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At least 1,549 records · Page 86Linked to original sources
USGS2011

Science supporting Gulf of Mexico oil-spill response, mitigation, and restoration activities-Assessment, monitoring, mapping, and coordination

The St. Petersburg Coastal and Marine Science Center of the U.S. Geological Survey (USGS) investigates physical processes related to coastal and marine environments and societal implications related to natural hazards, resource sustainability, and environmental change. Immediately after the Deepwater Horizon event, the USGS began responding to data requests, directing response personnel, and providing coastal and shelf geophysical data to coastal-resource managers. The USGS provided oil-spill responders with up-to-date coastal bathymetry, geologic data, and maps characterizing vulnerability and levels of risk from potential spill impacts in Louisiana, Mississippi, and Alabama. Baseline conditions prior to any spill impacts were documented through programs that included shoreline sampling and sediment coring from east Texas to the east coast of Florida and aerial photography of many environmentally sensitive Gulf coastal areas. The USGS responded to numerous verbal and written data requests from Federal, State, and local partners and academic institutions with USGS scientific staff participating in the Coast Guard Unified Commands (UC) and Operational Science Advisory Teams (OSAT). The USGS conducted technical review of reports and plans for many response activities. Oil-spill responders, managers, and personnel on the ground, including partners such as the National Park Service, Gulf Islands National Seashore, Chandeleur Islands Refuge, and State agencies, continue to rely on USGS products.

General Information Product↗
USGS2013

Wildlife disease and environmental health in Alaska

Environmental health is defined by connections between the physical environment, ecological health, and human health. Current research within the U.S. Geological Survey (USGS) recognizes the importance of this integrated research philosophy, which includes study of disease and pollutants as they pertain to wildlife and humans. Due to its key geographic location and significant wildlife resources, Alaska is a critical area for future study of environmental health.

Alaska↗
USGS1979

Outer Continental Shelf oil and gas information program; Pacific index

The Outer Continental Shelf Lands Act of 1953, as amended in 1978, (43 U.S.C. 1331 et seq.), grants to the Secretary of the Interior the authority to issue leases for minerals on the U.S. Outer Continental Shelf (OCS). It provides the authority and guidelines which the Secretary utilizes for expeditious exploration and development of the OCS while ensuring timely access to information by affected states and local governments in order that appropriate planning will anticipate and ameliorate impacts from such OCS activities. This document is prepared in accordance with Part 30 of the Code of Federal Regulations (CFR), Section 252.5 and 43 CFR, Section 3300.2, which require that the Directors of the U.S. Geological Survey and the Bureau of Land Management shall make available an Index, listing all relevant, actual or proposed programs, plans, reports, environmental impact statements and other lease sale information, on a regular basis, to each affected state and, upon request, to the executive of any local government whose jurisdiction covers an area affected by OCS activities. Accordingly, the Geological Survey and the Bureau of Land Management are cooperating in a joint effort to compile all relevant information on the OCS Oil and Gas Leasing Program in an Index with four volumes; Alaska, Atlantic, Gulf of Mexico and Pacific. This volume is a listing of documents used in the Pacific Area OCS decisionmaking process, and the sequence of information presented parallels this process. The bibliographic references are presented by lease sale number, in the sequence in which the documents are generated in the Federal OCS leasing program. Thus, the reader may compare all documents of one type in the Pacific Area or trace a single lease sale throughout the entire leasing process. Activities which generate information throughout the OCS lease sale process are described under Other Documentation and Supplemental Reading. Other Documentation pertains to Federal data gathering and analysis programs which are an integral part of the OCS decisionmaking process and are used throughout the process due to the usefulness of their subject matter. The Supplemental Reading documents (Appendix A) are not used in decisionmaking but are invaluable sources of general OCS information.

California, Oregon, Washington↗
USGS2013

Water-quality data collected to determine the presence, source, and concentration of lead in the drinking water supply at Pipe Spring National Monument, northern Arizona

Pipe Spring National Monument in northern Arizona contains historically significant springs. The groundwater source of these springs is the same aquifer that presently is an important source of drinking water for the Pipe Spring National Monument facilities, the Kaibab Paiute Tribe, and the community of Moccasin. The Kaibab Paiute Tribe monitored lead concentrations from 2004 to 2009; some of the analytical results exceeded the U.S. Environmental Protection Agency action level for treatment technique for lead of 15 parts per billion. The National Park Service and the Kaibab Paiute Tribe were concerned that the local groundwater system that provides the domestic water supply might be contaminated with lead. Lead concentrations in water samples collected by the U.S. Geological Survey from three springs, five wells, two water storage tanks, and one faucet were less than the U.S. Environmental Protection Agency action level for treatment technique. Lead concentrations of rock samples representative of the rock units in which the local groundwater resides were less than 22 parts per million.

