Science.gov

Sample records for bedrock geology forsmark

  1. Bedrock geologic map of Vermont

    USGS Publications Warehouse

    Ratcliffe, Nicholas M.; Stanley, Rolfe S.; Gale, Marjorie H.; Thompson, Peter J.; Walsh, Gregory J.; With contributions by Hatch, Norman L., Jr.; Rankin, Douglas W.; Doolan, Barry L.; Kim, Jonathan; Mehrtens, Charlotte J.; Aleinikoff, John N.; McHone, J. Gregory; Cartography by Masonic, Linda M.

    2011-01-01

    The Bedrock Geologic Map of Vermont is the result of a cooperative agreement between the U.S. Geological Survey (USGS) and the State of Vermont. The State's complex geology spans 1.4 billion years of Earth's history. The new map comes 50 years after the most recent map of the State by Charles G. Doll and others in 1961 and a full 150 years since the publication of the first geologic map of Vermont by Edward Hitchcock and others in 1861. At a scale of 1:100,000, the map shows an uncommon level of detail for State geologic maps. Mapped rock units are primarily based on lithology, or rock type, to facilitate derivative studies in multiple disciplines. The 1961 map was compiled from 1:62,500-scale or smaller maps. The current map was created to integrate more detailed (1:12,000- to 1:24,000-scale) modern and older (1:62,500-scale) mapping with the theory of plate tectonics to provide a framework for geologic, tectonic, economic, hydrogeologic, and environmental characterization of the bedrock of Vermont. The printed map consists of three oversize sheets (52 x 76 inches). Sheets 1 and 2 show the southern and northern halves of Vermont, respectively, and can be trimmed and joined so that the entire State can be displayed as a single entity. These sheets also include 10 cross sections and a geologic structure map. Sheet 3 on the front consists of descriptions of 486 map units, a correlation of map units, and references cited. Sheet 3 on the back features a list of the 195 sources of geologic map data keyed to an index map of 7.5-minute quadrangles in Vermont, as well as a table identifying ages of rocks dated by uranium-lead zircon geochronology.

  2. Bedrock Geologic Map of the New Milford Quadrangle, Litchfield and Fairfield Counties, Connecticut

    USGS Publications Warehouse

    Walsh, Gregory J.

    2004-01-01

    The bedrock geology of the New Milford quadrangle, Litchfield and Fairfield Counties, Connecticut is described in this report. The database includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, and photos.

  3. Novice to Expert Cognition During Geologic Bedrock Mapping

    NASA Astrophysics Data System (ADS)

    Petcovic, H. L.; Libarkin, J.; Hambrick, D. Z.; Baker, K. M.; Elkins, J. T.; Callahan, C. N.; Turner, S.; Rench, T. A.; LaDue, N.

    2011-12-01

    Bedrock geologic mapping is a complex and cognitively demanding task. Successful mapping requires domain-specific content knowledge, visuospatial ability, navigation through the field area, creating a mental model of the geology that is consistent with field data, and metacognition. Most post-secondary geology students in the United States receive training in geologic mapping, however, not much is known about the cognitive processes that underlie successful bedrock mapping, or about how these processes change with education and experience. To better understand cognition during geologic mapping, we conducted a 2-year research study in which 67 volunteers representing a range from undergraduate sophomore to 20+ years professional experience completed a suite of cognitive measures plus a 1-day bedrock mapping task in the Rocky Mountains, Montana, USA. In addition to participants' geologic maps and field notes, the cognitive suite included tests and questionnaires designed to measure: (1) prior geologic experience, via a self-report survey; (2) geologic content knowledge, via a modified version of the Geoscience Concept Inventory; (3) visuospatial ability, working memory capacity, and perceptual speed, via paper-and-pencil and computerized tests; (4) use of space and time during mapping via GPS tracking; and (5) problem-solving in the field via think-aloud audio logs during mapping and post-mapping semi-structured interviews. Data were examined for correlations between performance on the mapping task and other measures. We found that both geological knowledge and spatial visualization ability correlated positively with accuracy in the field mapping task. More importantly, we found a Visuospatial Ability × Geological Knowledge interaction, such that visuospatial ability positively predicted mapping performance at low, but not high, levels of geological knowledge. In other words, we found evidence to suggest that visuospatial ability mattered for bedrock mapping for the

  4. Quantitative mapping and statistical evaluation of fracture minerals in the granitic bedrock at Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Löfgren, Martin; Sidborn, Magnus

    2016-03-01

    Abstract This article provides quantitative data on occurrences and amounts of fracture minerals that coat discrete fractures in granitic rock at the Forsmark site in Sweden. The data are useful for retardation modelling of radionuclide and other contaminants, and for groundwater composition calculations. In a unique campaign, 2071 open fractures in groundwater conducting rock have been mapped with respect to chlorite, calcite, and pyrite. In total 767 m of drill core has been studied from very shallow rock down to ~1000 m depth. The occurrences of fracture minerals, their thicknesses, and their fractions of surface coverage have been recorded for up to eight layers for each fracture. Detection limits are, for each layer, 0.1 mm for the thickness and 1 % for the surface coverage, except for pyrite crystals where surface coverages down to 0.01 % are detectable. The abundance of data has permitted statistical treatment, using parametric and non-parametric methods. Parametric fittings have been made to log-normal, truncated log-normal, and beta distributions. Chlorite, calcite, and pyrite were found in 57 %, 52 %, and 10 % of all mapped fractures, respectively. The fracture mineral thickness was 0.1 mm for calcite, 0.2 mm for chlorite, and 2 μm for pyrite, as averaged over the fracture surface area. For 50 % and 99 % of all fractures the total fracture coating thickness was less than 0.1 mm and 1 mm, respectively, which is important for diffusion resistance estimates. Average surface coverages were 18 % for calcite, 38 % for chlorite, and 0.5 % for pyrite. These data may be used for calculating the reaction capacity of flow paths.

  5. Preliminary Bedrock Geologic Map of the Old Lyme Quadrangle, New London and Middlesex Counties, Connecticut

    USGS Publications Warehouse

    Walsh, Gregory J.; Scott, Robert B.; Aleinikoff, John N.; Armstrong, Thomas R.

    2006-01-01

    This report presents a preliminary map of the bedrock geology of the Old Lyme quadrangle, New London and Middlesex Counties, Connecticut. The map depicts contacts of bedrock geologic units, faults, outcrops, and structural geologic information. The map was published as part of a study of fractured bedrock aquifers and regional tectonics.

  6. Bedrock geology of the Mount Carmel and Southington quadrangles, Connecticut

    USGS Publications Warehouse

    Fritts, Crawford Ellswroth

    1962-01-01

    New data concerning the geologic structure, stratigraphy, petrography, origin, and ages of bedrock formations in an area of approximately 111 square miles in south-central Connecticut were obtained in the course of detailed geologic mapping from 1957 to 1960. Mapping was done at a scale of 1:24,000 on topographic base maps having a 10-foot contour interval. Bedrock formations are classified in two principal categories. The first includes metasedimentary, meta-igneous, and igneous rocks of Precambrian to Devonian age, which crop out in the western parts of both quadrangles. The second includes sedimentary and igneous rocks of the Newark Group of Late Triassic age, which crop out in the eastern parts of the quadrangles. Diabase dikes, which are Late Triassic or younger in age, intruded rocks in both the western and eastern parts of the map area. Rocks in the western part of the area underwent progressive regional metamorphism in Middle to Late Devonian time. The arrangement of the chlorite, garnet, biotite, staurolite, and kyanite zones here is approximately the mirror-image of metamorphic zones in Dutchess County, New York. However, garnet appeared before biotite in politic rocks in the map area, because the ration MgO/FeO is low. Waterbury Gneiss and the intrusive Woodtick Gneiss are parts of a basement complex of Precambrian age, which forms the core of the Waterbury dome. This structure is near the southern end of a line of similar domes that lie along the crest of a geanticline east of the Green Mountain anticlinorium. The Waterbury Gneiss is believed to have been metamorphosed in Precambrian time as well as in Paleozoic time. The Woodtick Gneiss also may have been metamorphosed more than once. In Paleozoic time, sediments were deposited in geosynclines during two main cycles of sedimentation. The Straits, Southington Mountain, and Derby Hill Schists, which range in age from Cambrian to Ordovician, reflect a transition from relatively clean politic sediments to

  7. Bedrock geologic map of the Worcester South quadrangle, Worcester County, Massachusetts

    USGS Publications Warehouse

    Walsh, Gregory J.; Merschat, Arthur J.

    2015-01-01

    The bedrock geology was mapped to study the tectonic history of the area and to provide a framework for ongoing hydrogeologic characterization of the fractured bedrock of Massachusetts. This report presents mapping by Gregory J. Walsh and Arthur J. Merschat from 2008 to 2010. The report consists of a map and GIS database, both of which are available for download at http://dx.doi.org/ 10.3133/sim3345. The database includes contacts of bedrock geologic units, faults, outcrop locations, structural information, and photographs.

  8. Bedrock Geology of the Turkey Creek Drainage Basin, Jefferson County, Colorado

    USGS Publications Warehouse

    Char, Stephen J.

    2000-01-01

    This geospatial data set describes bedrock geology of the Turkey Creek drainage basin in Jefferson County, Colorado. It was digitized from maps of fault locations and geologic map units based on age and lithology. Created for use in the Jefferson County Mountain Ground-Water Resources Study, it is to be used at a scale no more detailed than 1:50,000.

  9. Bedrock Geologic Map of the Greater Lefkosia Area, Cyprus

    USGS Publications Warehouse

    Harrison, Richard W.; Newell, Wayne; Panayides, Ioannis; Stone, Byron; Tsiolakis, Efthymios; Necdet, Mehmet; Batihanli, Hilmi; Ozhur, Ayse; Lord, Alan; Berksoy, Okan; Zomeni, Zomenia; Schindler, J. Stephen

    2008-01-01

    The island of Cyprus has a long historical record of earthquakes that have damaged pre-Roman to modern human settlements. Because the recurrent damaging earthquakes can have a significant economic and social impact on Cyprus, this project was initiated to develop a seismic-hazard assessment for a roughly 400 square kilometer area centered on Cyprus' capital and largest city, whose European name is Nicosia and whose local name is Lefkosia. In addition, geologic and seismotectonic evaluations for the project extended beyond the perimeter of the geologic map. Additional structural, stratigraphic, and paleontological data were collected island-wide as well as data from literature research throughout the eastern Mediterranean region, in order to accurately place the geology and seismic hazards of the Lefkosia area in a regional tectonic framework.

  10. Bedrock geologic map of the Nashua South quadrangle, Hillsborough County, New Hampshire, and Middlesex County, Massachusetts

    USGS Publications Warehouse

    Walsh, Gregory J.; Jahns, Richard H.; Aleinikoff, John N.

    2013-01-01

    The bedrock geology of the 7.5-minute Nashua South quadrangle consists primarily of deformed Silurian metasedimentary rocks of the Berwick Formation. The metasedimentary rocks are intruded by a Late Silurian to Early Devonian diorite-gabbro suite, Devonian rocks of the Ayer Granodiorite, Devonian granitic rocks of the New Hampshire Plutonic Suite including pegmatite and the Chelmsford Granite, and Jurassic diabase dikes. The bedrock geology was mapped to study the tectonic history of the area and to provide a framework for ongoing hydrogeologic characterization of the fractured bedrock of Massachusetts and New Hampshire. This report presents mapping by G.J. Walsh and R.H. Jahns and zircon U-Pb geochronology by J.N. Aleinikoff. The complete report consists of a map, text pamphlet, and GIS database. The map and text pamphlet are only available as downloadable files (see frame at right). The GIS database is available for download in ESRITM shapefile and Google EarthTM formats, and includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, photographs, and a three-dimensional model.

  11. Spatial Pattern of Groundwater Arsenic Occurrence and Association with Bedrock Geology in Greater Augusta, Maine, USA

    PubMed Central

    Yang, Qiang; Jung, Hun Bok; Culbertson, Charles W.; Marvinney, Robert G.; Loiselle, Marc C.; Locke, Daniel B.; Cheek, Heidi; Thibodeau, Hilary; Zheng, Yan

    2009-01-01

    In New England, groundwater arsenic occurrence has been linked to bedrock geology on regional scales. To ascertain and quantify this linkage at intermediate (100-101 km) scales, 790 groundwater samples from fractured bedrock aquifers in the greater Augusta, Maine area are analyzed. 31% of the sampled wells have arsenic >10 μg/L. The probability of [As] exceeding 10 μg/L mapped by indicator kriging is highest in Silurian pelite-sandstone and pelite-limestone units (~40%). This probability differs significantly (p<0.001) from those in the Silurian-Ordovician sandstone (24%), the Devonian granite (15%) and the Ordovician-Cambrian volcanic rocks (9%). The spatial pattern of groundwater arsenic distribution resembles the bedrock map. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at intermediate scales relevant to water resources planning. The arsenic exceedance rate for each rock unit is considered robust because low, medium and high arsenic occurrences in 4 cluster areas (3-20 km2) with a low sampling density of 1-6 wells per km2 are comparable to those with a greater density of 5-42 wells per km2. About 12,000 people (21% of the population) in the greater Augusta area (~1135 km2) are at risk of exposure to >10 μg/L arsenic in groundwater. PMID:19475939

  12. Spatial pattern of groundwater arsenic occurrence and association with bedrock geology in greater augusta, maine

    USGS Publications Warehouse

    Yang, Q.; Jung, H.B.; Culbertson, C.W.; Marvinney, R.G.; Loiselle, M.C.; Locke, D.B.; Cheek, H.; Thibodeau, H.; Zheng, Yen

    2009-01-01

    In New England, groundwater arsenic occurrence has been linked to bedrock geology on regional scales. To ascertain and quantify this linkage at intermediate (100-101 km) scales, 790 groundwater samples from fractured bedrock aquifers in the greater Augusta, Maine area are analyzed, and 31% of the sampled wells have arsenic concentrations >10 ??g/L. The probability of [As] exceeding 10 ??g/L mapped by indicator kriging is highest in Silurian pelite-sandstone and pelite-limestone units (???40%). This probability differs significantly (p < 0.001) from those in the Silurian - Ordovician sandstone (24%), the Devonian granite (15%), and the Ordovician - Cambrian volcanic rocks (9%). The spatial pattern of groundwater arsenic distribution resembles the bedrock map. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at intermediate scales relevant to water resources planning. The arsenic exceedance rate for each rock unit is considered robust because low, medium, and high arsenic occurrences in four cluster areas (3-20 km2) with a low sampling density of 1-6 wells per km2 are comparable to those with a greater density of 5-42 wells per km2. About 12,000 people (21% of the population) in the greater Augusta area (???1135 km2) are at risk of exposure to >10 ??g/L arsenic in groundwater. ?? 2009 American Chemical Society.

  13. Spatial pattern of groundwater arsenic occurrence and association with bedrock geology in greater Augusta, Maine.

    PubMed

    Yang, Qiang; Jung, Hun Bok; Culbertson, Charles W; Marvinney, Robert G; Loiselle, Marc C; Locke, Daniel B; Cheek, Heidi; Thibodeau, Hilary; Zheng, Yan

    2009-04-15

    In New England, groundwater arsenic occurrence has been linked to bedrock geology on regional scales. To ascertain and quantify this linkage at intermediate (10(0)-10(1) km) scales, 790 groundwater samples from fractured bedrock aquifers in the greater Augusta, Maine area are analyzed, and 31% of the sampled wells have arsenic concentrations >10 microg/L. The probability of [As] exceeding 10 microg/L mapped by indicator kriging is highest in Silurian pelite-sandstone and pelite-limestone units (approximately 40%). This probability differs significantly (p < 0.001) from those in the Silurian-Ordovician sandstone (24%),the Devonian granite (15%), and the Ordovician-Cambrian volcanic rocks (9%). The spatial pattern of groundwater arsenic distribution resembles the bedrock map. Thus, bedrock geology is associated with arsenic occurrence in fractured bedrock aquifers of the study area at intermediate scales relevant to water resources planning. The arsenic exceedance rate for each rock unit is considered robust because low, medium, and high arsenic occurrences in four cluster areas (3-20 km2) with a low sampling density of 1-6 wells per km2 are comparable to those with a greater density of 5-42 wells per km2. About 12,000 people (21% of the population) in the greater Augusta area (approximately 1135 km2) are at risk of exposure to >10 microg/L arsenic in groundwater. PMID:19475939

  14. Bedrock geologic map of the central block area, Yucca Mountain, Nye County, Nevada

    SciTech Connect

    Day, W.C.; Potter, C.J.; Sweetkind, D.S.; Dickerson, R.P.; San Juan, C.A.

    1998-11-01

    Bedrock geologic maps form the foundation for investigations that characterize and assess the viability of the potential high-level radioactive waste repository at Yucca Mountain, Nevada. This study was funded by the US Department of Energy Yucca Mountain Project to provide a detailed (1:6,000-scale) bedrock geologic map for the area within and adjacent to the potential repository area at Yucca Mountain, Nye County, Nevada. Prior to this study, the 1:12,000-scale map of Scott and Bon, (1984) was the primary source of bedrock geologic data for the Yucca Mountain Project. However, targeted detailed mapping within the central block at Yucca Mountain revealed structural complexities along some of the intrablock faults that were not evident at 1:12,000 (Scott and Bonk, 1984). As a result, this study was undertaken to define the character and extent of the dominant structural features in the vicinity of the potential repository. In addition to structural considerations, ongoing subsurface excavation and geologic mapping within the exploratory Studies Facility (ESF), development of a three-dimensional-framework geologic model, and borehole investigations required use of a constituent stratigraphic system to facilitate surface to underground comparisons. The map units depicted in this report correspond as closely as possible to the proposed stratigraphic nomenclature by Buesch and others (1996), as described here.

  15. Bedrock geologic map of the Uxbridge quadrangle, Worcester County, Massachusetts, and Providence County, Rhode Island

    USGS Publications Warehouse

    Walsh, Gregory J.

    2014-01-01

    The bedrock geology of the 7.5-minute Uxbridge quadrangle consists of Neoproterozoic metamorphic and igneous rocks of the Avalon zone. In this area, rocks of the Avalon zone lie within the core of the Milford antiform, south and east of the terrane-bounding Bloody Bluff fault zone. Permian pegmatite dikes and quartz veins occur throughout the quadrangle. The oldest metasedimentary rocks include the Blackstone Group, which represents a Neoproterozoic peri-Gondwanan marginal shelf sequence. The metasedimentary rocks are intruded by Neoproterozoic arc-related plutonic rocks of the Rhode Island batholith. This report presents mapping by G.J. Walsh. The complete report consists of a map, text pamphlet, and GIS database. The map and text pamphlet are available only as downloadable files (see frame at right). The GIS database is available for download in ESRI™ shapefile and Google Earth™ formats, and includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, geochemical data, and photographs.

  16. A Test of the Circumvention-of-Limits Hypothesis in Scientific Problem Solving: The Case of Geological Bedrock Mapping

    ERIC Educational Resources Information Center

    Hambrick, David Z.; Libarkin, Julie C.; Petcovic, Heather L.; Baker, Kathleen M.; Elkins, Joe; Callahan, Caitlin N.; Turner, Sheldon P.; Rench, Tara A.; LaDue, Nicole D.

    2012-01-01

    Sources of individual differences in scientific problem solving were investigated. Participants representing a wide range of experience in geology completed tests of visuospatial ability and geological knowledge, and performed a geological bedrock mapping task, in which they attempted to infer the geological structure of an area in the Tobacco…

  17. Geological Influences on Bedrock Topography and East Antarctic Ice Sheet Dynamics in the Wilkes Subglacial Basin

    NASA Astrophysics Data System (ADS)

    Ferraccioli, F.; Armadillo, E.; Young, D. A.; Blankenship, D. D.; Jordan, T. A.; Balbi, P.; Bozzo, E.; Siegert, M. J.

    2014-12-01

    The Wilkes Subglacial Basin (WSB) extends for 1,400 km from George V Land into the interior of East Antarctica and hosts several major glaciers that drain a large sector of the East Antarctic Ice Sheet (EAIS). This region is of key significance for the long-term stability of the ice sheet in East Antarctica, as it lies well below sea level and its bedrock deepens inland, making it potentially prone to marine ice sheet instability, much like areas of the West Antarctic Ice Sheet (WAIS) that are presently experiencing significant mass loss. We present new enhanced potential field images of the WSB combined with existing radar imaging to study geological controls on bedrock topography and ice flow regimes in this key sector of the ice sheet. These images reveal mayor Precambrian and Paleozoic basement faults that exert tectonic controls both on the margins of the basin and its sub-basins. Several major sub-basins can be recognised: the Eastern Basin, the Central Basins and the Western Basins. Using ICECAP aerogeophysical data we show that these tectonically controlled interior basins connect to newly identified basins underlying the Cook Ice Shelf region. This connection implies that any ocean-induced changes at the margin of the EAIS could potentially propagate rapidly further into the interior. With the aid of simple magnetic and gravity models we show that the WSB does not presently include major post Jurassic sedimentary infill. Its bedrock geology is highly variable and includes Proterozoic basement, Neoproterozoic and Cambrian sediments, intruded by Cambrian arc rocks, and cover rocks formed by Beacon sediments intruded by Jurassic Ferrar sills. Enhanced ice flow in this part of the EAIS occurs therefore in a area of mixed and spatially variable bedrock geology. This contrasts with some regions of the WAIS where more extensive sedimentary basins may represent a geological template for the onset and maintenance of fast glacial flow.

  18. Bedrock geologic map of the Montpelier and Barre West quadrangles, Washington and Orange Counties, Vermont

    USGS Publications Warehouse

    Walsh, Gregory J.; Kim, Jonathan; Gale, Marjorie H.; King, Sarah M.

    2010-01-01

    The bedrock geology of the Montpelier and Barre West quadrangles consists of Silurian and Devonian metasedimentary rocks of the Connecticut Valley-Gaspe synclinorium (CVGS) and metasedimentary, metavolcanic, and metaintrusive rocks of the Cambrian and Ordovician Moretown and Cram Hill Formations. Devonian granite dikes occur throughout the two quadrangles but are more abundant in the Silurian and Devonian rocks. The pre-Silurian rocks are separated from the rocks of the CVGS by the informally named 'Richardson Memorial Contact,' historically interpreted as either an unconformity or a fault. The results of this report represent mapping by G.J. Walsh, Jonathan Kim, and M.H. Gale from 2002 to 2005. S.M. King assisted Kim and Gale from 2002 to 2003. A.M. Satkoski (Indiana University) assisted Walsh, and L.R. Pascale (University of Vermont) and C.M. Orsi (Middlebury College) assisted Kim and Gale as summer interns in 2003. This study was designed to map the bedrock geology in the area. This map supersedes a preliminary map of the Montpelier quadrangle (Kim, Gale, and others, 2003). A companion study in the Barre West quadrangle (Walsh and Satkoski, 2005) determined the levels of naturally occurring radioactivity in the bedrock from surface measurements at outcrops during the course of 1:24,000-scale geologic mapping to identify which rock types were potential sources of radionuclides. Results of that study indicate that the carbonaceous phyllites in the CVGS have the highest levels of natural radioactivity.

  19. Bedrock geologic map of the Yucca Mountain area, Nye County, Nevada

    SciTech Connect

    Day, W.C.; Potter, C.J.; Sweetkind, D.S.; Fridrich, C.J.; Dickerson, R.P.; San Juan, C.A.; Drake, R.M. II

    1998-11-01

    Yucca Mountain, Nye County, Nevada, has been identified as a potential site for underground storage of high-level radioactive nuclear waste. Detailed bedrock geologic maps form an integral part of the site characterization program by providing the fundamental framework for research into the geologic hazards and hydrologic behavior of the mountain. This bedrock geologic map provides the geologic framework and structural setting for the area in and adjacent to the site of the potential repository. The study area comprises the northern and central parts of Yucca Mountain, located on the southern flank of the Timber Mountain-Oasis Valley caldera complex, which was the source for many of the volcanic units in the area. The Timber Mountain-Oasis Valley caldera complex is part of the Miocene southwestern Nevada volcanic field, which is within the Walker Lane belt. This tectonic belt is a northwest-striking megastructure lying between the more active Inyo-Mono and Basin-and-Range subsections o f the southwestern Great Basin.

  20. Steeply dipping heaving bedrock, Colorado: Part 1 - Heave features and physical geological framework

    USGS Publications Warehouse

    Noe, D.C.; Higgins, J.D.; Olsen, H.W.

    2007-01-01

    Differentially heaving bedrock has caused severe damage near the Denver metropolitan area. This paper describes heave-feature morphologies, the underlying bedrock framework, and their inter-relationship. The heave features are linear to curvilinear and may attain heights of 0.7 m (2.4 ft), widths of 58 m (190 ft), and lengths of 1,067 m (3,500 ft). They are nearly symmetrical to highly asymmetrical in cross section, with width-to-height ratios of 45:1 to 400:1, and most are oriented parallel with the mountain front. The bedrock consists of Mesozoic sedimentary formations having dip angles of 30 degrees to vertical to overturned. Mixed claystone-siltstone bedding sequences up to 36-m (118-ft) thick are common in the heave-prone areas, and interbeds of bentonite, limestone, or sandstone may be present. Highly fractured zones of weathered to variably weathered claystone extend to depths of 19.5 to 22.3 m (64 to 73 ft). Fracture spacings are 0.1 to 0.2 m (0.3 to 0.7 ft) in the weathered and variably weathered bedrock and up to 0.75 m (2.5 ft) in the underlying, unweathered bedrock. Curvilinear shear planes in the weathered claystone show thrust or reverse offsets up to 1.2 m (3.9 ft). Three associations between heave-feature morphologies and the geological framework are recognized: (1) Linear, symmetrical to asymmetrical heaves are associated with primary bedding composition changes. (2) Linear, highly asymmetrical heaves are associated with shear planes along bedding. (3) Curvi-linear, highly asymmetrical heaves are associated with bedding-oblique shear planes.

  1. Preliminary bedrock geologic map of the Seward Peninsula, Alaska, and accompanying conodont data

    USGS Publications Warehouse

    Till, Alison B.; Dumoulin, Julie A.; Werdon, Melanie B.; Bleick, Heather A.

    2010-01-01

    This 1:500,000-scale geologic map depicts the bedrock geology of Seward Peninsula, western Alaska, on the North American side of the Bering Strait. The map encompasses all of the Teller, Nome, Solomon, and Bendeleben 1:250,000-scale quadrangles, and parts of the Shishmaref, Kotzebue, Candle, and Norton Bay 1:250,000-scale quadrangles (sheet 1; sheet 2). The geologic map is presented on Sheet 1. The pamphlet includes an introductory text, unit descriptions, tables of geochronologic data, and an appendix containing conodont (microfossil) data and a text about those data. Sheet 2 shows metamorphic and tectonic units, conodont color alteration indices, key metamorphic minerals, and locations of geochronology samples listed in the pamphlet.

  2. Bedrock geologic map of the Seward Peninsula, Alaska, and accompanying conodont data

    USGS Publications Warehouse

    Till, Alison B.; Dumoulin, Julie A.; Werdon, Melanie B.; Bleick, Heather A.

    2011-01-01

    This 1:500,000-scale geologic map depicts the bedrock geology of Seward Peninsula, western Alaska, on the North American side of the Bering Strait. The map encompasses all of the Teller, Nome, Solomon, and Bendeleben 1:250,000-scale quadrangles, and parts of the Shishmaref, Kotzebue, Candle, and Norton Bay 1:250,000-scale quadrangles (sh. 1; sh. 2). The geologic map is presented on Sheet 1. The pamphlet includes an introductory text, detailed unit descriptions, tables of geochronologic data, and an appendix containing conodont (microfossil) data and a text explaining those data. Sheet 2 shows metamorphic and tectonic units, conodont color alteration indices, key metamorphic minerals, and locations of geochronology samples listed in the pamphlet. The map area covers 74,000 km2, an area slightly larger than West Virginia or Ireland.

  3. Bedrock geologic Map of the Central Block Area, Yucca Mountain, Nye County, Nevada

    SciTech Connect

    W.C. Day; C. Potter; D. Sweetkind; R.P. Dickerson; C.A. San Juan

    1998-09-29

    Bedrock geologic maps form the foundation for investigations that characterize and assess the viability of the potential high-level radioactive waste repository at Yucca Mountain, Nevada. As such, this map focuses on the central block at Yucca Mountain, which contains the potential repository site. The central block is a structural block of Tertiary volcanic rocks bound on the west by the Solitario Canyon Fault, on the east by the Bow Ridge Fault, to the north by the northwest-striking Drill Hole Wash Fault, and on the south by Abandoned Wash. Earlier reconnaissance mapping by Lipman and McKay (1965) provided an overview of the structural setting of Yucca Mountain and formed the foundation for selecting Yucca Mountain as a site for further investigation. They delineated the main block-bounding faults and some of the intrablock faults and outlined the zoned compositional nature of the tuff units that underlie Yucca Mountain. Scott and Bonk (1984) provided a detailed reconnaissance geologic map of favorable area at Yucca Mountain in which to conduct further site-characterization studies. Of their many contributions, they presented a detailed stratigraphy for the volcanic units, defined several other block-bounding faults, and outlined numerous intrablock faults. This study was funded by the U.S. Department of Energy Yucca Mountain Project to provide a detailed (1:6,000-scale) bedrock geologic map for the area within and adjacent to the potential repository area at Yucca Mountain, Nye County, Nevada. Prior to this study, the 1:12,000-scale map of Scott and Bonk (1984) was the primary source of bedrock geologic data for the Yucca Mountain Project. However, targeted detailed mapping within the central block at Yucca Mountain revealed structural complexities along some of the intrablock faults that were not evident at 1:12,000 (Scott and Bonk, 1984). As a result, this study was undertaken to define the character and extent of the dominant structural features in the

  4. Bedrock geologic map of the Hartland and North Hartland quadrangles, Windsor County, Vermont, and Sullivan and Grafton Counties, New Hampshire

    USGS Publications Warehouse

    Walsh, Gregory J.

    2016-01-01

    This report consists of sheets 1 and 2 as well as an online geographic information systems database that includes contacts of bedrock geologic units, faults, outcrops, structural geologic information, and photographs. Sheet 2 of this report shows three cross sections, a tectonic map, and two brittle features maps that show measured outcrop-scale strike and dip results with summary stereonets and rose diagrams.

  5. Multipurpose bedrock surficial, and environmental geologic maps, New River valley, southwest Virginia

    SciTech Connect

    Schultz, A. ); Collins, T. )

    1994-03-01

    Multipurpose bedrock, surficial, and environmental geologic maps have recently been completed for portions of the Valley and Ridge province of southwest VA. The maps, at both 1:100,000 and 1:24,000 scales, show generalized and detailed bedrock geology grouped by lithology and environmental hazard associations. Also shown are a variety of alluvial, colluvial, debris flow, and landslide deposits, as well as karst features. Multidisciplinary research topics addressed during the mapping included slope evolution and geomorphology, drainage history and terrace distribution, ancient large-scale landsliding, and sinkhole development. The maps have been used by land-use planners and engineering firms in an evaluation of Appalachian paleoseismicity and to assess potential groundwater contamination and subsidence in karst areas. The maps are being used for environmental hazard assessment and site selection of a proposed large electric powerline that crosses the Jefferson National Forest. Also, the maps are proving useful in planning for a public access interpretive geologic enter focused on large-scale slope failures. Some of the largest known landslides in eastern North America took place within the map area. Field comparisons and detailed structure mapping of similar features along the Front Range of the Colorado Rockies indicate that the landslides were probably emplaced during a single catastrophic event of short duration. Although the giles County seismic zone is nearby, stability analyses of slopes in the map area have shown that failure need not have been initiated by a seismic event. Several distinct colluvial units mapped within the area of landslides document a period of extensive weathering that postdates slide emplacement. Radiocarbon dates from landslide sag ponds indicate a minimum age of 9,860 B.P. for emplacement of some of the landslides. These results indicate that pre-slide colluvial and debris flow deposits are at least Pleistocene in age.

  6. Geologic Controls on Groundwater Flow and Contaminant Transport in Fractured Bedrock

    NASA Astrophysics Data System (ADS)

    Warner, J.; Truskowski, M.; Fieber, L.; Ernstmann, G.; Tisoncik, D.; Wells, T.; Stanhope, J.; Henrich, B.

    2003-12-01

    This project involves strategic hydrogeologic investigation and remediation of chlorinated solvents in fractured bedrock and overlying alluvium in Northern California. Primary contaminants include 1,1,1-TCA, 1,1-DCE and 1,1- DCA. The source area includes recoverable DNAPL, with a maximum accumulated thickness of 29 feet in a well, and dissolved concentrations in excess of 500 mg/L. The dissolved plume extends away from the source through an extensive fracture network to a depth of 450 feet. The investigation involved drilling monitoring wells to depths up to 700 feet, borehole geophysics, a seismic reflection survey, and aquifer testing. Optical and acoustic televiewer logging were used to map the fracture network, which is dominated by west, southwest, south, and east dipping features. The seismic reflection survey identified en-echelon, southeast dipping normal faults and antithetic, southwest dipping reverse faults that are generally consistent with the orientation of structures in the nearby San Andreas fault zone. The primary fault strikes are generally parallel to those of the dominant fracture sets. Notable lithologic discontinuities in the Franciscan bedrock were documented across major faults, possibly related to significant vertical and strike-slip offset. The seismic reflection survey provided a useful guide for drilling by predicting areas of higher fracture density. Slug tests and acoustic wave-form, conductivity, temperature, and static/dynamic heat pulse flow meter logging were used to establish that flow is primarily through the fractures and conductive portions of the alluvium. These data were used to install an effective multilevel well network, establish a ground water flow pattern that reflects geologic controls and regional gradient, and support remediation evaluations. Remediation evaluations include dissolved phase remediation bench tests, DNAPL recovery, and monitored natural attenuation (MNA). The dissolved phase bench tests are in progress

  7. Origin and magnetic properties of soil profiles developed on different geological bedrock

    NASA Astrophysics Data System (ADS)

    Szuszkiewicz, Marcin; Magiera, Tadeusz; Łukasik, Adam; Wawer, Małgorzata; Mendakiewicz, Maria

    2014-05-01

    Soil magnetic susceptibility anomaly is a result of accumulation in soil profile magnetic minerals (mostly iron oxides and hydroxides) of both natural and anthropogenic origin. The proper interpretation of magnetic susceptibility distribution in soil profile needs the information about magnetic properties of particles present in, respectively geological bedrock, subsoil horizons and topsoils horizons. The study was aimed on characterization mineralogical composition as well as physicochemical properties of mineral soil horizons. The essence of these research is to show, with the application of magnetic measurements, the character and diversification of selected rocks types and its influence on magnetic properties in soil profiles, in the local scale. The collected rock material included some sedimentary, igneous rocks (i.e. plutonic and volcanic) and metamorphic rocks, occurring in Poland. Magnetic properties of bedrock and soil samples were determined according to the measurements of mass magnetic susceptibility (Ξ) and thermomagnetic curves. Technogenic character and nature of research sites of magnetic susceptibility anomalies, was distinctly observed only in the uppermost part of soil profiles. Except the anthropogenic peak of magnetic susceptibility observed in organic soil horizons, the vertical distribution of Ξ in the whole soil profiles developed on sedimentary rocks is relatively low values ranging from ~0.5 to 75 ×10-8m3kg-1. In some studied profiles noticeable Ξ value increment is observed in subsoil horizons, revealing pedogenic character of magnetic susceptibility (influence of soil forming process - presence of superparamagnetic particles). Analyses of thermomagnetic curves support the presence of pedogenic iron minerals in subsoil horizons. The strong geogenic character with increasing Ξ values downward the soil profile was observed in soils developed on basalt, serpentinite, gabbro and andesite rocks. Here the Ξ value measured in the bedrock

  8. Geologic Framework for Aeolis Palus Bedrock, and Its Relationship to Mt. Sharp, Mars

    NASA Astrophysics Data System (ADS)

    Grotzinger, J. P.; Blake, D. F.; Crisp, J. A.; Edgett, K. S.; Gellert, R.; Gupta, S.; Lewis, K. W.; Mahaffy, P. R.; Malin, M. C.; Newsom, H. E.; Parker, T. J.; Rice, M. S.; Rubin, D. M.; Siebach, K. L.; Stack, K.; Sumner, D. Y.; Wiens, R. C.; Williams, R. M. E.

    2014-12-01

    For the past 30 months the Curiosity rover has encountered stratified bedrock along a drive route extending from Bradbury Landing à Yellowknife Bay à Kimberley à Pahrump, a distance of ~9 km. Curiosity still has ~2.5 km to make it to Murray Buttes, taken as the base of Mt. Sharp. All bedrock outcrops expose sedimentary rocks, including mud/silt/sandstones, and conglomerate, all of basaltic composition. These rocks all form part of a fluvio-lacustrine facies association, with small volumes of co-mingled eolian deposits. Most are simply interpreted as distal alluvial fan deposits. Paleocurrent data from the Shaler outcrop (Yellowknife Bay) suggests a dominant component of southwesterly flow, and scattered outcrops within the Kimberley region provide evidence for southward-prograding clinoforms. Thus, most of the volume of sedimentary rock observed during the drive from Yellowknife Bay to the Kimberley is consistent with derivation of sediments from erosion of the northern crater rim. However, some stratigraphic intervals may derive from other source areas simply due to the lack of paleocurrent information. A major compositional change is observed in the Yellowknife Bay formation where lower members (Sheepbed, Gillespie) are slightly more mafic than average martian crust, whereas the overlying Glenelg member are more depleted in MgO+FeO, and more enriched in K2O (and Na2O locally). This signature of elevated K2O has been observed commonly in outcrops extending all the way the Kimberley where the drilled Windjana sandstone revealed significant quantities of potassium feldspar. Conglomerates may differ from sandstones in containing a greater fraction of plagioclase feldspar. This suggests that much of the bedrock that underlies Aeolis Palus between Yellowknife Bay and the Kimberley is derived from alkaline source rocks, likely located along the northern rim. In contrast, the lower part of Yellowknife Bay, including the Sheepbed mudstone - with finer grain size

  9. Relation of bedrock aquifer property and geological structure in Mockcheon area, Korea

    NASA Astrophysics Data System (ADS)

    Hamm, S.-Y.; Kang, L. S.; Choi, S. J.; Lee, B. D.

    2003-04-01

    In Korea, 72 companies are producing natural mineral water mostly from bedrock aquifer of different depths (Sung et al., 2002). It is important to insure quantity of natural mineral water. However, when several natural mineral-water companies are gathered in small area, the amount of producing water can be often limited by pumping rate of the companies in the area. In the study area, five natural mineral water producing companies (Siwon Semmul, Daejeong Eumryo, Jain Guanguang, Cheongsu Eumryo and Hanju Sikpum) are located in range of 2 km radius. Consequently, wells for natural mineral water of five companies and other private wells are drilled in Mockchun area. These wells produce groundwater from bedrock with total discharge rate 1,991m3/day. Thus, it is necessary to understand the hydrogeological characteristics of bedrock groundwater to preserve groundwater quantity in the study area. Geology was investigated to understand geological structure controlling aquifer characteristics in the study area. Precambrian metamorphic rocks (metamorphosed limestone, biotite schist, augen gneiss and porphyroblastic gneiss) are intruded by Jurassic porphyritic granite and two-mica granite and by numerous acidic and intermediate dykes. Alluvium overlies older rocks by unconformity (Kang and Lim, 1974; Shin et al., 1975). Two NS-direction thrusts are developed in the study area. Main aquifer is formed between the lower thrust and the upper thrust, and the lower thrust plays role as impermeable layer. It is considered that the main aquifer was developed by brecciation during the thrust faulting. Thus, pumping wells of mineral water are also located along the thrusts. Wells of Siwon Semmul, Daejeong Eumryo and Jain Guanguang mineral water producing companies are drilled in different aquifers. However, the wells of Chungsoo Eumryo and Hanjoo Sikpoom are drilled in the same aquifer, and are influenced each other during pumping. To understand hydrogeological characteristics, field

  10. Attributes for NHDPlus Catchments (Version 1.1) in the Conterminous United States: Bedrock Geology

    USGS Publications Warehouse

    Wieczorek, Michael E.; LaMotte, Andrew E.

    2010-01-01

    This data set represents the area of bedrock geology types in square meters compiled for every catchment of NHDPlus for the conterminous United States. The source data set is the "Geology of the Conterminous United States at 1:2,500,000 Scale--A Digital Representation of the 1974 P.B. King and H.M. Beikman Map" (Schuben and others, 1994). The NHDPlus Version 1.1 is an integrated suite of application-ready geospatial datasets that incorporates many of the best features of the National Hydrography Dataset (NHD) and the National Elevation Dataset (NED). The NHDPlus includes a stream network (based on the 1:100,00-scale NHD), improved networking, naming, and value-added attributes (VAAs). NHDPlus also includes elevation-derived catchments (drainage areas) produced using a drainage enforcement technique first widely used in New England, and thus referred to as "the New England Method." This technique involves "burning in" the 1:100,000-scale NHD and when available building "walls" using the National Watershed Boundary Dataset (WBD). The resulting modified digital elevation model (HydroDEM) is used to produce hydrologic derivatives that agree with the NHD and WBD. Over the past two years, an interdisciplinary team from the U.S. Geological Survey (USGS), and the U.S. Environmental Protection Agency (USEPA), and contractors, found that this method produces the best quality NHD catchments using an automated process (USEPA, 2007). The NHDPlus dataset is organized by 18 Production Units that cover the conterminous United States. The NHDPlus version 1.1 data are grouped by the U.S. Geologic Survey's Major River Basins (MRBs, Crawford and others, 2006). MRB1, covering the New England and Mid-Atlantic River basins, contains NHDPlus Production Units 1 and 2. MRB2, covering the South Atlantic-Gulf and Tennessee River basins, contains NHDPlus Production Units 3 and 6. MRB3, covering the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy River basins, contains NHDPlus

  11. Bedrock Geologic Map of the Old Lyme Quadrangle, New London and Middlesex Counties, Connecticut

    USGS Publications Warehouse

    Walsh, Gregory J.; Scott, Robert B.; Aleinikoff, John N.; Armstrong, Thomas R.

    2009-01-01

    The bedrock geology of the Old Lyme quadrangle consists of Neoproterozoic and Permian gneisses and granites of the Gander and Avalon terranes, Silurian metasedimentary rocks of the Merrimack terrane, and Silurian to Devonian metasedimentary rocks of uncertain origin. The Avalon terrane rocks crop out within the Selden Neck block, and the Gander terrane rocks crop out within the Lyme dome. The Silurian to Devonian rocks crop out between these two massifs. Previous mapping in the Old Lyme quadrangle includes the work by Lawrence Lundgren, Jr. Lundgren's work provides an excellent resource for rock descriptions and detailed modal analyses of rock units that will not be duplicated in this current report. New research that was not covered in detail by Lundgren is the focus of this report and includes (1) evaluation of the rocks in the core of the Lyme dome in an effort to subdivide units in this area; (2) structural analysis of foliations and folds in and around the Lyme dome; (3) geochronology of selected units within the Lyme dome; and (4) analysis of joints and the fracture properties of the rocks.

  12. Bedrock geologic and joint trend map of the Pinardville quadrangle, Hillsborough County, New Hampshire

    USGS Publications Warehouse

    Burton, William C.; Armstrong, Thomas R.

    2013-01-01

    The bedrock geology of the Pinardville quadrangle includes the Massabesic Gneiss Complex, exposed in the core of a regional northeast-trending anticlinorium, and highly deformed metasedimentary rocks of the Rangeley Formation, exposed along the northwest limb of the anticlinorium. Both formations were subjected to high-grade metamorphism and partial melting: the Rangeley during the middle Paleozoic Acadian orogeny, and the Massabesic Gneiss Complex during both the Acadian and the late Paleozoic Alleghanian orogeny. Granitoids produced during these orogenies range in age from Devonian (Spaulding Tonalite) to Permian (granite at Damon Pond), each with associated pegmatite. In the latest Paleozoic the Massabesic Gneiss Complex was uplifted with respect to the Rangeley Formation along the ductile Powder Hill fault, which also had a left-lateral component. Uplift continued into the early Mesozoic, producing the 2-kilometer-wide Campbell Hill fault zone, which is marked by northwest-dipping normal faults and dilational map-scale quartz bodies. Rare, undeformed Jurassic diabase dikes cut all older lithologies and structures. A second map is a compilation of joint orientations measured at all outcrops in the quadrangle. There is a great diversity of strike trends, with northeast perhaps being the most predominant.

  13. Uranium and thorium series radionuclides in drinking water from drilled bedrock wells: correlation to geology and bedrock radioactivity and dose estimation.

    PubMed

    Isam Salih, M M; Pettersson, H B L; Lund, E

    2002-01-01

    Natural radioactivity in drinking water from 328 drilled wells was studied in correlation to source parameters. Poor correlation to both aquifer geology and bedrock radioactivity was observed. Concentrations of 238U, 226Ra, 228Ra, 222Rn and 210Po in groundwater samples was in the ranges <0.027-5.3, <0.016-4.9, <0.014-1.24, 5-8105 and <0.05-0.947 Bq.l(-1) respectively. In about 80% of the sites the radon concentration exceeds the Nordic recommended exemption level for radon in drinking water and 15% of the sites exceed the action limit. The effective doses from ingestion were calculated and presented in association with geology. Doses due to ingestion ranged between 0.05 and 20.4 mSv.y(-1), where the average contribution from 222Rn amounted to 75%. In comparison, the effective doses from inhalation of indoor 222Rn ranged between 0.2 and 20 mSv.y(-1). The average contribution from inhalation of 222Rn in air to the total effective dose (ingestion+inhalation) was 58 +/- 22%, 73 +/- 18% and 77 +/- 16% (1 SD) for the age categories 1 y, 10 y and adults respectively. PMID:12430963

  14. Bedrock Geology and Asbestos Deposits of the Upper Missisquoi Valley and Vicinity, Vermont

    USGS Publications Warehouse

    Cady, Wallace Martin; Albee, Arden Leroy; Chidester, A.H.

    1963-01-01

    The upper Missisquoi Valley and vicinity as described in this report covers an area of about 250 square miles at the headwaters of the Missisquoi River in north-central Vermont. About 90 percent of the area is forested and the remainder is chiefly farm land. The topography reflects the geologic structure and varied resistance of the bedrock to erosion. Most of the area is on the east limb of the Green Mountain anticlinorium, which is the principal structural feature of Vermont. The bedrock is predominantly sedimentary and volcanic rock that has been regionally metamorphosed. It was intruded before metamorphism by mafic and ultramafic igneous rocks, and after metamorphism by felsic and mafic igneous rocks. The metamorphosed sedimentary and volcanic rocks range in age from Cambrian(?) to Middle Silurian, the intrusive igneous rocks from probably Late Ordovician to probably late Permian. Metamorphism and principal folding in the region occurred in Middle Devonian time. The metamorphosed sedimentary and volcanic rocks make up a section at least 25,000 feet thick and can be divided into nine formations. The Hazens Notch formation of Cambrian(?) and Early Cambrian age is characterized by carbonaceous schist. It is succeeded in western parts of the area by the Jay Peak formation of Early Cambrian age, which is chiefly a schist that is distinguished by the general absence of carbonaceous zones; in central parts of the area the Hazens Notch formation is followed by the Belvidere Mountain amphibolite, probably the youngest of the formations of Early Cambrian age. The Ottauquechee formation, composed of carbonaceous phyllite and quartzite, and phyllitic graywacke, is of Middle Cambrian age. The Stowe formation of Late Cambrian(?) and Early(?) Ordovician age overlies the Ottauquechee and is predominantly noncarbonaceous schist, though it also contains greenstone and carbonaceous schist and phyllite. The Umbrella Hill formation of Middle Ordovician age is characteristically a

  15. Digital bedrock mapping at the Geological Survey of Norway: BGS SIGMA tool and in-house database structure

    NASA Astrophysics Data System (ADS)

    Gasser, Deta; Viola, Giulio; Bingen, Bernard

    2016-04-01

    Since 2010, the Geological Survey of Norway has been implementing and continuously developing a digital workflow for geological bedrock mapping in Norway, from fieldwork to final product. Our workflow is based on the ESRI ArcGIS platform, and we use rugged Windows computers in the field. Three different hardware solutions have been tested over the past 5 years (2010-2015). (1) Panasonic Toughbook CE-19 (2.3 kg), (2) Panasonic Toughbook CF H2 Field (1.6 kg) and (3) Motion MC F5t tablet (1.5 kg). For collection of point observations in the field we mainly use the SIGMA Mobile application in ESRI ArcGIS developed by the British Geological Survey, which allows the mappers to store georeferenced comments, structural measurements, sample information, photographs, sketches, log information etc. in a Microsoft Access database. The application is freely downloadable from the BGS websites. For line- and polygon work we use our in-house database, which is currently under revision. Our line database consists of three feature classes: (1) bedrock boundaries, (2) bedrock lineaments, and (3) bedrock lines, with each feature class having up to 24 different attribute fields. Our polygon database consists of one feature class with 38 attribute fields enabling to store various information concerning lithology, stratigraphic order, age, metamorphic grade and tectonic subdivision. The polygon and line databases are coupled via topology in ESRI ArcGIS, which allows us to edit them simultaneously. This approach has been applied in two large-scale 1:50 000 bedrock mapping projects, one in the Kongsberg domain of the Sveconorwegian orogen, and the other in the greater Trondheim area (Orkanger) in the Caledonian belt. The mapping projects combined collection of high-resolution geophysical data, digital acquisition of field data, and collection of geochronological, geochemical and petrological data. During the Kongsberg project, some 25000 field observation points were collected by eight

  16. Bedrock geology and outcrop fracture trends in the vicinity of the Savage Municipal Well Superfund site, Milford, New Hampshire

    USGS Publications Warehouse

    Burton, William C.; Harte, Philip T.

    2013-01-01

    The Savage Municipal Well Superfund site consists of an eastward-directed plume of volatile organic compounds, principally tetrachloroethylene (PCE), in alluvium and glacial sand and gravel in the Souhegan River valley, just south of the river and about 4 kilometers west of the town of Milford, New Hampshire. Sampling of monitoring wells at the site has helped delineate the extent of the plume and has determined that some contaminant has migrated into the underlying crystalline bedrock, including bedrock north of the river within 200 meters of a nearby residential development that was constructed in 1999. Borehole geophysical logging has identified a northeast preferential trend for bedrock fractures, which may provide a pathway for the migration of contaminant under and north of the Souhegan River. The current study investigates the bedrock geologic setting for the site, including its position relative to known regional geologic structures, and compiles new strike and dip measurements of joints in exposed bedrock to determine if there are dominant trends in orientation similar to what was found in the boreholes. The site is located on the northwestern limb of a northeast-trending regional anticlinorium that is southeast of the Campbell Hill fault zone. The Campbell Hill fault zone defines the contact between granite and gneiss of the anticlinorium and granite and schist to the northwest and is locally marked by lenses of massive vein quartz, minor faults, and fracture zones that could potentially affect plume migration. The fault zone was apparently not intercepted by any of the boreholes that were drilled to delineate the contaminant plume and therefore passes to the north of the northernmost borehole in the vicinity of the new residential area. Joints measured in surface exposures indicate a strong preferred direction of strike to the north-northeast corroborating the borehole data and previous outcrop and geophysical studies. The north-northeast preferred

  17. Bedrock Geologic Map of New Hampshire, a Digital Representation of Lyons and Others 1997 Map and Ancillary Files

    USGS Publications Warehouse

    Bennett, Derek S.; Lyons, John B.; Wittkop, Chad A.; Dicken, Connie L.

    2006-01-01

    The New Hampshire Geological Survey collects data and performs research on the land, mineral, and water resources of the State, and disseminates the findings of such research to the public through maps, reports, and other publications. The Bedrock Geologic Map of New Hampshire, by John B. Lyons, Wallace A. Bothner, Robert H. Moench, and James B. Thompson, was published in paper format by the U.S. Geological Survey (USGS) in 1997. The online version of this CD contains digital datasets of the State map that are intended to assist the professional geologist, land-use planners, water resource professionals, and engineers and to inform the interested layperson. In addition to the bedrock geology, the datasets include geopolitical and hydrologic information, such as political boundaries, quadrangle boundaries, hydrologic units, and water-well data. A more thorough explanation for each of these datasets may be found in the accompanying metadata files. The data are spatially referenced and may be used in a geographic information system (GIS). ArcExplorer, the Environmental Systems Research Institute's (ESRI) free GIS data viewer, is available at http://www.esri.com/software/arcexplorer. ArcExplorer provides basic functions that are needed to harness the power and versatility of the spatial datasets. Additional information on the viewer and other ESRI products may be found on the ArcExplorer website. Although extensive review and revisions of the data have been performed by the USGS and the New Hampshire Geological Survey, these data represent interpretations made by professional geologists using the best available data, and are intended to provide general geologic information. Use of these data at scales larger than 1:250,000 will not provide greater accuracy. The data are not intended to replace site-specific or specific-use investigations. The U.S. Geological Survey, New Hampshire Geological Survey, and State of New Hampshire make no representation or warranty

  18. Beneath it all: bedrock geology of the Catskill Mountains and implications of its weathering.

    PubMed

    Ver Straeten, Charles A

    2013-09-01

    The Devonian-age bedrock of the Catskill Mountains has been the focus of many studies. This paper reviews the character and composition of the rocks of the Catskills, and examines weathering (rock decay) processes and their implications in the Catskills. Rocks of the Catskills and closest foothills consist of siliciclastic rocks (sandstones, mudrocks, conglomerates) with minimal, locally dispersed carbonate rocks. The former are dominated by quartz, metamorphic and sedimentary rock fragments, and clay minerals. Other minor sediment components include cements, authigenic and heavy minerals, and fossil organic matter. Physical, chemical, and biological weathering of the Catskill bedrock since uplift of the Appalachian region, combined with glaciation, have dissected a plateau of nearly horizontally layered rocks into a series of ridges, valleys, and peaks. The varied weathering processes, in conjunction with many factors (natural and anthropogenic), fragment the rocks, forming sediment and releasing various elements and compounds. These may have positive, neutral, or negative implications for the region's soils, waters, ecology, and human usage. A new generation of studies and analyses of the Catskill bedrock is needed to help answer a broad set of questions and problems across various fields of interest. PMID:23895551

  19. Surficial and bedrock geologic map database of the Kelso 7.5 Minute quadrangle, San Bernardino County, California

    USGS Publications Warehouse

    Bedford, David R.

    2003-01-01

    This geologic map database describes geologic materials for the Kelso 7.5 Minute Quadrangle, San Bernardino County, California. The area lies in eastern Mojave Desert of California, within the Mojave National Preserve (a unit of the National Parks system). Geologic deposits in the area consist of Proterozoic metamorphic rocks, Cambrian-Neoproterozoic sedimentary rocks, Mesozoic plutonic and hypabyssal rocks, Tertiary basin fill, and Quaternary surficial deposits. Bedrock deposits are described by composition, texture, and stratigraphic relationships. Quaternary surficial deposits are classified into soil-geomorphic surfaces based on soil characteristics, inset relationships, and geomorphic expression. The surficial geology presented in this report is especially useful to understand, and extrapolate, physical properties that influence surface conditions, and surface- and soil-water dynamics. Physical characteristics such as pavement development, soil horizonation, and hydraulic characteristics have shown to be some of the primary drivers of ecologic dynamics, including recovery of those ecosystems to anthropogenic disturbance, in the eastern Mojave Desert and other arid and semi-arid environments.

  20. Aluminum forms in stream sediment: Relation to bedrock geology and water chemistry

    SciTech Connect

    Turner, R.R.; Bogle, M.A.; Zeiler, M.A.; Mulholland, P.J.; Elwood, J.W.; Cook, R.B.

    1987-01-01

    Longitudinal gradients in sediment and water chemistry were characterized in a high elevation stream in the southern Appalachian Mountains, USA, to elucidate the geochemical behavior of aluminum across gradients in pH (4.5 to 6.5) and elevation (1120 to 1895 m). Observed gradients are driven in part by the presence of pyritic bedrock, which occurs at higher elevations and yields acidity when exposed to oxidation by landslide activity. Exchangeable Al in sediment (estimated using potassium chloride) varied in response to monomeric Al in streamwater and thus decreased downstream. Organic Al in sediment (estimated using sodium pyrophosphate) did not vary in proportion to the organic carbon content of sediment. Amorphous Al in sediment (estimated as the difference between oxalate- and pyrophosphate-extractable Al) and Al extractable with acidified streamwater (pH 4.5) was lowest at the more acidic sites. These results suggest that increases in soluble Al in downstream reaches during episodic pH depressions could be due in part to the release of adsorbed and/or precipitated Al in sediment.

  1. Approaches and algorithms for groundwater flow modeling in support of site investigations and safety assessment of the Forsmark site, Sweden

    NASA Astrophysics Data System (ADS)

    Hartley, Lee; Joyce, Steven

    2013-09-01

    The Swedish Nuclear Fuel and Waste Management Company (SKB) has in 2011 finalized a safety assessment project, SR-Site, with the objective to assess the long term safety of a final repository for spent nuclear fuel at Forsmark in Northern Uppland of Sweden. Prior to the safety assessment, comprehensive site investigations were conducted at the Forsmark site to build understanding and characterize the site. An essential part of the site investigations were to describe hydrological properties and characteristics of the site and use this to assess the groundwater pathway. The geological structural context of the crystalline bedrock at Forsmark implied a fracture network concept was the natural description for interpreting site data and assessing the groundwater pathway. Of primary importance to the description of the fracture system was the assignment of down-borehole flow-logging measurements to individual fractures identified by imaging techniques, providing the basis to relate hydrogeological characteristics such as anisotropy and heterogeneity to the geological structural framework. Also, the key input quantities to the assessment of long-term safety can be closely related to the derived fracture flow-rate distributions. Key success factors for this project were to develop and test strategies for modeling methodologies, as described in this paper, from an early stage, hand-in-hand with the planning and phased acquisition of site data as well as successive safety assessments.

  2. Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Bedrock Geology

    USGS Publications Warehouse

    Wieczorek, Michael E.; LaMotte, Andrew E.

    2010-01-01

    This tabular data set represents the area of bedrock geology types in square meters compiled for every catchment of MRB_E2RF1 catchments for Major River Basins (MRBs, Crawford and others, 2006). The source data set is the "Geology of the Conterminous United States at 1:2,500,000 Scale--A Digital Representation of the 1974 P.B. King and H.M. Beikman Map" (Schuben and others, 1994). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every MRB_E2RF1 catchment for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

  3. Use of Bedrock and Geomorphic Mapping Compilations in Assessing Geologic Hazards at Recreation Sites on National Forests in NW California

    NASA Astrophysics Data System (ADS)

    de La Fuente, J. A.; Bell, A.; Elder, D.; Mowery, R.; Mikulovsky, R.; Klingel, H.; Stevens, M.

    2010-12-01

    Geologic hazards on US Forest Service lands have a long history of producing catastrophic events. In 1890 (prior to the establishment of the Forest Service), the China Mine landslide buried a miner’s camp along the Trinity River in NW California, killing a number of miners. An earthquake in southwestern Montana triggered a massive landslide which killed 28 people in a US Forest Service campground in 1959. In 1980, Mount St. Helens erupted in Oregon, killing 57 people. Debris flows from a winter storm in 2003 on the burned hillslopes of the San Bernardino National Forest in California killed 14 people at the St. Sophia youth Camp. A rockfall in the summer of 2009 in Lassen National Park killed a 9 year old boy. The most recent catastrophe occurred on June 11, 2010 when 20 people died in a flash flood at the Albert Pike Campground on the Ouachita National Forest. These and other disasters point out the need for geologic hazard mapping and assessments on the National Forests. The US Forest Service (USFS) is currently assessing geologic hazards in the Northern Province of USFS Region 5 (Pacific Southwest Region), which includes the Klamath, Mendocino, Shasta-Trinity, and Six Rivers National Forests. The most common geologic hazards (relatively short return intervals) in this area include landslides, rock falls, debris flows, flooding, temporary dam failures (landslide or woody debris), naturally occurring hazardous materials, (asbestos radon, etc), and rarely, karst subsidence. Seismic and volcanic hazards are also important at longer return intervals. This assessment will be conducted in three phases, and is patterned after a process developed by Region 8 of the US Forest Service. The first phase is a reconnaissance level assessment based on existing information such as spatial databases, aerial photos, Digital Elevation Models, State of California Alquist-Priolo Earthquake Fault Zone maps, previous investigations and anecdotal accounts of past events. The bedrock

  4. Bedrock geology of snyderville basin: Structural geology techniques applied to understanding the hydrogeology of a rapidly developing region, Summit County, Utah

    USGS Publications Warehouse

    Keighley, K.E.; Yonkee, W.A.; Ashland, F.X.; Evans, J.P.

    1997-01-01

    The availability of ground water is a problem for many communities throughout the west. As these communities continue to experience growth, the initial allocation of ground water supplies proves inadequate and may force restrictions on existing, and future, development plans. Much of this new growth relies on ground water supplies extracted from fractured bedrock aquifers. An example of a community faced with this problem is western Summit County, near Park City, Utah, This area has experienced significant water shortages coupled with a 50% growth rate in the past 10-15 years. Recent housing development rests directly on complexly deformed Triassic to Jurassic sedimentary rocks in the hanging wall of the Mount Raymond-Absaroka thrust system. The primary fractured bedrock aquifers are the Nugget Sandstone, and limestones in the Thaynes and Twin Creek Formations. Ground water production and management strategies can be improved if the geometry of the structures and the flow properties of the fractured and folded bedrock can be established. We characterize the structures that may influence ground water flow at two sites: the Pinebrook and Summit Park subdivisions, which demonstrate abrupt changes (less than 1 mi/1.6 km) within the hydrogeologic systems. Geologic mapping at scales of 1:4500 (Pinebrook) and 1:9600 (Summit Park), scanline fracture mapping at the outcrop scale, geologic cross sections, water well data, and structural analysis, provides a clearer picture of the hydrogeologic setting of the aquifers in this region, and has been used to successfully site wells. In the Pinebrook area, the dominate map-scale structures of the area is the Twomile Canyon anticline, a faulted box-like to conical anticline. Widely variable bedding orientations suggest that the fold is segmented and is non-cylindrical and conical on the western limb with a fold axis that plunges to the northwest and also to the southeast, and forms a box-type fold between the middle and eastern

  5. Miscellaneous investigations series: Bedrock geologic map of the Lone Mountain pluton area, Esmeralda County, Nevada

    SciTech Connect

    Maldonado, F.

    1984-12-31

    The joint attitudes were measured in the field and plotted on aerial photos at a scale of 1:24,000. The pluton is intensely jointed, primarily as a result of cooling and movement of the magma within a northwest-trending stress field. Foliation, in general, is poorly developed, and quality varies from area to area, but it is best developed close to the contacts with the metasedimentary rocks. A prominent northwest foliation direction was observed that parallels the northwest elongation of the exposed pluton. Faults in the pluton are difficult to identify because of the homogeneity of the rock. Several faults were mapped in the northern part of the area where they have a northeast trend and intersect the northwest-trending lamprophyre dikes with little apparent displacement. A major fault that bounds the northern part of the pluton is downthrown to the north and strikes northeast. This fault offsets the alluvium, the metasedimentary rocks, and the pluton and forms fault scraps as high as 10 m. Aeromagnetic data (US Geological Survey, 1979) suggest the following: (1) the local magnetic highs in the central part of the Lone Mountain pluton are probably related to topographic highs (peaks) where the flight lines are closer to the pluton; (2) a magnetic low in the northeastern part of Lone Mountain coincides with the pluton-country rock contact, which may be very steep; (3) the contours for the southwestern part of the mapped area indicate that the pluton-country rock contact is not as steep as that in the northeastern part and that the pluton probably coalesces at depth with the Weepah pluton, a pluton exposed south of the mapped area; and (4) the contours for the area of the Lone Mountain pluton express a northwest-trending gradient that parallels the northwest elongation of the Lone Mountain pluton and the northwest-trending stress field. 10 refs.

  6. Elevation contours of the bedrock surface, North Platte 1- by 2-degree Quadrangle, Nebraska, digitized from a published 1:250,000-scale geologic map

    USGS Publications Warehouse

    Zelt, Ronald B.

    1995-01-01

    A geologic map showing the configuration of the bedrock surface for the North Platte, Nebraska, 1- by 2-degree quadrangle was published at a scale of 1:250,000 in 1991. This report describes the conversion of the bedrock-surface elevation map into a digital geographic data set and includes those data at a nominal scale of 1:500,000. A film separation of the published elevation contours was scanned to produce a file of digital graphics data. The digital graphics data were processed further to produce a digital geographic data set. Geographic feature attributes and data-set documentation also are included in the digital data set. The digital geographic data are formatted for distribution in accordance with the Spatial Data Transfer Standard approved by the U.S. National Institute of Standards and Technology.

  7. Bedrock geologic map of the southern part of the Diorite and Champion 7 1/2 minute quadrangles, Marquette County, Michigan

    USGS Publications Warehouse

    Cannon, William F.; Klasner, John S.

    1977-01-01

    This map illustrates the bedrock geology of part of the Marquette iron range in the Diorite and Champion 7 ½-minute quadrangles. The area includes part of the Marquette trough, a synclinorium containing rocks of the Marquette Range Supergroup (Precambrian X) and older Precambrian W basement gneiss. Among the Precambrian X rocks is the economically important banded iron-formation, and the oldest rocks of the Precambrian W gneiss consist of a mafic-ultramafic volcanic-intrusive complex that contains gold deposits.

  8. Preliminary bedrock and surficial geologic map of the west half of the Sanders 30' x 60' quadrangle, Navajo and Apache Counties, northern Arizona

    USGS Publications Warehouse

    Amoroso, Lee; Priest, Susan S.; Hiza-Redsteer, Margaret

    2014-01-01

    The bedrock and surficial geologic map of the west half of the Sanders 30' x 60' quadrangle was completed in a cooperative effort of the U.S. Geological Survey (USGS) and the Navajo Nation to provide regional geologic information for management and planning officials. This report provides baseline geologic information that will be useful in future studies of groundwater and surface water resources, geologic hazards, and the distribution of soils and plants. The west half of the Sanders quadrangle encompasses approximately 2,509 km2 (980 mi2) within Navajo and Apache Counties of northern Arizona and is bounded by lat 35°30' to 35° N., long 109°30' to 110° W. The majority of the land within the map area lies within the Navajo Nation. South of the Navajo Nation, private and State lands form a checkerboard pattern east and west of Petrified Forest National Park. In the west half of the Sanders quadrangle, Mesozoic bedrock is nearly flat lying except near folds. A shallow Cenozoic erosional basin that developed about 20 Ma in the western part of the map area cut across late Paleozoic and Mesozoic rocks that were subsequently filled with flat-lying Miocene and Pliocene mudstone and argillaceous sandstone and fluvial sediments of the Bidahochi Formation and associated volcanic rocks of the Hopi Buttes volcanic field. The Bidahochi rocks are capped by Pliocene(?) and Pleistocene fluvial sediments and Quaternary eolian and alluvial deposits. Erosion along northeast-southwest-oriented drainages have exposed elongated ridges of Bidahochi Formation and basin-fill deposits that are exposed through shallow eolian cover of similarly oriented longitudinal dunes. Stokes (1964) concluded that the accumulation of longitudinal sand bodies and the development of confined parallel drainages are simultaneous processes resulting in parallel sets of drainages and ridges oriented along the prevailing southwest wind direction on the southern Colorado Plateau.

  9. Bedrock topography of western Cape Cod, Massachusetts, based on bedrock altitudes from geologic borings and analysis of ambient seismic noise by the horizontal-to-vertical spectral-ratio method

    USGS Publications Warehouse

    Fairchild, Gillian M.; Lane, Jr., John W.; Voytek, Emily B.; LeBlanc, Denis R.

    2013-01-01

    This report presents a topographic map of the bedrock surface beneath western Cape Cod, Massachusetts, that was prepared for use in groundwater-flow models of the Sagamore lens of the Cape Cod aquifer. The bedrock surface of western Cape Cod had been characterized previously through seismic refraction surveys and borings drilled to bedrock. The borings were mostly on and near the Massachusetts Military Reservation (MMR). The bedrock surface was first mapped by Oldale (1969), and mapping was updated in 2006 by the Air Force Center for Environmental Excellence (AFCEE, 2006). This report updates the bedrock-surface map with new data points collected by using a passive seismic technique based on the horizontal-to-vertical spectral ratio (HVSR) of ambient seismic noise (Lane and others, 2008) and from borings drilled to bedrock since the 2006 map was prepared. The HVSR method is based on a relationship between the resonance frequency of ambient seismic noise as measured at land surface and the thickness of the unconsolidated sediments that overlie consolidated bedrock. The HVSR method was shown by Lane and others (2008) to be an effective method for determining sediment thickness on Cape Cod owing to the distinct difference in the acoustic impedance between the sediments and the underlying bedrock. The HVSR data for 164 sites were combined with data from 559 borings to bedrock in the study area to create a spatially distributed dataset that was manually contoured to prepare a topographic map of the bedrock surface. The interpreted bedrock surface generally slopes downward to the southeast as was shown on the earlier maps by Oldale (1969) and AFCEE (2006). The surface also has complex small-scale topography characteristic of a glacially eroded surface. More information about the methods used to prepare the map is given in the pamphlet that accompanies this plate.

  10. Groundtruthing and potential for predicting acid deposition impacts in headwater streams using bedrock geology, GIS, angling, and stream chemistry.

    PubMed

    Kirby, C S; McInerney, B; Turner, M D

    2008-04-15

    Atmospheric acid deposition is of environmental concern worldwide, and the determination of impacts in remote areas can be problematic. Rainwater in central Pennsylvania, USA, has a mean pH of approximately 4.4. Bedrock varies dramatically in its ability to neutralize acidity. A GIS database simplified reconnaissance of non-carbonate bedrock streams in the Valley and Ridge Province and identified potentially chronically impacted headwater streams, which were sampled for chemistry and brook trout. Stream sites (n=26) that originate in and flow through the Tuscarora had a median pH of 5.0 that was significantly different from other formations. Shawangunk streams (n=6) and non-Tuscarora streams (n=20) had a median pH of 6.0 and 6.3, respectively. Mean alkalinity for non-Tuscarora streams (2.6 mg/L CaCO(3)) was higher than the mean for Tuscarora streams (0.5 mg/L). Lower pH and alkalinity suggest that the buffering capability of the Tuscarora is inferior to that of adjacent sandstones. Dissolved aluminum concentrations were much higher for Tuscarora streams (0.2 mg/L; approximately the lethal limit for brook trout) than for non-Tuscarora streams (0.03 mg/L) or Shawangunk streams (0.02 mg/L). Hook-and-line methods determined the presence/absence of brook trout in 47 stream reaches with suitable habitat. Brook trout were observed in 21 of 22 non-Tuscarora streams, all 6 Shawangunk streams, and only 9 of 28 Tuscarora stream sites. Carefully-designed hook-and-line sampling can determine the presence or absence of brook trout and help confirm biological impacts of acid deposition. 15% of 334 km of Tuscarora stream lengths are listed as "impaired" due to atmospheric deposition by the Pennsylvania Department of Environmental Protection. 65% of the 101 km of Tuscarora stream lengths examined in this study were impaired. PMID:18258282

  11. High-resolution morphologic and spectral characteristics of Crater-exposed Bedrock on Mars: Insights into the petrogenesis, stratigraphy and geologic history of the Martian crust

    NASA Astrophysics Data System (ADS)

    Tornabene, L. L.; Caudill, C. M.; McEwen, A. S.; Osinski, G.; Wray, J. J.; Mustard, J. F.; Skok, J. R.; Marzo, G.; Grant, J. A.

    2010-12-01

    Rocks form under a variety of geologic settings and conditions, thus the mineral composition, texture, structures and stratigraphic relationships of exposed rocks provide geologists a means to access information about the past geologic and climatic history. Typically, tectonic events (e.g., orogenic) and erosional processes expose sections of older terrestrial rocks at the surface. On Mars, a lack of complex tectonics and lower erosion rates make these tectonic exposures virtually non-existent. Impacts, however, generate localized displacements and structural uplift of target rocks and exposes them within the crater rim, walls, terraces and central structural uplifts. Imagery from the High Resolution Imaging Science Experiment (HiRISE) of this Crater-Exposed Bedrock (CEB) reveals unprecedented meter to decameter textural and structural detail [1]. Our initial work, based on previous efforts [1-3], has revealed that not all craters are well exposed due to impact melt coatings and ongoing degradation, infilling, and mantling of crater rims, floors and walls. Thus, making a database (DB) of craters with good exposures is an essential step towards understanding the spatial and temporal distribution of CEB textures, structures and compositions. When complete, the DB will aid our ability to make inferences regarding the petrogenesis, evolution and geologic history of the upper crust at regional and potentially global scales. Our CEB DB will be used to focus on spectral units that specifically correlate with CEB textures and stratigraphic relationships. Our preliminary results suggest that CEB can be classified into three textural categories, 1) Megabreccias (MB), 2) Intact layered Stratigraphy (IS), and 3) a massive textured Fractured Bedrock (FB), with each of these classifications being informative with respect to a specific geologic setting or possible set of histories (e.g., late-heavy bombardment, cyclical volcanism and sedimentation). Preliminary spectral analyses

  12. Predicting multi-scale relationships between geomorphology and bedrock geology of the rocky intertidal in Central and Northern California

    NASA Astrophysics Data System (ADS)

    Wheeler, A.; Aiello, I. W.

    2014-12-01

    Substratum geology is fundamental in shaping rocky shore morphology. Specific lithologies have various responses to wave action, tectonic features (e.g. fractures, faults) and sedimentary structures (e.g. bedding), creating distinctive weathering profiles. Along with local oceanography and climate forcing, different rock substrata create coastal morphologies that can vary distinctly between scales, ranging from mm to km. Despite the complexity of the system, qualitative observations show coastal areas with similar rock types share similar geomorphologies. Thus, a statistic relationship between geomorphology (expressed for instance by surface parameter rugosity) and geology can be envisaged. There are multiple benefits of finding such a relationship, as rocky intertidal geomorphology can be an important determinant in which organisms can settle, grow, and survive in near shore communities: allowing the prediction of geomorphologic parameters determining coastal ecology solely based on substratum geology, a crucial aspect in guiding the selection of marine protected areas. This study presents preliminary results of multi-scale geospatial surveys (cm to tens of meters) of rocky intertidal outcrops from Central to Northern California using a Terrestrial Laser Scanner. The outcrops investigated are representative of the most common igneous and sedimentary rocks in California (granitoids, conglomerates, sandstones, mudstones) and metamorphic units. The statistical analysis of the survey data support the hypothesis that surface properties can change significantly with changing scale, each rock type having distinct surface characteristics which are similar to comparable lithologies exposed at different locations. These scale dependent variations are controlled by different lithologic and structural characteristics of the outcrop in question. Our data also suggests lithologic variability within a rock unit could be a very significant factor in controlling changes in

  13. Quantitative bedrock geology of east and Southeast Asia (Brunei, Cambodia, eastern and southeastern China, East Timor, Indonesia, Japan, Laos, Malaysia, Myanmar, North Korea, Papua New Guinea, Philippines, far-eastern Russia, Singapore, South Korea, Taiwan, Thailand, Vietnam)

    NASA Astrophysics Data System (ADS)

    Peucker-Ehrenbrink, Bernhard; Miller, Mark W.

    2004-01-01

    We quantitatively analyze the area-age distribution of sedimentary, igneous and metamorphic bedrock based on data from the most recent digital geologic maps of East and Southeast Asia (Coordinating Committee for Coastal and Offshore Geosciences Programmes in East and Southeast Asia (CCOP) and the Geologic Survey of Japan, 1997; 1:2,000,000), published as Digital Geoscience Map G-2 by the Geological Survey of Japan. Sedimentary rocks, volcanic rocks, plutonic rocks, ultramafic rocks and metamorphic rocks cover 73.3%, 8.5%, 8.8%, 0.9%, and 8.6% of the surface area, respectively. The average ages of major lithologic units, weighted according to bedrock area, are as follows: sedimentary rocks (average stratigraphic age of 123 Myr/median age of 26 Myr), volcanic rocks (84 Myr/20 Myr), intrusive rocks (278 Myr/195 Myr), ultramafic rocks (unknown) and metamorphic rocks (1465 Myr/1118 Myr). The variability in lithologic composition and age structure of individual countries reflects the complex tectonic makeup of this region that ranges from Precambrian cratons (e.g., northeast China and North Korea) to Mesozoic-Cenozoic active margins (e.g., Japan, the Philippines, Indonesia and New Guinea). The spatial resolution of the data varies from 44 km2 per polygon (Japan) to 1659 km2 per polygon (Taiwan) and is, on average (490 km2/polygon), similar to our previous analyses of the United States of America and Canada. The temporal and spatial resolution is sufficiently high to perform age-area analyses of individual river basins larger than ˜10,000 km2 and to quantitatively evaluate the relationship between bedrock geology and river chemistry. As many rivers draining tropical, mountainous islands of East and Southeast Asia have a disproportionate effect on the dissolved and particulate load delivered to the world oceans, bedrock geology in such river drainage basins disproportionately affect ocean chemistry.

