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Sample records for offset alluvial fan

  1. Late Quaternary Offset of Alluvial Fan Surfaces along the Central Sierra Madre Fault, Southern California

    NASA Astrophysics Data System (ADS)

    Hanson, A.; Burgette, R. J.; Scharer, K. M.; Midttun, N. C.

    2015-12-01

    The Sierra Madre fault (SMF) is an east-west trending reverse fault system along the southern flank of the San Gabriel Mountains near Los Angeles, California. The ~140 km long SMF is separated into four segments, we focus on the multi-stranded, ~60 km long Central Sierra Madre fault (CSMF; W118.3-W117.7) as it lacks a well-characterized long-term geologic slip rate. We combine 1-m lidar DEM with geologic and geomorphic mapping to correlate alluvial fan surfaces along strike and across the fault strands in order to derive fault slip rates that cross the CSMF. We have refined mapping on two sets of terraces described by Crook et al. (1987) and references therein: a flight of Q3 surfaces (after nomenclature of Crook et al., 1987; McFadden, 1982) in Arroyo Seco with distinct terraces ~30 m, ~40 m, ~50 m, and ~55 m above the modern stream and in Pickens Canyon divided a Q3 and Q2 surface, with heights that are ~35 m and ~25 m above the modern stream respectively. Relative degree of clast weathering and soil development is consistent with geomorphic relationships; for example, hues of 7.5 YR to 10 YR are typical of Q3, while hues of 10 YR to 2.5 Y are typical of Q2. A scarp in the Q3 surface at Arroyo Seco has a vertical offset of ~16 m and a scarp in the Q3 at Pickens Canyon has a vertical offset of ~14 m, while the Q2 surface is not faulted. Our Quaternary dating strategy is focused on dating suites of terraces offset along CSMF scarps in order to provide broader stratigraphic context for the cosmogenic radionuclide and luminescence dating. We will present (pending) cosmogenic radionuclide depth profiles from the Q3 surfaces. A better-constrained slip rate for the CSMF will improve earthquake hazard assessment for the Los Angeles area and help clarify the tectonic role of the SMF in the broader plate boundary system. Additionally, the fan chronology will provide information about the timing of alluvial fan aggradation and incision in the western Transverse Ranges.

  2. Alluvial Fans on Mars

    NASA Technical Reports Server (NTRS)

    Kraal, E. R.; Moore, J. M.; Howard, A. D.; Asphaug, E. A.

    2005-01-01

    Moore and Howard [1] reported the discovery of large alluvial fans in craters on Mars. Their initial survey from 0-30 S found that these fans clustered in three distinct regions and occurred at around the +1 km MOLA defined Mars datum. However, due to incomplete image coverage, Moore and Howard [1]could not conduct a comprehensive survey. They also recognized, though did not quantitatively address, gravity scaling issues. Here, we briefly discuss the identification of alluvial fans on Mars, then consider the general equations governing the deposition of alluvial fans and hypothesize a method for learning about grain size in alluvial fans on Mars.

  3. Large Alluvial Fans on Mars

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Howard, Alan D.

    2004-01-01

    Several dozen distinct alluvial fans, 10 to greater than 40 km long downslope are observed exclusively in highlands craters. Within a search region between 0 deg. and 30 deg. S, alluvial fan-containing craters were only found between 18 and 29 S, and they all occur at around plus or minus 1 km of the MOLA-defined Martian datum. Within the study area they are not randomly distributed but instead form three distinct clusters. Fans typically descend greater than 1 km from where they disgorge from their alcoves. Longitudinal profiles show that their surfaces are very slightly concave with a mean slope of 2 degrees. Many fans exhibit very long, narrow low-relief ridges radially oriented down-slope, often branching at their distal ends, suggestive of distributaries. Morphometric data for 31 fans was derived from MOLA data and compared with terrestrial fans with high-relief source areas, terrestrial low gradient alluvial ramps in inactive tectonic settings, and older Martian alluvial ramps along crater floors. The Martian alluvial fans generally fall on the same trends as the terrestrial alluvial fans, whereas the gentler Martian crater floor ramps are similar in gradient to the low relief terrestrial alluvial surfaces. For a given fan gradient, Martian alluvial fans generally have greater source basin relief than terrestrial fans in active tectonic settings. This suggests that the terrestrial source basins either yield coarser debris or have higher sediment concentrations than their Martian counterpoints. Martian fans and Basin and Range fans have steeper gradients than the older Martian alluvial ramps and terrestrial low relief alluvial surfaces, which is consistent with a supply of coarse sediment. Martian fans are relatively large and of low gradient, similar to terrestrial fluvial fans rather than debris flow fans. However, gravity scaling uncertainties make the flow regime forming Martian fans uncertain. Martian fans, at least those in Holden crater, apparently

  4. Long-term slip rate of the southern San Andreas Fault, from 10Be-26Al surface exposure dating of an offset alluvial fan

    SciTech Connect

    der Woerd, J v; Klinger, Y; Sieh, K; Tapponnier, P; Ryerson, F; M?riaux, A

    2006-01-13

    We determine the long-term slip rate of the southern San Andreas Fault in the southeastern Indio Hills using {sup 10}Be and {sup 26}Al isotopes to date an offset alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images allow to precisely determine piercing points across the fault zone that are used to measure an offset of 565 {+-} 80 m. A total of twenty-six quartz-rich cobbles from three different fan surfaces were collected and dated. The tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history, negligible prior exposure and erosion, and yield an age of 35.5 {+-} 2.5 ka. The long-term slip rate of the San Andreas Fault south of Biskra Palms is thus 15.9 {+-} 3.4 mm/yr. This rate is about 10 mm/yr slower than geological (0-14 ka) and short-term geodetic estimates for this part of the San Andreas Fault implying changes in slip rate or in faulting behavior. This result puts new constraints on the slip rate of the San Jacinto and on the Eastern California Shear Zone for the last 35 ka. Our study shows that more sites along the major faults of southern California need to be targeted to better constrain the slip-rates over different time scales.

  5. Hydraulic processes on alluvial fans

    SciTech Connect

    French, R.H.

    1987-01-01

    Alluvial fans are among the most prominent landscape features in the American Southwest and throughout the semi-arid and arid regions of the world. The importance of developing a qualitative and quantitative understanding of the hydraulic processes which formed, and which continue to modify, these features derives from their rapid and significant development over the past four decades. As unplanned urban sprawl moved from valley floors onto alluvial fans, the serious damage incurred from infrequent flow events has dramatically increased. This book presents a discussion of our current and rapidly expanding knowledge of hydraulic processes on alluvial fans. It addresses the subject from a multidisciplinary viewpoint, acquainting the reader with geological principles pertinent to the analysis of hydraulic processes on alluvial fans.

  6. Northern San Andreas Fault slip rates on the Santa Cruz Mountain section: 10Be dating of an offset alluvial fan complex, Sanborn County Park, Saratoga, CA

    NASA Astrophysics Data System (ADS)

    Guns, K. A.; Prentice, C. S.; DeLong, S. B.; Kiefer, K.; Blisniuk, K.; Burgmann, R.

    2015-12-01

    To better assess seismic hazard and fault behavior along the southern peninsula in the San Francisco Bay Area on the Santa Cruz Mountain section of the San Andreas Fault, we combine field observations and high-resolution lidar topography data with 10Be exposure dating on offset landforms to estimate geologic fault slip rates. Our mapping at Sanborn County Park near Saratoga reveals a progression of alluvial fans and debris flows offset from their upstream sources by dextral slip on the San Andreas Fault. These upstream sources are 3 drainages, Todd Creek, Service Road Creek and Aubry Creek. Coarse alluvial deposits from each of these creeks contain large Tertiary sandstone boulders of varying size and abundance, derived from the Vaqueros Formation, that allow us to constrain the provenance of offset alluvial deposits to their upstream sources. Initial reconstruction, based on clast-count data on lithology and size from Todd Creek (n=68), Service Road Creek (N=32) and the offset deposits (n=68), suggest ≥140 m of dextral fault movement. Initial 10Be cosmogenic dating of sandstone boulders on an offset deposit from Service Road Creek yields a maximum date of 8 ka, a date uncorrected for hillslope residence and fluvial transport of inherited 10Be concentrations. These data suggest a minimum slip rate of at least 17 mm/yr on the Santa Cruz Mountain section of the San Andreas Fault in the peninsula. Ongoing analysis will refine this fault slip rate. Our preliminary data underscore the potential of this site to provide geologic slip rate estimates, and therefore answer a question critical to seismic hazard assessment, in a region where steep terrain, mass wasting, vegetation and urban development have generally made slip rate estimates challenging to obtain.

  7. First Constraints On the Slip Rate of the Yammouneh Fault (Levant Fault System) Determined by Cosmogenic \\textsuperscript{36}Cl Exposure Dating of Offset Alluvial Fans

    NASA Astrophysics Data System (ADS)

    Daëron, M.; Benedetti, L.; Tapponnier, P.; Sursock, A.; Finkel, R.

    2003-12-01

    The most active seismogenic structure along the eastern shore of the Mediterranean is the left-lateral strike-slip Levant fault, plate boundary between Arabia and Africa. To this day there is consensus neither on its present slip rate and segmentation, nor on the exact size and frequence of the earthquakes it generates. Between latitudes 33\\textsuperscript{o} N and 35\\textsuperscript{o} N in Lebanon, the Levant fault's trace veers eastwards by 24\\textsuperscript{o}, forming a 160km-long restraining bend, responsible for the uplift of Mount Lebanon (3083m). Most of the resulting transpressive deformation is partitioned between two main structures: the offshore Tripoli-Beirut thrust and the Yammouneh strike-slip fault, whose degree of seismogenic activity has been questioned (various estimations of its modern slip rate range from 0 to 8mm/yr). Using aerial photographs, satellite images, topographic maps and field observations, we mapped and measured left-laterally offset alluvial fans and gullies along the Yammouneh fault. The measured offsets range from less than 10m to about 3km. To constrain the slip rate of the Yammouneh fault, limestone cobbles were sampled on three alluvial fans, each offset by 40--50m. The concentrations of \\textsuperscript{36}Cl\\ and stable Chlorine in the 48 samples were measured by accelerator mass spectrometry at the LLNL-CAMS. The first results suggest an average slip rate of 5--10mm/yr along the Yammouneh fault in the last 8,000 years.

  8. Cosmogenic 10Be and 36Cl geochronology of offset alluvial fans along the northern Death Valley fault zone: Implications for transient strain in the eastern California shear zone

    USGS Publications Warehouse

    Frankel, K.L.; Brantley, K.S.; Dolan, J.F.; Finkel, R.C.; Klinger, R.E.; Knott, J.R.; Machette, M.N.; Owen, L.A.; Phillips, F.M.; Slate, J.L.; Wernicke, B.P.

    2007-01-01

    The northern Death Valley fault zone (NDVFZ) has long been recognized as a major right-lateral strike-slip fault in the eastern California shear zone (ECSZ). However, its geologic slip rate has been difficult to determine. Using high-resolution digital topographic imagery and terrestrial cosmogenic nuclide dating, we present the first geochronologically determined slip rate for the NDVFZ. Our study focuses on the Red Wall Canyon alluvial fan, which exposes clean dextral offsets of seven channels. Analysis of airborne laser swath mapping data indicates ???297 ?? 9 m of right-lateral displacement on the fault system since the late Pleistocene. In situ terrestrial cosmogenic 10Be and 36C1 geochronology was used to date the Red Wall Canyon fan and a second, correlative fan also cut by the fault. Beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 +22/-20 ka for the offset landforms. The minimum age of the alluvial fan deposits based on 36Cl depth profiles is 63 ?? 8 ka. Combining the offset measurement with the cosmogenic 10Be date yields a geologic fault slip rate of 4.2 +1.9/-1.1 mm yr-1, whereas the 36Cl data indicate 4.7 +0.9/-0.6 mm yr-1 of slip. Summing these slip rates with known rates on the Owens Valley, Hunter Mountain, and Stateline faults at similar latitudes suggests a total geologic slip rate across the northern ECSZ of ???8.5 to 10 mm yr-1. This rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the Mojave section of the ECSZ does not extend north of the Garlock fault. Although the overall geodetic rates are similar, the best estimates based on geology predict higher strain rates in the eastern part of the ECSZ than to the west, whereas the observed geodetic strain is relatively constant. Copyright 2007 by the American Geophysical Union.

  9. Long-term slip rates of the Elsinore-Laguna Salada fault, southern California, by U-series Dating of Pedogenic Carbonate in Progressively Offset Alluvial fan Remnants.

    NASA Astrophysics Data System (ADS)

    Fletcher, K. E.; Rockwell, T. K.; Sharp, W. D.

    2007-12-01

    The Elsinore-Laguna Salada (ELS) fault is one of the principal strands of the San Andreas fault system in southern California, however its seismic potential is often de-emphasized due to previous estimates of a low slip rate. Nevertheless, the fault zone has produced two historic earthquakes over M6, with the 1892 event estimated at >M7; thus further investigation of the long-term slip rate on the ELS fault is warranted. On the western slopes of the Coyote Mountains (CM), southwest Imperial Valley, a series of alluvial fans are progressively offset by the Elsinore fault. These fans can be correlated to their source drainages via distinctive clast assemblages, thereby defining measurable offsets on the fault. Dating of the CM fans (to compute slip rates), however, is challenging. Organic materials appropriate for C-14 dating are rare or absent in the arid, oxidizing environment. Cosmogenic surface exposure techniques are limited by the absence of suitable sample materials and are inapplicable to numerous buried fan remnants that are otherwise excellent strain markers. Pedogenic carbonate datable by U-series, however, occurs in CM soil profiles, ubiquitously developed in fan gravels, and is apparent in deposits as young as ~1 ka. In CM gravels 10's ka and older, carbonate forms continuous, dense, yellow coatings up to 3 mm thick on the undersides of clasts. Powdery white carbonate may completely engulf clasts, but is not dateable. Carefully selected samples of dense, innermost carbonate lamina weighing 10's of milligrams and analyzed by TIMS, are geochemically favorable for precise U-series dating (e.g., U = 1-1.5 ppm, median 238U/232Th ~ 7), and yield reproducible ages for coatings from the same microstratigraphic horizon (e.g., 48.2 ± 2.7 and 49.9 ± 2.2 ka), indicating that U-Th systems have remained closed and that inherited coatings, though present, have been avoided. Accordingly, U-series on pedogenic carbonate provides reliable minimum ages for deposition of

  10. Provenance of alluvial fan deposits to constrain the mid-term offsets along a strike-slip active fault: the Elsinore fault in the Coyote Mountains, Imperial Valley, California.