Arizona↗
USGS2006

Land-Cover Trends of the Central Basin and Range Ecoregion

The U.S. Geological Survey (USGS) Land Cover Trends research project is focused on understanding the amounts, rates, trends, causes, and implications of contemporary land-use and land-cover (LU/LC) change in the United States. This project is supported by the USGS Geographic Analysis and Monitoring Program in collaboration with the U.S. Environmental Protection Agency (EPA) and the National Aeronautics and Space Administration (NASA). LU/LC change is a pervasive process that modifies landscape characteristics and affects a broad range of socioeconomic, biologic, and hydrologic systems. Understanding the impacts and feedbacks of LU/LC change on environmental systems requires an understanding of the rates, patterns, and driving forces of past, present, and future LU/LC change. The objectives of the Land Cover Trends project are to (1) determine and describe the amount, rates, and trends of contemporary LU/LC change by ecoregion for the period 1973-2000 for the conterminous United States, (2) document the causes, driving forces, and implications of change, and (3) synthesize individual ecoregion results into a national assessment of LU/LC change. The Land Cover Trends research team includes staff from the USGS National Center for Earth Resources Observation and Science (EROS), Rocky Mountain Geographic Science Center, Eastern Geographic Science Center, Mid-Continent Geographic Science Center, and the Western Geographic Science Center. Other partners include researchers at South Dakota State University, University of Southern Mississippi, and State University of New York College of Environmental Science and Forestry. This report presents an assessment of LU/LC change in the Central Basin and Range ecoregion for the period 1973-2000. The Central Basin and Range ecoregion is one of 84 Level-III ecoregions as defined by the Environmental Protection Agency. Ecoregions have served as a spatial framework for environmental resource management and to denote areas that contain a geographically distinct assemblage of biotic and abiotic phenomena including geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. The established Land Cover Trends methodology generates estimates of LU/LC change using a probability sampling approach and change-detection analysis of thematic land-cover images derived from Landsat satellite imagery.

Scientific Investigations Report↗
USGS2016

Collection methods and descriptions of coral cores extracted from massive corals in Dry Tortugas National Park, Florida, U.S.A.

Cores from living coral colonies were collected from Dry Tortugas National Park, Florida, U.S.A., to obtain skeletal records of past coral growth and allow geochemical reconstruction of environmental variables during the corals’ centuries-long lifespans. The samples were collected as part of the U.S. Geological Survey Coral Reef Ecosystems Studies project ( http:/coastal.er.usgs.gov/crest ) that provides science to assist resource managers tasked with the stewardship of coral reef resources. Three colonies each of the coral species Orbicella faveolata and Siderastrea siderea were collected in May 2012 using the methods described herein and as approved under National Park Service scientific collecting permit number DRTO-2012-SCI-0001 and are cataloged under accession number DRTO-353. These coral samples can be used to retroactively construct environmental parameters, including sea-surface temperature, by measuring the elemental composition of the coral skeleton. The cores described here, and others (see http://olga.er.usgs.gov/coreviewer/ ), can be requested, on loan, for scientific study. Photographic images for each coral in its ocean environment, the coral cores as curated and slabbed, and the X-rays of the slabs can be found in an associated U.S. Geological Survey Data Release.

Florida↗
USGS1994

Overview of environmental and hydrogeologic conditions at Dillingham, Alaska

The remote city of Dillingham is at the northern end of Bristol Bay in southwestern Alaska. The hydrology of the area is strongly affected by the mild maritime climate and local geologic conditions. Dillingham residents obtain drinking water from both deep and shallow aquifers composed of gravels and sands and separated by layers of clay underlying the community. Alternative sources of drinking water are limited to the development of new wells because surface-water sources are of inadequate quantity or quality or are located at too great a distance from the population. The Federal Aviation Administration owns or operates airway support facilities in Dillingham and wishes to consider the severity of contamination and the current environmental setting when they evaluate options for compliance with environmental regulations at their facilities. This report describes the climate. vegetation, geology, soils, ground-water and surface-water hydrology, and flood potential of the areas surrounding the Federal Aviation Administration facilities near Dillingham.