  14. Environmental impacts of oil production on soil, bedrock, and vegetation at the U.S. Geological Survey Osage-Skiatook Petroleum Environmental Research site A, Osage County, Oklahoma

    USGS Publications Warehouse

    Otton, J.K.; Zielinski, R.A.; Smith, B.D.; Abbott, M.M.; Keeland, B.D.

    2005-01-01

    The U.S. Geological Survey is investigating the impacts of oil and gas production on soils, groundwater, surface water, and ecosystems in the United States. Two sites in northeastern Oklahoma (sites A and B) are presently being investigated under the Osage-Skiatook Petroleum Environmental Research project. Oil wells on the lease surrounding site A in Osage County, Oklahoma, produced about 100,000 bbl of oil between 1913 ard 1981. Prominent production features on the 1.5-ha (3.7-ac) site A include a tank battery, an oil-filled trench, pipelines, storage pits for both produced water and oil, and an old power unit. Site activities and historic releases have left open areas in the local oak forest adjacent to these features and a deeply eroded salt scar downslope from the pits that extends to nearby Skiatook Lake. The site is underlain by surficial sediments comprised of very fine-grained eolian sand and colluvium as much as 1.4 m (4.6 ft) thick, which, in turn, overlie flat-lying, fractured bedrock comprised of sandstone, clayey sandstone, mudstone, and shale. A geophysical survey of ground conductance and concentration measurements of aqueous extracts (1:1 by weight) of core samples taken in the salt scar and adjacent areas indicate that unusual concentrations of NaCl-rich salt are present at depths to at least 8 m (26 ft) in the bedrock; however, little salt occurs in the eolian sand. Historic aerial photographs, anecdotal reports from oil-lease operators, and tree-ring records indicate that the surrounding oak forest was largely established after 1935 and thus postdates the majority of surface damage at the site. Blackjack oaks adjacent to the salt scar have anomalously elevated chloride (>400 ppm) in their leaves and record the presence of NaCl-rich salt or salty water in the shallow subsurface. The geophysical measurements also indicate moderately elevated conductance beneath the oak forest adjoining the salt scar. Copyright ?? 2005. The American Association of

  15. Reflection seismic imaging of the deeper structures at the Forsmark spent nuclear fuel repository site, central Sweden

    NASA Astrophysics Data System (ADS)

    Sharifi Brojerdi, Fatemeh; Juhlin, Christopher; Malehmir, Alireza; Stephens, Michael B.

    2013-02-01

    The Forsmark area belongs to the Paleoproterozoic Svecokarelian orogen (c. 1.9-1.8 Ga), the principal geological entity inside the Fennoscandian Shield, and is the site where Sweden has proposed to store its spent nuclear fuel. Three major sub-vertical (at the surface), composite ductile and brittle deformation zones that strike in a WNW or NW direction are present in the area. In between these zones the bedrock is less deformed and considered suitable for a repository. We present reprocessed reflection seismic data from seven profiles in which we have focused on improving the images in the depth range 1-5 km by passing lower frequencies through the processing flow at the cost of poorer resolution in the near-surface realm. The new images indicate that sub-horizontal to moderately dipping structures are possibly more extensive at depth than previously thought. Three main deeper reflective zones have been identified, one that is sub-horizontal and two that dip moderately to the southwest. The sub-horizontal reflective zone may represent a 1.27-1.26 Ga dolerite sill at about 3 km depth. One of the moderately dipping reflective zones may originate either from another dolerite sill or from a brittle fault system. The other moderately dipping structure may be present throughout most of the area and could cut all three sub-vertical deformation zones at depth. The new images and corresponding interpretation do not require a re-evaluation of the Forsmark site for storage of spent fuel, but they do influence how to interpret the deeper structures and, as a consequence, the tectonic evolution of the area.

  16. Generalized geologic map of bedrock lithologies and surficial deposits in the Great Smoky Mountains National Park region, Tennessee and North Carolina

    USGS Publications Warehouse

    Southworth, Scott; Schultz, Art; Denenny, Danielle

    2005-01-01

    The geology of the Great Smoky Mountain National Park (GSMNP) region of Tennessee and North Carolina was studied from 1993 to 2003 as part of a cooperative investigation with the National Park Service (NPS). This work has been compiled as a 1:100,000-scale map derived from mapping done at 1:24,000 and 1:62,500 scale. The geologic data are intended to support cooperative investigations with NPS, the development of a new soil map by the Natural Resources Conservation Service, and the All Taxa Biodiversity Inventory (http://www.discoverlifeinamerica.org/). At the request of NPS, we mapped areas previously not visited, revised the geology where stratigraphic and structural problems existed, and developed a map database for use in interdisciplinary research, land management, and interpretive programs for park visitors.

  17. Bedrock and surficial geologic map of the Satan Butte and Greasewood 7.5’ quadrangles, Navajo and Apache Counties, northern Arizona

    USGS Publications Warehouse

    Amoroso, Lee; Priest, Susan S.; Hiza-Redsteer, Margaret

    2013-01-01

    The geologic map of the Satan Butte and Greasewood 7.5’ quadrangles is the result of a cooperative effort of the U.S. Geological Survey (USGS) and the Navajo Nation to provide regional geologic information for management and planning officials. This map provides geologic information useful for range management, plant and animal studies, flood control, water resource investigations, and natural hazards associated with sand-dune mobility. The map provides connectivity to the regional geologic framework of the Grand Canyon area of northern Arizona. The map area encompasses approximately 314 km2 (123 mi2) within Navajo and Apache Counties of northern Arizona and is bounded by lat 35°37'30" to 35°30' N., long 109°45' to 110° W. The quadrangles lie within the southern Colorado Plateau geologic province and within the northeastern portion of the Hopi Buttes (Tsézhin Bií). Large ephemeral drainages, Pueblo Colorado Wash and Steamboat Wash, originate north of the map area on the Defiance Plateau and Balakai Mesa respectively. Elevations range from 1,930 m (6,330 ft) at the top of Satan Butte to about 1,787 m (5,860 ft) at Pueblo Colorado Wash where it exits the southwest corner of the Greasewood quadrangle. The only settlement within the map area is Greasewood, Arizona, on the north side of Pueblo Colorado Wash. Navajo Highway 15 crosses both quadrangles and joins State Highway 264 northwest of Ganado. Unimproved dirt roads provide access to remote parts of the Navajo Reservation.

  18. Bedrock cores from 89° North: Implications for the geologic framework and Neogene paleoceanography of Lomonosov Ridge and a tie to the Barents shelf

    USGS Publications Warehouse

    Grantz, Arthur; Pease, Victoria L.; Willard, Debra A.; Phillips, R.L.; Clark, David L.

    2001-01-01

    Two piston cores from the Eurasian flank of Lomonosov Ridge near lat 88.9°N, long 140°E provide the first samples of bedrock from this high-standing trans-Arctic ridge. Core 94-PC27 sampled nonmarine siltstone similar in facies and age to uppermost Triassic to lower Lower Jurassic and mid– Lower Cretaceous beds in the 4 to > 5 km Mesozoic section on Franz Josef Land, on the outer Barents shelf. A ca. 250 Ma peak in the cumulative frequency curve of detrital zircons from the siltstone, dated by U- Th-Pb analysis, suggests a source in the post-tectonic syenites of northern Taymyr and nearby islands in the Kara Sea. Textural trends reported in the literature indicate that the Lower Jurassic nonmarine strata of Franz Josef Land coarsen to the southeast; this suggests the existence of a sedimentary system in which detrital zircons could be transported from the northern Taymyr Peninsula to the outer Barents shelf near the position of core 94-PC27 prior to opening of the Eurasia Basin. Correlation of the coaly siltstone in core 94-PC27 with part of the Mesozoic section on Franz Josef Land is compatible with the strong evidence from seafloor magnetic anomalies and bathymetry that Lomonosov Ridge is a continental fragment rifted from the Barents shelf during the Cenozoic. It also suggests that Lomonosov Ridge near the North Pole is underlain by a substantial section of unmetamorphosed Mesozoic marine and nonmarine sedimentary strata. Core 94-PC29 sampled cyclical deposits containing ice-rafted debris (IRD) overlying weakly consolidated laminated olive-black anoxic Neogene siltstone and mudstone with an average total organic carbon (TOC) of 4.1 wt%. The high TOC content of the mudstone indicates that during the Neogene, prior to the introduction of IRD into the Arctic seas about 3.3 Ma (early late Pliocene), the shallow waters of the central Arctic Ocean supported significant primary photosynthetic organic production near the North Pole. These deposits also contain fine

  19. MAINE BEDROCK SOURCE WATER PROTECTION AREAS

    EPA Science Inventory

    Bedrocksqpa_region_pws is a REGIONS SDE layer of bedrock source water protection areas in Maine with a high, moderate, or low probability of contributing water to community public water supplies. The Maine Drinking Water Program (MEDWP), in cooperation with the Maine Geological S...

  20. Geology

    SciTech Connect

    Reidel, Stephen P.

    2008-01-17

    This chapter summarizes the geology of the single-shell tank (SST) farms in the context of the region’s geologic history. This chapter is based on the information in the geology data package for the SST waste management areas and SST RFI Appendix E, which builds upon previous reports on the tank farm geology and Integrated Disposal Facility geology with information available after those reports were published.

  1. Multi-scale groundwater flow modeling during temperate climate conditions for the safety assessment of the proposed high-level nuclear waste repository site at Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Joyce, Steven; Hartley, Lee; Applegate, David; Hoek, Jaap; Jackson, Peter

    2014-09-01

    Forsmark in Sweden has been proposed as the site of a geological repository for spent high-level nuclear fuel, to be located at a depth of approximately 470 m in fractured crystalline rock. The safety assessment for the repository has required a multi-disciplinary approach to evaluate the impact of hydrogeological and hydrogeochemical conditions close to the repository and in a wider regional context. Assessing the consequences of potential radionuclide releases requires quantitative site-specific information concerning the details of groundwater flow on the scale of individual waste canister locations (1-10 m) as well as details of groundwater flow and composition on the scale of groundwater pathways between the facility and the surface (500 m to 5 km). The purpose of this article is to provide an illustration of multi-scale modeling techniques and the results obtained when combining aspects of local-scale flows in fractures around a potential contaminant source with regional-scale groundwater flow and transport subject to natural evolution of the system. The approach set out is novel, as it incorporates both different scales of model and different levels of detail, combining discrete fracture network and equivalent continuous porous medium representations of fractured bedrock.

  2. Can arsenic occurrence rates in bedrock aquifers be predicted?

    PubMed Central

    Yang, Qiang; Jung, Hun Bok; Marvinney, Robert G.; Culbertson, Charles W.; Zheng, Yan

    2012-01-01

    A high percentage (31%) of groundwater samples from bedrock aquifers in the greater Augusta area, Maine was found to contain greater than 10 µg L−1 of arsenic. Elevated arsenic concentrations are associated with bedrock geology, and more frequently observed in samples with high pH, low dissolved oxygen, and low nitrate. These associations were quantitatively compared by statistical analysis. Stepwise logistic regression models using bedrock geology and/or water chemistry parameters are developed and tested with external data sets to explore the feasibility of predicting groundwater arsenic occurrence rates (the percentages of arsenic concentrations higher than 10 µg L−1) in bedrock aquifers. Despite the under-prediction of high arsenic occurrence rates, models including groundwater geochemistry parameters predict arsenic occurrence rates better than those with bedrock geology only. Such simple models with very few parameters can be applied to obtain a preliminary arsenic risk assessment in bedrock aquifers at local to intermediate scales at other localities with similar geology. PMID:22260208

  3. Can arsenic occurrence rate in bedrock aquifers be predicted?

    USGS Publications Warehouse

    Yang, Qiang; Jung, Hun Bok; Marvinney, Robert G.; Culbertson, Charles W.; Zheng, Yan

    2012-01-01

    A high percentage (31%) of groundwater samples from bedrock aquifers in the greater Augusta area, Maine was found to contain greater than 10 μg L–1 of arsenic. Elevated arsenic concentrations are associated with bedrock geology, and more frequently observed in samples with high pH, low dissolved oxygen, and low nitrate. These associations were quantitatively compared by statistical analysis. Stepwise logistic regression models using bedrock geology and/or water chemistry parameters are developed and tested with external data sets to explore the feasibility of predicting groundwater arsenic occurrence rates (the percentages of arsenic concentrations higher than 10 μg L–1) in bedrock aquifers. Despite the under-prediction of high arsenic occurrence rates, models including groundwater geochemistry parameters predict arsenic occurrence rates better than those with bedrock geology only. Such simple models with very few parameters can be applied to obtain a preliminary arsenic risk assessment in bedrock aquifers at local to intermediate scales at other localities with similar geology.

  4. Bedrock Geology of the Thiel Mountains, Antarctica.

    PubMed

    Ford, A B; Aaron, J M

    1962-09-01

    Cordierite-bearing, hyper-sthene-quartz monzonite porphyry, the most widespread rock unit, is intruded by biotite granite and porphyritic biotite granite. Sedimentary and metasedimentary rocks, mainly quartzites and argillites, have been metamorphosed locally to hornfels and have been involved in high-angle faulting. Shear zones are common in the plutonic rocks. PMID:17732193

  5. Geology

    NASA Technical Reports Server (NTRS)

    Stewart, R. K.; Sabins, F. F., Jr.; Rowan, L. C.; Short, N. M.

    1975-01-01

    Papers from private industry reporting applications of remote sensing to oil and gas exploration were presented. Digitally processed LANDSAT images were successfully employed in several geologic interpretations. A growing interest in digital image processing among the geologic user community was shown. The papers covered a wide geographic range and a wide technical and application range. Topics included: (1) oil and gas exploration, by use of radar and multisensor studies as well as by use of LANDSAT imagery or LANDSAT digital data, (2) mineral exploration, by mapping from LANDSAT and Skylab imagery and by LANDSAT digital processing, (3) geothermal energy studies with Skylab imagery, (4) environmental and engineering geology, by use of radar or LANDSAT and Skylab imagery, (5) regional mapping and interpretation, and digital and spectral methods.

  6. Bedrock and soil geochemistry from Voyageurs National Park, Minnesota

    USGS Publications Warehouse

    Woodruff, Laurel G.; Cannon, William F.; Dicken, Connie L.; Pimley, Shana

    2002-01-01

    Bedrock, forest floor, and mineral soil sampling in Voyageurs National Park (VNP), Minnesota in 2000 and 2001 is part of a multidisciplinary project that includes the U. S. Geological Survey, National Park Service, University of Wisconsin – La Crosse, Minnesota Pollution Control Agency, and the Minnesota Department of Natural Resources. The joint project is examining the distribution of mercury in age-1 perch, lake water, bedrock and soils for eighteen watersheds in the interior of VNP. The purpose of the project was to establish the background and baseline geochemistry for bedrock and soil in the region, and to determine terrestrial mercury sources and sinks in VNP.

  7. Stratigraphy of Martian Bedrock

    NASA Astrophysics Data System (ADS)

    Aharonson, Oded; Lewis, K.; Grotzinger, J.; Squyres, S. W.; MER Science Team

    2006-09-01

    Layered bedrock has been observed on Mars, at a range of scales from meters in orbital images, to sub-centimeter in Spirit and Opportunity images. These data enable for the first time quantitative analyses of the structural information embedded in the stratigraphic column. Here we review the state of knowledge and present examples from orbital and surface images. New results on the structure of Home Plate (bed dip and strike orientations) as measured by the Spirit Mars Exploration Rover are described. We demonstrate techniques for determining bed geometries from stereo imagery, and interpret the preliminary results. Future applications to stratigraphic problems on Mars are motivated.

  8. Periodic bedrock ridges on Mars

    NASA Astrophysics Data System (ADS)

    Montgomery, David R.; Bandfield, Joshua L.; Becker, Scott K.

    2012-03-01

    Evidence for sediment transport and erosion by wind is widespread over the surface of Mars today and was likely a major geomorphic process for much of its geological past. Although Martian surface features resembling aeolian dunes and ripples have been recognized since the Mariner and Viking missions, such features have been interpreted previously as active, indurated, or exhumed sedimentary forms. Here we report evidence based on High Resolution Imaging Science Experiment images that show some megaripple forms are eroded into cohesive substrate rather than being composed of loose granular material or fossilized dunes. Exposure of stratigraphic continuity within layered, cohesive material extending crest to trough through features with mean wavelengths of 18 to 51 m demonstrates the primarily erosional formation of what we term periodic bedrock ridges (PBRs). Hence some surfaces on Mars previously considered to be covered by wind-deposited material are actually wind-carved exposures that offer windows into Martian history. PBRs lack the distinctive streamlining associated with wind-parallel yardangs and comparison of PBR orientation to yardangs, megayardangs, and active sedimentary dunes in the same vicinity confirm that these PBRs formed transverse to prevailing winds. Observed wavelengths of PBRs are comparable to those predicted by a simple model for erosional wavelengths of periodic transverse bed forms owing to the spacing of flow separations within the flow. Recognition of these transverse aeolian erosional forms brings up the question of how widespread Martian PBRs are and how many have been misinterpreted as active or indurated (fossilized) sedimentary dunes.

  9. Approaches to confirmatory testing of a groundwater flow model for sparsely fractured crystalline rock, exemplified by data from the proposed high-level nuclear waste repository site at Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Follin, Sven; Hartley, Lee

    2014-03-01

    The Svensk Kärnbränslehantering AB (SKB) has proposed the Forsmark site as a future repository for spent high-level nuclear fuel, involving disposal at about 470 m depth in sparsely fractured crystalline bedrock. An essential part of the completed inter-disciplinary site investigation was to develop an integrated account of the site and its regional setting, including the current state of the geosphere and the biosphere as well as natural processes affecting long-term evolution. First, this report recollects the integrated understanding and some key hydraulic characteristics of the crystalline bedrock at Forsmark along with a description of the flow model set-up and the methodology used for paleoclimatic flow modeling. Second, the protocol used for site-scale groundwater flow and solute transport modeling is demonstrated. In order to conduct a quantitative assessment of groundwater flow paths at Forsmark, the standard guide for groundwater flow modeling was elaborated on, to support both discrete and porous media flow approaches. In total, four independent types of data were used to confirm that the final groundwater flow model for the crystalline bedrock was representative of site conditions.

  10. New approaches to subglacial bedrock drilling technology

    NASA Astrophysics Data System (ADS)

    Talalay, Pavel; Sun, Youhong; Zhao, Yue; Xue, Jun; Chen, Chen; Markov, Alexey; Xu, Huiwen; Gong, Wenbin; Han, Wei; Zheng, Zhichuan; Cao, Pinlu; Wang, Rusheng; Zhang, Nan; Yu, Dahui; Fan, Xiaopeng; Hu, Zhengyi; Yang, Cheng; Han, Lili; Sysoev, Mikhail

    2013-04-01

    Drilling to bedrock of ice sheets and glaciers offers unique opportunities to research processes acting at the bed for paleo-climatic and paleo-environmental recording, basal sliding studies, subglacial geology and tectonics investigations, prospecting and exploration for minerals covered by ice. Retrieving bedrock samples under ice sheets and glaciers is a very difficult task. Drilling operations are complicated by extremely low temperature at the surface of, and within glaciers, and by glacier flow, the absence of roads and infrastructures, storms, winds, snowfalls, etc. In order to penetrate through the ice sheet or glacier up to the depth of at least 1000 m and to pierce the bedrock to the depth of several meters from ice - bedrock boundary the development activity already has been started in Polar Research Center at Jilin University, China. All drilling equipment (two 50-kW diesel generators, winch, control desk, fluid dumping station, etc.) is installed inside a movable sledge-mounted warm-keeping and wind-protecting drilling shelter that has dimensions of 8.8 ×2.8 × 3.0 m. Mast has two positions: horizontal for transportation and vertical working position (mast height is 12 m). Drilling shelter can be transported to the chosen site with crawler-tractor, aircraft or helicopter. In case of carriage by air the whole drilling shelter was designed to be disassembled into pieces "small" enough to ship by aircraft. Weight and sizes of each component has been minimized to lower the cost of transportation and to meet weight restrictions for transportation. Total weight of drilling equipment (without drilling fluid) is near 15 tons. Expected time of assembling and preparing for drilling is 2 weeks. If drilling shelter is transported with crawler-tractor (for example, in Antarctic traverses) all equipment is ready to start drilling immediately upon arrival to the site. To drill through ice and bedrock a new, modified version of the cable-suspended electromechanical

  11. COMPARISON OF FRACTURED BEDROCK REMEDIATION

    EPA Science Inventory

    This report compares the technologies/approaches used at 7 Superfund sites to treat contaminated groundwater in fractured bedrock. The comparison shows how well each technology/approach met the stated goal, problems encountered, and lessons learned.

  12. Bedrock topography of southeast Iowa

    USGS Publications Warehouse

    Hansen, Robert E.

    1973-01-01

    The bedrock in Iowa is covered nearly everywhere by unconsolidated deposits of glacial drift and alluvium, which range in thickness from less than 1 foot to more than 400 feet, and from less than 1 foot to about 60 feet, respectively. The configuration of the bedrock surface is the result of a complex system of ancient drainage courses which were developed during a long period of preglacial erosion and during shorter, but more intesne periods of interglacial erosion. 

  13. Bedrock topography of northeast Iowa

    USGS Publications Warehouse

    Hansen, Robert E.

    1975-01-01

    The bedrock in Iowa (Hershey, 1969) is generally overlain by deposits of glacial drift and alluvium, which range in thickness from less than 1 foot (0.3 m) to more than 400 ft (18 m), respectively. The configuration of the bedrock surface is the result of a complex system of ancient drainage courses when were developed during a long period of preglacial erosion and during shorter, but more intense, periods of interglacial erosion. 

  14. Bedrock topography of central Iowa

    USGS Publications Warehouse

    Hansen, R.E.

    1985-01-01

    The bedrock in Iowa (Hershey, 1969) generally is ovelain by deposits of glacial drift and alluvium. The drift, comprised of glacial till and glacial outwash, varies in thickness from less than 1 foot to more than 400 feet; the alluvium in central Iowa varies in thickness from less than 1 foot to about 60 feet. The configuration of the bedrock suface is the result of a complex system of ancient drainage courses which were developed during a long period of preglacial erosion and during shorter, but more intense, periods of interglacial erosion. This map, for a 10 county area in central Iowa, is the seventh of a series of 9 reports that will provide statewide coverage of the bedrock surface of Iowa. 

  15. Bedrock topography of southwest Iowa

    USGS Publications Warehouse

    Sendlein, Lyle V.A.; Gilmore, Jack L.

    1980-01-01

    The bedrock in Iowa (Hershey, 1969) is generally overlain by unconsolidataed deposits consisting of glacial drift, alluvium, and loess. Loess deposits are most extensive in areas bordering the Missouri River flood plain, attaining a thickness of over 200ft in some places. The total thickness of the unconsolidated sediments ranges from less than 1 ft to more than 450 ft. The configuration of the underlying bedrock surface is the result of a complex system of ancient drainage courses that were developed during shorter, but more intense, periods of interglacial erosion. 

  16. Landslides and the interplay of infiltration, soil permeability and bedrock exfiltration on steep slopes

    NASA Astrophysics Data System (ADS)

    Schneider, Philipp; Brönnimann, Cornelia; Stähli, Manfred; Seibert, Jan

    2015-04-01

    Shallow landslides pose substantial risks to people and infrastructure in mountain areas. Their occurrence is influenced by soil and bedrock characteristics and triggered by precipitation-induced pore water dynamics. The bedrock may drain or contribute to groundwater in the overlying soil depending on permeability, degree of fracturing, saturation and hydraulic head. Here, we present a case study from Central Switzerland designed to illuminate a situation where such interactions are decisive and investigate runoff formation processes at hillslopes prone to slide. The bedrock in the study area represents a succession of fissured conglomerate-sandstone and weathered marlstone layers, overlaid by a gleysol. Evidence of a temporally confined aquifer in bedrock fractures was gathered from a severe storm event in August 2005. First, a geological model of the investigated slope derived from electrical resistivity tomography surveys, borehole data, and bedrock outcrops formed the basis for test site instrumentation. Second, the soil moisture and the groundwater response to 32 storm events were monitored in different soil and bedrock layers. Although the subsoil horizons are not particularly permeable, a fast and substantial rise of hydraulic heads in the bedrock was observed, suggesting that rapid percolation through bedrock fractures caused the immediate increase of pore water pressures. The data document how pore water pressure builds up in fractured bedrock below a low-permeable soil during storms, which may trigger shallow landslides. Third, sprinkling experiments were conducted on subplots with variable rainfall intensities and different dye tracers to identify preferential infiltration, percolation and storm runoff formation at the hillslope. Brilliant blue dye stained the entire organic topsoil, vertical soil fractures, and macropores. Lateral drainage in the subsoil or at the soil-bedrock interface was not observed; drainage was limited to the organic topsoil. In

  17. Bedrock topography of northwest Iowa

    USGS Publications Warehouse

    Hansen, R.E.; Runkle, D.L.

    1986-01-01

    Bedrock in Iowa (Hershey, 1969) generally is overlain by deposits of glacial drive and alluvium. The drift, consisting of glacial till and glacial outwash, ranges in thickness from zero to more than 500 feet in western Iowa; the alluvium in stream valleys ranges in thickness from less than 1 foot to more than 70 feet. The configuration of the bedrock surface is the result of a complex system of ancient drainage courses that were developed during a long period of preglacial erosion. This map, for a 12 county area in west-central Iowa, is the eighth in a series of nine reports that will provide statewide coverage of the bedriock topography of Iowa. 

  18. Bedrock geologic map of the Spring Valley, West Plains, and parts of the Piedmont and Poplar Bluff 30'x60' quadrangles, Missouri, including the upper Current River and Eleven Point River drainage basins

    USGS Publications Warehouse

    Weary, David J.; Harrison, Richard W.; Orndorff, Randall C.; Weems, Robert E.; Schindler, J. Stephen; Repetski, John E.; Pierce, Herbert A.

    2015-01-01

    Potentially economic mineral resources are present in the subsurface in the map area. Exploration drill-hole data indicate that anomalously high concentrations of base-metal sulfides locally occur within the Cambrian Bonneterre Formation. The geologic setting of these anomalous concentrations is similar to that found in the Viburnum Trend, part of the largest lead-mining district in the world. The southernmost part of the Viburnum Trend extends into the northern part of the map area and is exploited by the Sweetwater Mine. Undeveloped and potentially economic occurrences of base metals are known also beneath Blair Creek, a tributary to the Current River in the north-central part of the map area.

  19. Full waveform inversion of seismic reflection data from the Forsmark planned repository for spent nuclear fuel, eastern central Sweden

    NASA Astrophysics Data System (ADS)

    Zhang, Fengjiao; Juhlin, Christopher

    2014-02-01

    The Swedish Nuclear Fuel and Waste Management Company (SKB) has been carrying out extensive studies at the planned repository for spent nuclear fuel at the Forsmark site in the eastern part of central Sweden since 2002. Identification of subhorizontal to gently dipping seismic reflections is especially important since these may represent transport routes for radionuclides. Studies have shown that such reflections can be generated by water filled fracture zones that have a lower velocity than the surrounding bedrock. Lithological changes, that is, mafic sills, may also be responsible for reflections in some cases. At the Forsmark site, it is difficult to distinguish fracture zones from mafic sills in the standard reflection seismic processed sections. However, since mafic sills usually have a positive velocity contrast with the background velocity field compared to fractures zones that have a negative one, the two possibilities could be differentiated if we could reconstruct the underground velocity field. Seismic full waveform inversion has the potential to perform this reconstruction, allowing us to discriminate between fractures zones and mafic sills. In this study, we apply a 2-D waveform inversion code on crooked line data sets acquired at the Forsmark site. This implies we are dealing with a 3-D geometry. We handle this problem by applying 3-D to 2-D coordinate projections. First, we perform a synthetic benchmark test with a similar geometry to that of the projected real data. We test both amplitude and phase inversion and phase only inversion on the synthetic data. The results show that the phase only inversion has fewer artefacts and is more stable. After successful application on the synthetic data, we apply the phase only waveform inversion on the real data. The resulting velocity fields show more details compared with the starting model based on first arrival traveltime tomography. Time domain synthetic data sets generated from the final velocity fields

  20. Investigating Lithologic Controls on the Morphology and Evolution of Bedrock Streams, Ouachita Mountains, Central Arkansas.

    NASA Astrophysics Data System (ADS)

    Swanson, C. D., II; Gasparini, N. M.

    2014-12-01

    The incision of bedrock streams largely controls the topographic evolution of mountainous areas, and patterns of incision into bedrock hold information critical to unraveling past climate and tectonic uplift patterns. A popular tool in studying patterns of incision in bedrock streams is the channel steepness index, or channel gradient normalized by drainage area. The three main factors that are thought to affect channel steepness index are uplift rate, climate, and lithology. The Ouachita Mountains of central Arkansas provide a study site with currently uniform uplift (essentially zero) and climate, allowing us to explore how changes in lithology affect local channel steepness values. The Ouachita Mountains are an intensely folded and faulted highland region, structurally related to the Appalachian Mountains to the east. Folding and faulting of this region occurred during the Paleozoic, and is no longer active. The trellised morphology of the stream network is controlled by past folding, as stream channels in the region generally flow along fold hinges. Bedrock in the area consists of Arkansas Novaculite, a massive chert that is highly resistant to erosion, and less resistant shale and sandstone members of the Bigfork and Mississippi Mountain Formation. Sense of bedding of geologic units is generally steep, although local folding causes high variation in bedding orientation.Where bedrock channels transition from novaculite to shale, knickpoints and high channel steepness index values are observed in some streams, while others seem unaffected by this lithologic boundary. We explore 5 bedrock streams that flow over the novaculite/shale boundary to determine what lithologic factors have the largest impact on incision of bedrock channels. Analysis consists of measurements of channel morphology, detailed local geologic mapping of bedding and fold orientation, and measurements of rock strength along stream channels. Understanding how lithologic differences affect local

  1. Controls of bedrock geochemistry on soil and plant nutrients in Southeastern Utah

    USGS Publications Warehouse

    Neff, J.C.; Reynolds, R.; Sanford, R.L., Jr.; Fernandez, D.; Lamothe, P.

    2006-01-01

    The cold deserts of the Colorado Plateau contain numerous geologically and geochemically distinct sedimentary bedrock types. In the area near Canyonlands National Park in Southeastern Utah, geochemical variation in geologic substrates is related to the depositional environment with higher concentrations of Fe, Al, P, K, and Mg in sediments deposited in alluvial or marine environments and lower concentrations in bedrock derived from eolian sand dunes. Availability of soil nutrients to vegetation is also controlled by the formation of secondary minerals, particularly for P and Ca availability, which, in some geologic settings, appears closely related to variation of CaCO3 and Ca-phosphates in soils. However, the results of this study also indicate that P content is related to bedrock and soil Fe and Al content suggesting that the deposition history of the bedrock and the presence of P-bearing Fe and Al minerals, is important to contemporary P cycling in this region. The relation between bedrock type and exchangeable Mg and K is less clear-cut, despite large variation in bedrock concentrations of these elements. We examined soil nutrient concentrations and foliar nutrient concentration of grasses, shrubs, conifers, and forbs in four geochemically distinct field sites. All four of the functional plant groups had similar proportional responses to variation in soil nutrient availability despite large absolute differences in foliar nutrient concentrations and stoichiometry across species. Foliar P concentration (normalized to N) in particular showed relatively small variation across different geochemical settings despite large variation in soil P availability in these study sites. The limited foliar variation in bedrock-derived nutrients suggests that the dominant plant species in this dryland setting have a remarkably strong capacity to maintain foliar chemistry ratios despite large underlying differences in soil nutrient availability. ?? 2006 Springer Science

  2. Bedrock channel reaches morphology: examples from the Northern Marche Region (Italy)

    NASA Astrophysics Data System (ADS)

    Tiberi, V.; di Agostino, V.; Troiani, F.; Nesci, O.; Savelli, D.

    2009-04-01

    The Northern Marche rivers, on account of a significant variability of their catchment geology, geodynamics and geomorphology, can be regarded as excellent natural laboratories for the study of the morphology, dynamics and evolution of bedrock channel reaches. Hence a geomorphologic study has been carried on in order to map and describe -from qualitative and quantitative point of view- some bedrock channel types of this area, to detect morphological controls at different scales (from the local scale up to the catchment one), and to assess human perturbations on the drainage systems. The study is based on detailed field surveying concerning channel shape and dynamics, floodplain configurations, slope geomorphologic processes, bedrock structure and composition. In addiction, a good aero photograph documentation dating back to the 1955 allowed a reliable reconstruction of the main evolution trends of bedrock channel reaches in the latest past. In the reported rivers the bedrock channel reaches vary in length from a few tens to hundreds of meters, and alternate with alluvial and mixed bedrock-alluvial channel reaches. In many cases specific numerical relations among geometric parameters of bedrock channels have been discovered and some similarities in both morphology and dynamics of rock-cut channels with alluvial channel reaches have been pointed out. Specifically, with regard of their morphologic arrangement, geometric parameters, and flow dynamics several bedrock channels are quite similar to step pool channels found along gravelly channel reaches. Nonetheless, along a given segment of the hydrographical network where an individual alluvial-channel pattern (e.g. a wandering) is found both upstream and downstream a rock-cut channel reach, the occurrence of this latter (e.g. planar bedrock-floored channel) simply breaks the along-stream continuity of the alluvial-bed morphology.

  3. Identification Of Rippability And Bedrock Depth Using Seismic Refraction

    SciTech Connect

    Ismail, Nur Azwin; Saad, Rosli; Nawawi, M. N. M; Muztaza, Nordiana Mohd; El Hidayah Ismail, Noer; Mohamad, Edy Tonizam

    2010-12-23

    Spatial variability of the bedrock with reference to the ground surface is vital for many applications in geotechnical engineering to decide the type of foundation of a structure. A study was done within the development area of Mutiara Damansara utilising the seismic refraction method using ABEM MK8 24 channel seismograph. The geological features of the subsurface were investigated and velocities, depth to the underlying layers were determined. The seismic velocities were correlated with rippability characteristics and borehole records. Seismic sections generally show a three layer case. The first layer with velocity 400-600 m/s predominantly consists of soil mix with gravel. The second layer with velocity 1600-2000 m/s is suggested to be saturated and weathered area. Both layers forms an overburden and generally rippable. The third layer represents granite bedrock with average depth and velocity 10-30 m and >3000 m/s respectively and it is non-rippable. Steep slope on the bedrock are probably the results of shear zones.

  4. Fluorine geochemistry in bedrock groundwater of South Korea.

    PubMed

    Chae, Gi-Tak; Yun, Seong-Taek; Mayer, Bernhard; Kim, Kyoung-Ho; Kim, Seong-Yong; Kwon, Jang-Soon; Kim, Kangjoo; Koh, Yong-Kwon

    2007-10-15

    High fluoride concentrations (median=4.4 mg/L) in deep bedrock groundwater of South Korea prevent the usage of it as a drinking water source. The hydrogeochemistry of deep thermal groundwaters (N=377) in diverse bedrocks has been studied in order to evaluate the geologic and geochemical controls on fluoride concentrations in groundwater. The groundwater samples were clustered geologically, and the average and median concentrations of fluoride were compared by the Mann-Whitney U test. The order of median fluoride concentration with respect to geology is as follows: metamorphic rocks> or =granitoids > or =complex rock>volcanic rocks> or =sedimentary rocks. This result indicates that the geological source of fluoride in groundwater is related to the mineral composition of metamorphic rocks and granitoids. With respect to groundwater chemistry, the fluoride concentration was highest in Na-HCO3 type groundwater and lowest in Ca-HCO3 type groundwater. Ionic relationships also imply that the geochemical behavior of fluoride in groundwater is related to the geochemical process releasing Na and removing Ca ions. The thermodynamic relationship between the activities of Ca and F indicates that fluoride concentration is controlled by the equilibrium of fluorite (CaF2). In other words, the upper limits of fluoride concentration are determined by the Ca ion; i.e., Ca concentrations play a crucial role in fluoride behavior in deep thermal groundwater. The result of this study suggests that the high fluoride in groundwater originates from geological sources and fluoride can be removed by fluorite precipitation when high Ca concentration is maintained. This provides a basis for a proper management plan to develop the deep thermal groundwater and for treatment of high fluoride groundwater frequently found in South Korea. PMID:17655916

  5. Large floods, alluvial overprint, and bedrock erosion

    NASA Astrophysics Data System (ADS)

    Turowski, J. M.; Badoux, A.; Leuzinger, J.; Hegglin, R.

    2012-04-01

    Depending on their behaviour during extreme floods, streams can be divided into two distinct classes. 'Flood-cleaning' streams erode during high flows and deposit during small and medium flows. 'Flood-depositing' streams deposit during high flows and erode during small and medium flows. Rivers with a wide range of drainage areas and other characteristics can be classified as either 'flood-cleaning' or 'flood-depositing'. In bedrock channels, this behaviour can lead to a feedback effect, the 'overprint effect', between sediment transport processes and bedrock erosion, which can modulate long-term bedrock erosion rates. The 'overprint effect' arises when alluvium covers the bedrock and typical alluvial channel forms (e.g., meandering or braiding patterns, armour layers or bedforms) develop, which influence sediment transport rates. This effect may accelerate or decelerate sediment export from a reach, causing increased or decreased long-term bedrock erosion rates.

  6. A Computationally Efficient Bedrock Model

    NASA Astrophysics Data System (ADS)

    Fastook, J. L.

    2002-05-01

    Full treatments of the Earth's crust, mantle, and core for ice sheet modeling are often computationally overwhelming, in that the requirements to calculate a full self-gravitating spherical Earth model for the time-varying load history of an ice sheet are considerably greater than the computational requirements for the ice dynamics and thermodynamics combined. For this reason, we adopt a ``reasonable'' approximation for the behavior of the deforming bedrock beneath the ice sheet. This simpler model of the Earth treats the crust as an elastic plate supported from below by a hydrostatic fluid. Conservation of linear and angular momentum for an elastic plate leads to the classical Poisson-Kirchhoff fourth order differential equation in the crustal displacement. By adding a time-dependent term this treatment allows for an exponentially-decaying response of the bed to loading and unloading events. This component of the ice sheet model (along with the ice dynamics and thermodynamics) is solved using the Finite Element Method (FEM). C1 FEMs are difficult to implement in more than one dimension, and as such the engineering community has turned away from classical Poisson-Kirchhoff plate theory to treatments such as Reissner-Mindlin plate theory, which are able to accommodate transverse shear and hence require only C0 continuity of basis functions (only the function, and not the derivative, is required to be continuous at the element boundary) (Hughes 1987). This method reduces the complexity of the C1 formulation by adding additional degrees of freedom (the transverse shear in x and y) at each node. This ``reasonable'' solution is compared with two self-gravitating spherical Earth models (1. Ivins et al. (1997) and James and Ivins (1998) } and 2. Tushingham and Peltier 1991 ICE3G run by Jim Davis and Glenn Milne), as well as with preliminary results of residual rebound rates measured with GPS by the BIFROST project. Modeled responses of a simulated ice sheet experiencing a

  7. Radon in Quaternary aquifers related to underlying bedrock geology

    SciTech Connect

    Morland, G.; Skarphagen, H.; Strand, T.; Furuhaug, L.; Banks, D.

    1998-01-01

    A survey of radon concentrations in water abstracted from 31 of Norway`s largest waterworks, using ground water from Quaternary fluvial and glaciofluvial sediments, returned values of between 0.4 Bq/L and 83 Bq/L, with a median of 23 Bq/L. Significantly higher Rn concentrations were present in ground water from Quaternary aquifers underlain by gneissic and granitic lithologies compared with those underlain by metasandstones, phyllites and mica schists. Compared to the recommended national action level of 500 Bq/L and concentrations of up to 19,900 Bq/L, which have been detected in boreholes in Norwegian granite aquifers, the concentrations measured in Quaternary aquifers are regarded as unproblematic for consumers, although a more detailed assessment may be required for workers spending a lot of time in wellhead areas.

  8. Bedrock geology of the northern Columbia Plateau and adjacent areas

    NASA Technical Reports Server (NTRS)

    Swanson, D. A.; Wright, T. L.

    1978-01-01

    The Columbia Plateau is surrounded by a complex assemblage of highly deformed Precambrian to lower Tertiary continental and oceanic rocks that reflects numerous episodes of continental accretion. The plateau itself is comprised of the Columbia River basalt group formed between about 16.5 x 1 million years B.P. and 6 x 1 million years B.P. Eruptions were infrequent between about 14 and 6 x 1 million years B.P., allowing time for erosion and deformation between successive outpourings. The present-day courses of much of the Snake River, and parts of the Columbia River, across the plateau date from this time. Basalt produced during this waning activity is more heterogeneous chemically and isotopically than older flows, reflecting its prolonged period of volcanism.

  9. Bedrock geologic map of the Westhampton Quadrangle, Hampshire County, Massachusetts

    SciTech Connect

    Clark, S.F. Jr.

    1987-01-01

    The Westhampton Quadrangle lies on the east flank of the Precambrian Berkshire Massif between the Goshen Dome to the north, the Woronoco Dome to the south, and the Mesozoic Hartford Basin to the east. The area is underlain almost entirely by metasedimentary rocks of Early Devonian age. The quadrangle offers a comparison of strikingly different map patterns of the Goshen and Waits River formations and contains several excellent exposures that straddle the contact between them.

  10. Application of Microtremor Array Analysis to Estimate the Bedrock Depth in the Beijing Plain area

    NASA Astrophysics Data System (ADS)

    Xu, P.; Ling, S.; Liu, J.; Su, W.

    2013-12-01

    With the rapid expansion of large cities around the world, urban geological survey provides key information regarding resource development and urban construction. Among the major cities of the world, China's capital city Beijing is among the largest cities possessing complex geological structures. The urban geological survey and study in Beijing involves the following aspects: (1) estimating the thickness of the Cenozoic deposit; (2) mapping the three-dimensional structure of the underlying bedrock, as well as its relations to faults and tectonic settings; and (3) assessing the capacity of the city's geological resources in order to support its urban development and operation safety. The geological study of Beijing in general was also intended to provide basic data regarding the urban development and appraisal of engineering and environment geological conditions, as well as underground space resources. In this work, we utilized the microtremor exploration method to estimate the thickness of the bedrock depth, in order to delineate the geological interfaces and improve the accuracy of the bedrock depth map. The microtremor observation sites were located in the Beijing Plain area. Traditional geophysical or geological survey methods were not effective in these areas due to the heavy traffic and dense buildings in the highly-populated urban area. The microtremor exploration method is a Rayleigh-wave inversion technique which extracts its phase velocity dispersion curve from the vertical component of the microtremor array records using the spatial autocorrelation (SPAC) method, then inverts the shear-wave velocity structure. A triple-circular array was adopted for acquiring microtremor data, with the observation radius in ranging from 40 to 300 m, properly adjusted depending on the geological conditions (depth of the bedrock). The collected microtremor data are used to: (1) estimation of phase velocities of Rayleigh-wave from the vertical components of the microtremor

  11. Combining airborne electromagnetic and geotechnical data for automated depth to bedrock tracking

    NASA Astrophysics Data System (ADS)

    Christensen, Craig William; Pfaffhuber, Andreas Aspmo; Anschütz, Helgard; Smaavik, Tone Fallan

    2015-08-01

    Airborne electromagnetic (AEM) survey data was used to supplement geotechnical investigations for a highway construction project in Norway. Heterogeneous geology throughout the survey and consequent variable bedrock threshold resistivity hindered efforts to directly track depth to bedrock, motivating us to develop an automated algorithm to extract depth to bedrock by combining both boreholes and AEM data. We developed two variations of this algorithm: one using simple Gaussian or inverse distance weighting interpolators, and another using ordinary kriging and combined probability distribution functions of input parameters. Evaluation shows that for preliminary surveys, significant savings in boreholes required can be made without sacrificing bedrock model accuracy. In the case study presented, we estimate data collection savings of 1000 to 10,000 NOK/km (c. 160 to 1600 USD/km) would have been possible for early phases of the investigation. However, issues with anthropogenic noise, low signal, and uncertainties in the inversion model likely reduced the comparative advantage that including AEM provided. AEM cannot supersede direct sampling where the model accuracy required exceed the resolution possible with the geophysical measurements. Nevertheless, with the algorithm we can identify high probability zones for shallow bedrock, identify steep or anomalous bedrock topography, and estimate the spatial variability of depth at earlier phases of investigation. Thus, we assert that our method is still useful where detailed mapping is the goal because it allows for more efficient planning of secondary phases of drilling.

  12. Bedrock topography of south-central Iowa

    USGS Publications Warehouse

    Cagle, J.W.

    1973-01-01

    The bedrock surface in Iowa is covered nearly everywhere by unconsolidated deposits of glacial drift and alluvium which range in thickness from less than 1 foot to more than 400 feet, and from less than 1 foot to about 60 feet, respectively. The bedrock surface is the result of a complex system of ancient drainage courses, which were developed during the long period of preglacial erosion and during shorter, but more intense, periods of interglacial erosion.

  13. Bedrock topography of north-central Iowa

    USGS Publications Warehouse

    Hansen, R.E.

    1978-01-01

    The bedrock in Iowa (Hershey, 1969) is generally overlain by deposits of glacial drift and alluvium, which range in thickness from less than 1 ft to more than 400 ft, and from less than 1 ft to about 60 ft respectively. The configuration of the bedrock surface is the result of a complex system of ancient drainage courses which were developed during a long period of preglacial erosion and during shorter, but mroe intense, periods of interglacial erosion.

  14. A Fresh Crater Drills to Tharsis Bedrock

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this image of a newly formed impact crater in the Tharsis region of Mars at 1316 UTC (8:16 a.m. EST) on Jan. 13, 2007, near 17.0 degrees north latitude, 246.4 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered by the image is just over 10 kilometers (6 miles) wide at its narrowest point.

    The Tharsis region is a high volcanic plateau that stands about 5 kilometers (3 miles) above the surrounding plains. The rocks forming Tharsis are younger than in most parts of mars, as evidenced by their low density of craters. The best estimate of their age is comparable to the age of Shergotty-class meteorites thought to originate from Mars. However, Tharsis is covered by a nearly unbroken, meters-thick layer of dust that has frustrated all attempts to measure its bedrock composition remotely, and to determine if it matches the composition of Shergotty-class meteorites.

    The recent discovery of dark, newly formed impact craters on Mars has provided the CRISM team a chance, finally, to measure the rocks that make up Tharsis. Over the lifetime of the Mars Global Surveyor mission, its high-resolution Mars Orbiter Camera monitored the surface and documented the very recent formation of some two dozen small impact craters. Several of them are in Tharsis and pierce the plateau's dust blanket to expose bedrock. MRO's instruments have been trained on these 'drill holes' into Mars' volcanic crust, including the crater shown here.

    The top image was constructed from three infrared wavelengths that usually highlight compositional variations. This image shows the impact crater, a ring of dark, excavated rock (inset), and a surrounding system of rays. Crater rays are common around young impact craters, and they form when ejected boulders reimpact the surface and stir up the local rock

  15. Mapping the geophysical bedrock of the Moesian Platform using H/V ratios and borehole data.

    NASA Astrophysics Data System (ADS)

    Florinela Manea, Elena; Michel, Clotaire; Fäh, Donat; Ortanza Cioflan, Carmen

    2016-04-01

    The strong effects at long periods observed in the extra-Carpathian area of Romania during large Vrancea intermediate-depth earthquakes were explained by the influence of both source mechanism and mechanical properties of the geological structure. Complex basin geometry and the low seismic velocities of the sediments are the primary responsible for the large amplification and long duration of the seismic records from the extra-Carpathian area during intermediate-depth earthquakes. The aim of this study is to map the geophysical bedrock of this area correlating and interpolating the results obtained from local resonance phenomena evaluation with the available surface geological data. The site was investigated through the computation of H/V spectral ratios from three-directional single station measurements of ambient vibration. The first step was to estimate the depth of the geophysical bedrock at all the Romanian seismic stations located in the extra-Carpathian area (velocity sensors) using the fundamental frequency retrieved from the H/V curves. In the second stage of the study all the relevant peaks from the H/V curves were interpreted in consonance with the available information of the geology. The geological data were obtained from the database developed in the national BIGSEES project by National Institute of Earth Physics. In this database are integrated all the geological, geophysical data from all the past projects, contracts, studies (as refraction, reflexion, etc.), geotechnical drillings and other information publicly available. The mapping of the geophysical bedrock was done interpolating the geological database and information gathered/resulted from H/V using a geographical informational system(GIS). The geology of this area displays very complex features as outcrops in small zones/lines/ near the Danube and then is gradually dipping to about 2 km depth in the N-NE. The depth of the bedrock is (nearly) constant around 100 m depth on the right side of

  16. Cyclic steps incised on experimental bedrock

    NASA Astrophysics Data System (ADS)

    Yokokawa, M.; Kyogoku, A.; Kotera, A.; Izumi, N.

    2013-12-01

    In rivers flowing in mountain areas, a series of steps are often observed on bedrock. They are thought to be cyclic steps formed due to erosion of bedrock, which should be driven by abrasion due to bedload sediment transport. We demonstrated a series of flume experiments of the formation of cyclic steps on bedrock by abrasion due to bedload transportation using weak mortar as the model bedrock. We also compared the shapes of the steps reproduced in the experiments with those obtained in the analysis. The experiments were conducted using a 1.5 m long, 2 cm wide, and 20 cm deep flume made of glass in Osaka Institute of Technology. The flume has 10-cm-high weirs at both ends, so that there is a 10-cm-deep reservoir. We put mortar into the reservoir and hardened it. In order to make a highly erodible mortar, we casted the mortar with extremely low amount of cement. The ratio of cement, sand (0.2 mm in diameter), and water is x:150:50 (x ranges 1-3). The flume is tilted by 10 degrees. The water and colored sand is supplied from a head tank to the upstream end of the flume, flows on 'model bedrock' in the flume, and was dropped from the downstream end. We observed morphological changes of the surface of the bedrock by photos. We also used a laser displacement sensor to measure the surface topography of the 'model bedrock' before and after each run. The configuration of steps largely depends on the hardness of model bedrocks. In the case of the softest model bedrock (cement-sand-water ratio is 1:150:50) with small amount of sand, long-drawn potholes tend to be formed. Clear cyclic steps are formed on harder model bedrocks with large cement-sand-water ratios such as 2:150:50 and 3:150:50. When a series of steps are formed on the bed, typical wavelength and wave height are approximately 20 cm, and 2 - 3 cm, respectively. The general shape of a step is characterized by a relatively long downward-inclined slope just upstream of a short upward-inclined slope. The feature of

  17. Reflection seismic imaging of a hydraulically conductive fracture zone in a high noise area, Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Juhlin, C.; Stephens, M. B.; Cosma, C.

    2007-05-01

    High resolution reflection seismic methods have proven to be useful tools for locating fracture zones in crystalline rock. Siting of potential high-level nuclear waste repositories is a particularly important application of these methods. By using small explosive sources (15-75 grams), high resolution images of the sub-surface have been obtained in the depth range 100 m to 2 km in Sweden, Canada and elsewhere. Although ambient noise conditions in areas such as the Fennoscandian and Canadian shields are generally low, industrial noise can be high in some areas, particularly at potential sites suitable for repositories, since these are often close to existing infrastructure. In addition, the presence of this infrastructure limits the choice of sources available to the geophysicist. Forsmark, located about 140 km north of Stockholm, is one such potential site where reflection seismics have been carried out. Existing infrastructure includes nuclear reactors for power generation and a low- level waste repository. In the vicinity of the reactors, it was not possible to use an explosive source due to permitting restrictions. Instead, a VIBSIST system consisting of a tractor mounted hydraulic hammer was used in the vicinity of the reactors. By repeatedly hitting the pavement, without breaking it, at predefined sweeps and then stacking the signals, shot records comparable to explosive data could be generated. These shot records were then processed using standard methods to produce stacked sections along 3 profiles within the reactor area. Clear reflections are seen in the uppermost 600 m along 3 of these profiles. Correlation of crossing profiles shows that the strongest reflection (B8) is generated by a gently east-southeast dipping interface. Prior to construction of the reactors, several boreholes were drilled to investigate the bedrock in the area. One of these boreholes was located close to where two of the profiles cross. Projection of the B8 reflection into the

  18. Bedrock topography of west-central Iowa

    USGS Publications Warehouse

    Hansen, R.E.; Runkle, D.L.

    1986-01-01

    Bedrock in Iowa (Hershey 1969) generally is overlain by deposits of glacial drift and alluvium. The drift, consisting of glacial till and glacial outwash, ranges in thickness from zero to more than 500 feet in western Iowa; the alluvium in stream valleys ranges in thickness from less than 1 to more than 70 feet. The configuration of the bedrock surface is the result of a long period of preglacial erosion and during shorter, but more intense, periods of interglacial erosion. This map, for a 12-county area in west-central Iowa, is the eighth of a series of nine reports that will provide statewide coverage of the bedrock topograhy of Iowa. 

  19. Climatic control of bedrock river incision.

    PubMed

    Ferrier, Ken L; Huppert, Kimberly L; Perron, J Taylor

    2013-04-11

    Bedrock river incision drives the development of much of Earth's surface topography, and thereby shapes the structure of mountain belts and modulates Earth's habitability through its effects on soil erosion, nutrient fluxes and global climate. Although it has long been expected that river incision rates should depend strongly on precipitation rates, quantifying the effects of precipitation rates on bedrock river incision rates has proved difficult, partly because river incision rates are difficult to measure and partly because non-climatic factors can obscure climatic effects at sites where river incision rates have been measured. Here we present measurements of river incision rates across one of Earth's steepest rainfall gradients, which show that precipitation rates do indeed influence long-term bedrock river incision rates. We apply a widely used empirical law for bedrock river incision to a series of rivers on the Hawaiian island of Kaua'i, where mean annual precipitation ranges from 0.5 metres to 9.5 metres (ref. 12)-over 70 per cent of the global range-and river incision rates averaged over millions of years can be inferred from the depth of river canyons and the age of the volcanic bedrock. Both a time-averaged analysis and numerical modelling of transient river incision reveal that the long-term efficiency of bedrock river incision across Kaua'i is positively correlated with upstream-averaged mean annual precipitation rates. We provide theoretical context for this result by demonstrating that our measurements are consistent with a linear dependence of river incision rates on stream power, the rate of energy expenditure by the flow on the riverbed. These observations provide rare empirical evidence for the long-proposed coupling between climate and river incision, suggesting that previously proposed feedbacks among topography, climate and tectonics may occur. PMID:23579679

  20. Bedrock topography beneath the Red Lake peatlands

    SciTech Connect

    Miller, P.; Shaw, G.H. . Geology Dept.); Glaser, P. . Limnological Research Center); Siegel, D. . Dept. of Geology)

    1992-01-01

    Detailed hydrologic investigations of peat landforms in the Red Lake Peatlands have revealed that groundwater flow is significantly related to the type of landform and vegetation community present at a given site. Hydrogeologic modeling of shallow groundwater systems suggests that bedrock topography is an important, perhaps the vital, boundary condition controlling groundwater flow. Determination of depth to bedrock beneath different peat landforms is necessary to test the hydrogeologic models and obtain a better understanding of the processes which produce them. Direct determination of bedrock depth in peatlands is hampered by the difficult conditions and high costs of boring. In addition, environmental impacts from boring activities would probably be substantial in these sensitive ecosystems. Shallow seismic methods appear to be the most promising approach to obtain the necessary data. Unfortunately the 2+ meters of peat covering Lake Agassiz sediments overlying the bedrock is not only a poor substrate for geophone emplacement, but is a strong attenuator of seismic waves. These difficulties have been overcome by constructing a tool which allows the geophones to be emplaced beneath the peat and into the top of the sediments. The shotgun cartridge source is also located beneath the peat. This combination results in very good seismic records, far better than those possible with surface sources and geophones. The results from a preliminary survey along a 600m line show that there are significant variations in bedrock topography below the peat. In a distance of less than 500m, depth to bedrock changes by about 30%, from about 55m to about 40m. This is similar to variations indicated by the models.

  1. Controls on bedrock bedform development beneath the Uummannaq Ice Stream onset zone, West Greenland

    NASA Astrophysics Data System (ADS)

    Lane, Timothy P.; Roberts, David H.; Rea, Brice R.; Ó Cofaigh, Colm; Vieli, Andreas

    2015-02-01

    This paper investigates the controls on the formation of subglacially eroded bedrock bedforms beneath the topographically confined region upstream of the Uummannaq Ice Stream (UIS). During the last glacial cycle, palaeoglaciological conditions are believed to have been similar for all sites in the study, characterised by thick, fast-flowing ice moving over a rigid bedrock bed. Classic bedrock bedforms indicative of glacially eroded terrain were mapped, including p-forms, roches moutonnées, and whalebacks. Bedform long axes and plucked face orientations display close correlation (parallel and perpendicular) to palaeo-ice flow directions inferred from striae measurements. Across all sites, elongation ratios (length to width) varied by an order of magnitude between 0.8:1 and 8.4:1. Bedform properties (length, height, width, and long axis orientation) from four subsample areas, form morphometrically distinct populations, despite their close proximity and hypothesised similarity in palaeoglaciological conditions. Variations in lithology and geological structures (e.g., joint frequency; joint dip; joint orientation; bedding plane thickness; and bedding plane dip) provide lines of geological weakness, which focus the glacial erosion, in turn controlling bedform geometries. Determining the relationship (s) between bedding plane dip relative to palaeo-ice flow and bedform shape, relative length, amplitude, and wavelength has important ramifications for understanding subglacial bed roughness, cavity formation, and likely erosion style (quarrying and/or abrasion) at the ice-bed interface. This paper demonstrates a direct link between bedrock bedform geometries and geological structure and emphasises the need to understand bedrock bedform characteristics when reconstructing palaeoglaciological conditions.

  2. Direct and Indirect Influence of Parental Bedrock on Streambed Microbial Community Structure in Forested Streams▿

    PubMed Central

    Mosher, Jennifer J.; Findlay, Robert H.

    2011-01-01

    A correlative study was performed to determine if variation in streambed microbial community structure in low-order forested streams can be directly or indirectly linked to the chemical nature of the parental bedrock of the environments through which the streams flow. Total microbial and photosynthetic biomass (phospholipid phosphate [PLP] and chlorophyll a), community structure (phospholipid fatty acid analysis), and physical and chemical parameters were measured in six streams, three located in sandstone and three in limestone regions of the Bankhead National Forest in northern Alabama. Although stream water flowing through the two different bedrock types differed significantly in chemical composition, there were no significant differences in total microbial and photosynthetic biomass in the sediments. In contrast, sedimentary microbial community structure differed between the bedrock types and was significantly correlated with stream water ion concentrations. A pattern of seasonal variation in microbial community structure was also observed. Further statistical analysis indicated dissolved organic matter (DOM) quality, which was previously shown to be influenced by geological variation, correlated with variation in bacterial community structure. These results indicate that the geology of underlying bedrock influences benthic microbial communities directly via changes in water chemistry and also indirectly via stream water DOM quality. PMID:21926206

  3. A transmissivity model for deformation zones in fractured crystalline rock and its possible correlation to in situ stress at the proposed high-level nuclear waste repository site at Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Follin, Sven; Stigsson, Martin

    2014-03-01

    The Forsmark site was recently proposed by the Svensk Kärnbränslehantering AB (SKB) to serve as the potential site for construction of a future geological repository for spent high-level nuclear fuel at about 470 m depth in fractured crystalline rock. The considerations included, among other things, distance from regionally significant deformation zones with highly strained rock, lithological homogeneity, low hydraulic conductivity, groundwater salinity with an acceptable range, and lack of potential mineral resources. This report describes the calculation of transmissivity of deduced deformation zones at Forsmark and the transmissivity model used in the regional groundwater flow modeling carried out in support of the integrated site description. Besides significant decrease with increasing depth (more than four orders of magnitude over a depth of about 1 km), the calculated transmissivity values also reveal considerable spatial variability along the strikes of the zones, i.e. lateral heterogeneity (more than two orders of magnitude). A hydro-mechanical coupling is discussed, based on presented models for the tectonic evolution and the principal stress tensor. Tentatively, laboratory-scale relationships developed from normal stress experiments on a single fracture in crystalline rock can be used to estimate the maximum values of transmissivity of deduced deformation zones at Forsmark.

  4. Multichannel analysis of surface waves to map bedrock

    USGS Publications Warehouse

    Miller, Richard D.; Xia, Jianghai; Park, Choon B.; Ivanov, Julian M.

    1999-01-01

    High velocity gradients within the shear wave velocity field consistent with drill confirmed bedrock are considered diagnostic of the bedrock surface and were used to map the top of bedrock on all four lines connected at this site. Calculating the shear wave velocity field from surface wave arrivals was accomplished with a high degree of accuracy regardless of cultural noise. Improved resolution on the surface of the bedrock provides insight into the texture of bedrock and permits identification and appraisal of short wavelength variations in the bedrock surface.

  5. CHARACTERIZATION OF FRACTURED BEDROCK FOR STEAM INJECTION

    EPA Science Inventory

    The most difficult setting in which to conduct groundwater remediation is that where chlorinated solvents have penetrated fractured bedrock. To demonstrate the potential viability of steam injection as a means of groundwater clean-up in this type of environment, steam will be in...

  6. The bedrock electrical conductivity structure of Northern Ireland

    NASA Astrophysics Data System (ADS)

    Beamish, David

    2013-08-01

    An airborne geophysical survey of the whole of Northern Ireland has provided over 4.8 M estimates of the bedrock conductivity over the wide range of geological formations present. This study investigates how such data can be used to provide additional knowledge in relation to existing digital geological map information. A by-product of the analysis is a simplification of the spatially aggregated information obtained in such surveys. The methodology used is a GIS-based attribution of the conductivity estimates using a lithological classification of the bedrock formations. A 1:250k geological classification of the data is performed leading to a 56 unit lithological and geostatistical analysis of the conductivity information. The central moments (medians) of the classified data are used to provide a new digital bedrock conductivity map of Northern Ireland with values ranging from 0.32 to 41.36 mS m-1. This baseline map of conductivities displays a strong correspondence with an existing 4 quadrant, chrono-geological description of Northern Ireland. Once defined, the baseline conductivity map allows departures from the norm to be assessed across each specific lithological unit. Bulk electrical conductivity is controlled by a number of petrophysical parameters and it is their variation that is assessed by the procedures employed. The igneous rocks are found to display the largest variability in conductivity values and many of the statistical distributions are multi-modal. A sequence of low-value modes in these data are associated with intrusives within volcanic complexes. These and much older Neoproterzoic rocks appear to represent very low porosity formations that may be the product of rapid cooling during emplacement. By way of contrast, extensive flood basalts (the Antrim lavas) record a well-defined and much higher median value (12.24 mS m-1) although they display complex spatial behaviour in detail. Sedimentary rocks appear to follow the broad behaviours anticipated

  7. Steeply dipping heaving bedrock, Colorado: Part 3 - Environmental controls and heaving processes

    USGS Publications Warehouse

    Noe, D.C.; Higgins, J.D.; Olsen, H.W.

    2007-01-01

    This paper examines the environmental processes and mechanisms that govern differential heaving in steeply dipping claystone bedrock near Denver, Colorado. Three potential heave mechanisms and causal processes were evaluated: (1) rebound expansion, from reduced overburden stress; (2) expansive gypsum-crystal precipitation, from oxidation of pyrite; and (3) swelling of clay minerals, from increased ground moisture. First, we documented the effect of short-term changes in overburden stress, atmospheric exposure, and ground moisture on bedrock at various field sites and in laboratory samples. Second, we documented differential heaving episodes in outcrops and at construction and developed sites. We found that unloading and exposure of the bedrock in construction-cut areas are essentially one-time processes that result in drying and desiccation of the near-surface bedrock, with no visible heaving response. In contrast, wetting produces a distinct swelling response in the claystone strata, and it may occur repeatedly as natural precipitation or from lawn irrigation. We documented 2.5 to 7.5 cm (1 to 3 in.) of differential heaving in 24 hours triggered by sudden infiltration of water at the exposed ground surface in outcrops and at construction sites. From these results, we interpret that rebound and pyrite weathering, both of which figure strongly into the long-term geologic evolution of the geologic framework, do not appear to be major heave mechanisms at these excavation depths. Heaving of the claystone takes two forms: (1) hydration swelling of dipping bentonitic beds or zones, and (2) hydration swelling within bedrock blocks accommodated by lateral, thrust-shear movements, along pre-existing bedding and fracture planes.

  8. Bedrock structure and the interpretation of palaeo ice stream footprints: examples from the Pleistocene British Ice Sheet

    NASA Astrophysics Data System (ADS)

    Krabbendam, M.; Bradwell, T.

    2009-04-01

    To model past and future behaviour of ice sheets, a good understanding of both modern and ancient ice streams is required. The study of present-day ice streams provides detailed data of short-term dynamic changes, whilst the study of Pleistocene palaeo-ice streams can provide crucial constraints on the longer-term evolution of ice sheets. To date, palaeo-ice streams, such as the classical Dubawnt Lake palaeo-ice stream of the former Laurentide Ice Sheet, have been recognised largely on the basis of extremely elongate drumlins and megascale glacial lineations; all soft-sediment features. Whilst it appears that topographically unconstrained ice streams (eg. within the West Antarctic Ice Sheet) are generally underlain by deformable till, topographically constrained ice streams such as Jakobshavn Isbrae do not require deformable sediment and may occur on a bedrock-dominated bed. Analysis of DEM data and geomorphology and structural geology fieldwork in Northern Scotland and Northern England has shown the occurrence of highly streamlined bedforms in bedrock of the former base of topographically controlled palaeo-ice streams, which drained parts of the British Ice Sheet. The bedforms are predominantly bedrock megagrooves with asymmetric cross-profiles. In the Ullapool tributary of the Minch palaeo ice stream, bedrock megagrooves form the dominant evidence for ice streaming. The megagrooves are typically 5-15 m deep, 10-30 m wide and 500 - 3000 m long. Spacing of megagrooves is typically 100 - 200 m. In both study areas, the bedrock is strongly anisotropic, either consisting of thin-bedded strata or strongly foliated metasedimentary rocks, with the strata or foliation having a gentle dip. Megagrooves are best developed where the strike of the anisotropy is sub-parallel (within 10 - 20°) with palaeo ice flow. The bedrock in both areas has a well-developed, relatively densely spaced (< 1m), conjugate joint system. We suggest that asymmetric megagrooves are formed by

  9. River terrace sand and gravel deposit reserve estimation using three-dimensional electrical resistivity tomography for bedrock surface detection

    NASA Astrophysics Data System (ADS)

    Chambers, J. E.; Wilkinson, P. B.; Penn, S.; Meldrum, P. I.; Kuras, O.; Loke, M. H.; Gunn, D. A.

    2013-06-01

    We describe the application of 3D electrical resistivity tomography (ERT) to the characterisation and reserve estimation of an economic fluvial sand and gravel deposit. Due to the smoothness constraints used to regularise the inversion, it can be difficult to accurately determine the geometry of sharp interfaces. We have therefore considered two approaches to interface detection that we have applied to the 3D ERT results in an attempt to provide an accurate and objective assessment of the bedrock surface elevation. The first is a gradient-based approach, in which the steepest gradient of the vertical resistivity profile is assumed to correspond to the elevation of the mineral/bedrock interface. The second method uses an intrusive sample point to identify the interface resistivity at a location within the model, from which an iso-resistivity surface is identified that is assumed to define the interface. Validation of these methods has been achieved through direct comparison with observed bedrock surface elevations that were measured using real-time-kinematic GPS subsequent to the 3D ERT survey when quarrying exposed the bedrock surface. The gradient-based edge detector severely underestimated the depth to bedrock in this case, whereas the interface resistivity method produced bedrock surface elevations that were in close agreement with the GPS-derived surface. The failure of the gradient-based method is attributed to insufficient model sensitivity in the region of the bedrock surface, whereas the success of the interface resistivity method is a consequence of the homogeneity of the mineral and bedrock, resulting in a consistent interface resistivity. These results highlight the need for some intrusive data for model validation and for edge detection approaches to be chosen on the basis of local geological conditions.

  10. Digital Bedrock Compilation: A Geodatabase Covering Forest Service Lands in California

    NASA Astrophysics Data System (ADS)

    Elder, D.; de La Fuente, J. A.; Reichert, M.

    2010-12-01

    This digital database contains bedrock geologic mapping for Forest Service lands within California. This compilation began in 2004 and the first version was completed in 2005. Second publication of this geodatabase was completed in 2010 and filled major gaps in the southern Sierra Nevada and Modoc/Medicine Lake/Warner Mountains areas. This digital map database was compiled from previously published and unpublished geologic mapping, with source mapping and review from California Geological Survey, the U.S. Geological Survey and others. Much of the source data was itself compilation mapping. This geodatabase is huge, containing ~107,000 polygons and ~ 280,000 arcs. Mapping was compiled from more than one thousand individual sources and covers over 41,000,000 acres (~166,000 km2). It was compiled from source maps at various scales - from ~ 1:4,000 to 1:250,000 and represents the best available geologic mapping at largest scale possible. An estimated 70-80% of the source information was digitized from geologic mapping at 1:62,500 scale or better. Forest Service ACT2 Enterprise Team compiled the bedrock mapping and developed a geodatabase to store this information. This geodatabase supports feature classes for polygons (e.g, map units), lines (e.g., contacts, boundaries, faults and structural lines) and points (e.g., orientation data, structural symbology). Lookup tables provide detailed information for feature class items. Lookup/type tables contain legal values and hierarchical groupings for geologic ages and lithologies. Type tables link coded values with descriptions for line and point attributes, such as line type, line location and point type. This digital mapping is at the core of many quantitative analyses and derivative map products. Queries of the database are used to produce maps and to quantify rock types of interest. These include the following: (1) ultramafic rocks - where hazards from naturally occurring asbestos are high, (2) granitic rocks - increased

  11. Bacterial Transport Experiments in Fractured Crystalline Bedrock

    USGS Publications Warehouse

    Becker, M.W.; Metge, D.W.; Collins, S.A.; Shapiro, A.M.; Harvey, R.W.

    2003-01-01

    The efficiency of contaminant biodegradation in ground water depends, in part, on the transport properties of the degrading bacteria. Few data exist concerning the transport of bacteria in saturated bedrock, particularly at the field scale. Bacteria and microsphere tracer experiments were conducted in a fractured crystalline bedrock under forced-gradient conditions over a distance of 36 m. Bacteria isolated from the local ground water were chosen on the basis of physicochemical and physiological differences (shape, cell-wall type, motility), and were differentially stained so that their transport behavior could be compared. No two bacterial strains transported in an identical manner, and microspheres produced distinctly different breakthrough curves than bacteria. Although there was insufficient control in this field experiment to completely separate the effects of bacteria shape, reaction to Gram staining, cell size, and motility on transport efficiency, it was observed that (1) the nonmotile, mutant strain exhibited better fractional recovery than the motile parent strain; (2) Gram-negative rod-shaped bacteria exhibited higher fractional recovery relative to the Gram-positive rod-shaped strain of similar size; and (3) coccoidal (spherical-shaped) bacteria transported better than all but one strain of the rod-shaped bacteria. The field experiment must be interpreted in the context of the specific bacterial strains and ground water environment in which they were conducted, but experimental results suggest that minor differences in the physical properties of bacteria can lead to major differences in transport behavior at the field scale.

  12. Carbon and nitrogen dynamics across a bedrock-regulated subarctic pH gradient

    NASA Astrophysics Data System (ADS)

    Tomczyk, N.; Heim, E. W.; Sadowsky, J.; Remiszewski, K.; Varner, R. K.; Bryce, J. G.; Frey, S. D.

    2014-12-01

    Bedrock geochemistry has been shown to influence landscape evolution due to nutrient limitation on primary production. There may also be less direct interactions between bedrock-derived chemicals and ecosystem function. Effects of calcium (Ca) and pH on soil carbon (C) and nitrogen (N) cycling have been shown in acid impacted forests o f North America. Understanding intrinsic factors that affect C and nutrient dynamics in subarctic ecosystems has implications for how these ecosystems will respond to a changing climate. How the soil microbial community allocates enzymes to acquire resources from the environment can indicate whether a system is nutrient or energy limited. This study examined whether bedrock geochemistry exerts pressure on nutrient cycles in the overlying soils. In thin, weakly developed soils, bedrock is the primary mineral material and is a source of vital nutrients. Nitrogen (N) and C are not derived from bedrock, but their cycling is still affected by reactions with geologically-derived chemicals. Our study sites near Abisko, Sweden (~68°N) were selected adjacent to five distinct bedrock outcrops (quartzite, slate, carbonate, and two different metasedimenty units). All sites were at a similar elevation (~700 m a.s.l.) and had similar vegetation (subarctic heath). Nutrient concentrations in bedrock and soils were measured in addition to soil microbial biomass and extracellular enzyme activity. We found a statistically significant correlation between soil Ca concentrations and soil pH (r = 0.88, p < 0.01). There were also significant relationships between soil pH and the ratio of C-acquiring to N-acquiring enzyme activity (r = -0.89, p < 0.01), soil pH and soil C-to-N ratio (r = -0.76, p < 0.01), and the ratio of C-acquiring to N-acquiring enzyme activity and soil C-to-N ratio (r = 0.78, p < 0.01). These results suggest that soil Ca concentrations influence C and N cycling dynamics in these soils through their effect on soil pH.

  13. New insights into the mechanics of fluvial bedrock erosion through flume experiments and theory

    NASA Astrophysics Data System (ADS)

    Lamb, Michael P.; Finnegan, Noah J.; Scheingross, Joel S.; Sklar, Leonard S.

    2015-09-01

    River incision into bedrock drives the topographic evolution of mountainous terrain and may link climate, tectonics, and topography over geologic time scales. Despite its importance, the mechanics of bedrock erosion are not well understood because channel form, river hydraulics, sediment transport, and erosion mechanics coevolve over relatively long time scales that prevent direct observations, and because erosive events occur intermittently and are difficult and dangerous to measure. Herein we synthesize how flume experiments using erodible bedrock simulants are filling these knowledge gaps by effectively accelerating the pace of landscape evolution under reduced scale in the laboratory. We also build on this work by providing new theory for rock resistance to abrasion, thresholds for plucking by vertical entrainment, sliding and toppling, and by assessing bedrock-analog materials. Bedrock erosion experiments in the last 15 years reveal that the efficiency of rock abrasion scales inversely with the square of rock tensile strength, sediment supply has a dominant control over bed roughness and abrasion rates, suspended sediment is an efficient agent of erosion, and feedbacks with channel form and roughness strongly influence erosion rates. Erodibility comparisons across rock, concrete, ice, and foam indicate that, for a given tensile strength, abrasion rates are insensitive to elasticity. The few experiments that have been conducted on erosion by plucking highlight the importance of block protrusion height above the river bed, and the dominance of block sliding and toppling at knickpoints. These observations are consistent with new theory for the threshold Shields stress to initiate plucking, which also suggests that erosion rates in sliding- and toppling-dominated rivers are likely transport limited. Major knowledge gaps remain in the processes of erosion via plucking of bedrock blocks where joints are not river-bed parallel; waterfall erosion by toppling and

  14. Effects of increased pumpage on a fractured-bedrock aquifer system in central Orange County, New York

    USGS Publications Warehouse

    Garber, Murray

    1985-01-01

    The bedrock in central Orange County consists of highly indurated siltstone, shale, and conglomerate containing two major fault systems and extensive fracturing; it is overlain by 50 to 100 feet of till. The fracturing permits unusually high well yields. Wells tapping the bedrock yield 75 to 200 gallons per minute; those tapping bedrock in adjacent areas yield only a few tens of gallons per minute. The bedrock aquifer is recharged mainly by percolation of water from precipitation through the till. In 1983, the U.S. Geological Survey studied the hydrologic effects of increased pumpage on the fractured bedrock aquifer system near the Village of Kiryas Joel, in the Town of Monroe. Water levels were measured in several wells in the village 's two well fields from February to October 1983, and pumpage data from the same period were tabulated. Water levels responded to variations in both pumpage and precipitation. Pumping tests and water levels in the southeastern well field in 1983 had no effect on the northwestern well field. An observation well between the two fields shows about 20 feet of seasonal fluctuation from recharge and the effects of pumping at the northwestern well field. Aquifer-test data indicate a transmissivity of 900 feet squared per day and a storage coefficient of 0.0001. (USGS)

  15. VTT test borehole for bedrock investigations

    NASA Astrophysics Data System (ADS)

    Okko, Olli; Hassinen, Pertti; Front, Kai

    1994-02-01

    A borehole of depth 150 m and diameter 56 mm has been drilled in the area adjacent to the premises of the Technical Research Center of Finland (VTT) at Otaniemi, Espoo, for the purposes of calibrating geophysical measurement devices. The report presents the test results obtained so far and illustrates the processing of these, in which the various measurements are plotted as curves and combinations of curves. The interpretations provided so far consist of analyses of lithological variations, bedrock fracturing, the nature and occurrence of fracture zones and groundwater flow patterns. Samples were taken from those parts of the core shown by the borehole measurements to be homogeneous and thin sections made from these for mineralogical determinations. The rock mechanical and petrophysical properties of the same points were examined. The core is in the possession of VTT, and the hole itself is available to outsiders for the calibration and testing of borehole measurement equipment.

