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At least 577 records · Page 32Linked to original sources

USGS2003

Hydromechanical coupling in geologic processes

Earth's porous crust and the fluids within it are intimately linked through their mechanical effects on each other. This paper presents an overview of such "hydromechanical" coupling and examines current understanding of its role in geologic processes. An outline of the theory of hydromechanics and rheological models for geologic deformation is included to place various analytical approaches in proper context and to provide an introduction to this broad topic for nonspecialists. Effects of hydromechanical coupling are ubiquitous in geology, and can be local and short-lived or regional and very long-lived. Phenomena such as deposition and erosion, tectonism, seismicity, earth tides, and barometric loading produce strains that tend to alter fluid pressure. Resulting pressure perturbations can be dramatic, and many so-called "anomalous" pressures appear to have been created in this manner. The effects of fluid pressure on crustal mechanics are also profound. Geologic media deform and fail largely in response to effective stress, or total stress minus fluid pressure. As a result, fluid pressures control compaction, decompaction, and other types of deformation, as well as jointing, shear failure, and shear slippage, including events that generate earthquakes. By controlling deformation and failure, fluid pressures also regulate states of stress in the upper crust. Advances in the last 80 years, including theories of consolidation, transient groundwater flow, and poroelasticity, have been synthesized into a reasonably complete conceptual framework for understanding and describing hydromechanical coupling. Full coupling in two or three dimensions is described using force balance equations for deformation coupled with a mass conservation equation for fluid flow. Fully coupled analyses allow hypothesis testing and conceptual model development. However, rigorous application of full coupling is often difficult because (1) the rheological behavior of geologic media is complex and poorly understood and (2) the architecture, mechanical properties and boundary conditions, and deformation history of most geologic systems are not well known. Much of what is known about hydromechanical processes in geologic systems is derived from simpler analyses that ignore certain aspects of solid-fluid coupling. The simplifications introduce error, but more complete analyses usually are not warranted. Hydromechanical analyses should thus be interpreted judiciously, with an appreciation for their limitations. Innovative approaches to hydromechanical modeling and obtaining critical data may circumvent some current limitations and provide answers to remaining questions about crustal processes and fluid behavior in the crust.

Hydrogeology Journal↗

USGS2024

Planned geological investigations of the Europa Clipper mission

Geological investigations planned for the Europa Clipper mission will examine the formation, evolution, and expression of geomorphic structures found on the surface. Understanding geologic features, their formation, and any recent activity are key inputs in constraining Europa’s potential for habitability. In addition to providing information about the moon’s habitability, the geologic study of Europa is compelling in and of itself. Here we provide a high-level, cross-instrument, and cross-discipline overview of the geologic investigations planned within the Europa Clipper mission. Europa’s fascinating collection of ice-focused geology provides an unparalleled opportunity to investigate the dynamics of icy shells, ice-ocean exchange processes, and global-scale tectonic and tidal stresses. We present an overview of what is currently known about the geology of Europa, from global to local scales, highlighting outstanding issues and open questions, and detailing how the Europa Clipper mission will address them. We describe the mission’s strategy for searching for and characterizing current activity in the form of possible active plumes, thermal anomalies, evidence for surface changes, and extremely fresh surface exposures. The complementary and synergistic nature of the data sets from the various instruments and their integration will be key to significantly advancing our understanding of Europa’s geology.

Space Science Reviews↗

USGS2011

The key to commercial-scale geological CO2 sequestration: Displaced fluid management

