Science.gov

Sample records for red sand beds

  1. White Sands, Carrizozo Lava Beds, NM

    NASA Technical Reports Server (NTRS)

    1973-01-01

    A truly remarkable view of White Sands and the nearby Carrizozo Lava Beds in southeast NM (33.5N, 106.5W). White Sands, site of the WW II atomic bomb development and testing facility and later post war nuclear weapons testing that can still be seen in the cleared circular patterns on the ground.

  2. 20. View of sand filtration bed. Wheelbarrow was used to ...

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

    20. View of sand filtration bed. Wheelbarrow was used to remove schmutzdeck (top, dirty sand layer containing particulate contamination, dead microorganisms and debris) for cleaning and or disposal. - Lake Whitney Water Filtration Plant, Filtration Plant, South side of Armory Street between Edgehill Road & Whitney Avenue, Hamden, New Haven County, CT

  3. Coupled changes in sand grain size and sand transport driven by changes in the upstream supply of sand in the Colorado River: relative importance of changes in bed-sand grain size and bed-sand area

    USGS Publications Warehouse

    Topping, D.J.; Rubin, D.M.; Melis, T.S.

    2007-01-01

    Sand transport in the Colorado River in Marble and Grand canyons was naturally limited by the upstream supply of sand. Prior to the 1963 closure of Glen Canyon Dam, the river exhibited the following four effects of sand supply limitation: (1) hysteresis in sediment concentration, (2) hysteresis in sediment grain size coupled to the hysteresis in sediment concentration, (3) production of inversely graded flood deposits, and (4) development or modification of a lag between the time of a flood peak and the time of either maximum or minimum (depending on reach geometry) bed elevation. Construction and operation of the dam has enhanced the degree to which the first two of these four effects are evident, and has not affected the degree to which the last two effects of sand supply limitation are evident in the Colorado River in Marble and Grand canyons. The first three of the effects involve coupled changes in suspended-sand concentration and grain size that are controlled by changes in the upstream supply of sand. During tributary floods, sand on the bed of the Colorado River fines; this causes the suspended sand to fine and the suspended-sand concentration to increase, even when the discharge of water remains constant. Subsequently, the bed is winnowed of finer sand, the suspended sand coarsens, and the suspended-sand concentration decreases independently of discharge. Also associated with these changes in sand supply are changes in the fraction of the bed that is covered by sand. Thus, suspended-sand concentration in the Colorado River is likely regulated by both changes in the bed-sand grain size and changes in the bed-sand area. A physically based flow and suspended-sediment transport model is developed, tested, and applied to data from the Colorado River to evaluate the relative importance of changes in the bed-sand grain size and changes in the bed-sand area in regulating suspended-sand concentration. Although the model was developed using approximations for steady

  4. Erosion of sand from a gravel bed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cleaning of fine sediment out of gravel stream beds has become an important method to restore impacted stream habitats. Introducing the increased flows needed to entrain fine sediments without eroding the coarser fractions of the bed and potentially destroying its usefulness as a habitat requires c...

  5. Modeling downstream fining in sand-bed rivers. I: Formulation

    USGS Publications Warehouse

    Wright, S.; Parker, G.

    2005-01-01

    In this paper a numerical modeling formulation is presented for simulation of the development of the longitudinal profile and bed sediment distribution in sand-bed rivers. The objective of the model application, which is presented in the companion paper (Wright and Parker, 2005), is to study the development of two characteristics of large, low-slope, sand-bed rivers: (1) a downstream decrease in bed slope (i.e. concave upward longitudinal profile) and (2) a downstream decrease in characteristic bed sediment diameter (e.g. the median bed surface size D50). Three mechanisms that lead to an upward concave profile and downstream fining are included in the modeling formulation: (1) a delta prograding into standing water at the downstream boundary, (2) sea-level rise, and (3) tectonic subsidence. In the companion paper (Wright and Parker, 2005) the model is applied to simulate the development of the longitudinal profile and downstream fining in sand-bed rivers flowing into the ocean during the past 5000 years of relatively slow sea-level rise. ?? 2005 International Association of Hydraulic Engineering and Research.

  6. Erosion depth of sand from an immobile gravel bed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Abstract This study was conducted to provide information on the depth of erosion of sand (D50 = 0.3, 0.9 mm) from immobile gravel (D50 = 36.1 mm) under steady uniform flows with bed shear stresses from 0.1 to 0.9 of that required to entrain the gravel. This situation, often encountered downstream o...

  7. MODELING LARGE WOOD STRUCTURES IN SAND BED STREAMS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In-stream large wood structures (LWS) are becoming increasingly popular throughout the world. The LWS improve aquatic habitat quality and protect banks from erosion. While most reports describe the LWS in the Northwest as successful, LWS in one Mississippi sand-bed stream had an unacceptable failure...

  8. Design of Large Wood Structures in Sand-Bed Streams

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Large woody structures (LWS) are potentially an efficient and cost effective way to protect streambanks from erosion while enhancing aquatic habitat. While LWS have been successful in some cases in the Pacific Northwest when ballasted with rock, the failure rate in sand-bed streams typical of the mi...

  9. Sand Bed Morphodynamics under Standing Waves and Vegetated Conditions

    NASA Astrophysics Data System (ADS)

    Landry, B. J.; Garcia, M. H.

    2010-12-01

    Littoral processes such as sediment transport, wave attenuation, and boundary layer development are governed by the presence of bathymetric features, which include large-scale sand bars upon which smaller-scale sand ripples are superimposed, as well as the presence of submarine vegetation. Numerous studies on sand ripples and bars have aided to elucidate the dynamics in oscillatory flows; however, the effect of vegetation on the system is less understood. Recent laboratory studies have focused on quantifying wave attenuation by emergent vegetation as a natural method to mitigate storm surges. The emergent vegetation, while promising for coastal protection, alters sediment transport rates directly by the physical presence of the plants near the bed and indirectly from reduction in near-bed shear stresses due to attenuated wave energy. The experimental work herein focuses on the area near the deeply submerged vegetated canopy limit (current work has a ratio of mean still water depth to plant height, H/h, = 7.9) to minimize the effect on the surface waves and discern the direct impact vegetation has on sand bed morphodynamics. Experiments were conducted in the large wave tank (49-m long by 1.83-m wide by 1.22-m deep) in the Ven Te Chow Hydrosystems Laboratory at the University of Illinois in which a high reflection wave forcing was used over a uniform sand bed with a 0.25-mm median sediment diameter in which staggered and uniform arrangements of idealized vegetation (i.e., 6.35-mm diameter rigid wooden cylinders) were positioned along the bed (e.g., at predetermined sand bar troughs and over an entire sand bar). The resulting bathymetric evolution from the vegetated case experiments were compared to the base case of no vegetation using two optical methods: a high-resolution laser displacement sensor for three-dimensional surveys and digitized profiles via high-definition panoramic images of the entire test section. The experimental findings illustrate the profound

  10. Fractional dispersion in a sand bed river

    NASA Astrophysics Data System (ADS)

    Bradley, D. Nathan; Tucker, Gregory E.; Benson, David A.

    2010-03-01

    Random walk models of fluvial bed load transport use probability distributions to describe the distance a grain travels during an episode of transport and the time it rests after deposition. These models typically employ probability distributions with finite first and second moments, reflecting an underlying assumption that all the factors that influence sediment transport tend to combine in such a way that the length of a step or the duration of a rest can be characterized by a mean value surrounded by a specific amount of variability. The observation that many transport systems exhibit apparent scale-dependent behavior and non-Fickian dispersion suggests that this assumption is not always valid. We revisit a nearly 50 year old tracer experiment in which the tracer plume exhibits the hallmarks of dispersive transport described by a step length distribution with a divergent second moment and no characteristic dispersive size. The governing equation of this type of random walk contains fractional-order derivatives. We use the data from the experiment to test two versions of a fractional-order model of dispersive fluvial bed load transport. The first version uses a heavy-tailed particle step length distribution with a divergent second moment to reproduce the anomalously high fraction of tracer mass observed in the downstream tail of the spatial distribution. The second version adds a feature that partitions mass into a detectable mobile phase and an undetectable, immobile phase. This two-phase transport model predicts other features observed in the data: a decrease in the amount of detected tracer mass over the course of the experiment and enhanced particle retention near the source. The fractional-order models match the observed plume shape and growth rates better than prior attempts with classical models.

  11. Are discontinuous rating curves in sand bedded rivers due to bedform transitions or bed scour?

    NASA Astrophysics Data System (ADS)

    Yousfi, Y. M.; Sklar, L. S.; Dawdy, D. R.

    2013-12-01

    Estimating discharge from flow stage in sand-bedded rivers is complicated by non-monotonic relationships between gauge height and discharge. These discontinuous rating curves have an enigmatic region where stage decreases while discharge increases, such that the same stage is apparently associated with two possible discharges. Previous work has shown that this can occur due to changes in bed configuration that reduce roughness and increase flow conveyance. An alternative explanation is that the increase in conveyance is due to enhanced bed scour and changes in cross-section geometry. Here we investigate these two hypotheses using discharge gauge measurements from the San Juan River at Shiprock, New Mexico. We focus on the snowmelt hydrograph of 1941, for which the gauge operator made a unique set of notations indicating the presence of sand boils and sand waves. We use these field observations to calibrate a site-specific model for the flow conditions that create dune, plane and anti-dune bed configurations. For each gauged discharge, we back-calculate cross-section average roughness coefficients and flow conveyance area. From these data we evaluate the relative contribution of changes in bed configuration and cross-section geometry to the observed discontinuities in the stage-discharge relationship. The outcome of this analysis will be useful in modeling flow, and reducing errors in estimating discharge, in large sand-bedded rivers.

  12. Bed Bugs Drawn to Red and Black Colors

    MedlinePlus

    ... html Bed Bugs Drawn to Red and Black Colors Critters strongly prefer those bedroom hues to green ... 25, 2016 (HealthDay News) -- Bed bugs have favorite colors, new research has discovered. In a series of ...

  13. Predicting bed load transport of sand and gravel on Goodwin Creek

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bed load transport rates are difficult to predict in channels with bed material composed of sand and gravel mixtures. The transport of bed load was measured on Goodwin Creek, and in a laboratory flume channel with a similar bed material size distribution. The range of bed load transport rates meas...

  14. Bed Bugs Drawn to Red and Black Colors

    MedlinePlus

    ... 158493.html Bed Bugs Drawn to Red and Black Colors Critters strongly prefer those bedroom hues to ... the little blood suckers strongly preferred red and black and avoided green and yellow. Does that mean ...

  15. Centerline Bed Elevation Profile of Sand Bed Channel due to Bar Formation

    NASA Astrophysics Data System (ADS)

    Tholibon, D. A.; Ariffin, J.; Abdullah, J.; Muhamad, N. S.

    2016-07-01

    Numerous data on bar formation have been accumulated yet the methods to predict bar geometry especially bar height are still insufficient. Objectives of this study to determine the trend in term of a significant difference of centreline bed elevation profile along the longitudinal distance. This can be investigate by carried out an experimental work in an erodible sand bed channel using a large-scale physical river model. The study included the various hydraulic characteristics with steady flow rates and sediment supply. An experimental work consists of four matrices of flow rate and channel width with other variables namely grains size and bed slope were kept constant. Analysis have included the discussion on a significant difference of centreline bed elevation profile along the longitudinal distance. As a conclusion the higher velocity in the smaller channel width have induced erosion of the banks that resulted in elevation increase while the larger flow rates have contributed to higher elevation.

  16. Acoustic bed velocity and bed load dynamics in a large sand bed river

    USGS Publications Warehouse

    Gaeuman, D.; Jacobson, R.B.

    2006-01-01

    Development of a practical technology for rapid quantification of bed load transport in large rivers would represent a revolutionary advance for sediment monitoring and the investigation of fluvial dynamics. Measurement of bed load motion with acoustic Doppler current profiles (ADCPs) has emerged as a promising approach for evaluating bed load transport. However, a better understanding of how ADCP data relate to conditions near the stream bed is necessary to make the method practical for quantitative applications. In this paper, we discuss the response of ADCP bed velocity measurements, defined as the near-bed sediment velocity detected by the instrument's bottom-tracking feature, to changing sediment-transporting conditions in the lower Missouri River. Bed velocity represents a weighted average of backscatter from moving bed load particles and spectral reflections from the immobile bed. The ratio of bed velocity to mean bed load particle velocity depends on the concentration of the particles moving in the bed load layer, the bed load layer thickness, and the backscatter strength from a unit area of moving particles relative to the echo strength from a unit area of unobstructed bed. A model based on existing bed load transport theory predicted measured bed velocities from hydraulic and grain size measurements with reasonable success. Bed velocities become more variable and increase more rapidly with shear stress when the transport stage, defined as the ratio of skin friction to the critical shear stress for particle entrainment, exceeds a threshold of about 17. This transition in bed velocity response appears to be associated with the appearance of longer, flatter bed forms at high transport stages.

  17. Density stratification effects in sand-bed rivers

    USGS Publications Warehouse

    Wright, S.; Parker, G.

    2004-01-01

    In this paper the effects of density stratification in sand-bed rivers are studied by the application of a model of vertical velocity and concentration profiles, coupled through the use of a turbulence closure that retains the buoyancy terms. By making the governing equations dimensionless, it is revealed that the slope is the additional dimensionless parameter introduced by inclusion of the buoyancy terms. The primary new finding is that in general density stratification effects tend to be greater in large, low-slope rivers than in their smaller, steeper brethren. Under high flow conditions the total suspended load and size distribution of suspended sediment can be significantly affected by density stratification, and should be accounted for in any general theory of suspended transport. ?? ASCE.

  18. Modeling downstream fining in sand-bed rivers. II: Application

    USGS Publications Warehouse

    Wright, S.; Parker, G.

    2005-01-01

    In this paper the model presented in the companion paper, Wright and Parker (2005) is applied to a generic river reach typical of a large, sand-bed river flowing into the ocean in order to investigate the mechanisms controlling longitudinal profile development and downstream fining. Three mechanisms which drive downstream fining are studied: a delta prograding into standing water, sea-level rise, and tectonic subsidence. Various rates of sea-level rise (typical of the late Holocene) and tectonic subsidence are modeled in order to quantify their effects on the degree of profile concavity and downstream fining. Also, several other physical mechanisms which may affect fining are studied, including the relative importance of the suspended versus bed load, the effect of the loss of sediment overbank, and the influence of the delta bottom slope. Finally, sensitivity analysis is used to show that the grain-size distribution at the interface between the active layer and substrate has a significant effect on downstream fining. ?? 2005 International Association of Hydraulic Engineering and Research.

  19. Bed topography and sand transport responses to a step change in discharge and water depth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Ephemeral streams with sand and gravel beds may inherit bed topography caused by previous flow events, resulting in bed topography that is not in equilibrium with flow conditions, complicating the modeling of flow and sediment transport. Major flow events, resulting from rainfall with high intensity...

  20. Algorithm for resistance to flow and transport in sand-bed channels

    USGS Publications Warehouse

    Bennett, J.P.

    1995-01-01

    An algorithm is developed that relates depth to discharge and determines bed- and suspended-load transport for the entire range of bed forms found in sand-bed channels; equilibrium-state geometry of lower flow regime bedforms is also predicted. A Meyer-Peter-type formulation is used to compute sand transport in the bed-load layer and for computing suspended sand transport, McLean's procedure is adopted. A bed-form classifcation scheme is developed. The algorithm produces overall geometric averages of predicted to observed depth and predicted to observed transport of 1.00. For a verification data set of 855 observations, mostly from rivers and canals, the overall geometric averages of predicted to observed depth and transport are 0.87 and 1.14. -from Author

  1. Turbulent flow and sand transport over a cobble bed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The turbulence structure of flow over rough beds and its interaction with fine sediments in the bed are important for efforts to predict sediment transport downstream of dams. The advanced age and impending decommissioning of many dams have brought increased attention to the fate of sediments stored...

  2. Deposition of carbonate mud beds within high-energy subtidal sand Dunes, Bahamas

    SciTech Connect

    Dill, R.F.; Steinen, R.P.

    1988-01-01

    Laminated, carbonate mud beds are being deposited in the interisland channels of the Exuma Cays in the Bahamas. They are associated with stromatolites and interbedded with ooid sands that form large migrating subtidal dunes on flood tidal deltas and bars. Currents up to 3 knots sweep in and out of the 4-8 m deep channels 3 hours out of every 6 hours, creating a high-energy bank margin environment not usually considered to be the site of mud-sized particle deposition. Mud deposits reach thicknesses of 1 m and have individual beds 2-5 cm thick. When exposed to flowing seawater, bed surfaces become encrusted with carbonate cement and algal mats. The white interior of mud beds between the crusts appears homogeneous, is soft, and has the consistency of ''tooth paste.'' Loose uncemented ooid sand is found above and below the mud beds, showing that both are occupying the same depositional environment. Rip-up clasts of the crusted mud beds, formed by scour of underlying sands, are carried throughout the channels and accumulate as a lag deposit within the troughs of migrating dunes. Some clasts are colonized by algal mats that trap ooid and skeletal sands forming stromatolite structures that can grow up to 2 m high.

  3. Sand Transport, Flow Turbulence, and Bed Forms over an Immobile Gravel Bed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Channels downstream of dams often become armored because the sediment supply from upstream is cut off. Sand is generally supplied to these armored reaches intermittently from tributaries downstream of the dam or from sand bypassing. Accurate predictions of the rate of transport of sand over and th...

  4. Suppressing immature house and stable flies in outdoor calf hutches with sand, gravel, and sawdust bedding.

    PubMed

    Schmidtmann, E T

    1991-11-01

    Sand, gravel, sawdust, and pine shavings were used as bedding in outdoor calf hutches and compared with straw relative to the density of immature (maggot) house flies, Musca domestica, and stable flies, Stomoxys calcitrans. In 6-wk field trials, average densities of house and stable fly maggots in concrete mix sand ranged from only .3 to 1.6 and 0 to .1 maggots/L, respectively; pea size gravel bedding also strongly suppressed densities from less than .1 to .3 and less than .1 to .1 maggots/L, respectively. These densities represent reductions of 76 to greater than 99% relative to straw bedding, but both sand and gravel compacted and became soiled with calf feces, which resulted in unacceptable bedding sanitation and foul odors. Densities of house and stable fly maggots in pine shavings did not differ from those in straw bedding. Nevertheless, in sawdust bedding, maggot density was limited to averages of 1.4 to 8.3 house and 9.8 to 11.8 stable fly maggots/L; this represented reductions of 45 to 91% relative to straw. In a follow-up trial, house and stable fly maggot densities in sawdust averaged 11.3 and 43.9 maggots/L, respectively, reductions of 77 and 46%. These findings suggest that bedding calf hutches with sawdust during warm weather can be useful as an ecologically sound approach to controlling muscoid fly populations on dairy farms. PMID:1757634

  5. Measurement of bedload transport in sand-bed rivers: a look at two indirect sampling methods

    USGS Publications Warehouse

    Holmes, Robert R., Jr.

    2010-01-01

    Sand-bed rivers present unique challenges to accurate measurement of the bedload transport rate using the traditional direct sampling methods of direct traps (for example the Helley-Smith bedload sampler). The two major issues are: 1) over sampling of sand transport caused by “mining” of sand due to the flow disturbance induced by the presence of the sampler and 2) clogging of the mesh bag with sand particles reducing the hydraulic efficiency of the sampler. Indirect measurement methods hold promise in that unlike direct methods, no transport-altering flow disturbance near the bed occurs. The bedform velocimetry method utilizes a measure of the bedform geometry and the speed of bedform translation to estimate the bedload transport through mass balance. The bedform velocimetry method is readily applied for the estimation of bedload transport in large sand-bed rivers so long as prominent bedforms are present and the streamflow discharge is steady for long enough to provide sufficient bedform translation between the successive bathymetric data sets. Bedform velocimetry in small sandbed rivers is often problematic due to rapid variation within the hydrograph. The bottom-track bias feature of the acoustic Doppler current profiler (ADCP) has been utilized to accurately estimate the virtual velocities of sand-bed rivers. Coupling measurement of the virtual velocity with an accurate determination of the active depth of the streambed sediment movement is another method to measure bedload transport, which will be termed the “virtual velocity” method. Much research remains to develop methods and determine accuracy of the virtual velocity method in small sand-bed rivers.

  6. Flow and sand transport over an immobile gravel bed.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many dams in the USA and elsewhere have exceeded their design life and are being considered for remediation or removal, which will result in the reintroduction of fine sediments, often into coarse grained armored substrates, downstream of dams. The deposition of sand in the interstices of the grave...

  7. Reynolds averaged theory of turbulent shear flows over undulating beds and formation of sand waves.

    PubMed

    Bose, Sujit K; Dey, Subhasish

    2009-09-01

    Based on the Reynolds averaged Navier-Stokes (RANS) equations and the time-averaged continuity equation, a theory of turbulent shear flow over an undulating sand bed is developed addressing the instability criterion of plane sand beds in free-surface flows leading to the formation of sand waves. In the analysis, the integration of RANS equations leads to generalized Saint Venant equations, in which the time-averaged streamwise velocity is characterized by a power law obtained from turbulence closure, treating the curvilinear streamlines by the Boussinesq approximation. As a consequence, the modified pressure distribution has a departure from the traditionally linear hydrostatic pressure distribution. The instability analysis of a plane sand bed yields the curves of the Froude number versus nondimensional wave number, determining an instability zone for which at lower Froude numbers (less than 0.8), the plane bed becomes unstable with the formation of dunes; whereas at higher Froude numbers, the plane bed becomes unstable with the formation of standing waves and antidunes. For higher Froude numbers, the experimental data for antidunes lie within the unstable zone; while for lower Froude numbers, the same is found for dunes with some experimental scatter. PMID:19905209

  8. Acoustic observations of near-bed sediment concentration and flux statistics above migrating sand dunes

    NASA Astrophysics Data System (ADS)

    Wilson, G. W.; Hay, A. E.

    2016-06-01

    A coherent Doppler profiler was used to measure coincident time series of velocity (u,w), sediment mass concentration (c), and sediment grain size (d), above mobile sand dunes in unidirectional flow (˜1 m/s, ˜1 m water depth). The measurements are used to extract statistical distributions of sediment concentration and flux just above the bed. Observed mass fluxes (uc,wc) were well fit by quasi-exponential distributions, at all positions along the dune profile, similar to previous observations of single-particle momenta for bed load over flat beds. Observed concentrations of moving particles were well fit by negative-binomial distributions, also similar to previous observations over flat beds. These probability distributions relate to two recent stochastic theories, previously derived and verified for uniform flow over flat beds. It is hypothesized that these theories may also be used as a local approximation in natural-scale flows with bed forms.

  9. Managing vegetation on peat-sand filter beds for wastewater disposal. Forest Service research note

    SciTech Connect

    Elling, A.E.

    1985-01-01

    Five species of grass, one sedge, and cattail were grown on a peat-sand filter bed irrigated with sewage effluent. Yields, uptake of nitrogen and phosphorus, and lodging problems were determined for all species when grown to various heights ranging from 5 to 75 cm.

  10. RESPONSE OF FISHES AND AQUATIC HABITATS TO SAND-BED STREAM RESTORATION USING LARGE WOODY DEBRIS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Large woody debris structures hold promise as cost-effective stream corridor rehabilitation measures. Pre- and post construction data are presented that describe effects of habitat rehabilitation of Little Topashaw Creek, a sinuous, fourth-order sand-bed stream draining 37 km2 in northwest Mississip...

  11. Longitudinal variability in hydraulic geometry and substrate characteristics of a Great Plains sand-bed river

    NASA Astrophysics Data System (ADS)

    Costigan, Katie H.; Daniels, Melinda D.; Perkin, Joshuah S.; Gido, Keith B.

    2014-04-01

    Downstream trends in hydraulic geometry and substrate characteristics were investigated along a 200 km reach of the Ninnescah River in south central Kansas, USA. The Ninnescah River is a large sand-bed, perennial, braided river located in the Central Plains physiographic province and is a tributary of the Arkansas River. Hydraulic geometry characteristics were measured at eleven reaches and included slope, sinuosity, bankfull channel width, and bankfull channel depth. Results indicated that the Ninnescah River followed a predicted trend of decreasing slope and increasing depth and width downstream. There were localized divergences in the central tendency, most notability downstream of a substantial tributary that is impounded and at the end of the surveying reach where the Ninnescah River approaches the Arkansas River. Surface grain-size samples were taken from the top 10 cm of the bed at five points across the wetted cross-section within each of the 11 reaches. Sediment analyses demonstrated a significant trend in downstream fining of surface grain-sizes (D90 and D50) but unlike previous studies of sand-bedded rivers we observed coarsening of substrates downstream of the major tributary confluence. We propose that the overall low discharge from the tributary was the primary reason for coarsening of the bed downstream of the tributary. Results of this study provide valuable baseline information that can provide insight in to how Great Plains sand-bed systems may be conserved, managed, and restored in the future.

  12. Bacterial counts on teat skin and in new sand, recycled sand, and recycled manure solids used as bedding in freestalls.

    PubMed

    Rowbotham, R F; Ruegg, P L

    2016-08-01

    On modern dairy farms, environmental mastitis pathogens are usually the predominant cause of mastitis, and bedding often serves as a point of exposure to these organisms. The objective of this longitudinal study was to determine bacterial populations of 4 different bedding types [deep-bedded new sand (NES), deep-bedded recycled sand (RS), deep-bedded manure solids (DBMS), and shallow-bedded manure solids over foam core mattresses (SBMS)] and of teat skin swabs of primarily primiparous cows housed in a single facility over all 4 seasons. Samples of bedding were collected weekly (n=49wk) from pens that each contained 32 lactating dairy cows. Throughout the length of the same period, composite swabs of teat skin were collected weekly from all cows before and after premilking teat sanitation. Median numbers of streptococci and streptococci-like organisms (SSLO) were >8.6×10(6) cfu/g and >6.9×10(3) cfu/teat swab for all bedding types and teat swabs, respectively. Numbers of SSLO were greatest in samples of SBMS (2.1×10(8) cfu/g) and least in samples of NES (8.6×10(6) cfu/g), RS (1.3×10(7) cfu/g), and DBMS (1.7×10(7) cfu/g). Numbers of gram-negative bacteria in bedding (5.5×10(4) to 1.2×10(7) cfu/g) were fewer than numbers of SSLO (8.6×10(6) to 2.1×10(8) cfu/g). Numbers of coliform bacteria were greatest in samples of DBMS (2.2×10(6) cfu/g) and least in samples of NES (3.6×10(3) cfu/g). In general, the relative number of bacteria on teat skin corresponded to exposure in bedding. Numbers of gram-negative bacteria recovered from prepreparation teat swabs were greatest for cows bedded with DBMS (1.0×10(4) cfu/swab) and RS (2.5×10(3) cfu/swab) and least for cows bedded with NES (5.8×10(2) cfu/swab). Median numbers of coliform and Klebsiella spp. recovered from prepreparation teat swabs were below the limit of detection for all cows except those bedded with DBMS. Numbers of SSLO recovered from prepreparation teat swabs were least for cows bedded with DBMS (6.9

  13. Bed load and suspended load contributions to migrating sand dunes in equilibrium

    NASA Astrophysics Data System (ADS)

    Naqshband, S.; Ribberink, J. S.; Hurther, D.; Hulscher, S. J. M. H.

    2014-05-01

    Dunes dominate the bed of sand rivers and are of central importance in predicting flow roughness and water levels. The present study has focused on the details of flow and sediment dynamics along migrating sand dunes in equilibrium. Using a recently developed acoustic system (Acoustic Concentration and Velocity Profiler), new insights are obtained in the behavior of the bed and the suspended load transport along mobile dunes. Our data have illustrated that, due to the presence of a dense sediment layer close to the bed and migrating secondary bedforms over the stoss side of the dune toward the dune crest, the near-bed flow and sediment processes are significantly different from the near-bed flow and sediment dynamics measured over fixed dunes. It was observed that the shape of the total sediment transport distribution along dunes is mainly dominated by the bed load transport, although the bed load and the suspended load transport are of the same order of magnitude. This means that it was especially the bed load transport that is responsible for the continuous erosion and deposition of sediment along the migrating dunes. Whereas the bed load is entirely captured in the dune with zero transport at the flow reattachment point, a significant part of the suspended load is advected to the downstream dune depending on the flow conditions. For the two flow conditions measured, the bypass fraction was about 10% for flow with a Froude number (Fr) of 0.41 and 27% for flow with Froude number of 0.51. This means that respectively 90% (for the Fr = 0.41 flow) and 73% (for the Fr = 0.51 flow) of the total sediment load that arrived at the dune crests contributed to the migration of the dunes.

  14. Development of an inclined liquid fluidized bed for tar sand processing

    SciTech Connect

    Johnson, L.A. Jr.

    1989-12-01

    An inclined liquid fluidized-bed reactor (ILFBR) system has been developed and successfully operated for 24 hours. Modifications to the previously tested ILFBR systems include incorporation of a oil fluidizing zone in the front of the fluid bed, an increase in the angle of the fluid bed to {minus}12{degree} (the minus sign shows that the discharges is below the horizontal level of the inlet), and reduction of the fluidizing gas velocities equal to or below the minimum fluidization velocity. These changes produced a functional bubbling slurry bed for the processing of tar sand. The produced oils and spent sand resemble the products from screw pyrolysis reactor (SPR) tests suggesting that the ILFBR system functioned similar to the SPR systems with the recycle oil pyrolysis and extraction (ROPE{copyright}) process. With slight modifications in the heater control and placement, the system will be ready for development of operational parameters for the surface processing of tar sand. 10 refs., 2 figs., 1 tab.

  15. Geology of gas production from tight Abo red beds, east central New Mexico

    SciTech Connect

    Broadhead, R.F.

    1984-06-11

    Permian red-bed sandstones of the Abo formation currently produce dry natural gas from New Mexico's 700 mi/sup 2/ Pecos Slope Abo gas field. Since the Federal Energy Regulatory Commission's tight gas sand designation of the Abo in 1980, about 400 wells have been drilled and completed on 160-acre spacing. Data obtained for 92 completed wells indicate an average initial calculated open flow of 2,171,000 CF/day, ranging from 18,000 to 15,500,000 CF/day for individual wells. Online production averages about 400,000 CF/day per well. With recoverable reserves averaging about 500 million CF/well, the completed wells have a combined reserve of about 200 billion CF of gas.

  16. Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

    NASA Technical Reports Server (NTRS)

    Marshall, J. R.; Borucki, J.; Bratton, C.

    1999-01-01

    The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

  17. Stratigraphically controlled gas production from Abo red beds (Permian), east-central New Mexico

    SciTech Connect

    Broadhead, R.F.

    1984-01-01

    Red-bed sandstones of the Abo Formation currently produce natural gas from the Pecos Slope Abo field in northern Chaves County, New Mexico. The Pecos Slope Abo field is located on the Northwest shelf of the Permian Basin. Production currently comes from an approximately 700 mi/sup 2/ area. The Abo has been designated a tight gas sand, thus Abo gas can be sold for as much as $5.41 per MCF, $2.60 more than the regulated ceiling price of gas produced from formations not designated as tight. The tight-sand designation greatly stimulated drilling, and more than 350 wells have been drilled since field discovery in 1977. Because of low permeability, wells must be artificially fractured to obtain economic production. Initial calculated open flow rises from a few tens of MCFGPD before fracturing to an average of approximately 2200 MCFGPD after fracturing. The Abo red beds are subdivided vertically into three informal lithologic units on the Northwest shelf of the Permian Basin: a lower unit of granite wash, a middle unit of mudstone, and an upper unit of interbedded sandstone and mudstone. Gas is produced from sandstones of the upper unit. Primary porosity has been reduced by compaction to values near zero. The average in situ matrix permeability of Abo sandstones is only 0.0067 millidarcies. Such small amounts of matrix porosity and permeability probably do not contribute greatly to production. The Abo wells tap a gas-filled natural fracture system, and mudstones seal the fractured sandstone reservoirs. Because fluvial-deltaic deposits extend almost 100 mi (160 km) north of present production, the area underlain by potential Abo sandstone reservoirs is at least five times greater than the area that is currently productive. 79 references.

  18. Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

    NASA Technical Reports Server (NTRS)

    Marshall, J. R.; Borucki, J.; Bratton, C.

    1999-01-01

    The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

  19. Aeolian Sand Transport in the Planetary Context: Respective Roles of Aerodynamic and Bed-Dilatancy Thresholds

    NASA Astrophysics Data System (ADS)

    Marshall, J. R.; Borucki, J.; Bratton, C.

    1999-09-01

    The traditional view of aeolian sand transport generally estimates flux from the perspective of aerodynamic forces creating the airborne grain population, although it has been recognized that "reptation" causes a significant part of the total airborne flux; reptation involves both ballistic injection of grains into the air stream by the impact of saltating grains as well as the "nudging" of surface grains into a creeping motion. Whilst aerodynamic forces may initiate sand motion, it is proposed here that within a fully-matured grain cloud, flux is actually governed by two thresholds: an aerodynamic threshold, and a bed-dilatancy threshold. It is the latter which controls the reptation population, and its significance increases proportionally with transport energy. Because we only have experience with terrestrial sand transport, extrapolations of aeolian theory to Mars and Venus have adjusted only the aerodynamic factor, taking gravitational forces and atmospheric density as the prime variables in the aerodynamic equations, but neglecting reptation. The basis for our perspective on the importance of reptation and bed dilatancy is a set of experiments that were designed to simulate sand transport across the surface of a martian dune. Using a modified sporting crossbow in which a sand-impelling sabot replaced the bolt-firing mechanism, individual grains of sand were fired at loose sand targets with glancing angles typical of saltation impact; grains were projected at about 80 m/s to simulate velocities commensurate with those predicted for extreme martian aeolian conditions. The sabot impelling method permitted study of individual impacts without the masking effect of bed mobilization encountered in wind-tunnel studies. At these martian impact velocities, grains produced small craters formed by the ejection of several hundred grains from the bed. Unexpectedly, the craters were not elongated, despite glancing impact; the craters were very close to circular in planform

  20. Evaluation of an experimental LiDAR for surveying a shallow, braided, sand-bedded river

    USGS Publications Warehouse

    Kinzel, P.J.; Wright, C.W.; Nelson, J.M.; Burman, A.R.

    2007-01-01

    Reaches of a shallow (<1.0m), braided, sand-bedded river were surveyed in 2002 and 2005 with the National Aeronautics and Space Administration's Experimental Advanced Airborne Research LiDAR (EAARL) and concurrently with conventional survey-grade, real-time kinematic, global positioning system technology. The laser pulses transmitted by the EAARL instrument and the return backscatter waveforms from exposed sand and submerged sand targets in the river were completely digitized and stored for postflight processing. The vertical mapping accuracy of the EAARL was evaluated by comparing the ellipsoidal heights computed from ranging measurements made using an EAARL terrestrial algorithm to nearby (<0.5m apart) ground-truth ellipsoidal heights. After correcting for apparent systematic bias in the surveys, the root mean square error of these heights with the terrestrial algorithm in the 2002 survey was 0.11m for the 26 measurements taken on exposed sand and 0.18m for the 59 measurements taken on submerged sand. In the 2005 survey, the root mean square error was 0.18m for 92 measurements taken on exposed sand and 0.24m for 434 measurements on submerged sand. In submerged areas the waveforms were complicated by reflections from the surface, water column entrained turbidity, and potentially the riverbed. When applied to these waveforms, especially in depths greater than 0.4m, the terrestrial algorithm calculated the range above the riverbed. A bathymetric algorithm has been developed to approximate the position of the riverbed in these convolved waveforms and preliminary results are encouraging. ?? 2007 ASCE.

  1. Fecal Indicator Bacteria Entrainment from Streambed to Water Column: Transport by Unsteady Flow over a Sand Bed.

    PubMed

    Surbeck, Cristiane Q; Douglas Shields, F; Cooper, Alexandra M

    2016-05-01

    Storms cause a substantial increase in the fecal indicator bacteria (FIB) concentrations in stream water as a result of FIB-laden runoff and the release of FIB from stream sediments. Previous work has emphasized the association between FIB and bed sediments finer than sand. The objectives of this work were to elucidate the effect of various velocities on the entrainment of bed-dwelling coliforms in sand-bed streams and to refine methodologies for quantifying sandy streambeds as sources of FIB. Pump-induced hydrographs were created using a stainless steel nonrecirculating flume. Experiments consisted of simulating four storm hydrographs and collecting water samples upstream and downstream of a sand bed at selected intervals. Bed sediment samples were collected before and after each event. The highest concentrations of total coliform and suspended sediments generally occurred in the downstream samples during the rising limb of the hydrographs as a result of entrainment of coliforms and sand from the bed to the water column. There was a first flush effect in the system, as the upper layer of sand was influenced by a rapidly increasing velocity at ∼0.2 m s. Coliforms downstream of the sand bed increased rapidly as velocity exceeded this threshold but then declined even as velocity and discharge continued to increase. This likely reflects the depletion of coliforms as the more densely populated sediment layer was flushed out. There is evidence that streams with sand beds harbor enough FIB that development of total maximum daily loads (TMDLs) should include consideration of them as a source. PMID:27136173

  2. Exploring the Relationship Between Hydrograph Characteristics and the Time Evolution of Sand Bed Morphology

    NASA Astrophysics Data System (ADS)

    Ockelford, A.; Parsons, D. R.; Hardy, R. J.; Ashworth, P. J.; Best, J.

    2015-12-01

    The development of sand bed morphology in response to steady flow is adequately described in most bedform phase diagrams. This includes the prediction of bedform wavelength, height and shape, all important parameters in estimating flow resistance. However, during time-varying flow, such as that experienced during the passage of a flood wave, the implicit assumption that bedform adjustment tracks changes in flow depth and velocity does not hold true due to bedform hysteresis. Consequently, there is a need to understand which characteristics of unsteady flow drive the disequilibrium dynamics between bedform geometry and hydraulic conditions. This paper describes a series of experiments designed to identify the impacts of hydrograph characteristics on the morphodynamic evolution of alluvial dunes. Mobile sand bed (D50 of 450μm) experiments were undertaken in a 16m long, 1.6m wide flume. Sediment was water worked under steady unidirectional flow until equilibrium bed conditions were achieved, after which a hydrograph was applied. At the end of the hydrograph, a period of steady flow was once again run until equilibrium conditions were attained. Hydrograph one consisted of steeply rising (80 minutes) and falling (65 minutes) limbs with hydrograph two characterised by longer rising (170 minutes) and falling (230 minutes) limbs. During the hydrograph discharge was changed in discrete steps. Bed morphology profiles were measured continuously along a 5m by 0.6m, centreline transect using twelve ultrasonic sensors. Three-dimensional flow was measured with a stack of Acoustic Doppler Velocimeters downstream of the transect. Suspended sediment was quantified using a three-frequency set of Acoustic Backscatter Sensors. The impact of these differing hydrograph characteristics are discussed in terms of differences between equilibrium bed morphologies, evolving flow field characteristics and the dynamics of suspended sediment concentrations through the hydrographs.