  16. Linking sediment transport and channel roughness in bedrock rivers

    NASA Astrophysics Data System (ADS)

    Hodge, R. A.; Hoey, T.; Maniatis, G.

    2012-12-01

    Improved understanding of sediment transport processes in bedrock rivers is needed for both upland management and for prediction of landscape evolution. Recent advances have focussed on the sediment processes in bedrock rivers that have implications for both sediment transfer and bedrock incision. A significant component of grain-scale transport dynamics is the difference in roughness between bedrock and alluvial surfaces. Although bedrock surfaces typically exhibit roughness at a range of scales, they are often locally smooth at the scale of individual grains; significant roughness can however also exist at this length scale. Grains on smooth bedrock surfaces are more easily entrained than grains on alluvial patches because of the higher grain exposure and lower pivoting angles. Recent laboratory and modelling work has demonstrated the effect of these differing entrainment thresholds on the development of sediment cover in a smooth channel. Here we model the effect of the spatial distribution of roughness in a bedrock river on the total sediment transport capacity of the channel. The model represents the channel as two parallel strips; an alluvial strip and a bedrock strip with sparse sediment cover. We evaluate the effect of sediment cover on the sediment flux conveyed by the entire channel, including the total sediment flux integrated over multiple flow events. A range of conditions between two end members are explored; sediment cover is increased either by widening the alluvial strip, and/or by increasing the density of sediment cover on the bedrock strip (subject to the condition that there is not significant interaction between grains). Depending on the exact conditions applied, increasing sediment cover can actually decrease the total sediment flux in the channel as a result of the decreased mobility of the alluvial sediment. However, laboratory experiments show that sediment accumulation alters the spatial pattern of roughness in bedrock channels, affecting

  17. Estimated probability of arsenic in groundwater from bedrock aquifers in New Hampshire, 2011

    USGS Publications Warehouse

    Ayotte, Joseph D.; Cahillane, Matthew; Hayes, Laura; Robinson, Keith W.

    2012-01-01

    Probabilities of arsenic occurrence in groundwater from bedrock aquifers at concentrations of 1, 5, and 10 micrograms per liter (µg/L) were estimated during 2011 using multivariate logistic regression. These estimates were developed for use by the New Hampshire Environmental Public Health Tracking Program. About 39 percent of New Hampshire bedrock groundwater was identified as having at least a 50 percent chance of containing an arsenic concentration greater than or equal to 1 µg/L. This compares to about 7 percent of New Hampshire bedrock groundwater having at least a 50 percent chance of containing an arsenic concentration equaling or exceeding 5 µg/L and about 5 percent of the State having at least a 50 percent chance for its bedrock groundwater to contain concentrations at or above 10 µg/L. The southeastern counties of Merrimack, Strafford, Hillsborough, and Rockingham have the greatest potential for having arsenic concentrations above 5 and 10 µg/L in bedrock groundwater. Significant predictors of arsenic in groundwater from bedrock aquifers for all three thresholds analyzed included geologic, geochemical, land use, hydrologic, topographic, and demographic factors. Among the three thresholds evaluated, there were some differences in explanatory variables, but many variables were the same. More than 250 individual predictor variables were assembled for this study and tested as potential predictor variables for the models. More than 1,700 individual measurements of arsenic concentration from a combination of public and private water-supply wells served as the dependent (or predicted) variable in the models. The statewide maps generated by the probability models are not designed to predict arsenic concentration in any single well, but they are expected to provide useful information in areas of the State that currently contain little to no data on arsenic concentration. They also may aid in resource decision making, in determining potential risk for private

  18. Alluvial and bedrock aquifers of the Denver Basin; eastern Colorado's dual ground-water resource

    USGS Publications Warehouse

    Robson, Stanley G.

    1989-01-01

    Large volumes of ground water are contained in alluvial and bedrock aquifers in the semiarid Denver basin of eastern Colorado. The bedrock aquifer, for example, contains 1.2 times as much water as Lake Erie of the Great Lakes, yet it supplies only about 9 percent of the ground water used in the basin. Although this seems to indicate underutilization of this valuable water supply, this is not necessarily the case, for many factors other than the volume of water in the aquifer affect the use of the aquifer. Such factors as climatic conditions, precipitation runoff, geology and water-yielding character of the aquifers, water-level conditions, volume of recharge and discharge, legal and economic constraints, and water-quality conditions can ultimately affect the decision to use ground water. Knowledge of the function and interaction of the various parts of this hydrologic system is important to the proper management and use of the ground-water resources of the region. The semiarid climatic conditions on the Colorado plains produce flash floods of short duration and large peak-flow rates. However, snowmelt runoff from the Rocky Mountains produces the largest volumes of water and is typically of longer duration with smaller peak-flow rates. The alluvial aquifer is recharged easily from both types of runoff and readily stores and transmits the water because it consists of relatively thin deposits of gravel, sand, and clay located in the valleys of principal streams. The bedrock aquifer is recharged less easily because of its greater thickness (as much as 3,000 feet) and prevalent layers of shale which retard the downward movement of water in the formations. Although the bedrock aquifer contains more than 50 times as much water in storage as the alluvial aquifer, it does not store and transmit water as readily as the alluvial aquifer. For example, about 91 percent of the water pumped from wells is obtained from the alluvial aquifer, yet water-level declines generally have

  19. A comparison of methods used in mapping of Pleistocene-bedrock unconformity: Conventional manual versus surface modeling

    SciTech Connect

    Weibel, C.P.; Abert, C.C.; Kempton, J.P. )

    1993-03-01

    Surface modeling software packages allow geologists to model and map topographic and stratigraphic horizons. These map products, however, often differ from maps prepared without computerized mapping. The authors mapping of the Pleistocene-bedrock unconformity in east-central Illinois (1:100,000-scale), which includes the Mahomet paleovalley, illustrates this situation and demonstrates how both mapping methods, manual and computer, contribute to a better understanding of the paleovalley. A conventional hand-drawn map was constructed over a number of years by manually plotting and contouring bedrock elevations, primarily from water well logs, onto various county and local topographic bases. A computer-generated map of the same area was completed as part of a recent project to map the bedrock geology. It was prepared by carefully selecting data, which included geographic coordinates, unique well identification numbers, and bedrock elevations. Primary data sources were hydrocarbon exploration and storage wells. Digitizing the hand-drawn map allowed the two maps to be overlaid and compared. Several significant geomorphic features appeared on one map and not the other because of the use of different databases and inconsistent selection of data used for the hand-drawn map. The hand-drawn map appears more realistic, i.e., like a modern surface, because the mappers used their knowledge of geomorphic concepts in drawing the contours. Most of the data selection for the computer-generated map was completed prior to plotting of the map and therefore is less susceptible to bias interpretations. The computer-generated map, however, is less topographically realistic in areas where data are sparse because the extrapolation methods used to define the surface do not recognize geologic processes or bedrock lithology.

  20. Geophysical conceptualization of a fractured sedimentary bedrock riverbed using ground-penetrating radar and induced electrical conductivity

    NASA Astrophysics Data System (ADS)

    Steelman, C. M.; Kennedy, C. S.; Parker, B. L.

    2015-02-01

    Bedrock rivers exhibit very different hydraulic and ecological regimes compared to alluvial rivers. Groundwater-surface water interaction in rivers that flow directly on sedimentary bedrock surfaces with exposed fracture and conduit networks is generally based on alluvial river conceptual models. However, the dual and triple porosity systems of sedimentary rock (e.g., matrix, fractures and vugs) leads to highly variable hydraulic pathways and groundwater velocities that, in turn, result in processes that are very different than those derived from alluvial concepts. Relative to alluvial rivers there has been very little direct examination of dynamic interactions, such as fluxes, groundwater velocities, and mechanisms affecting water quality across the channel interface; this is largely because bedrock rivers are difficult to instrument and monitor given their heterogeneous and anisotropic flow systems. In this study, we evaluate the capacity of non-invasive, low impact ground-penetrating radar and frequency-domain electromagnetic induction methods capable of detecting discrete fracture and conduit features, mapping complex distributions of lithostratigraphic interfaces, and providing information about formation properties along a partially exposed section of the Eramosa River located in Ontario, Canada. Geophysical data are supported by direct hydrogeologic and geologic information obtained from a nearby borehole piezometer cluster and a continuous 15 m rock core. Valuable insights were gained into the lateral extent and geometry of structurally-controlled whydrostratigraphic units (e.g., dissolution-enhanced fractures, epikarst and karst features), which are expected to strongly influence groundwater and surface water interaction along the channel. An integrated application of GPR and EMI methods was necessary to fully understand the complex geometry of geologic boundaries and karst features within the shallow bedrock aquifer. The identification of epikarst below

  1. Plan of study for the Ohio-Indiana carbonate-bedrock and glacial- aquifer system

    USGS Publications Warehouse

    Bugliosi, E.F.

    1990-01-01

    The major aquifers of 35,000 sq mi area in western Ohio and eastern Indiana consist of Silurian and Devonian carbonate bedrock and Quaternary glacial deposits. These bedrock units and glacial deposits have been designated for study as part of the U.S. Geological Survey 's Regional Aquifer System Analysis program, a nationwide program to assess the regional hydrology, geology and water quality of the Nation 's most important aquifers. The purpose of the study is to define the hydrology, geochemistry, and geologic framework of the aquifer system within the Silurian and Devonian rocks and glacial deposits, with emphasis on describing the groundwater flow patterns and characterizing the water quality. The study, which began in 1988 , is expected to be completed in 1993. In 1980, the aquifers in the study area supplied more than 280 million gallons of water/day to industry, agriculture, and a population of more than 6.3 million people. With a projected future population growth to 7.1 million in 1990, and with intensified agricultural and industrial uses, water withdrawals from these bedrock and glacial aquifers are expected to be increased. The most significant groundwater problems in the study area result from the pronounced areal differences in availability and quality of the groundwater. These differences are related to the lateral discontinuity of many of the glacial deposits and to variations in secondary permeability of the bedrock aquifers associated with patterns of fracturing. Planned activities of the study include compilation of available geohydrologic and water quality data, such as groundwater levels, geohydrologic properties of aquifers, chemical analyses, land use and water use data, and ancillary data such as digital satellite images. Additional geohydrologic and water quality data may be collected from existing wells or wells that may be drilled for this study. A computerized, geographic information system will be used as a data base management tool and

  2. Characteristics of bedrock-alluvial anastomosed rivers: the Mekong River in Cambodia

    NASA Astrophysics Data System (ADS)

    Meshkova, Liubov. V.; Carling, Paul. A.

    2010-05-01

    The Mekong River is the 12th largest river in the world in terms of its length and mean annual discharge and yet it is poorly investigated. In the north eastern regions of Cambodia the Mekong River develops a multichannel pattern. It is characterised by a complex of intersecting bedrock channels, well vegetated alluvial and seasonally inundated islands, various types of sand bars, numerous bedrock exposures, rapids, waterfalls and deep bedrock pools which can be classified as a large mixed bedrock-alluvial anastomosed river of a tropical monsoonal climate zone. In order to complete a portrait of the river at the high level of details new data on morphology, geology and sediments were obtained during field surveys of a 120 km river section in Cambodia and combined with information from published literature and interpretation of available remote sensing images. This process has enabled to update and clarify knowledge on morphology of observed islands and floodplain, comprehensive geology and tectonic structures, hydrological regime and land cover. Complex analyses of the collected data have distinguished several geomorphological zones accordingly to frequency of morphological elements, the planview configuration of channels and vertical profile characteristics. The occurrence of each zone is a subject of variable controlling factors such as local topography, channel gradient, structural and tectonic elements and intercalating geological units. Evolution of the channel pattern has been considered at both short- and long term time scales. Historical cartographic and remote sensing materials were applied to determine planform channel changes over the last 50 years revealing the channels stability and cases of occasional, local erosion and deposition. The channel network was extracted from vector layers to examine channels and islands width and length parameters, bifurcation angles at the upstream end of islands and to obtain main channel network indices such as braiding

  3. Bedrock composition regulates mountain ecosystems and landscape evolution.

    PubMed

    Hahm, W Jesse; Riebe, Clifford S; Lukens, Claire E; Araki, Sayaka

    2014-03-01

    Earth's land surface teems with life. Although the distribution of ecosystems is largely explained by temperature and precipitation, vegetation can vary markedly with little variation in climate. Here we explore the role of bedrock in governing the distribution of forest cover across the Sierra Nevada Batholith, California. Our sites span a narrow range of elevations and thus a narrow range in climate. However, land cover varies from Giant Sequoia (Sequoiadendron giganteum), the largest trees on Earth, to vegetation-free swaths that are visible from space. Meanwhile, underlying bedrock spans nearly the entire compositional range of granitic bedrock in the western North American cordillera. We explored connections between lithology and vegetation using measurements of bedrock geochemistry and forest productivity. Tree-canopy cover, a proxy for forest productivity, varies by more than an order of magnitude across our sites, changing abruptly at mapped contacts between plutons and correlating with bedrock concentrations of major and minor elements, including the plant-essential nutrient phosphorus. Nutrient-poor areas that lack vegetation and soil are eroding more than two times slower on average than surrounding, more nutrient-rich, soil-mantled bedrock. This suggests that bedrock geochemistry can influence landscape evolution through an intrinsic limitation on primary productivity. Our results are consistent with widespread bottom-up lithologic control on the distribution and diversity of vegetation in mountainous terrain. PMID:24516144

  4. Bedrock composition regulates mountain ecosystems and landscape evolution

    PubMed Central

    Hahm, W. Jesse; Riebe, Clifford S.; Lukens, Claire E.; Araki, Sayaka

    2014-01-01

    Earth’s land surface teems with life. Although the distribution of ecosystems is largely explained by temperature and precipitation, vegetation can vary markedly with little variation in climate. Here we explore the role of bedrock in governing the distribution of forest cover across the Sierra Nevada Batholith, California. Our sites span a narrow range of elevations and thus a narrow range in climate. However, land cover varies from Giant Sequoia (Sequoiadendron giganteum), the largest trees on Earth, to vegetation-free swaths that are visible from space. Meanwhile, underlying bedrock spans nearly the entire compositional range of granitic bedrock in the western North American cordillera. We explored connections between lithology and vegetation using measurements of bedrock geochemistry and forest productivity. Tree-canopy cover, a proxy for forest productivity, varies by more than an order of magnitude across our sites, changing abruptly at mapped contacts between plutons and correlating with bedrock concentrations of major and minor elements, including the plant-essential nutrient phosphorus. Nutrient-poor areas that lack vegetation and soil are eroding more than two times slower on average than surrounding, more nutrient-rich, soil-mantled bedrock. This suggests that bedrock geochemistry can influence landscape evolution through an intrinsic limitation on primary productivity. Our results are consistent with widespread bottom-up lithologic control on the distribution and diversity of vegetation in mountainous terrain. PMID:24516144

  5. 3-DIMENSIONAL Geological Mapping and Modeling Activities at the Geological Survey of Norway

    NASA Astrophysics Data System (ADS)

    Jarna, A.; Bang-Kittilsen, A.; Haase, C.; Henderson, I. H. C.; Høgaas, F.; Iversen, S.; Seither, A.

    2015-10-01

    Geology and all geological structures are three-dimensional in space. Geology can be easily shown as four-dimensional when time is considered. Therefore GIS, databases, and 3D visualization software are common tools used by geoscientists to view, analyse, create models, interpret and communicate geological data. The NGU (Geological Survey of Norway) is the national institution for the study of bedrock, mineral resources, surficial deposits and groundwater and marine geology. The interest in 3D mapping and modelling has been reflected by the increase of number of groups and researches dealing with 3D in geology within NGU. This paper highlights 3D geological modelling techniques and the usage of these tools in bedrock, geophysics, urban and groundwater studies at NGU, same as visualisation of 3D online. The examples show use of a wide range of data, methods, software and an increased focus on interpretation and communication of geology in 3D. The goal is to gradually expand the geospatial data infrastructure to include 3D data at the same level as 2D.

  6. Floor Plans Foundation Plan at Bedrock and Subgrade Level ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Floor Plans - Foundation Plan at Bedrock and Subgrade Level Plan - Marshall Space Flight Center, F-1 Engine Static Test Stand, On Route 565 between Huntsville and Decatur, Huntsville, Madison County, AL

  7. DETAIL OF LAVA BEDROCK WHICH WILL ACT AS BASE SUPPORT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF LAVA BEDROCK WHICH WILL ACT AS BASE SUPPORT FOR REACTOR. INL NEGATIVE NO. 472. Unknown Photographer, 8/23/1950 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  8. Depth to bedrock in the upper San Pedro Valley, Cochise County, southeastern Arizona

    USGS Publications Warehouse

    Gettings, M.E.; Houser, Brenda B.

    2000-01-01

    to bedrock over this high is 200-500 m and the basin-fill unit ranges from 100 to 200 m thick there. A number of previously unrecognized faults were identified and the lengths of some of the known faults were extended based on reconnaissance geologic mapping, study of driller's logs, interpretation of aerial photographs and thematic mapper satellite images, and inspection of contoured gravity and aeromagnetic anomaly data. Many faults that segment the main San Pedro basin and shape the boundaries of the subbasins are apparently pre-existing faults that have been reactivated by Basin and Range extension.

  9. Carbon storage in Swedish bedrock - current status regarding potential storage areas and geophysical information

    NASA Astrophysics Data System (ADS)

    Bergman, B.; Juhojuntti, N. G.

    2010-12-01

    Carbon Capture and Storage (CCS) is increasingly considered as an option to reduce the release of CO2 to the atmosphere. There is today a significant interest from Swedish heavy industry in CCS-technology. Large point sources are found within process industry related to e.g. production of paper and steel (operating under European Union regulations). There is also significant emission of CO2 from burning of biomass for energy production. However, this process is considered to be climate neutral and thus the emissions are not included in the carbon trading schemes. Based on recent work at the Geological Survey of Sweden and by other organizations we discuss the possibilities for geological storage of CO2 in Sweden, including the locations of the potential storage sites and the main CO2 emitters. In this context, we also review the relevant geophysical data available at the Geological Survey, focusing on the seismic data but also including gravity and magnetic data. Deep saline aquifers are presently considered as the most realistic storage alternative in Sweden. Sedimentary bedrock containing such layers and which could be suitable for CO2 storage is mainly found within the southern Baltic Sea and around southernmost Sweden, close to Denmark. The knowledge about the sedimentary bedrock in these areas is mainly based on seismic measurements and drilling in connection with hydrocarbon prospecting during the 70’s and the 80’s. Approximately 40.000 km’s of seismic reflection profiles were acquired, mostly in the potential CO2 storage areas mentioned above. Data from these profiles are now archived at the Geological Survey, and currently the magnetic tapes (8000-9000 reels) are being transcribed to modern storage media, a work that will likely be finished during 2011. Despite the hydrocarbon prospecting in these areas there are remaining uncertainties regarding the suitability of the sedimentary bedrock for CO2 storage, in particular related to the porosity and

  10. Efficacy of bedrock erosion by subglacial water flow

    NASA Astrophysics Data System (ADS)

    Beaud, F.; Flowers, G. E.; Venditti, J. G.

    2015-09-01

    Bedrock erosion by sediment-bearing subglacial water remains little-studied, however the process is thought to contribute to bedrock erosion rates in glaciated landscapes and is implicated in the excavation of tunnel valleys and the incision of inner gorges. We adapt physics-based models of fluvial abrasion to the subglacial environment, assembling the first model designed to quantify bedrock erosion caused by transient subglacial water flow. The subglacial drainage model consists of a one-dimensional network of cavities dynamically coupled to one or several Röthlisberger channels (R-channels). The bedrock erosion model is based on the tools and cover effect, whereby particles entrained by the flow impact exposed bedrock. We explore the dependency of glacial meltwater erosion on the structure and magnitude of water input to the system, the ice geometry and the sediment supply. We find that erosion is not a function of water discharge alone, but also depends on channel size, water pressure and on sediment supply, as in fluvial systems. Modelled glacial meltwater erosion rates are one to two orders of magnitude lower than the expected rates of total glacial erosion required to produce the sediment supply rates we impose, suggesting that glacial meltwater erosion is negligible at the basin scale. Nevertheless, due to the extreme localization of glacial meltwater erosion (at the base of R-channels), this process can carve bedrock (Nye) channels. In fact, our simulations suggest that the incision of bedrock channels several centimetres deep and a few meters wide can occur in a single year. Modelled incision rates indicate that subglacial water flow can gradually carve a tunnel valley and enhance the relief or even initiate the carving of an inner gorge.

  11. Experiments on Bedrock Cover in a Highly Sinuous Channel

    NASA Astrophysics Data System (ADS)

    Parker, G.; Fernandez, R.; Stark, C. P.

    2015-12-01

    One of several mechanisms by which bedrock rivers can incise is abrasion of the bedrock surface by colliding sediment particles. This effect has been captured in terms of a "cover factor" corresponding to the areal fraction p of the bed that is covered with sediment. According to this formulation, a value of p equal to 1 corresponds to complete alluvial cover: sediment particles strike each other and no bedrock abrasion is accomplished. Correspondingly, a value of p equal to 0 corresponds to the absence of sediment: no particles are available to strike the bed, and again no bedrock abrasion is accomplished. Thus the condition 0 < p < 1 is hypothesized to be the condition for incision driven by abrasion. At the microscopic level, however, p can take only the binary values 0 and 1: either a point on the bedrock surface is covered or is not covered. Therefore, the value of p that enters into any morphodynamic formulation of cover must represent an average over some spatiotemporal window. Here we consider the case of a highly sinuous meandering flume. The bed is set in concrete to take the topography corresponding to purely alluvial mobile-bed equilibrium. The recirculation of sediment over this bed at below-capacity conditions leads to a complex pattern of free and forced bars that only partially cover the bed. At certain locations, such as near the inside of bends, the bed is always covered, where at other locations, such as right near the apexes of the very tight bends in the flume, the bed is almost never covered. At other locations, the instantaneous cover fluctuates between the binary values 0 and 1, reflecting the migration of bars of various sizes over the bedrock surface. The averaging of these binary values over appropriate time windows allows determination of the local spatial variation of p that can serve as input to a numerical model of the evolution of bedrock meandering channels.

  12. Bedrock composition limits mountain ecosystem productivity and landscape evolution (Invited)

    NASA Astrophysics Data System (ADS)

    Riebe, C. S.; Hahm, W.; Lukens, C.

    2013-12-01

    We used measurements of bedrock geochemistry, forest productivity and cosmogenic nuclides to explore connections among lithology, ecosystem productivity and landscape evolution across a lithosequence of 21 sites in the Sierra Nevada Batholith, California. Our sites span a narrow range in elevations and thus share similar climatic conditions. Meanwhile, underlying bedrock varies from granite to diorite and spans nearly the entire range of geochemical compositions observed in Cordilleran granitoids. Land cover varies markedly, from groves of Giant Sequoia, the largest trees on Earth, to pluton-spanning swaths of little or no soil and vegetative cover. This is closely reflected in measures of forest productivity, such as remotely sensed tree-canopy cover, which varies by more than an order of magnitude across our sites and often changes abruptly at mapped contacts between rock types. We find that tree-canopy cover is closely correlated with the concentrations in bedrock of major and minor elements, including several plant-essential nutrients. For example, tree-canopy cover is virtually zero where there is less than 0.3 mg/g phosphorus in bedrock. Erosion rates from these nearly vegetation-free, nutrient deserts are more than 2.5 times slower on average than they are from surrounding, relatively nutrient-rich, soil-mantled bedrock. Thus by influencing soil and forest cover, bedrock nutrient concentrations may provoke weathering-limited erosion and thus may strongly regulate landscape evolution. Our analysis suggests that variations in bedrock nutrient concentrations can also provoke an intrinsic limitation on primary productivity. These limitations appear to apply across all our sites. To the extent that they are broadly representative of conditions in granitic landscapes elsewhere around the world, our results are consistent with widespread, but previously undocumented lithologic control of the distribution and diversity of vegetation in mountainous terrain.

  13. Cable-suspended Ice and Bedrock Electromechanical Drill: Design and Tests

    NASA Astrophysics Data System (ADS)

    Wang, Rusheng; Talalay, Pavel; Sun, Youhong; Zheng, Zhichuan; Cao, Pinlu; Zhang, Nan; Chen, Chen; Xu, Huiwen; Xue, Hong; Xue, Jun; Yu, Dahui; Fan, Xiaopeng; Hu, Zhengyi; Yang, Cheng; Gong, Da; Liu, Chunpeng; Han, Junjie; Yu, Chengfeng; Hong, Jialing; Wang, Lili

    2014-05-01

    Directly obtaining the subglacial bedrock samples is one of the most important tasks of Antarctic exploration in the future, which has great significance to research the formation and evolution of the Antarctic ice sheet, research the environment at the junction of the ice and bedrock, and research the geologic structure in Polar Regions. To drill through ice and bedrock, a new modified version of the cable-suspended Ice and Bedrock Electromechanical Drill 'IBED' is designed. IBED drill has modulus construction. The upper part includes four sections: cable termination, slip rings section, antitorque system, electronic pressure chamber. The motor-gear system is differed by rotation speed of the output shaft of the gear-reducer. All modulus contain 3 kW AC3 × 380 V submersible motor. Gear-reducer for drilling in ice lowers the drill bit rotation speed to 100 rpm; gear reducer for subglacial drilling lowers the drill bit rotation speed to 500 rpm. In addition, module for dry core drilling contains vacuum pump for near bottom air reverse circulation instead of liquid-driven pump that is installed into other two variants. The rotation speed of air-driven pump is increased by the gear to 6000 rpm. In modules for drilling with liquid the gear pump is used with capacity of 38-41 L/min and maximal pressure of 0.2 MPa. IBED lower part for drilling in ice consists from two parts: chip chamber for filtration of drilling fluid and collecting chips, and core barrel with the drill bit. The outer/inner diameter of the ice core drill bit is 134/110 mm. Length of the core barrel is 2.5 m. Lower part of the bedrock drill is adapted for coring bedrock and contains standard 2-m length core barrel borrowed from conventional diamond drill string, chip chamber for gravity separation of rock cuttings and dead weights (appr. 200 kg) for increasing of the load on the diamond drill bit. The outer/inner diameters of the diamond bit are 59/41 mm. The IBED drill was tested in order to solve

  14. Geology and plate-tectonic development

    SciTech Connect

    Irwin, W.P.

    1990-01-01

    The San Andreas fault is a transform fault along the boundary between the Pacific and North American plates. Bedrock along the fault includes various lithologic units that range in age from Precambrian to Tertiary and younger. Some bedrock units that can be matched across the fault suggest strike-slip displacement of as much as 560 km. This chapter describes geologic formations of northern and central California, including Franciscan rocks, Coast Range ophiolite, Great Valley sequence, Coast Range thrust, Salinian block, displacement of pre-Quaternary rocks by the San Andreas fault, and the relation of geologic structure to seismic behavior. Formations of southern California which are described are the Transverse Ranges and the Salton Trough and displacement of basement rocks by the San Andreas fault. Plate-tectonic development of the San Andreas fault is also discussed.

  15. Initial yield to depth relation for water wells drilled into crystalline bedrock - Pinardville quadrangle, New Hampshire

    USGS Publications Warehouse

    Drew, L.J.; Schuenemeyer, J.H.; Amstrong, T.R.; Sutphin, D.M.

    2001-01-01

    A model is proposed to explain the statistical relations between the mean initial water well yields from eight time increments from 1984 to 1998 for wells drilled into the crystalline bedrock aquifer system in the Pinardville area of southern New Hampshire and the type of bedrock, mean well depth, and mean well elevation. Statistical analyses show that the mean total yield of drilling increments is positively correlated with mean total well depth and mean well elevation. In addition, the mean total well yield varies with rock type from a minimum of 46.9 L/min (12.4 gpm) in the Damon Pond granite to a maximum of 74.5 L/min (19.7 gpm) in the Permian pegmatite and granite unit. Across the eight drilling increments that comprise 211 wells each, the percentages of very low-yield wells (1.9 L/min [0.5 gpm] or less) and high-yield wells (151.4 L/min [40 gpm] or more) increased, and those of intermediate-yield wells decreased. As housing development progressed during the 1984 to 1998 interval, the mean depth of the wells and their elevations increased, and the mix of percentages of the bedrock types drilled changed markedly. The proposed model uses a feed-forward mechanism to explain the interaction between the increasing mean elevation, mean well depth, and percentages of very low-yielding wells and the mean well yield. The increasing percentages of very low-yielding wells through time and the economics of the housing market may control the system that forces the mean well depths, percentages of high-yield wells, and mean well yields to increase. The reason for the increasing percentages of very low-yield wells is uncertain, but the explanation is believed to involve the complex structural geology and tectonic history of the Pinardville quadrangle.

  16. Hydrogeological bedrock inferred from electrical resistivity model in Taichung Basin, Taiwan

    NASA Astrophysics Data System (ADS)

    Chiang, C. W.; Chang, P. Y.; Chang, L. C.

    2015-12-01

    The four-year project of the study of groundwater hydrogeology and recharge model was indicated by Central Geological Survey, MOEA, Taiwan (R.O.C.) to evaluate recharge groundwater areas in Taiwan where included Taipei, Taichung Basins, Lanyang and Chianan Plains. The groundwater recharge models of Lanyang Plain and Taipei Basin have successfully been estimated in two years ago (2013-2014). The third year of the project integrates with geophysical, geochemistry, and hydrogeology models to estimate the groundwater recharge model in Taichung Basin region. Taichung Basin is mainly covered by Pre-Pleistocene of thick gravel, sandy and muddy sediment rocks within a joint alluvial fan, whereas the depth of the hydrological bedrock remains uncertain. Two electrical resistivity geophysical tools were carried out utilizing direct current resistivity and audio-magnetotelluric (AMT) explorations, which could ideally provide the depth resolutions from shallow to depth for evaluating the groundwater resources. The study has carried out 21 AMT stations in the southern Taichung Basin in order to delineate hydrological bedrock in the region. All the AMT stations were deployed about 24 hours and processed with remote reference technique to reduce culture noises. The quality of most stations shows acceptable in the area which two stations were excluded due to near-field source effect in the southwestern basin. The best depth resolution is identified in 500 meters for the model. The preliminary result shows that the depths of the bedrock gradually changes from southern ~20 m toward to ~400 m in central, and eastern ~20 m to 180 m in the western basin inferred from the AMT model. The investigation shows that AMT method could be a useful geophysical tool to enhance the groundwater recharge model estimation without dense loggings in the region.

  17. Dynamics of Bedload Transport in a Bedrock-Alluvial River

    NASA Astrophysics Data System (ADS)

    Hodge, R. A.; Sharma, B. P.; Ferguson, R.; Hardy, R. J.; Warburton, J.

    2014-12-01

    The processes controlling the entrainment, transport and deposition of coarse sediment in bedrock-alluvial systems are key for understanding sediment fluxes in these systems. Theories have been developed for these processes, and assumptions are made about them in models of bedrock incision. However, there are relatively few field datasets from these rivers with which to test these ideas. We report results from a gravel tracer experiment in the bedrock-alluvial Trout Beck, UK. The 410 m long study section consists of alluvial, mixed bedrock-alluvial and bedrock reaches. There are no tributary inputs so discharge is constant throughout. Two sets of 270 magnet-tagged pebbles covering the grain size distribution of the in-situ sediment were seeded in August 2013. Tracers were placed in an alluvial reach and in a bedrock reach, enabling quantification of grain dynamics over different substrates but under the same flow conditions. Tracers were resurveyed six times over nine months. Concurrent measurements of stage, discharge and bedload impacts at various locations in the channel aid interpretation of the tracer measurements. Tracers installed in the bedrock reach were far more mobile than those in the alluvial reach, with mean travel distances of 70.6 and 2.4 m respectively in the first two months. The transport of tracers was largely size independent over the purely bedrock reach. This finding may be explained by bulk hydraulic measurements that indicate that effective shear stress is highest in this section of the channel. Once these tracers reached the downstream mixed bedrock-alluvial reach, transport distances became relatively shorter, though still greater than in the purely alluvial reach (mean distances of 27.6 and 15.4 m from month 2 to month 7), and became size selective. The second set of tracers seeded in the alluvial reach displayed size-selective transport throughout the experimental period. This study demonstrates how reach substrate exerts a strong

  18. Spatial bedrock erosion distribution in a natural gorge

    NASA Astrophysics Data System (ADS)

    Beer, A. R.; Turowski, J. M.; Kirchner, J. W.

    2015-12-01

    Quantitative analysis of morphological evolution both in terrestrial and planetary landscapes is of increasing interest in the geosciences. In mountainous regions, bedrock channel formation as a consequence of the interaction of uplift and erosion processes is fundamental for the entire surface evolution. Hence, the accurate description of bedrock channel development is important for landscape modelling. To verify existing concepts developed in the lab and to analyse how in situ channel erosion rates depend on the interrelations of discharge, sediment transport and topography, there is a need of highly resolved topographic field data. We analyse bedrock erosion over two years in a bedrock gorge downstream of the Gorner glacier above the town of Zermatt, Switzerland. At the study site, the Gornera stream cuts through a roche moutonnée in serpentine rock of 25m length, 5m width and 8m depth. We surveyed bedrock erosion rates using repeat terrestrial laser scanning (TLS) with an average point spacing of 5mm. Bedrock erosion rates in direction of the individual surface normals were studied directly on the scanned point clouds applying the M3C2 algorithm (Lague et al., 2013, ISPRS). The surveyed erosion patterns were compared to a simple stream erosivity visualisation obtained from painted bedrock sections at the study location. Spatially distributed erosion rates on bedrock surfaces based on millions of scan points allow deduction of millimeter-scale mean annual values of lateral erosion, incision and downstream erosion on protruding streambed surfaces. The erosion rate on a specific surface point is shown to depend on the position of this surface point in the channel's cross section, its height above the streambed and its spatial orientation to the streamflow. Abrasion by impacting bedload was likely the spatially dominant erosion process, as confirmed by the observed patterns along the painted bedrock sections. However, a single plucking event accounted for the half

  19. Bedrock Channels: Towards a Process-Based Understanding

    NASA Astrophysics Data System (ADS)

    Parsons, D. R.; Darby, S. E.; Hackney, C. R.; Leyland, J.; Best, J.; Nicholas, A. P.; Aalto, R. E.; Horn, C. A. P. T., III; Thy, M. R.

    2014-12-01

    Most previous studies on the genesis and evolution of bedforms in large rivers have focused on aggradational bedforms within alluvial sediments, with very few investigations that concern either erosive bedform evolution or bedrock channel abrasion processes. Detailed understanding of the processes within bedrock reaches of river channels is vital if an improved understanding of formation and evolution of bedrock scours and bedforms are to be elucidated. The paper presents high-resolution bathymetry and sidescan derived from multibeam sonar (MBES) and detailed flow mapping by acoustic Doppler current profiling (ADCP) to illustrate, in intricate detail, relations between morphology, flow and sediment transport processes through a bedrock reach of the Mekong River (Cambodia) during a large flood event. A 2 by 5 km reach of the Mekong river near Sambor was surveyed with a RESON 7125 MBES system revealing incredible >40 m scour features within the bedrock substrate, with sidescan imagery also revealing the routing of alluvial sediment through the scours. A series of ADCP transects were obtained, both transverse and perpendicular to the primary downstream flow, that map the flows into, around and within these scour features. The paper will conclude by looking at how advances in measurement capability have permitted the detailed processes in such channels to be investigated for the first time at this scale.

  20. Particle dynamics: The continuum of bedrock to alluvial river segments

    NASA Astrophysics Data System (ADS)

    Wohl, Ellen

    2015-07-01

    Particle dynamics refers to production, erosion, transport, and storage of particulate material including mineral sediment and organic matter. Particle dynamics differ significantly between the end members of bedrock and alluvial river segments and between alluvial river segments with different grain-size distributions. Bedrock segments are supply limited and resistant to change, with relatively slow, linear adjustments and predominantly erosion and transport. Particle dynamics in alluvial segments, in contrast, are transport limited and dominated by storage of mineral sediment and production of organic matter. Alluvial segments are resilient to change, with relatively rapid, multidirectional adjustments and stronger internal influences because of feedbacks between particles and biota. Bedrock segments are the governors of erosion within a river network, whereas alluvial segments are the biogeochemical reactors. Fundamental research questions for both types of river segments center on particle dynamics, which limit network-scale incision in response to base level fall (bedrock segments) and habitat, biogeochemical reactions, and biomass production (alluvial segments). These characterizations illuminate how the spatial arrangement of bedrock and alluvial segments within a river network influence network-scale resistance and resilience to external changes in relative base level, climate, and human activities.

  1. Spectroscopic analysis of bedrock exposures in the Martian highlands

    NASA Astrophysics Data System (ADS)

    Rogers, D.; Aharonson, O.; Bandfield, J. L.; Christensen, P. R.

    2005-12-01

    The THEMIS instrument aboard the 2001 Mars Odyssey spacecraft has provided a new view of the martian surface with 100 m/pixel daytime and nighttime multispectral infrared imaging. Numerous exposures of bedrock have been identified using THEMIS data. These exposures are found in a variety of southern highlands terrains, including crater floors and intercrater plains. We are characterizing the composition, thermophysical properties, and morphology of extensive, largely sediment-free bedrock surfaces in the intercrater plains of Mars. More than 30 spatially-contiguous, extensive, non-crater related bedrock surfaces with low albedo values (<0.16) have been identified to date. These bedrock exposures are investigated using THEMIS daytime and nighttime IR mosaics, MOC wide angle 256 ppd mosaic, MOLA elevation data binned at 128 ppd, and TES detector field-of-view overlays (full spatial resolution) of albedo and spectral emissivity. THEMIS and TES data are used for derivation of surface emissivity and estimation of mineral abundance allowing classification into units based on composition, morphology, texture and other noted characteristics. Building on previous global studies, we use infrared and VIS/NIR spectral data to determine surface mineralogy and examine how representative the martian surface layer is of near-surface underlying bedrock units. This study, for the first time, systematically probes a window into the stratigraphy and composition of globally distributed ancient terrains on Mars.

  2. International Geology

    ERIC Educational Resources Information Center

    Hoover, Linn

    1977-01-01

    Briefly discusses recent international programs in various areas of geology, including land-use problems, coping with geological hazards, and conserving the environment while searching for energy and mineral resources. (MLH)

  3. Mathematical Geology.

    ERIC Educational Resources Information Center

    Jones, Thomas A.

    1983-01-01

    Mathematical techniques used to solve geological problems are briefly discussed (including comments on use of geostatistics). Highlights of conferences/meetings and conference papers in mathematical geology are also provided. (JN)

  4. Effects on groundwater flow of abandoned engineered structures for the safety assessment of the proposed high-level nuclear waste repository site at Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Bockgård, Niclas; Marsic, Niko; Follin, Sven

    2014-09-01

    Effects on groundwater flow of abandoned engineered structures in relation to a potential geological repository for spent high-level nuclear fuel in fractured crystalline rock at the Forsmark site, Sweden, are studied by means of numerical modeling. The effects are analyzed by means of particle tracking, and transport-related performance measures are calculated. The impacts of abandoned, partially open repository tunnels are studied for two situations with different climate conditions: a "temperate" climate case with present-day boundary conditions, and a generic future "glacial" climate case with an ice sheet covering the repository. Then, the impact of abandoned open boreholes drilled through the repository is studied for present-day climate conditions. It is found that open repository tunnels and open boreholes can act as easy pathways from repository level to the ground surface; hence, they can attract a considerable proportion of particles released in the model at deposition hole positions within the repository. The changed flow field and flow paths cause some changes in the studied performance measures, i.e., increased flux at the deposition holes and decreased transport lengths and flow-related transport resistances. However, these effects are small and the transport resistance values are still high.

  5. Bedrock structures controlling the spatial occurrence and geometry of 1.8 Ga younger glacifluvial deposits - Example from First Salpausselkä, southern Finland

    NASA Astrophysics Data System (ADS)

    Skyttä, Pietari; Kinnunen, Jussi; Palmu, Jukka-Pekka; Korkka-Niemi, Kirsti

    2015-12-01

    The glacifluvial deposits within formerly glaciated areas of southern Finland comprise the predominance of well-sorted subglacial and ice marginal sediments. The deposits are less than 100 m thick and form significant aquifers utilized by the respective areas. The spatial correlation of subglacial deposits with bedrock structures, particularly the deformation zones, has been long recognized, but most often not systematically investigated. The purpose of this study was to understand how specific bedrock structures control the position and processes of formation of glacifluvial deposits, using the First Salpausselkä area of southern Finland as a model area. We apply a means of structural analysis to compile structural interpretations (form lines and 3D-surfaces) of the bedrock and correlate the results with the patterns of the glacifluvial deposits and the topography of the underlying bedrock surface. Two major E-W striking shear zones defining abrupt breaks at the bedrock surface along with secondary SW-NE striking splays, originating from the horsetail-like termination of the Somero shear zone, control the deposition of eskers and ice marginal deposits. Based on correlations between the bedrock topography, glacial erosion and sedimentation, we infer that laterally extensive shear zones may have indirectly affected the glacial dynamics within the areas of areal scour more than previously considered. Recognized deformation zones are important for modelling the internal stratigraphy of glacifluvial deposits, their hydrogeological properties and for mapping fresh water supplies within the Nordic countries and other glaciated areas which have undergone substantial tectonic deformation. The development of 3D geologic models is essential for understanding regional-scale correlations between Quaternary sediments and bedrock structures.

  6. Environmental Geology

    ERIC Educational Resources Information Center

    Passero, Richard N.

    1978-01-01

    1977 was a year of continued and expanding efforts in the application of the geosciences to land-use planning, especially as they relate to geologic hazards, and elucidating the role of geology in public policy. The work of environmental geological programs is reviewed. (Author/MA)

  7. Lithogeochemical character of the near-surface bedrock in the Connecticut, Housatonic, and Thames River Basins

    USGS Publications Warehouse

    Robinson, Gilpin R., Jr.; Peper, John D.; Steeves, Peter A.; DeSimone, Leslie A.

    1999-01-01

    This data layer shows the generalized lithologic and geochemical (lithogeochemical) character of near-surface bedrock in the Connecticut, Housatonic, and Thames River Basins and several other small basins that drain into Long Island Sound from Connecticut. The area includes most of Connecticut, western Massachusetts, eastern Vermont, western New Hampshire, and small parts of Rhode Island, New York, and Quebec, Canada.Bedrock geologic rock units are classified into 29 lithogeochemical rock units, on the basis of the relative reactivity of their constituent minerals to dissolution and other weathering reactions and the presence of carbonate or sulfide minerals. The 29 lithogeochemical units (28 of which can be found in the study area) can be grouped into 6 major categories: (1) carbonate-rich rocks, (2) carbonate-poor, clastic sedimentary rocks restricted to distinct depositional basins, (3) metamorphosed, clastic sedimentary rocks (primarily noncalcareous), (4) mafic igneous rocks and their metamorphic equivalents, (5) ultramafic rocks, and (6) felsic igneous and plutonic rocks and their metamorphic equivalents. The lithogeochemical rock units also are grouped into nine lithologic and physiographic provinces (lithophysiographic domains), which can be further grouped into three major regions: (1) western highlands and lowlands, (2) central lowlands, and (3) eastern highlands.

  8. Rapid formation of a modern bedrock canyon by a single flood event

    NASA Astrophysics Data System (ADS)

    Lamb, Michael P.; Fonstad, Mark A.

    2010-07-01

    Deep river canyons are thought to form slowly over geological time (see, for example, ref. 1), cut by moderate flows that reoccur every few years. In contrast, some of the most spectacular canyons on Earth and Mars were probably carved rapidly during ancient megaflood events. Quantification of the flood discharge, duration and erosion mechanics that operated during such events is hampered because we lack modern analogues. Canyon Lake Gorge, Texas, was carved in 2002 during a single catastrophic flood. The event offers a rare opportunity to analyse canyon formation and test palaeo-hydraulic-reconstruction techniques under known topographic and hydraulic conditions. Here we use digital topographic models and visible/near-infrared aerial images from before and after the flood, discharge measured during the event, field measurements and sediment-transport modelling to show that the flood moved metre-sized boulders, excavated ~7m of limestone and transformed a soil-mantled valley into a bedrock canyon in just ~3days. We find that canyon morphology is strongly dependent on rock type: plucking of limestone blocks produced waterfalls, inner channels and bedrock strath terraces, whereas abrasion of cemented alluvium sculpted walls, plunge pools and streamlined islands. Canyon formation was so rapid that erosion might have been limited by the ability of the flow to transport sediment. We suggest that our results might improve hydraulic reconstructions of similar megafloods on Earth and Mars.

  9. Parameterization and quantification of recharge in crystalline fractured bedrocks in Galicia-Costa (NW Spain)

    NASA Astrophysics Data System (ADS)

    Raposo, J. R.; Molinero, J.; Dafonte, J.

    2012-06-01

    Quantifying groundwater recharge in crystalline rocks presents great difficulties due to the high heterogeneity of the underground medium (mainly, due to heterogeneity in fracture network, which determines hydraulic parameters of the bedrock like hydraulic conductivity or effective porosity). Traditionally these rocks have been considered to have very low permeability, and their groundwater resources have usually been neglected; however, they can be of local importance when the bedrock presents a net of well-developed fractures. The current European Water Framework Directive requires an efficient management of all groundwater resources; this begins with a proper knowledge of the aquifer and accurate recharge estimation. In this study, an assessment of groundwater resources in the Spanish hydrologic district of Galicia-Costa, dominated by granitic and metasedimentary rocks, was carried out. A water-balance modeling approach was used for estimating recharge rates in nine pilot catchments representatives of both geologic materials. These results were cross-validated with an independent technique, i.e. the chloride mass balance (CMB). A relation among groundwater recharge and annual precipitation according to two different logistic curves was found for both granites and metasedimentary rocks, thus allowing the parameterization of recharge by means of only a few hydrogeological parameters. Total groundwater resources in Galicia-Costa were estimated to be 4427 hm3 yr-1. An analysis of spatial and temporal variability of recharge was also carried out.

  10. Lithologic controls on AIRSAR signatures of bedrock and alluvium, at Lunar Crater, Nevada

    NASA Technical Reports Server (NTRS)

    Rivard, Benoit; Diorio, Marc; Budkewitsch, Paul

    1995-01-01

    Radar backscatter intensity as measured by calibrated synthetic aperture radar (SAR) systems is primarily controlled by three factors: local incidence angle, wavelength-scale roughness, and dielectric permittivity of surface materials. In order to make adequate use of radar observations for geological investigations of surface type, the relationships between lithology and the above characteristics must be adequately understood. In arid terrains weathering signatures (e.g. fracturing, debris grain size and shape, slope characteristics) are controlled to some extent by lithologic characteristics of the parent bedrock. These textural features of outcrops and their associated debris control radar backscatter to varying degrees. The quad-polarization JPL AIRSAR system allows sampling of textures at three distinct wavelength scales: C-band (5.66 cm), L-band (23.98 cm), and P-band (68.13 cm). This paper presents a discussion of AIRSAR data using recent field observations of weathered felsic and basaltic volcanic rock units exposed in the southern part of the Lunar Crater Volcanic Field, in the Pancake Range of central Nevada. The focus is on the relationship of radar backscatter at multiple wavelengths to weathering style and parent bedrock lithology.

  11. Detection of Seismic Bedrock Using Radial Receiver Function

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Feng; Huang, Huey-Chu

    2016-06-01

    The receiver function (RF) method has been widely applied to estimate velocity structures of Earth's crust and mantle using teleseismic data. In this study, we perform a RF iterative deconvolution method to detect the depth variations of seismic bedrock in the Taipei basin and Chiayi area. We use strong motion data recorded by five and seven stations in the Taipei basin and Chiayi area, respectively. The Ps-P times appear at about 0.235-0.93 s for the Taipei basin and 1.015-1.685 s for the Chiayi area. The time differences imply gradually increases of the bedrock depth from southeast to northwest in the Taipei basin and from east to west in the Chiayi area. Our results show that the method can efficiently detect depth variations of seismic bedrock which are consistent with those from other geophysical observations as well.

  12. Geophysical imaging reveals topographic stress control of bedrock weathering.

    PubMed

    St Clair, J; Moon, S; Holbrook, W S; Perron, J T; Riebe, C S; Martel, S J; Carr, B; Harman, C; Singha, K; Richter, D deB

    2015-10-30

    Bedrock fracture systems facilitate weathering, allowing fresh mineral surfaces to interact with corrosive waters and biota from Earth's surface, while simultaneously promoting drainage of chemically equilibrated fluids. We show that topographic perturbations to regional stress fields explain bedrock fracture distributions, as revealed by seismic velocity and electrical resistivity surveys from three landscapes. The base of the fracture-rich zone mirrors surface topography where the ratio of horizontal compressive tectonic stresses to near-surface gravitational stresses is relatively large, and it parallels the surface topography where the ratio is relatively small. Three-dimensional stress calculations predict these results, suggesting that tectonic stresses interact with topography to influence bedrock disaggregation, groundwater flow, chemical weathering, and the depth of the "critical zone" in which many biogeochemical processes occur. PMID:26516279

  13. Dredged bedrock samples from the Amerasia Basin, Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Brumley, K. J.; Mukasa, S. B.; O'Brien, T. M.; Mayer, L. A.; Chayes, D. N.

    2013-12-01

    Between 2008-2012, as part of the U.S. Extended Continental Shelf project in the Amerasia Basin, Arctic Ocean, 17 dredges were successfully collected sampling the first rock outcrops in the Chukchi Borderland and surrounding regions for the purpose of describing the geologic nature of the bathymetric features in this area. Multiple lines of evidence indicate that the specimens were collected from submarine rock exposures and were not samples of ice rafted debris, common in the ice covered waters of the Arctic Ocean. Using the USCGC Healy, each dredge was collected along very steep slopes (>35 degrees) measured with high resolution multibeam swath bathymety data. Each haul yielded samples of similar lithologies and identical metamorphic grade with manganese crusts on the surfaces exposed to seawater and fresh surfaces where the rocks were broken from outcrop. High tension pulls on the dredge line also indicated sampling of bedrock exposures. Dredged samples from a normal fault scarp in the central Chukchi Borderland consisted of Silurian (c. 430 Ma) orthogneisses that intruded older (c. 487-500 Ma) gabbros and luecogranties that were all metamorphosed to amphibolite grade (Brumley et al., 2011). Samples from the northern Northwind Ridge consisted of metasediments (greenschist facies) interpreted to have been deposited in a proximal arc setting with detrital zircon U-Pb age peaks at 434, 980 Ma with lesser peaks between 500-600, 1100-2000 Ma, and rare 2800 Ma grains (Brumley et al, 2010). Other dredges in the region of the Northwind Ridge yielded deformed and metamorphosed calcareous sandstones and low-grade phyllites (O'Brien et al., 2013). Taken together these rocks indicate a relationship to the Pearya Terrane of northern Ellesmere Island and S.W. Svalbard that were thought to represent a Cambro-Ordovician volcanic arc terrane that was involved in Caledonian orogenesis (Brumley et al., 2011). These findings constrain plate tectonic reconstruction models and bring

  14. Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 1. Depth to Bedrock Determinations Using Shallow Seismic Data Acquired in the Straight Creek Drainage Near Red River, New Mexico

    USGS Publications Warehouse

    Powers, Michael H.; Burton, Bethany L.

    2004-01-01

    In late May and early June of 2002, the U.S. Geological Survey (USGS) acquired four P-wave seismic profiles across the Straight Creek drainage near Red River, New Mexico. The data were acquired to support a larger effort to investigate baseline and pre-mining ground-water quality in the Red River basin (Nordstrom and others, 2002). For ground-water flow modeling, knowledge of the thickness of the valley fill material above the bedrock is required. When curved-ray refraction tomography was used with the seismic first arrival times, the resulting images of interval velocity versus depth clearly show a sharp velocity contrast where the bedrock interface is expected. The images show that the interpreted buried bedrock surface is neither smooth nor sharp, but it is clearly defined across the valley along the seismic line profiles. The bedrock models defined by the seismic refraction images are consistent with the well data.

  15. Comparing spatial patterns of thrust belt architecture and bedrock river morphology across the southern Bolivian Andes

    NASA Astrophysics Data System (ADS)

    Syrek, J. F.; Barnes, J. B.

    2011-12-01

    Rivers set the pace of mountain landscape evolution, but their ability to incise into rock is often governed by numerous factors. The degree to which variations in lithology, relief, rock uplift rates, and climate may affect the form of channel profiles remain largely open questions. Empirical models of bedrock river incision, such as stream power (E = KAmSn), oversimplify these potentially important factors. For example, the influence of many factors such as channel geometry, hydraulic roughness, sediment flux, and substrate erodibility are combined into the coefficient of erosion, K. Here we investigate the spatial patterns of rock erodibility, bedrock river slope, concavity, and stream power-based estimates of incision across the southern Bolivian Andes. We hypothesize that bedrock river morphology correlates with the thrust-belt geology. For example, channels cutting through the strongest and least fractured rock units will exhibit the highest steepness values. We estimate rock erodibility by measuring (a) compressive rock strength with a Schmidt hammer and (b) fracture density from exposures proximal to river channels at ~80 total sites from all the major rock units exposed throughout the study area. We use a hydrologically-conditioned 90 m digital elevation model to map patterns of channel steepness (ksn) and concavity (θ) indices. Furthermore, we use the stream power model, combined with a previous local calibration of K, to estimate patterns of river incision along the study area rivers. The combined strength and fracture density measurements suggest the Neogene volcanics, Cretaceous sediments, and Devonian metasediments are the least erodible units and the Silurian and Ordovician metasediments are the weakest. In general, changes in channel steepness often correlate with (1) changes in rock erodibility, (2) high rock uplift rates associated with active structures in the Subandes, and (3) the major hinterland structural transition between the Eastern

  16. Conceptual uncertainty in crystalline bedrock: Is simple evaluation the only practical approach?

    USGS Publications Warehouse

    Geier, J.; Voss, C.I.; Dverstorp, B.

    2002-01-01

    A simple evaluation can be used to characterise the capacity of crystalline bedrock to act as a barrier to releases of radionuclides from a nuclear waste repository. Physically plausible bounds on groundwater flow and an effective transport-resistance parameter are estimated based on fundamental principles and idealised models of pore geometry. Application to an intensively characterised site in Sweden shows that, due to high spatial variability and uncertainty regarding properties of transport paths, the uncertainty associated with the geological barrier is too high to allow meaningful discrimination between good and poor performance. Application of more complex (stochastic-continuum and discrete-fracture-network) models does not yield a significant improvement in the resolution of geologic-barrier performance. Comparison with seven other less intensively characterised crystalline study sites in Sweden leads to similar results, raising a question as to what extent the geological barrier function can be characterised by state-of-the art site investigation methods prior to repository construction. A simple evaluation provides a simple and robust practical approach for inclusion in performance assessment.

  17. Conceptual uncertainty in crystalline bedrock: Is simple evaluation the only practical approach?

    USGS Publications Warehouse

    Geier, J.; Voss, C.I.; Dverstorp, B.

    2002-01-01

    A simple evaluation can be used to characterize the capacity of crystalline bedrock to act as a barrier to release radionuclides from a nuclear waste repository. Physically plausible bounds on groundwater flow and an effective transport-resistance parameter are estimated based on fundamental principles and idealized models of pore geometry. Application to an intensively characterized site in Sweden shows that, due to high spatial variability and uncertainty regarding properties of transport paths, the uncertainty associated with the geological barrier is too high to allow meaningful discrimination between good and poor performance. Application of more complex (stochastic-continuum and discrete-fracture-network) models does not yield a significant improvement in the resolution of geological barrier performance. Comparison with seven other less intensively characterized crystalline study sites in Sweden leads to similar results, raising a question as to what extent the geological barrier function can be characterized by state-of-the art site investigation methods prior to repository construction. A simple evaluation provides a simple and robust practical approach for inclusion in performance assessment.

  18. Evaluation of ERTS-1 imagery for geological sensing over the diverse geological terrains of New York State

    NASA Technical Reports Server (NTRS)

    Isachsen, Y. W.; Fakundiny, R. H.; Forster, S. W.

    1973-01-01

    Film positives of ERTS-1 imagery, both as received from NASA and photographically reprocessed, are analyzed by conventional and color additive viewing methods. The imagery reveals bedrock and surficial geological information at various scales. Features which can be identified to varying degrees include boundaries between major tectonic provinces, lithological contacts, foliation trends within massive gneisses, faults, and topographic lineaments. In the present imagery the greatest amount of spectral geology is displayed in the Adirondack region where bedrock geology is strongly linked to topography. Within this basement complex, the most prominantly displayed features are numerous north-northeast trending faults and topographic lineaments, and arcuate east-west valleys developed in some of the weaker metasedimentary rocks. The majority of the faults and lineaments shown on the geologic Map of New York at 1:250,000 appear in the ERTS imagery.

  19. Relation of arsenic, iron, and manganese in ground water to aquifer type, bedrock lithogeochemistry, and land use in the New England coastal basins

    USGS Publications Warehouse

    Ayotte, Joseph D.; Nielsen, Martha G.; Robinson, Gilpin R., Jr.; Moore, Richard B.

    1999-01-01

    In a study of arsenic concentrations in public-supply wells in the New England Coastal Basins, concentrations at or above 0.005 mg/L (milligrams per liter) were detected in more samples of water from wells completed in bedrock (25 percent of all samples) than in water from wells completed in stratified drift (7.5 percent of all samples). Iron and manganese were detected (at concentrations of 0.05 and 0.03 mg/L, respectively) at approximately the same frequency in water from wells in both types of aquifers. Concentrations of arsenic in public-supply wells drilled in bedrock (in the National Water-Quality Assessment Program New England Coastal Basins study unit) vary with the bedrock lithology. Broad groups of lithogeochemical units generalized from bedrock lithologic units shown on state geologic maps were used in the statistical analyses. Concentrations of arsenic in water from public-supply wells in metasedimentary bedrock units that contain slightly to moderately calcareous and calcsilicate rocks (lithogeochemical group Mc) were significantly higher than the concentrations in five other groups of bedrock units in the study unit. Arsenic was detected, at or above 0.005 mg/L, in water from 44 percent of the wells in the lithogeochemical group M c and in water from less than 28 percent of wells in the five other groups. Additionally, arsenic concentrations in ground water were the lowest in the metasedimentary rocks that are characterized as variably sulfidic (group Ms ). Generally, concentrations of arsenic were low in water from bedrock wells in the felsic igneous rocks (group If ) though locally some bedrock wells in granitic rocks are known to have ground water with high arsenic concentrations, especially in New Hampshire. The concentrations of arsenic in ground water also correlate with land-use data; significantly higher concentrations are found in areas identified as agricultural land use than in undeveloped areas. There is, however, more agricultural land in

  20. Landscape evolution and bedrock incision in the northern Alpine Foreland since the last 2 Ma

    NASA Astrophysics Data System (ADS)

    Claude, Anne; Akçar, Naki; Schlunegger, Fritz; Ivy-Ochs, Susan; Kubik, Peter; Christl, Marcus; Vockenhuber, Christof; Dehnert, Andreas; Kuhlemann, Joachim; Rahn, Meinert; Schlüchter, Christian

    2016-04-01

    The landscape evolution of the Swiss Alpine Foreland since the early Pleistocene is of utmost importance for modelling the long-term safety of deep geological repositories for nuclear waste disposal in the northern Alpine Foreland. The oldest Quaternary sediments in the northern foreland are proximal glaciofluvial sediments lying unconformably on Tertiary Molasse or Mesozoic carbonate bedrock. These deposits form topographically distinct and discontinuous isolated plateaus. Terrace morphostratigraphy has a reversed stratigraphic relationship, i.e. today older sediments are located at higher altitudes and vice versa. In this study, we focus on the landscape evolution and long-term bedrock incision in the Swiss Alpine Foreland. We reconstruct the terrace chronology in the foreland at six key locations at different altitudes ranging from 433 m a.s.l. to 675 m a.s.l. by applying cosmogenic depth-profile and isochron-burial dating techniques. First results from these sites indicate that the gravels at studied sites were accumulated in the foreland between 1 and 2 Ma. Based on this reconstructed chronology, long-term bedrock incision rates between 0.1 and 0.2 mm/a were calculated. Thus, we inferred a landscape at that time that was most likely characterized by smoother hillslopes than at present. During the Mid-Pleistocene Revolution (ca. 0.95 Ma), a re-organization of the drainage systems occurred in the Alpine Foreland with a significant lowering of the base level of stream channels. Existing data suggest slightly increased incision rates after this drainage network re-organisation compared to our results. The reconstruction of the chronology at the remaining sites may allow quantifying a pronounced incision as well as the exact timing of the acceleration in the incision rates. REFERENCES Heuberger, S. & Naef, H. (2014). NAB 12-35: Regionale GIS-Kompilation und -Analyse der Deckenschotter-Vorkommen im nördlichen Alpenvorland. Nagra Arbeitsbericht. Kuhlemann, J. & Rahn

  1. 10. CANAL CUT THROUGH SHALE BEDROCK ON PROMINENT POINT, LOOKING ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    10. CANAL CUT THROUGH SHALE BEDROCK ON PROMINENT POINT, LOOKING NORTH-NORTHEAST. NOTE CONCRETE ABUTMENTS PROBABLY INSTALLED IN 1935 TO PREVENT WATER FROM ESCAPING THROUGH A CANAL BANK BREACH. - Snake River Ditch, Headgate on north bank of Snake River, Dillon, Summit County, CO

  2. Diagnostic tests for conceptualizing transport in bedrock aquifers

    NASA Astrophysics Data System (ADS)

    Worthington, Stephen R. H.

    2015-10-01

    Transport in bedrock aquifers is complex because there is often substantial flow through fractures, and the apertures and interconnectivity of these fractures are usually uncertain. Single-porosity numerical models often give satisfactory results for simulating flow. However, simulating transport is more challenging and results based on single-porosity assumptions can yield inaccurate results. Seven cases are reviewed where travel times were found to be unexpectedly short. Results show that dual-porosity flow is common, with advective flow through fracture networks and immobile storage in the matrix. However, in some cases a dual- or multiple-permeability (or porosity) approach provides better simulations of aquifer behavior. Fracture porosity of bedrock aquifers is usually <1%, resulting in rapid groundwater velocities in many aquifers. Overestimation of the effective porosity is the most common reason for the overestimation of travel times. Residence times of artificial tracers in bedrock aquifers are typically two to three orders of magnitude less than residence times of environmental tracers because the latter are retarded by matrix diffusion. Fourteen diagnostic tests for determining the appropriate conceptual model for bedrock aquifers are described.

  3. Dynamic Response of Antarctic Ice Shelves to Bedrock Uncertainty

    NASA Astrophysics Data System (ADS)

    Sun, Sainan; Cornford, Stephen; Liu, Yan; Moore, John

    2014-05-01

    Bedrock geometry is an essential boundary condition in ice sheet modelling. The shape of the bedrock on fine scales can influences ice sheet evolution, for example through the formation of pinning points that alter grounding line dynamics. Here we test the sensitivity of the BISICLES adaptive mesh ice sheet model to small amplitude height fluctuations on different spatial scales in the bed rock topography provided by bedmap2 in the catchments of Pine Island Glacier, the Amery Ice Shelf, and a region of East Antarctica including the Denman and Totten Glaciers. We generate an ensemble of bedrock topographies by adding random noise to the bedmap2 data with amplitude determined by the accompanying estimates of bedrock uncertainty. Lower frequency coherent noise, which generates broad spatial scale (over 10s of km) errors in topography with relatively gently slopes, while higher frequency noise has steeper slopes over smaller spatial scales. We find that the small amplitude fluctuations result in only minor changes in the way these glaciers evolve. However, lower frequency noise is more important than higher frequency noise even when the features have the same height amplitudes and the total noise power is maintained. This provides optimism for credible sea level rise estimates with presently achievable densities of thickness measurements. Pine Island Glacier appears to be the most sensitive to errors in bed topography, while Lambert-Amery is stable under the present day observational data uncertainty. Totten-Denman region may undergo a retreat around Totten ice shelf, where the bedrock is lower than the sea level, especially if basal melt rates increase.

  4. Field measurements of incision rates following bedrock exposure: Implications for process controls on the long profiles of valleys cut by rivers and debris flows

    USGS Publications Warehouse

    Stock, Jonathan D.; Montgomery, David R.; Collins, Brian D.; Dietrich, William E.; Sklar, Leonard

    2005-01-01

    Until recently, published rates of incision of bedrock valleys came from indirect dating of incised surfaces. A small but growing literature based on direct measurement reports short-term bedrock lowering at geologically unsustainable rates. We report observations of bedrock lowering from erosion pins monitored over 1–7 yr in 10 valleys that cut indurated volcanic and sedimentary rocks in Washington, Oregon, California, and Taiwan. Most of these channels have historically been stripped of sediment. Their bedrock is exposed to bed-load abrasion, plucking, and seasonal wetting and drying that comminutes hard, intact rock into plates or equant fragments that are removed by higher flows. Consequent incision rates are proportional to the square of rock tensile strength, in agreement with experimental results of others. Measured rates up to centimeters per year far exceed regional long-term erosion-rate estimates, even for apparently minor sediment-transport rates. Cultural artifacts on adjoining strath terraces in Washington and Taiwan indicate at least several decades of lowering at these extreme rates. Lacking sediment cover, lithologies at these sites lower at rates that far exceed long-term rock-uplift rates. This rate disparity makes it unlikely that the long profiles of these rivers are directly adjusted to either bedrock hardness or rock-uplift rate in the manner predicted by the stream power law, despite the observation that their profiles are well fit by power-law plots of drainage area vs. slope. We hypothesize that the threshold of motion of a thin sediment mantle, rather than bedrock hardness or rock-uplift rate, controls channel slope in weak bedrock lithologies with tensile strengths below ∼3–5 MPa. To illustrate this hypothesis and to provide an alternative interpretation for power-law plots of area vs. slope, we combine Shields' threshold transport concept with measured hydraulic relationships and downstream fining rates. In contrast to fluvial

  5. Coincidence and spatial variability of geology, soils, and vegetation, Mill Run watershed, Virginia.

    USGS Publications Warehouse

    Olson, C.G.; Hupp, C.R.

    1986-01-01

    The Mill Run watershed is a structurally-controlled synclinal basin on the eastern limb of the Massanutten Mountain complex of NW Virginia. Bedrock contacts are obscured by coarse sandstone debris from exposures near basin divides. Colluvium blankets more than half the basin, masking geomorphic surfaces, affecting vegetation patterns, and contributing to the convexity of the alluvial, terrace, pediment and erosion surfaces. Vegetation is strongly interdependent with geomorphology, bedrock geology, and soils. - from Authors

  6. Effect of bedrock permeability on stream base flow mean transit time scaling relationships: 2. Process study of storage and release

    NASA Astrophysics Data System (ADS)

    Hale, V. Cody; McDonnell, Jeffrey J.; Stewart, Michael K.; Solomon, D. Kip; Doolitte, Jim; Ice, George G.; Pack, Robert T.

    2016-02-01

    In Part 1 of this two-part series, Hale and McDonnell (2016) showed that bedrock permeability controlled base flow mean transit times (MTTs) and MTT scaling relations across two different catchment geologies in western Oregon. This paper presents a process-based investigation of storage and release in the more permeable catchments to explain the longer MTTs and (catchment) area-dependent scaling. Our field-based study includes hydrometric, MTT, and groundwater dating to better understand the role of subsurface catchment storage in setting base flow MTTs. We show that base flow MTTs were controlled by a mixture of water from discrete storage zones: (1) soil, (2) shallow hillslope bedrock, (3) deep hillslope bedrock, (4) surficial alluvial plain, and (5) suballuvial bedrock. We hypothesize that the relative contributions from each component change with catchment area. Our results indicate that the positive MTT-area scaling relationship observed in Part 1 is a result of older, longer flow path water from the suballuvial zone becoming a larger proportion of streamflow in a downstream direction (i.e., with increasing catchment area). Our work suggests that the subsurface permeability structure represents the most basic control on how subsurface water is stored and therefore is perhaps the best direct predictor of base flow MTT (i.e., better than previously derived morphometric-based predictors). Our discrete storage zone concept is a process explanation for the observed scaling behavior of Hale and McDonnell (2016), thereby linking patterns and processes at scales from 0.1 to 100 km2.

  7. Structure contours of base of upper Arapahoe aquifer in "Structure, outcrop, and subcrop of the bedrock aquifers along the western margin of the Denver Basin, Colorado." Hydrologic Atlas 742

    USGS Publications Warehouse

    Rafferty, Sharon

    1998-01-01

    This digital geospatial data set consists of structure contours on the base of the upper member of the Arapahoe aquifer. The U.S. Geological Survey developed this data set as part of a project described in the report,"Structure, Outcrop, and Subcrop of the Bedrock Aquifers Along the Western Margin of the Denver Basin, Colorado" (Robson and others, 1998)

  8. Engineering Geology

    ERIC Educational Resources Information Center

    Hatheway, Allen W.

    1978-01-01

    Engineering geology remains a potpourri of applied classical geology, and 1977 witnessed an upswing in demand for these services. Traditional foundation-related work was slight, but construction related to national needs increased briskly. Major cities turned to concerns of transit waste-water treatment and solid-waste disposal. (Author/MA)

  9. Physical geology

    SciTech Connect

    Skinner, B.; Porter, S.

    1987-01-01

    The book integrates current thinking on processes (plate techtonics, chemical cycles, changes throughout geologic time). It is an introduction to investigations into the way the earth works, how mountains are formed, how the atmosphere, hydrosphere, crust and mantle interact with each other. Treatments on climate, paleoclimatology and landscape evolution are included, as is a discussion on how human activity affects geological interactions.

  10. A predictive geologic model of radon occurrence

    SciTech Connect

    Gregg, L.T. )

    1990-01-01

    Earlier work by LeGrand on predictive geologic models for radon focused on hydrogeologic aspects of radon transport from a given uranium/radium source in a fractured crystalline rock aquifer, and included submodels for bedrock lithology (uranium concentration), topographic slope, and water-table behavior and characteristics. LeGrand's basic geologic model has been modified and extended into a submodel for crystalline rocks (Blue Ridge and Piedmont Provinces) and a submodel for sedimentary rocks (Valley and Ridge and Coastal Plain Provinces). Each submodel assigns a ranking of 1 to 15 to the bedrock type, based on (a) known or supposed uranium/thorium content, (b) petrography/lithology, and (c) structural features such as faults, shear or breccia zones, diabase dikes, and jointing/fracturing. The bedrock ranking is coupled with a generalized soil/saprolite model which ranks soil/saprolite type and thickness from 1 to 10. A given site is thus assessed a ranking of 1 to 150 as a guide to its potential for high radon occurrence in the upper meter or so of soil. Field trials of the model are underway, comparing model predictions with measured soil-gas concentrations of radon.

  11. Altitude, depth, and thickness of the Galena-Platteville Bedrock Unit in the subcrop area of Illinois and Wisconsin

    USGS Publications Warehouse

    Brown, Timothy A.; Dunning, Charles P.; Sharpe, Jennifer B.

    2000-01-01

    The report series will enable investigators involved in site-specific studies within the subcrop area to understand the regional geologic framework of the unit and to find additional reference sources. This report consists of four sheets that show the altitude (sheet 1), depth from land surface (sheet 2), total thickness (sheet 3), and location of altitude data (sheet 4) of the lithologic units that constitute the Galena-Platteville bedrock unit within the subcrop area. The sheets also show major known geologic features within the Galena-Platteville study area in Illinois and Wisconsin. A geographic information system (GIS) was used to generate data layers (coverages) from point data and from published and unpublished contour maps at various scales and detail. Standard GIS procedures were used to change the coverages into the maps shown on the sheets presented in this report. A list of references for the data used to prepare the maps is provided. 

  12. Hydrogeologic Framework of Bedrock Units and Initial Salinity Distribution for a Simulation of Groundwater Flow for the Lake Michigan Basin

    USGS Publications Warehouse

    Lampe, David C.

    2009-01-01

    The U.S. Geological Survey is assessing groundwater availability in the Lake Michigan Basin. As part of the assessment, a variable-density groundwater-flow model is being developed to simulate the effects of groundwater use on water availability throughout the basin. The hydrogeologic framework for the Lake Michigan Basin model was developed by grouping the bedrock geology of the study area into hydrogeologic units on the basis of the functioning of each unit as an aquifer or confining layer within the basin. Available data were evaluated based on the areal extent of coverage within the study area, and procedures were established to characterize areas with sparse data coverage. Top and bottom altitudes for each hydrogeologic unit were interpolated in a geographic information system for input to the model and compared with existing maps of subsurface formations. Fourteen bedrock hydrogeologic units, making up 17 bedrock model layers, were defined, and they range in age from the Jurassic Period red beds of central Michigan to the Cambrian Period Mount Simon Sandstone. Information on groundwater salinity in the Lake Michigan Basin was compiled to create an input dataset for the variable-density groundwater-flow simulation. Data presented in this report are referred to as 'salinity data' and are reported in terms of total dissolved solids. Salinity data were not available for each hydrogeologic unit. Available datasets were assigned to a hydrogeologic unit, entered into a spatial database, and data quality was visually evaluated. A geographic information system was used to interpolate salinity distributions for each hydrogeologic unit with available data. Hydrogeologic units with no available data either were set equal to neighboring units or were vertically interpolated by use of values from units above and below.

  13. InSAR Identifies Mine-Dewatering Associated Bedrock Compaction and Subsidence in North- Central Nevada

    NASA Astrophysics Data System (ADS)

    Katzenstein, K. W.; Bell, J. W.; Watters, R. J.

    2007-12-01

    deeper zone of compaction and/or subsidence. The large aerial extent is likely a result of the fact that the vast majority of the pumping is from the deeper bedrock aquifer, with very small amounts of pumping from shallower siltstones and unconsolidated basin fill. The geology within the deformation signal is very complex. The dewatering is occurring in deep carbonates which are overlain by varying thicknesses of basin fill, volcanics, siliceous siltstones and mudstones and other limestone units. Close inspection of these units in the main open pit as well as a nearby underground mine suggests that while many of these units are highly fractured, most of the fractures have been healed with silica or are so tight that minimal fracture closing is possible. This suggests another mechanism causing the ground surface to subside, including compaction of intact bedrock. Groundwater related bedrock subsidence of this scale is rarely, if ever, observed, and therefore, poorly understood. Ongoing work at this site is focused on better understanding the mechanics of the observed bedrock compaction/subsidence, and possible implications to other high volume groundwater pumping sites.

  14. Reduction of Long-Term Bedrock Incision Efficiency by Short-Term Alluvial Cover Intermittency

    NASA Astrophysics Data System (ADS)

    Lague, D.

    2009-12-01

    Rapid mountain river incision through bedrock is an inherently stochastic process resulting from the long-term summation of flow and sediment discharge events at very variable rates and frequency. While the actual incision processes remains difficult to apprehend in situ and are the subject of ongoing research, there is no ambiguity on the inhibiting effect of a thick alluvial cover (several meters) on bed incision. This alluvial cover thickness strongly fluctuates as a function of stochastic supply of sediment by hillslopes, modulated by sediment transport and storage in the drainage network. Here, I study how this short-term stochasticity propagates into the long-term reduction of bedrock incision efficiency (the cover effect) at geological timescales, and how the upscaled cover model compare to existing empirical models. I introduce a new numerical model (SSTRIM, Stochastic Sediment Transport and River Incision Model) that resolves sediment transport and bedrock incision at daily timescales over a channel reach consisting of several trapezoidal cross-sections linked together. The model is run for thousands of years until a steady-state geometry is reached under the prevailing uplift, sediment supply and water discharge rates. The model incorporates (i) a stochastic sediment supply mimicking the pdf of sediment volume supplied by landsliding, (ii) a transport threshold and daily stochastic variations in water discharge, (iii) a freely evolving channel width and slope; (iv) an explicit treatment of alluvial thickness variations and corresponding bed incision reduction. Bed and bank incision are calculated as a function of bed and bank shear stress. Model results predict the existence of 2 cover dynamics regime: one in which the bed is almost permanently partially covered by sediment, and on in which intermittency dominates. In this later case, the cover effect operates over long-term by modulating the proportion of time where the channel is fully or not covered

  15. Controls on the geometry of potholes in bedrock channels

    NASA Astrophysics Data System (ADS)

    Pelletier, Jon D.; Sweeney, Kristin E.; Roering, Joshua J.; Finnegan, Noah J.