The Wyoming State Geological Survey has completed a thorough inventory and prioritization of all Wyoming stratigraphic units and geologic sites capable of sequestering commercial quantities of CO 2 (5–15 Mt CO 2 /year). This multi-year study identified the Paleozoic Tensleep/Weber Sandstone and Madison Limestone (and stratigraphic equivalent units) as the leading clastic and carbonate reservoir candidates for commercial-scale geological CO 2 sequestration in Wyoming. This conclusion was based on unit thickness, overlying low permeability lithofacies, reservoir storage and continuity properties, regional distribution patterns, formation fluid chemistry characteristics, and preliminary fluid-flow modeling. This study also identified the Rock Springs Uplift in southwestern Wyoming as the most promising geological CO 2 sequestration site in Wyoming and probably in any Rocky Mountain basin. The results of the WSGS CO 2 geological sequestration inventory led the agency and colleagues at the UW School of Energy Resources Carbon Management Institute (CMI) to collect available geologic, petrophysical, geochemical, and geophysical data on the Rock Springs Uplift, and to build a regional 3-D geologic framework model of the Uplift. From the results of these tasks and using the FutureGen protocol, the WSGS showed that on the Rock Springs Uplift, the Weber Sandstone has sufficient pore space to sequester 18 billion tons (Gt) of CO 2 , and the Madison Limestone has sufficient pore space to sequester 8 Gt of CO 2 .

Energy Procedia↗

USGS2011

U.S. Department of Energy's site screening, site selection, and initial characterization for storage of CO 2 in deep geological formations

The U.S. Department of Energy (DOE) is the lead Federal agency for the development and deployment of carbon sequestration technologies. As part of its mission to facilitate technology transfer and develop guidelines from lessons learned, DOE is developing a series of best practice manuals (BPMs) for carbon capture and storage (CCS). The "Site Screening, Site Selection, and Initial Characterization for Storage of CO 2 in Deep Geological Formations" BPM is a compilation of best practices and includes flowchart diagrams illustrating the general decision making process for Site Screening, Site Selection, and Initial Characterization. The BPM integrates the knowledge gained from various programmatic efforts, with particular emphasis on the Characterization Phase through pilot-scale CO 2 injection testing of the Validation Phase of the Regional Carbon Sequestration Partnership (RCSP) Initiative. Key geologic and surface elements that suitable candidate storage sites should possess are identified, along with example Site Screening, Site Selection, and Initial Characterization protocols for large-scale geologic storage projects located across diverse geologic and regional settings. This manual has been written as a working document, establishing a framework and methodology for proper site selection for CO 2 geologic storage. This will be useful for future CO 2 emitters, transporters, and storage providers. It will also be of use in informing local, regional, state, and national governmental agencies of best practices in proper sequestration site selection. Furthermore, it will educate the inquisitive general public on options and processes for geologic CO 2 storage. In addition to providing best practices, the manual presents a geologic storage resource and capacity classification system. The system provides a "standard" to communicate storage and capacity estimates, uncertainty and project development risk, data guidelines and analyses for adequate site characterization, and guidelines for reporting estimates within the classification based on each project's status.

Conference Paper↗

USGS2009

Assessment of planetary geologic mapping techniques for Mars using terrestrial analogs: The SP Mountain area of the San Francisco Volcanic Field, Arizona

We photogeologically mapped the SP Mountain region of the San Francisco Volcanic Field in northern Arizona, USA to evaluate and improve the fidelity of approaches used in geologic mapping of Mars. This test site, which was previously mapped in the field, is chiefly composed of Late Cenozoic cinder cones, lava flows, and alluvium perched on Permian limestone of the Kaibab Formation. Faulting and folding has deformed the older rocks and some of the volcanic materials, and fluvial erosion has carved drainage systems and deposited alluvium. These geologic materials and their formational and modificational histories are similar to those for regions of the Martian surface. We independently prepared four geologic maps using topographic and image data at resolutions that mimic those that are commonly used to map the geology of Mars (where consideration was included for the fact that Martian features such as lava flows are commonly much larger than their terrestrial counterparts). We primarily based our map units and stratigraphic relations on geomorphology, color contrasts, and cross-cutting relationships. Afterward, we compared our results with previously published field-based mapping results, including detailed analyses of the stratigraphy and of the spatial overlap and proximity of the field-based vs. remote-based (photogeologic) map units, contacts, and structures. Results of these analyses provide insights into how to optimize the photogeologic mapping of Mars (and, by extension, other remotely observed planetary surfaces). We recommend the following: (1) photogeologic mapping as an excellent approach to recovering the general geology of a region, along with examination of local, high-resolution datasets to gain insights into the complexity of the geology at outcrop scales; (2) delineating volcanic vents and lava-flow sequences conservatively and understanding that flow abutment and flow overlap are difficult to distinguish in remote data sets; (3) taking care to understand that surficial materials (such as alluvium and volcanic ash deposits) are likely to be under-mapped yet are important because they obscure underlying units and contacts; (4) where possible, mapping multiple contact and structure types based on their varying certainty and exposure that reflect the perceived accuracy of the linework; (5) reviewing the regional context and searching for evidence of geologic activity that may have affected the map area yet for which evidence within the map area may be absent; and (6) for multi-authored maps, collectively analyzing the mapping relations, approaches, and methods throughout the duration of the mapping project with the objective of achieving a solid, harmonious product.