  3. Pyrolysis of Uinta Basin Oil Sands in fluidized bed and rotary kiln reactors

    SciTech Connect

    Nagpal, S.; Fletcher, J.V.; Hanson, F.V.

    1995-12-31

    A pilot-scale fluidized bed reactor (FBR) was used to pyrolyze the mined and crushed ore from the PR Spring oil sands deposit which is located in the Uinta Basin of Utah. Liquid yields of approximately 80 wt% of the bitumen fed to the reactor were obtained. This compares to 55-70 wt% obtained from smaller laboratory scale fluidized bed reactors and a pilot-scale rotary kiln. The product yields and distributions exhibited no discernable trends with reactor temperature or solids retention time. The liquid products obtained from the pilot-scale fluidized bed reactor were upgraded compared to the bitumen in terms of volatility, viscosity, molecular weight, and metals (Ni and V) content. The nitrogen and sulphur contents of the total liquid products were also reduced relative to the bitumen. A comparison of oil sands pyrolysis yields from a pilot scale FBR and a rotary kiln of the same diameter (15.2 cm) was made. Under similar pyrolysis conditions, the rotary kiln produced a slightly more upgraded product but at lower total liquid yields. Kinetic modeling of the various reactors indicates that the pilot-scale FBR product distributions may be explained using a simplified two-reaction scheme. It is proposed that secondary cracking is suppressed in the large diameter FBR due to elimination of slugging and the superior quality of fluidization in the reactor. More experimental studies with the rotary kiln and an economic evaluation will be required before concluding which reactor is preferred for the thermal recovery process.

  4. Bedform dynamics in a large sand-bedded river using multibeam echo sounding

    NASA Astrophysics Data System (ADS)

    Elliott, C. M.; Jacobson, R. B.; Erwin, S.; Eric, A. B.; DeLonay, A. J.

    2014-12-01

    High-resolution repeat multibeam Echo Sounder (MBES) surveys of the Lower Missouri River in Missouri, USA demonstrate sand bedform movement at a variety of scales over a range of discharges. Understanding dune transport rates and the temporal and spatial variability in sizes across the channel has implications for how sediment transport measurements are made and for understanding the dynamics of habitats utilized by benthic organisms over a range of life stages. Nearly 800 miles of the Lower Missouri River has been altered through channelization and bank stabilization that began in the early 1900's for navigation purposes. Channelization of the Lower Missouri River has created a self-scouring navigation channel with large dunes that migrate downstream over a wide range of discharges. Until the use of MBES surveys on the Missouri River the spatial variability of dune forms in the Missouri River navigation channel was poorly understood. MBES surveys allow for visualization of a range of sand bedforms and repeat measurements demonstrate that dunes are moving over a wide range of discharges on the river. Understanding the spatial variability of dunes and dune movement across the channel and in different channel settings (bends, channel cross-overs, near channel structures) will inform emerging methods in sediment transport measurement that use bedform differencing calculations and provide context for physical bedload sediment sampling on large sand-bedded rivers. Multiple benthic fish species of interest including the endangered pallid sturgeon utilize Missouri River dune fields and adjacent regions for migration, feeding, spawning, early development and dispersal. Surveys using MBES and other hydroacoustic tools provide fisheries biologists with broad new insights into the functionality of bedforms as habitat for critical life stages of large river fish species in the Missouri River, and similar sand-bedded systems.

  5. Suspension of bed material over sand bars in the Lower Mississippi River and its implications for Mississippi delta environmental restoration

    NASA Astrophysics Data System (ADS)

    Ramirez, Michael T.; Allison, Mead A.

    2013-06-01

    specific pathways for sand transport in the lower reaches of large rivers, including the Mississippi, is a key for addressing multiple significant geologic problems, such as delta building and discharge to the oceans, and for environmental restoration efforts in deltaic environments threatened by rising sea levels. Field studies were performed in the Mississippi River 75-100 km upstream of the Gulf of Mexico outlet in 2010-2011 to examine sand transport phenomena in the tidally affected river channel over a range of discharges. Methods included mapping bottom morphology (multibeam sonar), cross-sectional and longitudinal measurements of water column velocity and acoustic backscatter, suspended sediment sampling, and channel-bed sampling. Substantial interaction was observed between the flow conditions in the river (boundary shear stress), channel-bed morphology (size and extent of sandy bedforms), and bed material sand transport (quantity, transport mode, and spatial distribution). A lateral shift was observed in the region of maximum bed material transport from deep to shallow areas of subaqueous sand bars with increasing water discharge. Bed material was transported both in traction and in suspension at these water discharges, and we posit that the downriver flux of sand grains is composed of both locally- and drainage basin-sourced material, with distinct transport pathways and relations to flow conditions. We provide suggestions for the optimal design and operation of planned river diversion projects.

  6. Validating Experimental Bedform Dynamics on Cohesive Sand-Mud Beds in the Dee Estuary

    NASA Astrophysics Data System (ADS)

    Baas, Jaco H.; Baker, Megan; Hope, Julie; Malarkey, Jonathan; Rocha, Renata

    2014-05-01

    Recent laboratory experiments and field measurements have shown that small quantities of cohesive clay, and in particular 'sticky' biological polymers, within a sandy substrate dramatically reduce the development rate of sedimentary bedforms, with major implications for sediment transport rate calculations and process interpretations from the sedimentary record. FURTHER INFORMATION Flow and sediment transport predictions from sedimentary structures found in modern estuaries and within estuarine geological systems are impeded by an almost complete lack of process-based knowledge of the behaviour of natural sediments that consist of mixtures of cohesionless sand and biologically-active cohesive mud. Indeed, existing predictive models are largely based on non-organic cohesionless sands, despite the fact that mud, in pure form or mixed with sand, is the most common sediment on Earth and also the most biologically active interface across a range of Earth-surface environments, including rivers and shallow seas. The multidisciplinary COHBED project uses state-of-the-art laboratory and field technologies to measure the erosional properties of mixed cohesive sediment beds and the formation and stability of sedimentary bedforms on these beds, integrating the key physical and biological processes that govern bed evolution. The development of current ripples on cohesive mixed sediment beds was investigated as a function of physical control on bed cohesion versus biological control on bed cohesion. These investigations included laboratory flume experiments in the Hydrodynamics Laboratory (Bangor University) and field experiments in the Dee estuary (at West Kirby near Liverpool). The flume experiments showed that winnowing of fine-grained cohesive sediment, including biological stabilisers, is an important process affecting the development rate, size and shape of the cohesive bedforms. The ripples developed progressively slower as the kaolin clay fraction in the sandy substrate

  7. Upper Pleistocene turbidite sand beds and chaotic silt beds in the channelized, distal, outer-fan lobes of the Mississippi fan

    SciTech Connect

    Nelson, C.H.; Lee, H.L. ); Twichell, D.C.; Schwab, W.C. ); Kenyon, N.H. )

    1992-08-01

    Cores from a Mississippi outer-fan depositional lobe demonstrate that sublobes at the distal edge contain a complex local network of channelized-turbidite beds of graded sand and debris-flow beds of chaotic silt. Off-lobe basin plains lack siliciclastic coarse-grained beds. The basin-plain mud facies exhibit low acoustic backscatter on SeaMARC IA sidescan sonar images, whereas high acoustic backscatter is characteristic of the lobe sand and silt facies. The depth of the first sand-silt layer correlates with relative backscatter intensity and stratigraphic age of the distal sublobes (i.e., shallowest sand = highest backscatter and youngest sublobe). The high proportion (> 50%) of chaotic silt compared to graded sand in the distal, outer-fan sublobes may be related to the unstable, muddy, canyon-wall source areas of the extensive Mississippi delta-fed basin slope. A predominance of chaotic silt in cores or outcrops from outer-fan lobes thus may predict similar settings for ancient fans.

  8. Improved statistical characterization of particle-size distributions in sand-bedded rivers

    NASA Astrophysics Data System (ADS)

    Huzurbazar, S.; Hajek, E.; Lynds, R.; Heller, P.; Mohrig, D.

    2007-12-01

    Measured particle-size distributions are commonly reduced to one characteristic value (e.g., median grain diameter) that is used in sediment transport modeling. While convenient, this approach cannot be used to explore the potential influence grain-size distributions may have on sediment transport and deposition. We statistically characterize grain-size distributions in samples of bed-material load, suspended load, and slackwater deposits from the sand-bedded Calamus, North Loup, and Niobrara rivers (Nebraska, USA). Transported sediment samples are best modeled with log-hyperbolic distributions, and slackwater deposits are bi- or multi-modal mixtures. Despite large overlaps in the grain sizes of bed-material-load and suspended-load samples, estimated parameters of fitted log-hyperbolic distributions show consistent differences between these samples across all rivers. Bed-material load samples have higher modes and positive (coarse-grained) asymmetry, whereas suspended load samples have lower modes and weaker asymmetry. In all three rivers, slackwater deposits contain the entire range of grain sizes present in suspended load, but with a significant component of very fine-grained (< 0.02 mm) material that is undetectable in suspended sediment samples. This suggests some degree of fractionated deposition of suspended sediment in areas of near-zero flow velocities. Ultimately, in order to explore the effect of grain-size distributions on sediment transport and river processes, these modeled distributions can be incorporated into a Bayesian hierarchical framework where standard sediment transport equations can be modeled in relation to probability-density particle curves for grain size.

  9. Thermal origin of continental red beds in SE China: An experiment study

    NASA Astrophysics Data System (ADS)

    Jiang, Lianting; Chen, Guoneng; Grapes, Rodney; Peng, Zhuolun

    2015-04-01

    The origin of continental red beds in SE China is the result of high diagenetic temperatures, rather than an arid climate during their deposition. Here we present results from an experimental study where black mud was heated to demonstrate the formation of red beds. Diffuse reflectance spectroscopy (DRS) of heated samples enables determination of the relative proportion of goethite and hematite. Iron in black mud is predominantly in the form of goethite that has an initial dehydration temperature of ca.150 °C. Increasing temperature or prolonged heating time is accompanied by decreasing goethite and organic content, increasing hematite and red colouration. Heat provided to subsiding red bed basins is supplied by cooling of an intracrustal granitic magma layer. The thermal model can explain vertical colour, temperature, redox and mineral zonation in red bed sequences, from red (hematite-bearing), through green-yellow (Cu, Zn, V sulphide mineralization) to grey-black (hydrocarbon, halite-bearing) sediments. The model can also be used to help prospect for hydrocarbon and halite deposits in the SE China red bed basins.

  10. IDENTIFICATION OF APPROPRIATE QUALIFICATION TESTING AND END-OF-LIFE WASTE STORAGE CONSIDERATIONS FOR DEEP BED SAND FILTERS

    SciTech Connect

    Matthews, K.

    2010-06-02

    Deep bed sand (DBS) filters have filtered radioactive particulates at two United States Department of Energy (DOE) sites since 1948. Some early DBS filters experienced issues with chemical attack on support tiles, requiring significant repairs. Designs of DBS filters constructed since 1970 paid greater attention to chemical compatibility, resulting in decades of reliable performance since 1975.

  11. Interactions among riparian vegetation, flow and sediment in a sand bed river: Implications for restoration

    NASA Astrophysics Data System (ADS)

    Gorrick, S.; Rodriguez, J. F.

    2012-12-01

    We present a set of laboratory experiments based on field site conditions on a sand bed stream in Australia that is currently being restored by reintroduction of lost riparian vegetation. Three experiments were conducted in order to investigate both the local and reach-scale impacts of bank vegetation on flow and sediment dynamics. The first experiment contained no bank vegetation and was similar to the original state of the stream. The second experiment placed a series of three inline vegetation patches along the outer bank, simulating the design of the ongoing restoration works. The third experiment used a continuous strip of vegetation along the outer bank, which represents a more traditional restoration technique. In each experiment flow and sediment measurements were carried out, including ADV velocities, water surface elevations, suspended and bedload sediment transport rates and bed evolution. The analysis focussed on the quantification of flow and sediment fluxes and the resulting stream morphology, which responded to the presence of vegetation and to changes in stream curvature and width. Both arrangements of vegetation provided effective bank protection; however the patches used less vegetation and were thus more efficient. The reach-scale effects included changes to stream curvature, stream width and redistribution of sediments, all of which have important implications for management. Recommendations also include the selection of optimum patch size and spacing as well as plant composition.

  12. Bedform development in mixed sand-mud: The contrasting role of cohesive forces in flow and bed

    NASA Astrophysics Data System (ADS)

    Baas, Jaco H.; Davies, Alan G.; Malarkey, Jonathan

    2013-01-01

    The majority of subaqueous sediment on Earth consists of mixtures of cohesive clay and cohesionless sand and silt, but the role of cohesion on the development and stability of sedimentary bedforms is poorly understood. The results of new laboratory flume experiments on bedform development in cohesive, mixed sand-mud beds are compared with the results of previous experiments in which cohesive forces in high concentration clay flows dominated bedform development. Even though both series of mixed sand-mud experiments were conducted at similar flow velocities, the textural and structural properties of the bedforms were sufficiently different to permit the designation of key criteria for identifying bedform generation under cohesive flows against bedform generation on cohesive substrates. These criteria are essential for improving bedform size predictions in sediment transport modelling in modern sedimentary environments and for the reconstruction of depositional processes in the geological record. The current ripples developing on the cohesive, mixed sand-mud beds, with bed mud fractions of up to 18%, were significantly smaller than equivalent bedforms in noncohesive sand. Moreover, the bedform height showed a stronger inversely proportional relationship with initial bed mud fraction than the bedform wavelength. This is in contrast with the bedforms developing under the cohesive clay flows, which tend to increase in size with increasing suspended clay concentration until the flow turbulence is fully suppressed. Selective removal of clay from the mixed beds, i.e., clay winnowing, was found to be an important process, with 82-100% clay entrained into suspension after 2 h of bedform development. This winnowing process led to the development of a sand-rich armouring layer. This armouring layer is inferred to have protected the underlying mixed sand-mud from prolonged erosion, and in conjunction with strong cohesive forces in the bed may have caused the smaller size of the

  13. Autogenic variability and dynamic steady-state in sand-bedded rivers

    NASA Astrophysics Data System (ADS)

    Jerolmack, D. J.; McElroy, B.; Mohrig, D.

    2004-12-01

    In sand-bedded rivers, the local physics of sediment transport produces spatially varying topography that evolves unpredictably in time, even when the structure of the stream-bed varies little in a statistical sense. Understanding autogenic adjustments within trains of bedforms under conditions of steady and uniform flow is necessary before we can predict the response of channel morphology to changes in flow conditions, e.g. the stage-discharge relationship. Also, dunes may coalesce to form bars, which are capable of laterally deflecting flow and ultimately modifying the path and shape of a channel. Bedforms are the link between sediment transport and channel morphology in sandy rivers, and their collective interactions maintain a dynamic steady-state on the river bottom. We document the evolution of fields of dunes under steady flow in the N. Loup River, NE, using topographic maps generated from low-altitude aerial photography. The distributions of bedform height, length and migration rate are broad (coefficient of variation 0.5 for each), but remain stationary in time. Individual bedforms, however, undergo substantial deformation during migration, through interactions with neighboring bedforms and the associated spatially varying sediment flux. Cross-correlation techniques show that the spatial/temporal correlation coefficient of the sediment-fluid interface decays exponentially with migration distance and time. Hence, the dunes themselves are inherently unstable objects and become unrecognizable from their original form after migrating a few wavelengths, corresponding here to a distance of 2 m and a time of 1 hour. If bedload is the dominant style of sediment transport, then sediment flux may be treated as responding instantaneously to the flow field. We build a simple mathematical model in which instantaneous sediment flux is computed locally from a combination of bed elevation and slope, and we deduce the general form of a surface evolution equation for

  14. Numerical Modeling of Bifurcation Evolution in a Sand-bed Braided River

    NASA Astrophysics Data System (ADS)

    De Haas, T.; Schuurman, F.; Kleinhans, M. G.

    2012-12-01

    River bifurcations are key units in a braided river. Although simple bifurcations are well understood and can be analyzed by 1D models (e.g. Bolla Pittaluga et al., 2003 and Kleinhans et al., 2008), predicting the stability and dynamics of multiple interacting bifurcations in a braided river with migrating bars requires understanding of the interaction between braid bars, channel network and bifurcations, in particular the upstream curvature and downstream backwater effects. Our objective is to understand the evolution of bifurcations at migrating bars in a braided river and the effects on bar evolution. We used the 3D numerical morphodynamic model Delft3D to produce a dynamically braiding sand bed river. This model solves the 3D-flow and computes sediment transport and bed level change accounting for effects of transverse bed slope. It includes a simple bank erosion model to reactivate emerged areas. The morphology of mid-channel bars produced by the model was analyzed and the partitioning of water and sediment over the bifurcating channels are compared with a 1D model concept. Next, the evolution of bars is linked to that of the bifurcations, in order to infer relations between bar morphology and bifurcation evolution. We find that upstream bar dynamics have a major effect on the stability of bifurcations. Migration and elongation of bars can close the upstream entrance of a bifurcation channel, independent of the stability of the bifurcation. Moreover, bifurcation angle and upstream curvature can be affected by upstream bar migration and elongation, which steers flow and sediment partitioning at the bifurcation. At the same time, the partitioning of water and sediment over a bifurcation affects bar shape. Sediment eroded at one of the bar sides just downstream of the bifurcation deposits downstream of the braid bar in the form of tail bars. Hence bar shape as observable on imagery contains useful information about the evolution of the upstream bifurcation and

  15. Development and design of a fluidized bed/upflow sand filter configuration for use in recirculating aquaculture systems

    SciTech Connect

    Burden, D.G.

    1988-01-01

    A fluidized bed/upflow sand filter configuration, was developed and designed for utilization in recirculating aquaculture system, specifically the soft-shell crab and soft-shell crawfish industries. These filters were selected and designed because of their ability to withstand clogging and still maintain high levels of water quality for aquaculture production. The effectiveness of sand grain size was used to evaluate fluidized bed filter performance with filter loadings ranging from 16 to 1285 pounds of crawfish per cubic foot of filter sand. A coarse sand grain size was recommended as a filter media because of it's ability to shear excessive biofilm growth from the and, thus prohibiting clogging from occurring within the filter bed. The fluidized bed/upflow sand filter combination was evaluated in terms of nitrification and oxygen consumption when used with a recirculating crab shedding system. The filter combination's carrying capacity (700 crabs per cubic foot of sand media) exceeded that observed with the submerged rock filter by more than 20 times and was largely explained by the filter's solids removal ability which significantly reduced the filter's oxygen loading rate (OLR). Nitrification rates with the filter combination were extremely high as total ammonia and nitrite levels remained below 1.0 mg-N/l. Verification of a volumetric loading criteria (150 pounds per cubic foot) for this filter combination was further established with performance data obtained from a commercial soft-shell crawfish facility. Water quality monitoring results indicated that the filters maintained total ammonia and nitrite levels below 1.0 mg-N/l under typical operating conditions. Shock loading, pH control, and over-feeding, rather than filter capacity, dominated water quality fluctuations, thereby indicating that the loading criteria was sufficient for commercial operation.

  16. RETRACTED: The influence of sand bed temperature on lift-off and falling parameters in windblown sand flux

    NASA Astrophysics Data System (ADS)

    Bo, Tian-Li; Duan, Shao-Zhen; Zheng, Xiao-Jing; Liang, Yi-Rui

    2014-01-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy) This article has been retracted at the request of the Editors-in-Chief. This article also contains significant similarity with parts of text, written by the same author(s), that have appeared in Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, The influence of sand diameter and wind velocity on sand particle lift-off and incident angles in the windblown sand flux, Sedimentary Geology, Volume 290, 15 May 2013, Pages 149-156. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, The influence of wind velocity and sand grain diameter on the falling velocities of sand particles, Powder Technology, Volume 241, June 2013, Pages 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Analysis of sand particles' lift-off and incident velocities in wind-blown sand flux, Acta Mechanica Sinica, April 2013, Volume 29, Issue 2, pp 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Influence of sand grain diameter and wind velocity on lift-off velocities of sand particles, The European Physical Journal E, May 2013, 36:50. The "slicing" of research that would form one meaningful paper into several different papers represents an abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

  17. Scaling of Sediment Dynamics in a Reach-Scale Laboratory Model of a Sand-Bed Stream with Riparian Vegetation

    NASA Astrophysics Data System (ADS)

    Gorrick, S.; Rodriguez, J. F.

    2011-12-01

    A movable bed physical model was designed in a laboratory flume to simulate both bed and suspended load transport in a mildly sinuous sand-bed stream. Model simulations investigated the impact of different vegetation arrangements along the outer bank to evaluate rehabilitation options. Preserving similitude in the 1:16 laboratory model was very important. In this presentation the scaling approach, as well as the successes and challenges of the strategy are outlined. Firstly a near-bankfull flow event was chosen for laboratory simulation. In nature, bankfull events at the field site deposit new in-channel features but cause only small amounts of bank erosion. Thus the fixed banks in the model were not a drastic simplification. Next, and as in other studies, the flow velocity and turbulence measurements were collected in separate fixed bed experiments. The scaling of flow in these experiments was simply maintained by matching the Froude number and roughness levels. The subsequent movable bed experiments were then conducted under similar hydrodynamic conditions. In nature, the sand-bed stream is fairly typical; in high flows most sediment transport occurs in suspension and migrating dunes cover the bed. To achieve similar dynamics in the model equivalent values of the dimensionless bed shear stress and the particle Reynolds number were important. Close values of the two dimensionless numbers were achieved with lightweight sediments (R=0.3) including coal and apricot pips with a particle size distribution similar to that of the field site. Overall the moveable bed experiments were able to replicate the dominant sediment dynamics present in the stream during a bankfull flow and yielded relevant information for the analysis of the effects of riparian vegetation. There was a potential conflict in the strategy, in that grain roughness was exaggerated with respect to nature. The advantage of this strategy is that although grain roughness is exaggerated, the similarity of

  18. Sedimentation and petrology of Fanshawe sand, Red Oak field, Arkoma basin, Oklahoma

    SciTech Connect

    Pittman, E.D.; Wray, L.L. )

    1989-08-01

    The Fanshawe sand, a very fine to fine-grained lithic sandstone, probably formed in moderate to deep water downslope from a delta system to the east. Sediment-laden discharge flowed from east to west as channelized, bottom-hugging density currents. Deposition of the Fanshawe sand seems to have been restricted to a west-southwest-trending zone approximately 2 mi wide on the north side of Red Oak field. The sand is a composite of a series of narrow, shifting, meandering submarine channels that often are stacked. Stratigraphic cross sections show extreme variability, even along depositional strike, and individual channels typically are narrower than the distance between development wells. Reservoir quality is enhanced where these narrow channels coalesce horizontally and vertically. Net sand thickness ranges from 36 to 180 ft with associated reserves of up to 14 bcf/well. Completion rates can reach 8 mmcf/day with decline rates averaging 6%. Preliminary results of an increased density drilling program further substantiate the narrow, sinuous nature of these fan channels. Air drilling causes severe hole washouts, making net pay determinations questionable. But by mapping overall net sand trends, it is possible to high-grade drilling prospects. Prediction of porosity development, however, remains difficult. Porosity in the Fanshawe is due to (1) precipitation of pore-lining chlorite, which retarded quartz cementation by blocking potential nucleation sites on detrital quartz grains and preserved primary porosity, and (2) dissolution of feldspars and lithic fragments. The better reservoir rock has both porosity types. Where pore-lining chlorite was absent, thin, or discontinuous, quartz overgrowths developed and intergranular porosity decreased. This created a pore geometry consisting of poorly interconnected, disseminated, intragranular/moldic, dissolution pores and low permeability.

  19. [Ectoparasites. Part 2: Bed bugs, Demodex, sand fleas and cutaneous larva migrans].

    PubMed

    Nenoff, P; Handrick, W; Krüger, C; Herrmann, J; Schmoranzer, B; Paasch, U

    2009-09-01

    Ectoparasites or epidermal parasites include a very heterogenous group of infections of the outer layers of the skin. Worldwide the most common are scabies, lice, tungiasis, and hookworm-induced cutaneous larva migrans. In recent years, bed bug infestations in hotels or vacation homes seem to have become more frequent. Demodex folliculorum and Demodex brevis are found in the facial and scalp hair follicles in 95% of individuals. Classic Demodex folliculitis is often overlooked in differential diagnostic considerations. This inflammatory sebaceous gland disease as well as Demodex blepharitis both provide a diagnostic and therapeutic challenge. Permethrin can be used topically against demodicosis. Vacationers who go barefoot on beaches in tropical Africa, South America and subtropical Asia risk infestations from female sand fleas. The lesions can be curetted or removed with a punch biopsy, then treated with antiseptics or even systemic antibiotics if a secondary infection develops. Cutaneous larva migrans is one of the most common imported ectoparasite infections from the tropics. Topical treatment measures include thiabendazole or cryotherapy. If the infestation is severe, systemic antihelminthics or ivermectin can be employed. PMID:19701614

  20. Experimental Observations About The Behavior of The Sheet Flow On Sand Bed Streams and The Reversal Gradation Effect.

    NASA Astrophysics Data System (ADS)

    Bateman, A.; Aguilar, C.; Roquer, R.; Andreatta, A.; Velasco, D.

    In our land, Catalonia, exists a lot of torrential ephemeral streams. Which are char- acterized by a great floods during typical convective storms. Sediment transport rates are very important in this gravel/sand torrent. Usually, near the cities, they show a 2- 3% slope bed profile. Engineering works or actuations have to deal with this kind of dynamic systems. The stabilization of this torrents is one of the aim of our research at the Polytechnic University of Catalonia (Hydraulic, Marine and environmental De- partment). Typical experiments in a hydraulic flume was normally used to observe the behavior of stabilization structures. The first step in the research is to know the general evolution of the bed profile. Agradation and degradation experiments in a laboratory flume of 20 m length was car- ried out to study the behavior of the steady and unsteady flow with sediment transport. The hydraulic regime of the experiments was set to be supercritical flat bed; sand flow rates about 300gr/s which gives near a 2% equilibrium slope. The most interesting results of those experiments was the reversal gradation of the sand sizes measured along the flume in the final steady state. This kind of effect was reported by Luca Solari and Gary Parker 2000. A 1-D numerical model to solve the Exner and Saint_Venant implicit system of equation were used to compare the evolu- tion of the different experiments. The sheet sand flow produces a great resistance to flow, the experiments shows the influence exhorted by the sand discharge in the flow resistance factor.

  1. Influence of bank materials, bed sediment, and riparian vegetation on channel form along a gravel-to-sand transition reach of the Upper Tualatin River, Oregon, USA

    NASA Astrophysics Data System (ADS)

    Labbe, Jim M.; Hadley, Keith S.; Schipper, Aafke M.; Leuven, Rob S. E. W.; Gardiner, Christine Perala

    2011-02-01

    We examined the role of bed sediment size, bank materials, riparian vegetation, and discharge on channel form along a 10-km reach of the Upper Tualatin River, encompassing both gravel and sand-bed reaches. Statistical correlations and analyses of downstream changes of channel morphology reveal that bank materials and bed sediment are the dominant controls on channel cross section form. A rapid downstream reduction in bed sediment size in the gravel-bed channel is followed by an abrupt transition to a narrower, deeper, and less sinuous sand-bed channel with more cohesive bank materials. The simultaneous reductions in channel slope, bed sediment size, and width-to-depth ratio indicate the channel crosses a geomorphic threshold to maintain continuity in sediment transport. This gravel-to-sand transition and associated change in channel form are induced by a break in valley slope and an increase in bank resistance from cohesive bank materials. Bank materials, measured as the average percent silt and clay in banks, are a primary influence on channel form within both subreaches but demonstrate a greater influence on channel width and vertical stability in the gravel-bed channel and on channel depth and lateral stability in the sand-bed channel. Riparian vegetation at current densities and compositions is not a significant control on contemporary channel cross section form and may be responding to the bank and channel stability provided by cohesive bank materials in the laterally dynamic gravel-bed channel.

  2. Contrasting red bed diagenesis: the southern and northern margin of the Central European Basin

    NASA Astrophysics Data System (ADS)

    Schöner, Robert; Gaupp, Reinhard

    2005-12-01

    We compare the diagenetic evolution of deeply buried Rotliegend (Permian) red bed sandstones at the southern and northern margin of the Central European Basin (CEB) in Germany. Main target is to evaluate the influence of maturation products from hydrocarbon (HC) source rocks during red bed diagenesis. At the southern margin of the CEB, thick coal-bearing Carboniferous source rocks are omnipresent beneath the Rotliegend. They contain dominantly gas-prone terrigenous organic material and some oil source rocks. Hydrocarbons were generated from Late Carboniferous onwards throughout most of basin subsidence. At the northern margin of the CEB, source rocks are almost absent due to deep erosion of Carboniferous rocks and a low TOC of local Lower Carboniferous relics. Early diagenetic processes are comparable at both basin margins. Significant differences in burial diagenetic evolution are spatially correlated to the occurrence of hydrocarbon source rocks. Burial diagenesis at the southern margin of the CEB is characterized especially by bleaching of red beds, major dissolution events, pervasive illite formation, impregnation of pore surfaces with bitumen, and formation of late Fe-rich cements. Almost none of these features were detected at the northern basin margin. Instead, relatively early cements are preserved down to maximum burial depths. This suggests that major diagenetic mineral reactions in deeply buried red bed sandstones are controlled by the presence or absence of maturing hydrocarbon source rocks.

  3. The mobility and distribution of heavy metals during the formation of first cycle red beds.

    USGS Publications Warehouse

    Zielinski, R.A.; Bloch, S.; Walker, T.R.

    1983-01-01

    Analysis of the heavy metal content in a Holocene-Pliocene red bed sequence near San Felipe in N Baja California, Mexico, has yielded new information on the mobility and distribution of these metals during ageing of iron oxyhydroxides from the amorphous to the crystalline state. Whole-rock samples (27) and a series of successive leachates were analysed for V, Al, Cr, Mn, Fe, Co, Ni, Cu and Zn by ICP spectrometry and for U by a delayed neutron technique. These data are supported by a variety of other mineralogical and petrographical observations. The results indicate that the metal content of the samples is predominantly inherited from the constituent detrital minerals. Reddening of the whole-rock samples does not promote major open-system migration of the heavy metals; rather, contained metals redistribute themselves on an intergranular scale, moving from detrital mineral hosts to the secondary iron oxides. The amount of secondary iron oxides and the fraction of whole-rock metals associated with these oxides increase during red-bed development. In addition, the abundance of well- crystallized iron oxides increases during this period. Differences in the leaching efficiency for various metals are related to differences in metal site distribution and intergranular permeability. Inferred conditions for rapid vs limited removal of metals from red beds are summarized. It is suggested that developed red beds which are well flushed by suitable pore fluids may be sources of significant quantities of heavy metals. -J.E.S.

  4. The accumulation and decay of near-bed suspended sand concentration due to waves and wave groups

    NASA Astrophysics Data System (ADS)

    Vincent, Christopher E.; Hanes, Daniel M.

    2002-09-01

    High resolution acoustic measurements were made of suspended sand and bedform dimensions caused by prototype-scale waves, both regular and in groups, over a mobile sand bed, in a very large wave channel. The changes in wave height at the beginning of the regular waves and within wave groups provides an opportunity to examine the time lag in the response of the sediment. For regular waves suspended sand concentrations lagged the forcing waves with the lag increasing with distance from the seabed. Typically, near-bed (1-2 cm) concentrations reached an equilibrium one to two wave-periods after the waves themselves had reached their steady height while at elevations of 10-15 cm the lag was longer. This lag was interpreted as due to the continual injection of turbulence into the water column from vortex processes associated with the oscillatory wave boundary layer over bedforms. A similar pattern was seen for wave groups, with the sand concentration near the bed lagging by the waves by one to two wave-periods and increasing with distance from the bed. Despite the controlled nature of these prototype-scale suspension experiments, with detailed measurements of bedforms and attempts to achieve 'equilibrium' bedforms, considerable variability (±30%) in the suspended sand concentration occurred between 'similar' forcing conditions, both at a wave-to-wave level and on the scale of groups and longer. The results suggest that considerable variability (a factor of two or more) should be expected in the suspension due to turbulence produced from wave boundary layers in natural environments, where bedforms are frequently continually evolving as the waves change their height, period and direction. A simple wave-average suspended-load model is used to describe the major temporal features of the suspension and to quantify the lag of the suspended sediment in relation to the waves and wave groups. Quantification of the lag is essential for assessing the transport of sand at infra

  5. Palaeogeography of Late Triassic red-beds in Singapore and the Indosinian Orogeny

    NASA Astrophysics Data System (ADS)

    Oliver, Grahame; Prave, Anthony

    2013-10-01

    A red-bed facies of the Upper Triassic Jurong Formation has been logged on Sentosa Island, Singapore. An overall coarsening and thickening-upward pattern is well developed. The lower part of the section is dominated by purple-red, massive to finely laminated illite-smectite-kaolin-rich mudstones containing thin, discontinuous lenses of fine sandstone marked by low-angle lamination and small ripples. One dinosaur-like foot print has been discovered in a loose block of red mudstone. It is concluded that this is a lacustrine sequence and it is proposed to name the lake, Lake Sentosa. The upper part of the sequence consists of flat-laminated to trough cross-bedded medium-grained sandstone and granule to cobble conglomerates alternating with purple-red mudstone. The mudstone-sandstone packages are arranged in decametre-scale coarsening-upward cycles. The channelling and decimetre-scale cross-bedding characterising the sandstone and conglomeratic beds is evidence for deposition by flashy fluvial flood processes, possibly feeding into the lake as a fresh water delta. One possible dinosaur trackway in granule size conglomerate has been located. Detrital zircon U-Pb ages vary from 2.7 Ba to 209 Ma with significant populations at ˜245 Ma and 220 Ma. These ages throw light on the timing of the Indosinian Orogeny. The molasse red-beds of the Jurong Formation were deposited in a half graben formed in the hangingwall of the Bukit Timah Fault when central Peninsular Malaysia went into extension following the climax of the Indosinian Orogeny in the Late Triassic.

  6. Evaluation of ADCP apparent bed load velocity in a large sand-bed river: Moving versus stationary boat conditions

    USGS Publications Warehouse

    Jamieson, E.C.; Rennie, C.D.; Jacobson, R.B.; Townsend, R.D.

    2011-01-01

    Detailed mapping of bathymetry and apparent bed load velocity using a boat-mounted acoustic Doppler current profiler (ADCP) was carried out along a 388-m section of the lower Missouri River near Columbia, Missouri. Sampling transects (moving boat) were completed at 5- and 20-m spacing along the study section. Stationary (fixed-boat) measurements were made by maintaining constant boat position over a target point where the position of the boat did not deviate more than 3 m in any direction. For each transect and stationary measurement, apparent bed load velocity (vb) was estimated using ADCP bottom tracking data and high precision real-time kinematic (RTK) global positioning system (GPS). The principal objectives of this research are to (1) determine whether boat motion introduces a bias in apparent bed load velocity measurements; and (2) evaluate the reliability of ADCP bed velocity measurements for a range of sediment transport environments. Results indicate that both high transport (vb>0.6 m/s) and moving-boat conditions (for both high and low transport environments) increase the relative variability in estimates of mean bed velocity. Despite this, the spatially dense single-transect measurements were capable of producing detailed bed velocity maps that correspond closely with the expected pattern of sediment transport over large dunes. ?? 2011 American Society of Civil Engineers.

  7. Vertebrate biochronology of late Triassic red beds in New Mexico

    SciTech Connect

    Hunt, A.P. )

    1989-09-01

    Four vertebrate biochrons can be recognized in Late Triassic strata of New Mexico: (A) Metoposaurus-Rutiodon-Desmatosuchus-Calyptosuchus-Placerias occurs in the Los Esteros member of the Santa Rosa formation near Lamy and is less well known from the lower Petrified Forest Member of the Chinle Formation near San Ysidro, at Mesa del Oro, near Fort Wingate, at Ojo Huelos, and in the Joyita hills. (B) Anaschisma-Belodon-Typothorax-Desmatosuchus-Paratypothorax occurs in the lower Bull Canyon formation in Bull Canyon and near Tucumcari, in the Trujillo Formation near Tucumcari, and possibly in the Travesser Formation of the Dry Cimarron valley, the Petrified Forest Member near Carthage, and the Garita Creek formation near Lamy and Conchas Lake. (C) Anaschisma-Belodon-Typothorax occurs in the upper Bull Canyon formation in Bull Canyon, in the upper Petrified Forest Member near San Ysidro, at Ghost Ranch, near Albuquerque (Correo Sandstone Bed), and possibly in the Sloan Canyon Formation of the Dry Cimarron valley. (D) Anaschisma-new phytosaur, cf. Typothorax-new sphenosuchian, occurs in the Redonda Formation near Tucumcari. The biochronologic ranges of significant vertebrate taxa within New Mexico follow: metoposaurs - Metoposaurus (A-B ), Anaschisma (B-D); phytosuars - Rutiodon (A), Belodon (B-C), new taxon (D); aetosaurs - Calyptosuchus (A), Desmatosuchus (A-B), Paratypothorax (B), Typothorax (B-D ); rauisuchians - Postosuchus (A-B), Chatterjeea (B-C); sphenosuchians - new taxon 1 (A), Hesperosuchus (B), new taxon 2 (D); dinosaurs - ornithischians (B), Coelophysis (C), other theropods (B-C); therapsids - Placerias (A), Pseudotriconodon (C). Biochron A may be Carnian in age, whereas biochrons B-D are probably early to middle ( ) Norian.

  8. Spatial patterns of scour and fill in dryland sand bed streams 1843

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spatial patterns of scour and fill in two dryland ephemeral stream channels with sandy bed material have been measured with dense arrays of scour chains. Although the depth and areal extent of bed activity increased with discharge, active bed reworking at particular locations within the reaches res...

  9. Application of CFD modeling to hydrodynamics of CycloBio fluidized sand bed in recirculating aquaculture systems

    NASA Astrophysics Data System (ADS)

    Liu, Yao; Song, Xiefa; Liang, Zhenlin; Peng, Lei

    2013-11-01

    To improve the efficiency of a CycloBio fluidized sand bed (CB FSB) in removal of dissolved wastes in recirculating aquaculture systems, the hydrodynamics of solid-liquid flow was investigated using computational fluid dynamics (CFD) modeling tools. The dynamic characteristics of silica sand within the CB FSB were determined using three-dimensional, unsteady-state simulations with the granular Eulerian multiphase approach and the RNG k-ɛ turbulence model, and the simulation results were validated using available lab-scale measurements. The bed expansion of CB FSB increased with the increase in water inflow rate in numerical simulations. Upon validation, the simulation involving 0.55 mm particles, the Gidaspow correlation for drag coefficient model and the Syamlal-O'Brien correlation for kinetic granular viscosity showed the closest match to the experimental results. The volume fraction of numerical simulations peaked as the wall was approached. The hydrodynamics of a pilot-scale CB FSB was simulated in order to predict the range of water flow to avoid the silica sand overflowing. The numerical simulations were in agreement with the experimental results qualitatively and quantitatively, and thus can be used to study the hydrodynamics of solid-liquid multiphase flow in CB FSB, which is of importance to the design, optimization, and amplification of CB FSBs.

