence times and cooler, higher salinity water results in less exposure to land runoff. Understanding coastal circulation patterns and water-column properties in NPSA’s waters along north-central Tutuila may help to better understand how meteorological and oceanographic processes, at the regional and local scale, affect coral reef health and sustainability in this region.

Open-File Report↗
USGS1994

U.S. Geological Survey yearbook, fiscal year 1993: At work across the Nation

The need for earth science has never been more paramount. The devastating flooding of the Mississippi River this past year, strikingly portrayed on the cover and discussed in detail in this report (p. 37-42), was a sobering reminder of nature's elemental power. As a Nation, we face many environmental and economic challenges, such as natural hazards, that can be addressed effectively only through science. Water quality, resource assessments, climate change, and toxic wastes are all critical issues that can best be dealt with when approached from a sound scientific base. The goal of the U.S. Geological Survey is to provide hydrologic, geologic, and topographic information and understanding that contribute to the wise management of the Nation's natural resources and that promote the health, safety, and well-being of all Americans. FY1993 has proven to be a particularly challenging one for the USGS. We entered into a time of transition from the long-term leadership of Director Dallas Peck and Associate Director Doyle Frederick to the appointment of a new director. We thank Dallas and Doyle for their many years of service and for their support during the transition.

Yearbook↗
USGS2025

Stories in stone: The geoheritage significance of U.S. National Park Service stratotypes

The U.S. National Park Service stratotype inventory has systematically documented hundreds of published stratotypes across the country that represent a quintessential component of America’s geoheritage and possess significant scientific, educational, cultural, historic, and aesthetic values. As valuable geologic reference standards, stratotypes record intervals of Earth history relating to our nation’s unique geologic evolution, biological progression, cultural traditions, historical narratives, and stunning landforms. However, the general lack of awareness and knowledge regarding the scope, significance, distribution, and scale of stratotypes can result in these resources being overlooked. Consequently, stratotypes may inadvertently experience accidental alteration, damage, or destruction through both natural and anthropogenic processes. As with many American geoheritage sites, stratotypes lack specific recognition through legislation, policies, or other management strategies to ensure their preservation and protection. Through education and outreach, we hope to inform, increase awareness, and engage the public about these internationally and nationally significant geologic reference sites, unite various geoheritage communities, and promote their preservation for future generations.

Geoheritage↗
USGS2017

Elemental, isotopic, and geochronological variability in Mogollon-Datil volcanic province archaeological obsidian, southwestern USA: Solving issues of intersource discrimination

Solving issues of intersource discrimination in archaeological obsidian is a recurring problem in geoarchaeological investigation, particularly since the number of known sources of archaeological obsidian worldwide has grown nearly exponentially in the last few decades, and the complexity of archaeological questions asked has grown equally so. These two parallel aspects of archaeological investigation have required more exacting understanding of the geological relationship between sources and the more accurate analysis of these sources of archaeological obsidian. This is particularly the case in the North American Southwest where the frequency of archaeological investigation is some of the highest in the world, and the theory and method used to interpret that record has become increasingly nuanced. Here, we attempt to unravel the elemental similarity of archaeological obsidian in the Mogollon-Datil volcanic province of southwestern New Mexico where some of the most important and extensively distributed sources are located and the elemental similarity between the sources is great even though the distance between the sources is large. Uniting elemental, isotopic, and geochronological analyses as an intensive pilot study, we unpack this complexity to provide greater understanding of these important sources of archaeological obsidian.

New Mexico↗
USGS2019

Bayesian analysis of the impact of rainfall data product on simulated slope failure for North Carolina locations

In the past decades, many different approaches have been developed in the literature to quantify the load-carrying capacity and geotechnical stability (or the Factor of Safety, F_s) of variably saturated hillslopes. Much of this work has focused on a deterministic characterization of hillslope stability. Yet, simulated F_s values are subject to considerable uncertainty due to our inability to characterize accurately the soil mantle’s properties (hydraulic, geotechnical and geomorphologic) and spatiotemporal variability of the moisture content of the hillslope interior. This is particularly true at larger spatial scales. Thus, uncertainty-incorporating analyses of physically based models of rain-induced landslides are rare in the literature. Such landslide modeling is typically conducted at the hillslope scale using gauge-based rainfall forcing data with rather poor spatiotemporal coverage. For regional landslide modeling, the specific advantages and/or disadvantages of gauge-only, radar-merged and satellite-based rainfall products are not clearly established. Here, we compare and evaluate the performance of the Transient Rainfall Infiltration and Grid-based Regional Slope-stability analysis (TRIGRS) model for three different rainfall products using 112 observed landslides in the period between 2004 and 2011 from the North Carolina Geological Survey database. Our study includes the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis Version 7 (TMPA V7), the North American Land Data Assimilation System Phase 2 (NLDAS-2) analysis, and the reference ‘truth’ Stage IV precipitation. TRIGRS model performance was rather inferior with the use of literature values of the geotechnical parameters and soil hydraulic properties from ROSETTA using soil textural and bulk density data from SSURGO (Soil Survey Geographic database). The performance of TRIGRS improved considerably after Bayesian estimation of the parameters with the DiffeRential Evolution Adaptive Metropolis (DREAM) algorithm using Stage IV precipitation data. Hereto, we use a likelihood function that combines binary slope failure information from landslide event and ‘null’ periods using multivariate frequency distribution-based metrics such as the False Discovery and False Omission Rates. Our results demonstrate that the Stage IV-inferred TRIGRS parameter distributions generalize well to TMPA and NLDAS-2 precipitation data, particularly at sites with considerably larger TMPA and NLDAS-2 rainfall amounts during landslide events than null periods. TRIGRS model performance is then rather similar for all three rainfall products. At higher elevations, however, the TMPA and NLDAS-2 precipitation volumes are insufficient and their performance with the Stage IV-derived parameter distributions indicate their inability to accurately characterize hillslope stability.

