Sample records for jurassic navajo sandstone

  1. A REVIEW OF THE VERTEBRATE FAUNA OF THE LOWER JURASSIC NAVAJO SANDSTONE IN ARIZONA

    Microsoft Academic Search

    RANDALL B. IRMIS

    2005-01-01

    The Lower Jurassic Navajo Sandstone of northern Arizona and southern Utah has yielded a diverse assemblage of late Early Jurassic terrestrial tetrapods from eolian and associated paleoenvironments. Although rare, vertebrate body fossils are represented by specimens of tritylodonts, crocodylomorphs, sauropodomorphs, and basal theropods (including Segisaurus halli). The vertebrate ichnofossil record is diverse and includes synapsids (Brasilichnium), crocodylomorphs (cf. Batrachopus), ornithischians

  2. Contrasting styles of large-scale displacement of unconsolidated sand: examples from the early Jurassic Navajo Sandstone on the Colorado Plateau, USA

    NASA Astrophysics Data System (ADS)

    Bryant, Gerald

    2015-04-01

    Large-scale soft-sediment deformation features in the Navajo Sandstone have been a topic of interest for nearly 40 years, ever since they were first explored as a criterion for discriminating between marine and continental processes in the depositional environment. For much of this time, evidence for large-scale sediment displacements was commonly attributed to processes of mass wasting. That is, gravity-driven movements of surficial sand. These slope failures were attributed to the inherent susceptibility of dune sand responding to environmental triggers such as earthquakes, floods, impacts, and the differential loading associated with dune topography. During the last decade, a new wave of research is focusing on the event significance of deformation features in more detail, revealing a broad diversity of large-scale deformation morphologies. This research has led to a better appreciation of subsurface dynamics in the early Jurassic deformation events recorded in the Navajo Sandstone, including the important role of intrastratal sediment flow. This report documents two illustrative examples of large-scale sediment displacements represented in extensive outcrops of the Navajo Sandstone along the Utah/Arizona border. Architectural relationships in these outcrops provide definitive constraints that enable the recognition of a large-scale sediment outflow, at one location, and an equally large-scale subsurface flow at the other. At both sites, evidence for associated processes of liquefaction appear at depths of at least 40 m below the original depositional surface, which is nearly an order of magnitude greater than has commonly been reported from modern settings. The surficial, mass flow feature displays attributes that are consistent with much smaller-scale sediment eruptions (sand volcanoes) that are often documented from modern earthquake zones, including the development of hydraulic pressure from localized, subsurface liquefaction and the subsequent escape of fluidized sand toward the unconfined conditions of the surface. The origin of the forces that produced the lateral, subsurface movement of a large body of sand at the other site is not readily apparent. The various constraints on modeling the generation of the lateral force required to produce the observed displacement are considered here, along with photodocumentation of key outcrop relationships.

  3. Sandstone Formation on the Navajo Loop Trail

    USGS Multimedia Gallery

    Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

  4. Naturally weathered feldspar surfaces in the Navajo Sandstone aquifer, Black Mesa, Arizona: Electron microscopic characterization

    Microsoft Academic Search

    Chen Zhu; David R. Veblen; Alex E. Blum; Stephen J. Chipera

    2006-01-01

    Naturally weathered feldspar surfaces in the Jurassic Navajo Sandstone at Black Mesa, Arizona, was characterized with high-resolution transmission and analytical electron microscope (HRTEM-AEM) and field emission gun scanning electron microscope (FEG-SEM). Here, we report the first HRTEM observation of a 10-nm thick amorphous layer on naturally weathered K-feldspar in currently slightly alkaline groundwater. The amorphous layer is probably deficient in

  5. Downslope coarsening in aeolian grainflows of the Navajo Sandstone

    NASA Astrophysics Data System (ADS)

    Loope, David B.; Elder, James F.; Sweeney, Mark R.

    2012-07-01

    Downslope coarsening in grainflows has been observed on present-day dunes and generated in labs, but few previous studies have examined vertical sorting in ancient aeolian grainflows. We studied the grainflow strata of the Jurassic Navajo Sandstone in the southern Utah portion of its outcrop belt from Zion National Park (west) to Coyote Buttes and The Dive (east). At each study site, thick sets of grainflow-dominated cross-strata that were deposited by large transverse dunes comprise the bulk of the Navajo Sandstone. We studied three stratigraphic columns, one per site, composed almost exclusively of aeolian cross-strata. For each column, samples were obtained from one grainflow stratum in each consecutive set of the column, for a total of 139 samples from thirty-two sets of cross-strata. To investigate grading perpendicular to bedding within individual grainflows, we collected fourteen samples from four superimposed grainflow strata at The Dive. Samples were analyzed with a Malvern Mastersizer 2000 laser diffraction particle analyser. The median grain size of grainflow samples ranges from fine sand (164 ?m) to coarse sand (617 ?m). Using Folk and Ward criteria, samples are well-sorted to moderately-well-sorted. All but one of the twenty-eight sets showed at least slight downslope coarsening, but in general, downslope coarsening was not as well-developed or as consistent as that reported in laboratory subaqueous grainflows. Because coarse sand should be quickly sequestered within preserved cross-strata when bedforms climb, grain-size studies may help to test hypotheses for the stacking of sets of cross-strata.

  6. CO2-Driven Convection Produced the Vertical Distribution of Sandstone Colors and Iron Concretions in Navajo Sandstone at Zion National Park, Utah (USA)

    NASA Astrophysics Data System (ADS)

    Kettler, R. M.; Loope, D. B.

    2011-12-01

    Along cliff faces exposed in Zion National Park (SW Utah), the porous and permeable Navajo Sandstone (Jurassic) is 700 m thick, and is capped by impermeable mudrocks and evaporites of the Carmel Formation. Previous workers have documented an areally extensive color pattern that is easily visible across much of southwestern and south-central Utah: the uppermost Navajo Sandstone is nearly white, the middle third of the formation is pink, and the lowermost fraction is reddish brown. To the northwest of the park, however, the formation is uniformly red (likely its primary color; G.B. Nielsen et al., 2009). Spheroidal concretions with dense, iron-oxide-cemented rinds and iron-poor cores are abundant in the pink and brown sandstones. Rhomb-shaped clots of iron oxide cement that are pseudomorphous after siderite are present in the cores of the largest concretions. The color variations are evidence that iron was transported from the upper portion of the Navajo SS to the lower portion. The pseudomorphs are evidence that the concretions are the oxidized remains of siderite-cemented precursors. The vertical iron transport and the precipitation of siderite require similar vertical transport of reducing, CO2-rich formation waters through the Navajo Sandstone. We argue that this circulation was driven in part by groundwater convection beneath a CO2 accumulation that was trapped below the Navajo-Carmel contact. This circulation caused aqueous iron and aqueous carbonate to be displaced downward and to accumulate (in the form of siderite) in the lower Navajo Sandstone. There are numerous CO2 reservoirs in the Colorado Plateau region; the gas was derived mainly from mantle sources. We hypothesize that, in the late Tertiary, the Carmel Formation capped a broad, structurally high accumulation of CO2 and CH4 in the Navajo Sandstone. The CH4 bleached the upper portion of the sandstone, releasing Fe2+ into the formation water. CO2 dissolved in the water, thereby increasing its density, and causing it to sink. The alkalinity of this down-welling water gradually increased as aqueous CO2 was either consumed via alteration of detrital feldspar grains or lost via degassing. Siderite then started to precipitate, and continued to precipitate as long as a source of iron was present in the down-welling water. Finally, the siderite was oxidized when uplift of the Colorado Plateau led to loss of the gas cap and ingress of oxidizing groundwater. Increased interest in the fate of CO2 injected into porous rocks has prompted detailed modeling of the convective overturn of the formation waters that underlie CO2 accumulations. The distribution and paragenesis of iron oxides in the Navajo Sandstone of southwestern Utah provide a well-exposed end product of this important geologic process.

  7. Aquifer tests of the Navajo sandstone near Caineville, Wayne County, Utah

    USGS Publications Warehouse

    Hood, J.W.; Danielson, T.W.

    1979-01-01

    Ground water in the Navajo Sandstone near Caineville, Wayne County, Utah, was studied during 1975-77 as part of an investigation of water in bedrock in the lower Dirty Devil River basin area. The purpose of the study near Caineville was to determine the water-bearing properties of the Navajo by utilizing data obtained mainly during test drilling and aquifer testing by the Intermountain Power Project.

  8. Navajo Sandstone–brine–CO 2 interaction: implications for geological carbon sequestration

    Microsoft Academic Search

    Peng LuQi; Qi Fu; William E. Seyfried; Anne Hereford; Chen Zhu

    2011-01-01

    The injection of CO2 into deep saline aquifers is being considered as an option for greenhouse gas mitigation. However, the response of an aquifer\\u000a to the injected CO2 is largely unknown. Experiments involving the reaction of Navajo Sandstone with acidic brine were conducted at 200°C and\\u000a 25 or 30 MPa to evaluate the extent of fluid–rock interactions. The first experiment examined

  9. Post-sedimentation transformations of Lower-Middle Jurassic sandstones of Great Caucases

    Microsoft Academic Search

    M. I. Tuchkova

    2003-01-01

    POST-SEDIMENTATION TRANSFORMATIONS OF LOWER-MIDDLE JURASSIC SANDSTONES OF GREAT CAUCASES M.I. Tuchkova Geological Institute Russian Academy of Sciences, Moscow, Russia tuchkova@geo.tv-sign.ru\\/ \\/Fax: (095) 2310443 Generalization of author's and literature data is based on the analysis of sandstones cement and structure, composition and politypism of clay minerals and index of mica crystallinity. Fore zones of sandstone transformations are distinguished for Lower-Middle Jurassic

  10. Depositional environment of jurassic smackover sandstones, Thomasville field, Rankin County, Mississippi 

    E-print Network

    Olsen, Rebecca Sarah Penfield

    1980-01-01

    DEPOSITIONAL ENVIRONMENT OF JURASSIC SMACKOVER SANDSTONES, THOMASVILLE FIELD, RANKIN COUNTY, MISSISSIPPI A Thesis by REBECCA SARAH PENFIELD OLSEN Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE May 1980 Major Subject: Geology DEPOSITIONAL ENVIRONMENT OF JURASSIC SMACKOVER SANDSTONES, THOYiASVILLE FIELD, RANKIN COUNTY, MISSISSIPPI A Thesis by REBECCA SARAH PENFIELD OLSEN Approved as to style...

  11. Properties of Cotton Valley sandstone reservoirs (Upper Jurassic), Terryville Field, Lincoln Parish, Louisiana 

    E-print Network

    McBride, Karen 'Cele

    1982-01-01

    PROPERTIES OF COTTON VALLEY SANDSTONE RESERVOIRS (UPPER JURASSIC), TERRYVILLE FIELD, LINCOLN PARISH, LOUISIANA A Thesis by KAREN 'CELE MCBRIDE Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement... for the degree of MASTER OF SCIENCE August 1982 Major Subject: Geology PROPERTIES OF COTTON VALLEY SANDSTONE RESERVOIRS (UPPER JURASSIC), TERRYVILLE FIELD, LINCOLN PARISH, LOUISIANA A Thesis by KAREN 'CELE MCBRIDE Approved as to style and content by...

  12. 3D visualization of liquefaction-induced dune collapse in the Navajo Sandstone, Utah, USA

    NASA Astrophysics Data System (ADS)

    Ford, Colby; Nick, Kevin; Bryant, Gerald

    2015-04-01

    The eolian Navajo Sandstone outcrop on the Canyon Overlook Trail in Zion National Park in Southern Utah is dissected by modern erosion in a way which reveals a great deal of the three-dimensional architecture of a major soft-sediment deformation event. The feature is bounded below by a well-developed interdune complex made up of two superimposed carbonate lenses, above by an irregular truncational surface, and incorporates 3 - 10 m of sandstone over an approximately 2 km area. The material above the deformed interval is undeformed cross-bedded sandstone, with crossbeds downlapping onto the surface of truncation. The stratigraphic confinement of deformation and the irregularity of the upper bounding surface suggests a deformation process which created topography, which was in turn covered by the next upwind dune before it could be eroded flat. The deformed material itself is laterally segmented by a stacked succession of shear surfaces, which all strike approximately perpendicular to the paleo-wind direction and dip at decreasing angles in the down paleo-wind direction. These factors point to the collapse of a major dune into the downwind interdune area, likely initiated by liquefaction in the interdune complex. The foundering of the dune's toe into the liquefied area created a powerful lateral stress field which did not extend significantly into the subsurface. The dune collapse process has been used in the past to describe other soft-sediment deformation features in the Navajo Sandstone, but this site provides a wealth of physical details which were not previously associated with dune collapse. Shear surfaces originate in the interdune deposit as slip between laminae, then the cohesive muds provided support as they were thrust upward to angles of up to 50 degrees. The margins of the site also contain important paleoenvironmental indicators. Dinosaur tracks are exposed both at the extreme upwind and downwind margins of the interdune deposit in and slightly above the deformed interval. In addition, a smaller liquefaction feature is visible in the deposit just below the interdune deposit, far enough away from the main feature to suggest that it is a separate event, not directly caused by the dune collapse. It may have been an earlier episode, or was initiated by the same trigger, but it illustrates the susceptibility of this particular interdune to liquefaction. Details such as the confinement of deformation between irregular bounding surfaces, development of major shear planes, and nearby indicators of liquefaction may be used as new and more robust criteria for the recognition of dune collapse features in other localities and deposits.

  13. Net-Infiltration Map of the Navajo Sandstone Outcrop Area in Western Washington County, Utah

    USGS Publications Warehouse

    Heilweil, Victor M.; McKinney, Tim S.

    2007-01-01

    As populations grow in the arid southwestern United States and desert bedrock aquifers are increasingly targeted for future development, understanding and quantifying the spatial variability of net infiltration and recharge becomes critically important for inventorying ground-water resources and mapping contamination vulnerability. A Geographic Information System (GIS)-based model utilizing readily available soils, topographic, precipitation, and outcrop data has been developed for predicting net infiltration to exposed and soil-covered areas of the Navajo Sandstone outcrop of southwestern Utah. The Navajo Sandstone is an important regional bedrock aquifer. The GIS model determines the net-infiltration percentage of precipitation by using an empirical equation. This relation is derived from least squares linear regression between three surficial parameters (soil coarseness, topographic slope, and downgradient distance from outcrop) and the percentage of estimated net infiltration based on environmental tracer data from excavations and boreholes at Sand Hollow Reservoir in the southeastern part of the study area. Processed GIS raster layers are applied as parameters in the empirical equation for determining net infiltration for soil-covered areas as a percentage of precipitation. This net-infiltration percentage is multiplied by average annual Parameter-elevation Regressions on Independent Slopes Model (PRISM) precipitation data to obtain an infiltration rate for each model cell. Additionally, net infiltration on exposed outcrop areas is set to 10 percent of precipitation on the basis of borehole net-infiltration estimates. Soils and outcrop net-infiltration rates are merged to form a final map. Areas of low, medium, and high potential for ground-water recharge have been identified, and estimates of net infiltration range from 0.1 to 66 millimeters per year (mm/yr). Estimated net-infiltration rates of less than 10 mm/yr are considered low, rates of 10 to 50 mm/yr are considered medium, and rates of more than 50 mm/yr are considered high. A comparison of estimated net-infiltration rates (determined from tritium data) to predicted rates (determined from GIS methods) at 12 sites in Sand Hollow and at Anderson Junction indicates an average difference of about 50 percent. Two of the predicted values were lower, five were higher, and five were within the estimated range. While such uncertainty is relatively small compared with the three order-of-magnitude range in predicted net-infiltration rates, the net-infiltration map is best suited for evaluating relative spatial distribution rather than for precise quantification of recharge to the Navajo aquifer at specific locations. An important potential use for this map is land-use zoning for protecting high net-infiltration parts of the aquifer from potential surface contamination.

  14. Acoustic Emission and Ultrasonic Characterization of Jurassic Navajo Formation Deformation During Axisymmetric Compression Testing

    NASA Astrophysics Data System (ADS)

    Rinehart, A. J.; Dewers, T. A.; Holcomb, D. J.; Broome, S. T.

    2011-12-01

    Linking continuum-scale and microscale brittle damage in rock remains a challenge impacting CO2 sequestration, secondary recovery, structural monitoring, and other geotechnical engineering applications. We examine if the mode of micromechanical failure scales directly up to continuum-scale damage-induced velocity anisotropy. Axisymmetric drained lab-dry compression experiments are performed on facies of moderately cemented finely laminated quartz arenite from the Jurassic Navajo Formation, a target reservoir rock for CO2 sequestration in Utah. The tests are 1 unconfined uniaxial compression test, 1 hydrostatic compression test, and 3 triaxial compression tests. Microscale damage is monitored using acoustic emissions (AE) and continuum scale damage is monitored with ultrasonic velocity scans. During the non-hydrostatic tests, three to five unload loops are performed pre-failure, with one unload loop performed post-failure. While stresses are increasing, AEs are monitored continuously using 1.6-mm diameter, 0.5-mm thick PZT-5A pins attached circumferentially around the cylindrical sample, and with 6-mm diameter, 2-mm thick PZT-5A discs at the ends of the sample. Before and after each unload loop, the test is paused and the AE transducers sequentially emit an ultrasonic pulse to measure wave speeds. The resulting elastic wave is detected by the other AE transducers. Post-test, the changing anisotropic velocity structure of the rock during compression and failure is compared to the locations, frequency, and relative moment tensors of the AEs measured between ultrasonic scans. Pre- and post-test visual and x-ray CT scan observations of the sample are compared to the acoustic metrics. These tiered observations of rock damage will further elucidate the scaling of microscale brittle failure to the continuum-scale This work was supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  15. NEW INFORMATION ON SEGISAURUS HALLI, A SMALL THEROPOD DINOSAUR FROM THE EARLY JURASSIC OF ARIZONA

    E-print Network

    Hutchinson, John

    NEW INFORMATION ON SEGISAURUS HALLI, A SMALL THEROPOD DINOSAUR FROM THE EARLY JURASSIC OF ARIZONA, a small Early Jurassic dinosaur and the only theropod known from the Navajo Sandstone. Our study unknown in dinosaurs), seemingly solid centra and limb bones (atypical for theropods), and accessory

  16. Reservoir petrology of analogous Middle Jurassic sandstones from Haltenbanken, Norway, and Jameson Land, east Greenland

    SciTech Connect

    Cheatwood, C.J.; Mansfield, C.F.

    1986-05-01

    Stratigraphically equivalent Middle Jurassic sandstones from wells in the Haltenbanken area, offshore Norway, and outcrops in Jameson Land, east Greenland, are petrographically similar. Both are subarkosic and display similar diagenetic features, notably well-developed secondary porosity. The well-exposed Jurassic strata of east Greenland provided effective depositional and stratigraphic models for the prolific oil fields of the North Sea and Norwegian shelf, because sediments were deposited in closely related tectono-stratigraphic settings. Conversely, the productive Middle Jurassic sandstones of the North Sea and Norwegian shelf suggest analogous reservoirs should occur on the east Greenland shelf. Potential reservoir sandstones of east Greenland are moderately to well sorted and fine to medium grained, with porosity ranging from 10 to 30%. Much of the porosity is secondary, created by the dissolution of framework grains and carbonate cements. The pores are commonly oversize, elongated, and bridged by clusters of sutured quartz grains. Pore throats are large, suggesting high reservoir permeability. Two types of nonreservoir sandstones are observed: (1) slightly finer grained versions of the reservoir sandstones that are tightly cemented by up to 40 vol. % carbonate cement and smaller amounts of authigenic kaolinite, and (2) fine-grained sandstones rich in micrite lithic fragments (rip-ups) and detrital micas. The variation of porosity with grain size implies influence by original porosity and permeability that is ultimately controlled by depositional environment.

  17. Lower Jurassic Navaho-Aztec-Equivalent Sandstones in southern Arizona and their paleogeographic significance

    SciTech Connect

    Bilodeau, W.L.; Keith, S.B.

    1986-06-01

    Thick sequences of Lower Jurassic rhyolitic and andesitic volcanic rocks in several mountain ranges of southern Arizona contain interbedded quartzarenites. Locally up to 250 m thick, these sandstone lenses, composed of well-sorted and well-rounded quartz grains, commonly contain large-scale cross-stratification and are considered to be eolian sand deposits. The eolian sands were blown up against the continental side of the Early Jurassic volcanic arc that trended northwest-southeast across the southwestern margin of the North American continent and/or plate at that time. Paleocurrent data suggest southerly eolian transport of the sands from the Colorado Plateau area. Correlation of these sandstones with the Lower Jurassic Navaho and Aztec Sandstones is indicated by the paleocurrent data as well as radiometric dating of the interbedded volcanics. Eolian sand transport southward across central Arizona in the Early Jurassic indicates that the Mogollon highlands either did not then exist, or were merely low, discontinuous inselbergs on a broad back-arc ramp, more appropriately called the Mogollon slope.

  18. Frisco City sandstone: Upper Jurassic play in southern Alabama

    SciTech Connect

    Montgomery, S.L. [Petroleum Consultant, Seattle, WA (United States); Baria, L.R. [Jura-Search, Inc., Jackson, MS (United States); Handford, C.R. [Bureau of Economic Geology, Austin, TX (United States)

    1997-10-01

    The Frisco City sandstone play in southern Alabama is an example of hydrocarbon entrapment on the flanks of basement erosional features, with principal reservoirs occurring in proximal alluvial-fan to marine shoreface facies. Productive fields are developed on four-way closures of complex geometry, with reservoir sandstones showing maximum thickness along the margins of basement highs that are roughly 1.3-5.18 km{sup 2} in size and have 136-151 m of relief. Detailed analysis of sandstone facies indicates a downdip progression from alluvial-fan through wadi, eolian, beach, tidal-flat, and shoreface deposits. A sequence stratigraphic model based on identification of backstepping strata representing successive transgressive events is useful in predicting maximum reservoir occurrence in the vicinity of inselbergs. Reservoir quality in productive sandstones is high, with porosities ranging from 13 to 27% and permeabilities of 50 md to 5 d. Hydrocarbon occurrence is related to the distribution of high-quality source rock in the Smackover Formation and to maturation history.

  19. Navajo Dome

    USGS Multimedia Gallery

    Navajo Dome, one of the more notable features within Capitol Reef National Park. Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the...

  20. Navajo Peak

    USGS Multimedia Gallery

    A view of Navajo Peak from Rainbow Point in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the s...

  1. Oxfordian-Kimmeridgian (Late Jurassic) reservoir sandstones in the Witch Ground Graben, U. K. North Sea

    SciTech Connect

    Harker, S.D. (Occidental Petroleum (Caledonia) Ltd., Aberdeen (United Kingdom)); Mantel, K.A. (Narwhal, London (United Kingdom)); Morton, D.J. (Deminex U.K. Oil and Gas Ltd., London (United Kingdom)); Riley, L.A. (Paleoservices, Watford (United Kingdom))

    1991-03-01

    Oil-bearing Late Jurassic Oxfordian-Kimmeridgian sandstones of the Sgiath and Piper formations are of major economic importance in the Witch Ground Graben. They form the reservoirs in Scott, which in 1993 will be the largest producing North Sea oil field to come on stream for more than a decade. Together with Scott, the Piper, Saltire, Tartan, Highlander, Petronella, Rob Roy, and Ivanhoe fields contained almost 2 Bbbl of recoverable reserves in these formations. The Sgiath and Piper represent two phases of Late Jurassic transgression and regression, initially represented by paralic deposited sand culminating in a wave-dominated delta sequence. The history of the Sgiath and Piper formations is reviewed and lithostratigraphic and biostratigraphic correlations presented to illustrate the distribution of the reservoir sandstones.

  2. Post-sedimentation transformations of Lower-Middle Jurassic sandstones of Great Caucases

    NASA Astrophysics Data System (ADS)

    Tuchkova, M. I.

    2003-04-01

    POST-SEDIMENTATION TRANSFORMATIONS OF LOWER-MIDDLE JURASSIC SANDSTONES OF GREAT CAUCASES M.I. Tuchkova Geological Institute Russian Academy of Sciences, Moscow, Russia tuchkova@geo.tv-sign.ru/ /Fax: (095) 2310443 Generalization of author’s and literature data is based on the analysis of sandstones cement and structure, composition and politypism of clay minerals and index of mica crystallinity. Fore zones of sandstone transformations are distinguished for Lower-Middle Jurassic sedimentary complexes of Great Caucases: 1) zone of neogenic chlorite and muscovite (index of crystallinity IC=1.0-2.0 mm) with wide development of epidote; solubility, blastic and spinulose structures, 2) zone of neogenic chlorite and sericite (IC=2.0-3.0 mm); solubility and spinulose structures, 3) zone of neogenic hydromica (IC=2.5-3.5 mm), kaolinite and/or montmorillonite minerals with microstylolite, conformal and conformal-regenerational contacts between grains, 4) zone of kaolinite and/or montmorillonite, mixed-layered and chlorite minerals with carbonate cement of pores filling, ferugination and conformal and microstylolite contacts between grains. Index of crystallinity of mica mineral IC=3.5-5.5 mm. In modern geological structure the region with most intensive transformations (zone 1) is traced in sandstones of here and there preserved Sinemurian-Lower Pliensbachian and Toarcian deposits in the belt of Jurassic deposits of the southern slope of Great Caucases. The extent of rock transformation increases northward and southward from the axial zone of Great Caucases. Represented zonality doesn’t depend on deposits thickness and doesn’t coincide with stratigraphycal borders. Post-sedimentation zonality of Jurassic deposits originated as a result of stress during the period of folding at the end of Middle and the beginning of Late Jurassic following the thrusting of northern flank of Great Caucases basin onto its axial part. The rocks of lowest part of Jurassic deposits of the southern slope, observed at the base of tectonically imbricated slices, were affected maximum transformations. They weren’t including in the subduction zone, but were only near this zone, so full sequence (up to metamorphism) of their transformations is not observed. The work was funded by RFBR, grant 02-05-64477.

  3. Strength and failure characteristics of Jurassic Red-Bed sandstone under cyclic wetting-drying conditions

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenhua; Jiang, Qinghui; Zhou, Chuangbing; Liu, Xinting

    2014-08-01

    Due to cyclic fluctuations of reservoir water levels, bank slopes in drawdown areas are subjected to wetting-drying cycles. In order to reasonably evaluate the stabilities of sandstone slopes in the drawdown area of the Three Gorges Reservoir, it is a primary premise to obtain the strength and failure characteristics of the sandstones undergoing wetting-drying cycles. In this paper, the conventional triaxial compression tests, ultrasonic velocity and porosity measurements and microstructural observations were conducted on Jurassic Red-Bed sandstone (JRS) specimens undergoing wetting-drying cycles. The results from the triaxial experiments indicate that the peak strengths of the JRS are dramatically reduced after the first wetting-drying cycle, and then remain approximately constant with increasing number of wetting-drying cycles. The failure modes of the JRS samples undergoing different wetting-drying cycles are all brittle failures under low confining pressures ( ? 15 MPa). The decrease in P-wave velocity and increase in porosity with increasing number of wetting-drying cycles reveals the raise of damage level of the sandstone specimens, which is the main reason for the decline of peak strength. Detailed microstructural analysis has shown obvious argillization phenomena after undergoing wetting-drying cycles, which weakens the cements between grains in the sandstone and increases the damage of the sandstone.

  4. Petrology and diagenesis of Upper Triassic and Lower Jurassic graben-fill sandstones of Jameson land basin, central east Greenland

    SciTech Connect

    Davee, K.W.; Mansfield, C.F.

    1986-05-01

    Sands of the Upper Triassic-Lower Jurassic Kap Stewart and Lower Jurassic Neill Klinter Formations were deposited during the early development of a major Jurassic rift basin. Depositional environments have been interpreted as alluvial fan, fluvial, and deltaic for the Kap Stewart, and as tidal estuary for the Neill Klinter. Most of these sandstones are fine to medium-grained quartz and subarkosic wackestones. Clay matrix is abundant and comprises mostly diagenetic kaolinite, illite, and complex clay mixtures derived from the breakdown of labile framework grains, especially plagioclase and biotite. Early emplacement of carbonate cement in some sandstones prevented development of diagenetic clay matrix. The carbonate cement is poikilotopic and constitutes up to 30% of some samples. The current high level of maturity indicated by the quartz-feldspar-lithic composition for these sandstones results from selective diagenetic decomposition of labile grains. The original, more feldspathic compositions reflect less maturity and an earlier stage of basin fill than the Middle Jurassic, high-porosity arenites, which also contain abundant quartz and up to 25% feldspar. Because of Upper Triassic and Lower Jurassic sands were deposited in continental and low-energy marine environments, they likely underwent greater in-situ alteration but less winnowing of labile grains than the overlying Middle Jurassic sands deposited in higher energy marine settings.

  5. New information on Segisaurus halli, a small theropod dinosaur from the Early Jurassic of Arizona

    Microsoft Academic Search

    Matthew T. Carrano; John R. Hutchinson; Scott D. Sampson

    2005-01-01

    Here we redescribe the holotype and only specimen of Segisaurus halli, a small Early Jurassic dinosaur and the only theropod known from the Navajo Sandstone. Our study highlights several important and newly recognized features that clarify the relationships of this taxon. Segisaurus is clearly a primitive theropod, although it does possess a tetanuran-like elongate scapular blade. Nonetheless, it appears to

  6. Sedimentology and sequence stratigraphy of paralic and shallow marine Upper Jurassic sandstones in the northern Danish Central Graben

    Microsoft Academic Search

    Peter N. Johannessen

    Paralic and shallow marine sandstones were deposited in the Danish Central Graben during Late Jurassic rifting when half-grabens were developed and the overall eustatic sea level rose. During the Kimmeridgian, an extensive plateau area consisting of the Heno Plateau and the Gertrud Plateau was situated between two highs, the Mandal High to the north, and the combined Inge and Mads

  7. U–Pb ages of detrital zircons from Permian and Jurassic eolian sandstones of the Colorado Plateau, USA: paleogeographic implications

    Microsoft Academic Search

    William R. Dickinson; George E. Gehrels

    2003-01-01

    Detrital zircon grains (n=468) from eolian sandstones of Permian and Jurassic sand seas on the Colorado Plateau of southwest Laurentia fall into six separable age populations defined by discrete peaks on age–probability plots. The eolian sands include significant contributions from all Precambrian age belts of the Laurentian craton and all key plutonic assemblages of the Appalachian orogen marking the Laurentia–Gondwana

  8. Environment of deposition and reservoir facies of the Taylor "B" Sandstone, Cotton Valley group (Upper Jurassic), Kildare Field, Cass County, Texas 

    E-print Network

    Black, Cynthia England

    1983-01-01

    plotted with gamma, SP and resistivity logs, and lithological column to show the vertical sequence of major sandstone facies in Hllliard Oakland 3 (HO3) . . 22 LISi OF FIGURES (continued) Figure Generalized composition and textural data plotted... in the Taylor "B" Sandstone, Kildare field. . 66 Summary ot log properties for Oakland Corp 3 and Rawles I, Kildare field, Cass County, Texas. . . 76 INTRODUCTION Sandstones of the Jurassic Cotton Valley Group produce gas and oil over a large area...

  9. Detrital Zircon Ages from Late Jurassic-Early Cretaceous Myrgovaam Basin Sandstones (Rauchua Trough), Western Chukotka, NE Russia

    NASA Astrophysics Data System (ADS)

    Miller, E. L.; Toro, J.; Gehrels, G.; Tuchkova, M.; Katkov, S.

    2004-12-01

    Late Jurassic to Early Cretaceous Myrgovaam Basin sediments (previously Rauchua Trough) are regionally significant because of the stratigraphic constraints they provide on the age and progression of deformation in the Chukotka fold belt, a possible along-strike continuation of the Alaskan Brooks Range fold-and-thrust belt. Existing descriptions of the structural and stratigraphic relations of Myrgovaam Basin sediments to underlying strata are contradictory. Some maps portray the basin fill as deposited unconformably over deformed Triassic and Jurassic strata of the Chukotka fold-belt. In other publications, the deposits are described as structurally detached and imbricated by N-verging thrust sheets (Baranov, 1996). Field studies reveal that underlying strata are tightly folded compared to overlying strata and that the contact is a structural discordance not an unconformity. More locally, we observed arkosic sandstones typical of the Myrgovaam Basin interbedded with underlying Late Jurassic strata or present as submarine channel deposits cut into older rocks, suggesting an original stratigraphic relationship. To reconcile these observations we suggest regional deformation post-dates deposition of Myrgovaam Basin deposits, and that the disharmony in deformational style between underlying thin-bedded Triassic sandstones and shales and (stratigraphically) overlying massive quartzites, is due to their different mechanical properties. Petrographic studies indicate that fine-grained Triassic-early Jurassic sandstones represent a distal recycled orogen source, while Myrgovaam Basin sandstones originated from a proximal orogenic source containing granitoid and crystalline basement rocks (microcline, biotite, muscovite and fragments of multiply deformed schist) and intermediate to felsic volcanic rocks. Laser Ablation ICPMS was used to date zircons (100 grains) from sandstones of the Myrgovaam Basin and compare them to those in Triassic sandstones (300 grains) and verify that Myrgovaam Basin deposits represent a major change in clastic source regions. Zircon populations from Triassic sandstones have age peaks in cumulative probability plots at 247, 298, 380, 453, 504 and 566 Ma (63 percent of zircon population). Only 12 percent of the grains are older than 1.8 Ga. In contrast, zircons from Rauchua Formation sandstones have age peaks at 180, 270, 322, 390-420 (43 percent of the grains). Over 40 percent of the zircons are 1.8-2.2 Ga. The immaturity of sandstones of the Myrgovaam Basin and their abundance of Precambrian zircons, suggest basement-involved faulting during deposition. Since Myrgovaam Basin deposits likely pre-date folding in the Chukotka fold-belt, faulting could be related to either the onset of rifting of the Arctic Alaska-Chukotka plate away from its parental continent or to the beginning of collision-related thrust faulting, but there are no known exposures of 1.8-2.2 Ga rocks in Chukotka. Jurassic zircons, representing a very small part of the population, suggest a proximal magmatic source and provide a maximum age for these strata.

  10. Regional diagenesis of sandstone in the Upper Jurassic Morrison Formation, San Juan Basin, New Mexico and Colorado

    SciTech Connect

    Hansley, P.L.

    1990-01-01

    The author reports that early authigenic mineral assemblages and vitroclastic textures are very well preserved in upper sandstones of the Upper Jurassic Morrison Formation. The distributions of the authigenic minerals were controlled, in part, by chemical gradients in a large saline, alkaline lake (Lake T'oo'dichi) that existed in late Morrison time. Sandstones on lake margins were cemented by smectite and silica, whereas sandstones nearer the lake center, in which waters were most saline and alkaline, were cemented by zeolites. Diagenetic alterations in sandstones were promoted by alkaline interstitial waters that emanated from adjacent fine-grained, tuffaceous lake beds. Metastable phases that precipitated first were replaced relatively quickly by more stable, ordered phases in the geochemically favorable environment of the closed basin setting. Elevation of temperatures above the geothermal gradient was proved by the influx of warm, deep-basin waters that locally modified early diagenetic assemblages during burial diagenesis. In organic- (and commonly also uranium ore-) bearing sandstones located primarily in the southern part of the basin, complex diagenetic assemblages resulted from water/rock reactions involving soluble organic complexes.

  11. Sedimentation of the Triassic–Jurassic Adigrat Sandstone Formation, Blue Nile (Abay) Basin, Ethiopia

    Microsoft Academic Search

    A. Wolela

    2008-01-01

    Exploration of oil and gas deposits in the Blue Nile Basin targeted the Adigrat Sandstone Formation as a reservoir objective. Conglomerates, gravely sandstones, coarse to medium-grained sandstones, very fine-grained cross-bedded sandstones, siltstones and mudstones of the Adigrat Sandstone Formation were deposited in semi-arid to arid climates. The North-western highlands are the main source for the sedimentation. The poorly-sorted, crudely-bedded conglomerates

  12. Investigation of exfoliation joints in Navajo sandstone at the Zion National Park and in granite at the Yosemite National Park by tectonofractographic techniques

    SciTech Connect

    Bahat, D.; Grossenbacher, K.; Karasaki, K.

    1995-04-01

    Tectonofractographic techniques have been applied to the study of joint exfoliation in the Navajo sandstone at Zion National Park and in the granite at Yosemite National Park. New types of fracture surface morphologies have been observed which enabled the discerning of incipient joints and consequent fracture growth in these rocks. Incipient jointing in the sandstone is mostly manifested by elliptical and circular fractures (meters to tens meters across) initiating from independent origins. They interfere with each other and grow to larger circular fractures producing exfoliation surfaces up to hundreds of meters across. Less frequently, series of large concentric undulations demonstrate the propagation of a large fracture front producing exfoliation from an individual origin. One such fracture front reveals refraction of undulations at a layer boundary. Certain en echelon fringes surround the joint mirror plane with well defined rims of en echelons and hackles which enable the determination of the tensile fracture stress, {sigma}f. Arches in Zion National Park are ubiquitous in shape and size, revealing stages in their evolution by a mechanical process, which was associated with exfoliation, but independent of local faulting. Exfoliation and arching mostly occurred on vertical surfaces of N-NNW and NE sets of prominent joints, but there are also deviations from this general trend. In Yosemite National Park large exfoliations (hundreds of meters in size) developed on the El Capitan cliff by the interaction and merging of many previous smaller incipient joints that vary in size from meters to tens of meter.

  13. Bryce Canyon's Navajo Loop Trail

    USGS Multimedia Gallery

    Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

  14. Sandstone Texture

    USGS Multimedia Gallery

    Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

  15. Field guide to sedimentary structures in the Navajo and Entrada sandstones in southern Utah and northern Arizona: Chapter in Field-trip guidebook, 100th annual meeting, The Geological Society of America, Phoenix, Arizona, October 26-29, 1987

    USGS Publications Warehouse

    Rubin, David M.; Hunter, Ralph E.

    1987-01-01

    This field-trip guide describes the common sedimentary structures that occur in eolian sands. The outcrops that are described occur in the Navajo and Entiaia Sandstones between the areas of Page, Arizona and St. George, Utah (figure I), but the sedimentary structures of these two sandstones are typical of most eolian deposits. The main part of the guide discusses the geologic setting and the origin of the various structures, and the road log discusses which structures are best displayed at selected outcrops.

  16. Paleomagnetic and rock magnetic evidence for a secondary yet early magnetization in large sandstone pipes and host Late Middle Jurassic (Callovian) Summerville Formation and Bluff Sandstone near Mesita, west central New Mexico

    Microsoft Academic Search

    John W. Geissman; Stephen S. Harlan

    2004-01-01

    Processes responsible for the acquisition of ancient yet secondary magnetizations are important facets of the geologic history of rocks and, when the age of such magnetizations can be estimated with confidence, provide useful information on the ancient geomagnetic field. In west central New Mexico near Mesita, on the Colorado Plateau, hematitic sandstone and siltstone beds of the Middle Jurassic (Callovian)

  17. Properties of Cotton Valley sandstone reservoirs (Upper Jurassic), Terryville Field, Lincoln Parish, Louisiana

    E-print Network

    McBride, Karen 'Cele

    1982-01-01

    from formation to group status (Swa1n, 1944), it was d1vided into the Bossier and Schule Formations (Figure Z). With increased well control, it was further divided into the Bossier Shale, Terryville Sandstone, Hico Shale, and Knowles Lime- stone..., Monroe Uplift, and the Sabine Uplift. TERRYVI LLE FIELD N RED SANDSTONE RED SHALE e $CHULER SANDSTONE FOR MAT I 0 N KNOWLES LS. ? ? -' ? ? 8 C ~O':'. r ' Hl CO Bo caw ' ', . $ HALE VAUGHN GREY SHALE W H I T E O U A R T 2 0 S E...

  18. LANDFORMS GENERATED BY WIND EROSION OF NAVAJO SANDSTONE OUTCROPS AT THE WAVE (COLORADO PLATEAU, UTAH / ARIZONA BORDER)

    E-print Network

    Nebraska-Lincoln, University of

    that are undercut by wind abrasion. In the photos above and to the left, note the microbially darkened rock surface accumulated, and the walls have been deeply undercut by strong, swirling winds. Sinuous scours abraded that formed two arches. Saltating sand has undercut microbial crusts developed on sandstone, forming a series

  19. U Pb ages of detrital zircons from Permian and Jurassic eolian sandstones of the Colorado Plateau, USA: paleogeographic implications

    NASA Astrophysics Data System (ADS)

    Dickinson, William R.; Gehrels, George E.

    2003-12-01

    Detrital zircon grains ( n=468) from eolian sandstones of Permian and Jurassic sand seas on the Colorado Plateau of southwest Laurentia fall into six separable age populations defined by discrete peaks on age-probability plots. The eolian sands include significant contributions from all Precambrian age belts of the Laurentian craton and all key plutonic assemblages of the Appalachian orogen marking the Laurentia-Gondwana suture within Pangaea. Nearly half the detrital zircon grains were derived ultimately from Grenvillian (1315-1000 Ma), Pan-African (750-500 Ma), and Paleozoic (500-310 Ma) bedrock sources lying within or along the flank of the Appalachian orogen. Recycled origins for Appalachian-derived grains, except for temporary residence of synorogenic detritus in the Appalachian foreland basin or in deformed Ouachita flysch and molasses along tectonic strike, are precluded by regional geology and known geochronology from other Laurentian sedimentary assemblages. We infer that transcontinental Permian and Jurassic river systems transported detritus of Appalachian provenance westward across the subdued surface of the Laurentian craton, for deposition as proximate sources for eolian systems feeding the ergs, on unconsolidated fluvial plains, deltas, and strandlines that lay up-paleowind along or near the Cordilleran paleoshoreline north and northeast of the Colorado Plateau. The postulated river systems headed in the remnant Appalachian orogen (Permian) or the incipient Atlantic rift belt (Jurassic), and additional transport of the Appalachian-derived detritus toward the Colorado Plateau was achieved by longshore drift of sediment southward along the Cordilleran paleoshoreline under the influence of prevailing trade winds in the Permian-Jurassic tropics. Only a quarter of the eolianite detrital zircons were derived or recycled from Mesoproterozoic (1470-1335 Ma) and younger Paleoproterozoic (1800-1615 Ma) basement of the Ancestral Rocky Mountains province adjacent to the Colorado Plateau. The final quarter of eolianite detrital zircons were derived from older Paleoproterozoic (2200-1800 Ma) and Archaean (3015-2580 Ma) basement of the Laurentian shield, or recycled from its sedimentary cover. Both Laurentian shield and Ancestral Rockies detritus may have entered the same transcontinental river systems (through tributary streams), or the same Cordilleran strandline system (by longshore drift), responsible for the delivery of Appalachian-derived sediment to positions near the Colorado Plateau ergs. As Colorado Plateau ergs received contributions from all the potential bedrock sources contiguous with Permian-Jurassic Laurentia and its orogenic-taphrogenic margins, detrital zircon studies of analogous ancient erg deposits elsewhere may help test reconstructions of Rodinia and other ancient paleocontinents by providing proxy records of the full age ranges of bedrock sources distributed across the surfaces of entire landmasses.

  20. ORIGINAL ARTICLE Navajo SandstonebrineCO2 interaction: implications

    E-print Network

    Zhu, Chen

    , Zn, and Ba, were mobilized. Keywords Navajo Sandstone Á Geological carbon sequestration Á Fluid as the target for one of the large-volume injection tests by the Big Sky Carbon Sequestration PartnershipORIGINAL ARTICLE Navajo Sandstone­brine­CO2 interaction: implications for geological carbon

  1. Stratigraphic analysis of eolian interactions with marine and fluvial deposits, Middle Jurassic Page Sandstone and Carmel Formation, Colorado Plateau, U.S.A.

    SciTech Connect

    Blakey, R.C.; Jones, L.S. [Northern Arizona Univ., Flagstaff, AZ (United States). Dept. of Geology; Havholm, K.G. [Univ. of Wisconsin, EauClaire, WI (United States). Dept. of Geology

    1996-03-01

    The eolian Page Sandstone (Middle Jurassic) in south-central Utah and adjacent Arizona consists of multiple mostly eolian sequences and sequence-bounding unconformities (super surfaces). The super surfaces are a powerful correlation tool that provide the basis for a detailed regional stratigraphic analysis of the Page Sandstone and coeval parts of the marine and coastal-plain Carmel Formation. Some Page Sandstone upper surfaces correlate with sharp lithologic breaks in the Carmel Formation that are interpreted as marine flooding surfaces. Others correlate with fluvial surfaces in the Carmel Formation. This study demonstrates that a sequence stratigraphic framework can be applied to sparsely fossiliferous eolian, sabkha, and restricted marine deposits in a marine-coastal setting. Using detailed sedimentologic and stratigraphic studies, tectonic, eustatic, and possibly climatic signals can be differentiated within the complex, cyclic facies patterns displayed in the Page Sandstone and Carmel Formation.

  2. Navajo (Dine)

    NSDL National Science Digital Library

    Grahame John

    This website consists of a fact sheet that provides a brief account of the ancient and modern history the Navajo peoples. The text discusses the Navajo transition from nomadic hunting and gathering people in the early Spanish period to the sheep herding, blanket-weaving peoples of the nineteenth century. Links within the text lead to a glossary of terms and additional information about the history and cultural heritage of the Navajo peoples.

  3. THE NAVAJOS.

    ERIC Educational Resources Information Center

    Navajo Tribe Public Relations and Information Dept., Window Rock, AZ.

    A STUDY OF NAVAJO AMERICAN INDIANS IS PRESENTED. INCLUDED ARE THE TRIBE'S HISTORY, RESOURCES, ECONOMIC SITUATION, AND WAYS TO IMPROVE IT. THE NAVAJOS ARE DIFFERENT FROM OTHER AMERICAN INDIAN TRIBES IN THAT THEY ARE RAPIDLY INCREASING, THEY HAVE INCREASED THE SIZE OF THEIR RESERVATION, THEY STILL LIVE IN ISOLATION AND IN A PRIMITIVE FASHION, AND…

  4. Navajo-English Dictionary.

    ERIC Educational Resources Information Center

    Wall, Leon; Morgan, William

    A brief summary of the sound system of the Navajo language introduces this Navajo-English dictionary. Diacritical markings and an English definition are given for each Navajo word. Words are listed alphabetically by Navajo sound. (VM)

  5. Hoodoo on the Navajo Loop Trail

    USGS Multimedia Gallery

    Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

  6. Snow on the Navajo Loop Trail

    USGS Multimedia Gallery

    Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

  7. Degradation processes and consolidation of Late Jurassic sandstone dinosaur tracks in museum environment (Museum of Lourinhã, Portugal)

    NASA Astrophysics Data System (ADS)

    Leal, Sofia; mateus, Octavio; Tomas, Carla; Dionisio, Amelia

    2014-05-01

    The current study aims to conciliate conservation and restoration museology diagnosis with paleontological and geological curational needs and has, as subject of study, dinosaur footprints (vertebrates fossils). The footprints have been being exposed since 2004 in the paleontology hall of the Museum of Lourinhã, Portugal, and are part of a important paleontological collection of Late Jurassic vertebrate fossils from Lourinhã Formation. Presently, it is considered a unique heritage in danger of disappearing due to high decay level of disaggregation of its geological structure. The dinosaur footprints, (ML557) found, more precisely, on a coastline cliff in Lourinhã, Porto das Barcas, Lagido do Forno (coordinate 39° 14. 178'N, 9° 20. 397'W), Jurassic period, on the 5th of June 2001, by Jesper Milàn. This cliff of high slope presents sedimentary stratigraphic characteristics of a sandstone/siltstone of gray and red colors, by the '' Munsell scale and Color Chart''. Geological the tracks are Late Jurassic in age, and colected in the Lourinhã Formation, Praia Azul Member, of the Lusitanian Basin. There are three natural infills tridactyl tracks, possibly ascribed to ornithopod, a bipedal herbivore, resultant of a left foot movement, right and left. Footprints have 300-400mm of wide and 330-360mm of height with round fingers, which are elongated due to some degradation/erosion. In 2001, the footprints were collected from the field, cleaned, consolidated and glued in the laboratory of the Museum of Lourinhã before being exhibited in a museum display. Stone matrix was removed and a consolidation product applied, probably a polyvinyl acetate, of the brand Plexigum. The footprint with broken central digit was glued with an epoxy resin, Araldite. Both applied products were confirmed by analysis of µ-FTIR (Fourier Transform Infrared Spectroscopy) and both presented colour change and detachment surface problems. After collecting and storing, in 2004, footprints were transferred to the current public paleontology hall, ground floor, placed on the floor without any protection framework or environmental control (temperature and relative humidity). Presently, footprints show major geological structure disintegration/deterioration problems and were diagnosed several pathologies :"Blistering", "Powdering", "Exfoliation"' as well as "Dirt", "Fracture"', "Inscriptions", "Consolidates" and "Adhesives". Several laboratorial analysed were conducted to evaluate the presence of salts. Moreover a microclimatic study was conducted inside the museum to evaluate the influence of thermohygrometric parameters on the decay processes observed. As future procedures, all tracks will suffer a superficial cleaning (dust removal) with brush without any solvent and also the application of a consolidant aiming to restore some coehesion of these footprints. Since stone consolidation is a very risky intervention, several laboratory tests are being conducted with stone samples taken from the same layer and location from Porto das Barcas and using different commercial consolidation products.

  8. Navajo Studies at Navajo Community College.

    ERIC Educational Resources Information Center

    Hatathli, Ned

    The document covers the Navajo Studies Program (NSP) at Navajo Community College (NCC). The Navajo Studies Program differs from other Indian Studies Programs in 7 ways, e.g.: (1) it is located on the Navajo Reservation and controlled by the tribe; (2) NCC incorporates Indian studies into every individual program and area of concentration--English…

  9. Reservoir characterization of tight gas sand: Taylor sandstone (upper Cotton Valley group, upper Jurassic), Rusk County, Texas

    Microsoft Academic Search

    C. L. Vavra; M. H. Scheihing; J. D. Klein

    1989-01-01

    An integrated petrographic, sedimentologic, and log analysis study of the Taylor sandstone in Rusk County, Texas, was conducted to understand the geologic controls on reservoir performance and to identify pay zones for reserves calculations. The Taylor sandstone interval consists of tightly cemented, fine-grained quartzose sandstones interbedded with mudstones, siltstones, and carbonates that occur in upward-coarsening sequences. Helium permeability rarely exceeds

  10. Paleomagnetic and rock magnetic evidence for a secondary yet early magnetization in large sandstone pipes and host Late Middle Jurassic (Callovian) Summerville Formation and Bluff Sandstone near Mesita, west central New Mexico

    NASA Astrophysics Data System (ADS)

    Geissman, John W.; Harlan, Stephen S.

    2004-07-01

    Processes responsible for the acquisition of ancient yet secondary magnetizations are important facets of the geologic history of rocks and, when the age of such magnetizations can be estimated with confidence, provide useful information on the ancient geomagnetic field. In west central New Mexico near Mesita, on the Colorado Plateau, hematitic sandstone and siltstone beds of the Middle Jurassic (Callovian) Summerville Formation and overlying Bluff Sandstone are host to numerous large (up to 100 m2 in map area) pipe-like sandstone bodies. The pipes are as strongly cemented by hematite (colors range from 10R 6/6 to 10R 3/4) as the host strata; paleomagnetic data from them and their host strata are interpreted to indicate that these rocks have been remagnetized, probably in association with sandstone pipe formation. Reverse polarity magnetizations isolated in both alternating field and thermal demagnetization from pipes are well grouped and are similar to, and not statistically distinct from, those in adjacent host strata. The grand-mean direction for 16 sites (7 sites in sandstone pipes and 9 in host strata), corrected for slight (5°) west-northwest tilt of the strata, is D = 163.0°, I = -44.3° (?95 = 2.7°, k = 169). This direction yields a pole position of 72.8°N, 135.7°E (dp = 2.1°, dm = 3.4°). Assuming a modest (i.e., ˜5°) clockwise rotation of the Colorado Plateau, the pole lies at 68.7°N, 143.8°E. Median destructive fields for the remanence in pipes and host strata are typically 40-50 mT; over 90% of the remanence is "unblocked" or removed during changes in the magnetic mineralogy by temperatures of ˜400-450°C. Isothermal remanent magnetization (IRM) acquisition data, and thermal demagnetization of "saturation" IRM, however, demonstrate that the dominant magnetic phase is of high coercivity and relatively high (above 600°C) laboratory unblocking temperatures in both sandstone pipes and host strata, yet it does not appear to contribute significantly to the characteristic remanent magnetization. The similarity in demagnetization properties between pipes and adjacent host strata, the absence of a well-defined high unblocking temperature remanence that is more typical of hematite-cemented detrital strata, and the essentially uniform reverse polarity of the remanence are all interpreted to indicate that pipes and host strata contain secondary, yet early acquired magnetizations and that magnetization acquisition continued after pipe injection. We propose that acquisition of the secondary magnetization took place in the presence of alkaline, high pH brines formed by the dissolution of the underlying gypsum-dominated Lower Jurassic Todilto Formation strata and therefore the remanence is early in age. On the basis of a comparison with Summerville and Morrison (Middle and Late Jurassic) paleomagnetic poles from rocks on the Colorado Plateau, we interpret the secondary remanence in Summerville strata and sandstone pipes near Laguna to be latest Middle to Late Jurassic in age. If realistic, this interpretation further emphasizes the importance of fluid-rock interaction in the acquisition of secondary magnetizations.

  11. Navajo Games.

    ERIC Educational Resources Information Center

    Cliff, Janet M.

    1990-01-01

    Reviews 163 sources on Navajo games, play, and toys. Includes an annotated bibliography of those materials. Examines relationships between games and religion, origin myths, and ceremonies. Discusses attitudes toward games, gambling, and cheating; and the dichotomy between children's and adults' games. Describes specific toys, games, and play…

  12. Geology Fieldnotes: Navajo National Monument, Arizona

    NSDL National Science Digital Library

    Navajo National Monument is located on the Colorado Plateau in Arizona. Information on this site focuses on the Native American history of the area, including details about Keet Seel, an Anasazi village built in a sandstone cliff alcove. Other resources include visitor information, maps, and links to additional facts.

  13. Erosional remnants and adjacent unconformities along an eolian-marine boundary of the Page Sandstone and Carmel Formation, Middle Jurassic, south-central Utah

    SciTech Connect

    Jones, L.S.; Blakey, R.C. (Univ. of Northern Arizona, Flagstaff, AZ (United States). Dept. of Geology)

    1993-09-01

    Sandstone ridges along the marine-eolian boundary of the Middle Jurassic Page Sandstone (eolian) with the lower Carmel Formation (restricted marine) in south-central Utah have been identified as erosional remnants consisting of strata of siliciclastic sabkha and eolian origin. The ridges lie within two distinct units of the Thousand Pockets Tongue of the Page. Two equally plausible models explain the genesis of these ridges. One model involves (1) early cementation of eolian and sabkha strata, (2) wind erosion leading to development of yardangs and unconformities, (3) yardang tilting due to evaporite dissolution, and (4) renewed deposition and burial. The alternative model explains ridge development through (1) subsidence, with tilting, of eolian and sabkha strata into evaporites due to loading from linear dunes, (2) evaporite dissolution and unconformity development, and (3) renewed deposition and burial. These models provide important clues about the nature of a missing part of the rock record. Reconstruction of units that were deposited but later eroded improves paleogeographic interpretation and here indicates that the Carmel paleo-shoreline was considerably farther to the northwest than previously believed.

  14. Two Bridges Formation on the Navajo Loop Trail

    USGS Multimedia Gallery

    Views along the Navajo Loop Trail in Bryce Canyon National Park. Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandston...

  15. Detrital Zircon Ages from Late Jurassic-Early Cretaceous Myrgovaam Basin Sandstones (Rauchua Trough), Western Chukotka, NE Russia

    Microsoft Academic Search

    E. L. Miller; J. Toro; G. Gehrels; M. Tuchkova; S. Katkov

    2004-01-01

    Late Jurassic to Early Cretaceous Myrgovaam Basin sediments (previously Rauchua Trough) are regionally significant because of the stratigraphic constraints they provide on the age and progression of deformation in the Chukotka fold belt, a possible along-strike continuation of the Alaskan Brooks Range fold-and-thrust belt. Existing descriptions of the structural and stratigraphic relations of Myrgovaam Basin sediments to underlying strata are

  16. Reservoir characterization of tight gas sand: Taylor sandstone (upper Cotton Valley group, upper Jurassic), Rusk County, Texas

    SciTech Connect

    Vavra, C.L.; Scheihing, M.H.; Klein, J.D.

    1989-03-01

    An integrated petrographic, sedimentologic, and log analysis study of the Taylor sandstone in Rusk County, Texas, was conducted to understand the geologic controls on reservoir performance and to identify pay zones for reserves calculations. The Taylor sandstone interval consists of tightly cemented, fine-grained quartzose sandstones interbedded with mudstones, siltstones, and carbonates that occur in upward-coarsening sequences. Helium permeability rarely exceeds 0.1 md, and porosity is rarely greater than 10%. Relationships between porosity and permeability are diffuse because of a string diagenetic overprint. Six major rock types or petrofacies are distinguished on the basis of pore type and dominant cement mineralogy. Three sandstone petrofacies - primary macroporous quartz cemented, moldic macroporous quartz cemented, and microporous clay cemented - have reservoir potential. Although these petrofacies have similar porosities and permeabilities, fluid saturations differ considerably due to differences in pore geometry as indicated by petrographic and capillary pressure analyses. These three reservoir-quality petrofacies can each be identified directly on wireline logs by applying cutoffs to the porosity and normalized gamma-ray logs.

  17. Navajo Adult Basic Education.

    ERIC Educational Resources Information Center

    Navajo Community Coll., Tsaile, AZ.

    The objectives of this Special Experimental Demonstration Project in Adult Basic Education for the Navajo were: (1) to raise the educational and social level of Navajo adult students who are unable to read, write, and speak English; (2) to assist the Navajo adult students to take advantage of occupational and vocational training programs; (3) to…

  18. Navajo History. Volume 1.

    ERIC Educational Resources Information Center

    Yazzie, Ethelou, Ed.

    This volume, an account of the prerecorded history of the Navajos, is the first of a series of two volumes. (Volume 2 will take up recorded history.) From the knowledge of verbal literature supplied by Navajos themselves, this composite was completed to help alleviate the lack of materials on Navajo culture. Consensus, the authors point out, was…

  19. Navajo Wisdom and Traditions.

    ERIC Educational Resources Information Center

    Yazzie, Ethelou

    The oral literature of the Navajo people generally falls into two categories: the sacred stories and the folk tales, which often, but not always, point a moral. Sacred stories relate the Navajo's emergence history. These stories tell how the universe holds two kinds of people: the "Earth Surface People" (both living and dead) and the "Holy People"…

  20. Annual monsoon rains recorded by Jurassic dunes.

    PubMed

    Loope, D B; Rowe, C M; Joeckel, R M

    2001-07-01

    Pangaea, the largest landmass in the Earth's history, was nearly bisected by the Equator during the late Palaeozoic and early Mesozoic eras. Modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality, but direct evidence for annual rainfall periodicity has been lacking. In the Mesozoic era, about 190 million years ago, thick deposits of wind-blown sand accumulated in dunes of a vast, low-latitude desert at Pangaea's western margin. These deposits are now situated in the southwestern USA. Here we analyse slump masses in the annual depositional cycles within these deposits, which have been described for some outcrops of the Navajo Sandstone. Twenty-four slumps, which were generated by heavy rainfall, appear within one interval representing 36 years of dune migration. We interpret the positions of 20 of these masses to indicate slumping during summer monsoon rains, with the other four having been the result of winter storms. The slumped lee faces of these Jurassic dunes therefore represent a prehistoric record of yearly rain events. PMID:11452305

  1. NAVAJO ELECTRIFICATION DEMONSTRATION PROJECT

    SciTech Connect

    Terry W. Battiest

    2008-06-11

    The Navajo Electrification Demonstration Project (NEDP) is a multi-year project which addresses the electricity needs of the unserved and underserved Navajo Nation, the largest American Indian tribe in the United States. The program serves to cumulatively provide off-grid electricty for families living away from the electricty infrastructure, line extensions for unserved families living nearby (less than 1/2 mile away from) the electricity, and, under the current project called NEDP-4, the construction of a substation to increase the capacity and improve the quality of service into the central core region of the Navajo Nation.

  2. Contemporary Navajo Affairs: Navajo History Volume III, Part B.

    ERIC Educational Resources Information Center

    Eck, Norman K.