  10. Cold test with a benchtop set-up for fluidized bed reactor using quartz sand to simulate gasification of coal cokes by concentrated solar radiation

    NASA Astrophysics Data System (ADS)

    Gokon, Nobuyuki; Tanabe, Tomoaki; Shimizu, Tadaaki; Kodama, Tatsuya

    2016-05-01

    The impacts of internal circulation of a mixture of coal-coke particles and quartz sand on the fluidization state in a fluidized bed reactor are investigated by a cold test with a benchtop set-up in order to design 10-30 kWth scale prototype windowed fluidized-bed reactor. Firstly, a basic relationship between pressure loss of inlet gas and gas velocity was experimentally examined using quartz sand with different particle sizes by a small-scale quartz tube with a distributor at ambient pressure and temperature. Based on the results, an appropriate particle range of quartz sand and layer height/layer diameter ratio (L/D ratio) was determined for a design of the fluidized bed reactor. Secondly, a windowed reactor mock-up was designed and fabricated for solar coke gasification using quartz sand as a bed material. The pressure loss between the inlet and outlet gases was examined, and descending cokes and sand particles on the sidewall of the reactor was observed in the reactor mock-up. The moving velocity and distance of descending particles/sands from the top to bottom of fluidized bed were measured by the visual observation of the colored tracer particles on outside wall of the reactor.

  11. Synthesis and characterization of black, red and yellow nanoparticles pigments from the iron sand

    SciTech Connect

    Mufti, Nandang Atma, T. Fuad, A.; Sutadji, E.

    2014-09-25

    The aim of this research is to synthesize nanoparticles of black pigment of Magnetite (Fe{sub 3}O{sub 4}), red pigment of hematite (α-Fe{sub 2}O{sub 3}), and yellow pigment of ghoetite (α-FeOOH) from the iron sand. The black pigment of Fe{sub 3}O{sub 4} and the yellow pigment α-FeOOH nanoparticles were synthesized by coprecipitation method with variation of pH. Whereas, the red pigment Fe{sub 2}O{sub 3} was synthesized by sintering Fe{sub 3}O{sub 4} nanoparticles at temperature between 400 °C and 700 7°C for 1 hour. All the pigments has been characterized using X-ray diffraction and SEM. The XRD results shown that the particle size of the black pigmen Fe{sub 3}O{sub 4}, red pigment Fe{sub 3}O{sub 4} and yellow pigment α-FeOOH are around 12, 32, and 30 nm respectively. The particle size of Fe{sub 2}O{sub 3} nanoparticles increase by increasing sintering temperature from 32 nm at 400 °C to 39 nm at 700 °C. For yellow pigment of α-FeOOH, the particle size increase by increasing pH from 30,54 nm at pH 4 to 48,60 nm at pH 7. The SEM results shown that the morphologies of black, yellow and red pigments are aglomarated.

  12. Chute Formation and Iterative Adjustment in Large, Sand-Bed Meandering Rivers

    NASA Astrophysics Data System (ADS)

    Grenfell, M. C.; Aalto, R. E.; Nicholas, A.

    2011-12-01

    The meandering-braided continuum is a planform manifestation of excess available river energy; a balance between the energy of flow (commonly quantified as unit steam power or shear stress), and dynamic resistance due to bed material calibre and bank strength. Single-thread meandering rivers plot in part of the continuum defined by low excess available river energy, while braided rivers plot in part of the continuum defined by high excess available river energy. Planform patterns that are transitional between single-thread meandering and braided occur where chute channel formation is prolific. In this presentation we will elucidate the morphodynamic implications of chute formation for sinuosity and planform pattern in large, sand-bed meandering rivers. We draw on the results of recent research that applied binary logistic regression analysis to determine the possibility of predicting chute initiation based on attributes of meander bend character and dynamics (Grenfell et al., accepted, ESP&L). Regression models developed for the Strickland River, Papua New Guinea (54 bends), the lower Paraguay River, Paraguay/Argentina (45 bends), and the Beni River, Bolivia (114 bends), revealed that the probability of chute initiation at a meander bend is a function of the bend extension rate (the rate at which a bend elongates). Image analyses of all rivers and field observations from the Strickland suggest that the majority of chute channels form during scroll-slough development. Rapid extension is shown to favour chute initiation by breaking the continuity of point bar deposition and vegetation encroachment at the inner bank, resulting in widely-spaced scrolls with intervening sloughs that are positively aligned with primary over-bar flow. The rivers plot in order of increasing chute activity on an empirical meandering-braided pattern continuum (Kleinhans and van den Berg, 2011, ESP&L 36) defined by potential specific stream power (ωpv) and bedload calibre (D50). Increasing

  13. Soft-hydrothermal processing of red cedar bedding reduces its induction of cytochrome P450 in mouse liver.

    PubMed

    Li, Z; Okano, S; Yoshinari, K; Miyamoto, T; Yamazoe, Y; Shinya, K; Ioku, K; Kasai, N

    2009-04-01

    Red cedar-derived bedding materials cause changes in cytochrome P450-dependent microsomal enzyme systems in laboratory animals. We examined the effect of essential oil of red cedar (EORC), as well as the effect of bedding from which it had been removed, on the hepatic expression cytochrome P450s in mice. EORC was obtained from liquid extracts of red cedar bedding by a soft-hydrothermal process and was administered orally to mice. Between days 1 and 2 after administration, hepatic P450s were significantly induced as follows: CYP3As, 7.1x; CYP1As, 1.6x; CYP2E1, 1.5x; CYP2Cs, 1.6x. A housing study of mice indicated that red cedar bedding increased the levels of these P450s in mouse liver, whereas mice housed in cedar bedding from which EORC had been removed (ST-cedar bedding) showed significantly lower levels of P450s, especially CYP3As, CYP1As and CYP2E1. Soft-hydrothermal processing partially removed many components of EORC. In particular, several volatile sesquiterpenes, naphthalene-derived aromatics and 4,4-dimethyl-13alpha-androst-5-ene were decreased in the ST-cedar bedding, suggesting that these may be responsible for P450 induction. This study demonstrated that the removal of these volatile compounds by soft-hydrothermal processing can decrease the hepatic P450-inducing effect of red cedar bedding. PMID:19116287

  14. Evaluating the potential for remote bathymetric mapping of a turbid, sand-bed river: 1. Field spectroscopy and radiative transfer modeling

    USGS Publications Warehouse

    Legleiter, C.J.; Kinzel, P.J.; Overstreet, B.T.

    2011-01-01

    Remote sensing offers an efficient means of mapping bathymetry in river systems, but this approach has been applied primarily to clear-flowing, gravel bed streams. This study used field spectroscopy and radiative transfer modeling to assess the feasibility of spectrally based depth retrieval in a sand-bed river with a higher suspended sediment concentration (SSC) and greater water turbidity. Attenuation of light within the water column was characterized by measuring the amount of downwelling radiant energy at different depths and calculating a diffuse attenuation coefficient, Kd. Attenuation was strongest in blue and near-infrared bands due to scattering by suspended sediment and absorption by water, respectively. Even for red wavelengths with the lowest values of Kd, only a small fraction of the incident light propagated to the bed, restricting the range of depths amenable to remote sensing. Spectra recorded above the water surface were used to establish a strong, linear relationship (R2 = 0.949) between flow depth and a simple band ratio; even under moderately turbid conditions, depth remained the primary control on reflectance. Constraints on depth retrieval were examined via numerical modeling of radiative transfer within the atmosphere and water column. SSC and sensor radiometric resolution limited both the maximum detectable depth and the precision of image-derived depth estimates. Thus, although field spectra indicated that the bathymetry of turbid channels could be remotely mapped, model results implied that depth retrieval in sediment-laden rivers would be limited to shallow depths (on the order of 0.5 m) and subject to a significant degree of uncertainty. ?? 2011 by the American Geophysical Union.

  15. Evaluating the potential for remote bathymetric mapping of a turbid, sand-bed river: 1. field spectroscopy and radiative transfer modeling

    USGS Publications Warehouse

    Legleiter, Carl J.; Kinzel, Paul J.; Overstreet, Brandon T.

    2011-01-01

    Remote sensing offers an efficient means of mapping bathymetry in river systems, but this approach has been applied primarily to clear-flowing, gravel bed streams. This study used field spectroscopy and radiative transfer modeling to assess the feasibility of spectrally based depth retrieval in a sand-bed river with a higher suspended sediment concentration (SSC) and greater water turbidity. Attenuation of light within the water column was characterized by measuring the amount of downwelling radiant energy at different depths and calculating a diffuse attenuation coefficient, Kd. Attenuation was strongest in blue and near-infrared bands due to scattering by suspended sediment and absorption by water, respectively. Even for red wavelengths with the lowest values of Kd, only a small fraction of the incident light propagated to the bed, restricting the range of depths amenable to remote sensing. Spectra recorded above the water surface were used to establish a strong, linear relationship (R2 = 0.949) between flow depth and a simple band ratio; even under moderately turbid conditions, depth remained the primary control on reflectance. Constraints on depth retrieval were examined via numerical modeling of radiative transfer within the atmosphere and water column. SSC and sensor radiometric resolution limited both the maximum detectable depth and the precision of image-derived depth estimates. Thus, although field spectra indicated that the bathymetry of turbid channels could be remotely mapped, model results implied that depth retrieval in sediment-laden rivers would be limited to shallow depths (on the order of 0.5 m) and subject to a significant degree of uncertainty.

  16. Red algal beds increase the condition of nekto-benthic fish

    NASA Astrophysics Data System (ADS)

    Ordines, Francesc; Bauzá, Marco; Sbert, Miquel; Roca, Pilar; Gianotti, Magdalena; Massutí, Enric

    2015-01-01

    The present study analysed the effect of three different benthic habitats, the maërl, Peyssonnelia red algal beds and sandy bottoms, on the condition of two nekto-benthic fish species: Serranus cabrilla and Trigloporus lastoviza. Sampling was conducted during the MEDITS 2010 and 2011 surveys around the Balearic Islands. The condition of the spawning females of both species was determined by using i) biochemical measurements of proteins and lipids in the muscle, liver and gonads, and ii) weight at length relationships based on eviscerated, liver, and gonad weights. Moreover, based on the total weight at length relationship, the mean somatic condition (SC) of the sexually inactive individuals of S. cabrilla and males of T. lastoviza was calculated. Lipid reserves were higher in the livers of S. cabrilla and T. lastoviza from the maërl beds. Additionally, S. cabrilla showed higher lipid reserves in the gonads both in the maërl and Peyssonnelia beds. The mean weights of the liver and gonads at a given individual length revealed the same pattern as the lipids, whereas the mean eviscerated weight was higher in the maërl beds but only for S. cabrilla. A positive correlation was detected between the SC and the biomass of the algal species characterizing the maërl beds for both S. cabrilla and T. lastoviza. The high habitat quality of the red algal beds off the Balearic Islands increased the condition of nekto-benthic fish. In oligotrophic areas, such as the archipelago, these "oases" could help fish to maintain healthy populations.

  17. Cretaceous oceanic red beds (CORBs): Different time scales and models of origin

    NASA Astrophysics Data System (ADS)

    Hu, Xiumian; Scott, Robert W.; Cai, Yuanfeng; Wang, Chengshan; Melinte-Dobrinescu, Mihaela C.

    2012-12-01

    The Cretaceous oceanic red bed (CORB) is a newly opened window on global oceanic and climate changes during the Cretaceous greenhouse world. As a result of the International Geoscience Programmes 463, 494 and 555 (2002-2010), CORBs have been documented in many places by numerous publications. The principle goal of this paper is to summarize scientific advances on CORBs including chronostratigraphy, sedimentology, mineralogy, elemental and isotopic geochemistry, and their relationship to oceanic anoxic events (OAEs), palaeoclimate and palaeoceanography. We propose a new geochemical classification of the CORBs using CaO, Al2O3 and SiO2 values, which lithologically refer to marly, clayey, and cherty CORBs respectively. Detailed mineralogical studies indicate that hematite, goethite and Mn2 +-bearing calcite are the minerals imparting the red color of CORBs. Hematite clusters of several to tens of nanometers in the calcite structure are the main cause of the red coloring of limestones, and the Mn2 +-bearing calcite gives additional red color. Goethite was thought to form originally with hematite, and was subsequently transformed to hematite during late diagenesis. Chronostratigraphic data allow the distinction of two groups of CORBs by their durations. Short-term CORBs are generally less than 1 myr in duration, and seem to be on the scale of Milankovitch cycles. During the deposition of Cretaceous reddish intervals from ODP cores 1049 and 1050, low primary productivity and relatively high surface temperature resulted in low organic carbon flux into the sediments which reduced oxygen demand and produced oxidizing early diagenetic conditions. In such an oxic environment, iron oxides formed imparting the reddish color. The long-term CORBs' depositional events lasted longer than 4 myr, and may be a possible consequence of the OAEs. Enhanced amounts of organic carbon and pyrite burial during and after the OAEs would have resulted in a large and abrupt fall in atmospheric CO

  18. Effect of Sand and Sawdust Bedding Materials on the Fecal Prevalence of Escherichia coli O157:H7 in Dairy Cows

    PubMed Central

    LeJeune, Jeffrey T.; Kauffman, Michael D.

    2005-01-01

    Farm management practices that reduce the prevalence of food-borne pathogens in live animals are predicted to enhance food safety. To ascertain the potential role of livestock bedding in the ecology and epidemiology of Escherichia coli O157:H7 on farms, the survival of this pathogen in used-sand and used-sawdust dairy cow bedding was determined. Additionally, a longitudinal study of mature dairy cattle housed on 20 commercial dairy farms was conducted to compare the prevalence of E. coli O157:H7 in cattle bedded on sand to that in cattle bedded on sawdust. E. coli O157:H7 persisted at higher concentrations in used-sawdust bedding than in used-sand bedding. The overall average herd level prevalence (3.1 versus 1.4%) and the number of sample days yielding any tests of feces positive for E. coli O157:H7 (22 of 60 days versus 13 of 60 days) were higher in sawdust-bedded herds. The choice of bedding material used to house mature dairy cows may impact the prevalence of E. coli O157:H7 on dairy farms. PMID:15640205

  19. Tectonic rotations south of the Bohemian Massif from palaeomagnetic directions of Permian red beds in Hungary

    USGS Publications Warehouse

    Marton, E.; Elston, D.P.

    1987-01-01

    Palaeomagnetic studies were carried out in Permian red beds of the Balaton Highlands, the Mecsek Mountains and the Bu??kk Mountains of Hungary. Statistically well defined directions were obtained from six localities in the Balaton Highlands and two localities in the Mecsek Mountains. No meaningful results were obtained from the Bu??kk Mountains. Three magnetic components were identified from red beds of the Balaton Highlands: (1) in haematite with a very high unblocking temperature (700??C), interpreted as a Permian magnetization (Dc= 79??, Ic=-11??, k = 24, ??95 = 13.6 ??), in six samples from three beds in a single locality (2) a secondary but ancient component residing mainly inmaghemite (D = 314??, I = 49??, k = 48, ??95 = 10.0??), in 84 samples from six localities with a within-locality scatter increasing on unfolding; and (3) a direction parallel to the present field (D = 7??, I = 62??, k = 46, ??95 = 7.7 ??), in nine samples from a single locality. For the Balaton Highlands, the component 1 direction agrees with directions obtained from Permian red beds and volcanics in the eastern part of the Southern and Eastern Alps and the Inner West Carpathians. All show large, apparent rotations relative to stable Europe since the Permian. Component 2 is of post-folding (post-Aptian) age. Its direction agrees with known Late Cretaceous directions from the Transdanubian Central Mountains, which also show significant counterclockwise rotation relative to stable Europe. The characteristic magnetization for the Mecsek Mountains resides in haematite and may be primary. The directions indicate only a slight net counterclockwise rotation of the Mecsek Mountains with respect to stable Europe since the Permian. ?? 1987.

  20. Mass balance and isotope effects during nitrogen transport through septic tank systems with packed-bed (sand) filters

    USGS Publications Warehouse

    Hinkle, S.R.; Böhlke, J.K.; Fisher, L.H.

    2008-01-01

    Septic tank systems are an important source of NO3- to many aquifers, yet characterization of N mass balance and isotope systematics following septic tank effluent discharge into unsaturated sediments has received limited attention. In this study, samples of septic tank effluent before and after transport through single-pass packed-bed filters (sand filters) were evaluated to elucidate mass balance and isotope effects associated with septic tank effluent discharge to unsaturated sediments. Chemical and isotopic data from five newly installed pairs and ten established pairs of septic tanks and packed-bed filters serving single homes in Oregon indicate that aqueous solute concentrations are affected by variations in recharge (precipitation, evapotranspiration), NH4+ sorption (primarily in immature systems), nitrification, and gaseous N loss via NH3 volatilization and(or) N2 or N2O release during nitrification/denitrification. Substantial NH4+ sorption capacity was also observed in laboratory columns with synthetic effluent. Septic tank effluent ??15N-NH4+ values were almost constant and averaged + 4.9??? ?? 0.4??? (1 ??). In contrast, ??15N values of NO3- leaving mature packed-bed filters were variable (+ 0.8 to + 14.4???) and averaged + 7.2??? ?? 2.6???. Net N loss in the two networks of packed-bed filters was indicated by average 10-30% decreases in Cl--normalized N concentrations and 2-3??? increases in ??15N, consistent with fractionation accompanying gaseous N losses and corroborating established links between septic tank effluent and NO3- in a local, shallow aquifer. Values of ??18O-NO3- leaving mature packed-bed filters ranged from - 10.2 to - 2.3??? (mean - 6.4??? ?? 1.8???), and were intermediate between a 2/3 H2O-O + 1/3 O2-O conceptualization and a 100% H2O-O conceptualization of ??18O-NO3- generation during nitrification.

  1. The Relation of Variability in Sand Bed Topography to Sediment Transport

    NASA Astrophysics Data System (ADS)

    McElroy, B.; Mohrig, D.

    2006-05-01

    The estimation of bed material flux by comparing successive bathymetric surveys was developed under a deterministic light. However, an analogous stochastic treatment can be straightforwardly cast as an extension to the original bedload equation. Instead of an analysis that presumes a regular, geometrically defined bed topography, this accepts the natural noisiness of sandy systems and uses it to explicitly calculate sediment flux. Further, the sediment flux can be treated as the sum of 2 components, a translative flux and a deformative flux. The terminology for these two parts is explicitly related to their relative impacts on the bed. Because the translational part is exactly the same as the original, deterministic model, it estimates only the flux that advects the bed topography. In contrast, the deformational part encompasses all of the remaining bed material flux, the component that serves to change the shape or arrangement of the bed topography. Also, the deformative flux is constant of integration obtained a from manipulation of Exner's equation into average flux; this has been assumed null since the inception of the bedload equation. Analysis of data from the N. Loup River, Nebraska, show that the ratio of deformative to translative fluxes is constant over relevant timescales. The consequences of this are twofold. First, the amount of deformation can be directly calculated and the associated estimates of moved sediment volume are valid as the bed translates many characteristic lengths. In this case the Qtotal=1.8*Qtranslative. Second, it suggests that the fraction of deformation can be explicitly related to the characteristic length of beds. If true, it would greatly improve estimates of flux for all sandy systems and not just those for which extensive amounts of data have been collected.

  2. Paleokarstic phenomena of the Lower Ordovician red bed sequences of the Arbuckle group, southern Oklahoma

    SciTech Connect

    Musselman, J.L. )

    1991-06-01

    Oil and gas production has been reported recently from paleokarstic Arbuckle reservoirs in the Ardmore and Arkoma basin. The West Spring Creek and the Kindblade formations apparently exhibit karstic features. The most extensive surface exposure of these formations is on the southern flank of the Arbuckle anticline along Interstate 35 north of Ardmore, Oklahoma. The lithology is predominantly limestone, ranging from argillaceous mudstone to oolitic and/or bioclastic grainstones. However, minor amounts of sandstone were also observed.These lithologies are characteristic of various peritidal facies. Of particular interest in this outcrop are three distinct red bed zones. Although the zones are part of the repetitive shallowing-upward cycles that characterize the West Spring Creek Formation, ample evidence suggests the red beds represent subaerial exposure surfaces where karstification took place. Many of the thin bedded, rubbly mudstones and wackestones actually represent varieties of breccia commonly associated with karst. Collapse and crackle breccia are most commonly observed. Small solution channels and other vugs are usually completely occluded by calcite cement. However, solution cavities or vugs with diameters larger than 10 cm (3.9 in.) are lined with drusy calcite. Hematite-impregnated sediment occurs as thinly laminated infilling of solution vugs and cavities and also acts as a cementing agent of collapse breccias. Preliminary evidence suggests that karstification processes were active during Arbuckle deposition.

  3. Bioremoval of heavy metals from industrial effluent by fixed-bed column of red macroalgae.

    PubMed

    Ibrahim, Wael M; Mutawie, Hawazin H

    2013-02-01

    Three different species of nonliving red algal biomass Laurancia obtusa, Geldiella acerosa and Hypnea sp. were used to build three types of fixed-bed column for the removal of toxic heavy metal ions such as Cu(2+), Zn(2+), Mn(2+) and Ni(2+) from industrial effluent. In general, the highest efficiency of metal ion bioremoval was recorded for algal column of L. obtusa followed by G. acerosa and the lowest one was recorded for Hypnea sp., with mean removal values of 94%, 85% and 71%, respectively. The obtained results showed that biological treatments of industrial effluents with these algal columns, using standard algal biotest, Pseudokirchneriella subcapitata, were capable of reducing effluent toxicities from 75% to 15%, respectively. Red algal column may be considered as an inexpensive and efficient alternative treatment for conventional removal technology, for sequestering heavy metal ions from industrial effluents. PMID:22661401

  4. Turbulence structure and sand transport over gravel and cobble beds in laboratory flumes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Characterizing the turbulence generated by flow over rough beds has become increasingly important in support of efforts to predict sediment transport downstream of dams. The advanced age and impending decommissioning of many dams have brought increased attention to the fate of sediments stored in r...

  5. Depositional mechanisms controlling formation of coarse fluvial conglomerates in the lower triassic continental red beds of middle europe

    NASA Astrophysics Data System (ADS)

    Mader, Detlef

    Coarse fluvial conglomerates containing numerous cobbles and boulders occur in various formations within the Lower Triassic continental red beds of Middle Europe. The rudites mainly originate as longitudinal gravel bars in highly-braided river systems with narrowly-spaced and straight to slightly sinuous channels. The high-energy stream sedimentation and the frequent and rapid lateral shifting of the watercourses control origin, distribution and preservation of finer-grained substratum deposits, topstratum sediments, aeolian dune sands and palaeosols within the alluvial plain which are governed by both internal and external mechanisms. The main processes operating within the alluvial plain which result in stacking of coarse conglomerates from successive cyclothems to multistorey complexes are primary-depositional restriction and suppression of formation and secondary-erosional destruction of finer-grained channel sediments, floodplain deposits, aeolian dune sands and palaeosols. The internal processes leading to vertical superimposition and lateral amalgamation of polygenetic conglomerate complexes are elements working under control of various external mechanisms. These are mainly slow subsidence of the basin allowing effective vertical and lateral erosion to take place during sidewards shifting of channels as well as supply of large amounts of coarse detritus from the source areas by tectonic uplift keeping pace with or even slightly exceeding erosional downcutting of relief, leading to inhibition of advance of the evolution of fluvial style beyond the initial stages of the depositional history. In the early stages of infilling of marginal parts of the basin, the partially considerable relief of the pre-Triassic basement provides locally shelter for parts of the floodplains by blocking off winds and deflection of alluvial channels. Depending on distribution of source areas, configuration of the basin and palaeocurrent pattern, wedge-shaped or sheet

  6. [Near Infrared Spectroscopy of the Cretaceous Red Beds in Inner Mongolia Dongshengmiao].

    PubMed

    Liao, Yi-peng; Cao, Jian-jin; Wu, Zheng-quan; Luo, Song-ying; Wang, Zheng-yang

    2015-09-01

    Take the cores and surface weathered soil from the Cretaceous red beds in the western of Dongshengmiao mine of Inner Mongolia and analysis with near-infrared spectroscopy. The result shows that near-infrared spectroscopy can identify mineral quickly through the characteristic absorption peaks of each group. The Cretaceous red beds in the western of Dongshengmiao mine is argillaceous cementation, it is mainly composed of quartz, feldspar, montmorillonite, illite, chlorite, muscovite etc, the mineral composition is mainly affected by the upstream source area. The clay mineral like montmorillonite water swelling and uneven drying shrinkage expands the original crack and creates new cracks, reduces its strength, which is the mainly reason of its disintegration. According to the composition of clay mineral, we speculate its weathering process is mainly physical weathering, the climate during the weathering is cold and dry. The results can not only improve the geological feature of the mining area, but also show that the near-infrared spectroscopy technology can analyze the mineral composition of soil and rock effectively on the basis of Mineral spectroscopy, which demonstrates the feasibility of the near-infrared spectroscopy can analyze minerals in soil and rock quickly, that shows the feasibility in geology study, provides new ideas for the future research of soil and rock. PMID:26669159

  7. Paleomagnetism of some Precambrian basaltic flows and red beds, Eastern Grand Canyon, Arizona

    USGS Publications Warehouse

    Elston, D.P.; Robert, Scott G.

    1973-01-01

    Lava flows and red sandstone beds near the middle of the Upper Precambrian Grand Canyon Series exhibit stable remanent magnetization. The beds are about 1000 m stratigraphically above rocks of the Grand Canyon Series for which paleomagnetic poles have been reported. All specimens were subjected to stepwise thermal (200??-700??C) or alternating field (25-5000 Oe) demagnetization for the determination of characteristic magnetization. The pole for two flows and an intercalated sandstone bed of the Cardenas Lavas of Ford, Breed and Mitchell (upper Unkar Group), is at 174.6W, 0.4N (N = 10, K = 50, ??95 = 6.9??). The pole for a weathered zone developed across the Cardenas Lavas is at 167.8W, 49.4N (N = 5, K = 79, ??95 = 8.6??). The pole for directly overlying sandstone of the Nankoweap Formation of Maxson is at 174.4E, 12.5N (N = 6, K = 105, ??95 = 6.6??). These poles lie on or near, and appear to follow, part of an apparent polar wandering path recently proposed for the Precambrian of North America by Spall. If the fit is not accidental, little or no rotation has occurred between north-central Arizona and parts of the North American continent used to define the proposed path. ?? 1973.

  8. Modeling the Threshold Wind Speed for Saltation Initiation over Heterogeneous Sand Beds

    NASA Astrophysics Data System (ADS)

    Turney, F. A.; Martin, R. L.; Kok, J. F.

    2015-12-01

    Initiation of aeolian sediment transport is key to understanding the formation of dunes, emission of dust into the atmosphere, and landscape erosion. Previous models of the threshold wind speed required for saltation initiation have assumed that the particle bed is monodisperse and homogeneous in arrangement, thereby ignoring what is in reality a distribution of particle lifting thresholds, influenced by variability in soil particle sizes and bed geometry. To help overcome this problem, we present a numerical model that determines the distribution of threshold wind speeds required for particle lifting for a given soil size distribution. The model results are evaluated against high frequency wind speed and saltation data from a recent field campaign in Oceano Dunes in Southern California. The results give us insight into the range of lifting thresholds present during incipient sediment transport and the simplifications that are often made to characterize the process. In addition, this study provides a framework for moving beyond the 'fluid threshold' paradigm, which is known to be inaccurate, especially for near-threshold conditions.

  9. Nature of remagnetization of Lower Triassic red beds in southwestern China

    NASA Astrophysics Data System (ADS)

    Liu, Chengying; Ge, Kunpeng; Zhang, Chunxia; Liu, Qingsong; Deng, Chenglong; Zhu, Rixiang

    2011-12-01

    Widely distributed haematite-bearing red beds are an important source of palaeomagnetic field records. However, unresolved issues regarding remagnetization and inclination shallowing in red beds have questioned the reliability of the palaeomagnetic results obtained from such materials. In this study, we investigated the remagnetization mechanism in red beds from Lower Triassic sandstones in Yunnan Province, southwestern China. Our results indicate that the characteristic remanent magnetizations (ChRMs) of most samples (112/125) are dominated by only one component at temperatures 80-660 °C, with a mean direction of D/I= 0.9/46.6° (k= 440.2, α95= 2.1°). The corresponding geomagnetic pole is 89.1°N, 331.7°E (k= 338.2, A95= 2.4°). This coincides with the present geomagnetic field, which is a strong indication that these ChRMs are remagnetized. Combined rock magnetic and microscope investigations reveal that the remagnetization is due to the acquisition of a chemical remanent magnetization (CRM) carried by authigenic maghemite and haematite. Despite the widespread remagnetization, about 7 per cent of the studied samples still record a magnetization that we consider to be primary that was isolated at high temperatures 610-660 °C, with a mean direction of D/I= 213.3/18.6° (k= 16.0, α95= 11.7°). We propose that the CRM overprinting is controlled by the overlapping degree of the unblocking temperature between the CRM carried by the authigenic haematite and the primary remanent magnetization carried by the detrital haematite. Our results further suggest that microscope investigation, rock magnetic proxies for the haematite concentration and susceptibility-temperature curves are useful methods for pre-selecting samples suitable for isolating the primary remanence at this region. The linkage among the palaeomagnetic results, rock magnetic proxies and CRM remagnetization mechanism could be extended to other studies, although the detailed proxy would be different due

  10. Expression of syndepositional tectonic uplift in Permian Goose Egg formation (Phosphoria equivalent) carbonates and red beds of Sheep Mountain anticline, Bighorn basin, Wyoming

    SciTech Connect

    Simmons, S.P.; Ulmer, D.S.; Scholle, P.A.

    1989-03-01

    Based on detailed field observations at Sheep Mountain, a doubly plunging anticline in the northeastern Bighorn basin in Wyoming, there appears to have been active tectonic uplift at this site contemporaneous with Pennsylvanian and Permian sedimentation. The Permian (Leonardian to Guadalupian) Goose Egg Formation at Sheep Mountain consists of 25-60 m of silty red beds (including minor carbonate and evaporite units) capped by 15-30 m of dominantly intertidal carbonates (the Ervay Member). A strong lateral variation of facies normal to the trend of the anticline is found within the red-bed sequence: carbonate beds on the anticline flanks are transitional with a gypsum/anhydrite facies along the crest. Similarly, shales on the anticline limbs grade into sandstones near the fold axis, indicating a paleohigh roughly coincidental with the present-day anticline crest. Ervay deposition (late Guadalupian) was marked by a more extensive uplifted structure in a marginal marine setting. On Sheep Mountain the unit is typified by intertidal fenestral carbonates, whereas outcrops to the east suggest a restricted marine facies and outcrops to the west reflect a more open marine environment. Thin sand lenses present in the Ervay are thought to represent terrigenous sediments blown onto the sometimes emergent bank which were then captured through adhesion and cementation. Anticlinal features similar to Sheep Mountain are common along the eastern margin of the Bighorn basin. When found in the subsurface, these structures are often associated with hydrocarbon production from the Ervay Member. Tectonic uplift contemporaneous with deposition of this unit may explain the localization of the productive fenestral facies on the present-day anticlines.

  11. Pedogenic slickensides, indicators of strain and deformation processes in red bed sequences of the Appalachian foreland

    SciTech Connect

    Gray, M.B. ); Nickelsen, R.P. )

    1989-01-01

    Pedogenic slickensides are convex-concave slip surfaces that form during expansion/contraction in expansive clay soils such as Vertisols. In the central Appalachians, they occur near the tops of fining-upward cycles in Paleozoic red beds such as the Bloomsburg, Catskill, and Mauch Chunk Formations. Pedogenic slickensides are found in association with other pedogenic (or paleosol) features such as clay-skinned peds, in situ calcareous nodules, and root impressions. Repeated movements along these shear planes during pedogenesis produce strongly aligned clay particles adjacent to pedogenic slickensides; as a result, they are preserved as discrete fractures throughout diagenesis, compaction, and superimposed tectonic deformation. During whole-rock deformation, pedogenic slickensides segregate penetratively deformed rocks into independent, foliate packets and serve as discontinuities that are followed by later structural features. Because the original morphology of pedogenic slickensides is known, they can be used as crude strain markers.

  12. Phosphate removal from aqueous solution using ZVI/sand bed reactor: Behavior and mechanism.

    PubMed

    Sleiman, Nathalie; Deluchat, Véronique; Wazne, Mahmoud; Mallet, Martine; Courtin-Nomade, Alexandra; Kazpard, Véronique; Baudu, Michel

    2016-08-01

    This research reports on phosphate removal from aqueous solution using ZVI/sand packed columns. The influence of column preconditioning, consisting of ZVI pre-oxidation before feeding the columns with phosphate solution, revealed that a column aged for 1 day was more efficient than un-conditioned column, 5-days and 10-days preconditioned columns. The distribution of phosphate trapped inside the columns was evaluated by measuring phosphate concentration in the solids at different levels (P1, P2 and P3) along the depth of the columns. The distribution of phosphate inside the columns was determined for a time period up to 46 days, corresponding to column saturation. Results showed heterogeneous trapping along the column before saturation and homogeneous distribution upon saturation. The maximum cumulative trapped phosphate after column dismantling was determined before saturation (after 17 days running) at 130, 68 and 31 mgP/gFe at the inlet-P1, P1-P2 and P2-P3 layers, respectively, whereas the homogeneous distribution of phosphate upon saturation was determined at 132 mgP/gFe throughout the column. Solid supports were characterized using SEM, XRD and XPS. Lepidocrocite and maghemite/magnetite were the only iron oxidation products identified at the different layers inside the columns. XPS results confirmed the sorption of phosphate at the surface of ZVI and its oxidation products and highlighted the formation of an iron phosphate complex. PMID:27135373

  13. Initiation and evolution of current ripples on a flat sand bed under turbulent water flow.

    PubMed

    Langlois, V; Valance, A

    2007-03-01

    We investigate the formation and dynamics of sand ripples under a turbulent water flow. Our experiments were conducted in an open flume with spherical glass beads between 100 and 500 microm in diameter. The flow Reynolds number is of the order of 10,000 and the particle Reynolds number of the order of 1 to 10. We study the development of ripples by measuring their wavelength and amplitude in course of time and investigate the influence of the grain size and the flow properties. In particular, we demonstrate two different regimes according to the grain size. For fine grains, a slow coarsening process (i.e., a logarithmic increase of the wavelength and amplitude) takes place, while for coarser grains, this process occurs at a much faster rate (i.e., with a linear growth) and stops after a finite time. In the later case, a stable pattern is eventually observed. Besides, we carefully analyze the wavelength of ripples in the first stages of the instability as a function of the grain size and the shear velocity of the flow, and compare our results with other available experimental data and with theoretical predictions based on linear stability analyses. PMID:17426938

  14. Granular spirals on erodible sand bed submitted to a circular fluid motion.

    PubMed

    Caps, H; Vandewalle, N

    2003-09-01

    An experimental study of a granular surface submitted to a circular fluid motion is presented. The appearance of an instability along the sand-water interface is observed beyond a critical radius r(c). This creates ripples with a spiral shape on the granular surface. A phase diagram of such patterns is constructed and discussed as a function of the rotation speed omega of the flow and as a function of the height of water h above the surface. The study of r(c) as a function of h, omega, and r parameters is reported. Thereafter, r(c) is shown to depend on the rotation speed according to a power law. The ripple wavelength is found to decrease when the rotation speed increases and is proportional to the radial distance r. The azimuthal angle epsilon of the spiral arms is studied. It is found that epsilon scales with homegar. This lead to the conclusion that epsilon depends on the fluid momentum. Comparison with experiments performed with fluids allows us to state that the spiral patterns are not the signature of an instability of the boundary layer. PMID:14524759

  15. Volcanic red-bed copper mineralisation related to submarine basalt alteration, Mont Alexandre, Quebec Appalachians, Canada

    NASA Astrophysics Data System (ADS)

    Cabral, Alexandre Raphael; Beaudoin, Georges

    2007-11-01

    Two types of native copper occur in Upper Silurian basaltic rocks in the Mont Alexandre area, Quebec Appalachians: (1) type 1 forms micrometric inclusions in plagioclase and is possibly magmatic in origin, whereas (2) type 2 occurs as coarse-grained patches rimmed by cuprite in altered porphyritic basalt. Type 1 has higher contents of sulphur (2,000-20,263 ppm) and arsenic (146-6,017 ppm), and a broader range of silver abundances (<65-2,186 ppm Ag) than type 2 (149-1,288 ppm S, <90-146 As, <65-928 ppm Ag). No mineral inclusions of sulphide or arsenide in native copper were observed at the electron-microprobe scale. Primary igneous fabrics are preserved, but the basaltic flows are pervasively oxidised and plagioclase is albitised. Chlorite replaces plagioclase and forms interstitial aggregates in the groundmass and has Fe/(Fe+Mg) ratios ranging from 0.29 to 0.36 with calculated temperatures between 155°C and 182°C. Copper sulphides in vacuoles and veinlets are associated with malachite, fibro-radiating albite and yarrowite (Cu9S8 with up to 0.3 wt% Ag). Bulk-rock concentrations of thallium and lithium range from 70 to 310 ppb and 10 to 22 ppm, respectively, and thallium is positively correlated with Fe2O3. Such concentrations of thallium and lithium are typical of spilitisation during heated seawater-basalt interaction. Spilitisation is consistent with the regional geological setting of deepwater-facies sedimentation, but is different from current models for volcanic red-bed copper, which indicate subaerial oxidation of volcanic flows. The volcanic red-bed copper model should be re-examined to account for native copper mineralisation in basalts altered by warm seawater.

  16. AMS Fabric of a CRM in Hematite-Bearing Samples: Evidence of DRMs in Natural Red Beds

    NASA Astrophysics Data System (ADS)

    Kodama, K. P.

    2002-12-01

    Anisotropy of magnetic susceptibility (AMS) and anisotropy of isothermal remanence (AIR) in red sedimentary rocks both typically show a bedding parallel foliation with minimum axes clustered perpendicular to the bedding plane. Our studies have observed this type of magnetic fabric in red bed units that have a range of ages and come from widespread localities. These units include the Mississippian Mauch Chunk Formation from the Appalachians, the Triassic Passaic Formation from the Newark basin in Pennsylvania, the Cretaceous Kapusaliang Formation from the Tarim basin in China, and the early Mesozoic Kayenta and Chinle Formations from the Colorado Plateau in southwestern North America. Bedding parallel foliations are also observed in magnetite-bearing rocks that carry a depositional remanence (DRM), suggesting the possibility of a DRM in red beds, even though the conventional wisdom is that they carry a post-depositional chemical remanent magnetization (CRM). Before the typical magnetic fabric of red beds can be used to indicate their type of remanence, we must determine what the magnetic fabric of a CRM looks like. For this reason, I conducted a series of hematite-growth experiments following the procedures outlined by Stokking and Tauxe (1987). I grew hematite in the laboratory on stacks of glass-fiber filter papers and in slurries of quartz and kaolinite. The hematite was grown from a ferric nitrate solution heated to 95° C for 8 hours. The samples were then dehydrated in a vacuum at room temperature for approximately 38 hours. It was possible to thermally demagnetize the eight filter paper samples to 350° C, but the six kaolinite-quartz samples were grown in plastic sample cubes and could only be thermally demagnetized to 150° C, enough to remove the thermoviscous magnetization acquired by the samples during the heating at 95° C. The mean CRM acquired by the red-brown magnetic phase grown in the experiments was within its alpha-95 of the steeply inclined

  17. Treatment of oil sands process-affected water using moving bed biofilm reactors: With and without ozone pretreatment.