Arizona↗

USGS2014

The digital global geologic map of Mars: Chronostratigraphic ages, topographic and crater morphologic characteristics, and updated resurfacing history

A new global geologic map of Mars has been completed in a digital, geographic information system (GIS) format using geospatially controlled altimetry and image data sets. The map reconstructs the geologic history of Mars, which includes many new findings collated in the quarter century since the previous, Viking-based global maps were published, as well as other discoveries that were made during the course of the mapping using new data sets. The technical approach enabled consistent and regulated mapping that is appropriate not only for the map's 1:20,000,000 scale but also for its widespread use by diverse audiences. Each geologic unit outcrop includes basic attributes regarding identity, location, area, crater densities, and chronostratigraphic age. In turn, units are grouped by geographic and lithologic types, which provide synoptic global views of material ages and resurfacing character for the Noachian, Hesperian, and Amazonian periods. As a consequence of more precise and better quality topographic and morphologic data and more complete crater-density dating, our statistical comparisons identify significant refinements for how Martian geologic terrains are characterized. Unit groups show trends in mean elevation and slope that relate to geographic occurrence and geologic origin. In comparison with the previous global geologic map series based on Viking data, the new mapping consists of half the number of units due to simpler, more conservative and globally based approaches to discriminating units. In particular, Noachian highland surfaces overall have high percentages of their areas now dated as an epoch older than in the Viking mapping. Minimally eroded (i.e., pristine) impact craters ≥3 km in diameter occur in greater proportion on Hesperian surfaces. This observation contrasts with a deficit of similarly sized craters on heavily cratered and otherwise degraded Noachian terrain as well as on young Amazonian surfaces. We interpret these as reflecting the relatively stronger, lava-rich, yet less-impacted materials making up much of the younger units. Reconstructions of resurfacing of Mars by its eight geologic epochs using the Hartmann and Neukum chronology models indicate high rates of highland resurfacing during the Noachian (peaking at 0.3 km 2 /yr during the Middle Noachian), modest rates of volcanism and transition zone and lowland resurfacing during the Hesperian (∼0.1 km 2 /yr), and low rates of mainly volcanic and polar resurfacing (∼0.01 km 2 /yr) for most of the Amazonian. Apparent resurfacing increased in the Late Amazonian (∼0.03 km 2 /yr), perhaps due to better preservation of this latest record.

Planetary and Space Science↗

USGS1999

Application of geologic map information to water quality issues in the southern part of the Chesapeake Bay watershed, Maryland and Virginia, eastern United States