    Written specifically for Navajo junior high through college students, but also serving those interested in modern reservation developments and processs, the third volume of a curricular series on Navajo history provides a synthesis of data and pictorial records on current events in the areas of Navajo government, economic development, and health.…

  3. Navajo Reflections on Climate Change

    NSDL National Science Digital Library

    WGBH Educational Foundation

    2012-03-23

    In this video segment adapted from Navajo Technical College, meet two members of the Navajo Nation, one Elder and one scientist, as they share their observations about how precipitation has changed since they were children.

  4. Architectural studies of Jurassic-Cretaceous fluvial units, Colorado Plateau

    SciTech Connect

    Miall, A.D.; Bromley, M.H.; Cowan, E.J.; Turner-Peterson, C.E.

    1989-03-01

    A sixfold hierarchy of architectural elements and bounding surfaces evolved from outcrop studies of three fluvial units: Westwater Canyon member (WCM), Morrison Formation, Upper Jurassic; Torrivio sandstone member (TSM), Gallup Sandstone, Upper Cretaceous, northwestern New Mexico; and Kayenta Formation (KF), Lower Jurassic, southwestern Colorado. This hierarchy is discussed.

  5. A Navajo Paradigm for Long Life Happiness--and for Reversing Navajo Language Shift.

    ERIC Educational Resources Information Center

    House, Deborah

    1997-01-01

    Describes a Navajo model by which individuals may assume responsibility for reversing Navajo language shift. Argues that reversing Navajo language shift requires that Navajos acknowledge the problem, that Navajo principles of balance and the natural order be applied to the problem, and that Navajo individuals and families make a commitment to…

  6. From Back-arc Drifting to Arc Accretion: the Late Jurassic-Early Cretaceous Evolution of the Guerrero Terrane Recorded by a Major Provenance Change in Sandstones from the Sierra de los Cuarzos, Central Mexico

    NASA Astrophysics Data System (ADS)

    Palacios Garcia, N. B.; Martini, M.

    2014-12-01

    The Guerrero terrane composed of Middle Jurassic-Early Cretaceous arc assemblages, were drifted from the North American continental mainland during lower Early Cretaceous spreading in the Arperos back arc basin, and subsequently accreted back to the continental margin in the late Aptian. Although the accretion of the Guerrero terrane represents one of the major tectonic processes that shaped the southern North American Pacific margin, the stratigraphic record related to such a regional event was not yet recognized in central Mexico. Due to the Sierra de los Cuarzos is located just 50 km east of the Guerrero terrane suture belt, its stratigraphic record should be highly sensitive to first order tectonic changes and would record a syn-tectonic deposits related to this major event. In that study area, were identified two main Upper Jurassic-Lower Cretaceous clastic units. The Sierra de los Cuarzos formation represents the lowermost exposed stratigraphic record. Sedimentary structures, sandstones composition, and U-Pb detrital zircon ages document that the Sierra de los Cuarzos formation reflects a vigorous mass wasting along the margin of the North American continental mainland, representing the eastern side of the Arperos back arc basin. Sandstones of the Sierra de los Cuarzos formation are free from detrital contributions related to the Guerrero terrane juvenile sources, indicating that the Arperos Basin acted like an efficient sedimentological barrier that inhibited the influence of the arc massifs on the continental mainland deposits. The Sierra de los Cuarzos formation is overlain by submarine slope deposits of the Pelones formation, which mark a sudden change in the depositional conditions. Provenance analysis documents that sandstones from the Pelones formation were fed by the mafic to intermediate arc assemblages of the Guerrero terrane, as well as by quartz-rich sources of the continental mainland, suggesting that, by the time of deposition of the Pelones formation, the Arperos Basin was closed and the Guerrero terrane was juxtaposed to the continental domain. Based on these data, we interpret the Pelones formation as the record of the major crustal reorganization in central Mexico related to the inversion of the Arperos back arc basin and accretion of the Guerrero terrane to the continental mainland.

  7. A History of Navajo Clans. First Edition.

    ERIC Educational Resources Information Center

    Lynch, Regina H.; And Others

    Pen and ink drawings illustrate characterizations of 29 Navajo clans in this book, which is intended to acquaint young Navajo people and others with Navajo history and culture. The introduction discusses the significance of the Navajo clan system and the relationship among family bonds, self-esteem, and cultural values. The illustrated text tells…

  8. Navajo Coal: Demands, Attitudes, and Environment.

    ERIC Educational Resources Information Center

    Goodman, James M.

    The operation of several coal mines with vast proven reserves on the Navajo reservation is a manifestation of conflict between: a power hungry external world; the preservationist attitudes of traditional Navajo culture; the disadvantaged socio-economic status of the average Navajo wage earner; and the Navajo Nation's long term needs for internal…

  9. Depressive illness and Navajo healing.

    PubMed

    Storck, M; Csordas, T J; Strauss, M

    2000-12-01

    What is the experience of Navajo patients in Navajo religious healing who, by the criteria and in the vernacular of contemporary psychiatry, would be diagnosed with the disorder called depression? We ask this question in the context of a double dialogue between psychiatry and anthropology and between these disciplines' academic constructs of illness and those of contemporary Navajos. The dialogue is conducted in the arena of patient narratives, providing a means for observing and explicating processes of therapeutic change in individuals, for illustrating variations in forms of Navajo religious healing sought out by patients demonstrating similar symptoms of distress, and for considering the heuristic utility of psychiatric diagnoses and nomenclature in the conceptualization of illness, recovery, and religious healing. From among the 37 percent of patients participating in the Navajo Healing Project who had a lifetime history of a major depressive illness, three are discussed herein, their selection based on two criteria: (1) all met formal psychiatric diagnostic criteria for a major depressive episode at the time of their healing ceremonies, and (2) together, their experiences illustrate the range of contemporary Navajo religious healing, including Traditional, Native American Church (NAC), and Christian forms. We suggest that, despite the explicit role of the sacred in religious healing interventions available to Navajo patients, differences between biomedical and religious healing systems may be of less significance than their shared existential engagement of problems such as those glossed as depression. PMID:11224981

  10. Navajo Rug with English Voice

    NSDL National Science Digital Library

    Jeneen Edgmon

    2011-01-01

    This interactive Flash lesson helps students to distinguish squares and triangles and be creative in the context of Navajo rug design. The animated pages give printed and voiced instructions in English. A teacher guide (pdf) is available - see #30 at MathActive Lessons for Grades K-2, cataloged separately. Navajo, Spanish, and non-spoken versions of the lesson are available also at the Lessons page.

  11. Ornithopod dinosaur tracks from the Lower Jurassic of Queensland

    Microsoft Academic Search

    Richard A. Thulborn

    1994-01-01

    Natural casts of seven small footprints have been identified on a single weathered block derived from the Precipice Sandstone (Lower Jurassic) of the Carnarvon Gorge, southeastern Queensland. The footprints are attributed to ornithopod dinosaurs and are referred to the ichnogenus Anomoepus. They appear to be most similar to the ichnospecies Anomoepus gracillimus, originally defined on footprints from the Lower Jurassic

  12. Reevaluation of upper Jurassic Morrison Formation, Western Interior

    Microsoft Academic Search

    Mantzios

    1989-01-01

    Comparison of the Brushy Basin member of the Upper Jurassic Morrison Formation in the Colorado Plateau with the Upper Jurassic-Lower Cretaceous Morrison-Cloverly sequence in the Bighorn basin, Wyoming, shows great similarities in their depositional environments and stratigraphy. The lower Brushy Basin member is a fluvial deposit composed of channel sandstones and overbank mudstones which display a great number of pedogenic

  13. Characterization of Roabiba Sandstones Reservoir in Bintuni Field, Papua, Indonesia 

    E-print Network

    Vera, Riene

    2011-02-22

    Bintuni Field has two Middle Jurassic gas reservoirs, Upper and Lower Roabiba Sandstone reservoirs, with the estimated reserve from eight appraisal drilled wells of 6.08 tcf. The field has not been producing commercially. ...

  14. Fault evolution in volcanic tuffs and quartz-rich eolian sandstone as mechanical analogs for faulting in Martian pyroclastic deposits

    NASA Astrophysics Data System (ADS)

    Okubo, C. H.

    2014-12-01

    In order to establish a foundation for studies of faulting in Martian rocks and soils in volcanic terrain, the distribution of brittle strain around faults within the North Menan Butte Tuff in the eastern Snake River Plain, Idaho and the Joe Lott Tuff Member of the Mount Belknap Volcanics, Utah, has been recently described. These studies employed a combination of macroscopic and microscopic observations, including measurements of in situ permeability as a proxy for non-localized brittle deformation of the host rock. In areas where the tuff retained its primary granular nature at the time of deformation, initial plastic yielding in both tuffs occurred along deformation bands. Both compactional and dilational types of deformation bands were observed, and faulting occurred along clusters of deformation bands. Where secondary alteration processes imparted a massive texture to the tuff, brittle deformation was accommodated along fractures. Host-rock permeability exhibits little variation from non-deformed values in the North Menan Butte Tuff, whereas host rock permeability is reduced by roughly an order of magnitude through compaction alone (no alteration) in the Joe Lott Tuff. To create a bridge between these observations in tuff and the more substantial body of work centered on deformation band formation and faulting in quartz-rich sandstones, the same techniques employed in the North Menan Butte Tuff and the Joe Lott Tuff have also been applied to a kilometer-scale fault in the Jurassic Navajo Sandstone in the Waterpocket Fold, Utah. These observations demonstrate that the manifestation of strain and evolution of faulting in the Mars-analog tuffs are comparable to that in quartz-rich sandstones. Therefore, current understanding of brittle deformation in quartz-rich sandstones can be used to inform investigations into fault growth within porous tuffs on Mars. A discussion of these observations, practical limitations, and directions for future work are presented here.

  15. Traditional Navajo Maps and Wayfinding

    ERIC Educational Resources Information Center

    Francis, Harris; Kelley, Klara

    2005-01-01

    An example of the way finding process when using verbal and other traditional maps among the Navajo Indians of the southwestern United States is presented. The scholarly literature on the Southwest offers examples of verbal maps that construct both linear space, such as trails, and broad geographical space, including hunting territories and large…

  16. Compensation of Navajo Uranium Miners

    NSDL National Science Digital Library

    World Information Service on Energy Uranium Project

    This site addresses policy issues of the compensation of Navajo uranium miners. The site provides an annotated index of current issues, legislation, papers and presentations, books, and links that lead to more information on uranium miners. Imbedded links throughout the text lead to related information.

  17. Navajo Art--A Way of Life.

    ERIC Educational Resources Information Center

    Clover, Faith

    This curriculum unit on Navajo art consists of three lessons, each of which can stand alone or be used in conjunction with the others. Teacher and students will explore Navajo traditions in the unit and use the insight gained to create artworks that connect people to their community and natural environment. The key artworks provide the foundation…

  18. Entrepreneurship and Economic Development: The Navajo Model.

    ERIC Educational Resources Information Center

    Devlin, J. Stuart; Carlin, William B.

    The Navajo Nation, in the summer of 1987, sponsored the Special Pre-Business Introduction for Navajo Students (SPINS) program through the business colleges at three universities: (1) University of Arizona; (2) University of New Mexico; and (3) New Mexico State University. SPINS provided entrepreneurial training, through entrepreneurship workshops,…

  19. A Jurassic Shock-Aftershock Earthquake Sequence Recorded by Small Clastic Pipes and Dikes within Dune Cross-Strata, Zion National Park, Utah

    NASA Astrophysics Data System (ADS)

    Loope, D. B.; Zlotnik, V. A.; Kettler, R. M.; Pederson, D. T.

    2012-12-01

    Eolian sandstones of south-central and southeast Utah contain large volumes of contorted cross-strata that have long been recognized as products of liquefaction caused by seismic shaking. Unlike most sites where Navajo Sandstone is exposed, in Zion National Park (southwestern Utah), the Navajo contains very, very few contorted strata. We have, however, mapped the distribution of more than 1,000 small-scale, vertical pipes and dikes in uncontorted cross-strata of the Navajo at two small study sites in Zion. Pipes are 2-5 cm in diameter and up to 3 m long; dikes are ~6 cm wide. Clusters of the water-escape structures lie directly above and below numerous, near-horizontal bounding surfaces. Dikes are restricted to the wind-ripple strata that lie above the bounding surfaces. Pipes are common both above and below the bounding surfaces. In map view, most pipes are arranged in lines. Near the bounding surfaces, pipes merge upward with shallow dikes trending parallel to the lines of pipes. Pipes formed in grainflows—homogeneous, well-sorted sand lacking cohesion. Dikes formed above the bounding surface, in more-cohesive, poorly sorted, wind-ripple strata. As liquefaction began, expansion of subsurface sand caused spreading within the unliquified (capping) beds near the land surface. Dikes intruded cracks in the wind-ripple strata, and pipes rose from the better-sorted sand to interdune surfaces, following trends of cracks. Because the wind-ripple strata had low cohesive strength, a depression formed around each rupture, and ejected sand built upward to a flat-topped surface rather than forming the cone of a classic sand volcano. In one 3 m2 portion of the map area, a cluster of about 20 pipes and dikes, many with truncated tops, record eight stratigraphically distinct seismic events. The large dunes that deposited the Navajo cross-strata likely moved ~1m/yr. When, in response to seismic shaking, a few liters of fluidized sand erupted onto the lowermost portion of the dune lee slope through a pipe, the erupted sand dried and was buried by climbing wind-ripple strata as the large dune continued to advance downwind. The mapped cluster recording eight distinct seismic events lies within thin-laminated sediment that was deposited by wind ripples during 1 m (~ 1 year) of southeastward dune migration. We conclude that the small pipes and dikes of our study sites are products of numerous >MM 5 earthquakes, some of which recurred at intervals of less than 2 months. We interpret one small cluster of pipes and dikes with well-defined upward terminations as a distinct shock-aftershock sequence. Because the largest modern earthquakes can produce surface liquefaction only up to about 175 km from their epicenters, the Jurassic epicenters must have been well within that distance. The tendency of modern plate boundaries to produce high-frequency aftershocks suggests that the epicenter for this Jurassic sequence lay to the southwest, within the plate boundary zone (not within continental rocks to the east). As eolian dunes steadily migrate over interdune surfaces underlain by water-saturated dune cross-strata, the thin, distinct laminae produced by the wind ripples that occupy dune toes can faithfully record high-frequency seismic events.

  20. Diné (Navajo) Ethno- and Archaeoastronomy

    NASA Astrophysics Data System (ADS)

    Chamberlain, Von Del

    The Navajo (Diné) are an Athabascan-speaking people who migrated from the far northwest of America into the desert southwest where they became the largest surviving Native American culture. Three words portray Diné philosophy - beauty, harmony, and balance. Their traditions are rich with astronomical symbolism found in literature, ceremony, iconography, artifacts, rock art, and the sacred landscape. This chapter summarizes Diné astronomical traditions, identification of stars known to be important to the Diné, and how these are depicted on artifacts and rock art.

  1. Final Report Navajo Transmission Project (NTP)

    SciTech Connect

    Bennie Hoisington; Steven Begay

    2006-09-14

    The Diné Power Authority is developing the Navajo Transmission Project (NTP) to relieve the constraints on the transmission of electricity west of the Four Corners area and to improve the operation flexibility and reliability of the extra-high-voltage transmission system in the region. The NTP creates the wholesale transmission capacity for more economical power transfers, sales, and purchases in the region. It will facilitate the development of Navajo energy resources, improve economic conditions on the Navajo Nation as well as allow DPA to participate in the western electrical utility industry.

  2. Sandstone Quarry

    USGS Multimedia Gallery

    A view of the Sandstone Quarry in Red Rock Canyon. Red Rock Canyon is a National Conservation Area managed by the Bureau of Land Management, located just outside of Las Vegas, Nevada. It is part of the Mojave Desert....

  3. The Role of Changing Woman and the Twins in the Navajo Origin Myth. An Effort to Correlate Navajo Legends With the Present Navajo Culture and Educational Needs.

    ERIC Educational Resources Information Center

    Mecham, Edward M.

    The Navajo origin myth is discussed by comparing recorded versions of the story of Changing Woman and the Twins. The myth clarifies the significance of many present-day tribal ceremonies and customs and provides a basis for the traditional upbringing of the Navajo child. The Navajo defines wrong as "that which produces disharmony within society,"…

  4. Jurassic petroleum trends in eastern Gulf Coastal Plain and central and eastern Gulf of Mexico

    SciTech Connect

    Mancini, E.A.; Mink, R.M.; Bearden, B.L.

    1986-05-01

    Three Jurassic petroleum trends can be delineated in Mississippi, Alabama, and Florida, and in the central and eastern Gulf of Mexico. These trends are recognized by characteristic petroleum traps, reservoirs, and hydrocarbon types. The source for the Jurassic hydrocarbons is Smackover algal mudstones. The Jurassic oil trend includes the area north of the regional peripheral fault systems in the tri-state area, and extends into the area north of the Destin anticline. Traps are basement highs and salt anticlines, with Smackover grainstones and dolostones and Norphlet marine, eolian, and wadi sandstones as reservoirs. This trend has potential for Jurassic oil accumulations in the eastern Gulf of Mexico. The Jurassic oil and gas-condensate trend includes the onshore area between the regional peripheral fault systems and Wiggins arch and extends into the area of the Destin anticline. Traps are basement highs, salt related anticlines, and extensional faults. Cotton Valley fluvial-deltaic sandstones, Haynesville carbonates and fluvial-deltaic sandstones, Smackover grainstones, packstones, dolostones, and marine sandstones, and Norphlet marine, eolian, and wadi sandstones serve as reservoirs. This trend contains most of the Jurassic fields in the eastern Gulf coastal plain. The trend has high potential for significant petroleum accumulations in the eastern Gulf of Mexico. The Jurassic deep natural gas trend includes the onshore area south of the Wiggins arch and extends into the Mississippi-Alabama shelf. Traps are faulted salt anticlines with basement highs as potential traps. Cotton Valley deltaic-strandplain sandstones and Norphlet eolian sandstones are the reservoirs. Several gas discoveries below 20,000 ft have been made in this trend in Mississippi and offshore Alabama. The trend has excellent potential for major gas accumulations in coastal Alabama and central Gulf of Mexico.

  5. Jurassic Paleolatitudes, Paleogeography, and Climate Transitions In the Mexican Subcontinen

    NASA Astrophysics Data System (ADS)

    Molina-Garza, R. S.; Geissman, J. W.; Lawton, T. F.

    2014-12-01

    Jurassic northward migration of Mexico, trailing the North America plate, resulted in temporal evolution of climate-sensitive depositional environments. Lower-Middle Jurassic rocks in central Mexico contain a record of warm-humid conditions, which are indicated by coal and compositionally mature sandstone deposited in continental environments. Preliminary paleomagnetic data indicate that these rocks were deposited at near-equatorial paleolatitudes. The Middle Jurassic (ca. 170 Ma) Diquiyú volcanic sequence in central Oaxaca give an overall mean of D=82.2º/ I= +4.1º (n=10; k=17.3, ?95=12º). In the Late Jurassic, the Gulf of Mexico formed as a subsidiary basin of the Atlantic Ocean, when the supercontinent Pangaea ruptured. Upper Jurassic strata, including eolianite and widespread evaporite deposits, across Mexico indicate dry-arid conditions. Available paleomagnetic data (compaction-corrected) from eolianites in northeast Mexico indicate deposition at ~15-20ºN. As North America moved northward during Jurassic opening of the Atlantic, different latitudinal regions experienced coeval Late Jurassic climatic shifts. Climate transitions have been widely recognized in the Colorado plateau region. The plateau left the horse-latitudes in the late Middle Jurassic to reach temperate humid climates at ~40ºN in the latest Jurassic. In turn, the southern end of the North America plate (central Mexico) reached arid horse-latitudes in the Late Jurassic. At that time, epeiric platforms developed in the circum-Gulf region after a long period of margin extension. We suggest that Upper Jurassic hydrocarbon source rocks in the circum-Gulf region accumulated on these platforms as warm epeiric hypersaline seas and the Gulf of Mexico itself were fertilized by an influx of wind-blown silt from continental regions. Additional nutrients were brought to shallow zones of photosynthesis by ocean upwelling driven by changes in the continental landmass configuration.

  6. History Comes to the Navajos: A Review Essay.

    ERIC Educational Resources Information Center

    Lyon, William H.

    1987-01-01

    Reviews "Through White Men's Eyes," six volumes of documentary evidence, arranged chronologically, covering Navajo history from early historic times to the treaty of 1968. Discusses the complicated interrelationships among rich and poor Navajos, Anglos, Hispanics, Pueblos, and other tribes. (SV)

  7. Dynamics of a Phreatomagmatic Eruption at Narbona Pass Volcano, Navajo Volcanic Field, Navajo Nation, New Mexico

    NASA Astrophysics Data System (ADS)

    Brand, B. D.; Clarke, A. B.; Semken, S. C.; Sandoval, C.

    2005-12-01

    We incorporate field investigations and analytical techniques to reconstruct vent geometry and evolution, magma/water ratio, zone of fragmentation and efficiency of fragmentation of a mid-Tertiary phreatomagmatic eruption. Narbona Pass maar, located in the Chuska Mountains of northwest New Mexico, is a center in the (28-19 Ma) Navajo Volcanic Field. Minette magma erupted through a sandstone aquifer approximately 25 Ma (Cather et al., 2003) creating a phreatomagmatic sequence of bedded tuffs capped by trachybasalt lava flows. Nine stratigraphic columns were measured documenting the types, proportions and distribution of deposits around the crater. Inner crater units include massive tuff breccias, interpreted as debris flows back into the crater, and large, symmetrical cross-strata, interpreted as base surge deposits. Outer crater deposits consist of alternating bedded tuff sequences of large, symmetrical to anti-dune cross-strata, both normal and reverse graded, planar-bedded lapilli tuff, and massive lapilli tuffs and tuff breccias. Soft sediment deformation occurs only intermittently throughout the deposits and no accretionary lapilli were found, both indicative of a relatively dry phreatomagmatic eruption. The contact between pyroclastic deposits and the substrate indicates that the thickest sections were deposited in a paleo-valley (Ehrenberg, 1978). Paleo-valley fill deposits are coarser-grained than the rest of the sequence, but otherwise exhibit the same cross strata as previously described. The percentage and composition of accidental sandstone fragments remain vertically consistent through the tuff sequence, possibly suggesting a fixed zone of fragmentation. However, the accidental lithics vary in percentage depending on location around the edifice, suggesting eruption asymmetry. Zones rich in dike- and sill-sourced accidental lithics are also common in the sequence. Several angular unconformities were observed indicating partial cone collapse and enlargement of the crater during the eruption. The end of the pyroclastic sequence is characterized by fine-grained ash deposits with abundant cross-stratification and soft sediment deformation, suggesting there was no gradual drying out period before the final magmatic stage. Instead the eruption may have suddenly depleted the external water source, the zone of magma flux may have dropped below the aquifer, or the eruption may have paused before the final effusive phase.

  8. Navajo Nation Scholarship Assistance Program: Plan of Operation.

    ERIC Educational Resources Information Center

    Navajo Tribe, Window Rock, AZ. Div. of Education.

    A resolution of the Advisory Committee of the Navajo Tribal Council describes how since 1972 the Navajo Nation through its Department of Higher Education has administered both the Navajo Trust Fund (graduate and post-graduate program) and the Bureau of Indian Affairs Higher Education Funds (undergraduate program). The tribal philosophy toward…

  9. Navajo Health Authority, Board of Commissioners, Annual Report, June 1975.

    ERIC Educational Resources Information Center

    Atcitty, Thomas E.

    The Navajo Health Authority (NHA) was created by the Navajo Tribal Council to guide and assist the Navajo people to improve their health and well-being. Its goals are to: (1) develop health manpower training programs appropriate to support the development of the American Indian Medical School and to meet the needs of the American Indians in…

  10. Health Problems of the Navajo Area and Suggested Interventions.

    ERIC Educational Resources Information Center

    Kaltenbach, Charles

    Analysis of morbidity, mortality, and demographic data on Navajo people was undertaken to identify leading health problems in the Navajo area and to suggest intervention activities. Comparisons with total U.S. population were made to provide perspective. Data on Navajo mortality showed: a ratio of male to female deaths of 2:1, more than 50 percent…

  11. Language Learning in the American Southwestern Borderlands: Navajo Speakers and Their Transition to Academic English Literacy.

    ERIC Educational Resources Information Center

    Dyc, Gloria

    2002-01-01

    The Navajo Nation wants a 2-year Navajo language requirement for regional colleges. At the same time, literacy in academic English is required for Navajo students wishing to enter the sciences, medicine, and law. The difficulties students face as they make the transition from English to Navajo and from Navajo to English are described. Four…

  12. Navajo Participation in Labor Unions. Lake Powell Research Project Bulletin Number 15, December 1975.

    ERIC Educational Resources Information Center

    Robbins, Lynn A.

    Navajo participation in labor unions and Navajo labor relations have undergone rapid and fundamental changes since the development of industry around Lake Powell and on Black Mesa. Early attempts to unionize Navajo workers met with stiff resistance from employees and the Navajo Tribal Council. Union entry into the Navajo Reservation was viewed as…

  13. Navajo Philosophy of Learning and Pedagogy.

    ERIC Educational Resources Information Center

    Benally, Herbert John

    1994-01-01

    Describes Navajo philosophy and implications for teaching and learning. Explains four branches of knowing that provide a framework for conceptualizing teaching content, as well as interrelationships within the framework providing opportunities for critical analysis and reflection. Advocates inquiry-oriented, experience-based instruction that…

  14. Determinants of Blood Pressure in Navajo Adolescents.

    ERIC Educational Resources Information Center

    Coulehan, John L.; And Others

    1990-01-01

    Among 580 Navajo adolescents, 11.1 percent of males and 1.6 percent of females had high blood pressure. Blood pressure was related to age in males and to body mass index in females but was not related to level of acculturation or traditionality. Contains 17 references. (SV)

  15. Ramah Navajo Radio and Cultural Preservation

    ERIC Educational Resources Information Center

    Rada, Stephen A.

    1978-01-01

    The Ramah leadership, aware of their isolation, the lack of economic opportunity, the Navajo's poor self image as a people, and the almost total absence of any sense of community, built a radio station. This study, conducted over three and a half years after the station was put into operation, is a preliminary assessment of its impact upon the…

  16. 78 FR 15036 - Renewal of Agency Information Collection for Navajo Partitioned Lands Grazing Permits

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-08

    ...Collection for Navajo Partitioned Lands Grazing Permits AGENCY: Bureau of Indian Affairs...information for Navajo Partitioned Lands Grazing Permits authorized by OMB Control Number...applicant to obtain, modify, or assign a grazing permit on Navajo Partitioned Lands...

  17. 25 CFR 161.307 - When may a permittee commence grazing on Navajo Partitioned Land?

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...false When may a permittee commence grazing on Navajo Partitioned Land? 161...AND WATER NAVAJO PARTITIONED LANDS GRAZING PERMITS Permit Requirements § 161.307 When may a permittee commence grazing on Navajo Partitioned Land?...

  18. 78 FR 32273 - Renewal of Agency Information Collection for Navajo Partitioned Lands Grazing Permits

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-29

    ...Collection for Navajo Partitioned Lands Grazing Permits AGENCY: Bureau of Indian Affairs...information for Navajo Partitioned Lands Grazing Permits authorized by OMB Control Number...applicant to obtain, modify, or assign a grazing permit on Navajo Partitioned Lands...

  19. 78 FR 23277 - Navajo Nation; Amendment No. 1 to Notice of a Major Disaster Declaration

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-18

    ...declaration for the Navajo Nation (FEMA-4104-DR), dated...declaration for the Navajo Nation is hereby amended to include...March 5, 2013. The Navajo Nation and associated lands for buildings and equipment (Category...

  20. Sandstone petrofacies in the northwestern sector of the Iberian Basin Petrofacies arenosas en el sector noroccidental de la Cuenca Ibérica

    Microsoft Academic Search

    J. Arribas; M. Ochoa; R. Mas; L. González-Acebrón

    During the most active rifting stages in the northwestern sector of the Iberian Basin (Cameros Basin and Aragonese Branch of the Iberian Range), thick sequences of continental clastic deposits were generated. Sandstone records from Rift cycle 1 (Permo-Trias- sic) and Rift cycle 2 (Late Jurassic-Early Cretaceous) show similarities in composition. Based on the most recent data, this paper describes sandstone

  1. Dinosaurs as Possible Avulsion Enablers in the Upper Jurassic Morrison Formation, East-Central Utah

    Microsoft Academic Search

    Lawrence S. Jones; Edmund R. Gustason

    2006-01-01

    The Upper Jurassic Salt Wash Member of the Morrison Formation in east-central Utah contains low sinuosity, ribbon-shaped fluvial channel sandstones enclosed by variegated mudstones. Channel sandstones formed when avulsion (the relatively abrupt shift of a river to a new channel) relocated a channel, after which extensive in-channel and minor near-channel sand deposition occurred. Interpretation of sedimentological, paleontological, and paleoclimatic data,

  2. Lung cancer among Navajo uranium miners

    SciTech Connect

    Gottlieb, L.S.; Husen, L.A.

    1982-04-01

    Lung cancer has been a rare disease among the Indians of the southwestern United States. However, the advent of uranium mining in the area has been associated with an increased incidence of lung cancer among Navajo uranium miners. This study centers on Navajo men with lung cancer who were admitted to the hospital from February 1965 to May 1979. Of a total of 17 patients with lung cancer, 16 were uranium miners, and one was a nonminer. The mean value of cumulative radon exposure for this group was 1139.5 working level months (WLMs). The predominant cancer type was the small cell undifferentiated category (62.5 percent). The low frequency of cigarette smoking in this group supports the view that radiation is the primary cause of lung cancer among uranium miners and that cigarette smoking acts as a promoting agent.

  3. Jurassic Park Safety Audit

    NSDL National Science Digital Library

    Using the first 30 minutes of the film Jurassic Park, the student will audit it for violations of safety rules and regulations, OSHA violations, and violations of HASP's. Access to the activity required free and quick registration with ATEEC.

  4. Jurassic Reef Park

    NSDL National Science Digital Library

    Reinhold Leinfelder

    This is a bilingual, educational website from Munich, Germany. The main feature is a virtual field trip to the reefs of the Jurassic period. Besides a view of the Jurassic reefs, their builders, and their ecological settings, there is also an emphasis on the importance of modern reefs as indicators of the state-of-health of the globe and evidence of how some changes in the composition of reefs may represent the forerunners of catastrophic, regional or global, environmental change.

  5. Jurassic Reef Park

    NSDL National Science Digital Library

    Dr. Reinhold Leinfelder of the University of Stuttgart, Germany created this interesting site in English and German, offering a "virtual trip to the reefs of the Jurassic Period." In the Introduction, viewers will find background material and comparisons of modern and ancient reefs. Further information is provided in the sections on reef architecture, reef formation, Jurassic reefs, and reefs and global climate change. Although the English language is slightly quirky, the content and images more than compensate, making this a worthwhile site.

  6. The Navajo Agricultural Projects Industry: Subsistence Farming to Corporate Agribusiness.

    ERIC Educational Resources Information Center

    Barry, Tom

    1979-01-01

    Originally designed to create small farms for individual Navajos, the irrigation project has grown into a single 110,000-acre corporate agribusiness, the land's management has fallen out of the grasp of individual Navajos, and the idea of subsistence farming has been plowed under for the planting of major money-making crops. (NQ)

  7. "Dine Bikeya": Teaching about Navajo Citizenship and Sovereignty

    ERIC Educational Resources Information Center

    Washington, Elizabeth Yeager; van Hover, Stephanie

    2011-01-01

    The Navajo Nation, comprising the largest land area allocated mainly to a Native American jurisdiction in the United States, offers a unique opportunity to enhance students' understandings of citizenship rights and sovereignty. For example, what does sovereignty mean on the reservation? What is the relationship between the Navajo Nation and the…

  8. Oral History Shares the Wealth of a Navajo Community.

    ERIC Educational Resources Information Center

    Begay, Sara L.; Jimmie, Mary; Lockard, Louise

    This paper describes a collaborative project in which K-3 Navajo students used oral history interviews, archival photos, and primary documents to explore the history of their communities. Participating students attended schools that were implementing the Dine (Navajo) Language and Culture teaching perspective, which is based on the premises that…

  9. Navajo Archaeologist Is Not an Oxymoron: A Tribal Archaeologist's Experience

    ERIC Educational Resources Information Center

    Two Bears, Davina R.

    2006-01-01

    Many Navajos, or Dines, and Native American people in general, are archaeologists or are becoming archaeologists. The distinction between "Native Americans" and "archaeologists" in academia, or elsewhere, is no longer accurate. This fact should not come as such a surprise. As the epigraph, a quote by Richard Begay, demonstrates, Navajo people, for…

  10. Social Interaction Patterns and Relative Urban Success: the Denver Navajo

    ERIC Educational Resources Information Center

    Snyder, Peter Z.

    1973-01-01

    This examination of the social factors of urban adaptation of Navajo Indian migrants to Denver, Colorado--based on reference-membership group theory--attempts to isolate primary groups within the Navajo urban enclave'' to investigate the relationship of group membership to adaptation. (JM)

  11. Health and health services among the Navajo Indians.

    PubMed

    Haraldson, S S

    1988-01-01

    The Navajo are the largest Indian tribe in the continental U.S. with a population in 1986 estimated at 171,097. The Navajo Nation (Reservation) is located along the borders where Arizona, New Mexico, Colorado and Utah meet. Social and economic changes have accrued among the Navajo at a rapid rate during this century. At present, revenues are derived from oil, coal and uranium and from federal grants and contracts. High unemployment rates have been a major problem among the Navajo. This article reviews health, disease and health care among the present day Navajo. Mortality rates from accidents and suicide are disproportionately high and have as their causes longstanding social and behavioral problems. Although there has been a sharp decline in morbidity and mortality from infectious diseases, there are still major environmental health problems. PMID:3068261

  12. Sea-level change and facies development across potential Triassic-Jurassic boundary horizons, SW Britain

    Microsoft Academic Search

    STEPHEN P. H ESSELBO; S T UA; RT A. RO; S U R LY K

    2004-01-01

    The Late Triassic to Early Jurassic aged succession of SW Britain (the Penarth and lower Lias Groups) comprises mudstone, sandstone and limestone strata deposited in a variety of marine to non-marine environments. Faunal and floral characteristics of these successions have led to the proposal that one location in SW England, St Audrie's Bay, should serve as the Global Stratotype Section

  13. Laughter: The Navajo Way. Humorous Stories of the People (in Navajo and English) Volume One.

    ERIC Educational Resources Information Center

    Wilson, Alan; Dennison, Gene

    This book has been prepared for the use of teachers, ethnologists, linguists, Indian studies scholars, language students and those who have an interest in the languages and cultures of the earlier inhabitants of this continent. The stories reflect the Navajo love for and genius with words and humor. Most of the humor represented is of three basic…

  14. Area Health Education Center of the Navajo Health Authority to Establish the Navajo Center for Health Professions Education.

    ERIC Educational Resources Information Center

    Navajo Health Authority, Window Rock, AZ.

    The Area Health Education Center (AHEC) is designed to provide educational opportunities in health and allied fields and to improve health care for the Navajo people and other Indians in the region that includes and immediately surrounds the Navajo Indian Reservation. As prime contractor, the University of New Meixco School of Medicine will…

  15. Collapsing the Fear of Mathematics: A Study of the Effects of Navajo Culture on Navajo Student Performance in Mathematics

    ERIC Educational Resources Information Center

    Fowler, Henry H.

    2010-01-01

    Collapsing the Fear of Mathematics: A Study of the Effects of Navajo Culture on Navajo Student Performance in Mathematics by Henry H Fowler Abstract American schools are in a state of "mediocrity" because of the low expectations in math (National Commission on Excellence in Education, 1983; No Child Left Behind Act of 2001; Duncan, 2009).…

  16. Deformation of Aztec Sandstone at Valley of Fire of Nevada: failure modes, sequence of deformation, structural products and their interplay with paleo fluids

    NASA Astrophysics Data System (ADS)

    Aydin, A.

    2014-12-01

    The Valley of Fire State Park, 60 km NE of Las Vegas, is a beacon of knowledge for deformation of Aztec Sandstone, a cross-bedded quartz arenite deposited in the Aztec-Navajo-Nugget erg in early Jurassic. It displays great diversity of physical properties, different localization types and micromechanics. The two deformation episodes, the Sevier folding & thrusting and the Basin & Range extension affected the area. The appearance of compaction bands marks the earliest deformation structure and their distribution, orientation, and dimension are controlled by the depositional architecture and loading. The earliest shear structures in the area are the Muddy Mountain, Summit, and Willow Tank thrusts and numerous small-scale bed-parallel faults. They altogether produced several kilometers of E-SE transport and shortening in the late Cretaceous and display numerous shear bands in its damage zone within the Aztec Sandstone. Shear bands also occur along dune boundaries and cross-bed interfaces. These observations indicate that the early deformation of the sandstone was accommodated by strain localization with various kinematics. The younger generation of faults in the area is of mid-Miocene age, and crops out pervasively. It includes a series of small offset normal faults (less than a few ten meters) which can be identified at steep cliff faces. These faults are highly segmented and are surrounded by a dense population of splay fractures. A large number of these splays were later sheared sequentially resulting in a well-defined network of left- and right-lateral strike-slip faults with slip magnitudes up to a few kilometers in the Park. The formation mechanisms of both the normal and strike-slip faults can be characterized as the sliding along planes of initial weaknesses and the accompanying cataclastic deformation. Some of the initial weak planes are associated with the depositional elements such as interdune boundaries and cross-bed interfaces while others are joint zones apparently not physically connected to any observable normal fault or dune boundary fault, but consistent with the earlier extension direction. The specific kinematics of this latter period of faulting is thought to be dictated by the orientation of the depositional and structural weaknesses and the orientation and rotation of the driving stresses.

  17. Uranium mining and lung cancer in Navajo men

    SciTech Connect

    Samet, J.M.; Kutvirt, D.M.; Waxweiler, R.J.; Key, C.R.

    1984-06-07

    We performed a population-based case-control study to examine the association between uranium mining and lung cancer in Navajo men, a predominantly nonsmoking population. The 32 cases included all those occurring among Navajo men between 1969 and 1982, as ascertained by the New Mexico Tumor Registry. For each case in a Navajo man, two controls with nonrespiratory cancer were selected. Of the 32 Navajo patients, 72 per cent had been employed as uranium miners, whereas no controls had documented experience in this industry. The lower 95 per cent confidence limit for the relative risk of lung cancer associated with uranium mining was 14.4. Information on cigarette smoking was available for 21 of the 23 affected uranium miners; eight were nonsmokers and median consumption by the remainder was one to three cigarettes daily. These results demonstrate that in a rural nonsmoking population most of the lung cancer may be attributable to one hazardous occupation.

  18. TECHNICAL SUPPORT TO NAVAJO NATION ON URANIUM MINING TENORM WASTES.

    EPA Science Inventory

    Assistance is being provided to the Navajo Nation to establish its own radiation protection standards, radiation action levels, identification of safe drinking water sources, safe disposal of radioactive TENORM wastes from abandoned uranium mines, and to locate and decontaminate ...

  19. The use of NMR spectroscopy to validate NMR logs from deeply buried reservoir sandstones

    Microsoft Academic Search

    H Rueslåtten; T Eidesmo; K. A Lehne; O. M Relling

    1998-01-01

    A Lower Jurassic deeply buried sandstone oil reservoir offshore Mid Norway was logged with NUMAR's MRIL-C tool. The NML data have been compared with standard logs as well as laboratory NMR and standard petrophysical core measurements. The two formations studied are in the oil zone, Formation A being characterised by an extensive distribution of pore lining chlorite, while asphalt staining

  20. URANIUM DEPOSITS UNDER CONGLOMERATIC SANDSTONE OF THE MORRISON FORMATION, COLORADO AND UTAH

    Microsoft Academic Search

    DAVID A. PHOENIX

    1958-01-01

    In southwestern Colorado and southeastern Utah, strata of conglomeratic ; sandstone are localized at the base of the Brushy Basin Member of the Morrison ; Formation of Jurassic age. These discrete lithologic units contain sedimentary ; structures oriented in a prevailing easterly direction. They are believed to ; cover about one-third of the underlying Salt Wash Member in southwestern Colorado

  1. 78 FR 16825 - Approval of Air Quality Implementation Plans; Navajo Nation; Regional Haze Requirements for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-19

    ...well as the singular importance of NGS to the Navajo...significant amount of time. On February 21...Navajo Nation the time and opportunity to...significant amount of time. EPA also recognizes the critical importance of active...

  2. 75 FR 16174 - Renewal of Agency Information Collection for Navajo Partitioned Lands Grazing Permits; Request...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-31

    ...Collection for Navajo Partitioned Lands Grazing Permits; Request for Comments AGENCY...titled ``Navajo Partitioned Lands Grazing Permits, 25 CFR 161'' to the Office...order to obtain, modify, or assign a grazing permit. DATES: Interested persons...

  3. 75 FR 4410 - Renewal of Agency Information Collection for Navajo Partitioned Lands Grazing Regulations Permits

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-27

    ...Collection for Navajo Partitioned Lands Grazing Regulations Permits AGENCY: Bureau of...titled ``Navajo Partitioned Lands Grazing Regulations Permits, 25 CFR 161'' to...order to obtain, modify, or assign a grazing permit. DATES: Interested persons...

  4. An extended Nishihara model for the description of three stages of sandstone creep

    NASA Astrophysics Data System (ADS)

    Jiang, Qinghui; Qi, Yajing; Wang, Zhijian; Zhou, Chuangbing

    2013-05-01

    Many gently dipping translational rock slides have taken place in red Jurassic strata in Wanzhou which is located in the middle bank area of the Three Gorges Reservoir, China. In order to study the mechanism of these translational rock slides, conventional triaxial tests and creep tests on sandstone specimens from red Jurassic strata in Wanzhou are performed, and the rheological properties of the sandstone at accelerating creep stage are discussed. The quasi-static Nishihara model for transient and steady-state creep is modified by adding a strain-triggered inertial element in series, resulting in a phase of quadratic accelerating creep. The model fits the experimental data at all stages of creep, allowing its parameters to be inferred from the data. Finally, a sensitivity study for the analytical solution of the proposed model is carried out, showing the effects of the inertial element and stress level on the creep strain of sandstone.

  5. Ednishodi Yazhe: The Little Priest and the Understanding of Navajo Culture.

    ERIC Educational Resources Information Center

    Lyon, William H.

    1987-01-01

    Describes the career of Father Berard Haile (1874-1961), a Franciscan missionary and anthropologist who befriended Navajo Indians in Arizona and studied their culture. Haile's career spanned five decades, and he maintained a Navajo residence longer than any other Navajo ethnologist. Describes his writings, special fields, scholarly limitations,…

  6. Students' Perspectives on Navajo Language and Learning: Voices of the Students

    ERIC Educational Resources Information Center

    Shepard, Marlena

    2012-01-01

    To determine if Navajo language classes made a difference in students' lives, thirty Navajo language and culture students were selected to be interviewed. The students selected were those who were in the language and culture programs in the elementary, middle and high school. The focus was to find out the students' perspectives on Navajo…

  7. Capitol Reef Sandstone Cliff

    USGS Multimedia Gallery

    A sandstone cliff within Capitol Reef National Park. Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

  8. Capitol Reef Sandstone Monolith

    USGS Multimedia Gallery

    A sandstone monolith within Capitol Reef National Park. Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

  9. Snow-covered Sandstone

    USGS Multimedia Gallery

    Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

  10. The Scalpel and the Silver Bear. The First Navajo Woman Surgeon Combines Western Medicine and Traditional Healing.

    ERIC Educational Resources Information Center

    Alvord, Lori Arviso; Van Pelt, Elizabeth Cohen

    In this autobiography, Lori Arviso Alvord describes her journey to become the first Navajo woman surgeon and her realization of the benefits of Navajo philosophy to the healing process. Raised on the Navajo reservation by a White mother and a Navajo father and grandmother, Alvord learned to walk in two worlds. Encouraged to get an education, she…

  11. STEM Summer Academy on the Navajo Reservation

    NASA Astrophysics Data System (ADS)

    Alexander, C. J.

    2012-12-01

    The US Rosetta Project is the NASA contribution to the International Rosetta Mission, an ESA cornerstone mission to comet Churyumov-Gerasimenko. While the project's outreach efforts span multi-media, and a variety of age and ethnic groups, a special emphasis has been made to find a way to provide meaningful outreach to the reservation communities. Because language preservation is an issue of urgent concern to the reservation communities, and because Rosetta, uniquely among NASA missions, has been named after the notion that keys to missing understanding of elements of the ancient past were found in the language on the original Rosetta stone, the US Rosetta Project has embarked upon outreach with a focus on STEM vocabulary in ancient US languages of the Navajo, Hopi, Ojibwe, and other tribal communities as the project expands. NASA image and science are used and described in the native language, alongside lay English and scientific English curriculum elements. Additionally, science (geology/chemistry/botany/physics) elements drawn from the reservation environment, including geomorphology, geochemistry, soil physics, are included and discussed in the native language as much as possible — with their analogs in other planetary environments (such as Mars). In this paper we will report on the most recent Summer Science Academy [2012], a four week summer course for middle school children, created in collaboration with teachers and administrators in the Chinle Unified School District. The concept of the Academy was initiated in 2011, and the first Academy was conducted shortly thereafter, in June 2011 with 14 children, 3 instructors, and a NASA teacher workshop. The community requested three topics: geology, astronomy, and botany. The 2012 Academy built on the curriculum already developed with more robust field trips, addressed to specific science topics, additional quantitative measurements and activities, with more written material for the cultural components from Navajo contributors. In 2012, the Academy was conducted with 45 children and 4 instructors. Following up on lessons learned in previous reports, it is clear that community involvement and buy-in is critical to the success of the program. This means that the US Rosetta Project modified its goals and curriculum to accommodate the teaching desires of teachers in the district, and the capabilities of the medicine men that agreed to participate. The use of NASA material and imagery can be shown to have a positive impact on the accessibility of the overall STEM material. Metrics used in the program will be discussed. Future work to extract STEM language elements to enhance the program will include organized Elder's Round Tables for discussion, and recording, of language with first speakers. Work on this project was supported by NASA at California Institute of Technology/Jet Propulsion Laboratory.

  12. Controls on the variability of net infiltration to desert sandstone

    USGS Publications Warehouse

    Heilweil, V.M.; McKinney, T.S.; Zhdanov, M.S.; Watt, D.E.

    2007-01-01

    As populations grow in and climates and desert bedrock aquifers are increasingly targeted for future development, understanding and quantifying the spatial variability of net infiltration becomes critically important for accurately inventorying water resources and mapping contamination vulnerability. This paper presents a conceptual model of net infiltration to desert sandstone and then develops an empirical equation for its spatial quantification at the watershed scale using linear least squares inversion methods for evaluating controlling parameters (independent variables) based on estimated net infiltration rates (dependent variables). Net infiltration rates used for this regression analysis were calculated from environmental tracers in boreholes and more than 3000 linear meters of vadose zone excavations in an upland basin in southwestern Utah underlain by Navajo sandstone. Soil coarseness, distance to upgradient outcrop, and topographic slope were shown to be the primary physical parameters controlling the spatial variability of net infiltration. Although the method should be transferable to other desert sandstone settings for determining the relative spatial distribution of net infiltration, further study is needed to evaluate the effects of other potential parameters such as slope aspect, outcrop parameters, and climate on absolute net infiltration rates. Copyright 2007 by the American Geophysical Union.

  13. Jurassic-Cretaceous clastic sequences of Chukotka: sedimentation, structural style and geodynamic implications for Russian East Arctic shelf.

    NASA Astrophysics Data System (ADS)

    Tuchkova, M. I.; Sokolov, S. D.; Verzhbitsky, V. E.

    2009-04-01

    Jurassic-Lower Cretaceous sedimentary sequence, exposed on the Chukotka continental margin is critical for understanding the timing, dynamics and sedimentary setting evolution of Chukotka-Eurasia collisional process (e.g., Sokolov et al., 2002) and so, represents one of the key regional stratigraphic units (Til'man,1973, Tibilov,1982; Miller et al., 2002, 2007). From the other hand, this research may shed the light on the widely discussing problem of the Canadian and Makarov basins opening (e.g., Miller, Verzhbitsky, in press). Jurassic-Lower Cretaceous sedimentary complexes of the Chukotka microcontinent are composed of terrigeneous deposites. Those sedimentary complexes are enriched by organic matter, and fresh clastic materials. Fragments of shales, sometimes laminated or cleaved are their indicator constituents. Sandstones are arkosic. The percentage of types of rocks fragments is different in Jurassic and Cretaceous deposits. Chemical composition of the Jurassic-Cretaceous rocks is not uniform too: Upper Jurassic sandstones form one group depleted in Na2O+K2O, Cretaceous sandstones, enriched in Na2O+K2O. Thus, our investigations indicate that Jurassic-Cretaceous sedimentary basins were related to different source provenance. We believe, that the stratigraphy and composition of Jurassic-Lower Cretaceous onshore sequences are crucial for prediction of the geological structure of East Siberian and Chukchi Sea shelf (1), understanding the evolution of Mesozoic sedimentary basins of East Arctic (2) and testifying the existing geodynamic models of Amerasian Basin opening (3). The work is supported by the Russian Foundation for Basic Research (grant 08-05-00547), program of ONZ RAS 14, and NSH-3172.2008.5.

  14. Jurassic Polar Movement Relative to North America

    Microsoft Academic Search

    ANY C. E. HELSLEY

    1972-01-01

    Previous palcomagnetic studies of Jurassic rocks have not given concordant results and have led to the conclusion that the Jurassic pole position was possibly close to the present geographic pole. To test that supposition, the Kayenta, Carmel, Entrada, and Summerville formations were sampled from the extensive Jurassic sedimentary sequence in eastern Utah. The Lower and Upper Jurassic Kayenta and Summerville

  15. 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.

  16. Navajo-Hopi Land Commission Renewable Energy Development Project (NREP)

    SciTech Connect

    Thomas Benally, Deputy Director,

    2012-05-15

    The Navajo Hopi Land Commission Office (NHLCO), a Navajo Nation executive branch agency has conducted activities to determine capacity-building, institution-building, outreach and management activities to initiate the development of large-scale renewable energy - 100 megawatt (MW) or larger - generating projects on land in Northwestern New Mexico in the first year of a multi-year program. The Navajo Hopi Land Commission Renewable Energy Development Project (NREP) is a one year program that will develop and market a strategic business plan; form multi-agency and public-private project partnerships; compile site-specific solar, wind and infrastructure data; and develop and use project communication and marketing tools to support outreach efforts targeting the public, vendors, investors and government audiences.

  17. Petrology of the Middle Jurassic (?) La Joya Formation, Sierra Madre Oriental, Southwestern Tamaulipas, Mexico 

    E-print Network

    Allen, Woods Wilkinson

    1976-01-01

    changes of the La Joya Formation and lithic variations of the bounding rock units. 28 Rock fragment content of 65 sandstone thin sections from the La Joya Formation. . . . . . . . . . Classification of. La Joya Formation sand- stones based... through the Upper Jurassic and Cretaceous limestones 22 exposing the La Joya Formation and older rocks. 23 LA JOYA FORNATION Lithostratigraphy Based on 8 measured sections in the southern part of the Huizachal-Peregrina Anticlinorium (Fig. 2, p. 5...

  18. Geographic information system (G.I.S.) research project at Navajo Community College - Shiprock Campus

    SciTech Connect

    Yazzie, R.; Peter, C.; Aaspas, B.; Isely, D.; Grey, R.

    1995-12-31

    The Navajo and Hopi GIS Project was established to assess the feasibility and impact of implementing GIS techology at Tribal institutions. Los Alamos and Lawrence Livermore National Laboratories funded the Navajo and Hopi Geographic Information System (G.I.S.) Project and assigned a mentor from LANL to help guide the project for three summer months of 1995. The six organizations involved were: LANL, LLNL, Navajo Community College, Navajo Nation Land Office, Northern Arizona University and San Juan College. The Navajo Land Office provided the system software, hardware and training. Northern Arizona University selected two students to work at Hopi Water Resource Department. Navajo Community College provided two students and two faculty members. San Juan College provided one student to work with the N.C.C. group. This made up two project teams which led to two project sites. The project sites are the Water Resource Department on the Hopi reservation and Navajo Community College in Shiprock, New Mexico.

  19. Reevaluation of upper Jurassic Morrison Formation, Western Interior

    SciTech Connect

    Mantzios, C.

    1989-03-01

    Comparison of the Brushy Basin member of the Upper Jurassic Morrison Formation in the Colorado Plateau with the Upper Jurassic-Lower Cretaceous Morrison-Cloverly sequence in the Bighorn basin, Wyoming, shows great similarities in their depositional environments and stratigraphy. The lower Brushy Basin member is a fluvial deposit composed of channel sandstones and overbank mudstones which display a great number of pedogenic features. Similar depositional setting has been observed in the Morrison Formation in the Bighorn basin, Wyoming, where pedogenic features suggest a distal floodplain setting with low-sinuosity channels cutting through. In both localities the dominant clay mineral is illite. The upper Brushy Basin member in the Colorado Plateau is composed mostly of gray and purpose mudstones rich in montmorillonite. Devitrified tuff beds and bentonite occur in certain levels throughout the unit. Pedogenic features are not conspicuously developed. The Lower Cretaceous Clovery Formation in the Bighorn basin, Wyoming, is strikingly similar in terms of lithological aspects. The depositional environment is interpreted in both localities as a playa deposit. A great variety of nodules is present such as silcretes, septaria, and silica-carbonate nodules. Radiometric dating of bentonites in central Utah revealed that the upper Brushy Basin member is Early Cretaceous in age. Field and geochemical data support these conclusions and aid the understanding of the exact nature of the depositional basin, environments, stratigraphy, and paleotectonics of the Upper Jurassic-Lower Cretaceous interval in the Western Interior.

  20. Middle Jurassic incised valley fill (eolian/estuarine) and nearshore marine petroleum reservoirs, Powder River basin

    SciTech Connect

    Ahlbrandt, T.S. [Geological Survey, Denver, CO (United States); Fox, J.E. [South Dakota School of Mines, Rapid City, SD (United States)

    1997-07-01

    Paleovalleys incised into the Triassic Spearfish Formation (Chugwater equivalent) are filled with a vertical sequence of eolian, estuarine, and marine sandstones of the Middle Jurassic (Bathonian age) Canyon Springs Sandstone Member of the Sundance Formation. An outcrop exemplifying this is located at Red Canyon in the southern Black Hills, Fall River County, South Dakota. These paleovalleys locally have more than 300 ft of relief and are as much as several miles wide. Because they slope in a westerly direction, and Jurassic seas transgressed into the area from the west there was greater marine-influence and more stratigraphic complexity in the subsurface, to the west, as compared to the Black Hills outcrops. In the subsurface two distinctive reservoir sandstone beds within the Canyon Springs Sandstone Member fill the paleovalleys. These are the eolian lower Canyon Springs unit (LCS) and the estuarine upper Canyon Springs unit (UCS), separated by the marine {open_quotes}Limestone Marker{close_quotes} and estuarine {open_quotes}Brown Shale{close_quotes}. The LCS and UCS contain significant proven hydrocarbon reservoirs in Wyoming (about 500 MMBO in-place in 9 fields, 188 MMBO produced through 1993) and are prospective in western South Dakota, western Nebraska and northern Colorado. Also prospective is the Callovian-age Hulett Sandstone Member which consists of multiple prograding shoreface to foreshore parasequences, as interpreted from the Red Canyon locality. Petrographic, outcrop and subsurface studies demonstrate the viability of both the Canyon Springs Sandstone and Hulett Sandstone members as superior hydrocarbon reservoirs in both stratigraphic and structural traps. Examples of fields with hydrocarbon production from the Canyon Springs in paleovalleys include Lance Creek field (56 MMBO produced) and the more recently discovered Red Bird field (300 MBO produced), both in Niobrara County, Wyoming.

  1. Characterization and mischaracterization of authigenic magnesium-bearing minerals: Examples from Norphlet Sandstone, Alabama, Florida, and Mississippi

    Microsoft Academic Search

    1993-01-01

    Jurassic Norphlet sandstones are significant gas, condensate, and carbon dioxide reservoirs in the eastern Gulf Coast region. Diagenetic factors affecting the quality of these reservoirs are variable at microscopic to megascopic scales. Major authigenic components of the reservoirs include quartz, albite, K-feldspar, a variety of carbonate minerals, anhydrite, pyrite, illite, and chlorite; minor components include zeolite, tourmaline, apatite, and anatase.

  2. Naturally weathered feldspar surfaces in the Navajo Sandstone aquifer, Black Mesa, Arizona: Electron microscopic characterization

    E-print Network

    Zhu, Chen

    emission gun scanning electron microscope (FEG- SEM). Here, we report the first HRTEM observation of a 10: Electron microscopic characterization Chen Zhu a,*, David R. Veblen b , Alex E. Blum c , Stephen J. Chipera, was characterized with high-reso- lution transmission and analytical electron microscope (HRTEM-AEM) and field

  3. The Science Behind Jurassic Park

    NSDL National Science Digital Library

    "The Science Behind Jurassic Park" is an html document describing how world renowned paleontologist Jack Horner is using computers and CAT scan machines to peer inside 30 million year old dinosaur fossils.

  4. Risk Factors for Suicide Attempts among Navajo Adolescents.

    ERIC Educational Resources Information Center

    Grossman, David C.; And Others

    1991-01-01

    Examines risk factors for adolescent suicide among Navajos by comparing survey responses of students having attempted suicide with those of other students. A history of mental health problems, alienation from family and community, and having a friend commit suicide put students at a higher risk for suicide. (CJS)

  5. The Man from South: Reconsidering Navajo Students' Stories.

    ERIC Educational Resources Information Center

    Benjamin, Rebecca

    1995-01-01

    Analyzes the structural and thematic elements of three stories written by a sixth-grade Navajo girl to challenge the notion that a linear pattern of growth is followed by all children as they learn to write stories. The results question the assumption that certain kinds of narratives and their American Indian authors are less able or less…

  6. Prevalence of Hepatitis A Virus Antibody Among Navajo School Children.

    ERIC Educational Resources Information Center

    Williams, Robert

    1986-01-01

    A serologic investigation of prevalence of immunity to hepatitis A (anti-HAV) was conducted in a rural school adjacent to a Navajo reservation in New Mexico. The results show rates of anti-HAV that are the highest reported at the ages tested in any subpopulation in the United States, comparable only with those in developing countries. (KH)

  7. The Navajo and Hopi Dispute over Land and Life.

    ERIC Educational Resources Information Center

    Kammer, Jerry

    1979-01-01

    The paper outlines the history of the long-standing dispute over land in Arizona co-owned by the Navajo and Hopi. It details the confusing history and predicted effects of related governmental action and legislation and describes the position of important personalities on all sides of the issue. (SB)

  8. Geohydrology and effects of water use in the Black Mesa area, Navajo and Hopi Indian Reservations, Arizona

    USGS Publications Warehouse

    Eychaner, James H.