    PubMed

    Shi, Yijing; Huang, Chunkai; Rocha, Ketley Costa; El-Din, Mohamed Gamal; Liu, Yang

    2015-09-01

    Two moving bed biofilm reactors (MBBRs) were operated to treat raw (untreated) and 30 mg/L ozone-treated oil sands process-affected water (OSPW). After 210 days, the MBBR process showed 18.3% of acid-extractable fraction (AEF) and 34.8% of naphthenic acids (NAs) removal, while the ozonation combined MBBR process showed higher removal of AEF (41.0%) and NAs (78.8%). Biodegradation of raw and ozone treated OSPW showed similar performance. UPLC/HRMS analysis showed a highest NAs removal efficiency with a carbon number of 14 and a -Z number of 4. Confocal laser scanning microscopy (CLSM) showed thicker biofilms in the raw OSPW MBBR (97 ± 5 μm) than in the ozonated OSPW MBBR (71 ± 12 μm). Quantitative polymerase chain reaction (q-PCR) results showed higher abundance of gene copies of total bacteria and nitrogen removal relevant bacteria in the ozonated OSPW MBBR, but no significant difference was found. MiSeq sequencing showed Proteobacteria, Nitrospirae, and Acidobacteria were dominant. PMID:26038326

  18. The Transfiguration continental red-bed Cu-Pb-Zn-Ag deposit, Quebec Appalachians, Canada

    NASA Astrophysics Data System (ADS)

    Cabral, Alexandre Raphael; Beaudoin, Georges; Taylor, Bruce E.

    2009-04-01

    The Transfiguration Cu-Pb-Zn-Ag deposit, enclosed within reduced grey sandstone, is associated with continental red beds of the Lower Silurian Robitaille Formation in the Quebec Appalachians, Canada. The Robitaille Formation rests unconformably on foliated Cambro-Ordovician rocks. The unconformity is locally cut by barite veins. The basal unit of the Robitaille Formation comprises green wacke and pebble conglomerate, which locally contain calcite nodules. The latter have microstructures characteristic of alpha-type calcretes, such as “floating” fabrics, calcite-filled fractures (crystallaria) and circumgranular cracks. Massive, grey sandstone overlies the basal green wacke and pebble conglomerate unit, which is overlain, in turn, by red, fine-grained sandstone. Mineralisation occurred underneath the red sandstone unit, chiefly in the grey sandstone unit, as disseminated and veinlet sulphides. Chalcopyrite, the most abundant Cu sulphide, replaced early pyrite. Calcrete, disseminated carbonate and vein carbonate have stable isotope ratios varying from -7.5‰ to -1.1‰ δ13C and from 14.7‰ to 21.3‰ δ18O. The negative δ13C values indicate the oxidation of organic matter in a continental environment. Sulphur isotope ratios for pyrite, chalcopyrite and galena vary from -19‰ to 25‰ δ34S, as measured on mineral concentrates by a conventional SO2 technique. Laser-assisted microanalyses (by fluorination) of S isotopes in pyrite show an analogous range in δ34S values, from -21‰ to 25‰. Negative and positive δ34S values are compatible with bacterial sulphate reduction (BSR) in systems open and closed with respect to sulphate. We interpret similarly high δ34S values for sulphide concentrates (25.1‰) and for vein barite (26.2‰) to result from rapid and complete thermochemical reduction of pore-water sulphate. Two early to late diagenetic stages of mineralisation best explain the origin of the Transfiguration deposit. The first stage was characterised

  19. Spatial Scaling of Environmental Variables Improves Species-Habitat Models of Fishes in a Small, Sand-Bed Lowland River

    PubMed Central

    Radinger, Johannes; Wolter, Christian; Kail, Jochem

    2015-01-01

    Habitat suitability and the distinct mobility of species depict fundamental keys for explaining and understanding the distribution of river fishes. In recent years, comprehensive data on river hydromorphology has been mapped at spatial scales down to 100 m, potentially serving high resolution species-habitat models, e.g., for fish. However, the relative importance of specific hydromorphological and in-stream habitat variables and their spatial scales of influence is poorly understood. Applying boosted regression trees, we developed species-habitat models for 13 fish species in a sand-bed lowland river based on river morphological and in-stream habitat data. First, we calculated mean values for the predictor variables in five distance classes (from the sampling site up to 4000 m up- and downstream) to identify the spatial scale that best predicts the presence of fish species. Second, we compared the suitability of measured variables and assessment scores related to natural reference conditions. Third, we identified variables which best explained the presence of fish species. The mean model quality (AUC = 0.78, area under the receiver operating characteristic curve) significantly increased when information on the habitat conditions up- and downstream of a sampling site (maximum AUC at 2500 m distance class, +0.049) and topological variables (e.g., stream order) were included (AUC = +0.014). Both measured and assessed variables were similarly well suited to predict species’ presence. Stream order variables and measured cross section features (e.g., width, depth, velocity) were best-suited predictors. In addition, measured channel-bed characteristics (e.g., substrate types) and assessed longitudinal channel features (e.g., naturalness of river planform) were also good predictors. These findings demonstrate (i) the applicability of high resolution river morphological and instream-habitat data (measured and assessed variables) to predict fish presence, (ii) the

  20. The Cyborg Astrobiologist: scouting red beds for uncommon features with geological significance

    NASA Astrophysics Data System (ADS)

    McGuire, Patrick Charles; Díaz-Martínez, Enrique; Ormö, Jens; Gómez-Elvira, Javier; Rodríguez-Manfredi, José Antonio; Sebastián-Martínez, Eduardo; Ritter, Helge; Haschke, Robert; Oesker, Markus; Ontrup, Jörg

    2005-04-01

    The `Cyborg Astrobiologist' has undergone a second geological field trial, at a site in northern Guadalajara, Spain, near Riba de Santiuste. The site at Riba de Santiuste is dominated by layered deposits of red sandstones. The Cyborg Astrobiologist is a wearable computer and video camera system that has demonstrated a capability to find uncommon interest points in geological imagery in real time in the field. In this second field trial, the computer vision system of the Cyborg Astrobiologist was tested at seven different tripod positions, on three different geological structures. The first geological structure was an outcrop of nearly homogeneous sandstone, which exhibits oxidized-iron impurities in red areas and an absence of these iron impurities in white areas. The white areas in these `red beds' have turned white because the iron has been removed. The iron removal from the sandstone can proceed once the iron has been chemically reduced, perhaps by a biological agent. In one instance the computer vision system found several (iron-free) white spots to be uncommon and therefore interesting, as well as several small and dark nodules. The second geological structure was another outcrop some 600 m to the east, with white, textured mineral deposits on the surface of the sandstone, at the bottom of the outcrop. The computer vision system found these white, textured mineral deposits to be interesting. We acquired samples of the mineral deposits for geochemical analysis in the laboratory. This laboratory analysis of the crust identifies a double layer, consisting of an internal millimetre-size layering of calcite and an external centimetre-size efflorescence of gypsum. The third geological structure was a 50 cm thick palaeosol layer, with fossilized root structures of some plants. The computer vision system also found certain areas of these root structures to be interesting. A quasi-blind comparison of the Cyborg Astrobiologist's interest points for these images with the

  1. Advancement of an Infra-Red Technique for Whole-Field Concentration Measurements in Fluidized Beds

    PubMed Central

    Medrano, Jose A.; de Nooijer, Niek C. A.; Gallucci, Fausto; van Sint Annaland, Martin

    2016-01-01

    For a better understanding and description of the mass transport phenomena in dense multiphase gas-solids systems such as fluidized bed reactors, detailed and quantitative experimental data on the concentration profiles is required, which demands advanced non-invasive concentration monitoring techniques with a high spatial and temporal resolution. A novel technique based on the selective detection of a gas component in a gas mixture using infra-red properties has been further developed. The first stage development was carried out using a very small sapphire reactor and CO2 as tracer gas. Although the measuring principle was demonstrated, the real application was hindered by the small reactor dimensions related to the high costs and difficult handling of large sapphire plates. In this study, a new system has been developed, that allows working at much larger scales and yet with higher resolution. In the new system, propane is used as tracer gas and quartz as reactor material. In this study, a thorough optimization and calibration of the technique is presented which is subsequently applied for whole-field measurements with high temporal resolution. The developed technique allows the use of a relatively inexpensive configuration for the measurement of detailed concentration fields and can be applied to a large variety of important chemical engineering topics. PMID:26927127

  2. 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.

  3. Advancement of an Infra-Red Technique for Whole-Field Concentration Measurements in Fluidized Beds.

    PubMed

    Medrano, Jose A; de Nooijer, Niek C A; Gallucci, Fausto; van Sint Annaland, Martin

    2016-01-01

    For a better understanding and description of the mass transport phenomena in dense multiphase gas-solids systems such as fluidized bed reactors, detailed and quantitative experimental data on the concentration profiles is required, which demands advanced non-invasive concentration monitoring techniques with a high spatial and temporal resolution. A novel technique based on the selective detection of a gas component in a gas mixture using infra-red properties has been further developed. The first stage development was carried out using a very small sapphire reactor and CO₂ as tracer gas. Although the measuring principle was demonstrated, the real application was hindered by the small reactor dimensions related to the high costs and difficult handling of large sapphire plates. In this study, a new system has been developed, that allows working at much larger scales and yet with higher resolution. In the new system, propane is used as tracer gas and quartz as reactor material. In this study, a thorough optimization and calibration of the technique is presented which is subsequently applied for whole-field measurements with high temporal resolution. The developed technique allows the use of a relatively inexpensive configuration for the measurement of detailed concentration fields and can be applied to a large variety of important chemical engineering topics. PMID:26927127

  4. The Role of Authigenic (pigment) Hematite in Controlling the Remanence, Rock Magnetic, and Magnetic Fabric Properties of Red Beds--If You Have Seen One Red Bed, You Certainly Have Not Seen Them All!

    NASA Astrophysics Data System (ADS)

    Geissman, J. W.

    2014-12-01

    Discussion continues on the relative role of authigenic (pigment) fine-grained hematite, relative to detrital, considerably coarser specular hematite (specularite) as a carrier of geologically meaningful remanence, as a determinant of rock magnetic properties, and as a contributor to magnetic fabrics in red beds. For one, many workers commonly assume that the laboratory unblocking temperature spectra (Tlub) of a red bed dominated by authigenic pigment does not reach the maximum Tlub as approximated by the Neel temperature (~948 K) because of the ultra fine grain size of the pigment. This issue was discussed as recently as the IRM Santa Fe meeting in late June, 2014. Many laboratories routinely utilize chemical demagnetization in concert with progressive thermal demagnetization to attempt to assess the relative role of pigment vs. detrital hematite. However, the utility of chemical demagnetization has been long challenged. In studying the anisotropy of magnetic susceptibility and remanence in red beds, recent work has considered separating the contributions of both types of hematite to the fabric signal. Three different red bed "types" (siltstones of the Triassic Chugwater Group, Gros Ventre Range, Wyoming; mudrocks of lowermost Triassic Quartermaster Formation, west Texas; and siltstones to medium sandstones of Upper Cretaceous age, northwest Vietnam) are used to evaluate the effects of varying contributions by pigment hematite to remanence, rock magnetic, and magnetic fabric properties. All rocks are well-characterized petrographically, so that the modal abundance of detrital oxides is known. The Chugwater siltstones are notable because of a relatively low Tlub spectra (below about 620o C), with no evidence of a low coercivity cubic phase. Rock magnetic and magnetic fabric properties are monitored as a function of progressive chemical demagnetization to further elucidate the role of hematite pigment in rocks that have contributed much to the paleomagnetic record

  5. Direct measurement of hematite individual particle anisotropy: implications for inclination shallowing in red bed DRMs.

    NASA Astrophysics Data System (ADS)

    Bilardello, D.; Kodama, K. P.

    2007-12-01

    Methods to correct for the observed inclination shallowing in sedimentary rocks have been proposed that are based on either models of the geomagnetic field and the resulting directional distribution of paleomagnetic vectors or the magnetic anisotropy of the magnetic minerals carrying the remanence. One limitation of the anisotropy method for hematite-bearing red beds has been the isolation and determination of a rock's detrital hematite individual particle anisotropy. Up to now, our red bed inclination shallowing corrections have been dependent on estimates of hematite individual particle anisotropy using data fit to theoretical correction curves. We have developed a technique for preferentially extracting the detrital hematite particles in a sample in order to directly measure their individual particle anisotropy. The method involves crushing of the sample followed by ball milling and sieving to ensure that the rock particles are smaller than 4Φ. The resulting slurry was then placed in an ultrasonic cleaner for at least 24 hours and finally centrifuged at 1000 rpm for 20 minutes in order to separate the dense, gray iron oxide particles from the red pigmentary grains. The gray, iron oxide-rich slurry was collected by hand and circulated in a magnetic extraction apparatus. The magnetic separate was then collected over a period of two to three weeks. Small amounts of the magnetic separates where mixed in a slow-drying epoxy resin for 24 hours and placed in a DC magnetic field (100 mT to 180 mT) in order to align the grains. The bulk IRM anisotropy of the epoxy samples provides an average individual particle anisotropy for the magnetic grains. Separates were collected from samples of the Mauch Chunk Fm. of Pennsylvania, the Maringouin and the Shepody Fms of New Brunswick/ Nova Scotia and the Kapusaliang Fm. of northwestern China. IRM acquisitions experiments were performed in fields of up to 1.2 T in order to identify the magnetic mineralogies present. Remanence

  6. Regional implications of Triassic or Jurassic age for basalt and sedimentary red beds in the South Carolina coastal plain

    USGS Publications Warehouse

    Gohn, G.S.; Gottfried, D.; Lanphere, M.A.; Higgins, B.B.

    1978-01-01

    Whole rock potassium-argon ages for samples of subsurface basalt recovered near Charleston, South Carolina, are interpreted to indicate a Triassic or Jurassic age for the basalt and underlying sedimentary red beds. This age is consistent with existing evidence indicating that an early Mesozoic basin is present in the subsurface of a large part of the coastal plain of South Carolina, Georgia, Florida, and Alabama.

  7. Paleomagnetism of the Cretaceous Yasin red beds from northern Pakistan: Tectonic implications

    NASA Astrophysics Data System (ADS)

    Zaman, H.; Otofuji, Y. I.; Khan, S. R.

    2003-04-01

    The Cretaceous Kohistan arc in northwestern Himalaya formed as an intraoceanic island arc, and subsequently, but before the arrival of India, it collided against the South Asian margin. The northern margin of the arc consists of a series of Cretaceous sediments and a unit of volcanic rocks. We sampled Cretaceous red beds and volcanics in the Ghizar and Gilgit districts of northern Pakistan. Here we present rock-and paleomagnetic results from two different stratas of red beds located on the opposite sides of the Yasin River. Rock magnetic investigations revealed pyrrhotite as dominant magnetic mineral in most of the studied samples while magnetite and hematite are present as subordinate remanence carriers. In two sites, pyrrhotite is found as an exclusive magnetic mineral, and thermal treatment clearly gave a uni-vectorial behavior of magnetization. Except these two sites, thermal demagnetization process generally revealed two remanance components. In samples from Yasin locality, soft component is isolated up to 350^oC, indicating pyrrohtite as remanence carrier. Hard component in these samples were demagnetized up to 600^oC, suggesting magnetite as remanence carrier. Because of very strong VRM above 640^oC, hematite related component could not be separated. In Sandi locality, the studied samples covered a wide stratigraphic thickness of variable lithologies. The soft component here is separated between 200 and 590^oC, which falls in to the unblocking range of pyrrohtite and magnetite. Due to very low NRM intensity after 600^oC, high stability component could not be clearly separated from Sandi area samples. Because of divergent paleomagnetic directions, separate formation-mean were calculated for the sites of each locality. For Yasin area, the fold test for both components are inconclusive at 95 and 99 percent level. This may indicate that both the components are syn-folding in natures, which were probably acquired as a result of post collision (India versus Asia

  8. Rock-magnetic properties of multicomponent natural remanent magnetization in alluvial red beds (NE Spain)

    NASA Astrophysics Data System (ADS)

    Kruiver, Pauline P.; Langereis, Cor G.; Dekkers, Mark J.; Krijgsman, Wout

    2003-05-01

    An earlier study of the cyclic Miocene red bed sequence of La Gloria (Spain) by Krijgsman et al. indicated complicated behaviour of the natural remanent magnetization (NRM) in parts of the section, particularly close to reversal boundaries. We resampled part of the section with high resolution and used extensive rock-magnetic analyses to characterize the magnetic remanence carriers. Below a conspicuous hydromorphous layer, the magnetic contributions of haematite and magnetite are approximately equal, while in the brown layers on top of the hydromorphous layer the contribution of magnetite is drastically reduced. This is probably related to a change in hydrological conditions. The NRM is characterized by: (1) a low-temperature (200-360 °C) overprint of unknown age, (2) a medium-temperature (360-580 °C) component, interpreted as the characteristic remanent magnetization (ChRM); and (3) a high-temperature haematite component (600- 680 °C), carrying the same directions as the medium-temperature component. There is no perceivable delay in NRM acquisition between the medium- and the high-temperature components; they are both regarded as primary. The behaviour of the NRM seems to be similar in the cyclic lithologies. The acquisition of NRM thus seems to be independent of lithology in the cyclic part of the section. The higher sampling resolution yielded the detection of a new polarity zone, which probably represents a geomagnetic feature according to rock-magnetic properties. However, the more detailed magnetostratigraphy of the resampled part of the section indicates that the earlier correlation to the geomagnetic polarity timescale is no longer tenable. Therefore, the La Gloria section should no longer be used as a magnetostratigraphic dating tool of mammal biochronology.

  9. Biostratinomy and facies analysis of the upper Cretaceous oyster storm shell beds of the Duwi formation, Qusseir District, Red Sea Region, Egypt

    NASA Astrophysics Data System (ADS)

    El-Ayyat, Abdalla M.; Kassab, Ahmed S.

    2004-06-01

    The Maastrichtian oyster Lopha villei (Coquand) occurs abundantly in the upper part of the Duwi Formation in the Red Sea region, Egypt. It forms thin undulating sharp-based shell beds that comprise both reclining and encrusting morphotypes of Lopha villei. Bed-by-bed biostratinomic and facies analyses of these shell beds confirm their shallow marine origin and formation by storm events. A tempestite model, explaining the mode of formation and the idealized sequence of events of such storm shell beds, has been inferred.

  10. Natural radioactivity in sand used in thermal therapy at the Red Sea Coast.

    PubMed

    El-Arabi, A M

    2005-01-01

    The development of climatotherapy in Safaga opens the field of medical tourism in Egypt, in order to detect any harmful radiation that would affect the patients during treatment and is becoming important economic resource. Studies and survey of natural radiation and radioactivity in upper Egypt conducted since 1990, included monitoring of the concentration of natural radionuclides in environmental samples. The results of the study reveals that, for all sand samples, the mean activity concentration of 40K (618+/-122-548+/-82 Bq kg(-1)) are much higher than that of both 226Ra (25.3+/-14-20.6+/-10 Bq kg(-1)) and 232Th (21.4+/-10-22.4+/-10 Bq kg(-1)). Different radiation hazard indices were calculated, the radiation dose to which workers are subjected is not negligible (26.5-50.9 nGy h(-1)), although depending on the inhalation of dust. PMID:15748657

  11. Continental Red Beds: How, Why, and When Can they Be Remagnetized, and What Would Don Elston Think?

    NASA Astrophysics Data System (ADS)

    Geissman, J. W.

    2006-12-01

    For logical reasons, continental red beds have served as the focus for thousands of paleomagnetic investigations; this author is becoming more and more convinced that the most accurate statements to make about how red beds are magnetized are: (1)no two red bed sequences are exactly the same and (2)understanding just how red beds are remagnetized (a nagging question pondered by several workers) may help us in more fully understanding aspects of how they acquire a geologically meaningful magnetization in the first place! Red beds of the Uinta Mountain Supergroup (UMS) serve as an excellent natural laboratory for studying magnetization acquisition and remagnetization processes. These rocks are exposed in the core of the Uinta Mountains, which formed during Laramide style shortening along the northern margin of the Colorado Plateau. In the eastern and central part of the range, strata are dominated by 3+ km of hematite-cemented medium to fine-grained sandstones, with relatively minor hematitic shales and conglomerates. Correlation of the upper part of the UMS section with the Chuar and Little Dal groups, and hence a mid-Neoproterozoic age for the strata, is based on the presence of the fossil Chuaria. At several localities in UMG strata, a dual polarity ChRM of about east-west declination and shallow inclination inferred to be primary) is smoothly and progressively unblocked between about 590 and 685°C, with no hint of changes in magnetic mineralogy and/or viscous behavior during unblocking. This magnetization provides a paleomagnetic pole of 0.8°N and 161.3°E (Weil,Geissman,and Ashby,2006, PC Res.) Several localities, in particular in the eastern part of the uplift, however, have been completely remagnetized and contain a pervasive and exceedingly well- defined, well-grouped magnetization that is consistent with a young, certainly post mid-Cretaceous, age of remagnetization. In chemical demagnetization, this secondary magnetization is completely removed over short

  12. Facies-related diagenetic alteration in lacustrine deltaic red beds of the Paleogene Ergeliin Zoo Formation (Erdene Sum area, S. Gobi, Mongolia)

    NASA Astrophysics Data System (ADS)

    Dill, H. G.; Khishigsuren, S.; Melcher, F.; Bulgamaa, J.; Bolorma, Kh.; Botz, R.; Schwarz-Schampera, U.

    2005-11-01

    The Late Eocene Ergeliin Zoo Formation, Mongolia, was subdivided into four facies associations/stratigraphic units which are characterized by various carbonate minerals: (I) mud-sand flat (low-Fe dolomite, high-Mg calcite), (II) delta front (high-Mn dolomite, low-Mg calcite), (III) delta plain (high-Mn calcite, low-Mg and moderate-Fe calcite), (IV) calcretes (high-Mg calcite). Besides carbonate minerals, prevailing among the cement minerals, some sheet silicates (Ca smectite, palygorskite, illite), apatite and Fe oxide-hydroxides occur in the siliciclastics of these lacustrine-deltaic red beds. The prodelta/mud-sand flat deposits (unit I) were dolomitized and cemented by high-Mg calcite during evaporative pumping at times of low lake-stand under redox conditions greater than 0 and intrastratal solutions of strong alkalinity. Manganoan dolomite is fairly widespread in the delta front sediments (unit II), the Mn content of which is likely to have been derived from decomposition of vertebrate remains. The Mn/Fe ratio in the carbonate minerals was controlled by the redox conditions and the shallow burial depth. In the porous delta front sediments Eh values around zero and pH values slightly above 7 occurred as a result of basinward fluid movements (high-Mn dolomite, high-Fe dolomite, low-Mg calcite). Fluid movement was locally impeded by finer-grained delta plain deposits (unit III), intertonguing with arenaceous aquifers (low Mg-moderate Fe calcite, high-Mn calcite). Higher up on the delta plain with deposits laid down in an environment transitional between distal alluvial and deltaic (unit IV), closed lake basin conditions reappeared as fluids emerged from the distal alluvial-fluvial deposits or were driven by capillary force to ascend and form calcretes abundant in Mg-bearing calcite. The climatic conditions in the Erdene Sum area, Mongolia, are likely to have been semi-arid transitional into arid.

  13. Combined use of thermal methods and seepage meters to efficiently locate, quantify, and monitor focused groundwater discharge to a sand-bed stream

    NASA Astrophysics Data System (ADS)

    Rosenberry, Donald O.; Briggs, Martin A.; Delin, Geoffrey; Hare, Danielle K.

    2016-06-01

    Quantifying flow of groundwater through streambeds often is difficult due to the complexity of aquifer-scale heterogeneity combined with local-scale hyporheic exchange. We used fiber-optic distributed temperature sensing (FO-DTS), seepage meters, and vertical temperature profiling to locate, quantify, and monitor areas of focused groundwater discharge in a geomorphically simple sand-bed stream. This combined approach allowed us to rapidly focus efforts at locations where prodigious amounts of groundwater discharged to the Quashnet River on Cape Cod, Massachusetts, northeastern USA. FO-DTS detected numerous anomalously cold reaches one to several m long that persisted over two summers. Seepage meters positioned upstream, within, and downstream of 7 anomalously cold reaches indicated that rapid groundwater discharge occurred precisely where the bed was cold; median upward seepage was nearly 5 times faster than seepage measured in streambed areas not identified as cold. Vertical temperature profilers deployed next to 8 seepage meters provided diurnal-signal-based seepage estimates that compared remarkably well with seepage-meter values. Regression slope and R2 values both were near 1 for seepage ranging from 0.05 to 3.0 m d-1. Temperature-based seepage model accuracy was improved with thermal diffusivity determined locally from diurnal signals. Similar calculations provided values for streambed sediment scour and deposition at subdaily resolution. Seepage was strongly heterogeneous even along a sand-bed river that flows over a relatively uniform sand and fine-gravel aquifer. FO-DTS was an efficient method for detecting areas of rapid groundwater discharge, even in a strongly gaining river, that can then be quantified over time with inexpensive streambed thermal methods.

  14. The influence of microbial mats on the formation of sand volcanoes and mounds in the Red Sea coastal plain, south Jeddah, Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Taj, Rushdi J.; Aref, Mahmoud A. M.; Schreiber, B. Charlotte

    2014-08-01

    Extensive areas covered by microbial mats have been found in the upper intertidal flats and supratidal pools in the Red Sea coastal plain of south Jeddah, Saudi Arabia. Numerous microbially controlled sediment-surface morphologies are evident, such as flat cohesive mats that commonly pass into mats with wrinkles, reticulates, and tufts, together with erosion pockets and mat chips. These microbial mats form cohesive surface layers that lead to biostabilization of the sediment surface. Fluidization of the underlying sediments is due to tidal influences and pressurized gas escape from decay and photosynthesis of microbial mats and causes deformation and rupture of the cohesive surface mat layer via vertical and sub-vertical pipes. Extrusion of fluidized sediments and water through these pipes leads to redeposition of sediment grains above the surface mat layer to form sand volcanoes and mounds. Most of the sand volcanoes present in the intertidal flats and supratidal pools show a symmetrical morphology, whereas in tidal channels asymmetrical forms are more common. Extrusion of underlying sediments through several adjacent vents leads to coalescence of sand volcanoes to form sand mounds. In this study sand volcanoes are also compared with other cone-like features from the Red Sea, such as gas domes and crab mounds. This comparison should help in differentiating similar cone-like features associated with microbial mats in the rock record.

  15. Mars ecopoiesis test bed: on earth and on the red planet

    NASA Astrophysics Data System (ADS)

    Todd, Paul; Kurk, Michael Andy; Boland, Eugene; Thomas, David; Scherzer, Christopher

    2016-07-01

    The concept of autotrophic organisms serving as planetary pioneers as a precursor to terraforming has been under consideration for several decades, and the term Ecopoiesis was introduced by the ecopoiets C. Sagan, M. Avener, R. Haynes and C. McKay to call attention to this possibility. There is a continuing need for experimental evidence to support this concept, one of them being the need to evaluate the survivability of terrestrial autotrophic microbes in a planetary environment. For this and other purposes a planetary simulation facility was constructed and operated at Techshot, Inc. in Indiana, USA. This facility has an accumulated record of more than one year's worth of experimentation under simulated Mars conditions. In a recent study this facility was operated for five weeks in a mode that simulated 35 sols on and just below the surface of Mars at low latitude. The diurnal lighting period was 12 hours:12 hours using xenon arc light filtered to simulate the solar intensity and spectrum on the Martian surface. A daily temperature profile followed that recorded at low latitudes with night-time minima at -80 C and noontime maxima at +26 C. Atmosphere was CO _{2} at <11 mbar. Moisture was monitored to confirm that no water could exist in the liquid phase. Test organisms included the cyanobacteria Anabena, sp., Chroococcidiopsis CCMEE171 and Plectonema boryanum and Eukaryota: Chlorella ellipsoidia maintained in the simulator under the above-described conditions. The exposed specimens were tested for intracellular esterase activity, chlorophyll content and reproductive survival. All tests yielded low-level positive survival results for these organisms. No definitive data relating to function and/or growth during exposure were sought. In parallel to these terrestrial studies a planned design study was undertaken for a proposed test bed to be operated on the surface of Mars. Design requirements include compact assembly for transport and installation on the planetary

  16. Paleomagnetism of the Oligocene Kangtuo Formation red beds (Central Tibet): Inclination shallowing and tectonic implications

    NASA Astrophysics Data System (ADS)

    Ding, Jikai; Zhang, Shihong; Chen, Weiwei; Zhang, Junhong; Yang, Tianshui; Jiang, Gaolei; Zhang, Kexin; Li, Haiyan; Wu, Huaichun

    2015-05-01

    A paleomagnetic study on the red beds of the Oligocene Kangtuo Formation (Fm) was carried out in the Gerze Basin of the Lhasa terrane. A total of 700 samples were collected from 37 sites. Stepwise thermal demagnetization revealed that the main magnetic carrier is hematite. The natural remnant magnetization (NRM) consists of two components. A low-temperature component (LTC) is identified below 300 °C and is interpreted to be a recent viscous overprint, whereas a high temperature component (HTC) unblocks at ∼665-690 °C and is interpreted to be the primary magnetization. The HTC distributions show a clear east-west elongated distribution, which is considered as reflecting inclination flattening of deposited magnetic remanence carriers. After inclination calibration using the E/I method, the HTC could pass both a reversal test and a fold test at 95% confidence level, showing the mean direction at Ds = 340.3°, Is = 44.2°, with k = 63.0, and α95 = 3.1°, corresponding to a paleopole at 71.7°N, 339.3°E (A95 = 3.1°), and the paleolatitude of the sampling site at 25.9 ± 3.1°N. The paleolatitude is consistent with that expected from the coeval pole of the Qiangtang terrane obtained from volcanic rocks, suggesting that there has been no paleomagnetically-discernable latitudinal motion between the Qiantang and Lhasa terranes since ∼30 Ma. Comparing our new data with the apparent polar wander paths (APWPs) of East Asian blocks (Cogné et al., 2013), Europe, and India (Besse and Courtillot, 2002), we have reached the following conclusions. (1) There is no significant paleolatitudinal difference observed between the Lhasa terrane and other central and northern Asian terranes at ∼30 Ma. (2) The observed paleolatitude of the Kangtuo Fm is 8.0 ± 4.9° lower than the expected paleolatitude deduced from the data of stable Europe, highlighting the 'Asian inclination anomaly' phenomenon, but is 4.6 ± 5.1° higher than that deduced from the data of the India Plate

  17. Tectonic significance of porosity and permeability regimes in the red beds formations of the South Georgia Rift Basin

    NASA Astrophysics Data System (ADS)

    Akintunde, Olusoga M.; Knapp, Camelia C.; Knapp, James H.

    2014-09-01

    A simple, new porosity/permeability-depth profile was developed from available laboratory measurements on Triassic sedimentary red beds (sandstone) from parts of the South Georgia Rift (SGR) basin in order to investigate the feasibility for long-term CO2 storage. The study locations were: Sumter, Berkeley, Dunbarton, Clubhouse Crossroad-3 (CC-3) and Norris Lightsey wells. As expected, both porosity and permeability show changes with depth at the regional scale that was much greater than at local scale. The significant changes in porosity and permeability with depth suggest a highly compacted, deformed basin, and potentially, a history of uplift and erosion. The permeability is generally low both at shallow (less than 1826 ft/556.56 m) and deeper depths (greater than 1826 ft/556.56 m). Both porosity and permeability follow the normal trend, decreasing linearly with depth for most parts of the study locations with the exception of the Norris Lightsey well. A petrophysical study on a suite of well logs penetrating the Norris Lightsey red beds at depths sampled by the core-derived laboratory measurements shows an abnormal shift (by 50%) in the acoustic travel time and/or in the sonic-derived P-wave velocity that indicates possible faulting or fracturing at depth. The departure of the Norris Lightsey's porosities and permeabilities from the normal compaction trend may be a consequence of the existence of a fault/fracture controlled abnormal pressure condition at depth. The linear and non-linear behaviors of the porosity/permeability distribution throughout the basin imply the composition of the SGR red beds, and by extension analog/similar Triassic-Jurassic formations within the Eastern North American Margin have been altered by compaction, uplift, erosion and possible faulting that have shaped the evolution of these Triassic formations following the major phase of rifting.

  18. Tectonic controls on the quality and distribution of Syn- to Post-Rift reservoir sands in the Southern Red Sea, offshore Western Yemen

    SciTech Connect

    Carter, J.M.L.

    1995-08-01

    Previous geophysical and drilling results in the southern Red Sea, and the presence of numerous oil seeps, indicate that the syn- to post-rift section is prospective for oil and gas. The relatively high geothermal gradient offshore western Yemen makes intra-salt and post-salt reservoir sands the only viable exploration targets. The quality and distribution of the reservoir sands remains one of the main unknown risk factors, An improved understanding of the controls on deposition of these sands is achieved by use of LandSat data, which provide evidence of a regional tectonic framework involving NE/SW-trending oceanic transform faults which are expressed onshore as strike-slip features, in some cases representing reactivated Precambrian lineaments. These faults are thought to have played two fundamental roles in the Neogene to Recent evolution of the southern Red Sea - firstly by directing clastic input from the rising Yemen Highlands into offshore depocentres, and secondly by influencing the location of salt diapirs sourced by Upper Miocene evaporates. By considering these factors, together with the pattern of heat flow from the developing oceanic rift of the southern Red Sea, it is possible to delineate areas of offshore western Yemen where reservoir characteristics are likely to be most favourable.

  19. Characterization of CO2-induced (?) bleaching phenomena in German red bed sediments by combined geochemical and evolved gas analysis

    NASA Astrophysics Data System (ADS)

    Hilse, Ulrike; Goepel, Andreas; Pudlo, Dieter; Heide, Klaus; Gaupp, Reinhard

    2010-05-01

    We investigated varied coloured Buntsandstein and Rotliegend sandstones in Central Germany (Thuringian Vorderrhön, Altmark) by thermogravimetric/pyrolytic (DEGAS- directly coupled evolved gas analysis) and geochemical (ICP-MS/OES) means to evaluate geochemical/mineralogical characteristics of red bed rocks and their presumably altered, bleached modifications. Commonly bleaching of primary red bed sediments is regarded as a result of fluid-rock reactions by the participation of CO2. This study is performed in the framework of the special research program 'GEOTECHNOLOGIEN' (funded by the German Ministry of Education and Research - BMBF) and is part of two BMBF sponsored projects - 'COMICOR', an analogue study on potential effects of CO2-bearing fluids on Buntsandstein and Rotliegend deposits in Hesse and Thuringia and 'CLEAN', an enhanced gas recovery (EGR) pilot project in cooperation with GDF SUEZ E&P Deutschland GmbH. The intention of CLEAN is to evaluate the feasibility of EGR techniques and the suitability of depleted natural gas reservoirs for potential industrial CO2 sequestration projects. According to rock colour variations two slices of handspecimens (M49, A1) were split into 12 and 15 equally sized samples for analytical work. The medium grained Lower Buntsandstein sample M49 from Thuringia is of fluvial origin and partially bleached with transitions from red (unbleached) to light colours (bleached). Bulk rock geochemistry of red bed and bleached subsamples of M49 are almost similar, including rare earth element (REE) content. Only the content of iron and related metals is depleted in bleached samples compared to the red bed types. All PAAS normalized pattern of M49 show positive Eu and slightly negative Ce anomalies, most likely caused by the presence of apatite and illite in the rocks. The degassing behavior observed by DEGAS of M49 subsamples is mainly controlled by the breakdown of sheet silicates, hydroxides and hydrates, as well as of carbonates and

  20. Voidage and pressure profile characteristics of sand-iron ore-coal-FCC single-particle systems in the riser of a pilot plant circulating fluidized bed

    SciTech Connect

    Das, M.; Meikap, B.C.; Saha, R.K.

    2008-06-15

    Hydrodynamic behaviors of single system of particles were investigated in a circulating fluidized bed (CFB) unit. Particles belonging to Geldart groups A and B like sand of various sizes (90, 300, 417, 522, 599, and 622 mu m), FCC catalyst (120 mu m), iron ore (166 and 140 {mu} m), and coal (335 and 168 {mu} m) were used to study the hydrodynamic characteristics. Superficial air velocity used in the present study ranged between 2.01 and 4.681 m/s and corresponding mass fluxes were 12.5-50 kg/(m{sup 2} s). A CFB needs the creation of some special hydrodynamic conditions, namely a certain combination of superficial gas velocity, solids circulation rate, particle diameter, density of particle, etc. which can give rise to a state wherein the solid particles are subjected to an upward velocity greater than the terminal or free fall velocity of the majority of the individual particles. The hydrodynamics of the bed was investigated in depth and theoretical analysis is presented to support the findings. Based on gas-solid momentum balance in the riser, a distinction between apparent and real voidage has been made. The effects of acceleration and friction on the real voidage have been estimated. Results indicated a 0.995 voidage for higher superficial gas velocity of 4.681. m/s.

  1. The effects of repeated cycles of calcination and carbonation on a variety of different limestones, as measured in a hot fluidized bed of sand

    SciTech Connect

    Paul S. Fennell; Roberta Pacciani; John S. Dennis; John F. Davidson; Allan N. Hayhurst

    2007-08-15

    The capacity of calcined limestone to react repeatedly with CO{sub 2}, according to CaO{sub cr} + CO{sub 2(g)} = CaCO{sub 3(cr)} (eq I), and also its regeneration in the reverse reaction have been studied in a small, electrically heated fluidized bed of sand, for five different limestones. The forward step of eq I is a promising way of removing CO{sub 2} from the exhaust of, for example, a coal-fired power station, ready for sequestration or as part of a scheme to generate H{sub 2} using an enhanced water-gas shift reaction. The reverse step regenerates the sorbent. The uptake of CO{sub 2} by CaO, produced by calcining limestone, was measured using a bed of sand fluidized by N{sub 2} at about 1023 K. For each experiment, a small quantity of limestone particles was added to the hot sand, whereupon the limestone calcined to produce CaO. Calcination was completed in about 500 s for particles of a mean diameter of about 600 {mu}m. Next, CO{sub 2} was added to the fluidizing nitrogen to carbonate the CaO for about 500 s. Measurements of (CO{sub 2}) in the off-gases enabled the rates of calcination and the subsequent carbonation to be measured as functions of time. Many successive cycles of calcination and carbonation were studied. The forward step of reaction I is shown to exhibit an apparent final conversion, which decreases with the number of cycles of reaction; the final conversion fits well to a correlation from the literature. The reverse (calcination) reaction always proceeded to completion. It was found that the carrying capacity of CaO for CO{sub 2} on the nth cycle of carbonation was roughly proportional to the voidage inside pores narrower than about 150 nm in the calcined CaO before carbonation began. Thus, morphological changes, including reduction in the volume of pores narrower than 150 nm within a calcined limestone, were found to be responsible for much of the fall in conversion of reaction I with increasing numbers of cycles. 19 refs., 9 figs., 4 tabs.