Open-File Report↗
USGS2020

Understanding and documenting the scientific basis of selenium ecological protection in support of site-specific guidelines development for Lake Koocanusa, Montana, U.S.A., and British Columbia, Canada

Modeling of ecosystems is a part of the U.S. Environmental Protection Agency’s protocol for developing site-specific selenium guidelines for protection of aquatic life. Selenium as an environmental contaminant is known to bioaccumulate and cause reproductive effects in fish and wildlife. Here we apply a modeling methodology—ecosystem-scale selenium modeling—to understand and document the scientific basis for predicting and validating ecological protection for Lake Koocanusa, a transboundary reservoir between Montana and British Columbia. A comprehensive set of site-specific data compiled from public databases (Federal, State, and Provincial) and reports by Teck Coal Ltd., is available in a companion U.S. Geological Survey data release. The tissue guideline used within modeling here to assess protection is the U.S. Environmental Protection Agency’s national selenium guideline for whole-body fish (dry weight); however, other numeric values for a whole-body guideline or other tissue types may be assumed if applicable tissue-to-tissue conversion factors are available. We consider the report assembled here as a working document that presents a model that can effectively address and structure the needs of (1) scientific understanding in representing the lake’s ecosystem and selenium biodynamics and (2) policy and management development during a decision-making process, but it is open to modification and updating as more ecologically detailed data become available. The approach brings together the main concerns involved in selenium toxicity: likelihood of high exposure, inherent species sensitivity, and close connectivity of ecosystem characteristics and behavioral ecology of predators. Detailed site-specific modeling equations are provided to document the linked factors that determine the responses of ecosystems to selenium. A series of scenarios quantifies the implications of choices of site-specific variables including food-web species, bioavailability of particulate material, and partitioning between the dissolved and particulate phases at the base of food webs. A gradient mapping tool applied to Lake Koocanusa provides a precedent for ecosystem-scale modeling of lakes by recognizing the importance of lake strata and hydrodynamics as components of modeling. Data requirements for ecosystem modeling, including ecological and hydrological process information fundamental to the dietary biodynamics of selenium in site-specific food webs, were assessed as a precursor to model validation for Lake Koocanusa. Understanding these relationships is necessary to connect modeling outcomes to reproductive effects and establish boundaries, in the case of Lake Koocanusa, for the influences of dam operation, fish-community viability, and its Clean Water Act impaired 303(d)-listing status on ecosystem function. We find that an assemblage of conditions affects the representation of Lake Koocanusa’s ecosystem within modeling scenarios but that the constructed gradient maps, mechanistic model, and associated bioaccumulation potentials portray and quantify the variables that are determinative to protection of predator species. Ecological and hydrological sorting of compiled individual data points on a site- and species-specific basis helps identify and address model uncertainties. Sources of uncertainty include (1) the scarcity of data for some environmental media compartments across time and locations, (2) the complexity of hydrodynamic conditions that can lead to seasonal ecological disconnects such as in selenium partitioning from water into particulates, and (3) the functional status of Lake Koocanusa’s ecosystem because of cumulative effects of various environmental stresses (for example, fish-community changes, flow regime changes, parasites, gonadal dysfunction, and increasing mining input-selenium concentrations since 1984). To this last point, it is important to determine where Lake Koocanusa is in an impairment-restoration cycle so as not to base protection on survivor bias, the maintenance of a currently degraded ecosystem, or normalized toxicity. In a broader context, one of the overall consequences of revised selenium regulations is that their derivation is now dependent on being able to define and understand the status of the ecosystem on which protection is based.

Montana, British Columbia↗
USGS2022

U.S. Geological Survey science strategy for Arctic Alaska, fiscal years 2022–24

Introduction The United States is an Arctic nation because of Alaska and thus maintains tremendous interests and stewardship responsibilities in the region, especially as the region undergoes substantial environmental transformation. This Arctic Science Strategy is intended to support those interests and responsibilities by expressing the core values, mission, vision, and the broad research goals and priority objectives of the U.S. Geological Survey (USGS) for science coordination in Arctic Alaska. It synthesizes strategic planning activities across the USGS in the Arctic over the next 3-year planning horizon, identifies some major networks of collaboration, and aligns with current research priorities of the Department of the Interior Climate Action Plan, released October 7, 2021 (U.S. Department of the Interior, 2021). Also, in recognition of the rapid pace of Arctic environmental changes and the corresponding need to move with urgency beyond routine patterns of operation, this strategy extends an implementation challenge to staff and colleagues in hopes of reaching for breakthrough results in some target areas of performance.