Geologic map units contain much information about the mineralogy, chemistry, and physical attributes of the rocks mapped. This paper presents information from regional-scale geologic maps in Maryland and Virginia, which are in the southern part of the Chesapeake Bay watershed in the eastern United States. The geologic map information is discussed and analyzed in relation to water chemistry data from shallow wells and stream reaches in the area. Two environmental problems in the Chesapeake Bay watershed are used as test examples. The problems, high acidity and high nitrate concentrations in streams and rivers, tend to be mitigated by some rock and sediment types and not by others. Carbonate rocks (limestone, dolomite, and carbonate-cemented rocks) have the greatest capacity to neutralize acidic ground water and surface water in contact with them. Rocks and sediments having high carbon or sulfur contents (such as peat and black shale) potentially contribute the most toward denitrification of ground water and surface water in contact with them. Rocks and sediments that are composed mostly of quartz, feldspar, and light-colored clay (rocks such as granite and sandstone, sediments such as sand and gravel) tend not to alter the chemistry of waters that are in contact with them. The testing of relationships between regionally mapped geologic units and water chemistry is in a preliminary stage, and initial results are encouraging.Geologic map units contain much information about the mineralogy, chemistry, and physical attributes of the rocks mapped. This paper presents information from regional-scale geologic maps in Maryland and Virginia, which are in the southern part of the Chesapeake Bay watershed in the eastern United States. The geologic map information is discussed and analyzed in relation to water chemistry data from shallow wells and stream reaches in the area. Two environmental problems in the Chesapeake Bay watershed are used as test examples. The problems, high acidity and high nitrate concentrations in streams and rivers, tend to be mitigated by some rock and sediment types and not by others. Carbonate rocks (limestone, dolomite, and carbonate-cemented rocks) have the greatest capacity to neutralize acidic ground water and surface water in contact with them. Rocks and sediments having high carbon or sulfur contents (such as peat and black shale) potentially contribute the most toward denitrification of ground water and surface water in contact with them. Rocks and sediments that are composed mostly of quartz, feldspar, and light-colored clay (rocks such as granite and sandstone, sediments such as sand and gravel) tend not to alter the chemistry of waters that are in contact with them. The testing of relationships between regionally mapped geologic units and water chemistry is in a preliminary stage, and initial results are encouraging.

Journal of Geochemical Exploration↗

USGS2026

Statewide surficial geologic map of Nebraska underscores Quaternary landscape evolution from the High Plains to the Central Lowland

Surficial geologic mapping in Nebraska has been conducted primarily at the 1:24,000 scale since the mid-1990s, although there have also been limited efforts to map generalized Quaternary and surficial geology within the state and the region. We compiled and evaluated disparate maps (1:24,000–1:1,000,000) and datasets—including geologic, soil and soil parent material, and geomorphic maps as well as LiDAR derivatives—to produce a single 1:500,000 scale surficial geologic map of Nebraska that is the first of its kind. This new map provides a coarse-scale surficial geologic map that will be incorporated into a nationwide U.S. Geological Survey Quaternary geologic map. It also reflects the variation and uniqueness of physical landscapes in the state, where the Great Plains and Central Lowland physiographic provinces meet, further developing a richer interdisciplinary understanding of regional geomorphology in the heart of North America.

Nebraska↗

USGS2010

Teachers guide to geologic trails in Delaware Water Gap National Recreation Area, Pennsylvania–New Jersey

T he Delaware Water Gap National Recreation Area (DEWA) contains a rich geologic and cultural history within its 68,714 acre boundary. Following the border between New Jersey and Pennsylvania, the Delaware River has cut a magnificent gorge through Kittatinny Mountain, the Delaware Water Gap, to which all other gaps in the Appalachian Mountains have been compared. Proximity to many institutions of learning in this densely populated area of the northeastern United States (Fig. 1 ) makes DEWA an ideal locality to study the geology of this part of the Appalachian Mountains. This one-day field trip comprises an overview discussion of structure, stratigraphy, geomorphology, and glacial geology within the gap. It will be highlighted by hiking a choice of several trails with geologic guides, ranging from gentle to difficult. It is hoped that the “professional” discussions at the stops, loaded with typical geologic jargon, can be translated into simple language that can be understood and assimilated by earth science students along the trails. This trip is mainly targeted for earth science educators and for Pennsylvania geologists needing to meet state-mandated education requirements for licensing professional geologists. The National Park Service, the U.S. Geological Survey, the New Jersey Geological Survey, and local schoolteachers had prepared “The Many Faces of Delaware Water Gap: A Curriculum Guide for Grades 3–6” ( Ferrence et al., 2003 ). Copies of this guide will be given to trip participants and can be downloaded from the GSA Data Repository 1 . The trip will also be useful for instruction at the graduate level. Much of the information presented in this guidebook is modified from Epstein (2006) .