    1981-01-01

    The main source of water in the 5,400-square-mile Black Mesa area is the N aquifer, which consists of the Navajo Sandstone and underlying Kayenta Formation and Wingate Sandstone. Water is under confined conditions in the central 3,300 square miles. Transmissivity is less than 1,000 feet squared per day. Storage coefficient is less than 0.0004 in the confined part of the aquifer and at least 0.1 in the unconfined part. Recharge is about 13,000 acre-feet per year, and storage at equilibrium, which was before 1965, was at least 180 million acre-feet. Ground-water withdrawals were less than 400 acre-feet per year before 1970 and increased to 5,300 acre-feet per year 1976-1979. By 1980, municipal-supply pumpage is expected to exceed that for a coal-slurry pipeline. Water levels have declined throughout the confined part of the aquifer. Decline of more than 100 feet was calculated for an area of 200 square miles through 1979 and was projected for 440 square miles through 2001. In the unconfined part, project declines averaged less than 1 foot. If pumping for coal slurry stopped, most of the decline would recover within 10 years. (USGS)

  9. Ages of zircons from Jurassic sediments of Bluefish River slope, NWT Canada, and the possible age of kimberlite activity on the Lena West property

    Microsoft Academic Search

    A. M. Agashev; S. S. Kuligin; Y. Orihashi; N. P. Pokhilenko; M. A. Vavilov; D. Clarke

    2008-01-01

    This work is based on a study of 30 zircons extracted from the heavy mineral fraction of a sedimentary rock sample with anomalously high contents of well-preserved kimberlite indicator minerals (KIM). The sample was taken from the basal horizon of Jurassic?Cretaceous sandstones on the slope of Bluefish River valley. The Bluefish River, located in the Northwest Territories (Canada) north of

  10. Promotion of a Healthy Weight Among Navajo Nation Women.infant and Children Families

    Microsoft Academic Search

    V. Browning; D. McGuire

    1996-01-01

    LEARNING OUTCOME: To identify three activities to use with paraprofessionals in promoting a healthy weight for children enrolled in the Navajo Nation Women, Infant and Children (WIC)programHigh weight-for-height (>95th percentile) has increased over the last twelve years in the Navajo Nation's infants and children. Out of 28,772 records examined by the 1994 CDC Pediatric Nutrition Surveillance System for the Navajo

  11. Rock Point, A Navajo Way to Go to School: A Valediction

    Microsoft Academic Search

    Agnes Holm; Wayne Holm

    1990-01-01

    Roughly two-thirds of school-age Navajo children now attend public schools; roughly a quarter still attend federal schools. Since the mid- 1950s, the federal government has put large amounts of money into effecting a shift on the Navajo Reservation from smaller one-community federal schools to larger multicommunity public schools on the Navajo Reservation. The federal schools that remain have become multicommunity

  12. Uranium ore rolls in Westwater Canyon sandstone, San Juan Basin, New Mexico

    Microsoft Academic Search

    1980-01-01

    Recent relatively deep uranium-exploration drilling in the Nose Rock area, San Juan Basin, McKinley County, New Mexico, has resulted in the discovery of previously unrecognized uranium ore rolls in gray, unoxidized Westwater Canyon Sandstone of the Morrison Formation. Both the Nose Rock ores and the primary Ambrosia Lake uranium ores were emplaced during the Late Jurassic-Early Cretaceous erosional interval under

  13. Implications of an eolian sandstone unit of Basal Morrison Formation, central Wyoming

    Microsoft Academic Search

    D. D. Weed; C. F. Vondra

    1987-01-01

    A laterally discontinuous fine-grained quartzarenite occurs at the base of the Upper Jurassic Morrison Formation in the southern Big Horn and Powder River basins and in the Wind River basin. The sandstone unit is interpreted to be an eolianite. Evidence for this includes high-angle (20-35°), medium to large-scale planar cross-beds that are tangential at the base, inversely graded foresets, and

  14. Promise made: The Navajo indian irrigation project and water politics in the American West. Doctoral thesis

    SciTech Connect

    Jacobsen, J.E.

    1989-01-01

    According to the 1962 legislation by which the U.S. Congress authorized the Navajo Indian Irrigation Project (NIIP), a federal reclamation project on the Navajo Reservation in northwest New Mexico, it was to bring economic development to the Navajo Tribe in the form of 18,000 jobs on family farms and related enterprises, all in 14 years. The project is today just over half completed, it is a single corporate agribusiness that employs a few hundred Navajo during the peak harvest season, and there are pressures to reduce the size of the project.

  15. A Jurassic mammal from South America

    Microsoft Academic Search

    Oliver W. M. Rauhut; Thomas Martin; Edgardo Ortiz-Jaureguizar; Pablo Puerta

    2002-01-01

    The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and

  16. Lichen on Sandstone

    USGS Multimedia Gallery

    Lichen on sandstone in Pine Creek Canyon. Lichen is a composite organism made up of algae and fungi, which form a symbiotic relationship. Pine Creek Canyon is a remnant ecosystem of loblolly pines. A remnant ecosystem is the last vestige of an ecosystem type that used to be more widespred. Red Roc...

  17. Aquia Creek Sandstone

    USGS Multimedia Gallery

    This Aquia Creek Sandstone originated from a quarry about 40 miles south of Washington, D.C., in Stafford County, Va. This type of stone was used in the construction of many of D.C.'s most famous landmarks, including the White House and the U.S. Capitol building....

  18. Sand and sandstone

    SciTech Connect

    Pettijohn, F.J.; Potter, P.E.; Siever, R.

    1987-01-01

    Here is a new, second edition of a classical textbook in sedimentology, petrology, and petrography of sand and sandstones. It has been extensively revised and updated, including: new techniques and their utility; new literature; new illustrations; new, explicitly stated problems for the student; and a wider scope.

  19. Geologic map of the Winslow 30’ × 60’ quadrangle, Coconino and Navajo Counties, northern Arizona

    USGS Publications Warehouse

    Billingsley, George H.; Block, Debra; Redsteer, Margaret Hiza

    2013-01-01

    The Winslow 30’ × 60’ quadrangle encompasses approximately 5,018 km2 (1,960 mi2) within Coconino and Navajo Counties of northern Arizona. It is characterized by gently dipping Paleozoic and Mesozoic strata that dip 1° to 2° northeastward in the southwestern part of the quadrangle and become nearly flat-lying in the northeastern part of the quadrangle. In the northeastern part, a shallow Cenozoic erosional basin developed about 20 million years ago, which subsequently was filled with flat-lying Miocene and Pliocene lacustrine sediments of the Bidahochi Formation, as well as associated volcanic rocks of the Hopi Buttes Volcanic Field. The lacustrine sediments and volcanic rocks unconformably overlie Triassic, Jurassic, and Cretaceous strata. Beginning about early Pliocene time, the Little Colorado River and its tributaries began to remove large volumes of Paleozoic and Mesozoic bedrock from the map area. This erosional development has continued through Pleistocene and Holocene time. Fluvial sediments accumulated episodically throughout this erosional cycle, as indicated by isolated Pliocene(?) and Pleistocene Little Colorado River terrace-gravel deposits on Tucker Mesa and Toltec Divide west of Winslow and younger terrace-gravel deposits along the margins of the Little Colorado River Valley. These gravel deposits suggest that the ancestral Little Colorado River and its valley has eroded and migrated northeastward toward its present location and largely parallels the strike of the Chinle Formation. Today, the Little Colorado River meanders within a 5-km (3-mi) wide valley between Winslow and Leupp, where soft strata of the Chinle Formation is mostly covered by an unknown thickness of Holocene flood-plain deposits. In modern times, the Little Colorado River channel has changed its position as much as a 1.5 km (1 mi) during flood events, but for much of the year the channel is a dry river bed. Surficial alluvial and eolian deposits cover extensive parts of the bedrock outcrops over the entire Winslow quadrangle.

  20. Middle Jurassic strata link Wallowa, Olds Ferry, and Izee terranes in the accreted Blue Mountains island arc, northeastern Oregon

    SciTech Connect

    White, J.D.L. (Dalhousie Univ., Halifax, Nova Scotia (Canada)); Vallier, T. (Geological Survey, Menlo Park, CA (United States)); Stanley, G.D. Jr. (Univ. of Montana, Missoula (United States)); Ash, S.R. (Weber State Univ., Odgen, UT (United States)); White, D.L.

    1992-08-01

    Middle Jurassic strata atop the Wallowa terrane in northeastern Oregon link the Wallowa, Izee, and Olds Ferry terranes as related elements of a single long-lived and complex oceanic feature, the Blue Mountains island arc. Middle Jurassic strata in the Wallowa terrane include a dacitic ash-flow deposit and contain fossil corals and bivalves of North American affinity. Plant fossils in fluvial sandstones support a Jurassic age and indicate a seasonal temperate climate. Corals in a transgressive sequence traditionally overlying the fluvial units are of Bajocian age and are closely related to endemic varieties of the Western Interior embayment. They are unlike Middle Jurassic corals in other Cordilleran terranes; their presence suggests that the Blue Mountains island arc first approached the North American craton at high paleolatitudes in Middle Jurassic time. The authors consider the Bajocian marine strata and underlying fluvial volcaniclastic units to be a basin-margin equivalent of the Izee terrane, a largely Middle Jurassic (Bajocian) succession of basinal volcaniclastic and volcanic rocks known to overlie the Olds Ferry and Baker terranes.

  1. Coping with arsenic-based pesticides on Dine (Navajo) textiles

    NASA Astrophysics Data System (ADS)

    Anderson, Jae R.

    Arsenic-based pesticide residues have been detected on Arizona State Museum's (ASM) Dine (Navajo) textile collection using a handheld portable X-ray (pXRF) spectrometer. The removal of this toxic pesticide from historic textiles in museums collections is necessary to reduce potential health risks to Native American communities, museum professionals, and visitors. The research objective was divided into three interconnected stages: (1) empirically calibrate the pXRF instrument for arsenic contaminated cotton and wool textiles; (2) engineer an aqueous washing treatment exploring the effects of time, temperature, agitation, and pH conditions to efficiently remove arsenic from wool textiles while minimizing damage to the structure and properties of the textile; (3) demonstrate the devised aqueous washing treatment method on three historic Navajo textiles known to have arsenic-based pesticide residues. The preliminary results removed 96% of arsenic from a high arsenic concentration (~1000 ppm) textile opposed to minimal change for low arsenic concentration textiles (<100 ppm).

  2. The Lowell Observatory Navajo-Hopi Astronomy Outreach Program

    NASA Astrophysics Data System (ADS)

    Herrmann, K. A.; Hunter, D. A.; Bosh, A. S.; Johnson, M.; Schindler, K.

    2012-08-01

    We present an overview of the Lowell Observatory Navajo-Hopi Astronomy Outreach Program, which is modeled after the ASP's Project ASTRO (Richter & Fraknoi 1994). Since 1996, our missions have been (1) to use the inherent excitement about the night sky to help teachers get Navajo and Hopi students excited about science and education, and (2) to help teachers of Navajo and Hopi students learn about astronomy and hands-on activities so that they will be better able to incorporate astronomy in their classrooms. Lowell astronomers pair up for a school year with an elementary or middle school (5th-8th grade) teacher and make numerous visits to their teachers' classes, partnering with the educators in leading discussions linked with hands-on activities. Lowell staff also work with educators and amateur astronomers to offer evening star parties that involve the family members of the students as well as the general community. Toward the end of the school year, teachers bring their classes to Lowell Observatory. The classes spend some time exploring the Steele Visitor Center and participating in tours and programs. They also voyage to Lowell's research facility in the evening to observe at two of Lowell's research telescopes. Furthermore, we offer biennial teacher workshops in Flagstaff to provide teachers with tools, curricula materials, and personalized training so that they are able to include astronomy in their classrooms. We also work with tribal educators to incorporate traditional astronomical knowledge. Funding for the program comes from many different sources.

  3. Palaeoenvironmental and sequence stratigraphic analyses of the Jurassic Datta Formation, Salt Range, Pakistan

    NASA Astrophysics Data System (ADS)

    Iqbal, Shahid; Jan, Irfan U.; Akhter, M. Gulraiz; Bibi, Mehwish

    2015-06-01

    The Lower Jurassic Datta Formation, western Salt Range, Pakistan, comprises three facies associations: (1) channel belt facies association (CBFA), (2) channel margin, and overbank facies association (CMOFA), and (3) lagoonal facies association (LFA). A cyclic fining-upward trend in the succession is represented by basal quartzose conglomerate/pebbly sandstone, through coarse to fine quartzose sandstone to siltstone and shales/claystone, which contains some carbonate accumulation. Two prominent depositional sequences are recognized in the Datta Formation with the lower high and upper low magnitude cycles. The Datta Formation thus represents a thick sedimentary succession and in the study area, i.e., western Salt Range, mainly channel belt, flood plain and/or delta top facies are exposed. The palaeocurrent analysis shows that the source area with acidic plutonic rocks laid to S-SE in the Indian shield, aravalies or older sedimentary rocks of the Indus Basin (i.e., Khewra, Tobra and Warchha formations). A tentative stratigraphic correlation of the Datta Formation with the lower Jurassic Lathi Formation, India invites further work in parts of India, which will elaborate the extent of the Datta Formation in the Greater Indian peninsula and develop palaeogeographic setting for this Lower Jurassic deltaic rock unit.

  4. 25 CFR 161.102 - What notifications are required that tribal laws apply to grazing permits on the Navajo...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...are required that tribal laws apply to grazing permits on the Navajo Partitioned Lands...LAND AND WATER NAVAJO PARTITIONED LANDS GRAZING PERMITS Tribal Policies and Laws Pertaining...are required that tribal laws apply to grazing permits on the Navajo Partitioned...

  5. Survey of Navajo Community Studies, 1936-1974. Lake Powell Research Project Bulletin Number 6, March 1975.

    ERIC Educational Resources Information Center

    Henderson, Eric B.; Levy, Jerrold E.

    Extant Navajo community studies conducted since the 1930's were surveyed. Data for selected social, economic, and demographic variables as reported in these studies were compared. Each community study was placed in one of three geographic classifications: western Navajo, eastern Navajo, and off-reservation. Each on-reservation area was subdivided…

  6. Triassic and Jurassic-Cretaceous deposits in the Western Chukotka: geodynamic implications, provenance studies and deformation

    NASA Astrophysics Data System (ADS)

    Tuchkova, M.

    2012-04-01

    Studied region is situated in western Chukotka, in Northeast Russia. We examine the part of Chukotka microplate, the key element in the evolution of the Amerasian basin. The Triassic of Chukotka is represented by up to 5 km of deposits. Triassic terrigeneous deposits consist of three different complexes: Lower-Middle Triassic, Upper Triassic Carnian, and Norian. All the complexes are represented by rhythmic intercalation of sandstones, siltstones and mudstones. Clastic material was carried by large rivers, possessing large reservoir on neighbouring continent. Progradation of delta system in deeper regions is observed. During the Triassic, sedimentation was represented by continental slope progradation. Petrographic study of mineral composition has established the sandstones as graywackes and lithic arenites, according to Pettijohn classification (1981). Sandstones with clasts of rock fragments of lower metamorphic grade rocks dominate at the base of Triassic deposits, sandstones with fragments of higher grade metamorphic rocks dominate in the Later Triassic deposits. This different shows that the Triassic represents an unroofing sequence sours of erosional processes that produced the clastic material eroded more deeply buried rocks through time. Detrital zircons from Triassic sedimentary rocks were collected for constain its paleogeographic links to source terranes. Zircons populations from these three samples are very similar, and youngest zircon ages show peaks at 236-255 Ma. Besides, we are dating the 9 samples for K-Ar and Rb-Sr methods. Data are similar and show 200-204 Ma, and we suppose that this isotopic data indicate the age of first stage of deformation in Chukotka's basin. The Jurassic-Cretaceous of Chukotka is represented by up to 3 km of deposits. The sedimentary complexes are enriched by organic matter, and fresh clastic materials. Fragments of shales, sometimes laminated or cleaved are their indicator constituents. Sandstones are arkosic. The chemical composition and mineral assemblages are different from Triassic sandstone. Besides, Upper Jurassic sandstones differs from Cretaceous sandstones. Our investigations indicate that Triassic, Upper Jurassic, and Lower Cretaceous sedimentary basins were related to different source provenance. In the paper will discuss the sedimentation, provenances, and geodynamic settings of Triassic and Jurassic-Cretaceous deposits. The studied part of western Chukotka is composed of variably deformed, folded and cleaved rhythmic deposits. Widely distributed and intensively deformed Triassic sequences (Tuchkova et al., 2007) and J-K units both intruded by Aptian-Albian postcollisional plutons and dikes (Katkov et al., 2010). Collisional-related fabric and subsequent granitoids are complicated by small-scale latest normal faults, in particular related to the westernmost segment of South Chukchi (Hope) basin development in Upper Cretaceous (?)-Cenozoic. Intensity of the compressional deformation of Jurassic-Cretaceous rocks is significantly less than in Triassic sequence. Work was supported by RBRR projects 11-05-00787, 11-05-00074, Scientific school # NSh-5177.2012.5, kontrakts No. 04.740.11.0190, and 01/14/20/11.

  7. The Ethical Issues in Uranium Mining Research in the Navajo Nation

    Microsoft Academic Search

    BINDU PANIKKAR; DOUG BRUGGE

    2007-01-01

    We explore the experience of Navajo communities living under the shadow of nuclear age fallout who were subjects of five decades of research. In this historical analysis of public health (epidemiological) research conducted in the Navajo lands since the inception of uranium mining from the 1950s untill the end of the 20th century, we analyze the successes and failures in

  8. Teenage Mothering on the Navajo Reservation: An Examination of Intergenerational Perceptions and Beliefs.

    ERIC Educational Resources Information Center

    Dalla, Rochelle L.; Gamble, Wendy C.

    2001-01-01

    A study examined attitudes towards teenage motherhood among 25 Navajo reservation residents, including 8 teenage mothers, their mothers, and 4 teenage fathers. Findings indicate that teenage parenting was discouraged despite the matrilineal nature of Navajo society, men were frequently absent from family life, single maternity was preferable to…

  9. Ethnicity and Gender in the Global Periphery: A Comparison of Basotho and Navajo Women.

    ERIC Educational Resources Information Center

    Harris, Betty J.

    1990-01-01

    Compares the economic status of Navajo and Basotho (Lesotho) female weavers, both indigenous groups in peripheral areas. Examines internal mechanisms for the incorporation of Basotho and Navajo societies into the world economic system, and implications for women's status in the labor force in each case. Contains 36 references. (SV)

  10. No One Remembers a Winter Like This: A Year at the Navajo Agency, 1882-1883.

    ERIC Educational Resources Information Center

    Lockard, Louise

    This paper documents a single year in the history of Navajo education from the perspective of the Navajo Agent Dennis Matthew Riordan. It draws on Riordan's correspondence, 1882-83, with the Secretary of the Interior, with Captain Richard Henry Pratt at the Carlisle Indian Industrial School, and with his brother. In December 1882, Riordan arrived…

  11. A Dine (Navajo) Perspective on Self-Determination: An Exposition of an Egalitarian Place

    ERIC Educational Resources Information Center

    Manuelito, Kathryn D.

    2006-01-01

    Worldview of any culture and society is explicated through epistemological principles that frame the way one sees the world. Dine (Navajo) worldview is explicated through epistemology that has been rejected and debased by the dominant society since contact centuries ago. However, enduring powerful Dine (Navajo) worldview persists in contemporary…

  12. The Circulation and Silence of Weaving Knowledge in Contemporary Navajo Life

    ERIC Educational Resources Information Center

    Yohe, Jill Ahlberg

    2012-01-01

    This article draws upon ethnographic fieldwork within a Navajo community to illustrate how weaving knowledge and practices shape contemporary notions of community identity and belonging. The ongoing exchange of Navajo weaving taboos and the careful management of weaving teachings offers community members various opportunities to share and keep…

  13. Peoples, Resources, and Lifestyles: The Hopi-Navajo Land Partition Act of 1974.

    ERIC Educational Resources Information Center

    Goodman, James M.

    The Hopi and Navajo tribes have been engaged in a long and complex land dispute within the 1882 Executive Order Area (Joint Use Area) of Arizona, an area recently redefined via the Partition Act of 1974 which calls for the relocation of 5 to 10,000 Navajos. This rearrangement of political domain threatens to influence the future management and…

  14. Depth and thickness of selected units in Upper Permian, Upper Jurassic, and Lower Cretaceous rocks in southwestern Kansas

    USGS Publications Warehouse

    Kume, Jack; Spinazola, Joseph M.

    1984-01-01

    As ground-water reserves decline in the Ogallala aquifer in an area of about 17,400 square miles in 26 counties of southwestern Kansas, sandstone aquifers in underlying Upper Jurassic and Lower and Upper Cretaceous rocks may be developed to supplement or replace the Ogallala as a source of water for some uses. Maps show that depths from land surface to Upper Permian rocks range from 0 at the outcrop to over 2,100 feet, depths to Upper Jurassic rocks ran from 0 at the outcrop to about 2,000 feet, depths to the Cheyenne Sandstone range from about 150 to about 1 ,950 feet, and depths to the Dakota Formation range from 0 at the outcrop to about 1,650 feet. Additional maps show that the thickness of Upper Jurassic rocks, where present, ranges from less than 50 feet to about 250 feet, the thickness of the Cheyenne Sandstone, where present, ranges from about 20 feet to about 250 feet, and the thickness of the Dakota Formation, where present, ranges from about 60 feet to about 460 feet. (USGS)

  15. The Navajo Atlas: Environments, Resources, People, and History of the Dine Bikeyah. The Civilization of the American Indian Series, Volume 157.

    ERIC Educational Resources Information Center

    Goodman, James M.

    The 48 maps and descriptive narratives in this atlas of the Navajo Reservation are divided into six sections. Part I, Navajo Country, displays Navajo land in relationship to the United States and the region, and becomes more detailed to place locations within the Dine Bikeyah, or Navajo Land, including administrative and political subdivisions of…

  16. The Rock Point Experience: A Longitudinal Study of a Navajo School Program (Saad Naaki Bee Na'nitin). Bilingual Education Series: 8. Papers in Applied Linguistics.

    ERIC Educational Resources Information Center

    Rosier, Paul; Holm, Wayne

    Conducted from 1975 to 1977, this reading achievement study examined the effects of initial literacy in Navajo on later reading in English and the effects of initial arithmetic instruction in Navajo on later arithmetic instruction in English by comparing two groups of Navajo students, both of whom began school essentially monolingual in Navajo

  17. Case hardening of sandstone

    NASA Astrophysics Data System (ADS)

    Conca, James L.; Rossman, George R.

    1982-10-01

    The case-hardened crust developed on the Aztec Sandstone in the Valley of Fire, Nevada, has been characterized by a variety of techniques, including electron microscopy and infrared spectroscopy. The case-hardened crust consists mainly of host rock, with a fine-grained cement and wind-deposited kaolinite. The cement is usually calcite, but in some cases the hydrated calcium borate, colemanite, was found to be the case-hardening cement.

  18. Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon Group, northern Arizona)

    NASA Astrophysics Data System (ADS)

    Padian, Kevin

    1989-05-01

    The Glen Canyon Group (Moenave, Wingate, Kayenta and Navajo Formations) of northern Arizona represents an extensive outcrop of early Mesozoic age terrestrial sediments. The age of these formations has long been disputed because independent stratigraphic data from marine tie-ins, paleobotanical and palynological evidence, and radiometric calibrations have been scanty or absent. The fauna of the Kayenta Formation in particular has been problematic because it has appeared to contain both typical Late Triassic and Early Jurassic taxa Here I report that the principal evidence for Late Triassic taxa, dermal scutes previously assigned to an aetosaur, in fact belongs to the thyreophoran ornithischian dinosaur Scelidosaurus, previously known only as a washed-in form found in marine sediments in the Early Jurassic of England. The presence of this dinosaur represents the first vertebrate biostratigraphic tie-in of the Glen Canyon Group horizons with reliably dated marine deposits in Europe. Together with revised systematic assessments of other vertebrates and independent evidence from fossil pollen, it supports an Early Jurassic age for the Kayenta Formation and most or all of the Glen Canyon Group.

  19. Identifying provenance-specific features of detrital heavy mineral assemblages in sandstones

    NASA Astrophysics Data System (ADS)

    Morton, Andrew C.; Hallsworth, Claire

    1994-05-01

    The composition of heavy mineral assemblages in sandstones may be heavily influenced by processes operating during transport, deposition and diagenesis. As a consequence, conventional heavy mineral data may not be a reliable guide to the nature of sediment source material. Certain features of heavy mineral suites, however, are inherited directly from the source area without significant modification, such as the varietal characteristics of individual mineral species. This paper describes an alternative approach to varietal studies that concentrates on relative abundances of minerals that are stable during diagenesis and have similar hydraulic behaviour. Ratios of apatite to tourmaline, TiO 2 minerals to zircon, monazite to zircon, and chrome spinel to zircon provide a good reflection of the source rock characteristics, because they are comparatively immune to alteration during the sedimentary cycle. These ratios are described as index values (ATi, RZi, MZi and CZi, respectively). This approach avoids some of the practical problems associated with varietal studies, such as the need to make subjective decisions about mineral properties or to use advanced analytical techniques that may not be accessible to the analyst. It also makes use of more components of the heavy mineral suite and thus provides a more balanced view of provenance characteristics. The use of these ratios is illustrated with examples from Upper Jurassic sandstones in the Outer Moray Firth area of the UK continental shelf and Triassic sandstones from onshore and offshore UK. Heavy mineral indices, notably ATi and MZi, show marked variations in Upper Jurassic Piper sandstones of the Outer Moray Firth. Main Piper sandstones have lower ATi and MZi values compared with Supra Piper sandstones, indicating significant stratigraphic evolution of provenance. The UK Triassic shows major regional variations in a number of index values, including ATi, MZi and CZi, demonstrating that sediment was supplied from several distinct source regions. This indicates a need for some modification of existing palaeogeographic models for the UK Triassic.

  20. Late Jurassic weather forecast, Four Corners area: Dry, hot, and partly sunny

    SciTech Connect

    Turner-Peterson, C.E.; Fishman, N.S. (Geological Survey, Denver, CO (USA))

    1989-09-01

    Interfingering between members of the Upper Jurassic Morrison Formation and inferences based on their various environments of deposition permit interpretation of a persistent paleoclimate during the Late Jurassic in the Colorado Plateau region. Paleoclimate interpretation is based on evaporites in the Tidwell member, at the base of the Morrison; eolian deposits in the Recapture and Bluff Sandstone members; and saline, alkaline-lake deposits (which indicate high evaporation rates) in the Brushy Basin member at the top of the Morrison. Interfingering of these members with all other members of the Morrison Formation implies that a semiarid to arid climate was likely throughout Morrison time. The semiarid to arid interpretation is consistent with the global climatic zone inferred from the paleogeographic/paleotectonic setting. The Four Corners area during the Late Jurassic was in the middle latitudes of the Northern Hemisphere and thus was affected by prevailing westerly winds. A magmatic arc located several hundred kilometers to the west of the Morrison depositional basin may have caused a broad rain-shadow effect, which contributed to a dry continental climate downwind. A typical Late Jurassic day in the Four Corners area is predicted to have been hot and dry, although seasonally heavy rains probably fed intermittent streams that transported sediments into the region. Explosive eruptions of silicic volcanic ash may have darkened the skies episodically, and thus partly sunny would have been a conservative forecast.

  1. Sandstone-body and shale-body dimensions in a braided fluvial system: Salt wash sandstone member (Morrison formation), Garfield County, Utah

    USGS Publications Warehouse

    Robinson, J.W.; McCabea, P.J.

    1997-01-01

    Excellent three-dimensional exposures of the Upper Jurassic Salt Wash Sandstone Member of the Morrison Formation in the Henry Mountains area of southern Utah allow measurement of the thickness and width of fluvial sandstone and shale bodies from extensive photomosaics. The Salt Wash Sandstone Member is composed of fluvial channel fill, abandoned channel fill, and overbank/flood-plain strata that were deposited on a broad alluvial plain of low-sinuosity, sandy, braided streams flowing northeast. A hierarchy of sandstone and shale bodies in the Salt Wash Sandstone Member includes, in ascending order, trough cross-bedding, fining-upward units/mudstone intraclast conglomerates, singlestory sandstone bodies/basal conglomerate, abandoned channel fill, multistory sandstone bodies, and overbank/flood-plain heterolithic strata. Trough cross-beds have an average width:thickness ratio (W:T) of 8.5:1 in the lower interval of the Salt Wash Sandstone Member and 10.4:1 in the upper interval. Fining-upward units are 0.5-3.0 m thick and 3-11 m wide. Single-story sandstone bodies in the upper interval are wider and thicker than their counterparts in the lower interval, based on average W:T, linear regression analysis, and cumulative relative frequency graphs. Multistory sandstone bodies are composed of two to eight stories, range up to 30 m thick and over 1500 m wide (W:T > 50:1), and are also larger in the upper interval. Heterolithic units between sandstone bodies include abandoned channel fill (W:T = 33:1) and overbank/flood-plain deposits (W:T = 70:1). Understanding W:T ratios from the component parts of an ancient, sandy, braided stream deposit can be applied in several ways to similar strata in other basins; for example, to (1) determine the width of a unit when only the thickness is known, (2) create correlation guidelines and maximum correlation lengths, (3) aid in interpreting the controls on fluvial architecture, and (4) place additional constraints on input variables to stratigraphie and fluid-flow modeling. The usefulness of these types of data demonstrates the need to develop more data sets from other depositional environments.

  2. Facies architecture of tidal shelf sandstone ridge: Tocito sandstone

    SciTech Connect

    Riley, G.W.; Nummedal, D. (Louisiana State Univ., Baton Rouge (USA))

    1989-09-01

    The lithofacies architecture of a single Tocito Sandstone Lentil has been documented in outcrops near the Hogback oil field west of Farmington with a very detailed outcrop study. This isolated Tocito sand body is composed of a three-tiered hierarchy of linear ridge elements. The large-scale Tocito Sandstone Lentil is approximately 5 km wide, 30 km long, and up to 16 m thick. The lentil is composed of at least three smaller scale ridges, which are up to 1 km wide, of unknown length, and up to 16 m thick. The small-scale ridges are arranged such that each new ridge accreted on the landward margin of the previous ridge. These smaller scale ridges consist of an ordered arrangement of four basic lithofacies: (1) burrowed, muddy sandstone, (2) interbedded clean and muddy sandstone, (3) cross-bedded sandstone, and (4) ripple-bedded sandstone. burrowed, muddy sandstone is found at the base of the small-scale ridges, is laterally extensive, and is interpreted as forming downcurrent from the most active portion of the ridge. The cross-bedded sandstone forms ribbon-shaped sand bodies elongate in the direction of ridge elongation. Typically the sand ribbons are 100-300 m wide, 2-4 m thick, and up to 1 km long. Usually two or more combine to form a small-scale ridge. The interbedded sandstone is found above the cross-bedded lithofacies as well as between the sand ribbons. The ripple-bedded facies is always found at the top of the section and represents the waning stage of ridge growth. The resulting architecture is one of coalesced sand ribbons combining to form the small-scale ridges, and subsequently small-scale ridges accreting landward to form a composite Tocito Sandstone Lentil.

  3. Sandstone Spire in Capitol Reef

    USGS Multimedia Gallery

    A view of a sandstone spire in Capitol Reef National Park. This area, known as the Fruita, is made up of three primary layers. The bottom sandstone layer is known as the Moenkopi Formation and is about 245 million years old. The middle gray-green layer is known as the Chinle Formation and was laid d...

  4. Sandstone Cliffs in Capitol Reef

    USGS Multimedia Gallery

    Sandstone cliffs in Capitol Reef National Park. Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

  5. Sandstone Cliff in Capitol Reef

    USGS Multimedia Gallery

    A sandstone cliff in Capitol Reef National Park. Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

  6. Sandstone Monolith in Capitol Reef

    USGS Multimedia Gallery

    A sandstone monolith in Capitol Reef National Park. Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

  7. Navajo Coal Combustion and Respiratory Health Near Shiprock, New Mexico

    DOE PAGESBeta

    Bunnell, Joseph E.; Garcia, Linda V.; Furst, Jill M.; Lerch, Harry; Olea, Ricardo A.; Suitt, Stephen E.; Kolker, Allan

    2010-01-01

    Indoor air pollution has been identified as a major risk factor for acute and chronic respiratory diseases throughout the world. In the sovereign Navajo Nation, an American Indian reservation located in the Four Corners area of the USA, people burn coal in their homes for heat. To explore whether/how indoor coal combustion might contribute to poor respiratory health of residents, this study examined respiratory health data, identified household risk factors such as fuel and stove type and use, analyzed samples of locally used coal, and measured and characterized fine particulate airborne matter inside selected homes. In twenty-five percent of homesmore »surveyed coal was burned in stoves not designed for that fuel, and indoor air quality was frequently found to be of a level to raise concerns. The average winter 24-hourPM2.5concentration in 20 homes was 36.0??g/m3. This is the first time thatPM2.5has been quantified and characterized inside Navajo reservation residents' homes.« less

  8. Navajo Coal Combustion and Respiratory Health Near Shiprock, New Mexico

    PubMed Central

    Bunnell, Joseph E.; Garcia, Linda V.; Furst, Jill M.; Lerch, Harry; Olea, Ricardo A.; Suitt, Stephen E.; Kolker, Allan

    2010-01-01

    Indoor air pollution has been identified as a major risk factor for acute and chronic respiratory diseases throughout the world. In the sovereign Navajo Nation, an American Indian reservation located in the Four Corners area of the USA, people burn coal in their homes for heat. To explore whether/how indoor coal combustion might contribute to poor respiratory health of residents, this study examined respiratory health data, identified household risk factors such as fuel and stove type and use, analyzed samples of locally used coal, and measured and characterized fine particulate airborne matter inside selected homes. In twenty-five percent of homes surveyed coal was burned in stoves not designed for that fuel, and indoor air quality was frequently found to be of a level to raise concerns. The average winter 24-hour PM2.5 concentration in 20 homes was 36.0??g/m3. This is the first time that PM2.5 has been quantified and characterized inside Navajo reservation residents' homes. PMID:20671946

  9. The Ramah Navajo Child-to-Child Program.

    PubMed

    Lamarine, R J

    1985-01-01

    The international CHILD-to-child program, conceptualized by Dr. David Morley of the University of London, is based on the concept that children in developing nations act as caregivers, teachers, and health workers in their families and communities. The critical component in the program is the ability and willingness of children to become actively involved as care givers. CHILD-to-child is an action-oriented approach that draws upon a vast reservoir of similar programs that have been successful in over forty developing countries of the Third World. Similarities between the Ramah Navajo Community in New Mexico and many Third World nations served as a stimulus in the initiation and development of this project. The Ramah Navajo CHILD-to-child Health Education Project involved the development of a school health education curriculum that supported Native American children in a community-based effort to improve the quality of health care and the standard of living for their families. With funding from the U.S. Department of Education as a national demonstration project, a needs assessment was conducted and a seven-unit curriculum was developed. PMID:20841148

  10. Petrography and diagenesis of Eagle Mills sandstones, subsurface - Northeast Texas and southwest Arkansas

    SciTech Connect

    Dawson, W.C.; Callender, C.A. (Texaco, Houston, TX (United States))

    1991-03-01

    The Eagle Mills Formation (Triassic-Jurassic) has been penetrated by several deep wells (12,000 to 18,000 ft) in northeast Texas and southwest Arkansas. It consists of green, red, and pink conglomeratic lithic arenites and fine- to coarse-grained feldspathic arenites, interbedded with red and greenish gray shales and siltstones. Lithic arenites contain basalt, chert, quartzite, and dolomite rock fragments; plagioclase is the predominant feldspar. All Eagle Mills sandstones have low textural and mineralogic maturities. Eagle Mills red beds and associated intrusive igneous rocks (diabase and basalt dikes and sills) represent the fillings of grabens or rift basins that actively subsided during deposition (in alluvial, fluvial-deltaic, and lacustrine paleoenvironments). Eagle Mills lithic and feldspathic sandstones have undergone a complex diagenetic history, including chlorite cementation (pore linings and pore fillings), compaction, quartz and feldspar overgrowths, dolomite cementation, chloritization and albitization of detrital feldspars, local dissolution of framework grains (igneous lithics and feldspars), precipitation of kaolinite, late Fe-calcite cementation, and saddle dolomite formation. Cement mineralogies are strongly correlative with lithofacies. Lithic sandstones contain the highest frequency of chlorite cements, whereas feldspathic sandstones are preferentially cemented with carbonates and anhydrite; quartz and feldspar overgrowths are ubiquitous. The suite of authigenic minerals in Eagle Mills sandstones records progressive burial into a deep, high-temperature (120-150C), semiclosed, diagenetic regime.

  11. Rulers of the Jurassic Seas

    NSDL National Science Digital Library

    Motani, Ryosuke.

    2000-01-01

    Available free from Scientific American's Website, this article takes a thorough and fascinating look at the marine reptiles known as Ichthyosaurs that lived during the Mesozoic Era. The text covers recent discoveries about the evolution of Ichthyosaurs from land dwelling reptiles, including limb adaptations. Highlights of the article are special sections about ichthyosaur eyes and diet, and color illustrations and diagrams. The text contains hyperlinks to related pages (Britannica.com, Tree of Life, American Cetacean Society, etc.). "Rulers of the Jurassic Seas" is a good read for students of paleontology or marine science.

  12. Jurassic Park Institute: Dino Lab

    NSDL National Science Digital Library

    Created as a "science-based and educationally focused program," the Jurassic Park Institute (JPI) aims to provide "kids, families, educators and scientists with the ultimate resource for dinosaur learning and fun." As would be expected from a project of Universal Studios, the JPI Dino Lab Web site is packed with cool computer animation and other multimedia features. Visitors to this site become virtual dinosaur paleontologists, interpreting discoveries and solving problems along the way. Educators can register for JPI Dino Lab's free Teacher Resources, which includes lesson plans, assessment tools, and teaching strategy tips. This site is best accessed with a high-speed connection.

  13. 40 CFR 147.3400 - Navajo Indian lands-Class II wells.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...and 1 CFR part 51. Copies may be obtained or inspected at the Navajo Nation Environmental Protection Agency UIC Office, Old NAPA Auto Parts Building (Tribal Bldg. #S009-080), Highway 64, Shiprock, New Mexico 87420...

  14. 40 CFR 147.3400 - Navajo Indian lands-Class II wells.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...and 1 CFR part 51. Copies may be obtained or inspected at the Navajo Nation Environmental Protection Agency UIC Office, Old NAPA Auto Parts Building (Tribal Bldg. #S009-080), Highway 64, Shiprock, New Mexico 87420...

  15. 40 CFR 147.3400 - Navajo Indian lands-Class II wells.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...and 1 CFR part 51. Copies may be obtained or inspected at the Navajo Nation Environmental Protection Agency UIC Office, Old NAPA Auto Parts Building (Tribal Bldg. #S009-080), Highway 64, Shiprock, New Mexico 87420...

  16. Strategies for assessing EarlyMiddle (PliensbachianAalenian) Jurassic

    E-print Network

    cyclostratigraphy of the Jurassic Period. First, Jurassic geochronology is not well constrained, due to a generalStrategies for assessing Early­Middle (Pliensbachian­Aalenian) Jurassic cyclochronologies By Linda in stratigraphic constraints. These problems are particularly troublesome in the Early to Middle Jurassic cyclic

  17. Uranium Mining on the Navajo Indian Reservation: An Environmental Examination of the Process and Impact

    Microsoft Academic Search

    Caitlin A McElroy

    2006-01-01

    Uranium mining on the Navajo Reservation created an environmental justice disaster which has strangely helped bring the Navajo Nation to achieve considerable self-determination within the United States.\\u000aThe United States’ need for uranium to fuel the nuclear weapons and energy program brought the Atomic Energy Commission to establish an extensive mining operation on Southwestern edge of the Colorado Plateau. Many

  18. Solar membrane distillation: desalination for the Navajo Nation.

    PubMed

    Karanikola, Vasiliki; Corral, Andrea F; Mette, Patrick; Jiang, Hua; Arnoldand, Robert G; Ela, Wendell P

    2014-01-01

    Provision of clean water is among the most serious, long-term challenges in the world. To an ever increasing degree, sustainable water supply depends on the utilization of water of impaired initial quality. This is particularly true in developing nations and in water-stressed areas such as the American Southwest. One clear example is the Navajo Nation. The reservation covers 27,000 square miles, mainly in northeastern Arizona. Low population density coupled with water scarcity and impairment makes provision of clean water particularly challenging. The Navajos rely primarily on ground water, which is often present in deep aquifers or of brackish quality. Commonly, reverse osmosis (RO) is chosen to desalinate brackish ground water, since RO costs are competitive with those of thermal desalination, even for seawater applications. However, both conventional thermal distillation and RO are energy intensive, complex processes that discourage decentralized or rural implementation. In addition, both technologies demand technical experience for operation and maintenance, and are susceptible to scaling and fouling unless extensive feed pretreatment is employed. Membrane distillation (MD), driven by vapor pressure gradients, can potentially overcome many of these drawbacks. MD can operate using low-grade, sub-boiling sources of heat and does not require extensive operational experience. This presentation discusses a project on the Navajo Nation, Arizona (Native American tribal lands) that is designed to investigate and deploy an autonomous (off-grid) system to pump and treat brackish groundwater using solar energy. ?ench-scale, hollow fiber MD experiment results showed permeate water fluxes from 21 L/m2·d can be achieved with transmembrane temperature differences between 40 and 80?C. Tests run with various feed salt concentrations indicate that the permeate flux decreases only about 25% as the concentration increases from 0 to 14% (w/w), which is four times seawater salt concentration. The quality of the permeate water remains constant at about 1 mg/L regardless of the changes in the influent salt concentration. A nine-month MD field trial, using hollow fiber membranes and completely off-the-shelf components demonstrated that a scaled-up solar-driven MD system was practical and economically viable. Based on these results, a pilot scale unit will be constructed and deployed on the tribal lands. PMID:24552961

  19. Sandstone Formations in Capitol Reef

    USGS Multimedia Gallery

    Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

  20. Healthy gardens/healthy lives: Navajo perceptions of growing food locally to prevent diabetes and cancer.

    PubMed

    Lombard, Kevin A; Beresford, Shirley A A; Ornelas, India J; Topaha, Carmelita; Becenti, Tonia; Thomas, Dustin; Vela, Jaime G

    2014-03-01

    Poor access to nutritious foods, departure from traditional diets, and reduced physical activity are associated with a rise in type 2 diabetes and certain types of cancers among the Navajo. Diabetes in particular is of concern because of its increased prevalence among Navajo youth. Gardening can successfully address issues of poor availability of fruits and vegetables and offer many other social and health benefits. Our assessment aimed to determine Navajo attitudes about gardening and health in San Juan County, New Mexico. We conducted seven focus groups (including 31 people) to assess knowledge and attitudes related to gardening and uncover barriers and facilitators to participation in a garden project. Each group session was moderated by two Navajo students. Transcripts revealed that many Navajo are aware of adverse health issues that occur on the reservation, predominantly obesity and diabetes. Participants expressed a preference for educational approaches that incorporated cultural traditions, respect for elders, use of visual aids, and experiential learning. Several social and agronomic barriers to gardening were also mentioned. Results suggested a broad interest in promoting gardening especially to reduce the risk of diabetes with the added value of enhancing social capital in Navajo communities. PMID:23855020

  1. Navajo Generating Station and Clean-Energy Alternatives: Options for Renewables

    SciTech Connect

    Hurlbut, D. J.; Haase, S.; Turchi, C. S.; Burman, K.

    2012-06-01

    In January 2012, the National Renewable Energy Laboratory delivered to the Department of the Interior the first part of a study on Navajo Generating Station (Navajo GS) and the likely impacts of BART compliance options. That document establishes a comprehensive baseline for the analysis of clean energy alternatives, and their ability to achieve benefits similar to those that Navajo GS currently provides. This analysis is a supplement to NREL's January 2012 study. It provides a high level examination of several clean energy alternatives, based on the previous analysis. Each has particular characteristics affecting its relevance as an alternative to Navajo GS. It is assumed that the development of any alternative resource (or portfolio of resources) to replace all or a portion of Navajo GS would occur at the end of a staged transition plan designed to reduce economic disruption. We assume that replacing the federal government's 24.3% share of Navajo GS would be a cooperative responsibility of both the U.S. Bureau of Reclamation (USBR) and the Central Arizona Water Conservation District (CAWCD).

  2. Healthy Gardens/Healthy Lives: Navajo perceptions of growing food locally to prevent diabetes and cancer

    PubMed Central

    Beresford, Shirley A.A.; Ornelas, India; Topaha, Carmelita; Becenti, Tonia; Thomas, Dustin; Vela, Jaime G.

    2013-01-01

    Poor access to nutritious foods, departure from traditional diets, and reduced physical activity are associated with a rise in type-2 diabetes and certain types of cancers among the Navajo. Diabetes in particular is of concern because of its increased prevalence among Navajo youth. Gardening can successfully address issues of poor availability of fruits and vegetables and offer many other social and health benefits. Our assessment aimed to determine Navajo attitudes about gardening and health in San Juan County, New Mexico. We conducted seven focus groups (including 31 people) to assess knowledge and attitudes related to gardening, and uncover barriers and facilitators to participation in a garden project. Each group session was moderated by two Navajo students. Transcripts revealed that many Navajo are aware of adverse health issues, predominantly obesity and diabetes, which occur on the reservation. Participants expressed a preference for educational approaches that incorporated cultural traditions, respect for elders, use of visual aids and experiential learning. Several social and agronomic barriers to gardening were also mentioned. Results suggested a broad interest in promoting gardening especially to reduce the risk of diabetes with the added value of enhancing social capital in Navajo communities. PMID:23855020

  3. A Jurassic mammal from South America.

    PubMed

    Rauhut, Oliver W M; Martin, Thomas; Ortiz-Jaureguizar, Edgardo; Puerta, Pablo

    2002-03-14

    The Jurassic period is an important stage in early mammalian evolution, as it saw the first diversification of this group, leading to the stem lineages of monotremes and modern therian mammals. However, the fossil record of Jurassic mammals is extremely poor, particularly in the southern continents. Jurassic mammals from Gondwanaland are so far only known from Tanzania and Madagascar, and from trackway evidence from Argentina. Here we report a Jurassic mammal represented by a dentary, which is the first, to our knowledge, from South America. The tiny fossil from the Middle to Late Jurassic of Patagonia is a representative of the recently termed Australosphenida, a group of mammals from Gondwanaland that evolved tribosphenic molars convergently to the Northern Hemisphere Tribosphenida, and probably gave rise to the monotremes. Together with other mammalian evidence from the Southern Hemisphere, the discovery of this new mammal indicates that the Australosphenida had diversified and were widespread in Gondwanaland well before the end of the Jurassic, and that mammalian faunas from the Southern Hemisphere already showed a marked distinction from their northern counterparts by the Middle to Late Jurassic. PMID:11894091

  4. Jurassic sequence stratigraphy of the eastern Gulf Coastal Plain: Applications to hydrocarbon exploration

    SciTech Connect

    Tew, B.H.; Mancini, E.A.; Mink, R.M. (Geological Survey of Alabama, Tuscaloosa (United States))

    1991-03-01

    Based on regional stratigraphic and sedimentologic data, three unconformity-bounded depositional sequences associated with cycles of relative sea-level change and coastal onlap are recognized for Jurassic strata in the eastern Gulf Coastal Plain area. These sequences are designated, in ascending order, the LZAGC (Lower Zuni A Gulf Coast)-3.1, the LZAGC-4.1, and the LZAGC-4.2 sequences and include Callovian through Kimmeridgian Stage strata. An understanding of the relationship of Jurassic reservoirs to sequence stratigraphy can serve as an aid to hydrocarbon exploration in the eastern gulf area. The most extensive and productive Jurassic hydrocarbon reservoirs in the study area occur within the progradational, regressive highstand deposits of the LZAGC-3.1 and LZAGC-4.1 depositional sequences. For example, the majority of Norphlet sandstone reservoirs in the onshore and offshore Alabama area are interpreted to have accumulated in eolian dune, interdune, and wadi (fluvial) depositional environments, which occurred in association with the highstand regressive system of the LZAGC-3.1 sequence. The most important Smackover reservoirs generally consist of partially to completely dolomitized ooid and peloid packstones and grainstones in the upper portion of the unit. These reservoirs occur in subtidal to supratidal, shoaling-upward carbonate mudstone to grainstone cycles in the highstand regressive system of the LZAGC-4.1 sequence. In addition, minor reservoirs that are discontinuous and not well developed are associated with the shelf margin and transgressive systems of the LZAGC-4.1.

  5. Lower Cretaceous and Upper Jurassic oil reservoirs of the updip basement structure play: Southwest Alabama

    SciTech Connect

    Mink, R.M.; Mancini, E.A. [Geological Survey of Alabama, Tuscaloosa, AL (United States)

    1995-10-01

    Exploration for Lower Cretaceous and Upper Jurassic reservoirs associated with updip basement structures currently is the most active exploratory oil play in Alabama. High initial flow rates, on the order of hundreds to thousands of barrels of oil per day, are commonly encountered at depths between 8,200 and 14,500 feet. Fifty-one fields have been established and 25 million barrels of oil have been produced from these fields developed in Lower Cretaceous Hosston and Upper Jurassic Haynesville, Smackover, and Norphlet reservoirs. Production from Smackover carbonates began at Toxey field in 1967 and from Haynesville sandstones at Frisco City field in 1986. As of September 1994, Smackover wells averaged 88 barrels of oil per day and Haynesville wells averaged 284 barrels of oil per day. In 1994, production was established in the Norphlet at North Excel field and in the Hosston at Pleasant Home field. Reservoirs in the updip basement structure play cluster in three distinct areas; (1) a western area on the Choctaw ridge complex, (2) a central area on the Conecuh ridge complex, and (3) an eastern area in the Conecuh embayment. Reservoir lithologies include Smackover limestones and dolostones and Hosston, Haynesville, Smackover, and Norphlet sandstones. Hydrocarbon traps are structural or combination traps where reservoirs occur on the flanks or over the crests of basement palohighs. An understanding of the complex reservoir properties and trap relationships is the key to successful discovery and development of Lower Cretaceous and Upper Jurassic oil reservoirs of the updip basement structure play of southwest Alabama.

  6. The Lower Cretaceous Chouf Sandstone of Lebanon: is it a syn-rift clastic sequence?

    NASA Astrophysics Data System (ADS)

    Hatzenbichler, Georg; Bauer, Harald; Grasemann, Bernhard; Tari, Gabor; Nader, Fadi H.; Church, Jonathan; Schneider, Dave

    2013-04-01

    The lowermost unit of the Cretaceous succession onshore Lebanon is a widespread prominent sandstone formation traditionally known as the "Grès de Base". The Chouf Sandstone is one of the most distinctive geologic units in Lebanon and is extensively quarried as building sand. The formation commonly consists of a brown to white sandstone with associated claystones, shales, locally volcanics and lignites. Based on outcrop samples taken in the central and northern parts of Mount Lebanon the petrographical composition of the typical Chouf Sandstone is dominated by monocrystalline quartz (85-95%) indicating a well-sorted sandstone. Sedimentological observations suggest deposition of the formation was typically in fluvial, coastal plain and deltaic environments. The Chouf Sandstone is variable in thickness, ranging from a few metres to 300 m. In certain areas rapid lateral thickness changes have been reported which may reflect a paleo-topography or syn-depositional block faulting. Similar thickness variations in the underlying Upper Jurassic formations might be interpreted as the result of syn-rift normal faulting. In order to test the syn-rift nature of the Chouf Sandstone, modern high-resolution satellite data sets (with ~ 0.75 m horizontal and 4 m vertical resolution) were used to derive thickness data points for the Chouf Sandstone in NW Lebanon. One important reason to use high-resolution satellite data for onshore Lebanon is the general lack of structural measurements on the existing vintage geologic maps. In lieu of these basic data, the common surface point method was used to derive this information in a consistent manner across the study area. First results obtained by remote sensing techniques do reveal local variations in the thickness of the Chouf Sandstone, on order of tens to hundreds of meters. These isopach variations in a map-view sense are interpreted to be the result of deposition in individual extensional half-grabens in a much larger overall basin. As the overlying Lower Cretaceous neritic carbonate formations do not exhibit these thickness variations, the syn-rift character of the Chouf Sandstone appears to be a reasonable interpretation at this preliminary stage of this ongoing study.

  7. World petroleum systems with Jurassic source rocks

    SciTech Connect

    Klemme, H.D. (Geo Basins Ltd., Bondville, VT (United States))

    1993-11-08

    Fourteen petroleum systems with Upper Jurassic source rocks contain one quarter of the world's discovered oil and gas. Eleven other systems with Lower and Middle Jurassic source rocks presently have a minor but significant amount of discovered oil and gas. The purpose of this article is to review the systems geologically, describe their location in space and time on a continental scale, estimate their relative petroleum system recovery efficiencies, and outline the effect their essential elements and processes have on their petroleum plumbing.

  8. Jurassic-Neocomian biostratigraphy, North Slope, Alaska

    SciTech Connect

    Mickey, M.B.; Haga, H.

    1985-04-01

    The foraminiferal and palynological biostratigraphy of subsurface Jurassic and Neocomian (Early Cretaceous) age strata from the North Slope were investigated to better define biostratigraphic zone boundaries and to help clarify the correlation of the stratigraphic units in the National Petroleum Reserve in Alaska (NPRA). Through use of micropaleontologic data, eight principal biostratigraphic units have been identified. The Neocomian and Jurassic strata have each been subdivided into four main units.

  9. Upper Jurassic ramp carbonate and associated evaporite, Neuquen Province, Argentina

    SciTech Connect

    Nickelsen, B.H.; Merrill, D.A.

    1986-05-01

    The Oxfordian La Manga Limestone (10-65 m) and overlying Auquilco Gypsum (315 m maximum thickness) crop out along the west flank of the Neuquen basin, Neuquen Province, Argentina (36/sup 0/40/sup 0/S lat.). The contact with the underlying Lotena Sandstone is gradational, and both formations are cut by the Late Jurassic Araucanian angular unconformity. Seven lithofacies have been identified within sections measured through the entire interval along the northeast to southwest trending, 30-km long Sierra de la Vaca Muerta ridge (38/sup 0/30'-39/sup 0/S). The La Manga Limestone is interpreted as a temperate ramp carbonate that developed over the Lotena Formation siliciclastic shelf. Interpretations of lithofacies from southwest to northeast are: behind-barrier subtidal lagoon with washovers; coral and red algae biostromes; ooid and peloid sand shoals; downslope wackestone and packstone mud mounds; and deep-water carbonate turbidites. A minor regression separates La Manga and Auquilco Formations. Lithofacies of the Auquilco Formation indicate a shallowing-up sequence comprised of initially deep (hundreds of meters) subaqueous evaporite deposition followed by shallow, subtidal carbonate peloidal and shell fragment grainstones and evaporites. Thickness of the subaqueous evaporite gives an order of magnitude estimate of Auquilco basin depths of a few hundred meters at most. The Neuquen basin has an intermediate proportion of carbonate in comparison to relatively carbonate-poor basins to the south and carbonate-rich basins to the north.

  10. Trace fossil evidence from the Adigrat Sandstone for an Ordovician glaciation in Eritrea, NE Africa

    NASA Astrophysics Data System (ADS)

    Kumpulainen, R. A.; Uchman, A.; Woldehaimanot, B.; Kreuser, T.; Ghirmay, S.

    2006-08-01

    Trace fossils are described here from the Adigrat Sandstone formation of hitherto uncertain Palaeozoic-Mesozoic age in south-central Eritrea. The formation is subdivided into a lower unit, the Adi MaEkheno Member, and an upper informal unit, Member 2. The formation was deposited on the locally mudcracked top of the glacigenic Edaga Arbi Beds, suggesting that these two rock units were formed in a very short time interval. The Adi MaEkheno Member and the lower part of Member 2 contain trace fossils Arthrophycus alleghaniensis (Harlan), Arthrophycus ?brongniartii (Harlan), Didymaulichnus lyelli (Rouault), Palaeophycus tubularis Hall, Taenidium isp., thin winding ridges, winding ridges and furrows, simple cylinders, and 'stellate' forms. A. alleghaniensis is distinctively of Ordovician-Silurian (?Early Devonian) age. The trace fossil association belongs to the Cruziana ichnofacies that indicates a shallow marine environment between the normal and storm wave bases. The trace fossil data and stratigraphic relationships indicate that the Adigrat Sandstone formation and the Edaga Arbi Beds in Eritrea are Ordovician-Silurian in age. The Edaga Arbi Beds are correlated with other Upper Ordovician (Hirnantian) glacial units in northern Africa and the Arabian Peninsula, lending these beds the status of a marker unit in the Lower Palaeozoic stratigraphy of the Horn of Africa. The Jurassic "Adigrat Sandstone" in central-west and eastern Ethiopia cannot be correlated with the Adigrat Sandstone formation in its type area and in Eritrea.

  11. A subsurface study of the Denkman sandstone member, Norphlet Formation, hatters Pond field, Mobile County, Alabama

    SciTech Connect

    Young, L.M.; Anderson, E.G.; Baria, L.R. (Northeast Louisiana Univ., Monroe (USA)); Higginbotham, R.S.

    1990-09-01

    Hatters Pond field is in east-central Mobile County in southwestern Alabama and it produces from both the Norphlet and Smackover formations. The structural trap involves salt movement along the west side of the Mobile Fault System that resulted in a faulted salt anticline. The Norphlet Formation of southwestern Alabama consists of red to gray siltstone and pinkish to gray sandstone with conglomerate layers. Three facies have been distinguished within the Norphlet Formation: a lower shale, a red siltstone sequence, and an upper quartzose unit. The thickness of the formation ranges from a feather edge to more than 800 ft (234.8 m) in southwestern Alabama. The Upper Jurassic Denkman Sandstone Member of the Norphlet Formation at Hatters Pond field is a medium- to fine-grained, well-sorted arkosic sandstone between the underlying Norphlet redbed lithofacies and the carbonates of the overlying Smackover Formation. Here, the Denkman Member can be subdivided into a massive upper unit and a low- to high-angle cross-stratified lower unit. The sandstones are quartz-rich with a high percentage of feldspars. The majority of the feldspar grains observed are potassium feldspar. Microcline is usually less altered when compared with other types of feldspar grains. The major types of feldspar replacement include illitization, hematitization, dolomitization, chloritization, calcitization, vacuolization, and anhydritization. Carbonate replacement of feldspars is very abundant, mostly by ferroan dolomite. Rock fragments are not abundant in the Denkman Member, although there is good evidence of a metamorphic/volcanic source area. The sandstones are cemented by dolomite, calcite, anhydrite, and quartz and feldspar overgrowths. The lower Denkman unit is slightly more porous than the upper Denkman unit. The pore-lining authigenic clay, illite, greatly reduces permeability and porosity in these sandstones.

  12. Physical stratigraphy of Swift-Morrison and Kootenai-Colorado depositional sequences in the Late Jurassic-Early Cretaceous overfilled backarc and foreland basins, western Montana

    SciTech Connect

    Meyers, J.H. (Winona State Univ., MN (United States). Dept. of Geology); O'Malley, P.J. (Indiana Univ., Bloomington, IN (United States). Dept. of Geosciences)

    1993-04-01

    Late Jurassic-Early Cretaceous sedimentation in western Montana includes two depositional sequences. The older sequence (Swift-Morrison Formations) was deposited in the Sundance foreland basin and ensuing Morrison back-arc basin. The younger sequence (Kootenal Formation-Colorado Group) was deposited in the overfilled early Rocky Mountain foreland basin. Swift strata record coastal onlap and marine progradation over a dissected structural complex (Belt Island) and include a laterally restricted basal conglomerate (0--4 m-thick) representing estuarine paleovalley fill, and an overlying pervasive 16--25 m-thick upward-fining sandstone body dominated by tidal features. To the south, the sandstone body is conformably overlain by distal alluvial-fan and coastal-plain green mudstone, interbedded thin micritic limestone, and red mudstone of the lower and middle Morrison Formation. Morrison red mudstones contain thin sheet sandstones and sparse thick lenticular sandstones, representing northeastward dispersal of detritus in a mud-dominated distal alluvial fan. Northward, the Morrison thins and is mostly green and gray mudstone with thin interbedded sheet sandstone and rare intraformational-pebble-bearing ribbon sandstone. To the south, Kootenai rocks unconformably overlie the Morrison Formation and include a thick basal sandstone deposited in northeast-flowing truck rivers whose courses were controlled by subtle structural topography developed along reactivated basement faults. In the Great Falls area this sandstone (K1-Cutbank of Foster, 1992) may represent distributary channels in a prograding fluvial-dominated delta in the Sunburst sea. Overlying mudstones and thick nodular limestones (K2) represent alluvial-plain sedimentation and paleosol development. Thin shallow-marine sandstone (K3-Sunburst) caps the fluvial-deltaic sequence in the Great Falls area.

  13. Impact Crater Identified on the Navajo Nation Near Chinle, Arizona

    NASA Astrophysics Data System (ADS)

    Shoemaker, E. M.; Roddy, D. J.; Moore, C. B.; Pfeilsticker, R.; Curley, C. L.; Dunkelman, T.; Kuerzel, K.; Taylor, M.; Shoemaker, C.; Donnelly, P.