    NASA Astrophysics Data System (ADS)

    Masana, Eulalia; Stepancikova, Petra; Rockwell, Thomas

    2013-04-01

    The lateral variation in rates along a fault and its constancy along time is a matter of discussion. To give light to this discussion, short, mid and long term offset distribution along a fault is needed. Many studies analyze the short-term offset distribution along a strike-slip fault that can be obtained by the analysis of offset features imprinted in the morphology of the near-fault area. We present an example on how to obtain the mid- to long-term offset values based on the composition of alluvial fans that are offset by the fault. The study area is on the southern tip of the Elsinore fault, which controls the mountain front of the Coyote Mountains (California). The Elsinore-Laguna Salada fault is part of the San Andreas fault (SAF) system, extending 250 km from the Los Angeles Basin southeastward into the Gulf of California, in Mexico. The slip-rate on the southern Elsinore fault is believed to be moderate based on recent InSAR observations, although a recent study near Fossil Canyon (southern Coyote Mountains) suggests a rate in the range of 1-2 mm/yr. For this study we processed the airborne LiDAR dataset (EarthScope Southern & Eastern California, SoCal) to map short to mid-term alluvial offsets. We reprocessed the point clouds to produce DEMs with 0.5m and 0.25m grids and we varied the insolation angles to illuminate the various fault strands and the offset features. We identified numerous offset features, such as rills, channel bars, channel walls, alluvial fans, beheaded channels and small erosional basins that varied in displacement from 1 to 350 m. For the mid- to long-term offsets of the alluvial fans we benefited from the diverse petrological composition of their sources. Moreover, we recognized that older alluvium, which is offset by greater amounts, is in some cases buried beneath younger alluvial fan deposits and separated by buried soils. To determine the source canyon of various alluvial elements, we quantified the clast assemblage of each source

  11. Modern and ancient alluvial fan deposits

    SciTech Connect

    Nilsen, T.H.

    1985-01-01

    Understanding the structure and depositional processes of alluvial fans (river outwash deposits) has a special interest for those involved with the exploration of petroleum and many minerals. This collection of facsimile reprints of significant and classical research papers sheds new light on the subject. This reference covers the stratigraphy, sedimentology, and depositional processes of modern and ancient alluvial fans. Geographical areas considered include Arctic Canada, the American Southwest, Australia, Wyoming, Norway, and Spain. It includes a state-of-the-art introduction by the editor along with commentaries on all the papers included, a master author citation index and a subject index, and a chronological listing of early studies of alluvial fans.

  12. Laboratory alluvial fans in one dimension.

    PubMed

    Guerit, L; Métivier, F; Devauchelle, O; Lajeunesse, E; Barrier, L

    2014-08-01

    When they reach a flat plain, rivers often deposit their sediment load into a cone-shaped structure called alluvial fan. We present a simplified experimental setup that reproduces, in one dimension, basic features of alluvial fans. A mixture of water and glycerol transports and deposits glass beads between two transparent panels separated by a narrow gap. As the beads, which mimic natural sediments, get deposited in this gap, they form an almost one-dimensional fan. At a moderate sediment discharge, the fan grows quasistatically and maintains its slope just above the threshold for sediment transport. The water discharge determines this critical slope. At leading order, the sediment discharge only controls the velocity at which the fan grows. A more detailed analysis reveals a slight curvature of the fan profile, which relates directly to the rate at which sediments are transported. PMID:25215729

  13. Laboratory alluvial fans in one dimension.

    PubMed

    Guerit, L; Métivier, F; Devauchelle, O; Lajeunesse, E; Barrier, L

    2014-08-01

    When they reach a flat plain, rivers often deposit their sediment load into a cone-shaped structure called alluvial fan. We present a simplified experimental setup that reproduces, in one dimension, basic features of alluvial fans. A mixture of water and glycerol transports and deposits glass beads between two transparent panels separated by a narrow gap. As the beads, which mimic natural sediments, get deposited in this gap, they form an almost one-dimensional fan. At a moderate sediment discharge, the fan grows quasistatically and maintains its slope just above the threshold for sediment transport. The water discharge determines this critical slope. At leading order, the sediment discharge only controls the velocity at which the fan grows. A more detailed analysis reveals a slight curvature of the fan profile, which relates directly to the rate at which sediments are transported.

  14. No surface breaking on the Ecemiş Fault, central Turkey, since Late Pleistocene (~ 64.5 ka); new geomorphic and geochronologic data from cosmogenic dating of offset alluvial fans

    NASA Astrophysics Data System (ADS)

    Sarıkaya, M. A.; Yıldırım, C.; Çiner, A.

    2015-05-01

    The Ecemiş Fault Zone (EF) has been recognized as a major left lateral strike-slip fault in the Central Anatolian Fault Zone (CAFZ) of Turkey. However, its Quaternary slip-rate has been challenging to determine due to the difficulty of dating offset markers. Using high-precision offset measurements and 36Cl cosmogenic nuclide dating, we present the first geochronologically determined Late Quaternary slip-rate for the EF. Our study focuses on the excellent exposures of offset alluvial fan surfaces, originating from the Aladağlar, a Late Quaternary glaciated mountain. Analysis of airborne orthophotogrametry and GNSS (Global Navigation Satellite System) surveys indicates 168 ± 2 m left lateral and 31 ± 1 m vertical displacements. In-situ terrestrial cosmogenic 36Cl geochronology obtained from eleven surface boulders provides a minimum abandonment/incision age of 104.2 ± 16.5 ka for the oldest offset alluvial fan surface. Our geomorphic observations together with Self-potential geophysical surveys revealed the presence of an unfaulted alluvial fan terrace, which allows us to constrain the timing of deformation. The abandonment/incision age of this fan is 64.5 ± 5.6 ka based on thirteen 36Cl depth profile samples. Accordingly, we obtained a geologic fault slip-rate of 4.2 ± 1.9 mm a- 1 horizontally and 0.8 ± 0.3 mm a- 1 vertically for the time frame between 104.2 ± 16.5 ka and 64.5 ± 5.6 ka. Our analysis indicates that the EF has not been producing a major surface breaking earthquake on the main strand at least since 64.5 ± 5.6 ka (mid-Late Pleistocene). This could be the result of abandonment of the main strand and accommodation of deformation by other faults within the EF. Nevertheless, a recently occurred (30 September 2011) low magnitude (ML: 4.3) left lateral strike-slip earthquake indicates recent seismic activity of the EF. Comparison of the recent GPS velocity field with the longer slip history along the CAFZ indicates a constant but low strain

  15. Experimental Study of Alluvial Fan Formation

    NASA Astrophysics Data System (ADS)

    Delorme, P.; Devauchelle, O.; Barrier, L.; Métivier, F.

    2015-12-01

    At the outlet of mountain ranges, rivers flow onto flatter lowlands. The associated change of slope causes sediment deposition. As the river is free to move laterally, it builds conical sedimentary structures called alluvial fans. Their location at the interface between erosional and depositional areas makes them valuable sedimentary archives. To decipher these sedimentary records, we need to understand the dynamics of their growth. Most natural fans are built by braided streams. However, to avoid the complexity of braided rivers, we develop a small-scale experiment in which an alluvial fan is formed by a single channel. We use a mixture of water and glycerol to produce a laminar river. The fluid is mixed with corindon sand (~ 300 μm) in a tilted channel and left free to form a fan around its outlet. The sediment and water discharges are constant during an experimental run. We record the fan progradation and the channel morphology with top-view pictures. We also generate an elevation map with an optical method based on the deformation of a moiré pattern. We observe that, to leading order, the fan remains self-affine as it grows, with a constant slope. We compare two recent studies about the formation of one-dimensionnal fan [Guerit et al. 2014] and threshold rivers [Seizilles et al. 2013] to our experimental findings. In particular, we propose a theory witch relates the fan morphology to the control parameters ( fluid and sediment discharges, grain size). Our observation accord with the predictions, suggesting that the fan is built near the threshold of sediment motion. Finally, we intend to expand our interpretation to alluvial fans build by single-thread channels ( Okavango, Bostwana; Taquari and Paraguay, Brasil; Pastaza, Peru).

  16. Controls on alluvial fan long-profiles

    USGS Publications Warehouse

    Stock, J.D.; Schmidt, K.M.; Miller, D.M.

    2008-01-01

    Water and debris flows exiting confined valleys have a tendency to deposit sediment on steep fans. On alluvial fans where water transport of gravel predominates, channel slopes tend to decrease downfan from ???0.10-0.04 to ???0.01 across wide ranges of climate and tectonism. Some have argued that this pattern reflects grain-size fining downfan such that higher threshold slopes are required just to entrain coarser particles in the waters of the upper fan, whereas lower slopes are required to entrain finer grains downfan (threshold hypothesis). An older hypothesis is that slope is adjusted to transport the supplied sediment load, which decreases downfan as deposition occurs (transport hypothesis). We have begun to test these hypotheses for alluvial fan long-profiles using detailed hydraulic and particle-size data in sediment transport models. On four alluvial fans in the western U.S., we find that channel hydraulic radiiare largely 0.5-0.9 m at fan heads, decreasing to 0.1-0.2 m at distal margins. We find that median gravel diameter does not change systematically along the upper 60%-80% of active fan channels as slope declines, so downstream gravel fining cannot explain most of the observed channel slope reduction. However, as slope declines, channel-bed sand cover increases systematically downfan from areal fractions of <20% above fan heads to distal fan values in excess of 70%. As a result, entrainment thresholds for bed material might decrease systematically downfan, leading to lower slopes. However, current models of this effect alone tend to underpredict downfan slope changes. This is likely due to off-channel gravel deposition. Calculations that match observed fan long-profiles require an exponential decline in gravel transport rate, so that on some fans approximately half of the load must be deposited off channel every -0.20-1.4 km downfan. This leads us to hypothesize that some alluvial fan long-proffies are statements about the rate of overbank deposition of

  17. The Shape of Trail Canyon Alluvial Fan, Death Valley

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.; Dohrenwend, John C.

    1993-01-01

    A modified conic equation has been fit to high-resolution digital topographic data for Trail Canyon alluvial fan in Death Valley, California. Fits were accomplished for 3 individual fan units of different age.

  18. Distribution and Orientation of Alluvial Fans in Martian Craters

    NASA Technical Reports Server (NTRS)

    Kraal, E. R.; Moore, J. M.; Howard, A. D.; Asphaug, E. I.

    2005-01-01

    We present the results of the complete survey of Martian alluvial fans from 0-30 S, initiated by Moore and Howard. Nineteen impact craters contain alluvial fans. They are regionally grouped into three distinct areas. We present our initial results regarding their distribution and orientation in order to understand what controls their formation. Since alluvial fans are formed by water transport of sediment, these features record wetter episodes of Martian climate. In addition, their enigmatic distribution (in regional groups and in some craters, but not similar adjacent ones) needs to be understood, to see how regional geology, topographic characteristics, and/or climate influence their formation and distribution.

  19. Design of flood protection for transportation alignments on alluvial fans

    SciTech Connect

    French, R.H.

    1991-01-01

    The method of floodplain delineation on alluvial fans developed for the national flood insurance program is modified to provide estimates of peak flood flows at transportation alignments crossing an alluvial fan. The modified methodology divides the total alignment length into drainage design segments and estimates the peak flows that drainage structures would be required to convey as a function of the length of the drainage design segment, the return period of the event, and the location of the alignment on the alluvial fan. An example of the application of the methodology is provided. 16 refs., 5 figs.

  20. Spatial features of hydraulic conductivity in alluvial fans

    NASA Astrophysics Data System (ADS)

    Dai, Z.; Zhu, L.; Ke, Y.; Pan, Y.; Gong, H.; Li, Y.

    2015-12-01

    Alluvial fans are highly heterogeneous due to the complicated depositional processes, which make it difficult to characterize the spatial distributions of the hydraulic conductivity and to evaluate the evolution trends. This study develops a methodology to identify the spatial statistical parameters (mean, variance, correlation range) of the hydraulic conductivity by using the hydraulic and geophysical data. The Chaobai River alluvial fan in the Beijing Plain, China, is used as an example to test the developed methodology for depicting the spatial variations of the alluvial fan. Due to the non-stationary property of the hydraulic conductivity distributions in the alluvial fan, a multi-zone parameterization approach is applied to analyze conductivity statistical properties of different hydrofacies and the composite variance of each zone is computed to describe the evolution of the conductivity along the flow direction of the alluvial fan. Results show that conductivity variances of medium-coarse sand and gravel decrease from Zone 1 to Zone 3 along the flow direction, which is consistent with the scales of the sedimentary transport energy. In the upper zone of the alluvial fan sediments were formed by higher-energy flooding, which induces bad sorting and larger conductivity variances in the sediments. The variance of fine sand also decreases from Zone 1 to Zone 3. The variances of the sub-clay and clay increase from the upper zone of the alluvial fan to the lower zone, where multiple layers of the sub-clay and clay formed by different flooding events have quite different conductivity distributions and statistical properties. With a much larger thickness in the lower zone, the vertical variations of conductivity contribute mainly to the relatively increased variance. The result of this study will provide insight for understanding conductivity heterogeneity and a method for characterizing the conductivity spatial distributions in alluvial fans.