  2. Red iron-ore beds of Silurian age in northeastern Alabama, northwestern Georgia, and eastern Tennessee

    USGS Publications Warehouse

    Whitlow, Jesse W.

    1962-01-01

    Geological studies have determined the lithology and approximate extent of the red iron ores of Silurian age in the Southeast. Detailed investigations have been made by private companies and government agencies. Most of this work has been in the Birmingham, Ala., district, and the remainder of the region has relatively little study in recent years. 

  3. Vertebrate fossils and trace fossils in Upper Jurassic-Lower cretaceous red beds in the Atacama region, Chile

    NASA Astrophysics Data System (ADS)

    Bell, C. M.; Suárez, M.

    Pterosaur, dinosaur, and crocodile bones are recorded here for the first time in Upper Jurassic-Lower Cretaceous red beds in the Atacama region east of Copiapó, Chile. Trace fossils produced by vertebrate animals include the footprints of theropod dinosaurs and the depressions of sandstone laminae interpreted as burrows and foot impressions. The fossils occur in the 1500-meter-thick Quebrada Monardes Formation, which consists predominantly of the aeolian and alluvial deposits of a semi-arid terrestrial environment. Vertebrate fossils are very rare in Chile. Dinosaur bones and footprints have previously been recorded at only seven locations, and pterosaur remains at only one location. The newly discovered dinosaur bones are the oldest to be described in Chile.

  4. A wind tunnel study of flow structure adjustment on deformable sand beds containing a surface-mounted obstacle

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, Cheryl; Bédard, OttO

    2015-09-01

    Roughness elements of varied scale and geometry commonly appear on the surfaces of sedimentary deposits in a wide range of planetary environments. They perturb the local fluid flow so that the entrainment, transport, and deposition of particles surrounding each element are fundamentally altered. Fluid dynamists have expended much effort in examining the flow structures surrounding idealized elements mounted on fixed, planar walls. However self-regulation occurs in sedimentary systems as a result of the bed surface undergoing rapid topographic modification with sediment transport, until it reaches a stable form that enhances the net physical roughness. The present wind tunnel study examines how the flow pattern surrounding an isolated cylinder, a problem extensively studied in classical fluid mechanics, is altered through morphodynamic development of a deep well that envelopes the windward face and sidewalls of the roughness element. Spatial patterns in the fluid velocity, turbulence intensity, and Reynolds stress obtained from laser Doppler anemometer measurements suggest that the flow structures surrounding such a cylinder are fundamentally altered through self-regulation of the bed topography as it reaches steady state. For example, flow stagnation and the turbulent dissipation of momentum are substantially increased at selected points surrounding the upwind face and sidewalls of the cylinder, respectively. Along the center line of the wake flow to the rear of the cylinder, several structures arising from flow separation are annihilated by strong upwelling of the airflow exhausted from the terminus of the well. Feedback plays a complex, time-dependent role in this system.

  5. Recovery comparisons--hot nitrogen Vs steam regeneration of toxic dichloromethane from activated carbon beds in oil sands process.

    PubMed

    Ramalingam, Shivaji G; Pré, Pascaline; Giraudet, Sylvain; Le Coq, Laurence; Le Cloirec, Pierre; Baudouin, Olivier; Déchelotte, Stéphane

    2012-02-29

    The regeneration experiments of dichloromethane from activated carbon bed had been carried out by both hot nitrogen and steam to evaluate the regeneration performance and the operating cost of the regeneration step. Factorial Experimental Design (FED) tool had been implemented to optimize the temperature of nitrogen and the superficial velocity of the nitrogen to achieve maximum regeneration at an optimized operating cost. All the experimental results of adsorption step, hot nitrogen and steam regeneration step had been validated by the simulation model PROSIM. The average error percentage between the simulation and experiment based on the mass of adsorption of dichloromethane was 2.6%. The average error percentages between the simulations and experiments based on the mass of dichloromethane regenerated by nitrogen regeneration and steam regeneration were 3 and 12%, respectively. From the experiments, it had been shown that both the hot nitrogen and steam regeneration had regenerated 84% of dichloromethane. But the choice of hot nitrogen or steam regeneration depends on the regeneration time, operating costs, and purity of dichloromethane regenerated. A thorough investigation had been made about the advantages and limitations of both the hot nitrogen and steam regeneration of dichloromethane. PMID:22244342

  6. Measuring remanence anisotropy of hematite in red beds: anisotropy of high-field isothermal remanence magnetization (hf-AIR)

    NASA Astrophysics Data System (ADS)

    Bilardello, Dario; Kodama, Kenneth P.

    2009-09-01

    The potential of using high-field anisotropy of isothermal remanence magnetization (hf-AIR) measurements for determining the origin of natural remanent magnetization in red beds and for identifying and correcting possible red-bed inclination shallowing was investigated for specimens of the Carboniferous Shepody Formation of New Brunswick and Nova Scotia, Canada. The technique makes it possible for a typical paleomagnetic laboratory to measure the remanence anisotropy of high-coercivity hematite. High-field (hf) AIR was used in conjunction with 100 mT alternating field (af) and 120°C thermal demagnetization to separate the contribution of hematite to the remanence anisotropy from that of magnetite/maghemite and goethite, respectively. A 5-T impulse DC magnetic field was used for the hf-AIR to reset the magnetic moment of high-coercivity hematite so that demagnetization between AIR orientations was not necessary. The ability of a 5-T field to reset the magnetization was tested by generating an isothermal remanent magnetization acquisition curve for hematite by using impulse DC magnetic fields up to 5 T in one orientation and followed by applying a field in the opposite direction at each step. Each field application was treated by 120°C heating and 100 mT af demagnetization before measurement. At 5 T, the difference between the magnetizations applied in opposite directions disappeared indicating that no magnetic memory persisted at this field strength. We performed a validity and reproducibility test of our hf-AIR measurement technique by measuring three specimens multiple times along two orthogonal coordinate systems. The method yielded highly reproducible results and, on rotating the specimen's coordinates, the fabric rotated by 90° as expected, showing that it is not an artifact of the technique. We also measured hf-AIR on samples that had previously been chemically demagnetized in 3N HCl to remove the secondary, chemically grown pigmentary hematite. The hf

  7. Impact of ozonation pre-treatment of oil sands process-affected water on the operational performance of a GAC-fluidized bed biofilm reactor.

    PubMed

    Islam, Md Shahinoor; Dong, Tao; McPhedran, Kerry N; Sheng, Zhiya; Zhang, Yanyan; Liu, Yang; Gamal El-Din, Mohamed

    2014-11-01

    Treatment of oil sands process-affected water (OSPW) using biodegradation has the potential to be an environmentally sound approach for tailings water reclamation. This process is both economical and efficient, however, the recalcitrance of some OSPW constituents, such as naphthenic acids (NAs), require the pre-treatment of raw OSPW to improve its biodegradability. This study evaluated the treatment of OSPW using ozonation followed by fluidized bed biofilm reactor (FBBR) using granular activated carbon (GAC). Different organic and hydraulic loading rates were applied to investigate the performance of the bioreactor over 120 days. It was shown that ozonation improved the adsorption capacity of GAC for OSPW and improved biodegradation by reducing NAs cyclicity. Bioreactor treatment efficiencies were dependent on the organic loading rate (OLR), and to a lesser degree, the hydraulic loading rate (HLR). The combined ozonation, GAC adsorption, and biodegradation process removed 62 % of chemical oxygen demand (COD), 88 % of acid-extractable fraction (AEF) and 99.9 % of NAs under optimized operational conditions. Compared with a planktonic bacterial community in raw and ozonated OSPW, more diverse microbial communities were found in biofilms colonized on the surface of GAC after 120 days, with various carbon degraders found in the bioreactor including Burkholderia multivorans, Polaromonas jejuensis and Roseomonas sp. PMID:25104220

  8. A Devonian paleomagnetic pole from red beds of the Tarim Block, China

    SciTech Connect

    Li, Yianping; McWilliams, M.; Sharps, R.; Cox, A. ); Li, Yongan; Li, Qiang; Gao, Zhengjia ); Zhang, Zhengkun ); Zhai, Yongjian )

    1990-11-10

    The authors present new Devonian paleomagnetic results from 59 sites in three stratigraphic sections exposed on the northwestern margin of the Tarim Block. At one section, 1,998 m of red sandstone is continuously exposed; the other two sections can be correlated with the first on both magnetostratigraphic and lithologic grounds. Progressive thermal demagnetization reveals three characteristic magnetizations. One is a Late Permian overprint which is isolated below 578C at sites near contacts with Late Permian dikes. The other two components are approximately antipodal, have a much higher unblocking temperature than the overprint, and are directionally distinct from the Late Permian overprint. They believe that these are characteristic Devonian magnetizations. Within the continuous 1,998 m section, results denote a 395 m reversed polarity zone overlying a 1,603 m normal polarity zone. One reversed event is recorded at the base of the section. A paleomagnetic pole calculated by averaging results from 47 normal and reversed sites lies at {lambda}{sub p}=16.5{degree}N, {phi}{sub p}=165.0{degree}E, K=25, and A{sub 95}=4.3{degree}. This pole is statistically distinct from a previously reported Late Devonian pole for Tarim. On the basis of field geologic and rock magnetic studies, they believe that the previously reported pole, in addition to results from one of their three sections, reflects at least partial contamination in the form of a thermal overprint caused by Late Permian igneous activity. An analysis of Devonian to Late Carboniferous polar wander suggests that the Tarim Block was attached to a subducting plate, and moved northward and rotated clockwise during the late Paleozoic. Comparison of the Devonian paleolatitudes of Siberian, Kazakhstan, Tarim and South China Blocks indicates that both the Tarim and South China Blocks were located in equatorial regions and were far south of the northern Angaran plate (Siberia and Kazakhstan).

  9. An Experimental Study of Sand Transport over an Immobile Gravel Substrate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of a stepwise addition of sand to an immobile gravel bed on the sand transport rate and configuration of the sand bed was investigated in a laboratory flume channel. Detailed measurements of sand transport rate, bed texture, and bed topography were collected for four different discharge...

  10. Fluvial conglomerates in continental red beds of the Buntsandstein (Lower Triassic) in the Eifel (F.R.G.) and their palaeoenvironmental, palaeogeographical and palaeotectonic significance

    NASA Astrophysics Data System (ADS)

    Mader, Detlef

    1985-05-01

    Fluvial conglomerates occur in a variety of facies within the continental red bed sequence of the Buntsandstein (Lower Triassic) in the Eifel at the western margin of the Mid-European Triassic Basin. The alluvial rudites are classified into channel-floor lag, channel-bar, channel-top lag, crevasse-splay and floodplain-lag conglomerates. The conglomerates were predominantly deposited in Scott-type, and in subordinate amounts also in Donjek-type and South Sasketchewan-type braided rivers. The vertical distribution of clast size and frequency within the megacycles reflects the palaeotectonic sequence of uplift events in the source area, resulting in supply of large amounts of coarse detritus which cause recurrences in fluvial style. Gradually upwards diminishing size and abundance of gravel indicate continuous lowering of source area relief during weakening endogenic activity or even tectonic quiescence after final peneplanation. The palaeoenvironmental interpretation of the individual members and the palaeotectonic analysis of the conglomerate successions are combined with a reconstruction of the depositional history of the Eifel Buntsandstein which comprises an evolution of fluvial deposition. The terminal stage of the palaeoenvironmental evolution is highlighted by a climax of regional diversification of conglomerate sedimentary milieu. The horizontal distribution of clast size and abundance delineates the palaeogeographical evolution of the elongated Eifel Basin, giving evidence of a progressive sidewards extension of the depositional area with time. Lateral supply from parts of the western margin and mixing of proximally derived coarse clasts with distantly delivered fine detritus result in highly inhomogeneous gravel distributions within the sedimentary region often not being characterized by gradually decreasing size and abundance of gravel in downstream direction. The stepwise southwestwards shift of the marginal centre of supply of coarse gravel with time

  11. Palaeomagnetism and magnetic anisotropy of Carboniferous red beds from the Maritime Provinces of Canada: evidence for shallow palaeomagnetic inclinations and implications for North American apparent polar wander

    NASA Astrophysics Data System (ADS)

    Bilardello, Dario; Kodama, Kenneth P.

    2010-03-01

    A palaeomagnetic and magnetic anisotropy study was conducted on the lower-middle Carboniferous Maringouin and Shepody red bed formations of the Maritime Provinces of Canada to detect and correct inclination shallowing. Because of the shallow inclinations commonly observed in red beds and the strong dependence of North America's Palaeo-Mesozoic apparent polar wander (APW) on red beds, inclination shallowing may substantially affect large portions of North America's APW path. Hematite is the primary magnetic mineral carrier in these red beds, accompanied by secondary magnetite, maghemite, goethite and pigmentary hematite. Thermal and chemical demagnetization of the Shepody Fm. successfully isolated characteristic remanence directions of D = 177°, I = 20.4°, α95 = 6.5°, N = 19 and D = 177.8° I = 17.7°, α95 = 6.9°, N = 16, respectively. Thermal demagnetization of the Maringouin Fm. isolated a characteristic remanence direction of D = 178.7°, I = 24.9°, α95 = 14.5°, N = 9. High field anisotropy of isothermal remanence followed by alternating field and thermal cleaning on leached samples was used to isolate the fabric of hematite. Individual particle anisotropy was measured directly from magnetic separates using a new technique. Hematite's magnetic fabric and particle anisotropy were used to apply an inclination correction. Our inclination corrections indicate up to 10° of inclination shallowing, corresponding to corrected palaeopole positions of 27.2°N, 118.3°E, A95 = 6.2° and 27.4°N, 117.2°E, A95 = 13.1° for the Shepody and Maringouin formations, respectively. This correction corresponds to a ~ 6° increase in colatitude for Carboniferous North America, which translates into approximately a 650 km change in North America's palaeogeographic position. The proposed position of North America supports a Pangea B-type reconstruction.

  12. Suspended sediment transport response to upstream wash-load supply in the sand-bed reach of the Upper Yellow River, China

    NASA Astrophysics Data System (ADS)

    Ta, Wanquan; Wang, Haibin; Jia, Xiaopeng

    2015-09-01

    Wash load is a major component of suspended sediment transport in the sand-bed reach of the Upper Yellow River, China. This wash load sediment originates from the Loess region, with the high runoff mainly originating from the rock mountains of its upstream basin. These characteristics result in a mismatch between water and sediment sources and a low probability of high runoffs meeting high suspended sediment concentration (SSC) flows. As a result, higher runoff with lower SSC levels (HR-LS) and lower runoff with higher SSC values (HS) occur, whose SSCs do not follow the typical power form for flow discharges, Ci = αQβ, where Ci and Q are SSC and flow discharge, respectively. Here, we modify the traditional power form with an upstream wash-load supply function C1-β to satisfy the relation between the water and wash load sediment concentrations in water-sediment mismatched cases, Ci = αQβC1-β, where C is an input flow's SSC. Using the daily flow discharges and SSCs of nine typical HR-LS flows and 18 HS flows in our study reach from 1960 to 2012, we find that β changes in response to input flow conditions and downstream transport distances. When the downstream transport distance is between 360 and 663.5 km, β varies between 0.3 and 0.6 in a HS input flow condition, while in the HR-LS input flow case, β tends to be greater than 0.6 (between 0.74 and 0.65). The entrainment rate of an HR-LS flow and the deposition rate of an HS flow appear to be asymmetrically balanced, establishing a primary mechanism for channel aggradation and upward fining of floodplains in our study reach.

  13. Geological setting and paleomagnetism of the Eocene red beds of Laguna Brava Formation (Quebrada Santo Domingo, northwestern Argentina)

    NASA Astrophysics Data System (ADS)

    Vizán, H.; Geuna, S.; Melchor, R.; Bellosi, E. S.; Lagorio, S. L.; Vásquez, C.; Japas, M. S.; Ré, G.; Do Campo, M.

    2013-01-01

    The red bed succession cropping out in the Quebrada Santo Domingo in northwestern Argentina had been for long considered as Upper Triassic-Lower Jurassic in age based on weak radiometric and paleontological evidence. Preliminary paleomagnetic data confirmed the age and opened questions about the nature of fossil footprints with avian features discovered in the section. Recently the stratigraphic scheme was reviewed with the identification of previously unrecognized discontinuities, and a radiometric dating obtained in a tuff, indicated an Eocene age for the Laguna Brava Formation and the fossil bird footprints, much younger than the previously assigned. We present a detailed paleomagnetic study interpreted within a regional tectonic and stratigraphic framework, looking for an explanation for the misinterpretation of the preliminary paleomagnetic data. The characteristic remanent magnetizations pass a tilt test and a reversal test. The main magnetic carrier is interpreted to be low Ti titanomagnetites and to a lesser extent hematite. The characteristic remanent magnetization would be essentially detrital. The obtained paleomagnetic pole (PP) for the Laguna Brava Formation has the following geographic coordinates and statistical parameters: N = 29, Lon. = 184.5° E, Lat. = 75.0° S, A95 = 5.6° and K = 23.7. When this PP is compared with another one with similar age obtained in an undeformed area, a declination anomaly is recognized. This anomaly can be interpreted as Laguna Brava Formation belonging to a structural block that rotated about 16° clockwise along a vertical axis after about 34 Ma. This block rotation is consistent with the regional tectonic framework, and would have caused the fortuitous coincidence of the PP with Early Jurassic poles. According to the interpreted magnetostratigraphic correlation, the Laguna Brava Formation would have been deposited during the Late Eocene with a mean sedimentation rate of about 1.4 cm per thousand years, probably in

  14. Controls of channel morphology and sediment concentration on flow resistance in a large sand-bed river: A case study of the lower Yellow River

    NASA Astrophysics Data System (ADS)

    Ma, Yuanxu; Huang, He Qing

    2016-07-01

    effectively extracted from multisource satellite images. We expect that the empirical methods developed in this study can be used as an effective surrogate in estimation of flow resistance in the large sand-bed rivers like the lower Yellow River.

  15. Paleomagnetism of Cretaceous Oceanic Red Beds(CORBs) from Gyangze, Northern Tethys Himalaya: Evidence for introoceanic Subduction System

    NASA Astrophysics Data System (ADS)

    Tan, X.

    2015-12-01

    In the northern Tethys Himalaya, sporadically distributed oceanic red beds (the Chuangde Formation) have been described. The sequence was interpreted to be firstly deposited in the outer continental shelf and upper slope, and later slumped into deep basin. Based on this model, and paleomagnetic data of shallow water deposits from the southern Tethys Himalaya, the CORBs were derived from the northern tip of the passive margin of the greater India. If so, the CORBs would provide more accurate record of the northern extent of the greater India, which is an important parameter for estimating the initial time of India-Asia continental collision and the amount of crustal shortening. The well studied and most accessible section is located in the Chuangde village, about 40km east from the Gyangze city. The formation is about 25m thick, ranging from 84 to 75Ma in age according to fossil records of planktonic foraminiferal species. The lower and upper parts are 2 and 5 meter thick marlstones, respectively, and the middle section is dominated by shale with a few layers of centimeter scale marlstones. Fifty cores were collected from the marlstones of the section, and for the purpose of fold test, 30 more cores were collected from the upper part of the formation from a second section located in the Pulong village, ~10km to the north of the Chuangde village. All samples were subject to stepwise thermal demagnetization. About 60% of the samples yielded interpretable demagnetization results. The middle part of the formation show reversed high temperature component, and the lower and upper parts show normal polarity. The Chuangde section data failed reversal test, because the normal polarity direction is likely not fully resolved from overprint component. However, the well resolved reversal direction from the Chuangde village and the normal direction from Pulong pass both reversal and fold tests. The mean paleomagnetic data indicate a paleolatitude of 10+/-2 degree north, ~2000 km

  16. Anisotropy of thermoremanent magnetisation of Cryogenian glaciogenic and Ediacaran red beds, South Australia: Neoproterozoic apparent or true polar wander?

    NASA Astrophysics Data System (ADS)

    Schmidt, Phillip W.; Williams, George E.

    2013-11-01

    Determining the effects of compaction-related inclination shallowing of remanence directions is crucial for ascertaining the validity of low palaeolatitudes for Neoproterozoic red beds in South Australia that are central to the debate concerning low-latitude Proterozoic glaciation. The inclination correction (or flattening) factor, f, is defined as tan(ID)/tan(IF), where ID and IF are the inclinations of the measured detrital remanence and the ancient inducing field, respectively. The anisotropy can be estimated using anisotropy of magnetic susceptibility and the anisotropy of high-field isothermal remanence (hf-AIR). The elongation-inclination (E-I) method has also been used to infer inclination shallowing. We add the anisotropy of thermoremanent magnetisation (ATR) to these methods. For the late Cryogenian Elatina Formation arenites, which constitute the bulk of the Elatina data set, the inclination correction using f = 0.738 derived from ATR increases the palaeolatitude of the Elatina Formation from 6.5 ± 2.2° to 8.8 ± 3.2°, which confirms that the Elatina glaciation occurred near the palaeoequator. Inclination corrections for the Ediacaran argillaceous Brachina and Wonoka formations, using f = 0.35-0.38 derived from ATR, are significantly greater than for the more arenaceous Elatina Formation, which increases their palaeolatitudes from ~ 12° to ~ 30°. Carbonates from the basal Ediacaran Nuccaleena Formation yielded f = 0.8 from ATR, which represents only a small palaeolatitude correction from 19° to 23°. The anisotropy results imply that the characteristic remanent magnetisations carried by all these units were acquired early as depositional remanent magnetisations, essentially at the time of deposition. The shift of the palaeopoles from argillaceous units indicating significantly higher palaeolatitudes introduces a distinctive loop into the late Cryogenian-Ediacaran-Cambrian pole path for Australia. This loop shows similarities with the North American

  17. Acquisition of chemical remanent magnetization during experimental ferrihydrite-hematite conversion in Earth-like magnetic field-implications for paleomagnetic studies of red beds

    NASA Astrophysics Data System (ADS)

    Jiang, Zhaoxia; Liu, Qingsong; Dekkers, Mark J.; Tauxe, Lisa; Qin, Huafeng; Barrón, Vidal; Torrent, José

    2015-10-01

    Hematite-bearing red beds are renowned for their chemical remanent magnetization (CRM). If the CRM was acquired substantially later than the sediment was formed, this severely compromises paleomagnetic records. To improve our interpretation of the natural remanent magnetization, the intricacies of the CRM acquisition process must be understood. Here, we contribute to this issue by synthesizing hematite under controlled 'Earth-like' field conditions (≲ 100 μ T). CRM was imparted in 90 oriented samples with varying inclinations. The final synthesis product appeared to be dominated by hematite with traces of ferrimagnetic iron oxides. When the magnetic field intensity is ≳ 40 μ T, the CRM records the field direction faithfully. However, for field intensities ≲ 40 μ T, the CRM direction may deviate considerably from that of the applied field during synthesis. The CRM intensity normalized by the isothermal remanent magnetization (CRM/IRM@2.5 T) increases linearly with the intensity of growth field, implying that CRM could potentially be useful for relative paleointensity studies if hematite particles of chemical origins have consistent properties. CRM in hematite has a distributed unblocking temperature spectrum from ˜200 to ˜650 °C, while hematite with a depositional remanent magnetization (DRM) has a more confined spectrum from ˜ 600to 680 °C because it is usually coarser-grained and more stoichiometric. Therefore, the thermal decay curves of CRM with their concave shape are notably different from their DRM counterparts which are convex. These differences together are suggested to be a potential discriminator of CRM from DRM carried by hematite in natural red beds, and of significance for the interpretation of paleomagnetic studies on red beds.

  18. The paleoclimatic and geochronologic utility of coring red beds and evaporites: a case study from the RKB core (Permian, Kansas, USA)

    NASA Astrophysics Data System (ADS)

    Soreghan, Gerilyn S.; Benison, Kathleen C.; Foster, Tyler M.; Zambito, Jay; Soreghan, Michael J.

    2015-09-01

    Drill core is critical for robust and high-resolution reconstructions of Earth's climate record, as well demonstrated from both marine successions and modern long-lived lake systems. Deep-time climate reconstructions increasingly require core-based data, but some facies, notably red beds and evaporites, have garnered less attention for both paleoclimatic and geochronologic analyses. Here, we highlight studies from the Rebecca K. Bounds (RKB) core, a nearly continuous, >1.6 km drill core extending from the Cretaceous to the Mississippian, recovered from the US Midcontinent by Amoco Production Company in 1988, and serendipitously made available for academic research. Recent research conducted on this core illustrates the potential to recover high-resolution data for geochronologic and climatic reconstructions from both the fine-grained red bed strata, which largely represent paleo-loess deposits, and associated evaporite strata. In this case, availability of core was instrumental for (1) accessing a continuous vertical section that establishes unambiguous superposition key to both magnetostratigraphic and paleoclimatic analyses, and (2) providing pristine sample material from friable, soluble, and/or lithofacies and mineralogical species otherwise poorly preserved in surface exposures. The potential for high-resolution paleoclimatic reconstruction from coring of deep-time loess strata in particular remains severely underutilized.

  19. Sidewinding snakes on sand

    NASA Astrophysics Data System (ADS)

    Marvi, Hamidreza; Dimenichi, Dante; Chrystal, Robert; Mendelson, Joseph; Goldman, Daniel; Hu, David; Georgia Tech and Zoo Atlanta Collaboration

    2012-11-01

    Desert snakes such as the rattlesnake Crotalus cerastes propel themselves over sand using sidewinding, a mode of locomotion relying upon helical traveling waves. While sidewinding on hard ground has been described, the mechanics of movement on more natural substrates such as granular media remain poorly understood. In this experimental study, we use 3-D high speed video to characterize the motion of a sidewinder rattlesnake as it moves on a granular bed. We study the movement both on natural desert sand and in an air-fluidized bed trackway which we use to challenge the animal on different compactions of granular media. Particular attention is paid to rationalizing the snake's thrust on this media using friction and normal forces on the piles of sand created by the snake's body. The authors thank the NSF (PHY-0848894), Georgia Tech, and the Elizabeth Smithgall Watts endowment for support. We would also like to thank Zoo Atlanta staff for their generous help with this project.

  20. Identifying beach sand sources and pathways in the San Francisco Bay Coastal System through the integration of bed characteristics, geochemical tracers, current measurements, and numerical modeling

    NASA Astrophysics Data System (ADS)

    Barnard, P.; Foxgrover, A. C.; Elias, E.; Erikson, L. H.; Hein, J. R.; McGann, M. L.; Mizell, K.; Rosenbauer, R. J.; Swarzenski, P. W.; Takesue, R. K.; Wong, F. L.; Woodrow, D. L.

    2012-12-01

    A unique, multi-faceted provenance study was performed to definitively establish the primary sources, sinks, and transport pathways of beach sized-sand in the San Francisco Bay Coastal System. This integrative program is based on comprehensive surficial sediment sampling of the San Francisco Bay Coastal System, including the seabed, bay floor, area beaches, adjacent rock units, and major drainages. Analyses of sample morphometrics and biological composition (e.g., foraminifera) were then integrated with a suite of tracers including 87Sr/86Sr and 143Nd/144Nd isotopes, rare earth elements, semi-quantitative X-ray diffraction mineralogy, and heavy minerals, and with process-based numerical modeling, in situ current measurements, and bedform asymmetry, to robustly determine the provenance of beach-sized sand in the region. Cross-validating geochemical analyses, numerical modeling, physical process measurements, and proxy-based techniques (e.g., bedform asymmetry, grain size morphometrics) is proved an effective technique for confidently defining sources, pathways, and sinks of sand in complex coastal-estuarine systems. The consensus results highlight the regional impact of a sharp reduction in the primary sediment source, the Sierras, to the San Francisco Bay Coastal System over the last century in driving erosion of the bay floor, ebb-tidal delta, and the outer coast south of the Golden Gate.A) Calculated transport directions based on the integration of the provenance techniques. B) Number of techniques applied for each grid cell to determine the final transport directions.

  1. Integration of bed characteristics, geochemical tracers, current measurements, and numerical modeling for assessing the provenance of beach sand in the San Francisco Bay coastal system

    USGS Publications Warehouse

    Barnard, Patrick L.; Foxgrover, Amy C.; Elias, Edwin P.L.; Erikson, Li H.; Hein, James R.; McGann, Mary; Mizell, Kira; Rosenbauer, Robert J.; Swarzenski, Peter W.; Takesue, Renee K.; Wong, Florence L.; Woodrow, Donald L.

    2013-01-01

    Over 150 million m3 of sand-sized sediment has disappeared from the central region of the San Francisco Bay Coastal System during the last half century. This enormous loss may reflect numerous anthropogenic influences, such as watershed damming, bay-fill development, aggregate mining, and dredging. The reduction in Bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches, wetlands, and submarine environments. A unique, multi-faceted provenance study was performed to definitively establish the primary sources, sinks, and transport pathways of beach-sized sand in the region, thereby identifying the activities and processes that directly limit supply to the outer coast. This integrative program is based on comprehensive surficial sediment sampling of the San Francisco Bay Coastal System, including the seabed, Bay floor, area beaches, adjacent rock units, and major drainages. Analyses of sample morphometrics and biological composition (e.g., Foraminifera) were then integrated with a suite of tracers including 87Sr/86Sr and 143Nd/144Nd isotopes, rare earth elements, semi-quantitative X-ray diffraction mineralogy, and heavy minerals, and with process-based numerical modeling, in situ current measurements, and bedform asymmetry to robustly determine the provenance of beach-sized sand in the region.

  2. Integration of bed characteristics, geochemical tracers, current measurements, and numerical modeling for assessing the provenance of beach sand in the San Francisco Bay Coastal System

    USGS Publications Warehouse

    Barnard, Patrick L.; Foxgrover, Amy; Elias, Edwin P.L.; Erikson, Li H.; Hein, James; McGann, Mary; Mizell, Kira; Rosenbauer, Robert J.; Swarzenski, Peter W.; Takesue, Renee K.; Wong, Florence L.; Woodrow, Don

    2013-01-01

    Over 150 million m3 of sand-sized sediment has disappeared from the central region of the San Francisco Bay Coastal System during the last half century. This enormous loss may reflect numerous anthropogenic influences, such as watershed damming, bay-fill development, aggregate mining, and dredging. The reduction in Bay sediment also appears to be linked to a reduction in sediment supply and recent widespread erosion of adjacent beaches, wetlands, and submarine environments. A unique, multi-faceted provenance study was performed to definitively establish the primary sources, sinks, and transport pathways of beach-sized sand in the region, thereby identifying the activities and processes that directly limit supply to the outer coast. This integrative program is based on comprehensive surficial sediment sampling of the San Francisco Bay Coastal System, including the seabed, Bay floor, area beaches, adjacent rock units, and major drainages. Analyses of sample morphometrics and biological composition (e.g., Foraminifera) were then integrated with a suite of tracers including 87Sr/86Sr and 143Nd/144Nd isotopes, rare earth elements, semi-quantitative X-ray diffraction mineralogy, and heavy minerals, and with process-based numerical modeling, in situ current measurements, and bedform asymmetry to robustly determine the provenance of beach-sized sand in the region.

  3. Technical note: Whole-pen assessments of nutrient excretion and digestibility from dairy replacement heifers housed in sand-bedded freestalls

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our objectives were to describe and test refined procedures for quantifying excreta produced from whole pens of dairy heifers. Previous research efforts attempting to make whole-pen measurements of excreta output have been complicated by the use of organic bedding, which requires cumbersome analytic...

  4. Paleomagnetism of Upper Cretaceous red-beds from the eastern Qiangtang Block: Clockwise rotations and latitudinal translation during the India-Asia collision

    NASA Astrophysics Data System (ADS)

    Tong, Ya-Bo; Yang, Zhenyu; Gao, Liang; Wang, Heng; Zhang, Xu-Dong; An, Chun-Zhi; Xu, Yin-Chao; Han, Zhi-Rui

    2015-12-01

    High-temperature magnetization component was isolated between 600 °C and 680 °C from Upper Cretaceous red-beds in the Mangkang area, in the eastern end of the Qiangtang Block, Tibetan Plateau. The tilt-corrected site-mean direction is Ds/Is = 51.3°/56.1°, with k = 31.0 and α95 = 6.5°, corresponding to a paleolatitude of 36.7 ± 6.7°N. Positive fold and reversal tests indicate a primary magnetization. Inclination shallowing tests show that inclination bias is not present in the Upper Cretaceous red-beds of the Qiangtang Block that might induce through depositional and/or compaction process. However, previous paleomagnetic data obtained from Cretaceous and Paleocene-Eocene volcanic rocks show that the paleolatitudes of the Lhasa Block were 17.1 ± 3.3°N and 22.3 ± 4.4°N, respectively, and 28.7 ± 3.7°N for the central Qiangtang Block yielded from Eocene volcanic rocks. These results show that there was a ∼10° latitudinal discrepancy between the Lhasa Block and Qiangtang relative to Eurasia. However, the Mangkang area of the southeastern Qiangtang Block experienced ∼3.2 ± 7.8° to 7.3 ± 5.2° southward extrusion and ∼40° clockwise rotational movement relative to Eurasia since the Cretaceous, which coincided with the Early Cenozoic rotational extrusion of the Indochina and Shan-Thai Blocks. The crustal deformation in the eastern Qiangtang Block should have been caused by the Indian Plate penetrating into Eurasia in the eastern end of Tibetan Plateau and the formation of the Eastern Himalaya Syntaxis since the Oligocene/Miocene.

  5. Influence of riparian vegetation on channel widening and subsequent contraction on a sand-bed stream since European settlement: Widden Brook, Australia

    NASA Astrophysics Data System (ADS)

    Erskine, Wayne; Keene, Annabelle; Bush, Richard; Cheetham, Michael; Chalmers, Anita

    2012-04-01

    Widden Brook in the Hunter Valley, Australia, was first settled by Europeans in 1831 and had widened substantially by the 1870s due to frequent floods during a flood-dominated regime impacting on highly disturbed banks whose riparian trees had been either ringbarked or cleared, and whose understorey had been grazed. Catastrophic floods in 1950 (many), two in August 1952 and one in February 1955 effected the final phase of channel widening at the onset of a second flood-dominated regime more than half a century after the initial widening. Contraction has been active since 1963 by a combination of five biogeomorphic processes. Firstly, rapid channel widening, migration and cutoffs totally reworked the pre-European floodplain and were followed by active floodplain formation. Initial bar formation was replaced by sand splay and overbank deposition which constructed a new floodplain and narrower channel. Secondly, overwidened channel segments that were produced by the catastrophic 1955 flood have contracted since 1963 by the formation of up to four bank-attached, discontinuous benches below the floodplain. Each bench has a bar nucleus of pebbly coarse sand overlain by stratified fine-medium sand and mud. Colonisation by River Sheoaks (Casuarina cunninghamiana subsp. cunninghamiana) or grasses (Cynodon dactylon, Paspalum distichum, Pennisetum clandestinum) is important in converting bars to benches. Thirdly, narrower segments which developed since 1963 have contracted by small-scale accretion on both banks. These deposits are steeply dipping, interbedded sand and mud trapped by stoloniferous and rhizomatous grasses (C. dactylon, P. distichum, P. clandestinum) which also rapidly stabilise the deposits. Fourthly, rare laterally migrating, small radius bends have contracted by recent point bar formation greatly exceeding cutbank recession rates. Point bar formation is controlled by secondary currents producing inclined stratified coarse sands without the influence of

  6. Modelling hydrodynamics in the Rio Paraná, Argentina: An evaluation and inter-comparison of reduced-complexity and physics based models applied to a large sand-bed river

    NASA Astrophysics Data System (ADS)

    Nicholas, Andrew P.; Sandbach, Steven D.; Ashworth, Philip J.; Amsler, Mario L.; Best, James L.; Hardy, Richard J.; Lane, Stuart N.; Orfeo, Oscar; Parsons, Daniel R.; Reesink, Arnold J. H.; Sambrook Smith, Gregory H.; Szupiany, Ricardo N.