    1995-09-01

    A small impact crater has been identified about 8 km north of Chinle, Arizona on the Navajo Nation. Preliminary studies show that the crater is elongate in a N-S direction, measuring about 23 by 34 m in diameter, with a depth of about 1.3 m. The impact origin of the crater is identified by its shape, subsurface deformation, and an iron-nickel oxide fragment. We estimate the age to be about 150 to 250 years. The impact site is on the east side of the Chinle Valley at an altitude of 1685 m and is about 2 km east of Chinle Wash. The crater formed on an alluvial surface that slopes gently west toward the Wash. About 2 m of reddish brown alluvial sand and silt of the Jeddito Formation of late Pleistocene age rests on the Petrified Forest Member of the Chinle Formation of late Triassic age. A moderately developed late Pleistocene pedocal soil has developed on the Jeddito. Several thin discontinuous caliche horizons occur at a depth of about 1 m. The caliche horizons provided easily traced markers by which we could delimit the original walls of the crater and recognize deformation along the crater walls. Three trenches were excavated down to the top of the Chinle bedrock: 1) an east- west trench 31 m long across the center of the crater, 2) a north-south trench 13 m long in the north crater rim, and 3) a north-south trench 12 m long in the south crater rim. Excavation width was about 1 m and provided excellent exposures of the subsurface stratigraphy and deformation. The trenches revealed that the original crater was about 23 m wide and 27 m long. The original rim crests have entirely eroded away so that no perceptible raised rim remains. At the center of the crater, the original depth was about 3 m; material washed from the rims now fills the crater floor to a depth of 1.5 m. The crater is symmetrical; however, the deepest part of the original crater lies south of the center and was not reached in the south trench. The east-west trench showed that the initial floor of the crater was scoured down to the Jeddito-Chinle contact across the center of the crater. Some of the Chinle was excavated by impact south of the center, as seen in the trench in the south wall. The original crater walls slope inward about 30 degrees on the east and west sides, about 20 degrees on the north, and about 45 degrees on the south. Beds are dragged up along the east, west, and south walls, but not along the north wall. The deformation is restricted to within about 0.5 m of the wall. From the asymmetry of shape and deformation in the walls, we believe that the impacting body struck at an oblique angle and was traveling from north to south. A small, magnetic, iron oxide fragment, about 1 mm across, was collected from material excavated from the south crater wall area. Analyses of this fragment by electron microprobe detected a significant nickel concentration of 5%. Two senior Navajo women (70-80 year age range) independently remember this crater as being much deeper during their childhood and both suggest that the impact was witnessed 3 to 4 generations ago. Interestingly, many persons in the Navajo community thought that this crater was of impact origin. Additional work is planned, including a broader aerial search for other possible impact sites.

  14. Bedrock aquifers in the northern San Rafael Swell area, Utah, with special emphasis on the Navajo Sandstone

    USGS Publications Warehouse

    Hood, J.W.; Patterson, D.J.

    1984-01-01

    The northern San Rafael Swell area in southeastern Utah includes about 2,880 square miles (7,460 square kilometers) and ranges in altitude from about 3,290 to 7,921 feet (1,195 to 2,414 meters). Precipitation, the main source of water in the area, ranges from slightly less than 6 inches (152 millimeters) to slightly more than 12 inches (305 millimeters).

  15. "Enemies Like a Road Covered with Ice": The Utah Navajos' Experience during the Long Walk Period, 1858-1868

    ERIC Educational Resources Information Center

    Hornsby, Sarah; McPherson, Robert S.

    2009-01-01

    Much has been written of the Navajo Long Walk period when the Navajo people, following what appears to be a fairly short resistance, surrendered in droves to the US military, collected at Fort Defiance and other designated sites, then moved in a series of "long walks" to Fort Sumner (Hweeldi) on the Pecos River in eastern New Mexico. There was…

  16. The prevalence and incidence of end-stage renal disease in Native American adults on the Navajo reservation

    Microsoft Academic Search

    M E Hochman; J P Watt; R Reid; K L O'Brien

    2007-01-01

    Whereas members of the Navajo Nation are at high risk for diabetes mellitus, there are no recent published estimates of the burden of end-stage renal disease (ESRD), an important sequela of diabetes, on the Navajo Nation, a 16 million acre area in Arizona, New Mexico, and Utah with more than 200 000 tribal members. We used data from the US

  17. Wind directions predicted from global circulation models and wind directions determined from eolian sandstones of the western United States---A comparison

    Microsoft Academic Search

    JUDITH TOTMAN PARRISH; FRED PETERSON

    1988-01-01

    Panfish, J.T. and Peterson, F., 1988. Wind directions predicted from global circulation models and wind directions determined from eolian sandstones of the western United States--A comparison. In: G. Kocurek (Editor), Late Paleozoic and Mesozoic Eolian Deposits of the Western Interior of the United States. Sediment. Geol., 56: 261-282. Wind directions for Middle Pennsylvanian through Jurassic time are predicted from global

  18. Navajo birth outcomes in the Shiprock uranium mining area

    SciTech Connect

    Shields, L.M.; Wiese, W.H.; Skipper, B.J.; Charley, B.; Benally, L. (Navajo Community College, Shiprock, NM (United States))

    1992-11-01

    The role of environmental radiation in the etiology of birth defects, stillbirths, and other adverse outcomes of pregnancy was evaluated for 13,329 Navajos born at the Public Health Service/Indian Health Service Hospital in the Shiprock, NM, uranium mining area (1964-1981). More than 320 kinds of defective congenital conditions were abstracted from hospital records. Using a nested case-control design, families of 266 pairs of index and control births were interviewed. The only statistically significant association between uranium operations and unfavorable birth outcome was identified with the mother living near tailings or mine dumps. Among the fathers who worked in the mines, those of the index cases had histories of more years of work exposure but not necessarily greater gonadal dosage of radiation. Also, birth defects increased significantly when either parent worked in the Shiprock electronics assembly plant. Overall, the associations between adverse pregnancy outcome and exposure to radiation were weak and must be interpreted with caution with respect to implying a biogenetic basis.

  19. Navajo oral history of a pre-Columbian amphitheater in Chaco Canyon, New Mexico

    NASA Astrophysics Data System (ADS)

    Blackhorse, Taft, Jr.; Williams, Jay S.

    2002-11-01

    A large performance space attached to a natural amphitheater in the cliff face has recently been identified at the center of the pre-Columbian Chaco Complex in Chaco Canyon, New Mexico. This location is known in the ceremonial history of the Navajo people (Din) as Tsbiinaholtsa Yalti (Concavity in Bedrock that Speaks). Tsbiinaholtsa Yalti is a portal to the dimension of the deities and it is opened by way of tonally induced acousma. The physical manifestation of the amphitheater and its acoustical properties invoke the concepts of Tal (Chants) and Taal (Ceremonial pathway). Navajo ceremonies are called Haataal and religious practitioners Hataalii (Chanters). The origin of the tones which give power to contemporary Navajo chants may be traced to the Tsbiinaholtsa Yalti. These tones are produced vocally and are accompanied by the shell trumpet, eagle bone whistle, and reed flute (jadzoosh).

  20. Assessments of aquifer sensitivity on Navajo Nation and adjacent lands and ground-water vulnerability to pesticide contamination on the Navajo Indian Irrigation Project, Arizona, New Mexico, and Utah

    USGS Publications Warehouse

    Blanchard, Paul J.

    2002-01-01

    The U.S. Environmental Protection Agency requested that the Navajo Nation conduct an assessment of aquifer sensitivity on Navajo Nation lands and an assessment of ground-water vulnerability to pesticide contamination on the Navajo Indian Irrigation Project. Navajo Nation lands include about 17,000 square miles in northeastern Arizona, northwestern New Mexico, and southeastern Utah. The Navajo Indian Irrigation Project in northwestern New Mexico is the largest area of agriculture on the Navajo Nation. The Navajo Indian Irrigation Project began operation in 1976; presently (2001) about 62,000 acres are available for irrigated agriculture. Numerous pesticides have been used on the Navajo Indian Irrigation Project during its operation. Aquifer sensitivity is defined by the U.S. Environmental Protection Agency as 'The relative ease with which a contaminant [pesticide] applied on or near a land surface can migrate to the aquifer of interest. Aquifer sensitivity is a function of the intrinsic characteristics of the geologic material in question, any underlying saturated materials, and the overlying unsaturated zone. Sensitivity is not dependent on agronomic practices or pesticide characteristics.' Ground-water vulnerability is defined by the U.S. Environmental Protection Agency as 'The relative ease with which a contaminant [pesticide] applied on or near a land surface can migrate to the aquifer of interest under a given set of agronomic management practices, pesticide characteristics, and aquifer sensitivity conditions.' The results of the aquifer sensitivity assessment on Navajo Nation and adjacent lands indicated relative sensitivity within the boundaries of the study area. About 22 percent of the study area was not an area of recharge to bedrock aquifers or an area of unconsolidated deposits and was thus assessed to have an insignificant potential for contamination. About 72 percent of the Navajo Nation study area was assessed to be in the categories of most potential or intermediate potential for contamination. About 6 percent of the study area was assessed to have the least potential for contamination, mostly in areas where the slope of the land surface is more than 12 percent. Nearly all fields on the Navajo Indian Irrigation Project were assessed to have the most potential for contamination. The assessment of ground-water vulnerability to pesticide contamination on the Navajo Indian Irrigation Project was based on pesticide application to various crops on part of the Navajo Indian Irrigation Project during 1997-99. The assessment indicated that ground water underlying fields of beans, wheat, barley, and alfalfa was most vulnerable to pesticide contamination; ground water underlying fields of corn and potatoes was intermediately vulnerable to pesticide contamination; and ground water underlying fields of hay was least vulnerable to pesticide contamination.

  1. Jurassic igneous-related metallogeny of southwestern North America

    E-print Network

    Barton, Mark D.

    Jurassic igneous-related metallogeny of southwestern North America Mark D. Barton*, James D Jurassic magmatism and related hydrothermal systems formed across much of southwestern North America, advanced argillic, metallogeny, magmatism, southwestern North America INTRODUCTION The Great Basin

  2. The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962

    E-print Network

    The Lower Jurassic ornithischian dinosaur Heterodontosaurus tucki Crompton & Charig, 1962: cranial 27 August 2010 The cranial anatomy of the Lower Jurassic ornithischian dinosaur Heterodontosaurus commonly seen in basal archosaurs and saurischian dinosaurs). Evidence for tooth replacement (which has

  3. TriassicJurassic boundary events: Problems, progress, possibilities 1. Problems

    E-print Network

    McRoberts, Christopher A.

    As for most geological period boundaries, the Triassic­Jurassic (T­J) transition, 200 million years agoEditorial Triassic­Jurassic boundary events: Problems, progress, possibilities 1. Problems to reconstruct past events, a physical record of their passing is essential. Here again the Triassic­Jurassic

  4. Late Jurassic salamandroid from western Liaoning, China.

    PubMed

    Gao, Ke-Qin; Shubin, Neil H

    2012-04-10

    A Jurassic salamander, Beiyanerpeton jianpingensis (gen. et sp. nov.), from a recently found site in western Liaoning Province, China is the earliest known record of Salamandroidea. As a Late Jurassic record of the group, it extends the range of the clade by ~40 Ma. The Late Jurassic taxon is neotenic and represented by exceptionally preserved specimens, including fully articulated cranial and postcranial skeletons and bony gill structures close to the cheek region. The fossil beds, consisting of dark-brown volcanic ash shales of the Upper Jurassic Tiaojishan (Lanqi) Formation (Oxfordian), underlie trachyandesite rocks that have yielded a SHRIMP zircon U-Pb date of 157 ± 3 Ma. The fossiliferous beds are substantially older than the Jehol Group, including the Yixian Formation ((40)Ar/(39)Ar dates of 122-129 Ma), but slightly younger than the Middle Jurassic Daohugou horizon ((40)Ar/(39)Ar date of 164 ± 4 Ma). The early fossil taxon shares with extant salamandroids derived character states, including: separated nasals lacking a midline contact, angular fused to the prearticular in the lower jaw, and double-headed ribs on the presacral vertebrae. In contrast to extant salamandroids, however, the salamander shows a discrete and tooth-bearing palatine, and unequivocally nonpedicellate and monocuspid marginal teeth in large and presumably mature individuals. The finding provides insights into the evolution of key characters of salamanders, and also provides direct evidence supporting the hypothesis that the split between Cryptobranchoidea and Salamandroidea had taken placed before the Late Jurassic Oxfordian time. In this aspect, both paleontological and molecular data now come to agree. PMID:22411790

  5. Upper jurassic dinosaur egg from utah.

    PubMed

    Hirsch, K F; Stadtman, K L; Miller, W E; Madsen, J H

    1989-03-31

    The Upper Jurassic egg described here is the first known egg from the 100-million-year gap in the fossil record between Lower Jurassic (South Africa) and upper Lower Cretaceous (Utah). The discovery of the egg, which was found mixed in with thousands of dinosaur bones rather than in a nest, the pathological multilayering of the eggshell as found in modern and fossil reptilians, and the pliable condition of the eggshell at the time of burial indicate an oviducal retention of the egg at the time of burial. PMID:17751281

  6. Log interpretation of shaly sandstones

    E-print Network

    Baker, Joel Foster

    1987-01-01

    Log Interpretation of Shaly Sandstones. (August 1987) Joel Foster Baker, B. S. , Texas A&M University Chair of Advisory Committee: Dr. Robert R. Berg The determination of water saturation from the resistivity logs to evaluate the potential... to the Union Oil Company of California and to the Society of Professional Nell Log Analysts for their grants to help fund the project. Special thanks go to Dr. Berg for his help, and more importantly, his availability and willingness to give help. Last...

  7. Microstructure of deformed graywacke sandstones

    Microsoft Academic Search

    Dengler

    1980-01-01

    Microsctures in low-permeability graywacke sandstones were studied by optical and scanning electron microscopy (SEM). SEM specimens were prepared by ion-bombardment of thick polished samples. The undeformed rock contains grains in a matrix composed primarily of authigenic chlorite and kaolinite. Chlorite platelets are randomly arranged in face-to-edge relation to one another. Kaolinite occurs as pseudohexagonal crystals stacked face-to-face in pore filling

  8. Of Mother Earth and Father Sky: A Photographic Study of Navajo Culture.

    ERIC Educational Resources Information Center

    McCarty, T. L.; And Others

    Utilizing 52 black and white photographs, the book tells a story about the Navajo people, their hopes and problems, the strategies they have adopted to cope with the problems, their interactions with each other and with the land, and their feelings about the land which provides a basis for their livelihood. Part of a series of curriculum materials…

  9. Maslow's Hierarchy of Needs and Navajo Students' Struggle for Self Esteem.

    ERIC Educational Resources Information Center

    Walker, Kay

    1996-01-01

    Maslow's theory of a hierarchy of needs is used to analyze Navajo youths' struggles for identity, fulfillment, and self-esteem. Answers to the challenges of substance abuse, violence, and gang membership are offered based upon George Bearden's eight-step plan, which stresses the importance of understanding human needs to perceive and transform…

  10. The Navajo Nation has collected hydroclimate data throughout the Nation lands but the system has been

    E-print Network

    Fay, Noah

    The Navajo Nation has collected hydroclimate data throughout the Nation lands but the system has- toring network, data collection and quality control systems. Investigators Gregg Garfin (UA) - Lead-based advice to improve data collection and processing in support of climate, drought and hydrologic analyses

  11. Qualitative Study of the Use of Traditional Healing by Asthmatic Navajo Families

    ERIC Educational Resources Information Center

    Van Sickle, David; Morgan, Frank; Wright, Anne L.

    2003-01-01

    Despite increasing prevalence of asthma among American Indians and/or Alaska Natives, little is known about their use of traditional healing in its management. A convenience sample of 24 Navajo families with asthmatic members (n=35) was interviewed between June 1997 and September 1998. While 46% of families had previously used traditional healing,…

  12. The Goal Wheel: Adapting Navajo Philosophy and the Medicine Wheel to Work with Adolescents

    ERIC Educational Resources Information Center

    Garner, Holly; Bruce, Mary Alice; Stellern, John

    2011-01-01

    The purpose of this article is to describe a group counseling model that is based on the indigenous medicine wheel as well as Navajo philosophy by which to help troubled adolescents restore harmony and balance in their lives, through establishing goals and sequential steps to accomplish these goals. The authors call this model the Goal Wheel. A…

  13. Coping and Responses to Stress in Navajo Adolescents: Psychometric Properties of the Responses to Stress Questionnaire

    ERIC Educational Resources Information Center

    Wadsworth, Martha E.; Rieckmann, Traci; Benson, Molly A.; Compas, Bruce E.

    2004-01-01

    This study tested the factor structure of coping and stress responses in Navajo adolescents and examined the reliability and validity of the Responses to Stress Questionnaire (RSQ; Connor-Smith, Compas, Wadsworth, Thomsen, & Saltzman, 2000) with this population. Confirmatory factor analyses revealed that a correlated five-factor model of stress…

  14. Educational Expectations in a Democratic Society Held by Navajo Parents and Their Children.

    ERIC Educational Resources Information Center

    Parent, Sydney B.; Bunderson, Eileen D.

    Navajo students have a 31% dropout rate, and it has been getting worse. Although considerable research has examined the reasons behind this dropout rate, little attention has been given to parental expectations of their children's education. Interviews with 45 parents of students attending Montezuma Creek Elementary School, a public school on the…

  15. Communications Workshops for Navajos in a Community Setting: A Course Plan.

    ERIC Educational Resources Information Center

    Smith, Michael F.

    Two communications skills courses were developed to improve the English fluency of Navajo students. Communications Workshop I (English 100) emphasizes basic skills review, by focusing on reading and writing short papers based on responses to readings and class discussions, and on personal experience. The course is intended to familiarize the…

  16. Pressures on Arizona Water and Energy Policy: Case Study of the Navajo Generating Station

    E-print Network

    Fay, Noah

    1 Pressures on Arizona Water and Energy Policy: Case Study of the Navajo Generating Station Sonya Fellowship #12;2 Arizona water concern at issue: Water's connection to energy and climate Water, climate, and energy are closely linked in Arizona. When a person turns on the tap in Tucson, part of that water

  17. The Navajo Learning Network and the NASA Life Sciences/AFOSR Infrastructure Development Project

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The NSF-funded Navajo Learning Network project, with help from NASA Life Sciences and AFOSR, enabled Dine College to take a giant leap forward technologically - in a way that could never had been possible had these projects been managed separately. The combination of these and other efforts created a network of over 500 computers located at ten sites across the Navajo reservation. Additionally, the college was able to install a modern telephone system which shares network data, and purchase a new higher education management system. The NASA Life Sciences funds further allowed the college library system to go online and become available to the entire campus community. NSF, NASA and AFOSR are committed to improving minority access to higher education opportunities and promoting faculty development and undergraduate research through infrastructure support and development. This project has begun to address critical inequalities in access to science, mathematics, engineering and technology for Navajo students and educators. As a result, Navajo K-12 education has been bolstered and Dine College will therefore better prepare students to transfer successfully to four-year institutions. Due to the integration of the NSF and NASA/AFOSR components of the project, a unified project report is appropriate.

  18. Perceptions of Living Skills among Navajo High School Students in Arizona.

    ERIC Educational Resources Information Center

    Belon, Amy; And Others

    1983-01-01

    Analyzes 116 Navajo senior class students attending Chinle High School on their perceptions of difficulties in migrating from the reservation and adjusting to urban life, Examines four variables related to basic survival skills for successful urban living: mobility, communication, social networking, and money management. (ERB)

  19. Navajo County Community College District; Its History, Its Future, 1961-1985.

    ERIC Educational Resources Information Center

    Northland Pioneer Coll., Holbrook, AZ.

    This document presents an overview of the history and characteristics of Northland Pioneer College (NPC), established in 1974 to serve Navajo County, a rural, sparsely populated area in northeastern Arizona (70 percent Indian Reservation land). The information presented in this document is intended to be of assistance in future planning for NPC.…

  20. Tidal influence within Pennsylvanian sandstones

    SciTech Connect

    Archer, A.W. (Kansas State Univ., Manhattan (United States))

    1991-08-01

    Within Pennsylvanian-age strata of the Illinois basin, large-scale linear sand bodies have been previously interpreted as fluvial and deltaic in origin. Nonetheless, analyses of fine-scale sedimentology and bed forms within such sandstones and the associated shales indicate that tidal processes greatly influenced the depositional environments within such lithofacies. Recent work on Mid-Continent Pennsylvanian-age sandstones indicates the occurrence of similar depositional environments. Based upon the pervasive tidal influence observed within such strata, environmental analogs other than fluvial and deltaic bear consideration. In general, tidally influenced estuarine models seem particularly appropriate. Within such settings, the changeover from a fluvially dominated deposystem to tidally influenced estuary occurs during transgressive phases. Despite the tidal influence that can be interpreted from the sedimentology, the strata contain few, if any, marine indicators because of the low salinities that occurred during deposition. Ongoing work in the Mid-Continent indicates that Morrowan, Atokan, Desmoinesian, Missourian, and Virgilian sands share a number of similarities with the tidally influenced environments delineated in the Illinois basin studies. Thus a tidal/estuarine interpretation might be a generalizable model for many Pennsylvanian sandstones. In addition, enhanced understanding of the siliciclastic parts of Mid-Continent cyclothems provides a more useful framework for documentation of carbonate/siliciclastic interrelationships. Oscillations of carbonate/siliciclastic environments may be more readily explainable by climatic cycles rather than by traditionally popular depth-related facies models.

  1. New Early Jurassic Tetrapod Assemblages Constrain Triassic-Jurassic Tetrapod Extinction Event

    NASA Astrophysics Data System (ADS)

    Olsen, P. E.; Shubin, N. H.; Anders, M. H.

    1987-08-01

    The discovery of the first definitively correlated earliest Jurassic (200 million years before present) tetrapod assemblage (Fundy basin, Newark Supergroup, Nova Scotia) allows reevaluation of the duration of the Triassic-Jurassic tetrapod extinction event. Present are tritheledont and mammal-like reptiles, prosauropod, theropod, and ornithischian dinosaurs, protosuchian and sphenosuchian crocodylomorphs, sphenodontids, and hybodont, semionotid, and palaeonisciform fishes. All of the families are known from Late Triassic and Jurassic strata from elsewhere; however, pollen and spore, radiometric, and geochemical correlation indicate an early Hettangian age for these assemblages. Because all ``typical Triassic'' forms are absent from these assemblages, most Triassic-Jurassic tetrapod extinctions occurred before this time and without the introduction of new families. As was previously suggested by studies of marine invertebrates, this pattern is consistent with a global extinction event at the Triassic-Jurassic boundary. The Manicouagan impact structure of Quebec provides dates broadly compatible with the Triassic-Jurassic boundary and, following the impact theory of mass extinctions, may be implicated in the cause.

  2. Jurassic stratigraphy of the Wiggins Arch, Mississippi

    SciTech Connect

    Rhodes, J.A.; Maxwell, G.B. (Mobil Oil Company, Houston, TX (United States))

    1993-09-01

    Mobil and Shell jointly explored the Wiggins arch area in southern Mississippi from 1985 to 1991. The effort concentrated on the Jurassic Norphlet and Smackover formations. Two wells were drilled into Paleozoic crystalline rocks and one well into the Pine Hill formation. Two of these wells were located on the southern side of the Wiggins arch and provide significant data for interpreting Jurassic stratigraphy. The Mobil No. 1 U.S.A. well encountered a complete Jurassic section, but with some significantly different facies than those encountered by wells to the north. A granite wash section is the equivalent to the Frisco City formation previously only found 100 mi to the north-northeast. All 300 ft of Smackover is crystalline dolomite. The Norphlet section is entirely granite wash. The Pine Hill anhydrite is unusually thick and interpreted to be equivalent to the Louann Salt. Correlations to other wells on the Wiggins arch, particularly the Conoco No. 1 Higgins, indicate that the Jurassic can be divided into three transgressive events separated by the Norphlet/Pine Hill and Frisco City/Buckner regressive events.

  3. Jurassic evolution of the Tien-Shan

    SciTech Connect

    Bebeshev, I.I. [Geological Institute, Moscow (Russian Federation)

    1994-09-01

    Complex studies led to identification of three stages in Jurassic deposits. The stages reflect development periods of the studied deposits. Each stage is represented by a paleogeographic map that indicates the evolution of ancient landforms in the Tien-Shan region in time and space.

  4. The Early Jurassic Ornithischian Dinosaurian Ichnogenus Anomoepus

    E-print Network

    Olsen, Paul E.

    Jurassic footprint genus produced by a relatively small, gracile orni- thischian dinosaur. It has, Edward Hitchcock described the first of what we now recognize as dinosaur tracks from Early Juras- sic.1 and 19.2). Because skeletons of dinosaur feet were not known at the time, he naturally attributed

  5. Discovering the "-Ologies" on the Jurassic Coast

    ERIC Educational Resources Information Center

    Peacock, Alan

    2007-01-01

    The Jurassic Coast is Britain's only natural World Heritage site, a tangible time-line that takes one through 185 million years of history in 95 miles of coast. It provides individuals with a world-famous educational resource and an unrivalled outdoor classroom that has played a key role in the study of earth sciences. The author is keen to ignite…

  6. Didactyl Tracks of Paravian Theropods (Maniraptora) from the ?Middle Jurassic of Africa

    PubMed Central

    Mudroch, Alexander; Richter, Ute; Joger, Ulrich; Kosma, Ralf; Idé, Oumarou; Maga, Abdoulaye

    2011-01-01

    Background A new dinosaur tracksite from ?Middle Jurassic sediments of the Irhazer Group on the plains of Agadez (Rep. Niger, northwest Africa) revealed extraordinarily well preserved didactyl tracks of a digitigrade bipedal trackmaker. The distinct morphology of the pes imprints indicates a theropod trackmaker from a paravian maniraptoran closely related to birds. Methodology/Principal Findings The early age and the morphological traits of the tracks allow for description of the new ichnotaxon Paravipus didactyloides. A total of 120 tracks are assigned to 5 individual trackways. The ‘medium-sized’ tracks with an average footprint length of 27.5 cm and footprint width of 23.1 cm are deeply imprinted into the track bearing sandstone. Conclusions/Significance A comparison with other didactyl tracks gives new insights into the foot morphology of advanced maniraptoran theropods and contributes to knowledge of their evolutionary history. The new ichnotaxon takes an important position in the ichnological fossil record of Gondwana and the mid-Jurassic biota worldwide, because it is among the earliest known records of paravian maniraptorans and of didactyl theropod tracks from Africa. PMID:21339816

  7. Recoverable natural gas reserves from Jurassic Norphlet Formation, Alabama coastal waters

    SciTech Connect

    Mancini, E.A.; Mink, R.M.; Bearden, B.L.; Hamilton, R.P.

    1987-09-01

    To date, 11 Norphlet gas fields have been established in offshore Alabama. These fields are part of a deep Jurassic gas trend that extends across southern Mississippi and Alabama into the Gulf of Mexico. Recoverable gas reserves of 4.9-8.1 tcf are estimated for the Norphlet Formation in Alabama's coastal waters. Proven gas reserves are estimated to be 3.7-4.6 tcf and potential reserves are estimated to be 1.2-3.5 tcf. The natural gas is trapped in a series of generally east-west-trending salt anticlines. The mechanism of structure formation appears to be salt flowage that has formed broad, low-relief anticlines, most of which are faulted, and many of which are related to small-scale growth faults. Salt movement is the critical factor in the formation of these petroleum traps. The primary Norphlet reservoir lithofacies are eolian dune and interdune sandstones that range in thickness from 140 to over 600 ft in Alabama's coastal waters. Gas pay can exceed 280 ft in thickness. Porosity is principally secondary, developed as a result of decementation and grain dissolution. Jurassic Smackover algal carbonate mudstones were the main source for the Norphlet hydrocarbons. The seal for the gas is the nonpermeable upper portion of the Norphlet Formation. The overlying lower Smackover carbonates are also nonpermeable and may serve as part of the seal.

  8. Sequence stratigraphy of middle and upper Jurassic strata of Southwestern Alabama

    SciTech Connect

    Wade, W.J.; Moore, C.H. Jr. (Louisiana State Univ., Baton Rouge, LA (United States))

    1993-09-01

    Middle and Upper Jurassic systems tracts of southwestern Alabama differ from those of the western Gulf rim, showing: (1) profound influence of antecedent topography; (2) low early subsidence rates; and (3) greater clastic influx from adjacent uplands. Werner Anhydrite and Louann Salt represent the earliest marine incursion onto the Gulf rim following initial rifting; they onlap upper Paleozoic basement and garben-filling Eagle Mills red beds. Because basin-wide evaporative drawdowns overprint even higher order eustatic sea level changes, transgressive systems tracts (TST) and highstand systems tracts (HST) are indistinguishable. Anhydrite and shale caps accumulated via interstratal halite dissolution. Oxfordian Norphlet siliciclastics form a continental lowstand systems tract as illustrated by abrupt contact with underlying marine evaporites without intervening progradational marginal marine facies. Marine-reworked uppermost Norphlet sandstone marks the base of a subsequent TST, which includes overstepping lower Smackover lithofacies (laminated mudstone, algal-laminated mudstone, and pellet wackestone). The upper Smackover HST is characterized by formation of rimmed shelves upon which algal mounds and aggrading ooid grainstone parasequences accumulated. Shallow lagoonal carbonate and evaporite saltern deposition occurred behind ooid shoals; fine-grained siliciclastics accumulated in updip areas. Equivalents of Smackover A, Smackover B, Bossier, and Gilmer sequences are largely masked by influx of Haynesville and Cotton Valley continental clastics. Lack of biostratigraphic data, a consequence of restricted fauna, precludes useful age assignments for these sequences in Alabama. Middle and Upper Jurassic systems tracts of southwestern Alabama are regionally atypical and cannot serve as a model for Gulf-wide sequences.

  9. Bird-like anatomy, posture, and behavior revealed by an early jurassic theropod dinosaur resting trace

    USGS Publications Warehouse

    Milner, A.R.C.; Harris, J.D.; Lockley, M.G.; Kirkland, J.I.; Matthews, N.A.

    2009-01-01

    Background: Fossil tracks made by non-avian theropod dinosaurs commonly reflect the habitual bipedal stance retained in living birds. Only rarely-captured behaviors, such as crouching, might create impressions made by the hands. Such tracks provide valuable information concerning the often poorly understood functional morphology of the early theropod forelimb. Methodology/Principal Findings: Here we describe a well-preserved theropod trackway in a Lower Jurassic (???198 millionyear- old) lacustrine beach sandstone in the Whitmore Point Member of the Moenave Formation in southwestern Utah. The trackway consists of prints of typical morphology, intermittent tail drags and, unusually, traces made by the animal resting on the substrate in a posture very similar to modern birds. The resting trace includes symmetrical pes impressions and well-defined impressions made by both hands, the tail, and the ischial callosity. Conclusions/Significance: The manus impressions corroborate that early theropods, like later birds, held their palms facing medially, in contrast to manus prints previously attributed to theropods that have forward-pointing digits. Both the symmetrical resting posture and the medially-facing palms therefore evolved by the Early Jurassic, much earlier in the theropod lineage than previously recognized, and may characterize all theropods.

  10. Characterization of Petroleum Residue in the Entrada Sandstone, Colorado National Monument

    USGS Publications Warehouse

    Lillis, Paul G.; King, J. David

    2007-01-01

    Introduction As part of the U.S. Geological Survey's (USGS) petroleum resource assessment of the Uinta-Piceance Province, Colorado and Utah, in 2000 (USGS Uinta-Piceance Assessment Team, 2003), some 170 oils, oil stains, and oil seeps were geochemically characterized and divided into genetic types (Lillis and others, 2003). Recognized oil types include Minturn, Phosphoria, Grassy Trail Creek, Mancos, Mesaverde, and Green River. Subsequent to that study, the existence and general locality of petroleum residue in the Middle Jurassic Entrada Sandstone in Colorado National Monument (CNM) was brought to the attention of the authors (Scott and others, 2001). Because the analysis of such non-commercial petroleum deposits commonly yields valuable regional resource-trend information, we collected and characterized the reported CNM petroleum residue and compared the results with identified oil types in the Uinta-Piceance Province. Three samples of Entrada Sandstone with petroleum residue were collected near Little Park Road along the south edge of the CNM in sec.20, T.12S., R.101W. The approximate extent of the petroleum staining was determined by field testing with solvent, and the stains appear to be restricted to the upper part of the 'board beds' unit (informal name, Scott and others, 2001) of the Entrada Sandstone between the two fault traces of the Glade Park fault.

  11. Stratigraphy of Upper Jurassic Morrison and Lower Cretaceous Cloverly formations of Big Horn basin, northern Wyoming

    SciTech Connect

    Kvale, E.P.; Vondra, C.F.

    1983-08-01

    The Morrison and Cloverly Formations in the Big Horn basin of northern Wyoming and southern Montana are part of a distal edge of a westward-thickening clastic wedge of sediment deposited in an elongate intracontinental basin in the western North American craton. These formations reflect orogenic and volcanic activity in the western Cordillera during Late Jurassic and the subsequent eastward migration of volcanic centers during Early Cretaceous. The Morrison Formation (Upper Jurassic) conformably overlies the Jurassic marine Sundance Formation and consists of light olive-green, lenticular, calcareous siltstones and mudstones interbedded with white to buff or yellowish green, massive and cross laminated, calcareous quartz-arenites. The Cloverly Formation (Lower Cretaceous) consists of three members: the Pryor Conglomerate, and Little Sheep Mudstone, and the Himes; it overlies the Morrison Formation both conformably and unconformably. Both the Morrison and Cloverly Formations are characterized by high ratios of overbank fines relative to coarse channel sands. It has been assumed, but not documented by detailed sedimentologic study, that the deposits were part of an aggrading alluvial flood plain complex dotted by seasonal lakes and swamps and crossed by braided rivers. This model deviates from most modern braided systems which are characterized by rapid lateral mobility and the lack of fine-grained overbank material. The large ratio of fine-grained siltstones and mudstones to coarser grained sandstones can be explained by a number of processes, the most probable being rapid overbank aggradation as a result of a large influx of windblown volcanic material from vents to the west.

  12. Strontium isotopes in Early Jurassic seawater

    NASA Astrophysics Data System (ADS)

    Jones, Charles E.; Jenkyns, Hugh C.; Hesselbo, Stephen P.

    1994-02-01

    The analysis of well-preserved, well-dated belemnites and oysters from the Jurassic of Great Britain has resulted in a well-constrained, detailed seawater strontium isotope curve for the Early Jurassic. The preservation of fossil low-Mg calcite was monitored using Mn, Fe, ?13C, and ?18O. Iron was the most useful indicator, with about 75% of the samples containing more than 150 ppm Fe showing 87Sr /86Sr ratios elevated relative to adjacent points on the curve. High Mn concentrations less often correlated with elevated 87Sr /86Sr ratios; however, low Mn concentrations (<25 ppm Mn) were consistently associated with apparently well-preserved 87Sr /86Sr . ?13C and ?18O proved to be insensitive to diagenesis as it affects 87Sr /86Sr . The principal features of the strontium isotope curve include a rise to about 0.70772 in the latest Triassic and earliest Jurassic (Hettangian). From the Hettangian, the curve begins a roughly linear descent through the Sinemurian and Pliensbachian. Following a small levelling off and increase in the late Pliensbachian, the curve falls rapidly to its Early Jurassic minimum of 0.70706. It then gently increases through the Toarcian until the falciferum zone, where it shows an apparently abrupt increase to 0.70719 before continuing its slow increase to 0.70728 in the Aalenian-Bajocian (Middle Jurassic). This reversal of the downwards trend established in the Sinemurian and Pliensbachian had not been previously identified. The Sinemurian and Pliensbachian section of the curve potentially allows correlation and dating to within 1 or 2 ammonite subzones (±0.5 to 1 Ma).

  13. Middle Jurassic Oseberg delta, northern North Sea: A sedimentological and sequence stratigraphic interpretation

    SciTech Connect

    Muto, T. [Nagasaki Univ. (Japan); Steel R.J. [Univ. of Wyoming, Laramie, WY (United States)

    1997-07-01

    The Aalenian Oseberg Formation (0-80 m thick) is an important reservoir unit in the Middle Jurassic Brent Group in the northern North Sea, consisting of multiple sets of sandy Gilbert-type deltas. Small-scale (1.5-10 m) fining-upward units seen in the gamma-ray log correspond with individual delta sets, as independently confirmed by steepening-upward trends seen in the dip log. Within each set, the steep foreset slopes typically show thinly bedded sandstone facies (avalanche grain flows), whereas the lower foreset slopes, toesets, and bottomsets are formed largely by massive sandstone facies (sandy debris flows). On an intermediate scale (up to 40 m), the gamma-ray logs show both fining-upward and coarsening-upward trends through stacked delta sets, and these trends, traceable between wells, are interpreted in terms of decelerating and accelerating rates of relative sea level rise, respectively. The relative abundance of the sandy debris-flow deposits reflects a periodic and significant instability of the delta`s upper foreset slope, probably during times of increased water depth in front of the delta. The normal progradation of individual Gilbert-type sets, however, is likely to have been along a subhorizontal topography during periods of little or no change in water depth. The long-term change to produce the observed vertical stacking of deltaic sets was one of a generally rising relative sea level.

  14. Sandstone Strata in Capitol Reef National Park

    USGS Multimedia Gallery

    A detail view of some sandstone strata within Capitol Reef National Park. Capitol Reef is primarily made up of sandstone formations within the Waterpocket Fold, monocline that extends nearly 100 miles. A monocline is a step-like fold in rock strata that can resemble an enormous wrinkle in the earth....

  15. Snow-covered Sandstone at Bryce Canyon

    USGS Multimedia Gallery

    Bryce Canyon is a unique sandstone formation in southern Utah. It is home to a large number of hoodoos, which are oddly shaped pillars of rock that formed due to different erosion rates for the dolomite that caps them and the sandstone that forms their base. Bryce Canyon is also home to large numbe...

  16. Clastic Pipes: Proxies of High Water Tables and Strong Ground Motion, Jurassic Carmel Formation, Southern Utah

    NASA Astrophysics Data System (ADS)

    Wheatley, David; Chan, Marjorie

    2015-04-01

    Multiple soft sediment deformation features from bed-scale to basin-scale are well preserved within the Jurassic Carmel Formation of Southern Utah. Field mapping reveals thousands of small-scale clastic injectite pipes (10 cm to 10 m diameter, up to 20 m tall) in extremely high densities (up to 500+ pipes per 0.075 square kilometers). The pipes weather out in positive relief from the surrounding host strata of massive sandstone (sabkha) and crossbedded sands with minor conglomerate and shale (fluvial) deposits. The host rock shows both brittle and ductile deformation. Reverse, normal, and antithetical faulting is common with increased frequency, including ring faults, surrounding the pipes. The pipes formed from liquefaction and subsequent fluidization induced by strong ground motion. Down-dropped, graben blocks and ring faults surrounding pipes indicate initial sediment volume increase during pipe emplacement followed by sediment volume decrease during dewatering. Complex crosscutting relationships indicate several injection events where some pipe events reached the surface as sand blows. Multiple ash layers provide excellent stratigraphic and temporal constraints for the pipe system with the host strata deposited between 166 and 164 Ma. Common volcanic fragments and rounded volcanic cobbles occur within sandstone and conglomerate beds, and pipes. Isolated volcanic clasts in massive sandstone indicate explosive volcanic events that could have been the exogenic trigger for earthquakes. The distribution of pipes are roughly parallel to the Middle Jurassic paleoshoreline located in marginal environments between the shallow epicontinental Sundance Sea and continental dryland. At the vertical stratigraphic facies change from dominantly fluvial sediments to dominantly massive sabkha sediments, there is a 1-2 m-thick floodplain mudstone that was a likely seal for underlying, overpressurized sediments. The combination of loose porous sediment at a critical depth of water saturation made the system extremely susceptible to liquefaction. Fluid inclusions of carbonate nodules present on the pipe margins indicate salinity, temperature, and character of possible early diagenetic fluids before significant burial. These inclusions can reveal information about brines from point sources or fed via groundwater. Overall, the combination of clastic pipes and their related soft deformation structures in the host rock provide proxies for the existence of high water table conditions within arid climate regimes and transitional paleoenvironments previously assumed to be devoid of significant amounts of water. The pipe distribution and evidence of multiple injectite events paralleling an ancient paleoshoreline provides basin-scale insights on repeated paleoseismicity and volcanism along the convergent boundary of the Cordilleran.

  17. Paleoenvironments and hydrocarbon potential of Upper Jurassic Norphlet Formation of southwestern Alabama and adjacent coastal water area

    SciTech Connect

    Mancini, E.A.; Mink, R.M.; Bearden, B.L.

    1984-09-01

    Upper Jurassic Norphlet sediments in southwestern Alabama and the adjacent coastal water area accumulated under arid climatic conditions. The Appalachian Mountains of the eastern United States extended into southwestern Alabama, providing a barrier for air and water circulation during Norphlet deposition. Norphlet paleogeography was dominated by a broad desert plain rimmed to the north and east by the Appalachians and to the south by a developing shallow sea. Initiation of Norphlet sedimentation was a result of erosion of the southern Appalachians. Norphlet conglomerates were deposited in coalescing alluvial fans in proximity to an Appalachian source. The conglomeratic sandstones grade downdip into red-bed lithofacies that accumulated in distal portions of alluvial fan and wadi systems. Quartzose sandstones (Denkman Member) were deposited as dune and interdune sediments on a broad desert plain. The source of the sand was the updip and adjacent alluvial fan, plain, and wadi deposits. A marine transgression was initiated late in Denkman deposition, resulting in the reworking of previously deposited Norphlet sediments. Norphlet hydrocarbon potential in southwestern and offshore Alabama is excellent with four oil and gas fields already established. Petroleum traps discovered to date are primarily structural traps involving salt anticlines, faulted salt anticlines, and extensional fault traps associated with salt movement. Reservoir rocks consist of quartzose sandstones, which are principally eolian in origin. Smackover algal carbonate mudstones were probably the source for the Norphlet hydrocarbons.

  18. Jurassic hydrocarbon exploration of southern Florida

    SciTech Connect

    Mitchell-Tapping, H.J. [Retog, Inc., DeSoto, TX (United States)

    1994-09-01

    South Florida Jurassic exploration has been overlooked as a viable exploration target due to lack of data and plate-tectonics application. In Florida, {open_quotes}basement{close_quotes} is defined as crystalline, igneous, metamorphic, and unmetamorphosed sediments of Paleozoic age. Age-dating of zircons has proven that the Florida lower Paleozoic terrane is not akin to that of North America but is part of the West African Guinean shield. Previous published reconstructions of late Paleozoic fits of crustal plates and continents have failed to account for the differences in peninsula Florida basement and the geologic and tectonic continuities of peninsula Florida, Yucatan, Cuba, Hispaniola, and Bahamas. Pre-Atlantic reconstruction of the Gulf of Mexico in this study proposes that there was a Florida connection to Yucatan-Cuba-Africa during the Triassic. This reconstruction also shows that the Jurassic sediments that are well known in the northern Gulf Coast should have been deposited in similar depositional environments in southern Florida. Deep drilling on the Florida peninsula has confirmed this hypothesis. By using plate tectonic reconstruction based on the rising of the North Atlantic Ocean and evidence from petrology of basement samples from deep wells together with petrographic analyses of Jurassic sediments, a Smackover-equivalent exploration play can be developed. Petrographic and petrophysical analysis of these wells that have encountered Jurassic marine shales, anhydrite, dolomite, carbonate, and elastic sediments has determined that these sediments are from shallow-water subtidal, tidal, intertidal, and supratidal environments. Excellent gas shows, oil stain in the pores and high TOC values in the marine shales, indicate that large accumulations of hydrocarbon are present.

  19. Age spectra of detrital zircon of the Jurassic clastic rocks of the Mino-Tanba AC belt in SW Japan: Constraints to the provenance of the mid-Mesozoic trench in East Asia

    NASA Astrophysics Data System (ADS)

    Fujisaki, Wataru; Isozaki, Yukio; Maki, Kenshi; Sakata, Shuhei; Hirata, Takafumi; Maruyama, Shigenori

    2014-07-01

    U-Pb ages of detrital zircon grains were determined from an upper Middle Jurassic siliceous mudstone and two lower Upper Jurassic sandstones of the Mino-Tanba belt, Southwest Japan, by Laser-ablation ICPMS. The age spectra of detrital zircon grains of the three analyzed samples show multiple age clusters: 175-198 Ma (Early Jurassic), 202-284 Ma (Permian to Triassic), 336-431 Ma (Silurian to Carboniferous), and 1691-2657 Ma (Neoarchean to Paleoproterozoic). As per the Precambrian grains, the prominent peak exists around 1800-2000 Ma in all analyzed samples. The age clusters of 175-198 Ma, 202-284 Ma, and 336-431 Ma suggest that pre-Middle Jurassic Japan has exposed older granitic batholiths. The corresponding batholiths occur in the Cathaysian part of South China block. In contrast, the absence of them in modern Japan suggests that these batholiths were totally consumed by post-Jurassic tectonic erosion. The Neoarchean to Paleoproterozoic detrital zircon grains were derived from South China, North China, or possibly both of them; nonetheless, the circumstantial geologic lines of evidence point to South China, in particular to Cathaysia, rather than North China.

  20. Effects of one and two seasons irrigation on vegetal response, Navajo Mine, northwest New Mexico

    SciTech Connect

    Hyder, D.; Buchanan, H.; Burchanan, B.A. [Buchanan Consultants Ltd., Farmington, NM (United States)] [and others

    1995-09-01

    An irrigation study was established in 1990 to compare the effects of one and two seasons of irrigation on reclamation success. Two study plots were located in the Mason 90 Reclamation Area, Navajo Mine, Northwestern New Mexico. Vegetational data was collected and in early 199, prior to the plot receiving the second season of irrigation. Additional vegetal data has been collected in 1992, 1993, and 1994. Total vegetal cover was generally higher for the plot receiving two seasons of irrigation in 1991 and 1992. However, by 1993 and in 1994, the vegetal responses for the two plots were nearly the same. It appears one season of irrigation may be adequate to establish successful reclamation at Navajo Mine.

  1. Monitoring and analysis of sand dune movement and growth on the Navajo Nation, southwestern United States

    USGS Publications Warehouse

    Redsteer, Margaret Hiza; Bogle, Rian C.; Vogel, John M.

    2011-01-01

    Recurring drought and rising temperatures have caused reactivation and renewed growth of sand dunes on the lands of the Navajo Nation on the Colorado Plateau. Migrating dunes threaten health, housing, and transportation pathways. U.S. Geological Survey (USGS) scientists are conducting research to better understand the processes of dune growth and movement. This research will provide critical data to the Native peoples of the region in their response to the changing environment.

  2. Psychological effects of technological/human-caused environmental disasters: examination of the Navajo and uranium.

    PubMed

    Markstrom, Carol A; Charley, Perry H

    2003-01-01

    Disasters can be defined as catastrophic events that challenge the normal range of human coping ability. The technological/human-caused disaster, a classification of interest in this article, is attributable to human error or misjudgment. Lower socioeconomic status and race intersect in the heightened risk for technological/human-caused disasters among people of color. The experience of the Navajo with the uranium industry is argued to specifically be this type of a disaster with associated long-standing psychological impacts. The history of the Navajo with uranium mining and milling is reviewed with a discussion of the arduous efforts for compensation. The psychological impacts of this long-standing disaster among the Navajo are organized around major themes of: (a) human losses and bereavement, (b) environmental losses and contamination, (c) feelings of betrayal by government and mining and milling companies, (d) fears about current and future effects, (e) prolonged duration of psychological effects, (f) anxiety and depression, and (g) complicating factors of poverty and racism. The paper concludes with suggestions for culturally-appropriate education and intervention. PMID:12955630

  3. Vegetation associated with the major soils and reclamation areas on the Navajo Mine, New Mexico

    SciTech Connect

    Buchanan, B.A.; Wood, M.K. [New Mexico State Univ., Las Cruces, NM (United States); Ruzzo, W. [BHP - Utah International Inc., Fruitland, NM (United States)

    1990-12-31

    Mine-land reclamation success is usually measured by comparing reclaimed areas to be the pre-mined or native conditions. Establishing standards of reclamation is made more difficult when the native conditions are extremely variable as for the Navajo Mine. The Navajo mine lease has annual grazing capacities ranging from 12 hectares (30 acres) to 80 hectares (200 acres) per sheep. The objective of this research was to determine the vegetal characteristics combining the most extensive or most productive native soil types on the Navajo Lease. Then to compare these data using weighted means (based on percent area) to the vegetal characteristics of topdressed and non-topdressed reclamation plots. Some native areas have high cover, shrub density and phytomass. However, these vegetal characteristics are lower for the average native condition than the average for either the topdressed or non-topdressed reclamation plots. The weighted mean of the native area is low because of the extensive amount (>65%) of badland and natrargid type soils. These two mapping units have extremely low cover, shrub density and phytomass. Reclaimed plots without topdressing have higher cover and phytomass than topdressed reclamation plots. This is because of the high schrub density. However, the topdressed reclamation areas produce more perennial forbs and grasses than non topdressed plots. This is considered to be more desirable for reclamation success.

  4. Building community capacity for agricultural injury prevention in a Navajo community.

    PubMed

    Helitzer, D; Willging, C; Hathorn, G; Benally, J

    2009-01-01

    This article describes the process of building community capacity to plan, implement, and evaluate culturally appropriate agricultural injury prevention programs on the Navajo Nation. Navajo farmers and ranchers, the community stakeholders in this model program, experience significantly greater farm-related occupational mortality compared to other ethnic groups in the southwestern U.S. In this population, effective agricultural injury prevention projects designed to change livestock and pesticide handling practices are likely to reduce agricultural-related injuries and deaths. Community-based organizations and community members may benefit from training to develop the capacity to undertake systematic planning and evaluation. Using a community-based participatory research approach that addressed the need for such training, a stakeholder group consisting of university faculty and community members implemented a sequential planning process that incorporated scientific principles and activities. Over five years, community stakeholders identified criteria to define capacity improvement and then proceeded to implement activities to enhance their ability to develop, implement, and evaluate agricultural injury prevention projects. Specifically, stakeholders developed, translated, and administered a baseline survey of agricultural practices among Navajo farmers and ranchers, used survey results to design two agricultural safety projects, and implemented and evaluated the interventions. The results of the evaluation of capacity building suggest that the project was successful. This project may serve as an innovative model for increasing community involvement in the development of agricultural injury prevention interventions with underserved populations where mortality and morbidity are high, and strategies for prevention have either not been effective or adequately studied. PMID:19266882

  5. Exploration models for submarine slope sandstones

    SciTech Connect

    Slatt, R.M.

    1986-09-01

    Recent published studies have demonstrated a far greater potential than previously recognized for submarine slope sandstones to contain significant oil and gas reserves in the Gulf Coast and elsewhere. Comparison of modern slopes with outcrop and subsurface analogs from several areas provided the framework for developing the following submarine slope sandstone exploration models: submarine canyon fill, slope gully/channel fill, slope spillover sand sheets, and intraslope basin fill. Submarine canyon fill is mainly shale, but sandstone beds that form stratigraphic traps may be present. Canyon shale fill juxtaposed against older sandstones can also form stratigraphic traps. Gully/channel fills are sandstones deposited on shallow-gradient slopes or ramps. The proximity of these sandstones to slope shales provides opportunities for stratigraphic traps to develop. Spillover sand sheets are resedimented from a shelf to a shallow-gradient slope and are associated with gully/channel fills. Intraslope basin fill is mainly shale, but elongate, sheetlike, or fan-shaped turbidite sandstones can provide stratigraphic traps. In all of these deposits, slope shales may be sufficiently enriched in organic carbon to be potential hydrocarbon source rocks; the potential for organic-rich shales to accumulate is highest in intraslope basin fill.

  6. A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago

    Microsoft Academic Search

    Ursula B. Göhlich; Luis M. Chiappe

    2006-01-01

    Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the

  7. Massive dissociation of gas hydrate during a Jurassic

    E-print Network

    Hesselbo, Stephen P.

    .............................................................................................................................................. In the Jurassic period, the Early Toarcian oceanic anoxic event (about 183 million years ago) is associated hydrate during a Jurassic oceanic anoxic event Stephen P. Hesselbo*, Darren R. Gro¨cke*, Hugh C. Jenkyns together, these 13 C curves depict a period of gradual rise in isotopic values which is interrupted

  8. He Will Lift Up His Head: A Report to the Developmental Disabilities Office on the Situation of Handicapped Navajos and the Implications Thereof for All Native Americans.

    ERIC Educational Resources Information Center

    Haskins, James S.; Stifle, J. M.

    Issues involved in education of handicapped Navajo children are examined. Background sections contrast the history of treatment for the handicapped in America with the treatment received by handicapped Navajos. Unemployment, substandard housing, lack of accessibility within the reservation, overpopulation, language barriers, and the relationship…

  9. Memorandum on possibility of developing ground water for irrigation along Toc Chinlin Wash near Emmanuel Mission, Navajo Indian Reservation, Apache County, Arizona

    USGS Publications Warehouse

    Whitcomb, H.A.; Repenning, C.A.

    1950-01-01

    On November 21, 1949, the writers accompanied Mr. Chester Wilson of the Navajo Service Water Supply Office to Emmanuel Mission, Arizona, to investigate the adequacy of ground-water supplies adequate for irrigation along Toc Chinlin Wash. The investigation was made as part of the ground-water studies of the Geological Survey on the Navajo Indiana Reservation.

  10. Lower Cretaceous Avile Sandstone, Neuquen basin, Argentina - Exploration model for a lowstand clastic wedge in a back-arc basin

    SciTech Connect

    Ryer, T.A. (Apache International, Denver, CO (United States))

    1991-03-01

    The Neuquen basin of western Argentina is a back-arc basin that was occupied by epeiric seas during much of Jurassic and Cretaceous time. The Avile Sandstone Member of the Agrio Formation records a pronounced but short-lived regression of the Agrio sea during middle Hauterivian (Early Cretaceous) time. Abrupt lowering of relative sea level resulted in emergence and erosion of the Agrio sea floor; shoreline and fluvial facies characteristic of the Centenario Formation shifted basinward. The Avile rests erosionally upon lower Agrio shale over a large area; well-sorted, porous sandstones within the member pinch out laterally against the base-Avile erosional surface. Avile deposition closed with an abrupt transgression of the shoreline to the approximate position it had occupied prior to the Avile regression. The transgressive deposits are carbonate rich, reflecting starvation of the basin as a consequence of sea-level rise. The Avile lowstand clastic wedge consists predominantly of sandstones deposited in fluvial to shallow-marine paleoenvironments; eolian sandstones probably constitute an important component in the eastern part of the area. The sandstones locally have excellent reservoir characteristics; they constitute the reservoirs in the Puesto Hernandez, Chihuido de la Sierra Negra, and Filo Morado fields. The pinch-out of the Avile lowstand clastic wedge has the potential to form stratigraphic traps in favorable structural positions. The depositional model indicates that there may be a viable stratigraphic play to be made along the Avile pinch-out in the deep, relatively undrilled, northwestern part of the Neuquen basin.

  11. A clean-burning biofuel as a response to adverse impacts of woodsmoke and coalsmoke on Navajo health

    SciTech Connect

    Shultz, E.B. Jr.; Bragg, W.G. [Enable International, Wheaton, IL (United States); Whittier, J. [NEOS Corporation, Lakewood, CO (United States)] [and others

    1994-12-31

    Because over 60% of Navajo households are heated with woodfuel and coal, and indoor air pollution from woodsmoke and coalsmoke is problematic, most Navajos are probably at risk of respiratory and other smoke-induced illnesses. A previous study has shown that Navajo children living in homes heated by a wood/coal stove are nearly five times more likely to contract acute lower respiratory tract infections than children from homes that do not use those fuels. Stove and flue improvements to reduce leakage of smoke into the home would help. So would clean-burning solid fuels in replacement of woodfuel and coal. The authors describe a clean-burning fast-growing carbohydrate biofuel, prepared by sun-drying the roots of a wild southwestern gourd plant, Cucurbita foetidissima. They call it {open_quotes}rootfuel.{close_quotes} A test plot is growing during the 1994 season at the NMSU Agricultural Science Center on the Navajo Nation, near Farmington, New Mexico. Irrigation requirements are being measured. In the Fall, a preliminary needs assessment will be conducted to learn more about how fuel usage impacts Navajo health. The acceptability of rootfuel in selected homes will be tested during the upcoming heating season.

  12. Diagenesis and fluid flow in the San Juan Basin, New Mexico - regional zonation in the mineralogy and stable isotope composition of clay minerals in sandstone.

    USGS Publications Warehouse

    Whitney, G.; Northrop, H.R.

    1987-01-01

    The Westwater Canyon Member of the Upper Jurassic Morrison Formation is a relatively homogeneous, hydrologically continuous 100-m-thick sequence of massive fluvial sandstone, bounded above and below by relatively heterogeneous, hydrologically discontinuous units and has served as a primary conduit for fluids within this stratigraphic interval. Patterns of mineral-fluid reactions suggest a basinwide hydrologic regime in which warm, evolved fluids migrated up-dip from the center of the basin under the influence of a regional hydraulic head. -from Authors

  13. "Sydney sandstone": Heritage Stone from Australia

    NASA Astrophysics Data System (ADS)

    Cooper, Barry; Kramar, Sabina

    2014-05-01

    Sydney is Australia's oldest city being founded in 1788. The city was fortunate to be established on an extensive and a relatively undeformed layer of lithified quartz sandstone of Triassic age that has proved to be an ideal building stone. The stone has been long identified by geologists as the Hawkesbury Sandstone. On the other hand the term "Sydney sandstone" has also been widely used over a long period, even to the extent of being utilised as the title of published books, so its formal designation as a heritage stone will immediately formalise this term. The oldest international usage is believed to be its use in the construction of the Stone Store at Kerikeri, New Zealand (1832-1836). In the late 19th century, public buildings such as hospitals, court houses as well as the prominent Sydney Town Hall, Sydney General Post Office, Art Gallery of New South Wales, State Library of New South Wales as well as numerous schools, churches, office building buildings, University, hotels, houses, retaining walls were all constructed using Sydney sandstone. Innumerable sculptures utilising the gold-coloured stone also embellished the city ranging from decorative friezes and capitals on building to significant monuments. Also in the late 19th and early 20th century, Sydney sandstone was used for major construction in most other major Australian cities especially Melbourne, Adelaide and Brisbane to the extent that complaints were expressed that suitable local stone materials were being neglected. Quarrying of Sydney sandstone continues today. In 2000 it was recorded noted that there were 33 significant operating Sydney sandstone quarries including aggregate and dimension stone operations. In addition sandstone continues to be sourced today from construction sites across the city area. Today major dimension stone producers (eg Gosford Quarries) sell Sydney sandstone not only into the Sydney market but also on national and international markets as cladding and paving products as well as block. Recent international projects by Gosford Quarries include Mishima Golf Club in Japan, Al Awadi Tower in Kuwait, New World Resort in China and a Hard Rock Café in Florida, USA. Arguably Sydney sandstone is Australia's most prominent potential Global Heritage Stone Resource and details are readily available in existing publications to make the nomination.

  14. Exhumed hydrocarbon traps in East Greenland: Analogs for the lower-middle Jurassic play of northwest Europe

    SciTech Connect

    Price, S.P.; Whitham, A.G. [Univ. of Cambridge (United Kingdom)

    1997-02-01

    Four exhumed hydrocarbon traps crop out in the Traill 0 region of East Greenland, each at the footwall crest of a fault-block formed during Early Cretaceous rifting. Former oil accumulations are indicated by a pore fill or pore lining of solid bitumen within the Jurassic sandstone-dominated Vardekloft and Olympen formations. The Vardekloft Formation is divided into an undated fluvial-dominated lower unit (0-520 m) and a Bajocian-Callovian upper unit (65-1020 m) deposited in a shallow-marine environment. The Oxfordian Olympen Formation (0-250 m) contains shallow-marine and fluviodeltaic deposits. The sandstones are dominantly quartzarenites, and petrographic fabrics, such as dissolved feldspar, late quartz cement, and stylolites, are consistent with burial depths in excess of 2.5 km. Porosities ranged from 7 to 27% (generally about 20%, about one-half of which was primary), and permeabilities ranged from 1 to 622 md, prior to the formation of solid bitumen. The distribution of solid bitumen in each trap can be mapped out, allowing sealing elements and original oil-water contacts to be defined. Three of the four exhumed traps (Mols Bjerge, Laplace Bjerg, and Bjornedal) were simple one-seal structural traps. Conformable Upper Jurassic mudstone, unconformable Albian-Cenomanian mudstone, and normal faults are the three top-sealing elements. The fourth (Svinhufvuds Bjerge) was a poly-seal trap with a combined top-seal and a low-side fault closure. Preliminary estimates of the volume of original oil in place within these structures range from 0.2-1.1 billion bbl for the Mols Bjerge trap to 5.3-11.9 billion bbl for the Bjornedal trap. These estimates are prone to large errors, due to uncertainties in estimating original trap geometry, hydrocarbon saturation, and net/gross ratio, and in the understanding of volume changes of hydrocarbon in each trap during thermal degradation of the oil.

  15. Total petroleum systems of the Bonaparte Gulf Basin area, Australia; Jurassic, Early Cretaceous-Mesozoic; Keyling, Hyland Bay-Permian; Milligans-Carboniferous, Permian

    USGS Publications Warehouse

    Bishop, M.G.