  1. Directional scales of heterogeneity in alluvial fan aquifers

    SciTech Connect

    Neton, M.J.; Dorsch, J.; Young, S.C.; Olson, C.D. . Dept. of Geological Sciences Tennessee Valley Authority Engineering Lab., Norris, TN )

    1992-01-01

    Abrupt lateral and vertical permeability changes of up to 12 orders of magnitude are common in alluvial fan aquifers due to depositional heterogeneity. This abrupt heterogeneity is problematic, particularly in construction of a continuous hydraulic conductivity field from point measurements. Site characterization is improved through use of a scale-and-directionally-related model of fan heterogeneities. A directional classification of alluvial fan aquifer heterogeneities is proposed. The three directional scales of heterogeneity in alluvial fan aquifers are: (1) within-fan, (2) between-fan (strike-parallel), and (3) cross-fan (strike-perpendicular). Within-fan heterogeneity ranges from very small-scale intergrain relationships which control the nature of pores, to larger scale permeability trends between fan apex and toe, and includes abrupt lateral and vertical facies relationships. Between-fan heterogeneities are of a larger-scale and include differences between adjacent (non)coalescent fans along a basin-margin fault due primarily to changes in lithology between adjacent upland source basins. These differences produce different (a) grain and pore fluid compositions, (b) lithologic facies and proportions, and (c) down-fan fining trends, between adjacent fans. Cross-fan heterogeneities extend from source to basin. Fan deposits are in abrupt contact upgradient with low permeability, basin-margin source rock. Downgradient, fan deposits are in gradational to abrupt contact with time-equivalent, generally lower permeability deposits of lake, desert, longitudinal braided and meandering river, volcanic, and shallow marine environments. Throughout basin history these environments may abruptly cover the fan with low permeability horizons.

  2. Timescales of alluvial fan development by precipitation on Mars

    NASA Astrophysics Data System (ADS)

    Armitage, John J.; Warner, Nicholas H.; Goddard, Kate; Gupta, Sanjeev

    2011-09-01

    Dozens of large, low-gradient alluvial fans are present within impact crater basins on the cratered highlands of Mars. The timescales and climate conditions that were required to generate such fans are unknown, but testable through our understanding of terrestrial hill slope erosion in the presence of precipitation. Previous estimates of fan formation time vary from years to millions of years. Here, we use an idealised physical model of 2-D catchment-fan evolution to present a framework within which the development of Martian alluvial fans should be considered. We simplify the erosional and depositional system so that there are only three variables: erodibility due to gravity, amount of water runoff due to precipitation, and catchment-fan boundary elevation. Within this framework, to generate large, low-gradient (<6°) alluvial fans on Mars requires significant periods of erosion due to runoff. We suggest two climate scenarios, either: (1) rates of precipitation that are similar to arid terrestrial climates over timescales of 107 to 108 yr or (2) a shorter duration of semiarid to temperate climate conditions over a period on the order of 106 yr. Hyper-arid conditions generate low-gradient alluvial fans under conditions of a topographically lowered fan-catchment boundary and only over timescales >108 yr if the substrate is extremely erodible relative to terrestrial examples.

  3. Geomorphologic flood-hazard assessment of alluvial fans and piedmonts

    USGS Publications Warehouse

    Field, J.J.; Pearthree, P.A.

    1997-01-01

    Geomorphologic studies are an excellent means of flood-hazard assessment on alluvial fans and piedmonts in the southwestern United States. Inactive, flood-free, alluvial fans display well developed soils, desert pavement, rock varnish, and tributary drainage networks. These areas are easily distinguished from flood-prone active alluvial fans on aerial photographs and in the field. The distribution of flood-prone areas associated with alluvial fans is strongly controlled by fanhead trenches dissecting the surface. Where fanhead trenches are permanent features cut in response to long-term conditions such as tectonic quiescence, flood-prone surfaces are situated down-slope from the mountain front and their positions are stable for thousands of years. Since the length and permanency of fanhead trenches can vary greatly between adjacent drainages, it is not appropriate to use regional generalizations to evaluate the distribution and stability of flood-hazard zones. Site-specific geomorphologic studies must be carried out if piedmont areas with a high risk of flooding are to be correctly identified and losses due to alluvial-fan flooding minimized. To meet the growing demand for trained professionals to complete geomorphologic maps of desert piedmonts, undergraduate and graduate geomorphology courses should adopt an instructional unit on alluvial-fan flood hazards that includes: 1) a review of geomorphologic characteristics that vary with surface age; 2) a basic mapping exercise; and 3) a discussion of the causes of fanhead trenching.

  4. Alluvial fans and fan deltas: a guide to exploration for oil and gas

    SciTech Connect

    Fraser, G.S.; Suttner, L.

    1986-01-01

    This volume is a result of a series of lectures presented to an oil company in 1985 and is intended for an audience of explorationists. Material is presented in the order in which an exploration program might proceed in a frontier area. The volume is divided into six chapters that cover definitions and tectonic setting, alluvial-fan morphology, processes and facies on alluvial fans, geomorphic controls, effects of extrinsic controls (chiefly tectonism and climate) on alluvial-fan sequences, and diagenesis. Previously published black-and-white line drawings from studies of modern and ancient fans and fan deltas provide almost all the illustrative material; only one photograph is included, an aerial view of fans in part of Death Valley. The authors emphasize the complexity and variability of fan deposits and their resultant architecture. Although the volume contains a useful review of previous literature, it contains little new material, and it is remarkably lacking subsurface examples and data for a volume intended for the exploration community. In addition, fan deltas receive only brief attention; the overwhelming part of the book is devoted to alluvial fans. The volume will be of interest to those involved in studies of modern and ancient alluvial-fan deposits. 165 references.

  5. Geometry and evolution of a syntectonic alluvial fan, Southern Pyrenees

    SciTech Connect

    Arminio, J.F. ); Nichols, G.J. )

    1993-02-01

    Syntectonic alluvial fans formed on the northern margin of the Ebro Foreland Basin along the South Pyrenean thrust front during late orogenic thrust movements in the late Oligocene/early Miocene. The present-day geometry, structural relations and sedimentology of one of these fans, the Aguero fan in the province of Huesca, Spain, were studied. Field observations of the architecture of depositional facies and the geometries of syn-tectonic folds and unconformities indicate that the Aguero fan formed as the result of several phases of sedimentation which were primarily controlled by periods of tectonic activity and quiescence. The syntectonic unconformities and growth folds in the fan deposits provide a detailed record of the evolution of a fan adjacent to an active thrust front. Using a computer program to simulate sedimentation and deformation of an alluvial fan it is possible to constrain rates of both sedimentary and tectonic processes by modeling the evolution of the fan body. A facies model for the fan phases indicates that the facies change from proximal (coarse-grained, amalgamated) to distal (finger grained, stacked fining up cycles) in less than 1 km across a fan of radius estimated to be about 2 km.

  6. Experimental study of a single channel alluvial fan

    NASA Astrophysics Data System (ADS)

    Delorme, Pauline; Devauchelle, Olivier; Barrier, Laurie; Métivier, François

    2016-04-01

    At the outlet of mountain ranges, rivers reach a flat plain and start to depose their sediment load into a conical sedimentary structure called alluvial fan. To decipher these sedimentary records, we need to understand the dynamics of their growth. Most natural fans are built by braided streams. However, to avoid the complexity of braided rivers, we develop a small-scale experiment in which an alluvial fan is formed by a single channel. We use a mixture of water and glycerol to produce a laminar river. The fluid is mixed with corindon sand (~ 300 μm) in a tilted channel and left free to form a fan around its outlet. The sediment and water discharges are constant during an experimental run. We record the fan progradation and the channel morphology with top-view pictures. We also generate an elevation map with an optical method based on the deformation of a moiré pattern. We observe that, to leading order, the fan remains self-affine as it grows, with a constant slope. We compare two recent studies about the formation of one-dimensionnal fan [Guerit et al. 2014] and threshold rivers [Seizilles et al. 2013] to our experimental findings. In particular, we propose a theory witch relates the fan morphology to the control parameters (fluid and sediment discharges, grain size). Our observations accord with the predictions, suggesting that the fan is built near the threshold of sediment motion. At the first order, the fan profile is linear and control by the water discharge. The downstream decrease in sediment discharge add a curvature to this profile. Finally, we intend to expand our interpretation to alluvial fans build by single-thread channels ( Okavango, Bostwana; Taquari and Paraguay, Brasil).

  7. Experimental alluvial fans: Advances in understanding of fan dynamics and processes

    NASA Astrophysics Data System (ADS)

    Clarke, Lucy E.

    2015-09-01

    Alluvial fans are depositional systems that develop because of a disparity between the upstream and downstream sediment transport capacity of a system, usually at the base of mountain fronts as rivers emerge from the constrained mountain area onto the plain. They are dynamic landforms that are prone to abrupt changes on a geomorphological (decades to centuries) time scale, while also being long-term deposition features that preserve sedimentary strata and are sensitive indictors of environmental change. The complexity of interactions between catchment characteristics, climate, tectonics, internal system feedbacks, and environmental processes on field alluvial fans means that it is difficult to isolate individual variables in a field setting; therefore, the controlled conditions afforded by experimental models has provided a novel technique to overcome some of these complexities. The use of experimental models of alluvial fans has a long history and these have been implemented over a range of different research areas utilising various experimental designs. Using this technique, important advances have been made in determining the primary factors influencing fan slope, understanding of avulsion dynamics, identifying autogenic processes driving change on fan systems independent of any change in external conditions, and the mechanics of flow and flood risk on alluvial fans, to name a few. However, experiments cannot be carried out in isolation. Thus, combining the findings from experimental alluvial fans with field research and numerical modelling is important and, likewise, using these techniques to inform experimental design. If this can be achieved, there is potential for future experimental developments to explore key alluvial fan issues such as stratigraphic preservation potential and simulating extra terrestrial fan systems.

  8. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  9. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  10. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  11. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  12. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  13. New techniques in defining allocyclicity in dry alluvial fan sequences

    SciTech Connect

    Walker, D.; Grigsby, J.

    1986-05-01

    Allocyclicity in alluvial fan sedimentation can be attributed to changes in three extrinsic factors: (1) tectonism, (2) climate, and (3) eustatic sea level. This study examines the viability of two methods for identifying allocyclic variations in dry alluvial fan sequences. These include largescale (> 100 m) vertical trends in the ratio of trough cross-stratified to horizontally laminated sediments (reflecting progradation or retreat of the midfan environment), and the petrographic ratio of volcanic rock fragments to feldspar grains. Variations in climate should be reflected by this ratio due to the higher susceptibility of rock fragments to chemical weathering. Midfan and distal fan alluvial sediments comprise 923 m of the Hayner Ranch and Rincon Valley Formations (Miocene) at San Diego Mountain, New Mexico. These sediments were derived exclusively from volcanic and sedimentary source rocks, and were deposited in a closed basin, eliminating eustatic sea level change as a possible allocyclic variable. Analysis of the vertical trends in average maximum clast size results in the delineation of two allocyclic trends. These trends are also reflected in the ratio of trough cross-stratified to horizontally laminated sediments. The ratio of volcanic rock fragments to feldspar grains lacks these trends, indicating a near constant climate. This apparent uniformity in climate is in agreement with other observed climatic indicators. These relationships allow a high degree of confidence in the interpretation of the two allocyclic sequences as being tectonic in origin, and suggest that the use of these factors may be valid criteria for determining allocyclicity in similar alluvial fan deposits.

  14. Alluvial Fan Morphology, distribution and formation on Titan

    NASA Astrophysics Data System (ADS)

    Birch, S. P. D.; Hayes, A. G.; Howard, A. D.; Moore, J. M.; Radebaugh, J.

    2016-05-01

    Titan is a hydrologically active world, with dozens of alluvial fans that are evidence of sediment transport from high to low elevations. However, the distribution and requirements for the formation of fans on Titan are not well understood. We performed the first global survey of alluvial fans on Titan using Cassini Synthetic Aperture Radar (SAR) data, which cover 61% of Titan's surface. We identified 82 fans with areas ranging from 28 km2 to 27,000 km2. A significant fraction (∼60%) of the fans are restricted to latitudes of ±50-80°, suggesting that fluvial sediment transport may have been concentrated in the near-polar terrains in the geologically recent past. The density of fans is also found to be correlated with the latitudes predicted to have the highest precipitation rates by Titan Global Circulation Models. In equatorial regions, observable fans are not generally found in proximity to dune fields. Such observations suggest that sediment transport in these areas is dominated by aeolian transport mechanisms, though with some degree of recent equatorial fluvial activity. The fan area-drainage area relationship on Titan is more similar to that on Earth than on Mars, suggesting that the fans on Titan are smaller than what may be expected, and that the transport of bedload sediment is limited. We hypothesize that this has led to the development of a coarse gravel-lag deposit over much of Titan's surface. Such a model explains both the morphology of the fans and their latitudinal concentration, yielding insight into the sediment transport regimes that operate across Titan today.