North Carolina↗
USGS1994

Tectonics and geology of spreading ridge subduction at the Chile Triple Junction: a synthesis of results from Leg 141 of the Ocean Drilling Program

An active oceanic spreading ridge is being subducted beneath the South American continent at the Chile Triple Junction. This process has played a major part in the evolution of most of the continental margins that border the Pacific Ocean basin. A combination of high resolution swath bathymetric maps, seismic reflection profiles and drillhole and core data from five sites drilled during Ocean Drilling Program (ODP) Leg 141 provide important data that define the tectonic, structural and stratigraphic effects of this modern example of spreading ridge subduction. A change from subduction accretion to subduction erosion occurs along-strike of the South American forearc. This change is prominently expressed by normal faulting, forearc subsidence, oversteepening of topographic slopes and intensive sedimentary mass wasting, overprinted on older signatures of sediment accretion, overthrusting and uplift processes in the forearc. Data from drill sites north of the triple junction (Sites 859-861) show that after an important phase of forearc building in the early to late Pliocene, subduction accretion had ceased in the late Pliocene. Since that time sediment on the downgoing oceanic Nazca plate has been subducted. Site 863 was drilled into the forearc in the immediate vicinity of the triple junction above the subducted spreading ridge axis. Here, thick and intensely folded and faulted trench slope sediments of Pleistocene age are currently involved in the frontal deformation of the forearc. Early faults with thrust and reverse kinematics are overprinted by later normal faults. The Chile Triple Junction is also the site of apparent ophiolite emplacement into the South American forearc. Drilling at Site 862 on the Taitao Ridge revealed an offshore volcanic sequence of Plio-Pleistocene age associated with the Taitao Fracture Zone, adjacent to exposures of the Pliocene-aged Taitao ophiolite onshore. Despite the large-scale loss of material from the forearc at the triple junction, ophiolite emplacement produces a large topographic promontory in the forearc immediately after ridge subduction, and represents the first stage of forearc rebuilding. ?? 1994 Springer-Verlag.

Geologische Rundschau↗
USGS2020

Compilation of mercury data and associated risk to human and ecosystem health, Bad River Band of Lake Superior Chippewa, Wisconsin

Mercury is an environmentally ubiquitous neurotoxin, and its methylated form presents health risks to humans and other biota, primarily through dietary intake. Because methylmercury bioaccumulates and biomagnifies in living tissue, concentrations progressively increase at higher trophic positions in ecosystem food webs. Therefore, the greatest health risks are for organisms at the highest trophic positions and for humans who consume organisms such as fish from these high trophic positions. Data on environmental mercury concentrations in various media and biota provide a basis for comparison among sites and regions and for evaluating ecosystem health risks. The U.S. Geological Survey, in cooperation with the Natural Resources Department, Bad River Band of Lake Superior Chippewa, have compiled a dataset from analyses of mercury concentrations in surface water, bed sediment, fish tissue, Rana clamitans (green frog) tissue, Haliaeetus leucocephalus (bald eagle) feathers, Lontra canadensis (North American river otter) hair, Zizania palustris (northern wild rice), and litterfall from samples collected in the Bad River watershed, Wisconsin during 2004–18. These data originated from either the Natural Resources Department or another agency based on samples collected within or near to Bad River Tribal lands before transfer to the U.S. Geological Survey for compilation and analysis at the onset of the project. This report describes the compiled mercury dataset, provides comparisons to similar measurements in the region and elsewhere, and evaluates health risks to humans and to the sampled biota. Except for litterfall, data were not collected on a consistent, regular basis over a sufficient period to evaluate temporal patterns. The reported mercury concentrations are generally similar to those reported elsewhere in the upper Great Lakes region. Reported values are consistent with atmospheric deposition as the principal source and reflect a favorable environment for mercury methylation. Fish mercury concentrations increased at higher food web positions and generally increased with length in most species measured. Sander vitreus (walleye) present the greatest risk to humans among fishes considered here because of their high trophic position and associated elevated mercury concentrations in combination with relatively high walleye consumption rates by the Native American community. Methylmercury concentrations in wild rice are generally low and likely pose little health risk. Despite reports of declining atmospheric mercury deposition across eastern North America during the past decade, a downward trend in litterfall mercury deposition was not evident in samples collected during 2012–18. Limitations in this data compilation and analysis were noted due to missing information such as collection dates and site locations for some samples. Regular monitoring of mercury in litterfall and surface waters along with periodic collection of fish would enable evaluation of temporal change in the mercury cycle that might affect future risk to humans and aquatic ecosystem inhabitants.