    1999-01-01

    The Bonaparte Gulf Basin Province (USGS #3910) of northern Australia contains three important hydrocarbon source-rock intervals. The oldest source-rock interval and associated reservoir rocks is the Milligans-Carboniferous, Permian petroleum system. This petroleum system is located at the southern end of Joseph Bonaparte Gulf and includes both onshore and offshore areas within a northwest to southeast trending Paleozoic rift that was initiated in the Devonian. The Milligans Formation is a Carboniferous marine shale that sources accumulations of both oil and gas in Carboniferous and Permian deltaic, marine shelf carbonate, and shallow to deep marine sandstones. The second petroleum system in the Paleozoic rift is the Keyling, Hyland Bay-Permian. Source rocks include Lower Permian Keyling Formation delta-plain coals and marginal marine shales combined with Upper Permian Hyland Bay Formation prodelta shales. These source-rock intervals provide gas and condensate for fluvial, deltaic, and shallow marine sandstone reservoirs primarily within several members of the Hyland Bay Formation. The Keyling, Hyland Bay-Permian petroleum system is located in the Joseph Bonaparte Gulf, north of the Milligans-Carboniferous, Permian petroleum system, and may extend northwest under the Vulcan graben sub-basin. The third and youngest petroleum system is the Jurassic, Early Cretaceous-Mesozoic system that is located seaward of Joseph Bonaparte Gulf on the Australian continental shelf, and trends southwest-northeast. Source-rock intervals in the Vulcan graben sub-basin include deltaic mudstones of the Middle Jurassic Plover Formation and organic-rich marine shales of the Upper Jurassic Vulcan Formation and Lower Cretaceous Echuca Shoals Formation. These intervals produce gas, oil, and condensate that accumulates in, shallow- to deep-marine sandstone reservoirs of the Challis and Vulcan Formations of Jurassic to Cretaceous age. Organic-rich, marginal marine claystones and coals of the Plover Formation (Lower to Upper Jurassic), combined with marine claystones of the Flamingo Group and Darwin Formation (Upper Jurassic to Lower Cretaceous) comprise the source rocks for the remaining area of the system. These claystones and coals source oil, gas, and condensate accumulations in reservoirs of continental to marine sandstones of the Plover Formation and Flamingo Group. Shales of the regionally distributed Lower Cretaceous Bathurst Island Group and intraformational shales act as seals for hydrocarbons trapped in anticlines and fault blocks, which are the major traps of the province. Production in the Bonaparte Gulf Basin Province began in 1986 using floating production facilities, and had been limited to three offshore fields located in the Vulcan graben sub-basin. Cumulative production from these fields totaled more than 124 million barrels of oil before the facilities were removed after production fell substantially in 1995. Production began in 1998 from three offshore wells in the Zone of Cooperation through floating production facilities. After forty years of exploration, a new infrastructure of pipelines and facilities are planned to tap already discovered offshore reserves and to support additional development.

  16. Crossroads and Connections: An Evolving Relationship between NASA and the Navajo Nation

    NASA Astrophysics Data System (ADS)

    Scalice, D.; Carron, A.

    2010-08-01

    Is working with Native Americans business as usual? We live in a project-based world that operates on three-to-five-year grants. A long term commitment can be next to impossible to keep, even if you have the best of intentions. Are there things one "must know" before approaching an indigenous population? How is it best to evaluate projects and programs involving Native Americans? In the NASA and the Navajo Nation project, which will turn five in January, 2010, we have compiled some key lessons learned that we hope will inform and encourage future partnerships between the space science education and Native American communities.

  17. Paleomagnetism of Jurassic dolerites from Northern Victoria Land, Antarctica - Onset of rapid Jurassic pole shift?

    NASA Astrophysics Data System (ADS)

    Kirscher, U.; Bachtadse, V.; Petersen, N.; Rolf, C.; Lemna, O. S.

    2014-12-01

    Flood basalts (Kirkpatrick) and sills (Ferrar) of the Transantarctic mountains (183Ma) have been studied paleomagnetically in detail in the 60's to 90's of the 1900's yielding two groups of paleopole positions plotting at ~55°S (A) or at ~80°S (B). Group A poles have been interpreted to reflect the Early Jurassic Earth magnetic field but the significance of Group B poles is less clear. Here we report new data from the Kirkpatrick basalts at Gair Mesa (73.47°S; 162.87°E), where about 800 stratigraphic meters including 23 volcanic flows were sampled. After removal of a steep magnetic overprint straight linear segments trending toward the origin of the projection plane are identified in 151 samples from 22 sites. All characteristic directions are of normal polarity and interpreted to be carried by magnetite. The resulting mean pole plots at 66.4°S; 227.7°E, A95=6.2°, k = 25.7 similar to group B poles. Reflecting light microscopy suggests that the original magnetization has survived low temperature alteration. Since secular variation has been averaged (Sb=15.9°) we argue that the Gair Mesa basalts have recorded the time averaged geomagnetic field during early to mid Jurassic times. Hence, we conclude that both groups A and B are of primary origin and consequently speculate that group B paleopoles might reflect the onset of the recently postulated Jurassic pole shift.

  18. Microstructure of deformed graywacke sandstones

    SciTech Connect

    Dengler, L.A.

    1980-03-05

    Microsctures in low-permeability graywacke sandstones were studied by optical and scanning electron microscopy (SEM). SEM specimens were prepared by ion-bombardment of thick polished samples. The undeformed rock contains grains in a matrix composed primarily of authigenic chlorite and kaolinite. Chlorite platelets are randomly arranged in face-to-edge relation to one another. Kaolinite occurs as pseudohexagonal crystals stacked face-to-face in pore filling books. Uniaxial-stress experiments covered a range of confining pressures from .1 to 600 MPa. Below 50 MPa confining pressure, intergranular fracturing occurs within the fault zone and near the sample's cylindrical surface. Between 100 and 300 MPa confining pressure, fault zones contain highly fractured grains, gauge and slickensides on grain surfaces. At 600 MPa, the sample contains a diffuse shear zone of highly fractured grains and no well-defined fault. In all samples, the distribution of microcracks is heterogeneous. Different clay minerals exhibit different modes of deformation. Chlorite structure responds to applied stress by compaction, reducing both pore size and volume. Chlorite platelets are plastically deformed in even the least strained samples. Kaolinite does not deform plastically in any of the samples examined. Deformation of kaolinite is restricted to toppling of the book structure. Dilatant crack growth was studied in two samples unloaded prior to failure. Uniaxially-strained samples deform primarily along grain boundaries, producing intergranular cracks and realignment of chlorite platelets. Intragranular crack density is linearly related to axial-strain, although grains are less fractured than in uniaxially-stressed samples tested at equivalent mean pressures. Cracks are rarely longer than a grain diameter. Nuclear-explosively deformed samples were recovered after the Rio Blanco gas stimulation experiment. (JGB)

  19. Stratigraphic and structural configuration of the Navajo (Jurassic) through Ouray (Mississippian-Devonian) formations in the vicinity of Davis and Lavender Canyons, southeastern Utah

    SciTech Connect

    McCleary, J.R.; Romie, J.E.

    1986-04-01

    This study developed a three-dimensional computer model of stratigraphic and structural relationships within a 3497-km/sup 2/ (1350-mi/sup 2/) study area centered on the proposed site for a high-level nuclear waste repository in southeastern Utah. The model consists of a sequence of internally reconciled isopach and structure contour maps horizontally registered and stored in stratigraphic order. This model can be used to display cross sections, perspective block diagrams, or fence diagrams at any orientation; estimate depth of formation contacts and thicknesses for any new stratigraphic or hydrologic boreholes; facilitate ground-water modeling studies; and evaluate the structural and stratigraphic evolution of the study area. This study also includes limited evaluations of aquifer continuity in the Elephant Canyon and Honaker Trail Formations, and of salt dissolution and flowage features as interpreted from geophysical logs. The study identified a long history of movement in the fault system in the north-central part of the study area and a major salt flowage feature in the northeastern part. It describes the Elephant Canyon Formation aquifer as laterally limited, the Honaker Trail Formation aquifer as fairly continuous over the area, and Beef Basin in the southern part of the area as a probable dissolution feature. It also concludes that the Shay-Bridger Jack-Salt Creek Graben system is apparently a vertically continuous feature between the basement and ground surface. No stratigraphic or structural discontinuities were detected in the vicinity of Davis Canyon that appear to be detrimental to the siting of a waste repository.

  20. Jurassic sequence stratigraphy in Mississippi interior salt basin: an aid to petroleum exploration in eastern Gulf of Mexico area

    SciTech Connect

    Mancini, E.A.; Mink, R.M.; Tew, B.H.

    1988-02-01

    An understanding of sequence stratigraphy of Jurassic units in onshore basins can serve as an aid to identify potential petroleum reservoir and source rocks in the eastern Gulf of Mexico area. Three depositional sequences associated with cycles of eustatic sea level change and coastal onlap have been identified in the Mississippi Interior Salt basin. Three depositional sequences probably correspond to the J2.4, J3.1, and J3.2 sequences of Vail et al for Callovian through Kimmeridgian strata. In the Mississippi Interior salt basin, the lower depositional sequence is bounded by a basal type 2 unconformity and an upper type 2 unconformity in the Callovian. This sequence includes Louann evaporites (transgressive), Pine Hill anhydrites and shales (condensed section), and Norphlet eolian sandstones (highstand regressive). The middle depositional sequence reflects relative sea level rise in the late Callovian. This sequence includes Norphlet marine sandstones and lower Smackover packstones and mudstones (transgressive), middle Smackover mudstones (condensed section), and upper Smackover grainstones and anhydrites (highstand regressive).

  1. Jurassic play pattern in Mississippi comes into focus

    Microsoft Academic Search

    1969-01-01

    A fast-moving play across Central Mississippi has shoved its production to an all time high. Buttressed with new oil from deep-lying Jurassic formations, the state expects to climb above 170,000 bpd. Providing this additional crude are 29 new fields, most all of them found in the last 4 yr. Jurassic production accounts for nearly 30% of Mississippi's total oil output.Current

  2. Navajo Environmental Health Review by the National Environmental Health Association (Window Rock, Arizona, May 24-27, 1976).

    ERIC Educational Resources Information Center

    Navajo Health Authority, Window Rock, AZ.

    The Indian Health Committee met with key staff of the Indian Health Service (IHS) Area Office to review the environmental health services provided on the Navajo Reservation and make recommendations for improvement or expansion of current programs, if needed. Recommendations were made regarding environmental health and institutional personnel,…

  3. 25 CFR 161.102 - What notifications are required that tribal laws apply to grazing permits on the Navajo...

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...What notifications are required that tribal laws apply to grazing permits on the Navajo...LANDS GRAZING PERMITS Tribal Policies and Laws Pertaining to Permits § 161.102 What notifications are required that tribal laws apply to grazing permits on the...

  4. The Impact of Power Developments on the Navajo Nation. Lake Powell Research Project Bulletin Number 7, April 1975.

    ERIC Educational Resources Information Center

    Robbins, Lynn A.

    The Federal government and private corporations involved in energy production are placing great emphasis on the strip-mining of vast coal reserves. The Navajo Nation, whose lands contain 20 billion tons of low-sulphur coal, sells vast quantities of its natural resources for use in the urban centers of Arizona and southern California. However, the…

  5. A Study of Navajo Perceptions of the Impact of Environmental Changes Relating to Energy Resource Development. Final Report.

    ERIC Educational Resources Information Center

    Schoepfle, G. Mark; And Others

    Ethnographic interview methods were utilized to determine the social costs of energy development (i.e. uranium mining) and the mitigation of these costs. Determination was made from the viewpoint of the Navajos in the Burnhams Chapter (a geopolitical unit) in Western New Mexico; they anticipated four major costs (losses) to their present way of…

  6. Triassic/Jurassic faulting patterns of Conecuh Ridge, southwest Alabama

    SciTech Connect

    Hutley, J.K.

    1985-02-01

    Two major fault systems influenced Jurassic structure and deposition on the Conecuh Ridge, southwest Alabama. Identification and dating of these fault systems are based on seismic-stratigraphic interpretation of a 7-township grid in Monroe and Conecuh Counties. Relative time of faulting is determined by fault geometry and by formation isopachs and isochrons. Smackover and Norphlet Formations, both Late Jurassic in age, are mappable seismic reflectors and are thus reliable for seismicstratigraphic dating. The earlier of the 2 fault systems is a series of horsts and grabens that trends northeast-southwest and is Late Triassic to Early Jurassic in age. The system formed in response to tensional stress associated with the opening of the Atlantic Ocean. The resulting topography was a series of northeast-southwest-trending ridges. Upper Triassic Eagle Mills and Jurassic Werner Formations were deposited in the grabens. The later fault system is also a series of horsts and grabens trending perpendicular to the first. This system was caused by tensional stress related to a pulse in the opening of the Gulf of Mexico. Faulting began in Early Jurassic and continued into Late Jurassic, becoming progressively younger basinward. At the basin margin, faulting produced a very irregular shoreline. Submerged horst blocks became centers for shoaling or carbonate buildups. Today, these blocks are exploration targets in southwest Alabama.

  7. Late Jurassic plutonism in the southwest U.S. Cordillera

    USGS Publications Warehouse

    Barth, A.P.; Wooden, J.L.; Howard, K.A.; Richards, J.L.

    2008-01-01

    Although plate reconstructions suggest that subduction was an approximately steady-state process from the mid-Mesozoic through the early Tertiary, recent precise geochronologic studies suggest highly episodic emplacement of voluminous continental-margin batholiths in the U.S. Cordillera. In central and southern California and western Arizona, major episodes of batholithic magmatism are known to have occurred in Permian-Triassic, Middle Jurassic, and late Early to Late Cretaceous time. However, recent studies of forearc-basin and continental-interior sediments suggest that Late Jurassic time was probably also a period of significant magmatism, although few dated plutons of this age have been recognized. We describe a belt of Late Jurassic plutonic and hypabyssal rocks at least 200 km in length that extends from the northwestern Mojave Desert through the Transverse Ranges. The belt lies outboard of both the voluminous Middle Jurassic arc and the ca. 148 Ma Independence dike swarm at these latitudes. The plutons include two intrusive suites emplaced between 157 and 149 Ma: a calc-alkaline suite compositionally unlike Permian-Triassic and Middle Jurassic mon-zonitic suites but similar to Late Cretaceous arc plutons emplaced across this region, and a contemporaneous but not comagmatic alkaline suite. The Late Jurassic was thus a time of both tectonic and magmatic transitions in the southern Cordillera. ?? 2008 The Geological Society of America.

  8. Stratigraphy and facies architecture of the fluvial aeolian lacustrine Sergi Formation (Upper Jurassic), Recôncavo Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Scherer, Claiton M. S.; Lavina, Ernesto L. C.; Dias Filho, Dorval C.; Oliveira, Flávio M.; Bongiolo, Daniela E.; Aguiar, Eduardo S.

    2007-02-01

    The Sergi Formation encompasses an upper Jurassic fluvial-eolian-lacustrine succession deposited within a wide intracratonic basin. Its sand bodies represent the largest and more important reservoirs in the Recôncavo Basin, hosting 362 million m 3 of oil in place. The main goal of this paper is to provide a detailed stratigraphic analysis of the Sergi Formation based on core and outcrop data. It was achieved through the recognition and correlation of regional surfaces that have allowed the subdivision of this unit into distinct depositional sequences, and the reconstruction of its depositional history. The studied succession can be subdivided into three unconformity-bounded sequences. Sequence I is composed of lacustrine mudstone at its base, which is overlain by fine- to medium-grained sandstone related to aeolian dune and sand sheet and ephemeral fluvial stream deposits. Fluvial strata indicate northeastward-flowing streams whereas aeolian dune deposits suggest the action of southwestward-blowing winds. The regional unconformity bounding sequences I and II denotes both a climate change and tectonic rearrangement of the basin. This surface delineates a change in the depositional style, from fluvial-aeolian-lacustrine (Sequence I) to entirely fluvial (Sequence II). The latter includes coarse-grained to conglomeratic sandstone deposited within northwestward-flowing braided channel-belts. Changes in fluvial palaeocurrent, from sequence I to II, indicate rearrangement of the drainage system related to basin tectonism. Furthermore, a change in the fluvial discharge regime took place as a result of a change from a drier to a wetter climate. Fluvial deposition in Sequence I was related to ephemeral streams whereas fluvial facies architecture of the Sequence II deposits indicates perennial braided streams with significant discharge variation. Another regional unconformity, this time related to a stratigraphic base level fall and consequent widespread, basinwide aeolian deflation, separates the braided fluvial facies of Sequence II from the fine- to medium-grained sandstones ascribed to sheet-floods, aeolian dunes and aeolian sand sheets of Sequence III. The resumption of aeolian sedimentation indicates a return to drier conditions in the basin. The abrupt change from fluvial-aeolian deposits to the lacustrine deposits of the overlying Itaparica Formation suggest a rapid rise of the water table and consequent basinwide flooding.

  9. Increasing Vulnerability to Drought and Climate Change on the Navajo Nation, southwestern United States

    NASA Astrophysics Data System (ADS)

    Hiza, M. M.; Kelley, K. B.; Francis, H.

    2011-12-01

    The Navajo Nation of Arizona, New Mexico, and Utah, is an ecologically sensitive semi-arid to arid area where rapid growth of one of the largest population of Native Americans is outstripping the capacity of the land to sustain them. Recent drought conditions, combined with increasing temperatures, are significantly altering the habitability of a region already characterized by harsh living conditions. In addition to altered landscape conditions due to climatic change, drought, and varying land use practices over the last 200 years, the Navajo people have been affected by land use policies and harsh economic conditions that weaken their cultural fabric. Increasing aridity combined with drought threaten the very existence of Navajo culture and the survival of traditional Navajo communities. People presently living on these Native lands are unique in American society as their traditional lifestyle requires intimate knowledge of the ecosystem, knowledge that has been passed on for generations through oral traditions. We present data from the lifelong observations of 73 Native American elders that provide a record of the changes in plants and animals, water availability, weather, and sand or dust storms. This information is used to complement the scant long-term meteorological records and historical documentation for the region to further refine our understanding of the historical trends and local impacts of climate change and drought. Among the most cited changes is a long-term decrease in the amount of annual snowfall over the past century, a transition from wet conditions to dry conditions in the 1940s, and a decline in surface water features. The lack of available water, in addition to changing socioeconomic conditions, was mentioned as a leading cause for the decline in the ability to grow corn and other crops. Other noted changes include the disappearance of springs, and of plant and animal populations (particularly medicinal plants, cottonwood trees, beavers, and eagles). Changes in the frequency of wind, sand and dust storms (more frequent in the 1950s and increasing in the 1990s) were also observed. Important information that cannot be easily gleaned from meteorological and stream flow records are also recorded in our consultations. For example, they include observations of soil moisture and the description of disappearing migratory birds that rely on water sources. Local monitoring of soil moisture conditions today indicates that a rapid decline occurs in the Springtime. The fact that soil moisture was noted in the past to persist through the spring dry season, until the late summer monsoon season has profound implications for impacts to ecosystem viability that may have already occurred with climate change and drought. In addition, these changes in soil moisture also help us understand the mechanisms contributing to current drought severity. We conclude that a long-term drying trend and decreasing snowpack, superimposed on regional drought cycles, will magnify the cultural and literal erosion and desertification of the Navajo Nation and leave its people increasingly vulnerable to climate extremes.

  10. Variations in fluvial style in the Westwater Canyon Member, Morrison formation (Jurassic), San Juan basin, Colorado plateau

    USGS Publications Warehouse

    Miall, A.D.; Turner-Peterson, C. E.

    1989-01-01

    Techniques of architectural element analysis and lateral profiling have been applied to the fluvial Westwater Canyon Member of the Morrison Formation (Jurassic) in southern San Juan Basin. On a large scale, the sandstone-body architecture consists mainly of a series of tabular sandstone sheets 5-15 m thick and hundreds of meters wide, separated by thin fine-grained units. Internally these sheets contain lateral accretion surfaces and are cut by channels 10-20 m deep and at least 250 m wide. On a more detailed scale, interpretations made from large-scale photomosaics show a complex of architectural elements and bounding surfaces. Typical indicators of moderate- to high-sinuosity channels (lateral accretion deposits) coexist in the same outcrop with downstream-accreted macroform deposits that are typical of sand flats of low-sinuosity, multiple-channel rivers. Broad, deep channels with gently to steeply dipping margins were mapped in several of the outcrops by carefully tracing major bounding surfaces. Locally thick accumulations of plane-laminated and low-angle cross-laminated sandstone lithofacies suggest rapid flow, probably transitional to upper flow regime conditions. Such a depositional style is most typical of ephemeral rivers or those periodically undergoing major seasonal (or more erratic) stage fluctuations, an interpretation consistent with independent mineralogical evidence of aridity. Fining-upward sequences are rare in the project area, contrary to the descriptions of Campbell (1976). The humid alluvial fan model of Galloway (1978) cannot be substantiated and, similarly, the architectural model of Campbell (1976) requires major revision. Comparisons with the depositional architecture of the large Indian rivers, such as the Ganges and Brahmaputra, still seem reasonable, as originally proposed by Campbell (1976), although there is now convincing evidence for aridity and for major stage fluctuations, which differs both from those modern rivers and Campbell's interpretation. ?? 1989.

  11. Contrasting styles of fault control on position of pre-Dakota unconformity and on depositional environments of Dakota sandstone, northern San Juan basin, Colorado

    SciTech Connect

    Ridgley, J.L. (Geological Survey, Denver, CO (USA))

    1989-09-01

    Detailed subsurface analyses of depositional environments and sandstone geometry of rocks from the upper part of the Upper Jurassic Morrison Formation through the Upper Cretaceous Dakota Sandstone indicate that faulting was a major control on distribution and preservation of lithofacies in the northern San Juan basin. The faults have a predominant northwest trend and were episodically active from Late Jurassic through early Late Cretaceous time. The main effect of faulting on the Morrison Formation and Lower Cretaceous Burro Canyon Formation was in the preservation and/or erosion of rock. These formations were uniformly deposited across the study area and then locally removed across horsts. Although depositional thinning of the Morrison occurs from west to east across the northern part of the basin, thickness differences (as much as 200 ft) between the Bridge Creek Limestone Member of the Mancos Shale and the Todilto Limestone of the Wanakah Formation cannot be solely attributed to regional thinning. Among closely spaced drill holes (1-3 mi apart) erosion is evidenced by thinning or local absence of the Burro Canyon and/or loss of section at the top of the underlying Morrison. The unconformity below the Dakota is not a simple regionally inclined surface from north to south across the San Juan basin. Rather, its development in the northern part of the basin is more intense on uplifted areas among a series of parallel northwest-trending vertical faults.

  12. Correlation of capillary number relationships for sandstone

    Microsoft Academic Search

    I. Chatzis; N. R. Morrow

    1981-01-01

    Capillary number relationships are presented for displacement of residual oil, and for displacement of oil which is initially continuous from water-wet sandstone having permeabilities which varied over about two orders of magnitude. It was found that the onset of mobilization could be correlated with sample permeability. Relationships between normalized reduced residual oil saturation and capillary number were correlated satisfactorily for

  13. Estimation of dynamic tensile strength of sandstone

    Microsoft Academic Search

    Shiro Kubota; Yuji Ogata; Yuji Wada; Ganda Simangunsong; Hideki Shimada; Kikuo Matsui

    2008-01-01

    A series of dynamic tests on Kimachi sandstone for measuring dynamic tensile strength are carried out using underwater shock waves. An emulsion explosive is used as the source of dynamic loading, and a pipe filled with water was arranged between the explosive and a cylindrical specimen. The length of the pipe is varied to produce different strengths of the incidence

  14. Fractures and stresses in Bone Spring sandstones

    SciTech Connect

    Lorenz, J.C.; Warpinski, N.R.; Sattler, A.R.; Northrop, D.A.

    1990-09-01

    This project is a collaboration between Sandia National Laboratories and Harvey E. Yates Company being conducted under the auspices of the Oil Recovery Technology Partnership. The project seeks to apply perspectives related to the effects of natural fractures, stress, and sedimentology to the simulation and production of low-permeability gas reservoirs to low-permeability oil reservoirs as typified by the Bone Spring sandstones of the Permian Basin, southeast New Mexico. This report presents the results and analysis obtained in 1989 from 233 ft of oriented core, comprehensive suite of logs, various in situ stress measurements, and detailed well tests conducted in conjunction with the drilling of two development wells. Natural fractures were observed in core and logs in the interbed carbonates, but there was no direct evidence of fractures in the sandstones. However, production tests of the sandstones indicated permeabilities and behavior typical of a dual porosity reservoir. A general northeast trend for the maximum principal horizontal stress was observed in an elastic strain recovery measurements and in strikes of drilling-induced fractures; this direction is subparallel to the principal fracture trend observed in the interbed carbonates. Many of the results presented are believed to be new information for the Bone Spring sandstones. 57 figs., 18 tabs.

  15. A giant pliosaurid skull from the late Jurassic of England.

    PubMed

    Benson, Roger B J; Evans, Mark; Smith, Adam S; Sassoon, Judyth; Moore-Faye, Scott; Ketchum, Hilary F; Forrest, Richard

    2013-01-01

    Pliosaurids were a long-lived and cosmopolitan group of marine predators that spanned 110 million years and occupied the upper tiers of marine ecosystems from the Middle Jurassic until the early Late Cretaceous. A well-preserved giant pliosaurid skull from the Late Jurassic Kimmeridge Clay Formation of Dorset, United Kingdom, represents a new species, Pliosaurus kevani. This specimen is described in detail, and the taxonomy and systematics of Late Jurassic pliosaurids is revised. We name two additional new species, Pliosaurus carpenteri and Pliosaurus westburyensis, based on previously described relatively complete, well-preserved remains. Most or all Late Jurassic pliosaurids represent a globally distributed monophyletic group (the genus Pliosaurus, excluding 'Pliosaurus' andrewsi). Despite its high species diversity, and geographically widespread, temporally extensive occurrence, Pliosaurus shows relatively less morphological and ecological variation than is seen in earlier, multi-genus pliosaurid assemblages such as that of the Middle Jurassic Oxford Clay Formation. It also shows less ecological variation than the pliosaurid-like Cretaceous clade Polycotylidae. Species of Pliosaurus had robust skulls, large body sizes (with skull lengths of 1.7-2.1 metres), and trihedral or subtrihedral teeth suggesting macropredaceous habits. Our data support a trend of decreasing length of the mandibular symphysis through Late Jurassic time, as previously suggested. This may be correlated with increasing adaptation to feeding on large prey. Maximum body size of pliosaurids increased from their first appearance in the Early Jurassic until the Early Cretaceous (skull lengths up to 2360 mm). However, some reduction occurred before their final extinction in the early Late Cretaceous (skull lengths up to 1750 mm). PMID:23741520

  16. Pediatric motor vehicle related injuries in the Navajo Nation: the impact of the 1988 child occupant restraint laws

    PubMed Central

    Phelan, K; Khoury, J; Grossman, D; Hu, D; Wallace, L; Bill, N; Kalkwarf, H

    2002-01-01

    Background: Navajo motor vehicle mortality is the highest among the 12 Indian Health Service (IHS) administrative areas. In July 1988, the Navajo Nation enacted a primary enforcement safety belt use and a child restraint law. Objective: Assess the impact of the laws on the rate and severity of pediatric (0–19 years) motor vehicle injury resulting in hospitalizations in the Navajo Nation. Methods: Hospitalizations associated with motor vehicle related injury discharges were identified by International Classification of Diseases, 9th revision, CM E codes, 810–825 (.0,.1) from the Navajo IHS hospital discharge database. Age specific rates for the period before the law, 1983–88, were compared with those after enactment and enforcement, 1991–95. Severity of injury, measured by the abbreviated injury scale (AIS) score and new injury severity score (NISS), was determined with ICDMAP-90 software. Wilcoxon rank sum and ?2 tests were used for analysis. Results: Discharge rates (SE) for motor vehicle injury (per 100 000) decreased significantly in all age groups: 0–4 years (62 (7) to 28 (4)), 5–11 years (55.3 (6) to 26 (4)), and 15–19 years (139 (14) to 68 (7)); p=0.0001. In children 0–4 years, the median AIS score decreased from 1.5 (1,3) (25th, 75th centile) to 1 (1,2), p=0.06, and the median NISS decreased from 3.5 (1,9) to 2 (1,5), p=0.07. The proportion of children with NISS scores >4 decreased significantly for the 0–4 year age group (p=0.03). Conclusions: Concurrent with enactment of the Navajo Nation occupant and child restraint laws there was a reduction in the rate of motor vehicle related hospital discharges for children. Severity of injury declined in very young Navajo children. The effect of enactment and enforcement of this Native American child occupant restraint law may serve as an example of an effective injury control effort directed at Native American children. PMID:12226119

  17. Assistive technology provision within the Navajo Nation: user and provider perceptions.

    PubMed

    Reisinger, Kim D; Ripat, Jacquie D

    2014-11-01

    In this study we explored the factors that affect assistive technology (AT) provision within the Navajo Nation using a qualitative approach to inquiry. Focus groups were held in which AT users discussed their awareness of AT and their need for, use of, and satisfaction with AT devices and services. Twenty-eight individuals who used wheelchairs, orthotics or prosthetics, hearing aids, communication aids, vision aids, and other AT participated in one of seven focus groups. Seven AT providers discussed the facilitators and barriers that affect AT provision. The findings revealed six themes common to both stakeholder groups and two additional themes for AT users. The central theme for AT users centered on (not) feeling understood; the central theme for AT providers revolved around the processes, activities, and roles the providers engaged in at times for different clients. Activities to increase awareness and to promote successful AT provision and satisfaction with AT devices were proposed. PMID:25147224

  18. Vegetation, substrate, and eolian sediment transport at Teesto Wash, Navajo Nation, 2009-2012

    USGS Publications Warehouse

    Draut, Amy E.; Redsteer, Margaret Hiza; Amoroso, Lee

    2012-01-01

    On the Navajo Nation, southwestern United States, warming temperatures and recent drought have increased eolian (windblown) sediment mobility such that large, migrating sand dunes affect grazing lands, housing, and road access. We present an assessment of seasonal variations in sand transport, mobility, and ground cover (vegetation and substrate) within a 0.2-km2 study area near Teesto Wash, southern Navajo Nation, as part of a multiyear study measuring the effects of drought on landscape stability. Sand mobility in the study area decreased substantially as one year (2010) with near-normal monsoon rainfall somewhat abated a decade-long drought, temporarily doubling vegetation cover. The invasive annual plant Russian thistle (Salsola sp.), in particular, thrived after the monsoon rains of 2010. Vegetation that grew during that year with adequate rain died off rapidly during drier conditions in 2011 and 2012, and the proportion of bare, open sand area increased steadily after summer 2010. We infer that isolated seasonal increases in rainfall will not improve landscape stability in the long term because sustained increase in perennial plants, which are more effective than annual plants at stabilizing sand against wind erosion, requires multiple consecutive seasons of adequate rain. On the basis of climate projections, a warmer, drier climate and potentially enhanced sediment supply from ephemeral washes may further increase eolian sediment transport and dune activity, worsening the present challenges to people living in this region. Connections between climate, vegetation cover, and eolian sediment erodibility in this region also are highly relevant for studies in other regions worldwide with similar environmental characteristics.

  19. Strategies for assessing Early{Middle (Pliensbachian{Aalenian) Jurassic cyclochronologies

    Microsoft Academic Search

    J. P ark

    1999-01-01

    There are a number of fundamental problems in assessing the astronomically forced cyclostratigraphy of the Jurassic Period. First, Jurassic geochronology is not well constrained, due to a general scarcity of radiometric dates, inferior precision of the existing ones, and large inaccuracies in stratigraphic constraints. These problems are particularly troublesome in the Early to Middle Jurassic cyclic carbonates of the Colle

  20. Middle and upper jurassic depositional environments at outer shelf and slope of Baltimore Canyon Trough

    Microsoft Academic Search

    L. A. Gamboa; P. L. Stoffa; M. Truchan

    1985-01-01

    New CDP data acquired in the Baltimore Canyon Trough during project LASE made it possible to map a continuous Jurassic sedimentary sequence from the continental margin to the abyssal plain without interruption by basement structures. Intense carbonate sedimentation is inferred at the outer shelf during the Middle and Late Jurassic. Carbonate sedimentation probably started during the Middle Jurassic with a

  1. Geological model of the Jurassic section in the State of Kuwait

    SciTech Connect

    Yousif, S.; Nouman, G.

    1995-11-01

    Until the end of the seventies, the knowledge of Jurassic Geology in the State of Kuwait was very limited, since only one deep well was drilled and bottomed in the Triassic sediments. Few scattered wells partially penetrated the Jurassic sequence. During the eighties, appreciable number of wells were drilled through the Jurassic, and added a remarkable volume of information. consequently it was necessary to analyze the new data, in order to try to construct a geological model for the Jurassic in the State of Kuwait. This paper includes a number of isopach maps explaining the Jurassic depositional basin which also helps in trying to explain the Jurassic basin in the Arabian Gulf basin. Structural evolution of the Jurassic sequence indicated an inversion of relief when compared with the Cretaceous sequence. In fact, the main Cretaceous arches were sites of sedimentation troughs during the Jurassic period. This fact marks a revolution in the concepts for the Jurassic oil exploration. One of the very effective methods of the definition of the Jurassic structures is the isopaching of the Gotnia Formation. Najmah, Sargelu and Marrat Formations include the main Jurassic reservoirs which were detected as a result of the exploration activities during the eighties. Selective stratigraphic and structural cross sections have been prepared to demonstrate and explain the nature of the Jurassic sediments.

  2. Geological Society of America Paleogeographic and tectonic implications of Jurassic sedimentary

    E-print Network

    Busby, Cathy

    -marine rocks as Jurassic instead of Triassic suggests a period of uplift and erosion or nondeposition extending of Jurassic sedimentary and volcanic sequences in the central Mojave block Elizabeth R. Schermer Department that at least part, and possibly all, of the Fairview Valley For- mation is late Early Jurassic in age. We

  3. Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription of Iguanodonichnus frenki)

    E-print Network

    Benton, Michael

    Occurrence of sauropod dinosaur tracks in the Upper Jurassic of Chile (redescription studied Upper Jurassic dinosaur unit in South America, the Ban~os del Flaco Formation, Chile. Keywords: Chile; Dinosaur footprints; Parabrontopodus; Sauropod; Upper Jurassic Resu´men En el presente

  4. Harvestmen (Arachnida: Opiliones) from the Middle Jurassic of China

    NASA Astrophysics Data System (ADS)

    Huang, Diying; Selden, Paul A.; Dunlop, Jason A.

    2009-08-01

    Harvestmen (Arachnida: Opiliones) are familiar animals in most terrestrial habitats but are rare as fossils, with only a handful of species known from each of the Palaeozoic, Mesozoic, and Cenozoic eras. Fossil harvestmen from Middle Jurassic (ca. 165 Ma) strata of Daohugou, Inner Mongolia, China, are described as Mesobunus martensi gen. et sp. nov. and Daohugopilio sheari gen. et sp. nov.; the two genera differ primarily in the relative length of their legs and details of the pedipalps. Jurassic arachnids are extremely rare and these fossils represent the first Jurassic, and only the fourth Mesozoic, record of Opiliones. These remarkably well-preserved and modern-looking fossils are assigned to the Eupnoi, whereby M. martensi demonstrably belongs in Sclerosomatidae. It thus represents the oldest record of a modern harvestman family and implies a high degree of evolutionary stasis among one of the most widespread and abundant groups of long-legged, round-bodied harvestmen.

  5. Radionuclide transport in sandstones with WIPP brine

    SciTech Connect

    Weed, H.C.; Bazan, F.; Fontanilla, J.; Garrison, J.; Rego, J.; Winslow, A.M.

    1981-02-01

    Retardation factors (R) have been measured for the transport of /sup 3/H, /sup 95m/Tc, and /sup 85/Sr in WIPP brine using St. Peter, Berea, Kayenta, and San Felipe sandstone cores. If tritium is assumed to have R=1, /sup 95m/Tc has R=1.0 to 1.3 and therefore is essentially not retarded. Strontium-85 has R = 1.0 to 1.3 on St. Peter, Berea, and Kayenta, but R=3 on San Felipe. This is attributed to sorption on the matrix material of San Felipe, which has 45 volume % matrix compared with 1 to 10 volume % for the others. Retardation factors (R/sub s/) for /sup 85/Sr calculated from static sorption measurements are unity for all the sandstones. Therefore, the static and transport results for /sup 85/Sr disagree in the case of San Felipe, but agree for St. Peter, Berea, and Kayenta.

  6. Fractures and stresses in Bone Spring sandstones

    SciTech Connect

    Warpinski, N.R.; Sattler, A.R.; Lorenz, J.C.; Northrop, D.A.

    1992-06-01

    This project was a collaboration between Sandia National Laboratories and the Harvey E. Yates Company (Heyco), Roswell, NM, conducted under the auspices of Department of Energy's Oil Recovery Technology Partnership. The project applied Sandia perspectives on the effects of natural fractures, stress, and sedimentology for the stimulation and production of low permeability gas reservoirs to low permeability oil reservoirs, such as those typified by the Bone Spring sandstones of the Delaware Basin, southeast New Mexico. This report details the results and analyses obtained in 1990 from core, logs, stress, and other data taken from three additional development wells. An overall summary gives results from all five wells studied in this project in 1989--1990. Most of the results presented are believed to be new information for the Bone Spring sandstones.

  7. Matrix versus fracture permeability in a regional sandstone aquifer (Wajid sandstone, SW Saudi Arabia)

    NASA Astrophysics Data System (ADS)

    Al Ajmi, Hussain; Hinderer, Matthias; Rausch, Randolf; Hornung, Jens; Bassis, Alexander; Keller, Martin; Schüth, Christoph

    2014-06-01

    Sandstones are often characterized as fractured aquifers. We present a case study of the Wajid sandstone, which forms a regional aquifer system in SW Saudi Arabia, where matrix, fracture, and large-scale hydraulic conductivities are coincident. The measurements deal with different scales and methods and are based on porosity and permeability measurements in the laboratory, as well as pumping tests in the field. Porosities of the sandstone samples in general are high and range between less than 5 % and more than 45 %. Gas permeabilities for strongly cemented samples are < 1 mD, whereas most samples range in between 500 and 5,000 mD. There is only a weak anisotropy with preference of the horizontal x-, y-directions. Hydraulic conductivities of the matrix samples (5.5 · 10-6 m/s and 1.1 · 10-5 m/s for the Upper and Lower Wajid sandstone, respectively) were in the same order of magnitude compared to hydraulic conductivities derived from pumping tests (8.3 · 10-5 m/s and 2.2 · 10-5 m/s for the Upper and Lower Wajid sandstone, respectively).

  8. Constraints on Upper Jurassic palaeogeography in the Ula Gyda trend

    SciTech Connect

    Mundal, I.; Milton, N.; Robinson, N. [BP Norge, Stavanger (Norway)

    1995-08-01

    BP Norway`s semi-regional 3D database in the Central Trough covers an area of nearly 3000 sq.km. around BP Norway`s two producing fields, Ula and Gyda, and includes strategic acreage within tie-back distance to the fields. Prospectivity in the Ula Gyda trend involves complex salt influenced structures and localized Upper Jurassic depositional systems. The objective of this paper is to demonstrate how the understanding of the semi-regional structures and salt tectonics helped constrain the interpretation of the Upper Jurassic palaeogeography. The control of basement structures (Permian) on cover structures (Upper Jurassic/Base Cretaceous) through Zechstein Salt was interpreted using the 3D semi-regional dataset. Analogue sandbox experiments from the Austin Geodynamics Laboratory provide support for the complex structures which were interpreted on the 3D seismic data. Sandbox models mimic the interpreted monoclinal drape of the Triassic and Jurassic section over the critical basin bounding fault in the Base Zechstein. Structural cells can be identified with the help of the salt isochore. The understanding of the relationship between structural development and salt distribution was a major control on the interpretation. This interpretation coupled with the Upper Jurassic reservoir distribution from well data provided the primary evidence for the gross depositional environment maps which were used in prospect evaluation in the area. 3D visualization and shaded relief displays of the interpreted horizons and isochores played a significant part in developing an understanding of the interplay between the deeper structures and the likely Upper Jurassic palaeogeography and depocentres.

  9. Jurassic faults of southwest Alabama and offshore areas

    SciTech Connect

    Mink, R.M.; Tew, B.H.; Bearden, B.L.; Mancini, E.A. (Geological Survey of Alabama, Tuscaloosa (United States))

    1991-03-01

    Four fault groups affecting Jurassic strata occur in the southwest and offshore Alabama areas. They include the regional basement rift trend, the regional peripheral fault trend, the Mobile graben fault system, and the Lower Mobile Bay fault system. The regional basement system rift and regional peripheral fault trends are distinct and rim the inner margin of the eastern Gulf Coastal Plain. The regional basement rift trend is genetically related to the breakup of Pangea and the opening of the Gulf of Mexico in the Late Triassic-Early Jurassic. This fault trend is thought to have formed contemporaneously with deposition of Late Triassic-Early Jurassic Eagle Mills Formation and to displace pre-Mesozoic rocks. The regional peripheral fault trend consists of a group of en echelon extensional faults that are parallel or subparallel to regional strike of Gulf Coastal Plain strata and correspond to the approximate updip limit of thick Louann Salt. Nondiapiric salt features are associated with the trend and maximum structural development is exhibited in the Haynesville-Smackover section. No hydrocarbon accumulations have been documented in the pre-Jurassic strata of southwest and offshore Alabama. Productive hydrocarbon reservoirs occur in Jurassic strata along the trends of the fault groups, suggesting a significant relationship between structural development in the Jurassic and hydrocarbon accumulation. Hydrocarbon traps are generally structural or contain a major structural component and include salt anticlines, faulted salt anticlines, and extensional fault traps. All of the major hydrocarbon accumulations are associated with movement of the Louann Salt along the regional peripheral fault trend, the Mobile graben fault system, or the Lower Mobile Bay fault system.

  10. Diagenesis of Miocene sandstones, South Louisiana 

    E-print Network

    Smith, Richard Lee

    1983-01-01

    undergone the most. The difference in mechari- cal compaction between, rhese sandstones is primarily du= to the depth at which calcite cementation begins to h 'nder compaction in each sand, and the persistance of this ement in the subsurface. Dissolucion.... precipitation, and minor episodes of dissolution, of nearly pure calcite cement; mechanical compact'on hindered by cementation, but continues during periods of dissolution 4, major, almost total, dissolution of calcite cement, resulting in secondary porosity...

  11. Alkali solution treatment on sandstone cores 

    E-print Network

    Lee, Suk Jin

    1978-01-01

    by the injection of an alkali solution. This work should provide the first step in developing a technique that can be used in the stimulation of oil and gas wells. A series of tests was conducted in which sodium hydroxide solutions with concentrations ranging... reduction in the permeability of the sandstone cores before the injection of sodium hydroxide solution and in other cases the samples were not damaged by the injection of distilled water before the sodium hydroxide solution treatment. It was found...

  12. Diagenesis of Miocene sandstones, South Louisiana

    E-print Network

    Smith, Richard Lee

    1983-01-01

    Many of these traps may be diagenetically controlled since diagenesis alters the composition and texture of sandstones. The Miocene section of South Louisiana is one of the most pro- lific hydrocarbon producing trends in the Gul Coast province. Various... deposited in coastal and shallow marine environments, mostly in deltaic depo- centers. Interpretation of the depositional environment of the sand- stones examined in this study is a primary ob]ective since diagenesis may be controlled by the environment...

  13. Apatite Fission-Track Analysis of the Middle Jurassic Todos Santos Formation from Chiapas, Mexico.

    NASA Astrophysics Data System (ADS)

    Abdullin, Fanis; Solé, Jesús; Shchepetilnikova, Valentina; Solari, Luigi; Ortega-Obregón, Carlos

    2014-05-01

    The Sierra de Chiapas (SCH), located in the south of Mexico, is a complex geological province that can be divided on four different lithological or tectonic areas: (1) the Chiapas Massif Complex (CMC); (2) the Central Depression; (3) the Strike-slip Fault Province, and (4) the Chiapas Fold-and-thrust Belt. The CMC mostly consists of Permian granitoids and meta-granitoids, and represents the basement of the SCH. During the Jurassic period red beds and salt were deposited on this territory, related to the main pulse of rifting and opening of the Gulf of Mexico. Most of the Cretaceous stratigraphy contains limestones and dolomites deposited on a marine platform setting during the postrift stage of the Gulf of Mexico rift. During the Cenozoic Era took place the major clastic sedimentation along the SCH. According the published low-temperature geochronology data (Witt et al., 2012), SCH has three main phases of thermo-tectonic history: (1) slow exhumation between 35 and 25 Ma, that affected mainly the basement (CMC) and is probably related to the migration of the Chortís block; (2) fast exhumation during the Middle-Late Miocene caused by strike-slip deformation that affects almost all Chiapas territory; (3) period of rapid cooling from 6 to 5 Ma, that affects the Chiapas Fold-and-thrust Belt, coincident with the landward migration of the Caribbean-North America plate boundaries. The two last events were the most significant on the formation of the present-day topography of the SCH. However, the stratigraphy of the SCH shows traces of the existence of earlier tectonic events. This study presents preliminary results of apatite fission-track (AFT) dating of sandstones from the Todos Santos Formation (Middle Jurassic). The analyses are performed with in situ uranium determination using LA-ICP-MS (e.g., Hasebe et al., 2004). The AFT data indicate that this Formation has suffered high-grade diagenesis (probably over 150 ºC) and the obtained cooling ages, about 70-60 Ma, correspond to a Late Cretaceous event. This tectonic event is contemporaneous with a startup of the Laramide Orogeny occurred in North America. The constructed time-temperature paths show the rapid cooling during the Middle-Late Miocene (15-10 Ma), like other published data. References: Hasebe et al. (2004) Chemical Geology, 207, 135-145 Witt et al. (2012) Tectonics, 31, TC6001, doi:10.1029/2012TC003141

  14. Permian Bone Spring formation: Sandstone play in the Delaware basin. Part I - slope

    Microsoft Academic Search

    Scott L. Montgomery

    1997-01-01

    New exploration in the Permian (Leonardian) Bone Spring formation has indicated regional potential in several sandstone sections across portions of the northern Delaware basin. Significant production has been established in the first, second, and third Bone Spring sandstones, as well as in a new reservoir interval, the Avalon sandstone, above the first Bone Spring sandstone. These sandstones were deposited as

  15. The second Jurassic dinosaur rush and the dawn of dinomania.

    PubMed

    Brinkman, Paul D

    2010-09-01

    During the second Jurassic dinosaur rush museum paleontologists raced to display the world's first mounted sauropod dinosaur. The American Museum of Natural History triumphed in 1905 when its Brontosaurus debuted before an admiring crowd of wealthy New Yorkers. The Carnegie Museum of Natural History in Pittsburgh, the Field Columbian Museum in Chicago and other institutions were quick to follow with their own sauropod displays. Thereafter, dinomania spread far and wide, and big, showpiece dinosaurs became a museum staple. This brief but intensely competitive period of acquisitiveness fostered important Jurassic dinosaur revisions and crucial innovations in paleontological field and lab techniques. PMID:20667597

  16. Power, Prayers, and Protection: Comb Ridge as a Case Study in Navajo Thought

    ERIC Educational Resources Information Center

    McPherson, Robert S.

    2010-01-01

    Beginning in 2005, a five-year survey of cultural resources began to unfold in southeastern Utah along a prominent sandstone rock formation known as Comb Ridge. This visually dramatic monocline stretches a considerable distance from the southwestern corner of Blue Mountain (Abajos) in Utah to Kayenta, Arizona, approximately one hundred miles to…

  17. Lessons Learned: Tribal Community Engagement, Remediation and Restoration of a Uranium Mine Tailings Site, Navajo Nation - 12484

    SciTech Connect

    Wadsworth, Donald K. [New World Environmental Inc., Livermore California 94550 (United States); Hicks, Allison H. [New World Environmental Inc., Irvine California 92614 (United States)

    2012-07-01

    In May, 2011 New World Environmental Inc. was awarded a contract by the Navajo Nation Environmental Protection Agency to remediate an illegal radioactive waste disposal site located in the Navajo Nation. The initial scope included the excavation and shipment of an estimated 3,000 cubic yards of Uranium mine tailings and associated industrial waste. In this instance Stakeholders were supportive of the project, remediation and restoration, yet the movement of residual radioactive materials through tribal communities was a controversial issue. Other Stakeholder issues included site security, water sources for remediation activities, local residents' temporary re-location and care of livestock, right of way permissions and local workforce development. This presentation recaps the technical and non-technical issues encountered in the remediation and restoration the seven acre site and the outreach to surrounding communities. Cultural and equity issues resulting from historical problems associated with this and other sites in the immediate area and education and training. (authors)

  18. Development and Pilot Evaluation of Native CREST – a Cancer Research Experience and Student Training Program for Navajo Undergraduate Students

    PubMed Central

    Hughes, Christine A.; Bauer, Mark C.; Horazdovsky, Bruce F.; Garrison, Edward R.; Patten, Christi A.; Petersen, Wesley O.; Bowman, Clarissa N.; Vierkant, Robert A.

    2012-01-01

    The Mayo Clinic Cancer Center and Diné College received funding for a 4-year collaborative P20 planning grant from the National Cancer Institute in 2006. The goal of the partnership was to increase Navajo undergraduates’ interest in and commitment to biomedical coursework and careers, especially in cancer research. This paper describes the development, pilot testing and evaluation of Native CREST (Cancer Research Experience & Student Training), a 10-week cancer research training program providing mentorship in a Mayo Clinic basic science or behavioral cancer research lab for Navajo undergraduate students. Seven Native American undergraduate students (5 females, 2 males) were enrolled during the summers of 2008 - 2011. Students reported the program influenced their career goals and was valuable to their education and development. These efforts may increase the number of Native American career scientists developing and implementing cancer research, which will ultimately benefit the health of Native American people. PMID:23001889

  19. Paleomagnetism of the Middle-Late Jurassic to Cretaceous red beds from the Peninsular Thailand: Implications for collision tectonics

    NASA Astrophysics Data System (ADS)

    Yamashita, Itaru; Surinkum, Adichat; Wada, Yutaka; Fujihara, Makoto; Yokoyama, Masao; Zaman, Haider; Otofuji, Yo-ichiro

    2011-02-01

    Jurassic to Cretaceous red sandstones were sampled at 33 sites from the Khlong Min and Lam Thap formations of the Trang Syncline (7.6°N, 99.6°E), the Peninsular Thailand. Rock magnetic experiments generally revealed hematite as a carrier of natural remanent magnetization. Stepwise thermal demagnetization isolates remanent components with unblocking temperatures of 620-690 °C. An easterly deflected declination ( D = 31.1°, I = 12.2°, ?95 = 13.9°, N = 9, in stratigraphic coordinates) is observed as pre-folding remanent magnetization from North Trang Syncline, whereas westerly deflected declination ( D = 342.8°, I = 22.3°, ?95 = 12.7°, N = 13 in geographic coordinates) appears in the post-folding remanent magnetization from West Trang Syncline. These observations suggest an occurrence of two opposite tectonic rotations in the Trang area, which as a part of Thai-Malay Peninsula received clockwise rotation after Jurassic together with Shan-Thai and Indochina blocks. Between the Late Cretaceous and Middle Miocene, this area as a part of southern Sundaland Block experienced up to 24.5° ± 11.5° counter-clockwise rotation with respect to South China Block. This post-Cretaceous tectonic rotation in Trang area is considered as a part of large scale counter-clockwise rotation experienced by the southern Sundaland Block (including the Peninsular Malaysia, Borneo and south Sulawesi areas) as a result of Australian Plate collision with southeast Asia. Within the framework of Sundaland Block, the northern boundary of counter-clockwise rotated zone lies between the Trang area and the Khorat Basin.

  20. Building a Seismic Sequence Stratigraphy Model Using HorizonCubes: A Jurassic Case Study in the Arabian Basin

    NASA Astrophysics Data System (ADS)

    AlYousuf, T. Y.

    2012-12-01

    Understanding the regional stratigraphic framework of the Middle and Upper Jurassic (Late Callovian-Oxfordian - Early Kimmeridgian) formations in the Arabian Basin is extremely important for unlocking the area's hydrocarbon potential. With recent advances in computing power and interpretation software, seismic sequence stratigraphy has become an important tool in reservoir characterization, and for reducing exploration risk. This paper provides a workflow that can be used to model seismic horizons using a dip steering volume. The workflow consists of data conditioning to produce a dip steering volume to generate a volume of densely spaced, automatically tracked seismic horizons, a "HorizonCube". The horizons are derived from the dip and azimuth information stored in the dip steered seismic volume model. In the Wheeler domain, the seismic volume is recomputed and flattened accordingly to match the Wheeler transformed HorizonCube. Based on the HorizonCube model, it is possible to identify stratigraphic carbonate buildups and depositional sequences. Isolating the horizon cube into smaller packages shows the dynamic variation in the deposition of sediments through time and space during the Jurassic period, starting from the top of Minjur sandstone to the Arab D limestone. The geologist is also able to identify system tracts with stratigraphic surfaces and estimate a stratigraphic base level curve. The approach is extended to integrate with the well correlation panel for better confidence in picking well tops. Visualizing system tract-interpretations together with the HorizonCube and overlaying the seismic and Wheeler-transformed domains helps to identify depositional features of interest that may form stratigraphic traps.

  1. Pangean (Late Carboniferous–Middle Jurassic) paleoenvironment and lithofacies

    Microsoft Academic Search

    J Golonka; D Ford

    2000-01-01

    Six time interval maps were constructed that depict the plate tectonic configuration, paleogeography and lithofacies for Pangea from the Late Carboniferous through the Middle Jurassic. Generally, the individual maps illustrate the conditions present during the maximum marine transgressions of higher frequency cyclicity within the Absaroka sequence of Sloss. The relative sea-level cyclicity, chronostratigraphy and regional unconformities provide the basis to

  2. Hydrothermal venting of greenhouse gases triggering Early Jurassic global warming

    Microsoft Academic Search

    Henrik Svensen; Sverre Planke; Luc Chevallier; Anders Malthe-Sørenssen; Fernando Corfu; Bjørn Jamtveit

    2007-01-01

    The climate change in the Toarcian (Early Jurassic) was characterized by a major perturbation of the global carbon cycle. The event lasted for approximately 200,000 years and was manifested by a global warming of ?6 °C, anoxic conditions in the oceans, and extinction of marine species. The triggering mechanisms for the perturbation and environmental change are however strongly debated. Here, we present

  3. Stratigraphy of the Jurassic system in northern Egypt

    SciTech Connect

    Keeley, M.L.; Shaw, D.; Forbes, G.A.

    1988-08-01

    A regional synthesis is presented of the stratigraphy of Jurassic strata in Egypt north of 30/degree/N, based on the study of about 80 wells and outcrops from northeastern Egypt. Almost all fossil groups have been investigated for biostratigraphic control. Published work on ammonite faunas from Gebel el Maghara (north Sinai) is integrated with extensive original work on palynofloras (and, to a lesser extent, ostracod/foraminiferal faunas) recovered from marine rocks in the subsurface. The recovery of rich dinocyst assemblages enables the recognition of a ten-fold zonation scheme, largely within the Middle-Late Jurassic sedimentary package. The upper limit of this package is marked by the Cimmerian erosional event; strata younger than Oxfordian are rarely preserved. Only east of 30/degree/E is significant sedimentation known to have occurred immediately prior to the major early Bajocian transgressive event. Thereafter mean sea level rose steadily. The Lower Triassic-Lower Jurassic sedimentary package is poorly understood, largely the result of scanty and ambiguous stratigraphic evidence. However, regional correlations suggest that only very thin earliest Jurassic (Hettangian ) clastic deposition succeeded a sequence of Upper Triassic carbonates and evaporites (Wadi en Natrun Formation) in the north. Arising from these studies is a standard lithostratigraphical scheme. The upper sedimentary package, the Gebel el Maghara Group, comprises three formations (Masajid, Khatatba, and Inmar) and seven members; new units are defined and old units redefined.

  4. Jurassic epithermal Au–Ag deposits of Patagonia, Argentina

    Microsoft Academic Search

    I. B Schalamuk; M Zubia; A Genini; R. R Fernandez

    1997-01-01

    Important precious metal deposits have been discovered during the last 10 years in the Deseado Massif region of Patagonia, Argentina. This region is a plateau consisting of Middle to Upper Jurassic volcanic rocks that host fracture-controlled epithermal Au–Ag mineralization. These mineral deposits represent low sulfidation type hydrothermal systems and formed following the main period of volcanism, probably during the Late

  5. Let the Volgian stage stay in the Jurassic

    Microsoft Academic Search

    V. A. Zakharov; M. A. Rogov

    2008-01-01

    In 1996 the Volgian Stage was divided into the Jurassic and Cretaceous units, removed from the Geological Time Scale, and substituted by the Tithonian Stage according to the guidelines of the Interdepartmental Stratigraphic Committee of the Russian Federation (ISC RF). Consequently, the Upper Volgian Substage including three zones (five subzones) was placed into the Berriasian Stage (the Cretaceous) proceeding from

  6. MEGASPORES FROM THE JURASSIC OF THE ISLAND OF BORNHOLM, DENMARK

    Microsoft Academic Search

    HELGE GRY

    An account is given of the lithology, areal extent and depositional history of the Jurassic sediments and a preliminary description is given of the megaspore content of the sediments (excluding new species). The deltaic deposits below the marine Lias y horizon are Lias a in age and the deltaic deposits above this horizon are referred to the Dogger.

  7. Investigation of the geomagnetic field polarity during the Jurassic

    Microsoft Academic Search

    Maureen B. Steiner

    1980-01-01

    A large number of sedimentary rock formation the Colorado Plateau and in the Wyoming foreland have been investigated paleomagnetically in an attempt to determine the geomagnetic polarity during the Middle and the early Late Jurassic, a period frequently postulated to have been of constant normal polarity. A survey of published paleomagnetic litature shows this postulate to be without grounds. A

  8. INVESTIGATION OF THE GEOMAGNETIC FIELD POLARITY DURING THE JURASSIC

    Microsoft Academic Search

    Maureen B. Steiner

    1980-01-01

    A large number of sedimentary rock formations on the Colorado Plateau and in the Wyoming foreland have been investigated paleo- magnetically in an attempt to determine the geo- magnetic polarity during the Middle and the ear- ly Late Jurassic, a period frequently postulated to have been of constant normal polarity. A sur- vey of published paleomagnetic litature shows this postulate

  9. A Late Jurassic Early Cretaceous convergent margin of Northeastern Asia and sedimentary serpentinite

    NASA Astrophysics Data System (ADS)

    Sokolov, S. D.; Lagabrielle, Y.; Ganelin, A. V.; Kamenetsky, D.; Tuchkova, M. I.

    2003-04-01

    The Upper Jurassic Lower Cretaceous complexes of Uda-Murgal island arc were formed along the convergent boundary between the Northeastern Asia and northwestern Pacific plates. The northern part of the complex exposes volcanic, pyroclastic, and sedimentary deposits from the axial zone of the palaeo-volcanic arc; the central part consists of terrigenous/tuffaceous rocks of the ancient forearc; and the southern part expose turbidites and terrigenous melanges of the accretionary prism. Serpentinite bodies and associated sedimentary serpentinites occur among Lower Cretaceous terrigeneous rocks of the Upupkin terrane in the central part of the Penzhina segment of the island arc. All the serpentinite bodies are rootless and, in plan view, are equant or elongate in shape. The largest ultramafic outcrop (42 km2 in area, 12 km long, 4 km in maximal width) is exposed on the slopes of Mt. Dlinnaya among terrigenous rocks of the Tylakryl Fm. (Hauterivian Barremian). In cross section, this is a sheet ca. 1 km thick dipping generally S30° 60°E Ultramafic rocks include massive and brecciated, serpentinites and serpentinized harzburgites; lherzolites, and dunites. Minor bodies of amphibolized gabbro are less abundant. Sedimentary serpentinites are represented by breccias, conglomerates, gravelstones, sandstones, and siltstones. Monomict, polymict, well-bedded, and chaotic varieties are distinguished. The "monomictic" sedimentary serpentinite lithologies consist only of fragments of ultramafic rocks of various types. The “polymictic” lithologies contain fragments of gabbro, metavolcanites, diabase, amphibolite, spilite, metachert, siltstone, quartz mica schist, and marble along with fragments of various types of serpentinite. Sedimentary serpentinites of the Penzhina segment were formed on the forearc slope of the Uda Murgal island arc due to emplacement and erosion of serpentinite diapirs and are viewed as possible equivalent of forearc serpentinite seamounts of the Mariana and Izu Bonin convergent boundary (ODP Leg 125). Research is supported by INTAS (96-1880) and RFBR (02-05-64217) grants.