    2015-02-01

    Potholes (circular depressions carved into bedrock) are the dominant roughness elements in many bedrock channels. Here we show, using data from previous studies and new data from the Smith River, Oregon, that pothole depths increase in proportion to both the mean pothole radius (such that the most common pothole depth-to-radius ratio is 2) and the diameter of the largest clasts episodically stored in potholes. We present a theory for these observations based on computational fluid dynamics and sediment transport modeling of vortices in cylindrical cavities of different shapes and sizes. We show that the shear stress at the bottom of a pothole (which controls the rate of pothole growth) is maximized for potholes with a depth-to-radius ratio of approximately 1 and decreases nonlinearly with increasing depth-to-radius ratio such that potholes with depth-to-radius ratios larger than 3 are uncommon. Our model provides a mechanistic explanation for pothole shapes and sizes.

  16. Field Monitoring of Bedrock Channel Erosion and Morphology

    NASA Astrophysics Data System (ADS)

    Johnson, J. P.; Whipple, K. X.; Sklar, L. S.

    2005-12-01

    We present field measurements of erosional morphology and fluvial incision into Navajo Sandstone bedrock along a short human-perturbed channel reach in the Henry Mountains, Utah. Bedrock rivers flow in self-formed channels and form diverse erosional morphologies. The parameters that collectively define channel morphology (e.g. width, slope, bed roughness, bedrock exposure, sediment size distribution) all dynamically adjust in poorly understood ways to imposed fluid and sediment fluxes. The picture of erosion that emerges from our field monitoring is consistent with laboratory flume experiments conducted under sediment-starved transport conditions. We find that erosion is a sensitive function of the evolving bed topography because of feedbacks between the turbulent flow field, sediment transport, and bottom roughness. To facilitate highway construction over Swett Creek in the early 1970s, the Utah Department of Transportation created a natural experiment by filling in part of the original canyon and routing flow through a culvert and blasted bedrock slot. The vertical-walled, blasted channel has an upper reach (the ``flume'', length ~80 m, slope ~0.022, width ~5 m) and a shorter downstream reach that steeply slopes into the original channel (the ``flume mouth'', length ~17 m, slope ~0.18). The field-scale flume thus constructed provides an excellent opportunity to observe the morphology of a bedrock channel that has eroded from a well constrained initial geometry over a known amount of time. Ephemeral channel flow only occurs during spring snowmelt and flash floods. We monitor water depth, and we have a limited number of direct bedload transport measurements. In addition, we have installed bolts in the bedrock and are currently monitoring active erosion and morphological changes in the channel reach. Bedrock incision into the Navajo Sandstone occurs mostly by abrasion, with dramatic sculpted forms apparently carved by the finer bedload that becomes locally suspended

  17. Surficial Geologic Map of The Loop and Druid Arch Quadrangles, Canyonlands National Park, Utah

    USGS Publications Warehouse

    Billingsley, George H.; Block, Debra L.; Felger, Tracey J.

    2002-01-01

    This geologic map is a product of a cooperative project between the U.S. Geological Survey and the U.S. National Park Service to provide geologic information about this part of Canyonlands National Park, Utah. This digital map database contains bedrock data from previously published data that has been modified by the author. New mapping of the surficial deposits represents the general distribution of surficial deposits of the Druid Arch and The Loop 7.5-minute quadrangles.

  18. MTR CAISSONS WERE DRILLED INTO BEDROCK. IN CENTER OF VIEW, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MTR CAISSONS WERE DRILLED INTO BEDROCK. IN CENTER OF VIEW, CONCRETE FLOWS FROM TRUCK INTO DRUM, WHICH IS LOWERED INTO CAISSON AND RELEASED AT BOTTOM OF HOLE. BEYOND, TRUCK-MOUNTED DRILLING RIG DRILLS HOLE FOR ANOTHER CAISSON NEAR EDGE OF EXCAVATION. MATERIAL REMOVED FROM HOLE IS CARRIED BY CONVEYOR TO WAITING TRUCK. INL NEGATIVE NO. 307. Unknown Photographer, 6/1950. - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  19. Bedrock incision by bedload: insights from direct numerical simulations

    NASA Astrophysics Data System (ADS)

    Aubert, Guilhem; Langlois, Vincent J.; Allemand, Pascal

    2016-04-01

    Bedload sediment transport is one of the main processes that contribute to bedrock incision in a river and is therefore one of the key control parameters in the evolution of mountainous landscapes. In recent years, many studies have addressed this issue through experimental setups, direct measurements in the field, or various analytical models. In this article, we present a new direct numerical approach: using the classical methods of discrete-element simulations applied to granular materials, we explicitly compute the trajectories of a number of pebbles entrained by a turbulent water stream over a rough solid surface. This method allows us to extract quantitatively the amount of energy that successive impacts of pebbles deliver to the bedrock, as a function of both the amount of sediment available and the Shields number. We show that we reproduce qualitatively the behaviour observed experimentally by Sklar and Dietrich (2001) and observe both a "tool effect" and a "cover effect". Converting the energy delivered to the bedrock into an average long-term incision rate of the river leads to predictions consistent with observations in the field. Finally, we reformulate the dependency of this incision rate with Shields number and sediment flux, and predict that the cover term should decay linearly at low sediment supply and exponentially at high sediment supply.

  20. Geologic Map of the Cane Quadrangle, Coconino County, Northern Arizona

    USGS Publications Warehouse

    Billingsley, George H.; Wellmeyer, Jessica L.

    2001-01-01

    This digital map database is compiled from unpublished data and new mapping by the authors, represents the general distribution of surficial and bedrock geology in the mapped area. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the area. The database delineate map units that are identified by age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution of the database to 1:24,000 or smaller.

  1. GAMBIT--Gamburtsev Aerogeophysical Mapping of Bedrock and Ice Targets During IPY

    NASA Astrophysics Data System (ADS)

    Studinger, M.; Finn, C. A.; Bell, R. E.; Gogineni, S.; Hayden, L.; Braaten, D.

    2004-12-01

    Antarctica is a key element in Earth's climatic and geodynamic systems, yet on the eve of the 50th anniversary of the International Geophysical Year, we lack fundamental geologic and geophysical data from the deep interior of this vast continent. Despite the central role that Antarctica has played in shaping the present global environment, fundamental, first-order parameters such as ice volume and stratigraphy, bedrock elevation, lithology, structure, age, and tectonic history remain poorly known over large portions of the continent, including the Gamburtsev Subglacial Mountains. Given the extensive ice cover, airborne geophysical data is the best and most cost-effective method to characterize broad areas of sub-ice basement and expand our knowledge of Antarctica. Under a program entitled, GAMBIT--Gamburtsev Aerogeophysical Mapping of Bedrock and Ice Targets, we propose to conduct airborne gravity, magnetic and radar surveys over the Gamburtsev Subglacial Mountains, a priority for geophysical and drilling studies by the solid Earth and glaciology communities for many years. This proposal will help develop long-range aerogeophysical capabilities and provide data to the Antarctic community within a year after collection to help answer fundamental science questions of global significance. By integrating these with international efforts during the IPY, we can maximize and broaden the use of all data sets. Specifically, we propose to image the East Antarctic ice sheet and bedrock with airborne geophysical surveys through the GAMBIT project in order to: 1) determine ice volume for mass balance calculations and identify internal layers reflecting the accumulation history of the East Antarctic ice sheet in the Gamburtsev Subglacial Mountains region; 2) characterize the gravity, magnetic, and elevation signatures of the East Antarctic crustal basement of the Gamburtsev Subglacial Mountains; 3) integrate these data with existing and new data collected during IPY over

  2. Stratigraphic architecture of bedrock reference section, Victoria Crater, Meridiani Planum, Mars

    USGS Publications Warehouse

    Edgar, Lauren A.; Grotzinger, John P.; Hayes, Alex G.; Rubin, David M.; Squyres, Steve W.; Bell, James F.; Herkenhoff, Ken E.

    2012-01-01

    The Mars Exploration Rover Opportunity has investigated bedrock outcrops exposed in several craters at Meridiani Planum, Mars, in an effort to better understand the role of surface processes in its geologic history. Opportunity has recently completed its observations of Victoria crater, which is 750 m in diameter and exposes cliffs up to ~15 m high. The plains surrounding Victoria crater are ~10 m higher in elevation than those surrounding the previously explored Endurance crater, indicating that the Victoria crater exposes a stratigraphically higher section than does the Endurance crater; however, Victoria strata overlap in elevation with the rocks exposed at the Erebus crater. Victoria crater has a well-developed geomorphic pattern of promontories and embayments that define the crater wall and that reveal thick bedsets (3–7m) of large-scale cross-bedding, interpreted as fossil eolian dunes. Opportunity was able to drive into the crater at Duck Bay, located on the western margin of Victoria crater. Data from the Microscopic Imager and Panoramic Camera reveal details about the structures, textures, and depositional and diagenetic events that influenced the Victoria bedrock. A lithostratigraphic subdivision of bedrock units was enabled by the presence of a light-toned band that lines much of the upper rim of the crater. In ascending order, three stratigraphic units are named Lyell, Smith, and Steno; Smith is the light-toned band. In the Reference Section exposed along the ingress path at Duck Bay, Smith is interpreted to represent a zone of diagenetic recrystallization; however, its upper contact also coincides with a primary erosional surface. Elsewhere in the crater the diagenetic band crosscuts the physical stratigraphy. Correlation with strata present at nearby promontory Cape Verde indicates that there is an erosional surface at the base of the cliff face that corresponds to the erosional contact below Steno. The erosional contact at the base of Cape Verde

  3. Mathematical Geology.

    ERIC Educational Resources Information Center

    McCammon, Richard B.

    1979-01-01

    The year 1978 marked a continued trend toward practical applications in mathematical geology. Developments included work in interactive computer graphics, factor analysis, the vanishing tons problem, universal kriging, and resource estimating. (BB)

  4. Engineering Geology

    ERIC Educational Resources Information Center

    Lee, Fitzhugh T.

    1974-01-01

    Briefly reviews the increasing application of geologic principles, techniques and data to engineering practices in the areas of land use and zoning controls, resource management energy programs and other fields. (BR)

  5. Experimental evidence for bedrock erosion by suspended sediment

    NASA Astrophysics Data System (ADS)

    Scheingross, J. S.; Brun, F.; Lo, D. Y.; Omerdin, K.; Lamb, M. P.

    2013-12-01

    Fluvial bedrock incision influences channel evolution and sets the pace of landscape lowering. Bedrock incision often occurs via abrasion, and existing theory is divided on the erosional efficiency of sediment transported in suspension versus bed load, due in part to a lack of data to test model predictions. This represents a major knowledge gap as suspended sediment can account for the majority of the total fluvial sediment load, and untested models make opposite predictions of bedrock erosion in steep channels and during large floods. We performed controlled abrasion mill experiments examining suspended and bed load erosion, making use of an erodible polyurethane foam substrate as a bedrock analog to overcome previous experimental limitations and allow for measureable suspension erosion. Our results show foam erodes similar to natural rock, where erodibility is a function of tensile strength and density. To explore the role of the mode of sediment transport on erosion, we varied sediment size from gravel (42 mm diameter) to medium sand (0.4 mm diameter), while holding fixed hydraulics, sediment load, and substrate strength. Under these conditions, volumetric erosion rates decreased across the bed load (~101 - 103 cm3/hr) to suspended load (~0.01 - 100 cm3/hr) transition due to lower near-bed sediment concentrations (~25 g/l vs. 115 g/l), slower settling velocity (0.09 m/s vs. 0.49 m/s), and viscous damping of impacts (for particle Stokes numbers less than ~75) for suspended particles. Our results provide direct experimental evidence of erosion by suspended load, and upscaling results to field scale shows suspension erosion can outpace bed load erosion by up to a factor ~4 during large floods which suspend coarse sand and gravel, and where suspended sediment dominates the total load. These results imply that suspension erosion may also dominate on very steep slopes where commonly used bedrock incision models (which ignore suspension erosion) predict zero erosion

  6. Fractured Bedrock Storm Flow: a New Pathway for Runoff Generation

    NASA Astrophysics Data System (ADS)

    Oshun, J.; Salve, R.; Rempe, D. M.; Dietrich, W. E.; Fung, I.

    2010-12-01

    Groundwater dynamics in the fractured weathered bedrock underlying hillslopes may dominate storm runoff in many hilly and mountainous areas Few studies, however, have explored this runoff generation process. Here we use an intensively monitored site to study the spatial relationships between fractured bedrock and hydraulic properties in the weathered zone below a forested hillslope. The study site, Rivendell, is a 4000 m2 catchment draining directly into Elder Creek in the Angelo Coast Range Reserve (ACRR) in Northern California. The site is underlain by highly fractured and weak mudstones and boudinaged, ridge-forming sandstones that are turbidite sequences of the Coastal Franciscan Belt. The site receives an average of 1800mm of precipitation annually, with the vast majority falling between October and May. Rivendell has a thinly mantled soil layer underlain by a fractured rock zone, which thickens upslope to a depth of up to 30 m. Standard penetration tests show a consistent increase in bedrock resistance at depth before an abrupt lower boundary upon which the water table is perched. We use seven monitoring wells, precipitation data, soil moisture data, a steam gauge in Elder Creek, and well pump tests to characterize water movement through the fractured rock zone.. We analyze the lag time between peak rainfall and peak response at seven wells and Elder Creek from 2007-2010. The water table varies across the slope between 4 and 25 m below the ground surface, and the dynamic range of well water level increases with distance from Elder Creek. The magnitude and timing of well response shows a relationship to depth, magnitude of rainfall and antecedent moisture conditions. Although nearly all runoff is generated through fractured bedrock, we observe that Elder Creek consistently shows the shortest lag times compared to the wells on the hillslope. Wells show different trends in magnitude and timing of response throughout the rainy season. Pump tests reveal a

  7. Bedrock erosion by sliding wear in channelized granular flow

    NASA Astrophysics Data System (ADS)

    Hung, C. Y.; Stark, C. P.; Capart, H.; Smith, B.; Maia, H. T.; Li, L.; Reitz, M. D.

    2014-12-01

    Boundary forces generated by debris flows can be powerful enough to erode bedrock and cause considerable damage to infrastructure during runout. Bedrock wear can be separated into impact and sliding wear processes. Here we focus on sliding wear. We have conducted experiments with a 40-cm-diameter grainflow-generating rotating drum designed to simulate dry channelized debris flows. To generate sliding erosion, we placed a 20-cm-diameter bedrock plate axially on the back wall of the drum. The rotating drum was half filled with 2.3-mm-diameter grains, which formed a thin grain-avalanching layer with peak flow speed and depth close to the drum axis. The whole experimental apparatus was placed on a 100g-ton geotechnical centrifuge and, in order to scale up the stress level, spun to a range of effective gravity levels. Rates and patterns of erosion of the bedrock plate were mapped after each experiment using 3d micro-photogrammetry. High-speed video and particle tracking were employed to measure granular flow dynamics. The resulting data for granular velocities and flow geometry were used to estimate impulse exchanges and forces on the bedrock plate. To address some of the complexities of granular flow under variable gravity levels, we developed a continuum model framed around a GDR MiDi rheology. This model allowed us to scale up boundary forcing while maintaining the same granular flow regime, and helped us to understand important aspects of the flow dynamics including e.g. fluxes of momentum and kinetic energy. In order to understand the detailed processes of boundary forcing, we performed numerical simulations with a new contact dynamics model. This model confirmed key aspects of our continuum model and provided information on second-order behavior such as fluctuations in the forces acting on the wall. By combining these measurements and theoretical analyses, we have developed and calibrated a constitutive model for sliding wear that is a threshold function of

  8. Geologic investigation :an update of subsurface geology on Kirtland Air Force Base, New Mexico.

    SciTech Connect

    Van Hart, Dirk

    2003-06-01

    The objective of this investigation was to generate a revised geologic model of Kirtland Air Force Base (KAFB) incorporating the geological and geophysical data produced since the Site-Wide Hydrogeologic Characterization Project (SWHC) of 1994 and 1995. Although this report has certain stand-alone characteristics, it is intended to complement the previous work and to serve as a status report as of late 2002. In the eastern portion of KAFB (Lurance Canyon and the Hubbell bench), of primary interest is the elevation to which bedrock is buried under a thin cap of alluvium. Elevation maps of the bedrock top reveal the paleodrainage that allows for the interpretation of the area's erosional history. The western portion of KAFB consists of the eastern part of the Albuquerque basin where bedrock is deeply buried under Santa Fe Group alluvium. In this area, the configuration of the down-to-the-west, basin-bounding Sandia and West Sandia faults is of primary interest. New geological and geophysical data and the reinterpretation of old data help to redefine the location and magnitude of these elements. Additional interests in this area are the internal stratigraphy and structure of the Santa Fe Group. Recent data collected from new monitoring wells in the area have led to a geologic characterization of the perched Tijeras Arroyo Groundwater system and have refined the known limits of the Ancestral Rio Grande fluvial sediments within the Santa Fe Group. Both the reinterpretation of the existing data and a review of the regional geology have shown that a segment of the boundary between the eastern and western portions of KAFB is a complicated early Tertiary (Laramide) wrench-fault system, the Tijeras/Explosive Ordnance Disposal Area/Hubbell Spring system. A portion of this fault zone is occupied by a coeval ''pull-apart'' basin filled with early Tertiary conglomerates, whose exposures form the ''Travertine Hills''.

  9. Effects Of Bedrock Shape And Hillslope Gradient On The Pore-Water Pressure Development: Implication For Slope Stability

    NASA Astrophysics Data System (ADS)

    Lanni, Cristiano; McDonnell, Jeff

    2010-05-01

    Shallow Landslides are one of the most important causes of loss of human life and socio-economic damage related to the hydro-geological risk issues. The danger of these phenomena is related to their speed of development, the diffculty of foreseeing their location, and the high density of individual phenomena, whose downhill trajectories have a relevant probability of interfering with urbanized areas. Research activity on precipitation-induced landslides has focused mainly on developing predictive understanding of where and when landslides are likely to occur. Nevertheless, some major aspects that may be related to activation of landslides have been poorly investigated. For instance, landslide susceptibility zones are generally predicted assuming constant thickness of soil over an impervious bedrock layer. Nevertheless, recent studies showed subsurface topography could be a first order control for subsurface water-flow dynamics, because of the effects of its own irregular shape. Tromp-van Meerveld and McDonnell (2006) argued that connectivity of patches of transient saturation were a necessary prerequisite for exceeding the rainfall threshold necessary to drive lateral flow. Connectivity - "how the hillslope architecture controls the filling and spilling of isolated patches of saturation" (Hopp and McDonnell, 2009) - appears to be a possible unifying concept and theoretical platform for moving hillslope and watershed hydrology forward. Connectivity could also have important implications on triggering of shallow landslides, because the particular shape of bedrock may limit the water-flow downhill. Here we present a number of virtual numerical experiments performed to investigate the role of bedrock shape and hillslope gradient on pore-water pressure development. On this purpose, our test is represented by the subsurface topography of the Panola Experiment Hillslope (PEH). That is because scientific literature on PEH provides substantial documentation about the role

  10. Mapping a near surface variable geologic regime using an integrated geophysical approach

    SciTech Connect

    Rogers, N.T.; Sandberg, S.K.; Miller, P.; Powell, G.

    1997-10-01

    An integrated geophysical approach involving seismic, electromagnetic, and electrical methods was employed to map fluvial, colluvial and bedrock geology, to delineate bedrock channels, and to determine fracture and joint orientations that may influence migration of petroleum hydrocarbons at the Glenrock Oil Seep. Both P (primary)-wave and S (shear)-wave seismic refraction techniques were used to map the bedrock surface topography, bedrock minima, stratigraphic boundaries, and possible structure. S-wave data were preferred because of better vertical resolution due to the combination of slower velocities and lower frequency wave train. Azimuthal resistivity/EP (induced polarization) and azimuthal electromagnetics were used to determine fracture orientations and groundwater flow directions. Terrain conductivity was used to map the fluvial sedimentary sequences (e.g., paleochannel and overbank deposits) in the North Platte River floodplain. Conductivity measurements were also used to estimate bedrock depth and to assist in the placement and recording parameters of the azimuthal soundings. The geophysical investigation indicated that groundwater flow pathways were controlled by the fluvial paleochannels and bedrock erosional features. Primary groundwater flow direction in the bedrock and colluvial sediments was determined from the azimuthal measurements and confirmed by drilling to be N20-40W along the measured strike of the bedrock and joint orientations. Joint/fracture orientations were measured at N20-40W and N10-30E from the azimuthal data and confirmed from measurements at a bedrock outcrop south of the site. The bedrock has an apparent N10E anisotropy in the seismic velocity profiles on the old refinery property that closely match that of measured joint/fracture orientations and may have a minor effect on groundwater flow.

  11. Mapping urban geology of the city of Girona, Catalonia

    NASA Astrophysics Data System (ADS)

    Vilà, Miquel; Torrades, Pau; Pi, Roser; Monleon, Ona

    2016-04-01

    A detailed and systematic geological characterization of the urban area of Girona has been conducted under the project '1:5000 scale Urban geological map of Catalonia' of the Catalan Geological Survey (Institut Cartogràfic i Geològic de Catalunya). The results of this characterization are organized into: i) a geological information system that includes all the information acquired; ii) a stratigraphic model focused on identification, characterization and correlation of the geological materials and structures present in the area and; iii) a detailed geological map that represents a synthesis of all the collected information. The mapping project integrates in a GIS environment pre-existing cartographic documentation (geological and topographical), core data from compiled boreholes, descriptions of geological outcrops within the urban network and neighbouring areas, physico-chemical characterisation of representative samples of geological materials, detailed geological mapping of Quaternary sediments, subsurface bedrock and artificial deposits and, 3D modelling of the main geological surfaces. The stratigraphic model is structured in a system of geological units that from a chronostratigrafic point of view are structured in Palaeozoic, Paleogene, Neogene, Quaternary and Anthropocene. The description of the geological units is guided by a systematic procedure. It includes the main lithological and structural features of the units that constitute the geological substratum and represents the conceptual base of the 1:5000 urban geological map of the Girona metropolitan area, which is organized into 6 map sheets. These map sheets are composed by a principal map, geological cross sections and, several complementary maps, charts and tables. Regardless of the geological map units, the principal map also represents the main artificial deposits, features related to geohistorical processes, contours of outcrop areas, information obtained in stations, borehole data, and contour

  12. Status report on the geology of the Oak Ridge Reservation

    SciTech Connect

    Hatcher, R.D. Jr.; Lemiszki, P.J.; Foreman, J.L.; Dreier, R.B.; Ketelle, R.H.; Lee, R.R.; Lee, Suk Young; Lietzke, D.A.; McMaster, W.M.

    1992-10-01

    This report provides an introduction to the present state of knowledge of the geology of the Oak Ridge Reservation (ORR) and a cursory introduction to the hydrogeology. An important element of this work is the construction of a modern detailed geologic map of the ORR (Plate 1), which remains in progress. An understanding of the geologic framework of the ORR is essential to many current and proposed activities related to land-use planning, waste management, environmental restoration, and waste remediation. Therefore, this report is also intended to convey the present state of knowledge of the geologic and geohydrologic framework of the ORR and vicinity and to present some of the available data that provide the basic framework for additional geologic mapping, subsurface geologic, and geohydrologic studies. In addition, some recently completed, detailed work on soils and other surficial materials is included because of the close relationships to bedrock geology and the need to recognize the weathered products of bedrock units. Weathering processes also have some influence on hydrologic systems and processes at depth.

  13. Destination: Geology?

    NASA Astrophysics Data System (ADS)

    Price, Louise

    2016-04-01

    "While we teach, we learn" (Roman philosopher Seneca) One of the most beneficial ways to remember a theory or concept is to explain it to someone else. The offer of fieldwork and visits to exciting destinations is arguably the easiest way to spark a students' interest in any subject. Geology at A-Level (age 16-18) in the United Kingdom incorporates significant elements of field studies into the curriculum with many students choosing the subject on this basis and it being a key factor in consolidating student knowledge and understanding. Geology maintains a healthy annual enrollment with interest in the subject increasing in recent years. However, it is important for educators not to loose sight of the importance of recruitment and retention of students. Recent flexibility in the subject content of the UK curriculum in secondary schools has provided an opportunity to teach the basic principles of the subject to our younger students and fieldwork provides a valuable opportunity to engage with these students in the promotion of the subject. Promotion of the subject is typically devolved to senior students at Hessle High School and Sixth Form College, drawing on their personal experiences to engage younger students. Prospective students are excited to learn from a guest speaker, so why not use our most senior students to engage and promote the subject rather than their normal subject teacher? A-Level geology students embarking on fieldwork abroad, understand their additional responsibility to promote the subject and share their understanding of the field visit. They will typically produce a series of lessons and activities for younger students using their newly acquired knowledge. Senior students also present to whole year groups in seminars, sharing knowledge of the location's geology and raising awareness of the exciting destinations offered by geology. Geology fieldwork is always planned, organised and led by the member of staff to keep costs low, with recent visits

  14. Floods, landslides and short-term meandering bedrock river dynamics

    NASA Astrophysics Data System (ADS)

    Lague, D.; Bonnet, S.; Davies, T. R.; Davy, P.

    2012-12-01

    Actively incising bedrock meanders are an ubiquitous feature of mountain belts, but the mechanisms leading to their formation and evolution are still poorly understood. As for straight bedrock rivers, we expect the combination of stochastic discharge, sediment supply and river transport capacity to play a key role in the partitioning between vertical and lateral incision. But the sinuous planform geometry yields localized high rates of outer bank incision driving localized hillslope mass wasting processes. The resulting deposits may alter patterns of sedimentation and incision leading to a strongly coupled channel-hillslope system. We aim at better understanding this coupling following two approaches : a detailed quantification of channel response to individual floods and mass-wasting events using Terrestrial Laser Scanner surveys and recent historical data; and the integration of this short-term dynamics at longer-timescales through numerical modelling. In particular, we note that many of these rivers exhibits numerous strath terraces abandoned in their inner bend documenting an evolution which is not purely continuous but rather punctuated by rapid changes in the balance between vertical and lateral erosion. Whether these changes can be tied to specific extreme events (floods, landslides, major earthquakes...) or an intrinsic instability is a key question to better understand bedrock meandering dynamics. It also has potentially important implications for the reconstruction of paleo-extremes from dated terraces or for the management of infrastructures located near actively migrating meandering bedrock rivers. This presentation focuses on the use of Terrestrial Laser Scanner to investigate the spatio-temporal patterns of bank erosion in the Rangitikei river (New-Zealand) over 3 years. The Rangitikei river is incising weakly consolidated mudstone at an average rate of 5 mm/yr since 15 kyr and has developed a very sinuous meandering pattern with several cut

  15. Structural Geology

    NASA Astrophysics Data System (ADS)

    Weber, John; Frankel, Kurt L.

    2011-05-01

    Structural geology and continental tectonics were ushered in to the modern quantitative age of geosciences with the arrival of the global plate tectonics paradigm (circa 1968), derived using new data from the oceans' depths, and John Ramsay's 1967 seminal work, Folding and Fracturing of Rocks. Fossen is to be applauded for crafting a unique, high-caliber, and accessible undergraduate textbook on structural geology that faithfully reflects this advance and the subsequent evolution of the discipline. This well-written text draws on Fossen's wealth of professional experience, including his broad and diverse academic research and experience in the petroleum industry. This book is beautifully illustrated, with excellent original color diagrams and with impressive color field photographs that are all keyed to locations and placed into geologic context.

  16. Experimental study on coarse grain saltation dynamics in bedrock channels

    NASA Astrophysics Data System (ADS)

    Chatanantavet, Phairot; Whipple, Kelin X.; Adams, Mark A.; Lamb, Michael P.

    2013-06-01

    of bed load particles on bedrock surfaces is important for landscape evolution and bedrock incision in steep landscapes. However, few studies have investigated saltation in bedrock channels where, unlike alluvial channels, the bed roughness height and the sediment size may be independent. To address this data gap, we measured the saltation hop height, hop length, and velocity of gravel saltating over a planar bed using 80-160 readings from high-speed photography and direct measurements. Two separate dimensional analyses are used: one leading to a bed shear stress scaling and another leading to a Froude number (Fr) scaling. Our new saltation data coupled with numerous data from previous studies suggest that both shear stress and Fr-scaling analyses are valid in characterizing bed load saltation dynamics with bed roughness ranging from smooth to alluvial beds. However, the Fr approach has the advantages that (1) there is no need to estimate a critical Shields stress τc*, which alone can vary up to 2 orders of magnitude (e.g., 0.001-0.1) due to changes in relative bed roughness and slope and (2) the Fr-based scaling fits the saltation data set better in a least squares sense. Results show that the saltation velocity of bed load is independent of grain density and grain size and is linearly proportional to flow velocity. Saltation height has a nonlinear dependence on grain size. Saltation length increases primarily with flow velocity, and it is inversely proportional to submerged specific density. Our results suggest that either τc* or bed roughness coefficient must be properly estimated to yield accurate results in saltation-abrasion models.

  17. Natural attenuation of trichloroethylene in fractured shale bedrock.

    PubMed

    Lenczewski, M; Jardine, P; McKay, L; Layton, A

    2003-07-01

    This paper describes one of the first well-documented field examples of natural attenuation of trichloroethylene (TCE) in groundwater in a fractured shale bedrock. The study was carried out adjacent to a former waste burial site in Waste Area Grouping 5 (WAG5) on the Oak Ridge Reservation, Oak Ridge, TN. A contaminant plume containing TCE and its daughter products were detected downgradient from the buried waste pits, with most of the contamination occurring in the upper 6 m of the bedrock. The monitoring well array consists of a 35-m-long transect of multilevel sampling wells, situated along a line between the waste pits and a seep which discharges into a small stream. Concentrations of volatile organic carbons (VOCs) were highest in the waste trenches and decreased with distance downgradient towards the seep. Sampling wells indicated the presence of overlapping plumes of TCE, cis-dichloroethylene (cDCE), vinyl chloride (VC), ethylene, ethane, and methane, with the daughter products extending further downgradient than the parent (TCE). This type of distribution suggests anaerobic biodegradation. Measurements of redox potential at the site indicated that iron-reduction, sulfate reduction, and potentially methanogensis were occurring and are conducive to dechlorination of TCE. Bacteria enrichment of groundwater samples revealed the presence of methanotrophs, methanogens, iron-reducing bacteria and sulfate-reducing bacteria, all of which have previously been implicated in anaerobic biodegradation of TCE. 16S rDNA sequence from DNA extracted from two wells were similar to sequences of organisms previously implicated in the anaerobic biodegradation of chlorinated solvents. The combined data strongly suggest that anaerobic biodegradation of the highly chlorinated compounds is occurring. Aerobic biodegradation may also be occurring in oxygenated zones, including near a seep where groundwater exits the site, or in the upper bedrock during seasonal fluctuations in water

  18. Effects of Bedrock Landsliding on Cosmogenically Determined Erosion Rates

    NASA Technical Reports Server (NTRS)

    Niemi, Nathan; Oskin, Mike; Burbank, Douglas; Heimsath, Arjun

    2005-01-01

    The successful quantification of long-term erosion rates underpins our understanding of landscape. formation, the topographic evolution of mountain ranges, and the mass balance within active orogens. The measurement of in situ-produced cosmogenic radionuclides (CRNs) in fluvial and alluvial sediments is perhaps the method with the greatest ability to provide such long-term erosion rates. In active orogens, however, deep-seated bedrock landsliding is an important erosional process, the effect of which on CRN-derived erosion rates is largely unquantified. We present a numerical simulation of cosmogenic nuclide production and distribution in landslide-dominated catchments to address the effect of bedrock landsliding on cosmogenic erosion rates in actively eroding landscapes. Results of the simulation indicate that the temporal stability of erosion rates determined from CRN concentrations in sediment decreases with increased ratios of landsliding to sediment detachment rates within a given catchment area, and that larger catchment areas must be sampled with increased frequency of landsliding in order to accurately evaluate long-term erosion rates. In addition, results of this simulation suggest that sediment sampling for CRNs is the appropriate method for determining long-term erosion rates in regions dominated by mass-wasting processes, while bedrock surface sampling for CRNs is generally an ineffective means of determining long-term erosion rates. Response times of CRN concentrations to changes in erosion rate indicate that climatically driven cycles of erosion may be detected relatively quickly after such changes occur, but that complete equilibration of CRN concentrations to new erosional conditions may take tens of thousands of years. Simulation results of CRN erosion rates are compared with a new, rich dataset of CRN concentrations from the Nepalese Himalaya, supporting conclusions drawn from the simulation.

  19. Geologic controls of subdivision damage near Denver, Colorado

    USGS Publications Warehouse

    Noe, D.C.

    2005-01-01

    This case study investigates the geologic controls on damaging ground deformations in a residential subdivision near Denver, Colo. Moderate to severe damage has occurred in certain areas where linear, parallel heave features with up to 0.3 in (1 ft) of differential displacement have formed across roads and under houses. Other areas have small, localized depressions that have formed in the roadsides with no discernable damage to nearby houses. Still other areas show no evidence of ground movements. The bedrock beneath the subdivision consists of steeply dipping Cretaceous strata of the Benton Shale, Niobrara Formation, and Pierre Shale. Quaternary soil deposits and fill, 0-16 m (0-53 ft) thick, overlie the bedrock. The most pronounced and damaging linear-heave features are coincident with steeply dipping, silty claystone with thin layers of very highly plastic bentonite. These heave features diminish as the depth to bedrock increases, and become small to negligible where the bedrock is overlain by 3 m (10 ft) or more of overburden soil deposits or fill. In contrast, areas having no visible damage and those having localized surface depressions are typically underlain by 1-12 m (3-39 ft) of alluvial-terrace deposits or fill. The depressions appear to have been caused by settlement over improperly filled water-and-sewer line trenches. The overall relationship between geology and ground deformations as seen in this subdivision may be useful for predicting, and thereby reducing, damage for future subdivision projects. Journal of Geotechnical and Geoenvironmental Engineering ?? ASCE.

  20. Arsenic evolution in fractured bedrock wells in central Maine, USA

    NASA Astrophysics Data System (ADS)

    Yang, Q.; Zheng, Y.; Culbertson, C.; Schalk, C.; Nielsen, M. G.; Marvinney, R.

    2010-12-01

    Elevated arsenic concentration in fractured bedrock wells has emerged as an important and challenging health problem, especially in rural areas without public water supply and mandatory monitoring of private wells. This has posed risks of skin, bladder, prostate diseases and cancers to private well users. In central Maine, including the study site, 31% of bedrock wells in meta-sedimentary formations have been reported of elevated arsenic concentrations of > 10 µg/L. Geophysical logging and fracture specific water sampling in high arsenic wells have been conducted to understand how water flowing through the aquifers enters the boreholes and how arsenic evolves in the fracture bedrock wells. Two domestic wells in Manchester, Maine, located 50 meter apart with 38 µg/L and 73 µg/L of arsenic in unfiltered water, were investigated to characterize fractures by geophysical logging and to determine flow rates by pumping test. Water samples, representing the bore hole and the fractures, were collected and analyzed for arsenic under ambient and pumping conditions. Transmissivity of the fractures was estimated at 0.23-10.6 m2/day. Water with high dissolved arsenic was supplied primarily by high yielding fractures near the bottom of the borehole. Dissolved arsenic concentrations in borehole water increased as fracture water with high arsenic was replacing borehole water with initially low dissolved arsenic in response to pumping. The precipitation of iron particulates enriched in arsenic was common during and after pumping. Laboratory experiment on well water samples over a period of 16 days suggested that in the borehole arsenic was mainly settled with iron enriched particles, likely amorphous ferric oxyhydroxides, with possibly minor adsorption on the iron minerals. Another bedrock well in Litchfield, Maine, with 478 µg/L of arsenic in the unfiltered well water, is being investigated to quantify and reconstruct of the groundwater flow under ambient and pumping conditions

  1. Theoretical geology

    NASA Astrophysics Data System (ADS)

    Mikeš, Daniel

    2010-05-01

    Theoretical geology Present day geology is mostly empirical of nature. I claim that geology is by nature complex and that the empirical approach is bound to fail. Let's consider the input to be the set of ambient conditions and the output to be the sedimentary rock record. I claim that the output can only be deduced from the input if the relation from input to output be known. The fundamental question is therefore the following: Can one predict the output from the input or can one predict the behaviour of a sedimentary system? If one can, than the empirical/deductive method has changes, if one can't than that method is bound to fail. The fundamental problem to solve is therefore the following: How to predict the behaviour of a sedimentary system? It is interesting to observe that this question is never asked and many a study is conducted by the empirical/deductive method; it seems that the empirical method has been accepted as being appropriate without question. It is, however, easy to argument that a sedimentary system is by nature complex and that several input parameters vary at the same time and that they can create similar output in the rock record. It follows trivially from these first principles that in such a case the deductive solution cannot be unique. At the same time several geological methods depart precisely from the assumption, that one particular variable is the dictator/driver and that the others are constant, even though the data do not support such an assumption. The method of "sequence stratigraphy" is a typical example of such a dogma. It can be easily argued that all the interpretation resulting from a method that is built on uncertain or wrong assumptions is erroneous. Still, this method has survived for many years, nonwithstanding all the critics it has received. This is just one example of the present day geological world and is not unique. Even the alternative methods criticising sequence stratigraphy actually depart from the same

  2. Modelling radionuclide transport in large fractured-media systems: the example of Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Schwartz, Michael O.

    2012-06-01

    The planned high-level nuclear waste repository at Forsmark, Sweden, will accommodate 6,824 containers with a total of 13,920 tonnes of uranium in burnt fuel at approximately 400 m depth in a fractured-granite aquifer. The transport of radionuclides, which may be released from the disposed waste, is simulated with the TOUGHREACT code for a three-dimensional model with 305,571 elements. The model performs coupled flow-transport simulations. It aims to achieve more realistic simulations of contaminant transport than the commonly used decoupled procedure consisting of three-dimensional flow and one-dimensional transport simulations. The model has a relatively small problem size because it is designed as a double-porosity model (one matrix continuum) that is the parameterised equivalent of a much larger multiple-interacting continua (MINC) model, i.e. a model with a finely discretised matrix (several matrix continua). The parameterisation is performed with two-dimensional models. Only one or two variables among three variables (diffusive transport distance between fracture and matrix, retardation factor and effective diffusivity) have to be parameterised. The results obtained with the parameterised three-dimensional model are very close to those that can be obtained with a much larger MINC model but may be quite different from those that can be obtained with the conventional decoupled procedure.

  3. Hematite Helium Dating of Bedrock Fractures and Faults (HeHe BFF)

    NASA Astrophysics Data System (ADS)

    Reiners, P. W.

    2011-12-01

    Despite their importance for hydrologic and geophysical properties of the shallow crust, the age and origins of bedrock-hosted fractures, faults, and veins are often difficult to determine. This is partly because existing geochronologic methods are not very good at dating the limited range of secondary phases that form in them. Fe(III)-oxides, especially hematite, are extremely common in such features in shallow crustal rocks, where their formation is associated with fluid flow and deformation episodes occurring long after host rock formation. The (U-Th)/He system poses potential for dating these secondary Fe-oxides because they contain variable but often high (often tens to hundreds of ppm) concentrations of U and/or Th and little to no initial He. Hematite (U-Th)/He (HeHe) dates from bedrock faults and fractures (BFF) (and veins) in several geologic settings illustrate the potential of this approach for understanding a range of phenomena related to fluid flow and deformation. For example, thin (~1-5 mm) hematite veins in Proterozoic crystalline basement from four locations in central Arizona have ages of HeHe dates of 425-525 Ma, 570-630 Ma, 750-930 Ma, and 800-900 Ma. These could be interpreted as the timing of vein formation during the penultimate near-surface exhumation episode (the last one being that which exhumed them in the late Cenozoic) that exposed these rocks to migrating oxidized groundwater. Not all hematite veins in crystalline basement are that old, however, and in some cases their ages may be easier to associate with regional tectonic events. A thin hematite vein in the Boulder Creek batholith just below the basal Fountain Formation yields HeHe ages of 171 ± 4.6 Ma. This corresponds to a major unconformity in the overlying sedimentary sequence, and a sharp increase in basin subsidence and magmatic input in the Utah-Idaho trough/Arapien basin several hundred kilometers to the west. Similarly, in the Galiuro Mountains of southern Arizona, 1.1-Ga

  4. City Geology.

    ERIC Educational Resources Information Center

    Markle, Sandra

    1989-01-01

    This article provides information on the evolution of the building material, concrete, and suggests hands-on activities that allow students to experience concrete's qualities, test the heat absorbency of various ground surface materials, discover how an area's geology changes, and search for city fossils. A reproducible activity sheet is included.…

  5. Geologic Time.

    ERIC Educational Resources Information Center

    Albritton, Claude C., Jr.

    1984-01-01

    Discusses the historical development of the concept of geologic time. Develops the topic by using the major discoveries of geologists, beginning with Steno and following through to the discovery and use of radiometric dating. An extensive reference list is provided. (JM)

  6. Initial yield to depth relation for water wells drilled into crystalline bedrock--Pinardville quadrangle, New Hampshire.

    PubMed

    Drew, L J; Schuenemeyer, J H; Armstrong, T R; Sutphin, D M

    2001-01-01

    A model is proposed to explain the statistical relations between the mean initial water well yields from eight time increments from 1984 to 1998 for wells drilled into the crystalline bedrock aquifer system in the Pinardville area of southern New Hampshire and the type of bedrock, mean well depth, and mean well elevation. Statistical analyses show that the mean total yield of drilling increments is positively correlated with mean total well depth and mean well elevation. In addition, the mean total well yield varies with rock type from a minimum of 46.9 L/min (12.4 gpm) in the Damon Pond granite to a maximum of 74.5 L/min (19.7 gpm) in the Permian pegmatite and granite unit. Across the eight drilling increments that comprise 211 wells each, the percentages of very low-yield wells (1.9 L/min [0.5 gpm] or less) and high-yield wells (151.4 L/min [40 gpm] or more) increased, and those of intermediate-yield wells decreased. As housing development progressed during the 1984 to 1998 interval, the mean depth of the wells and their elevations increased, and the mix of percentages of the bedrock types drilled changed markedly. The proposed model uses a feed-forward mechanism to explain the interaction between the increasing mean elevation, mean well depth, and percentages of very low-yielding wells and the mean well yield. The increasing percentages of very low-yielding wells through time and the economics of the housing market may control the system that forces the mean well depths, percentages of high-yield wells, and mean well yields to increase. The reason for the increasing percentages of very low-yield wells is uncertain, but the explanation is believed to involve the complex structural geology and tectonic history of the Pinardville quadrangle. PMID:11554245

  7. Determination of Bedrock Variations and S-wave Velocity Structure in the NW part of Turkey for Earthquake Hazard Mitigation

    NASA Astrophysics Data System (ADS)

    Ozel, A. O.; Arslan, M. S.; Aksahin, B. B.; Genc, T.; Isseven, T.; Tuncer, M. K.

    2015-12-01

    Tekirdag region (NW Turkey) is quite close to the North Anatolian Fault which is capable of producing a large earthquake. Therefore, earthquake hazard mitigation studies are important for the urban areas close to the major faults. From this point of view, integration of different geophysical methods has important role for the study of seismic hazard problems including seismotectonic zoning. On the other hand, geological mapping and determining the subsurface structure, which is a key to assist management of new developed areas, conversion of current urban areas or assessment of urban geological hazards can be performed by integrated geophysical methods. This study has been performed in the frame of a national project, which is a complimentary project of the cooperative project between Turkey and Japan (JICA&JST), named as "Earthquake and Tsunami Disaster Mitigation in the Marmara Region and Disaster Education". With this principal aim, this study is focused on Tekirdag and its surrounding region (NW of Turkey) where some uncertainties in subsurface knowledge (maps of bedrock depth, thickness of quaternary sediments, basin geometry and seismic velocity structure,) need to be resolved. Several geophysical methods (microgravity, magnetic and single station and array microtremor measurements) are applied and the results are evaluated to characterize lithological changes in the region. Array microtremor measurements with several radiuses are taken in 30 locations and 1D-velocity structures of S-waves are determined by the inversion of phase velocities of surface waves, and the results of 1D structures are verified by theoretical Rayleigh wave modelling. Following the array measurements, single-station microtremor measurements are implemented at 75 locations to determine the predominant frequency distribution. The predominant frequencies in the region range from 0.5 Hz to 8 Hz in study area. On the other hand, microgravity and magnetic measurements are performed on

  8. Field Verification of Stable Perched Groundwater in Layered Bedrock Uplands

    USGS Publications Warehouse

    Carter, J.T.; Gotkowitz, M.B.; Anderson, M.P.

    2011-01-01

    Data substantiating perched conditions in layered bedrock uplands are rare and have not been widely reported. Field observations in layered sedimentary bedrock in southwestern Wisconsin, USA, provide evidence of a stable, laterally extensive perched aquifer. Data from a densely instrumented field site show a perched aquifer in shallow dolomite, underlain by a shale-and-dolomite aquitard approximately 25 m thick, which is in turn underlain by sandstone containing a 30-m-thick unsaturated zone above a regional aquifer. Heads in water supply wells indicate that perched conditions extend at least several kilometers into hillsides, which is consistent with published modeling studies. Observations of unsaturated conditions in the sandstone over a 4-year period, historical development of the perched aquifer, and perennial flow from upland springs emanating from the shallow dolomite suggest that perched groundwater is a stable hydrogeologic feature under current climate conditions. Water-table hydrographs exhibit apparent differences in the amount and timing of recharge to the perched and regional flow systems; steep hydraulic gradients and tritium and chloride concentrations suggest there is limited hydraulic connection between the two. Recognition and characterization of perched flow systems have practical importance because their groundwater flow and transport pathways may differ significantly from those in underlying flow systems. Construction of multi-aquifer wells and groundwater withdrawal in perched systems can further alter such pathways. ?? 2010 The Author(s). Journal compilation ?? 2010 National Ground Water Association.

  9. 10Be chronometry of bedrock-to-soil conversion rates

    NASA Astrophysics Data System (ADS)

    Monaghan, Marc C.; McKean, James; Dietrich, William; Klein, Jeffrey

    1992-07-01

    We report concentrations of cosmogenic 10Be ( t1/2 = 1.5 × 10 6 yrs) in soil excavated from a soil-mantled hillslope in Black Diamond Mines Regional Park, Contra Costa County, California. The most striking features of the data are: (1) the similarity in the downward decreasing trends of 10Be concentrations in two soil profiles collected 75 m apart, (2) the coincidence in each soil profile of the soil/bedrock interface (as defined by visual inspection of soil pits) and the level at which 10Be concentrations attain very low values ( ˜4 × 10 6 atoms/g), and (3) the extremely low 10Be concentrations in the underlying regolith (0.5 × 10 6 atoms/gram). The inventory of 10Be in these soils is low, equivalent to about 6000 yrs of 10Be accumulation in a soil initially containing no 10Be. On the basis of these measurements, and with the aid of simple models of soil ( 10Be) motions on the hillslope, we conclude that 10Be loss from the surface is dominated by its removal in soil by creep. We calculate local rates of bedrock-to-soil conversion of between 0.15 and 0.27 km/10 6 yrs. Comparing these with uplift rates determined for coastal regions of California indicates that soil creep alone is capable of removing soil from the local geomorphic system at a rate equivalent to the rate of uplift of much of the coast.

  10. Field verification of stable perched groundwater in layered bedrock uplands.

    PubMed

    Carter, Jonathon T V; Gotkowitz, Madeline B; Anderson, Mary P

    2011-01-01

    Data substantiating perched conditions in layered bedrock uplands are rare and have not been widely reported. Field observations in layered sedimentary bedrock in southwestern Wisconsin, USA, provide evidence of a stable, laterally extensive perched aquifer. Data from a densely instrumented field site show a perched aquifer in shallow dolomite, underlain by a shale-and-dolomite aquitard approximately 25 m thick, which is in turn underlain by sandstone containing a 30-m-thick unsaturated zone above a regional aquifer. Heads in water supply wells indicate that perched conditions extend at least several kilometers into hillsides, which is consistent with published modeling studies. Observations of unsaturated conditions in the sandstone over a 4-year period, historical development of the perched aquifer, and perennial flow from upland springs emanating from the shallow dolomite suggest that perched groundwater is a stable hydrogeologic feature under current climate conditions. Water-table hydrographs exhibit apparent differences in the amount and timing of recharge to the perched and regional flow systems; steep hydraulic gradients and tritium and chloride concentrations suggest there is limited hydraulic connection between the two. Recognition and characterization of perched flow systems have practical importance because their groundwater flow and transport pathways may differ significantly from those in underlying flow systems. Construction of multi-aquifer wells and groundwater withdrawal in perched systems can further alter such pathways. PMID:21671502

  11. Experimental Bedrock Channel Incision: Scaling, Sculpture and Sediment Transport

    NASA Astrophysics Data System (ADS)

    Johnson, J. P.; Whipple, K. X.

    2004-12-01

    Abrasion by sediment in turbulent flows often sculpts bedrock channels into dramatic forms; quantifying the feedbacks between fluid flow, sediment impacts, and channel morphology is needed to refine models of fluvial incision into bedrock. We present data from laboratory flume experiments funded by the National Center for Earth-Surface Dynamics and conducted at St. Anthony Falls Laboratory, University of Minnesota that show how the spatial and temporal distribution of erosion is strongly coupled to the evolving topography of the bed. These experiments focus on the high Froude number and tool-starved end of parameter space, where bed cover tends to be negligible. Independent variables include flume slope, water flux and sediment flux and size distribution. Sediment moves energetically as bedload, suspended load, or locally transitional between transport modes. Quantitative measurements of the evolving bed topography show that the synthetic brittle "bedrock" in the flume (cured sand-cement mixture) eroded to form narrow incised channels with tight scoops and potholes. The experimental erosional forms are similar in morphology, and sometimes in scale, to those observed in natural bedrock rivers in southeast Utah and other field settings. The experiments demonstrate that both the mean and distribution of measured erosion rates change as the bed topography evolves, even with constant water and sediment discharges. Even starting with a plane bed geometry, erosion and sediment transport very quickly become localized in interconnected topographic lows. Positive feedback develops between the evolving topography and the fluid velocity and sediment transport fields, resulting in the incision of an inner channel. Once formed, the erosion rate in the axis of the inner channel decreases as local bed shear stresses and fluid velocities are reduced by increasing wall drag, and sediment fluxes through the channel but causes less incision (no deposition). Decreasing the sediment

  12. Uranium and thorium distribution in soils and weathered bedrock in south Texas

    USGS Publications Warehouse

    Dickinson, Kendell A.

    1977-01-01

    The distribution of uranium and thorium in soils and weathered bedrock in areas of calich soil development on various kinds of sedimentary bedrock in south Texas indicates that uranium and thorium are leached from the surface layers and deposited deeper in the soil or weathered bedrock. The data provide field evidence that uranium is mobilized during dry-climate weathering, and suggest that caution be used in the interpretation of airborne, radioactive surveys that measure uranium at the surface.

  13. Approach to estimating the maximum depth for glacially induced hydraulic jacking in fractured crystalline rock at Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Lönnqvist, M.; Hökmark, H.

    2013-09-01

    Hydraulic jacking is a significant dilation of a fracture that occurs when the pore pressure within it exceeds the sum of the fracture's normal stress and tensile strength. This phenomenon may occur during a glacial period because of changes in hydraulic and mechanical boundary conditions. Since hydraulic jacking may alter flow patterns and the transport capacity of the rock mass, its possible effects on the long-term performance of a nuclear waste repository should be considered. We develop an approach to assess glacially induced hydraulic jacking in fractured crystalline rock and establish bounding estimates of the maximum jacking depth for the Swedish Nuclear Fuel and Waste Management Company's (SKB) repository site at Forsmark. The pore pressure is estimated using mechanically uncoupled two-dimensional poroelastic continuum models with hydraulic and mechanical conditions based on SKB's reconstruction of the Weichselian glaciation at this site (120-0 ka B.P.). For warm-based conditions, the water pressure at the ice/bed interface is set at 98% of the mechanical load, whereas for glacial conditions with extensive proglacial permafrost, the corresponding water pressure is set at a (lower) annual average value. We demonstrate that the pore pressure within the uppermost kilometer of rock is mainly governed by the water pressure at the ice/bed interface and that the mechanical impact of the ice load on the pore pressure is sufficiently small to be ignored. Given the current and estimated future stress conditions at Forsmark, hydraulic jacking is mainly of concern for subhorizontal fractures, i.e., it is sufficient to consider situations when the pore pressure exceeds the vertical stress. We conclude that hydraulic jacking at Forsmark will be confined to the uppermost 200 m of the rock mass.

  14. Application of advanced geophysical logging methods in the characterization of a fractured-sedimentary bedrock aquifer, Ventura County, California

    USGS Publications Warehouse

    Williams, John H.; Lane, Jr., John W.; Singha, Kamini; Haeni, F. Peter

    2002-01-01

    An integrated suite of advanced geophysical logging methods was used to characterize the geology and hydrology of three boreholes completed in fractured-sedimentary bedrock in Ventura County, California. The geophysical methods included caliper, gamma, electromagnetic induction, borehole deviation, optical and acoustic televiewer, borehole radar, fluid resistivity, temperature, and electromagnetic flowmeter. The geophysical logging 1) provided insights useful for the overall geohydrologic characterization of the bedrock and 2) enhanced the value of information collected by other methods from the boreholes including core-sample analysis, multiple-level monitoring, and packer testing. The logged boreholes, which have open intervals of 100 to 200 feet, penetrate a sequence of interbedded sandstone and mudstone with bedding striking 220 to 250 degrees and dipping 15 to 40 degrees to the northwest. Fractures intersected by the boreholes include fractures parallel to bedding and fractures with variable strike that dip moderately to steeply. Two to three flow zones were detected in each borehole. The flow zones consist of bedding-parallel or steeply dipping fractures or a combination of bedding-parallel fractures and moderately to steeply dipping fractures. About 75 to more than 90 percent of the measured flow under pumped conditions was produced by only one of the flow zones in each borehole.

  15. Bedrock controls on the mineralogy and chemistry of PM10 extracted from Australian desert sediments

    NASA Astrophysics Data System (ADS)

    Moreno, Teresa; Amato, Fulvio; Querol, Xavier; Alastuey, Andrés; Elvira, Josep; Gibbons, Wes

    2009-03-01

    Given the relevance of desert aerosols to environmental issues such as dust storms, climate change and human health effects, we provide a demonstration of how the bedrock geology of an arid area influences the mineralogy and geochemistry of even the finest particulate matter (i.e., the inhalable fraction <10 μm in size: PM10). PM10 samples extracted from desert sediments at geologically contrasting off-road sites in central and southeastern Australia (granitic, high grade metamorphic, quartzitic sandstone) were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). The “granitic” PM10 are highly alkali feldspathic and illitic, with a wide range of accessory minerals including rutile (TiO2), monazite [(Ce, La, Nd, Th, Y) PO4], xenotime (YPO4), apatite [Ca5(PO4)3 (F, OH, Cl)], hematite (Fe3O4), zircon (ZrSiO4) and thorite (ThSiO4). This mineralogy is reflected in the geochemistry which shows notable enrichments in rare earth elements (REE) and most high field strength elements (both held in the accessory minerals), and higher than normal levels of low (<2.0) ionic potential elements (Na, K, Li, Cs, Rb: held in alkali feldspar and illite). The “metamorphic” resuspended PM10 define a mineralogy clearly influenced by local exposures of pelitic and calc-silicate schists (sillimanite, muscovite, calcite, Ca-amphibole), a dominance of monazite over other REE-bearing phases, and a geochemistry distinguished by enrichments in alkaline earth metals (Ca, Mg, Ba, Sr) and depletion in heavy REE. The “quartzite” PM10, derived from rocks already recycled by Precambrian erosion and sedimentary transport, show a sedimentologically mature mineralogy of mostly quartz and kaolinite, detrital accessory ilmenite, rutile, monazite and hematite, and the strongest geochemical depletion (especially K, Rb, Cs, Na, Ca, Mg, Ba).

  16. Geology Fulbrights

    NASA Astrophysics Data System (ADS)

    Fulbright grants in geology for 1988-89 remain open. Specific opportunities are available in Egypt, German Democratic Republic, Hungary, Iceland, Iraq, Kuwait, Morocco, Mozambique, Oman, Poland, Sudan, Syria, Tanzania, Turkey, U.S.S.R., West Bank, Yemen, and Zimbabwe. Other countries are also open to applications in any discipline, and geology is among their preferred fields.The grants are available until awarded and are open only to U.S. citizens. In Central and South America and French-speaking Africa, knowledge of host-country language is required. For more information, contact the Council for International Exchange of Scholars (CIES), 11 Dupont Circle N.W., Suite 300, Washington, DC 20036; tel. 202-939-5401.

  17. Event scale variability of mixed alluvial-bedrock channel dynamics

    NASA Astrophysics Data System (ADS)

    Cook, Kristen; Turowski, Jens; Hovius, Niels

    2015-04-01

    The relationship between flood events and fluvial behavior is critical for understanding how rivers may respond to the changing hydrologic forcing that may accompany climate change. In mixed bedrock-alluvial rivers, the response of the system to a flood event can be affected by a large number of factors, including coarse sediment availability in the channel, sediment supply from the hillslopes, bedrock-controlled changes in channel width and planform, and the shape of the hydrograph. We use the Daan River Gorge in western Taiwan as a case study to directly observe the effect of individual flood events on channel evolution. The 1200 m long and up to 20 m deep bedrock gorge formed in response to uplift of the riverbed during the 1999 Chi-Chi earthquake. The extremely rapid pace of change ensures that flood events have measurable and often dramatic effects on the channel. Taiwan is subject to both summer typhoons and a spring monsoon, resulting in numerous channel-altering floods with a range of magnitudes. Discharge is therefore highly variable, ranging from 5 to over 2000 m3/s, and changes in the channel are almost entirely driven by discrete flood events. Since early 2009 we have monitored changes in the gorge with repeated RTK GPS surveys, laser rangefinder measurements, and terrestrial LIDAR surveys. Six rainfall stations and five water level gauges provide hydrological data for the basin. We find a distinct relationship between flood magnitude and the magnitude of geomorphic change; however, we do not find a clear relationship between flood characteristics and the direction of change - whether the channel experienced aggradation or erosion in a particular flood. Upstream coarse sediment supply and the influence of abrupt changes in channel width on bedload flux through the gorge appear to have important influences on the channel response. The better understand these controls, we use the model sedFlow (Heimann et al., 2014) to explore the effects of interactions

  18. Methane in Crystalline Bedrock: the Outokumpu Deep Drill Hole, Finland

    NASA Astrophysics Data System (ADS)

    Kietäväinen, R.; Ahonen, L.; Niinikoski, P.; Itävaara, M.; Kukkonen, I. T.

    2014-12-01

    Carbon is a key element for life. One of the most interesting forms of carbon is methane, as it is both consumed and produced by microorganisms. Methane has also several possible ways of abiotic origin, some of which could provide understanding of the origin of life itself. The study of methane is thus important in order to understand deep subsurface ecosystems such as those found in the 2516 m deep Outokumpu Deep Drill Hole within the Precambrian Fennoscandian Shield in eastern Finland. There rock types differ from graphite-bearing mica schist and black schist to serpentinite and pegmatitic granodiorite and saline, gas-rich water, with up to 32 mmol l-1 of methane, and residence times of tens of millions of years occupies the fracture zones which host diverse microbial life, including methanogenic archaea. In order to understand methane systematics in crystalline bedrock, we analysed several forms of carbon, including dissolved inorganic carbon (DIC), methane and ethane from the Outokumpu Deep Drill Hole for their isotopic composition. In addition, isotopic compositions of water and hydrogen were determined. The results show that hydrogen is in isotopic equilibrium in the system H2O-H2-CH4 at ambient temperatures, which could either indicate equilibration due to long residence time or relatively recent production of methane in situ. Therefore hydrogen is not a very useful indicator for the origin of methane in this case. Carbon isotope analysis shows that both methane and DIC becomes generally more enriched in 13C with depth, which could indicate higher amounts of microbial methane in the upper part of the bedrock. Based on carbon isotope composition, two types of ethane can be discerned. Taken all the evidence together, this leads us to suggest that at least two mechanisms are responsible for the methane production in Outokumpu: 1) Biotic which comprise most of methane and 2) abiotic which dominates in the deeper parts of the bedrock. The former type may include

  19. Relationships of soil, grass, and bedrock over the Kaweah Serpentinite Melange through spectral mixture analysis of AVIRIS data

    NASA Technical Reports Server (NTRS)

    Mustard, John F.

    1993-01-01

    A linear mixing model is used to model the spectral variability of an AVIRIS scene from the western foothills of the Sierra Nevada and calibrate these radiance data to reflectance. Five spectral endmembers from the AVIRIS data, plus an ideal 'shade' endmember were required to model the continuum reflectance of each pixel in the image. Three of the endmembers were interpreted to model the surface constituents green vegetation, dry grass, and illumination. Comparison of the fraction images to the bedrock geology maps indicates that substrate composition must be a factor contributing to the spectral properties of these endmembers. Detailed examination of the reflectance spectra of the three soil endmembers reveals that differences in the amount of ferric and ferrous iron and/or organic constituents in the soils is largely responsible for the differences in spectral properties of these endmembers.

  20. Reconnaissance geologic mapping in the Dry Valleys of Antarctica using the Earth Resources Technology Satellite

    NASA Technical Reports Server (NTRS)

    Houston, R. S. (Principal Investigator); Zochol, F. W.; Smithson, S. B.

    1973-01-01

    The author has identified the following significant results. Reconnaissance geologic mapping can be done with 60-70% accuracy in the Dry Valleys of Antarctica using ERTS-1 imagery. Bedrock geology can be mapped much better than unconsolidated deposits of Quaternary age. Mapping of bedrock geology is facilitated by lack of vegetation, whereas mapping of Quaternary deposits is hindered by lack of vegetation. Antarctic images show remarkable clarity and under certain conditions (moderate relief, selection of the optimum band for specific rock types, stereo-viewing) irregular contacts can be mapped in local areas that are amazing like those mapped at a scale of 1:25,000, but, of course, lack details due to resolution limitations. ERTS-1 images should be a valuable aid to Antarctic geologists who have some limited ground truth and wish to extend boundaries of geologic mapping from known areas.

  1. Geomorphology of the Alluvial Sediments and Bedrock in an Intermontane Basin: Application of Variogram Modeling to Electrical Resistivity Soundings

    NASA Astrophysics Data System (ADS)

    Khan, Adnan Ahmad; Farid, Asam; Akhter, Gulraiz; Munir, Khyzer; Small, James; Ahmad, Zulfiqar

    2016-05-01

    The study describes a methodology used to integrate legacy resistivity data with limited geological data in order to build three-dimensional models of the near subsurface. Variogram analysis and inversion techniques more typically found in the petroleum industry are applied to a set of 1D resistivity data taken from electrical surveys conducted in the 1980s. Through careful integration with limited geological data collected from boreholes and outcrops, the resultant model can be visualized in three dimensions to depict alluvium layers as lithological and structural units within the bedrock. By tuning the variogram parameters to account for directionality, it is possible to visualize the individual lithofacies and geomorphological features in the subsurface. In this study, an electrical resistivity data set collected as part of a groundwater study in an area of the Peshawar basin in Pakistan has been re-examined. Additional lithological logs from boreholes throughout the area have been combined with local outcrop information to calibrate the data. Tectonic activity during the Himalayan orogeny has caused uplift in the area and generated significant faulting in the bedrock resulting in the formation of depressions which are identified by low resistivity values representing clays. Paleo-streams have reworked these clays which have been eroded and replaced by gravel-sand facies along paleo-channels. It is concluded that the sediments have been deposited as prograding fan-shaped bodies and lacustrine deposits with interlayered gravel-sand and clay-silt facies. The Naranji area aquifer system has thus been formed as a result of local tectonic activity with fluvial erosion and deposition and is characterized by coarse sediments with high electrical resistivities.

  2. Geomorphology of the Alluvial Sediments and Bedrock in an Intermontane Basin: Application of Variogram Modeling to Electrical Resistivity Soundings

    NASA Astrophysics Data System (ADS)

    Khan, Adnan Ahmad; Farid, Asam; Akhter, Gulraiz; Munir, Khyzer; Small, James; Ahmad, Zulfiqar

    2016-02-01

    The study describes a methodology used to integrate legacy resistivity data with limited geological data in order to build three-dimensional models of the near subsurface. Variogram analysis and inversion techniques more typically found in the petroleum industry are applied to a set of 1D resistivity data taken from electrical surveys conducted in the 1980s. Through careful integration with limited geological data collected from boreholes and outcrops, the resultant model can be visualized in three dimensions to depict alluvium layers as lithological and structural units within the bedrock. By tuning the variogram parameters to account for directionality, it is possible to visualize the individual lithofacies and geomorphological features in the subsurface. In this study, an electrical resistivity data set collected as part of a groundwater study in an area of the Peshawar basin in Pakistan has been re-examined. Additional lithological logs from boreholes throughout the area have been combined with local outcrop information to calibrate the data. Tectonic activity during the Himalayan orogeny has caused uplift in the area and generated significant faulting in the bedrock resulting in the formation of depressions which are identified by low resistivity values representing clays. Paleo-streams have reworked these clays which have been eroded and replaced by gravel-sand facies along paleo-channels. It is concluded that the sediments have been deposited as prograding fan-shaped bodies and lacustrine deposits with interlayered gravel-sand and clay-silt facies. The Naranji area aquifer system has thus been formed as a result of local tectonic activity with fluvial erosion and deposition and is characterized by coarse sediments with high electrical resistivities.

  3. Geologic map of the Upper Hurricane Wash and vicinity, Mohave County, northwestern Arizona

    USGS Publications Warehouse

    Billingsley, George H.; Dyer, Helen C.

    2003-01-01

    This digital map database is compiled from unpublished open file reports by the author and represents the general distribution of surficial and bedrock geology in the mapped area. The map area lies within the Shivwits and Uikaret Plateaus, together with the accompanying pamphlet, it provides current information on the geologic structure, stratigraph, and Cenozoic geology of the area. The database delineates map units that are identified by age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution of the database to 1:31,680 or smaller.

  4. Geology of Damon Mound Salt Dome, Texas

    SciTech Connect

    Collins, E.W.

    1989-01-01

    Geological investigation of the stratigraphy, cap-rock characteristics, deformation and growth history, and growth rate of a shallow coastal diapir. Damon Mound salt dome, located in Brazoria County, has salt less than 600 feet and cap rock less than 100 feet below the surface; a quarry over the dome provides excellent exposures of cap rock as well as overlying Oligocene to Pleistocene strata. These conditions make it ideal as a case study for other coastal diapirs that lack bedrock exposures. Such investigations are important because salt domes are currently being considered by chemical waste disposal companies as possible storage and disposal sites. In this book, the author reviews previous research, presents additional data on the subsurface and surface geology at Damon Mound, and evaluates Oligocene to post-Pleistocene diapir growth.

  5. Preconditioning of the Eibsee rock avalanche by deglaciation and development of critical bedrock stresses

    NASA Astrophysics Data System (ADS)

    Leith, Kerry; Hofmayer, Felix; Kessler, Barbara; Krautblatter, Michael

    2016-04-01

    The impact of glacier retreat on rock slope instability since the Last Glacial Maximum is the subject of ongoing debate. Rock slope activity since ice retreat is typically attributed to increased kinematic freedom as a result of erosion during glaciation, debuttressing of valley walls which may have been supported by glacier ice, specific patterns of Holocene seismicity, or an exposure of rock slopes to increased chemical and biological weathering during the present interglacial. Here, rather than looking for a particular driver or trigger for rock slope instability, we evaluate the potential for rock mass degradation in response to an increase in tensile stress or micro-cracking in critically stressed near-surface bedrock (0 - 2 km depth). Instead of focusing on a specific driver, this allows us to identify regions in which fracture development is likely to be ongoing, and slope stability is therefore decreasing with time. Combining two orthogonal cross-sections, we evaluate stress changes and fracture development in the Zugspitze region of the Wetterstein Mountains (southern Germany) using an elasto-plastic 2-D FEM model (Phase2 from Rocscience). Based on geological evidence, we reconstruct the 3-D topography of the former Zugspitze peak, prior to what we estimate to be a 165 Mm3 collapse (previously dated at 3700 B.P.). We then impose initial stress conditions consistent with the tectonic and exhumation history of the region, as well as rock mechanical attributes derived from a fracture survey of the Zugspitzplatt and results of standard laboratory testing of Wettersteinkalk, the dominant lithology in the region. By imposing ice loading through a series of glacial-interglacial cycles, we are able to generate, and maintain critical stresses and low levels of fracture propagation beneath the Zugspitzplatt and at the location of the rock avalanche release throughout deglaciation, supporting our field observations. We then simulate weathering near the model surface

  6. Geological map of the vineyards of southern Burgenland

    NASA Astrophysics Data System (ADS)

    Heinrich, Maria; Untersweg, Thomas; Reitner, Heinz

    2015-04-01

    During the study a detailed geological map of the vineyards of southern Burgenland was created. The detailed fieldwork was carried out with hand augers and boreholes, augmented by sampling of soil and bedrock and mineralogical, clay mineralogical, sedimentological and geochemical analysis of the samples, to amend existing small-scale maps on soil and geology. With these results the variation of chemical composition and grain size distribution can be described. These will support winegrowers and consultants in taking viticultural measures such as choosing stock and varieties and provide means to enhance the delineation of the vineyards.

  7. A methodology to constrain the parameters of a hydrogeological discrete fracture network model for sparsely fractured crystalline rock, exemplified by data from the proposed high-level nuclear waste repository site at Forsmark, Sweden

    NASA Astrophysics Data System (ADS)

    Follin, Sven; Hartley, Lee; Rhén, Ingvar; Jackson, Peter; Joyce, Steven; Roberts, David; Swift, Ben

    2014-03-01

    The large-scale geological structure of the crystalline rock at the proposed high-level nuclear waste repository site at Forsmark, Sweden, has been classified in terms of deformation zones of elevated fracture frequency. The rock between deformation zones was divided into fracture domains according to fracture frequency. A methodology to constrain the geometric and hydraulic parameters that define a discrete fracture network (DFN) model for each fracture domain is presented. The methodology is based on flow logging and down-hole imaging in cored boreholes in combination with DFN realizations, fracture connectivity analysis and pumping test simulations. The simulations suggest that a good match could be obtained for a power law size distribution where the value of the location parameter equals the borehole radius but with different values for the shape parameter, depending on fracture domain and fracture set. Fractures around 10-100 m in size are the ones that typically form the connected network, giving inflows in the simulations. The report also addresses the issue of up-scaling of DFN properties to equivalent continuous porous medium (ECPM) bulk flow properties. Comparisons with double-packer injection tests provide confidence that the derived DFN formulation of detailed flows within individual fractures is also suited to simulating mean bulk flow properties and their spatial variability.

  8. Digital geologic map of Yellowstone National Park, Idaho, Montana, Wyoming and vicinity

    USGS Publications Warehouse

    Christiansen, Robert L.; Wahl, Ronald R.

    1999-01-01

    The geology coverage was developed from the 1972 USGS Geologic Map of Yellowstone National Park. It contains polygons of bedrock formations, dikes, and faults. Errors in the 1972 map were corrected and an area outside the Park boundary on the west and south was added. Attributes attached to each polygon include a formation code, formation name, formation age, and a generalized unit name. Line attributes include water, contacts, and faults. Updated information includes a break down of Tertiary, and Quaternary volcanic rock units.

  9. Bedrock infiltration estimates using catchment water storage in the mountain rain snow transition zone

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Estimates of bedrock infiltration from mountain catchments in the western U.S. are essential to water resource managers because they provide an estimate of mountain block recharge to regional aquifers. On smaller scales, bedrock infiltration is an important term in water mass balance studies, which...

  10. Geologic nozzles

    USGS Publications Warehouse

    Werner, Kieffer S.

    1989-01-01

    The importance of the low characteristic velocities of geologic fluids has not been widely recognized, and as a result, the importance of supercritical and supersonic flow in geological processes has generally been underestimated. The lateral blast at Mount St. Helens, Washington, propelled a gas heavily laden with dust into the atmosphere. Because of the low sound speed in this gas (about 100 m/s), the flow was internally supersonic. Old Faithful Geyser, Wyoming, is a converging-diverging nozzle in which liquid water refilling the conduit during the recharge cycle changes during eruption into a two-phase liquid-vapor mixture with a very low sound velocity. The high sound speed of liquid water determines the characteristics of harmonic tremor observed at the geyser during the recharge interval, whereas the low sound speed of the liquid-vapor mixture influences the fluid flow characteristics of the eruption. At the rapids of the Colorado River in the Grand Canyon, Arizona, the channel is constricted into the shape of a converging-diverging nozzle by the debris flows that enter from tributary canyons. Both subcritical and supercritical flow occur within the rapids. -from Author

  11. The Natural Terrestrial Carbon Sequestration Potential of Rocky Mountain Soils Derived From Volcanic Bedrock

    NASA Astrophysics Data System (ADS)

    Yager, D. B.; Burchell, A.; Johnson, R. H.

    2008-12-01

    The possible economic and environmental ramifications of climate change have stimulated a range of atmospheric carbon mitigation actions, as well as, studies to understand and quantify potential carbon sinks. However, current carbon management strategies for reducing atmospheric emissions underestimate a critical component. Soils represent between 18 - 30% of the terrestrial carbon sink needed to prevent atmospheric doubling of CO2 by 2050 and a crucial element in mitigating climate change, natural terrestrial sequestration (NTS), is required. NTS includes all naturally occurring, cumulative, biologic and geologic processes that either remove CO2 from the atmosphere or prevent net CO2 emissions through photosynthesis and microbial fixation, soil formation, weathering and adsorption or chemical reactions involving principally alumino- ferromagnesium minerals, volcanic glass and clays. Additionally, NTS supports ecosystem services by improving soil productivity, moisture retention, water purification and reducing erosion. Thus, 'global climate triage' must include the protection of high NTS areas, purposeful enhancement of NTS processes and reclamation of disturbed and mined lands. To better understand NTS, we analyzed soil-cores from Colorado, Rocky Mountain Cordillera sites. North-facing, high-plains to alpine sites in non-wetland environments were selected to represent temperate soils that may be less susceptible to carbon pool declines due to global warming than soils in warmer regions. Undisturbed soils sampled have 2 to 6 times greater total organic soil carbon (TOSC) than global TOSC averages (4 - 5 Wt. %). Forest soils derived from weathering of intermediate to mafic volcanic bedrock have the highest C (34.15 Wt. %), C:N (43) and arylsulfatase (ave. 278, high 461 μg p-nitrophenol/g/h). Intermediate TOSC was identified in soils derived from Cretaceous shale (7.2 Wt. %) and Precambrian, felsic gneiss (6.2 Wt. %). Unreclaimed mine-sites have the lowest C (0

  12. AN EXPERIMENT AND NUMERICAL SIMULATION OF SLURRY-EROSION CAUSED BY BEDLOAD ON BEDROCK

    NASA Astrophysics Data System (ADS)

    Oikawa, Shin; Iwasaki, Toshiki; Yamaguchi, Satomi; Shimizu, Yasuyuki; Kimura, Ichiro

    The bed degradation is going rapidly in the upper part of the Ishikari River recently, owing to exposed bedrock erosion caused by bedload on the bedrock. In order to estimate the erosion rate of bedrock, we performed an experiment by a circular channel flume with artificial bedrock made of plaster. We applied the erosion rate estimated by the present experiment to a numerical simulation of bed deformation on the bedrock by using horizontal 2D flow model and the bedload layer model. The result of the simulation shows that gut pattern appeared in the simulated results which is very similar to the experimental result. It was found that the bed degradation was progressed by the erosion caused by sediment transport itself.

  13. Introducing a terrestrial carbon pool in warm desert bedrock mountains, southwestern USA

    NASA Astrophysics Data System (ADS)

    Harrison, Emma J.; Dorn, Ronald I.

    2014-03-01

    Growth of the Phoenix metropolitan area led to road cut or house platform exposures of the internal bedrock material of surrounding semiarid mountain ranges. Similar exposures in the surrounding Sonoran and Mojave Deserts reveal the presence of sedimentary calcium carbonate infilling the preexisting fracture matrix of the bedrock. Field surveys at 31 sites with bedrock fractures filled with carbonate, referred to as BFFC in the following text, reveal an average of 0.079 ± 0.036 mTC/m2 stored in the upper 2 m of analyzed bedrock exposures. Backscattered electron microscopy images indicate the presence of carbonate at the micron scale, not included in this estimate of carbon storage. Pilot radiocarbon and Sr isotope analyses suggest that one of the surveyed BFFC veins was flushed into the bedrock from a nonbedrock source during the wetter last glacial period in the late Pleistocene.

  14. Structure contours of top of Laramie-Fox Hills aquifer in "Structure, outcrop, and subcrop of the bedrock aquifers along the western margin of Denver Basin, Colorado." Hydrologic Atlas 742

    USGS Publications Warehouse

    Rafferty, Sharon

    1998-01-01

    This digital geospatial data set consists of structure contours of the top of the Laramie-Fox Hills aquifer along the Front Range of Colorado. The U.S. Geological Survey developed this data set as part of a project described in the report, "Structure, Outcrop, and Subcrop of the Bedrock Aquifers Along the Western Margin of the Denver Basin, Colorado" (Robson and others, 1998).