    2012-10-01

    Depth-averaged velocities and unit discharges within a 30 km reach of one of the world's largest rivers, the Rio Paraná, Argentina, were simulated using three hydrodynamic models with different process representations: a reduced complexity (RC) model that neglects most of the physics governing fluid flow, a two-dimensional model based on the shallow water equations, and a three-dimensional model based on the Reynolds-averaged Navier-Stokes equations. Flow characteristics simulated using all three models were compared with data obtained by acoustic Doppler current profiler surveys at four cross sections within the study reach. This analysis demonstrates that, surprisingly, the performance of the RC model is generally equal to, and in some instances better than, that of the physics based models in terms of the statistical agreement between simulated and measured flow properties. In addition, in contrast to previous applications of RC models, the present study demonstrates that the RC model can successfully predict measured flow velocities. The strong performance of the RC model reflects, in part, the simplicity of the depth-averaged mean flow patterns within the study reach and the dominant role of channel-scale topographic features in controlling the flow dynamics. Moreover, the very low water surface slopes that typify large sand-bed rivers enable flow depths to be estimated reliably in the RC model using a simple fixed-lid planar water surface approximation. This approach overcomes a major problem encountered in the application of RC models in environments characterised by shallow flows and steep bed gradients. The RC model is four orders of magnitude faster than the physics based models when performing steady-state hydrodynamic calculations. However, the iterative nature of the RC model calculations implies a reduction in computational efficiency relative to some other RC models. A further implication of this is that, if used to simulate channel morphodynamics

  7. Kinetic studies on degradation of Reactive Red 120 dye in immobilized packed bed reactor by Bacillus cohnii RAPT1.

    PubMed

    Padmanaban, V C; Geed, Sachin RameshRao; Achary, Anant; Singh, R S

    2016-08-01

    The degradation of Reactive Red 120 using Bacillus cohnii RAPT1 immobilized on polyurethane was studied. Initial experiments indicated that the percentage removal of dye in immobilized batch was significantly higher than batch (without immobilization). The optimum process parameters such as effect of dye concentration, time of immobilization on Poly Urethane Foam, initial inoculum size, pH and temperature for removal of dye were investigated and was found as 200ppm, 36h, 300*10(6) colony forming units/ml, 8.0 and 35°C respectively. Under optimum conditions, 100% removal of dye was obtained within 4h. The kinetics of biodegradation for the batch with free cells and immobilised packed batch was found to be IInd order with kinetic constant and initial rate of reaction as 0.0408, 0.084L/(mgday) and 1632, 3360 (mg/Lday) respectively. PMID:26968121

  8. Paleomagnetism of Cretaceous Oceanic Red Beds (CORBs) from Gyangze, northern Tethys Himalaya: Evidence for Intra-oceanic Subduction System and Southern Paleolatitute Limit for the Lhasa Block

    NASA Astrophysics Data System (ADS)

    Tan, Xiaodong

    2016-04-01

    In the northern Tethys Himalaya, sporadically distributed Cretaceous oceanic red beds (CORBs, the Chuangde Formation) have been described. The sequence was interpreted to be firstly deposited in the outer continental shelf and upper slope, and later slumped into deep basin. Based on this model, and paleomagnetic data of shallow water deposits from the southern Tethys Himalaya, the CORBs were derived from the northern tip of the passive margin of the greater India. If so, the CORBs would provide more accurate record of the northern extent of the greater India, which is an important parameter for estimating the initial time of India-Asia continental collision and the amount of crustal shortening. The well studied and most accessible section is located in the Chuangde village, about 40km east from the Gyangze city. The formation is about 25m thick, ranging from 84 to 75Ma in age according to fossil records of planktonic foraminiferal species. The lower and upper parts are 2 and 5 meter thick marlstones, respectively, and the middle section is dominated by shale with a few layers of centimeter scale marlstones. Fifty cores were collected from the marlstones of the section, and for the purpose of fold test, 30 more cores were collected from the upper part of the formation from a second section located in the Pulong village, ~3km to the northeast of the Chuangde village. All samples were subject to stepwise thermal demagnetization. About 60% of the samples yielded interpretable demagnetization results. The bottom of the upper part of the formation show reversed high temperature component, and the rest of the upper part and the lower part show normal polarity. The Chuangde section data failed reversal test, because the normal polarity direction is likely not fully resolved from overprint component. However, the well resolved reversal direction from the Chuangde village and the normal direction from Pulong pass both reversal and fold tests. The mean paleomagnetic data

  9. Analysis of naticid gastropod predation across the trans-Arctic invasion in the Tjörnes beds, Iceland, and the Red Crag Formation, East Anglia, England

    NASA Astrophysics Data System (ADS)

    Neely, Samuel H.; Kelley, Patricia H.

    2016-04-01

    Invasive species are wreaking havoc on modern ecosystems; however, species invasions are not new threats to ecosystems. The fossil record allows conservationists to acquire deep-time perspectives on long-term effects of natural invasions before anthropogenic impacts. Drill holes from invasive naticid gastropod predators on bivalve prey can be quantified to provide evidence of the impact of these invasive predators on ecosystems. An asymmetrical faunal interchange, known as the trans-Arctic invasion (TAI), occurred between the Pacific and Atlantic oceans during the Pliocene (˜3.5 Ma) because of the opening of the Bering Strait. This interchange could have changed naticid gastropod drilling predation on bivalves due to the migration of Pacific fauna into the Atlantic Ocean. The Tjörnes locality of northeast Iceland well characterizes the TAI because this site has preserved genera in three distinct levels that divide the invasion into the pre-invasion (Tapes and Mactra zones) and the post-invasion (Serripes zone). Temporal comparisons can be made between these pre- and post-invasion zones to analyze drilling predation across the TAI. Spatial comparisons of drilling predation in the post-invasion deposits can be made by correlating the Serripes zone (3.6-2.6 Ma) to the Red Crag Formation (2.54 Ma) of East Anglia, England, because these localities are of similar age and contain similar taxa. Specimens from the Tjörnes Beds, Iceland, were analyzed in collections housed at the Icelandic Institute of Natural History. Red Crag Formation specimens were analyzed at the Academy of Natural Sciences at Drexel University, Philadelphia, PA. Height and length of bivalve specimens were measured. The occurrence of complete and incomplete (unsuccessful) drill holes and drill hole diameter were recorded for all whole bivalves. Drilling frequency (DF = % mortality) and prey effectiveness (PE = % of attempted drill holes that were incomplete) were calculated. Icelandic samples

  10. An optical method of measuring the temperature in a fluidised bed combustor

    SciTech Connect

    Zukowski, Witold; Baron, Jerzy; Bulewicz, Elzbieta M.; Kowarska, Beata

    2009-07-15

    The paper analyses the dynamic aspects of the temperature field in a fluidised bed of solids particles (e.g., sand) in which a gaseous fuel is being burned. Such a hot bed emits electromagnetic radiation within the visible range and this can be recorded using a digital video camera. This fact has been used to develop a method for measuring the bed's temperature in the line of sight, through the quartz sides of the reactor. A solid probe is only used for calibration. Video recordings were obtained covering different regions of the bed over three wavelength bands, red, green and blue. In the course of an experiment, the mean temperature of the bed, measured with thermocouples, was raised from ambient to 1300 K, at a rate of {proportional_to} 1 K/s. The data collected were used for calibration, with the brightness of individual pixels converted to a temperature scale. The calibration can then be used to investigate the dynamic temperature distribution within the field of view, in individual elements of the bed. This can also help the study of heat transfer in the bed, its distribution and dissipation. Using this method, it is possible to make direct observations of the intermittent combustion of gaseous fuels in a bubbling fluidised bed. The results provide direct proof that the temperature gradients observed within such beds are associated with exothermic processes within fast moving bubbles. The method could be adapted to studying, e.g., the combustion of solid fuels. (author)

  11. Molecular phylogeny of the subfamily Amphistichinae (Teleostei: Embiotocidae) reveals parallel divergent evolution of red pigmentation in two rapidly evolving lineages of sand-dwelling surfperch.

    PubMed

    Westphal, M F; Morey, S R; Uyeda, J C; Morgan, T J

    2011-08-01

    Pigment evolution was reconstructed in the subfamily Amphistichinae, a six-species clade of the surfperches, family Embiotocidae. Assignment was confirmed for all species within the subfamily, but low levels of differentiation were found among species within the subfamily, suggesting a recent radiation. The new phylogeny differs from previous hypotheses by the placement of the spotfin surfperch Hyperprosopon anale at the base of the subfamily, while still preserving the calico surfperch Amphistichus koelzi and the redtailed surfperch Amphistichus rhodoterus as sister species. Phenotypically, A. rhodoterus, A. koelzi and the silver surfperch Hyperprosopon ellipticum express high levels of red pigmentation. The barred surfperch, Amphistichus argenteus and the walleye surfperch Hyperprosopon argenteum express little to no red pigment, while basal H. anale expresses an intermediate amount of red pigment. Red pigmentation is proposed to have experienced parallel divergent evolution in each genus within the subfamily. PMID:21781095

  12. Dual Fluidized Bed Biomass Gasification

    SciTech Connect

    2005-09-30

    The dual fluidized bed reactor is a recirculating system in which one half of the unit operates as a steam pyrolysis device for biomass. The pyrolysis occurs by introducing biomass and steam to a hot fluidized bed of inert material such as coarse sand. Syngas is produced during the pyrolysis and exits the top of the reactor with the steam. A crossover arm, fed by gravity, moves sand and char from the pyrolyzer to the second fluidized bed. This sand bed uses blown air to combust the char. The exit stream from this side of the reactor is carbon dioxide, water and ash. There is a second gravity fed crossover arm to return sand to the pyrolysis side. The recirculating action of the sand and the char is the key to the operation of the dual fluidized bed reactor. The objective of the project was to design and construct a dual fluidized bed prototype reactor from literature information and in discussion with established experts in the field. That would be appropriate in scale and operation to measure the relative performance of the gasification of biomass and low ranked coals to produce a high quality synthesis gas with no dilution from nitrogen or combustion products.

  13. Effects of silt loading on turbulence and sand transport

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The transport of bed material and fluid turbulence are affected by many factors, including the fine sediment load being carried in a channel. Current research has focused on sand-sized particles introduced to gravel beds, while the effect of silt load on sand transport has received less attention. ...

  14. Paleomagnetism of Late Jurassic to Early Cretaceous red beds from the Cardamom Mountains, southwestern Cambodia: Tectonic deformation of the Indochina Peninsula

    NASA Astrophysics Data System (ADS)

    Tsuchiyama, Yukiho; Zaman, Haider; Sotham, Sieng; Samuth, Yos; Sato, Eiichi; Ahn, Hyeon-Seon; Uno, Koji; Tsumura, Kosuke; Miki, Masako; Otofuji, Yo-ichiro

    2016-01-01

    Late Jurassic to Early Cretaceous red beds of the Phuquoc Formation were sampled at 33 sites from the Sihanoukville and Koah Kong areas of the Phuquoc-Kampot Som Basin, southwestern Cambodia. Two high-temperature remanent components with unblocking temperature ranging 650°-670 °C and 670-690 °C were identified. The magnetization direction for the former component (D = 5.2 °, I = 18.5 ° with α95 = 3.1 ° in situ) reveals a negative fold test that indicates a post-folding secondary nature. However, the latter component, carried by specular hematite, is recognized as a primary remanent magnetization. A tilt-corrected mean direction of D = 43.4 °, I = 31.9 ° (α95 = 3.6 °) was calculated for the primary component at 11 sites, corresponding to a paleopole of 47.7°N, 178.9°E (A95 = 3.6 °). When compared with the 130 Ma East Asian pole, a southward displacement of 6.0 ° ± 3.5 ° and a clockwise rotation of 33.1 ° ± 4.0 ° of the Phuquoc-Kampot Som Basin (as a part of the Indochina Block) with respect to East Asia were estimated. This estimate of the clockwise rotation is ∼15° larger than that of the Khorat Basin, which we attribute to dextral motion along the Wang Chao Fault since the mid-Oligocene. The comparison of the herein estimated clockwise rotation with the counter-clockwise rotation reported from the Da Lat area in Vietnam suggests the occurrence of a differential tectonic rotation in the southern tip of the Indochina Block. During the southward displacement of the Indochina Block, the non-rigid lithosphere under its southern tip moved heterogeneously, while the rigid lithosphere under the Khorat Basin moved homogeneously.

  15. SHRIMP U-Pb ages of xenotime and monazite from the Spar Lake red bed-associated Cu-Ag deposit, western Montana: Implications for ore genesis

    USGS Publications Warehouse

    Aleinikoff, John N.; Hayes, Timothy S.; Evans, Karl V.; Mazdab, Frank K.; Pillers, Renee M.; Fanning, C. Mark

    2012-01-01

    Xenotime occurs as epitaxial overgrowths on detrital zircons in the Mesoproterozoic Revett Formation (Belt Supergroup) at the Spar Lake red bed-associated Cu-Ag deposit, western Montana. The deposit formed during diagenesis of Revett strata, where oxidizing metal-bearing hydrothermal fluids encountered a reducing zone. Samples for geochronology were collected from several mineral zones. Xenotime overgrowths (1–30 μm wide) were found in polished thin sections from five ore and near-ore zones (chalcocite-chlorite, bornite-calcite, galena-calcite, chalcopyrite-ankerite, and pyrite-calcite), but not in more distant zones across the region. Thirty-two in situ SHRIMP U-Pb analyses on xenotime overgrowths yield a weighted average of 207Pb/206Pb ages of 1409 ± 8 Ma, interpreted as the time of mineralization. This age is about 40 to 60 m.y. after deposition of the Revett Formation. Six other xenotime overgrowths formed during a younger event at 1304 ± 19 Ma. Several isolated grains of xenotime have 207Pb/206Pb ages in the range of 1.67 to 1.51 Ga, and thus are considered detrital in origin. Trace element data can distinguish Spar Lake xenotimes of different origins. Based on in situ SHRIMP analysis, detrital xenotime has heavy rare earth elements-enriched patterns similar to those of igneous xenotime, whereas xenotime overgrowths of inferred hydrothermal origin have hump-shaped (i.e., middle rare earth elements-enriched) patterns. The two ages of hydrothermal xenotime can be distinguished by slightly different rare earth elements patterns. In addition, 1409 Ma xenotime overgrowths have higher Eu and Gd contents than the 1304 Ma overgrowths. Most xenotime overgrowths from the Spar Lake deposit have elevated As concentrations, further suggesting a genetic relationship between the xenotime formation and Cu-Ag mineralization.

  16. Sands-on Learning.

    ERIC Educational Resources Information Center

    Vandervoort, Frances S.

    1989-01-01

    Provides information for the development of a lesson which teaches students about sand, discusses facts about sands, sand studies, life in the sands, and sand activities. Includes diagrams showing the range in sand grain shape, formation of sand ripples, and sand samples from around the world. (RT)

  17. High temperature thermal energy storage in moving sand

    NASA Technical Reports Server (NTRS)

    Turner, R. H.; Awaya, H. I.

    1978-01-01

    Several high-temperature (to 500 C) heat-storage systems using sand as the storage medium are described. The advantages of sand as a storage medium include low cost for sand, widespread availability, non-toxicity, non-degradation characteristics, easy containment, and safety. The systems considered include: stationary sand with closely spaced tubes throughout the volume, the use of a fluidized bed, use of conveyor belt transporter, and the use of a blower rapid transport system. For a stationary sand bed, very close spacing of heat transfer tubes throughout the volume is required, manifesting as high power related system cost. The suggestion of moving sand past or around pipes is intended to reduce the power related costs at the penalty of added system complexity. Preliminary system cost estimates are offered. These rough calculations indicate that mobile sand heat storage systems cost less than the stationary sand approach.

  18. The gravel-sand transition: Sediment dynamics in a diffuse extension

    NASA Astrophysics Data System (ADS)

    Venditti, Jeremy G.; Domarad, Natalia; Church, Michael; Rennie, Colin D.

    2015-06-01

    As gravel-bedded rivers fine in the downstream direction, they characteristically exhibit an abrupt transition from gravel- to sand-bedded conditions. The prevailing theory for why abrupt gravel-sand transitions emerge is based on bed load sorting of a bimodal sediment. The abruptness is thought to be a consequence of sand overwhelming the gravel-sand mixture once it reaches a critical coverage on the bed. The role suspension plays in the development of gravel-sand transitions has not been fully appreciated. The Fraser River, British Columbia, is an archetypical abrupt gravel-sand transition with a "diffuse extension" composed of a sand bed with some patches of gravel. We examine flow, shear stress, and suspended sediment flux in the diffuse extension to better understand sediment dynamics where the sand bed emerges. Sand is carried in suspension upstream of the primary abrupt gravel-sand transition, but in the diffuse extension, sand is moved as both bed load and suspended load. We do not observe downstream gradients in shear stress or suspended sand flux through the diffuse extension that would suggest a gradual "rain out" of sand moving downstream, which raises the question, how is the sand bed formed? Sediment advection length scales indicate that with the exception of very fine sand that moves as wash load in the diffuse extension, fractions coarser than the median sand size cannot be carried in suspension for more than one channel width. This suggests that sand is deposited en masse at the beginning of the diffuse extension, forming a sediment slug at low flood flows that is smeared downstream at high flood flows to form the sand reach.

  19. The extraction of bitumen from western tar sands. Annual report, July 1990--July 1991

    SciTech Connect

    Oblad, A.G.; Bunger, J.W.; Deo, M.D.; Hanson, F.V.; Miller, J.D.; Seader, J.D.

    1992-04-01

    Contents of this report include the following: executive summary; characterization of the native bitumen from the Whiterocks oil sand deposit; influence of carboxylic acid content on bitumen viscosity; water based oil sand separation technology; extraction of bitumen from western oil sands by an energy-efficient thermal method; large- diameter fluidized bed reactor studies; rotary kiln pyrolysis of oil sand; catalytic upgrading of bitumen and bitumen derived liquids; ebullieted bed hydrotreating and hydrocracking; super critical fluid extraction; bitumen upgrading; 232 references; Appendix A--Whiterocks tar sand deposit bibliography; Appendix B--Asphalt Ridge tar sand deposit bibliography; and Appendix C--University of Utah tar sands bibliography.

  20. Tar sands

    SciTech Connect

    Wennekers, J.H.N.

    1981-10-01

    The four largest oil sand deposits contain over 90% of the world's known heavy oil. The total heavy oil and bitumen in place, estimated at nearly 6 trillion barrels is almost entirely concentrated in western Canada, principally Alberta, and eastern Venezuela. The known tar sand resource in the United States consists of about 550 occurrences located in 22 states. The total oil in place in 39 of these occurrences is estimated to be between 23.7 billion and 32.7 billion barrels. At least 90% of this resource is located in Utah. Other significant deposits are in Texas, New Mexico, California, and Kentucky. Bituminous sand deposits and petroleum-impregnated rocks are found in Malagasy, Albania, Rumania, the USSR, and Trinidad. 4 figures, 2 tables. (DP)

  1. Prediction of Bed Load Transport on Small Gravel-Bed Streams

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rates and size distributions of bed load were calculated using 3 transport relations and compared to data collected on three streams with sand-gravel beds in the Goodwin Creek Experimental Watershed in north central Mississippi, USA. Bed load transport rates were greatly over predicted by two of th...

  2. SLUDGE DEWATERING AND DRYING ON SAND BEDS

    EPA Science Inventory

    Dewatering of water and wastewater treatment sludges was examined through mathematical modeling and experimental work. The various components of the research include: (1) chemical analyses of water treatment sludges, (2) drainage and drying studies of sludges, (3) a mathematical ...

  3. Dynamical evolution of sand ripples under water.

    PubMed

    Stegner, A; Wesfreid, J E

    1999-10-01

    We have performed an experimental study on the evolution of sand ripples formed under the action of an oscillatory flow. An annular sand-water cell was used in order to investigate a wide range of parameters. The sand ripples follow an irreversible condensation mechanism from small to large wavelength until a final state is reached. The wavelength and the shape of these stable sand patterns are mainly governed by the fluid displacement and the static angle of the granular media. A strong hysteresis affects the evolution of steep ripples. When the acceleration of the sand bed reaches a critical value, the final pattern is modified by the superficial fluidization of the sand layer. PMID:11970264

  4. Defrosting Sand

    NASA Technical Reports Server (NTRS)

    2005-01-01

    19 June 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark spots formed in carbon dioxide frost that covers the surfaces of patches of sand in the south polar region. As spring arrived this year in the martian southern hemisphere, so began the annual defrosting process. The fact that sand dunes begin to defrost earlier than other surfaces, and that the defrosting process involves the formation of spots like these, has been known since the earliest days of the MGS mission.

    Location near: 66.8oS, 15.7oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  5. Improved lignin pyrolysis for phenolics production in a bubbling bed reactor--Effect of bed materials.

    PubMed

    Li, Dongbing; Briens, Cedric; Berruti, Franco

    2015-01-01

    Lignin pyrolysis was studied in a bubbling fluidized bed reactor equipped with a fractional condensation train, using nitrogen as the fluidization gas. The effect of different bed materials (silica sand, lignin char, activated lignin char, birch bark char, and foamed glass beads) on bio-oil yield and quality was investigated for a pyrolysis temperature of 550 °C. Results how that a bed of activated lignin char is preferable to the commonly used silica sand: pyrolysis of Kraft lignin with a bed of activated lignin char not only provides a pure char product, but also a higher dry bio-oil yield (with a relative increase of 43%), lower pyrolytic water production, and better bio-oil quality. The bio-oil obtained from Kraft lignin pyrolysis with a bed of activated lignin char has a lower average molecular weight, less tar, more phenolics, and less acidity than when sand is used as bed material. PMID:25863324

  6. Granular size segregation in underwater sand ripples.

    PubMed

    Rousseaux, G; Caps, H; Wesfreid, J-E

    2004-02-01

    We report an experimental study of a binary sand bed under an oscillating water flow. The formation and evolution of ripples is observed. The appearance of a granular segregation is shown to strongly depend on the sand bed preparation. The initial wavelength of the mixture is measured. In the final steady state, a segregation in volume is observed instead of a segregation at the surface as reported before. The correlation between this phenomenon and the fluid flow is emphasised. Finally, different "exotic" patterns and their geophysical implications are presented. PMID:15052430

  7. Three-dimensional mapping of red stingray ( Dasyatis akajei) movement with reference to bottom topography

    NASA Astrophysics Data System (ADS)

    Otaki, Takayoshi; Hamana, Masahiro; Tanoe, Hideaki; Miyazaki, Nobuyuki; Shibuno, Takuro; Komatsu, Teruhisa

    2015-06-01

    Most demersal fishes maintain strong relations with bottom substrates and bottom depths and/or topography during their lives. It is important to know these relations to for understand their lives. In Tokyo Bay, red stingray, Dasyatis akajei, classified as near-threatened species by IUCN, has increased since the 1980s. It is a top predator and engages in ecosystem engineer by mixing the sand bed surface through burring behavior, and greatly influences a coastal ecosystem. It is reported that this species invades in plage and tidal flats and has sometimes injured beachgoers and people gathering clams in Tokyo bay. Thus, it is necessary to know its behavior and habitat use to avoid accidents and to better conserve the biodiversity of ecosystems. However, previous studies have not examined its relationship with the bottom environment. This study aims to describe its behavior in relation to the bottom environment. We sounded three dimensional bottom topography of their habitat off Kaneda Cove in Tokyo Bay with interferometric sidescan sonar system and traced the movement of red stingrays by attaching a data logger system to survey their migration. The results revealed that red stingray repeated vertical movement between the surface and bottom, and used not only sand beds but also rocky beds.

  8. Storm graded sand at 200 m water depth, Scotian Shelf, Eastern Canada

    NASA Astrophysics Data System (ADS)

    Kontopoulos, Nikos; Piper, David J. W.

    1982-03-01

    Graded sand-to-mud beds are a common shelf facies in the rock record. Similar beds were studied in nine cores from the sandmud transition at the edge of Emerald Basin to determine their frequency and mode of origin. Graded sand-to-mud beds 5 to 20 cm thick can be correlated between cores and thicken basinwards, with average sand content decreasing from 60% to 5% over 7 km. European weed pollen distribution indicates only the top bed is less than 200 years old. The graded beds were deposited from suspension during storms with a several hundred year recurrence interval.

  9. Numerical modeling of subaqueous sand dune morphodynamics

    NASA Astrophysics Data System (ADS)

    Doré, Arnaud; Bonneton, Philippe; Marieu, Vincent; Garlan, Thierry

    2016-03-01

    The morphodynamic evolution of subaqueous sand dunes is investigated, using a 2-D Reynolds-averaged Navier-Stokes numerical model. A laboratory experiment where dunes are generated under stationary unidirectional flow conditions is used as a reference case. The model reproduces the evolution of the erodible bed until a state of equilibrium is reached. In particular, the simulation exhibits the different stages of the bed evolution, e.g., the incipient ripple generation, the nonlinear bed form growing phase, and the dune field equilibrium phase. The results show good agreement in terms of dune geometrical dimensions and time to equilibrium. After the emergence of the first ripple field, the bed growth is driven by cascading merging sequences between bed forms of different heights. A sequence extracted from the simulation shows how the downstream bed form is first eroded before merging with the upstream bed form. Superimposed bed forms emerge on the dune stoss sides during the simulation. An analysis of the results shows that they emerge downstream of a slight deflection on the dune profile. The deflection arises due to a modification of the sediment flux gradient consecutive to a reduction in the turbulence relaxation length while the upstream bed form height decreases. As they migrate, superimposed bed forms grow on the dune stoss side and eventually provoke the degeneration of the dune crest. Cascading merging sequences and superimposed bed forms dynamics both influence the dune field evolution and size and therefore play a fundamental role in the dune field self-organization process.

  10. Submarine sand ridges and sand waves in the eastern part of the China Sea

    NASA Astrophysics Data System (ADS)

    Wu, Ziyin; Li, Shoujun; Shang, Jihong; Zhou, Jieqiong; Zhao, Dineng; Liang, Yuyang

    2016-04-01

    Integrated with multi-beam and single-beam echo sounding data, as well as historical bathymetric data, submarine bathymetric maps of the eastern part of the China Sea, including the Bohai Sea, Huanghai Sea, and East China Sea, are constructed to systematically study submarine sand ridges and sand waves in the eastern part of the China Sea, combined with high-resolution seismic, sub-bottom profile and borehole data. Submarine sand ridges are extraordinarily developed in the eastern part of the China Sea, and 7 sand ridge areas can be divided from north to south, that is, the Laotieshan Channel sand ridge area in the Bohai Sea, the Korea Bay sand ridge area in the southern Huanghai Sea, the sand ridge area in the eastern Huanghai islands and the Huanghai Troughs, the Jianggang sand ridge area in the western Huanghai Sea, the sand ridge area in the East China Sea shelf, and the sand ridge and sand wave area in the Taiwan Strait and Taiwan Banks. The distribution area of the sand ridges and sand waves covers more than 450,000 km2, wherein ~10,000 km2 in the Bohai Bay, ~200,000 km2 in the Huanghai Sea, ~200,000 km2 in the East China Sea shelf, and ~40,000 km2 in the Taiwan Strait and Taiwan Banks, respectively. The great mass of sand ridges are distributed within water depth of 5-160 m, with a total length of over 160 km and a main width of 5-10 km. The inner structure of the sand ridges presents features of high-angle inclined beddings, with main lithology of sands, sand-mud alternations partly visible, and a small number of mud cores. Dating results indicate that the sand ridges in the eastern part of the China Sea are mainly developed in the Holocene. Sea-level variation dominates the sand ridge evolution in the eastern part of the China Sea since the LGM, and the sand ridges developed in the area of < 60m water depth are appeared in bad activity, meanwhile sand ridges with good activity are still developed in large scale.

  11. Industrial sand and gravel

    USGS Publications Warehouse

    Dolley, T.P.

    2011-01-01

    Domestic production of industrial sand and gravel in 2010 was about 26.5 Mt (29.2 million st), a 6-percent increased from 2009. Certain end uses of industrial sand and gravel, such as sand for container glass, golf course sand, recreational sand, specialty glass and water filtration, showed increased demand in 2010.

  12. Sand Diver

    NASA Astrophysics Data System (ADS)

    Scott, Alan J.

    2005-01-01

    A few years ago, I was preparing to teach a summer enrichment program for middle school students at the University of Wisconsin-Stout. With swimming on the minds of most kids during the summer, I thought buoyancy would be a fun topic to discuss. An interesting way to introduce this concept is by discussing the beer-drinking balloonist who, in a lawn chair, floated to 11,000 feet above Los Angeles in 1997. However, I needed a hands-on project and was not about to go purchase some lawn chairs to duplicate this experiment. A simple submersible called the "Sand Diver" was designed and is now used as a hands-on activity for my introductory physics course.

  13. Bed bugs.

    PubMed

    Foulke, Galen T; Anderson, Bryan E

    2014-09-01

    The term bed bug is applied to 2 species of genus Cimex: lectularius describes the common or temperate bed bug, and hemipterus its tropical cousin. Cimex lectularius is aptly named; its genus and species derive from the Latin words for bug and bed, respectively. Though the tiny pest is receiving increased public attention and scrutiny, the bed bug is hardly a new problem. PMID:25577850

  14. Occurrence of Radium-224, Radium-226 and Radium-228 in Water from the Vincentown and Wenonah-Mount Laurel Aquifers, the Englishtown Aquifer System, and the Hornerstown and Red Bank Sands, Southwestern and South-Central New Jersey

    USGS Publications Warehouse

    dePaul, Vincent T.; Szabo, Zoltan

    2007-01-01

    This investigation is the first regionally focused study of the presence of natural radioactivity in water from the Vincentown and Wenonah-Mount Laurel aquifers, Englishtown aquifer system, and the Hornerstown and Red Bank Sands. Geologic materials composing the Vincentown and Wenonah-Mount Laurel aquifers and the Hornerstown and Red Bank Sands previously have been reported to contain radioactive (uranium-enriched) phosphatic strata, which is common in deposits from some moderate-depth coastal marine environments. The decay of uranium and thorium gives rise to natural radioactivity and numerous radioactive progeny, including isotopes of radium. Naturally occurring radioactive isotopes, especially those of radium, are of concern because radium is a known human carcinogen and ingestion (especially in water used for drinking) can present appreciable health risks. A regional network in southwestern and south-central New Jersey of 39 wells completed in the Vincentown and Wenonah-Mount Laurel aquifers, the Englishtown aquifer system, and the Hornerstown and Red Bank Sands was sampled for determination of gross alpha-particle activity; concentrations of radium radionuclides, major ions, and selected trace elements; and physical properties. Concentrations of radium-224, radium-226, and radium-228 were determined for water from 28 of the 39 wells, whereas gross alpha-particle activity was determined for all 39. The alpha spectroscopic technique was used to determine concentrations of radium-224, which ranged from less than 0.5 to 2.7 pCi/L with a median concentration of less than 0.5pCi/L, and of radium-226, which ranged from less than 0.5 to 3.2 pCi/L with a median concentration of less than 0.5 pCi/L. The beta-counting technique was used to determine concentrations of radium-228. The concentration of radium-228 ranged from less than 0.5 to 4.3 pCi/L with a median of less than 0.5. Radium-228, when quantifiable, had the greatest concentration of the three radium

  15. Sand resistance of sunscreens.

    PubMed

    Caswell, Michael; Wood, Caryl; Martinez, Alexa

    2012-01-01

    Like water resistance in sunscreens, sand resistance in sunscreens is the ability of the sunscreen to retain its effectiveness while undergoing sand treatment. The influence of the type of sand on the sand resistance of sunscreens has not been described. The sand resistance of a control standard sunscreen, P2, and data on three grades of Quickrete commercial grade sand, #1961, #1962, and #1152, are described. These sands represent a fine sand, a medium sand, and an all-purpose sand. Using the methodology described in the 2007 proposed amendment of the Final Monograph (1) with one exception, we obtained an SPF of 16.5 (1.6) for the control standard, compared to the expected SPF of 16.3 (3.4). After a five-minute treatment of sand #1961, #1962, or #1151, the SPF of the control standard was 18.3 (1.6), 18.4 (2.0), and 17.5 (2.2), respectively. Thus, all three sands exhibited a similar sand-resistance response. Thus, there was no significant difference in the average SPF with and without sand. The medium grade sand, Quickrete commercial grade #1962, was preferred for sand-resistance testing because the fine sand was difficult to remove from the subject's backs and the coarse sand was unpleasant to the subjects. PMID:23193889

  16. Red Bluff, Marion County, Mississippi: a Citronelle braided-stream deposit

    SciTech Connect

    Smith, M.L.; Meylan, M.A.

    1983-09-01

    Red Bluff is an erosional escarpment located on the western margin of the Pearl River flood plain in northwestern Marion County, Mississippi. The sand grains are composed primarily of quartz, with small amounts of heavy minerals and feldspar. The gravel is composed of varying percentages of chert, flint, jasper, rip-up clasts, quartz, and tripoli, including a small fraction of silicified Paleozoic fossils. Grain-size analysis of the sediment and investigation of the sedimentary structures suggest a braided-fluvial environment of deposition. The most conspicuous sedimentary structures at Red Bluff are graded bedding, low-angle to medium-angle cross-bedding, and well-developed paleochannels. A statistical comparison (discriminant analysis) of the seven most abundant heavy minerals of Red Bluff, with the same suite of heavy minerals found at the type section of the Citronelle Formation (Pliocene-Pleistocene), and outcrops of a known Miocene coarse clastic unit indicates a correlation of Red Bluff to the Citronelle Formation. These heavy minerals are kyanite, staurolite, rutile, tourmaline, zircon, black opaques (primarily ilmenite and magnetite), and white opaques (primarily leucoxene). The suite of heavy minerals present at Red Bluff belongs to the east Gulf province. This metamorphic assemblage of heavy minerals implies the source area of the sediments at Red Bluff to be the southern Appalachians. The silicified pebble-size Devonian-Mississippian fossils were derived most likely from formations flanking the southern Appalachians in northern Alabama.

  17. Monitoring and characterisation of sand-mud sedimentation processes

    NASA Astrophysics Data System (ADS)

    Cuthbertson, Alan J. S.; Ibikunle, Olugbenga; McCarter, W. John; Starrs, Gerard

    2016-07-01

    Estuaries and tidal inlets are often characterised by the presence of both cohesive and non-cohesive sediments. Knowledge of the sedimentation behaviour of sand-mud mixtures is therefore crucial to the understanding and prediction of the time-dependent structure (i.e. mixed or segregated), composition and erodibility of sediment bed deposits developing within these environments. In the current study, a series of settling column tests are conducted to investigate the hindered settling and initial bed consolidation phases of a range of sand-clay mixtures to determine the parametric conditions under which bed segregation occurs. A new, non-invasive, electrical resistivity measurement technique is employed to capture both temporal and spatial changes in the density, porosity and composition of the evolving sand-clay bed deposits, complimented by time-lapsed images of the sedimentation process within the column. The results show that the formation of segregated (sand-clay) bed layers with bed deposits is largely controlled by the initial fractional composition (i.e. relative sand and clay concentrations). Specifically, mixtures with low clay contents are shown to form well-defined (sand-clay) layer segregation within the resulting deposits, while higher clay contents result in more transitional segregation patterns or no layer segregation (for very high clay concentrations). The physical mechanisms under which these different segregation types can be generated are illustrated through predictions from an existing polydisperse hindered settling model. This model indicates that the degree of bed segregation, and time scale over which this occurs, correlates well with the difference in predicted hindered settling characteristics and upward displacements associated with the sand and clay fractions, respectively. In this regard, the new experimental dataset provides validation for the polydisperse model (for the first time), with the combined data and model predictions

  18. Monitoring and characterisation of sand-mud sedimentation processes

    NASA Astrophysics Data System (ADS)

    Cuthbertson, Alan J. S.; Ibikunle, Olugbenga; McCarter, W. John; Starrs, Gerard

    2016-05-01

    Estuaries and tidal inlets are often characterised by the presence of both cohesive and non-cohesive sediments. Knowledge of the sedimentation behaviour of sand-mud mixtures is therefore crucial to the understanding and prediction of the time-dependent structure (i.e. mixed or segregated), composition and erodibility of sediment bed deposits developing within these environments. In the current study, a series of settling column tests are conducted to investigate the hindered settling and initial bed consolidation phases of a range of sand-clay mixtures to determine the parametric conditions under which bed segregation occurs. A new, non-invasive, electrical resistivity measurement technique is employed to capture both temporal and spatial changes in the density, porosity and composition of the evolving sand-clay bed deposits, complimented by time-lapsed images of the sedimentation process within the column. The results show that the formation of segregated (sand-clay) bed layers with bed deposits is largely controlled by the initial fractional composition (i.e. relative sand and clay concentrations). Specifically, mixtures with low clay contents are shown to form well-defined (sand-clay) layer segregation within the resulting deposits, while higher clay contents result in more transitional segregation patterns or no layer segregation (for very high clay concentrations). The physical mechanisms under which these different segregation types can be generated are illustrated through predictions from an existing polydisperse hindered settling model. This model indicates that the degree of bed segregation, and time scale over which this occurs, correlates well with the difference in predicted hindered settling characteristics and upward displacements associated with the sand and clay fractions, respectively. In this regard, the new experimental dataset provides validation for the polydisperse model (for the first time), with the combined data and model predictions

  19. Controls on the abruptness of gravel-sand transitions

    NASA Astrophysics Data System (ADS)

    Venditti, J. G.; Church, M. A.; Lamb, M. P.; Domarad, N.; Rennie, C. D.

    2014-12-01

    As gravel-bedded rivers fine downstream, they characteristically exhibit an abrupt transition from gravel- to sand-bed. This is the only abrupt transition in grain-size that occurs in the fluvial system and has attracted considerable attention. A number of competing theories have been proposed to account for the abruptness of the transition, including base-level control, attrition of ~10mm gravel to produce sand, and sediment sorting processes. The prevailing theory for the emergence of abrupt transitions is size selective sorting of bimodal sediment wherein gravel deposits due to downstream declining shear stress, fining the bedload until a sand-bed emerges. We explored this hypothesis by examining grain-size, shear stress, gravel mobility and sand suspension thresholds through the gravel-sand transition (GST) of the Fraser River, British Columbia. The Fraser GST is an arrested gravel wedge with patches of gravel downstream of the wedge forming a diffuse extension. There is an abrupt change in bed slope through the transition that leads to an abrupt change in shear stress. The GST, bed-slope change and backwater caused by the ocean are all coincident spatially, which enhances the sharpness of the GST. Interestingly, the bimodal reach of the river occurs downstream of the GST and exhibits no downstream gradients in shear stress, suspended sediment flux, gravel mobility or sand suspension thresholds. This calls into question the prevailing theory for the emergence of an abrupt GST by size selective sorting. We provide evidence, both empirical and theoretical, that suggests the emergence of an abrupt GST is caused by rapid deposition of sand when fine gravel deposits. We argue that the emergence of gravel-sand transitions is a consequence of gravel-bedded rivers adopting a steeper slope than sand-bedded rivers. The abruptness arises because the bed slope required to convey the gravel load fixes the distal location of a terminal gravel wedge, and once the river has

  20. Sand dunes as migrating strings.

    PubMed

    Guignier, L; Niiya, H; Nishimori, H; Lague, D; Valance, A

    2013-05-01

    We develop a reduced complexity model for three-dimensional sand dunes, based on a simplified description of the longitudinal and lateral sand transport. The spatiotemporal evolution of a dune migrating over a nonerodible bed under unidirectional wind is reduced to the dynamics of its crest line, providing a simple framework for the investigation of three-dimensional dunes, such as barchan and transverse dunes. Within this model, we derive analytical solutions for barchan dunes and investigate the stability of a rectilinear transverse dune against lateral fluctuations. We show, in particular, that the latter is unstable only if the lateral transport on the dune slip face prevails over that on the upwind face. We also predict the wavelength and the characteristic time that control the subsequent evolution of an unstable transverse dune into a wavy ridge and the ultimate fragmentation into barchan dunes. PMID:23767529

  1. Sand dunes as migrating strings

    NASA Astrophysics Data System (ADS)

    Guignier, L.; Niiya, H.; Nishimori, H.; Lague, D.; Valance, A.

    2013-05-01

    We develop a reduced complexity model for three-dimensional sand dunes, based on a simplified description of the longitudinal and lateral sand transport. The spatiotemporal evolution of a dune migrating over a nonerodible bed under unidirectional wind is reduced to the dynamics of its crest line, providing a simple framework for the investigation of three-dimensional dunes, such as barchan and transverse dunes. Within this model, we derive analytical solutions for barchan dunes and investigate the stability of a rectilinear transverse dune against lateral fluctuations. We show, in particular, that the latter is unstable only if the lateral transport on the dune slip face prevails over that on the upwind face. We also predict the wavelength and the characteristic time that control the subsequent evolution of an unstable transverse dune into a wavy ridge and the ultimate fragmentation into barchan dunes.

  2. The extraction of bitumen from western oil sands. Final report, July 1989--September 1993

    SciTech Connect

    Oblad, A.G.; Bunger, J.W.; Dahlstrom, D.A.; Deo, M.D.; Fletcher, J.V.; Hanson, F.V.; Miller, J.D.; Seader, J.D.