  10. Samples from the Jurassic ocean crust beneath Gran Canaria, La Palma and Lanzarote (Canary Islands)

    NASA Astrophysics Data System (ADS)

    Schmincke, Hans-Ulrich; Klügel, Andreas; Hansteen, Thor H.; Hoernle, Kaj; van den Bogaard, Paul

    1998-11-01

    Gabbro and minor metabasalt fragments of MORB composition were found on three of the seven Canary Islands. On Gran Canaria, they occur as metamorphosed (greenschist facies) metabasalt and metagabbro clasts in Miocene fanglomerates and sandstones overlying the shield basalts. On Lanzarote and La Palma, MORB gabbros occur as xenoliths in Pleistocene and historic basanite scoria cones and lava flows. The MORB xenoliths are interpreted as fragments of layers 2 and 3 of the underlying Mesozoic oceanic crust, based on mineral compositions (An-rich plagioclase, Ti- and Al-poor clinopyroxene, ± orthopyroxene ± olivine), depleted major and trace element signatures, and Jurassic ages (ca. 180 Ma) determined on single primary plagioclase and secondary amphibole crystals using the 40Ar/ 39Ar laser technique. The Lanzarote gabbros are very mafic (mg# 87 to 89 in clinopyroxene), moderately deformed, and highly depleted. Gran Canaria gabbros are more evolved (mg# 69 to 83 in clinopyroxene) and texturally mostly isotropic. La Palma MORB gabbros have a range of compositions (mg# 68 to 83 in clinopyroxene), some rocks being strongly metasomatized by interaction with basanite magma. The occurrence of MORB fragments on Lanzarote provides definite evidence that oceanic crust beneath the Canary Island archipelago continues at least as far east as the eastern Canary Islands. We postulate that MORB gabbros on Lanzarote which are commonly associated with peridotite xenoliths, represent the base of oceanic layer 3 where gabbros and peridotites were possibly tectonically interleaved. Such tectonic mixing would explain the enigmatic seismic velocities in this area. Gabbro xenoliths from La Palma were derived from within layer 3, probably from wall rock close to magma reservoirs emplaced during the Pleistocene/Holocene growth of La Palma. The Gran Canaria xenoliths are interpreted to represent the metamorphosed layer 2 and upper layer 3. The abundance of lower crustal xenoliths emphasizes the importance of the lower crust and crust-mantle boundary zone as a major level of magma accumulation.

  11. Depositional environment of woodbine sandstones, Polk, Tyler and San Jacinto Counties, Texas

    E-print Network

    Foss, Deane Campbell

    1978-01-01

    . 6 percent have been recorded for Lower, Middle, and non-bioturbated Upper sandstones in the same well. Lower and Middle sandstones are thinly to thickly bedded and isolated in black, non-bioturbated shales. Thinner sandstones average 0. 25 ft... represent channel deposits while the thinner sandstones with more complete bedsets represent overbank deposits. Thinly bedded, non- bioturbated Upper sandstones are gradational upward into the thickly bedded, bioturbated sandstones. The non...

  12. Environment of deposition of the Pennsylvanian Bartlesville Sandstone, Labette County, Kansas 

    E-print Network

    Johnson, Charles Truman Lars

    1973-01-01

    of Bartles- ville Sandstone in cored interval TW2 . . 25 8. Permeability and porosity of Bartles- ville Sandstone in cored interval TW2 . . 26 9. Grain size and composition of Bartles- ville Sandstone in cored interval TD4. 5. 27 10. Permeability... and porosity of Bartles- ville Sandstone in cored interval TD4. 5. . 28 ll. Grain size and composition of Bartlesville Sandstone in cored interval TB8 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 29 12. Permeability and porosity of Bartles- ville Sandstone in cored...

  13. Multi-stage metamorphism in the South Armenian Block during the Late Jurassic to Early Cretaceous: Tectonics over south-dipping subduction of Northern branch of Neotethys

    NASA Astrophysics Data System (ADS)

    Hässig, M.; Rolland, Y.; Sahakyan, L.; Sosson, M.; Galoyan, G.; Avagyan, A.; Bosch, D.; Müller, C.

    2015-04-01

    The geologic evolution of the South Armenian Block (SAB) in the Mesozoic is reconstructed from a structural, metamorphic, and geochronologic study including U-Pb and 40Ar/39Ar dating. The South Armenian Block Crystalline Basement (SABCB) outcrops solely in a narrow tectonic window, NW of Yerevan. The study of this zone provides key and unprecedented information concerning closing of the Northern Neotethys oceanic domain north of the Taurides-Anatolides platform from the Middle Jurassic to the Early Cretaceous. The basement comprises of presumed Proterozoic orthogneiss overlain by metamorphosed pelites as well as intrusions of granodiorite and leucogranite during the Late Jurassic and Early Cretaceous. Structural, geochronological and petrological observations show a multiphased evolution of the northern margin of the SAB during the Late Jurassic and Early Cretaceous. A south-dipping subduction under the East Anatolian Platform-South Armenian Block (EAP-SAB) is proposed in order to suit recent findings pertaining emplacement of relatively hot subduction related granodiorite as well as the metamorphic evolution of the crystalline basement in the Lesser Caucasus area. The metamorphism is interpreted as evidencing: (1) M1 Barrovian MP-MT conditions (staurolite-kyanite) at c. 157-160 Ma and intrusion of dioritic magmas at c. 150-156 Ma, (2) near-adiabatic decompression is featured by partial melting and production of leucogranites at c. 153 Ma, followed by M2 HT-LP conditions (andalusite-K-feldspar). A phase of shearing and recrystallization is ascribed to doming at c. 130-150 Ma and cooling at 400 °C by c. 123 Ma (M3). Structural observations show (1) top to the north shearing during M1 and (2) radial extension during M2. The extensional event ends by emplacement of a thick detrital series along radial S, E and W-dipping normal faults. Further, the crystalline basement is unconformably covered by Upper Cretaceous-Paleocene series dated by nannofossils, evolving from Maastrichtian marly sandstones to Paleocene limestones.

  14. Environmental significance of foraminiferal assemblages dominated by small-sized Ammodiscus and Trochammina in Triassic and Jurassic delta-influenced deposits

    NASA Astrophysics Data System (ADS)

    Nagy, Jenö; Hess, Silvia; Alve, Elisabeth

    2010-04-01

    The sediment packages analyzed for benthic foraminifera consist of mudstones with interbedded sandstones deposited in shallow delta-influenced shelf to deltaic environments. The sections are located in Spitsbergen, the Barents Sea, northern North Sea and Yorkshire, and range in age from Late Triassic to Middle Jurassic. Salient features of the foraminiferal successions are: (1) The assemblages consist entirely or dominantly of agglutinated taxa. (2) The faunal diversities are extremely low. (3) The dominant genera are Ammodiscus and Trochammina. (4) The species are generally of small size compared to usual dimensions within the genera. The features listed above suggest that the assemblages were adapted to restricted conditions (clearly divergent from those of a normal marine shelf), where the main limiting factors were low salinity and reduced amount of dissolved oxygen in unstable, storm-influenced environments. Evidence for environmental conditions is obtained from modern analogues, although the large evolutionary changes in foraminifera during post-Jurassic time make it difficult to find such analogues. Additional information is derived from functional morphology, sedimentary features and paleogeography. The analyzed sediment packages show close faunal similarities suggesting opening of a marine pathway, which connected the paleo-Arctic Ocean with the western European shelf seas in Early Jurassic. A depositional biofacies model of the small-sized Ammodiscus- Trochammina assemblages envisages a delta-influenced shelf environment, where high freshwater influx would have created a density-stratified water column with a tendency to develop hypoxic conditions in its deeper parts. The depth interval between fair-weather and storm wave base (the offshore-transition zone) is indicated as the habitat of the small-sized Ammodiscus- Trochammina assemblages. In this zone, benthic biota would have been stressed by intermittent periods with moderate hypoxia combined with lowered salinity and storm impacts.

  15. New insights into regional tectonics of the Indochina Peninsula inferred from Lower-Middle Jurassic paleomagnetic data of the Sibumasu Terrane

    NASA Astrophysics Data System (ADS)

    Fujiwara, Katsuya P.; Zaman, Haider; Surinkum, Adichat; Chaiwong, Nikhom; Fujihara, Makoto; Ahn, Hyeon-Seon; Otofuji, Yo-ichiro

    2014-11-01

    The post-Jurassic occurrence of differential tectonic rotation between the Indochina and South Sundaland blocks remains an issue to be properly investigated. New paleomagnetic study is used here to find the role of Sibumasu Terrane in this rotation, which is located between a clockwise rotated Indochina Block and a counter-clockwise rotated South Sundaland Block. For this purpose, lower to middle Jurassic red sandstones of the Umphang Group in the Sibumasu Terrane were sampled at 21 sites in the Ratchaburi area (13.6°E, 99.6°E), Thailand. Stepwise thermal demagnetization by 680 °C unblocked a pre-folding characteristic remanent magnetization. A mean direction of this component at 100% unfolding is Ds = 348.5°, Is = 24.7°, ?95 = 10.5°, k = 10.7, N = 20, corresponding to an Early-Middle Jurassic pole of ? = 78.6°N, ? = 10.6°E (A95 = 9.3). Comparison of this direction with those reported from other localities of the Umphang Group (Kalaw, Mae Sot and North Trang Syncline localities) reveal variable declinations (between 348.5° and 44.7°) for the Sibumasu Terrane. We ascribe this variation to differential tectonic deformation in the Sibumasu Terrane, as reflected from sinusoidal shaped structural features in the study area. The presence of such features in the granitic rocks indicates the occurrences of deformational activities after their intrusion, which took place in the period between 130 Ma and 51 Ma. The Sibumasu Terrane behaved as an independent fragment at a time when Indochina was undergoing a clockwise rotation and southward displacement, as a result of extrusion tectonics after the gigantic India-Asia collision. Taking into consideration a westerly deflected declination (D = 342.8°) from the West Trang area in Peninsular Thailand, a counterclockwise rotation of 15° is estimated for the Sibumasu Terrane, as a result of continuous northward indentation of the Australian Plate into South Sundaland Block.

  16. Hydrocarbon potential of a new Jurassic play, central Tunisia

    SciTech Connect

    Beall, A.O. (Arthur O. Beall International E P, Houston, TX (United States)); Law, C.W. (Geomath, Houston, TX (United States))

    1996-01-01

    A largely unrecognized Jurassic Sag Basin has been identified in central Tunisia, proximal to the Permo-Carboniferous flexure delineating the northern boundary of the Saharan platform of north Africa. The northwestern margin of the Sag is delineated by an extensive region of salt-cored anticlines and localized salt diapirs extending north and west. Due to lack of deep drilling, delineation of the Sag is largely based on regional gravity data. Subsidence of the Jurassic Sag Basin is characterized by rapid expansion of Jurassic sediments from 400 m. of tidal flat and shelf carbonate at the western outcrop to over 2000 meters of tidal flat and basinal carbonate and shale within the basin center, a five-fold expansion. Rapid loading of the basin continued into Lower Cretaceous time, marked by lateral flowage of Triassic salt into pronounced structural trends. Published source rock data and interpreted subsurface well data provided the basis for GENEX 1-D hydrocarbon generation and expulsion modeling of the Sag. Middle Jurassic black source shales typically contain Type II and Type III kerogens with T.O.C.'s ranging up to 4 percent. Modeling results indicate that middle Jurassic shales are presently mature for liquid generation within portions of the Sag, with maximum generation taking place during the Tertiary. Potential hydrocarbon generation yields, based on 60 meters of mature source shale, are 20,000 BOE/acre for gas and 75,000 BOE/acre for liquids. Prospects within the region could contain an estimated potential reserve of several T.C.F. or over 1 billion barrels of oil.

  17. Hydrocarbon potential of a new Jurassic play, central Tunisia

    SciTech Connect

    Beall, A.O. [Arthur O. Beall International E& P, Houston, TX (United States); Law, C.W. [Geomath, Houston, TX (United States)

    1996-12-31

    A largely unrecognized Jurassic Sag Basin has been identified in central Tunisia, proximal to the Permo-Carboniferous flexure delineating the northern boundary of the Saharan platform of north Africa. The northwestern margin of the Sag is delineated by an extensive region of salt-cored anticlines and localized salt diapirs extending north and west. Due to lack of deep drilling, delineation of the Sag is largely based on regional gravity data. Subsidence of the Jurassic Sag Basin is characterized by rapid expansion of Jurassic sediments from 400 m. of tidal flat and shelf carbonate at the western outcrop to over 2000 meters of tidal flat and basinal carbonate and shale within the basin center, a five-fold expansion. Rapid loading of the basin continued into Lower Cretaceous time, marked by lateral flowage of Triassic salt into pronounced structural trends. Published source rock data and interpreted subsurface well data provided the basis for GENEX 1-D hydrocarbon generation and expulsion modeling of the Sag. Middle Jurassic black source shales typically contain Type II and Type III kerogens with T.O.C.`s ranging up to 4 percent. Modeling results indicate that middle Jurassic shales are presently mature for liquid generation within portions of the Sag, with maximum generation taking place during the Tertiary. Potential hydrocarbon generation yields, based on 60 meters of mature source shale, are 20,000 BOE/acre for gas and 75,000 BOE/acre for liquids. Prospects within the region could contain an estimated potential reserve of several T.C.F. or over 1 billion barrels of oil.

  18. Ramah Navajo School Board, Inc., et al., v. Bureau of Revenue of New Mexico. Appeal from the Court of Appeals of New Mexico. Argued April 28, 1982--Decided July 2, 1982. No. 80-2162.

    ERIC Educational Resources Information Center

    Marshall, J.; And Others

    An appeal to the Supreme Court addressd the question whether federal law preempts a state (New Mexico) tax imposed on the gross receipts that a non-Indian construction company (Lembke Construction Company) receives from a tribal school board (Ramah Navajo School Board) for the construction of a school for Navajo children on the reservation. The…

  19. Our Community -- Today and Yesterday. Book One (Nihil Hahoodzodoo -- Diijiidi doo Adaadaa. Naaltsoos T'aala'i Gone Yits'iligii). Fourth Grade Navajo Bilingual-Bicultural Social Studies Curriculum.

    ERIC Educational Resources Information Center

    Bia, Fred; And Others

    Presented in five chapters, book 1 of the Rough Rock fourth grade Navajo social studies program text is written in Navajo and English. The first chapter is on the community of Rough Rock (Arizona) illustrated by photographs of the community and people. Chapter II discusses the four elements (air, water, earth, and fire) the community needs to…

  20. Decay of sandstone in urban areas correlated with atmospheric aerosol

    Microsoft Academic Search

    C. Sabbioni; G. Zappia

    1992-01-01

    The decay of sandstone in urban areas has been investigated. Patterns and composition of the damage layers sampled on monuments and historical buildings are described. The elemental concentrations of black surface crusts are reported. Enrichment factors in relation to the sandstone and crustal rock composition have been calculated in order to point out the component due to atmospheric deposition. The

  1. Effect of drilling fluids on permeability of uranium sandstone

    Microsoft Academic Search

    J. K. Ahlness; D. I. Johnson; D. R. Tweeton

    1984-01-01

    The Bureau of Mines conducted laboratory and field experiments to determine the amount of permeability reduction in uranium sandstone after its exposure to different drilling fluids. Seven polymer and two bentonite fluids were laboratory-tested in their clean condition, and six polymer fluids were tested with simulated drill cuttings added. Sandstone cores cut from samples collected at an open pit uranium

  2. New isotopic evidence for the origin of groundwater from the Nubian Sandstone Aquifer in the Negev, Israel

    USGS Publications Warehouse

    Vengosh, A.; Hening, S.; Ganor, J.; Mayer, B.; Weyhenmeyer, C.E.; Bullen, T.D.; Paytan, A.

    2007-01-01

    The geochemistry and isotopic composition (H, O, S, Osulfate, C, Sr) of groundwater from the Nubian Sandstone (Kurnub Group) aquifer in the Negev, Israel, were investigated in an attempt to reconstruct the origin of the water and solutes, evaluate modes of water-rock interactions, and determine mean residence times of the water. The results indicate multiple recharge events into the Nubian sandstone aquifer characterized by distinctive isotope signatures and deuterium excess values. In the northeastern Negev, groundwater was identified with deuterium excess values of ???16???, which suggests local recharge via unconfined areas of the aquifer in the Negev anticline systems. The ??18OH2O and ??2H values (-6.5??? and -35.4???) of this groundwater are higher than those of groundwater in the Sinai Peninsula and southern Arava valley (-7.5??? and -48.3???) that likewise have lower deuterium excess values of ???10???. Based on the geochemical differences between groundwater in the unconfined and confined zones of the aquifer, a conceptual geochemical model for the evolution of the groundwater in the Nubian sandstone aquifer has been reconstructed. The isotopic composition of shallow groundwater from the unconfined zone indicates that during recharge oxidation of pyrite to SO4 (??34SSO4 ???-13???; ??18OSO4 ???+7.7???) and dissolution of CaCO3 (87Sr/86Sr ???0.70787; ??13CDIC = -3.7???) occur. In the confined zone of the aquifer, bacterial SO4 reduction removes a significant part of dissolved SO42 -, thereby modifying its isotopic composition (??34SSO4 ???-2???; ??18OSO4 ???+8.5???) and liberating dissolved inorganic C that contains little or no radiocarbon (14C-free) with low ??13CDIC values (<-12???). In addition to local recharge, the Sr and S isotopic data revealed contribution of external groundwater sources to the Nubian Sandstone aquifer, resulting in further modifications of the groundwater chemical and isotopic signatures. In the northeastern Negev, it is shown that SO4-rich groundwater from the underlying Jurassic aquifer contributes significantly to the salt budget of the Nubian Sandstone aquifer. The unique chemical and isotopic composition of the Jurassic groundwater (??34SSO4 ??? +14???; ??18OSO4 ??? 14???; 87Sr/86Sr ???0.70764) is interpreted as reflecting dissolution of Late Triassic marine gypsum deposits. In the southern Arava Valley the authors postulate that SO4-rich groundwater with distinctively high Br/Cl (3 ?? 10-3) low 87Sr/86Sr (0.70734), and high ??34SSO4 values (+15???) is derived from mixing with underlying brines from the Paleozoic units. The radiocarbon measurements reveal low 14C activities (0.2-5.8 pmc) in both the northeastern Negev and southern Arava Valley. Taking into account dissolution of carbonate rocks and bacterial SO4 reduction in the unconfined area, estimated mean residence times of groundwater in the confined zone in the northeastern Negev are on the order of 21-38 ka, which suggests recharge predominantly during the last glacial period. The 14C signal in groundwater from the southern Arava Valley is equally low but due to evidence for mixing with external water sources the residence time estimates are questionable. ?? 2007 Elsevier Ltd. All rights reserved.

  3. Anisotropy of permeability in faulted porous sandstones

    NASA Astrophysics Data System (ADS)

    Farrell, N. J. C.; Healy, D.; Taylor, C. W.

    2014-06-01

    Studies of fault rock permeabilities advance the understanding of fluid migration patterns around faults and contribute to predictions of fault stability. In this study a new model is proposed combining brittle deformation structures formed during faulting, with fluid flow through pores. It assesses the impact of faulting on the permeability anisotropy of porous sandstone, hypothesising that the formation of fault related micro-scale deformation structures will alter the host rock porosity organisation and create new permeability pathways. Core plugs and thin sections were sampled around a normal fault and oriented with respect to the fault plane. Anisotropy of permeability was determined in three orientations to the fault plane at ambient and confining pressures. Results show that permeabilities measured parallel to fault dip were up to 10 times higher than along fault strike permeability. Analysis of corresponding thin sections shows elongate pores oriented at a low angle to the maximum principal palaeo-stress (?1) and parallel to fault dip, indicating that permeability anisotropy is produced by grain scale deformation mechanisms associated with faulting. Using a soil mechanics 'void cell model' this study shows how elongate pores could be produced in faulted porous sandstone by compaction and reorganisation of grains through shearing and cataclasis.

  4. A Late Jurassic fossil assemblage in Gondwana: Biostratigraphy and correlations of the Tacuarembó Formation, Parana Basin, Uruguay

    NASA Astrophysics Data System (ADS)

    Perea, Daniel; Soto, Matías; Veroslavsky, Gerardo; Martínez, Sergio; Ubilla, Martín

    2009-08-01

    The Tacuarembó Formation has yielded a fossil assemblage that includes the best known body fossils, consisting of isolated scales, teeth, spines, and molds of bones, recovered from thin and patchy bonebeds, from the Botucatu Desert, Parana Basin, South America. The remains are preserved in the sandstones widespread around the city of Tacuarembó. We propose a new formalized nomenclature for the Tacuarembó Formation, naming its "Lower" and "Upper" members as the Batoví (new name) and Rivera (new rank) members, respectively. An assemblage zone is defined for the Batoví Member (fluviolacustrine and aeolian deposits). In this unit, the freshwater hybodontid shark Priohybodusarambourgi D'Erasmo is well represented. This species was previously recorded in Late Jurassic-Early Cretaceous units of the Sahara and the southern Arabian Peninsula. Globally considered, the fossil assemblage of this member ( P. arambourgi, dipnoan fishes, Ceratosaurus-like theropods, and conchostracans) is indicative of a Kimmeridgian-Tithonian age, which in combination with the stratigraphic relationships of the Tacuarembó Formation with the overlying basalts of the Arapey Formation (132 My average absolute age) implies that the latter was deposited during the Kimmeridgian-Hauterivian interval.

  5. A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago.

    PubMed

    Göhlich, Ursula B; Chiappe, Luis M

    2006-03-16

    Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus, neither of which is well preserved. Here we describe a small new theropod dinosaur from the Late Jurassic period of Schamhaupten in southern Germany. Being exquisitely preserved and complete from the snout to the distal third of the tail, the new fossil is the best-preserved predatory, non-avian dinosaur in Europe. It possesses a suite of characters that support its identification as a basal coelurosaur. A cladistic analysis indicates that the new taxon is closer to maniraptorans than to tyrannosauroids, grouping it with taxa often considered to be compsognathids. Large portions of integument are preserved along its tail. The absence of feathers or feather-like structures in a fossil phylogenetically nested within feathered theropods indicates that the evolution of these integumentary structures might be more complex than previously thought. PMID:16541071

  6. Brittle and compaction creep in porous sandstone

    NASA Astrophysics Data System (ADS)

    Heap, Michael; Brantut, Nicolas; Baud, Patrick; Meredith, Philip

    2015-04-01

    Strain localisation in the Earth's crust occurs at all scales, from the fracture of grains at the microscale to crustal-scale faulting. Over the last fifty years, laboratory rock deformation studies have exposed the variety of deformation mechanisms and failure modes of rock. Broadly speaking, rock failure can be described as either dilatant (brittle) or compactive. While dilatant failure in porous sandstones is manifest as shear fracturing, their failure in the compactant regime can be characterised by either distributed cataclastic flow or the formation of localised compaction bands. To better understand the time-dependency of strain localisation (shear fracturing and compaction band growth), we performed triaxial deformation experiments on water-saturated Bleurswiller sandstone (porosity = 24%) under a constant stress (creep) in the dilatant and compactive regimes, with particular focus on time-dependent compaction band formation in the compactive regime. Our experiments show that inelastic strain accumulates at a constant stress in the brittle and compactive regimes leading to the development of shear fractures and compaction bands, respectively. While creep in the dilatant regime is characterised by an increase in porosity and, ultimately, an acceleration in axial strain to shear failure (as observed in previous studies), compaction creep is characterised by a reduction in porosity and a gradual deceleration in axial strain. The overall deceleration in axial strain, AE activity, and porosity change during creep compaction is punctuated by excursions interpreted as the formation of compaction bands. The growth rate of compaction bands formed during creep is lower as the applied differential stress, and hence background creep strain rate, is decreased, although the inelastic strain required for a compaction band remains constant over strain rates spanning several orders of magnitude. We find that, despite the large differences in strain rate and growth rate (from both creep and constant strain rate experiments), the characteristics (geometry, thickness) of a compaction band remain essentially the same. Several lines of evidence, notably the similarity between the differential stress dependence of creep strain rate in the dilatant and compactive regimes, suggest that, as for dilatant creep, compactant creep is driven by subcritical stress corrosion cracking. We highlight the attendant implications for time-dependent porosity loss, subsidence, and permeability reduction in sandstone reservoirs.

  7. Hydrological modelling in sandstone rocks watershed

    NASA Astrophysics Data System (ADS)

    Ponížilová, Iva; Unucka, Jan

    2015-04-01

    The contribution is focused on the modelling of surface and subsurface runoff in the Plou?nice basin. The used rainfall-runoff model is HEC-HMS comprising of the method of SCS CN curves and a recession method. The geological subsurface consisting of sandstone is characterised by reduced surface runoff and, on the contrary, it contributes to subsurface runoff. The aim of this paper is comparison of the rate of influence of sandstone on reducing surface runoff. The recession method for subsurface runoff was used to determine the subsurface runoff. The HEC-HMS model allows semi- and fully distributed approaches to schematisation of the watershed and rainfall situations. To determine the volume of runoff the method of SCS CN curves is used, which results depend on hydrological conditions of the soils. The rainfall-runoff model assuming selection of so-called methods of event of the SCS-CN type is used to determine the hydrograph and peak flow rate based on simulation of surface runoff in precipitation exceeding the infiltration capacity of the soil. The recession method is used to solve the baseflow (subsurface) runoff. The method is based on the separation of hydrograph to direct runoff and subsurface or baseflow runoff. The study area for the simulation of runoff using the method of SCS CN curves to determine the hydrological transformation is the Plou?nice basin. The Plou?nice is a hydrologically significant river in the northern part of the Czech Republic, it is a right tributary of the Elbe river with a total basin area of 1.194 km2. The average value of CN curves for the Plou?nice basin is 72. The geological structure of the Plou?nice basin is predominantly formed by Mesozoic sandstone. Despite significant initial loss of rainfall the basin response to the causal rainfall was demonstrated by a rapid rise of the surface runoff from the watershed and reached culmination flow. Basically, only surface runoff occures in the catchment during the initial phase of this extreme event. The increase of the baseflow runoff is slower and remains constant after reaching a certain level. The rise of the baseflow runoff is showed in a descending part of the hydrograph. The recession method in this case shows almost 20 hours delay. Results from the HEC-HMS prove availability of both methods for the runoff modeling in this type of catchment. When simulating extreme short-term rainfall-runoff episodes, the influence of geological subsurface is not significant, but it is manifested. Using more relevant rainfall events would bring more satisfactory results.

  8. Jurassic Magmatism and Tectonics of the North American Cordillera

    NASA Astrophysics Data System (ADS)

    Boettcher, Stefan

    The relationship of Jurassic magmatic arc rocks to the tectonic evolution of the North American Cordilleran continental margin is a principle theme of Geological Society of America Special Paper 299. The volume gives readers a comprehensive view of the early stages of magmatic arc evolution on a continental margin and is a tribute to the contributions of Richard Lee Armstrong, whose pioneering studies provide a framework for current geologic investigations of the North American Cordillera.

  9. Astronomical pacing of methane release in the Early Jurassic period

    Microsoft Academic Search

    David B. Kemp; Angela L. Coe; Anthony S. Cohen; Lorenz Schwark

    2005-01-01

    A pronounced negative carbon-isotope (delta13C) excursion of ~5-70\\/00 (refs 1-7) indicates the occurrence of a significant perturbation to the global carbon cycle during the Early Jurassic period (early Toarcian age, ~183 million years ago). The rapid release of 12C-enriched biogenic methane as a result of continental-shelf methane hydrate dissociation has been put forward as a possible explanation for this observation.

  10. Jurassic sedimentary basins in the Central Asian orogenic belt

    SciTech Connect

    Bebeshev, I.I. [Geological Institute, Moscow (Russian Federation)

    1995-05-01

    The principal stages of development of Jurassic sedimentary basins (from their origin to the end of their existence) in the Central Asian orogenic belt are considered. The interrelations of the basins with the surrounding paleorises are investigated. Paleogeographic maps are compiled representing the evolution of paleolandscapes and revealing their interrelations in space and time for each stage. Areas with the highest prospects for coal are found.

  11. Paleointensity Determination on the Late Jurassic Lavas in Northeastern China

    NASA Astrophysics Data System (ADS)

    Shi, R.; Zhu, R.; Pan, Y.

    2003-12-01

    The variations in the strength of the geomagnetic field over geologic time is crucial to a complete understand of the workings of Earth­_s dynamo. While many paleointensity data were recently reported and hence enhancing our understanding of the geodynamo, few data except one datum from SBG in the present paleointensity database were obtained from the late Jurassic by passing certain criteria (Thellier method with system p-TRM check and so on) and, in particular, the lack of data from East Asia. We recently carried out an integrated paleomagnetic, rock-magnetic and paleointensity study of the late Jurassic volcanic succession from Beipiao in the west of Liaoning province, northeastern China. A total of 19 lava flows were sampled. The eruption ages of these lava flows were dated by SHRIMP, about 145Ma. Detailed rock magnetic experiments of thermomagnetic curves and hysteresis loops show the primary carrier of remanence to be pseudo-single domain hematite. Stepwise alternating field and thermal demagnetizations isolated a well-defined direction of characteristic remanent magnetization in all studied lava flows. The modified version (Coe, 1967) of Thellier method with system p-TRM check was used to determine paleointensity. Eight out of nineteen lava flows met the selection criteria (positive p-TRM check, at least three points in a line) and the paleointensity and corresponded VDM values were calculated. An average of about fifth of the present day magnetic field, (1.5+/-0.6)E+22 Am2, was recorded by the eight lava flows. This is the first paleointensity results obtained from the Chinese lava flows erupted in the late Jurassic and well-consistent with the results from SBG (Juarez et al., 1998), suggesting the MDL into the late Jurassic, and further confirming the inverse relationship between reversal frequency and paleointensity.

  12. Direct evidence of hybodont shark predation on Late Jurassic ammonites

    Microsoft Academic Search

    Romain Vullo

    2011-01-01

    Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body\\u000a fossil associations attesting to this predator–prey relationship have never been described so far. Here, I report a unique\\u000a finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont

  13. Jurassic and triassic hydrocarbon exploration of southern Florida

    SciTech Connect

    Mitchell-Tapping, H.J. [Retog, Inc., DeSoto, TX (United States)

    1994-12-31

    The Triassic and Jurassic of South Florida have been overlooked as a viable exploration target because of lack of data and plate tectonics application. In Florida {open_quotes}basement{close_quotes} is defined as crystalline, igneous, metamorphic and unmetamorphosed sediments of Paleozoic age. Age-dating of zircons has shown that the Florida lower Paleozoic terrain is not akin to that of North America but is part of the West African Guinean Shield. Pre-Atlantic reconstruction of the Gulf of Mexico in this study suggests that there was a Florida connection to Yucatan-Cuba-Africa during the Triassic. This reconstruction also shows that Jurassic rocks that are well known in the Northern Gulf Coast should have been deposited in similar depositional environments in southern Florida. Deep drilling on the Florida peninsula has confirmed this hypothesis. By using plate tectonic reconstruction based on the rifting of the North Atlantic Ocean and evidence from petrology of basement samples from deep wells, together with petrographic analyses of Jurassic sedimentary rocks, a Smackover-equivalent exploration play can be developed. Petrographic and petrophysical analysis of wells that have encountered Jurassic marine shales, anhydrite, dolomite, carbonate, and clastic sedimentary rocks has determined that they were deposited in shallow-water subtidal to supratidal environments. Excellent gas shows, oil stain in pores, and high TOC values in marine shales indicate that there are accumulations of hydrocarbon present. Application of analogous Gulf Coast Smackover stratigraphic models to this area, based on petrology and hydrogeology, should reduce risk and help define productive oil and gas reservoirs.

  14. Preventing Caries in Preschoolers: Successful Initiation of an Innovative Community-Based Clinical Trial in Navajo Nation Head Start

    PubMed Central

    Quissell, David O.; Bryant, Lucinda L.; Braun, Patricia A.; Cudeii, Diana; Johs, Nikolas; Smith, Vongphone L.; George, Carmen; Henderson, William G.; Albino, Judith

    2014-01-01

    Navajo Nation children have the greatest prevalence of early childhood caries in the United States. This protocol describes an innovative combination of community-based participatory research and clinical trial methods to rigorously test a lay native Community Oral Health Specialists-delivered oral health intervention, with the goal of reducing the progression of disease and improving family knowledge and behaviors. Methods/Design This cluster-randomized trial designed by researchers at the Center for Native Oral Health Research at the University of Colorado in conjunction with members of the Navajo Nation community compares outcomes between the manualized 2-year oral health fluoride varnish-oral health promotion intervention and usual care in the community (child-caregiver dyads from 26 Head Start classrooms in each study arm; total of 1016 dyads). Outcome assessment includes annual dental screening and an annual caregiver survey of knowledge, attitudes and behaviors; collection of cost data will support cost-benefit analyses. Discussion The study protocol meets all standards required of randomized clinical trials. Aligned with principles of community-based participatory research, extended interaction between members of the Navajo community and researchers preceded study initiation, and collaboration between project staff and a wide variety of community members informed the study design and implementation. We believe the benefits of adding CBPR methods to those of randomized clinical studies outweigh the barriers and constraints, especially in studies of health disparities and in challenging settings. When done well, this innovative mix of methods will increase the likelihood of valid results that communities can use. PMID:24469238

  15. Upper Jurassic depositional systems and hydrocarbon potential of southeast Mississippi

    SciTech Connect

    Meendsen, F.C.; Moore, C.H.; Heydari, E.; Sassen, R.

    1987-09-01

    Upper Jurassic sedimentation in southeast Mississippi was controlled by eustatic sea level fluctuations and locally modified by salt tectonism and basement structure. This study, using conventional core data and geophysical logs, indicates that a stable carbonate platform developed along the updip margin of the Mississippi interior salt basin. The basin was partially barred from the main Gulf of Mexico water mass by the Wiggins uplift, and became evaporitic during the Late Jurassic. Moldic, intercrystalline, and vuggy dolomite porosity is developed on the crests of intermediate and high-amplitude salt highs and on the Wiggins uplift. Jurassic source rocks are lower Smackover laminated lime mudstones. Migration into adjacent reservoirs postdated formation of porosity and the growth of salt anticlines, the most common trap type. A large potential Norphlet-Smackover gas play extends along the southern flank of the Wiggins uplift. Salt anticlines within the interior basin remain viable targets. Small oil discoveries should continue in stratigraphic traps, subtle salt structures, and basement blocks on the platform.

  16. Unusual occurrence of some sedimentary structures and their significance in Jurassic transgressive clastic successions of Northern Ethiopia

    NASA Astrophysics Data System (ADS)

    Dubey, N.; Bheemalingeswara, K.

    2009-04-01

    Mesozoic sedimentary successions produced by marine transgression and regression of sea in northeastern part of Africa are well preserved in Mekelle basin of Ethiopia. Here, a typical second order sequence is well developed and preserved overlying the Precambrian basement rocks or patchy Palaeozoic sedimentary successions. Initiation of Mesozoic sedimentation in Mekelle basin has started with deposition of Adigrat Sandstone Formation (ASF). It is a retrogradational succession of siliciclastics in coastline/beach environment due to transgression of sea from southeast. ASF is followed by Antallo Limestone Formation (ALF)- an aggradational succession of carbonates in tidal flat environment; Agula Shale/Mudstone Formation (AMF); and Upper/Ambaradom Sandstone Formation (USF)- a progradational succession formed during regression in ascending order (Dubey et al., 2007). AMF is deposited in a lagoonal evaporatic environment whereas USF in a fluvial coastal margin. ASF is an aggregate of cyclically stacked two lithologies ASF1 and ASF2 produced by sea-level rise and fall of a lower order mini-cycle. ASF1 is a thick, multistoried, pink to red, friable, medium to fine grained, cross-bedded sandstone deposited in a high energy environment. ASF2 is a thin, hard and maroon colored iron-rich mudstone (ironstones) deposited in a low energy environment. ASF1 has resulted during regressive phase of the mini-cycle when rate of sedimentation was extremely high due to abundant coarser clastic supply from land to the coastal area. On the other hand, ASF2 has resulted during transgressive phase of the mini-cycle which restricted the supply of the coarser clastic to the coastal area and deposited the muddy ferruginous sediments in low energy offshore part of the basin where sedimentation rate was very low. Apart from these two major lithologies, there are also few other minor lithologies like fine-grained white sandstone, carbonate (as bands), claystone and mudstone present in ASF. ASF is a well developed lithostratigraphic unit of northern Ethiopia and represents the Jurassic transgressive clastic succession of Mekelle basin. The physical and biogenic sedimentary structures reported in this paper are observed from the terminal part of ASF. Their occurrence is unusual, rare, unknown so far and unreported. It includes (i) mud cracks (including their casts filled with overlying lithology) representing subaerial exposure which is unusual during transgressive phase, (ii) vertical traces of Skolithos burrows in ASF2 produced by suspension feeders in high energy environment of deposition (Dubey et al., 2007), (iii) tiny bivalve moulds and casts (external- and internal-moulds) of body fossils, and (iv) elliptical negative epirelief (potato shaped empty depressions - external moulds of eggs or nodules?). Fifty two such randomly oriented external moulds are noticed within 2 m2 area on an upper bedding plane of thin, white and fine- grained sandstone. Their in- fills are missing/removed as they are present on a gently dipping bed. Therefore, it is difficult to ascertain their biogenic (egg) or abiogenic (nodule) origin. Their detail investigation is under progress. Since ASF developed during marine transgression, presence of mud cracks in its terminal part indicates subaerial exposure. This provides suitable sites for nesting eggs (reptile?) in wet sands. Removal of such preserved eggs can provide potato depressions. Though it is difficult to relate these moulds to the eggs because of the missing in-fills, their shape, size and restricted occurrence supports biogenic origin. Reference Dubey, N., Bheemalingeswara, K. and Tadesse, N. (2007). Sedimentology and lithostratigraphy of the Mesozoic successions of Mekelle Basin, Ethiopia, Norteastern Africa. Geophysical Research Abstracts, Vol.9, 11471. (SRef-ID: 1607-7962/gra/EGU2007-A-11471).

  17. Contractional deformation of porous sandstone: Insights from the Aztec Sandstone, SE Nevada, USA

    NASA Astrophysics Data System (ADS)

    Fossen, Haakon; Zuluaga, Luisa F.; Ballas, Gregory; Soliva, Roger; Rotevatn, Atle

    2015-05-01

    Contractional deformation of highly porous sandstones is poorly explored, as compared to extensional deformation of such sedimentary rocks. In this work we explore the highly porous Aztec Sandstone in the footwall to the Muddy Mountain thrust in SE Nevada, which contains several types of deformation bands in the Buffington tectonic window: 1) Distributed centimeter-thick shear-enhanced compaction bands (SECBs) and 2) rare pure compaction bands (PCBs) in the most porous parts of the sandstone, cut by 3) thin cataclastic shear-dominated bands (CSBs) with local slip surfaces. Geometric and kinematic analysis of the SECBs, the PCBs and most of the CSBs shows that they formed during ?E-W (?100) shortening, consistent with thrusting related to the Cretaceous to early Paleogene Sevier orogeny of the North American Cordilleran thrust system. Based on stress path modeling, we suggest that the compactional bands (PCBs and SECBs) formed during contraction at relatively shallow burial depths, before or at early stages of emplacement of the Muddy Mountains thrust sheet. The younger cataclastic shear bands (CSBs, category 3), also related to E-W Sevier thrusting, are thinner and show larger shear offsets and thus more intense cataclasis, consistent with the initiation of cataclastic shear bands in somewhat less porous materials. Observations made in this work support earlier suggestions that contraction lead to more distributed band populations than what is commonly found in the extensional regime, and that shear-enhanced compaction bands are widespread only where porosity (and permeability) is high.

  18. A New Look at the Magnetostratigraphy and Paleomagnetism of the Upper Triassic to Lower Jurassic Moenave Formation, St. George Area, Southwestern Utah.

    NASA Astrophysics Data System (ADS)

    Donohoo-Hurley, L. L.; Geissman, J. W.; Lucas, S. G.; Roy, M.

    2006-12-01

    Paleomagnetic data from rocks exposed on and off the Colorado Plateau provide poles that young westward during the Late Triassic (to about 52^{O} E longitude) and young eastward during the Early Jurassic. This pattern has been used to posit the existence of a J-1 cusp in the North American APW path at the Triassic- Jurassic boundary (TJB), at about 199.6 Ma. Considerable debate has focused on the morphology and placement of the J-1 cusp due to poorly exposed and/or incompletely sampled sections, debates about the magnitude of Colorado Plateau rotation, and disagreements regarding stratigraphic relationships. Red beds of the Whitmore Point (~25 m of mostly lacustrine deposits) and Dinosaur Canyon (~55 m of hematitic fluvial sandstones and siltstones) members of the Moenave Formation (MF) are inferred to have been deposited across the TJB based on palynostratigraphy and vertebrate biostratigraphy. Two previously unsampled sections (Leeds and Warner Valley) of the MF are well exposed near St. George, Utah, and located in the transition zone that defines the western boundary of the Colorado Plateau. Preliminary data from samples collected from the Whitmore Point and Dinosaur Canyon members yield exclusively normal polarity magnetizations, which is consistent with previous studies and the normal polarity TJB magnetozone. Thermal demagnetization response suggests that the remanence is carried mainly in hematite. The degree of hematite pigmentation varies in both sections, and several Leeds sites show a weak overprint component that unblocks by 400^{O}-450^{O} C, with a higher unblocking temperature components, consistent with an Early Triassic Late Jurassic age that fully unblock around 670^{O}-680^{O} C. Individual beds (treated as specific sites) in part of the Dinosaur Canyon Member yield site mean directions with declinations between about 020 and 030, and may define the easternmost position (i.e. 60-50^{O} E latitude) of the NAMAPW path and thus the approximate the TJB. This interpretation is consistent with recent biostratigraphic arguments that the TJB lies in the upper part of the Dinosaur Canyon Member. The Whitmore Point Member yields more north-directed declinations, suggesting an earliest Jurassic (post-cusp) age. It is likely that more complete data from these and related sections will provide a further refinement of the stratigraphic placement of the TJB and the geometry of the J-1 cusp.

  19. Jurassic plutons in the Desolation wilderness, northern Sierra Nevada batholith, California: A new segment in the Jurassic magmatic arc

    SciTech Connect

    Sabine, C. (Desert Research Inst., Reno, NV (United States). Quaternary Sciences Center)

    1993-04-01

    A 164[+-]7 Ma U-P zircon date establishes a Middle- to Late-Jurassic age for the Pyramid Peak granite and synplutonic dioritoids and hybrid rocks that comprise the Crystal Range suite, located southwest of Lake Tahoe. A Jurassic age is also assigned to the Keiths Dome quartz monzonite and the Desolation Valley and Camper Flat granodiorites (Loomis', 1983, Early Granitic Group) which are distinctly older than surrounding Cretaceous granitoids. The Keiths Dome quartz monzonite, the oldest pluton of the group, may be as old as 180 Ma and is distinguished by ductile shear zones and recrystallization textures which indicate an episode of deformation not undergone by other plutons. The Camper flat and Desolation Valley granodiorites are the youngest plutons of the group. ENE-trending microdiorite dikes filled extensional fractures, perpendicular to the direction of shortening, in all Jurassic plutons but on none of the Cretaceous bodies. Jurassic plutons may help constrain ages of metasedimentary and metavolcanic rocks and associated structures in the Mount Tallac roof pendant. The Pyramid Peak granite intrudes the Sailor Canyon Formation which bears Late Pliensbachian ammonites (Fisher, 1990), and the Keiths Dome quartz monzonite intrudes the overlying Tuttle Lake Formation and transects faults and shear zones in the pendant. Initial Sr isotope ratios for the Pyramid Peak granite range between 0.705427 and 0.706874, spanning the 0.706 value taken by some to mark the western limit of sialic lower crust. Data suggest an isotopically mixed source containing mantle and crustal components. Such an environment is not inconsistent with a passive continental margin where mafic magma invades rifted continental crust.

  20. 18. View of east trestle approach and sandstone pier banded ...

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

    18. View of east trestle approach and sandstone pier banded with concrete. View to southeast. - Selby Avenue Bridge, Spanning Short Line Railways track at Selby Avenue between Hamline & Snelling Avenues, Saint Paul, Ramsey County, MN

  1. 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.

  2. Age and Growth of the Utah Chub, Gila Atraria (Girard), in Panguitch Lake and Navajo Lake, Utah, from Scales and Opercular Bones

    Microsoft Academic Search

    John M. Neuhold

    1957-01-01

    Age and growth were calculated for 222 Utah chubs collected from Panguitch Lake and 212 Utah chubs collected from Navajo Lake, southern Utah, in 1952–1953 from both scales and opercular bones. Scales were measured with the aid of a projector. Opercular bones were measured directly. The center of growth of the opercular bone is posterior to the posterior lip of

  3. A Survey of Fertility Histories and Contraceptive Use Among a Group of Navajo Women. Lake Powell Research Project Bulletin No. 21, June 1976.

    ERIC Educational Resources Information Center

    Kunitz, Stephen J.

    In an effort to determine female Navajo fertility histories, patterns of contraceptive use, educational levels, residence patterns, and modes of communication re: family planning, a five-part questionnaire (personal data, marital history, pregnancy history, knowledge of contraception, and comments on family planning) was administered to 42 women…

  4. Food Security Status and Produce Intake Behaviors, Health Status, and Diabetes Risk Among Women With Children Living on a Navajo Reservation

    Microsoft Academic Search

    Emma Bah Ray; David H. Holben; John P. Holcomb Jr

    2012-01-01

    This study of adult women living on a Navajo reservation with at least one child less than 18 years old attending a primary school on the reservation investigated the relationship of food security to produce intake and behaviors, health status, and diabetes risk of these adult women. Of the 42 participants completing the survey, 8 (19.0%) were living in fully

  5. We'vs a Story to Tell the Nations: A Plan for Decentralized Library Services, Northland Pioneer College, Navajo County, Arizona.

    ERIC Educational Resources Information Center

    Rothlisberg, Allen P.

    Northland Pioneer College (NPC) consists of five mini-centers located throughout Navajo County (Arizona), and extension classes offered in areas where no centers have been established. Because it was financially impossible to create separate libraries to service all these areas, a decentralized library system was needed. The Holbrook Center, which…

  6. Provenance and geochronology of Cenozoic sandstones of northern Borneo

    NASA Astrophysics Data System (ADS)

    van Hattum, M. W. A.; Hall, R.; Pickard, A. L.; Nichols, G. J.

    2013-10-01

    The Crocker Fan of Sabah was deposited during subduction of the Proto-South China Sea between the Eocene and Early Miocene. Collision of South China microcontinental blocks with Borneo in the Early Miocene terminated deep water sedimentation and resulted in the major regional Top Crocker Unconformity (TCU). Sedimentation of fluvio-deltaic and shallow marine character resumed in the late Early Miocene. The Crocker Fan sandstones were derived from nearby sources in Borneo and nearby SE Asia, rather than distant Asian and Himalayan sources. The Crocker Fan sandstones have a mature composition, but their textures and heavy mineralogy indicate they are first-cycle sandstones, mostly derived from nearby granitic source rocks, with some input of metamorphic, sedimentary and ophiolitic material. The discrepancy between compositional maturity and textural immaturity is attributed to the effects of tropical weathering. U-Pb ages of detrital zircons are predominantly Mesozoic. In the Eocene sandstones Cretaceous zircons dominate and suggest derivation from granites of the Schwaner Mountains of southern Borneo. In Oligocene sandstones Permian-Triassic and Palaeoproterozoic zircons become more important, and are interpreted to be derived from Permian-Triassic granites and Proterozoic basement of the Malay Tin Belt. Miocene fluvio-deltaic and shallow marine sandstones above the TCU were mostly recycled from the deformed Crocker Fan in the rising central mountain range of Borneo. The provenance of the Tajau Sandstone Member of the Lower Miocene Kudat Formation in north Sabah is strikingly different from other Miocene and older sandstones. Sediment was derived mainly from granitic and high-grade metamorphic source rocks. No such rocks existed in Borneo during the Early Miocene, but potential sources are present on Palawan, to the north of Borneo. They represent continental crust from South China and subduction-related metamorphic rocks which formed an elevated region in the Early Miocene which briefly supplied sediment to north Sabah.

  7. Petrography and diagenesis of the Hosston Sandstone, Washington Parish, Louisiana 

    E-print Network

    Winker, Gregory James

    1982-01-01

    that the sandstones are fine-grained, well sorted quartz arenites composed, on the average, of 68'4 quartz, 17% rock fragments, 7% matrix, 6% other minerals, and 2% feldspar. Authigenic cements present include silica and carbonate which respectively make up 8... are filled by authigenic clays which render these pores to be classified as microporosity. Po- rosity appears to be related to the amount of authigenic clay and inversely related to authigenic cement content. Permeability of the sandstones ranges from...

  8. Cementation factor and water saturation exponent in low porosity sandstones 

    E-print Network

    Owen, Stephen Douglas

    1984-01-01

    December 1984 Major Subject: Petroleum Engineering CEMENTATION FACTOR AND WATER SATURATION EXPONENT IN LOW POROSITY SANDSTONES A Thesis by STEPHEN DOUGLAS OWEN Approved as to style and content by: J. S. Osoba ( a' rman of Committee) R. W. Heins... (Member) J. T. oppi er (Member) W. D Von Go ten (He of Department) December 1984 ABSTRACT Cementation Factor and Water Saturation Exponent in Low porosity Sandstones. (December 1984) Stephen D. Owen, B. S. , Lubbock Christian College Chairman...

  9. Feldspar diagenesis in the Yowlumne sandstone, Kern County, California 

    E-print Network

    Pike, John David

    1981-01-01

    Comparison between molalities of dissolved species in seawater and in subsurface sandstone formation waters (data from Blatt et al. , 1972; Chave, 1960; White, 1965; and Graf et al. , 1966). . . . . . . . . . . . . . . . . 15 Effect of cation composition.... Meyers and Van Siclen (1964) found that abnormally pressured sandstones contained pore waters diluted by shale dewatering. Pore waters may also be diluted by meteoric waters near outcrops (Chave, 1960). Cation concentrations relative to Cl in both...

  10. Diagenesis in upper Miocene sandstones, Louisiana Gulf Coast

    Microsoft Academic Search

    Gold

    1985-01-01

    Study of diagenesis in upper Miocene sandstones of coastal Louisiana documents depth-related cementation and geochemical changes of primary detrital mineralogy. Samples were collected from depths of 8000-20,000 ft (2600-6500 m) in an area roughly corresponding to the upper Miocene depocenter in the Terrebonne trough of southeast Louisiana. Sandstones are primarily subarkoses and sublitharenites with minor amounts of feldspathic litharenites and

  11. Jurassic hot spring deposits of the Deseado Massif (Patagonia, Argentina): Characteristics and controls on regional distribution

    Microsoft Academic Search

    Diego M. Guido; Kathleen A. Campbell

    2011-01-01

    The Deseado Massif, Santa Cruz Province, Argentinean Patagonia, hosts numerous Middle to Late Jurassic age geothermal and epithermal features represented by siliceous and calcareous chemical precipitates from hot springs (sinters and travertines, respectively), hydrothermal breccias, quartz veins, and widespread hydrothermal silicification. They indicate pauses in explosive volcanic activity, marking the final stages in the evolution of an extensive Jurassic (ca.

  12. A new Bathonian (Middle Jurassic) microvertebrate site, within the Chipping Norton Limestone Formation at Hornsleasow Quarry,

    E-print Network

    Benton, Michael

    A new Bathonian (Middle Jurassic) microvertebrate site, within the Chipping Norton Limestone. & DARTNALL, D. L. 1992. A new Bathonian (Middle Jurassic) microvertebrate site within the Chipping Norton the palaeokarst and overlying soils (with their indigenous flora and fauna) suggest a period of emergence

  13. Jurassic crustal deformation in west-central part of Colorado Plateau

    SciTech Connect

    Peterson, F.

    1985-05-01

    Although the Jurassic Period is commonly thought of as a time of tectonic quiescence, updated isopach maps and new sedimentologic information indicate that it was a time of notable crustal deformation on the Colorado Plateau. A significant change in structural style occurred in Middle Jurassic time, especially during the erosion interval that produced the J-3 unconformity. Prior to late Middle Jurassic time, the region had been tilted westward and structural troughs formed in the area of the present-day Circle Cliffs uplift and in the vicinity of the Circle Cliffs and Black Mesa regions were uplifted and the nearby Henry and Kaiparowits regions began to be downwarped as troughs or basins. It cannot be determined if or how the present-day monoclines flexed during the Jurassic. However, the direction of structural tilt across these areas changed from west side down to east side down during the late Middle and early Late Jurassic. The Monument region, the largest and most persistent structural element in the region, changed from a structural bench to a positive structure in the early Late Jurassic. In most cases the positive structures subsided more slowly than adjacent downwarps. Two exceptions during the Late Jurassic are the Black Mesa and Emery uplifts. These are the only uplifts that actually rose above the level of sediment accumulation. Jurassic rocks are not known to contain significant hydrocarbon resources in this region, but their tectonic history may offer clues to the structural history of underlying Paleozoic strata, which are the primary hydrocarbon exploration targets.

  14. A NEW LATE JURASSIC TURTLE FROM SPAIN: PHYLOGENETIC IMPLICATIONS, TAPHONOMY AND

    E-print Network

    Benton, Michael

    A NEW LATE JURASSIC TURTLE FROM SPAIN: PHYLOGENETIC IMPLICATIONS, TAPHONOMY AND PALAEOECOLOGY.schouten@bristol.ac.uk Typescript received 26 October 2010; accepted in revised form 27 May 2011 Abstract: The Jurassic was an important period in the evo- lution of Testudinata and encompasses the origin of many clades

  15. Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation in the Fundy basin

    E-print Network

    Olsen, Paul E.

    Magnetic polarity stratigraphy and paleolatitude of the Triassic^Jurassic Blomidon Formation] characterized the Triassic as perhaps the most arid period of the Phanerozoic, citing evidence for widespread,5] and the apparent expan- sion of deserts in the Triassic and Early Jurassic to an extent not since repeated [6

  16. Jurassic crustal deformation in west-central part of Colorado Plateau

    Microsoft Academic Search

    1985-01-01

    Although the Jurassic Period is commonly thought of as a time of tectonic quiescence, updated isopach maps and new sedimentologic information indicate that it was a time of notable crustal deformation on the Colorado Plateau. A significant change in structural style occurred in Middle Jurassic time, especially during the erosion interval that produced the J-3 unconformity. Prior to late Middle

  17. Testing the fossil record: Sampling proxies and scaling in the British TriassicJurassic

    E-print Network

    Benton, Michael

    Testing the fossil record: Sampling proxies and scaling in the British Triassic­Jurassic Alexander March 2014 Available online 30 March 2014 Keywords: Palaeodiversity Fossil record Sampling Proxy Triassic Jurassic The quality of the fossil record varies immensely across taxa, geographic regions

  18. A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom

    E-print Network

    Cambridge, University of

    A new large-bodied theropod dinosaur from the Middle Jurassic of Warwickshire, United Kingdom ROGER dinosaur from the Middle Jurassic of Warwickshire, United Kingdom. Acta Palaeontologica Polonica 55 (1): 35-bodied theropod dinosaur, distinct from the contemporaneous Megalosaurus bucklandii. Cruxicheiros newmanorum gen

  19. The first Lower Jurassic dinosaur from Scotland: limb bone of a ceratosaur theropod from Skye

    E-print Network

    Benton, Michael

    The first Lower Jurassic dinosaur from Scotland: limb bone of a ceratosaur theropod from Skye M. J right tibia of a carnivorous dinosaur is reported from the Lower Jurassic Broadford Beds Formation characteristic features of the ceratosaur theropods, a group of medium-sized predatory dinosaurs that were

  20. 2006 Nature Publishing Group A new carnivorous dinosaur from the Late Jurassic

    E-print Network

    Cai, Long

    © 2006 Nature Publishing Group A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago Ursula B. Go¨hlich1 & Luis M. Chiappe2 Small Late Jurassic theropod dinosaurs are rare worldwide. In Europe these carnivorous dinosaurs are represented primarily by only two skeletons of Compsognathus1

  1. Reconstruction of the Upper Jurassic Morrison Formation extinct ecosystem—a synthesis

    Microsoft Academic Search

    Christine E. Turner; Fred Peterson

    2004-01-01

    A synthesis of recent and previous studies of the Morrison Formation and related beds, in the context of a conceptual climatic\\/hydrologic framework, permits reconstruction of the Late Jurassic dinosaurian ecosystem throughout the Western Interior of the United States and Canada. Climate models and geologic evidence indicate that a dry climate persisted in the Western Interior during the Late Jurassic. Early

  2. Paleogeographic evidence on the Jurassic tectonic history of the Pontides: new paleomagnetic data from the Sakarya continent and Eastern Pontides

    Microsoft Academic Search

    Mualla Cengiz Çinku

    2011-01-01

    The Jurassic paleogeographic position of the Pontides is not well studied because of insufficient paleomagnetic data. For this reason, a paleomagnetic study was carried out in order to constrain the paleolatitudinal drift of the Turkish blocks during the Jurassic period. A total of 32 sites were sampled from volcanic and volcanoclastic rocks of the Lower\\/Middle Jurassic Kelkit formation (Eastern Pontides),

  3. Paleogeographic evidence on the Jurassic tectonic history of the Pontides: new paleomagnetic data from the Sakarya continent and Eastern Pontides

    Microsoft Academic Search

    Mualla Cengiz Cinku

    2010-01-01

    The Jurassic paleogeographic position of the Pontides is not well studied because of insufficient paleomagnetic data. For this reason, a paleomagnetic study was carried out in order to constrain the paleolatitudinal drift of the Turkish blocks during the Jurassic period. A total of 32 sites were sampled from volcanic and volcanoclastic rocks of the Lower\\/Middle Jurassic Kelkit formation (Eastern Pontides),

  4. Detailed record of the mid-Oxfordian (Late Jurassic) positive carbon-isotope excursion in two hemipelagic sections (France

    E-print Network

    Gilli, Adrian

    Detailed record of the mid-Oxfordian (Late Jurassic) positive carbon-isotope excursion in two 2007 Abstract The Oxfordian (Late Jurassic) was a time of widespread change in Jurassic marine coincide with the first calcareous sediments recurring after a period of reduced carbonate accumulation

  5. Lake-mire deposition, earthquakes and wildfires along a basin margin fault; Rønne Graben, Middle Jurassic, Denmark

    Microsoft Academic Search

    Lars Henrik Nielsen; Henrik I. Petersen; Karen Dybkjær; Finn Surlyk

    2010-01-01

    Regional uplift of structural highs took place in the greater North Sea region in early Middle Jurassic times, resulting in a change from marine shelf deposition in the Early Jurassic to widespread emergence, erosion and localized deposition in grabens. The Middle Jurassic Bagå Formation exposed on the island of Bornholm in the Baltic Sea was deposited in the Rønne Graben,

  6. First occurrence of Brachiosaurus (Dinosauria: Sauropoda) from Brachiosaurus (Dinosauria: Sauropoda) from Brachiosaurus the Upper Jurassic Morrison Formation of Oklahoma

    Microsoft Academic Search

    MATTHEW F. BONNAN; MATHEW J. WEDEL

    The giant sauropod Brachiosaurus is one of the rarest sauropods from the Upper Jurassic of North America. The Brachiosaurus is one of the rarest sauropods from the Upper Jurassic of North America. The Brachiosaurus genus has previously been reported from Colorado, Utah, and Wyoming. OMNH 01138 is a sauropod metacarpal of unusual proportions from the Upper Jurassic Morrison Formation of

  7. Latest Jurassic-early Cretaceous regressive facies, northeast Africa craton

    SciTech Connect

    van Houten, F.B.

    1980-06-01

    Nonmarine to paralic detrital deposits accumulated in six large basins between Algeria and the Arabo-Nubian shield during major regression in latest Jurassic and Early Cretaceous time. The Ghadames Sirte (north-central Libya), and Northern (Egypt) basins lay along the cratonic margin of northeastern Africa. The Murzuk, Kufra, and Southern (Egypt) basins lay in the south within the craton. Data for reconstructing distribution, facies, and thickness of relevant sequences are adequate for the three northern basins only. High detrital influx near the end of Jurassic time and in mid-Cretaceous time produced regressive nubian facies composed largely of low-sinuosity stream and fahdelta deposits. In the west and southwest the Ghadames, Murzuk, and Kufra basins were filled with a few hundred meters of detritus after long-continued earlier Mesozoic aggradation. In northern Egypt the regressive sequence succeeded earlier Mesozoic marine sedimentation; in the Sirte and Southern basins correlative deposits accumulated on Precambrian and Variscan terranes after earlier Mesozoic uplift and erosion. Waning of detrital influx into southern Tunisia and adjacent Libya in the west and into Israel in the east initiated an Albian to early Cenomanian transgression of Tethys. By late Cenomanian time it had flooded the entire cratonic margin, and spread southward into the Murzuk and Southern basins, as well as onto the Arabo-Nubian shield. Latest Jurassic-earliest Cretaceous, mid-Cretaceous, and Late Cretaceous transgressions across northeastern Africa recorded in these sequences may reflect worldwide eustatic sea-level rises. In contrast, renewed large supply of detritus during each regression and a comparable subsidence history of intracratonic and marginal basins imply regional tectonic control. 6 figures.