New Jersey, Pennsylvania↗

USGS2025

Applying geological unit distribution and chemical weathering indices to evaluate potential lithological sources of Al, As and Pb to the San Juan River, Four Corners region, USA

In arid to semi-arid landscapes, sporadic monsoonal events, varying widely in scale and distribution, can generate overland flow resulting in streamflow in ephemeral channels. These channels may contain metal-laden sediments that are a by-product of the weathering and erosion of local geological units. To evaluate the potential for local geology to contribute aluminium (Al), arsenic (As) and lead (Pb) to the San Juan River, northwestern New Mexico, USA, the distributions of geological units were delineated for 12 hydrological basins within the greater San Juan River watershed. Concentrations of Al, As and Pb in the predominant geological units were compiled from data in the National Geochemical Database. Chemical indices of weathering (CIW) were calculated for geological units with greater than 5% coverage in the entire San Juan River watershed. Based on CIWs of the major geological units, the Mesaverde Group (CIW = 95.2), Chinle and Dolores Formations ( combined ) (CIW = 93.3), and Mancos Shale ( combined ) (CIW = 82.6) are the most likely units to weather, erode and contribute sediments with elevated concentrations of Al, As and Pb to the San Juan River. The results of this study show the importance of understanding geological sources of sediments because they could be substantial contributors of constituents of concern to water, especially in arid environments where surface water may be the only source of water in the region.

Arizona, Colorado, New Mexico, Utah↗

USGS2020

Economic valuation of health benefits from using geologic data to communicate radon risk potential

Background: Radon exposure is the second leading cause of lung cancer worldwide and represents a major health concern within and outside the United States. Mitigating exposure to radon is especially critical in places with high rates of tobacco smoking (e.g., Kentucky, USA), as radon-induced lung cancer is markedly greater among people exposed to tobacco smoke. Despite homes being a common source of radon exposure, convincing homeowners to test and mitigate for radon remains a challenge. A new communication strategy to increase radon testing among Kentucky homeowners utilizes fine-scale geologic map data to create detailed radon risk potential maps. We assessed the health benefits of this strategy via avoided lung cancer and associated premature mortality and quantified the economic value of these benefits to indicate the potential utility of using geologic map data in radon communication strategies. Methods: We estimated the change in radon testing among all 120 counties in Kentucky following a new communication strategy reliant on geologic maps. We approximated the resultant potential change in radon mitigation rates and subsequent expected lung cancer cases and mortality avoided among smokers and non-smokers exposed to ≥4 pCi/L of radon in the home. We then applied the value of a statistical life to derive the economic value of the expected avoided mortality. Results: The new communication strategy is estimated to help 75 Kentucky residents in one year avoid exposure to harmful radon levels via increased testing and mitigation rates. This equated to the potential avoidance of approximately one premature death due to lung cancer, with a net present value of \$3.4 to \$8.5 million (2016 USD). Conclusions: Our analysis illustrates the potential economic value of health benefits associated with geologic map data used as part of a communication strategy conveying radon risk to the public. Geologic map data are freely available in varying resolutions throughout the United States, suggesting Kentucky’s radon communication strategy using geologic maps can be employed in other states to educate the public about radon. As this is only a single application, in a single state, the economic and health benefits of geologic map data in educating the public about radon are likely to exceed our estimates.

Kentucky↗

USGS1987

The geologic story of Yosemite National Park

Within 150 years, Yosemite has moved from great obscurity to worldwide fame as one of the most visited of our national parks. As a remarkable place where people can enjoy unparalleled scenes of natural beauty and where many easily observed geologic features are concentrated, the park is rivaled by few other areas on the planet. The majesty and immense variety of these features have inspired artists and photographers, intrigued tourists, and stirred controversy among geologists. Field studies in the Yosemite area have contributed to the development of our ideas about geologic processes, including the different actions of streams and glaciers in the evolution of the landscape, and the formation of granite, the basic bedrock of much of the Earth's continents. The park's role as a natural laboratory for geologic research cannot be overemphasized, and its investigation has led to many landmark studies by U.S. Geological Survey geologists over the past 70 years. In 1913, the first detailed program of research on the geology of the park and the origin ofYosemite Valley was begun by Francois Matthes and Frank Calkins. Their work, along with that of later generations of Survey geologists, myself included, serves as the basis for our present understanding of the geologic history of Yosemite and of the processes that formed and continue to mold its landscape. This book, which makes available in one volume a comprehensive summary of the current geologic knowledge of Yosemite National Park, is an excellent example of the Survey's continuing effort to provide earth-science information in the public service.