Alaska↗
USGS2024

Interdisciplinary science approach for harmful algal blooms (HABs) and algal toxins—A strategic science vision for the U.S. Geological Survey

Executive Summary Algal blooms in water, soils, dusts, and the environment have captured national attention because of concerns associated with exposure to algal toxins for humans and animals. Algal blooms naturally occur in all surface-water types and are important primary producers for aquatic ecosystems. However, excessive algae growth can be associated with many harmful effects ranging from aesthetic to toxicity concerns, so this excessive growth is commonly called a harmful algal bloom (HAB). Ecological imbalances that can lead to excessive algal growth, such as increased nutrient availability to waterbodies from natural and anthropogenic sources, are well documented in scientific literature. On the other hand, fundamental scientific understandings of environmental causes and controls leading to algal toxin production, environmental exposures, and adverse health outcomes for humans and animals could benefit from more attention by U.S. Geological Survey (USGS) scientists. Understanding when, why, and how the toxin is produced by individual algal cells or communities and why the toxin is released to the surrounding waterbody requires fundamental research to determine a toxin’s role, whether it provides competitive advantage or if other potential reasons exist for toxin production and release, such as secretions from otherwise benign biological processes. This research will require groundbreaking scientific discovery about underlying biologic and abiotic (non-living) processes commonly complicated by local variation in land use, microbial species composition, and ecosystem structure of the surrounding watershed. Although underlying processes by which HABs form may be similar from one waterbody to another, individual waterbodies may be controlled by local factors for HAB development and toxin production that are unique to the watershed. Consequently, many fundamental science gaps exist that prevent informed mitigation and prevention of toxic HAB events. There are also gaps in understanding local conditions that control algal growth unique to specific watersheds. Addressing these science gaps is needed to inform evidence-based decisions that protect human and animal health and that reduce recreational and socioeconomic losses.

Circular↗
USGS2002

An index of biological integrity for northern Mid-Atlantic Slope drainages

An index of biological integrity (IBI) was developed for streams in the Hudson, Delaware, and Susquehanna River drainages in the northeastern United States based on fish assemblage data from the Mohawk River drainage of New York. The original IBI, developed for streams in the U.S. Midwest, was modified to reflect the assemblage composition and structure present in Mid-Atlantic Slope drainages. We replaced several of the Midwestern IBI metrics and criteria scores because fishes common to the Midwest are absent from or poorly represented in the Northeast and because stream fish assemblages in the Northeast are less rich than those in the Midwest. For all replacement metrics we followed the ecology-based rationale used in the development of each of the metrics of the Midwestern IBI so that the basic theoretical underpinnings of the IBI remained unchanged. The validity of this modified IBI is demonstrated by examining the quality of streams in the Hudson, Delaware, and lower Susquehanna River basins. The relationships between the IBI and other indicators of environmental quality are examined using data on assemblages of fish and benthic macroinvertebrates and on chemical and physical stream characteristics obtained during 1993-2000 by the U.S. Geological Survey's National Water Quality Assessment Program in these three river basins. A principal components analysis (PCA) of chemical and physical variables from 27 sites resulted in an environmental quality gradient as the primary PCA axis (eigenvalue, 0.41 ). Principal components analysis site scores were significantly correlated with such benthic macroinvertebrate metrics as the percentage of Ephemeroptera, Plecoptera, and Trichoptera taxa (Spearman R = -0.66, P < 0.001). Index of biological integrity scores for sites in these three river basins were significantly correlated with this environmental quality gradient (Spearman R = -0.78, P = 0.0001). The northern Mid-Atlantic Slope IBI appears to be sensitive to environmental degradation in all three of the river basins addressed in this study. Adjustment of metric scoring criteria may be warranted, depending on composition of fish species in streams in the study area and on the relative effort used in the collection of fish assemblage data.