  8. Triassic-Jurassic mass extinction as trigger for the Mesozoic radiation of crocodylomorphs.

    PubMed

    Toljagic, Olja; Butler, Richard J

    2013-06-23

    Pseudosuchia, one of the two main clades of Archosauria (Reptilia: Diapsida), suffered a major decline in lineage diversity during the Triassic-Jurassic (TJ) mass extinction (approx. 201 Ma). Crocodylomorpha, including living crocodilians and their extinct relatives, is the only group of pseudosuchians that survived into the Jurassic. We reassess changes in pseudosuchian morphological diversity (disparity) across this time interval, using considerably larger sample sizes than in previous analyses. Our results show that metrics of pseudosuchian disparity did not change significantly across the TJ boundary, contrasting with previous work suggesting low pseudosuchian disparity in the Early Jurassic following the TJ mass extinction. However, a significant shift in morphospace occupation between Late Triassic and Early Jurassic taxa is recognized, suggesting that the TJ extinction of many pseudosuchian lineages was followed by a major and geologically rapid adaptive radiation of crocodylomorphs. This marks the onset of the spectacularly successful evolutionary history of crocodylomorphs in Jurassic and Cretaceous ecosystems. PMID:23536443

  9. Inter-layered clay stacks in Jurassic shales

    NASA Technical Reports Server (NTRS)

    Pye, K.; Krinsley, D. H.

    1983-01-01

    Scanning electron microscopy in the backscattered electron mode is used together with energy-dispersive X-ray microanalysis to show that Lower Jurassic shales from the North Sea Basin contain large numbers of clay mineral stacks up to 150 microns in size. Polished shale sections are examined to determine the size, shape orientation, textural relationships, and internal compositional variations of the clays. Preliminary evidence that the clay stacks are authigenic, and may have formed at shallow burial depths during early diagenesis, is presented.

  10. Peri-equatorial paleolatitudes for Jurassic radiolarian cherts of Greece

    USGS Publications Warehouse

    Aiello, I.W.; Hagstrum, J.T.; Principi, G.

    2008-01-01

    Radiolarian-rich sediments dominated pelagic deposition over large portions of the Tethys Ocean during middle to late Jurassic time as shown by extensive bedded chert sequences found in both continental margin and ophiolite units of the Mediterranean region. Which paleoceanographic mechanisms and paleotectonic setting favored radiolarian deposition during the Jurassic, and the nature of a Tethys-wide change from biosiliceous to biocalcareous (mainly nannofossil) deposition at the beginning of Cretaceous time, have remained open questions. Previous paleomagnetic analyses of Jurassic red radiolarian cherts in the Italian Apennines indicate that radiolarian deposition occurred at low peri-equatorial latitudes, similar to modern day deposition of radiolarian-rich sediments within equatorial zones of high biologic productivity. To test this result for other sectors of the Mediterranean region, we undertook paleomagnetic study of Mesozoic (mostly middle to upper Jurassic) red radiolarian cherts within the Aegean region on the Peloponnesus and in continental Greece. Sampled units are from the Sub-Pelagonian Zone on the Argolis Peninsula, the Pindos-Olonos Zone on the Koroni Peninsula, near Karpenissi in central Greece, and the Ionian Zone in the Varathi area of northwestern Greece. Thermal demagnetization of samples from all sections removed low-temperature viscous and moderate-temperature overprint magnetizations that fail the available fold tests. At Argolis and Koroni, however, the cherts carry a third high-temperature magnetization that generally exhibits a polarity stratigraphy and passes the available fold tests. We interpret the high-temperature component to be the primary magnetization acquired during chert deposition and early diagenesis. At Kandhia and Koliaky (Argolis), the primary declinations and previous results indicate clockwise vertical-axis rotations of ??? 40?? relative to "stable" Europe. Due to ambiguities in hemispheric origin (N or S) and thus paleomagnetic polarity, the observed declinations could indicate either clockwise (CW) or counterclockwise (CCW) vertical-axis rotations. Thus at Adriani (Koroni), the primary declinations indicate either CW or CCW rotations of ??? 95?? or ??? 84??, depending on paleomagnetic polarity and age. The primary inclinations for all Peloponnesus sites indicate peri-equatorial paleolatitudes similar to those found for coeval radiolarian cherts exposed in other Mediterranean orogenic belts. Our new paleomagnetic data support the interpretation that Mesozoic radiolarites within the Tethys Ocean were originally deposited along peri-equatorial belts of divergence and high biologic productivity. ?? 2007 Elsevier B.V. All rights reserved.

  11. Direct chemical evidence for eumelanin pigment from the Jurassic period.

    PubMed

    Glass, Keely; Ito, Shosuke; Wilby, Philip R; Sota, Takayuki; Nakamura, Atsushi; Bowers, C Russell; Vinther, Jakob; Dutta, Suryendu; Summons, Roger; Briggs, Derek E G; Wakamatsu, Kazumasa; Simon, John D

    2012-06-26

    Melanin is a ubiquitous biological pigment found in bacteria, fungi, plants, and animals. It has a diverse range of ecological and biochemical functions, including display, evasion, photoprotection, detoxification, and metal scavenging. To date, evidence of melanin in fossil organisms has relied entirely on indirect morphological and chemical analyses. Here, we apply direct chemical techniques to categorically demonstrate the preservation of eumelanin in two > 160 Ma Jurassic cephalopod ink sacs and to confirm its chemical similarity to the ink of the modern cephalopod, Sepia officinalis. Identification and characterization of degradation-resistant melanin may provide insights into its diverse roles in ancient organisms. PMID:22615359

  12. Direct chemical evidence for eumelanin pigment from the Jurassic period

    PubMed Central

    Glass, Keely; Ito, Shosuke; Wilby, Philip R.; Sota, Takayuki; Nakamura, Atsushi; Bowers, C. Russell; Vinther, Jakob; Dutta, Suryendu; Summons, Roger; Briggs, Derek E. G.; Wakamatsu, Kazumasa; Simon, John D.

    2012-01-01

    Melanin is a ubiquitous biological pigment found in bacteria, fungi, plants, and animals. It has a diverse range of ecological and biochemical functions, including display, evasion, photoprotection, detoxification, and metal scavenging. To date, evidence of melanin in fossil organisms has relied entirely on indirect morphological and chemical analyses. Here, we apply direct chemical techniques to categorically demonstrate the preservation of eumelanin in two > 160 Ma Jurassic cephalopod ink sacs and to confirm its chemical similarity to the ink of the modern cephalopod, Sepia officinalis. Identification and characterization of degradation-resistant melanin may provide insights into its diverse roles in ancient organisms. PMID:22615359

  13. Deep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications for the geomagnetic polarity reversal timescale and

    E-print Network

    ., 113, B07110, doi:10.1029/2007JB005527. 1. Introduction [2] The Jurassic period appears to be a time of the Jurassic magnetic field. It was once suggested that this Jurassic ``Quiet Zone'' (JQZ) reflects a periodDeep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications

  14. Astronomical constraints on the duration of the early Jurassic Hettangian stage and recovery rates following the end-Triassic mass extinction

    E-print Network

    Utrecht, Universiteit

    for the base of the Jurassic period and the duration of lower Jurassic stages largely vary between studiesAstronomical constraints on the duration of the early Jurassic Hettangian stage and recovery rates Available online 10 May 2010 Editor: P. DeMenocal Keywords: Triassic Jurassic cyclostratigraphy astronomical

  15. A Jurassic ceratosaur from China helps clarify avian digital homologies.

    PubMed

    Xu, Xing; Clark, James M; Mo, Jinyou; Choiniere, Jonah; Forster, Catherine A; Erickson, Gregory M; Hone, David W E; Sullivan, Corwin; Eberth, David A; Nesbitt, Sterling; Zhao, Qi; Hernandez, Rene; Jia, Cheng-kai; Han, Feng-lu; Guo, Yu

    2009-06-18

    Theropods have traditionally been assumed to have lost manual digits from the lateral side inward, which differs from the bilateral reduction pattern seen in other tetrapod groups. This unusual reduction pattern is clearly present in basal theropods, and has also been inferred in non-avian tetanurans based on identification of their three digits as the medial ones of the hand (I-II-III). This contradicts the many developmental studies indicating II-III-IV identities for the three manual digits of the only extant tetanurans, the birds. Here we report a new basal ceratosaur from the Oxfordian stage of the Jurassic period of China (156-161 million years ago), representing the first known Asian ceratosaur and the only known beaked, herbivorous Jurassic theropod. Most significantly, this taxon possesses a strongly reduced manual digit I, documenting a complex pattern of digital reduction within the Theropoda. Comparisons among theropod hands show that the three manual digits of basal tetanurans are similar in many metacarpal features to digits II-III-IV, but in phalangeal features to digits I-II-III, of more basal theropods. Given II-III-IV identities in avians, the simplest interpretation is that these identities were shared by all tetanurans. The transition to tetanurans involved complex changes in the hand including a shift in digit identities, with ceratosaurs displaying an intermediate condition. PMID:19536256

  16. Amphibious flies and paedomorphism in the Jurassic period.

    PubMed

    Huang, Diying; Nel, André; Cai, Chenyang; Lin, Qibin; Engel, Michael S

    2013-03-01

    The species of the Strashilidae (strashilids) have been the most perplexing of fossil insects from the Jurassic period of Russia and China. They have been widely considered to be ectoparasites of pterosaurs or feathered dinosaurs, based on the putative presence of piercing and sucking mouthparts and hind tibio-basitarsal pincers purportedly used to fix onto the host's hairs or feathers. Both the supposed host and parasite occur in the Daohugou beds from the Middle Jurassic epoch of China (approximately 165 million years ago). Here we analyse the morphology of strashilids from the Daohugou beds, and reach markedly different conclusions; namely that strashilids are highly specialized flies (Diptera) bearing large membranous wings, with substantial sexual dimorphism of the hind legs and abdominal extensions. The idea that they belong to an extinct order is unsupported, and the lineage can be placed within the true flies. In terms of major morphological and inferred behavioural features, strashilids resemble the recent (extant) and relict members of the aquatic fly family Nymphomyiidae. Their ontogeny are distinguished by the persistence in adult males of larval abdominal respiratory gills, representing a unique case of paedomorphism among endopterygote insects. Adult strashilids were probably aquatic or amphibious, shedding their wings after emergence and mating in the water. PMID:23426262

  17. Jurassic extension and Alpine inversion of the northern Morocco

    SciTech Connect

    Zizi, M. (Rice Univ., Houston, TX (United States))

    1993-09-01

    The lower Mesozoic half grabens of northern Morocco form part of an extensional system that is related to the opening of the western Tethys. They appear to be somewhat younger than the Triassic-Jurassic systems associated with the opening the Atlantic Ocean. During the Tertiary and as consequence of the Alpine collision of Africa with Europe, these half graben systems were inverted as shown by the High and the Middle Atlas mountains. Seismic illustrations of similar but smaller inversion structures are available from the Guercif area and the [open quotes]Rides Prerifaines[close quotes] of northern Morocco. These seismic profiles serve as small models for the much larger Atlas Mountains. In the Guercif area, the inversions are limited in scope, but in the [open quotes]Ride Prerifaines[close quotes] are extensive decollement systems that sole out in the Triassic evaporites. These systems evolve into complex thrust faults and associated lateral ramps that are strongly influenced by the configuration of the Jurassic transtensional systems. Significant hydrocarbon accumulation have been known for some time from the [open quotes]Rides Prerifaines.[close quotes] A review of the geometry of the inverted half-graben systems, combined with detailed stratigraphic studies, is likely to lead to the discovery of additional reserves in the area.

  18. Isotopic constraints on the petrogenesis of jurassic plutons, Southeastern California

    USGS Publications Warehouse

    Mayo, D.P.; Anderson, J.L.; Wooden, J.L.

    1998-01-01

    The 165 Ma Eagle Mountain intrusion is a heterogeneous, enclave-bearing, metaluminous remnant of the Cordilleran Jurassic arc that cuts regionally metamorphosed pre-Mesozoic rocks in the southeastern Mojave Desert of California. The main phase of the intrusion consists of granodiorite to tonalite host facies, diorite mixed facies, and homogeneous monzogranite facies. The host facies contains microdiorite enclaves interpreted as intermingled masses of mafic magma. Late-phase leucogranite stocks cut the main phase. Mineral equilibria indicate emplacement at ???6.5 km depth, with solidus temperatures ranging from 760??C for diorite to 700??C for felsic granodiorite. Although uniform radiogenic-isotope compositions (Sri = 0.7085, ???Ndi = -9.4) suggest derivation from a single source, no known source has the composition required. A hybrid source is proposed, consisting of various proportions of juvenile mantle and recycled lower crust. Calculations indicate that the source of the Eagle Mountain intrusion comprised >60% juvenile mantle and <40% recycled crust. On the basis of their isotopic compositions, other mafic Jurassic plutons in the region were derived from sources containing different proportions of mantle and crustal components.

  19. Geochemical features of metabasic rocks from an Early to Middle Jurassic Accretionary Complex (Refahiye metamorphics, Eastern Pontides, NE Turkey): Implications for Late Jurassic-Early Cretaceous magmatic lull

    NASA Astrophysics Data System (ADS)

    Göçmengil, G.; Topuz, G.; Çelik, Ö. F.; Alt?nta?, Ä.°. E.; Özkan, M.

    2012-04-01

    The Refahiye metamorphics (Eastern Pontides, NE Turkey) represent a metamorphosed accretionary complex of Early to Middle Jurassic age and occur as an interleave between coeval ophiolite. This Early to Middle Jurassic metamorphics and ophiolites are bound by a Permo-Triassic accretionary complex in the north and a Late Cretaceous accretionary complex in the south. The Refahiye metamorphics are made up of greenschist, marble, serpentine, phyllite and subordinately amphibolite, micaschist, eclogite and metachert knockers. The Jurassic and Late Cretaceous accretionary complexes in Eastern Mediterranean are related to the consumption of a Mesozoic ocean, the so-called Neo-Tethys. Regional geology in the Eastern Pontides indicate that the Early to Middle Jurassic and Late Cretaceous times correspond to volumious igneous activity, while Late Jurassic and Early Cretaceous time to an igneous lull. Here we present whole-rock geochemical data on metabasic rocks from the Refahiye accretionary complex, and discuss these data in terms of accreted material and its implications for the Jurassic evolution of the Eastern Pontides. All the metabasic rocks are well recrystallized, free of any relict texture and are variably hydrated (LOI ~ 1.3-5.1 wt%). Some samples are characterized by the unusually high-Al2O3 contents (up to 20.8 wt%) suggestive of derivation from high-Al basalts. Geochemically three distinct metabasic group are distinguished, on the basis of fluid immobile HFSEs and REEs. Group I is characterized by moderately to strongly fractionated REE patterns [(La/Yb)cn ~8-18], absence of any Nb-Ta anomaly in multi element variation diagrams and high Ti and low Zr/Nb ratios (3.68-5.72), corresponding to unorogenic alkaline basalts (ocean island basalt). Group II characterized by moderately fractionated REE ratios [(La/Yb)cn ~0.6-2.6], absence of any Nb-Ta anomaly, resembling unorogenic tholeiitic basalts (E and N-MORB). Group III on the other hand, displays unfractionated, nearly flat REE patterns [(La/Yb)cn ~0.6-1.1], negative Nb-Ta anomaly and enormously high Zr/Nb values (38-62), corresponding to orogenic tholeeitic basalts. These data indicate accretion of unorogenic alkaline and tholeiitic basalts similar to those in seamounts, MORB and IAB during the Early to Middle Jurassic subduction. This together with widespread Early to Middle Jurassic magmatism in Eastern Pontides and Crimea and absence in the southern Menderes-Taurus continental block, conclusively indicate for a northvergent subduction. On the basis of the general absence of a Middle to Upper Jurassic unconformity, we tentatively ascribe the Late Jurassic-Early Cretaceous magmatic lull to the accretion of large submarine topographic highs to the subduction zone.

  20. Development geology study of Weber sandstone, Rangely field, Colorado

    SciTech Connect

    Jackson, W.D.; Bowker, K. (Chevron U.S.A. Inc., Houston, TX)

    1989-09-01

    The Pennsylvanian-Permian Weber Sandstone formation is the major producing horizon at the giant Rangely field, Rio Blanco County, Colorado. The Weber has been separated into six lithofacies using core descriptions, core analyses, optical and scanning-electron microscopy, x-ray diffraction, and special-core analyses. Two of the lithofacies (eolian) are productive. The subarkosic laminated sandstones (which have the best reservoir quality) have an average Boyle's Law porosity of 9.7%. Permeability varies directionally on a small scale because of differential cementation within the graded laminae; the very fine-grained portion of the laminae is more tightly cemented by carbonate minerals than are the fine-grained portions. Permeability along the laminae averages 1.2 md; permeability across the laminae is less than 1 md. The second productive lithofacies is massive (bioturbated) and more thoroughly cemented than the first; it is also composed of fine and very fine-grained sandstones. These massive subarkosic sandstones have an average porosity of 7% and permeability averaging less than 1 md. Fractures alter permeability in portions of the field. The remaining four lithofacies (fluvial) are not productive and act as intraformational permeability barriers. Arkosic sandstones, arkosic siltstones, shales, and rare carbonates comprise this group. The relationship of the lithofacies to the depositional environment and the recognition of them on electric logs has allowed correlations across the field. This has proven an important contribution to the management of the current CO{sub 2} flood.

  1. Numerical analysis of sandstone composition, provenance, and paleogeography

    SciTech Connect

    Smosma, R.; Bruner, K.R.; Burns, A. [West Virginia Univ., Morgantown, WV (United States). Dept. of Geology and Geography

    1999-09-01

    Cretaceous deltaic sandstones of the National Petroleum Reserve in Alaska exhibit an extreme variability in their mineral makeup. A series of numerical techniques, however, provides some order to the petrographic characteristics of these complex rocks. Ten mineral constituents occur in the sandstones, including quartz, chert, feldspar, mica, and organic matter, plus rock fragments of volcanics, carbonates, shale, phyllite, and schist. A mixing coefficient quantities the degree of heterogeneity in each sample. Hierarchical cluster analysis then groups sandstones on the basis of similarities among all ten mineral components--in the Alaskan example, six groupings characterized mainly by the different rock fragments. Multidimensional scaling shows how the clusters relate to one another and arranges them along compositional gradients--two trends in Alaska based on varying proportions of metamorphic/volcanic and shale/carbonate rock fragments. The resulting sandstone clusters and petrographic gradients can be mapped across the study area and compared with the stratigraphic section. This study confirms the presence of three different source areas that provided diverse sediment to the Cretaceous deltas as well as the general transport directions and distances. In addition, the sand composition is shown to have changed over time, probably related to erosional unroofing in the source areas. This combination of multivariate-analysis techniques proves to be a powerful tool, revealing subtle spatial and temporal relationships among the sandstones and allowing one to enhance provenance and paleogeographic conclusions made from compositional data.

  2. Material invariant properties and reconstruction of microstructure of sandstones by nanoindentation and microporoelastic analysis

    E-print Network

    Bobko, Christopher Philip, 1981-

    2005-01-01

    The diversity of sandstones and sandstone properties that exist in nature pose a significant problem for engineers who deal with these materials, whether in oil well exploration and exploitation or art and architectural ...

  3. The geology of the basal sandstone-mudstone unit of the Blackhawk Landslide, Lucerne Valley, California

    E-print Network

    Kuzior, Jerry Linn

    1983-01-01

    for thin, localized, basal layers of sandstone, gneiss, and mixed breccia. Within Blackhawk Canyon, Member 2 lies with slickensided, horizontal contact on Old Woman Sandstone and is interpreted to be a landside that occurred prior to, but attained less...

  4. Significance of Jurassic radiolarians from the Cache Creek terrane, British Columbia

    NASA Astrophysics Data System (ADS)

    Cordey, Fabrice; Mortimer, N.; Dewever, Patrick; Monger, J. W. H.

    1987-12-01

    The discovery of new radiolarian localities in the western belt of the Cache Creek terrane in southern British Columbia possibly changes its upper age limit from Late Triassic to Early or Middle Jurassic. It favors a Middle Jurassic, rather than a Late Triassic, age of amalgamation for the Cache Creek terrane and Quesnellia (parts of superterrane I) in southern British Columbia. The new Jurassic ages also mean that the western Cache Creek terrane could be equivalent in age to the Bridge River Hozameen terrane in British Columbia and to terranes containing the Tethyan fusulinid Yabeina in northwest Washington and the Klamath Mountains of California.

  5. Timescales of orogeny: Jurassic construction of the Klamath Mountains

    NASA Astrophysics Data System (ADS)

    Hacker, Bradley R.; Donato, Mary M.; Barnes, Calvin G.; McWilliams, M. O.; Ernst, W. G.

    1995-06-01

    An electronic supplement of this material may be obtained on a diskette or Anonymous FTP from KOSMOS.AGU.ORG (LOGIN to AGU's FTP account using ANONYMOUS as the username and GUEST as the password. Go to the right directory by typing CD APEND. Type LS to see what files are available. Type GET and the name of the file to get it. Finally, type EXIT to leave the system.) (Paper 94YCJ2454, Timescales of orogeny: Jurassic construction of the Klamath Mountains, B.R. Hacker, M.M. Donato, C.G. Barnes, M.O. McWilliams, and W.G. Ernst). Diskette may be ordered from American Geophysical Union, 2000 Florida Avenue, N.W., Washington, DC 20009; $15.00. Payment must accompany order. Classical interpretations of orogeny were based on relatively imprecise biostratigraphic and isotopic age determinations that necessitated grouping apparently related features that may in reality have been greatly diachronous. Isotopic age techniques now have the precision required to resolve the timing of orogenic events on a scale much smaller than that of entire mountain belts. Forty-five new 40Ar/39Ar ages from the Klamath Mountains illuminate the deformation, metamorphism, magmatism, and sedimentation involved in the Jurassic construction of that orogen, leading to a new level of understanding regarding how preserved orogenic features relate to ancient plate tectonic processes. The new geochronologic relationships show that many Jurassic units of the Klamath Mountains had 200 Ma or older volcanoplutonic basement. Subsequent formation of a large ˜170 Ma arc was followed by contractional collapse of the arc. Collision with a spreading ridge may have led to large-scale NW-SE extension in the central and northern Klamaths from 167 to ˜155 Ma, coincident with the crystallization of voluminous plutonic and volcanic suites. Marked cooling of a large region of the central Klamath Mountains to below ˜350°C at ˜150 Ma may have occurred as the igneous belt was extinguished by subduction of colder material at deeper structural levels. These data demonstrate that the Klamath Mountains—and perhaps other similar orogens—were constructed during areally and temporally variant episodes of contraction, extension, and magmatism that do not fit classical definitions of orogeny.

  6. Continuity and internal properties of Gulf Coast sandstones and their implications for geopressured fluid production

    SciTech Connect

    Morton, R.A.; Ewing, T.E.; Tyler, N.

    1983-01-01

    The intrinsic properties of the genetic sandstone units that typify many geopressured geothermal aquifers and hydrocarbon reservoirs in the Gulf Coast region were systematically investigated classified, and differentiated. The following topics are coverd: structural and stratigraphic limits of sandstone reservoirs, characteristics and dimensions of Gulf Coast sandstones; fault-compartment areas; comparison of production and geologic estimates of aquifer fluid volume; geologic setting and reservoir characteristics, Wells of Opportunity; internal properties of sandstones; and implications for geopressured fluid production. (MHR)

  7. Ionic surface electrical conductivity in sandstone

    NASA Astrophysics Data System (ADS)

    Glover, Paul W. J.; Meredith, Philip G.; Sammonds, Peter R.; Murrell, Stanley A. F.

    1994-11-01

    Recent analyses of complex conductivity measurements have indicated that high-frequency dispersions encountered in rocks saturated with low-salinity fluids are due to ionic surface conduction and that the form of these dispersions may be dependent upon the nature of the pore and crack surfaces within the rock (Ruffet et al., 1991). Unfortunately, the mechanisms of surface conduction are not well understood, and no model based on rigorous physical principles exists. This paper is split into two parts: an experimental section followed by the development of a theoretical description of adsorption of ions onto mineral surfaces. We have made complex conductivity measurements upon samples of sandstone saturated with a range of different types and concentrations of aqueous solution with a frequency range of 20 Hz to 1 MHz. The frequency dependence of complex conductivity was analyzed using the empirical model of Cole and Cole (1941). The 'fractal' surface models of Le Mehaute and Crepy (1983), Po Zen Wong (1987), the Ruffet el at. (1991) were used to calculate apparent fractal pore surface dimensions for samples saturated with different solution types and concentrations. These showed a pronounced decrease of apparent fractal surface dimension with decreasing electrolyte concentration and a decrease of apparent fractal dimension with increasing relative ionic radius of the dominant cation in solution. A model for ionic surface concentration (ISCOM I) has been developed as the first step in producing a rigorous physicochemical model of surface conduction in quartz-dominated rocks. The results from ISCOM I show that quartz surfaces are overwhelmingly dominated by adsorbed Na(+) when saturated with NaCl solutions of salinities and pH found in actual geological situations. ISCOM I also shows that the concentration threshold for dominance of surface conduction over bulk conduction is aided by depletion of ions from the bulk fluid as a result of their adsorption onto the mineral surfaces as well as by changes in the ionic mobility in the surface conduction double-layer as the wetting solution becomes more dilute.

  8. Development of Shear Banding in Berea Sandstone

    NASA Astrophysics Data System (ADS)

    Riedel, J. J.; Labuz, J. F.

    2004-05-01

    Closed-loop, servo-controlled testing was used to investigate the development of shear failure in Berea sandstone under low confining pressure. The experiments were performed with the University of Minnesota Plane-Strain Apparatus, designed to allow the failure plane to propagate in an unrestricted manner. Deformation was imposed into the strain softening regime and controlled so that the specimens remained intact. Thin-section microscopy provided direct observation in, adjacent to, and around the tip of the rupture zone. The shear band appeared to initiate near a stress concentration, either the corner of the specimen or, when present, an imperfection (3 mm diameter hole) introduced into the specimen. Intragranular microcracking was the dominant observable failure mechanism. The intensity of grain cracking was greatest near the initiation point and decreased as the failure surface was traced towards the tip. Areas of high crack density also appeared to have the greatest amount of grain size reduction and there seemed to be a larger amount of pore space. In areas where intragranular microcracks were distinguishable, (e.g. near the tip of the rupture zone), microcracks showed very little or no shear displacement, suggesting the features were not reoriented after formation. Microcrack orientations showed a dominant direction of -16 degrees from the maximum principal stress direction and -26 degrees from the failure surface. A numerical imaging technique was developed to provide an efficient means for analyzing the relative porosity of epoxy-impregnated thin-sections. The code was set up to receive a digital image (*.bmp), where three parameters (R, G, and B) describe the color of each pixel. The intensity of the R channel consistently defined the boundary of grain and pore space and was used to differentiate blue pore space from the white grains composing the matrix. Porosity increase within the rupture zone was 3-4 grain diameters wide. An absence of notable porosity change beyond the tip (last observable intragranular microcrack) of the rupture zone suggested the altered porosity developed contemporaneously with intragranular microcracks. A cohesive zone model with a linear distribution of traction to represent a process zone and a constant distribution of traction to represent the frictional resistance along the rupture surface were used to examine the stress field near the process zone, which showed similarities to principal compressive stress orientations interpreted from intragranular microcracks. Observations of the process zone and increased shear deformation along the rupture surface were consistent with a cohesive zone model of shear fracture.

  9. Simulation of sandstone acidizing of a damaged perforation

    SciTech Connect

    Lea, C.M.; Hill, A.D.; Sepehrnoori, K. (Univ. of Texas (US))

    1992-05-01

    A mathematical model was developed to study the effect of acidizing on the productivity of a single perforation penetrating a sandstone reservoir as a function of the distribution of damage around the perforation. Assuming the perforation to be ellipsoidal, the authors derived a 2D model that describes the single-phase flow of an acid through a perforated sandstone that contains two pseudochemical minerals dissolving at different rates. This paper presents cases that show the effectiveness of acidizing in removing both drilling-fluid damage and perforation damage. The most effective stimulation occurs when the perforation damage is removed by the acid.

  10. Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone

    USGS Publications Warehouse

    Anderson, P.B.; Chidsey, T.C., Jr.; Ryer, T.A.

    1997-01-01

    East-central Utah has world-class outcrops of dominantly fluvial-deltaic Turonian to Coniacian aged strata deposited in the Cretaceous foreland basin. The Ferron Sandstone Member of the Mancos Shale records the influences of both tidal and wave energy on fluvial-dominated deltas on the western margin of the Cretaceous western interior seaway. Revisions of the stratigraphy are proposed for the Ferron Sandstone. Facies representing a variety of environments of deposition are well exposed, including delta-front, strandline, marginal marine, and coastal-plain. Some of these facies are described in detail for use in petroleum reservoir characterization and include permeability structure.

  11. Geometry and reservoir heterogeneity of tertiary sandstones: a guide to reservoir continuity and geothermal resource development

    Microsoft Academic Search

    R. A. Morton; T. E. Ewing

    1981-01-01

    External and internal continuity of Tertiary sandstones are controlled by various factors including structural trends, sand body geometry, and the distribution of mineral framework, matrix, and intersticies within the sand body. Except for the limits imposed by faults, these factors are largely inherited from the depositional environment and modified during sandstone compaction and cementation. Sandstone continuity affects energy exploration and

  12. Factors controlling reservoir quality in tertiary sandstones and their significance to geopressured geothermal production

    Microsoft Academic Search

    R. G. Loucks; D. L. Richmann; K. L. Milliken

    1981-01-01

    Variable intensity of diagenesis is the factor primarily responsible for contrasting regional reservoir quality of Tertiary sandstones from the upper and lower Texas coast. Detailed comparison of Frio sandstone from the Chocolate Bayou\\/Danbury Dome area, Brazoria County, and Vicksburg sandstones from the McAllen Ranch Field area, Hidalgo County, reveals that extent of diagenetic modification is most strongly influenced by (1)

  13. Direct evidence of hybodont shark predation on Late Jurassic ammonites

    NASA Astrophysics Data System (ADS)

    Vullo, Romain

    2011-06-01

    Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body fossil associations attesting to this predator-prey relationship have never been described so far. Here, I report a unique finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont shark Planohybodus. Some possible tooth puncture marks are also observed. This is the first direct evidence of such a trophic link between these two major Mesozoic groups, allowing an accurate identification of both organisms. Although Planohybodus displays a tearing-type dentition generally assumed to have been especially adapted for large unshelled prey, our discovery clearly shows that this shark was also able to attack robust ammonites such as aspidoceratids. The direct evidence presented here provides new insights into the Mesozoic marine ecosystem food webs.

  14. Three new Jurassic euharamiyidan species reinforce early divergence of mammals.

    PubMed

    Bi, Shundong; Wang, Yuanqing; Guan, Jian; Sheng, Xia; Meng, Jin

    2014-10-30

    The phylogeny of Allotheria, including Multituberculata and Haramiyida, remains unsolved and has generated contentious views on the origin and earliest evolution of mammals. Here we report three new species of a new clade, Euharamiyida, based on six well-preserved fossils from the Jurassic period of China. These fossils reveal many craniodental and postcranial features of euharamiyidans and clarify several ambiguous structures that are currently the topic of debate. Our phylogenetic analyses recognize Euharamiyida as the sister group of Multituberculata, and place Allotheria within the Mammalia. The phylogeny suggests that allotherian mammals evolved from a Late Triassic (approximately 208 million years ago) Haramiyavia-like ancestor and diversified into euharamiyidans and multituberculates with a cosmopolitan distribution, implying homologous acquisition of many craniodental and postcranial features in the two groups. Our findings also favour a Late Triassic origin of mammals in Laurasia and two independent detachment events of the middle ear bones during mammalian evolution. PMID:25209669

  15. Direct evidence of hybodont shark predation on Late Jurassic ammonites.

    PubMed

    Vullo, Romain

    2011-06-01

    Sharks are known to have been ammonoid predators, as indicated by analysis of bite marks or coprolite contents. However, body fossil associations attesting to this predator-prey relationship have never been described so far. Here, I report a unique finding from the Late Jurassic of western France: a complete specimen of the Kimmeridgian ammonite Orthaspidoceras bearing one tooth of the hybodont shark Planohybodus. Some possible tooth puncture marks are also observed. This is the first direct evidence of such a trophic link between these two major Mesozoic groups, allowing an accurate identification of both organisms. Although Planohybodus displays a tearing-type dentition generally assumed to have been especially adapted for large unshelled prey, our discovery clearly shows that this shark was also able to attack robust ammonites such as aspidoceratids. The direct evidence presented here provides new insights into the Mesozoic marine ecosystem food webs. PMID:21452053

  16. Triassic-Jurassic Mass Extinction: Evidence for Bolide Impact?

    NASA Astrophysics Data System (ADS)

    Perry, R.; Becker, L.; Haggart, J.; Poreda, R.

    2003-04-01

    The Triassic-Jurassic (TJ) mass extinction event is one of the most severe in geologic history and is one of the five largest in the Phanerozoic with as many as 80% of the species lost. It is also one of the most poorly understood. Only a few geologic sections have been identified for the TJ extinction and most of those are not well preserved. Previously, the paucity of suitable stratigraphic sections has prevented corroborative geochemical studies. Recently a well-preserved stratigraphic section spanning the Triassic-Jurassic boundary (˜200 mya) was identified at Kennecott Point, Queen Charlotte, Islands, British Columbia. Initial studies have shown that the Kennecott Point sequence is one of the best preserved and contains one of the most complete radiolarian microfossil turnovers known. Analyses of stable isotopes have shown that a 13C perturbation exits within the sequence and suggests a decline in organic productivity (Ward et al., 2001). Preliminary results of laser desorption mass spectrometry (LDMS) of selected Queen Charlotte samples suggest that fullerenes (C60 to C200) may be present in the Kennecott Point stratigraphic sequence. Previous studies have shown that fullerenes are present in the mass extinction boundary of the Permian-Triassic (˜251 mya) as well as the well-known "dinosaur" extinction event of the Cretaceous-Tertiary (˜65 mya). Therefore, three of the big five extinction events appear to have associated fullerenes. The possible presence of fullerenes along with the productivity collapse (rapid environmental change) suggests that a cometary or asteroidal impact may have occurred. Although no known impact crater exists, we hope to present chemical evidence that an impact or multiple impacts may have been responsible for the TJ mass extinction.

  17. A food store-based environmental intervention is associated with reduced BMI and improved psychosocial factors and food-related behaviors on the Navajo nation.

    PubMed

    Gittelsohn, Joel; Kim, Elizabeth M; He, Siran; Pardilla, Marla

    2013-09-01

    The prevalence of obesity is significantly higher among American Indians (AIs) and is associated with increased rates of diabetes, hypertension, and cardiovascular disease. We implemented a 14-mo intervention trial (Navajo Healthy Stores) on the Navajo Nation that sought to increase availability of healthier foods in local food stores and to promote these foods at the point of purchase and through community media. We divided the Navajo Nation into 10 store regions, half of which were randomized to intervention and half to comparison. We evaluated the program by using a pre-post sample of systematically sampled adult Navajo consumers (baseline, n = 276; postintervention, n = 145). Intervention impact was examined by analyzing pre-post differences by intervention group and by intervention exposure level. When intervention and comparison groups were compared, only body mass index (BMI) showed a trend toward impact of the intervention (P = 0.06). However, greater exposure to the intervention was associated with significantly reduced BMI (P ? 0.05) and improved healthy food intentions (P ? 0.01), healthy cooking methods (P ? 0.05), and healthy food getting (P ? 0.01). With increasing exposure, the odds of improving overweight or obese status was 5.02 (95% CI: 1.48, 16.99; P ? 0.01) times the odds of maintaining or worsening overweight or obese status. In summary, a food store intervention was associated with reduced overweight/obesity and improved obesity-related psychosocial and behavioral factors among those persons most exposed to the intervention on an AI reservation. PMID:23864511

  18. A Food Store–Based Environmental Intervention Is Associated with Reduced BMI and Improved Psychosocial Factors and Food-Related Behaviors on the Navajo Nation123

    PubMed Central

    Gittelsohn, Joel; Kim, Elizabeth M.; He, Siran; Pardilla, Marla

    2013-01-01

    The prevalence of obesity is significantly higher among American Indians (AIs) and is associated with increased rates of diabetes, hypertension, and cardiovascular disease. We implemented a 14-mo intervention trial (Navajo Healthy Stores) on the Navajo Nation that sought to increase availability of healthier foods in local food stores and to promote these foods at the point of purchase and through community media. We divided the Navajo Nation into 10 store regions, half of which were randomized to intervention and half to comparison. We evaluated the program by using a pre-post sample of systematically sampled adult Navajo consumers (baseline, n = 276; postintervention, n = 145). Intervention impact was examined by analyzing pre-post differences by intervention group and by intervention exposure level. When intervention and comparison groups were compared, only body mass index (BMI) showed a trend toward impact of the intervention (P = 0.06). However, greater exposure to the intervention was associated with significantly reduced BMI (P ? 0.05) and improved healthy food intentions (P ? 0.01), healthy cooking methods (P ? 0.05), and healthy food getting (P ? 0.01). With increasing exposure, the odds of improving overweight or obese status was 5.02 (95% CI: 1.48, 16.99; P ? 0.01) times the odds of maintaining or worsening overweight or obese status. In summary, a food store intervention was associated with reduced overweight/obesity and improved obesity-related psychosocial and behavioral factors among those persons most exposed to the intervention on an AI reservation. PMID:23864511

  19. The Lower Jurassic of the Eastern Caspian region and the Middle Caspian Basin: Lithology, facies, taphonomy

    NASA Astrophysics Data System (ADS)

    Kiritchkova, A. I.; Nosova, N. V.

    2014-09-01

    Lithofacies of the productive Upper Triassic-Lower Jurassic deposits of the Eastern Caspian region, studied in wells on the Caspian coast and exposed in the outcrops of the Mountainous Mangyshlak, are described and analyzed. The similarity of the structure of the Mesozoic sedimentary beds of the Middle Caspian Basin and of those of the land adjacent to its eastern coast is confirmed. Comparative analysis of lithofacies allowed the reconstruction of the paleogeographic setting and depositional environments in the studied region during the Early Jurassic. A unique fossil plant occurrence is discovered in the upper part of the Lower Jurassic series (in the lower subformation of the Kokala Formation; Eastern Caspian region). Fossil plant taphonomy and the lithology of host rocks in the occurrence resulted from unusual paleogeographic settings that existed in the Middle Caspian Basin at the time of the Early-Middle Jurassic boundary.

  20. Paleobiology and skeletochronology of Jurassic dinosaurs: implications from the histology and oxygen

    E-print Network

    Schöne, Bernd R.

    Paleobiology and skeletochronology of Jurassic dinosaurs: implications from the histology Abstract Fossil biogenic phosphate of fast-growing primary bone tissue of dinosaurs can preserve dinosaurs with different histologic patterns of bone growth, high-resolution oxygen isotope profiles were

  1. Fe-Ni Micrometorites from Upper Jurassic Cañadon Asfalto Fm., Patagonia, Argentina

    NASA Astrophysics Data System (ADS)

    Matteini, M.; Hauser, N.; Cabaleri, N.; Silva Nieto, D.; Cuadros, F. A.; Reyes, S.

    2014-09-01

    Microspherules from an upper Jurassic sediments from Patagonia, show mineralogical, geochemical and textural features very similar to those reported for I-type micrometeorites whereas some spherules are interpreted as typical G-type micrometeorites.

  2. Depositional and diagenetic history of some Jurassic carbonates, Indian Rock-Gilmer Field, Upshur County, Texas

    E-print Network

    Fall, Steven Anthony

    1974-01-01

    as late as Eagle Mills time (Eaton, 1960; Halbouty, 1966), Jurassic transgression of the Texas portion of the uplift is confirmed Amerada No . 1 Stri ckland well in Shelby County, Texas, which penetrated a weathered syenite basement beneath Eagle Mills...

  3. Jurassic sequences of the Hebrides Basin, Isle of Skye, Scotland STEPHEN P. HESSELBO*

    E-print Network

    Hesselbo, Stephen P.

    Jurassic sequences of the Hebrides Basin, Isle of Skye, Scotland STEPHEN P. HESSELBO* and ANGELA L the Outer Isles to the mainland SE of Skye, showing structural disposition of the main Mesozoic sedimentary

  4. Depositional and diagenetic history of the Upper Jurassic Haynesville Formation, Teague Townsite Field, Freestone County, Texas 

    E-print Network

    Faucette, Robert Christian

    1981-01-01

    (December, 1981). Robert Christian Faucette, B, S. , Texas ARM University Chairman of Advisory Committee: Dr. Wayne M. Ahr The Upper Jurassic Haynesville Formation in the east Texas area was depsoited in a shallow, restricted basin on a gently dipping...%%u or greater poros1ty in the study area 73 74 75 INTRODUCTION The Upper Jurassic Haynesville Formation in the east Texas area was deposited in a shallow, restricted basin on a gently dipping ramp (Ahr, 1973). The Haynesville is predominantly...

  5. Fossil Plants and Global Warming at the Triassic-Jurassic Boundary.

    PubMed

    McElwain; Beerling; Woodward

    1999-08-27

    The Triassic-Jurassic boundary marks a major faunal mass extinction, but records of accompanying environmental changes are limited. Paleobotanical evidence indicates a fourfold increase in atmospheric carbon dioxide concentration and suggests an associated 3 degrees to 4 degrees C "greenhouse" warming across the boundary. These environmental conditions are calculated to have raised leaf temperatures above a highly conserved lethal limit, perhaps contributing to the >95 percent species-level turnover of Triassic-Jurassic megaflora. PMID:10464094

  6. Late Triassic-Jurassic paleogeography and origin of Gulf of Mexico basin

    SciTech Connect

    Salvador, A.

    1987-04-01

    The basic structural and stratigraphic framework of the Gulf of Mexico Basin was established during the Late Triassic and the Jurassic. During the Late Triassic and Early Jurassic, as the North American plate started to separate from the South American and African plates, the area of the future basin was part of an extensive landmass broken by tensional grabens that were filled by red beds and volcanics. Marine deposition was restricted to embayments of the Pacific Ocean in northwestern and central Mexico. These marine embayments persisted during the early Middle Jurassic, but seawater did not reach the future Gulf of Mexico Basin until the Callovian. Widespread salt deposits known today from two separate areas of the basin resulted from this initial flooding. During the Late Jurassic, marine conditions progressively extended over increasingly larger parts of the Gulf of Mexico Basin. However, the basin was not connected to the Atlantic Ocean until late in the Jurassic. This paleogeographic reconstruction suggests that the Gulf of Mexico Basin formed as a result of the southward drift of the Yucatan continental block away from the remainder of the North American plate. The separation began in the Late Triassic, continued slowly and sporadically during the Early and Middle Jurassic, and quickened after the Middle Jurassic salt formed. As a result, the salt deposits were split into the two segments known today, and oceanic crust formed in the center of the basin. Early in the Late Jurassic, the Yucatan platform reached its present position and the Gulf of Mexico Basin was born. 14 figures.

  7. Dinosaur remains from the La Quinta Formation (Lower or Middle Jurassic) of the Venezuelan Andes

    Microsoft Academic Search

    Paul M. Barrett; Richard J. Butler; Scott C. Moore-Fay; Fernando E. Novas; John M. Moody; James M. Clark; Marcelo R. Sänchez-Villagra

    2008-01-01

    Dinosaur remains are exceptionally scarce in northern South America and Jurassic faunas from this area are particularly poorly\\u000a known. We provide descriptions of new dinosaur specimens from a bonebed in the La Quinta Formation (Early or Middle Jurassic)\\u000a of western Venezuela. The specimens are disarticulated and associations of elements are rare, but at least two distinct taxa\\u000a appear to be

  8. Oldest isotopically characterized fish otoliths provide insight to Jurassic continental climate of Europe

    Microsoft Academic Search

    William P. Patterson

    1999-01-01

    Large, shallow, epeiric seas and adjacent lagoons such as those described herein likely played a significant role in moderating Jurassic coastal and continental climate. Jurassic (Bathonian) ocean surface temperatures in Scotland have been calculated from delta18O(CaCO3) values of a suite of the oldest well-preserved fish otoliths analyzed to date. Otolith delta18O values range from -4.70\\/00 to -1.90\\/00 (Vienna Peedee belemnite,

  9. A new species of Progonocimicidae (Hemiptera, Coleorrhyncha) from the Middle Jurassic of China

    Microsoft Academic Search

    Qiu-ping Dong; Yun-zhi Yao; Dong Ren

    2012-01-01

    Dong Q.P., Yao Y.Z. & Ren D., 2012. A new species of Progonocimicidae (Hemiptera, Coleorrhyncha) from the Middle Jurassic of China. Alcheringa, 1–7. ISSN 0311-5518. A new fossil species, Cicadocoris assimilis, of the family Progonocimicidae is described from the Middle Jurassic Jiulongshan Formation of Daohugou Village, Inner Mongolia, China. Cicadocoris Becker-Migdisova, 1958 and Mesocimex Hong, 1983 show no significant differences

  10. Late Jurassic-Early Cretaceous evolution of the eastern Indian Ocean adjacent to northwest Australia 

    E-print Network

    Fullerton, Lawrence Gilliam

    1987-01-01

    LATE JURASSIC-EARLY CRETACEOUS EVOLUTION OF THE EASTERN INDIAN OCEAN ADJACENT TO NORTHWEST AUSTRALIA A Thesis by LAWRENCE GILLIAM FULLERTON Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE December 1987 Major Subject: Oceanography LATE JURASSIC-EARLY CRETACEOUS EVOLUTION OF THE EASTERN INDIAN OCEAN ADJACENT TO NORTHWEST AUSTRALIA A Thesis by LAWRENCE GILLIAM FULLERTON Approved as to style and content by...

  11. 20. Detail of sandstone pier under north line of trusses ...

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

    20. Detail of sandstone pier under north line of trusses showing granite pier cap (darker stone) which supports the vertical strut. View to east. - Selby Avenue Bridge, Spanning Short Line Railways track at Selby Avenue between Hamline & Snelling Avenues, Saint Paul, Ramsey County, MN

  12. Lithological variability of electrical parameters in a sandstone sequence

    SciTech Connect

    Amabeoku, M.O.; Mimoune, K.; Al-Nufaili, S.

    1995-10-01

    Electrical parameters are the constants in the Archie equation and variants thereof, to calculate water saturation, original oil-in-place, and residual oil saturation from resistivity well logs. The applicability of these parameters in the laboratory should be done at conditions that reflect, as closely as possible, those prevailing in the reservoir, with respect to temperature, pressure, and fluids. The formation factor, cementation exponent, and saturation index vary with lithology as well. The lithofacies identified in this sandstone sequence include clean sandstone, shaly sandstone, and sideritic sandstone. X-ray diffraction analysis shows the mineralogical composition to be clays, ankerite, siderite and quartz. An experimental program has been conducted to determine these electrical parameters at reservoir conditions using native crude oil on two of the lithofacies identified in the reservoir. This paper discusses results of these measurements. The results are grouped by lithology so that a regime of application can be defined. The importance of this lithological grouping is that different parameter values and lithology flags (or indicators) can be programmed into the water saturation calculation scheme to refine the well log determination of water saturation from Archie-type equations.

  13. Architecture of the upper Sego Sandstone, Book Cliffs, Utah

    E-print Network

    Birkhead, Stanley Scott

    2006-04-12

    , even though net sediment was directed offshore in a suspended ebb-oriented hypopycnal plume and as fluid mud during uncommon river floods. Deposits above high-relief erosion surfaces observed to cut down into the upper Sego Sandstone do not meet...

  14. Cryptoendolithic alteration of Antarctic sandstones: Pioneers or opportunists?

    Microsoft Academic Search

    R. L. Blackhurst; M. J. Genge; A. T. Kearsley; M. M. Grady

    2005-01-01

    The cryptoendolithic habitat of the Antarctic Dry Valleys has been considered a good analogy for past Martian ecosystems, if life arose on the planet. Yet cryptoendoliths are thought to favor the colonization of rocks that have a preexisting porous structure, e.g., sandstones. This may weaken their significance as exact analogues of potential rock-colonizing organisms on Mars, given our current understanding

  15. New Precambrian fossils from the Arumbera Sandstone, Northern Territory, Australia

    Microsoft Academic Search

    M. F. Glaessner; M. R. Walter

    1975-01-01

    Large fossil structures occurring commonly on certain bedding planes in the Arumbera Sandstone southwest of Alice Springs are described as Arumberia banksi gen. et sp. nov. These structures are interpreted as the remains of cupshaped animals, probably of coelenterate grade, that resemble two genera described from the Nama Group of South-West Africa and one from near Lake Baikal, Siberia.

  16. Biotitic Meta-Sandstone in the Gunsight Formation

    USGS Multimedia Gallery

    Outcrop of biotitic meta-sandstone in the lower part of the Gunsight Formation, cut by white quartz veins with alteration envelopes of coarsely crystalline black biotite and minor muscovite. USGS intern, Shane Kostka prepares to collect representative samples from this outcrop....

  17. Fault facies and its application to sandstone reservoirs

    E-print Network

    Fossen, Haakon

    Fault facies and its application to sandstone reservoirs Alvar Braathen, Jan Tveranger, Haakon The concept of fault facies is a novel approach to fault de- scription adapted to three-dimensional reservoir. The fault envelope consists of a varying number of discrete fault facies originating from the host rock

  18. A complex investigation of building sandstones from Saxony (Germany)

    SciTech Connect

    Goetze, Jens [TU Bergakademie Freiberg, Institute of Mineralogy, Brennhausgasse 14, D-09596, Freiberg (Germany)], E-mail: goetze@mineral.tu-freiberg.de; Siedel, Heiner [Dresden University of Technology, Department of Geotechnical Engineering, D-01062 Dresden (Germany)

    2007-11-15

    The present paper provides a methodology for the investigation and characterization of building sandstones. This analytical scheme was designed for distinguishing mature arenites, which in general show very similar properties and are difficult to distinguish. This is shown for Cretaceous sandstones from various occurrences in Saxony (Germany), which have been used for centuries as building materials. The procedure is mainly based on the combination of macroscopic rock description, thin section polarizing microscopy (phase composition, texture, grain-size distribution) and cathodoluminescence (CL) microscopy (quartz types, feldspar and kaolinite content) coupled with image analysis, scanning electron microscopy (accessories, pore cement, diagenetic grain surface features), and analysis of pore space data. Sometimes, additional data from X-ray diffraction or chemical analyses (major and trace elements) can be used. Especially in the case of quartz rich arenites, CL is a powerful tool for provenance analysis. The detailed analysis of sandstone material in most cases allows us to assign historically used building material to a specific sandstone occurrence. These results are important for both interpreting the weathering behaviour of the building material and the conservation, reconstruction and stone replacement of historical monuments.

  19. Evidence for preferential flow through sandstone aquifers in Southern Wisconsin

    USGS Publications Warehouse

    Swanson, S.K.; Bahr, J.M.; Bradbury, K.R.; Anderson, K.M.

    2006-01-01

    Sandstones often escape extensive hydrogeologic characterization due to their high primary porosity and perceived homogeneity of permeability. This study provides evidence for laterally extensive, high permeability zones in the Tunnel City Group, an undeformed, Cambrian-aged sandstone unit that exists in the subsurface throughout much of central and southern Wisconsin, USA. Several discrete high-permeability zones were identified in boreholes using flow logging and slug tests, and the interconnectedness of the features was tested using a site-specific numerical model for springs in the region. Explicit incorporation of a high-permeability layer leads to improvements in the flux calibration over simulations that lack the features, thus supporting the hydraulic continuity of high-permeability zones in the sandstone aquifer over tens of kilometers. The results suggest that stratigraphically controlled heterogeneities like contrasts in lithology or bedding-plane fractures, which have been shown to strongly influence the flow of groundwater in more heterogeneous sedimentary rocks, may also deserve close examination in sandstone aquifers. ?? 2005 Elsevier B.V. All rights reserved.

  20. HUGONIOT PROPERTIES OF DRY YORKSHIRE SANDSTONE UP TO 8 GPA

    Microsoft Academic Search

    E. A. Taylor; K. Tsembelis; D. Chapman; W. G. Proud; C. S. Cockell

    A series of plate impact experiments has been performed to assess the dynamic behaviour of dry Yorkshire sandstone up to 8 GPa. Standard manganin gauges were inserted between samples in order to determine the principal Hugoniot curve. A VISAR system was used to measure the free surface velocity of the target. This work is in part of a research programme

  1. A New Unfree Fluid Index in Sandstones Through NMR Studies

    Microsoft Academic Search

    G. C. Borgia

    1996-01-01

    Nuclear magnetic resonance (NMR) of ¹H nuclei of liquids in saturated porous rocks furnishes an increasingly important tool in core analysis as well as in well-logging. In particular, there are several basic questions regarding NMR downhole logging in reservoir sandstones. For this reason, it is of interest to investigate the laboratory NMR properties to identify some important basic mechanisms. This

  2. Arsenic Occurrence, Mobility, and Retardation in Sandstone and

    E-print Network

    Sahai, Nita

    Arsenic Occurrence, Mobility, and Retardation in Sandstone and Dolomite Formations of the Fox River of groundwater arsenic (100 µg L-1 ) 1.3 × 10-6 M) are found in the Fox River Valley, eastern Wisconsin, shown previously to cause elevated arsenic in groundwater. Detailed mineralogical and chemical analyses

  3. Acidizing of Sandstone Reservoirs Using HF and Organic Acids 

    E-print Network

    Yang, Fei

    2012-10-19

    , and illite) were examined to react with formic-HF acid mixtures which contain different concentrations of HF. Coreflood experiments on sandstone cores featured by different mineralogy with dimensions of 1.5 in. x 6 in. were also conducted at a flow rate of 5...

  4. Depositional environment of upper Cretaceous woodbine sandstones, Kurten field, Brazos County, Texas 

    E-print Network

    Watkins, John Mark

    1982-01-01

    and the locations of the cross sections (Figs. 9, IO, and 11) are shown. Al so shown is the location of the limits of pre-Austin erosion of this sandstone. Note the lens-like appearance 2B 13 Net sandstone isopach of the Woodbine "B" sand- stone... and the location of the limit of pre- Austin erosion of this sandstone. Note the lens-like appearance 29 14 Net sandstone i sopach of the Woodbine "C" sand- stone and the location of the limit of pre- Austin erosion of this sandstone. Note the lack of a lens...

  5. Fining-upward cycles in the sandy braided-river deposits of the Westwater Canyon Member (Upper Jurassic), Morrison Formation, New Mexico

    NASA Astrophysics Data System (ADS)

    Godin, P. D.

    1991-02-01

    Vertical and lateral profiles demonstrate that fining-upward cycles are present in the sandy braided fluvial units of the Westwater Canyon Member, an Upper Jurassic, Morrison Formation, sheet sandstone in northwestern New Mexico. The technique of bounding-surface classification successfully delineates these cycles on three scales of sedimentary influence, namely the macroform-scale cycle, the channel-scale cycle, and the sheet-scale cycle. Autocyclic macroform-scale cycles are generally 1-6 m in thickness, and bounded above and below by 3rd- or higher-order surfaces, one of which must be of 3rd- or 4th-order. Channel-scale cycles, deposits infilling large-scale scours and possibly individual channels, are 1-10 m in thickness, bounded above and below by laterally inextensive 5th- or 6th- order surfaces. Sheet-scale cycles, in contrast, are 4-16 m in thickness, the products of autocyclic channel avulsion processes, bounded both above and below by laterally extensive, planar 5th- or 6th-order surfaces. A proposal by previous workers that lithofacies cyclicity also exists in the Westwater Canyon Member, is examined and rejected following field work and Markov chain analysis. Further theoretical discussion of Markov chain analysis points out several problems with the identification of cycles, including the need for proper definition of the bounding-surfaces that mark lithofacies transitions.

  6. Thermal maturity of Jurassic shales from the Newark Basin, U.S.A.: influence of hydrothermal fluids and implications to basin modeling

    USGS Publications Warehouse

    Walters, C.C.; Kotra, R.K.

    1990-01-01

    Organic geochemical investigations were conducted on a series of cores that systematically sampled the uppermost Jurassic strata from the northern Newark Basin. Each sedimentary unit consists of fluvial red sandstones and siltstones with cyclic deposits of interbedded black lacustrine shales and gray deltaic siltstones. In a suite of organic-rich shales from the Boonton, Towaco and Feltville Formations, organic maturation parameters were used to determine aspects of the thermal history of the Newark Basin. Comparisons of model calculations and measured maturities support39 Ar/40 Ar-geochronometer studies that indicate a hydrothermal event occurred ???175 Ma ago. An increase in the regional geothermal gradient to ???7.5??C/100 m for ???5 Ma best conforms to the organic geochemical observations. Biomarker compounds in Boonton and Towaco strata should have been relatively unaltered by this regional event, but anomalous molecular distributions in the organic-rich rocks may have resulted from localized heating by hydrothermal fluids. The effects of this interaction would be very subtle and may be indistinguishable from variations caused by differences in organic facies. Within this uncertainty, sterane and hopane isomerization and steroid aromatization reactions advanced in the Boonton and Towaco Formation strata primarily because of burial and normal geothermal heating that followed the hydrothermal event. Biomarker kinetic models indicate that ???2400 m of Boonton and post-Boonton strata were eroded after basinal uplift commenced ???50 Ma ago. ?? 1990.

  7. Provenance of Mesozoic Sandstones in the Banda Arc, Indonesia

    NASA Astrophysics Data System (ADS)

    Zimmermann, S.; Hall, R.

    2014-12-01

    Quartz-rich sandstones in the Banda Arc islands of Tanimbar, Babar, Timor and Sumba are equivalent of Mesozoic sandstones on the Australian margin where they are important hydrocarbon reservoirs. They have been exposed by on-going collision providing an opportunity to study their provenance. Previous studies suggested that rivers draining Australia provided most input. New light mineral, heavy mineral and detrital zircon data provide information on sources of sediments and constraints on palaeogeographic models. Conventional light mineral plots of sandstones from the islands typically show a recycled orogen and continental block origin, consistent with an Australian source. However many of the sandstones are texturally immature. Many samples also contain volcanic quartz and volcanic lithic fragments. Heavy mineral assemblages of most samples contain material from acid igneous and metamorphic rocks, with few indications of mafic or ultramafic sources. Rounded ultrastable minerals are typical, but these are commonly mixed with angular grains. Detrital zircon (LA-ICP-MS) U-Pb ages range from Archean to Mesozoic, but variations in age populations indicate differences in source areas along the Banda Arc in locality and time. We recognise distinctive Permo-Triassic, older Palaeozoic and Proterozoic ages characteristic of a Bird's Head, New Guinea, acid igneous source and this component diminishes from east to west. On Tanimbar and Babar, sediment came from both Australia and the Bird's Head. Sandstones in Timor have immature textures and show differences from east to west. They contain zircons derived from the Birds Head, as well as Precambrian zircons suggesting a northern Australian origin. In contrast, immature textures, heavy minerals and Cretaceous zircon ages in rocks from Sumba suggest that they were mainly derived from metamorphic sources. Mesozoic to Archean zircons indicate derivation from Australian crust that had collided in Sulawesi during the Cretaceous.

  8. Constraints on the Jurassic time scale by /sup 40/Ar//sup 39/Ar dating of North Caucasian volcanic rocks

    SciTech Connect

    Hess, J.C.; Lippolt, H.J.; Borsuk, A.M.

    1987-07-01

    /sup 40/Ar//sup 39/Ar age measurements on biotites and high-temperature plagioclases of Jurassic basaltic to rhyolitic subvolcanic rocks from the Northern Great Caucasus (USSR) yielded plateau and total argon ages between 190 and 180 Ma. The dated rocks are intrusive sills, dikes and laccoliths in sediments of the middle to upper Pliensbachian and of the lower Toarcian (Lower Jurassic). Pebbles of the volcanic rocks exist in the basal conglomerates of the Aalenian (base of the Middle Jurassic). Thus, their stratigraphic age is restricted to the Lower Jurassic stages of middle to upper Pliensbachian and Toarcian. Because of the scarcity of tie-points in the Lower Jurassic, the isotopic ages of these volcanic rocks, in spite of their rather large stratigraphic range, may serve as new calibration points for the improvement of the Jurassic time-scale.