California↗

USGS1985

Geologic characteristics of sediment- and volcanic-hosted disseminated gold deposits - Search for an occurrence model

The current expansion of resource information, particularly on "disseminated" gold, and the improved technologies now available for resource investigations should place us in an enhanced position for developing a better predictive methodology for meeting one of the important responsibilities of the U.S. Geological Survey-to examine and assess the mineral resources of the geologic terranes composing the public (and privately owned) lands of the United States. The first step is systematic organization of these data. Geologic-occurrence models are an effective systematic method by which to organize large amounts of resource information into a logical sequence facilitating its use more effectively in meeting several industry and Survey objectives, which include the exploration for resources and the assessment of resource potential for land-use decisions. Such models also provide a scientific basis for metallogenesis research, which considers the observable features or attributes of ore occurrence and their "fit" into the Earth's resource puzzle. The use of models in making resource assessments/appraisals was addressed by Shawe (1981), who reported the results of a workshop on methods for resource appraisal of Wilderness and Conterminous United States Mineral Appraisal Program (CUSMAP; 1:250,000-scale quadrangles) areas. The Survey's main objective in the 1982 workshop was to evaluate the status of knowledge about disseminated or very fine grained gold deposits and, if possible, to develop an occurrence model(s). This report on the workshop proceedings has three main objectives: (1) Education through the publication of a summary review and presentation of new thinking and observations about the scientific bases for those geologic processes and environments that foster disseminated gold-ore formation; (2) systematic organization of available geologic, geochemical, and geophysical information for a range of typical disseminated gold deposits (including recognition of gaps in those data); and (3) assessment of current understanding (as presented in objective 2) toward formulating an empirical ore-occurrence model for this type of deposit. As such, this volume represents a preliminary first step at classification and provides a source of pertinent background information. Readers of this volume will soon discover, however, that full agreement has not yet been achieved in the interpretation of some of the geologic evidence. The resulting variations in tentative occurrence models for these controversial deposits ultimately will be resolved by filling the gaps in information that have already been identified. Thus, this volume does not report a U.S. Geological Survey consensus; the conclusions expressed in each chapter represent the particular interpretations of the various workshop participants.

Arizona, California, Idaho, Nevada, Utah↗

USGS1994

Airborne remote sensing for geology and the environment; present and future

In 1988, a group of leading experts from government, academia, and industry attended a workshop on airborne remote sensing sponsored by the U.S. Geological Survey (USGS) and hosted by the Branch of Geophysics. The purpose of the workshop was to examine the scientific rationale for airborne remote sensing in support of government earth science in the next decade. This report has arranged the six resulting working-group reports under two main headings: (1) Geologic Remote Sensing, for the reports on geologic mapping, mineral resources, and fossil fuels and geothermal resources; and (2) Environmental Remote Sensing, for the reports on environmental geology, geologic hazards, and water resources. The intent of the workshop was to provide an evaluation of demonstrated capabilities, their direct extensions, and possible future applications, and this was the organizational format used for the geologic remote sensing reports. The working groups in environmental remote sensing chose to present their reports in a somewhat modified version of this format. A final section examines future advances and limitations in the field. There is a large, complex, and often bewildering array of remote sensing data available. Early remote sensing studies were based on data collected from airborne platforms. Much of that technology was later extended to satellites. The original 80-m-resolution Landsat Multispectral Scanner System (MSS) has now been largely superseded by the 30-m-resolution Thematic Mapper (TM) system that has additional spectral channels. The French satellite SPOT provides higher spatial resolution for channels equivalent to MSS. Low-resolution (1 km) data are available from the National Oceanographic and Atmospheric Administration's AVHRR system, which acquires reflectance and day and night thermal data daily. Several experimental satellites have acquired limited data, and there are extensive plans for future satellites including those of Japan (JERS), Europe (ESA), Canada (Radarsat), and the United States (EOS). There are currently two national airborne remote sensing programs (photography, radar) with data archived at the USGS' EROS Data Center. Airborne broadband multispectral data (comparable to Landsat MSS and TM but involving several more channels) for limited geographic areas also are available for digital processing and analysis. Narrow-band imaging spectrometer data are available for some NASA experiment sites and can be acquired for other locations commercially. Remote sensing data and derivative images, because of the uniform spatial coverage, availability at different resolutions, and digital format, are becoming important data sets for geographic information system (GIS) analyses. Examples range from overlaying digitized geologic maps on remote sensing images and draping these over topography, to maps of mineral distribution and inferred abundance. A large variety of remote sensing data sets are available, with costs ranging from a few dollars per square mile for satellite digital data to a few hundred dollars per square mile for airborne imaging spectrometry. Computer processing and analysis costs routinely surpass these expenses because of the equipment and expertise necessary for information extraction and interpretation. Effective use requires both an understanding of the current methodology and an appreciation of the most cost-effective solution.