  15. Morphometric Characterization and Classification of Alluvial Fans in Eastern Oman

    NASA Astrophysics Data System (ADS)

    Leuschner, Annette; Mattern, Frank; van Gasselt, Stephan

    2015-04-01

    Morphologic characteristics of alluvial fans are a product of fluvial erosion, transportation and deposition. Consequently, fans have been described and defined on the basis of their shape, their composition, conditions and processes under which they from, their so-called "controlling factors", and their geomorphic and tectonic settings. The aim of our study is to reconstruct the morphologic evolution and to relate it to past and present climate conditions. In order to achieve this, we first characterize alluvial fans based on their climatic settings and conditions and classify them accordingly using satellite image data and digital elevation models. For mapping of different alluvial fan bodies multispectral images of the Landsat Enhanced Thematic Mapper (ETM+) with a scale of 15-30 m/px were utilized. For the detection of morphometric parameters as input data for subsequent hydrological studies digital terrain model data of the Shuttle Radar Topography Mission (SRTM) and the ASTER GDEM with a scale of 90 m/px and 30m, respectively, were used. Using these datasets morphological characteristics, such as sizes of drainage basins, transport areas and areas of deposition derived from spatial semi-automatic analysis, have been computed. The area of Muscat at the Oman Mountains has been selected as a study area because of its size, accessibility and climate conditions and it is considered well-suited for studying the development of alluvial fans and their controlling factors. The Oman Mountains are well-known for the world's largest intact and best exposed obducted ophiolite complex, the Semail Ophiolite. They are today subjected to a mild desert climate (Bwh), influenced by the Indian Ocean but they have experienced extensive pluvial periods in the geologic past. Formation of alluvial fans was, therefore, likely triggered by the interplay of increased sediment production caused by high rainfalls with enhanced erosion of hillslopes and transport rates during pluvial

  16. Coastal alluvial fans (fan deltas) of the Gulf of Aqaba (Gulf of Eilat), Red Sea

    NASA Astrophysics Data System (ADS)

    Hayward, A. B.

    1985-04-01

    Coastal sediments of the Gulf of Aqaba are dominated by alluvial fans that prograde directly into the sea. The fans can be subdivided into four types: (1) largely inactive alluvial fans that merge into a braided fluvial system and pass seaward into sabkha flats, lagoons, mangroves and fringing reefs; (2) large alluvial fans that pass directly into the sea with one major entrenched channel and a fringing reef with a large incised canyon; both of these were formed during the Pleistocene, present fluvial activity is confined to the entrenched channels; (3) medium-sized (1-2 km long, 3-4 km wide) moderate to highly active alluvial fans with fringing reefs and backreef lagoons; and (4) small short-headed wadis that empty directly into the sea. The scale, overall sediment body geometry and facies associations of type (3) coastal alluvial fans (fan deltas) provide a close and useful modern analogue for many ancient fan-delta sedimentary sequences. On subaerial parts of the fan, disorganised cobbles and boulders, at the apex, deposited by debris flows pass downslope into longitudinal bars deposited during the high flood stage of periodic flash-flood events. The bars extend over the entire fan surface becoming progressively smaller and finer grained down fan. In general, the fans are characterised by a low proportion of floodplain deposits and extensive modification by aeolian processes, producing widespread gravel pavements and small dune fields over inactive areas of the lower fan. In the marine environment the fans are modified by a combination of wave action and longshore drift. Sand beaches are characterised by low-angle seaward-dipping lamination. On shingle beaches all gravel clasts have a strong preferred seaward dipping orientation. In areas where the fringing reefs are situated offshore from the fan, mixed quartz-bioclastic sand-filled lagoons develop. The nearshore lagoon areas are characterised by large sand bars orientated parallel to the shore. These pass

  17. Surface exposure dating of moraines and alluvial fans in the Southern Central Andes

    NASA Astrophysics Data System (ADS)

    Terrizzano, Carla; Zech, Roland; García Morabito, Ezequiel; Haghipour, Negar; Christl, Marcus; Likermann, Jeremías; Tobal, Jonathan; Yamin, Marcela

    2016-04-01

    The role of tectonics versus climate in controlling the evolution of alluvial fans in discussed controversially. The southern Central Andes and their forelands provide a perfect setting to study climate versus tectonic control of alluvial fans. On the one hand, the region is tectonically active and alluvial fan surfaces are offset by faults. The higher summits, on the other hand, are glaciated today, and glacial deposits document past periods of lower temperatures and increased precipitation. We applied 10Be surface exposure dating on 5 fan terraces 4 moraines of the Ansilta range (31.6°S - 69.8°W) using boulders and amalgamated pebbles to explore their chronological relationship. From youngest to oldest, the alluvial fan terraces yield minimum ages of 15 ± 1 ka (T1), 97 ± 9 ka (T2), 141 ± 9 ka (T3), 286 ± 14 ka (T4) and 570 ± 57 ka (T5). Minimum ages derived from moraines are 14 ± 1 ka (M1), 22 ± 2 ka (M2), 157 ± 14 ka (M3) and 351 ± 33 ka (M4), all calculations assuming no erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. The moraines document glacial advances during cold periods at the marine isotope stages (MIS) 2, 6 and 10. The terraces T1, T3 seem to be geomorphologic counterparts during MIS 2 and 6. We suggest that T2, T4 and T5 document aggradation during the cold periods MIS 5d, 8 and 14 in response to glacial advances, although the respective moraines are not preserved. Our results highlight: i) the arid climate in the Southern Central Andes favors the preservation of glacial and alluvial deposits allowing landscape and climate reconstructions back to ~570 ka), ii) alluvial deposits correlate with moraines or fall into cold glacial times, so that climate, and in particular the existence of glaciers, seems to be the main forcing of alluvial fan formation at our study site. References Lal, D., 1991: Cosmic ray labeling of erosion surfaces: In situ nuclide production rates and erosion models. Earth and Planetary

  18. Are North Slope surface alluvial fans pre-Holocene relicts?

    USGS Publications Warehouse

    Reimnitz, Erk; Wolf, Stephen C.

    1998-01-01

    The surface morphology of the northern slope of the Brooks Range (North Slope) from the Canning River, Alaska, eastward is dominated by a series of large alluvial fans and braided streams floored by coarse alluvium. On the basis of our studies, we conclude that the fans are not prograding now nor have they been prograding at any time during the Holocene. During the latest transgression and the following sea-level highstand, the North Slope depositional environment and climate probably differed greatly from the present ones.

  19. Detectability of minerals on desert alluvial fans using reflectance spectra

    NASA Technical Reports Server (NTRS)

    Shipman, Hugh; Adams, John B.

    1987-01-01

    The visible and near-infrared reflectance spectra of soil samples collected from desert alluvial and colluvial surfaces in the Cuprite mining district, Nevada, were analyzed. These surfaces are downslope from hydrothermally altered volcanic rocks that contain spectrally characteristic minerals such as alunite and kaolinite. Coarse fractions of the soils on the alluvial fans are mineralogically variable and express the upslope lithologies; fine fractions are remarkably similar mineralogically and spectrally in all samples because of dilution of local mineral components by regionally derived windblown dust. Theoretical models for spectral mixing and for particle-size effects were used to model the observed spectral variations. Diagnostic mineral absorption bands in the spectra of fan materials were enhanced by computationally removing the spectrum of the homogeneous fine-soil component. Results show that spectral mixing models are useful for analyzing data with high spectral resolution obtained by field and aircraft spectrometers.

  20. Sedimentology of Holocene debris flow-dominated alluvial fans, northwest Wyoming: Contributions to alluvial fan facies models

    SciTech Connect

    Cechovic, M.T.; Schmitt, J.G. . Dept. of Earth Sciences)

    1993-04-01

    Facies models for debris flow-dominated alluvial fans are based exclusively upon studies of relatively few fans in the arid American southwest. Detailed geomorphic, stratigraphic, and sedimentologic analyses of several highly-active, debris flow-dominated alluvial fans in northern Yellowstone National Park, WY (temperature, semi-arid) serve to diversify and increase the usefulness of alluvial fan facies models. These fans display an intricate distributary pattern of incised active (0--6 m deep; 700--900 m long) and abandoned channels (1--4 m deep; 400 m long) with levees/levee complexes (<3 m high; <20 m wide; <750 m long) and lobes constructed by pseudoplastic to plastic debris flows. The complex pattern of debris flow deposits is due to repeated channel back filling and overtopping by debris flows behind in-channel obstructions which subsequently lead to channel abandonment. Debris-flow deposition is dominant due to: (1) small, steep (up to 35 degrees) source area catchments, (2) extensive mud rock outcrops in the source area, and (3) episodic summer rainfall events. Proximal to distal fan surfaces exhibit sheetflood deposits several cm thick and up to 70 m in lateral extent. Vertical lithofacies profiles reveal: (1) massive, matrix- and clast-supported gravel units (1--2 m thick) deposited by clast-poor and clast-rich debris flows respectively, with reworked; scoured tops overlain by thin (<0.25 m) trough cross-bedded gravel and ripple cross-laminated sand intervals, and (2) volumetrically less significant 1--2 m thick intervals comprising fining-upward sequences of interbedded cm-scale trough cross-bedded pebbly gravel, massive sand, horizontally stratified sand, and mud rock deposited by hyperconcentrated flow and stream flow during decelerating sheetflood events. Organic rich layers record periods of non-deposition. Channelized stream flow is restricted to minor reworking of in-channel debris flow and hyperconcentrated flow deposits.

  1. Timing and nature of alluvial fan development along the Chajnantor Plateau, northern Chile

    NASA Astrophysics Data System (ADS)

    Cesta, Jason M.; Ward, Dylan J.

    2016-11-01

    Alluvial systems in the Atacama Desert provide a unique opportunity to elucidate the sedimentary response to climate variability, particularly changes in precipitation, in hyperarid environments. Alluvial fans along the eastern margin of the Salar de Atacama, adjacent to the Chajnantor Plateau in the Atacama Desert of northern Chile, provide an archive of climate-modulated sediment transfer and erosion at an extreme of Earth's climate. Three regional alluvial fan surfaces (Qf1 [oldest] to Qf3 [youngest]) were mapped along the western flank of the Chajnantor Plateau. The alluvial fans were examined with geomorphic and terrestrial cosmogenic 36Cl surface exposure dating methods to define the timing of alluvial fan formation and to determine the role of climatic processes on fan development in a hyperarid environment. Alluvial fans in the study area are comprised of hyperconcentrated flow and boulder-rich debris flow deposits that reflect deposition transitioning between cohesive and noncohesive regimes. Alluvial fan surfaces yield exposure ages that range from 49.6 ± 4.4 to 194 ± 12 ka, while debris flow boulders yield exposure ages ranging from 12.4 ± 2.1 to 229 ± 53 ka. Cosmogenic 36Cl exposure ages indicate that abandonment of alluvial fan surfaces Qf1, Qf2, and Qf3 date to 175 ± 22.6 ka (MIS 6), 134.5 ± 9.18 ka (MIS 6), and 20.07 ± 6.26 ka (MIS 2), respectively. A 36Cl concentration-depth profile through alluvial fan Qf1 suggests a simple depositional history with minimal nuclide inheritance implying relatively rapid aggradation (6 m in ca. 25 kyr) followed by surface abandonment ca. 180-200 ka. Our data support a strong climatic control on alluvial fan evolution in the region, and we propose that the alluvial fans along the margins of the Salar de Atacama form according to the humid model of fan formation.

  2. Braided alluvial fan in the Terra Sirenum region, Mars

    NASA Astrophysics Data System (ADS)

    Adeli, S.; Hauber, E.; Le Deit, L.; Kleinhans, M. G.; Platz, T.; Fawdon, P.; Jaumann, R.

    2015-10-01

    Here we report the presence of an Amazonian-aged outflow channel located on the rim of the Ariadnes Colles basin (37°S/178°E) that has an alluvial fan on its downstream part. The study area is located in the Noachian highlands of Terra Sirenum, the site of a large hypothesized paleolake [3]. This so-called Eridania lake existed during the Late Noachian -Early Hesperian and drained into Ma'adim Vallis, one of the largest valleys on Mars. The Ariadnes Colles basin was part of the Eridania paleolake and hosted later a closed lake.

  3. Morphometry of Alluvial Fans in a Polar Desert (Svalbard, Norway): Implications for Interpreting Martian Fans

    NASA Astrophysics Data System (ADS)

    Hauber, E.; Preusker, F.; Trauthan, F.; Reiss, D.; Zanetti, M.; Jaumann, R.; Hiesinger, H.

    2009-04-01

    Alluvial fan-like landforms have been identified on Mars [e.g., 1-3]. Alluvial fans contain information on several controlling factors (tectonism, climate, lithology/geology), and therefore the investigation of possible Martian fans can reveal information about the planet`s climate. In lieu of direct observations of active depositional processes on Martian fans, comparisons with terrestrial analogues can constrain models of Martian fan formation derived from remote sensing data. Since present-day Mars is cold and dry, alluvial fans formed in cold deserts should be considered as useful analogues. The probably closest climatic analogue to Mars on Earth are the Antarctic Dry Valleys [5], but polar deserts can also be found in the Arctic. We report on our field work in summer 2008 and a simultaneous flight campaign with an airborne version (HRSC-AX) of the High Resolution Stereo Camera (HRSC) onboard Mars Express [6]. The results are compared with measurements of Martian fans, based on HRSC DEM. Our study area is in Svalbard near Longyearbyen (78°13'0"N, 15°38'0"E), around mountains of Mesozoic layered sandstones and shales) on the northern side of Adventfjorden. Climate data are available from the nearby Longyearbyen airport (just a few km from the study area). The present climate is arctic [7], with low mean annual air temperatures and very low precipitation, mostly as snow. Stereo images acquired in July 2008 (at the end of the snow melting season) were processed to orthoimages with a spatial resolution of 20 cm/pixel, and corresponding Digital Elevation Models (DEM) with a grid spacing of 50 cm/pixel. Simultaneous field measurements focused on channels and levees (widths, depths, heights), which were determined at vertical increments of 10 m, together with the local slope. Alluvial fans in the study area are present on slopes of all orientations. They typically coalesce into bajadas. Basically all alluvial fans in the study area are characterized by sinuous

  4. Asymmetric alluvial fans along strike-slip faults: A potential slip-rate record?

    NASA Astrophysics Data System (ADS)

    Morelan, A. E., III; Oskin, M. E.