  9. Paleogeographic evidence on the Jurassic tectonic history of the Pontides: new paleomagnetic data from the Sakarya continent and Eastern Pontides

    Microsoft Academic Search

    Mualla Cengiz Çinku

    The Jurassic paleogeographic position of the Pontides is not well studied because of insufficient paleomagnetic data. For\\u000a this reason, a paleomagnetic study was carried out in order to constrain the paleolatitudinal drift of the Turkish blocks\\u000a during the Jurassic period. A total of 32 sites were sampled from volcanic and volcanoclastic rocks of the Lower\\/Middle Jurassic\\u000a Kelkit formation (Eastern Pontides),

  10. A New Basal Sauropod Dinosaur from the Middle Jurassic of Niger and the Early Evolution of Sauropoda

    PubMed Central

    Remes, Kristian; Ortega, Francisco; Fierro, Ignacio; Joger, Ulrich; Kosma, Ralf; Marín Ferrer, José Manuel; Ide, Oumarou Amadou; Maga, Abdoulaye

    2009-01-01

    Background The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification. Principal Findings A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography. Conclusions Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification. PMID:19756139

  11. Comprehensive database on Induan (Lower Triassic) to Sinemurian (Lower Jurassic) marine bivalve genera and their paleobiogeographic record

    E-print Network

    Ros-Franch, Sonia; Marquez-Aliaga, Ana; Damborenea, Susana

    2014-04-10

    Marine bivalve genera that were described or mentioned for Triassic and Lower Jurassic deposits worldwide are reviewed in terms of their validity, stratigraphic range, paleogeographic distribution, paleoautecology, and ...

  12. Chasing the Late Jurassic APW Monster Shift in Ontario Kimberlites

    NASA Astrophysics Data System (ADS)

    Kent, D. V.; Muttoni, G.; Gee, J. S.; Kjarsgaard, B. A.

    2012-12-01

    A 30° gap was recognized in a composite APW path when global poles from predominantly igneous rocks were assembled in North American coordinates using plate reconstructions (Kent & Irving 2010 JGR). The 'monster shift' occurred between a 160-190 Ma cluster of mean poles at 75-80°N 90-110°E to a 140-145 Ma grouping centered at 60-65°N ~200°E. There are hardly any intermediate igneous poles whereas the rather divergent directions from the Late Jurassic Morrison Formation published by Steiner & Helsley (1975 GSA Bulletin) are subject to adjustments for Colorado Plateau rotation and sedimentary inclination error, neither of which are precisely known for this redbed unit sampled in Colorado. On the other hand, similar large rapid swings have been recognized in the Late Jurassic APW path for Adria (Channell et al. 2010 Paleo3), suggesting a global phenomena. In an effort to fill the data gap between ~145 and 160 Ma, we sampled accessible outcrops/subcrops of kimberlites in the Timiskaming area of Ontario, Canada, that are associated with high precision U-Pb perovskite ages (Heamon & Kjarsgaard 2000 EPSL). We report initial results from two of the intrusions: the 153.6±2.4 Ma Peddie kimberlite from outcrop and the Triple B kimberlite that was accessible by trenching and is assumed to be the same age as the nearby 153.7±1.8 Ma Seed kimberlite as delineated by aeromagnetic surveys and borings. Systematic progressive thermal demagnetization indicated in each unit a dominant characteristic component with unblocking temperatures to 575° that presumably reflect a magnetite carrier that will be checked by further rock magnetic experiments. Samples from the Peddie kimberlite had stable downward (normal polarity) magnetizations whose mean direction gives a paleopole at 73°N 184°E. In contrast, samples from the Triple B kimberlite have upward (reverse polarity) magnetizations with a well-grouped direction whose (north) paleopole is 78°N 197°E, proximal to the Peddie pole. The normal and reverse polarities suggest that sufficient time elapsed between emplacement of the Triple B and Peddie to give an opportunity to average secular variation. The combined ~154 Ma Triple B and Peddie pole encouragingly lies about halfway between igneous poles from North America nearest in age: the 169 Ma Moat volcanics and the 142 Ma Ithaca kimberlites. However, preliminary paleomagnetic results from some of the other sampled kimberlite bodies are more problematical and require further paleomagnetic and geochronological work.

  13. Fission track ages of detrital zircons from sandstones of the Umpqua Group and Tyee Formation, Oregon coast range

    SciTech Connect

    Vance, J.A. (Univ. of Washington, Seattle, WA (United States). Dept. of Geological Sciences); Brandon, M.T. (Yale Univ., New Haven, CT (United States). Dept. of Geology and Geophysics)

    1993-04-01

    Detrital zircons from Paleogene sandstones of the Umpqua Group (UG) and the Tyee Fm (TF) yield contrasting FT age patterns which distinguish these two units and cast new light on their regional extent, correlation and provenance. In the Roseburg (Rg) area of the southern Oregon Coast Range, where most widely exposed, the UG consists of continental and marine clastic beds which overlie submarine lavas of the Coast Range Basalt. K-Ar And Ar-Ar dating of the basement basalts shows a younging trend from about 62 Ma at Rg at the south to 56 Ma at Siletz River and 53 Ma at Tillamook to the north. Detrital zircons from the Rg area are characterized by old FT ages. Of 192 grains dated, 90% are older than 90 Ma; the median age is 129 Ma. A diorite cobble from an UG conglomerate gave a zircon FT age of 105 Ma. These ages point to a source in the Jurassic plutons in the Klamath Mountains nearby to the south. The authors have determined FT cooling ages of 110 and 120 Ma for zircons from the Mt. Ashland and Grants Pass plutons. Continental and shallow marine clastic strata of the TF overly the UG beds west of Rg. The UG is not widely exposed north of Rg where it thins and pinches out above the Coast Range Basalt and is overlain by a northern turbidite facies of the TF. Three TF sandstones from the latitude of Rg and three others from west and south of Corvallis yielded distinctive and identical zircon FT age patterns characterized by young ages. Of 335 zircons dated, 80% are younger than 90 Ma; the median age is 61 Ma. This maximum age is very close to that of the overlying Tillamook and Fisher Fms. The flood of detrital zircons with young FT ages in the TF marks the abrupt change from a nearby Klamath source for the UG beds to a distant, easterly TF source in a recently uplifted plutonic-metamorphic terrane.

  14. Neuroanatomy of the Marine Jurassic Turtle Plesiochelys etalloni (Testudinata, Plesiochelyidae)

    PubMed Central

    Carabajal, Ariana Paulina; Sterli, Juliana; Müller, Johannes; Hilger, André

    2013-01-01

    Turtles are one of the least explored clades regarding endocranial anatomy with few available descriptions of the brain and inner ear of extant representatives. In addition, the paleoneurology of extinct turtles is poorly known and based on only a few natural cranial endocasts. The main goal of this study is to provide for the first time a detailed description of the neuroanatomy of an extinct turtle, the Late Jurassic Plesiochelysetalloni, including internal carotid circulation, cranial endocast and inner ear, based on the first digital 3D reconstruction using micro CT scans. The general shape of the cranial endocast of P. etalloni is tubular, with poorly marked cephalic and pontine flexures. Anteriorly, the olfactory bulbs are clearly differentiated suggesting larger bulbs than in any other described extinct or extant turtle, and indicating a higher capacity of olfaction in this taxon. The morphology of the inner ear of P. etalloni is comparable to that of extant turtles and resembles those of slow-moving terrestrial vertebrates, with markedly low, short and robust semicircular canals, and a reduced lagena. In P. etalloni the arterial pattern is similar to that found in extant cryptodires, where all the internal carotid branches are protected by bone. As the knowledge of paleoneurology in turtles is scarce and the application of modern techniques such as 3D reconstructions based on CT scans is almost unexplored in this clade, we hope this paper will trigger similar investigations of this type in other turtle taxa. PMID:23844257

  15. Palaeoceanography: methane release in the Early Jurassic period.

    PubMed

    Wignall, Paul B; McArthur, John M; Little, Crispin T S; Hallam, Anthony

    2006-06-01

    Dramatic global warming, triggered by release of methane from clathrates, has been postulated to have occurred during the early Toarcian age in the Early Jurassic period. Kemp et al. claim that this methane was released at three points, as recorded by three sharp excursions of delta13C(org) of up to 3 per thousand magnitude. But they discount another explanation for the excursions: namely that some, perhaps all, of the rapid excursions could be a local signature of a euxinic basin caused by recycling of isotopically light carbon from the lower water column. This idea has been proposed previously (see ref. 3, for example) and is supported by the lack evidence for negative delta13C excursions in coeval belemnite rostra. Kemp et al. dismiss this alternative, claiming that each abrupt shift would have required the recycling of about double the amount of organic carbon that is currently present in the modern ocean; however, their measurements are not from an ocean but from a restricted, epicontinental seaway and so would not require whole-ocean mixing to achieve the excursions. PMID:16738612

  16. Astronomical pacing of methane release in the Early Jurassic period.

    PubMed

    Kemp, David B; Coe, Angela L; Cohen, Anthony S; Schwark, Lorenz

    2005-09-15

    A pronounced negative carbon-isotope (delta13C) excursion of approximately 5-7 per thousand (refs 1-7) indicates the occurrence of a significant perturbation to the global carbon cycle during the Early Jurassic period (early Toarcian age, approximately 183 million years ago). The rapid release of 12C-enriched biogenic methane as a result of continental-shelf methane hydrate dissociation has been put forward as a possible explanation for this observation. Here we report high-resolution organic carbon-isotope data from well-preserved mudrocks in Yorkshire, UK, which demonstrate that the carbon-isotope excursion occurred in three abrupt stages, each showing a shift of -2 per thousand to -3 per thousand. Spectral analysis of these carbon-isotope measurements and of high-resolution carbonate abundance data reveals a regular cyclicity. We interpret these results as providing strong evidence that methane release proceeded in three rapid pulses and that these pulses were controlled by astronomically forced changes in climate, superimposed upon longer-term global warming. We also find that the first two pulses of methane release each coincided with the extinction of a large proportion of marine species. PMID:16163353

  17. Understanding Jurassic salt tectonics: An integrated approach utilizing visualization

    SciTech Connect

    Paul, D.R. [Photon Systems, Limited, Calgary, Alberta (Canada)

    1996-12-31

    Understanding the mechanisms of salt deformation are critical in the identification of key prospects in a Jurassic salt basin. Understanding the geometry of the complex salt body significantly reduces risk in such prospects. A volume of 3D data was depth migrated to improve the delineation of the salt geometry. The major velocity changes with depth were interpreted in a state of the art seismic interpretation package. The results were then analyzed in 3D velocity visualization package which permitted refinement of the original model and validation via ray tracing. This velocity model was then reapplied to the Omega KK post stack depth migration process to create a final depth volume. The main prospects were interpreted using floodfill autopicking technology and mapped using conventional gridding and contouring techniques. The interpretations were then validated in a visual 3D palinspastic restoration package. Backstripping through time allowed the analysis of the salt deformation with respect to sediment loading. The validated interpretations were then analyzed in 3D voxel space to gain a true understanding of the salt geometry and its effect on the two key prospective reservoirs. Reservoir volumes were estimated using 3D sub volume detection. Finally a deviated wellbore was designed in order to test both prospects. The entire process shows the manner in which 3D visualization tools may be applied in a multi-disciplinary environment to better understand the prospect and communicate this understanding among team members.

  18. Closely associated theropod trackways from the Jurassic of Zimbabwe.

    PubMed

    Lingham-Soliar, Theagarten; Broderick, Tim; Ait Kaci Ahmed, Ali

    2003-12-01

    Eighty-eight tracks of large theropod dinosaurs were found in the mid-Jurassic of Zimbabwe. Among the tracks, at least five adjacent trackways are recorded. The adjacent tracks were probably made by animals traveling as a group, given that they are in relatively close succession; that there are three overlapping tracks (among just 23) suggesting reasonably close associations of the animals; that all the tracks are apparently of the same ichnotaxon; that the preservational types of the tracks are similar; and that the tracks are all of animals traveling in one general direction closely associated in time (there are no returning tracks of the same animals or of those of other species; presence of such tracks would be highly probable if the tracks were made over a period of time of even several hours). Nearby, recently discovered giant sauropod tracks, the first in sub-Saharan Africa, indicate a realistic potential of predator/prey interactions between the two groups of dinosaurs. PMID:14676955

  19. Revision of the Late Jurassic teleosaurid genus Machimosaurus (Crocodylomorpha, Thalattosuchia)

    PubMed Central

    Young, Mark T.; Hua, Stéphane; Steel, Lorna; Foffa, Davide; Brusatte, Stephen L.; Thüring, Silvan; Mateus, Octávio; Ruiz-Omeñaca, José Ignacio; Havlik, Philipe; Lepage, Yves; De Andrade, Marco Brandalise

    2014-01-01

    Machimosaurus was a large-bodied genus of teleosaurid crocodylomorph, considered to have been durophagous/chelonivorous, and which frequented coastal marine/estuarine ecosystems during the Late Jurassic. Here, we revise the genus based on previously described specimens and revise the species within this genus. We conclude that there were three European Machimosaurus species and another taxon in Ethiopia. This conclusion is based on numerous lines of evidence: craniomandibular, dental and postcranial morphologies; differences in estimated total body length; geological age; geographical distribution; and hypothetical lifestyle. We re-diagnose the type species Machimosaurus hugii and limit referred specimens to only those from Upper Kimmeridgian–Lower Tithonian of Switzerland, Portugal and Spain. We also re-diagnose Machimosaurus mosae, demonstrate that it is an available name and restrict the species to the uppermost Kimmeridgian–lowermost Tithonian of northeastern France. We re-diagnose and validate the species Machimosaurus nowackianus from Harrar, Ethiopia. Finally, we establish a new species, Machimosaurus buffetauti, for the Lower Kimmeridgian specimens of France and Germany (and possibly England and Poland). We hypothesize that Machimosaurus may have been analogous to the Pliocene–Holocene genus Crocodylus in having one large-bodied taxon suited to traversing marine barriers and additional, geographically limited taxa across its range.

  20. Ice age at the Middle-Late Jurassic transition?

    NASA Astrophysics Data System (ADS)

    Dromart, G.; Garcia, J.-P.; Picard, S.; Atrops, F.; Lécuyer, C.; Sheppard, S. M. F.

    2003-08-01

    A detailed record of sea surface temperatures in the Northern Hemisphere based on migration of marine invertebrate fauna (ammonites) and isotopic thermometry (?18O values of shark tooth enamel) indicates a severe cooling at the Middle-Late Jurassic transition (MLJT), about 160 Ma ago. The magnitude of refrigeration (1-3°C for lower middle latitudes) and its coincidence in time with an abrupt global-scale fall of sea level documented through sequence stratigraphy are both suggestive of continental ice formation at this time. Ice sheets may have developed over the high-latitude mountainous regions of Far-East Russia. The drastic cooling just post-dated the Middle-Late Callovian widespread deposition of organic-rich marine sediments (e.g. northwestern Europe, Central Atlantic, and Arabian Peninsula). This thermal deterioration can thus be ascribed to a downdraw in atmospheric CO2 via enhanced organic carbon burial which acted as a negative feedback effect (i.e. the inverse greenhouse effect). The glacial episode of the MLJT climaxed in the Late Callovian, lasted about 2.6 Myr, and had a pronounced asymmetrical pattern composed of an abrupt (˜0.8 Myr) temperature fall opposed to a long-term (˜1.8 Myr), stepwise recovery. The glacial conditions at the MLJT reveal that atmospheric CO2 levels could have dropped temporarily to values lower than 500 ppmv during Mesozoic times.

  1. Extreme adaptations for aquatic ectoparasitism in a Jurassic fly larva.

    PubMed

    Chen, Jun; Wang, Bo; Engel, Michael S; Wappler, Torsten; Jarzembowski, Edmund A; Zhang, Haichun; Wang, Xiaoli; Zheng, Xiaoting; Rust, Jes

    2014-01-01

    The reconstruction of ancient insect ectoparasitism is challenging, mostly because of the extreme scarcity of fossils with obvious ectoparasitic features such as sucking-piercing mouthparts and specialized attachment organs. Here we describe a bizarre fly larva (Diptera), Qiyia jurassica gen. et sp. nov., from the Jurassic of China, that represents a stem group of the tabanomorph family Athericidae. Q. jurassica exhibits adaptations to an aquatic habitat. More importantly, it preserves an unusual combination of features including a thoracic sucker with six radial ridges, unique in insects, piercing-sucking mouthparts for fluid feeding, and crocheted ventral prolegs with upward directed bristles for anchoring and movement while submerged. We demonstrate that Q. jurassica was an aquatic ectoparasitic insect, probably feeding on the blood of salamanders. The finding reveals an extreme morphological specialization of fly larvae, and broadens our understanding of the diversity of ectoparasitism in Mesozoic insects.DOI: http://dx.doi.org/10.7554/eLife.02844.001. PMID:24963142

  2. Field measurement and analysis of climatic factors affecting dune mobility near Grand Falls on the Navajo Nation, southwestern United States

    NASA Astrophysics Data System (ADS)

    Bogle, Rian; Redsteer, Margaret Hiza; Vogel, John

    2015-01-01

    Aeolian sand covers extensive areas of the Navajo Nation in the southwestern United States. Much of this sand is currently stabilized by vegetation, although many drier parts of these Native lands also have active and partly active dunes. Current prolonged drought conditions that started in the mid-1990s are producing significant changes in dune mobility. Reactivation of regional aeolian deposits due to drought or increasing aridity from rising temperatures resulting from climate change could have serious consequences for human and animal populations, agriculture, grazing, and infrastructure. To understand and document the current and future potential for mobility, seasonally repeated surveys were used to track the location of multiple active barchan dunes. By utilizing Real-Time Kinematic GPS field surveys and simultaneously collecting in-situ meteorological data, it is possible to examine climatic parameters and seasonal variations that affect dune mobility and their relative influences. Through analysis of the recorded data, we examined the fit of various climate parameters, and demonstrate that under the current prolonged drought, wind power is the dominant factor controlling dune mobility.

  3. Presence of the dinosaur Scelidosaurus indicates Jurassic age for the Kayenta Formation (Glen Canyon Group, northern Arizona)

    Microsoft Academic Search

    Kevin Padian

    1989-01-01

    The Glen Canyon Group (Moenave, Wingate, Kayenta and Navajo Formations) of northern Arizona represents an extensive outcrop of early Mesozoic age terrestrial sediments. The age of these formations has long been disputed because independent stratigraphic data from marine tie-ins, paleobotanical and palynological evidence, and radiometric calibrations have been scanty or absent. The fauna of the Kayenta Formation in particular has

  4. A new unfree fluid index in sandstones through NMR studies

    SciTech Connect

    Borgia, G.C. [Univ. of Bologna (Italy)

    1996-06-01

    Nuclear magnetic resonance (NMR) of {sup 1}H nuclei of liquids in saturated porous rocks furnishes an increasingly important tool in core analysis as well as in well-logging. In particular, there are several basic questions regarding NMR downhole logging in reservoir sandstones. For this reason, it is of interest to investigate the laboratory NMR properties to identify some important basic mechanisms. This paper presents new correlations among porosity, {phi}, irreducible water saturation, S{sub wi}, formation resistivity factor, F, and the geometric mean longitudinal relaxation time, T{sub 1}g. Equilibrium magnetization and longitudinal relaxation, T{sub 1}, measurements were performed on 57 clean sandstone samples from 12 oil and gas reservoirs.

  5. Pore-throat sizes in sandstones, siltstones, and shales: Reply

    USGS Publications Warehouse

    Nelson, Philip H.

    2011-01-01

    In his discussion of my article (Nelson, 2009), W. K. Camp takes issue with the concept that buoyancy is not the dominant force in forming and maintaining the distribution of gas in tight-gas accumulations (Camp, 2011). I will restrict my response to the issues he raised regarding buoyant versus nonbuoyant drive and to a few comments regarding water saturation and production. I claim that the pressure generated in petroleum source rocks (Pg), instead of the buoyancy pressure (Pb), provides the energy to charge most tight sandstones with gas. The arguments are fourfold: (1) buoyant columns of sufficient height seldom exist in low-permeability sand-shale sequences, (2) tight-gas systems display a pressure profile that declines instead of increases upward, (3) gas is pervasive in overpressured systems, and (4) source rocks can generate pore pressures sufficiently high to charge tight sandstones.

  6. Fractures and stresses in Bone Spring sandstones. Final report

    SciTech Connect

    Warpinski, N.R.; Sattler, A.R.; Lorenz, J.C.; Northrop, D.A.

    1992-06-01

    This project was a collaboration between Sandia National Laboratories and the Harvey E. Yates Company (Heyco), Roswell, NM, conducted under the auspices of Department of Energy`s Oil Recovery Technology Partnership. The project applied Sandia perspectives on the effects of natural fractures, stress, and sedimentology for the stimulation and production of low permeability gas reservoirs to low permeability oil reservoirs, such as those typified by the Bone Spring sandstones of the Delaware Basin, southeast New Mexico. This report details the results and analyses obtained in 1990 from core, logs, stress, and other data taken from three additional development wells. An overall summary gives results from all five wells studied in this project in 1989--1990. Most of the results presented are believed to be new information for the Bone Spring sandstones.

  7. Environment of deposition and reservoir facies of the Taylor "B" Sandstone, Cotton Valley group (Upper Jurassic), Kildare Field, Cass County, Texas

    E-print Network

    Black, Cynthia England

    1983-01-01

    generous with their moral support, encouragement and technical assistance at various stages in of the research. I would particularly like to thank Jim Bonds, Cy Chen, Isenn Chi, Rick Borkowski, Steve Levine, Joanna Michie, Doug Ming, Bill Strange, John...

  8. Anticrack inclusion model for compaction bands in sandstone

    Microsoft Academic Search

    Kurt R. Sternlof; John W. Rudnicki; David D. Pollard

    2005-01-01

    Detailed observations of compaction bands exposed in the Aztec Sandstone of southeastern Nevada indicate that these thin, tabular, bounded features of localized porosity loss initiated at pervasive grain-scale flaws, which collapsed in response to compressive tectonic loading. From many of these Griffith-type flaws, an apparently self-sustaining progression of collapse propagated outward to form bands of compacted grains a few centimeters

  9. Diagenesis of upper Cretaceous Teapot sandstones, Powder River basin, Wyoming

    SciTech Connect

    Conner, S.P.; Tieh, T.T.

    1984-04-01

    The Upper Cretaceous Teapot sandstones of Well Draw field, Converse County, Wyoming, are turbidite fan deposits bounded stratigraphically by marine shales. They presently occur from 6360 to 7200 ft (1920 to 2195 m), dipping to the northwest. Cored samples selected from nonbioturbated A bedsets show that the sandstones are fine to very fine-grained feldspathic litharenites. Major authigenic minerals include carbonate cement, quartz overgrowths, and clay minerals. The clay minerals originated either as alteration rims on detrital silicates or as precipitated from pore fluids. Alteration rims typically consist of illite, smectite, mixed layer illite/smectite, and lesser chlorite. Feldspars are altered to kaolinite. Precipitated clays occur as thin, unoriented, grain coating chlorite and kaolinite; pore lining mixed layer illite/smectite and lesser chlorite oriented with (001) normal to the pore wall; and unoriented, poorly crystalline, pore filling chlorite. The diagenetic sequence is: compaction and limited quartz overgrowth development; complete calcite cementation and precipitation of grain-coating clays; dissolution of carbonate cement; precipitation of pore lining and later pore filling clays; and development of second stage quartz overgrowths. Development of silicate alteration rims occurred throughout the diagenetic history. Dissolution of carbonate cement produced the majority of present-day porosity; however, this secondary porosity was reduced by precipitation of clays minerals. In the downdip sandstones, hydrodynamic flow and an increase in the abundance of detrital labile grains have caused an increased abundance of clay mineral precipitates, reducing the reservoir potential. The pore fluids which controlled sandstones diagenesis were likely provided by dewatering and diagenesis of enclosing shales.

  10. Laboratory measurements of mechanical properties of sandstones and shales

    SciTech Connect

    Sensey, P.E.

    1983-03-01

    Laboratory tests were performed on specimens of sandstones, shales, siltstones and mudstones from thirty horizons in the Piceance Basin in support of the DOE Western Gas Sands Project Multi-Well Experiment. The objective of these tests was to determine tensile strength, compressive strength and elastic constants. Data obtained show that these properties vary substantially from horizon to horizon, and do not correlate well with either lithology or depth.

  11. Log-Derived evaluation of shaly sandstone reservoirs

    Microsoft Academic Search

    Fertl

    1984-01-01

    Significant natural gas resources are known to exist in the United States in tight, low-permeability sandstones that cover a prospective area of 1,000,000 mi² (2,590,000 km²). Characterization and reliable estimation of their production potential based on well logs are important although difficult task. Proper evaluation of low permeability sands based on conventional log-interpretation techniques is frequently inadequate. Furthermore, while empirical

  12. Scanning electron microscope studies of an experimentally deformed graywacke sandstone

    Microsoft Academic Search

    Dengler

    1976-01-01

    Uniaxial-strain and uniaxial-stress tested samples of graywacke sandstone were examined with an SEM to study the relation among microstructure, dilatancy, and brittle versus ductile failure. Uniaxial-strain loading caused occasional short transgranular cracks. Clay minerals have been compacted perpendicular to the axis of maximum principal stress (sigmaâ). The uniaxial strain loading path coincides with the onset of dilatancy in a uniaxial

  13. Early and Middle Jurassic climate changes: implications for palaeoceanography and tectonics

    NASA Astrophysics Data System (ADS)

    Korte, Christoph; Hesselbo, Stephen P.; Ullmann, Clemens V.; Ruhl, Micha; Thibault, Nicolas R.

    2014-05-01

    The occurrence of 'ice ages' within the overall warm Jurassic Period has been the subject of much controversy. It has been suggested on the basis of occurrence of glendonites in circum-Arctic basins that cold episodes took place in the Jurassic (Price, 1999; Rogov and Zakharov, 2010). Here we present new high-resolution oxygen isotope datasets from marine calcitic fossils of different European basins that indicate strong temperature fluctuations during the Pliensbachian-Bajocian time span. The already reported cold Late Pliensbachian episode comprises at least three pronounced oxygen isotope 'Ice Age' cycles. The subsequent well known Toarcian Oceanic Anoxic 'supergreenhouse' Event is followed by very warm seawater temperatures in the late Toarcian. A very pronounced cooling occurred during the latest Toarcian to early Aalenian (Early-Middle Jurassic Boundary Event). This episode resulted in substantial expansion of Arctic climates to palaeolatitudes as low as 45° and in distinctly cooler seawater temperatures in lower latitude European seas. We propose that the extensive cooling at the Early-Middle Jurassic Boundary Event was driven by substantial changes in oceanic current patterns initiated by uplift of the North Sea Dome preventing the transport of heat to Polar Regions via the Viking Corridor. Literature Price, G. D. (1999). The evidence and implications of polar ice during the Mesozoic, Earth-Sci. Rev., 48, 183-210. Rogov, M. A., Zakharov, V. A. (2010). Jurassic and Lower Cretaceous glendonite occurrences and their implication for Arctic paleoclimate reconstructions and stratigraphy. Earth Science Frontiers 17, 345-347.

  14. Sparta sandstones: future exploration potential in south-central Louisiana

    SciTech Connect

    Lemoine, R.C.; Moslow, T.F.; Sassen, R.; Ferrell, R.E.

    1989-03-01

    The middle Eocene Sparta Formation is an important exploration objective within the prolific Eocene-Oligocene trend of south-central Louisiana. Cumulative production from 20 multiple-reservoir fields in the trend exceeds 269 million bbl of crude, 50 million bbl of condensate, and 1.5 billion ft/sup 3/ of gas. Additional reservoirs include the lower Eocene Wilcox, upper Eocene Cockfield, and Oligocene Frio Formations. This trend, coincident with the location of the Lower Cretaceous carbonate shelf edge, represents a series of unstable progradational clastic shelf margins. Principal structural traps are rollover anticlines, associated with down-to-the-basin growth faults, and salt domes. Recent Sparta production is associated with progradational barrier island complexes. Storm washover fan sandstones (22% porosity, 324 md permeability), tidal-inlet channel sandstones (20% porosity, 140 md permeability), and upper shoreface sandstones (19% porosity, 113 md permeability) represent the optimum-quality reservoir facies. Organic-rich basinal shales are source rocks for crude oil downdip from production where they are thermally mature. Lateral migration best explains emplacement of hydrocarbons in reservoirs.

  15. Eolian sandstone unit of Morrison Formation, central Wyoming

    SciTech Connect

    Uhlir, D.M.

    1986-08-01

    The fine-grained quartzarenite that overlies the Sundance Formation in the southwestern Powder River basin, Wind River basin, and southern Bighorn basin is interpreted as being primarily the result of eolian deposition. This unit, often more than 20 m (65.6 ft) thick, is the probable correlative of the Unkpapa Sandstone member of the Morrison Formation of the southeastern Black Hills region. An eolian interpretation is based on the presence of large-scale sets of high-angle, planar cross-stratification. Observed considerable variation in the thickness of the unit is likely to be an expression of the depositional (dune-form) topography rather than the result of later erosion. Discrete dunes are exposed near Thermopolis along the northern margin of the unit: the transitional marine deposits of the uppermost Sundance formation are the most likely source of the wind-transported sand. Stratigraphic and facies relationships and lithologic similarity support correlation of the eolian unit with the Unkpapa Sandstone. Together, the units represent regions of significant eolian deposition within the predominantly fluvial Morrison depositional environment. The properties of the eolian sandstone, its thickness, its superposition above the marine Sundance Formation, and the possibility of its persistence in the subsurface of the southern Powder River basin give it potential as a petroleum reservoir. These anomalous eolian deposits may record the positions of gentle structures developed in central Wyoming and western South Dakota at the onset of, and in association with, Sevier compression.

  16. Diagenesis in upper Miocene sandstones, Louisiana Gulf Coast

    SciTech Connect

    Gold, P.B.

    1985-02-01

    Study of diagenesis in upper Miocene sandstones of coastal Louisiana documents depth-related cementation and geochemical changes of primary detrital mineralogy. Samples were collected from depths of 8000-20,000 ft (2600-6500 m) in an area roughly corresponding to the upper Miocene depocenter in the Terrebonne trough of southeast Louisiana. Sandstones are primarily subarkoses and sublitharenites with minor amounts of feldspathic litharenites and lithic arkoses. Plagioclase feldspar (oligoclase/andesine composition) composes approximately 60% of the detrital feldspar. Dominant rock fragments are siltstone or mudstone, silicified volcanic rock, and chert. Authigenic minerals and cements occur in the following order: dolomite, chlorite grain coats, albite overgrowths on plagioclase and K-feldspar, quartz, calcite, kaolinite, and ankerite. Calcite composition remains nearly constant with depth, but ankerite composition differs both with depth and within individual samples. In general, the mineralogy and order of cements resemble that of the lower Tertiary sandstones of the Texas Gulf Coast; however, in the upper Miocene, the volume of each cement is much less and the depth of first occurrence is greater. Feldspars have reacted substantially with pore fluids. With increasing depth, feldspar becomes more sodic because of albitization and dissolution of calcic plagioclase. At approximately 20,000 ft, 75% of the plagioclase is nearly pure albite. Alteration of K-feldspar is not common above 17,000 ft; below 17,000 ft occurrences are rare because of dissolution.

  17. Spectral gamma-ray evaluation of Lower Jurassic basalts and lacustrine sediments from the Fundy Basin (Nova Scotia, Canada)

    NASA Astrophysics Data System (ADS)

    Silva, Ricardo L.; Wach, Grant; Wong, Carlos

    2014-05-01

    In the Fundy Basin (Nova Scotia, Canada), the McCoy Brook Formation corresponds to the first sedimentary unit of Early Jurassic (Hettangian-Pliensbachian) age deposited after the North Mountain basalts, part of the Central Atlantic Magmatic Province (CAMP). The McCoy Brook Formation includes at its base the Scots Bay Member, comprising red and green lutites, silicified limestones, cherts, stromatolites and sandstones. Deposition of the Scots Bay Member occurred in a shallow and oxygenated lake, where the trophic state varied from oligotrophic to eutrophic. The McCoy Brook Formation is less than 100ky younger than the end-Triassic extinction event (Olsen and Et-Touhami, 2008 and references therein). We analysed the spectral gamma-ray (GR) response of the top of the North Mountain basalts and base of the Scots Bay member at Broad Cove (Kings County, Nova Scotia, Canada) in order to calibrate outcrop with borehole wireline data and test uranium as a proxy for organic matter richness. The North Mountain basalts have a constant and low GR profile, varying from 58-92 cts. Potassium varies from 0.5-1.3%, U from 0-3.1ppm and Th from 0-5.1ppm. Average content of these elements are 1.0 %, 1.9ppm and 2.5ppm, respectively. The Scots Bay Member presents more variation, from 162 cts at the base to 68 cts at the top. Potassium varies from 0.4-2.3%, U from 0-6.4ppm and Th from 0-10.0ppm. Average content of these elements are 1.2%, 3.4ppm and 4.1ppm, respectively. The use of U contents to estimate TOC (see for example, Correia et al., 2012) generates non-significant results, where limestones have TOC of 11wt%. Olsen and Et-Touhami (2008) report that these outcrops are organically lean, with TOC lower that 1wt%. It is apparent that the high U contents and the overestimation of authigenic U is linked with U mineralization due the stromatolites and microbial activity, highlighting that lithological and mineralogical components are critical to accurate petrophysical interpretation of borehole wireline data through the studied time interval. We acknowledge ExxonMobil Canada Proprieties, on behalf of the Sable Offshore Energy Project, for financial support of through the Petroleum Geoscience Research Grant to Dalhousie University (Basin and Reservoir Lab). Correia GG, Duarte LV, Pereira A, Silva RL (2012) Outcrop gamma-ray spectrometry: Applications to the Sinemurian-Pliensbachian organic-rich facies of the Lusitanian Basin (Portugal). Journal of Iberian Geology, 38, 373-388 Olsen PE and Et-Touhami M (2008) Field Trip #1: Tropical to subtropical syntectonic sedimentation in the Permian to Jurassic Fundy rift basin, Atlantic Canada, in relation to the Moroccan conjugate margin. Central Atlantic Conjugate Margins Conference Halifax, 121 pp.

  18. A possible terrestrial analogue for haematite concretions on Mars.

    PubMed

    Chan, Marjorie A; Beitler, Brenda; Parry, W T; Ormö, Jens; Komatsu, Goro

    2004-06-17

    Recent exploration has revealed extensive geological evidence for a water-rich past in the shallow subsurface of Mars. Images of in situ and loose accumulations of abundant, haematite-rich spherical balls from the Mars Exploration Rover 'Opportunity' landing site at Meridiani Planum bear a striking resemblance to diagenetic (post-depositional), haematite-cemented concretions found in the Jurassic Navajo Sandstone of southern Utah. Here we compare the spherical concretions imaged on Mars to these terrestrial concretions, and investigate the implications for analogous groundwater-related formation mechanisms. The morphology, character and distribution of Navajo haematite concretions allow us to infer host-rock properties and fluid processes necessary for similar features to develop on Mars. We conclude that the formation of such spherical haematite concretions requires the presence of a permeable host rock, groundwater flow and a chemical reaction front. PMID:15201902

  19. Ostracoda (marine\\/nonmarine) and palaeoclimate history in the Upper Jurassic of Central Europe and North America

    Microsoft Academic Search

    Michael E. Schudack

    1999-01-01

    The role of Ostracoda in determining climate developments in the Upper Jurassic of Central Europe and North America is reviewed, based upon two different studies. The Late Jurassic is a period of time for which a change from a humid to a more arid climate has been suggested for several parts of the world. However, a correlation, though almost logical,

  20. Progress in Natural Science Vol.16 (Special 1ssue), June 2006 Marine and Non-marine Jurassic : Boundary Events and Correlation

    E-print Network

    Olsen, Paul E.

    ) The Jurassic, spanning about 201 to 145 is an important period in geological history for the evolution of life-21] . In addition, there were great biotic changes during the Jurassic Period including the ma- jor biodiversity-marine Jurassic : Boundary Events and Correlation Jingeng SHA'" , Nicol MORT ON^, Yongdong WANG' , Paul OLSEN

  1. Journal of the Geological Society, London, Vol. 161, 2004, pp. 365379. Printed in Great Britain. Sea-level change and facies development across potential TriassicJurassic

    E-print Network

    Hesselbo, Stephen P.

    or a global context. Keywords: Triassic, Jurassic, extinction, sea-level change. Period boundaries commonly. 365 Sea-level change and facies development across potential Triassic­Jurassic boundary horizons, SW: The Late Triassic to Early Jurassic aged succession of SW Britain (the Penarth and lower Lias Groups

  2. Properties of natural gas reservoirs in Cotton Valley sandstones, northwest Louisiana 

    E-print Network

    Sonnenberg, Stephen Arnold

    1975-01-01

    , the Davis sandstones are highly quartzose, with an average of 86$ quartz, and minor amounts of 'll feldspar, . 7X rock fragments, and 6X, clay matrix. Matrix is found only in lower shoreface. The sandstones are well cemented with an average of 9%%d... and composition came from approximately the same intervals where porosity and permeability were mea- sured, but the samples were not identical. Cementation is largely responsible for reduction of primary porosities and permeabilities of the sandstones to low...

  3. Paleomagnetic study of satyavedu sandstones of cretaceous age from Andhra Pradesh, India

    Microsoft Academic Search

    G. S. Mital; R. K. Verma; G. Pullaiah

    1970-01-01

    The paleomagnetism of twenty six oriented samples of red sandstones from three different sites located in Satyavedu hills (near 13°30'N, 79°55'E) and belonging to coastal upper Gondwana formations of India has been studied. These sandstones have been considered to be equivalent of Tirupati sandstones of Lower to Middle Cretaceous age from Godavari valley on stratigraphic considerations. Consistent directions of magnetization

  4. Diagenesis of the Dakota sandstone, West Lindrith Field, Rio Arriba County, New Mexico 

    E-print Network

    Franklin, Stanley Powell

    1987-01-01

    , illite, mixed-layer clay, and vermiculite. The composition and texture of the Dakota sandstone has been pervasively altered by the diagenetic processes of compaction, authigenesis, and dissolution. Authigenic cements include quartz overgrowths, calcite... Texture and Mineralogy of Clay Minerals Types and Distribution of Porosity 26 26 35 44 58 PROVENANCE OF THE DAKOTA SANDSTONE DIAGENESIS OF THE DAKOTA SANDSTONE 69 Compaction Authigenesis Cementation Clay Authigenesis Dissolution and Secondary...

  5. Integrated geological, geophysical, and geochemical interpretation of Upper Jurassic petroleum trends in eastern Gulf of Mexico

    SciTech Connect

    Mancini, E.A.; Mink, R.M.; Bearden, B.L.

    1986-09-01

    The petroleum potential of the Upper Jurassic strata in the eastern Gulf of Mexico region is excellent. At least three Upper Jurassic petroleum trends can be delineated in the region. An oil trend can be identified onshore in the area north of the regional peripheral fault trend and is interpreted to extend offshore into the area north of the Destin anticline in the eastern Gulf of Mexico. An oil and gas-condensate trend can be defined onshore between the regional peripheral fault trend and the Wiggins arch. This trend is projected to extend offshore into the area of the Destin anticline. A deep natural gas trend can be delineated onshore south of the Wiggins arch and extends offshore into the Mississippi-Alabama shelf area. These trends are recognized by hydrocarbon types, basinal position, and relationship to regional structural features. The main petroleum source rocks for the Upper Jurassic hydrocarbons are Smackover carbonate mudstones.

  6. Sequential stratigraphy of Jurassic and Cretaceous in the central Saudi Arabian platform

    SciTech Connect

    Le Nindre, Y.M.; Manivit, J.; Vaslet, D. (Bureau de Recherches Geologiques et Minieres, Orleans (France)); Manivit, H. (Bureau de Recherches Geologiques et Minieres, Orleans (France) Univ. Pierre et Marie Curie, Paris (France))

    1991-08-01

    Depositional sequences and system tracts in the Jurassic and Cretaceous sedimentary rocks of the Central Saudi Arabian platform have been established on the basis of precise lithofacies analysis, detailed sedimentologic interpretation, and accurate age determination by ammonites, nautoli, brachipods, echinoids, and nannoflora. A eustatic depositional model integrated with accepted worldwide sequential stratigraphic data is proposed, and appears to correlate fairly well with the 1988 global sea level chart by Haq and others, particularly for the Lower and Middle Jurassic and the Middle and Upper Cretaceous. Ages determined by accurate biostratigraphic data enable time correlations to be made with third-order eustatic cycles from Vail's 1988 global chart. Eustatic changes therefore appear to be the main factors of sedimentary control during the Jurassic and Cretaceous on the Arabian platform.

  7. Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary

    PubMed Central

    Thorne, Philippa M.; Ruta, Marcello; Benton, Michael J.

    2011-01-01

    Ichthyosaurs were important marine predators in the Early Jurassic, and an abundant and diverse component of Mesozoic marine ecosystems. Despite their ecological importance, however, the Early Jurassic species represent a reduced remnant of their former significance in the Triassic. Ichthyosaurs passed through an evolutionary bottleneck at, or close to, the Triassic-Jurassic boundary, which reduced their diversity to as few as three or four lineages. Diversity bounced back to some extent in the aftermath of the end-Triassic mass extinction, but disparity remained at less than one-tenth of pre-extinction levels, and never recovered. The group remained at low diversity and disparity for its final 100 Myr. The end-Triassic mass extinction had a previously unsuspected profound effect in resetting the evolution of apex marine predators of the Mesozoic. PMID:21536898

  8. Polar record of Early Jurassic massive carbon injection

    NASA Astrophysics Data System (ADS)

    Suan, Guillaume; Nikitenko, Boris L.; Rogov, Mikhail A.; Baudin, François; Spangenberg, Jorge E.; Knyazev, Valeriy G.; Glinskikh, Larisa A.; Goryacheva, Anna A.; Adatte, Thierry; Riding, James B.; Föllmi, Karl B.; Pittet, Bernard; Mattioli, Emanuela; Lécuyer, Christophe

    2011-12-01

    The Toarcian Oceanic Anoxic Event (T-OAE) (ca. 182 Myr, Early Jurassic) represents one of the best-recognized examples of greenhouse warming, decreased seawater oxygenation and mass extinction. The leading hypothesis to explain these changes is the massive injection of thermogenic or gas hydrate-derived 13C-depleted carbon into the atmosphere, resulting in a > 3 per mil negative carbon isotope excursion (CIE), accelerated nutrient input and dissolved oxygen consumption in the oceans. Nevertheless, the lack of a precisely dated record of the T-OAE outside low latitudes has led to considerable debate about both its temporal and spatial extent and hence concerning its underlying causes. Here we present new isotopic and lithological data from three precisely dated N Siberian sections, which demonstrate that mass extinction and onset of strong oxygen-deficiency occurred near synchronously in polar and most tropical sites and were intimately linked to the onset of a marked 6‰ negative CIE recorded by bulk organic carbon. Rock Eval pyrolysis data from Siberia and comparisons with low latitudes show that the CIE cannot be explained by the extent of stratification of the studied basins or changes in organic matter sourcing and suggest that the negative CIE reflects rapid 13C-depleted carbon injection to all exchangeable reservoirs. Sedimentological and palynological indicators show that the injection coincided with a change from cold (abundant glendonites and exotic boulder-sized clasts) to exceptionally warm conditions (dominance of the thermophyllic pollen genus Classopollis) in the Arctic, which likely triggered a rapid, possibly partly glacioeustatic sea-level rise. Comparisons with low latitude records reveal that warm climate conditions and poor marine oxygenation persisted in continental margins at least 600 kyr after the CIE, features that can be attributed to protracted and massive volcanic carbon dioxide degassing. Our data reveal that the T-OAE profoundly affected Arctic climate and oceanography and suggest that the CIE was a consequence of global and massive 13C-depleted carbon injection.

  9. Greybull Sandstone Petroleum Potential on the Crow Indian Reservation, South-Central Montana

    SciTech Connect

    Lopez, David A.

    2002-05-13

    The focus of this project was to explore for stratigraphic traps that may be present in valley-fill sandstone at the top of the Lower Cretaceous Kootenai Formation. This sandstone interval, generally known as the Greybull Sandstone, has been identified along the western edge of the reservation and is a known oil and gas reservoir in the surrounding region. The Greybull Sandstone was chosen as the focus of this research because it is an excellent, well-documented, productive reservoir in adjacent areas, such as Elk Basin; Mosser Dome field, a few miles northwest of the reservation; and several other oil and gas fields in the northern portion of the Bighorn Basin.

  10. The Early Jurassic climate: General circulation model simulations and the paleoclimate record

    SciTech Connect

    Chandler, M.A.

    1992-01-01

    This thesis presents the results of several general circulation model simulations of the Early Jurassic climate. The general circulation model employed was developed at the Goddard Institute for Space Studies while most paleoclimate data were provided by the Paleographic Atlas Project of the University of Chicago. The first chapter presents an Early Jurassic base simulation, which uses detailed reconstructions of paleogeography, vegetation, and sea surface temperature as boundary condition data sets. The resulting climatology reveals an Earth 5.2[degrees]C warmer, globally, than at present and a latitudinal temperature gradient dominated by high-latitude warming (+20[degrees]C) and little tropical change (+1[degrees]C). Comparisons show a good correlation between simulated results and paleoclimate data. Sensitivity experiments are used to investigate any model-data mismatches. Chapters two and three discuss two important aspects of Early Jurassic climate, continental aridity and global warming. Chapter two focuses on the hydrological capabilities of the general circulation model. The general circulation model's hydrologic diagnostics are evaluated, using the distribution of modern deserts and Early Jurassic paleoclimate data as validating constraints. A new method, based on general circulation model diagnostics and empirical formulae, is proposed for evaluating moisture balance. Chapter three investigates the cause of past global warming, concentrating on the role of increased ocean heat transport. Early Jurassic simulations show that increased ocean heat transports may have been a major factor in past climates. Increased ocean heat transports create latitudinal temperature gradients that closely approximate paleoclimate data and solve the problem of tropical overheating that results from elevated atmospheric carbon dioxide. Increased carbon dioxide cannot duplicate the Jurassic climate without also including increased ocean heat transports.

  11. The timing of Jurassic orogenesis in the continental arc terrane of the western US Cordillera: Jackston Mountains, northwestern Nevada

    SciTech Connect

    Quinn, M.J.; Wright, J.E. (Rice Univ., Houston, TX (United States). Dept. of Geology and Geophysics)

    1993-04-01

    Pre-Nevadan, Jurassic orogenesis appears to be characteristic of many Mesozoic arc assemblages of the western US Cordillera. In most places this deformation is Middle Jurassic ([approximately]170--160 Ma). The authors recent work in the Black Rock Desert (BRD) documents an episode of Early Jurassic metamorphism and tectonism in the Jackson Mountains (JM). Here, an extensive arc section, including the Norian to Middle ( ) Jurassic Happy Creek Volcanics and Early to Middle Jurassic plutons, indicate vigorous arc magmatism in the arly Mesozoic. Among the southwest flank of the range the lower Mesozoic section is overridden by an east vergent thrust sheet carrying upper Paleozoic rocks of the McGill Canyon Unit. Another thrust package is located on the same side of the range, but further to the north, and contains variably metamorphosed clastic rocks, carbonate, and mafic volcanics. There is also an abrupt drop in metamorphic grade across the main thrust fault where greenschist facies rocks are in contact with virtually unmetamorphosed Happy Creek Volcanics. Two plutons with U/Pb zircon age of 188 [+-] 2 Ma and 193 [+-] 3 Ma crosscut the northern thrust fault. These relations suggest than an episode of regional metamorphism followed by E-W compressional tectonism was completed during the Early Jurassic in this portion of the arc terrane. These results differ significantly from previous studies that have interpreted all compressive deformation in the JM to have taken place between the Middle Jurassic and Cretaceous. The authors new data indicate that pre-Nevada Jurassic deformation is somewhat older in the BRD than that documented in other parts of the Mesozoic arc. Because voluminous Jurassic magmatism also began at an earlier time (Early Jurassic) in the BRD than elsewhere, they suggest that deformation and metamorphis within the arc may be facilitated and localized during periods of high heat flux related to magmatic input.

  12. The Jurassic-early Cretaceous Ilo batholith of southern coastal Peru: geology, geochronology and geochemistry

    NASA Astrophysics Data System (ADS)

    Boekhout, Flora; Sempere, Thierry; Spikings, Richard; Schaltegger, Urs

    2010-05-01

    The Ilo batholith (17°00 - 18°30 S) crops out in an area of about 20 by 100 km, along the coast of southern Peru. This batholith is emplaced into the ‘Chocolate‘ Formation of late Permian to middle Jurassic age, which consists of more than 1000 m of basaltic and andesitic lavas, with interbedded volcanic agglomerates and breccias. The Ilo Batholith is considered to be a rarely exposed fragment of the Jurassic arc in Peru. Our aim is to reconstruct the magmatic evolution of this batholith, and place it within the context of long-lasting magma genesis along the active Andean margin since the Paleozoic. Sampling for dating and geochemical analyses was carried out along several cross sections through the batholith that were exposed by post-intrusion eastward tilting of 20-30°. Sparse previous work postulates early to middle Jurassic and partially early Cretaceous emplacement, on the basis of conventional K/Ar and 40Ar/39Ar dating methods in the Ilo area. Twenty new U-Pb zircon ages (LA-ICP-MS and CA-ID-TIMS) accompanied by geochemical data suggests the Ilo batholith formed via the amalgamation of middle Jurassic and early Cretaceous, subduction-related plutons. Preliminary Hf isotope studies reveal a primitive mantle source for middle Jurassic intrusions. Additional Sr, Nd and Hf isotope analyses are planned to further resolve the source regions of different pulses of plutonic activity. We strongly suggest that batholith emplacement was at least partly coeval with the emplacement of the late Permian to middle Jurassic Chocolate Formation, which was deposited in an extensional tectonic regime. Our age results and geochemical signature fit into the scheme of episodic emplacement of huge amounts of subduction related magmatism that is observed throughout the whole Andean event, particularly during the middle Jurassic onset of the first Andean cycle (southern Peru, northern Chile and southern Argentina). Although the exact geodynamic setting remains to be precisely defined, these events can be linked to extensional episodes during the breakup of Pangea, which commenced at 230-220 Ma along the western South American margin, with a period of rifting, and culminated in the Jurassic with arc and back-arc extension.

  13. A basal alvarezsauroid theropod from the early Late Jurassic of Xinjiang, China.

    PubMed

    Choiniere, Jonah N; Xu, Xing; Clark, James M; Forster, Catherine A; Guo, Yu; Han, Fenglu

    2010-01-29

    The fossil record of Jurassic theropod dinosaurs closely related to birds remains poor. A new theropod from the earliest Late Jurassic of western China represents the earliest diverging member of the enigmatic theropod group Alvarezsauroidea and confirms that this group is a basal member of Maniraptora, the clade containing birds and their closest theropod relatives. It extends the fossil record of Alvarezsauroidea by 63 million years and provides evidence for maniraptorans earlier in the fossil record than Archaeopteryx. The new taxon confirms extreme morphological convergence between birds and derived alvarezsauroids and illuminates incipient stages of the highly modified alvarezsaurid forelimb. PMID:20110503

  14. Jurassic Lake T'oo'dichi': a large alkaline, saline lake, Morrison Formation, eastern Colorado Plateau

    USGS Publications Warehouse

    Turner, C.E.; Fishman, N.S.

    1991-01-01

    Recognition of alkaline, saline-lake deposits in the Morrison Formation significantly alters interpretations of depositional environments of this formation, and it also has important implications for paleoclimatic interpretation. Late Jurassic climate was apparently much more arid than had previously been thought. In fact, sedimentologic evidence suggests that the lake basin was typically dry for extended periods and enjoyed only brief wet intervals. This conclusion has important consequences for environmental interpretation of the habitat that was favorable for large herbivorous dinosaurs, which thrived in the Late Jurassic. -from Authors

  15. Analysis of the Magnitude and Frequency of Peak Discharges for the Navajo Nation in Arizona, Utah, Colorado, and New Mexico

    USGS Publications Warehouse

    Waltemeyer, Scott D.

    2006-01-01

    Estimates of the magnitude and frequency of peak discharges are necessary for the reliable flood-hazard mapping in the Navajo Nation in Arizona, Utah, Colorado, and New Mexico. The Bureau of Indian Affairs, U.S. Army Corps of Engineers, and Navajo Nation requested that the U.S. Geological Survey update estimates of peak discharge magnitude for gaging stations in the region and update regional equations for estimation of peak discharge and frequency at ungaged sites. Equations were developed for estimating the magnitude of peak discharges for recurrence intervals of 2, 5, 10, 25, 50, 100, and 500 years at ungaged sites using data collected through 1999 at 146 gaging stations, an additional 13 years of peak-discharge data since a 1997 investigation, which used gaging-station data through 1986. The equations for estimation of peak discharges at ungaged sites were developed for flood regions 8, 11, high elevation, and 6 and are delineated on the basis of the hydrologic codes from the 1997 investigation. Peak discharges for selected recurrence intervals were determined at gaging stations by fitting observed data to a log-Pearson Type III distribution with adjustments for a low-discharge threshold and a zero skew coefficient. A low-discharge threshold was applied to frequency analysis of 82 of the 146 gaging stations. This application provides an improved fit of the log-Pearson Type III frequency distribution. Use of the low-discharge threshold generally eliminated the peak discharge having a recurrence interval of less than 1.4 years in the probability-density function. Within each region, logarithms of the peak discharges for selected recurrence intervals were related to logarithms of basin and climatic characteristics using stepwise ordinary least-squares regression techniques for exploratory data analysis. Generalized least-squares regression techniques, an improved regression procedure that accounts for time and spatial sampling errors, then was applied to the same data used in the ordinary least-squares regression analyses. The average standard error of prediction for a peak discharge have a recurrence interval of 100-years for region 8 was 53 percent (average) for the 100-year flood. The average standard of prediction, which includes average sampling error and average standard error of regression, ranged from 45 to 83 percent for the 100-year flood. Estimated standard error of prediction for a hybrid method for region 11 was large in the 1997 investigation. No distinction of floods produced from a high-elevation region was presented in the 1997 investigation. Overall, the equations based on generalized least-squares regression techniques are considered to be more reliable than those in the 1997 report because of the increased length of record and improved GIS method. Techniques for transferring flood-frequency relations to ungaged sites on the same stream can be estimated at an ungaged site by a direct application of the regional regression equation or at an ungaged site on a stream that has a gaging station upstream or downstream by using the drainage-area ratio and the drainage-area exponent from the regional regression equation of the respective region.

  16. Diné (Navajo) parents' and community leaders' perceptions of agriculture-related injury risk to youth: a social narrative.

    PubMed

    Shumway, K; Pate, M L; McNeal, L G

    2014-01-01

    The purpose of this study was to provide a formative needs assessment of Diné (Navajo) parents for the prevention of childhood injuries resulting from livestock and horses. The research objectives were to identify parents' perceived livestock and horse related injury risks to Diné children and describe Diné community stakeholder input on prevention interventions for reducing injury risks to children associated with livestock and horse related activities on farms or ranches. The assessment used a survey constructed of closed and open-response questions to gauge Diné farmers' and ranchers' perceptions of injury risks to children who live or work on agricultural operations. Additional questions were asked to gauge Diné acceptance of an online training program as a prevention intervention to reduce livestock and horse related injuries to children. A total of 96 individuals agreed to participate in the survey and provided usable responses. A total of 53.2% (f = 50) of participants were female. Sixty-three percent of participants (f = 58) perceived that youth who work with intact male livestock were at high risk for injury. A total of 25 individuals perceived that youth who ride horses without equestrian helmets were at high risk for injury. Approximately 96% (f = 89) of those surveyed agreed or strongly agreed that they would use an online training program to promote agricultural health and safety for Diné youth. When participants were asked if there were safety issues associated with having youth working on a farm or ranch, a very large portion felt that the biggest issue was a lack of education and instruction from elders. A recommendation for an injury prevention practice included developing a user-friendly online network, giving parents and community leaders access to resources to assist in educating youth in local agricultural traditions integrated with safety training. PMID:24804462

  17. The Point Lookout Sandstone: a tale of two cores, or petrology, diagenesis, and reservoir properties of Point Lookout Sandstone, Southern Ute Indian Reservation, San Juan Basin, Colorado

    USGS Publications Warehouse

    Keighin, C.W.; Zech, R.S.; Dunbar, R.W.

    1993-01-01

    The Point Lookout sandstones are quartz-rich, fine to very-fine grained, and contain moderately variable quantities of potassium feldspar (2 to 20 modal percent) and lithic fragments (9 to 20 modal percent). Locally, sandstone is tightly cemented by carbonate cement; clays are not important as cementing agents, although they significantly reduce permeability of some samples. Pores are small; many are intergranular micropores between crystals of authigenic clay. Depositional environments are highly variable and range from lower shoreface to coastal plain and include minor deltaic environments. The best reservoir characteristics are generally in the upper shoreface sandstones. -from Authors

  18. Strontium isotopic variations in Jurassic and Cretaceous seawater

    NASA Astrophysics Data System (ADS)

    Jones, Charles E.; Jenkyns, Hugh C.; Coe, Angela L.; Stephen, Hesselbo P.

    1994-07-01

    A high-resolution seawater strontium isotope curve has been generated through the analysis of well-dated and well-preserved belemnites and oysters from the Middle and Upper Jurassic and the Lower Cretaceous of Great Britain. Analysis of Fe and Mn concentrations in these fossils has yielded criteria for eliminating samples that are diagenetically altered. The strontium isotope curve remains relatively flat through the Aalenian and early Bajocian, rapidly descends through the late Bajocian and Bathonian, and reaches a minimum in the Callovian and Oxfordian. It then begins a rapid increase in the Kimmeridgian and Portlandian that continues through much of the early Cretaceous. The curve levels off in the Barremian, suddenly dips downwards in the Aptian, and recovers gradually through the Albian. The strontium isotopic variations are sufficiently large and the data are presented with sufficient stratigraphic detail to allow precise correlation to the classic ammonite zones and lithologic sections of Great Britain using the techniques of strontium isotope stratigraphy. Model results indicate that much of the variation in seawater 87Sr /86Sr between 120 and 40 Ma can be explained by changing the intensity of mid-ocean ridge hydrothermal fluxes proportionally to estimated mid-ocean ridge crustal generation rates. It is also possible that the variations during the rest of the Mesozoic and the Permian are primarily reflections of changing hydrothermal inputs. The model results have several important implications. First, they provide an example in which the variations in the strontium isotope curve are not necessarily driven by changes in fluvial inputs. Second, they suggest that from at least the Aptian through the Eocene variations in continental weathering were minimal. This heightens the importance of the rapid rise in seawater 87Sr /86Sr beginning ~ 40 Ma as a significant transition to an extended period of increasing fluvial 87Sr fluxes continuing to the present. Finally, the results suggest that several documented short-term excursions towards lower 87Sr /86Sr in the latest Triassic, Pliensbachian-Toarcian, Callovian-Oxfordian, Aptian-Albian, and Cenomanian-Turonian are interpretable as pulses of seafloor hydrothermal activity. If so, the strontium isotope record offers a means of constraining the timing, duration, and magnitude of known or proposed hydrothermal events in the geological record.

  19. Facies relationships in the Steven Sandstone, Kern County, California 

    E-print Network

    Findley, Richard Lee

    1975-01-01

    the environment of deposition. The Stevens Sandstone is of turbidite origin and contains three facies defined on the basis of bed thickness and sequence of sedi- mentary structures: outer fan, inner fan, and gorge fill. The outer- fan facies is characterized..., but individual beds are thicker than those in the outer-fan facies. The thick, incomplete iv sequences are believed to have originated as channelized turbidites. The gorge-fill facies is characterized by thick beds, 20 ft thick, that display only the graded...

  20. Reservoir characterization of Pennsylvanian sandstone reservoirs. Final report

    SciTech Connect

    Kelkar, M.

    1995-02-01

    This final report summarizes the progress during the three years of a project on Reservoir Characterization of Pennsylvanian Sandstone Reservoirs. The report is divided into three sections: (i) reservoir description; (ii) scale-up procedures; (iii) outcrop investigation. The first section describes the methods by which a reservoir can be described in three dimensions. The next step in reservoir description is to scale up reservoir properties for flow simulation. The second section addresses the issue of scale-up of reservoir properties once the spatial descriptions of properties are created. The last section describes the investigation of an outcrop.