  15. Sediment dynamics and the burial and exhumation of bedrock reefs along an emergent coastline as elucidated by repetitive sonar surveys: Northern Monterey Bay, CA

    USGS Publications Warehouse

    Storlazzi, C.D.; Fregoso, T.A.; Golden, N.E.; Finlayson, D.P.

    2011-01-01

    Two high-resolution bathymetric and acoustic backscatter sonar surveys were conducted along the energetic emergent inner shelf of northern Monterey Bay, CA, USA, in the fall of 2005 and the spring of 2006 to determine the impact of winter storm waves, beach erosion, and river floods on biologically-important siliclastic bedrock reef habitats. The surveys extended from water depths of 4 m to 22 m and covered an area of 3.14 km2, 45.8% of which was bedrock, gravel, and coarse-grained sand and 54.2% was fine-grained sand. Our analyses of the bathymetric and acoustic backscatter data demonstrates that during the 6 months between surveys, 11.4% of the study area was buried by fine-grained sand while erosion resulted in the exposure of bedrock or coarse-grained sand over 26.5% of the study area. The probability of burial decreased with increasing water depth and rugosity; the probability of exhumation increased with increasing wave-induced near-bed shear stress, seabed slope and rugosity. Much of the detected change was at the boundary between bedrock and unconsolidated sediment due to sedimentation and erosion burying or exhuming bedrock, respectively. In a number of cases, however, the change in seabed character was apparently due to changes in sediment grain size when scour exposed what appeared to be an underlying coarser-grained lag or the burial of coarser-grained sand and gravel by fine-grained sand. These findings suggest that, in some places, (a) burial and exhumation of nearshore bedrock reefs along rocky, energetic inner shelves occurs over seasonal timescales and appears related to intrinsic factors such as seabed morphology and extrinsic factors such as wave forces, and (b) single acoustic surveys typically employed for geologic characterization and/or habitat mapping may not adequately characterize the geomorphologic and sedimentologic nature of these types of environments that typify most of the Pacific Ocean and up to 50% of the world's coastlines.

  16. Intermediate conditions: The Goldilocks hypothesis defines sediment transport processes and pothole forms in bedrock streams

    NASA Astrophysics Data System (ADS)

    Goode, J.; Wohl, E. E.; Buffington, J. M.; Yager, E. M.

    2012-12-01

    Recent studies suggest that unique attributes of bedrock rivers (bedforms, sculpted forms, variation in alluvial patches) limit the extent to which sediment transport equations, developed for alluvial rivers, can be applied in bedrock streams. Without accurate prediction of sediment transport processes in these systems, fluvial incision models that parameterize incision via abrasion are insufficient. Potholes are noted features of enhanced local incision and sediment accumulation in many bedrock rivers. A detailed understanding of pothole erosion can thereby contribute to better parameterization of incision models for bedrock streams. We provide field evidence from the Ocoee River, TN for a feedback relationship between incision via potholes, bedrock bedforms, and sediment cover, invoking the tools vs. cover relationship in the vertical dimension. In all four stream reaches, the likelihood of pothole occurrence tends to be greatest at intermediate bed elevations, suggesting that channel hydraulics, tools, and erosion are optimized in these locations. In contrast, sediment tends to accumulate at lower elevations, oversupplying tools and effectively "shutting off" incision within potholes; at higher elevation, flow contraction and acceleration do not allow for tools to accumulate and abrade bedrock surfaces. We link our field observations to results from flume experiments, which suggest that sediment mobility within potholes is maximized by the combination of intermediate sediment fill volumes (expressed as a percentage of total pothole volume) and intermediate reach-averaged hydraulics (expressed non-dimensionally using the Froude number). The Froude number in the flume experiments provides a surrogate for the local hydraulics implicated as a factor in pothole formation at intermediate bed elevations in the field. Although complex bedrock bed topography, roughness and resulting turbulent flow patterns affect sediment mobility and incision in bedrock streams, results

  17. Application of shuttle imaging radar to geologic mapping

    NASA Technical Reports Server (NTRS)

    Labotka, T. C.

    1986-01-01

    Images from the Shuttle Imaging Radar - B (SIR-B) experiment covering the area of the Panamint Mountains, Death Valley, California, were examined in the field and in the laboratory to determine their usefulness as aids for geologic mapping. The covered area includes the region around Wildrose Canyon where rocks ranging in age from Precambrian to Cenozoic form a moderately rugged portion of the Panamint Mountains, including sharp ridges, broad alluviated upland valleys, and fault-bounded grabens. The results of the study indicate that the available SIR-B images of this area primarily illustrate variations in topography, except in the broadly alluviated areas of Panamint Valley and Death Valley where deposits of differing reflectivity can be recognized. Within the mountainous portion of the region, three textures can be discerned, each representing a different mode of topographic expression related to the erosion characteristics of the underlying bedrock. Regions of Precambrian bedrock have smooth slopes and sharp ridges with a low density of gullies. Tertiary monolithologic breccias have smooth, steep slopes with an intermediate density of gullies with rounded ridges. Tertiary fanglomerates have steep rugged slopes with numerous steep-sided gullies and knife-sharp ridges. The three topographic types reflect the consistancy and relative susceptibility to erosion of the bedrock; the three types can readily be recognized on topographic maps. At present, it has not been possible to distinguish on the SIR-B image of the mountainous terrain the type of bedrock, independent of the topographic expression.

  18. Testing bedrock incision models: Holocene channel evolution, High Cascades, Oregon

    NASA Astrophysics Data System (ADS)

    Sweeney, K. E.; Roering, J. J.; Fonstad, M. A.

    2013-12-01

    There is abundant field evidence that sediment supply controls the incision of bedrock channels by both protecting the bed from incision and providing tools to incise the bed. Despite several theoretical models for sediment-dependent bedrock abrasion, many investigations of natural channel response to climatic, lithologic, or tectonic forcing rely on the stream power model, which does not consider the role of sediment. Here, we use a well-constrained fluvial channel cut into a Holocene lava flow in the High Cascades, Oregon to compare incision predictions of the stream power model and of the full physics of theoretical models for saltation-abrasion incision by bedload and suspended load. The blocky andesite of Collier lava flow erupted from Collier Cone ~1500 years ago, paving over the existing landscape and erasing fine-scale landscape dissection. Since the eruption, a 6 km stream channel has been incised into the lava flow. The channel is comprised of three alluvial reaches with sediment deposits up to 2 m thick and two bedrock gorges with incision of up to 8 m, with larger magnitude incision in the upstream gorge. Abraded forms such as flutes are present in both gorges. Given the low magnitude and duration of modern snowmelt flow in the channel, it is likely that much of the incision was driven by sediment-laden outburst floods from the terminus of Collier Glacier, which is situated just upstream of the lava flow and has produced two outburst floods in the past 100 years. This site is well suited for comparing incision models because of the relatively uniform lithology of the lava flow and our ability to constrain the timing and depth of incision using the undissected lava surface above the channel as an initial condition. Using a simple finite difference scheme with airborne-Lidar-derived pre-incision topography as an initial condition, we predict incision in the two gorges through time with both stream power and sediment-dependent models. Field observations

  19. On the reliability of manually produced bedrock lineament maps

    NASA Astrophysics Data System (ADS)

    Scheiber, Thomas; Viola, Giulio; Fredin, Ola; Jarna, Alexandra; Gasser, Deta; Łapinska-Viola, Renata

    2016-04-01

    Manual extraction of topographic features from digital elevation models (DEMs) is a commonly used technique to produce lineament maps of fractured basement areas. There are, however, several sources of bias which can influence the results. In this study we investigated the influence of the factors (a) scale, (b) illumination azimuth and (c) operator on remote sensing results by using a LiDAR (Light Detection and Ranging) DEM of a fractured bedrock terrain located in SW Norway. Six operators with different backgrounds in Earth sciences and remote sensing techniques mapped the same LiDAR DEM at three different scales and illuminated from three different directions. This resulted in a total of 54 lineament maps which were compared on the basis of number, length and orientation of the drawn lineaments. The maps show considerable output variability depending on the three investigated factors. In detail: (1) at larger scales, the number of lineaments drawn increases, the line lengths generally decrease, and the orientation variability increases; (2) Linear features oriented perpendicular to the source of illumination are preferentially enhanced; (3) The reproducibility among the different operators is generally poor. Each operator has a personal mapping style and his/her own perception of what is a lineament. Consequently, we question the reliability of manually produced bedrock lineament maps drawn by one person only and suggest the following approach: In every lineament mapping study it is important to define clear mapping goals and design the project accordingly. Care should be taken to find the appropriate mapping scale and to establish the ideal illumination azimuths so that important trends are not underrepresented. In a remote sensing project with several persons included, an agreement should be reached on a given common view on the data, which can be achieved by the mapping of a small test area. The operators should be aware of the human perception bias. Finally

  20. Geologic information from satellite images. [geological interpretation of ERTS-1 and Skylab multispectral photography of Rocky Mountain areas

    NASA Technical Reports Server (NTRS)

    Lee, K.; Knepper, D. H., Jr. (Principal Investigator); Sawatzky, D. L.

    1974-01-01

    The author has identified the following significant results. Extracting geologic information from ERTS and Skylab/EREP images is best done by a geologist trained in photointerpretation. The information is at a regional scale, and three basic types are available: rock and soil, geologic structures, and landforms. Discrimination between alluvium and sedimentary or crystalline bedrock, and between units in thick sedimentary sequences is best, primarily because of topographic expression and vegetation differences. Discrimination between crystalline rock types is poor. Folds and fractures are the best displayed geologic features. They are recognizable by topographic expression, drainage patterns, and rock or vegetation tonal patterns. Landforms are easily discriminated by their familar shapes and patterns. It is possible to optimize the scale, format, spectral bands, conditions of acquisition, and sensor systems for best geologic interpretation. Several examples demonstrate the applicability of satellite images to tectonic analysis and petroleum and mineral exploration.

  1. Sources of geologic and hydrologic information pertinent to ground-water resources in Rhode Island

    USGS Publications Warehouse

    Trench, Elaine C.

    1995-01-01

    This report summarizes sources of geologic and hydrologic information useful to water managers and others involved in the investigation, appraisal, development, and protection of ground-water resources in Rhode Island. The geographic scope of the report includes Rhode Island and small adjoining areas of Massachusetts and Connecticut, where drainage basins are shared with these States. The information summarized is found in maps and reports prepared by the U.S. Geological Survey and published by either the U.S. Geological Survey or by the State of Rhode Island. Information sources are presented in maps and tables. Reference maps show drainage divides, town lines, and the 7.5-minute grid of latitude and longitude for the State. Maps show availability of surficial geologic maps, bedrock geologic maps, and ground-water studies by 7.5-minute quadrangle, and show availability of ground-water studies by drainage basin, subbasin, and special study area. Sources of geologic and hydrologic information for the thirty-seven 7.5-minute quadrangles covering Rhode Island have been compiled based on the following information categories: surficial geology, bedrock geology, subsurface materials, altitude of bedrock surface, water-table altitudes, water-table contours, saturated thickness, hydraulic conductivity, transmissivity, drainage divides, recharge areas, ground-water reservoirs, induced infiltration, and ground-water quality. A table for each of the 37 quadrangles lists the major categories of information available for that quadrangle, provides references to the publications in which the information can be found, and indicates the format, scale, and other pertinent attributes of the information. A table organized by report series gives full citations for publications prepared by the U.S. Geological Survey pertaining to the geology and hydrology of Rhode Island. To facilitate location of information for particular municipalities, a table lists cities and towns in the State and

  2. Fluoride concentrations in a crystalline bedrock aquifer Marathon County, Wisconsin

    NASA Astrophysics Data System (ADS)

    Ozsvath, David L.

    2006-05-01

    Water samples from 2,789 private water-supply wells in Marathon County, Wisconsin reveal that fluoride concentrations in the crystalline bedrock range from <0.01 to 7.60 mg/L, with 0.6% of the values exceeding the Environmental Protection Agency’s (EPA’s) maximum contaminant level of 4 mg/L, and 8.6% exceeding the EPA’s secondary maximum contaminant level of 2.0 mg/L. Roughly a quarter of the wells contain dissolve fluoride within the range considered optimal for human health (between 0.5 and 1.5 mg/L), whereas 63.3% fall below 0.5 mg/L. Consistent with studies conducted in other regions, felsic rocks have significantly higher fluoride concentrations than mafic and metasedimentary rocks. Syenites yield the most fluoriferous groundwaters, but the highest median concentration occurs in a sodium-plagioclase granite. A relationship between plagioclase composition and fluoride concentrations suggests that dissolved fluoride levels are controlled by fluorite solubility and that higher fluoride concentrations are found in soft, sodium-rich groundwater.

  3. Vegetation and wildfire controls on sediment yield in bedrock landscapes

    NASA Astrophysics Data System (ADS)

    Dibiase, Roman A.; Lamb, Michael P.

    2013-03-01

    rocky landscapes commonly exhibit high sediment yields and are especially sensitive to climate, tectonics, and wildfire. Predicting landscape response to these perturbations demands a quantitative understanding of erosion processes. However, existing models for hillslope sediment production and transport do not apply to landscapes with patchy soil and slopes that exceed the angle for sediment stability. Here we present field measurements in southern California, USA, which indicate that sediment storage on steep slopes is enabled by vegetation that traps sediment upslope. We find that the storage capacity of unburned vegetation dams follows a geometric scaling model with a cubic dependence on effective plant width and an inverse dependence on local slope. Measured sediment volumes behind burned vegetation dams indicate a loss of at least 75% relative to unburned dams, and when expanded to the catchment scale, our measurements match records of postfire sediment yield from nearby retention basins. Contrary to existing models, our observations indicate that wildfire-induced sediment yield is driven by transient storage and release of sediment by vegetation dams, rather than increased bedrock-to-soil conversion rates. Without a feedback between soil production and wildfire, fire may play little role in long-term landscape evolution, and increasing fire frequency in response to climate change may not result in heightened sedimentation hazards due to supply limitations.

  4. Simulation of bedrock groundwater dynamics in a distributed rainfall-runoff model

    NASA Astrophysics Data System (ADS)

    Sayama, T.; Iwami, Y.; Kosugi, K.

    2014-12-01

    Recent field studies have shown that bedrock groundwater may play an important role to control the dynamics of the saturated subsurface flow in humid and steep mountainous regions. However many of existing hydrologic models typically assume impermeable bedrock and simulate saturated subsurface flow as a dominant runoff process. The objective of this study is to develop a simple groundwater model for mountainous bedrock aquifer incorporated to a distributed rainfall-runoff model to assess the importance of the bedrock groundwater for hydrologic simulations. The proposed model assumes the exponential-decline hydraulic conductivity in the bedrock to avoid defining the unknown bottom boundary. For the soil layer, it employs a stage-discharge relationship to simulate the unsaturated and saturated subsurface flows and surface flow. The developed model was applied to two Japanese catchments with weathered granite and sedimentary bedrock. We evaluated the simulation not only by the agreement with observed hydrographs but also in terms of the characteristics of their recessions and dynamic storage changes. Compared to the sedimentary rock catchment, the granite rock catchment showed stronger hysteresis in the recession and also dynamic storage change and discharge relationship estimated from the observed discharge. The original model with only surface soil layer failed to simulate these patterns, while the proposed model with groundwater component improved significantly the representation of the special patterns. Our study indicated the importance of bedrock groundwater for controlling lateral subsurface flow in particular the granite catchment we studied here.

  5. Uplift of the Transantarctic Mountains and the bedrock beneath the East Antarctic ice sheet

    USGS Publications Warehouse

    ten Brink, U.S.; Hackney, R.I.; Bannister, S.; Stern, T.A.; Makovsky, Y.

    1997-01-01

    In recent years the Transantarctic Mountains (TAM), the largest noncontractional mountain belt in the world, have become the focus of modelers who explained their uplift by a variety of isostatic and thermal mechanisms. A problem with these models is a lack of available data to compare with model predictions. We report here the results of a 312-km-long geophysical traverse conducted in 1993/1994 in the hinterland of the TAM. Using detailed subglacial topography and gravity measurements, we confirm the origin of the TAM as a flexural uplift of the edge of East Antarctica. Using an elastic model with a free edge, we can jointly fit the topography and the gravity with a plate having an elastic thickness of 85 ?? 15 km and a preuplift elevation of 700 ?? 50 m for East Antarctica. Using a variety of evidence, we argue that the uplift is coincident with a relatively minor tectonic event of transtensional motion between East and West Antarctica during the Eocene rather than the Late Cretaceous rifting event that created the Ross Embayment. We suggest that this transtensional motion caused the continuous plate to break, which created an escarpment that significantly increased the rates of erosion and exhumation. Results from the geophysical traverse also extend our knowledge of the bedrock geology from the exposures within the TAM to the ice covered interior. Our interpretation suggests that the Ferrar flood basalts extend at least 100 km westward under the ice. The Beacon Supergroup of Paleozoic and Mesozoic sediments thins gradually under the ice and its reconstructed thickness is reminiscent of profiles of foreland basins. Finally, there is no indication in the gravity field for an incomplete rebound due to significant melting of the East Antarctic ice sheet since the last glacial period.

  6. Isotopic Evidence for Microbial Activity in Crystalline Bedrock Fractures - a Case Study from Olkiluoto, SW Finland

    NASA Astrophysics Data System (ADS)

    Sahlstedt, E. K.; Karhu, J.; Pitkänen, P.

    2015-12-01

    Changes in the geochemical environment in crystalline bedrock fractures were investigated using the stable isotopes of C, O and S in fracture filling minerals as tracers. Of special interest were the possible changes which may occur in the subsurface at low temperatures. Especially, the influence of microbial activity was recognized as a catalyst for inducing changes in the geochemical environment. The study site is the Olkiluoto island located on the western coast of Finland, planned to host a geological repository for nuclear waste. Fracture surfaces were investigated to recognize the latest mineralizations at the site. These fillings were comprised of thin plates or small euhedral crystals of calcite and pyrite. The carbon and sulfur isotope compositions of calcite and pyrite were measured from bulk material by conventional IRMS, and in situ by secondary ion mass spectrometry. A notable feature of the late-stage fillings was high variabilities in the δ13C values of calcite and the δ34S values of pyrite, which ranged from -53.8 ‰ to +31.6 ‰ and from -50.4 ‰ to +77.7 ‰, respectively. Based on the isotopic compositions of the fillings, several features in the past hydrogeochemical environment could be recognized. The isotopic composition of the fracture fillings indicate an environment which was stratified with respect to depth. Characteristic features include bacterial sulfate reduction (BSR) occurring at depths <111 m (bsl), and a methanogenetic environment at depths >50 m. It appears that methanic conditions were replaced by sulfate reduction at depths >50 m likely due to infiltration of SO42--rich brackish waters. Sulfate reducing bacteria used mainly surface derived organic carbon as electron donors. Some indication of minor methanotrophic activity was recognized in anomalously low δ13C values of calcite, down to -53.8 ‰, at the depth range of 34-54 m. This methanotrophic activity may have been related to bacteria using CH4 as an electron donor in

  7. Interpreting tracer breakthrough tailing from different forced-gradient tracer experiment configurations in fractured bedrock

    USGS Publications Warehouse

    Becker, M.W.; Shapiro, A.M.

    2003-01-01

    Conceptual and mathematical models are presented that explain tracer breakthrough tailing in the absence of significant matrix diffusion. Model predictions are compared to field results from radially convergent, weak-dipole, and push-pull tracer experiments conducted in a saturated crystalline bedrock. The models are based upon the assumption that flow is highly channelized, that the mass of tracer in a channel is proportional to the cube of the mean channel aperture, and the mean transport time in the channel is related to the square of the mean channel aperture. These models predict the consistent -2 straight line power law slope observed in breakthrough from radially convergent and weak-dipole tracer experiments and the variable straight line power law slope observed in push-pull tracer experiments with varying injection volumes. The power law breakthrough slope is predicted in the absence of matrix diffusion. A comparison of tracer experiments in which the flow field was reversed to those in which it was not indicates that the apparent dispersion in the breakthrough curve is partially reversible. We hypothesize that the observed breakthrough tailing is due to a combination of local hydrodynamic dispersion, which always increases in the direction of fluid velocity, and heterogeneous advection, which is partially reversed when the flow field is reversed. In spite of our attempt to account for heterogeneous advection using a multipath approach, a much smaller estimate of hydrodynamic dispersivity was obtained from push-pull experiments than from radially convergent or weak dipole experiments. These results suggest that although we can explain breakthrough tailing as an advective phenomenon, we cannot ignore the relationship between hydrodynamic dispersion and flow field geometry at this site. The design of the tracer experiment can severely impact the estimation of hydrodynamic dispersion and matrix diffusion in highly heterogeneous geologic media.

  8. Old Geology and New Geology

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 28 May 2003

    Mangala Vallis one of the large outflow channels that channeled large quantities of water into the northern lowlands, long ago on geological timescales. This valley is one of the few in the southern hemisphere, as well as one of the few west of the Tharsis bulge. A closer look at the channel shows more recent weathering of the old water channel: the walls of the channel show small, dark slope streaks that form in dusty areas; and much of the surrounding terrain has subtle linear markings trending from the upper left to the lower right, which are probably features sculpted and streamlined by the wind. Geology still shapes the surface of Mars today, but its methods over the eons have changed.

    Image information: VIS instrument. Latitude -6, Longitude 209.6 East (150.4 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in

  9. A bottom-up control on fresh-bedrock topography under landscapes

    PubMed Central

    Rempe, Daniella M.; Dietrich, William E.

    2014-01-01

    The depth to unweathered bedrock beneath landscapes influences subsurface runoff paths, erosional processes, moisture availability to biota, and water flux to the atmosphere. Here we propose a quantitative model to predict the vertical extent of weathered rock underlying soil-mantled hillslopes. We hypothesize that once fresh bedrock, saturated with nearly stagnant fluid, is advected into the near surface through uplift and erosion, channel incision produces a lateral head gradient within the fresh bedrock inducing drainage toward the channel. Drainage of the fresh bedrock causes weathering through drying and permits the introduction of atmospheric and biotically controlled acids and oxidants such that the boundary between weathered and unweathered bedrock is set by the uppermost elevation of undrained fresh bedrock, Zb. The slow drainage of fresh bedrock exerts a “bottom up” control on the advance of the weathering front. The thickness of the weathered zone is calculated as the difference between the predicted topographic surface profile (driven by erosion) and the predicted groundwater profile (driven by drainage of fresh bedrock). For the steady-state, soil-mantled case, a coupled analytical solution arises in which both profiles are driven by channel incision. The model predicts a thickening of the weathered zone upslope and, consequently, a progressive upslope increase in the residence time of bedrock in the weathered zone. Two nondimensional numbers corresponding to the mean hillslope gradient and mean groundwater-table gradient emerge and their ratio defines the proportion of the hillslope relief that is unweathered. Field data from three field sites are consistent with model predictions. PMID:24760824

  10. Finite Amplitude Bars in Mixed Bedrock-Alluvial River Channel Bends

    NASA Astrophysics Data System (ADS)

    Nelson, P. A.; Seminara, G.; Bolla Pittaluga, M.

    2012-12-01

    A common and well-understood feature of alluvial rivers is the tendency for channel curvature to induce bed deformations, producing a point bar on the inner bank and scour on the outer bank. However, for mixed bedrock-alluvial rivers, where the amount of sediment supplied from upstream is less than the local sediment transport capacity, our understanding of this phenomenon is less clear. Our goal here is to develop a theory capable of answering the question: How does channel curvature influence sediment deposition and bedrock exposure in mixed bedrock-alluvial rivers? We have developed a nonlinear asymptotic theory of fully developed flow and bed topography in a wide channel of constant curvature to describe finite-amplitude perturbations of bottom topography, subject to an inerodible bedrock layer. The flow field is evaluated at leading order of approximation as a slowly varying sequence of locally uniform flows, slightly perturbed by a weak curvature-induced secondary flow. Using the constraint of constant fluid discharge, we calculate an analytical solution for the cross-sectional profile of flow depth and bed topography, and we determine the average slope in the bend necessary to transport the sediment supplied from a straight, alluvial, upstream reach. Both fully-alluvial bends and bends with partial bedrock exposure are shown to require a larger average slope than a straight upstream reach; the relative slope increase is much larger for partially alluviated bends. Curvature has a strong effect on the characteristics of the point bars in mixed bedrock-alluvial channels, with higher curvature bends exhibiting bars of larger amplitude and more bedrock exposure through the cross section. Differences in the relative roughness of sediment and bedrock have a smaller, secondary effect on point bar characteristics. This theory can potentially be extended to the not fully developed case, and should ultimately lead to an improved understanding of the formation of

  11. A bottom-up control on fresh-bedrock topography under landscapes.

    PubMed

    Rempe, Daniella M; Dietrich, William E

    2014-05-01

    The depth to unweathered bedrock beneath landscapes influences subsurface runoff paths, erosional processes, moisture availability to biota, and water flux to the atmosphere. Here we propose a quantitative model to predict the vertical extent of weathered rock underlying soil-mantled hillslopes. We hypothesize that once fresh bedrock, saturated with nearly stagnant fluid, is advected into the near surface through uplift and erosion, channel incision produces a lateral head gradient within the fresh bedrock inducing drainage toward the channel. Drainage of the fresh bedrock causes weathering through drying and permits the introduction of atmospheric and biotically controlled acids and oxidants such that the boundary between weathered and unweathered bedrock is set by the uppermost elevation of undrained fresh bedrock, Zb. The slow drainage of fresh bedrock exerts a "bottom up" control on the advance of the weathering front. The thickness of the weathered zone is calculated as the difference between the predicted topographic surface profile (driven by erosion) and the predicted groundwater profile (driven by drainage of fresh bedrock). For the steady-state, soil-mantled case, a coupled analytical solution arises in which both profiles are driven by channel incision. The model predicts a thickening of the weathered zone upslope and, consequently, a progressive upslope increase in the residence time of bedrock in the weathered zone. Two nondimensional numbers corresponding to the mean hillslope gradient and mean groundwater-table gradient emerge and their ratio defines the proportion of the hillslope relief that is unweathered. Field data from three field sites are consistent with model predictions. PMID:24760824

  12. Geohydrology of bedrock aquifers in the Northern Great Plains in parts of Montana, North Dakota, South Dakota, and Wyoming

    USGS Publications Warehouse

    Downey, J.S.

    1986-01-01

    Rocks of Paleozoic and Mesozoic age underlie the entire northern Great Plains of the United States. These rocks form 5 artesian aquifer systems that are recharged in the mountainous areas of Montana, South Dakota, and Wyoming and extend more than 600 miles to discharge areas in the northeastern part of North Dakota and in the Canadian Province of Manitoba. Generally, the principal direction of flow in each aquifer is deflected to the north and south around the Williston basin. Flow through the Williston basin is restricted because of geologic structure, and decreased permeability of rocks in the deeper parts of the basin. Major fracture systems or lineaments traverse the geologic section and are either vertical or horizontal conduits, or barriers to, groundwater flow. Vertical leakage from the aquifers is restricted by shale of minimal permeability, halite beds, and stratigraphic traps or minimal-permeability zones associated with petroleum accumulations. Interaquifer leakage appears to occur through and along some of the major lineaments. During the Pleistocene Epoch, thick ice sheets completely covered the discharge areas of the bedrock aquifers. This effectively blocked flow northeastward from the system and, at some locations, it may have caused a reversal of flow. The existing flow, system therefore, may not have reached hydrologic equilibrium with the stress of the last glacial period. (USGS)

  13. Land-Surface Subsidence and Open Bedrock Fractures in the Tully Valley, Onondaga County, New York

    USGS Publications Warehouse

    Hackett, William R.; Gleason, Gayle C.; Kappel, William M.

    2009-01-01

    Open bedrock fractures were mapped in and near two brine field areas in Tully Valley, New York. More than 400 open fractures and closed joints were mapped for dimension, orientation, and distribution along the east and west valley walls adjacent to two former brine fields. The bedrock fractures are as much as 2 feet wide and over 50 feet deep, while linear depressions in the soil, which are 3 to 10 feet wide and 3 to 6 feet deep, indicate the presence of open bedrock fractures below the soil. The fractures are probably the result of solution mining of halite deposits about 1,200 feet below the land surface.

  14. Gravity survey and depth to bedrock in Carson Valley, Nevada-California

    USGS Publications Warehouse

    Maurer, D.K.

    1985-01-01

    Gravity data were obtained from 460 stations in Carson Valley, Nevada and California. The data have been interpreted to obtain a map of approximate depth to bedrock for use in a ground-water model of the valley. This map delineates the shape of the alluvium-filled basin and shows that the maximum depth to bedrock exceeds 5,000 feet, on the west side of the valley. A north-south trending offset in the bedrock surface shows that the Carson-Valley/Pine-Nut-Mountain block has not been tilted to the west as a simple unit, but is comprised of several smaller blocks. (USGS)

  15. Geologic map of the greater Denver area, Front Range urban corridor, Colorado

    USGS Publications Warehouse

    Trimble, Donald E.; Machette, Michael N.

    1979-01-01

    This digital map shows the areal extent of surficial deposits and rock stratigraphic units (formations) as compiled by Trimble and Machette from 1973 to 1977 and published in 1979 under the Front Range Urban Corridor Geology Program. Trimble and Machette compiled their geologic map from published geologic maps and unpublished geologic mapping having varied map unit schemes. A convenient feature of the compiled map is its uniform classification of geologic units that mostly matches those of companion maps to the north (USGS I-855-G) and to the south (USGS I-857-F). Published as a color paper map, the Trimble and Machette map was intended for land-use planning in the Front Range Urban Corridor. This map recently (1997-1999) was digitized under the USGS Front Range Infrastructure Resources Project. In general, the mountainous areas in the western part of the map exhibit various igneous and metamorphic bedrock units of Precambrian age, major faults, and fault brecciation zones at the east margin (5-20 km wide) of the Front Range. The eastern and central parts of the map (Colorado Piedmont) depict a mantle of unconsolidated deposits of Quaternary age and interspersed outcroppings of Cretaceous or Tertiary-Cretaceous sedimentary bedrock. The Quaternary mantle comprises eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and a few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone, shale, and limestone bedrock formations form hogbacks and intervening valleys.

  16. Reach-Scale Channel Adjustments to Channel Network Geometry in Mountain Bedrock Streams

    NASA Astrophysics Data System (ADS)

    Plitzuweit, S. J.; Springer, G. S.

    2008-12-01

    surveys in order to analyze whether stream power and shear stress are adjusted to reflect CNG at the reach- scale. These models are compared to those with discharges calculated using drainage area and precipitation totals alone. We conclude that gradients in bedrock mountain streams may reflect basin-scale hydrology (CNG) and not simply local geological or geomorphic factors. This challenges the conclusions of others who ascribe local channel adjustments to: i) lithology and structure alone, or ii) local colluvium grain sizes.

  17. Geologic map database of the El Mirage Lake area, San Bernardino and Los Angeles Counties, California

    USGS Publications Warehouse

    Miller, David M.; Bedford, David R.

    2000-01-01

    This geologic map database for the El Mirage Lake area describes geologic materials for the dry lake, parts of the adjacent Shadow Mountains and Adobe Mountain, and much of the piedmont extending south from the lake upward toward the San Gabriel Mountains. This area lies within the western Mojave Desert of San Bernardino and Los Angeles Counties, southeastern California. The area is traversed by a few paved highways that service the community of El Mirage, and by numerous dirt roads that lead to outlying properties. An off-highway vehicle area established by the Bureau of Land Management encompasses the dry lake and much of the land north and east of the lake. The physiography of the area consists of the dry lake, flanking mud and sand flats and alluvial piedmonts, and a few sharp craggy mountains. This digital geologic map database, intended for use at 1:24,000-scale, describes and portrays the rock units and surficial deposits of the El Mirage Lake area. The map database was prepared to aid in a water-resource assessment of the area by providing surface geologic information with which deepergroundwater-bearing units may be understood. The area mapped covers the Shadow Mountains SE and parts of the Shadow Mountains, Adobe Mountain, and El Mirage 7.5-minute quadrangles. The map includes detailed geology of surface and bedrock deposits, which represent a significant update from previous bedrock geologic maps by Dibblee (1960) and Troxel and Gunderson (1970), and the surficial geologic map of Ponti and Burke (1980); it incorporates a fringe of the detailed bedrock mapping in the Shadow Mountains by Martin (1992). The map data were assembled as a digital database using ARC/INFO to enable wider applications than traditional paper-product geologic maps and to provide for efficient meshing with other digital data bases prepared by the U.S. Geological Survey's Southern California Areal Mapping Project.

  18. Geologic Technician New Curriculum

    ERIC Educational Resources Information Center

    Karp, Stanley E.

    1970-01-01

    Describes a developing two-year geologic technician program at Bakersfield College in which a student may major in five areas - geologic drafting, land and legal, geologic assistant, engineering or paleontology. (RR)

  19. Estimating the Bedrock Topography of the Gangotri Glacier in India

    NASA Astrophysics Data System (ADS)

    Gantayat, P.; Kulkarni, A. V.; Srinivasan, J.

    2014-12-01

    Himalayan glaciers make useful contribution in the runoff of many rivers in South Asia. Knowledge of depth and bottom topography is useful in understanding future distribution of glaciers; the evolution of periglacial morphology and the subglacial drainage pattern. In this investigation, we have estimated the bedrock topography of Gangotri glacier which is located in the Indian part of Central Himalayas. The Gangotri glacier is one of the largest glaciers and has an areal extent of around 140 Km2.It is considered traditionally to be the source of River Ganges which is one of the main source of water for a large population living in the Indo-Gangetic plains. The bottom topography was estimated using the ice thickness and surface elevation. Ice thickness was estimated using an ice flow model, surface velocities and slope. Surface velocities were estimated using sub-pixel correlation of Landsat TM and ETM+ imagery for the years 2009 and 2010. The velocities that were estimated ranged from 14-85 m/a in the upper reaches to 20-30 m/a near the snout. The surface elevation was estimated using ASTER DEM and varied from ~4100 m near the snout to ~6600 m in the upper reaches. The combination of surface elevation and depth was used to estimate spatial distribution of bottom topography. The estimated bottom topography varies from ~3900 to 6100 masl and also shows number of depressions as deep as 50-100m. These depressions are potential sites for the formation of periglacial lakes, influencing future retreat and security of the region.

  20. Characterization of Fracture and Matrix Flow within Bedrock Aquifers

    NASA Astrophysics Data System (ADS)

    West, A. C.; Novakowski, K. S.

    2006-12-01

    This article describes new methods for the characterization of fractured bedrock aquifers and, via their application to a set of field data collected at Smithville, Ontario, Canada, provides new insight into the nature of fracture versus matrix flow in rock. Two complementary Maximum Likelihood methods are developed that provide log-normal parameter estimates from borehole measurements of interval transmissivities. The methods are tested using the Monte Carlo method based on interval transmissivities simulated from the properties of specified fracture populations. The first method was shown to estimate the transmissivity distribution of the most transmissive fractures from among the population at a user-specified scale (the inverse of the density of the Poisson Point Process assumed to describe their locations along the borehole), while the second method was shown to estimate sums of the transmissivities of the remaining fractures. The properties of the first method were shown to resolve certain difficulties resulting from the use of existing methods for both the analysis and design of fixed-interval length hydraulic testing programs, while the properties of the two complementary methods together provide tractable definitions for fracture versus matrix flow. Expressions for aquifer hydraulic conductivity and average linear groundwater velocity per unit hydraulic gradient are developed in terms of the fracture set scale parameter, the log-normal parameter estimates for the fractures transmissivity, and log-normal parameter estimates for the matrix interval transmissivity. Estimation accuracy for these important quantities is shown to be optimal for a moderately-heavy-tailed distribution for the fracture population transmissivities. It is pointed out that the job of drilling-geologists during core logging and analysts of hydraulic test data is one and the same. That is, to determine at what scale and with what physical properties such a fracture set exists.

  1. Groundwater chemistry of a nuclear waste reposoitory in granite bedrock

    SciTech Connect

    Rydberg, J.

    1981-09-01

    This report concerns the prediction of the maximum dissolution rate for nuclear waste stored in the ground. That information is essential in judging the safety of a nuclear waste repository. With a limited groundwater flow, the maximum dissolution rate coincides with the maximum solubility. After considering the formation and composition of deep granite bedrock groundwater, the report discusses the maximum solubility in such groundwater of canister materials, matrix materials and waste elements. The parameters considered are pH, Eh and complex formation. The use of potential-pH (Pourbaix) diagrams is stressed; several appendixes are included to help in analyzing such diagrams. It is repeatedly found that desirable basic information on solution chemistry is lacking, and an international cooperative research effort is recommended. The report particularly stresses the lack of reliable data about complex formation and hydrolysis of the actinides. The Swedish Nuclear Fuel Safety (KBS) study has been used as a reference model. Notwithstanding the lack of reliable chemical data, particularly for the actinides and some fission products, a number of essential conclusions can be drawn about the waste handling model chosen by KBS. (1) Copper seems to be highly resistant to groundwater corrosion. (2) Lead and titanium are also resistant to groundwater, but inferior to copper. (3) Iron is not a suitable canister material. (4) Alumina (Al/sub 2/O/sub 3/) is not a suitable canister material if groundwater pH goes up to or above 10. Alumina is superior to copper at pH < 9, if there is a risk of the groundwater becoming oxidizing. (5) The addition of vivianite (ferrous phosphate) to the clay backfill around the waste canisters improves the corrosion resistance of the metal canisters, and reduces the solubility of many important waste elements. This report does not treat the migration of dissolved species through the rock.

  2. Soil phosphate stable oxygen isotopes across rainfall and bedrock gradients.

    PubMed

    Angert, Alon; Weiner, Tal; Mazeh, Shunit; Sternberg, Marcelo

    2012-02-21

    The stable oxygen isotope compositions of soil phosphate (δ(18)O(p)) were suggested recently to be a tracer of phosphorus cycling in soils and plants. Here we present a survey of bioavailable (resin-extractable or resin-P) inorganic phosphate δ(18)O(p) across natural and experimental rainfall gradients, and across soil formed on sedimentary and igneous bedrock. In addition, we analyzed the soil HCl-extractable inorganic δ(18)O(p), which mainly represents calcium-bound inorganic phosphate. The resin-P values were in the range 14.5-21.2‰. A similar range, 15.6-21.3‰, was found for the HCl-extractable inorganic δ(18)O(p), with the exception of samples from a soil of igneous origin that show lower values, 8.2-10.9‰, which indicate that a large fraction of the inorganic phosphate in this soil is still in the form of a primary mineral. The available-P δ(18)O(p) values are considerably higher than the values we calculated for extracellular hydrolysis of organic phosphate, based on the known fractionation from lab experiments. However, these values are close to the values expected for enzymatic-mediated phosphate equilibration with soil-water. The possible processes that can explain this observation are (1) extracellular equilibration of the inorganic phosphate in the soil; (2) fractionations in the soil are different than the ones measured at the lab; (3) effect of fractionation during uptake; and (4) a flux of intercellular-equilibrated inorganic phosphate from the soil microbiota, which is considerably larger than the flux of hydrolyzed organic-P. PMID:22243529

  3. A lithology-based model for 87Sr/86Sr values of bedrock and water in the conterminous US

    NASA Astrophysics Data System (ADS)

    Bataille, C. P.; Bowen, G. J.

    2010-12-01

    Although variation in 87Sr/86Sr has been widely pursued as a tracer of provenance in environmental studies, forensics, archeology and food traceability, accurate models of the large-scale variation in environmental 87Sr/86Sr are not available. In this paper, we build upon earlier efforts to model 87Sr/86Sr in the USA bedrock by considering the effects of lithological variation on rock and surface water. For each major group of rock, we developed combined theoretical/empirical equations describing variations of 87Sr/86Sr as a function of lithology and time and fitted the parameters to a global database of rock 87Sr/86Sr (GEOROCK-Start). Marine carbonates were modeled separately based on the work of Shield and Veizer, 2002. Evaluated relative to 300 rock Sr isotope data from the USA, the new model explains 74% of the Sr isotope variance and closely matches the real value with a standard deviation of 0.0018. In comparison, the earlier model describes 34% of the variance in the same dataset with a standard deviation 0.0039. We developed a second model to predict the Sr isotopic composition of river waters based on bedrock, but also considering differential weathering rates and strontium concentration (GEOROCK_start) for different kind of rock. The results demonstrate that the water model is necessary to account for the effect of carbonates and/or differential weathering rate of Sr-rich rock in many watersheds. In addition, it illustrates a strong linear correlation between the water model and surface water in most of the watersheds. However, in order to accurately predict surface water values, it is also necessary to account for surficial geology and local deposition phenomenon.

  4. Faulting and erosion in the Argentine Precordillera during changes in subduction regime: Reconciling bedrock cooling and detrital records

    NASA Astrophysics Data System (ADS)

    Fosdick, Julie C.; Carrapa, Barbara; Ortíz, Gustavo

    2015-12-01

    The Argentine Precordillera is an archetypal retroarc fold-and-thrust belt that records tectonics associated with changing subduction regimes. The interactions between exhumation and faulting in the Precordillera were investigated using apatite and zircon (U-Th-Sm)/He and apatite fission track thermochronometry from the Precordillera and adjacent geologic domains. Inverse modeling of thermal histories constrains eastward in-sequence rock cooling associated with deformation and erosion from 18 to 2 Ma across the Central Precordillera tracking thrusting during this time. The youngest AHe ages (5-2 Ma) and highest erosion rates are located in the eastern and western extremities of the Precordillera and indicate that recent denudation is concentrated at its structural boundaries. Moreover, synchronous rapid Pliocene cooling of the Frontal Cordillera, Eastern Precordillera, and Sierra del Valle Fértil was coeval with initiation of basement-involved faulting in the foreland. Detrital zircon U-Pb geochronology from the ca. 16-8.1 Ma Bermejo foreland basin strata suggests fluvial connectivity westward beyond the Frontal Cordillera to the Main Cordillera and Coast Range followed by an important shift in sediment provenance at ca. 10 Ma. At this time, we suggest that a substantial decrease in Permo-Triassic igneous sources in the Frontal Cordillera and concurrent increase in recycled zircons signatures of Paleozoic strata are best explained by uplift and erosion of the Precordillera during widening of the thrust-belt. Bedrock thermochronology and modeling indicate a 2-6 Myr lag time between faulting-related cooling in the hinterland and the detrital record of deformation in the foreland basin, suggesting that for tectonically active semi-arid settings, bedrock cooling may be more sensitive to onset of faulting. We suggest that high erosion rates in the Frontal Cordillera and Eastern Precordillera are associated with increased interplate coupling during shallowing of the

  5. Graffiti for science: Qualitative detection of erosional patterns through bedrock erosion painting

    NASA Astrophysics Data System (ADS)

    Beer, Alexander R.; Kirchner, James W.; Turowski, Jens M.

    2016-04-01

    Bedrock erosion is a crucial constraint on stream channel incision, and hence whole landscape evolution, in steep mountainous terrain and tectonically active regions. Several interacting processes lead to bedrock erosion in stream channels, with hydraulic shear detachment, plucking, and abrasion due to sediment impacts generally being the most efficient. Bedrock topography, together with the sediment tools and cover effects, regulate the rate and spatial pattern of in situ surface change. Measurements of natural bedrock erosion rates are valuable for understanding the underlying process physics, as well as for modelling landscape evolution and designing engineered structures. However, quantifying spatially distributed bedrock erosion rates in natural settings is challenging and few such measurements exist. We studied spatial bedrock erosion in a 30m-long bedrock gorge in the Gornera, a glacial meltwater stream above Zermatt. This stream is flushed episodically with sediment-laden streamflow due to hydropower operations upstream, with negligible discharge in the gorge in between these flushing events. We coated several bedrock surface patches with environmentally safe, and water-insoluble outdoor paint to document the spatial pattern of surface abrasion, or to be more precise, to document its driving forces. During four consecutive years, the change of the painted areas was recorded repeatedly with photographs before the painting was renewed. These photographs visually documented the spatial patterns of vertical erosion (channel incision), of lateral erosion (channel widening) and of downstream-directed erosion (channel clearance). The observed qualitative patterns were verified through comparison to quantitative change detection analyses based on annual high-resolution terrestrial laser scanning surveys of the bedrock surfaces. Comparison of repeated photographs indicated a temporal cover effect and a general height limit of the tools effect above the streambed

  6. Geologic map of the Lower Grand Wash cliffs and vicinity, Mohave County, Northwestern Arizona

    USGS Publications Warehouse

    Billingsley, George H.; Beard, L. Sue; Priest, Susan S.; Wellmeyer, Jessica L.; Block, Debra L.

    2004-01-01

    This digital map database is compiled from unpublished data and new mapping by the authors and represents the general distribution of surficial and bedrock geology in the mapped area. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the area. The database dilineates map units that are identified by age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution of the database to 1:31,680 or smaller.

  7. Geologic Map of the House Rock Quadrangle, Coconino County, Northern Arizona

    USGS Publications Warehouse

    Billingsley, George H.; Wellmeyer, Jessica L.; Block, Debra L.

    2001-01-01

    This digital map database is compiled from unpublished data and new mapping by the authors, represents the general distribution of surficial and bedrock geology in the mapped area. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the area. The database dilineate map units that are identified by age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution of the database to 1:24,000 or smaller.

  8. Geologic Map of the House Rock Spring Quadrangle, Coconino County, Northern Arizona

    USGS Publications Warehouse

    Billingsley, George H.; Hampton, Haydee M.

    2001-01-01

    This digital map database is compiled from unpublished data and new mapping by the authors, represents the general distribution of surficial and bedrock geology in the mapped area. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the area. The database delineate map units that are identified by age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution of the database to 1:24,000 or smaller.

  9. Geologic map of the Lower Hurricane Wash and vicinity, Mohave County, Northwestern Arizona

    USGS Publications Warehouse

    Billingsley, George H.; Graham, Scott E.

    2003-01-01

    This digital map database is compiled from published open file reports, and new mapping by the author, and represents the general distribution of surficial and bedrock geology in the mapped area. The map area lies within the Shivwits and Uinkaret Plateaus, subplateaus of the southwestern part of the Colorado Plateau hypsographic province. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the area. The database delineates map units that are identified by age and lithology, following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution of the database to 1:31,680 or smaller.

  10. Visible Geology - Interactive online geologic block modelling

    NASA Astrophysics Data System (ADS)

    Cockett, R.

    2012-12-01

    Geology is a highly visual science, and many disciplines require spatial awareness and manipulation. For example, interpreting cross-sections, geologic maps, or plotting data on a stereonet all require various levels of spatial abilities. These skills are often not focused on in undergraduate geoscience curricula and many students struggle with spatial relations, manipulations, and penetrative abilities (e.g. Titus & Horsman, 2009). A newly developed program, Visible Geology, allows for students to be introduced to many geologic concepts and spatial skills in a virtual environment. Visible Geology is a web-based, three-dimensional environment where students can create and interrogate their own geologic block models. The program begins with a blank model, users then add geologic beds (with custom thickness and color) and can add geologic deformation events like tilting, folding, and faulting. Additionally, simple intrusive dikes can be modelled, as well as unconformities. Students can also explore the interaction of geology with topography by drawing elevation contours to produce their own topographic models. Students can not only spatially manipulate their model, but can create cross-sections and boreholes to practice their visual penetrative abilities. Visible Geology is easy to access and use, with no downloads required, so it can be incorporated into current, paper-based, lab activities. Sample learning activities are being developed that target introductory and structural geology curricula with learning objectives such as relative geologic history, fault characterization, apparent dip and thickness, interference folding, and stereonet interpretation. Visible Geology provides a richly interactive, and immersive environment for students to explore geologic concepts and practice their spatial skills.; Screenshot of Visible Geology showing folding and faulting interactions on a ridge topography.

  11. Bedrock mapping of buried valley networks using seismic reflection and airborne electromagnetic data

    NASA Astrophysics Data System (ADS)

    Oldenborger, G. A.; Logan, C. E.; Hinton, M. J.; Pugin, A. J.-M.; Sapia, V.; Sharpe, D. R.; Russell, H. A. J.

    2016-05-01

    In glaciated terrain, buried valleys often host aquifers that are significant groundwater resources. However, given the range of scales, spatial complexity and depth of burial, buried valleys often remain undetected or insufficiently mapped. Accurate and thorough mapping of bedrock topography is a crucial step in detecting and delineating buried valleys and understanding formative valley processes. We develop a bedrock mapping procedure supported by the combination of seismic reflection data and helicopter time-domain electromagnetic data with water well records for the Spiritwood buried valley aquifer system in Manitoba, Canada. The limited spatial density of water well bedrock observations precludes complete depiction of the buried valley bedrock topography and renders the water well records alone inadequate for accurate hydrogeological model building. Instead, we leverage the complementary strengths of seismic reflection and airborne electromagnetic data for accurate local detection of the sediment-bedrock interface and for spatially extensive coverage, respectively. Seismic reflection data are used to define buried valley morphology in cross-section beneath survey lines distributed over a regional area. A 3D model of electrical conductivity is derived from inversion of the airborne electromagnetic data and used to extrapolate buried valley morphology over the entire survey area. A spatially variable assignment of the electrical conductivity at the bedrock surface is applied to different features of the buried valley morphology identified in the seismic cross-sections. Electrical conductivity is then used to guide construction of buried valley shapes between seismic sections. The 3D locus of points defining each morphological valley feature is constructed using a path optimization routine that utilizes deviation from the assigned electrical conductivities as the cost function. Our resulting map represents a bedrock surface of unprecedented detail with more

  12. Topographic roughness as a signature of the emergence of bedrock in eroding landscapes

    NASA Astrophysics Data System (ADS)

    Milodowski, D. T.; Mudd, S. M.; Mitchard, E. T. A.

    2015-10-01

    Rock is exposed at the Earth surface when rates of erosion locally exceed rates of soil production. The thinning of soils and emergence of bedrock has implications spanning geomorphology, ecology and hydrology. Soil-mantled hillslopes are typically shaped by diffusion-like sediment transport processes that act to smooth topography through time, generating the familiar smooth, convex hillslope profiles that are common in low relief landscapes. Other processes, however, can roughen the landscape. Bedrock emergence can produce rough terrain; in this contribution we exploit the contrast between rough patches of bedrock outcrop and smooth, diffusion-dominated soil to detect bedrock outcrops. Specifically, we demonstrate that the local variability of surface normal vectors, measured from 1 m resolution airborne LiDAR data, can be used as a topographic signature to identify areas within landscapes where rock exposure is present. We then use this roughness metric to investigate the transition from soil-mantled to bedrock hillslopes as erosion rates increase in two transient landscapes, Bald Rock Basin, which drains into the Middle Fork Feather River, California, and Harrington Creek, a tributary of the Salmon River, Idaho. Rather than being abrupt, as predicted by traditional soil production models, in both cases the transition from fully soil-mantled to bedrock hillslopes is gradual and spatially heterogeneous, with rapidly eroding hillslopes supporting a patchwork of bedrock and soil that is well documented by changes in topographic roughness, highlighting the utility of this metric for testing hypotheses concerning the emergence of bedrock and adding to a growing body of evidence that indicates the persistence of partial soil mantles in steep, rapidly eroding landscapes.

  13. Denitrification and dilution along fracture flowpaths influence the recovery of a bedrock aquifer from nitrate contamination.

    PubMed

    Kim, Jonathan J; Comstock, Jeff; Ryan, Peter; Heindel, Craig; Koenigsberger, Stephan

    2016-11-01

    In 2000, elevated nitrate concentrations ranging from 12 to 34mg/L NO3N were discovered in groundwater from numerous domestic bedrock wells adjacent to a large dairy farm in central Vermont. Long-term plots and contours of nitrate vs. time for bedrock wells showed "little/no", "moderate", and "large" change patterns that were spatially separable. The metasedimentary bedrock aquifer is strongly anisotropic and groundwater flow is controlled by fractures, bedding/foliation, and basins and ridges in the bedrock surface. Integration of the nitrate concentration vs. time data and the physical and chemical aquifer characterization suggest two nitrate sources: a point source emanating from a waste ravine and a non-point source that encompasses the surrounding fields. Once removed, the point source of NO3 (manure deposited in a ravine) was exhausted and NO3 dropped from 34mg/L to <10mg/L after ~10years; however, persistence of NO3 in the 3 to 8mg/L range (background) reflects the long term flux of nitrates from nutrients applied to the farm fields surrounding the ravine over the years predating and including this study. Inferred groundwater flow rates from the waste ravine to either moderate change wells in basin 2 or to the shallow bedrock zone beneath the large change wells are 0.05m/day, well within published bedrock aquifer flow rates. Enrichment of (15)N and (18)O in nitrate is consistent with lithotrophic denitrification of NO3 in the presence of dissolved Mn and Fe. Once the ravine point-source was removed, denitrification and dilution collectively were responsible for the down-gradient decrease of nitrate in this bedrock aquifer. Denitrification was most influential when NO3N was >10mg/L. Our multidisciplinary methods of aquifer characterization are applicable to groundwater contamination in any complexly-deformed and metamorphosed bedrock aquifer. PMID:27355518

  14. Abiotic controls of emergent macrophyte density in a bedrock channel - The Cahaba River, AL (USA)

    NASA Astrophysics Data System (ADS)

    Vaughn, Ryan S.; Davis, Lisa

    2015-10-01

    Research examining bedrock channels is growing. Despite this, biotic-abiotic interactions remain a topic mostly addressed in alluvial systems. This research identified hydrogeomorphic factors operating at the patch-scale (100-102 m) in bedrock shoals of the Cahaba River (AL) that help determine the distribution of the emergent aquatic macrophyte, Justicia americana. Macrophyte patch density (number of stems/m2) and percent bedrock void surface area (rock surface area/m2 occupied by joints, fractures, and potholes) were measured (n = 24 within two bedrock shoals) using stem counts and underwater photography, respectively. One-dimensional hydrologic modeling (HEC-RAS 4.1.0) was completed for a section within a shoal to examine velocity and channel depth as controlling variables for macrophyte patch density. Results from binary logistic regression analysis identified depth and velocity as good predictors of the presence or absence of Justicia americana within shoal structures (depth p = 0.001, velocity p = 0.007), which is a similar finding to previous research conducted in alluvial systems. Correlation analysis between bedrock surface void area and stem density demonstrated a statistically significant positive correlation (r = 0.665, p = 0.01), elucidating a link between abiotic-biotic processes that may well be unique to bedrock channels. These results suggest that the amount of void space present in bedrock surfaces, in addition to localized depth and velocity, helps control macrophyte patch density in bedrock shoal complexes. The utility of geomorphology in explaining patch-scale habitat heterogeneity in this study highlights geomorphology's potential to help understand macrophyte habitat heterogeneity at the reach scale, while also demonstrating its promise for mapping and understanding habitat heterogeneity at the system scale.

  15. Rate estimates for lateral bedrock erosion based on radiocarbon ages, Duck River, Tennessee

    SciTech Connect

    Brakenridge, G.R.

    1985-02-01

    Rates of bedrock erosion in ingrown meandering rivers can be inferred from the location of buried relict flood-plain and river-bank surfaces, associated paleosols, and radiocarbon dates. Two independent methods are used to evaluate the long-term rates of limestone bedrock erosion by the Duck River. Radiocarbon dates on samples retrieved from buried Holocene flood-plain and bank surfaces indicate lateral migration of the river bank at average rates of 0.6-1.9 m/100 yr. Such rates agree with lateral bedrock cliff erosion rates of 0.5-1.4 m/100 yr, as determined from a comparison of late Pleistocene and modern bedrock cliff and terrace scarp positions. These results show that lateral bedrock erosion by this river could have occurred coevally with flood-plain and terrace formation and that the resulting evolution of valley meander bends carved into bedrock is similar in many respects to that of channel meanders cut into alluvium. 11 references, 5 figures.

  16. Modeling of strategies for performance monitoring of groundwater contamination at sites underlain by fractured bedrock.

    PubMed

    Chen, Yaming; Smith, Leslie; Beckie, Roger

    2012-06-01

    A three dimensional flow and transport modeling using FRAC3DVS was undertaken to examine factors which influence plume detection in a performance monitoring network for a site where an unconfined aquifer composed of uniform unconsolidated sediments overlies fractured bedrock. The bedrock is assumed to contain a fracture system with three orthogonal fracture sets embedded in a low permeable homogeneous rock matrix. A dissolved phase, non-reactive contaminant is released from a source zone located at the ground surface. The processes which influence plume geometry, and probabilities of plume detection for a performance monitoring network located between the contaminant source and a downstream compliance boundary, are evaluated. Factors considered include the hydraulic conductivity of the unconfined aquifer, the geometric properties of the fracture network and the matrix permeability of the bedrock, and the contaminant detection threshold concentration. The simulations demonstrate that the character of the fracture network not only controls contaminant transport and plume detection in the bedrock but also influences plume detection in the overlying unconfined aquifer. The ratio of the hydraulic conductivity of the unconfined aquifer to the effective hydraulic conductivity of the fractured bedrock, and the contaminant detection threshold concentration, are principal factors influencing detection probability in the performance monitoring network. Results suggest that in many instances encountered in field practice, the unconfined aquifer and fractured bedrock should be viewed as an integrated hydrogeologic system from a monitoring perspective. PMID:22579666

  17. Effects of bedrock groundwater on landslide occurrences in a steep headwater catchment

    NASA Astrophysics Data System (ADS)

    Kosugi, K.; Fujimoto, M.; Sando, Y.; Mizuyama, T.; Kinoshita, A.

    2011-12-01

    Previous studies have shown that the formation of groundwater in the soil mantle greatly affects slope instability on steep landscapes. To predict landslides, mathematical models based on a geographic information system, which organize geographic data such as information on upslope contributing areas and the local slope gradient, have been developed and tested. Although such models can be used to calculate the topographically driven convergence of rainwater and groundwater table developments in the soil mantle, thus providing a spatially distributed prediction of landslide occurrences, the accuracy of these mathematical models is still limited, mainly because they ignore storm responses in underlying bedrock. Recent research has provided credible information on the importance of bedrock groundwater on surface hydrological processes in headwater catchments. To elucidate the effects of bedrock groundwater, the dynamics of bedrock groundwater should be measured directly. However, intensive monitoring of bedrock groundwater is rare in mountains with steep topography. Consequently, how bedrock groundwater controls landslides in a steep headwater catchment is in dispute. In this study, we conducted long-term hydrological observations using densely nested bedrock wells along with monitoring of discharge hydrograph and soil mantle groundwater in a steep headwater catchment underlain by granitic bedrock. Bedrock wells with depths of 7-78 m were drilled at 31 points within the 2.10-ha catchment. Results showed that a hollow of bedrock aquifer was located at a ridge in the surface topography, clearly indicating bedrock groundwater flow across topographic divides. Around a point where the bedrock groundwater exfiltrated, we found scars of landslides. Such landslides cannot be explained by mathematical hydrology models, which calculate the topographically driven convergence of rainwater in the soil mantle. Moreover, at a point along the main hollow of the watershed, we observed

  18. Laboratory measurements of grain-bedrock interactions using inertial sensors.

    NASA Astrophysics Data System (ADS)

    Maniatis, Georgios; Hoey, Trevor; Hodge, Rebecca; Valyrakis, Manousos; Drysdale, Tim

    2016-04-01

    Sediment transport in steep mountain streams is characterized by the movement of coarse particles (diameter c.100 mm) over beds that are not fully sediment-covered. Under such conditions, individual grain dynamics become important for the prediction of sediment movement and subsequently for understanding grain-bedrock interaction. Technological advances in micro-mechanical-electrical systems now provide opportunities to measure individual grain dynamics and impact forces from inside the sediments (grain inertial frame of reference) instead of trying to infer them indirectly from water flow dynamics. We previously presented a new prototype sensor specifically developed for monitoring sediment transport [Maniatis et al. EGU 2014], and have shown how the definition of the physics of the grain using the inertial frame and subsequent derived measurements which have the potential to enhance the prediction of sediment entrainment [Maniatis et al. 2015]. Here we present the latest version of this sensor and we focus on beginning of the cessation of grain motion: the initial interaction with the bed after the translation phase. The sensor is housed in a spherical case, diameter 80mm, and is constructed using solid aluminum (density = 2.7 kg.m-3) after detailed 3D-CAD modelling. A complete Inertial Measurement Unit (a combination of micro- accelerometer, gyroscope and compass) was placed at the center of the mass of the assembly, with measurement ranges of 400g for acceleration, and 1200 rads/sec for angular velocity. In a 0.9m wide laboratory flume, bed slope = 0.02, the entrainment threshold of the sensor was measured, and the water flow was then set to this value. The sensor was then rolled freely from a static cylindrical bar positioned exactly on the surface of the flowing water. As the sensor enters the flow we record a very short period of transport (1-1.5 sec) followed by the impact on the channel bed. The measured Total Kinetic Energy (Joules) includes the

  19. Quantifying fluvial bedrock erosion using repeat terrestrial Lidar

    NASA Astrophysics Data System (ADS)

    Cook, Kristen

    2013-04-01

    The Da'an River Gorge in western Taiwan provides a unique opportunity to observe the formation and evolution of a natural bedrock gorge. The 1.2 km long and up to 20 m deep gorge has formed since 1999 in response to uplift of the riverbed during the Chi-Chi earthquake. The extremely rapid pace of erosion enables us to observe both downcutting and channel widening over short time periods. We have monitored the evolution of the gorge since 2009 using repeat RTK GPS surveys and terrestrial Lidar scans. GPS surveys of the channel profile are conducted frequently, with 24 surveys to date, while Lidar scans are conducted after major floods, or after 5-9 months without a flood, for a total of 8 scans to date. The Lidar data are most useful for recording erosion of channel walls, which is quite episodic and highly variable along the channel. By quantifying the distribution of wall erosion in space and time, we can improve our understanding of channel widening processes and of the development of the channel planform, particularly the growth of bends. During the summer of 2012, the Da'an catchment experienced two large storm events, a meiyu (plum rain) event on June 10-13 that brought 800 mm of rain and a typhoon on August 1-3 that brought 650 mm of rain. The resulting floods had significant geomorphic effects on the Da'an gorge, including up to 10s of meters of erosion in some sections of the gorge walls. We quantify these changes using Lidar surveys conducted on June 7, July 3, and August 30. Channel wall collapses also occur in the absence of large floods, and we use scans from August 23, 2011 and June 7, 2012 to quantify erosion during a period that included a number of small floods, but no large ones. This allows us to compare the impact of 9 months of normal conditions to the impact of short-duration extreme events. The observed variability of erosion in space and time highlights the need for 3D techniques such as terrestrial Lidar to properly quantify erosion in this

  20. History of Geology.

    ERIC Educational Resources Information Center

    Greene, Mott T.

    1985-01-01

    Discusses: (1) geologists and the history of geology; (2) American historians and the history of geology; (3) history of geology in the 1980s; (4) sources for the history of geology (bibliographies, dictionaries, encyclopedias, handbooks, periodicals, public/official histories, compilations, and books); (5) research opportunities; and (6) other…

  1. Gusev Crater Geology as Seen from Above

    NASA Technical Reports Server (NTRS)

    2004-01-01

    As NASA's Mars Exploration Rover Spirit continues to explore the 'Columbia Hills' within Gusev Crater, scientists are planning to take a closer look for layered rocks in a steep valley straight ahead before directing the rover to turn south toward the summit of 'Husband Hill.' Two of the geologic formations the six-wheeled robotic geologist has discovered during 2004 are shown here. One is labeled 'Columbia Hills material,' representing bedrock of the higher slopes and peaks, and one is labeled 'transition zone material,' representing rocks that are gradational in character and composition between the hills to the east and the plains to the west. The map also shows Spirit's line of travel through the rover's 344th martian day, or sol (Dec. 21, 2004), beginning on the left edge at about the 182nd sol (July 7, 2004).

  2. Mapping the seafloor geology offshore of Massachusetts

    USGS Publications Warehouse

    Barnhardt, Walter A.; Andrews, Brian D.

    2006-01-01

    Geologic and bathymetric maps help us understand the evolutionary history of the Massachusetts coast and the processes that have shaped it. The maps show the distribution of bottom types (for example, bedrock, gravel, sand, mud) and water depths over large areas of the seafloor. In turn, these two fundamental parameters largely determine the species of flora and fauna that inhabit a particular area. Knowledge of bottom types and water depths provides a framework for mapping benthic habitats and managing marine resources. The need for coastal–zone mapping to inform policy and management is widely recognized as critical for mitigating hazards, creating resource inventories, and tracking environmental changes (National Research Council, 2004; U.S. Commission on Ocean Policy, 2004).

  3. Computation of bedrock-aquifer recharge in northern Westchester County, New York, and chemical quality of water from selected bedrock wells

    USGS Publications Warehouse

    Wolcott, Stephen W.; Snow, Robert F.

    1995-01-01

    An empirical technique was used to calculate the recharge to bedrock aquifers in northern Westchester County. This method requires delineation of ground-water divides within the aquifer area and values for (1) the extent of till and exposed bedrock within the aquifer area, and (2) mean annual runoff. This report contains maps and data needed for calculation of recharge in any given area within the 165square-mile study area. Recharge was computed by this technique for a 93-square-mile part of the study area and used a ground-water-flow model to evaluate the reliability of the method. A two-layer, steady-state model of the selected area was calibrated. The area consists predominantly of bedrock overlain by small localized deposits of till and stratified drill Ground-water-level and streamflow data collected in mid-November 1987 were used for model calibration. The data set approximates average annual conditions. The model was calibrated from (1) estimates of recharge as computed through the empirical technique, and (2) a range of values for hydrologic properties derived from aquifer tests and published literature. Recharge values used for model simulation appear to be reasonable for average steady-state conditions. Water-quality data were collected from 53 selected bedrock wells throughout northern Westchester County to define the background ground-water quality. The constituents and properties for which samples were analyzed included major cations and anions, temperature, pH, specific conductance, and hardness. Results indicate little difference in water quality among the bedrock aquifers within the study area. Ground water is mainly the calcium-bicarbonate type and is moderately hard. Average concentrations of sodium, sulfate, chloride, nitrate, iron, and manganese were within acceptable limits established by the U.S. Environmental Protection Agency for domestic water supply.

  4. Connecting streamlined subglacial bedforms with the geological/geographical environment in which they are located.

    NASA Astrophysics Data System (ADS)

    Dowling, Tom; Möller, Per; Greenwood, Sarah; Spagnolo, Matteo; Åkesson, Maria; Fraser, Stephen; Hughs, Anna; Clark, Chris

    2016-04-01

    Much work has qualitatively shown that there appears to be a relationship between the morphology of streamlined subglacial bedforms (drumlinoids) and the geological/geographical environment in which said bedforms are located upon, particularly in terms of bedrock influence. However, the one quantitative study that has been carried out on this connectivity (Greenwood and Clark, 2010) found that there appears to be a connection between bedrock type and morphology only at a local scale. At a regional scale the most important geological factor seemed to be the properties of the substrate, usually till. In order to investigate these connections further, self-organising maps (SOM) are used to investigate the role of contextual geology/geography in drumlinoid morphology. The SOM method allows the statistical exploration of data that cannot normally be evaluated by traditional means; categorical data (e.g. bedrock type) can be used in the same analysis as continuous/vector data (e.g. drift depth). Here, three large morphological data sets from Sweden (20 041), Britain (36 104) and Ireland (13 454) are combined with bedrock type, drift depth, basal elevation and distance to esker to see if there are any relationships to be found between them. The results indicate that there are pervasive, statistically significant, and weak to very weak correlations between contextual geological/geographical factors and drumlinoid morphology. The most important contextual factor appears to be 'drift depth', followed by 'distance to esker'. Therefore, models of drumlinoid formation and any efforts to use such features for palaeo-ice reconstruction must take into account the geological and geographical environment in which they are situated. The logical extension of this is that models of ice-sheet growth and retreat must also take into account and be sensitive to the type of substratum present beneath the ice. Further research into the effect of drift properties on the flow of ice is needed.

  5. Bedform genesis and evolution in bedrock substrates: a new experimental approach

    NASA Astrophysics Data System (ADS)

    Parsons, D. R.; Yin, N.; Peakall, J.

    2014-12-01

    Most previous studies on the genesis and evolution of bedforms have focused on aggradational bedforms within cohesionless sediments, with very few investigations that concern either erosive bedform genesis and evolution or bedrock channel abrasion processes. The study presented here details experiments that involve the genesis and formation of erosional bedform features within natural (soft clay) cohesive sediment beds and analogue bedrock substrates by modelling clay under the effect of both open-channel plain water flows, and sediment-laden flows. A new approach without using plaster-of-Paris or real bedrock developed provides a feasible method to simulate the genesis and evolution of the erosional bedforms in cohesive sediment beds and sculpted forms in bedrock channels on relatively short time-scales in the laboratory by using a realistic substrate substitute.A series of flume experiments are presented herein where the undrained shear strength of two different kinds of substrate material is systematically varied under constant flow conditions. Experiments using plain water flow indicated that erosive bedforms in cohesive sediment substrate cannot be produced only under the effect of sediment-free flow. Particulate-laden flows do form erosional bedforms in both kinds of clay beds and the shear strength of the bed material plays a key role in determining the diversity of erosional features forming on such substrates. Optimisation of modelling clay beds has enabled us to successfully replicate a suite of bedrock bedforms, including potholes, flutes, longitudinal furrows, etc., that have clear equivalents to those observed in bedrock rivers and contributed to investigate the genesis and evolution process of them and explore the flow structures within and above them in experimental analogue bedrock substrate for the first time.

  6. Bedrock erosion surface beneath the rocky flats alluvial fan, Jefferson and Boulder counties, Colorado

    USGS Publications Warehouse

    Knepper, D.H., Jr.

    2005-01-01

    The early Pleistocene Rocky Flats alluvial fan formed at the mouth of unglaciated Coal Creek Canyon along the eastern flank of the Colorado Front Range. The fan consists of boulder, cobble, and pebble gravel deposited on an erosional surface cut on tilted Mesozoic sedimentary strata. A north-trending hogback of steeply dipping Cretaceous Laramie Formation and Fox Hills Sandstone is exposed through the gravel across the central portion of the fan. Elevations on the gravel-bedrock contact were used in a GIS to reconstruct the bedrock surface at the base of the gravel, providing a glimpse of the geomorphology of the early Pleistocene Colorado Piedmont. The reconstructed erosional bedrock surface portrays a landscape carved by a series of easterly flowing streams that eroded headward to the resistant hogback units, creating a bedrock step up to 37 m high. East-trending ridges on the bedrock surface are remnants of drainage divides between the Pleistocene streams. Water gaps in the bedrock step allowed the streams access to the upper surface of the step. This entire surface, except the hogback, was covered by gravel about 1.35 to 1.5 Ma ago. Subsequent erosion of the alluvial fan has been by headward (westward) erosion of easterly flowing streams incising into the eastern portion of the fan. Because the gravel is more resistant than the underlying bedrock, modern streams are established over the Pleistocene drainage divides, where the gravel was thinnest. Thicker gravel in the Pleistocene paleovalleys now caps modern drainage divides, producing an inverted topography.

  7. What about the regolith, the saprolite and the bedrock? Proposals for classifying the subsolum in WRB

    NASA Astrophysics Data System (ADS)

    Juilleret, Jérôme; Dondeyne, Stefaan; Hissler, Christophe

    2014-05-01

    Since soil surveys in the past were mainly conducted in support of agriculture, soil classification tended to focus on the solum representing mainly the upper part of the soil cover that is exploited by crops; the subsolum was largely neglected. When dealing with environmental issues - such as vegetation ecology, groundwater recharge, water quality or waste disposal - an integrated knowledge of the solum to subsolum continuum is required. In the World Reference Base for soil resources (WRB), the lower boundary for soil classification is set at 2 m, including both loose parent material as well as weathered and continuous rock. With the raised concern for environmental issues and global warming, classification concepts in WRB have been widened over the last decades. Cryosols were included as a separate Reference Soil Group to account for soils affected by perennial frost; Technosols were included to account for soils dominated by technical human activity. Terms for describing and classifying the subsolum are however still lacking. Nevertheless, during soil surveys a wealth of information on the subsolum is also collected. In Luxembourg, detailed soil surveys are conducted according to a national legend which is correlated to WRB. Quantitative data on characteristics of the subsolum, such as bedding, cleavage, fractures density and dipping of the layer, are recorded for their importance in relation to subsurface hydrology. Drawing from this experience, we propose defining four "subsolum materials" and which could be integrated into WRB as qualifiers. Regolitic materials are composed of soil and rock fragments deposited by water, solifluction, ice or wind; Paralithic materials consist of partly weathered rock with geogenic structural features; Saprolitic materials are formed from in situ weathering of the underlying geological deposits; Lithic materials correspond to unaltered bedrock. We discuss how these characteristics could be integrated into WRB and how additional

  8. Characterization of ground-water discharge from bedrock aquifers to the Mississippi and Minnesota Rivers at three areas, Minneapolis-St. Paul area, Minnesota

    USGS Publications Warehouse

    Schoenberg, M.E.

    1994-01-01

    The hydrogeology at three areas along the Mississippi and Minnesota Rivers in the Minneapolis-St. Paul area were studied to characterize ground-water discharge from bedrock aquifers to the two rivers. Along the Mississippi River between Fridley and Brooklyn Center, a buried valley underlying the Mississippi River cuts through the overlying terrace deposits and glacial-drift deposits into two underlying bedrock hydro- geologic units: the St Peter aquifer, and a rubble zone between the St. Peter and Prairie du Chien-Jordan aquifers. Shallow ground-water flow in the near-surface gray and upper red tills and sand and gravel outwash aquifer discharges to springs along the edge of the river. Ground water flowing through the rubble zone and upper part of the Prairie du Chien-Jordan aquifer probably discharges through alluvial deposits to the river. In study area 2, along the Minnesota River between Eagan and Bloomington, almost 200 feet of post-glacial alluvium, glaciofluvial sand and gravel, Pleistocene lake deposits, and peat fill a bedrock valley under the present-day Minnesota River. As much as 40 feet of post-glacial peat, silty clay, clay, and muck lie near the river-valley walls. Confining units beneath the river channel impede the discharge of ground water from the underlying Prairie du Chien-Jordan aquifer to the river. Ground water discharges to wetlands, lakes, and springs along both the north and south side of the river. Along the Mississippi River at Minneapolis about 5 miles upstream of the confluence of the Minnesota and Mississippi Rivers, the Mississippi River lies in a post-glacial valley cut through thin glacial drift into the St. Peter aquifer. Beneath the river, ground water flows from the St. Peter aquifer through the overlying post-glacial ailuvium to the Mississippi River. No confining unit separates the St. Peter aquifer and the river.

  9. Flood magnitude frequency and lithologic control on bedrock river incision in post-orogenic terrain

    NASA Astrophysics Data System (ADS)

    Jansen, John D.

    2006-12-01

    Mixed bedrock-alluvial rivers-bedrock channels lined with a discontinuous alluvial cover-are key agents in the shaping of mountain belt topography by bedrock fluvial incision. Whereas much research focuses upon the erosional dynamics of such rivers in the context of rapidly uplifting orogenic landscapes, the present study investigates river incision processes in a post-orogenic (cratonic) landscape undergoing extremely low rates of incision (< 5 m/Ma). River incision processes are examined as a function of substrate lithology and the magnitude and frequency of formative flows along Sandy Creek gorge, a mixed bedrock-alluvial stream in arid SE-central Australia. Incision is focused along a bedrock channel with a partial alluvial cover arranged into riffle-pool macrobedforms that reflect interactions between rock structure and large-flood hydraulics. Variations in channel width and gradient determine longitudinal trends in mean shear stress ( τb) and therefore also patterns of sediment transport and deposition. A steep and narrow, non-propagating knickzone (with 5% alluvial cover) coincides with a resistant quartzite unit that subdivides the gorge into three reaches according to different rock erodibility and channel morphology. The three reaches also separate distinct erosional styles: bedrock plucking (i.e. detachment-limited erosion) prevails along the knickzone, whereas along the upper and lower gorge rock incision is dependent upon large formative floods exceeding critical erosion thresholds ( τc) for coarse boulder deposits that line 70% of the channel thalweg (i.e. transport-limited erosion). The mobility of coarse bed materials (up to 2 m diameter) during late Holocene palaeofloods of known magnitude and age is evaluated using step-backwater flow modelling in conjunction with two selective entrainment equations. A new approach for quantifying the formative flood magnitude in mixed bedrock-alluvial rivers is described here based on the mobility of a key

  10. Applications of Landsat imagery to geological research in Minnesota

    NASA Technical Reports Server (NTRS)

    Weiblen, P. W.; Morey, G. B.; Walton, M. S.