    2014-12-01

    We investigate the phenomenon of asymmetric alluvial fan morphology along strike-slip faults. From analysis of high-resolution topographic data, we find that asymmetric alluvial fans are common along several strike-slip faults in the western United States. Affected fans are steeper in the direction of translation of the sediment source, often resulting in stream deflections counter to that expected from the sense of fault slip (e.g. left deflected streams along dextral faults). We hypothesize that fan asymmetry results from lateral translation of the sediment source relative to the depocenter. This relative motion changes the accommodation space in such a way that one side of the alluvial fan continuously progrades while the other is gradually abandoned. Therefore, lateral translation results in radial asymmetry of slopes about the fan apex. As a first approximation, we model this asymmetry as a result of diffusive sediment transport down fan. From this analysis, we predict that the degree of asymmetry of the alluvial fan is controlled by the ratio of sediment flux to fault slip rate. Qualitatively, more rapidly slipping faults should host more highly asymmetric fans; conversely, high sediment flux will obscure asymmetry. By measuring the sediment flux, through catchment-average concentration of cosmogenic isotopes or other means, we show that it is theoretically possible to quantify strike-slip fault slip-rates and alluvial-fan sediment transport rates using alluvial fan morphometry.

  5. Volcaniclastic alluvial fan sedimentation, northern Rio Grande rift

    SciTech Connect

    McPherson, J.G.; Waresback, D.B.; Self, S.

    1986-05-01

    The Pliocene Puye Formation is a well-exposed, volcanogenic, alluvial fan sequence 150+ m thick, representing a range of volcaniclastic deposits (proximal, medial, and distal) that may be generated in response to long-lived, multicompositional (basaltic to rhyolitic) volcanism in a rift setting. The deposits are a composite of eruptives (effusives and pyroclastics) and epiclastics (reworked primary volcanics). An almost complete record of source-area volcanics (style, intensity, and composition) is preserved in the volcaniclastic fan deposits, as sedimentation rates were high and basinal subsidence was continuous because of concomitant rift downfaulting. At least eight silicic, primary airfall beds are interstratified through the fan deposits and provide a reliable stratigraphic control for establishing vertical and lateral lithofacies correlations. Proximal (inner fan) lithofacies include voluminous block-and-ash deposits that have downfan facies equivalents as pyroclastic flows and mudflows. Other proximal facies include very coarse clast-bearing debris flows, boulder-rich stream-channel and hyperconcentrated flood-flow deposits, and minor sheet-flood sequences. Medial (midfan) deposits display the greatest variability in lithofacies and provide details of the rate and intensity of volcanism by means of a distinctive vertical lithofacies assemblage: a basal plinian layer, stacked debris flows, and stacked mudflows, capped by a fluvial reworking phase of interstratified stream-channel and sheetflood deposits. Debris flows (clast and matrix rich), mudflows, and hyperconcentrated flood-flow deposits are abundant; the latter show evidence of transformation to mudflows with increasing transport distance, as they incorporate added fines (ash). Sheetflood deposits increase in number and thickness at the expense of stream-channel deposits.

  6. Depositional facies and Hohokam settlement patterns of Holocene alluvial fans, N. Tucson Basin, Arizona

    SciTech Connect

    Field, J.J.

    1985-01-01

    The distribution of depositional facies on eight Holocene alluvial fans of varying dimensions is used to evaluate prehistoric Hohokam agricultural settlement patterns. Two facies are recognized: channel gravelly sand facies and overbank silty sand facies. No debris flow deposits occur. The channel facies is characterized by relatively well sorted stratified sands and gravels with common heavy mineral laminations. Overbank facies deposits are massive and very poorly sorted due to heavy bioturbation. Lithostratigraphic profiles from backhoe trenches and sediment size analysis document headward migration of depositional facies which results in fining upward sequences. Each sequence is a channel fan lobe with an underlying coarse grained channel sand which fines to overbank silty sands. Lateral and vertical variations in facies distributions show that depositional processes are affected by drainage basin area (fan size) and distance from fan head. Gravelly channel sands dominate at the headward portions of the fan and are more pervasive on large fans; overbank silty sands are ubiquitous at fan toes and approach closer to the fan head of smaller alluvial fans. When depositional facies are considered as records of water flow over an alluvial surface, the farming potential of each fan can be analyzed. Depositional models of alluvial fan sedimentation provide the basis for understanding Hohokam settlement patterns on active alluvial surfaces.

  7. Methodologies for hydraulic hazard mapping in alluvial fan areas

    NASA Astrophysics Data System (ADS)

    Milanesi, L.; Pilotti, M.; Ranzi, R.; Valerio, G.

    2014-09-01

    Hydraulic hazards in alluvial fan areas are mainly related to torrential floods and debris flows. These processes are characterized by their fast time evolution and relevant sediment load. Rational approaches for the estimation of hazard levels in flood-prone areas make use of the maps of depth and velocity, which are provided by numerical simulations of the event. This paper focuses on national regulations regarding quantitative debris-flow hazard mapping and compares them to a simple conceptual model for the quantification of the hazard levels on the basis of human stability in a flood. In particular, the proposed method takes into account, in a conceptual fashion, both the local slope and the density of the fluid, that are crucial aspects affecting stability for processes in mountain environments. Physically-based hazard criteria provide more comprehensible and objective maps, increasing awareness among stakeholders and providing more acceptable constraints for land planning.

  8. Isotopic evidence for climatic influence on alluvial-fan development in Death Valley, California

    SciTech Connect

    Dorn, R.I.; DeNiro, M.J.; Ajie, H.O.

    1987-02-01

    At least three semiarid to arid cycles are recorded by ..delta../sup 13/C values of organic matter in layers of rock varnishes on surfaces of Hanaupah Canyon and Johnson Canyon alluvial fans, Death Valley, California. These isotopic paleoenvironmental signals are interpreted as indicating major periods of fan aggradation during relatively more humid periods and fan entrenchment during subsequent lengthy arid periods.

  9. Sustainable Water Use System of Artesian Water in Alluvial Fan

    NASA Astrophysics Data System (ADS)

    Kishi, K.; Tsujimura, M.; Tase, N.

    2013-12-01

    The traditional water use system, developed with the intelligence of the local residents, usually takes advantage of local natural resources and is considered as a sustainable system, because of its energy saving(only forces of nature). For this reason, such kind of water use system is also recommended in some strategic policies for the purpose of a symbiosis between nature and human society. Therefore, it is important to clarify the relationship between human activities and water use systems. This study aims to clarify the mechanism of traditional water use processes in alluvial fan, and in addition, to investigate the important factors which help forming a sustainable water use system from the aspects of natural conditions and human activities. The study area, an alluvial fan region named Adogawa, is located in Shiga Prefecture, Japan and is in the west of Biwa Lake which is the largest lake in Japan. In this alluvial region where the land use is mainly occupied by settlements and paddy fields, a groundwater flowing well system is called "kabata" according to local tradition. During field survey, we took samples of groundwater, river water and lake water as well as measured the potential head of groundwater. The results showed that the upper boundary of flowing water was approximately 88m amsl, which is basically the same as the results reported by Kishi and Kanno (1966). In study area, a rapid increase of water pumping for domestic water use and melting snow during last 50 years, even if the irrigation area has decreased about 30% since 1970, and this fact may cause a decrease in recharge rate to groundwater. However, the groundwater level didn't decline based on the observed results, which is probably contributed by some water conservancy projects on Biwa Lake which maintained the water level of the lake. All the water samples are characterized by Ca-HCO3 type and similar stable isotopic value of δD and δ18O. Groundwater level in irrigation season is higher

  10. Formation and Evolution Process of Typical Alluvial fan in North China Plain

    NASA Astrophysics Data System (ADS)

    Hongmei, Z.; Hua, Z.

    2012-12-01

    Through Quaternary scientific drilling, well-logging, sampling and testing at Hutuo River Alluvial Fan in North China Plain, combined with existing lithology and lithofacies data of borehole, and comprehensive analysises with approaches of sedimentology, palaeontology, climatostratigraphy, we have identified the formation and evolution process of Hutuo River Alluvial Fan, our results indicate that: 1) There are three phases of large-scale alluvial fan during Quaternary period in the Hutuo River alluvial fan, which were buried in the depth of 40 ~ 70m, 70 ~ 130m, 130 ~ 160m respectively, with corresponding geological age are middle Pleistocene, early and mid-term of early Pleistocene, early-term of early Pleistocene. The leading edge of Hutuo River Alluvial Fan reached to counties of Ning jin, Hengshui, Wuqiang and, Raoyang. 2) The sedimentary facies of Hutuo River Alluvial Fan include alluvial facies and lake - swamp facies. Alluvial facies have been widely distributed from the piedmont area to Xinji county, including two sub-facies of river bed and alluvial flat facies. Lake-swamp facies mainly appeared at Shen county and it's east, and also scattered in the piedmont and the central of the fan. 3) On the basis of the lithology, lithofacies characteristics and stratigraphic cycles, and combined with biostratigraphic characteristics and luminescence age, we can definite the division of Quaternary geological boundary of Hutuo River Alluvial Fan as follows: Q4 / Q3 - -8.85m; Q3 / Q2 -32.68 m; Q2 / Q1 -73.84m; Q1 / N2 - 157.04m.

  11. A Numerical Model of Retreating Alluvial Fan Coasts

    NASA Astrophysics Data System (ADS)

    Hicks, M.; Dickson, M.; Coco, G.

    2006-12-01

    A numerical model has been developed that simulates the wave-driven retreat of partially-consolidated alluvial- fan shores over millennium time-scales. It has been developed to reproduce the shore profiles and coastal erosion rates observed along the Pleistocene glacial-outwash fan built by the Waitaki River on the east coast of New Zealand's South Island. This cliffed shore is currently fronted by a narrow sand-and-gravel beach. The nearshore seabed is formed in Pleistocene substrate and has only a thin and patchy cover of sand. The motivation is to examine the sensitivity of the erosion rates to wave-climate change, sea-level rise, and river sediment supplies. The model is forced by two wave conditions that, when randomly sampled, represent the storm-wave and normal-swell climates of the prototype coast. These each operate for a fixed proportion of the model's yearly time-step. Morphological change is driven by a series of coupled process models. These include scour of the nearshore seabed by shoaling waves, cross-shore exchanges of sand and gravel between the nearshore and beach, berm construction during normal wave conditions, berm overtopping by storm waves with consequent beach stripping and scour of the exposed sub-aerial substrate and cliff-toe notch-cutting, gravity-failure of the cliffs and talus construction between storm events, and beach sediment abrasion. The scour, notching, and transport models are generally based on energetics principles and are calibrated with linear scaling coefficients to match field observations from the prototype coast. Negative feedback regulates the rate of cliff erosion through the protection that is afforded by cliff and substrate material added to the beach. The starting model condition is a sloping alluvial fan inundated by the sea-level rise that followed the last glacial epoch, and the model is run for 6000 years to the present assuming a stable sea level. Initially, the gentle slope of the alluvial fan results in

  12. The Alluvial Fan Complex in Holden Crater: Implications for the Environment of Early Mars

    NASA Astrophysics Data System (ADS)

    Irwin, R. P.; Grant, J. A.; Howard, A. D.

    2008-03-01

    The alluvial fan complex in Holden crater is the largest deposit of this type on Mars and preserves topographic and sedimentary indicators of its formative environment around the Noachian/Hesperian transition.

  13. Statistic inversion of multi-zone transition probability models for aquifer characterization in alluvial fans

    SciTech Connect

    Zhu, Lin; Dai, Zhenxue; Gong, Huili; Gable, Carl; Teatini, Pietro

    2015-06-12

    Understanding the heterogeneity arising from the complex architecture of sedimentary sequences in alluvial fans is challenging. This study develops a statistical inverse framework in a multi-zone transition probability approach for characterizing the heterogeneity in alluvial fans. An analytical solution of the transition probability matrix is used to define the statistical relationships among different hydrofacies and their mean lengths, integral scales, and volumetric proportions. A statistical inversion is conducted to identify the multi-zone transition probability models and estimate the optimal statistical parameters using the modified Gauss–Newton–Levenberg–Marquardt method. The Jacobian matrix is computed by the sensitivity equation method, which results in an accurate inverse solution with quantification of parameter uncertainty. We use the Chaobai River alluvial fan in the Beijing Plain, China, as an example for elucidating the methodology of alluvial fan characterization. The alluvial fan is divided into three sediment zones. In each zone, the explicit mathematical formulations of the transition probability models are constructed with optimized different integral scales and volumetric proportions. The hydrofacies distributions in the three zones are simulated sequentially by the multi-zone transition probability-based indicator simulations. Finally, the result of this study provides the heterogeneous structure of the alluvial fan for further study of flow and transport simulations.

  14. Statistic inversion of multi-zone transition probability models for aquifer characterization in alluvial fans

    DOE PAGES

    Zhu, Lin; Dai, Zhenxue; Gong, Huili; Gable, Carl; Teatini, Pietro

    2015-06-12

    Understanding the heterogeneity arising from the complex architecture of sedimentary sequences in alluvial fans is challenging. This study develops a statistical inverse framework in a multi-zone transition probability approach for characterizing the heterogeneity in alluvial fans. An analytical solution of the transition probability matrix is used to define the statistical relationships among different hydrofacies and their mean lengths, integral scales, and volumetric proportions. A statistical inversion is conducted to identify the multi-zone transition probability models and estimate the optimal statistical parameters using the modified Gauss–Newton–Levenberg–Marquardt method. The Jacobian matrix is computed by the sensitivity equation method, which results in anmore » accurate inverse solution with quantification of parameter uncertainty. We use the Chaobai River alluvial fan in the Beijing Plain, China, as an example for elucidating the methodology of alluvial fan characterization. The alluvial fan is divided into three sediment zones. In each zone, the explicit mathematical formulations of the transition probability models are constructed with optimized different integral scales and volumetric proportions. The hydrofacies distributions in the three zones are simulated sequentially by the multi-zone transition probability-based indicator simulations. Finally, the result of this study provides the heterogeneous structure of the alluvial fan for further study of flow and transport simulations.« less

  15. Morphometry and Geomorphic Characteristics of Large Alluvial fans and Megafans in South America

    NASA Astrophysics Data System (ADS)

    Latrubesse, E. M.; Sounny-Slitine, M. A.