    1994-03-01

    Research and development of surface extraction and upgrading processes of western tar sands are described. Research areas included modified hot water, fluidized bed, and rotary kiln pyrolysis of tar sands for extraction of bitumen. Bitumen upgrading included solvent extraction of bitumen, and catalytic hydrotreating of bitumen. Characterization of Utah tar sand deposits is also included.

  3. Industrial sand and gravel

    USGS Publications Warehouse

    Dolley, T.P.

    2012-01-01

    Domestic production of industrial sand and gravel in 2011 was about 30 Mt (33 million st), increasing slightly compared with 2010. Some important end uses for industrial sand and gravel include abrasives, filtration, foundry, glassmaking, hydraulic fracturing sand (frac sand) and silicon metal applications.

  4. Industrial sand and gravel

    USGS Publications Warehouse

    Dolley, T.P.

    2013-01-01

    Domestic production of industrial sand and gravel in 2012 was about 49.5 Mt (55 million st), increasing 13 percent compared with that of 2011. Some important end uses for industrial sand and gravel include abrasives, filtration, foundry, glassmaking, hydraulic fracturing sand (frac sand) and silicon metal applications.

  5. Wet sand flows better than dry sand

    NASA Astrophysics Data System (ADS)

    Wagner, Christian

    2015-03-01

    Wet sand that does not contain too much water is known to be stiff enough to build sand castles or in physical words has a significant yield stress. However, we could recently show that there are quite a few conditions under which such wet sand opposes less resistant to flow than its dry counterpart. This effect might have been already known to the old Egyptians: The Ancient painting of El Bersheh at the tomb of Tehutihetep shows that there was liquid poured in front of the sledge that was used to transport heavy weight stones and statues. While archeologist have attributed this to a sacral ceremony, our data clearly show that wetting the sand ground drastically decreases the effective sliding friction coefficient. We first study the stress-strain behavior of sand with and without small amounts of liquid under steady and oscillatory shear. Using a technique to quasistatically push the sand through a tube with an enforced parabolic (Poiseuille-like) profile, we minimize the effect of avalanches and shear localization. We observe that the resistance against deformation of the wet (partially saturated) sand is much smaller than that of the dry sand, and that the latter dissipates more energy under flow. Second we show experimentally that the sliding friction on sand is greatly reduced by the addition of some--but not too much--water. The formation of capillary water bridges increases the shear modulus of the sand, which facilitates the sliding.

  6. The extraction of bitumen from western oil sands: Volume 1. Final report

    SciTech Connect

    Oblad, A.G.; Dahlstrom, D.A.; Deo, M.D.; Fletcher, J.V.; Hanson, F.V.; Miller, J.D.; Seader, J.D.

    1997-11-26

    The program is composed of 20 projects, of which 17 are laboratory bench or laboratory pilot scale processes or computer process simulations that are performed in existing facilities on the University of Utah campus in north-east Salt Lake City. These tasks are: (1) coupled fluidized-bed bitumen recovery and coked sand combustion; (2) water-based recovery of bitumen; (3) oil sand pyrolysis in a continuous rotary kiln reactor; (4) oil sand pyrolysis in a large diameter fluidized bed reactor; (5) oil sand pyrolysis in a small diameter fluidized bed reactor; (6) combustion of spent sand in a transport reactor; (7) recovery and upgrading of oil sand bitumen using solvent extraction methods; (8) fixed-bed hydrotreating of Uinta Basin bitumens and bitumen-derived hydrocarbon liquids; (9) ebullieted bed hydrotreating of bitumen and bitumen derived liquids; (10) bitumen upgrading by hydropyrolysis; (11) evaluation of Utah`s major oil sand deposits for the production of asphalt, high-energy jet fuels and other specialty products; (12) characterization of the bitumens and reservoir rocks from the Uinta Basin oil sand deposits; (13) bitumen upgrading pilot plant recommendations; (14) liquid-solid separation and fine tailings thickening; (15) in-situ production of heavy oil from Uinta Basin oil sand deposits; (16) oil sand research and development group analytical facility; and (17) process economics. This volume contains an executive summary and reports for five of these projects. 137 figs., 49 tabs.

  7. The extraction of bitumen from western oil sands: Volume 2. Final report

    SciTech Connect

    Oblad, A.G.; Dahlstrom, D.A.; Deo, M.D.; Fletcher, J.V.; Hanson, F.V.; Miller, J.D.; Seader, J.D.

    1997-11-26

    The program is composed of 20 projects, of which 17 are laboratory bench or laboratory pilot scale processes or computer process simulations that are performed in existing facilities on the University of Utah campus in north-east Salt Lake City. These tasks are: (1) coupled fluidized-bed bitumen recovery and coked sand combustion; (2) water-based recovery of bitumen; (3) oil sand pyrolysis in a continuous rotary kiln reactor; (4) oil sand pyrolysis in a large diameter fluidized bed reactor; (5) oil sand pyrolysis in a small diameter fluidized bed reactor; (6) combustion of spent sand in a transport reactor; (7) recovery and upgrading of oil sand bitumen using solvent extraction methods; (8) fixed-bed hydrotreating of Uinta Basin bitumens and bitumen-derived hydrocarbon liquids; (9) ebullieted bed hydrotreating of bitumen and bitumen derived liquids; (10) bitumen upgrading by hydropyrolysis; (11) evaluation of Utah`s major oil sand deposits for the production of asphalt, high-energy jet fuels and other specialty products; (12) characterization of the bitumens and reservoir rocks from the Uinta Basin oil sand deposits; (13) bitumen upgrading pilot plant recommendations; (14) liquid-solid separation and fine tailings thickening; (15) in-situ production of heavy oil from Uinta Basin oil sand deposits; (16) oil sand research and development group analytical facility; and (17) process economics. This volume contains reports on nine of these projects, references, and a bibliography. 351 refs., 192 figs., 65 tabs.

  8. Diagenetic effects on porosity-permeability relationships in red beds of the Lower Triassic Bunter Sandstone Formation in the North German Basin

    NASA Astrophysics Data System (ADS)

    Olivarius, Mette; Weibel, Rikke; Hjuler, Morten L.; Kristensen, Lars; Mathiesen, Anders; Nielsen, Lars H.; Kjøller, Claus

    2015-05-01

    Carbonate and anhydrite cement, clay clasts and inter-granular clay are the main components that reduce reservoir quality in the studied Bunter Sandstone Formation. The impacts of these parameters on porosity and permeability are determined by combining petrographic mineral quantification with conventional core analysis of samples from the Danish part of the North German Basin. The depositional environments are considered because they largely control the distribution of cements, clays and grain sizes. The lateral variability of depositional environments is defined by the position in the basin and the proximity to the source areas. The stratigraphic distribution of depositional environments is related both to local topography and to climate because high aridity promoted aeolian deposition. The Bunter Sandstone Formation has high porosity and permeability in most of the sandstone intervals in the northern North German Basin. The reservoir quality is good as long as the cements and clays are present as confined bodies that leave the remaining pore spaces available for flow. In contrast, inter-granular clay and pervasive cementation hinder virtually all flow through the sandstone. The ephemeral fluvial deposits have an average porosity and permeability of 20.3% and 810 mD, respectively, and the values are 24.6% and 807 mD for the aeolian sandstones, excluding the unconsolidated aeolian sands which presumably have higher porosity and permeability. The aeolian sandstones of the Volpriehausen Member have very good reservoir quality since they have a thickness of about 25 m, are laterally continuous, are largely clay-free and the cement occurs in small amounts. The sandstones of the Solling Member consist mainly of ephemeral fluvial deposits, which generally have good reservoir quality. However, some intervals have high contents of inter-granular clays or pervasive carbonate, anhydrite or halite cement and these components reduce the permeability significantly. The lateral

  9. A Threshold Continuum for Aeolian Sand Transport

    NASA Astrophysics Data System (ADS)

    Swann, C.; Ewing, R. C.; Sherman, D. J.

    2015-12-01

    The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.

  10. Sand boils induced by the 1993 Mississippi River flood: Could they one day be misinterpreted as earthquake-induced liquefaction?

    USGS Publications Warehouse

    Li, Y.; Craven, J.; Schweig, E.S.; Obermeier, S.F.

    1996-01-01

    In areas that are seismically active but lacking clear surficial faulting, many paleoearthquake studies depend on the interpretation of ancient liquefaction features (sand blows) as indicators of prehistoric seismicity. Sand blows, however, can be mimicked by nonseismic sand boils formed by water seeping beneath levees during floods. We examined sand boils induced by the Mississippi River flood of 1993 in order to compare their characteristics with sand blows of the New Madrid earthquakes of 1811-1812. We found a number of criteria that allow a distinction between the two types of deposits. (1) Earthquake-induced liquefaction deposits are broadly distributed about an epicentral area, whereas flood-induced sand boils are limited to a narrow band along a river's levee. (2) The conduits of most earthquake-induced sand blows are planar dikes, whereas the conduits of flood-induced sand boils are most commonly tubular. (3) Depression of the preearthquake ground surface is usual for sand blows, not for sand boils. (4) Flood-induced sand boils tend to be better sorted and much finer than sand-blow deposits. (5) Source beds for earthquake-induced deposits occur at a wide range of depths, whereas the source bed for sand boils is always near surface. (6) Materials removed from the walls surrounding the vent of a sand blow are seen inside sand blows, but are rarely seen inside sand boils. In general, flood-induced sand boils examined are interpreted to represent a less-energetic genesis than earthquake-induced liquefaction.

  11. The Cenozoic rotational extrusion of the Chuan Dian Fragment: New paleomagnetic results from Paleogene red-beds on the southeastern edge of the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Tong, Ya-Bo; Yang, Zhenyu; Wang, Heng; Gao, Liang; An, Chun-Zhi; Zhang, Xu-Dong; Xu, Ying-Chao

    2015-09-01

    Paleomagnetic studies were conducted on the Eocene and Oligocene strata at the western part of the Chuan Dian Fragment in order to describe the crustal deformation induced by continuous penetration of the Indian plate into Eurasia during the late Cenozoic. High-temperature magnetic components with unblocking temperatures of ~ 680 °C were isolated, and positive fold and/or reversal tests reveal the primary nature of the magnetization. The tilt-corrected site-mean directions obtained from the Oligocene and middle-early Eocene strata are, respectively, Ds = 200.9°, Is = - 31.3°, k = 52.8, α95 = 7.7° and Ds = 29.7°, Is = 32.0°, k = 44.9, α95 = 5.6°. Comparison of these results with previous paleomagnetic data from the Chuan Dian Fragment shows that the western and central parts of the Chuan Dian Fragment experienced ~ 20° integral clockwise rotation relative to East Asia since the middle Miocene. However, the eastern part of the Chuan Dian Fragment has experienced different rotational deformation relative to East Asia since the Pliocene, because of the intense regional crustal deformation and activity on fault systems. The eastern boundary of the Chuan Dian Fragment was bounded by the Yuanmou-Luezhijiang left lateral strike-slip fault prior to the Pliocene, and then substituted by the Xiaojiang left lateral strike-slip fault since the Pliocene, due to the eastwards spreading of the clockwise rotational movement of the Chuan Dian Fragment. The evolutionary characteristics of the Ailaoshan-Red River and Xianshuihe-Xiaojiang strike-slip faults were controlled by the difference between the clockwise rotational extrusion velocities of the Chuan Dian Fragment and the Indochina Block.

  12. Evaluation of integrated anaerobic/aerobic fixed-bed sequencing batch biofilm reactor for decolorization and biodegradation of azo dye acid red 18: comparison of using two types of packing media.

    PubMed

    Hosseini Koupaie, E; Alavi Moghaddam, M R; Hashemi, S H

    2013-01-01

    Two integrated anaerobic/aerobic fixed-bed sequencing batch biofilm reactor (FB-SBBR) were operated to evaluate decolorization and biodegradation of azo dye Acid Red 18 (AR18). Volcanic pumice stones and a type of plastic media made of polyethylene were used as packing media in FB-SBBR1 and FB-SBBR2, respectively. Decolorization of AR18 in both reactors followed first-order kinetic with respect to dye concentration. More than 63.7% and 71.3% of anaerobically formed 1-naphthylamine-4-sulfonate (1N-4S), as one of the main sulfonated aromatic constituents of AR18 was removed during the aerobic reaction phase in FB-SBBR1 and FB-SBBR2, respectively. Based on statistical analysis, performance of FB-SBBR2 in terms of COD removal as well as biodegradation of 1N-4S was significantly higher than that of FB-SBBR1. Spherical and rod shaped bacteria were the dominant species of bacteria in the biofilm grown on the pumice stones surfaces, while, the biofilm grown on surfaces of the polyethylene media had a fluffy structure. PMID:23138064

  13. Sedimentological, Mineralogical and Geochemical Characterization of Sand Dunes in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Benaafi, Mohammed; Abdullatif, Osman

    2014-05-01

    Sedimentological, mineralogical, morphological and geochemical studies of sand dunes from ten locations in Saudi Arabia were conducted in order to determine the differences between them and to find out the provenance and tectonic setting of these sand dunes. Sixty seven samples were collected from different sand dunes types ranging in morphology from linear, barchans, parabolic to stars dunes. In overall, the sand dunes are fine to coarse grained mean grain size, moderately sorted, near symmetrical skewness with mesokurtic distribution characterized sand dunes in most locations. The sand dunes grains are subrounded in all locations except in the Red sea, Qassim, central Arabia and the eastern province which showed sub-angular grains. The main mineral compositions of studied aeolian sand dunes are quartz, feldspar, calcite, and mica. Quartz is the dominant mineral in locations with significant amount of feldspars and mica in Najran, Red sea and Central Arabia locations. Moreover, calcite is present in Sakaka and NW Empty Quarter (Jafurah). Basement related sand dunes in Najran, Central Arabia and Red sea locations are sub-mature in terms of their mineralogical maturity. Whereas, sand dunes in other locations are texturally mature except those from the Red sea which showed sub-mature sand. The sands are classified as quartz arenite, except in the basement related sand dunes in Najran, central Arabia and the Red sea are ranging from sub-arkose, sub-litharenite and lithraenite. Morphologically, parallel to sub-parallel sand ridges with NE-SW orientation occurred in east and north parts of Empty Quarter (Najran and Jafurah) and NW-SE orientation in Dahna and Nafud deserts in central and north regions of Saudi Arabia. Parabolic sand dunes characterized the Nafud desert (Hail, Sakaka, Tayma locations). Barchans and star sand dunes characterize the Empty Quarter (Jafurah). Major, trace, and rare earth elements studies were carried out to determine the composition

  14. Assessment of different bedding systems for lactating cows in freestall housing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to compare different bedding systems for lactating cows in freestall housing. Bedding systems included new sand (NS), recycled byproducts of manure separation (organic solids [OS] and recycled sand [RS]), and foam-core mattresses with a shallow layer of OS (MS). The e...

  15. Sand waves, bars, and wind-blown sands of the Rio Orinoco, Venezuela and Colombia

    USGS Publications Warehouse

    Nordin, Carl F.; Perez-Hernandez, David

    1989-01-01

    During March 1982, a reconnaissance study was carried out along a reach of the Rio Orinoco between Puerto Ayacucho and Ciudad Bolivar. This was the low-flow season. Samples of bed material and suspended sediments were collected, sonic records of the bed were obtained at several locations, and the exposed bars and sand waves were studied at four locations. Sounding records were obtained at two of these locations during June and November when flow covered the bars, and additional studies were made on the ground at some of these same sites during March 1983. The bed of the river is mostly sand with small quantities, about 5 percent by weight on average, of gravel. Suspended- sediment concentrations were low, ranging between 20 milligrams per liter above Rio Apure to almost 40 milligrams per liter below its confluence with the Rio Orinoco. The annual sediment load is estimated to be 240x10 6 megagrams per year. During the dry season, 35 percent or more of the bed is exposed in the form of large bars composed of many sand waves. Trade winds blow upriver and there is substantial upriver transport of river sediments by the wind. If the bars contain very coarse sands and fine gravel, deflation forms a lag deposit that armors the bar surface and prevents further erosion. Theoretical calculations show that the lower limit for the fraction of the bed that needs to be covered with nonmoving particles to prevent further erosion and the smallest size of the armor particles depend only on wind speed. Calculations of bed-material transport were made for a typical wide and narrow section of the river; the annual load, excluding the wash load, is about 30 x 10 6 megagrams per year. A new definition for wash load is proposed; it is material that can be suspended as soon as its motion is initiated. For the Rio Orinoco, this is material finer than 0.1 millimeters.

  16. Influence of bedding material on ammonia emissions from cattle excreta.

    PubMed

    Misselbrook, T H; Powell, J M

    2005-12-01

    Dairy cattle barns are a major source of NH3 emissions to the atmosphere. Previous studies have shown that the bedding material used in the barn can influence the magnitude of NH3 emissions, but little is known about which bedding characteristics are important in this respect. The aims of this study were to assess, at a laboratory scale, the relative importance of the chemical [pH, cation exchange capacity (CEC), C:N] and physical (urine absorbance capacity, bulk density) characteristics of 5 bedding materials (chopped wheat straw, sand, pine shavings, chopped newspaper, chopped corn stalks, and recycled manure solids) on NH3 emissions from dairy cattle urine. Recycled manure solids were the most absorbent of the bedding types (4.2 g of urine/g of bedding), and sand was the least (0.3 g of urine/g of bedding). When beddings were soaked in urine to their absorbance capacities, NH3 emissions over 48 h (expressed as a proportion of the urine N absorbed) were not significantly different among bedding types, despite differences in initial bedding pH, CEC, and C:N. When equal volumes of urine were applied to equal depths of dry bedding, NH3 emissions over 48 h were significantly less from sand and pine shavings (23 and 42% of applied urine N, respectively) than from chopped newspaper, chopped corn stalks, and recycled manure solids (62, 68, and 65% of applied urine N, respectively), whereas emissions from chopped wheat straw (55% applied urine N) only differed significantly from that from sand. Differences in the chemical characteristics of the beddings did not explain differences in emission; NH3 emissions increased linearly with CEC contrary to expectations, and there was no significant relationship with initial bedding pH. The physical characteristics of bedding materials were of more importance, as NH3 emissions increased linearly with absorbance capacity and decreased as the bulk density of the packed beddings increased. PMID:16291621

  17. Percolation of Blast Waves though Sand

    NASA Astrophysics Data System (ADS)

    Proud, William

    2013-06-01

    Previous research has concentrated on the physical processes occurring when samples of sand, of varying moisture content, were shock compressed. In this study quartz sand samples are subjected to blast waves over a range of pressure and duration. Aspects of particle movement are discussed; the global movement of a bed hundreds of particles thick is a fraction of particle width. The main diagnostics used are pressure sensors and high-speed photography. Results are presented for a range of particle sizes, aspect ratio, density and moisture content. While the velocity of the percolation through the bed is primarily controlled by density and porosity the effect of moisture reveals a more complex dependence. The ISP acknowledges the support of the Atomic Weapons Establishment and Imperial College London.

  18. Giant desiccation fissures filled with calcareous eolian sand, Hermosa Formation (Pennsylvanian), southeastern Utah

    NASA Astrophysics Data System (ADS)

    Loope, David B.; Haverland, Zsolt E.

    1988-04-01

    At two stratigraphic intervals within the upper member of the Upper Pennsylvanian Hermosa Formation, calcareous eolian sand fills downward-tapering fissures that are as much as 18 cm wide and 5.7 m deep. Fissure fillings define orthogonal polygons 10 m or more in diameter. One of the host beds is primarily composed of subtidally deposited limestone, the other is a thinly laminated, nonmarine red siltstone. Both systems of fissure fillings are directly overlain and underlain by large-scale cross-stratified, calcareous eolianites. The limestone host bed contains chert pseudomorphs after gypsum. Compaction of host rocks contorted fissure fillings and caused doming of eolian strata over each fissure. Platy mineral grains in fissure fillings are aligned subparallel to bedding in the host rocks, supporting the view that the fissures were passively filled rather than forcefully injected. These ancient fissure systems are similar in scale and pattern to those that define giant desiccation polygons in numerous Great Basin playas. The Pennsylvanian fissures, like their Holocene counterparts, probably formed when groundwater tables dropped from shallow levels within fine-grained, impermeable deposits into underlying aquifers, greatly decreasing the extent of the capillary fringe. Our study of the fissures and host rocks supports the hypothesis that carbonate grains within the eolianites were deflated from uncemented marine sediments that were broadly exposed during regressive intervals.

  19. Eolian cover sands: a sedimentologic model and paleoenvironmental implications

    SciTech Connect

    Lea, P.D.

    1985-01-01

    In periglacial areas, accumulations of eolian sand commonly form low-relief blankets without well-developed dunes. Internally, these sandsheet deposits exhibit subhorizontal lamination rather than high-angle cross-bedding. Such cover sands of late-Pleistocene age mantle extensive areas in northern Europe, but have been reported more rarely from North America. The processes by which cover sands, as opposed to dunes, accumulate have not yet been determined conclusively. Wind ripples and sand dunes do not form a continuum; flow separation and avalanching and negligible in the former and vital in the latter. Accretion of a sand patch into a mound sufficient to cause flow separation and dune growth requires a consistently available supply of loose sand. In cover-sand areas, sand may be immobilized prior to dune development by several factors: (1) a sparse vegetation cover, (2) moist ground conditions, (3) snow cover, and (4) a shallow permafrost table and/or an ice-cemented active layer. Detailed sedimentologic studies may allow discrimination among these various controls. The importance of the individual controlling factors can vary seasonally in a given deposit, as well as between deposits in different paleogeographic settings. However, all factors imply more mesic conditions than those associated with many dune deposits. The association of cover sands with paraboloid dunes is also consistent with somewhat moist conditions. The relatively mesic nature of cover sands controls their Pleistocene distribution; they become decreasingly important relative to dunes in maritime-to-continental transects across Alaska and northern Europe.

  20. Paleoenvironment and depositional environment of Miocene Olcese Sand, Bakersfield, California

    SciTech Connect

    Olson, H.C.

    1986-04-01

    The Olcese Sand near Bakersfield, California, contains evidence of a range of paleoenvironments including nonmarine, estuarine, and outer shelf depositional settings. Foraminifera from surface and subsurface samples place the Olcese in the Saucesian and Relizian of the California benthic stages. A pumice bed in the Olcese has been dated by fission track methods at 15.5 Ma. The Olcese Sand interfingers with the underlying Freeman Silt and the overlying Round Mountain Silt. In the type area, in Round Mountain oil field, the Olcese is 300-360 m thick. The Olcese is subdivided into three environmental facies. In the Knob Hill Quadrangle, the lower Olcese consists of (1) thinly bedded to blocky white tuffaceous silt and sand, or (2) planar cross-bedded fine to coarse-grained sand with pumice pebbles lining the bedding surfaces. Fossil mollusks and skate teeth indicate a shallow marine environment for the lower Olcese. Although the Olcese is predominantly a marine unit, the middle Olcese is nonmarine, with lenses of marine deposition. The middle Olcese is well exposed in the Knob Hill, Oil Center, and Rio Bravo Ranch Quadrangles, and is characterized by fine to coarse sand with occasional gravel lenses, strong cross-bedding, and a blue-gray color. The upper Olcese is a very fine to medium-grained, marine sand that fines upward into a sandy siltstone southward toward the Kern River. Foraminifera and mollusks from outcrops in the Rio Bravo Ranch Quadrangle indicate outer shelf to estuarine environments for the upper Olcese. The varying environments in the Olcese Sand reflect slight but frequent fluctuations in water depth and can be used to interpret the basin-margin history.

  1. The gravel sand transition in a disturbed catchment

    NASA Astrophysics Data System (ADS)

    Knighton, A. David

    1999-03-01

    More than 40 million cubic metres of mining waste were supplied to the Ringarooma River between 1875 and 1984, leading to successive phases of aggradation and degradation. The natural bed material is gravel but, given the volume of introduced load and the fact that much of the input was less than 5 mm in diameter, the size composition of the bed changed from gravel to sand during the phase of downstream progressive aggradation. A very sharp gravel-sand transition developed in which median grain size decreased from over 30 mm to under 3 mm in less than 500 m. With upstream supplies of mining debris becoming depleted first, degradation followed the same downstream progressive pattern as aggradation, causing the transition to migrate downstream. By 1984, the river could be regarded as a series of zones, each characterized by a particular bed condition: a natural cobble-gravel bed, unaffected by mining inputs (0-32 km); pre-disturbance bed re-exposed by degradation over 35-40 years (32-53 km); sandy substrate with a gravel armour produced by differential transport during degradation (53-65 km); sand dominated but with developing surface patches of coarser material (65-75 km); sandy bed reflecting the size composition of the original mining input (75-118 km). Although the gravel-sand transition itself is sharp, the transitional zone is lengthy (53-75 km). As degradation continues, the gravel-sand transition is expected to progress downstream but it has remained in a stable position for 12 years. Indeed, two major floods during the period released large quantities of sand from the sub-armour layer and newly-formed banks of mine tailings, causing fining both above and below the transition. Surface grain size is an adjustable component in the transitional zone as the river strives to recover from a major anthropogenic disturbance.

  2. Extreme 13Ccarb enrichment in ca. 2.0 Ga magnesite-stromatolite-dolomite-`red beds' association in a global context: a case for the world-wide signal enhanced by a local environment

    NASA Astrophysics Data System (ADS)

    Melezhik, Victor A.; Fallick, Anthony E.; Medvedev, Pavel V.; Makarikhin, Vladimir V.

    1999-12-01

    The Palaeoproterozoic positive excursion of δ 13Ccarb is now considered as three positive shifts of δ 13Ccarb separated by returns to 0‰, which all occurred between 2.40 and 2.06 Ma. This isotopic event is unique in terms of both duration (>300 Ma) and 13C enrichment (up to +18‰). The mechanism responsible for one of the most significant carbon isotopic shifts in Earth history remains highly debatable. To date, δ 13C of +10‰ to +15‰ cannot be balanced by organic carbon burial ( forg) as there is no geological evidence for an enhanced C org accumulation prior to or synchronous with the excursion. Instead, termination of these excursions is followed by formation of a vast reservoir of 13C-depleted organic material (-45‰ at Shunga) and by one of the earliest known oil-generation episodes at 2.0 Ga. None of the three positive excursions of δ 13Ccarb is followed by a negative isotopic shift significantly below 0‰, as has always been observed in younger isotopic events, reflecting an overturn of a major marine carbon reservoirs. This may indicate that forg was constant: implying that the mechanism involved in the production of C org was different. Onset of intensive methane cycling resulting in Δc change is another possibility. The majority of sampled 13Ccarb-rich localities represents shallow-water stromatolitic dolostones, `red beds' and evaporites formed in restricted intracratonic basins, and may not reflect global δ 13Ccarb values. Closely spaced drill core samples ( n=73) of stromatolitic dolostones from the >1980±27 Ma Tulomozerskaya Formation in the Onega palaeobasin, Russian Karelia, have been analysed for δ 13Ccarb and δ 18Ocarb in order to demonstrate that different processes were involved in the formation of 13Ccarb-rich carbonates. The 800 m-thick magnesite-stromatolite-dolomite-`red beds' succession formed in a complex combination of environments on the Karelian craton: peritidal shallow marine, low-energy protected bights, barred

  3. The role of biophysical cohesion on subaqueous bed form size

    NASA Astrophysics Data System (ADS)

    Parsons, Daniel R.; Schindler, Robert J.; Hope, Julie A.; Malarkey, Jonathan; Baas, Jaco H.; Peakall, Jeffrey; Manning, Andrew J.; Ye, Leiping; Simmons, Steve; Paterson, David M.; Aspden, Rebecca J.; Bass, Sarah J.; Davies, Alan G.; Lichtman, Ian D.; Thorne, Peter D.

    2016-02-01

    Biologically active, fine-grained sediment forms abundant sedimentary deposits on Earth's surface, and mixed mud-sand dominates many coasts, deltas, and estuaries. Our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt, sand, and gravel. This approach underpins many paleoenvironmental reconstructions of sedimentary successions, which rely on analysis of cross-stratification and bounding surfaces produced by migrating bed forms. Here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology. The results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships. The findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record.

  4. The Unified Gravel-Sand (TUGS) Model: Simulating the Transport of Gravel-Sand Mixtures in Rivers

    NASA Astrophysics Data System (ADS)

    Cui, Y.

    2006-12-01

    TUGS Model was developed by employing the surface-based bedload equation of Wilcock and Crowe (2003) and linking grain size distributions in the bedload, surface layer, and subsurface sediment deposit with the gravel transfer function of Hoey and Ferguson (1994) and Toro-Escobar et al. (1996), and a hypothetical sand transfer function. The unmodified model was applied to simulate the sedimentation process in Marmot Reservoir, Sandy River, Oregon and produced similar stratified sediment deposit as observed through coring exercises. The model was also examined with three runs of large-scale flume experiments conducted at St. Anthony Falls Laboratory (SAFL) by Seal et al. (1995). With a very minor modification to Wilcock and Crowe (2003) equation, the model excellently reproduced the longitudinal profiles, gravel grain size distributions and sand fractions in the deposits for all the three SAFL runs. Following its examination, TUGS model was applied to simulate the sediment transport dynamics in the Sandy River, Oregon under a few hypothetical scenarios, focusing on the dynamics of sand fractions in gravel-bedded channel deposits. Results of the exploratory runs on the Sandy River indicate that (a) surface and subsurface sand fractions generally increase in the downstream direction, similar to observed in the field; (b) sand fraction in the deposit is positively correlated with sand supply as expected; (c) extremely high sand supply under similar gravel supply and hydrologic conditions can transform the river into predominantly sand-bedded; (d) increased discharge under the same sand and gravel supply conditions results in decreased sand fraction in the deposit as expected; and (e) there can be significant increase in surface and subsurface sand fractions in the backwater zones near the mouth of the river as expected.

  5. Industrial sand and gravel

    USGS Publications Warehouse

    Dolley, T.P.

    2006-01-01

    In 2005, domestic production of industrial sand and gravel was about 31 Mt, a 5% increase from 2004. This increase was bouyed by robust construction and petroleum sectors of the US economy. Based on estimated world production figures, the United States was the world's leading producer and consumer of industrial sand and gravel. In the short term, local shortages of industrial sand and gravel will continue to increase.

  6. Numerical modeling of wind-blown sand on Mars.

    PubMed

    Huang, HaoJie; Bo, TianLi; Zheng, XiaoJing

    2014-09-01

    Recent observation results show that sand ripples and dunes are movable like those on Earth under current Martian climate. And the aeolian process on Mars therefore is re-attracting the eyes of scientific researchers in different fields. In this paper, the spatial and temporal evolution of wind-blown sand on Mars is simulated by the large-eddy simulation method. The simulations are conducted under the conditions of both friction wind speed higher and lower than the "fluid threshold", respectively. The fluid entrainment of the sand particles, the processes among saltation sand particles and sand bed, and the negative feedback of sand movement to flow field are considered. Our results show that the "overshoot" phenomenon also exists in the evolution of wind-blown sand on Mars both temporally and spatially; impact entrainment affects the sand transport rate on Mars when the wind speed is smaller or larger than the fluid threshold; and both the average saltation length and height are one order of magnitudes larger than those on Earth. Eventually, the formulas describing the sand transport rate, average saltation length and height on Mars are given, respectively. PMID:25236498

  7. Trajectories of saltating sand particles behind a porous fence

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Lee, Sang Joon; Chen, Ting-Guo

    2015-01-01

    Trajectories of aeolian sand particles behind a porous wind fence embedded in a simulated atmospheric boundary layer were visualized experimentally, to investigate the shelter effect of the fence on sand saltation. Two sand samples, one collected from a beach (d = 250 μm) and the other from a desert (d = 100 μm), were tested in comparison with the previous studies of a 'no-fence' case. A wind fence (ε = 38.5%) was installed on a flat sand bed filled with each sand sample. A high-speed photography technique and the particle tracking velocimetry (PTV) method were employed to reconstruct the trajectories of particles saltating behind the fence. The collision processes of these sand particles were analyzed, momentum and kinetic energy transfer between saltating particles and ground surface were also investigated. In the wake region, probability density distributions of the impact velocities agree well with the pattern of no-fence case, and can be explained by a log-normal law. The horizontal component of impact velocity for the beach sand is decreased by about 54%, and about 76% for the desert sand. Vertical restitution coefficients of bouncing particles are smaller than 1.0 due to the presence of the wind fence. The saltating particles lose a large proportion of their energy during the collision process. These results illustrate that the porous wind fence effectively abates the further evolution of saltating sand particles.

  8. Aeolian Sand Transport with Collisional Suspension

    NASA Technical Reports Server (NTRS)

    Jenkins, James T.; Pasini, Jose Miguel; Valance, Alexandre

    2004-01-01

    Aeolian transport is an important mechanism for the transport of sand on Earth and on Mars. Dust and sand storms are common occurrences on Mars and windblown sand is responsible for many of the observed surface features, such as dune fields. A better understanding of Aeolian transport could also lead to improvements in pneumatic conveying of materials to be mined for life support on the surface of the Moon and Mars. The usual view of aeolian sand transport is that for mild winds, saltation is the dominant mechanism, with particles in the bed being dislodged by the impact of other saltating particles, but without in-flight collisions. As the wind becomes stronger, turbulent suspension keeps the particles in the air, allowing much longer trajectories, with the corresponding increase in transport rate. We show here that an important regime exists between these two extremes: for strong winds, but before turbulent suspension becomes dominant, there is a regime in which in-flight collisions dominate over turbulence as a suspension mechanism, yielding transport rates much higher than those for saltation. The theory presented is based on granular kinetic theory, and includes both turbulent suspension and particle-particle collisions. The wind strengths for which the calculated transport rates are relevant are beyond the published strengths of current wind tunnel experiments, so these theoretical results are an invitation to do experiments in the strong-wind regime. In order to make a connection between the regime of saltation and the regime of collisional suspension, it is necessary to better understand the interaction between the bed and the particles that collide with it. This interaction depends on the agitation of the particles of the bed. In mild winds, collisions with the bed are relatively infrequent and the local disturbance associated with a collision can relax before the next nearby collision. However, as the wind speed increases, collision become more frequent

  9. RETRACTED: The influence of sand diameter and wind velocity on sand particle lift-off and incident angles in the windblown sand flux

    NASA Astrophysics Data System (ADS)

    Bo, Tian-Li; Zheng, Xiao-Jing; Duan, Shao-Zhen; Liang, Yi-Rui

    2013-05-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal. This article has been retracted at the request of the Editors-in-Chief. This article also contains significant similarity with parts of text, written by the same author(s), that have appeared in Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, The influence of wind velocity and sand grain diameter on the falling velocities of sand particles, Powder Technology, Volume 241, June 2013, Pages 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Analysis of sand particles' lift-off and incident velocities in wind-blown sand flux, Acta Mechanica Sinica, April 2013, Volume 29, Issue 2, pp 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Influence of sand grain diameter and wind velocity on lift-off velocities of sand particles, The European Physical Journal E, May 2013, 36:50. Tian-Li Bo, Shao-Zhen Duan, Xiao-Jing Zheng, Yi-Rui Liang, The influence of sand bed temperature on lift-off and falling parameters in windblown sand flux, Geomorphology, Volume 204, 1 January 2014, Pages 477-484. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

  10. Have the northwest Negev dunefield sands reddened since their deposition?

    NASA Astrophysics Data System (ADS)

    Roskin, Joel; Tsoar, Haim; Blumberg, Dan G.; Porat, Naomi; Rozensten, Ofer

    2010-05-01

    Sand grain coating redness has been extensively both in coastal and inland desert dunes. In Israel, sand redness has been quantified by calculating a spectral redness index (RI) using single RGB bands (RI= R2/(B*G3)) from reflectance spectroscopy. The RI values have been correlated to ferric oxide mass that was dissolved from sand grain coatings (Ben Dor et al., 2006; Tsoar et al., 2008). Five main requirements have been proposed to enhance sand grain reddening: iron source from the weathering of iron-bearing minerals originating from parent rock or aeolian dust, minimum moisture content, oxidizing interstitial conditions, sediment stability and time. Thus, as many researches have suggested, when the source factors and climatic conditions are homogenous, redder sands indicate increased maturity. The northwest Negev dunefield has been classified by Tsoar et al. (2008) into 3 incursion units based upon contouring a grid of RI values for surface sand samples. The central incursion unit has been suggested to be younger due to relatively lower RI values that decrease to the east. This work tests the relationship between RI values and optically stimulated luminescence (OSL) ages of aeolian sand sampled from the near surface down to dune substrate throughout the NW Negev dunefield. Room-dried sand samples were measured in the laboratory with an ASD FieldSpec spectrometer and RI was calculated. Dune sections have been found to usually have similar RI values throughout their vertical profile despite OSL ages ranging between recent and Late Pleistocene. Along a W-E transect, RI values also tend to be similar. The central (Haluzza) part of the dunefield exhibits significantly lower RI values than RI of sands south of the Qeren Ridge. Dune base OSL ages possibly representing burial/stabilization of an initial incursion are slightly more mature in the south and may be evidence of the earliest dune incursion into the Negev. Thus the increased redness may be attributed to an

  11. Steam sand dryer in northeast part of sand tower. View ...

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

    Steam sand dryer in northeast part of sand tower. View to northeast - Duluth & Iron Range Rail Road Company Shops, Sand Tower, Southwest of downtown Two Harbors, northwest of Agate Bay, Two Harbors, Lake County, MN

  12. Sand dunes on the central Delmarva Peninsula, Maryland and Delaware

    USGS Publications Warehouse

    Denny, Charles Storrow; Owens, James Patrick

    1979-01-01

    Inconspicuous ancient sand dunes are present in parts of the central Delmarva Peninsula, Maryland and Delaware. Many dunes are roughly V-shaped, built by northwest winds, especially on the east sides of some of the large rivers. On the uplands, the form and spacing of the dunes are variable. A surficial blanket composed mainly of medium and fine-grained sand-the Parsonsburg Sand-forms both the ancient dunes and the broad plains between the dunes. The sand that forms the dunes is massive and intensely burrowed in the upper part; traces of horizontal or slightly inclined bedding appear near the base. Quartz is the dominant mineral constituent of the sand. Microline is abundant in the very fine to fine sand fraction. The heavy-mineral assemblages (high zircon, tourmaline, rutile) are more mature than in most of the possible source rocks. The most abundant minerals in the clay-sized fraction are dioctahedral vermiculite, kaolinite, illite, montmorillonite, and gibbsite. The first four minerals are common in deposits of late Wisconsin and Holocene age. The gibbsite may be detrital, coming from weathered rocks of Tertiary age. The soil profile in the dune sand is weakly to moderately developed. At or near the base of the Parsonsburg Sand are peaty beds that range in age from about 30,000 to about 13,000 radiocarbon years B.P. Microfloral assemblages in the peaty beds suggest that the dunes on the uplands formed in a spruce parkland during the late Wisconsin glacial maximum. The river dunes may also be of late Wisconsin age, but could be Holocene.