Bulletin↗

USGS1987

COGEOMAP; a new era in cooperative geologic mapping

A program of cooperative geologic mapping was established between the U.S. Geological Survey and the State geological surveys in fiscal year 1985. The main purpose of the program is to increase general-purpose geologic mapping throughout the Nation. By combining State and Federal resources for geologic mapping through this cooperative program, new mapping has been started, and both geologic and geophysical maps that resulted from the program have already been published. The program grew from mapping projects in 18 States in fiscal year 1985 to a program involving 29 States in 1986, as the combined State and Federal resources in the program grew from about $2 million to nearly $3 million. As the program enlarges its scope, it faces the challenge of producing high-quality maps with uniform standards while promoting the use of new technologies to increase the speed of geologic and geophysical mapping and map production.

Circular↗

USGS1990

Digitization of a geologic map for the Quebec-Maine-Gulf of Maine global geoscience transect

The Bedrock Geologic Map of Maine was digitized and combined with digital geologic data for Quebec and the Gulf of Maine for the Quebec-Maine-Gulf of Maine Geologic Transect Project. This map is being combined with digital geophysical data to produce three-dimensional depictions of the subsurface geology and to produce cross sections of the Earth's crust. It is an essential component of a transect that stretches from the craton near Quebec City, Quebec, to the Atlantic Ocean Basin south of Georges Bank. The transect is part of the Global Geosciences Transect Project of the International Lithosphere Program. The Digital Line Graph format is used for storage of the digitized data. A coding scheme similar to that used for base category planimetric data was developed to assign numeric codes to the digitized geologic data. These codes were used to assign attributes to polygon and line features to describe rock type, age, name, tectonic setting of original deposition, mineralogy, and composition of igneous plutonic rocks, as well as faults and other linear features. The digital geologic data can be readily edited, rescaled, and reprojected. The attribute codes allow generalization and selective retrieval of the geologic features. The codes allow assignment of map colors based on age, lithology, or other attribute. The Digital Line Graph format is a general transfer format that is supported by many software vendors and is easily transferred between systems.

Circular↗

USGS1977

The United States Geological Survey in Alaska: Organization and status of programs in 1977

United States Geological Survey projects in Alaska include a wide range of topics of economic and scientific interest. Studies in 1976 include economic geology, regional geology, stratigraphy, environmental geology, engineering geology, hydrology, and marine geology. Discussions of the findings or, in some instances, narratives of the course of the investigations are grouped in eight subdivisions corresponding to the six major onshore geographic regions, the offshore projects, and projects that are statewide in scope. Locations of the study areas are shown. In addition, many reports and maps covering various aspects of the geology and mineral and water resources of the State were published. These publications are listed. (Woodard-USGS)

Circular↗

USGS1977

The United States Geological Survey in Alaska: Accomplishments during 1976

Circular↗