    2015-12-01

    Alluvial megafans are 'large' fan-shaped bodies of sediment that form from lateral migrations of a river as it exits a topographic front. They differ from large alluvial fans (radial length between 30-100km) with sizes greater than 100-km in radial length. This study characterizes and describes megafans and large alluvial fan through morphometrics. We cataloged the fans into a geodatabase delineating size and extent of basins both upstream and downstream from the apex. Through remote sensing, elevation modeling and geomorphic mapping, we populated the database with fan morphometric measurements, qualitative descriptions and basin parameters. Metrics include planform area, catchment area, gradient, relief index, drainage density, and others. These were compared to longitudinal/transverse profiles, satellite imagery, and geomorphic maps. The database is global, however since the largest megafans of the world are located in South America, this preliminary analysis will focus on the continent. We found morphometric and characteristic differences between large alluvial fans and megafans in the region. These include difference in relationship between morphometrics, for example the ratio between catchment and fan size area. These properties of fans could be a better approach in differentiating megafans from large alluvial fans. The current criteria is an artificial scale divide, which varies in the literature, with the most common being a 100-km apex-to-toe length. Alternative values as little of 30-km apex-to-toe length have been proposed, as well as alternative metrics like coverage areas of greater than 10,000 square-km. We propose that geomorphic characteristics and morphometrics provide an intrinsic approach to differentiating megafans from larger alluvial fans.

  16. Flood hazard assessment on alluvial fans: an examination of the methodology

    SciTech Connect

    French, R.H.

    1984-08-01

    The report presents the results of a critical examination of assumptions and methodology recommended by the Federal Emergency Management Agency (FEMA) to assess flood hazard on alluvial fans. The conculsions reached are as follows. First, the assumption that a flow on an alluvial fan has an equal probability of crossing any point on a given contour seems to be a very conservative assumption. Second, given the data from the Nevada Test Site, it would appear that the assumption that fans have critical to supercritical slopes is acceptable. Third, the present methods of estimating channel width and depth on alluvial fans seem to be invalid. Fourth, the specific flood hazard evaluation procedures recommended by FEMA are not valid in some cases because they are based on the assumption that sufficient records exist to do a standard peak flow analysis. Fifth, the validity of the implied assumption that debris flows present no risk can only be assessed after a location on a fan relative to the intersection point has been established. It is concluded that the current methods of flood hazard assessment on alluvial fans are not adequate given the current and projected economic value of structures and development on alluvial fans in the southwestern United States. 55 references, 5 figures, 5 tables.

  17. Large Well-Exposed Alluvial Fans in Deep Late-Noachian Craters

    NASA Technical Reports Server (NTRS)

    Moore, J. M.; Howard, A. D.

    2004-01-01

    Large, fresh-appearing alluvial fans (typically greater than 10 km long) have been identified during a systematic search of 100 m/pixel low-sun daylight THEMIS IR imaging in deep late-Noachian or early-Hesperian craters. Our study of these fans was augmented with MOLA-derived topography and high-resolution MOC and THEMIS VIS images where available. The influence of alluvial fan deposition on the topography of crater floors has been recognized in previous topographic studies. Recent Mars Odyssey-era studies have also identified and described in detail a fluvial delta or fan of approximately the same age as the alluvial fans of this study. Our results, at the time of this writing, indicate that these fans are only found in less than 5% of all craters greater than or equal to 70 kilometers in diameter within a large study region. In every case the fan-containing craters were restricted to a latitude belt between 20 degrees S and 30 degrees S. All of which had significant topographic relief and appeared morphologically younger than typical mid-Noachian craters in the size range. However, large fans were not found in the most pristine (and presumably youngest) craters in this size range. Most Martian fans have morphologies consistent with terrestrial debris-flow-dominated fans.

  18. Large Well-exposed Alluvial Fans in Deep Late-Noachian Craters

    NASA Technical Reports Server (NTRS)

    Moore, J. M.; Howard, A.D.

    2004-01-01

    Large, fresh-appearing alluvial fans (typically greater than 10 km long) have been identified during a systematic search of 100 m/pixel low-sun daylight THEMIS IR imaging in deep late-Noachian or early- Hesperian craters. Our study of these fans was augmented with MOLA-derived topography and high-resolution MOC and THEMIS VIS images where available. The influence of alluvial fan deposition on the topography of crater floors has been recognized in previous topographic studies. Recent Mars Odyssey-era studies have also identified and described in detail a fluvial delta or fan of approximately the same age as the alluvial fans of this study. Our results, at the time of this writing, indicate that these fans are only found in less than 5% of all craters = 70 km in diameter within a large study region. In every case the fan-containing craters were restricted to a latitude belt between 20 deg S and 30 deg S. All of which had significant topographic relief and appeared morphologically younger than typical mid-Noachian craters in the size range. However, large fans were not found in the most pristine (and presumably youngest) craters in this size range. Most Martian fans have morphologies consistent with terrestrial debris-flow-dominated fans.

  19. Differentiating tectonic from climatic factors in the evolution of alluvial fans

    SciTech Connect

    Wilson, D.S.; West, R.B. . Dept. of Geology)

    1993-04-01

    Alluvial fans are integral parts of landscapes of arid and semi-arid regions and are most commonly found along the flanks of tectonically active mountain ranges. Alluvial fans are sensitive indicators of tectonic and climatic activity through time. Three dimensional fan modelling has the potential to discriminate between these two forces and provide quantitative estimates of deformation of fan surfaces due to tilting, faulting, or folding. The model has tremendous potential for seismic hazard evaluation at both the reconnaissance and detailed level of investigation. The ability to recognize deformation of alluvial fans alleviates the need for postulation of complex interactions between climate and internal variables in the depositional system leading to present fan morphology. The greatest problems associated with fan modelling come from failure to identify individual segments. Inclusion of more than one segment can lead to poor model performance or, more likely, inaccurate results. The long term tectonic influence on a fan's evolution can be assessed from the differences in deformation of different segments. Reliable correlations of segments from different fans along the same mountain front can provide a means to asses regional deformation. Once tectonic effects are taken into account, then climatic effects can be evaluated. Previous fan models have failed to recognize areal limitations, failed to account for deformation, or assumed deformation geometry.

  20. Use of TOPSAR digital elevation data to determine the 3-dimensional shape of an alluvial fan

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.

    1995-01-01

    Landforms in arid regions record the interplay between tectonic forces and climate. Alluvial fans are a common landform in desert regions where the rate of uplift is greater than weathering or sedimentation. Changes in uplift rate or climatic conditions can lead to isolation of the currently forming fan surface through entrenchment and construction of another fan either further from the mountain front (decreased uplift or increased runoff) or closer to the mountain front (increased uplift or decreased runoff). Thus, many alluvial fans are made up of a mosaic of fan units of different age, some older than 1 million years. For this reason, determination of the stages of fan evolution can lead to a history of uplift and runoff. In an attempt to separate the effects of tectonic (uplift) and climatic (weathering, runoff, sedimentation) processes on the shapes of alluvial fan units, a modified conic equation developed by Troeh (1965) was fitted to TOPSAR digital topographic data for the Trail Canyon alluvial fan in Death Valley, California. This allows parameters for the apex position, slope, and radial curvature to be compared with unit age.

  1. Estimating alluvial fan surface ages using Landsat 8 multispectral imagery

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Mason, Philippa J.; Whittaker, Alexander C.; Roda Boluda, Duna C.

    2015-04-01

    Accurate exposure age models are now essential for geomorphological and stratigraphic field research, and generally depend on laboratory analyses such as radiocarbon, cosmogenic nuclide or luminescence approaches. However, these techniques cannot be deployed in situ in the field, meaning other methods are needed to produce a preliminary age model, map depositional surfaces of different ages, and select sampling sites for the types of laboratory analyses outlined above. With the widespread availability of high-resolution multispectral imagery, a promising approach is to use remotely sensed data to discriminate depositional surfaces with different ages. Here, we use new Landsat 8 Operational Land Imager (OLI) multispectral imagery to characterise the reflectance of 35 alluvial fan surfaces in the semi-arid Owens Valley, California. These surfaces have been mapped in detail in the field, have similar granitic compositions, and have well-constrained exposure ages ranging from modern to ~ 125 ka, measured using a high density of 10-Be cosmogenic nuclide samples. We identify a clear age signal recorded in the spectral properties of these surfaces. With increasing exposure age, there is a predictable redshift effect in the reflectance of the surfaces across the visible and short-wave infrared spectrum. Simple calculations, such as the brightness ratio of red/blue wavelengths, produce sensitive power law relationships with exposure age for at least 125 ka, meaning Landsat 8 imagery can be used to estimate surface exposure age remotely, at least in this calibrated dryland location. The ability to remotely sense exposure age has useful implications for field mapping, selecting suitable sampling sites for laboratory-based exposure age techniques, and correlating existing age constraints to previously un-sampled surfaces. We present the uncertainties associated with this spectral approach to exposure dating, evaluate its likely physical origins, and discuss its applicability

  2. Characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data

    NASA Astrophysics Data System (ADS)

    Frankel, Kurt L.; Dolan, James F.

    2007-06-01

    Range-front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages. These distinct landforms are often defined by descriptions of their surface morphology, desert varnish accumulation, clast rubification, desert pavement formation, soil development, and stratigraphy. Although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past, high-resolution airborne laser swath mapping (ALSM) digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail. Here we use ALSM data to calculate surface roughness on two alluvial fans in northern Death Valley, California. We define surface roughness as the standard deviation of slope in a 5-m by 5-m moving window. Comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99% confidence level. Furthermore, there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10Be and 36Cl surface exposure ages of ˜70 ka. Beyond 70 ka, alluvial landforms become progressively rougher with age. These data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces.

  3. Reconnaissance of alluvial fans as potential sources of gravel aggregate, Santa Cruz River valley, Southeast Arizona

    USGS Publications Warehouse

    Lindsey, David A.; Melick, Roger

    2002-01-01

    This investigation was conducted to provide information on the aggregate potential of alluvial fan sediments in the Santa Cruz River valley. Pebble lithology, roundness, and particle size were determined in the field, and structures and textures of alluvial fan sediments were photographed and described. Additional measurements of particle size on digital photographs were made on a computer screen. Digital elevation models were acquired and compiled for viewing the areal extent of selected fans. Alluvial fan gravel in the Santa Cruz River valley reflects the lithology of its source. Gravel derived from granitic and gneissic terrane of the Tortolita, Santa Catalina, and Rincon Mountains weathers to grus and is generally inferior for use as aggregate. Gravel derived from the Tucson, Sierrita, and Tumacacori Mountains is composed mostly of angular particles of volcanic rock, much of it felsic in composition. This angular volcanic gravel should be suitable for use in asphalt but may require treatment for alkali-silica reaction prior to use in concrete. Gravel derived from the Santa Rita Mountains is of mixed plutonic (mostly granitic rocks), volcanic (mostly felsic rocks), and sedimentary (sandstone and carbonate rock) composition. The sedimentary component tends to make gravel derived from the Santa Rita Mountains slightly more rounded than other fan gravel. The coarsest (pebble, cobble, and boulder) gravel is found near the heads (proximal part) of alluvial fans. At the foot (distal part) of alluvial fans, most gravel is pebble-sized and interbedded with sand and silt. Some of the coarsest gravel was observed near the head of the Madera Canyon, Montosa Canyon, and Esperanza Wash fans. The large Cienega Creek fan, located immediately south and southeast of Tucson, consists entirely of distal-fan pebble gravel, sand, and silt.

  4. Tectonic controls on the morphometry of alluvial fans around Danehkhoshk anticline, Zagros, Iran

    NASA Astrophysics Data System (ADS)

    Bahrami, Shahram

    2013-01-01

    Alluvial fans are important landforms where their morphology and morphometry reflect changes in tectonic, climate, base level, and drainage basin characteristics. Along the margins of tectonically active mountain ranges like the Zagros Mountains, alluvial fans are generally assumed to act as useful landforms for identifying the level of tectonic activity. The purpose of this paper is to evaluate the relationship between active tectonics and morphometric characteristics of alluvial fans around Danehkhoshk anticline in the Simply Folded Belt of Zagros. Morphometric characteristics of alluvial fans, such as area (FA), slope (SF) length of base (BF), width/length ratio (W/L), radius (R), sweep angle (SA) and entrenchment (E) as well as valley floor width-to-height ratio (Vf) and strata dips of anticline limbs (DAL), were measured. The study area was sub-divided into eight tectonic zones and then the mean values of the above-mentioned parameters were calculated in each zone. Result reveals that values of SA, BF and E are directly proportional to DAL. The poor relationships between catchment characteristics (slope and area) and fan parameters are probably due to extensive karstic landforms of catchments having complex hydrologic systems and, hence, result in complex catchment/fan relations. The highly entrenched fans with high sweep angles and long bases are characteristic of tectonically active fronts of Danehkhoshk anticline, having V-shaped valleys (higher Vf values), steep triangular facets and more rotated limbs (higher DAL values). Apart from the tectonic control on fan development, the fan head entrenchment and negative accumulation spaces on most alluvial fans can be attributed to decreased sediment load and discharge the drier the present-day climate regime.

  5. FUTURE STUDIES AT PENA BLANCA: RADIONUCLIDE MIGRATION IN THE VADOSE ZONE OF AN ALLUVIAL FAN

    SciTech Connect

    P. Goodell; J. Walton; P.J. Rodriguez

    2005-07-11

    The pathway to the accessible environment at Yucca Mountain contains volcanic rocks and alluvial fill. Transport properties in alluvial fill, specifically retardation and dispersivity, may be significant in determining the overall performance of the repository. Prior relevant studies, with the exception of the Nye County Tracer Test, are almost entirely in bedrock material. The proposed study will provide field data on radionuclide migration in alluvial material. High grade uranium ore was mined at the Nopal I deposit. This mined ore (60,000 tons) was moved in 1994 to its present site as open piles on an alluvial fan in the Boquilla Colorada Microbasin. Precipitation is approximately 20 cm/year, and has caused migration of radionuclides into the subsurface. We propose partial removal of an ore pile, excavation into the alluvial fan, sampling, and determination of radionuclide mobilities from the uranium decay chain. The proposed research would be taking advantage of a unique opportunity with a known time frame for migration.