Transactions of the American Fisheries Society↗
USGS2023

Generating a reference flow network with improved connectivity to support durable data integration and reproducibility in the coterminous US

This report presents a reference flow network for the conterminous United States that is built from the best available information from the U.S. Geological Survey, the National Oceanic and Atmospheric Administration National Weather Service, and the U.S. Environmental Protection Agency. The work is intended to support durable data integration and reproducibility. Originating from the National Hydrography Dataset Plus (NHDPlus) V2.1, the reference flow network incorporates network connectivity enhancements from federal agency efforts. After incorporating these network improvements, many original NHDPlus attributes were regenerated to enable network navigation and related operations. After introducing the motivation and background for this work, this report describes the attribute generation workflow and data quality checks that were performed in preparation of the dataset. The reference flow network follows the NHDPlus data model and is described using terms defined in the Mainstem and Drainage Basin logical model and WaterML2 Part3: Surface Hydrology Features conceptual model.

Environmental Modelling and Software↗
USGS1997

Hydrologic investigations in the Mammoth Corridor, Yellowstone National Park and vicinity, U.S.A.

The Mammoth Corridor in and adjacent to Yellowstone National Park encompasses a N-S alignment of geothermal features that extends from the Norris Geyser Basin adjacent to the Yellowstone caldera through Mammoth Hot Springs to the Corwin Springs Known Geothermal Resources Area (KGRA). Thermal springs in this region discharge water that ranges from NaKCl, silica-depositing type to CaNaHC0 3 SO 4 , travertine-depositing type. Although only a few relatively shallow wells have been drilled in the corridor, the region is of special interest because of the environmental issues associated with potential geothermal development adjacent to Yellowstone National Park. The U.S. Geological Survey conducted an intensive hydrogeologic study of this region during 1988–1990 and continued to collect hydrologic and geophysical data until 1994. The results of these investigations document the rates of discharge of thermal water and heat within the corridor, evidence for a magmatic heat source beneath the Mammoth Hot Springs area, and evidence for separate geothermal systems associated with Mammoth Hot Springs and with thermal waters discharging in the KGRA in the vicinity of La Duke Hot Springs. These investigations also indicate that limited development of the 70°C geothermal resource in the La Duke area would not affect thermal springs in Yellowstone National Park.

Geothermics↗
USGS2020

Robotic environmental DNA bio-surveillance of freshwater health

Autonomous water sampling technologies may help to overcome the human resource challenges of monitoring biological threats to rivers over long time periods and large geographic areas. The Monterey Bay Aquarium Research Institute has pioneered a robotic Environmental Sample Processor (ESP) that overcomes some of the constraints associated with traditional sampling since it can automate water sample filtration and preservation of the captured material or homogenize it for immediate analyses in situ. The ESP was originally developed for marine environment applications. Here we evaluated whether the ESP can provide reliable, timely information on environmental (e)DNA detections of human and fish pathogens and introduced fishes at U.S. Geological Survey streamgage sites in freshwater rivers. We compared eDNA collected via ESP at high frequency (e.g., every 3 h) with manual eDNA collections collected at lower frequency (e.g., weekly). We found that water samples filtered and preserved by ESPs successfully detected the DNA of human pathogens, fish pathogens and introduced fishes. Both ESP and manually collected samples provided similar information about target DNA presence. We suggest that the greatest current benefit of the ESP is the cost savings of high frequency, bio-surveillance at remote or hard to access sites. The full potential of robotic technologies like the ESP will be realized when they can more easily execute in situ analyses of water samples and rapidly transmit results to decision-makers.

Idaho, Montana, Wyoming↗
USGS2024

Application of a workflow to determine the feasibility of using simulated streamflow for estimation of streamflow frequency statistics

Streamflow records from hydrologic models are attractive for use in operational hydrology, such as a streamflow frequency analysis. The amount of bias inherent to simulated streamflow from hydrologic models is often unknown, but it is likely present in derivative products. Therefore, a workflow may help determine where streamflow frequency analysis is credibly feasible from simulated streamflow and allow for a systematic way to assess and correct for bias. The proposed workflow consists of hydrologically matching model output locations with streamflow-gauging station (stream gauge) locations, computing the desired statistic from the simulated and observed streamflow record, computing the differences between the simulated and observed statistic (i.e., the bias), and constructing generalized additive models (GAMs) from the differences to determine bias corrections. The US Geological Survey, in cooperation with the Gulf Coast Ecosystem Restoration Council and the US Environmental Protection Agency, is testing the proposed workflow on a low-streamflow frequency (LFF) analysis. Simulated streamflows for the LFF analysis were sourced from a machine-learning model that estimated daily streamflow at Level-12 hydrologic unit code (HUC12) pour points (outlets) in the southern and southeastern US for 1950–2010. The comparison data set consists of 497 stream gauges that are coincident with a HUC12 outlet. The simulated LFF statistics were being overestimated on average; thus, there are limits to using simulated streamflow for frequency analysis. The magnitude of the overprediction generally increases where no-flow conditions are common. Bias corrections determined from the GAMs decreased the magnitude of bias observed in the simulated LFF statistics on average, suggesting it is feasible to expand the operational use of simulated streamflows to frequency analyses with the proposed workflow. The proposed workflow could be advantageous to practitioners interested in leveraging existing and future simulated streamflow data sets with regional and or global coverage.