    1975-01-01

    A large part of northeastern Minnesota north of Lake Superior was studied using Landsat images. The area is being studied for its intercontinental rift and for large, low grade, copper-nickel deposits. By using Landsat imagery in conjunction with field data, it is possible to develop a much higher level of continuity and structural resolution in interpretations of the bedrock geology. Preliminary results indicate that it is possible to distinguish various surficial morphological features such as the Vermilion and Highland moraines, the Toimi drumlin field, and an unnamed drumlin field apparently associated with the Highland moraine.

  11. Using domestic well records to determine fractured bedrock watersheds and recharge rates.

    PubMed

    Metcalf, Meredith J; Robbins, Gary A

    2014-01-01

    This study presents an approach for delineating groundwater basins and estimating rates of recharge to fractured crystalline bedrock. It entailed the use of completion report data (boring logs) from 2500 domestic wells in bedrock from the Coventry Quadrangle, which is located in northeastern Connecticut and characterized by metamorphic gneiss and schist. Completion report data were digitized and imported into ArcGIS(®) for data analysis. The data were processed to delineate groundwater drainage basins for the fractured rock based on flow conditions and to estimate groundwater recharge to the bedrock. Results indicate that drainage basins derived from surface topography, in general, may not correspond with bedrock drainage basins due to scale. Estimates of recharge to the bedrock for the study area indicate that only a small fraction of the precipitation or the amount of water that enters the overburden recharges the rock. The approach presented here can be a useful method for water resource-related assessments that involve fractured rock aquifers. PMID:24102252

  12. Permafrost in steep bedrock slopes and its temperature-related destabilization following climate change

    NASA Astrophysics Data System (ADS)

    Gruber, S.; Haeberli, W.

    2007-06-01

    Permafrost in steep bedrock is abundant in many cold-mountain areas, and its degradation can cause slope instability that is unexpected and unprecedented in location, magnitude, frequency, and timing. These phenomena bear consequences for the understanding of landscape evolution, natural hazards, and the safe and sustainable operation of high-mountain infrastructure. Permafrost in steep bedrock is an emerging field of research. Knowledge of rock temperatures, ice content, mechanisms of degradation, and the processes that link warming and destabilization is often fragmental. In this article we provide a review and discussion of existing literature and pinpoint important questions. Ice-filled joints are common in bedrock permafrost and possibly actively widened by ice segregation. Broad evidence of destabilization by warming permafrost exists despite problems of attributing individual events to this phenomenon with certainty. Convex topography such as ridges, spurs, and peaks is often subject to faster and deeper thaw than other areas. Permafrost degradation in steep bedrock can be strongly affected by percolating water in fractures. This degradation by advection is difficult to predict and can lead to quick and deep development of thaw corridors along fractures in permafrost and potentially destabilize much greater volumes of rock than conduction would. Although most research on steep bedrock permafrost originates from the Alps, it will likely gain importance in other geographic regions with mountain permafrost.

  13. Paraglacial fluvial bedrock incision in postglacial landscapes: the NW Scottish Highlands

    NASA Astrophysics Data System (ADS)

    Whitbread, Katie; Jansen, John; Bishop, Paul; Fabel, Derek

    2010-05-01

    Glacial landscape forms are inherited by rivers following deglaciation. Hillslopes and valley floors configured by glacial erosion control the distribution of bedrock channels and potential sites for fluvial incision. The importance of 'stream power' parameters, channel slope and drainage area (discharge), in controlling the rate of incision is widely accepted, but the rate, timing and mechanisms of incision have yet to be quantified in these settings. The dual controls of glacially conditioned bedrock slopes and sediment supply set two of the key boundary conditions for temporally and spatially dynamic fluvial bedrock incision. Measurement of incision rates in these settings is key to understanding the influence of controls on fluvial erosion, and the role of the process in long-term evolution of deglaciated landscapes. In tectonically-passive, hard-rock terrains, such as the Scottish Highlands, incisional fluvial features such as bedrock channels, gorges and waterfalls are common on glacially carved valley steps. Here we report preliminary data on fluvial incision rates measured with cosmogenic 10Be. Our results confirm a postglacial age of bedrock straths in the NW Scottish Highlands and indicate a vertical incision rate of 0.3 mm/yr into resistant quartzites. Further work will explore erosion mechanisms and rates of incision across the Scottish Highlands, and assess controls on fluvial incision, including the potential role of paraglacial sediment.

  14. Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA

    USGS Publications Warehouse

    Rengers, Francis; Tucker, G.E.; Mahan, Shannon

    2016-01-01

    This study explores the frequency of bedrock exposure in a soil-mantled low-relief (i.e. non-mountainous) landscape. In the High Plains of eastern Colorado, gully headcuts are among the few erosional features that will incise through the soil mantle to expose bedrock. We measured the last time of bedrock exposure using optically stimulated luminescence dating of alluvial sediment overlying bedrock in gully headcuts. Our dating suggests that headcuts in adjacent gullies expose bedrock asynchronously, and therefore, the headcuts are unlikely to have been triggered by a base-level drop in the trunk stream. This finding supports the hypothesis that headcuts can develop locally in gullies as a result of focused scour in locations where hydraulic stress during a flash flood is sufficiently high, and/or ground cover is sufficiently weak, to generate a scour hole that undermines vegetation. Alluvium dating also reveals that gullies have been a persistent part of this landscape since the early Holocene. 

  15. Substrate, sediment, and slope controls on bedrock channel geometry in postglacial streams

    NASA Astrophysics Data System (ADS)

    Whitbread, Katie; Jansen, John; Bishop, Paul; Attal, Mikaël.

    2015-05-01

    The geometry of channels controls the erosion rate of rivers and the evolution of topography following environmental change. We examine how sediment, slope, and substrate interact to constrain the development of channels following deglaciation and test whether theoretical relationships derived from streams reacting to tectonic uplift apply in these settings. Using an extensive data set of channel geometry measurements from postglacial streams in the Scottish Highlands, we find that a power law width-drainage area scaling model accounts for 81% of the spatial variation in channel width. Substrate influences channel form at the reach scale, with bedrock channels found to be narrower and deeper than alluvial channels. Bedrock channel width does not covary with slope, which may be due to downstream variations in sediment flux. Bedrock channel width-to-depth ratios increase with discharge (or area) and sediment flux, consistent with increasing bed cover promoting lateral widening. We find steep, wide, and shallow bedrock channels immediately below lakes, which we interpret as the result of limited erosion due to a lack of sediment "tools." Where sediment supply is sufficient to exceed transport capacity, alluvial channels develop wider, shallower geometries constrained primarily by flow hydraulics. Our results indicate that simple scaling models of channel width with drainage area are applicable at regional scale, but locally, channel width varies with substrate, and in the case of bedrock channels, with sediment flux.

  16. The bedrock and structural geology of Tuckerman Ravine and Boott Spur in the Presidential Range, N. H

    SciTech Connect

    Johnson, A.H.; Maconochie, J.M. . Dept. of Geology)

    1993-03-01

    Detailed mapping has been done of the polydeformed, lower sillimanite grade, Silurian and Devonian metasedimentary rocks in the southeast part of the Presidential Range, N.H. These rocks are part of the cover sequence in the Central Maine Terrane of the northern Appalachians. Folding and associated metamorphism is thought to be related to the Acadian and Alleghanian( ) orogenics. The Silurian Rangeley Formation, the oldest unit, is a schist and quartzite which has been subdivided into two members based on the presence or absence of calc-silicate pods. In places it is highly migmitized due to the intrusion of the Glen Boulder granite in the southern section of the field area. The Silurian Smalls Falls Formation, a rusty schist, highly susceptible to weathering, overlies the Rangeley Formation. Overlying this is the Silurian Madrid Formation, a well layered calc-silicate granofels. On top of the sequence lies a thick section of schists and quartzites of varying thicknesses and relative abundances. This section has been sub-divided into ten members that collectively form the lower Devonian Littleton Formation. The area has undergone three phases of deformation. Field data and structural analysis indicate that an early macroscopic fold, F1, dominates the area and has an average trend of 325[degree] and plunge of 25[degree]. The axial surface, S1, strikes north and dips moderately west. This fold exposes inverted beds in the northwest limb and up-right beds in the southeast limb. Asymmetric, east vergent, F2 folds are abundant. These folds have an average trend of 112[degree] and plunge of 53[degree], with associated axial planar cleavage, S2, striking north and dipping moderately to the west. Pegmatite veins are folded by F2 indicating that they and similar igneous bodies likely predate F2 folding. Evidence for later stage F3 folding also exists.

  17. Map Showing Principal Coal Beds and Bedrock Geology of the Ucross-Arvada Area, Central Powder River Basin, Wyoming

    USGS Publications Warehouse

    Molnia, Carol L.

    2013-01-01

    The Ucross-Arvada area is part of the Powder River Basin, a large, north-trending structural depression between the Black Hills on the east and the Bighorn Mountains on the west. Almost all of the study area is within Sheridan and Johnson Counties, Wyoming. Most of the Ucross-Arvada area lies within the outcrop of the Wasatch Formation of Eocene age; the extreme northeast corner falls within the outcrop of the Tongue River Member of the Fort Union Formation of Paleocene age. Within the Powder River Basin, both the Wasatch Formation and the Tongue River Member of the Fort Union Formation contain significant coal resources. The map includes locations and elevations of coal beds at 1:50,000 scale for an area that includes ten 7½-minute quadrangles covering some 500 square miles. The Wasatch Formation coal beds shown (in descending order) are Monument Peak, Walters (also called Ulm 1), Healy (also called Ulm 2), Truman, Felix, and Arvada. The Fort Union Formation coal beds shown (in descending order) are Roland (of Baker, 1929) and Smith.

  18. Bedrock Geologic Map of the Headwaters Region of the Cullasaja River, Macon and Jackson Counties, North Carolina

    USGS Publications Warehouse

    Burton, William C.

    2007-01-01

    The headwaters region of the Cullasaja River is underlain by metasedimentary and meta-igneous rocks of the Neoproterozoic Ashe Metamorphic Suite, including gneiss, schist, and amphibolite, that were intruded during Ordovician time by elongate bodies of trondhjemite, a felsic plutonic rock. Deformation, metamorphism, and intrusion occurred roughly simultaneously during the Taconic orogeny, about 470 million years ago, under upper-amphibolite-facies metamorphic conditions. Two generations of foliation and three major phases of folds are recognized. The second- and third-generation folds trend northeast and exert the most control on regional foliation trends. Since the orogeny, the region has undergone uplift, fracturing, and erosion. Resistance to erosion by the plutonic rock may be the primary reason for the relatively gentle relief of the high-elevation basin, compared to surrounding areas. Amphibolite is the most highly fractured lithology, followed by trondhjemite; the latter may have the best ground-water potential of the mapped lithologies by virtue of its high fracture density and high proportion of subhorizontal fractures.

  19. Bedrock geology and mineral resources of the Knoxville 1° x 2° quadrangle, Tennessee, North Carolina, and South Carolina

    USGS Publications Warehouse

    Robinson, Gilpin R., Jr.; Lesure, Frank G.; Marlowe, J. I., II; Foley, Nora K.; Clark, S.H.

    2004-01-01

    Vermiculite produced from a large deposit near Tigerville, S.C-, in the Inner Piedmont. Deposit worked out and mine backfilled. Smaller deposits associated with ultramafic rocks in the east flank of the Blue Ridge are now uneconomic and have not been worked in the past 20 years. C. Metals: Copper in three deposits, the Fontana and Hazel Creek mines in the Great Smoky Mountains Abstract Figure 1.

  20. Bedrock geology of the Paducah 1 degree x 2 degrees CUSMAP quadrangle, Illinois, Indiana, Kentucky, and Missouri

    USGS Publications Warehouse

    Nelson, W. John

    1998-01-01

    The Paducah 1? by 2? quadrangle (hereafter referred to as the Paducah quadrangle) encompasses the eastern flank of the Ozark dome, the southern end of the Illinois Basin, and the northern end of the Mississippi Embayment. Resting on Proterozoic basement, sedimentary rocks of Cambrian through Permian age in the Illinois Basin and Ozark dome are overlapped by weakly lithified Cretaceous, Paleocene, Eocene, and Pliocene strata in the embayment. This is one of the most intensely faulted areas of the North American Midcontinent. A Proterozoic crustal terrane boundary (coincident with part of the Ste. Genevieve fault zone) and a failed intracratonic rift (Reelfoot rift and Rough Creek graben) have been reactivated repeatedly under various stress fields from Proterozoic through late Tertiary times. ? ' 2 ? quadrangle (hereafter referred to as the Paducah quadrangle) encompasses the eastern flank of the Ozark dome, the southern end of the Illinois Basin, and the northern end of the Mississippi Embayment. Resting on Proterozoic basement, sedimentary rocks of Cambrian through Permian age in the Illinois Basin and Ozark dome are overlapped by weakly lithified Cretaceous, Paleocene, Eocene, and Pliocene strata in the embayment. This is one of the most intensely faulted areas of the North American Midcontinent. A Proterozoic crustal terrane boundary (coincident with part of the Ste. Genevieve fault zone) and a failed intracratonic rift (Reelfoot rift and Rough Creek graben) have been reactivated repeatedly under various stress fields from Proterozoic through late Tertiary times.

  1. Geological evaluation and applications of ERTS-1 imagery over Georgia

    NASA Technical Reports Server (NTRS)

    Pickering, S. M.; Jones, R. C.

    1974-01-01

    ERTS-1 70mm and 9 x 9 film negatives are being used by conventional and color enhancement methods as a tool for geologic investigation. Geologic mapping and mineral exploration by conventional methods is very difficult in Georgia. Thick soil cover and heavy vegetation cause outcrops of bed rock to be small, rare and obscure. ERTS imagery, and remote sensing in general have helped delineate: (1) major tectonic boundaries; (2) lithologic contacts; (3) foliation trends; (4) topographic lineaments; and (5) faults. The ERTS-1 MSS imagery yields the greatest amount of geologic information on the Piedomont, Blue Ridge, and Valley and Ridge Provinces of Georgia where topography is strongly controlled by the bedrock geology. ERTS imagery, and general remote sensing techniques, have provided us with a powerful tool to assist geologic research; have significantly increased the mapping efficiency of our field geologists; have shown new lineaments associated with known shear and fault zones; have delineated new structural features; have provided a tool to re-evaluate our tectonic history; have helped to locate potential ground water sources and areas of aquifer recharge; have defined areas of geologic hazards; have shown areas of heavy siltation in major reservoirs; and by its close interval repetition, have aided in monitoring surface mine reclamation activities and the environmental protection of our intricate marshland system.

  2. Geologic Map of the Big Spring Quadrangle, Carter County, Missouri

    USGS Publications Warehouse

    Weary, David J.; McDowell, Robert C.

    2006-01-01

    The bedrock exposed in the Big Spring quadrangle of Missouri comprises Late Cambrian and Early Ordovician aged dolomite, sandstone, and chert. The sedimentary rocks are nearly flat lying except where they are adjacent to faults. The carbonate rocks are karstified, and the area contains numerous sinkholes, springs, caves, and losing streams. This map is one of several being produced under the U.S. Geological Survey (USGS) National Cooperative Geologic Mapping Program to provide geologic data applicable to land-use problems in the Ozarks of south-central Missouri. Ongoing and potential industrial and agricultural development in the Ozarks region has presented issues of ground-water quality in karst areas. A national park in this region (Ozark National Scenic Riverways, Missouri) is concerned about the effects of activities in areas outside of their stewardship on the water resources that define the heart of this park. This task applies geologic mapping and karst investigations to address issues surrounding competing land use in south-central Missouri. This task keeps geologists from the USGS associated with the park and allows the park to utilize USGS expertise and aid the NPS on how to effectively use geologic maps for park management. For more information, see: http://geology.er.usgs.gov/eespteam/Karst/index.html

  3. Relationships of soil, grass, and bedrock over the Kaweah serpentine melange through spectral mixture analysis of AVIRIS data

    NASA Technical Reports Server (NTRS)

    Mustard, John F.

    1991-01-01

    A linear mixing model is used to model the spectral variability of an AVIRIS scene from the western foothills of the Sierra Nevada and calibrate these radiance data to reflectance. Five spectral endmembers from the AVIRIS data, plus an ideal 'shade' endmember were required to model the continuum reflectance of each pixel in the image. Three of the endmembers were interpreted to model the surface constituents green vegetation, dry grass, and illumination. These are the main transient surface constituents that are expected to change with shifts in land use or climatic influences and viewing conditions ('shade' only). The spectral distinction between the other three endmembers is very small, yet the spatial distributions are coherent and interpretable. These distributions cross anthropogenic and vegetation boundaries and are best interpreted as different soil types. Comparison of the fraction images to the bedrock geology maps indicates that substrate composition must be a factor contributing to the spectral properties of these endmembers. Detailed examination of the reflectance spectra of the three soil endmembers reveals that differences in the amount of ferric and ferrous iron and/or organic constituents in the soils is largely responsible for the differences in spectral properties of these endmembers.

  4. Spatial analysis of geologic and hydrologic features relating to sinkhole occurrence in Jefferson County, West Virginia

    USGS Publications Warehouse

    Doctor, Daniel H.; Doctor, Katarina Z.

    2012-01-01

    In this study the influence of geologic features related to sinkhole susceptibility was analyzed and the results were mapped for the region of Jefferson County, West Virginia. A model of sinkhole density was constructed using Geographically Weighted Regression (GWR) that estimated the relations among discrete geologic or hydrologic features and sinkhole density at each sinkhole location. Nine conditioning factors on sinkhole occurrence were considered as independent variables: distance to faults, fold axes, fracture traces oriented along bedrock strike, fracture traces oriented across bedrock strike, ponds, streams, springs, quarries, and interpolated depth to groundwater. GWR model parameter estimates for each variable were evaluated for significance, and the results were mapped. The results provide visual insight into the influence of these variables on localized sinkhole density, and can be used to provide an objective means of weighting conditioning factors in models of sinkhole susceptibility or hazard risk.

  5. Understanding and modelling dissolved gas transport in the bedrock of three Fennoscandian sites

    NASA Astrophysics Data System (ADS)

    Trinchero, Paolo; Delos, Anne; Molinero, Jorge; Dentz, Marco; Pitkänen, Petteri

    2014-05-01

    The origin and transport of dissolved gases in the geosphere is of interest for assessment studies of nuclear waste repositories. In this paper, we analyse available field measurements of helium, methane and hydrogen at three Fennoscandian sites: Forsmark and Laxemar in Sweden and Olkiluoto in Finland. The field data are interpreted using different analytical models all based on the one-dimensional diffusion equation. The results of the different models provide estimates about the amount of deep gas flux, the in situ production and the groundwater residence time of the considered sites. The computed helium fluxes, which fall within the lower range of crustal degassing fluxes reported by Torgersen (2010), are strictly related with the high tightness of the considered fracture media. The very high estimates of groundwater residence time indicate that, at the considered depths, there are only very few flowing fractures while in the rest of the fractured domain groundwater has been almost motionless during a whole glacial cycle.

  6. Terroir, the Relationship of Geology, Soils, and Climate to Wine: An Example from the Northern Willamette Valley of Oregon, USA

    NASA Astrophysics Data System (ADS)

    Burns, S. F.

    2012-12-01

    Wines differ from each other based on seven different factors: the type of grape; the bedrock geology and resulting soils; the climate; the soil hydrology; the physiography of the site; the winemaker; and the vineyard management techniques. The first five of these factors make up what the French call terroir, "the taste of the place". Bedrocks weather into soils which then liberate chemical nutrients to the grape vines. Twelve of the sixteen essential elements for wine grapes come from the soil. All around the world the geology and soils make up an important component of the terroir of the wine. Using examples from the Willamette Valley of Oregon, terroir of the region will be discussed because it is strongly influenced by the bedrock geology and soils. The four dominant groups are the volcanic soils, the Jory Soil Series, which developed on the Columbia River Basalts, the Willakenzie Soil Series, developed on uplifted marine sedimentary rocks in the foothills of the Oregon Coast Range, the Laurelwood Soil Series, developed from loess soils developed on basalt bedrock, and Woodburn Soil Series developed in Missoula Flood deposits on the valley bottoms. The wines made from the grapes of these four soils are very different.

  7. Identification of Bedrock Lithology using Fractal Dimensions of Drainage Networks extracted from Medium Resolution LiDAR Digital Terrain Models

    NASA Astrophysics Data System (ADS)

    Cámara, Joaquín; Gómez-Miguel, Vicente; Martín, Miguel Ángel

    2016-03-01

    Geologists know that drainage networks can exhibit different drainage patterns depending on the hydrogeological properties of the underlying materials. Geographic Information System (GIS) technologies and the increasing availability and resolution of digital elevation data have greatly facilitated the delineation, quantification, and study of drainage networks. This study investigates the possibility of inferring geological information of the underlying material from fractal and linear parameters describing drainage networks automatically extracted from 5-m-resolution LiDAR digital terrain model (DTM) data. According to the lithological information (scale 1:25,000), the study area is comprised of 30 homogeneous bedrock lithologies, the lithological map units (LMUs). These are mostly igneous and metamorphic rocks, but also include some sedimentary rocks. A statistical classification model of the LMUs by rock type has been proposed based on both the fractal dimension and drainage density of the overlying drainage networks. The classification model has been built using 16 LMUs, and it has correctly classified 13 of the 14 LMUs used for its validation. Results for the study area show that LMUs, with areas ranging from 177.83 ± 0.01 to 3.16 ± 0.01 km2, can be successfully classified by rock type using the fractal dimension and the drainage density of the drainage networks derived from medium resolution LiDAR DTM data with different flow support areas. These results imply that the information included in a 5-m-resolution LiDAR DTM and the appropriate techniques employed to manage it are the only inputs required to identify the underlying geological materials.

  8. Buried bedrock topography, evidence of overdeepening of Winimusset Brook bedrock valley, and reinterpretation of the extent of glacial Lake Winimusset, Ware quadrangle, Massachusetts

    USGS Publications Warehouse

    Lapham, W.W.; Maevsky, A.

    1991-01-01

    Results from 15 test borings and 8 seismic-refraction surveys in the northeastern quarter of the Ware quadrangle, Massachusetts, provide information on the buried-bedrock topography, evidence of overdeepening of Winimusset Brook valley, information on the thickness and lithology of lacustrine deposits in glacial Lake Winimusset, and indicate a need for reinterpretation of the areal extent of the lake. Glacial Lake Winimusset, which occupied this bedrock valley during the last stages of deglaciation, was more extensive and accumulated thicker lacustrine deposits than previously postulated. Lacustrine silt and clay deposited in this lake are as much as 100 feet thick. The lake extended at least 1 mile north of the Town of Wheelwright. -from Authors

  9. An evaluation of probable bedrock exposure in the Sinus Meridiani region of the Martian highlands

    NASA Technical Reports Server (NTRS)

    Zimbelman, J. R.; Craddock, R. A.

    1991-01-01

    Estimates of the amount of probable bedrock exposures visible in the highest-resolution Viking imaging data for a selected region of the Martian surface are presented. The study region includes portions of the classical low-albedo regions of Sinus Meridiani and Sinus Sabaeus and the high-albedo region of Arabia, and is completely within the cratered highlands of Mars. More than 400 images were used to estimate the percentage of the area of each frame having locally steep slopes. It is seen that 42 percent of the high-resolution frames have less than one percent probable bedrock exposure while three percent of the frames have 15 percent probable bedrock exposure.

  10. Focused view of bedrock structures nearby EPICA drilling (Dome C, Antarctica)

    NASA Astrophysics Data System (ADS)

    Urbini, Stefano; Cafarella, Lili; Tabacco, Ignazio; Baskaradas, James; Zirizzotti, Achille

    2013-04-01

    In the last decades the study of Dome Concordia (Antarctica, 123° 20' E, 75° 20" S) represented a turning point especially for glaciology and climatology studies. Geophysical surveys played a fundamental role on several important issues like as the positioning of the EPICA drilling (European Project for Ice Coring in Antarctica) and revealing the physical assessment of the bedrock in the surrounding area. In this presentation, we show the last results pointed out by Radio Echo Sounding (RES) data collected during 2009, 2011 and 2012 Italian Antarctic Expeditions. The aim of these short-range campaigns was to obtain a high resolution image of the area surrounding the EPICA drilling site in order to enhance the knowledge on physical condition of ice bottom. The results revealed the presence of small scale bedrock structures. Nevertheless, the data acquired in 2011 and 2012 campaigns, showed unexpected characteristics that provide additional information on the nature of the interface between ice bottom and bedrock.

  11. Water chemistry at Snowshoe Mountain, Colorado: mixed processes in a common bedrock

    USGS Publications Warehouse

    Hoch, A.R.; Reddy, M.M.

    2001-01-01

    At Snowshoe Mountain the primary bedrock is quite homogeneous, but weathering processes vary as waters moves through the soils, vadose zone and phreatic zone of the subsurface. In the thin soil, physical degradation of tuff facilitates preferential dissolution of potassium ion from glass within the rock matrix, while other silicate minerals remain unaltered. In the vadose zone, in the upper few meters of fractured bedrock, dilute water infiltrates during spring snowmelt and summer storms, leading to preferential dissolution of augite exposed on fracture surfaces. Deeper yet, in the phreatic zone of the fractured bedrock, Pleistocene calcite fracture fillings dissolve, and dioctahedral and trioctahedral clays form as penetrative weathering alters feldspar and pyroxene. Alkalinity is generated and silica concentrations are buffered by mineral alteration reactions.

  12. Geophysics & Geology Inspected.

    ERIC Educational Resources Information Center

    Neale, E. R. W.

    1981-01-01

    Summarizes findings of a recently published report of the Canadian Geoscience Council, which includes the following topics regarding college geology: facilities; teaching; undergraduate enrollments; postgraduate enrollments; geologic research; and integration of Canadian geoscience with other countries. (CS)

  13. Geology for the Masses

    ERIC Educational Resources Information Center

    Dickinson, William R.

    1970-01-01

    Describes environmental geology as including planning to avoid natural hazards, acquire natural resources, and use land wisely. Describes philosophy and strategies for developing interdisciplinary, environmental geology education at the high school, college, professional graduate, and doctoral research levels. (PR)

  14. Geologic spatial analysis

    SciTech Connect

    Thiessen, R.L.; Eliason, J.R.

    1989-01-01

    This report describes the development of geologic spatial analysis research which focuses on conducting comprehensive three-dimensional analysis of regions using geologic data sets that can be referenced by latitude, longitude, and elevation/depth. (CBS)

  15. Impact of modeling Choices on Inventory and In-Cask Criticality Calculations for Forsmark 3 BWR Spent Fuel

    SciTech Connect

    Martinez-Gonzalez, Jesus S.; Ade, Brian J.; Bowman, Stephen M.; Gauld, Ian C.; Ilas, Germina; Marshall, William BJ J.

    2015-01-01

    Simulation of boiling water reactor (BWR) fuel depletion poses a challenge for nuclide inventory validation and nuclear criticality safety analyses. This challenge is due to the complex operating conditions and assembly design heterogeneities that characterize these nuclear systems. Fuel depletion simulations and in-cask criticality calculations are affected by (1) completeness of design information, (2) variability of operating conditions needed for modeling purposes, and (3) possible modeling choices. These effects must be identified, quantified, and ranked according to their significance. This paper presents an investigation of BWR fuel depletion using a complete set of actual design specifications and detailed operational data available for five operating cycles of the Swedish BWR Forsmark 3 reactor. The data includes detailed axial profiles of power, burnup, and void fraction in a very fine temporal mesh for a GE14 (10×10) fuel assembly. The specifications of this case can be used to assess the impacts of different modeling choices on inventory prediction and in-cask criticality, specifically regarding the key parameters that drive inventory and reactivity throughout fuel burnup. This study focused on the effects of the fidelity with which power history and void fraction distributions are modeled. The corresponding sensitivity of the reactivity in storage configurations is assessed, and the impacts of modeling choices on decay heat and inventory are addressed.

  16. Geologic map of the Battle Ground 7.5-minute quadrangle, Clark County, Washington

    USGS Publications Warehouse

    Howard, Keith A.

    2002-01-01

    This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits of the Battle Ground 7.5 minute quadrangle. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:24,000 or smaller.

  17. Influence of bedrock lithology on strath terrace formation in the Willapa River watershed, SW Washington, USA

    NASA Astrophysics Data System (ADS)

    Schanz, S. A.; Montgomery, D. R.

    2013-12-01

    River terraces in tectonically active regions such as the Cascadia subduction margin have been utilized as late Quaternary markers of rock uplift and climate, yet the important role of bedrock lithology as a control on terrace formation is rarely considered. This study investigates lithologic controls on strath terrace formation in the Willapa River basin, situated halfway between the Olympic and Oregon Coast Ranges along the Cascadia subduction zone. The Willapa River and its tributaries alternate flow through easily erodible marine sedimentary and resistant basalt bedrock. We estimate rates of fluvial incision and infer patterns of rock uplift through a combination of field mapping, surveying terrace tread and strath elevations, and radiocarbon dating of terrace abandonment. A long-term steady state between incision and rock uplift is assumed for the basin, and incision rates are calculated as the strath elevation above present thalweg divided by the age of strath abandonment. Radiocarbon dates reveal two extensive terrace sets approximately 150 and 10,000 years old, resulting in a regional rock uplift rate of 0.4×0.1 mm/yr. Terraces are present only in sedimentary bedrock whereas basalt bedrock reaches run through deep, narrow valleys lacking extensive floodplains or terraces. The marine sedimentary units erode easily both laterally and vertically with active erosion of millimeter thick flakes on subaerially exposed bedrock. In contrast, basalt bedrock erodes preferentially in large blocks along fracture planes, resulting in less laterally erodible banks and higher vertical than lateral incision rates. We estimate rock uplift rates of less than 0.5 mm/yr are high enough to initiate strath terrace formation following large, long cycle impetuses such as climatic changes, provided the bedrock lithology is weak enough to allow lateral erosion as well as vertical incision. Thus, disturbances from large climatic or base level changes initiate terrace formation, but

  18. The sinuous bedrock channel of the Tapi River, Central India: Its form and processes

    NASA Astrophysics Data System (ADS)

    Kale, Vishwas S.

    2005-09-01

    The Tapi Gorge lies in the monsoon-dominated region of the Indian subcontinent. Because of the seasonality of rainfall and flows all the fluvial activity in the bedrock gorge is confined to the monsoon season, in general, and during a few high-magnitude monsoon floods in particular. Field investigations along a 30-km reach of the sinuous bedrock gorge indicate that the river displays all the morphologic properties of a meandering alluvial channel albeit with a much higher level of energy expenditure. Considering the perimeter lithology and channel morphology two types of reaches are evident in the field: a predominantly rocky and relatively straight reach close to the gorge-head, and a longer, sinuous reach of gravel deposition downstream. Hydraulic modeling of a rainfall-induced dam-failure flood indicates that large-magnitude events that exceed the threshold of bedrock resistance for a sustained length of time are capable of erosion. It appears that the overall channel and gorge morphology is adjusted to two types of thresholds. A threshold of boulder-transport, which is associated with large floods that are competent to entrain boulders but are incapable of bedrock erosion; and another higher threshold that is exceeded by truly high-energy processes that generate large total energy and exceed the threshold of bedrock resistance. The later threshold is exceeded only episodically, with fairly long periods of little or no bedrock erosion in between. Interestingly, meso-scale erosional features such as inner channels and well-developed potholes are nearly absent or inconspicuous within the gorge section. Whilst this could be partly attributed to the bedrock resistance, it appears that under the present hydro-geomorphic conditions the dominant fluvial activity is not directed towards the channel bed, but towards the banks. This is evident from the concentration of erosion on the outer banks and deposition of coarse gravel on the inner banks, and armoring of the

  19. Quantification of confidence in a geological model of Cumbria, UK

    NASA Astrophysics Data System (ADS)

    Waters, Colin; Lark, Murray; Mathers, Steve; Marchant, Andrew; Hulbert, Andrew

    2015-04-01

    A three-dimensional geological model of Cumbria was constructed by several geologists, applying expert judgment to interpret available data, as both a fence network of cross-sections in GSI3d and surfaces in GOCAD®. Direct statistical measures of uncertainty of the model are not available. Neither is it feasible to undertake post hoc sampling at additional independent boreholes to estimate measures of model uncertainty. The study considered various qualitative and quantitative approaches to assessing the modelled surfaces and volumes. Modellers make judgments about the relative quality of different types of available data and the extent to which simple trends in the units of interest (e.g. a gentle dip) allow their structure to be extrapolated with confidence away from observations. Confidence decays with increasing distance from a hard observation, such as a field exposure, an interpreted borehole, or a "softer" observation such as a geophysical measurement. In the study area it is possible to make qualitative assessments of four distinct structural domains, marked by different levels in the confidence of the interpretation of the geological model through factors such as availability of deep borehole data, seismic lines, surface exposure and the complexity of the bedrock geology and an appraisal of the extent, amount and quality of the data used to constrain the boundaries presented within the model. The study also attempted to provide various quantitative approaches to assess the type and distribution of data. The quantification of a Confidence Index uses expert elicitation to assess the certainty of subsurface interpretations of modelled surfaces and volumes based upon a statistical analysis of the proximity to subsurface data (boreholes and seismic data). Application of this approach is presented as elevation and thickness grids for a principal aquifer in the region. This approach is directly applicable in areas where bedrock strata are poorly exposed and the

  20. Estimating Bedrock Topography beneath Ice and Sediment Fillings in High Mountain Valleys: Preliminary Results from a Method Comparison Study

    NASA Astrophysics Data System (ADS)

    Mey, J.; Scherler, D.; Strecker, M. R.; Zeilinger, G.

    2012-12-01

    Knowledge about the thickness distribution of ice and sediment fillings in high mountain valleys is important for many applications in the fields of Hydrology, Geology, Glaciology, Geohazards and Geomorphology. However, direct geophysical measurements of ice/sediment thickness are laborious and require infrastructure and logistics that is often not available, particularly in remote mountain regions. In the past years, several methods have been developed to approximate the valley fill thicknesses primarily based on digital elevation data. In the case of sediment fillings, the thickness estimates are mostly based on simple morphometric considerations, whereas in the case of ice, more complex methods have been established using glacier mass balance and ice-flow dynamics. In this study we compare three of these methods that have been frequently applied in the past. These include a physically based approach for estimating ice-thickness distribution of valley glaciers using mass fluxes and flow mechanics. Further we adopt a method that uses the prediction capability of artificial neural networks (ANN) and we investigate a method that is based on the extrapolation of the slopes of the valley walls into the subsurface. We set up a test series in which all methods are applied to four glaciers and two sediment-filled valleys in the European Alps. The resulting bedrock topography derived from each method is checked against available ground truth data, comprising ground penetrating radar-, seismic reflection- and borehole measurements. Obviously, the method developed for estimation of ice-thickness is applicable only to the cases where valleys are occupied by ice, whereas the ANN approach and the slope extrapolation method are independent of the sort of valley fill. Thus a direct comparison is restricted to glacier settings. First results show that all methods can qualitatively reconstruct bedrock topography with typical overdeepenings and trough-shaped cross-profiles. Due to

  1. Combination of Geophysical Methods to Support Urban Geological Mapping

    NASA Astrophysics Data System (ADS)

    Gabàs, A.; Macau, A.; Benjumea, B.; Bellmunt, F.; Figueras, S.; Vilà, M.

    2014-07-01

    Urban geological mapping is a key to assist management of new developed areas, conversion of current urban areas or assessment of urban geological hazards. Geophysics can have a pivotal role to yield subsurface information in urban areas provided that geophysical methods are capable of dealing with challenges related to these scenarios (e.g., low signal-to-noise ratio or special logistical arrangements). With this principal aim, a specific methodology is developed to characterize lithological changes, to image fault zones and to delineate basin geometry in the urban areas. The process uses the combination of passive and active techniques as complementary data: controlled source audio-magnetotelluric method (CSAMT), magnetotelluric method (MT), microtremor H/V analysis and ambient noise array measurements to overcome the limitations of traditional geophysical methodology. This study is focused in Girona and Salt surrounding areas (NE of Spain) where some uncertainties in subsurface knowledge (maps of bedrock depth and the isopach maps of thickness of quaternary sediments) need to be resolved to carry out the 1:5000 urban geological mapping. These parameters can be estimated using this proposed methodology. (1) Acoustic impedance contrast between Neogene sediments and Paleogene or Paleozoic bedrock is detected with microtremor H/V analysis that provides the soil resonance frequency. The minimum value obtained is 0.4 Hz in Salt city, and the maximum value is the 9.5 Hz in Girona city. The result of this first method is a fast scanner of the geometry of basement. (2) Ambient noise array constrains the bedrock depth using the measurements of shear-wave velocity of soft soil. (3) Finally, the electrical resistivity models contribute with a good description of lithological changes and fault imaging. The conductive materials (1-100 Ωm) are associated with Neogene Basin composed by unconsolidated detrital sediments; medium resistive materials (100-400 Ωm) correspond to

  2. Forensic geology exhumed

    NASA Astrophysics Data System (ADS)

    Martinez, Joseph Didier

    Forensic geology binds applied geology to the world of legal controversy and action. However, the term “forensic” is often misconstrued. Although even some attorneys apply it only to the marshalling of evidence in criminal cases, it has a much broader definition. One dictionary defines it as “pertaining to, connected with, or used in courts of law or public discussion and debate.” The American Geological Institute's Glossary of Geology defines forensic geology as “the application of the Earth sciences to the law.” The cited reference to Murray and Tedrow [1975], however, deals mostly if not exclusively with the gathering and use of evidence in criminal cases, despite the widespread involvement of geologists in more general legal matters. It seems appropriate to “exhume” geology's wider application to the law, which is encompassed by forensic geology.

  3. Geologic map of Yosemite National Park and vicinity, California

    USGS Publications Warehouse

    Huber, N.K.; Bateman, P.C.; Wahrhaftig, Clyde

    1989-01-01

    This digital map database represents the general distribution of bedrock and surficial deposits of the Yosemite National Park vicinity. It was produced directly from the file used to create the print version in 1989. The Yosemite National Park region is comprised of portions of 15 7.5 minute quadrangles. The original publication of the map in 1989 included the map, described map units and provided correlations, as well as a geologic summary and references, all on the same sheet. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:125,000 or smaller.

  4. Geologic map and map database of western Sonoma, northernmost Marin, and southernmost Mendocino counties, California

    USGS Publications Warehouse

    Blake, M.C., Jr.; Graymer, R.W.; Stamski, R.E.

    2002-01-01

    This digital map database, compiled from previously published and unpublished data, and new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying text file (wsomf.ps, wsomf.pdf, wsomf.txt), it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:62,500 or smaller.

  5. Analytical data for geologic units in Missouri and parts of Kansas, Oklahoma and Arkansas

    USGS Publications Warehouse

    Boerngen, Josephine G.; VanTrump, George; Ebens, Richard J.

    1975-01-01

    This report lists the geochemical data collected during the course of a reconnaissance study of compositional variation in the bedrock and surficial gelogic untis exposed in Missouri and adjoining parts of Kansas, Oklahoma, and Arkansas.  The primar object of the study was to assess scale-related components of geochemical variance with a view of determining the importance of regional geochemical variation in these units (cf. Connor and other, 1972).  Geologic evaluation, geochemical interpretation and summaries, and sampling designs employed in the collection of most of these data may be found in U.S. Geological Survey (1972a-1972f, 1973) and Connor and Shacklette (1975).

  6. Geologic interpretations of seismic data, relocation of Route 116, Stations 7-135 in Cheshire, Mass.

    USGS Publications Warehouse

    Willard, Max E.; Linehan, Rev. Daniel

    1950-01-01

    Three segments of the proposed relocation of Route 116, stations 7 to 135, in Cheshire, Mass. require shallow cuts. For the purpose of obtaining information on the depths to bedrock, and on the nature of the overlaying materials, seismic and geologic studies were made of the segments in October 1949. The work was done as part of the cooperative program of the Massachusetts Department of Public Works and the United States Department of the Interior, Geological Survey. On seismic transverse was made between stations 7 and 15, 1 between stations 80 and 82, 3 between stations 85 and 90, and 4 between stations 125 and 135.

  7. Geologic map of the Cerro Gordo Peak 7.5' Quadrangle, Inyo County, California

    USGS Publications Warehouse

    Stone, Paul; Dunne, George C.; Conrad, James E.; Swanson, Brian J.; Stevens, Calvin H.; Valin, Zenon C.

    2004-01-01

    This digital map database, compiled from new mapping by the authors, represents the general distribution of bedrock and surficial deposits in the mapped area. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:24,000 or smaller.

  8. Geologic map of the Grand Canyon 30' x 60' quadrangle, Coconino and Mohave Counties, northwestern Arizona

    USGS Publications Warehouse

    Billingsley, G.H.

    2000-01-01

    This digital map database, compiled from previously published and unpublished data as well as new mapping by the author, represents the general distribution of bedrock and surficial deposits in the map area. Together with the accompanying pamphlet, it provides current information on the geologic structure and stratigraphy of the Grand Canyon area. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the source maps limits the spatial resolution (scale) of the database to 1:100,000 or smaller.

  9. Geophysical characterization of fractured bedrock at Site 8, former Pease Air Force Base, Newington, New Hampshire

    USGS Publications Warehouse

    Mack, Thomas J.; Degnan, James R.

    2003-01-01

    Borehole-geophysical logs collected from eight wells and direct-current resistivity data from three survey lines were analyzed to characterize the fractured bedrock and identify transmissive fractures beneath the former Pease Air Force Base, Newington, N.H. The following logs were used: caliper, fluid temperature and conductivity, natural gamma radiation, electromagnetic conductivity, optical and acoustic televiewer, and heat-pulse flowmeter. The logs indicate several foliation and fracture trends in the bedrock. Two fracture-correlated lineaments trending 28? and 29?, identified with low-altitude aerial photography, are coincident with the dominant structural trend. The eight boreholes logged at Site 8 generally have few fractures and have yields ranging from 0 to 40 gallons per minute. The fractures that probably resulted in high well yields (20?40 gallons per minute) strike northeast-southwest or by the right hand rule, have an orientation of 215?, 47?, and 51?. Two-dimensional direct-current resistivity methods were used to collect detailed subsurface information about the overburden, bedrock-fracture zone depths, and apparent-dip directions. Analysis of data inversions from data collected with dipole-dipole and Schlumberger arrays indicated electrically conductive zones in the bedrock that are probably caused by fractured rock. These zones are coincident with extensions of fracture-correlated lineaments. The fracture-correlated lineaments and geophysical-survey results indicate a possible northeast-southwest anisotropy to the fractured rock.

  10. BEDROCK CREEK, NEZ PERCE AND CLEARWATER COUNTIES, IDAHO - WATER QUALITY STATUS REPORT, 1985

    EPA Science Inventory

    A water quality monitoring study was conducted on Bedrock Creek (17060306), a third order tributary to the Clearwater River in north-central Idaho. Objectives of the study were to assess water quality of the stream and its major tributary; to document the effects of storm runoff...

  11. MICROFRACTURE SURFACE GEOCHEMISTRY AND ADHERENT MICROBIAL POPULATION METABOLISM IN TCE-CONTAMINATED COMPETENT BEDROCK

    EPA Science Inventory

    A TCE-contaminated competent bedrock site in Portsmouth, NH was used to determine if a relation existed between microfracture (MF) surface geochemistry and the ecology and metabolic activity of attached microbes relative to terminal electron accepting processes (TEAPs) and TCE bi...

  12. A preliminary study of the distribution of saline water in the bedrock aquifers of eastern Wisconsin

    USGS Publications Warehouse

    Ryling, Roy W.

    1961-01-01

    The occurrence of saline water in the bedrock aquifers of eastern Wisconsin has been known for many years. Because of the ready availability of fresh water from other sources, little has been known of the extent of the saline-water area. Saline ground water is a potential source of contamination to wells if it moves into fresh-water zones.

  13. Microbial co-occurrence patterns in deep Precambrian bedrock fracture fluids

    NASA Astrophysics Data System (ADS)

    Purkamo, Lotta; Bomberg, Malin; Kietäväinen, Riikka; Salavirta, Heikki; Nyyssönen, Mari; Nuppunen-Puputti, Maija; Ahonen, Lasse; Kukkonen, Ilmo; Itävaara, Merja

    2016-05-01

    The bacterial and archaeal community composition and the possible carbon assimilation processes and energy sources of microbial communities in oligotrophic, deep, crystalline bedrock fractures is yet to be resolved. In this study, intrinsic microbial communities from groundwater of six fracture zones from 180 to 2300 m depths in Outokumpu bedrock were characterized using high-throughput amplicon sequencing and metagenomic prediction. Comamonadaceae-, Anaerobrancaceae- and Pseudomonadaceae-related operational taxonomic units (OTUs) form the core community in deep crystalline bedrock fractures in Outokumpu. Archaeal communities were mainly composed of Methanobacteriaceae-affiliating OTUs. The predicted bacterial metagenomes showed that pathways involved in fatty acid and amino sugar metabolism were common. In addition, relative abundance of genes coding the enzymes of autotrophic carbon fixation pathways in predicted metagenomes was low. This indicates that heterotrophic carbon assimilation is more important for microbial communities of the fracture zones. Network analysis based on co-occurrence of OTUs revealed possible "keystone" genera of the microbial communities belonging to Burkholderiales and Clostridiales. Bacterial communities in fractures resemble those found in oligotrophic, hydrogen-enriched environments. Serpentinization reactions of ophiolitic rocks in Outokumpu assemblage may provide a source of energy and organic carbon compounds for the microbial communities in the fractures. Sulfate reducers and methanogens form a minority of the total microbial communities, but OTUs forming these minor groups are similar to those found in other deep Precambrian terrestrial bedrock environments.

  14. Spatial variability in floodplain resistance to erosion on a large meandering, mixed bedrock-alluvial river

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spatial heterogeneities of the erosion-resistance properties of the channel banks and floodplains, such as grain size characteristics and the presence of vegetation and bedrock, can have a substantial influence on river morphodynamics, resulting in complex planform geometries and highly variable rat...

  15. Movement of Landslide Triggered by Bedrock Exfiltration with Nonuniform Pore Pressure Distribution

    NASA Astrophysics Data System (ADS)

    Jan, C. D.; Jian, Z. K.

    2014-12-01

    Landslides are common phenomena of sediment movement in mountain areas and usually pose severe risks to people and infrastructure around those areas. The occurrence of landslides is influenced by groundwater dynamics and bedrock characteristics as well as by rainfall and soil-mass properties. The bedrock may drain or contribute to groundwater in the overlying soil mass, depending on the hydraulic conductivity, degree of fracturing, saturation, and hydraulic head. Our study here is based on the model proposed by Iverson (2005). The model describes the relation between landslide displacement and the shear-zone dilation/contraction of pore water pressure. To study landslide initiation and movement, a block soil mass sliding down an inclined beck-rock plane is governed by Newton's equation of motion, while both the bedrock exfiltration and excess pore pressure induced by dilatation or contraction of basal shear zone are described by diffusion equations. The Chebyshev collocation method was used to transform the governing equations to a system of first-order ordinary differential equations, without the need of iteration. Then a fourth-order Runge-Kutta scheme was used to solve these ordinary differential equations. The effects of nonuniform bedrock exfiltration pressure distributions, such as the delayed peak, central peak, and advanced peak distributions, on the time of landslide initiation and the speed of landslide movement were compared and discussed.

  16. The keystone species of Precambrian deep bedrock biosphere belong to Burkholderiales and Clostridiales

    NASA Astrophysics Data System (ADS)

    Purkamo, L.; Bomberg, M.; Kietäväinen, R.; Salavirta, H.; Nyyssönen, M.; Nuppunen-Puputti, M.; Ahonen, L.; Kukkonen, I.; Itävaara, M.

    2015-11-01

    The bacterial and archaeal community composition and the possible carbon assimilation processes and energy sources of microbial communities in oligotrophic, deep, crystalline bedrock fractures is yet to be resolved. In this study, intrinsic microbial communities from six fracture zones from 180-2300 m depths in Outokumpu bedrock were characterized using high-throughput amplicon sequencing and metagenomic prediction. Comamonadaceae-, Anaerobrancaceae- and Pseudomonadaceae-related OTUs form the core community in deep crystalline bedrock fractures in Outokumpu. Archaeal communities were mainly composed of Methanobacteraceae-affiliating OTUs. The predicted bacterial metagenomes showed that pathways involved in fatty acid and amino sugar metabolism were common. In addition, relative abundance of genes coding the enzymes of autotrophic carbon fixation pathways in predicted metagenomes was low. This indicates that heterotrophic carbon assimilation is more important for microbial communities of the fracture zones. Network analysis based on co-occurrence of OTUs revealed the keystone genera of the microbial communities belonging to Burkholderiales and Clostridiales. Bacterial communities in fractures resemble those found from oligotrophic, hydrogen-enriched environments. Serpentinization reactions of ophiolitic rocks in Outokumpu assemblage may provide a source of energy and organic carbon compounds for the microbial communities in the fractures. Sulfate reducers and methanogens form a minority of the total microbial communities, but OTUs forming these minor groups are similar to those found from other deep Precambrian terrestrial bedrock environments.

  17. Bedrock refractive-flow cells: A passive treatment analog to funnel-and-gate

    SciTech Connect

    Dick, V.; Edwards, D.

    1997-12-31

    Funnel-and-gate technology provides a mechanism to passively treat groundwater contaminant plumes, but depends on placement of a sufficient barrier ({open_quotes}funnel{close_quotes}) in the plume flow path to channel the plume to a pass-through treatment zone ({open_quotes}gate{close_quotes}). Conventional barrier technologies limit funnel-and-gate deployment to unconsolidated overburden applications. A method has been developed which allows similar passive treatment to be applied to bedrock plumes. Rather than use barriers as the funnel, the method uses engineered bedrock zones, installed via precision blasting or other means, to refract groundwater flow along a preferred path to treatment (gate). The method requires orienting the refractive cell based on the Tangent Law and extending refractive cell limbs down gradient of the gate to disperse head and control flow. A typical Refractive-Flow cell may be{open_quotes}Y{close_quotes}shaped, with each limb 3-10 ft [1-3 m] wide and several tens to a few hundred feet [10 - 100 m] in length. Treatment takes place at the center of the X. MODFLOW modeling has been used to successfully simulate desired flow. Engineered blasting has been used at full scale application to create bedrock rubble zones for active collection/flow control for several years. The method provides a previously unavailable method to passively treat contaminated groundwater in bedrock at low cost.

  18. INFLUENCE OF SEDIMENT SUPPLY, LITHOLOGY, AND WOOD DEBRIS ON THE DISTRIBUTION OF BEDROCK AND ALLUVIAL CHANNELS

    EPA Science Inventory

    Field surveys in the Willapa River basin, Washington State, indicate that the drainage area?channel slope threshold describing the distribution of bedrock and alluvial channels is influenced by the underlying lithology and that local variations in sediment supply can overwhelm ba...

  19. Distribution of bedrock and alluvial channels in forested mountain drainage basins

    NASA Astrophysics Data System (ADS)

    Montgomery, David R.; Abbe, Tim B.; Buffington, John M.; Peterson, N. Phil; Schmidt, Kevin M.; Stock, Jonathan D.

    1996-06-01

    MOUNTAIN river networks often consist of both bedrock and alluvial channels1-5, the spatial distribution of which controls several fundamental geomorphological and ecological processes6,7. The nature of river channels can influence the rates of river incision and landscape evolution1,2, as well as the stream habitat characteristics affecting species abundance and aquatic ecosystem structure8-11. Studies of the factors controlling the distribution of bedrock and alluvial channels have hitherto been limited to anthropogenic badlands12. Here we investigate the distribution of channel types in forested mountain drainage basins, and show that the occurrence of bedrock and alluvial channels can be described by a threshold model relating local sediment transport capacity to sediment supply. In addition, we find that valley-spanning log jams create alluvial channels- hospitable to aquatic life-in what would otherwise be bedrock reaches. The formation of such jams depends critically on the stabilizing presence of logs derived from the largest trees in the riverside forests, suggesting that management strategies that allow harvesting of such trees can have a devastating influence on alluvial habitats in mountain drainage basins.

  20. Piezometric response in shallow bedrock at CB1: Implications for runoff generation and landsliding

    NASA Astrophysics Data System (ADS)

    Montgomery, David R.; Dietrich, William E.; Heffner, John T.

    2002-12-01

    Experimental observations comparing two steep unchanneled valleys in the Oregon Coast Range, one intensively instrumented (CB1) and the other monitored for runoff but which produced a debris flow (CB2), shed light on the mechanisms of shallow flow in bedrock, its interaction with the vadose zone, and its role in generating landslides. Previous work at CB1 led to the proposal that during storms pulses of rainfall transmit pressure waves through the vadose zone and down to the saturated zone to create rapid pore pressure response and runoff [, 1998]. Here, we document the associated rapid pore pressure response in the shallow fractured bedrock that underlies these colluvium-mantled sites and examine its influence on the generation of storm flow, seasonal variations in base flow, and slope stability in the overlying colluvial soil. Our observations document rapid piezometric response in the shallow bedrock and a substantial contribution of shallow fracture flow to both storm flow and seasonal variations in base flow. Saturated hydraulic conductivity in the colluvial soil decreases with depth below the ground surface, but the conductivity of the near-surface bedrock displays no depth dependence and varies over five orders of magnitude. Analysis of runoff intensity and duration in a series of storms that did and did not trigger debris flows in the surrounding area shows that the landslide inducing storms had the greatest intensity over durations similar to those predicted by a simple model of piezometric response. During a monitored storm in February 1992, the channel head at the base of the neighboring CB2 site failed as a debris flow. Automated piezometric measurements document that the CB2 debris flow initiated several hours after peak discharge, coincident with localized development of upward spikes of pressure head from near-surface bedrock into the overlying colluvial soil in CB1. Artesian flow observed exfiltrating from bedrock fractures on the failure surfaces

  1. An episode of rapid bedrock channel incision during the last glacial cycle, measured with 10Be

    USGS Publications Warehouse

    Reusser, L.; Bierman, P.; Pavich, M.; Larsen, J.; Finkel, R.

    2006-01-01

    We use 10Be to infer when, how fast, and why the Susquehanna River incised through bedrock along the U.S. Atlantic seaboard, one of the world's most prominent and ancient passive margins. Although the rate at which large rivers incise rock is a fundamental control on the development of landscapes, relatively few studies have directly measured how quickly such incision occurs either in tectonically active environments or along passive margins. Exposure ages of fluvially carve d, bedrock strath terraces, preserved along the lower Susquehanna River, demonstrate that even along a passive margin, large rivers are capable of incising through rock for short periods of time at rates approaching those recorded in tectonically active regions, such as the Himalayas. Over eighty samples, collected along and between three prominent levels of strath terraces within Holtwood Gorge, indicate that the Susquehanna River incised more than 10 meters into the Appalachian Piedmont during the last glacial cycle. Beginning ???36 ka, incision rates increased dramatically, and remained elevated until ???14 ka. The northern half of the Susquehanna basin was glaciated during the late Wisconsinan; however, similar rates and timing of incision occurred in the unglaciated Potomac River basin immediately to the south. The concurrence of incision periods on both rivers suggests that glaciation and associated meltwater were not the primary drivers of incision. Instead, it appears that changing climatic conditions during the late Pleistocene promoted an increase in the frequency and magnitude of flood events capable of exceeding thresholds for rock detachment and bedrock erosion, thus enabling a short-lived episode of rapid incision into rock. Although this study has constraine d the timing and rate of bedrock incision along the largest river draining the Atlantic passive margin, the dates alone cannot explain fully why, or by what processes, this incision occurred. However, cosmogenic dating offers

  2. The Dynamics of Coarse Sediment Transfer in an Upland Bedrock River

    NASA Astrophysics Data System (ADS)

    Warburton, J.; Hardy, R. J.; Ferguson, R. I.; Cray, A.

    2010-12-01

    Bedrock channels in UK environments have received relatively little attention despite their importance within upland river systems and their influence on controlling the conveyance of sediment downstream. This poster describes the transfer of coarse sediment through Trout Beck, an upland bedrock reach in the North Pennines, UK. The transport of coarse sediment has been quantified through field monitoring of sediment characteristics, repeat magnetic tracer surveys and in-situ bed load impact sensors. This was carried out in conjunction with surveys of channel morphology (using terrestrial laser scanning and repeat dGPS measurements) and continuous flow monitoring. The interaction between mobile sediment and channel morphology is partly conditioned by the extent of alluvial sediment cover. Sediment storage is patchy with partially alluvial and alluvial sections of the channel, interspersed with bedrock reaches containing very little sediment except in hydraulically sheltered sites. There are notable differences in sediment dynamics between these different sections of the river channel which have a considerable influence on conveyance of sediment through the reach. In bedrock sections the low resistance to flow and stable channel boundaries result in little sediment storage and during periods when flow is competent there is downstream conveyance of the full grain-size distribution of sediment. Detailed morphological survey has provided the necessary boundary conditions, along with the flow data, to apply a one-dimensional hydraulic model (HEC-RAS) of the bedrock study reach. The modelling results have quantified the hydraulic regime of the channel. Using local shear stress as a proxy for sediment transport, sediment transport potential for the dominant grain-size distribution of the reach (16-256 mm) has been assessed for different locations in the channel. There are significant differences in the critical threshold of shear stress for sediment transport down the

  3. Threshold bedrock channels in tectonically active mountains with frequent mass wasting

    NASA Astrophysics Data System (ADS)

    Korup, O.; Hayakawa, Y. S.; Codilean, A.; Oguchi, T.

    2013-12-01

    Models of how mountain belts grow and erode through time largely rely on the paradigm of fluvial bedrock incision as the main motor of response to differences in rock uplift, thus setting base levels of erosion in tectonically active landscapes. Dynamic feedbacks between rock uplift, bedrock river geometry, and mass wasting have been encapsulated within the concept of threshold hillslopes that attain a mechanically critical inclination capable of adjusting to fluvial incision rates via decreased stability and commensurately more frequent landsliding. Here we provide data that challenge the widely held view that channel steepness records tectonic forcing more faithfully than hillslope inclination despite much robust empirical evidence of such links between bedrock-river geometry and hillslope mass wasting. We show that the volume mobilized by mass wasting depends more on local topographic relief and the sinuosity of bedrock rivers than their mean normalized channel steepness. We derive this counterintuitive observation from an unprecedented inventory of ~300,000 landslides covering the tectonically active Japanese archipelago with substantial differences in seismicity, lithology, vertical surface deformation, topography, and precipitation variability. Both total landslide number and volumes increase nonlinearly with mean local relief even in areas where the fraction of steepest channel segments attains a constant threshold well below the maximum topographic relief. Our data document for the first time that mass wasting increases systematically with preferential steepening of flatter channel segments. Yet concomitant changes in mean channel steepness are negligible such that it remains a largely insensitive predictor of landslide denudation. Further, minute increases in bedrock-river sinuosity lead to substantial reduction in landslide abundance and volumes. Our results underline that sinuosity (together with mean local relief) is a key morphometric variable for

  4. Effects of bedrock nutrient density on vegetation and topography in the Sierra Nevada Batholith, California

    NASA Astrophysics Data System (ADS)

    Hahm, W.; Riebe, C. S.; Araki, S.

    2012-12-01

    Vegetation harnesses solar energy to promote soil stability and regolith production. Mechanistically, vegetation encourages chemical weathering both directly, by releasing organic acids, and indirectly, by stabilizing soils and increasing their contact time with corrosive natural waters. Empirically, global compilations indicate that millennial-scale erosion rates are an order of magnitude faster on average in soil-mantled landscapes compared to bare, exposed-bedrock surfaces. Hence, connections between vegetation and soil cover are central to long-term questions of landscape evolution and short-term issues of sustainability. Yet the factors that regulate the distribution of vegetation, and by extension the soil mantle, are not fully understood. The unglaciated, granitic plutons of the western Sierra Nevada host an unexplained landscape dichotomy, in which forested, soil-mantled hillslopes are juxtaposed with bare, exposed-bedrock hillslopes. Here we present new measurements of bedrock nutrient density that correlate strongly with tree canopy cover within a narrow band of elevation and climate. Bedrock phosphorus concentrations vary by more than an order of magnitude and change abruptly at plutonic contacts. These same contacts frequently mark transitions between vegetated, soil-mantled terrain and exposed bedrock surfaces, similar to sharp vegetative contacts around ultramafic substrates elsewhere in California. Major and minor element enrichment of soil relative to bedrock point to dust as a probable source of nutrients in at least one phosphorus-poor pluton, where sparse stunted forests persist in a landscape otherwise devoid of vegetation. This is consistent with an intrinsic nutrient deficiency that is partly offset by allocthonous nutrient inputs. Our observations are consistent with nutrient availability serving as a regulator that drives landscapes into two stable states. If nutrient availability is sufficient, vegetation takes hold, stabilizing soils

  5. Subsurface flow behavior in thick colluvium and fissured bedrock in Kumano-daira, Central Japan

    NASA Astrophysics Data System (ADS)

    Hattori, S.; Onda, Y.; Tanaka, T.; Shimamura, M.; Togari-Ohta, A.; Uchida, T.; Tsujimura, M.

    2005-12-01

    To study the groundwater flow path and runoff generation mechanism in the watershed underlain by thick volcanic tephra and permeable bedrock, hydrometric observations, rain water, subsurface water, and stream water sampling and chemical and isotopic analysis were performed. Four catchments were monitored; K1, K2, K3 and K4, underlain by Neogene tuff (6-10 m thick) and Rhyolite, in Kumanodaira area, Gunma Prefecture, Japan. Large landslides occurred in K4 catchment without marked rainfall in 1950, killed 50 people. Discharge was monitored outlet of each cachment. In K4 catchment, six tensiometers, buried 50-650 cm, 2 groundwater wells (9 and 12 m depth) were installed. In K4 catchment, stream runoff shows the longest recession limb compared with other catchments. The groundwater level of well B (12 m) in K4, which penetrates under the bedrock interface, shows delayed peak of 5 months after the major storm event, whereas groundwater level of well A (9 m) shows similar trend to the stream hydrograph. The chemical analysis of groundwater show that the ion concentrations of grandwater in well B are significantly differs from those stream and bedrock spring water in K4. The deuterium excess value of rainwater indicates lower at large storm events by a number of typhoons compared with smaller storm events. The deuterium excess values of stable isotopic also show the seasonal trend; a low value of rainfall is indicated in summer and a high value in winter. The deuterium excess value of soil water was found to be smaller as the depth increases. These data suggest that soil water near bedrock is mainly originated from larger rainfall events. Employing the dispersive model by using deuterium excess, mean residence times of ground water in well B was estimated as 420 days. The dispersion parameter of groundwater in well B estimated as 0.047, is smaller than that of grandwater in shallow soil (well A) estimated as 0.325. From above results, the ground water flow path in the

  6. Geological assessing of urban environments with a systematic mapping survey: The 1:5000 urban geological map of Catalonia

    NASA Astrophysics Data System (ADS)

    Vilà, Miquel; Pi, Roser; Cirés, Jordi; de Paz, Ana; Berástegui, Xavier

    2010-05-01

    The ground features of urban areas and the geologic processes that operate on them are, in general, strongly altered from their natural original condition as a result of anthropogenic activities. Assessing the stability of the ground, the flooding areas, and, the health risk as a consequence of soil pollution, are, among others, fundamental topics of urban areas that require a better understanding. The development of systematic urban geological mapping projects provides valuable resources to address these issues. Since 2007, the Institut Geologic de Catalunya (IGC) runs an urban geological mapping project, to provide accurate geologic information of county capitals and towns of more than 10000 inhabitants of Catalonia. The urban zones of 131 towns will be surveyed for this project, totalizing an area of about 2200 km2 to be mapped in 15 years. According to the 2008 census, the 82 % of the population of Catalonia (7.242.458 inhabitants) lives in the areas to be mapped in this project. The mapping project integrates in a GIS environment the following subjects: - Data from pre-existing geotechnical reports, historical geological and topographical maps and, from historical aerial photographs. - Data from available borehole databases. - Geological characterization of outcrops inside the urban network and neighbouring areas. - Geological, chemical and physical characterisation of representative rocks, sediments and soils. - Ortophotographs (0.5 m pixel size) and digital elevation models (5 meter grid size) made from historical aerial photographs, to depict land use changes, artificial deposits and geomorphological elements that are either hidden or destroyed by urban sprawl. - Detailed geological mapping of quaternary sediments, subsurface bedrock and artificial deposits. - Data from subsurface prospection in areas with insufficient or confuse data. - 3D modelling of the main geological surfaces such as the top of the pre-quaternary basement. All the gathered data is

  7. Glacial erosion of bedrock and preliminary Quaternary stratigraphy in the western Lake Erie coastal region

    SciTech Connect

    Shideler, G.I. ); Stone, B.D. )

    1994-04-01

    An analysis of 120 km of high-resolution seismic reflection profiles and onshore well records in the southwestern Lake Erie coastal zone shows a highly dissected bedrock surface. Regional subsurface data confirm extensive glacial modification of the preglacial landscape and the differential erosion of bedrock units. Areas of deep glacial scour coincide with shale and dolostone subcrop belts, in which bedrock strike direction was subparallel to glacial flow directions during early and late phases of glaciation. Locally, deep scouring also occurred over zones of fractured bedrock. In southeastern Michigan, large bedrock valleys, widened and deepened by glacial erosion, are preserved on the north side of the area of the Erie ice lobe. To the south in areas of axial flow of the Erie lobe and southerly ice flow during glacial maxima, traces of preglacial valleys have been more severely modified by glacial erosion in diverging directions. Striations in the region record three such diverging ice-flow directions of the last ice sheet. In one quarry, the position and cross-cutting erosional relationships of the three striation sets indicate their relative ages, from oldest to youngest: SSW, SW, and W. The SSW-trending set is overlain by a compact, loamy till containing abundant Canadian-shield crystalline gravel clasts. The till and the striations record the initial Late Wisconsinan ice advance into the region. The younger striation sets are overlain by the clayey, shale-rich till of the Erie lobe. Onshore, glaciolacustrine massive silty clay overlies the clayey till and fills broad troughs between areas of till at the surface. Offshore, seismic profiles reveal stratification in the clay, which is overlain by late Holocene mud. A nearby test hole through the beach west of Turtle Creek suggests a valley-fill sequence consisting of Late Wisconsinan till overlain by 5 m of organic mud deposited during the late Holocene transgression of Late Erie.

  8. Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood

    NASA Astrophysics Data System (ADS)

    Baggs Sargood, M.; Cohen, T. J.; Thompson, C. J.; Croke, J.

    2014-12-01

    The role of extreme events in shaping the earth's surface is one that has held the interests of Earth scientists for centuries. A catastrophic flood in a tectonically quiescent setting in eastern Australia in 2011 provides valuable insight into how bedrock channels respond to such events. Field survey data (3 reaches) and desktop analyses (10 reaches) with catchment areas ranging from 0.5 to 169 km2 show that the predicted discharge for the 2011 event ranged from 400 to 900 m3 s-1, with unit stream power estimates of up to 1000 W m-2. Estimated entrainment relationships predict the mobility of the entire grain size population and field data suggests the localised mobility of boulders up to 4.8 m in diameter. Analysis of repeat LiDAR data demonstrates that all reaches (field and desktop) were areas of net degradation via extensive scouring of mantled alluvium with a strong positive relationship between catchment area and normalised erosion (R2 = 0.8). The extensive scouring in the 2011 flood decreased thalweg variance significantly with the exposure of planar bedrock surfaces, marginal bedrock straths and bedrock steps, along with the formation of a plane-bed cobble morphology. Post-flood field data suggests a slight increase in thalweg variance as a result of the smaller 2013 flood, however the current nature and distribution of channel morphological units does not conform to previous classifications of upland river systems. This suggests that extreme events are significant for re-setting the morphology of in-channel units in such bedrock systems. As important, is the exposure of the underlying lithology to ongoing erosion.

  9. Variability of rock erodibility in bedrock-floored stream channels based on abrasion mill experiments

    NASA Astrophysics Data System (ADS)

    Small, Eric E.; Blom, Tevis; Hancock, Gregory S.; Hynek, Brian M.; Wobus, Cameron W.

    2015-08-01

    We quantify variations in rock erodibility, Kr, within channel cross sections using laboratory abrasion mill experiments on bedrock surfaces extracted from streams with sandstone bedrock in Utah and basaltic bedrock in the Hawaiian Islands. Samples were taken from the thalweg and channel margins, the latter at a height that is inundated annually. For each sample, a sequence of abrasion mill experiments was completed to quantify variations in erosion rate with erosion depth. Erosion rate data from these experiments shows two things. First, the erosion rate from channel margin samples is greater than for thalweg samples, with the greatest difference observed for the rock surface that was exposed in the stream channel. Second, erosion rate decreases with depth beneath the original rock surface, by an order of magnitude in most cases. The erosion rate becomes steady at depths of 1-3 mm for channel margin samples and 0.1-0.4 mm for thalweg samples. Because only rock properties and microtopography vary throughout the sequence of mill experiments, these results suggest that Kr of the bedrock surface exposed in stream channels is higher at the margins than near the channel center and that Kr decreases over depths of ~1 mm. The simplest explanation for these patterns is that Kr is enhanced, at the bedrock surface and along the channel margins, due to the effects of weathering on rock strength and surface roughness. We hypothesize that a balance exists between weathering-enhanced erodibility and episodic incision to allow channel margins to lower at rates similar to the thalweg.

  10. To evaluate ERTS-1 data for usefulness as a geological sensor in the diverse geological terranes of New York State

    NASA Technical Reports Server (NTRS)

    Isachsen, Y. W. (Principal Investigator)

    1972-01-01

    The author has identified the following significant results. In the present imagery, obtained during the full foliage of summer and fall, the greatest amount of spectral geology is displayed in the Adirondack region where bedrock geology is strongly linked to topography. Of the four spectral bands imaged, band 5 and 7 provide the most geological information. The boundary between the basement rocks of the Adirondack Dome and the surrounding Lower Paleozoic rocks is well delineated except in the Northwest Lowlands and along parts of the eastern Adirondacks. Within the basement complex, the most prominently displayed features are numerous north-northeast trending faults and topographic lineaments, and arcuate east-west valleys developed in some of the weaker metasedimentary rocks. The majority of the faults and lineaments shown on the geologic map of New York appear in the ERTS-1 imagery. In addition, many new linears were detected, as well as a number of anomalous curvilinear elements, some circular in plan and measuring up to 25 km in diameter, which do not bear any clear relationship to mapped geological contacts. The possibility that it is an astrobleme will be investigated after snow melts in the spring.

  11. Geology and ground shaking: The April 25--26, 1992 Cape Mendocino earthquake sequence

    SciTech Connect

    Moley, K.; Dengler, L. . Dept. of Geology)

    1993-04-01

    The authors present a simplified geologic map of Humboldt and Del Norte Counties, California and compare it to Modified Mercalli Intensities (MMI) produced by the April 25, 1992 M[sub S] = 7.1, and April 26 Ms = 6.6, and Ms = 6.7 Cape Mendocino earthquakes. The generalized geology was compiled from California Division of Mines and Geology Regional Geology Maps, and area geologic mapping by the USGS and Humboldt State University. Six rock/sediment groups are distinguished by considering lithology, consolidation, compaction, bedding orientation and degree of shearing: (1) landslides and glacial deposits; (2) bay muds and fill, alluvium, lake deposits and beach sand; (3) quaternary marine and non-marine deposits; (4) unstable bedrock; (5) moderately stable bedrock; (6) intrusions. Intensity values for the Saturday earthquake were calculated from over 2,000 surveys to individuals and businesses in the northcoast area by an algorithm based on a weighted sum of survey responses. Numerical data was compiled for over 100 locations in the region. The intensity VIII and greater zone encompassed an area of about 500 km[sup 2] including the communities of Petrolia, Ferndale and Rio Dell. Ground motion generally decays with distance in a roughly radial pattern. A different approach was taken to estimate the pattern of shaking in the two Sunday earthquakes. These earthquakes occurred when most respondents were sleeping and their perception of ground motion was likely to be affected.

  12. Mineralogical sources of groundwater fluoride in Archaen bedrock/regolith aquifers: mass balances from the Peninsular Granite Complex, southern India

    NASA Astrophysics Data System (ADS)

    Hallett, Bethan; Burgess, William; Valsami-Jones, Eugenia

    2014-05-01

    Fluoride in groundwater-sourced drinking water is a widespread concern in India, particularly in the granitic gneiss bedrock/regolith catchments of Andhra Pradesh, one of the most severely affected states. Mobilisation of F- to groundwater is ultimately the consequence of bedrock weathering and regolith development, yet in crystalline bedrock/regolith terrain of the Peninsular Granite Complex, which constitutes a strategically important aquifer environment in India, uncertainties persist in relation to the relative contribution of the different F-bearing minerals and their distribution between the bedrock and the regolith. Even the relative significance of the bedrock and regolith as sources of fluoride to groundwater is disputed, as are explanations of seasonal and/or secular trends in groundwater F-. There are important implications for management of the groundwater resource. Understanding the mechanisms and progress of chemical weathering of the granitic gneiss is key to these questions, ie how effectively is F removed from its primary source(s) as the bedrock weathers? And, to what extent is F- flushed from the weathering profile and/or re-sequestered by secondary mineral phases as the regolith develops? To address these questions we have applied optical petrography, XRD, scanning electron microprobe analysis, whole-rock chemical analysis and leaching experiments to samples of bedrock and regolith from two catchments in Andhra Pradesh. We have quantified the distribution of F between its individual mineralogical sources, and between bedrock and regolith. Experiments show there is no straightforward relationship between whole-rock F content and leached [F-]; in some instances regolith samples leach higher F- concentrations than the fresh granitic gneiss. Results shed light on conflicting conceptual models of F release to groundwater in gneissic bedrock/regolith aquifers. Accounting for groundwater [F-], simple estimates of groundwater flux in the catchments

  13. Geologic map of the Priest Rapids 1:100,000 quadrangle, Washington

    SciTech Connect

    Reidel, S.P.; Fecht, K.R.

    1993-09-01

    This map of the Priest Rapids 1:100,000-scale quadrangle, Washington, shows the geology of one of fifteen complete or partial 1:100,000-scale quadrangles that cover the southeast quadrant of Washington. Geologic maps of these quadrangles have been compiled by geologists with the Washington Division of Geology and Earth Resources (DGER) and Washington State University and are the principal data sources for a 1:250,000scale geologic map of the southeast quadrant of Washington, which is in preparation. Eleven of those quadrangles are being released as DGER open-file reports (listed below). The map of the Wenatchee quadrangle has been published by the US Geological Survey (Tabor and others, 1982), and the Moses Lake (Gulick, 1990a), Ritzville (Gulick, 1990b), and Rosalia (Waggoner, 1990) quadrangles have already been released. The geology of the Priest Rapids quadrangle has not previously been compiled at 1:100,000 scale. Furthermore, this is the first 1:100,000 or smaller scale geologic map of the area to incorporate both bedrock and surficial geology. This map was compiled in 1992, using published and unpublished geologic maps as sources of data.

  14. Groundwater contaminant science activities of the U.S. Geological Survey in New England

    USGS Publications Warehouse

    Weiskel, Peter K.

    2016-01-01

    Aquifers in New England provide water for human needs and natural ecosystems. In some areas, however, aquifers have been degraded by contaminants from geologic and human sources. In recent decades, the U.S. Geological Survey has been a leader in describing contaminant occurrence in the bedrock and surficial aquifers of New England. In cooperation with Federal, State, and local agencies, the U.S. Geological Survey has also studied the vulnerability of groundwater to contaminants, the factors affecting the geographic distribution of contaminants, and the geochemical processes controlling contaminant transport and fate. This fact sheet describes some of the major science needs in the region related to groundwater contaminants and highlights recent U.S. Geological Survey studies that provide a foundation for future investigations.

  15. The influence of variable sediment supply and bed roughness on the spatial distribution of incision in a laboratory bedrock channel

    NASA Astrophysics Data System (ADS)

    Demeter, G. I.; Sklar, L. S.; Davis, J. R.