  6. Large Alluvial Fans in the Araba Valley (Jordan) as a Record of Tectonic Deformation of the Southern Dead Sea Fault and Regional Paleoclimates

    NASA Astrophysics Data System (ADS)

    Le Beon, M.; Klinger, Y.; Al-Qaryouti, M.; Meriaux, A.; Finkel, R. C.; Mayyas, O.; Ryerson, F. J.; Tapponnier, P.

    2007-12-01

    The Dead Sea fault is the 1000 km-long strike-slip fault that accommodates northward motion of Arabia relative to Sinai at a rate of about 5 mm/yr. This study focuses on the southern segment of this fault, the Wadi Araba fault. From the Dead Sea basin to the Gulf of Aqaba, the fault runs along an axial valley, about 20 km wide and 150 km long, bounded to the east by the Jordanian Plateau, reaching 1500 m in elevation and to the west by the Negev Plateau, lower in elevation (500-700 m). The Araba valley is floored with Plio-Quaternary deposits and in particular with large alluvial fans that are cut by the fault and offset relative to their feeding channel. We mapped the valley floor in details and dated some of these fans first to assess their lateral offset and further constrain the slip rate on the fault, and secondly to try to correlate alluvial fan aggradation periods in this arid/semi-arid environment to paleoclimatic variations at the regional and global scales. To identify the possible sources of the large alluvial fans, we analyzed the drainage network and the catchment basins on the valley rims based on SRTM3 topography. Previous study suggested that these fans were Pliocene and underwent offsets of 15 to 30 km. Ages as young as 50 to 350 kyr derived from 10Be exposure dating of 33 samples from the surface of some of these fans indicate that such offsets are very unlikely. Actual offsets have to be smaller. Preliminary reconstructions suggest offsets of 700-1300 m and 1600-2000 m for fans dated at 160 +/- 20 kyr and 330 +/- 22 kyr respectively, and offsets of 2.5-3.5 and 4.4-5.4 km for older fans that have not been dated yet. Consistent ages at different sites suggest simultaneous fan emplacement controlled by some external controlling factor such as climate variations. The correlation between these aggradation episodes and paleoclimatic variations would allow us to draw hypotheses on the age of these older surfaces. These preliminary results provide new

  7. Rapid delineation of alluvial fans using IfSAR-derived DEM for selected provinces in the Philippines

    NASA Astrophysics Data System (ADS)

    Ortiz, Iris Jill; Aquino, Dakila; Norini, Gianluca; Narod Eco, Rodrigo; Mahar Lagmay, Alfredo

    2015-04-01

    Alluvial fans are fan-shaped geomorphic features formed when sediments from a watershed are transported and deposited downstream via tributaries flowing out from the sudden break of a slope. Hazards usually associated with alluvial fans are flooding and debris flows. In this study, we used an Interferometric Synthetic Aperture Radar-derived digital elevation model of Pangasinan and Nueva Ecija Provinces in the Philippines to identify and delineate alluvial fans. Primary parameters considered include the geomorphic characteristics of the catchment area, stream network and slopes ranging from 0.11 to 8 degrees. Using this method, 12 alluvial fans were identified in Pangasinan and 16 in Nueva Ecija with areas ranging from 0.35 to 80 sq. km. The largest fan identified is the Mangatarem-Aguilar fan in Pangaisnan with a total area of 80.87 sq km while the Gabaldon fan in Nueva Ecija with total area of 48.11 sq km. We observed from the results that some alluvial fans have multiple feeder streams, and others have overlapping lateral extents with adjacent fans. These overlapping fans are called bajadas. In addition, the general location of fans and their apices in the two provinces appear to coincide with segments of the Philippines Fault System. There are about people 1.4 million living within these alluvial fans. Mapping and characterizing and identifying their associated hazards is crucial in the disaster preparedness efforts of the exposed population.

  8. Alluvial fan deposition along a rift depocentre border from the Neuquén Basin, Argentina

    NASA Astrophysics Data System (ADS)

    Muravchik, Martin; Bilmes, Andrés; D'Elia, Leandro; Franzese, Juan R.

    2014-03-01

    The interaction between hangingwall block rotation and alluvial deposition is examined from Late Triassic-Early Jurassic successions exposed along the Catán Lil half-graben border fault system in the Neuquén Basin, Argentina. Analysis of transport and depositional processes, clast composition and rock body geometry allowed the identification of three distinctive fan-shaped alluvial units. The contrasting lithologic nature of the basement (igneous-metamorphic) and syn-rift fill (volcanic and volcanic-derived) permits detailed studies of clast provenance. The origin of each alluvial system (footwall- vs. hangingwall-derived) can thus be verified. A simple method was implemented to establish the geometry of each alluvial unit by comparing the stereographic projection of its bedding to that of an idealised fan shaped body. Results show that the three alluvial systems occupied the same relative location in the rift depocentre. Unit 1 is interpreted as an alluvial fan orientated transverse to the depocentre border fault system and fed from the footwall. Non-cohesive debris flow deposition was the dominant process in this environment. Unit 2 is interpreted as a mainly hangingwall-fed alluvial fan, parallel to the depocentre border fault system and shows an upward decrease in footwall-derived clasts. Hyperconcentrated flow was the principal transport process. Unit 3 represents a fan delta, parallel to the depocentre border fault system. Its components are completely hangingwall-derived and hyperconcentrated flow deposition was the dominant process. Differences in grain-size, composition, transport directions and fan body geometry are proved to be directly linked to variations in ground tilting induced by the direction of hangingwall block rotation in an endorheic rift depocentre.

  9. Nucleation of Waterfalls at Fault Scarps Temporarily Shielded By Alluvial Fan Aggradation.

    NASA Astrophysics Data System (ADS)

    Malatesta, L. C.; Lamb, M. P.

    2014-12-01

    Waterfalls are important components of mountain river systems and they can serve as an agent to transfer tectonic, climatic, or authigenic signals upstream through a catchment. Retreating waterfalls lower the local base level of the adjacent hillslopes, and temporarily increase sediment delivery to the fluvial system. Their creation is often attributed to seismic ruptures, lithological boundaries, or the coalescence of multiple smaller steps. We explore here a mechanism for the nucleation of waterfalls that does not rely on sudden seismic slip but on the build-up of accumulated slip during periods of fault burial by fluvial aggradation. Alluvial fans are common features at the front of mountain ranges bound by normal or thrust faults. Climate change or internal forcing in the mountain catchment modifies the equilibrium slope of alluvial fans. When alluvial fans aggrade, they shield the active fault scarp from fluvial erosion allowing the scarp to grow undisturbed. The scarp may then be exposed when the channel incises into the fan exposing a new bedrock waterfall. We explore this mechanism analytically and using a numerical model for bedrock river incision and sediment deposition. We find that the creation of waterfalls by scarp burial is limited by three distinct timescales: 1) the critical timescale for the scarp to grow to the burial height, 2) the timescale of alluvial re-grading of the fan, and 3) the timescale of the external or internal forcing, such as climate change. The height of the waterfall is controlled by i) the difference in equilibrium alluvial-fan slopes, ii) the ratio of the respective fan and catchment sizes, iii) the catchment wide denudation rate, and iv) the fault slip rate. We test whether an individual waterfall could be produced by alluvial shielding of a scarp, and identify the tectonic, climatic, or authigenic nature of waterfalls using example field sites in the southwest United States.

  10. Geomorphology, internal structure and evolution of alluvial fans at Motozintla, Chiapas, Mexico

    NASA Astrophysics Data System (ADS)

    Sánchez-Núñez, J. M.; Macías, J. L.; Saucedo, Ricardo; Zamorano, J. J.; Novelo, David; Mendoza, M. E.; Torres-Hernández, J. R.

    2015-02-01

    Alluvial fans and terraces develop in diverse regions responding to different tectonic and climatic conditions. The Motozintla basin is located in the State of Chiapas, southern Mexico and has an E-W orientation following the trace of the left-lateral Polochic Fault. The evolution of the Motozintla basin and the alluvial plain is related to several factors, such as fault movement, intense erosion by hydrometeorological events, and anthropogenic activity. This study presents the geomorphology of the alluvial plain that between the villages of Motozintla and Mazapa de Juárez exposes 31 alluvial fans, 5 hanging terraces and 13 ramps. Fourteen of these alluvial fans have been truncated by the Polochic fault, exposing maximum uplifts of ~ 12 m. The internal structure of truncated fans consists of single massive beds (monolithologic fans) or stacked beds (polygenetic fans). The fans' stratigraphy is made of debris flow deposits separated by paleosols and minor hyperconcentrated flows, fluviatile beds, and pyroclastic fall deposits. The reconstruction of the stratigraphy assisted by radiocarbon geochronology suggests that these fans have been active since late Pleistocene (25 ka) to the present. This record suggests that at least 10 events have been recorded at the fan interior during the past ~ 1840 years. One of these events at 355 ± 65 14C yrs. BP (cal yrs. AD 1438 to 1652) can be correlated across the fans and is likely associated with an extreme hydrometeorologic event. The presence of a 165 ± 60 14C yrs. BP (cal yrs. AD 1652-1949) debris flow deposit within the fans suggests that movement along the Polochic fault formed the fans' scarp afterwards. In fact, a historic earthquake along the fault occurred east of Motozintla on July 22, 1816 with a Mw of 7.5-7.75. Recent catastrophic floods have affected Motozintla in 1998 and 2005 induced by extreme hydrometeorological events and anthropogenic factors. Therefore, scenarios for Motozintla involved several types of

  11. Use of morphometric analysis and self-organizing maps for alluvial fan classification: case study on Ostorankooh altitudes, Iran

    NASA Astrophysics Data System (ADS)

    Mokarram, Marzieh; Seif, Abdollah; Sathyamoorthy, Dinesh

    2014-06-01

    The aim of this study is to classify alluvial fans formed by high-gradient braided streams and torrents that discharge into the Oshtorankook altitudes in the Lorestan province, Iran. The morphology of the fans and their watershed is quantitatively described through estimated morphometric parameters. For relationships between geomorphological features of the fans and their drainage basins, self-organizingmaps (SOM) were used. In SOM, according to both qualitative data and morphometric variables, the clustering tendency of alluvial fans was investigated using 15 alluvial fans parameters. The results of the analysis showed that several morphologically different fan types were recognizedbased on their geomorphological characteristics in the study area. A strong positive relationship was found between the drainage basin area and size of the fan with a simple power function. In addition, the relationship between fan slope and drainage area was found to be negative and moderately strong with a simple power function.

  12. A chronology of alluvial fan response to Late Quaternary sea level and climate change, Crete

    NASA Astrophysics Data System (ADS)

    Pope, Richard J. J.; Candy, Ian; Skourtsos, Emmanuel

    2016-09-01

    To better understand how fluvial systems respond to late Quaternary climatic forcing OSL and U-series dating was applied to stratigraphically significant sedimentary units within a small (<6.5 km2) alluvial fan system (the Sphakia fan) in southwest Crete. The resultant chronology (comprising 32 OSL and U-series ages) makes Sphakia fan one of the best dated systems in the Mediterranean and suggests that Cretan fans responded to climate in two ways. First, during the transitions between Marine Isotope Stage (MIS) 5a/4 and MIS 2/1 Sphakia fan was characterised by significant entrenchment and distal shift in the zone of deposition. It is proposed that the phases of entrenchment were driven by sea level induced base level fall during MIS 5a/4 and landscape stabilisation during the onset of the current interglacial (MIS 2/1). Second, with the exception of these two entrenchment episodes fan alluviation occurred across the entire last interglacial/glacial cycle in all climatic settings i.e. interglacials, interstadials and stadials. It is likely that the topographic setting of the catchment supplying sediment to Sphakia fan maintained high sediment transfer rates during most climatic settings enabling fan aggradation to occur except during major climatic driven transitions i.e. major sea level fall and postglacial vegetation development.

  13. Alluvial fan response to climatic change: Insights from numerical modeling (Invited)

    NASA Astrophysics Data System (ADS)

    Pelletier, J. D.

    2009-12-01

    Alluvial fans in the western U.S. exhibit a regionally correlative sequence of Plio-Quaternary deposits. Cosmogenic and U-series dating has greatly improved the age control on these deposits and their associated terraces and generally strengthened the case for aggradation during humid-to-arid transitions. Still, the linkages between climate change, upland basin response, and alluvial fan response are not well constrained. Fans may fill and cut as a result of autogenetic processes/internal adjustments, changes in regional temperature (which controls snowmelt-induced flooding), changes in the frequency-size distribution of rainfall events, and/or changes in upslope vegetation. Here I describe the results of a numerical modeling study designed to better constrain the relationships between different end-member forcing mechanisms and the geologic record of alluvial fan deposits and terraces. The model solves the evolution of the fan topography using Exner's equation (conservation of mass) coupled with a nonlinear, threshold-controlled transport relation for sand and gravel. Bank retreat is modeled using an advection equation with a rate proportional to bank shear stress. I begin by considering the building of a fan under conditions of constant water and sediment supply. This simple system exhibits all of the complexity of fans developed under experimental conditions, and it provides insights into the mechanisms that control avulsions and it provides a baseline estimate for the within-fan relief that can result from autogenetic processes. Relationships between the magnitude and period of variations in the sediment-to-water ratio and the geomorphic response of fans are then discussed. I also consider the response of a coupled drainage basin-fan system to changes in climate, including the hydrologic and vegetation response of upland hillslopes. Fans can aggrade or incise in response to the same climatic event depending on the relief of the upstream drainage basin, which

  14. Modelling the Holocene Evolution of a Drift-dominated Alluvial-fan Coast

    NASA Astrophysics Data System (ADS)

    Hicks, M.; Dickson, M.; Coco, G.