Wisconsin↗
USGS2004

Comparison of some sediment-hosted, stratiform barite deposits in China, the United States, and India

Shifts in world barite production since the 1980s have resulted in China becoming the world's largest barite-producing country followed by the US and India. Most barite produced for use in drilling fluids is derived from black shale- and chert-hosted, stratiform marine deposits. In China, Late Proterozoic to Early Cambrian marine barite deposits occur on the oceanic margins of the Yangtze platform, in the Qinling region in the north and the Jiangnan region in the south. Most US ore-grade deposits are in the Nevada barite belt; most commercial deposits occur in Ordovician and Devonian marine rocks along the western margin of the early Paleozoic North American continent. Production in India is predominantly from a single Middle Proterozoic deposit in a sedimentary basin located on Archean basement in Andrah Pradesh.The geologic and geochemical characteristics of the deposits are consistent with origins from a variety of sedimentary-exhalative processes, with biogenic processes contributing to the concentration of some seafloor barite. Linear distributions of clusters of lenticular deposits suggest a geographic relationship to syndepositional seafloor fault zones. Sulfur isotope data of the barite deposits range from values that are similar to coeval seawater sulfate to significantly higher ??34S values. Strontium isotope values of continental-margin-type deposits in Nevada and China are less radiogenic than those of cratonic-rift deposits (e.g. Meggen and Rammelsberg). Comparison of Lan/ Cen ratios of barite in the Qinling region of China with marine chert ratios suggests a relationship to hydrothermal fluids, whereas ratios from the Jiangnan region and Nevada can be interpreted as reflecting a biogenic influence.The California Borderland provides a potential modern analog where hydrothermal barium is being deposited on the seafloor in fault-block-bounded basins. Anoxic to dysaerobic conditions on some marine basin floors result from upwelling, nutrient-rich currents and high productivity in surface waters. In this setting, biogenic processes could contribute to the concentration of barium from hydrothermal sources. ?? 2003 Published by Elsevier B.V.

Ore Geology Reviews↗
USGS2008

Oceanic loading of wildfire-derived organic compounds from a small mountainous river

Small mountainous rivers (SMRs) export substantial amounts of sediment into the world's oceans. The concomitant yield of organic carbon (OC) associated with this class of rivers has also been shown to be significant and compositionally unique. We report here excessively high loadings of polycyclic aromatic hydrocarbons (PAHs), lignin, and levoglucosan, discharged from the Santa Clara River into the Santa Barbara Channel. The abundance of PAHs, levoglucosan, and lignin in Santa Barbara Channel sediments ranged from 201.7 to 1232.3 ng gdw-1, 1.3 to 6.9 ??g gdw-1, and 0.3 to 2.2 mg per 100 mg of the sedimentary OC, respectively. Assuming a constant rate of sediment accumulation, the annual fluxes of PAHs, levoglucosan, and lignin, to the Santa Barbara Channel were respectively, 885.5 ?? 170.2 ng cm-2 a-1, 3.5 ?? 1.9 ??g cm-2 a-1 and 1.4 ?? 0.3 mg per 100 mg OC cm-2 a-1, over ???30 years. The close agreement between PAHs, levoglucosan, and lignin abundance suggests that the depositional flux of these compounds is largely biomass combustion-derived. To that end, use of the Santa Clara River as a model for SMRs suggests this class of rivers may be one of the largest contributors of pyrolyzed carbon to coastal systems and the open ocean. Wildfire associated carbon discharged from other high yield fluvial systems, when considered collectively, may be a significant source of lignin, pyrolytic PAHs, and other pyrogenic compounds to the ocean. Extrapolating these methods over geologic time may offer useful historical information about carbon sequestration and burial in coastal sediments and affect coastal carbon budgets. Copyright 2008 by the American Geophysical Union.

Journal of Geophysical Research G: Biogeosciences↗