    2005-12-01

    Numerical models of river incision into bedrock typically predict incision rates averaged across the channel width and over a substantial reach length. However, at-a-point rates of bedrock wear are not likely to be spatially uniform but rather should depend strongly on local conditions, including the degree of partial bed alluviation, patterns of bedrock bed roughness, and variations in local shear stress. We report results of laboratory experiments in which we measured the spatial distribution of erosion under varying sediment supply, bedrock roughness and average boundary shear stress. The experiments utilized a tilting flume 8 m long and 0.3 m wide with an erodible bedrock bed made of sand and cement. We varied bedrock roughness, starting initially with a planar bed, which was roughened by chiseling and then allowed to evolve by repeated and sustained erosion. For a second set of runs we created an extreme initial bedrock roughness bed using egg-carton style mold, which then evolved as erosion significantly modified the bed surface. Digital elevation maps of the bedrock beds were made with a laser microtopography scanning device that has a resolution of 0.2 mm vertical and 5 mm horizontal. We calculated the local rate of bedrock wear by differencing the pre- and post-run local elevations. For each degree of bedrock roughness we systematically varied the rate of supply of uniform 5 mm gravel and measured sediment flux out the downstream end of the flume with a pair of submerged baskets suspended from load cells. Transient alluvial patches, if any, were repeatedly mapped by hand using a 5 cm grid transparent overlay. We also used the laser scanner to map the alluvial deposits left at the end of several runs. We found that high sediment feed rates tend to cover low points and erode the high points preferentially. In contrast, low sediment feed rates favor a positive feedback in which eroded low points capture bedload and erode more rapidly than neighboring high

  16. Organic Carbon Stabilization of Soils Formed on Acidic and Calcareous Bedrocks in Neotropical Alpine Grassland, Peru

    NASA Astrophysics Data System (ADS)

    Yang, Songyu; Cammeraat, Erik; Jansen, Boris; Cerli, Chiara; Kalbitz, Karsten

    2016-04-01

    Increasing evidence shows that Neotropical alpine ecosystems are vulnerable to global change. Since soils in the alpine grasslands of the Peruvian Andean region have large soil organic carbon (SOC) stocks, profound understanding of soil organic matter (OM) stabilization mechanisms will improve the prediction of the feedback between SOC stocks and global change. It is well documented that poor-crystalline minerals and organo-metallic complexes significantly contribute to the OM stabilization in volcanic ash soils, including those in the Andean region. However, limited research has focused on non-ash soils that also express significant SOC accumulation. A pilot study of Peruvian Andean grassland soils suggests that lithology is a prominent factor for such carbon accumulation. As a consequence of contrasting mineral composition and pedogenic processes in soils formed on different non-volcanic parent materials, differences in OM stabilization mechanisms may be profound and consequently may respond differently to global change. Therefore, our study aims at a further understanding of carbon stocks and OM stabilization mechanisms in soils formed on contrasting bedrocks in the Peruvian Andes. The main objective is to identify and compare the roles that organo-mineral associations and aggregations play in OM stabilization, by a combination of selective extraction methods and fractionations based on density, particle size and aggregates size. Soil samples were collected from igneous acidic and calcareous sedimentary bedrocks in alpine grassland near Cajamarca, Peru (7.17°S, 78.63°W), at around 3700m altitude. Samples were taken from 3 plots per bedrock type by sampling distinguishable horizons until the C horizons were reached. Outcomes confirmed that both types of soil accumulate large amounts of carbon: 405.3±41.7 t/ha of calcareous bedrock soil and 226.0±5.6 t/ha of acidic bedrock soil respectively. In addition, extremely high carbon contents exceeding 90g carbon per

  17. The Salzach Valley overdeeping: A most precise bedrock model of a major alpine glacial basin

    NASA Astrophysics Data System (ADS)

    Pomper, Johannes; Salcher, Bernhard; Eichkitz, Christoph

    2016-04-01

    Overdeepenings are impressive phenomena related to the erosion in the ablation zone of major glaciers. They are common features in glaciated and deglaciated regions worldwide and their sedimentary fillings may act as important archives for regional environmental change and glaciation history. Sedimentary fillings are also important targets of geotechnical exploration and construction including groundwater resource management, shallow geothermal exploitation, tunneling and the foundation of buildings. This is especially true in densely populated areas such as the European Alps and their foreland areas, regions which have been multiply glaciated during the last million years. However, due depths often exceeding some hundreds of meters, the overall knowledge on their geometry, formation and sedimentary content is still poor and commonly tied to some local spots. Here we present a bedrock model of the overall lower Salzach Valley, one of the largest glacial overdeepings in the European Alps. We utilized seismic sections from hydrocarbon exploration surveys and deep drillings together with topographic and modelling data to construct a 3D bedrock model. Through the existence of seismic inline and crossline valley sections, multiple drillings reaching the bedrock surface, log and abundant outcrop data we were, as far to our knowledge, able to create the most accurate digital bedrock topography of an alpine major overdeepening. We furthermore analyzed the sedimentary content of the valley as recorded by driller's lithologic logs. Our results suggest that the valley is far from being a regular U-shaped trough with constant depth, rather highlighting highs and lows of different magnitude and underground valley widths of variable extent. Data also indicates that the largest overdeepening of bedrock, reaching around 450 m below the alluvial fill, is not situated after a major glacial confluence following a prominent bedrock gorge but shifted several km down the valley. The

  18. Subsurface Evolution: Weathering and Mechanical Strength Reduction in Bedrock of Lower Gordon Gulch, Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Kelly, P. J.; Anderson, S. P.; Anderson, R. S.; Blum, A.; Foster, M. A.; Langston, A. L.

    2011-12-01

    Weathering processes drive mobile regolith production at the surface of the earth. Chemical and physical weathering weakens rock by creating porosity, opening fractures, and transforming minerals. Increased porosity provides habitat for living organisms, which aid in further breakdown of the rock, leaving it more susceptible to displacement and transport. In this study, we test mechanical and chemical characteristics of weathered profiles to better understand weathering processes. We collect shallow bedrock cores from tors and isovolumetrically weathered bedrock in lower Gordon Gulch to characterize the mechanical strength, mineralogy, and bulk chemistry of samples to track changes in the subsurface as bedrock weathers to mobile regolith. Gordon Gulch is a small (2.7 km2), E-W trending catchment within the Boulder Creek Critical Zone Observatory underlain by Pre-Cambrian gneiss and granitic bedrock. The basin is typical of the "Rocky Mountain Surface" of the Front Range, characterized by low relief, a lack of glacial or fluvial incision, and deep weathering. Although the low-curvature, low-relief Rocky Mountain Surface would appear to indicate a landscape roughly in steady-state, shallow seismic surveys (Befus et al., 2011, Vadose Zone Journal) indicate depth to bedrock is highly variable. Block style release of saprolite into mobile regolith could explain this high variability and should be observable in geotechnical testing. Gordon Gulch also displays a systematic slope-aspect dependent control on weathering, with N-facing hillslopes exhibiting deeper weathering profiles than the S-facing hillslope. We believe comparisons of paired geotechnical-testing, XRD, and XRF analyses may explain this hillslope anisotropy. Rock quality designation (RQD) values, a commonly used indicator of rock mass quality (ASTM D6032), from both N- and S- facing aspects in Gordon Gulch indicate that granitic bedrock in both outcrop and saprolitic rock masses is poor to very poor

  19. Reach-Scale Hydraulic Influence on Sediment Dynamics and Morphological Development in a Bedrock Influenced River

    NASA Astrophysics Data System (ADS)

    Entwistle, N. S.; Heritage, G. L.; Milan, D. J.; Tooth, S.

    2014-12-01

    Many large rivers in southern Africa are characterised by a macro-channel cut 10 - 20 m into the ancient planation surface. This has resulted in a variable channel morphology strongly influenced by bedrock outcrops. The influence of bedrock upon flow hydraulics and sediment transport often results in a repeat sequence of alluvial channel types behind bedrock obstructions. This study investigates the hydraulic controls on channel type sequencing on the Sabie River, which drains a 6500 km2 semi-arid catchment of the Lowveld of South Africa and Mozambique. Aerial LIDAR data within the Kruger National Park was interrogated to isolate a bedrock influenced anastomosing reach, together with its associated alluvial sequences up- and downstream. These data were used to create a 2m DEM and a 2D flow model (JFLOW) was used to simulate a sequence of flows from 20 m3s-1 to 5000 m3s-1, with spatial data on water surface, flow depth and channel velocity extracted from the model. Water surface data revealed the strong gradient control exerted by the bedrock influenced anastomosed channel, creating hydraulic conditions suitable for deposition upstream and restricting sedimentation downstream. Steepening of the gradient through the anastomosing reach resulted in altered hydraulics and a changed pattern of sedimentation. At moderate discharges, flow is distributed efficiently across numerous interconnected channels, over low berms and islands, promoting sedimentation. Similarly the backwater effect encourages deposition of fine sediments upstream to create and maintain the alluvial sequence. Under higher flows, water levels rise significantly in the confined upstream reach and shear stress exceeds the threshold necessary to strip stored sediment. In contrast, conditions within the anastomosed reach remain less energetic due to the continued effect of flow distribution. Under extreme flow conditions the bedrock influence is drowned out resulting in dramatically increased energy levels

  20. How does sediment affect the hydraulics of bedrock-alluvial rivers?

    NASA Astrophysics Data System (ADS)

    Hodge, Rebecca; Hoey, Trevor; Maniatis, George; Leprêtre, Emilie

    2016-04-01

    Relationships between flow, sediment transport and channel morphology are relatively well established in coarse-grained alluvial channels. Developing equivalent relationships for bedrock-alluvial channels is complicated by the two different components that comprise the channel morphology: bedrock and sediment. These two components usually have very different response times to hydraulic forcing, meaning that the bedrock morphology may be inherited from previous conditions. The influence of changing sediment cover on channel morphology and roughness will depend on the relative magnitudes of the sediment size and the spatial variations in bedrock elevation. We report results from experiments in a 0.9m wide flume designed to quantify the interactions between flow and sediment patch morphology using two contrasting bedrock topographies. The first topography is a plane bed with sand-scale roughness, and the second is a 1:10 scale, 3D printed, model of a bedrock channel with spatially variable roughness (standard deviation of elevations = 12 mm in the flume). In all experiments, a sediment pulse was added to the flume (D50 between 7 and 15 mm) and sediment patches were allowed to stabilise under constant flow conditions. The flow was then incrementally increased in order to identify the discharges at which sediment patches and isolated grains were eroded. In the plane bed experiments ˜20% sediment cover is sufficient to alter the channel hydraulics through the increased roughness of the bed; this impact is expressed as the increased discharge at which isolated grains are entrained. In the scaled bed experiments, partial sediment cover decreased local flow velocities on a relatively smooth area of the bed. At the scale of the entire channel, the bed morphology, and the hydraulics induced by it, was a primary control on sediment cover stability at lower sediment inputs. At higher inputs, where sediment infilled the local bed topography, patches were relatively more stable

  1. Using Muon Radiography to map the Bedrock Geometry underneath an active Glacier: A Case Study in the Central Swiss Alps

    NASA Astrophysics Data System (ADS)

    Lechmann, Alessandro; Mair, David; Nishiyama, Ryuichi; Ariga, Akitaka; Ariga, Tomoko; Ereditato, Antonio; Scampoli, Paola; Vladymyrov, Mykhailo; Schlunegger, Fritz

    2016-04-01

    In recent years, muon radiography has been successfully applied to tackle geological issues and has enjoyed an increasing interest, mainly because this methodology enriches the geophysical arsenal by another shallow subsurface imaging tool that may give independent constraints on material density. Muons that originate from the collision of cosmic particles with Earth's atmosphere are able to penetrate the material in question and can finally be recorded by a detector. The irradiation intensity can then be inverted to the density of the traversed material. Various successful two-dimensional attempts have already been made to image e.g. magma chambers inside volcanoes (Lesparre et al., 2012; Nishiyama et al., 2014; Tanaka et al., 2005), but this method has yet to be applied for mapping the base of glaciers, where the density contrasts between ice and underlying bedrock are even greater than those between magma and host rock. While a high Alpine setup limits the possibilities to deploy traditional geophysical methods for surveying the base of glaciers (because of inaccessible terrain, poor infrastructure or the presence of water in the ice), muon radiography might prove to be a promising alternative. The muon intensity data from stereo observation can be related to the three-dimensional geometry of the interface between the glacier and its bedrock. Given a suitable input model, this relation can be solved within the framework of geophysical inverse problems. The final model then gives geologists invaluable information on erosional mechanisms underneath active glaciers, as this has not yet been observed. We test this methodology for a site within the Jungfrau region, situated in the central Swiss Alps. Our first goal is to demonstrate the feasibility of the method through a case study at the Eiger glacier, starting from a toy model in a first phase and continuing with real data in a second phase. For this purpose, we installed cosmic-ray detectors at two sites inside

  2. Geometry of structures within crystalline bedrock constrained in 3D and their relevance for present day water infiltration.

    NASA Astrophysics Data System (ADS)

    Schneeberger, Raphael; de la Varga, Miguel; Florian Wellmann, J.; Kober, Florian; Berger, Alfons; Herwegh, Marco

    2016-04-01

    Fluid circulation in crystalline rocks is of key importance when exploring crystalline basement in light of, for example, deep-seated geothermal energy projects or selection of sites for nuclear waste repositories. Due to their enhanced permeability, fluid circulation within crystalline bedrock is mainly controlled by fault zones, which may originate from ductile mylonites but show a strong brittle overprint. In order to better constrain 3D flow paths, a well-founded knowledge on the 3D nature of the fault zone pattern is indispensable. We attempt to constrain the geometry of a complex 3D fault zone pattern in a case study of the Grimsel Test Site (GTS, central Switzerland). The constraints are based on mapping of both the surface as well as the GTS underground tunnel system, offering a unique opportunity to test the 3D model and associated uncertainties. We investigate the effect of increasing geoinformation on the quality and accuracy of the 3D model by using: (i) remote sensing surface data only, (ii) field surface mapping in combination with (i), and (iii) underground data combined with (i) and (ii). This approach allows for defining different steps in 3D geological modelling of a specific area, including a measure of the remaining uncertainty after each step. We obtain a best-estimate model by fitting results between surface and underground data by using a combination of field data and orientation obtained by Delaunay triangulation. We incorporate novel approaches to uncertainty analysis of fault orientations and investigate different fault planes showing the possible variation range of the structures investigated.

  3. Near and Thermal Infrared Remote Sensing of Bedrock and Sand in Dust-Covered Regions on Mars: Assessing Bedrock Mineralogy Through 'Windows' in the Dust

    NASA Astrophysics Data System (ADS)

    Lai, J. C.; Horgan, B. H.; Bell, J. F.

    2013-12-01

    Bright surface dust masks large regions of Mars from detailed mineralogical and petrological analysis using remote sensing. In order to help address this issue, we assessed a number of orbital data sets to identify and characterize small 'windows' through the dust that may reveal the underlying bedrock. Data sets assessed include the Mars Global Surveyor orbiter (MGS) Thermal Emission Spectrometer (TES) Dust Cover Index (DCI), Mars Odyssey orbiter Thermal Emission Imaging System (THEMIS) thermal imaging, and Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) color mapping observations. Data from the MGS Mars Orbiter Laser Altimeter (MOLA) and high-resolution visible-wavelength images from the MRO Context Camera (CTX) and High Resolution Imaging Science Experiment (HiRISE) provided important topographical and morphological context. We have identified and characterized 67 individual windows in four classically bright regions of Mars: Amazonis Planitia, Arabia Terra, Elysium Planitia, and Tharsis Montes. These windows are characterized by having one or more of the following characteristics in contrast with the surrounding terrain: low DCI value, low MARCI and/or TES albedo, and/or high THEMIS night/day temperature contrast. Windows are typically tens of kilometers across but larger ones hundreds of km across have also been found, most notably in Tharsis. The majority of windows are associated with impact craters, most commonly as intracrater splotches or streaks of warm and/or dark material emanating from the crater. Some of these craters contain outcrops and, in some cases, distinct layers of dark material on their walls or central mound, providing opportunities to analyze bedrock. Other types of windows have also been found in smaller numbers, including those located on the flanks and summits of Mars' most prominent volcanoes, in addition to the walls and bases of cliffs tens to hundreds of meters in height. Initial near-IR spectroscopic analysis using our

  4. Women in Early Geology.

    ERIC Educational Resources Information Center

    Elder, Eleanor S.

    1982-01-01

    Biographical sketches are given for several women who made early contributions to the science of geology. A short biography of Inge Lehmann is also included as a more recent example of a woman who has made a notable contribution to the geological field. (Author)

  5. Radiometric Dating in Geology.

    ERIC Educational Resources Information Center

    Pankhurst, R. J.

    1980-01-01

    Described are several aspects and methods of quantitatively measuring geologic time using a constant-rate natural process of radioactive decay. Topics include half lives and decay constants, radiogenic growth, potassium-argon dating, rubidium-strontium dating, and the role of geochronology in support of geological exploration. (DS)

  6. Glossary of geology

    SciTech Connect

    Bates, R.L.; Jackson, J.A.

    1987-01-01

    This third edition of the Glossary of Geology contains approximately 37,000 terms, or 1,000 more than the second edition. New entries are especially numerous in the fields of carbonate sedimentology, hydrogeology, marine geology, mineralogy, ore deposits, plate tectonics, snow and ice, and stratigraphic nomenclature. Many of the definitions provide background information.

  7. Advances in planetary geology

    NASA Technical Reports Server (NTRS)

    Woronow, A. (Editor)

    1981-01-01

    This second issue in a new series intended to serve the planetary geology community with a form for quick and thorough communications includes (1) a catalog of terrestrial craterform structures for northern Europe; (2) abstracts of results of the Planetary Geology Program, and (3) a list of the photographic holdings of regional planetary image facilities.

  8. People and Geology.

    ERIC Educational Resources Information Center

    Naturescope, 1987

    1987-01-01

    Provides background information on the many natural resources we extract from the earth's crust, including metals, graphite, and other minerals, as well as fossil fuels. Contains teaching activities such as a geologic scavenger hunt, a geology chronology, and the recycling of aluminum. Includes a reproducible handout for the activity on aluminum.…

  9. Advances in Planetary Geology

    NASA Technical Reports Server (NTRS)

    Woronow, A. (Editor)

    1982-01-01

    Advances in Planetary Geology is a new series intended to serve the planetary geology community with a form for quick and thorough communications. There are no set lists of acceptable topics or formats, and submitted manuscripts will not undergo a formal review. All submissions should be in a camera ready form, preferably spaced, and submitted to the editor.

  10. Geology of the Caribbean.

    ERIC Educational Resources Information Center

    Dillon, William P.; And Others

    1988-01-01

    Describes some of the geologic characteristics of the Caribbean region. Discusses the use of some new techniques, including broad-range swath imaging of the sea floor that produces photograph-like images, and satellite measurement of crustal movements, which may help to explain the complex geology of the region. (TW)

  11. Geologic time scale bookmark

    USGS Publications Warehouse

    U.S. Geological Survey

    2012-01-01

    This bookmark, designed for use with U.S. Geological Survey activities at the 2nd USA Science and Engineering Festival (April 26–29, 2012), is adapted from the more detailed Fact Sheet 2010–3059 "Divisions of Geologic Time." The information that it presents is widely sought by educators and students.

  12. Delineation of subglacial bedrock structure in glaciated regions using DEMs derived from stereoscopic satellite imagery: An example of the Land Glacier catchment, West Antarctica

    NASA Astrophysics Data System (ADS)

    Robertson, A. M.; Contreras, A.; Siddoway, C. S.; Gottfried, M.; Porter, C.

    2012-12-01

    The Land Glacier of coastal Marie Byrd Land is proximal to the inferred tectonic boundary between the Ross and Amundsen provinces of the Marie Byrd Land terrane in West Antarctica. Its asymmetrical upper catchment draws ice from the volcanic peaks of the western Flood Range, a linear mountain change that is thought to be fault-controlled. A north-flowing ice stream with velocities >1200m/yr, Land Glacier occupies a narrow outlet flanked by sparse rock exposures along the remote Hobbs Coast. The narrow configuration and high flow velocity of the ice stream, together with the contrast in rock types on either side, suggest that the locus of Land Glacier is controlled by bedrock structures, however no faults have been mapped in this remote region on the basis of traditional ground-based methods nor airborne geophysics. We employ a new approach to mapping of subglacial bedrock faults and geological contacts in this region that entails quantitative analysis of high resolution DEMs computed from high resolution WorldView stereographic imagery. DEMs are computed using ERDAS Imagine's LPS eATE algorithm, followed by MATLAB-based routines to interpolate and remove artifacts in the terrain model. The resolution of the ice sheet DEM is 3 to 5 m, providing sufficient resolution for identification of geometrically regular features in the ice surface topography that may be attributable to bedrock faults and lithological contacts. The first phase of our ongoing work focuses upon lineaments that form a systematic array with regular geometry and spacing, that may be fault-controlled. A procedure involving use of hillshade applied from multiple sun angles, slope aspect, and slope gradient analysis of the high resolution DEMs was carried out in ArcGIS for characterization of the surface lineaments. We used the following criteria to distinguish bedrock-controlled lineaments from ice flow lineations: 1) laterally continuous for a minimum distance of 3 km, 2) vertical relief of ≥ 50m

  13. Bedrock Denudation on Titan: Estimates of Vertical Extent and Lateral Debris Dispersion

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey; Howard, A. D.; Schenk, Paul Michael

    2013-01-01

    Methane rainfall and runoff, along with aeolian activity, have dominated the sculpting of Titan s landscape. A knowledge of the vertical extent of bedrock erosion and the lateral extent of the resulting sediment is useful for several purposes [1]. For instance, what is the magnitude and expression of modification of constructional landforms (e.g., mountains)? Does highland denudation and the filling of basins with sediment cause adjustments (uplift and subsidence) in the crustal ice shell? Here we report preliminary findings of putative eroded craters and the results of landform evolution modeling (Fig. 1) that suggest that approx. 250 m of net bedrock erosion has at least locally taken place and approx.1 km of maximum local erosion.

  14. Using surface curvature to map geomorphic process regimes in a bedrock landscape, Henry Mountains, Utah

    NASA Astrophysics Data System (ADS)

    Corbett, S.; Sklar, L. S.; Davis, J.

    2009-12-01

    Linkages between form and process are much better understood in soil-mantled landscapes than in bedrock landscapes, despite the wide occurrence of bedrock landscapes in arid and mountainous terrain. Soil-mantled hillslope topography can be characterized by hillslope gradient and its spatial derivative, which is commonly referred to as curvature and defined as the Laplacian of elevation. Surface curvature can also be quantified using techniques that are invariant to the orientation of the surface. These approaches are useful in many geoscience applications, including structural analysis of folded surfaces within deforming crustal blocks. Here we explore the use of surface curvature of bedrock topography as a metric to identify and map distinct geomorphic process regimes in a landscape devoid of soil cover. Our study site is Simpson Creek, a 2.5 km2 watershed on the east flank of Mt. Hillers in the Henry Mountains, Utah, which drains to the Colorado River in Glen Canyon. The land surface is entirely exposed Navajo Sandstone bedrock, with isolated patches of wind-blown sand deposits. The channel network is discontinuous, with alternating reaches of steep, deeply-incised, frequently-potholed slots, and lower-gradient, sand-bedded channels. Hillslope topography is characterized by dome-shaped and sub-linear ridges, and is influenced by prominent structural joints. We calculate two measures of the surface-normal curvature using an ALSM-derived digital elevation model. The mean and Gaussian surface curvatures are the average and product respectively of the magnitudes of the maximum and minimum curvature vectors, obtained by differentiating a polynomial fit at each point in a grid with 1 m spacing. Plots of mean versus Gaussian curvature reveal distinct clusters of landscape elements, which we associate with specific process regimes. In this parameter space, there are four quadrants, classified as dome, basin, synformal saddle and antiformal saddle. The channel and valley

  15. Field Geology/Processes

    NASA Technical Reports Server (NTRS)

    Allen, Carlton; Jakes, Petr; Jaumann, Ralf; Marshall, John; Moses, Stewart; Ryder, Graham; Saunders, Stephen; Singer, Robert

    1996-01-01

    The field geology/process group examined the basic operations of a terrestrial field geologist and the manner in which these operations could be transferred to a planetary lander. Four basic requirements for robotic field geology were determined: geologic content; surface vision; mobility; and manipulation. Geologic content requires a combination of orbital and descent imaging. Surface vision requirements include range, resolution, stereo, and multispectral imaging. The minimum mobility for useful field geology depends on the scale of orbital imagery. Manipulation requirements include exposing unweathered surfaces, screening samples, and bringing samples in contact with analytical instruments. To support these requirements, several advanced capabilities for future development are recommended. Capabilities include near-infrared reflectance spectroscopy, hyper-spectral imaging, multispectral microscopy, artificial intelligence in support of imaging, x ray diffraction, x ray fluorescence, and rock chipping.

  16. Analysis of Geological Structures

    NASA Astrophysics Data System (ADS)

    Price, Neville J.; Cosgrove, John W.

    1990-08-01

    A knowledge of structural geology is fundamental to understanding the processes by which the earth's crust has evolved. It is a subject of fundamental importance to students of geology, experienced field geologists and academic researchers as well as to petroleum and mining engineers. In contrast to many structural textbooks which dwell upon geometrical descriptions of geological structures, this book emphasises mechanical principles and the way in which they can be used to understand how and why a wide range of geological structures develop. Structures on all scales are considered but the emphasis of the book is on those that can be seen on the scale of hand specimen or outcrop. Drawing on their considerable teaching experience the authors present a coherent and lucid analysis of geological structures which will be welcomed by a wide variety of earth scientists.

  17. Global distribution of bedrock exposures on Mars using THEMIS high-resolution thermal inertia

    USGS Publications Warehouse

    Edwards, C.S.; Bandfield, J.L.; Christensen, P.R.; Fergason, R.L.

    2009-01-01

    We investigate high thermal inertia surfaces using the Mars Odyssey Thermal Emission Imaging System (THEMIS) nighttime temperature images (100 m/pixel spatial sampling). For this study, we interpret any pixel in a THEMIS image with a thermal inertia over 1200 J m-2 K-1 s-1/2 as "bedrock" which represents either in situ rock exposures or rock-dominated surfaces. Three distinct morphologies, ranked from most to least common, are associated with these high thermal inertia surfaces: (1) valley and crater walls associated with mass wasting and high surface slope angles; (2) floors of craters with diameters >25 km and containing melt or volcanics associated with larger, high-energy impacts; and (3) intercrater surfaces with compositions significantly more mafic than the surrounding regolith. In general, bedrock instances on Mars occur as small exposures (less than several square kilometers) situated in lower-albedo (<0.18), moderate to high thermal inertia (>350 J m-2 K-1 s-1/2), and relatively dust-free (dust cover index <0.95) regions; however, there are instances that do not follow these generalizations. Most instances are concentrated in the southern highlands, with very few located at high latitudes (poleward of 45oN and 58oS), suggesting enhanced mechanical breakdown probably associated with permafrost. Overall, Mars has very little exposed bedrock with only 960 instances identified from 75oS to 75oN with likely <3500 km2 exposed, representing???1% of the total surface area. These data indicate that Mars has likely undergone large-scale surface processing and reworking, both chemically and mechanically, either destroying or masking a majority of the bedrock exposures on the planet. Copyright 2009 by the American Geophysical Union.

  18. 3D Mapping of Glacially-Sculpted Bedrock in Central Park

    NASA Astrophysics Data System (ADS)

    Laderman, L.; Stark, C. P.; Creyts, T. T.

    2014-12-01

    The movement of glaciers and ice sheets through sliding over bedrock depends on the configuration of the subglacial hydrological system. Over time, the glacier erodes the bedrock, which in turn changes water drainage pathways, the overall interaction with the ice, and potentially sliding rates. Drainage can take many forms. At the largest scale, subglacial lakes tens of kilometers in length store water, but the individual pathways are often on the order of meters or smaller. Studies at such a fine scale are only possible by looking at deglaciated beds to infer water drainage. 3D mapping can resolve centimeter scale features and inform studies of the processes that created them. In this survey, Agisoft Photoscan's structure from motion algorithm is used to create a map of Umpire Rock in New York's Central Park from digital photographs. Over 3300 photographs are taken at a separation of roughly half a meter to cover the 1000 square meter survey area. The surface is imaged in separate sections and the resulting point clouds are each aligned with a central section using Photoscan's Align Chunks tool. This process allows additional areas to easily be added to the 3D map. The scale of the final model is accurate to 1mm across the survey area and 3D meshes with a surface resolution of up to 5mm can be created. The distribution of striation directions and sizes on surfaces across the outcrop gives the overall flow direction of the ice and, more locally, illustrates how ice deforms around bedrock features. In addition to striations, we identify cavities and subtle drainage features that are oblique to ice flow. This study demonstrates the relative ease of 3D mapping bedrock outcrops from digital photographs, and indicates the utility of applying this process to more recently deglaciated areas.

  19. Glacial erosion and bedrock properties in NW Scotland: Abrasion and plucking, hardness and joint spacing

    NASA Astrophysics Data System (ADS)

    Krabbendam, Maarten; Glasser, Neil F.

    2011-07-01

    Subglacial erosion beneath glaciers occurs predominantly by abrasion and plucking, producing distinct erosional forms. The controls on the relative importance of abrasion vs. plucking are poorly understood. On the one hand, glacial conditions that favour or suppress cavity formation (ice velocity, ice thickness, and water pressure) are thought to favour plucking or abrasion, respectively. Conversely, bedrock properties are also known to control landforms, but this has rarely been analysed quantitatively. In this study we compare landforms and bedrock properties of sandstone and quartzite at the bed of a palaeo-ice stream near Ullapool in NW Scotland. The boundary between the rock types is at right angles to the westward palaeo-ice flow, and palaeoglacial conditions on both rock types were similar. We report quantitative parameters for bedrock properties (Schmidt hammer hardness and joint spacing) and use morphometric parameters to analyse the landforms. Torridon sandstone is soft but thick-bedded and with a wide joint spacing. Erosional bedforms include roche moutonnées with smoothed tops and concave stoss sides, whalebacks, and elongate p-forms, indicating a high proportion of abrasion over plucking. Cambrian quartzite is hard but thin-bedded with narrow joint spacing. Erosional landforms are angular to subangular with abundant plucked lee faces, suggesting a high proportion of plucking over abrasion. Hardness and joint spacing thus exert a strong control on subglacial erosional landforms and the mechanisms that formed them. Thus glacial conditions (ice velocity, ice thickness) can only be inferred from glacial erosional landforms if the effects of bedrock properties of the substrate are considered.

  20. Hitting rock bottom: morphological responses of bedrock-confined streams to a catastrophic flood

    NASA Astrophysics Data System (ADS)

    Baggs Sargood, M.; Cohen, T. J.; Thompson, C. J.; Croke, J.

    2015-06-01

    The role of extreme events in shaping the Earth's surface is one that has held the interests of Earth scientists for centuries. A catastrophic flood in a tectonically quiescent setting in eastern Australia in 2011 provides valuable insight into how semi-alluvial channels respond to such events. Field survey data (3 reaches) and desktop analyses (10 reaches) with catchment areas ranging from 0.5 to 168 km2 show that the predicted discharge for the 2011 event ranged from 415 to 933 m3 s-1, with unit stream power estimates of up to 1077 W m-2. Estimated entrainment relationships predict the mobility of the entire grain-size population, and field data suggest the localised mobility of boulders up to 4.8 m in diameter. Analysis of repeat lidar data demonstrates that all reaches (field and desktop) were areas of net degradation via extensive scouring of coarse-grained alluvium with a strong positive relationship between catchment area and normalised erosion (R2 = 0.72-0.74). The extensive scouring in the 2011 flood decreased thalweg variance significantly removing previous step pools and other coarse-grained in-channel units, forming lengths of plane-bed (cobble) reach morphology. This was also accompanied by the exposure of planar bedrock surfaces, marginal bedrock straths and bedrock steps. Post-flood field data indicate a slight increase in thalweg variance as a result of the smaller 2013 flood rebuilding the alluvial overprint with pool-riffle formation. However, the current form and distribution of channel morphological units does not conform to previous classifications of bedrock or headwater river systems. This variation in post-flood form indicates that in semi-alluvial systems extreme events are significant for re-setting the morphology of in-channel units and for exposing the underlying lithology to ongoing erosion.

  1. Baseline geochemistry of soil and bedrock Tshirege Member of the Bandelier Tuff at MDA-P

    SciTech Connect

    Warren, R.G.; McDonald, E.V.; Ryti, R.T.

    1997-08-01

    This report provides baseline geochemistry for soils (including fill), and for bedrock within three specific areas that are planned for use in the remediation of Material Disposal Area P (MDA-P) at Technical Area 16 (TA-16). The baseline chemistry includes leachable element concentrations for both soils and bedrock and total element concentrations for all soil samples and for two selected bedrock samples. MDA-P operated from the early 1950s to 1984 as a landfill for rubble and debris generated by the burning of high explosives (HE) at the TA-16 Burning Ground, HE-contaminated equipment and material, barium nitrate sand, building materials, and trash. The aim of this report is to establish causes for recognizable chemical differences between the background and baseline data sets. In many cases, the authors conclude that recognizable differences represent natural enrichments. In other cases, differences are best attributed to analytical problems. But most importantly, the comparison of background and baseline geochemistry demonstrates significant contamination for several elements not only at the two remedial sites near the TA-16 Burning Ground, but also within the entire region of the background study. This contamination is highly localized very near to the surface in soil and fill, and probably also in bedrock; consequently, upper tolerance limits (UTLs) calculated as upper 95% confidence limits of the 95th percentile are of little value and thus are not provided. This report instead provides basic statistical summaries and graphical comparisons for background and baseline samples to guide strategies for remediation of the three sites to be used in the restoration of MDA-P.

  2. Megagrooves and streamlined bedrock in NW Scotland: The role of ice streams in landscape evolution

    NASA Astrophysics Data System (ADS)

    Bradwell, Tom; Stoker, Martyn; Krabbendam, Maarten

    2008-05-01

    New multibeam bathymetry data, onshore high-resolution elevation data (NEXTMap) and fieldwork in the Ullapool area of NW Scotland reveal large-scale megagrooves and streamlined bedrock forms in a well-defined ˜ 20 km wide zone. The landsystem is typical of a coherent flow corridor within a grounded ice sheet on bedrock-dominated terrain. We describe the morphology of the large-scale features, discuss their likely formation, and consider the wider implications for ice-sheet dynamics. Based on the strongly convergent bedform distribution, the presence of megagrooves and highly elongate bedrock forms, we interpret the erosional landscape to be the signature of a fast-flowing tributary that once fed the The Minch palaeo-ice stream — a major artery of the last British-Irish ice sheet. The exact genesis of bedrock megagrooves remains uncertain, although focused subglacial abrasion is likely to have carved most of the shallow, strongly parallel, features; whilst glacial meltwater may have carved or modified others. Bedform morphometry is used to discriminate zones reflecting the degree of glacial streamlining (elongation ratios < 5:1 or > 5:1). We interpret these zones to represent the transition from potentially cold-based slow ice-sheet flow to warm-based fast flow. Based on these results, and the presence of ribbed moraines, we suggest a bedform continuum model for onset zones of palaeo-ice streams on rigid beds. Rapid spatial bedform evolution is suggested to reflect an increase in subglacial erosive power that may be diagnostic of palaeo-ice-sheet thermal boundaries (i.e. from cold- to warm-based), and is also consistent with the expected downstream increase in ice velocity within an ice-stream onset zone. Finally, this study speculates on the role played by basal meltwater in ice-stream initiation and the role of ice streams and their tributaries in landscape evolution.

  3. Rivers meandering in bedrock: Lithologic, climatic, and process controls on form and evolution

    NASA Astrophysics Data System (ADS)

    Zunka, J. P.; Lancaster, S. T.

    2014-12-01

    Whereas meander wavelengths of alluvial rivers characteristically scale with bankfull discharge, bedrock meander wavelengths are typically 5-10 times greater than the scaling relationship for alluvial rivers would suggest, a fact that has led some to conclude that bedrock meanders are "underfit." Others, however, have reasoned that larger dominant discharges should be expected for bedrock meanders to erode bank toes and mobilize sediment in bank-shielding scree piles, which often accompany steep, even vertical, outside banks capable of supplying coarse debris via landslide, debris flow, and rockfall. We attempt to test this hypothesis by finding dominant discharges for the Buffalo National River, Arkansas, by several methods. First, assuming that, as with alluvial meanders, bedrock meander wavelengths are 7-15 times hydraulic width at dominant discharge, we use cross-sections extracted from LiDAR-derived DEMs to find discharges corresponding to objectively-determined meander wavelengths. Second, assuming that dominant discharge must mobilize scree mantling outer-bank toe slopes, we use measured grain size distributions and cross sections to determine this discharge. For each of these calculated discharges, we use flow-duration curves to find corresponding recurrence intervals. Third, assuming that mean residence times of scree are similar to dominant discharge recurrence intervals, we use measured scree volumes and flux rates inferred from lateral migration rates to find those residence times. Preliminary results for the site with the longest gauge record yield a mean recurrence interval of 26 yrs corresponding to a meander wavelength-to-width scaling ratio of 11 (9-139 yrs for scaling ratios of 7-15). Recurrence intervals found by the other methods await field and cosmogenic isotope concentration measurements.

  4. Using GIS and Remote Sensing to Map the Bedrock Morphology of Bering Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Snyder-Deaton, L. E.; Molnia, B. F.

    2014-12-01

    Subglacial environments are amongst the least known places on Earth. We have combined five different types of geophysical investigations in order to better understand the complex morphology of the >250 km long bed of Bering Glacier. The transect includes the bed segment underlying the present glacier and the segment previously under the glacier's seaward extension when it reached its maximum limit during the Pleistocene. This transect represents Bering Glacier's bed from the distal edge of the continental shelf, to its up-glacier point of origin east of the U.S.-Canadian border. The datasets used were: 1) marine air-gun and sparker seismic profiles used to define the bedrock morphology of Bering Trough, Bering Glacier's Pleistocene fiord cut into the Gulf of Alaska; 2) binary-explosive seismic refraction profiles used to confirm that fiord depth bedrock underlies the Bering Foreland coastal plain; 3) high-resolution mini-sparker seismic reflection profiles collected from Vitus Lake, Bering Glacier's ice marginal lake that confirm complex bed morphology buried under up to 100 m of recent glacial-marine sediment; 4) ice penetrating radar soundings used to measure the ice thickness and depth to bedrock at more than 30 Bering Glacier piedmont lobe locations; and 5) airborne monopulse radar profiles used for mapping nearly 190 km of glacier's current bed. Combining the results of these five geophysical investigations permits us to produce numerous cross-sections and maps that show the complexities of Bering Glacier's bedrock morphology. At its offshore end on the outer continental shelf, the bed is a trough as deep as 500 m below sea level. At its origin, east of the U.S.-Canadian Border the bed elevation is ~1,600 m above sea level.

  5. Lack of bedrock grain size influence on the soil production rate

    NASA Astrophysics Data System (ADS)

    Gontier, Adrien; Rihs, Sophie; Chabaux, Francois; Lemarchand, Damien; Pelt, Eric; Turpault, Marie-Pierre

    2015-10-01

    Our study deals with the part played by bedrock grain size on soil formation rates. U- and Th-series disequilibria were measured in two soil profiles developed from two different facies of the same bedrock, i.e., fine and coarse grain size granites, in the geomorphically flat landscape of the experimental Breuil-Chenue forest site, Morvan, France. The U- and Th-series disequilibria of soil layers and the inferred soil formation rate (1-2 mm ky-1) are nearly identical along the two profiles despite differences in bedrock grain size, variable weathering states and a significant redistribution of U and Th from the uppermost soil layers. This indicates that the soil production rate is more affected by regional geomorphology than by the underlying bedrock texture. Such a production rate inferred from residual soil minerals integrated over the age of the soil is consistent with the flat and slowly eroding geomorphic landscape of the study site. It also compares well to the rate inferred from dissolved solutes integrated over the shorter time scale of solute transport from granitic and basaltic watersheds under similar climates. However, it is significantly lower than the denudation or soil formation rates previously reported from either cosmogenic isotope or U-series measurements from similar climates and lithologies. Our results highlight the particularly low soil production rates of flat terrains in temperate climates. Moreover, they provide evidence that the reactions of mineral weathering actually take place in horizons deeper than 1 m, while a chemical steady state of both concentrations and U-series disequilibria is established in the upper most soil layers, i.e., above ∼70 cm depth. In such cases, the use of soil surface horizons for determining weathering rates is precluded and illustrates the need to focus instead on the deepest soil horizons.

  6. Constraining Paleo-Glacier Dynamics Using Optically Stimulated Luminescence (OSL) Bedrock Exposure Dating

    NASA Astrophysics Data System (ADS)

    Brun, F.; Valla, P.; King, G. E.; Herman, F.

    2014-12-01

    Quantifying glacier dynamics over the late-Pleistocene remains an important challenge for understanding glacial response to climate change. Historical glacier reconstructions are spatially limited (e.g. the European Alps) and cover only the last ~100 yrs, restricting their use as paleoclimatic proxies. Bedrock dating methods such as Terrestrial Cosmogenic Nuclides (TCN) dating or lichenometry allows glacier fluctuations to be reconstructed over longer timescales. However, these methods have limited temporal resolution, and therefore do not enable accurate dating of recent glacier fluctuations (e.g. short glacier re-advances). Here, we use a novel in situ dating method based on Optically Stimulated Luminescence (OSL) to fill this temporal/spatial gap. OSL dating is based on the time-accumulation of trapped electrons in the lattice defects of minerals. OSL-exposure dating is based on the bleaching (i.e. resetting) of the minerals' luminescence signal when they are exposed to light (Sohbati et al., 2012 JGR-Solid Earth), which depends on exposure time, effective photon flux and light attenuation by minerals. We analyzed 10 samples in the Val d'Hérens (Swiss Alps) where post-LGM glacier dynamics remain poorly constrained and short glacier re-advances are thought to occur during the Holocene. Bedrock samples were drilled and small cores were sliced into 1-mm thick discs from which natural luminescence profiles were measured. We calibrated the luminescence model parameters using historically-exposed bedrock samples (~100 yr) near the Mont-Miné glacier, and used this on-site calibration to date surface exposure of glacial bedrock at various elevations along the valley; initial relative dating results are promising. Although OSL-exposure dating appears an efficient tool for historical glacier reconstructions, OSL bleaching over longer timescales (i.e. late-Pleistocene to Holocene) requires more investigation before use as a chronometer.

  7. Waterfall formation driven by interacting flow hydraulics, sediment cover, and erosion in an experimental bedrock canyon

    NASA Astrophysics Data System (ADS)

    Scheingross, Joel; Lamb, Michael; Fuller, Brian

    2016-04-01

    Waterfalls are ubiquitous in steep landscapes and have been documented to retreat upstream at rates far outpacing standard fluvial incision into bedrock. While the formation of waterfalls following changes in climate and base-level lowering have been well-documented, little work has explored the formation of waterfalls via the internal dynamics from interacting flow hydraulics, sediment flux, and evolving channel morphology. Distinguishing between waterfalls formed via external versus internal forcing is important, as waterfall formation and retreat rate is often applied in inverse to determine the timing of external forcing. Here, we present results from a laboratory experiment designed to explore channel incision and waterfall formation. We fed water and sediment at constant rates over an initially planar surface tilted to 19.5% slope. A channel rapidly incised into the artificial bedrock substrate, and small-wavelength variations in erosion rate created steps and pools which grew in amplitude. As pools deepened, sediment cover at the downstream portion of pools locally limited erosion, while erosion in the upstream portion of the pool created steep faces. At the topographic breaks between these steep segments and their upstream treads, water detached from the bed forming ventilated waterfall jets which impacted the plunge pools below. Individual waterfalls were short-lived as pool-deepening promoted alluviation which prevented further pool-incision, while amplified erosion at the waterfall lip incised a new pool into the bedrock previously composing the waterfall face. Repetition of this process in our experiment suggests that interactions between bedrock erosion and sediment cover can result in the formation of a series of plunge pools which retreat upstream.

  8. Autocyclic Formation, Retreat, and Destruction of Waterfalls in an Experimental Bedrock Channel

    NASA Astrophysics Data System (ADS)

    Scheingross, J. S.; Fuller, B. M.; Lamb, M. P.

    2015-12-01

    Waterfalls are ubiquitous in steep landscapes and have been documented to retreat upstream at rates far outpacing standard fluvial incision into bedrock. While the formation of waterfalls following changes in climate and base-level lowering have been well-documented, little work has explored the formation of waterfalls via the internal dynamics from interacting flow hydraulics, sediment flux, and evolving channel morphology. Distinguishing between waterfalls formed via external versus internal forcing is important, as waterfall formation and retreat rate is often applied in inverse to determine the timing of external forcing. Here, we present results from a laboratory experiment designed to explore channel incision and waterfall formation. We fed water and sediment at constant rates over an initially planar surface at 19.5% slope. A channel rapidly incised into the artificial bedrock substrate, and small-wavelength variations in erosion rate created steps and pools which grew in amplitude. As pools deepened, erosion was focused on the upstream pool faces creating steep segments in the channel bed. At the topographic breaks between these steep segments and their upstream treads, water detached from the bed forming ventilated waterfall jets which impacted the plunge pools below. Continued pool deepening led to sediment deposition on the pool floors, locally inhibiting vertical incision while the upstream and downstream surfaces were free to erode. Amplified erosion at the waterfall lip incised a new pool into the bedrock previously composing the waterfall face while simultaneous lowering of the downstream pool lip resulted in the destruction of the original pool. Repetition of this process in our experiment suggests that interactions between bedrock erosion and sediment cover can result in the formation of a series of plunge pools which retreat upstream, and that care must be taken to distinguish between autocyclic versus allocyclic waterfall formation in studies

  9. Maps out, models in at the British Geological Survey!

    NASA Astrophysics Data System (ADS)

    Mathers, Steve; Kessler, Holger

    2013-04-01

    BGS has stopped its' systematic onshore geological surveying programme and the litho-printing of geological maps will cease after a final batch of completed maps are published. In future BGS will undertake integrated mapping and 3D modelling in user defined target areas considering all our available geospatial data (map, boreholes, geophysics etc) assessed in a single 3D workspace. The output will be 3D geological framework models that capture the understanding and interpretation of the survey geologist and honour all available data at the time. As well as building new models in these strategic areas, BGS is collating all existing models assembled over the last 25 years into a common framework to produce a multi-scaled National Geological Model of Britain. comprising crustal, bedrock and quaternary and anthropocene themes (http://www.bgs.ac.uk/research/UKGeology/nationalgeologicalmodel/home.html). Different to the traditional geological map, the national model will not be completed at any specific scale, but at every point in the model there may be a different geological resolution available, depending on the purpose mof the original model or the strategic national need for subsurface information. The need for a complete and robust nested stratigraphic framework (BGS Lexicon) is becoming more important as we advance this model. Archive copies of all legacy models will be approved and stored in their native formats. In addition a newly designed Geological Object Store will hold geological objects such as coverages, surfaces and cross-sections from these models inside a relational database to ensure versioning and long-term security of the National Geological Model. In the mid-term these models will be attributed with physical properties such as porosity and density and form inputs to process models such as groundwater and landslide models to help predict and simulate environmental change. A key challenge for geologists and their systems building the geological

  10. Modeling single-well injection experiments with delayed extraction in fractured bedrock aquifers - applications in CO2 geosequestration research

    NASA Astrophysics Data System (ADS)

    Yang, Q.; Stute, M.; Zakharova, N. V.; Matter, J.; Takahashi, T.; O'Mullan, G. D.; Goldberg, D.

    2013-12-01

    Characterization of the solute transport of anthropogenically introduced solutions in fractured bedrock aquifers has practical implications on environmental problems related to CO2 geological sequestration, hydraulic fracturing, and environmental fracturing remediation. Tracer tests using conservative chemicals, such as push-pull experiments in single borehole, provide a direct and reliable method to estimate the solute transport and have been used as a basis for further understanding of the biogeochemical processes in the subsurface. Obtaining analytical solutions often requires simplification of the hydrogeological processes and usually is not practical or very difficult. For example, environmental studies often require a delayed extraction to increase the reaction time and amplify the biogeochemical signals during the push-pull experiments. Simulating these processes by numerical models demands large computation resources, but can reveal the complexity and heterogeneity of aquifer and hydrological processes. Testing the sensitivity of model parameters in such simulations allows for an understanding of the most significant parameters of these processes. In this study, seven push-pull experiments with delayed extraction after the introduction of chemical salts (e.g. NaCl and KBr), gases (SF6, SF5CF3), or isotopic tracers (18O, 13C) were conducted in a test well in the Newark Basin at two different depths. Fracture zones at these depths correspond to the contact zone (232-240 m) between the Palisades diabase sill and the underlying Newark Basin sand and clay sediments and an interval (362-366 m) within the sedimentary rock formations. This study investigates the feasibility of CO2 geological sequestration and the potential environmental impact in the event of CO2 leakage into overlying groundwater aquifers in sedimentary formations. Analytical solutions were adapted using non-Fickian models to fit the observed tracer breakthrough curves. Normalized tracer

  11. Earth-Base: testing the temporal congruency of paleontological collections and geologic maps of North America

    NASA Astrophysics Data System (ADS)

    Heim, N. A.; Kishor, P.; McClennen, M.; Peters, S. E.

    2012-12-01

    Free and open source software and data facilitate novel research by allowing geoscientists to quickly and easily bring together disparate data that have been independently collected for many different purposes. The Earth-Base project brings together several datasets using a common space-time framework that is managed and analyzed using open source software. Earth-Base currently draws on stratigraphic, paleontologic, tectonic, geodynamic, seismic, botanical, hydrologic and cartographic data. Furthermore, Earth-Base is powered by RESTful data services operating on top of PostgreSQL and MySQL databases and the R programming environment, making much of the functionality accessible to third-parties even though the detailed data schemas are unknown to them. We demonstrate the scientific potential of Earth-Base and other FOSS by comparing the stated age of fossil collections to the age of the bedrock upon which they are geolocated. This analysis makes use of web services for the Paleobiology Database (PaleoDB), Macrostrat, the 2005 Geologic Map of North America (Garrity et al. 2009) and geologic maps of the conterminous United States. This analysis is a way to quickly assess the accuracy of temporal and spatial congruence of the paleontologic and geologic map datasets. We find that 56.1% of the 52,593 PaleoDB collections have temporally consistent ages with the bedrock upon which they are located based on the Geologic Map of North America. Surprisingly, fossil collections within the conterminous United States are more consistently located on bedrock with congruent geological ages, even though the USA maps are spatially and temporally more precise. Approximately 57% of the 37,344 PaleoDB collections in the USA are located on similarly aged geologic map units. Increased accuracy is attributed to the lumping of Pliocene and Quaternary geologic map units along the Atlantic and Gulf coastal plains in the Geologic Map of North America. The abundant Pliocene fossil collections

  12. Chemical weathering as a mechanism for the climatic control of bedrock river incision

    NASA Astrophysics Data System (ADS)

    Murphy, Brendan P.; Johnson, Joel P. L.; Gasparini, Nicole M.; Sklar, Leonard S.

    2016-04-01

    Feedbacks between climate, erosion and tectonics influence the rates of chemical weathering reactions, which can consume atmospheric CO2 and modulate global climate. However, quantitative predictions for the coupling of these feedbacks are limited because the specific mechanisms by which climate controls erosion are poorly understood. Here we show that climate-dependent chemical weathering controls the erodibility of bedrock-floored rivers across a rainfall gradient on the Big Island of Hawai‘i. Field data demonstrate that the physical strength of bedrock in streambeds varies with the degree of chemical weathering, which increases systematically with local rainfall rate. We find that incorporating the quantified relationships between local rainfall and erodibility into a commonly used river incision model is necessary to predict the rates and patterns of downcutting of these rivers. In contrast to using only precipitation-dependent river discharge to explain the climatic control of bedrock river incision, the mechanism of chemical weathering can explain strong coupling between local climate and river incision.

  13. Chemical weathering in active mountain belts controlled by stochastic bedrock landsliding

    NASA Astrophysics Data System (ADS)

    Emberson, Robert; Hovius, Niels; Galy, Albert; Marc, Odin

    2016-01-01

    A link between chemical weathering and physical erosion exists at the catchment scale over a wide range of erosion rates. However, in mountain environments, where erosion rates are highest, weathering may be kinetically limited and therefore decoupled from erosion. In active mountain belts, erosion is driven by bedrock landsliding at rates that depend strongly on the occurrence of extreme rainfall or seismicity. Although landslides affect only a small proportion of the landscape, bedrock landsliding can promote the collection and slow percolation of surface runoff in highly fragmented rock debris and create favourable conditions for weathering. Here we show from analysis of surface water chemistry in the Southern Alps of New Zealand that weathering in bedrock landslides controls the variability in solute load of these mountain rivers. We find that systematic patterns in surface water chemistry are strongly associated with landslide occurrence at scales from a single hillslope to an entire mountain belt, and that landslides boost weathering rates and river solute loads over decades. We conclude that landslides couple erosion and weathering in fast-eroding uplands and, thus, mountain weathering is a stochastic process that is sensitive to climatic and tectonic controls on mass wasting processes.

  14. Seismic refraction and GPR measurements of depth to bedrock: A case study from Randolph College, Virginia

    NASA Astrophysics Data System (ADS)

    Datta, A.; Pokharel, R.; Toteva, T.

    2007-12-01

    Randolph College is located in Lynchburg, VA, in the eastern edge of the Blue Ridge Mountains. Lynchburg city lies in the James River Synclinorium and consists of metasedimentary and metaigneous rocks. As part of College's plan to expand, a new soccer field will be build. For that purpose, part of a hill has to be excavated. Information was needed on the depth to the bedrock at the site. We conducted a seismic refraction experiment as part of an eight week summer research program for undergraduate students. We used 24 vertical geophones, spaced at 1.5 m interval. Our recording device was a 12 channel Geometrics geode (ES 3000). The source was an 8 pound sledge hummer. Source positions were chosen to be at 5, 10, 15 and 20 m on both sides of the array. We collected data along a tree line (in two segments) and across a hockey field. The data collected from the hockey field had very low signal to noise ratio and clear refraction arrivals. The other two acquisition lines were much noisier and difficult to interpret. Our results are consistent with data from seven bore holes in close proximity to the field site. We interpreted depth to bedrock to be between 4 and 12 m. The bedrock velocities are consistent with weathered gneiss. To improve the interpretation of the tree line records, we conducted a GPR survey. The preliminary radar images are showing highly heterogeneous subsurface with multiple point reflectors.

  15. Active Lakes of the Recovery Ice Stream, East Antarctica: A Bedrock-Controlled Subglacial Hydrological System

    NASA Astrophysics Data System (ADS)

    Fricker, H. A.; Scambos, T. A.; Bell, R. E.; Carter, S. P.

    2014-12-01

    A connected system of active sub-glacial lakes was revealed beneath the Recovery Ice Stream, East Antarctica by ICESat laser altimetry acquired from 2003 to 2008. Here we combine repeat-track analysis of ICESat (2003-2009), Operation IceBridge laser altimetry and radio-echo sounding (RES; 2011 and 2012), and MODIS image differencing (2009-2011) to learn more about the surface and bedrock topographic setting of the lakes and the constraints on water flow through the system. IceBridge data reveal a ~1500 m deep, ~1000 km long bedrock trough under the main trunk of Recovery Ice Stream. We extend the lake activity time series to 2012 for the three lower lakes using IceBridge data: one lake underwent a large deflation between 2009 and 2011; another lake, which had been continuously filling between 2003 and 2010, started to drain after 2011. Hydrologic connections among the lakes appear to be direct and responsive. We reproduce the lake activity using a simple subglacial water model. The hydrologic system beneath Recovery Ice Stream is controlled by unusually pronounced bedrock topography (and not ice surface topography, as is the case for most Antarctic systems studied to date). We discuss potential causes of non-steady hydrologic behavior in major Antarctic catchments.

  16. Chemical weathering as a mechanism for the climatic control of bedrock river incision.

    PubMed

    Murphy, Brendan P; Johnson, Joel P L; Gasparini, Nicole M; Sklar, Leonard S

    2016-04-14

    Feedbacks between climate, erosion and tectonics influence the rates of chemical weathering reactions, which can consume atmospheric CO2 and modulate global climate. However, quantitative predictions for the coupling of these feedbacks are limited because the specific mechanisms by which climate controls erosion are poorly understood. Here we show that climate-dependent chemical weathering controls the erodibility of bedrock-floored rivers across a rainfall gradient on the Big Island of Hawai'i. Field data demonstrate that the physical strength of bedrock in streambeds varies with the degree of chemical weathering, which increases systematically with local rainfall rate. We find that incorporating the quantified relationships between local rainfall and erodibility into a commonly used river incision model is necessary to predict the rates and patterns of downcutting of these rivers. In contrast to using only precipitation-dependent river discharge to explain the climatic control of bedrock river incision, the mechanism of chemical weathering can explain strong coupling between local climate and river incision. PMID:27075099

  17. Stochastic Seismic Response of an Algiers Site with Random Depth to Bedrock

    SciTech Connect

    Badaoui, M.; Mebarki, A.; Berrah, M. K.

    2010-05-21

    Among the important effects of the Boumerdes earthquake (Algeria, May 21{sup st} 2003) was that, within the same zone, the destructions in certain parts were more important than in others. This phenomenon is due to site effects which alter the characteristics of seismic motions and cause concentration of damage during earthquakes. Local site effects such as thickness and mechanical properties of soil layers have important effects on the surface ground motions.This paper deals with the effect of the randomness aspect of the depth to bedrock (soil layers heights) which is assumed to be a random variable with lognormal distribution. This distribution is suitable for strictly non-negative random variables with large values of the coefficient of variation. In this case, Monte Carlo simulations are combined with the stiffness matrix method, used herein as a deterministic method, for evaluating the effect of the depth to bedrock uncertainty on the seismic response of a multilayered soil. This study considers a P and SV wave propagation pattern using input accelerations collected at Keddara station, located at 20 km from the epicenter, as it is located directly on the bedrock.A parametric study is conducted do derive the stochastic behavior of the peak ground acceleration and its response spectrum, the transfer function and the amplification factors. It is found that the soil height heterogeneity causes a widening of the frequency content and an increase in the fundamental frequency of the soil profile, indicating that the resonance phenomenon concerns a larger number of structures.

  18. Stochastic Seismic Response of an Algiers Site with Random Depth to Bedrock

    NASA Astrophysics Data System (ADS)

    Badaoui, M.; Berrah, M. K.; Mébarki, A.

    2010-05-01

    Among the important effects of the Boumerdes earthquake (Algeria, May 21st 2003) was that, within the same zone, the destructions in certain parts were more important than in others. This phenomenon is due to site effects which alter the characteristics of seismic motions and cause concentration of damage during earthquakes. Local site effects such as thickness and mechanical properties of soil layers have important effects on the surface ground motions. This paper deals with the effect of the randomness aspect of the depth to bedrock (soil layers heights) which is assumed to be a random variable with lognormal distribution. This distribution is suitable for strictly non-negative random variables with large values of the coefficient of variation. In this case, Monte Carlo simulations are combined with the stiffness matrix method, used herein as a deterministic method, for evaluating the effect of the depth to bedrock uncertainty on the seismic response of a multilayered soil. This study considers a P and SV wave propagation pattern using input accelerations collected at Keddara station, located at 20 km from the epicenter, as it is located directly on the bedrock. A parametric study is conducted do derive the stochastic behavior of the peak ground acceleration and its response spectrum, the transfer function and the amplification factors. It is found that the soil height heterogeneity causes a widening of the frequency content and an increase in the fundamental frequency of the soil profile, indicating that the resonance phenomenon concerns a larger number of structures.

  19. The influence of bedrock hydrogeology on catchment-scale nitrate fate and transport in fractured aquifers.

    PubMed

    Orr, Alison; Nitsche, Janka; Archbold, Marie; Deakin, Jenny; Ofterdinger, Ulrich; Flynn, Raymond

    2016-11-01

    Characterising catchment scale biogeochemical processes controlling nitrate fate in groundwater constitutes a fundamental consideration when applying programmes of measures to reduce risks posed by diffuse agricultural pollutants to water quality. Combining hydrochemical analyses with nitrate isotopic data and physical hydrogeological measurements permitted characterisation of biogeochemical processes influencing nitrogen fate and transport in the groundwater in two fractured bedrock aquifers with contrasting hydrogeology but comparable nutrient loads. Hydrochemical and isotopic analyses of groundwater samples collected from moderately fractured, diffusely karstified limestone indicated nitrification controlled dissolved nitrogen fate and delivery to aquatic receptors. By contrast nitrate concentrations in groundwater were considerably lower in a low transmissivity highly lithified sandstone and pyrite-bearing shale unit with patchy subsoil cover. Geophysical and hydrochemical investigations showed shallower intervals contained hydraulically active fractures where denitrification was reflected through lower nitrogen levels and an isotopic enrichment ratio of 1.7 between δ(15)N and δ(18)O. Study findings highlight the influence of bedrock hydrogeological conditions on aqueous nitrogen mobility. Investigation results demonstrate that bedrock conditions need to be considered when implementing catchment management plans to reduce the impact of agricultural practices on the quality of groundwater and baseflow in receiving rivers. Nitrate isotopic signatures in the groundwater of a freely draining catchment underlain by a karstified aquifer and a poorly draining aquifer with a low transmissivity aquifer. PMID:27432726

  20. Modeling flow and sediment transport dynamics in the lowermost Mississippi River, Louisiana, USA, with an upstream alluvial-bedrock transition and a downstream bedrock-alluvial transition: Implications for land building using engineered diversions

    NASA Astrophysics Data System (ADS)

    Viparelli, Enrica; Nittrouer, Jeffrey A.; Parker, Gary

    2015-03-01

    The lowermost Mississippi River, defined herein as the river segment downstream of the Old River Control Structure and hydrodynamically influenced by the Gulf of Mexico, extends for approximately 500 km. This segment includes a bedrock (or more precisely, mixed bedrock-alluvial) reach that is bounded by an upstream alluvial-bedrock transition and a downstream bedrock-alluvial transition. Here we present a one-dimensional mathematical formulation for the long-term evolution of lowland rivers that is able to reproduce the morphodynamics of both the alluvial-bedrock and the bedrock-alluvial transitions. Model results show that the magnitude of the alluvial equilibrium bed slope relative to the bedrock surface slope and the depth of bedrock surface relative to the water surface base level strongly influence the mobile bed equilibrium of low-sloping river channels. Using data from the lowermost Mississippi River, the model is zeroed and validated at field scale by comparing the numerical results with field measurements. The model is then applied to predict the influence on the stability of channel bed elevation in response to delta restoration projects. In particular, the response of the river bed to the implementation of two examples of land-building diversions to extract water and sediment from the main channel is studied. In this regard, our model results show that engineered land-building diversions along the lowermost Mississippi River are capable of producing equilibrated bed profiles with only modest shoaling or erosion, and therefore, such diversions are a sustainable strategy for mitigating land loss within the Mississippi River Delta.

  1. Fundamentals of Structural Geology

    NASA Astrophysics Data System (ADS)

    Pollard, David D.; Fletcher, Raymond C.

    2005-09-01

    Fundamentals of Structural Geology provides a new framework for the investigation of geological structures by integrating field mapping and mechanical analysis. Assuming a basic knowledge of physical geology, introductory calculus and physics, it emphasizes the observational data, modern mapping technology, principles of continuum mechanics, and the mathematical and computational skills, necessary to quantitatively map, describe, model, and explain deformation in Earth's lithosphere. By starting from the fundamental conservation laws of mass and momentum, the constitutive laws of material behavior, and the kinematic relationships for strain and rate of deformation, the authors demonstrate the relevance of solid and fluid mechanics to structural geology. This book offers a modern quantitative approach to structural geology for advanced students and researchers in structural geology and tectonics. It is supported by a website hosting images from the book, additional colour images, student exercises and MATLAB scripts. Solutions to the exercises are available to instructors. The book integrates field mapping using modern technology with the analysis of structures based on a complete mechanics MATLAB is used to visualize physical fields and analytical results and MATLAB scripts can be downloaded from the website to recreate textbook graphics and enable students to explore their choice of parameters and boundary conditions The supplementary website hosts color images of outcrop photographs used in the text, supplementary color images, and images of textbook figures for classroom presentations The textbook website also includes student exercises designed to instill the fundamental relationships, and to encourage the visualization of the evolution of geological structures; solutions are available to instructors

  2. Geologic mapping of Kentucky; a history and evaluation of the Kentucky Geological Survey--U.S. Geological Survey Mapping Program, 1960-1978

    USGS Publications Warehouse

    Cressman, Earle Rupert; Noger, Martin C.

    1981-01-01

    . Paleontologists and stratigraphers of the U.S. Geological Survey cooperated closely with the program. Paleontologic studies were concentrated in the Ordovician of central Kentucky, the Pennsylvanian of eastern and western Kentucky, and the Mesozoic and Cenozoic of westernmost Kentucky. In addition to financial support, the Kentucky Geological Survey provided economic data, stratigraphic support, and drillhole records to the field offices. Geologists of the State Survey made subsurface structural interpretations, constructed bedrock topography maps, and mapped several quadrangles. Some of the problems encountered were the inadequacy of much of the existing stratigraphic nomenclature, the uneven quality of some of the mapping, and the effects of relative isolation on the professional development of some of the geologists. The program cost a total of $20,927,500. In terms of 1960 dollars, it cost $16,035,000; this compares with an original estimate of $12,000,000. Although it is difficult to place a monetary value on the geologic mapping, the program has contributed to newly discovered mineral wealth, jobs, and money saved by government and industry. The maps are used widely in the exploration for coal, oil and gas, fluorspar, limestone, and clay. The maps are also used in planning highways and locations of dams, in evaluating foundation and excavation conditions, in preparing environmental impact statements, and in land-use planning.

  3. Might rock moisture in shallow fractured bedrock underlying hillslopes provide vegetation resilience to future droughts?

    NASA Astrophysics Data System (ADS)

    Dietrich, W. E.; Dawson, T. E.; Salve, R.; Simonin, K. A.; Oshun, J.; Rempe, D.; Fung, I.

    2009-12-01

    Hilly and mountainous landscapes are often capped by relatively thin soil that mantles a thicker, but nonetheless relatively shallow fractured bedrock zone. The few studies that have quantitatively explored this near-surface zone have demonstrated that subsurface runoff, saturation overland flow, and pore pressure development are dominated by pathways through the bedrock—not through the soil. Hence, evolution of this weathered fractured zone, and its spatial variation strongly influences hydrologic and geomorphic processes. Here we report findings at a new study site (“Rivendell”) in the South Fork Eel River watershed in the Northern Coastal California area, where periods of essentially no rain can extend 5 to 6 months, yet 60 m tall conifer trees can prosper and continuous baseflow in modest sized drainages can sustain aquatic ecosystems. Dominant vegetation in the region correlates with lithology and we hypothesize that it is the extent of development of the shallow fractured bedrock that controls this relationship. To explore the linkages between climate, vegetation, and hydrology as mediated by bedrock conditions we have instrumented a 4000 m2 steep (32 degree) catchment under old-growth Douglas fir forest with a large number (over 300) of devices including rain gauges, temperature, humidity and soil moisture probes, TDR arrays, sap flow monitors and pressure transducers in wells—all of which report via a wireless solar powered system back to Berkeley for effectively real-time monitoring. Electrical resistivity tomography surveys have been repeatedly performed. Seven deep (up to 30 m) wells along the catchment reveal a ~20 m thick weathered, fractured bedrock zone that tapers downslope to about 7 m. Two years of monitoring show that all water passes through the shallow soil into the bedrock zone where it eventually collects at the base of the fracture zone, forming a dynamic perched groundwater table that generates storm runoff and slowly drops during

  4. HIGH ARSENIC CONCENTRATIONS AND ENRICHED SULFUR AND OXYGEN ISOTOPES IN A FRACTURED-BEDROCK GROUND-WATER SYSTEM

    EPA Science Inventory

    Elevated arsenic concentrations are coincident with enriched sulfur and oxygen isotopes of sulfate in bedrock ground water within Kelly's Cove watershed, Northport, Maine, USA. Interpretation of the data is complicated by the lack of correlations between sulfate concentrations an...

  5. Imaging 3D geological structure of the Mygdonian basin (Northern Greece) with geological numerical modeling and geophysical methods.

    NASA Astrophysics Data System (ADS)

    Cédric, Guyonnet-Benaize; Fabrice, Hollender; Maria, Manakou; Alexandros, Savvaidis; Elena, Zargli; Cécile, Cornou; Nikolaos, Veranis; Dimitrios, Raptakis; Artemios, Atzemoglou; Pierre-Yves, Bard; Nikolaos, Theodulidis; Kyriazis, Pitilakis; Emmanuelle, Chaljub

    2013-04-01

    The Mygdonian basin, located 30 km E-NE close to Thessaloniki, is a typical active tectonic basin, trending E-NW, filled by sediments 200 to 400 m thick. This basin has been chosen as a European experimental site since 1993 (European Commission research projects - EUROSEISTEST). It has been investigated for experimental and theoretical studies on site effects. The Mygdonian basin is currently covered by a permanent seismological network and has been mainly characterized in 2D and 3D with geophysical and geotechnical studies (Bastani et al, 2011; Cadet and Savvaidis, 2011; Gurk et al, 2007; Manakou et al, 2007; Manakou et al, 2010; Pitilakis et al, 1999; Raptakis et al, 2000; Raptakis et al, 2005). All these studies allowed understanding the influence of geological structures and local site conditions on seismic site response. For these reasons, this site has been chosen for a verification exercise for numerical simulations in the framework of an ongoing international collaborative research project (Euroseistest Verification and Validation Project - E2VP). The verification phase has been made using a first 3D geophysical and geotechnical model (Manakou, 2007) about 5 km wide and 15 km long, centered on the Euroseistest site. After this verification phase, it has been decided to update, optimize and extend this model in order to obtain a more detailed model of the 3D geometry of the entire basin, especially the bedrock 3D geometry which can affect drastically the results of numerical simulations for site effect studies. In our study, we build a 3D geological model of the present-day structure of the entire Mygdonian basin. This "precise" model is 12 km wide, 65 km long and is 400 m deep in average. It has been built using geophysical, geotechnical and geological data. The database is heterogeneous and composed of hydrogeological boreholes, seismic refraction surveys, array microtremor measurements, electrical and geotechnical surveys. We propose an integrated

  6. Essential Elements of Geologic Reports.

    ERIC Educational Resources Information Center

    Webb, Elmer James

    1988-01-01

    Described is a report outline for geologic reports. Essential elements include title; abstract; introduction; stratigraphy; petrography; geochemistry; petrology; geophysics; structural geology; geologic history; modeling; economics; conclusions; and recommendations. (Author/CW)

  7. Geology of caves

    USGS Publications Warehouse

    Morgan, I.M., Davies,W.E.

    1991-01-01

    A cave is a natural opening in the ground extending beyond the zone of light and large enough to permit the entry of man. Occurring in a wide variety of rock types and caused by widely differing geological processes, caves range in size from single small rooms to intercorinecting passages many miles long. The scientific study of caves is called speleology (from the Greek words spelaion for cave and logos for study). It is a composite science based on geology, hydrology, biology, and archaeology, and thus holds special interest for earth scientists of the U.S. Geological Survey.

  8. Formation evaluation: Geological procedures

    SciTech Connect

    Whittaker, A.

    1985-01-01

    This volume goes beyond a discussion of petroleum geology and the techniques of hydrocarbon (oil and gas) logging as a reservoir evaluation tool. It provides the logging geologist with a review of geological techniques and classification systems that will ensure the maximum development of communicable geological information. Contents include: 1. Introduction--cuttings recovery, cutting sampling, core sampling, rock classification; 2. Detrital rocks--classification, description; 3. Carbonate rocks--classification, description; 4. Chemical rocks-introduction, siliceous rocks, ferruginous rocks, aluminous rocks, phosphatic rocks, aluminous rocks, carbonaceous rocks; 5. Igneous and metamorpbic rocks; Appendix; References and Index.

  9. Catastrophism in geology

    NASA Astrophysics Data System (ADS)

    Hallam, A.

    An historical survey is presented of ideas relating to the concept of 'catastrophism' in geological studies during the last two centuries. It is noted in particular that the opposing concept of 'uniformitarianism', in which there is assumed to have been an overall constancy of geological processes through time so that there is no need to invoke catastrophic change, is now considered rather extreme. During the nineteen sixties and seventies, a neocatastrophist viewpoint has increasingly emerged in various branches of geology. Mass extinctions and their possible causes - bolide impact, climate, volcanism and sea-level change for example - are each considered in the context of this developing framework.

  10. Geological mapping of the Oak Ridge K-25 Site, Oak Ridge, Tennessee

    SciTech Connect

    Lemiszki, P.J.

    1994-01-01

    The Oak Ridge K-25 Site (formerly known as the Oak Ridge Gaseous Diffusion Plant) is located in the southern Appalachian Valley and Ridge province of east Tennessee and overlies an area of folded and faulted Cambrian through Ordovician sedimentary rocks in the footwall of the Whiteoak Mountain fault. Environmental restoration plans for the area require that the geology of the site be well understood because various aspects of the groundwater system are directly influenced by stratigraphic and structural characteristics of the bedrock. This study involved mapping the bedrock geology of an 18-square mile area in and around the plant site. Field mapping focused on: (1) checking the accuracy of previously mapped stratigraphic and fault contacts, (2) dividing the bedrock into distinct stratigraphic units based on field criteria, (3) determining the geometry of map-scale folds and faults, and (4) documenting various aspects of the local fracture system. Besides accomplishing all of the above tasks, results from this study have led to a number of new hypotheses regarding various aspects of the site geology. First, faulting and folding within carbonates of the Chickamauga Supergroup in the plant area has repeated certain rock units, which requires that there be a thrust fault in the subsurface below them. This thrust fault may project to the surface with the Carters Limestone. Second, thrust slices of the Rome Formation that overlie the Chickamauga carbonates may be extremely thin and have a limited aerial extent. Third, part of the Knox Group on McKinney Ridge is folded into an anticline. Evaluating the above hypotheses will require information about the subsurface that can only be acquired through drilling and surface geophysical surveys. The geologic map produced from this study can be used to evaluate the location of coreholes that will more effectively intersect a combination of stratigraphic, structural, and hydrologic targets.

  11. Hydrogeological characterization of soil/weathered zone and underlying fractured bedrocks in DNAPL contaminated areas using the electromagnetic flowmeter

    NASA Astrophysics Data System (ADS)

    Kang, E.; Yeo, I.

    2011-12-01

    Flowmeter tests were carried out to characterize hydrogeology at DNAPL contaminated site in Wonju, Korea. Aquifer and slug tests determined hydraulic conductivity of soil/weathered zone and underlying fractured bed rocks to be 2.95×10-6 to 7.11×10-6 m/sec and 9.14×10-7 to 2.59×10-6 m/sec, respectively. Ambient flowmeter tests under natural hydraulic conditions revealed that the inflow and outflow take place through the borehole of soil/weathered zone with a tendency of down flow in the borehole. In particular, the most permeable layer of 22 to 30 m below the surface was found to form a major groundwater flow channel. On the contrary, a slight inflow and outflow was observed in the borehole, and the groundwater that inflows in the bottom section of the fractured bedrock flows up and exits through to the most permeable layer. Hydraulic heads measured at nearby multi-level boreholes confirmed the down flow in the soil/weathered zone and the up flow in fractured bedrocks. It was also revealed that the groundwater flow converges to the most permeable layer. TCE concentration in groundwater was measured at different depths, and in the borehole of the soil/weathered zone, high TCE concentration was found with higher than 10 mg/L near to the water table and decreased to about 6 mg/L with depth. The fractured bedrocks have a relatively constant low TCE concentration through a 20 m thick screen at less than l mg/L. The hydrogeology of the up flow in the soil/weathered zone and the down flow in underlying fractured bedrock leads the groundwater flow, and subsequently TCE plume, mainly to the most permeable layer that also restricts the advective transport of TCE plume to underlying fractured bedrocks. The cross borehole flowmeter test was carried out to find any hydrogeological connection between the soil/weathered zone and underlying fractured bedrocks. When pumping groundwater from the soil/weathered zone, no induced flow by groundwater extraction was observed at the

  12. Meridiani Bedrock

    NASA Technical Reports Server (NTRS)

    2004-01-01

    23 December 2004 The Mars Exploration Rover (MER-B), Opportunity, spent much of this year exploring outcrops of light-toned, layered, sedimentary rock that occur just beneath the dark plains of Sinus Meridiani. To access these rocks, the rover had to look at the walls and rims of impact craters. Further to the north and east of where the rover landed, similar rocks outcrop at the surface -- in other words, they are not covered by dark sand and granules as they are at the rover site. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example from eastern Sinus Meridiani. All of the light-toned surfaces in this image are outcrops of ancient sedimentary rock. Similar rocks probably occur beneath the low albedo (dark) materials that mantle the lower-elevation surfaces in this area. This picture is located near 0.5oS, 356.7oW. The image covers an area about 3 km (1.9 mi) wide and sunlight illuminates the scene from the upper left.

  13. Monitoring the event-scale evolution of a rapidly eroding bedrock gorge

    NASA Astrophysics Data System (ADS)

    Cook, K. L.; Suppe, J.