  13. Punctuated sand transport in the lowermost Mississippi River

    NASA Astrophysics Data System (ADS)

    Nittrouer, Jeffrey A.; Mohrig, David; Allison, Mead

    2011-12-01

    Measurements of sand flux and water flow in the Mississippi River are presented for a portion of the system 35-50 km upstream from the head of its subaerial delta. These data are used to provide insight into how nonuniform flow conditions, present in the lower reaches of large alluvial rivers, affect the timing and magnitude of sand transport near the river outlet. Field surveys during both low and high water discharge include (1) sequential digital bathymetric maps defining mobile river bottom topography which were used to estimate bed material flux, (2) multiple water velocity profiles, and (3) multiple suspended sediment profiles collected using a point-integrated sampler. These data show that total sand transport increases by two orders of magnitude over the measured range in water discharge (11,300 to 38,400 m3 s-1). During low water discharge no sand is measured in suspension, and sand discharge via bed form migration is minimal. During high water discharge 54% of the sand discharge is measured in suspension while 46% of the sand discharge is part of bed form migration. The component of boundary shear stress associated with moving this sediment is estimated using a set of established sediment transport algorithms, and values for the total boundary shear stress are predicted by fitting logarithmic velocity functions to the measured profiles. The estimates of boundary shear stress, using measurements of suspended sand transport, bed form transport, and downstream oriented velocity profiles are internally consistent; moreover, the analyses show that boundary shear stress increases by nearly 10-fold over the measured water discharge range. We show how this increase in shear stress is consistent with backwater flow arising where the river approaches its outlet. The hydrodynamic properties of backwater flow affect the timing and magnitude of sand flux and produce punctuated sand transport through the lowermost Mississippi River. Our field data are used to evaluate

  14. China Dust and Sand

    Atmospheric Science Data Center

    2013-04-16

    ... article title:  Dust and Sand Sweep Over Northeast China     View Larger Image ... these views of the dust and sand that swept over northeast China on March 10, 2004. Information on the height of the dust and an ...

  15. An Affair with Sand.

    ERIC Educational Resources Information Center

    Stroud, Sharon

    1980-01-01

    Described is a resource idea developed for the teaching of oceanography to junior high students. Sand is studied to help make the study of beaches more relevant to students who may have never seen an ocean. Sand samples are brought into the classroom from various coastal cities, then analyzed and compared. (Author/DS)

  16. Numerical simulation of turbulence and sediment transport of medium sand

    NASA Astrophysics Data System (ADS)

    Schmeeckle, Mark W.

    2014-06-01

    A model of sand transport in water is produced by combining a turbulence-resolving large eddy simulation (LES) with a discrete element model (DEM) prescribing the motion of individual grains of medium sand. The momentum effect of each particle on the fluid is calculated at the LES cell containing the particle, and the fluid velocity and pressure, interpolated to each particle center, is used to derive fluid force on each particle in the DEM. Eleven numerical experiments are conducted of an initially flat bed of particles. The experiments span a range of motion, from essentially no motion to vigorous suspension. Hydraulic roughness is found to increase abruptly at the transition from bed load to suspended load transport. Suspended sediment extracts momentum from the flow and decreases the rate of shear. Whereas, slightly higher in the flow, vertical drag by suspended grains damps turbulence and increases the rate of shear. Vertical sediment diffusivity and effective particle settling velocity are much smaller than is commonly assumed in suspended sediment models. The bed load experiments suggest that saltation by itself is a poor model of bed load sand transport. In contrast to expectations from saltation models, the peak bed load flux occurs at essentially the same level as the bed, and grains move slowly in frequent contact with other grains. Higher- and faster-moving bed load grains that can be considered to be in saltation represent a smaller portion of the total flux. Entrainment of bed load grains occurs in response to fluid penetration of the bed by high-vorticity turbulence structures embedded within broader high speed fluid regions referred to as a sweeps or high-speed wedges.

  17. Bed Bugs FAQs

    MedlinePlus

    ... Tropical Diseases Laboratory Diagnostic Assistance [DPDx] Parasites Home Bed Bugs FAQs Recommend on Facebook Tweet Share Compartir On ... are bed bugs treated and prevented? What are bed bugs? Bed bugs ( Cimex lectularius ) are small, flat, parasitic ...

  18. Two-Phase Abrasion in Eolian Transport of Gypsum Sand, White Sands NM

    NASA Astrophysics Data System (ADS)

    Shaw, S.; Jerolmack, D. J.; Miller, K. L.

    2014-12-01

    Downstream rounding of grains is consistently observed in natural sediment transport settings. A recent theory put forth by Domokos et al. (2014) attributes particle rounding and size reduction to a geometric curvature-driven abrasion process. This process occurs in two phases, in which irregularly shaped or angular particles round to convex shapes with negligible change in axis dimension, then slowly reduce in particle diameter. Miller et al (in review) establish the existence of two-phase abrasion in the natural setting of a fluvial gravel stream. This study examines field samples from White Sands, NM to investigate the presence of two-phase abrasion in a different, non-idealized natural environment - a high-energy, eolian gypsum dunefield. Analysis of grain shapes from White Sands confirms the two-phase abrasion process, dependent upon mode of sediment transport. We find that large sand grains carried in saltation bed load transport exhibit shape change indicative of two-phase abrasion, while smaller particles carried in suspension do not. We observe rapid shape change in bed load particles approaching a convex shape, followed by slower reduction in grain axis dimensions. Confirmation of this process in a natural, non-idealized setting establishes two-phase abrasion as a general application for bed load transport.

  19. Flow fields, bed shear stresses, and suspended bed sediment dynamics in bifurcations of a large river

    NASA Astrophysics Data System (ADS)

    Szupiany, R. N.; Amsler, M. L.; Hernandez, J.; Parsons, D. R.; Best, J. L.; Fornari, E.; Trento, A.

    2012-11-01

    Channel bifurcations associated with bars and islands are important nodes in braided rivers and may control flow partitioning and thus affect downstream confluences, as well as the formation and dynamics of bars. However, the morphodynamic processes associated with bar formation are poorly understood, and previous studies have largely concerned laboratory experiments, small natural streams, or numerical analyses with large Froude numbers, high slopes, and low Shields stresses. In these cases, the morphologic changes at bifurcations are relatively rapid, with predominant bed load transport and the suspended load playing a minor role. In this paper, the evolution of the flow structure and suspended bed sediment transport along four expansion-diffluence units in the Rio Paraná, Argentina, are described. The Rio Paraná is a large multichannel river with a bed composed of medium and fine sands and possesses low Froude numbers and high suspended bed material transport. Primary and secondary flow velocity components were measured with an acoustic Doppler current profiler (ADCP) along the expansion-diffluence units, and the backscatter signal of the ADCP was calibrated to allow simultaneous measurements of suspended bed sediment concentrations. The interactions between these variables show that the cores of primary flow velocity and suspended bed sediment concentration do not necessarily follow the thalweg at the bifurcation and that inertial effects on the suspended bed sediment may influence the morphodynamics of bar formation. It is suggested that changes in flow stage, as well as the presence of vegetation, may further increase the deposition of suspended bed sediment at the bar head. This study suggests that the ratio of suspended bed material to bed load is an important factor controlling the morphodynamics of bifurcations in large sand bed braided rivers.

  20. 1. View looking east from sand bar on west side ...

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

    1. View looking east from sand bar on west side of bridge, upstream in the bed of Sugar Creek. West elevation of the bridge - Vigo County Bridge No. 139, Spanning Sugar Creek at Seventy-fourth Place, Terre Haute, Vigo County, IN

  1. Field assessment of alternative bed-load transport estimators

    USGS Publications Warehouse

    Gaeuman, G.; Jacobson, R.B.

    2007-01-01

    Measurement of near-bed sediment velocities with acoustic Doppler current profilers (ADCPs) is an emerging approach for quantifying bed-load sediment fluxes in rivers. Previous investigations of the technique have relied on conventional physical bed-load sampling to provide reference transport information with which to validate the ADCP measurements. However, physical samples are subject to substantial errors, especially under field conditions in which surrogate methods are most needed. Comparisons between ADCP bed velocity measurements with bed-load transport rates estimated from bed-form migration rates in the lower Missouri River show a strong correlation between the two surrogate measures over a wide range of mild to moderately intense sediment transporting conditions. The correlation between the ADCP measurements and physical bed-load samples is comparatively poor, suggesting that physical bed-load sampling is ineffective for ground-truthing alternative techniques in large sand-bed rivers. Bed velocities measured in this study became more variable with increasing bed-form wavelength at higher shear stresses. Under these conditions, bed-form dimensions greatly exceed the region of the bed ensonified by the ADCP, and the magnitude of the acoustic measurements depends on instrument location with respect to bed-form crests and troughs. Alternative algorithms for estimating bed-load transport from paired longitudinal profiles of bed topography were evaluated. An algorithm based on the routing of local erosion and deposition volumes that eliminates the need to identify individual bed forms was found to give results similar to those of more conventional dune-tracking methods. This method is particularly useful in cases where complex bed-form morphology makes delineation of individual bed forms difficult. ?? 2007 ASCE.

  2. Crest line minimal model for sand dune

    NASA Astrophysics Data System (ADS)

    Guignier, Lucie; Valance, Alexandre; Lague, Dimitri

    2013-04-01

    In desert, complex patterns of dunes form. Under unidirectional wind, transverse rectilinear dunes or crescent shaped dunes called barchan dunes can appear, depending on the amount of sediment available. Most rectilinear transverse sand dunes are observed to fragment, for example at White Sands (New Mexico, United States of America) or Walvis Bay (Namibia). We develop a reduced complexity model to investigate the morphodynamics of sand dunes migrating over a non-erodible bed under unidirectional wind. The model is simply based on two physical ingredients, namely, the sand capture process at the slip face and the cross-wind sand transport. The efficiency of the sand capture process is taken to be dependent of the dune height and lateral diffusion is considered on both the windward and lee sides of the dune. In addition, the dune cross section is assumed to be scale invariant and is approximated by a triangular shape. In this framework, the dune dynamics is reduced to the motion of a string representing the dune crest line and is expressed as a set of two coupled nonlinear differential equations. This simple model reveals its ability to reproduce basic features of barchan and transverse dunes. Analytical predictions are drawn concerning dune equilibrium shape, stability and long-term dynamics. We derive, in particular, analytical solutions for barchan dunes, yielding explicit relationships between their shape and the lateral sand diffusion; and analytical predictions for the migration speed and equilibrium sand flux. A stability analysis of a rectilinear transverse dune allows us to predict analytically the wavelength emerging from fluctuations of the dune crest. We also determine the characteristic time needed for the rectilinear dune to fragment into a multitude of barchan dunes. These outcomes show that extremely simple ingredients can generate complex patterns for migrating dunes. From several dune field data, we are able to determine values of the model

  3. Basaltic island sand provenance

    SciTech Connect

    Marsaglia, K.M. . Dept. of Geological Sciences)

    1992-01-01

    The Hawaiian Islands are an ideal location to study basaltic sand provenance in that they are a series of progressively older basaltic shield volcanoes with arid to humid microclimates. Sixty-two sand samples were collected from beaches on the islands of Hawaii, Maui, Oahu and Kauai and petrographically analyzed. The major sand components are calcareous bioclasts, volcanic lithic fragments, and monomineralic grains of dense minerals and plagioclase. Proportions of these components vary from island to island, with bioclastic end members being more prevalent on older islands exhibiting well-developed fringing reef systems and volcanic end members more prevalent on younger, volcanically active islands. Climatic variations across the island of Hawaii are reflected in the percentage of weathered detritus, which is greater on the wetter, northern side of the island. The groundmass of glassy, basaltic lithics is predominantly black tachylite, with lesser brown sideromelane; microlitic and lathwork textures are more common than holohyaline vitric textures. Other common basaltic volcanic lithic fragments are holocrystalline aggregates of silt-sized pyroxene or olivine, opaque minerals and plagioclase. Sands derived from alkalic lavas are texturally and compositionally indistinguishable from sands derived from tholeiitic lavas. Although Hawaiian basaltic sands overlap in composition with magmatic arc-derived sands in terms of their relative QFL, QmPK and LmLvLs percentages, they are dissimilar in that they lack felsic components and are more enriched in lathwork volcanic lithic fragments, holocrystalline volcanic lithic fragments, and dense minerals.

  4. Pore geometry, avalanching, and subsurface flow: A sand infiltration model

    NASA Astrophysics Data System (ADS)

    Leonardson, R.; Hunt, J. R.; Dietrich, W. E.

    2009-12-01

    The deposition of sand into gravel riverbeds has been well-documented, along with its negative impacts on developing salmon eggs and riverbank extraction for water supplies. Dam releases may be used on regulated rivers to flush the bed of fine sediment, but it is not generally known how deep the sand deposit extends or how much sand is there. One-dimensional (plane-bed) experiments consistently show that the depth of infiltration is a function of the sand and gravel grain size distributions and that the saturation sand fraction is near 8-10%. However, precise empirical relationships developed in individual studies do poorly at predicting the results of other experiments. Furthermore, no infiltration model includes the effect of flow conditions in the water column, although flow conditions clearly impact the deposit characteristics. We propose a mechanistic model for the infiltration of fine sediment and compare its predictions to the results of two recent infiltration experiments. This model is based on geometric arguments about pore and particle shape and five mechanisms: particle settling, particle capture, subsurface avalanching, average subsurface flow, and subsurface pressure fluctuations. The model successfully predicts for both experiments the fraction of sand deposited and the shape of that deposit as a function of depth.

  5. Industrial sand and gravel

    USGS Publications Warehouse

    Dolley, T.P.

    2010-01-01

    Domestic production of industrial sand and gravel in 2009 was about 27 Mt (30 million st), declining by 10 percent compared with 2008. Certain end uses of industrial sand and gravel, such as foundry and glassmaking sand, may have declined by a factor greater than 10 percent in 2009. U.S. apparent consumption was 24.7 Mt (27.2 million st) in 2009, down by 10 percent from the previous year, and imports declined to 83 kt (91,000 st).

  6. Large-eddy simulation of sand dune morphodynamics

    NASA Astrophysics Data System (ADS)

    Khosronejad, Ali; Sotiropoulos, Fotis; St. Anthony Falls Laboratory, University of Minnesota Team

    2015-11-01

    Sand dunes are natural features that form under complex interaction between turbulent flow and bed morphodynamics. We employ a fully-coupled 3D numerical model (Khosronejad and Sotiropoulos, 2014, Journal of Fluid Mechanics, 753:150-216) to perform high-resolution large-eddy simulations of turbulence and bed morphodynamics in a laboratory scale mobile-bed channel to investigate initiation, evolution and quasi-equilibrium of sand dunes (Venditti and Church, 2005, J. Geophysical Research, 110:F01009). We employ a curvilinear immersed boundary method along with convection-diffusion and bed-morphodynamics modules to simulate the suspended sediment and the bed-load transports respectively. The coupled simulation were carried out on a grid with more than 100 million grid nodes and simulated about 3 hours of physical time of dune evolution. The simulations provide the first complete description of sand dune formation and long-term evolution. The geometric characteristics of the simulated dunes are shown to be in excellent agreement with observed data obtained across a broad range of scales. This work was supported by NSF Grants EAR-0120914 (as part of the National Center for Earth-Surface Dynamics). Computational resources were provided by the University of Minnesota Supercomputing Institute.

  7. Statistical characterization of bed roughness due to bed forms: A field study in the Elbe River at Aken, Germany

    NASA Astrophysics Data System (ADS)

    Aberle, J.; Nikora, V.; Henning, M.; Ettmer, B.; Hentschel, B.

    2010-03-01

    Bed form geometry and dynamics in a straight section of the Elbe River in Germany is analyzed considering the measured bed surfaces as two-dimensional random fields of bed elevations. Statistically derived roughness parameters are evaluated from high-resolution digital elevation models, which were available for a range of flow rates from low flows to floods. The key results relate to the identification of characteristic scaling regions in the bed surface spectra, and to observed relationships between water discharge and both the standard deviation and a factor of the "-3" spectral law of bed elevations. Two-dimensional second-order structure functions of bed elevations are also analyzed to gain further insight into the spatial structure of sand wave beds. In addition, the interrelations between flow rate hysteresis and the statistical structure of bed forms, as well as effects of channel modification by groynes, are highlighted and discussed. The reported results demonstrate that statistical parameters of bed forms may be used for characterization and prediction of flow-dependent sand bed roughness.

  8. Drying of solids in fluidized beds

    SciTech Connect

    Kannan, C.S.; Thomas, P.P.; Varma, Y.B.G.

    1995-09-01

    Fluidized bed drying is advantageously adopted in industrial practice for drying of granular solids such as grains, fertilizers, chemicals, and minerals either for long shelf life or to facilitate further processing or handling. Solids are dried in batch and in continuous fluidized beds corresponding to cross-flow and countercurrent flow of phases covering a wide range in drying conditions. Materials that essentially dry with constant drying rate and then give a falling drying rate approximately linear with respect to solids moisture content (sand) as well as those with an extensive falling rate period with the subsequent falling rate being a curve with respect to the moisture content (mustard, ragi, poppy seeds) are chosen for the study. The performance of the continuous fluidized bed driers is compared with that of batch fluidized bed driers; the performance is predicted using batch kinetics, the residence time distribution of solids, and the contact efficiency between the phases.

  9. Foundry sand reclamation

    SciTech Connect

    Filipovitch, A.J.; Bleuenstein, J.M.

    1984-05-22

    A dry method of conditioning spent foundry sand is disclosed. After having sized the sand and removal of tramp metallic elements, the sand is subjected to a sequence of squeezing under a high-stress low kinetic energy system for a period of 5-30 minutes, and then propelled against a target with high-kinetic energy in the presence of a suction for several minutes. This sequence can be preferably repeated to increase the quality of the resulting product which should have 0.1% or less of fine particles, a pH of 6-9, a clay content and organic combustible content of substantially zero. The reclaimed sand will exhibit a density of at least 100 grams/biscuit when compacted for core making or molding.

  10. Sand Volcano Following Earthquake

    NASA Technical Reports Server (NTRS)

    1989-01-01

    Sand boil or sand volcano measuring 2 m (6.6 ft.) in length erupted in median of Interstate Highway 80 west of the Bay Bridge toll plaza when ground shaking transformed loose water-saturated deposit of subsurface sand into a sand-water slurry (liquefaction) in the October 17, 1989, Loma Prieta earthquake. Vented sand contains marine-shell fragments. Sand and soil grains have faces that can cause friction as they roll and slide against each other, or even cause sticking and form small voids between grains. This complex behavior can cause soil to behave like a liquid under certain conditions such as earthquakes or when powders are handled in industrial processes. Mechanics of Granular Materials (MGM) experiments aboard the Space Shuttle use the microgravity of space to simulate this behavior under conditions that carnot be achieved in laboratory tests on Earth. MGM is shedding light on the behavior of fine-grain materials under low effective stresses. Applications include earthquake engineering, granular flow technologies (such as powder feed systems for pharmaceuticals and fertilizers), and terrestrial and planetary geology. Nine MGM specimens have flown on two Space Shuttle flights. Another three are scheduled to fly on STS-107. The principal investigator is Stein Sture of the University of Colorado at Boulder. (Credit: J.C. Tinsley, U.S. Geological Survey)

  11. Effect of bed permeability and hyporheic flow on turbulent flow over bed forms

    NASA Astrophysics Data System (ADS)

    Blois, Gianluca; Best, James L.; Sambrook Smith, Gregory H.; Hardy, Richard J.

    2014-09-01

    This paper uses particle imaging velocimetry to provide the first measurements detailing the flow field over a porous bed in the presence of bed forms. The results demonstrate that flow downstream of coarse-grained bed forms on permeable beds is fundamentally different to that over impermeable beds. Most significantly, the leeside flow separation cell is greatly modified by jets of fluid emerging from the subsurface, such that reattachment of the separated flow does not occur and the Reynolds stresses bounding the separation zone are substantially lessened. These results shed new light on the underlying flow physics and advance our understanding of both ecological and geomorphological processes associated with permeable bed forms. Water fluxes at the bed interface are critically important for biogeochemical cycling in all rivers, yet mass and momentum exchanges across the bed interface are not routinely incorporated into flow models. Our observations suggest that ignoring such exchange processes in coarse-grained rivers may overlook important implications. These new results also provide insight to explain the distinctive morphology of coarse-grained bed forms, the production of openwork textures in gravels, and the absence of ripples in coarse sands, all of which have implications for modeling and prediction of sediment entrainment and flow resistance.

  12. The role of velocity, pressure, and bed stress fluctuations in bed load transport over bed forms: numerical simulation downstream of a backward-facing step

    NASA Astrophysics Data System (ADS)

    Schmeeckle, M. W.

    2015-02-01

    Bed load transport over ripples and dunes in rivers exhibits strong spatial and temporal variability due to the complex turbulence field caused by flow separation at bedform crests. A turbulence-resolving flow model downstream of a backward-facing step, coupled with a model integrating the equations of motion of individual sand grains, is used to investigate the physical interaction between bed load motion and turbulence downstream of separated flow. Large bed load transport events are found to correspond to low-frequency positive pressure fluctuations. Episodic penetration of fluid into the bed increases the bed stress and moves grains. Fluid penetration events are larger in magnitude near the point of reattachment than farther downstream. Models of bed load transport over ripples and dunes must incorporate the effects of these penetration events of high stress and sediment flux.

  13. The role of velocity, pressure, and bed stress fluctuations in bed load transport over bed forms: numerical simulation downstream of a backward-facing step

    NASA Astrophysics Data System (ADS)

    Schmeeckle, M. W.

    2014-07-01

    Bed load transport over ripples and dunes in rivers exhibits strong spatial and temporal variability due to the complex turbulence field caused by flow separation at bedform crests. A turbulence-resolving flow model downstream of a backward-facing step, coupled with a model integrating the equations of motion of individual sand grains, is used to investigate the physical interaction between bed load motion and turbulence downstream of separated flow. Large bed load transport events are found to correspond to low-frequency, positive pressure fluctuations. Episodic penetration of fluid into the bed increases the bed stress and moves grains. Fluid penetration events are larger in magnitude near the point of reattachment than further downstream. Models of bed load transport over ripples and dunes must incorporate the effects of these penetration events of high stress and sediment flux.

  14. Update on Regulation of Sand Transport in the Colorado River by Changes in the Surface Grain Size of Eddy Sandbars over Multiyear Timescales

    USGS Publications Warehouse

    Topping, David J.; Rubin, David M.; Schmidt, John C.

    2008-01-01

    In settings where the transport of sand is partially or fully supply limited, changes in the upstream supply of sand are coupled to changes in the grain size of sand on the bed. In this manner, the transport of sand under the supply-limited case is ?grain-size regulated.? Since the closure of Glen Canyon Dam in 1963, the downstream reach of the Colorado River in Marble and Grand Canyons has exhibited evidence of sand-supply limitation. Sand transport in the river is now about equally regulated by changes in the discharge of water and changes in the grain sizes of sand on the channel bed and eddy sandbars. Previous work has shown that changes in the grain size of sand on the channel bed (driven by changes in the upstream supply of sand owing to both tributary floods and high dam releases) are important in regulating sand transport over timescales of days to months. In this study, suspended-sand data are analyzed in conjunction with bed grain-size data to determine whether changes in the sand grain size on the channel bed, or changes in the sand grain size on the surface of eddy sandbars, have been more important in regulating sand transport in the postdam Colorado River over longer, multiyear timescales. The results of this study show that this combined theory- and field-based approach can be used to deduce which environments in a complicated setting are most important for regulating sediment transport. In the case of the regulated Colorado River in Marble and upper Grand Canyons, suspended-sand transport has been regulated mostly by changes in the surface grain size of eddy sandbars.

  15. Packed Bed Reactor Experiment

    NASA Video Gallery

    The purpose of the Packed Bed Reactor Experiment in low gravity is to determine how a mixture of gas and liquid flows through a packed bed in reduced gravity. A packed bed consists of a metal pipe ...

  16. RUN OUTS OCCUR WHEN IRON HAS UNSEATED MOLDING SAND AND ...

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

    RUN OUTS OCCUR WHEN IRON HAS UNSEATED MOLDING SAND AND RUN OUT OF THE MOLD UNDER POURING JACKETS AND SPILLS ONTO THE MOLDING PLATFORM. WORKERS GENERALLY WAIT SEVERAL MINUTES FOR THE IRON TO SOLIDIFY AND, WHILE IT IS STILL RED-HOT, REMOVE IT FROM THE PLATFORM AND SCRAP THE MOLD. - Southern Ductile Casting Company, Centerville Foundry, 101 Airport Road, Centreville, Bibb County, AL

  17. Non-dune eolian sand in Indian mounds

    NASA Astrophysics Data System (ADS)

    Tanner, William F.

    1980-02-01

    Indian mounds, near Careyville, Florida, about 2.0 m high, are located on hillsides and hilltops 10 to 20 m above the floodplain of the nearest river (Choctawhatchee). Each mound is composed largely of quartz sand, with a scattering of artefacts and stream pebbles (not in layers), but with no visible bedding. Probability plots showed 25 Gaussian distributions, 18 having the 'dune hump', three having the 'surf break' and nine being doubly-truncated or having other patterns of unknown or uncertain origin. The surf breaks probably were inherited from pre-Pleistocene marine terraces in the area. The pebbles and the sand were not introduced by the same agency. The sand probability plots, taken as a set, indicate an eolian origin. The rough symmetry of the mounds, and the lack of cross-bedding, argue against a migrating dune origin. On a variability plot (showing the variability of the means versus the variability of the standard deviations), one suite of samples fell clearly within the 'dune' number field, a second suite in the overlap area between 'dune' and 'beach', and a third suite, taken immediately adjacent to a creek bed, plotted in the overlap area between 'beach' and 'coastal plain stream'. The pebbles, of common Southern Appalachian types, are attributed to the activities of the inhabitants, perhaps children. The sand is thought to have been carried by the wind, perhaps from nearby river sand bars, or from areas burned either by lightning-set wildfires or as part of "slash-and-burn" agriculture. The mounds are thought to represent clearings (for huts), and hence good trapping devices for wind-borne sand.

  18. The extraction of bitumen from western oil sands. Quarterly report, July--September, 1993

    SciTech Connect

    Oblad, A.G.; Bunger, J.W.; Dahlstrom, D.A.; Deo, M.D.; Fletcher, J.V.; Hanson, F.V.; Miller, J.D.; Seader, J.D.

    1993-11-01

    This report cites task number followed by a brief statement of each task and the action taken this quarter. The tasks are: NEPA environmental information statement; coupled fluidized-bed bitumen recovery and coked sand combustion; water-based recovery of bitumen; rotary kiln process for recovery of bitumen and combustion of coke sand; recovery of bitumen from oil sands using fluidized bed reactors and combustion of spent sands in transport reactors; recovery of bitumen from oil sand and upgrading of bitumen by solvent extraction; catalytic and thermal upgrading of bitumens and bitumen-derived liquids; evaluation of Utah`s major oil sand deposits for the production of asphalt, high energy jet fuels, and other specialty products; development of mathematical models for bitumen recovery and processing; completion of the cost estimation study of the pilot plant restoration; development studies of equipment for three-product gravity separation of bitumen and sand; development studies of disposal of sand by conveying or pumping of high solids concentration sand-water slurries; and environmental studies of the North Salt Lake pilot plant rehabilitation and eventual operation and those environmental problems associated with eventual commercial products.

  19. Ganges Chasma Sand Sheet

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    Today's sand sheet is located in the Ganges Chasma portion of Valles Marineris. As with yesterday's image, note that the dune forms are seen only at the margin and that the interior of the sand sheet at this resolution appears to completely lack dune forms.

    Image information: VIS instrument. Latitude -6.4, Longitude 310.7 East (49.3 West). 19 meter/pixel resolution.

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

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

  20. Loading and Unloading Weaned Pigs: Effects of Bedding Types, Ramp Angle, and Bedding Moisture.

    PubMed

    Garcia, Arlene; McGlone, John J

    2014-01-01

    The use of non-slip surfaces during loading and unloading of weaned pigs plays an important role in animal welfare and economics of the pork industry. Currently, the guidelines available only suggest the use of ramps below 20° to load and unload pigs. Three ramp angles (0°, 10° or 20°), five bedding materials (nothing, sand, feed, wood shavings or wheat straw hay), two moistures (dry or wet bedding; >50% moisture) over two seasons (>23.9 °C summer, <23.9 °C winter) were assessed for slips/falls/vocalizations (n = 6,000 pig observations). "Score" was calculated by the sum of slips, falls, and vocalizations. With the exception of using feed as a bedding, all beddings provided some protection against elevated slips, falls, and vocalizations (P < 0.01). Providing bedding reduced (P < 0.05) scores regardless of whether the bedding was dry or wet. Scores increased as the slope increased (P < 0.01). Provision of bedding, other than feed, at slopes greater than zero, decreased slips, falls and vocalizations. The total time it took to load and unload pigs was affected by bedding type, ramp angle, and season (P < 0.05). Minimizing slips, falls, and vocalizations when loading and unloading pigs improved animal welfare. PMID:26479010

  1. Sand Dunes with Frost

    NASA Technical Reports Server (NTRS)

    2004-01-01

    9 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of frost-covered sand dunes in the north polar region of Mars in early spring, 2004. The dunes indicate wind transport of sand from left to right (west to east). These landforms are located near 78.1oN, 220.8oW. This picture is illuminated by sunlight from the lower left and covers an area about 3 km (1.9 mi) across.

  2. Direct numerical simulations of aeolian sand ripples

    PubMed Central

    Durán, Orencio; Claudin, Philippe; Andreotti, Bruno

    2014-01-01

    Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns out to be driven by resonant grain trajectories, whose length is close to a ripple wavelength and whose splash leads to a mass displacement toward the ripple crests. The pattern selection results from a compromise between this destabilizing mechanism and a diffusive downslope transport which stabilizes small wavelengths. The initial wavelength is set by the ratio of the sediment flux and the erosion/deposition rate, a ratio which increases linearly with the wind velocity. We show that this scaling law, in agreement with experiments, originates from an interfacial layer separating the saltation zone from the static sand bed, where momentum transfers are dominated by midair collisions. Finally, we provide quantitative support for the use of the propagation of these ripples as a proxy for remote measurements of sediment transport. PMID:25331873

  3. Direct numerical simulations of aeolian sand ripples.

    PubMed

    Durán, Orencio; Claudin, Philippe; Andreotti, Bruno

    2014-11-01

    Aeolian sand beds exhibit regular patterns of ripples resulting from the interaction between topography and sediment transport. Their characteristics have been so far related to reptation transport caused by the impacts on the ground of grains entrained by the wind into saltation. By means of direct numerical simulations of grains interacting with a wind flow, we show that the instability turns out to be driven by resonant grain trajectories, whose length is close to a ripple wavelength and whose splash leads to a mass displacement toward the ripple crests. The pattern selection results from a compromise between this destabilizing mechanism and a diffusive downslope transport which stabilizes small wavelengths. The initial wavelength is set by the ratio of the sediment flux and the erosion/deposition rate, a ratio which increases linearly with the wind velocity. We show that this scaling law, in agreement with experiments, originates from an interfacial layer separating the saltation zone from the static sand bed, where momentum transfers are dominated by midair collisions. Finally, we provide quantitative support for the use of the propagation of these ripples as a proxy for remote measurements of sediment transport. PMID:25331873

  4. BLAISDELL SLOW SAND FILTER WASHING MACHINE. VIEW LOOKING SOUTH. THE ...

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

    BLAISDELL SLOW SAND FILTER WASHING MACHINE. VIEW LOOKING SOUTH. THE SUCTION (INTAKE) HOSE IS SEEN AT THE LEFT RESTING ON THE FILTER BED SURFACE; THE DISCHARGE HOSE IS AT THE RIGHT, RUNNING FROM THE BOTTOM OF THE CENTRAL VERTICAL AXLE TO THE CENTRIFUGAL PUMP. FROM THE PUMP WATER IS DISCHARGED THROUGH THE HORIZONTAL PIPE LOCATED UNDER THE EDGE OF PLATFORM DECK INTO THE WASTE-WATER TROUGH (NOT SEEN IN THIS VIEW). - Yuma Main Street Water Treatment Plant, Blaisdell Slow Sand Filter Washing Machine, Jones Street at foot of Main Street, Yuma, Yuma County, AZ

  5. Incident Angle of Saltating Particles in Wind-Blown Sand

    PubMed Central

    Fu, Lin-Tao; Bo, Tian-Li; Gu, Hai-Hua; Zheng, Xiao-Jing

    2013-01-01

    Incident angle of saltating particles plays a very important role in aeolian events. In this paper, the incident angles of sand particles near the sand bed were measured in wind tunnel. It reveals that the incident angles range widely from 0° to 180° and thereby the means of angles are larger than published data. Surprisingly, it is found the proportion that angles of 5°–15° occupy is far below previous reports. The measuring height is probably the most important reason for the measurement differences between this study and previous investigations. PMID:23874470

  6. Tight Abo gas sands, east-central New Mexico

    SciTech Connect

    Broadhead, R.F.

    1983-03-01

    Red-bed sandstones of the Abo Formation (Lower Permian) currently produce natural gas from the Pecos Slope Abo field in northern Chaves County, New Mexico. The Pecos Slope Abo field is on the northwest shelf of the Permian basin. The tight-sand designation greatly stimulated drilling and over 250 wells have been drilled since field discovery in 1977. Because of low permeability, wells must be artificially fractured to obtain economic production. Initial production rises from a few tens of MCFGD before fracturing to an average of about 2200 MCFGD after fracturing. The lower granite wash interval is more than 800 ft (248 m) thick in some places and is composed of interbedded coarse-grained arkosic sandstones and arkosic conglomerates. The middle interval is about 100 ft (30 m) thick and conformably overlies the lower interval and the Hueco limestones. It is composed of calcareous, sparsely fossiliferous, argillaceous mudstone and minor fine-grained sandstone. The upper interval is about 600 ft (183 m) thick and is composed of interbedded mudstones and lenticular sandstones. It conformably overlies the middle interval and is disconformably overlain by the dolostones, anhydrites, and fine-grained sandstones of the Yeso Formation. Gas is produced from sandstones in the upper interval. The Abo wells tap a gas-filled natural fracture system. Mudstones seal the fractured sandstone reservoirs. Because fluvial-deltaic deposits extend almost 100 mi (161 km) north of present production, the area underlain by potential, fractured, Abo sandstone reservoirs is at least five times greater than the area which is currently productive.

  7. Loading and Unloading Finishing Pigs: Effects of Bedding Types, Ramp Angle, and Bedding Moisture

    PubMed Central

    Garcia, Arlene; McGlone, John J.

    2014-01-01

    Simple Summary Current guidelines suggest the use of ramps below 20 degrees to load and unload pigs; however, they do not suggest the use of any specific bedding. Bedding types (nothing, feed, sand, wood shavings, and hay) were tested with finishing pigs (70–120 kg) to determine which was most effective in reducing slips, falls, and vocalizations at three ramp angles, two moisture levels, over two seasons. Slips, falls, and vocalizations were summed to establish a scoring system for the types of beddings. Heart rate and the total time it took to load and unload pigs, increased as the slope increased. Bedding, bedding moisture, season, and ramp slope interacted to impact the total time it took for finishing pigs to load and unload the ramp. Selection of the best bedding depends on ramp slope, season, and wetness of bedding. Abstract The use of non-slip surfaces during loading and unloading of finishing pigs plays an important role in animal welfare and economics of the pork industry. Currently, the guidelines available only suggest the use of ramps with a slope below 20 degrees to load and unload pigs. However, the total time it takes to load and unload animals and slips, falls, and vocalizations are a welfare concern. Three ramp angles (0, 10 or 20 degrees), five bedding materials (nothing, sand, feed, wood shavings or wheat straw hay), two moistures (dry or wet bedding, >50% moisture) over two seasons (>23.9 °C summer, <23.9 °C winter) were assessed for slips/falls/vocalizations (n = 2400 pig observations) and analyzed with a scoring system. The use of bedding during summer or winter played a role in the total time it took to load and unload the ramp (p < 0.05). Bedding, bedding moisture, season, and slope significantly interacted to impact the total time to load and unload finishing pigs (p < 0.05). Heart rate and the total time it took to load and unload the ramp increased as the slope of the ramp increased (p < 0.05). Heart rates were higher during the

  8. A sand budget for Marble Canyon, Arizona: implications for long-term monitoring of sand storage change

    USGS Publications Warehouse

    Grams, Paul E.

    2013-01-01

    Recent U.S. Geological Survey research is providing important insights into how best to monitor changes in the amount of tributary-derived sand stored on the bed of the Colorado River and in eddies in Marble Canyon, Arizona. Before the construction of Glen Canyon Dam and other dams upstream, sandbars in Glen, Marble, and Grand Canyons were replenished each year by sediment-rich floods. Sand input into the Colorado River is crucial to protecting endangered native fish, animals, and plants and cultural and recreational resources along the river in Glen Canyon National Recreation Area and Grand Canyon National Park.

  9. Internal architecture and mobility of tidal sand ridges in the East China Sea

    NASA Astrophysics Data System (ADS)

    Liu, Zhenxia; Berné, Serge; Saito, Yoshiki; Yu, Hua; Trentesaux, Alain; Uehara, Katsuto; Yin, Ping; Paul Liu, J.; Li, Chaoxing; Hu, Guanghai; Wang, Xiangqin

    2007-07-01

    On the basis of bathymetric and seismic data and data from piston cores collected by the Chinese-French marine geology and geophysics investigation of 1996, we discuss the internal architecture and mobility of tidal sand ridges in the East China Sea (ECS). We characterized the sand ridges on the middle to outer shelf of the ECS as tide-dominated sand ridges with southwest dipping beds, indicating that the regional net sediment transport is toward the southwest. As the sand ridges gradually migrate toward the southwest, new sand ridges are continually replacing old ones, and several generations of sand ridges have developed in the study area. High-resolution seismic data, acoustic Doppler current profiler data, and two 14C-dated piston cores, DGKS9614 and DGKS9612—from a sand ridge swale and crest, respectively—show that these sand ridges, which are at water depths of 90-100 m, have been migrating for the last ca. 2-3 kyr at least, though these ridges have previously been interpreted as moribund or relict. Sequence stratigraphic interpretation of seismic profiles and core data show that tidal ridges in the ECS evolved from muddier sand ridges formed during the last transgression to sandier shelf sand ridges in response to the shoreline retreat, which resulted in a decrease of riverine muddy sediments and recycling of sandy materials by tidal currents. Most active sand ridge formation occurred during the last transgression, but the present sand ridges on the middle to outer shelf are still being influenced by the modern hydrodynamics. Therefore, these sand ridges on the ECS shelf should be referred to as "quasi-active sand ridges" rather than as moribund or relict sand ridges.

  10. Eye redness

    MedlinePlus

    Bloodshot eyes; Red eyes; Scleral infection; Conjunctival infection ... There are many causes of a red eye or eyes. Some are medical emergencies and some are a cause for concern, but not an emergency. Others are nothing to worry about. ...