Journal of Hydrologic Engineering↗
USGS2016

Fishes in paleochannels of the Lower Mississippi River alluvial valley: A national treasure

Fluvial geomorphology of the alluvial valley of the Lower Mississippi River reveals a fascinating history. A prominent occupant of the valley was the Ohio River, estimated to have flowed 25,000 years ago over western Tennessee and Mississippi to join the Mississippi River north of Baton Rouge, Louisiana, 750–800 km south of the present confluence. Over time, shifts in the Mississippi and Ohio rivers toward their contemporary positions have left a legacy of abandoned paleochannels supportive of unique fish assemblages. Relative to channels abandoned in the last 500 years, paleochannels exhibit harsher environmental conditions characteristic of hypereutrophic lakes and support tolerant fish assemblages. Considering their ecological, geological, and historical importance, coupled with their primordial scenery, the hundreds of paleochannels in the valley represent a national treasure. Altogether, these waterscapes are endangered by human activities and would benefit from the conservation attention afforded to our national parks and wildlife refuges.

Lower Mississippi River valley↗
USGS2000

The land cover trends project: A strategy for monitoring land cover change at a national scale

Policy-makers and scientists often require comprehensive data on the types and rates of land use and land cover change at a variety of scales. However, there is generally a lack of local, regional, and national land use and land cover data of sufficient reliability and temporal and geographic detail for providing accurate estimates of landscape change. The U.S. Geological Survey's EROS Data Center and the Landscape Ecology Branch of the U.S. Environmental Protection Agency are collaborating on a four-year research project to document the types, distributions, rates, drivers, and consequences of land cover change for the conterminous United States over the past 30 years. The project is using an ecoregion framework as a geographic stratifier. Both regional and national characteristics of change are determined by sampling land cover change for each of 84 ecoregions using five selected epochs of data from the nearly 30-year record of Landsat 1-7 data. Three types of land cover variables are being mapped or derived: (1) general land cover type; (2) landscape biophysical properties; and (3) landscape pattern. Assessments of the drivers and consequences of change within each ecoregion are then prepared. A pilot phase focusing on the analysis of five selected ecoregions is well underway and will be completed by the end of 2000. Methodologies established during the pilot phase will then be applied to the remaining ecoregions.

Conference Paper↗
USGS2010

Application of the surface azimuthal electrical resistivity survey method to determine patterns of regional joint orientation in glacial tills

Joints within unconsolidated material such as glacial till can be primary avenues for the flow of electrical charge, water, and contaminants. To facilitate the siting and design of remediation programs, a need exists to map anisotropic distribution of such pathways within glacial tills by determining the azimuth of the dominant joint set. The azimuthal survey method uses standard resistivity equipment with a Wenner array rotated about a fixed center point at selected degree intervals that yields an apparent resistivity ellipse. From this ellipse, joint set orientation can be determined. Azimuthal surveys were conducted at 21 sites in a 500-km2 (193 mi2) area around Milwaukee, Wisconsin, and more specifically, at sites having more than 30 m (98 ft) of glacial till (to minimize the influence of underlying bedrock joints). The 26 azimuthal surveys revealed a systematic pattern to the trend of the dominant joint set within the tills, which is approximately parallel to ice flow direction during till deposition. The average orientation of the joint set parallel with the ice flow direction is N77??E and N37??E for the Oak Creek and Ozaukee tills, respectively. The mean difference between average direct observation of joint set orientations and average azimuthal resistivity results is 8??, which is one fifth of the difference of ice flow direction between the Ozaukee and Oak Creek tills. The results of this study suggest that the surface azimuthal electrical resistivity survey method used for local in situ studies can be a useful noninvasive method for delineating joint sets within shallow geologic material for regional studies. Copyright ?? 2010 The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

Environmental Geosciences↗