    2010-12-01

    The Daan River Gorge in western Taiwan provides a unique opportunity to directly observe the impacts of individual flood events on channel evolution. The 1200 m long and up to 20 m deep bedrock gorge has formed in the past 11 years in response to uplift of the riverbed during the 1999 Chi-Chi earthquake. The extremely rapid pace of erosion ensures that flood events have measurable and often dramatic effects on the channel. Since early 2009 we have monitored evolution of the gorge with repeated RTK GPS surveys, laser rangefinder measurements, and terrestrial LIDAR surveys. Six rainfall stations and five water level gauges provide hydrological data for the basin. Discharge is highly variable, ranging from 5 to over 1000 m3/s, and incision is largely driven by floods associated with typhoons and other heavy rainfall events. Different sections of the channel may respond to floods in different ways. In the lower gorge, bedrock incision has ceased, and flood-related changes involve the deposition and removal of sediment. In the steeper upper gorge, flood impacts have included bedrock incision, knickpoint retreat, sediment deposition, and channel widening. Upstream of the bedrock gorge the river is cut into gravel fill, exposing bedrock in the channel bed. The river here is relatively mobile, and floods have caused bedrock incision, channel migration, sediment deposition and removal, and channel avulsion. Since monitoring began, the Daan River has experienced one typhoon (Typhoon Morakot, Aug. 2009) and four heavy rainfall events (April 2009, June 2009, June 2010 and July 2010). Typhoon Morakot, the largest of these events, with 984 mm of rain over five days and a discharge of 1000-1300 m3/s, was a net erosive event, causing 1.5 to 2 m of sediment removal from the lower gorge and a similar amount of bedrock incision in the preexisting upper gorge. In addition, an avulsion of the main channel ~2 km upstream of the gorge redirected flow into the gorge, triggering the

  14. Bedrock temperature as a potential method for monitoring change in crustal stress: Theory, in situ measurement, and a case history

    NASA Astrophysics Data System (ADS)

    Chen, Shunyun; Liu, Peixun; Liu, Liqiang; Ma, Jin

    2016-06-01

    Experimental studies have confirmed that temperature is notably affected by rock deformation; therefore, change in crustal stress should be indicated by measurable changes in bedrock temperature. In this work, we investigated the possibility that the bedrock temperature might be used to explore the state of crustal stress. In situ measurement of bedrock temperature at three stations from 2011 to 2013 was used as the basis for the theoretical analysis of this approach. We began with theoretical analyses of temperature response to change in crustal stress, and of the effect of heat conduction. This allowed distinction between temperature changes produced by crustal stress (stress temperature) from temperature changes caused by conduction from the land surface (conduction temperature). Stress temperature has two properties (synchronous response and a high-frequency feature) that allow it to be distinguished from conduction temperature. The in situ measurements confirmed that apparently synchronous changes in the stress temperature of the bedrock occur and that there exist obvious short-term components of the in situ bedrock temperature, which agrees with theory. On 20 April 2013, an earthquake occurred 95 km away from the stations, fortuitously providing a case study by which to verify our method for obtaining the state of crustal stress using temperature. The results indicated that the level of local or regional seismic activity, representing the level of stress adjustment, largely accords with the stress temperature. This means that the bedrock temperature is a tool that might be applied to understand the state of stress during seismogenic tectonics. Therefore, it is possible to record changes in the state of crustal stress in a typical tectonic position by long-term observation of bedrock temperature. Hereby, the measurement of bedrock temperature has become a new tool for gaining insight into changes in the status of shallow crustal stress.

  15. Quantitative extraction of bedrock exposed rate based on unmanned aerial vehicle data and TM image in Karst Environment

    NASA Astrophysics Data System (ADS)

    wang, hongyan; li, qiangzi; du, xin; zhao, longcai

    2016-04-01

    In the karst regions of Southwest China, rocky desertification is one of the most serious problems of land degradation. The bedrock exposed rate is one of the important indexes to assess the degree of rocky desertification in the karst regions. Because of the inherent merits of macro scale, frequency, efficiency and synthesis, remote sensing is the promising method to monitor and assess karst rocky desertification on large scale. However, the actual measurement of bedrock exposed rate is difficult and existing remote sensing methods cannot directly be exploited to extract the bedrock exposed rate owing to the high complexity and heterogeneity of karst environments. Therefore, based on the UAV and TM data, the paper selected Xingren County as the research area, and the quantitative extraction of the bedrock exposed rate based on the multi scale remote sensing data was developed. Firstly, we used the object oriented method to carry out the accurate classification of UAV image and based on the results of rock extraction, the bedrock exposed rate was calculated in the 30m grid scale. Parts of the calculated samples were as training data and another samples were as the model validation data. Secondly, in each grid the band reflectivity of TM data was extracted and we also calculated a variety of rock index and vegetation index (NDVI, SAVI etc.). Finally, the network model was established to extract the bedrock exposed rate, the correlation coefficient (R) of the network model was 0.855 and the correlation coefficient (R) of the validation model was 0.677, the root mean square error (RMSE) was 0.073. Based on the quantitative inversion model, the distribution map of the bedrock exposed rate in Xingren County was obtained. Keywords: Bedrock exposed rate, quantitative extraction, UAV and TM data, Karst rocky desertification.

  16. Bedrock gorges incising glacial hanging valleys (Western Alps, France): results from morphometric analysis, numerical modeling and 10Be cosmogenic dating

    NASA Astrophysics Data System (ADS)

    Valla, Pierre G.; van der Beek, Peter A.; Lague, Dimitri; Carcaillet, Julien

    2010-05-01

    Bedrock gorges are frequent features in glacial or post-glacial landscapes and allow measurements of fluvial bedrock incision in mountainous relief. Using digital elevation models, aerial photographs, topographic maps and field reconnaissance in the Pelvoux-Ecrins Massif (French Western Alps), we have identified ~30 tributary hanging valleys incised by gorges toward their confluence with the trunk streams. Longitudinal profiles of these tributaries are all convex and have abrupt knickpoints at the upper limit of oversteepened gorge reaches. From morphometric analyses, we find that mean channel gradients and widths, as well as knickpoint retreat rates, display a drainage-area dependence modulated by bedrock lithology. However, there appears to be no relation between horizontal retreat and vertical downwearing of knickpoints. Numerical modeling has been performed to test the capacity of different fluvial incision models to predict the inferred evolution of the gorges. Results from simple end-member models suggest transport-limited behavior of the bedrock gorges. Using a more sophisticated model including dynamic width adjustment and sediment-dependent incision rates, we show that bedrock gorge evolution requires significant supply of sediment from the gorge sidewalls triggered by gorge deepening, combined with pronounced inhibition of bedrock incision by sediment transport and deposition. We then use in-situ produced 10Be cosmogenic nuclides to date and quantify bedrock gorge incision into a single glacial hanging valley (Gorge du Diable). We have sampled gorge sidewalls and the active channel bed to derive both long-term and present-day incision rates. 10Be ages of sidewall profiles reveal rapid incision through the late Holocene (ca 5 ka), implying either delayed initiation of gorge incision after final ice retreat from internal Alpine valleys at ca 12 ka, or post-glacial surface reburial of the gorge. Both modeling results and cosmogenic dating suggest that

  17. Questa Baseline and Premining Ground-Water Quality Investigation 18. Characterization of Brittle Structures in the Questa Caldera and Their Potential Influence on Bedrock Ground-Water Flow, Red River Valley, New Mexico

    USGS Publications Warehouse

    Caine, Jonathan Saul

    2006-01-01

    This report presents a field-based characterization of fractured and faulted crystalline bedrock in the southern portion of the Questa caldera and its margin. The focus is (1) the identification and description of brittle geological structures and (2) speculation on the potential effects and controls that these structures might have on the potential fluxes of paleo to present-day ground water in relation to natural or mining-related metal and acid loads to surface and ground water. The entire study area is pervasively jointed with a few distinctive patterns such as orthogonal, oblique orthogonal, and conjugate joint sets. Joint intensity, the number of joints measured per unit line length, is high to extreme. Three types of fault zones are present that include partially silicified, low- and high-angle faults with well-developed damage zones and clay-rich cores and high-angle, unsilicified open faults. Conceptually, the joint networks can be thought of as providing the background porosity and permeability structure of the bedrock aquifer system. This background is cut by discrete entities such as the faults with clay-rich cores and open faults that may act as important hydrologic heterogeneities. The southern caldera margin runs parallel to the course of the Red River Valley, whose incision has left an extreme topographic gradient at high angles to the river. Many of the faults and fault intersections run parallel to this assumed hydraulic gradient; thus, these structures have great potential to provide paleo and present-day, discrete and anisotropic pathways for solute transport within the otherwise relatively low porosity and permeability bedrock background aquifer system. Although brittle fracture networks and faults are pervasive and complex, simple Darcy calculations are used to estimate the hydraulic conductivity and potential ground-water discharges of the bedrock aquifer, caldera margin, and other faults in order to gain insight into the potential

  18. A spatial database of bedding attitudes to accompany Geologic map of the greater Denver area, Front Range Urban Corridor, Colorado

    USGS Publications Warehouse

    Trimble, Donald E.; Machette, Michael N.; Brandt, Theodore R.; Moore, David W.; Murray, Kyle E.

    2003-01-01

    This digital map shows bedding attitude symbols display over the geographic extent of surficial deposits and rock stratigraphic units (formations) as compiled by Trimble and Machette 1973-1977 and published in 1979 (U.S. Geological Survey Map I-856-H) under the Front Range Urban Corridor Geology Program. Trimble and Machette compiled their geologic map from published geologic maps and unpublished geologic mapping having varied map unit schemes. A convenient feature of the compiled map is its uniform classification of geologic units that mostly matches those of companion maps to the north (USGS I-855-G) and to the south (USGS I-857-F). Published as a color paper map, the Trimble and Machette map was intended for land-use planning in the Front Range Urban Corridor. This map recently (1997-1999), was digitized under the USGS Front Range Infrastructure Resources Project (see cross-reference). In general, the mountainous areas in the west part of the map exhibit various igneous and metamorphic bedrock units of Precambrian age, major faults, and fault brecciation zones at the east margin (5-20 km wide) of the Front Range. The eastern and central parts of the map (Colorado Piedmont) depict a mantle of unconsolidated deposits of Quaternary age and interspersed outcroppings of Cretaceous or Tertiary-Cretaceous sedimentary bedrock. The Quaternary mantle is comprised of eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone, shale, and limestone bedrock formations form hogbacks and intervening valleys.

  19. Quantifying the role of forest soil and bedrock in the acid neutralization of surface water in steep hillslopes.

    PubMed

    Asano, Yuko; Uchida, Taro

    2005-02-01

    The role of soil and bedrock in acid neutralizing processes has been difficult to quantify because of hydrological and biogeochemical uncertainties. To quantify those roles, hydrochemical observations were conducted at two hydrologically well-defined, steep granitic hillslopes in the Tanakami Mountains of Japan. These paired hillslopes are similar except for their soils; Fudoji is leached of base cations (base saturation <6%), while Rachidani is covered with fresh soil (base saturation >30%), because the erosion rate is 100-1000 times greater. The results showed that (1) soil solution pH at the soil-bedrock interface at Fudoji (4.3) was significantly lower than that of Rachidani (5.5), (2) the hillslope discharge pH in both hillslopes was similar (6.7-6.8), and (3) at Fudoji, 60% of the base cations leaching from the hillslope were derived from bedrock, whereas only 20% were derived from bedrock in Rachidani. Further, previously published results showed that the stream pH could not be predicted from the acid deposition rate and soil base saturation status. These results demonstrate that bedrock plays an especially important role when the overlying soil has been leached of base cations. These results indicate that while the status of soil acidification is a first-order control on vulnerability to surface water acidification, in some cases such as at Fudoji, subsurface interaction with the bedrock determines the sensitivity of surface water to acidic deposition. PMID:15519722

  20. The role of geostatistics in medical geology

    NASA Astrophysics Data System (ADS)

    Goovaerts, Pierre

    2014-05-01

    Since its development in the mining industry, geostatistics has emerged as the primary tool for spatial data analysis in various fields, ranging from earth and atmospheric sciences, to agriculture, soil science, remote sensing, and more recently environmental exposure assessment. In the last few years, these tools have been tailored to the field of medical geography or spatial epidemiology, which is concerned with the study of spatial patterns of disease incidence and mortality and the identification of potential 'causes' of disease, such as environmental exposure, diet and unhealthy behaviors, economic or socio-demographic factors. On the other hand, medical geology is an emerging interdisciplinary scientific field studying the relationship between natural geological factors and their effects on human and animal health. This paper provides an introduction to the field of medical geology with an overview of geostatistical methods available for the analysis of geological and health data. Key concepts are illustrated using the mapping of groundwater arsenic concentrations across eleven Michigan counties and the exploration of its relationship to the incidence of prostate cancer at the township level. Arsenic in drinking-water is a major problem and has received much attention because of the large human population exposed and the extremely high concentrations (e.g. 600 to 700 μg/L) recorded in many instances. Few studies have however assessed the risks associated with exposure to low levels of arsenic (say < 50 μg/L) most commonly found in drinking water in the United States. In the Michigan thumb region, arsenopyrite (up to 7% As by weight) has been identified in the bedrock of the Marshall Sandstone aquifer, one of the region's most productive aquifers. Epidemiologic studies have suggested a possible associationbetween exposure to inorganic arsenic and prostate cancer mortality, including a study of populations residing in Utah. The information available for the

  1. Stratigraphy and structural geology

    NASA Technical Reports Server (NTRS)

    Carr, M. H.; Wilhelms, D. E.; Greeley, R.; Guest, J. E.

    1976-01-01

    The immediate goal of stratigraphy and structural geology is to reduce the enormous complexity of a planetary surface to comprehensible proportions by dividing the near-surface rocks into units and mapping their distribution and attitude.

  2. Geological science needs studied

    NASA Astrophysics Data System (ADS)

    The Geological Sciences Board of the National Academy of Science is conducting a study of the trends, needs, and priorities of the geological sciences for the 1980s. Many organizations and individuals already have been contacted regarding this task; however, in order to ensure that the forthcoming report is based broadly on ideas from the scientific community, the Geological Sciences Board solicits the thoughts of AGU members about the substance of the study. Please send your questions and comments by early this fall to William Dickinson, chairman of the Geological Sciences Board, National Academy of Sciences, Room 69, 2101 Constitution Ave., N.W., Washington, D.C. 20418. A draft report is expected in January 1983.

  3. Economic Geology (Oil & Gas)

    ERIC Educational Resources Information Center

    Geotimes, 1972

    1972-01-01

    Briefly reviews the worldwide developments in petroleum geology in 1971, including exploration, new fields, and oil production. This report is condensed from the October Bulletin of the American Association of Petroleum Geologists. (PR)

  4. Reconstructing the Geologic Timeline.

    ERIC Educational Resources Information Center

    Hemler, Deb; Repine, Tom

    2002-01-01

    Reports on the use of a non-traditional approach to constructing a geological timeline that allows students to manipulate data, explore their understanding, and confront misconceptions. Lists possible steps to use in engaging students in this constructivist activity. (DDR)

  5. Geologic Mapping of the Meridiani Region, Mars

    NASA Technical Reports Server (NTRS)

    Hynek, B. M.

    2008-01-01

    The light toned bedrock that has been observed at the Mars Exploration Rover Opportunity landing site is an upper layer in a sequence >600 m thick in places. These outcrops contain mineral and textural signatures that require interaction of, and possibly formation from, water. Many distinct layers are visible in the remote sensing data (e.g. Figure 1) and no work has ever characterized the full set of these materials that cover an area >3 105 km2 spanning 20 of longitude. Thus, whatever water-related process( es?) altered, and possibly formed, the rocks at the Opportunity landing site extended over a vast region of Mars. Yet many questions remain to be answered, such as: (1) in what capacity did water form and alter the deposits?, (2) what are the temporal and spatial relations with other major events known from ancient Mars?, and (3) would this type of environment have been conducive to the development of life? To address these questions we are completing a detailed geologic, stratigraphic, and thermophysical properties study of this widespread terrain. Specifically, we are drafting a 1:2M-scale geological map covering the full extent of these water-related deposits. In tandem with the mapping, Hynek and Phillips [1] have conducted a preliminary stratigraphic analysis of the stack of materials. After mapping is complete, we will study the thermophysical properties of the varied layers to derive possible compositional information of the materials. These tasks serve several purposes including gaining an understanding of the complex nature of these materials, their potential source region(s), and their timing of emplacement. All of these efforts are necessary to place the observations by the Opportunity Rover in a broader context and prepare for potential future landed missions to the region. Understanding the large-scale paleohydrology of Mars is central to NASA s goals and vital for determining if life ever arose on the planet.

  6. Advances in planetary geology

    SciTech Connect

    Not Available

    1987-06-01

    The surface of Mars displays a broad range of channel and valley features. There is as great a range in morphology as in scale. Some of the features of Martian geography are examined. Geomorphic mapping, crater counts on selected surfaces, and a detailed study of drainage basins are used to trace the geologic evolution of the Margaritifer Sinus Quandrangle. The layered deposits in the Valles Marineris are described in detail and the geologic processes that could have led to their formation are analyzed.

  7. Advances in Planetary Geology

    NASA Technical Reports Server (NTRS)

    Grant, John A., III; Nedell, Susan S.

    1987-01-01

    The surface of Mars displays a broad range of channel and valley features. There is as great a range in morphology as in scale. Some of the features of Martian geography are examined. Geomorphic mapping, crater counts on selected surfaces, and a detailed study of drainage basins are used to trace the geologic evolution of the Margaritifer Sinus Quandrangle. The layered deposits in the Valles Marineris are described in detail and the geologic processes that could have led to their formation are analyzed.

  8. Case study for delineating a contributing area to a well in a fractured siliciclastic-bedrock aquifer near Lansdale, Pennsylvania

    USGS Publications Warehouse

    Barton, Gary J.; Risser, Dennis W.; Galeone, Daniel G.; Goode, Daniel J.

    2003-01-01

    A supply well used by the North Penn Water Authority near Lansdale, Pa., was selected as a case study for delineating a contributing area in a fractured siliciclastic-bedrock aquifer. The study emphasized the importance of refining the understanding of factors that control ground-water movement to the well by conducting (1) geophysical logging and flow measurements, (2) ground-water level monitoring, (3) aquifer testing, and (4) geochemical sampling. This approach could be applicable for other wells in siliciclastic-bedrock terranes, especially those of Triassic age in southeastern Pennsylvania. The principal methods for refining the understanding of hydrology at supply well MG-1125 were aquifer testing, water-level measurements, and geophysical logging. Results of two constant-discharge aquifer tests helped estimate the transmissivity of water-producing units and evaluate the anisotropy caused by dipping beds. Results from slug tests provided estimates of transmissivity that were used to evaluate the results from the constant-discharge aquifer tests. Slug tests also showed the wide distribution of transmissivity, indicating that ground-water velocities must vary considerably in the well field. Water-level monitoring in observation wells allowed maps of the potentiometric surface near the well field to be drawn. The measurements also showed that the hydraulic gradient can change abruptly in response to pumping from nearby supply wells. Water levels measured at a broader regional scale in an earlier study also provided a useful view of the potentiometric surface for purposes of delineating the contributing area. Geophysical logging and measurements of flow within wells showed that about 60 percent of water from supply well MG-1125 probably is contributed from relatively shallow water-producing fractures from 60 to 125 feet below land surface, but measurable amounts of water are contributed by fractures to a depth of 311 feet below land surface. Chemical samples

  9. Lidar-enhanced geologic mapping, examples from the Medford and Hood River areas, Oregon

    NASA Astrophysics Data System (ADS)

    Wiley, T. J.; McClaughry, J. D.

    2012-12-01

    Lidar-based 3-foot digital elevation models (DEMs) and derivatives (slopeshade, hillshade, contours) were used to help map geology across 1700 km2 (650 mi2) near Hood River and Medford, Oregon. Techniques classically applied to interpret coarse DEMs and small-scale topographic maps were adapted to take advantage of lidar's high resolution. Penetration and discrimination of plant cover by the laser system allowed recognition of fine patterns and textures related to underlying geologic units and associated soils. Surficial geologic maps were improved by the ability to examine tiny variations in elevation and slope. Recognition of low-relief features of all sizes was enhanced where pixel elevation ranges of centimeters to meters, established by knowledge of the site or by trial, were displayed using thousands of sequential colors. Features can also be depicted relative to stream level by preparing a DEM that compensates for gradient. Near Medford, lidar-derived contour maps with 1- to 3-foot intervals revealed incised bajada with young, distal lobes defined by concentric contour lines. Bedrock geologic maps were improved by recognizing geologic features associated with surface textures and patterns or topographic anomalies. In sedimentary and volcanic terrain, structure was revealed by outcrops or horizons lying at one stratigraphic level. Creating a triangulated irregular network (TIN) facet from positions of three or more such points gives strike and dip. Each map area benefited from hundreds of these measurements. A more extensive DEM in the plane of the TIN facet can be subtracted from surface elevation (lidar DEM) to make a DEM with elevation zero where the stratigraphic horizon lies at the surface. The distribution of higher and lower stratigraphic horizons can be shown by highlighting areas similarly higher or lower on the same DEM. Poor fit of contacts or faults projected between field traverses suggest the nature and amount of intervening geologic structure

  10. Surficial Geologic Map of the Evansville, Indiana, and Henderson, Kentucky, Area

    USGS Publications Warehouse

    Moore, David W.; Lundstrom, Scott C.; Counts, Ronald C.; Martin, Steven L.; Andrews, William M., Jr.; Newell, Wayne L.; Murphy, Michael L.; Thompson, Mark F.; Taylor, Emily M.; Kvale, Erik P.; Brandt, Theodore R.

    2009-01-01

    The geologic map of the Evansville, Indiana, and Henderson, Kentucky, area depicts and describes surficial deposits according to their origin and age. Unconsolidated alluvium and outwash fill the Ohio River bedrock valley and attain maximum thickness of 33-39 m under Diamond Island, Kentucky, and Griffith Slough, south of Newburgh, Indiana. The fill is chiefly unconsolidated, fine- to medium-grained, lithic quartz sand, interbedded with clay, clayey silt, silt, coarse sand, granules, and gravel. Generally, the valley fill fines upward from the buried bedrock surface: a lower part being gravelly sand to sandy gravel, a middle part mostly of sand, and a surficial veneer of silt and clay interspersed with sandy, natural levee deposits at river's edge. Beneath the unconsolidated fill are buried and discontinuous, lesser amounts of consolidated fill unconformably overlying the buried bedrock surface. Most of the glaciofluvial valley fill accumulated during the Wisconsin Episode (late Pleistocene). Other units depicted on the map include creek alluvium, slackwater lake (lacustrine) deposits, colluvium, dune sand, loess, and sparse bedrock outcrops. Creek alluvium underlies creek floodplains and consists of silt, clayey silt, and subordinate interbedded fine sand, granules, and pebbles. Lenses and beds of clay are present locally. Silty and clayey slackwater lake (lacustrine) deposits extensively underlie broad flats northeast of Evansville and around Henderson and are as thick as 28 m. Fossil wood collected from an auger hole in the lake and alluvial deposits of Little Creek, at depths of 10.6 m and 6.4 m, are dated 16,650+-50 and 11,120+-40 radiocarbon years, respectively. Fossil wood collected from lake sediment 16 m below the surface in lake sediment was dated 33,100+-590 radiocarbon years. Covering the hilly bedrock upland is loess (Qel), 3-7.5 m thick in Indiana and 9-15 m thick in Kentucky, deposited about 22,000-12,000 years before present. Most mapped surficial

  11. Quaternary geologic map of the Chesapeake Bay 4 degrees x 6 degrees quadrangle, United States

    USGS Publications Warehouse

    State compilations by Cleaves, Emery T.; Glaser, John D.; Howard, Alan D.; Johnson, Gerald H.; Wheeler, Walter H.; Sevon, William D.; Judson, Sheldon; Owens, James P.; Peebles, Pamela C.; edited and integrated by Richmond, Gerald Martin; Fullerton, David S.; Weide, David L.

    1987-01-01

    The Quaternary Geologic Map of the Chesapeake Bay 4? x 6? Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the Earth. They make up the 'ground' on which we walk, the 'dirt' in which we dig foundations, and the 'soil' in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  12. Quaternary geologic map of the Sudbury 4 degree by 6 degree quadrangle, United States and Canada

    USGS Publications Warehouse

    Fullerton, David S.; Sado, Edward V., (compiler); Baker, C.L.; Farrand, William R.

    2004-01-01

    The Quaternary Geologic Map of the Sudbury 4 degrees x 6 degrees Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the earth. They make up the 'ground' on which we walk, the 'dirt' in which we dig foundations, and the 'soil' in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  13. Quaternary geologic map of the Dallas 4° x 6° quadrangle, United States

    USGS Publications Warehouse

    State compilations by Luza, Kenneth V.; Jensen, Kathleen M.; Fishman, W.D.; Wermund, E.G., Jr.; Richmond, Gerald Martin; edited and integrated by Richmond, Gerald Martin; Christiansen, Ann Coe; Digital edition by Bush, Charles A.

    1994-01-01

    The Quaternary Geologic Map of the Dallas 4° x 6° Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the Earth. They make up the ground on which we walk, the dirt in which we dig foundations, and the soil in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  14. Quaternary geologic map of the Quebec 4 degrees x 6 degrees quadrangle, United States and Canada

    USGS Publications Warehouse

    State compilations by Borns, H. W., Jr.; Gadd, N.R.; LaSalle, Pierre; Martineau, Ghismond; Chauvin, Luc; Fulton, R.J.; Chapman, W.F.; Wagner, W.P.; Grant, D.R.; edited and integrated by Richmond, Gerald Martin; Fullerton, David S.

    1987-01-01

    The Quaternary Geologic Map of the Quebec 4? x 6? Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the Earth. They make up the 'ground' on which we walk, the 'dirt' in which we dig foundations, and the 'soil' in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  15. Quaternary geologic map of the Ottawa 4 degrees x 6 degrees quadrangle, United States and Canada

    USGS Publications Warehouse

    Fullerton, David S.; Gadd, N. R., (compiler); Veillette, J.J.; Wagner, P.W.; Chapman, W.F.

    1993-01-01

    The Quaternary Geologic Map of the Ottawa 4 degree x 6 degree Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the earth. They make up the 'ground' on which we walk, the 'dirt' in which we dig foundations, and the 'soil' in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  16. Quaternary geologic map of the Boston 4 degrees x 6 degrees quadrangle, United States and Canada

    USGS Publications Warehouse

    State compilations by Hartshorn, Joseph H.; Thompson, W.B.; Chapman, W.F.; Black, R.F.; Richmond, Gerald Martin; Grant, D.R.; Fullerton, David S.; edited and integrated by Richmond, Gerald Martin

    1991-01-01

    The Quaternary Geologic Map of the Boston 4 deg x 6 deg Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the earth. They make up the 'ground' on which we walk, the 'dirt' in which we dig foundations, and the 'soil' in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  17. Quaternary geologic map of the Chicago 4 degrees x 6 degrees quadrangle, United States

    USGS Publications Warehouse

    State compilations by Lineback, Jerry A.; Bleuer, Ned K.; Mickelson, David M.; Farrand, William R.; Goldthwait, Richard P.; Edited and integrated by Richmond, Gerald M.; Fullerton, David S.

    1983-01-01

    The Quaternary Geologic Map of the Chicago 4 degree x 6 degree Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the earth. They make up the 'ground' on which we walk, the 'dirt' in which we dig foundations, and the 'soil' in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  18. Quaternary geologic map of the Ozark Plateau 4 ° x 6 ° quadrangle, United States

    USGS Publications Warehouse

    State compilations by Whitfield, John William; Ward, R.A.; Denne, J.E.; Holbrook, D.F.; Bush, W.V.; Lineback, J.A.; Luza, K.V.; Jensen, Kathleen M.; Fishman, W.D.; Richmond, Gerald Martin, (Edited By); Weide, David L.; Digital edition by Bush, Charles A.

    1993-01-01

    The Quaternary Geologic Map of the Ozark Plateau 4° x 6° Quadrangle was mapped as part of the Quaternary Geologic Atlas of the United States. The atlas was begun as an effort to depict the areal distribution of surficial geologic deposits and other materials that accumulated or formed during the past 2+ million years, the period that includes all activities of the human species. These materials are at the surface of the earth. They make up the "ground" on which we walk, the "dirt" in which we dig foundations, and the "soil" in which we grow crops. Most of our human activity is related in one way or another to these surface materials that are referred to collectively by many geologists as regolith, the mantle of fragmental and generally unconsolidated material that overlies the bedrock foundation of the continent. The maps were compiled at 1:1,000,000 scale.

  19. Environmental geologic studies of the Kaiparowits coal-basin area, Utah

    SciTech Connect

    Sargent, K.A.

    1984-01-01

    The Kaiparowits coal-basin area may contain as much as 20 billion tons of coal; it is a major coal-resource area and a potentially important energy supply area for the southwestern United States. However, the economic development of this coal could constitute a possible threat to the great natural beauty of the area. The impact caused by an attendant increase in population would be great. The US Geological Survey in 1975 started a series of studies of the Kaiparowits coal-basin area. The results of these studies are now being published as a folio consisting of 12 earth-resource maps showing hydrology, bedrock and surficial geology, coal resources, landslides, landforms, and scenic features related to geology. These maps are designed to help land-use planners and land developers make intelligent decisions on the most desirable use of this rich and beautiful land. 50 refs., 23 figs.

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

    USGS Publications Warehouse

    Wright, Bruce E.; Stewart, David B.

    1990-01-01

    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.

  1. Thermal regimes in bedrock and open fractures in the Nordnes rockslide, Norway

    NASA Astrophysics Data System (ADS)

    Hvidtfeldt Christiansen, Hanne; Harald Blikra, Lars

    2010-05-01

    The Nordnes rockslide site is located in the arctic part of the periglacial mountain landscape of Northern Norway at 69°30'N. It consists in the upper part of 1-10 m wide and 1-10 m deep open fractures. Extensive displacements measurements using GPS surveys, crackmeters, tiltmeter and lasers establish the intermunicipality monitoring programme, which shows ongoing deformation of the rockslide. In the rather special topographical setting of the open fractures we have during the International Polar Year 2007 to 2009 recorded the thermal regime of the upper part of the bedrock and of the air in the cracks for attempting to determine whether the recorded deformation can be geomorphologically controlled by bedrock surface expansion and contraction and/or by seasonal freezing or even by permafrost, or if only normal gravitational processes control the observed displacements. The upper 40 cm bedrock thermal conditions have been investigated in different exposures to identify the seasonal freezing depth and length, for determination of the influence of potential ice segregation processes causing weathering of the bedrock surfaces. The data show generally that that the bedrock surface is in the -3 to -8C freezing window for 3 to 6 months. Likewise 250 cm deep bedrock thermal monitoring have been carried out in three boreholes during one year at 900 m, 800 m and 625 m asl. extending over the area from the upper part of the unstable area and into the stable area above, for determination of the regional permafrost zone. These results in combination with thermal evidence from other deeper boreholes from the same setting in the same region show that seasonal freezing extends 5-10 m down, and that a potential active layer also is in the order of 5-10 m deep. The air temperatures in the cracks show significant cooling during winter, when the cracks have a thick snow cover, thus demonstrating the potential existence of permafrost in deeper part of the cracks and in the ground just

  2. Spatial variability in bank resistance to erosion on a large meandering, mixed bedrock-alluvial river

    NASA Astrophysics Data System (ADS)

    Konsoer, Kory M.; Rhoads, Bruce L.; Langendoen, Eddy J.; Best, James L.; Ursic, Mick E.; Abad, Jorge D.; Garcia, Marcelo H.

    2016-01-01

    Spatial heterogeneity in the erosion-resistance properties of the channel banks and floodplains associated with sediment characteristics, vegetation, or bedrock can have a substantial influence on the morphodynamics of meandering rivers, resulting in highly variable rates of bank erosion and complex patterns of planform evolution. Although past studies have examined the spatial variability in bank erodibility within small rivers, this aspect of the erosion-resistance properties for large rivers remains poorly understood. Furthermore, with the exception of recent numerical modeling that incorporates stochastic variability of floodplain erosional resistance, most models of meandering river dynamics have assumed uniform erodibility of the bank and floodplain materials. The present paper investigates the lateral and vertical heterogeneity in bank material properties and riparian vegetation within two elongate meander loops on a large mixed bedrock-alluvial river using several geotechnical field and laboratory methods. Additionally, the bank stability and toe-erosion numerical model (BSTEM) and repeat terrestrial LiDAR surveys are used to evaluate the capacity of the bank material properties to modify the rates and mechanisms of bank retreat. Results show that the textural properties of the bank materials, soil cohesion, and critical shear stress necessary for sediment entrainment differ substantially between the two bends and are also highly variable within each bend - laterally and vertically. Trees growing along the banks increase the resistance to erosion by contributing to the shear strength of the bank materials and are capable of increasing bank stability along a large river. Locally outcropping bedrock also influences bank erodibility in both bends. The results of this study demonstrate that spatial variability in the erosion-resistance properties of the channel banks is an important factor contributing to spatial variability in the rates and mechanisms of bank

  3. Is Frost Cracking By Segregation Ice Growth One of the Mechanisms That Erode Bedrock River Margins?

    NASA Astrophysics Data System (ADS)

    Alden, L. L.; Sklar, L. S.

    2014-12-01

    Rivers cut vertically and laterally into bedrock. However, control on the width of bedrock rivers is an unsolved problem. In alpine settings, frost cracking is one of the mechanisms that break down bedrock. Segregation ice drives growth of ice lenses within rock masses. When the temperature of the rock is within the "frost cracking window" of -3 to -8 °C, ice lenses can attract liquid water. Expanding ice lenses can exert sufficient pressure to fracture the rock. We hypothesize that alpine rivers may promote segregation ice growth at the river margin by supplying water, but also may inhibit frost cracking by supplying heat. We find support for this hypothesis in data collected along the Tuolumne and Mokelumne rivers in the Sierra Nevada, California. A 1D heat flow model predicts that frost cracking should occur above 2325 masl in this area. To test for a river effect, we measured fracture density along the Tuolumne River at ~2600 masl, finding that density at the river margin is significantly greater than on adjacent hillslopes in the Cathedral Peak granodiorite. We then deployed data loggers on the Mokelumne River (at 2486 masl) over the winter of 2013/2014 to record water, surface and subsurface rock temperatures at varying depths and distances from the river. Temperatures within the frost cracking window were only recorded at a distance of ~5 m from the river, suggesting an insulating effect from the river and snow cover. Rock temperatures 1 m deep equilibrated at ~ 2 °C, significantly colder than predicted by the 1D model. Ongoing work includes terrestrial LIDAR scans to detect erosion of the river bank at the Mokelumne site, and development of a 2D heat flow model to predict subsurface rock temperatures for varying surface boundary conditions and channel morphology. We expect that further analysis will reveal systematic relationships between the surface boundary conditions and rock temperature at depth, enabling predictive modeling of frost cracking

  4. Shallow bedrock storm-flow, rock moisture, and consequences for geomorphic, ecologic and, possibly, climatic processes

    NASA Astrophysics Data System (ADS)

    Dietrich, W. E.; Oshun, J.; Rempe, D. M.; Dawson, T. E.; Simonin, K.; Salve, R.; Fung, I.

    2010-12-01

    Field studies and models generally presume that the transition from the soil mantle to the underlying bedrock is a major hydrologic boundary: plants rely on soil moisture, shallow subsurface flow develops along the soil/rock boundary, and water that enters the bedrock takes a slow path, recharging deep groundwater. Three intensive field studies in the steep landscapes of the California and Oregon Coast Ranges demonstrate these assumptions to be wrong. Instead, essentially all precipitation-driven unsaturated flow enters the underlying fractured bedrock, penetrates to depths where fractures close and become poorly conductive. Here it forms a seasonally dynamic shallow water table that generates a subsurface storm flow and retains water through the long summer periods of no rain. Exfiltration from the fractured rock zone can lead to saturation overland flow, which in turn drives channel initiation, depending on vegetation cover. Localized exfiltration on steeper topography can sufficiently elevate pore pressures to cause the weaker soil mantle to mobilize as a landslide and head downstream as a debris flow. Rock moisture and the groundwater perched in the weather rock zone may provide essential water to vegetation during extended periods of no rain, greatly increasing the moisture availability compared to that contained just in the soil mantled. Water transpired by plants tapping this rock moisture in turn may influence local atmospheric humidity and temperature, and therefore regional climate. We are now conducting an intensive field investigation of these hypotheses at a site in Northern California and coupling that with studies to explore the pattern and controls on the weathered zone that may be a key reservoir for dry season and drought water.

  5. Revealing the unexplored fungal communities in deep groundwater of crystalline bedrock fracture zones in Olkiluoto, Finland

    PubMed Central

    Sohlberg, Elina; Bomberg, Malin; Miettinen, Hanna; Nyyssönen, Mari; Salavirta, Heikki; Vikman, Minna; Itävaara, Merja

    2015-01-01

    The diversity and functional role of fungi, one of the ecologically most important groups of eukaryotic microorganisms, remains largely unknown in deep biosphere environments. In this study we investigated fungal communities in packer-isolated bedrock fractures in Olkiluoto, Finland at depths ranging from 296 to 798 m below surface level. DNA- and cDNA-based high-throughput amplicon sequencing analysis of the fungal internal transcribed spacer (ITS) gene markers was used to examine the total fungal diversity and to identify the active members in deep fracture zones at different depths. Results showed that fungi were present in fracture zones at all depths and fungal diversity was higher than expected. Most of the observed fungal sequences belonged to the phylum Ascomycota. Phyla Basidiomycota and Chytridiomycota were only represented as a minor part of the fungal community. Dominating fungal classes in the deep bedrock aquifers were Sordariomycetes, Eurotiomycetes, and Dothideomycetes from the Ascomycota phylum and classes Microbotryomycetes and Tremellomycetes from the Basidiomycota phylum, which are the most frequently detected fungal taxa reported also from deep sea environments. In addition some fungal sequences represented potentially novel fungal species. Active fungi were detected in most of the fracture zones, which proves that fungi are able to maintain cellular activity in these oligotrophic conditions. Possible roles of fungi and their origin in deep bedrock groundwater can only be speculated in the light of current knowledge but some species may be specifically adapted to deep subsurface environment and may play important roles in the utilization and recycling of nutrients and thus sustaining the deep subsurface microbial community. PMID:26106376

  6. Bedrock knobs, San Francisco Bay: Do navigation hazards outweigh other environment problems?

    USGS Publications Warehouse

    Carlson, P.R.; Chin, J.L.; Wong, F.L.

    2000-01-01

    Three bedrock knobs (Arch, Harding, and Shag rocks) rise above the unconsolidated sediment of central San Francisco Bay to a water depth of less than -12 m (<-39.4 ft MLLW). These rocks are within the westbound vessel traffic area, and the northernmost, Harding Rock, is ~300 m (984 ft) from the two-way deep water traffic lane. The rocks pose a hazard to deep-draft vessels. Large ships with drafts deeper than -17 m (-55.8 ft) cross central San Francisco Bay bound for and returning from major port cities of the Bay estuary. Acoustic profiling data show that bedrock extends at a gentle to moderate slope away from the knobs. These data also show that two of the knobs, Harding and Shag, may be part of a bedrock ridge that extends to Alcatraz Island and perhaps southeast to Blossom Rock. The tops of these rocks should be lowered to a depth of -17 m (-55.8 ft), with a total volume of as much as 245,000 m3 (320,460 yd3), at an estimated cost of nearly 27 million dollars, to eliminate the possibility that a tanker would strike one and rupture. A resulting large oil spill would likely cost many times more than the 10 million dollars needed to clean up a small 1996 spill. If the rocks were removed, local habitat for striped bass and other game fish would be altered, with potential negative impact on sport fishing. Currently, public officials are studying the benefits to the Bay environment of lowering the rock knobs.

  7. Implications Of Fault Damaged Bedrock To Tectonic and Landscape Evolution In Coastal Alaska

    NASA Astrophysics Data System (ADS)

    Boucher, A.; Koons, P. O.; Roy, S. G.; Birkel, S. D.; Kaluzienski, L. M.; Campbell, S. W.

    2015-12-01

    Bedrock material strength properties heavily impact erosion rates in temperate glacial environments. We focus on the influence of localized tectonic crustal weakening in southeast Alaska on modern glacial erosion rates, thereby quantifying a primary feedback in tectonic/climatic coupling. Southeast Alaska, with its coincident high strain rates, vigorous glacial erosion and rapid sedimentation rates, provides an excellent setting in which to evaluate this interaction. To characterize the relationship between fault damage and glacial incision, we collected data in transects across the strike-slip Fairweather Fault in Yakutat and Disenchantment Bays, in deglaciated valleys below the Mendenhall, Herbert, Ptarmigan, and Lemon Creek Glaciers on the perimeter of the Juneau Icefield, and on deglaciated nunataks on the Echo and Vaughan Lewis Glaciers in the interior of the Juneau Icefield. The mechanical properties of the bedrock are characterized by estimates of fault spacing and material cohesion. In structurally-controlled bedrock valleys exploited by glaciers, fracture spacing may vary by several orders of magnitude across fault damage zones, from more than 10 m to less than 0.1 m. Analysis of active and quiescent fault zones indicate that this variation approximates a power law relationship and correlates with a gradient in cohesive strength varying from greater than 50 MPa to less than 50 kPa between intact bedrock and the core of fault damage zones. The width and orientation of the damage zones is highly variable and we have chosen our field sites to sample zones of very large total displacement, up to kilometers along the Fairweather Fault, and substantially smaller displacements, down to centimeters for the Juneau Icefield locales. Using a Cordilleran Ice sheet model to extend our modern observations into last glacial maximum conditions, we predict both erosion rates and sediment provenance for a material strength pattern influenced by tectonically induced fault

  8. Mapping Depth to Bedrock in a Tropical Pre-Montane Wet Forest in Costa Rica

    NASA Astrophysics Data System (ADS)

    Oien, R. P.; Burns, J. N.; Arnott, R.; Ackerson, J. P.; Morgan, C.

    2012-12-01

    Accounting for all components of the water balance in a watershed includes an estimate of soil water storage, which in turn depends on the depth to bedrock. The soils in this transitional tropical forest contain large amounts of amorphous material from the saprolitic tuff thus classifying the soils as Andisols. Measuring the depth to bedrock in tropical montane environments is complicated by aspect, elevation, slope, landslides, slumping and other mass wasting events. As part of a larger study, Texas A& M Costa Rica REU aimed to close the water budget for a tropical pre-montane forest, the focus of this study is to generate a map of the depth to saprolitic tuff and topographical information for the purpose of estimating the volume of soil water storage in the Howler Monkey Watershed at Texas A&M University Soltis Center for Research and Education, San Isidro de Peñas Blancas, Costa Rica. A map of the depth to saprolitic tuff was created using 101 hand- augured holes (over 2.63 ha) spatially distributed throughout the watershed. Saprolitic tuff was defined as being 50% of the sample and containing grittiness and cobble sized chunks. To characterize the soils throughout the watershed, soil horizons at three sites were described and 22 cores for particle size. The cores consisted of over 40-55% clay classifying them as clayey or clayey loam. The samples also ranged from 50-73% water content. A map showing the slopes within the watershed also shows the relationship of soil depth above the bedrock within the watershed. The slopes across the watershed vary from 12-65 degrees but only have a 24% correlation with the depth to saprolitic tuff. Results suggest that the depth of the saprolitic tuff is quite sensitive to small scale topographic variability. Soil with such high water content becomes an integral part of the water budget since a significant portion of the water is maintained within the soil. Depth to bedrock provides necessary data to estimate the total volume

  9. Submarine geology framework of the Strait of Gibralter

    SciTech Connect

    Mrah, M. )

    1991-03-01

    Three-dimensional, computer-generated bathymetric views and high-resolution sparker profiles are presented to illustrate the geologic framework of the Strait of Gibraltar. 'The Ridge,' an apparent structural feature, divides the Strait into a deeper, more narrow eastern portion and a shallower, wider and more irregular western portion. Sparker profiles show the Moroccan and Spanish shelves to be underlain by rocks whose deformation correlates with the structural deformation of the Betic and Rif Mountains. However, a portion of the center portion of the Strait is floored with approximately 700 m of horizontal sediments despite the adjacent structural deformation and the presence of strong bottom currents. The alternating sequence of well-layered and chaotic-layered sediments suggests periods of large-scale subaqueous landslides that post-date the structural deformation of the Strait. In other areas, the Strait appears to be free of unconsolidated sediments. Large bedrock horsts modify the topography of the floor and side walls.

  10. Geologic sources of asbestos in Seattle's tolt reservoir

    USGS Publications Warehouse

    Reid, M.E.; Craven, G.

    1996-01-01

    Water from Seattle's South Fork Tolt Reservoir contains chrysotile and amphibole asbestos fibers, derived from natural sources. Using optical petrographic techniques, X-ray diffraction, and scanning electron microscopy, we identified the geologic source of these asbestiform minerals within the watershed. No asbestos was found in the bedrock underlying the watershed, while both chrysotile and amphibole fibers were found in sediments transported by Puget-lobe glacial processes. These materials, widely distributed throughout the lower watershed, would be difficult to separate from the reservoir sediments. The probable source of this asbestos is in pods of ultramafic rock occurring north of the watershed. Because asbestos is contained in widespread Pugetlobe glacial materials, it may be naturally distributed in other watersheds in the Puget Sound area.

  11. Knickpoint retreat rates from cosmogenic 10Be; 30 exposure ages from western Scotland with implications for paraglacial bedrock incision

    NASA Astrophysics Data System (ADS)

    Jansen, J. D.; Fabel, D.; Codilean, A. T.; Bishop, P.; Hoey, Tb; Schnabel, C.; Xu, S.

    2009-04-01

    When a bedrock river is perturbed by accelerating rock uplift the perturbation is not transmitted instantaneously to the whole landscape; the new base level information must first spread through the channel network to hillslopes. Under detachment-limited conditions the new base level information is spread via knickpoint retreat, the rate of which ultimately governs response times to perturbation and therefore landscape evolution. Yet, owing to difficulties with measuring rates of erosional processes, knickpoint retreat rates are not widely documented. We examine bedrock river response to rapid, continuous rock uplift due to glacio-isostatic rebound following retreat of the Late Devensian icesheet from northern Britain. From four rivers in western Scotland, we infer knickpoint retreat rates from 30 measurements of cosmogenic 10Be concentrations on abandoned, fluvially-sculpted bedrock surfaces downstream of Holocene knickpoints. These data are among the first direct evidence that terrace exposure ages increase downstream consistent with the progressive abandonment of bedrock surfaces in the wake of a retreating knickpoint. We reflect upon our results in the context of paraglacial conditions that we infer to have involved initially high sediment flux declining over the Holocene. A simple unit stream power model is used to demonstrate how knickpoints affect erosional capacity along transient reaches. Bedrock channel width is insensitive to substrate erodibility, but we document here a sharp reduction in channel width at knickpoints, which is largely responsible for up to order-of-magnitude increases in stream power per unit area of the channel bed. The high rates of bedrock river incision that we document for postorogenic western Scotland are comparable to those reported for landside-dominated mountain belts. However, rather than stemming from towering relief or high-magnitude rock uplift, these rapid erosion rates seem to be the product of high sediment flux

  12. Practical estimates of field-saturated hydraulic conductivity of bedrock outcrops using a modified bottomless bucket method

    USGS Publications Warehouse

    Mirus, Benjamin B.; Perkins, Kim S.

    2012-01-01

    The bottomless bucket (BB) approach (Nimmo et al., 2009a) is a cost-effective method for rapidly characterizing field-saturated hydraulic conductivity Kfs of soils and alluvial deposits. This practical approach is of particular value for quantifying infiltration rates in remote areas with limited accessibility. A similar approach for bedrock outcrops is also of great value for improving quantitative understanding of infiltration and recharge in rugged terrain. We develop a simple modification to the BB method for application to bedrock outcrops, which uses a non-toxic, quick-drying silicone gel to seal the BB to the bedrock. These modifications to the field method require only minor changes to the analytical solution for calculating Kfs on soils. We investigate the reproducibility of the method with laboratory experiments on a previously studied calcarenite rock and conduct a sensitivity analysis to quantify uncertainty in our predictions. We apply the BB method on both bedrock and soil for sites on Pahute Mesa, which is located in a remote area of the Nevada National Security Site. The bedrock BB tests may require monitoring over several hours to days, depending on infiltration rates, which necessitates a cover to prevent evaporative losses. Our field and laboratory results compare well to Kfs values inferred from independent reports, which suggests the modified BB method can provide useful estimates and facilitate simple hypothesis testing. The ease with which the bedrock BB method can be deployed should facilitate more rapid in-situ data collection than is possible with alternative methods for quantitative characterization of infiltration into bedrock.

  13. Database for the east half of "Preliminary Geologic Map of the Blythe 30' by 60' quadrangle, California and Arizona"

    USGS Publications Warehouse

    Stone, Paul

    2006-01-01

    This digital map database was prepared from the published Preliminary Geologic Map of the Blythe 30' by 60' Quadrangle, California and Arizona (U.S. Geological Survey Open-File Report 90-497). This database represents the east half of the original published map. The database contains exactly the same scientific content as the original map; no data have been added to, subtracted from, or modified from the original map. Like the original paper map, this database represents the general distribution of bedrock and surficial deposits in the mapped area. It provides information on the geologic structure and stratigraphy of the area covered. The database delineates map units that are identified by general age and lithology following the stratigraphic nomenclature of the U.S. Geological Survey. The scale of the original published map limits the spatial resolution (scale) of the database to 1:100,000 or smaller.

  14. Geology at Yucca Mountain

    SciTech Connect

    1993-05-01

    Both advocates and critics disagree on the significance and interpretation of critical geological features which bear on the safety and suitability of Yucca Mountain as a site for the construction of a high-level radioactive waste repository. Critics believe that there is sufficient geological evidence to rule the site unsuitable for further investigation. Some advocates claim that there is insufficient data and that investigations are incomplete, while others claim that the site is free of major obstacles. We have expanded our efforts to include both the critical evaluations of existing geological and geochemical data and the collection of field data and samples for the purpose of preparing scientific papers for submittal to journals. Summaries of the critical reviews are presented in this paper.

  15. Geologic map of Mars

    USGS Publications Warehouse

    Tanaka, Kenneth L.; Skinner, James A.; Dohm, James M.; Irwin, Rossman P., III; Kolb, Eric J.; Fortezzo, Corey M.; Platz, Thomas; Michael, Gregory G.; Hare, Trent M.

    2014-01-01

    This global geologic map of Mars, which records the distribution of geologic units and landforms on the planet's surface through time, is based on unprecedented variety, quality, and quantity of remotely sensed data acquired since the Viking Orbiters. These data have provided morphologic, topographic, spectral, thermophysical, radar sounding, and other observations for integration, analysis, and interpretation in support of geologic mapping. In particular, the precise topographic mapping now available has enabled consistent morphologic portrayal of the surface for global mapping (whereas previously used visual-range image bases were less effective, because they combined morphologic and albedo information and, locally, atmospheric haze). Also, thermal infrared image bases used for this map tended to be less affected by atmospheric haze and thus are reliable for analysis of surface morphology and texture at even higher resolution than the topographic products.

  16. Geological fakes and frauds

    NASA Astrophysics Data System (ADS)

    Ruffell, Alastair; Majury, Niall; Brooks, William E.

    2012-02-01

    Some geological fakes and frauds are carried out solely for financial gain (mining fraud), whereas others maybe have increasing aesthetic appeal (faked fossils) or academic advancement (fabricated data) as their motive. All types of geological fake or fraud can be ingenious and sophisticated, as demonstrated in this article. Fake gems, faked fossils and mining fraud are common examples where monetary profit is to blame: nonetheless these may impact both scientific theory and the reputation of geologists and Earth scientists. The substitution or fabrication of both physical and intellectual data also occurs for no direct financial gain, such as career advancement or establishment of belief (e.g. evolution vs. creationism). Knowledge of such fakes and frauds may assist in spotting undetected geological crimes: application of geoforensic techniques helps the scientific community to detect such activity, which ultimately undermines scientific integrity.

  17. Global sedimentary geology program

    SciTech Connect

    Ginsburg, R.N.; Clifton, H.E.; Weimer, R.J.

    1986-07-01

    The Society of Economic Paleontologists and Mineralogists, in collaboration with the International Association of Sedimentologists and the International Union of Geological Sciences Committee on Sedimentology, is developing a new international study under the provisional title of Global Sedimentary Geology Program (GSGP). Initially, three research themes are being considered: (1) event stratigraphy-the documentation of examples of mass extinctions, eustatic fluctuations in sea level, major episodes of volcanisms, and changes in ocean composition; (2) facies models in time and space-an expansion of the existing data base of examples of facies models (e.G., deltas, fluvial deposits, and submarine fans) and global-scale study of the persistence of facies at various times in geologic history; and (3) sedimentary indices of paleogeography and tectonics-the use of depositional facies and faunas in paleogeography and in assessing the timing, locus, and characteristics of tectonism. Plans are being developed to organize pilot projects in each of these themes.

  18. Integrated characterization of the geologic framework of a contaminated site in West Trenton, New Jersey

    USGS Publications Warehouse

    Ellefsen, Karl J.; Burton, William C.; Lacombe, Pierre J.

    2012-01-01

    Fractured sedimentary bedrock and groundwater at the former Naval Air Warfare Center in West Trenton, New Jersey (United States of America) are contaminated with chlorinated solvents. Predicting contaminant migration or removing the contaminants requires an understanding of the geology. Consequently, the geologic framework near the site was characterized with four different methods having different spatial scales: geologic field mapping, analyses of bedrock drill core, analyses of soil and regolith, and S-wave refraction surveys. A fault zone is in the southeast corner of the site and separates two distinct sedimentary formations; the fault zone dips (steeply) southeasterly, strikes northeasterly, and extends at least 550 m along its strike direction. Drill core from the fault zone is extensively brecciated and includes evidence of tectonic contraction. Approximately 300 m east of this fault zone is another fault zone, which offsets the contact between the two sedimentary formations. The S-wave refraction surveys identified both fault zones beneath soil and regolith and thereby provided constraints on their lateral extent and location.

  19. Geological Corrections in Gravimetry

    NASA Astrophysics Data System (ADS)

    Mikuška, J.; Marušiak, I.

    2015-12-01

    Applying corrections for the known geology to gravity data can be traced back into the first quarter of the 20th century. Later on, mostly in areas with sedimentary cover, at local and regional scales, the correction known as gravity stripping has been in use since the mid 1960s, provided that there was enough geological information. Stripping at regional to global scales became possible after releasing the CRUST 2.0 and later CRUST 1.0 models in the years 2000 and 2013, respectively. Especially the later model provides quite a new view on the relevant geometries and on the topographic and crustal densities as well as on the crust/mantle density contrast. Thus, the isostatic corrections, which have been often used in the past, can now be replaced by procedures working with an independent information interpreted primarily from seismic studies. We have developed software for performing geological corrections in space domain, based on a-priori geometry and density grids which can be of either rectangular or spherical/ellipsoidal types with cells of the shapes of rectangles, tesseroids or triangles. It enables us to calculate the required gravitational effects not only in the form of surface maps or profiles but, for instance, also along vertical lines, which can shed some additional light on the nature of the geological correction. The software can work at a variety of scales and considers the input information to an optional distance from the calculation point up to the antipodes. Our main objective is to treat geological correction as an alternative to accounting for the topography with varying densities since the bottoms of the topographic masses, namely the geoid or ellipsoid, generally do not represent geological boundaries. As well we would like to call attention to the possible distortions of the corrected gravity anomalies. This work was supported by the Slovak Research and Development Agency under the contract APVV-0827-12.

  20. Modeling Recharge in a Fractured Bedrock Aquifer to Evaluate the Potential Effects of Climate Change on Groundwater Availability: new techniques

    NASA Astrophysics Data System (ADS)

    Wittman, Jack; Kelson, Vic; Lax, Samanta

    2010-05-01

    This paper describes how we modified a soil-water-budget model initially developed by the United States Geological Survey (USGS) to include fracture recharge through mapped fault zones and then to use this model to better understand the effects of a warming climate on the sustainability of an important groundwater supply. In extended drought conditions, the normally perennial streams in parts of the Western United States stop flowing and, for the City of Laramie, Wyoming, the Casper Aquifer becomes the only source of water to the local water utility. This community, situated in a high desert valley approximately 150 km North of Denver, Colorado, normally uses a combination of surface water from a local stream and groundwater wells. In this arid landscape groundwater is a critical component of the water supply but little is known about how much water enters the exposed recharge area along a mountain front East of town. Groundwater level measurements and geochemistry suggest that the aquifer system has a fast and slow component. Some runoff water becomes recharge where ephemeral streams intersect fractures at the surface and another component of slower recharge occurs as slower percolation through very thin soils. Based on monitoring data, recharge occurs primarily in late winter and early spring during snowmelt. In the past several decades the City Utility has seen annual groundwater levels dropping in municipal wells as the amount of water withdrawn exceeds annual inflows. However, in 1983 water levels in the Casper Aquifer rose significantly following a winter of higher than average snowfall. The analysis presented in this paper outlines how we adapted the general soil-water-budget model to calculate the various components of recharge and then how we considered the effects of warming winter conditions on the sustainability of the bedrock aquifer in this arid region of the country. Or analysis suggests that warming winter conditions could limit snowpack and nearly

  1. Bedrock aquifers and population growth in the Denver Basin, Colorado, USA

    USGS Publications Warehouse

    Moore, J.E.; Raynolds, R.G.; Dechesne, M.

    2007-01-01

    The Denver Basin bedrock aquifer system consists of Tertiary and Cretaceous age sedimentary rocks known as the Dawson, Denver, Arapahoe and Laramie-Fox Hills aquifers. The number of bedrock wells has increased from 12,000 in 1985 to over 33,700 in 2001 and the withdrawal of groundwater has caused water level declines in excess of 75 meters. Water level declines now range from 3 to 12 meters per year in the critical Arapahoe Aquifer. The groundwater supplies were once thought to be sufficient for 100 years but there is concern that they may be depleted in 10 to 15 years in areas on the west side of the basin. Groundwater is being mined from the aquifer system because the withdrawal through wells exceeds the rate of recharge. Increased groundwater withdrawal will cause further water level declines, increased costs to pump groundwater, and reduced yield from existing wells. In the Denver Basin, hydrologists have some capability to monitor declines in water levels for the Arapaho Aquifer, but generally have a limited ability to monitor water use. More complete and accurate water use data are needed to predict groundwater longevity for the Arapahoe Aquifer. The life of the Arapahoe Aquifer can be extended with artificial recharge using imported surface water, water reuse, restrictions on lawn watering, well permit restrictions and other conservation measures. Availability of groundwater may limit growth in the Denver Basin over the next 20 years unless residents are willing to pay for additional new sources of supply.

  2. Increased forest ecosystem carbon and nitrogen storage from nitrogen rich bedrock.

    PubMed

    Morford, Scott L; Houlton, Benjamin Z; Dahlgren, Randy A

    2011-09-01

    Nitrogen (N) limits the productivity of many ecosystems worldwide, thereby restricting the ability of terrestrial ecosystems to offset the effects of rising atmospheric CO(2) emissions naturally. Understanding input pathways of bioavailable N is therefore paramount for predicting carbon (C) storage on land, particularly in temperate and boreal forests. Paradigms of nutrient cycling and limitation posit that new N enters terrestrial ecosystems solely from the atmosphere. Here we show that bedrock comprises a hitherto overlooked source of ecologically available N to forests. We report that the N content of soils and forest foliage on N-rich metasedimentary rocks (350-950 mg N kg(-1)) is elevated by more than 50% compared with similar temperate forest sites underlain by N-poor igneous parent material (30-70 mg N kg(-1)). Natural abundance N isotopes attribute this difference to rock-derived N: (15)N/(14)N values for rock, soils and plants are indistinguishable in sites underlain by N-rich lithology, in marked contrast to sites on N-poor substrates. Furthermore, forests associated with N-rich parent material contain on average 42% more carbon in above-ground tree biomass and 60% more carbon in the upper 30 cm of the soil than similar sites underlain by N-poor rocks. Our results raise the possibility that bedrock N input may represent an important and overlooked component of ecosystem N and C cycling elsewhere. PMID:21886160

  3. Impacts of groundwater metal loads from bedrock fractures on water quality of a mountain stream.

    PubMed

    Caruso, Brian S; Dawson, Helen E

    2009-06-01

    Acid mine drainage and metal loads from hardrock mines to surface waters is a significant problem in the western USA and many parts of the world. Mines often occur in mountain environments with fractured bedrock aquifers that serve as pathways for metals transport to streams. This study evaluates impacts from current and potential future groundwater metal (Cd, Cu, and Zn) loads from fractures underlying the Gilt Edge Mine, South Dakota, on concentrations in Strawberry Creek using existing flow and water quality data and simple mixing/dilution mass balance models. Results showed that metal loads from bedrock fractures to the creek currently contribute <1% of total loads. Even if background water quality is achieved upstream in Strawberry Creek, fracture metal loads would be <5%. Fracture loads could increase substantially and cause stream water quality standards exceedances once groundwater with elevated metals concentrations in the aquifer matrix migrates to the fractures and discharges to the stream. Potential future metal loads from an upstream fracture would contribute a small proportion of the total load relative to current loads in the stream. Cd has the highest stream concentrations relative to standards. Even if all stream water was treated to remove 90% of the Cd, the standard would still not be achieved. At a fracture farther downstream, the Cd standard can only be met if the upstream water is treated achieving a 90% reduction in Cd concentrations and the median stream flow is maintained. PMID:18604589

  4. A volcanic environment for bedrock diagenesis at Meridiani Planum on Mars.

    PubMed

    McCollom, Thomas M; Hynek, Brian M

    2005-12-22

    Exposed bedrocks at Meridiani Planum on Mars display chemical and mineralogical evidence suggesting interaction with liquid water. On the basis of morphological observations as well as high abundances of haematite and sulphate minerals, the rocks have been interpreted as sediments that were deposited in a shallow body of briny water with subsequent evaporation leaving behind the sulphate minerals. The iron-sulphur mineralization at Meridiani has also been inferred to be analogous to that produced during oxidative weathering of metal sulphide minerals, such as occurs at acid mine drainage sites. Neither of these interpretations, however, is consistent with the chemical composition of the rocks. Here we propose an alternative model for diagenesis of Meridiani bedrock that involves deposition of volcanic ash followed by reaction with condensed sulphur dioxide- and water-bearing vapours emitted from fumaroles. This scenario does not require prolonged interaction with a standing body of surface water and may have occurred at high temperatures. Consequently, the model invokes an environment considerably less favourable for biological activity on Mars than previously proposed interpretations. PMID:16372002

  5. Rapid regolith formation over volcanic bedrock and implications for landscape evolution

    NASA Astrophysics Data System (ADS)

    Dosseto, Anthony; Buss, Heather L.; Suresh, P. O.

    2012-07-01

    The ability to quantify how fast weathering profiles develop is crucial to assessing soil resource depletion and quantifying how landscapes evolve over millennia. Uranium-series isotopes can be used to determine the age of the weathering front throughout a profile and to infer estimates of regolith production rates, because the abundance of U-series isotopes in a weathering profile is a function of chemical weathering and time. This technique is applied to a weathering profile in Puerto Rico developed over a volcaniclastic bedrock. U-series isotope compositions are modelled, revealing that it takes 40-60 kyr to develop an 18 m-thick profile. This is used to estimate an average regolith production rate of 334±46 mm/kyr. This value is higher by a factor of up to 30 when compared to production rates estimated for weathering profiles developed over granitic or shale lithologies. This quantitatively underpins the lithological control on rates of regolith production (in a neighbouring watershed but over a granitic bedrock, production rates are only ˜30-40 mm/kyr). Moreover, by comparing these results to a compilation of soil erosion rates, it is clear that landscapes are controlled by the balance (or imbalance) between regolith production and erosion: soil-mantled landscapes are the result of a relative balance between production and erosion, whereas in cratonic areas, thicker weathering profiles are generated because erosion fails to match regolith production rates.

  6. Geochemical impacts of groundwater heat pump systems in an urban alluvial aquifer with evaporitic bedrock.

    PubMed

    Garrido Schneider, Eduardo A; García-Gil, Alejandro; Vázquez-Suñè, Enric; Sánchez-Navarro, José Á

    2016-02-15

    In the last decade, there has been an extensive use of shallow geothermal exploitations in urban environments. Although the thermal interference between exploitations has been recently studied, there is a lack of knowledge regarding the geochemical impacts of those systems on the aquifers where they are installed. Groundwater flow line scale and well-doublet scale research work has been conducted at city scale to quantify the geochemical interaction of shallow geothermal exploitations with the environment. A comprehensive analysis was conducted on data obtained from a monitoring network specifically designed to control and develop aquifer policies related to thermal management of the aquifer. The geochemical impacts were evaluated from a thermodynamic point of view by means of saturation index (SI) calculations with respect to the different mineral species considered in the system. The results obtained indicate limited geochemical interaction with the urban environment in most of the situations. However, there are some cases where the interaction of the groundwater heat pump installations with the evaporitic bedrock resulted in the total disablement of the exploitation system operation wells. The application of the tool proposed proved to be pragmatic in the evaluation of geochemical impacts. Injection of water into the aquifer can trigger an important bedrock gypsum and halite dissolution process that is partly responsible for scaling in well casing pipes and collapse of the terrain in the vicinity of injection wells. PMID:26657381

  7. Active Microbial Communities Inhabit Sulphate-Methane Interphase in Deep Bedrock Fracture Fluids in Olkiluoto, Finland

    PubMed Central

    Bomberg, Malin; Nyyssönen, Mari; Pitkänen, Petteri; Lehtinen, Anne; Itävaara, Merja

    2015-01-01

    Active microbial communities of deep crystalline bedrock fracture water were investigated from seven different boreholes in Olkiluoto (Western Finland) using bacterial and archaeal 16S rRNA, dsrB, and mcrA gene transcript targeted 454 pyrosequencing. Over a depth range of 296–798 m below ground surface the microbial communities changed according to depth, salinity gradient, and sulphate and methane concentrations. The highest bacterial diversity was observed in the sulphate-methane mixing zone (SMMZ) at 250–350 m depth, whereas archaeal diversity was highest in the lowest boundaries of the SMMZ. Sulphide-oxidizing ε-proteobacteria (Sulfurimonas sp.) dominated in the SMMZ and γ-proteobacteria (Pseudomonas spp.) below the SMMZ. The active archaeal communities consisted mostly of ANME-2D and Thermoplasmatales groups, although Methermicoccaceae, Methanobacteriaceae, and Thermoplasmatales (SAGMEG, TMG) were more common at 415–559 m depth. Typical indicator microorganisms for sulphate-methane transition zones in marine sediments, such as ANME-1 archaea, α-, β- and δ-proteobacteria, JS1, Actinomycetes, Planctomycetes, Chloroflexi, and MBGB Crenarchaeota were detected at specific depths. DsrB genes were most numerous and most actively transcribed in the SMMZ while the mcrA gene concentration was highest in the deep methane rich groundwater. Our results demonstrate that active and highly diverse but sparse and stratified microbial communities inhabit the Fennoscandian deep bedrock ecosystems. PMID:26425566

  8. Estimated bedrock topography and ice thickness of the Renland Ice Cap, East Greenland

    NASA Astrophysics Data System (ADS)

    Koldtoft, Iben; Hvidberg, Christine; Panton, Christian

    2016-04-01

    The Renland Ice Cap in East Greenland (71.30°N, 26.72°W) is a separate ice cap located on a high mountain plateau in the Scoresbysund Fjord, with the highest elevation of 2340 m. In 1988 a 324.35 m long ice core was drilled near summit on the eastern dome of the ice cap. The recovered ice core contains a climate record reaching back to the Eemian. In the spring 2015 a new ice core (584 m) was drilled on Renland during the RECAP project. Knowledge of the basal topography of the Renland Ice Cap is very limited. However, old airborne radar surveys show that the bedrock topography is very mountainous. Knowledge of the bedrock topography and ice thickness was needed to locate the best possible drilling site for the new ice core. An iterative inverse method was used to present a modelled estimate of the subglacial topography and ice thickness of the Renland Ice Cap based on the knowledge of the surface topography and climate forcing. The modelled estimate showed initially twice as large ice thickness as expected, but having improved the surface topography with data from the field work on Renland Ice Cap, the modelled ice thickness are in the same order as radar measurements shows.

  9. Sediment transport through self-adjusting, bedrock-walled waterfall plunge pools

    NASA Astrophysics Data System (ADS)

    Scheingross, Joel S.; Lamb, Michael P.

    2016-05-01

    Many waterfalls have deep plunge pools that are often partially or fully filled with sediment. Sediment fill may control plunge-pool bedrock erosion rates, partially determine habitat availability for aquatic organisms, and affect sediment routing and debris flow initiation. Currently, there exists no mechanistic model to describe sediment transport through waterfall plunge pools. Here we develop an analytical model to predict steady-state plunge-pool depth and sediment-transport capacity by combining existing jet theory with sediment transport mechanics. Our model predicts plunge-pool sediment-transport capacity increases with increasing river discharge, flow velocity, and waterfall drop height and decreases with increasing plunge-pool depth, radius, and grain size. We tested the model using flume experiments under varying waterfall and plunge-pool geometries, flow hydraulics, and sediment size. The model and experiments show that through morphodynamic feedbacks, plunge pools aggrade to reach shallower equilibrium pool depths in response to increases in imposed sediment supply. Our theory for steady-state pool depth matches the experiments with an R2 value of 0.8, with discrepancies likely due to model simplifications of the hydraulics and sediment transport. Analysis of 75 waterfalls suggests that the water depths in natural plunge pools are strongly influenced by upstream sediment supply, and our model provides a mass-conserving framework to predict sediment and water storage in waterfall plunge pools for sediment routing, habitat assessment, and bedrock erosion modeling.

  10. Variables indicating nitrate contamination in Bedrock Aquifers, Newark Basin, New Jersey

    USGS Publications Warehouse

    Clawges, R.M.; Vowinkel, E.F.

    1996-01-01

    Variables that describe well construction, hydrogeology, and land use were evaluated for use as possible indicators of the susceptibility of ground water in bedrock aquifers in the Newark Basin. New Jersey, to contamination by nitrate from the land surface. Statistical analyses were performed on data for 132 wells located throughout the Newark Basin. Concentrations of nitrate (as nitrogen) did not exceed the U.S. Environmental Protection Agency maximum contaminant level of 10 milligrams per liter (mg/L) in any of the water samples (U.S. Environmental Protection Agency, 1991). Variables that describe hydrogeology and well construction were found not to be statistically significant in relation to concentrations of nitrate. This finding can be attributed to the complex nature of flow in bedrock aquifers and mixing of water from shallow and deep water-bearing zones that occurs within these wells, which are constructed with long open intervals. Distributions of nitrate concentrations were significantly different among land-use groups on the basis of land use within both a 400- and an 800-m radius zone of the well. The median concentrations of nitrate (as N) in water from wells in predominantly urban-residential (2.5 mg/L) and agricultural areas (1.8 mg/L) were greater than the median concentration of nitrate in water from wells in predominantly undeveloped areas (0.5 mg/L).

  11. Petrography and character of the bedrock surface beneath western Cape Cod, Massachusetts

    USGS Publications Warehouse

    Hallett, B.W.; Poppe, L.J.; Brand, S.G.

    2004-01-01

    Cores collected during recent drilling in western Cape Cod, Massachusetts provide insight into the topography and petrology of the underlying bedrock. 62 drill sites spread over a ???140 km2 study area produced cores of granitoids (31), orthogneisses (20), basalts/diabases (4), amphibolites (3), felsic mylonites (2), and dolomitic rock (2). Granitoid cores range in composition from granite to tonalite to quartz diorite, but are dominated by single-mica granites. Alteration is common in nearly all cores examined in this study, and is evidenced by the secondary growth of chlorite and epidote. The granitoids resemble rocks of the Dedham and Fall River terranes (Wones and Goldsmith 1991). Gneisses from the study area generally contain the mineral assemblage hornblende+plagioclase+quartz+biotite+epidote??chlorite?? sphene??K-feldspar??sericite+oxides. Based on mineral assemblages, we estimate peak metamorphic grade to be of lower amphibolite facies. X-ray powder diffraction of unmetamorphosed dolomitic cores shows presence of layered silicates (clays), plagioclase, and possible magnesite. Contours of the bedrock surface show locally irregular topography suggesting erosion by glacial scour. The distribution of lithologies suggests a possible continuation of the New Bedford gneissic terrane that outcrops 25 km to the west. Dolomitic rocks may represent a lithified fault gouge material at the eastern edge of the gneissic zone. Basalts/diabases are interpreted to be post-metamorphic dikes of Late Paleozoic age, or possibly associated with Mesozoic rifting.

  12. Comparison of dialysis membrane diffusion samplers and two purging methods in bedrock wells

    USGS Publications Warehouse

    Imbrigiotta, T.E.; Ehlke, T.A.; Lacombe, P.J.; Dale, J.M.

    2002-01-01

    Collection of ground-water samples from bedrock wells using low-flow purging techniques is problematic because of the random spacing, variable hydraulic conductivity, and variable contamination of contributing fractures in each well's open interval. To test alternatives to this purging method, a field comparison of three ground-water-sampling techniques was conducted on wells in fractured bedrock at a site contaminated primarily with volatile organic compounds. Constituent concentrations in samples collected with a diffusion sampler constructed from dialysis membrane material were compared to those in samples collected from the same wells with a standard low-flow purging technique and a hybrid (high-flow/low-flow) purging technique. Concentrations of trichloroethene, cis-1,2-dichloroethene, vinyl chloride, calcium, chloride, and alkalinity agreed well among samples collected with all three techniques in 9 of the 10 wells tested. Iron concentrations varied more than those of the other parameters, but their pattern of variation was not consistent. Overall, the results of nonparametric analysis of variance testing on the nine wells sampled twice showed no statistically significant difference at the 95-percent confidence level among the concentrations of volatile organic compounds or inorganic constituents recovered by use of any of the three sampling techniques.

  13. Sediment storage by vegetation in steep bedrock landscapes: Theory, experiments, and implications for postfire sediment yield

    NASA Astrophysics Data System (ADS)

    Lamb, Michael P.; Levina, Mariya; Dibiase, Roman A.; Fuller, Brian M.

    2013-06-01

    models for sediment transport on hillslopes are needed for applications ranging from landscape evolution to debris-flow hazards. Progress has been made for soil-mantled landscapes; however, little is known about sediment production and transport in bedrock landscapes that often maintain a patchy soil mantle, even though slopes exceed the angle of repose. Herein we investigate the hypothesis that patchy soil cover is stable on steep slopes due to local roughness such as vegetation dams that trap sediment upslope. To quantify local sediment storage, we developed a new theory and tested it against tilt-table experiments. Results show that trapped sediment volume scales with the cube of dam width. Where the dam width is less than about fifty grain diameters, particle force chains appear to enhance stability, resulting in greater trapped volumes and sediment-pile slopes that exceed the angle of repose. Trapped volumes are greatest for hillslopes that just exceed the friction slope and are independent of hillslope gradient for gradients greater than about twice the friction slope. For neighboring dams spaced less than about five grain diameters apart, grain bridging results in a single sediment pile that is larger than the sum of individual piles. This work provides a mass-conserving framework for quantifying sediment storage and nonlocal transport in bedrock landscapes. Results may explain the rapid increase in sediment yield following wildfire in steep terrain in the absence of rainfall; as sediment dams are incinerated, particles become gravitationally unstable and move rapidly downslope as dry ravel.

  14. Long-term geoelectrical monitoring of laboratory freeze-thaw experiments on bedrock samples

    NASA Astrophysics Data System (ADS)

    Kuras, Oliver; Uhlemann, Sebastian; Murton, Julian; Krautblatter, Michael

    2014-05-01

    Much attention has recently focussed on the continuous and near-real-time geophysical monitoring of permafrost-affected bedrock with permanently installed sensor arrays. It is hoped that such efforts will enhance process understanding in such environments (permafrost degradation, weathering mechanisms) and augment our capability to predict future instabilities of rock walls and slopes. With regard to electrical methods for example, recent work has demonstrated that temperature-calibrated electrical resistivity tomography (ERT) is capable of imaging recession and re-advance of rock permafrost in response to the ambient temperature regime. However, field experience also shows that several fundamental improvements to ERT methodology are still required to achieve the desired sensitivity, spatial-temporal resolution and long-term robustness that must underpin continuous geophysical measurements. We have applied 4D geoelectrical tomography to monitoring laboratory experiments simulating permafrost growth, persistence and thaw in bedrock over a period of 26 months. Six water-saturated samples of limestone and chalk of varying porosity represented lithologies commonly affected by permafrost-related instability. Time-lapse imaging of the samples was undertaken during multiple successive freeze-thaw cycles, emulating annual seasonal change over several decades. Further experimental control was provided by simultaneous measurements of vertical profiles of temperature and moisture content within the bedrock samples. These experiments have helped develop an alternative methodology for the volumetric imaging of permafrost bedrock and tracking active layer dynamics. Capacitive resistivity imaging (CRI), a technique based upon low-frequency, capacitively-coupled measurements emulates ERT methodology, but without the need for galvanic contact on frozen rock. The latter is perceived as a key potential weakness, which could lead to significant limitations as a result of the variable

  15. U. S. Geological Survey begins seismic ground response experiments in Washington State

    USGS Publications Warehouse

    Tarr, A.C.; King, K.W.

    1987-01-01

    The men were Denver-based U.S Geological Survey (USGS) geophysicists working on the Urban Hazards Field Investigations project. On the previous day they had recorded two events on their seismographs-a distant nuclear explosion in Nevada and a blast at amine near Centralia, Washington. On another day, they used seismic refraction equipment to locate the de