    2007-12-01

    A numerical model is being developed to simulate shore evolution along an alluvial fan coast over the Holocene. The alluvial fan of the Waitaki River, on the east coast of New Zealand's South Island, was built by Pleistocene glacial advances but has been eroded back by waves over recent millennia. The retreat has left a cliffed shore fronted by a narrow beach of mixed sand and gravel and a gently sloping seabed with only a thin, patchy sand cover over the Pleistocene substrate. The study motivation is to examine the sensitivity of shoreline movements in this setting to wave-climate change, sea-level rise, and river sediment supplies. The modelling couples a profile evolution model with a shoreline model. The profile evolution model is operational and is driven by a series of coupled process models which include seabed scour, berm construction during normal waves, berm overtopping and subsequent beach-stripping and scour of the exposed substrate and cliff-toe notching by storm waves, gravity failure of the cliffs and talus construction, and beach sediment abrasion. Negative feedback regulates the rate of cliff erosion through the protection provided by the new material added into the beach from the eroding cliffs and substrate. The model is forced by two wave conditions: a normal swell and a randomly-varying storm wave. These operate for proportions of the yearly time step. The model was begun on a sloping fan surface inundated by the last stages of post-glacial sea-level rise (8000 yr BP). The initial response is for rapid growth of a gravel beach ridge fed by wave-excavation of the nearshore. As the nearshore profile nears equilibrium with the wave climate, the onshore feed wanes below the abrasion rate and the beach ridge loses volume. As sea level rises the beach ridge moves upward and landward, but its capacity to do so is limited by the rate of sediment feed from the nearshore. When the beach size reduces to a threshold at which storm waves periodically

  15. Sedimentary facies of alluvial fan deposits, Death Valley, California

    SciTech Connect

    Middleton, G.V. )

    1992-01-01

    Fans in Death Valley include both diamicts and bedded gravels. Seven facies may be recognized. The diamicts include: (1) matrix-rich, coarse wackestones; (2) thin, matrix-rich, fine wackestones, that may show grading; (3) matrix-poor, coarse packstones, transitional to wackestones. The bedded facies include: (4) weakly bedded, poorly sorted packstones or grainstones, that show patchy imbrication, and cut-and-fill structures; (5) packed, imbricated cobble lenses, generally interbedded in facies 4; (6) distinctly bedded gravels, that are better bedded, finer and better sorted, and show better imbrication than facies 4, but still do not show clear separation of sand and gravel beds; (7) backfill cross-bedded gravels. Sand beds are not seen in fan deposits. Sand is present in eolian deposits, as plane-laminated, back-eddy deposits in Death Valley Wash, and as laminated or rippled sand in the Amargosa River. The most remarkable features of the fan deposits are the very weak segregation of sand and gravel, and the complete absence of any lower flow-regime structures produced by ripples or dunes. During floods, the slope of fan and even large wash surfaces is steep enough to produce upper flow regimes. There are also very few trends in facies abundance down fans: most fans in Death Valley itself are not strongly dominated by debris flow deposits (diamicts). The facies characteristics of a given fan vary little from proximal to distal regions, but may differ strongly from the facies seen in adjacent fans. Ancient deposits that show clear segregation of gravel from cross-bedded sand beds, or strong proximal to distal facies transitions, must have been deposited in environments quite different from Death Valley.

  16. Investigating selective transport and abrasion on an alluvial fan using quantitative grain size and shape analysis

    NASA Astrophysics Data System (ADS)

    Litwin, K. L.; Jerolmack, D. J.

    2011-12-01

    Selective sorting and abrasion are the two major fluvial processes that are attributed to the downstream fining of sediments in rivers and alluvial fans. Selective transport is the process by which smaller grains are preferentially transported downstream while larger grains are deposited closer to the source. Abrasion is defined by the production of fine sediments and sand that occurs by saltation of gravel, where particle-to-particle collisions supply the energy required to break apart grains. We hypothesize that abrasion results in the gradual fining of large grains and the production of fine sands and silts, while sorting accounts for the differences in transport of these two grain-size fractions produced from abrasion, thereby creating the abrupt gravel-sand transition observed in many channel systems. In this research, we explore both selective transport and abrasion processes on the Dog Canyon alluvial fan near Alamogordo, New Mexico. We complete an extensive grain size analysis down the main channel of the fan employing an image-based technique that utilizes an autocorrelation process. We also characterize changes in grain shape using standard shape parameters, as well as Fourier analysis, which allows the study of contributions of grain roughness on a variety of length scales. Sorting appears to dominate the upper portion of the fan; the grain-size distribution narrows moving downstream until reaching a point of equal mobility, at which point sorting ceases. Abrasion exerts a subtle but persistent effect on grains during transport down the fan. Shape analysis reveals that particles become more rounded by the removal of small-scale textural features, a process that is expected to only modestly influence grain size of gravel, but should produce significant quantities of sand. This study provides a better understanding of the importance of grain abrasion and sorting on the downstream fining of channel grains in an alluvial fan, as well as an improved knowledge

  17. Hydrogeochemical indicators of groundwater flow systems in the Yangwu River alluvial fan, Xinzhou Basin, Shanxi, China.

    PubMed

    Han, Dongmei; Liang, Xing; Jin, Menggui; Currell, Matthew J; Han, Ying; Song, Xianfang

    2009-08-01

    Based on analysis of groundwater hydrochemical and isotopic indicators, this article aims to identify the groundwater flow systems in the Yangwu River alluvial fan, in the Xinzhou Basin, China. Groundwater delta(2)H and delta(18)O values indicate that the origin of groundwater is mainly from precipitation, with local evaporative influence. d-excess values lower than 10% in most groundwaters suggest a cold climate during recharge in the area. Major ion chemistry, including rCa/rMg and rNa/rCl ratios, show that groundwater salinization is probably dominated by water-rock interaction (e.g., silicate mineral weathering, dissolution of calcite and dolomite and cation exchange) in the Yangwu River alluvial fan, and locally by intensive evapotranspiration in the Hutuo River valley. Cl and Sr concentrations follow an increasing trend in shallow groundwater affected by evaporation, and a decreasing trend in deep groundwater. (87)Sr/(86)Sr ratios reflect the variety of lithologies encountered during throughflow. The groundwater flow systems (GFS) of the Yangwu River alluvial fan include local and intermediate flow systems. Hydrogeochemical modeling results, simulated using PHREEQC, reveal water-rock interaction processes along different flow paths. This modeling method is more effective for characterizing flow paths in the intermediate system than in the local system. Artificial exploitation on groundwater in the alluvial fan enhances mixing between different groundwater flow systems. PMID:19548025

  18. Hydrogeochemical indicators of groundwater flow systems in the Yangwu River alluvial fan, Xinzhou Basin, Shanxi, China.

    PubMed

    Han, Dongmei; Liang, Xing; Jin, Menggui; Currell, Matthew J; Han, Ying; Song, Xianfang

    2009-08-01

    Based on analysis of groundwater hydrochemical and isotopic indicators, this article aims to identify the groundwater flow systems in the Yangwu River alluvial fan, in the Xinzhou Basin, China. Groundwater delta(2)H and delta(18)O values indicate that the origin of groundwater is mainly from precipitation, with local evaporative influence. d-excess values lower than 10% in most groundwaters suggest a cold climate during recharge in the area. Major ion chemistry, including rCa/rMg and rNa/rCl ratios, show that groundwater salinization is probably dominated by water-rock interaction (e.g., silicate mineral weathering, dissolution of calcite and dolomite and cation exchange) in the Yangwu River alluvial fan, and locally by intensive evapotranspiration in the Hutuo River valley. Cl and Sr concentrations follow an increasing trend in shallow groundwater affected by evaporation, and a decreasing trend in deep groundwater. (87)Sr/(86)Sr ratios reflect the variety of lithologies encountered during throughflow. The groundwater flow systems (GFS) of the Yangwu River alluvial fan include local and intermediate flow systems. Hydrogeochemical modeling results, simulated using PHREEQC, reveal water-rock interaction processes along different flow paths. This modeling method is more effective for characterizing flow paths in the intermediate system than in the local system. Artificial exploitation on groundwater in the alluvial fan enhances mixing between different groundwater flow systems.

  19. Controls on modern tributary-junction alluvial fan occurrence and morphology: High Atlas Mountains, Morocco

    NASA Astrophysics Data System (ADS)

    Stokes, Martin; Mather, Anne E.

    2015-11-01

    Modern tributary-junction alluvial fans (cone-shaped depositional landforms formed in confined valley settings) were analysed from a 20-km-long reach of the Dades River in the distal part of the fold-thrust belt region in the south-central High Atlas Mountains of Morocco. Here, a deeply dissected network of ephemeral tributary streams and a perennial trunk drainage characterised by an arid mountain desert climate are configured onto a folded and thrust faulted Mesozoic sedimentary sequence. Out of 186 tributary streams, only 29 (16%) generated alluvial fans at their tributary junctions. The fan-generating catchments possess higher relief, longer lengths, lower gradients, and larger areas than nonfan-generating catchments. Whilst geologically, fan-generating catchments are underlain by folded/steeply dipping weak bedrock conducive to high sediment yield. Tributary-junction fans are built from debris flow or fluvial processes into open or confined canyon trunk valley settings. The proximity of the perennial trunk drainage combined with the valley morphology produces lobate or foreshortened trimmed fan forms. Analysis of fan (area, gradient, process), catchment (area, relief, length, gradient), and tributary valley (width) variables reveals weak morphometric relationships, highlighted by residual plots that show dominance of smaller and lower gradient than expected fan forms. These morphometric relationships can be explained by interplay between the catchment and trunk drainage geology, morphology, climate, and flood regime that are combined into a conceptual 'build and reset' model. Ephemeral tributary-junction fans develop progressively during annual localised winter-spring storm events, attempting to build towards a morphological equilibrium. However, the fans never reach an equilibrium morphological form as they are reset by rare (> 10 year) large floods along the River Dades that are linked to regional incursions of Atlantic low pressure troughs. The model

  20. Early Holocene and Late Pleistocene slip rates of the southern Dead Sea Fault determined from 10Be cosmogenic dating of offset alluvial deposits

    NASA Astrophysics Data System (ADS)

    Le BéOn, Maryline; Klinger, Yann; Al-Qaryouti, Mahmoud; MéRiaux, Anne-Sophie; Finkel, Robert C.; Elias, Ata; Mayyas, Omar; Ryerson, Frederick J.; Tapponnier, Paul

    2010-11-01

    Two sites located along the Wadi Araba Fault (WAF) segment of the Dead Sea Fault are targeted for tectonic-morphological analysis. 10Be cosmogenic radionuclide (CRN) dating of embedded cobbles is used to constrain the age of offset alluvial surfaces. At the first site a 48 ± 7 m offset alluvial fan, for which 10Be CRN model ages average 11.1 ± 4.3 ka, yield a slip rate of 5.4 ± 2.7 mm/a, with conservative bounds of 1.3-16.4 mm/a. At the second site the scattered distributions of the 10Be CRN ages from an offset bajada attest to the complex processes involved in sediment transport and emplacement. There, two offsets were identified. The 160 ± 8 m offset of an incised alluvial fan dated at 37 ± 5 ka shows a slip rate of 4.5 ± 0.9 mm/a, with a conservative minimum value of 3.2 mm/a. A larger offset, 626 ± 37 m, is derived from a prominent channel incised into the bajada. Cobbles from the bajada surface have ages from 33 to 141 ka, with a mean of 87 ± 26 ka. A slip rate of 8.1 ± 2.9 mm/a is derived from the mean age, with conservative bounds of 3.8-22.1 mm/a. These results and other published slip rates along the linear WAF segment, from GPS to geological time scales, lack the resolution to fully resolve the question of temporal variations versus consistency of the fault slip rate of the WAF. Yet, given the uncertainties, they are not inconsistent with each other.

  1. Fire, Holocene Climate Change, and Geomorphic Response Recorded in Alluvial Fan Sediments

    NASA Astrophysics Data System (ADS)

    Pierce, J. L.; Meyer, G. A.

    2004-12-01

    Alluvial fan stratigraphic sequences record fire history in charcoal-rich deposits and buried burned soil surfaces. Deposit characteristics provide information about the magnitude of fire-related sedimentation events and severity of associated fires, and radiocarbon-dating of charcoal establishes the timing of fires. Unlike lakes, alluvial fans are ubiquitous in mountain environments. Although alluvial-fan fire records lack the annual resolution of tree-ring records, compilation of data from many alluvial fan sites provides a statistical sample of fire timing and approximate severity that can be related to climate variations over centennial to millennial timescales. We examine alluvial fan records from xeric Pinus ponderosa-dominated forests of central Idaho, and compare them with similar records from cooler, high-elevation Pinus contorta-dominated forests of Yellowstone National Park. Identification of charcoal macrofossils from Idaho fan deposits limits inbuilt age errors in radiocarbon dating, and shows that similar forest compositions have existed over the last ca. 4000 years in the fan drainage basins. Limited data from ca. 4000-7000 yr ago suggest that Pinus ponderosa was either sparse or absent in the 4 basins represented. Large fire-related debris flows in both Idaho and Yellowstone indicate severe fires during the ca. 1050-750 cal yr BP Medieval Climatic Anomaly (MCA), which included widespread and severe western US droughts. Another such episode 2700-1600 cal yr BP is less prominent in the Idaho record. Numerous small, fire-induced sedimentation events in Idaho ca. 350-500 (Little Ice Age), 1200-1400, and 2800-3000 cal yr BP likely indicate frequent low- to mixed-severity fires, and coincide with indicators of generally cool, moist conditions in the western USA and North Atlantic, and with minimal fire activity in Yellowstone. We infer that these effectively wetter periods allow greater grass growth, fueling frequent surface fires in ponderosa forests

  2. Self-similar growth of an alluvial fan fed with bimodal sediment

    NASA Astrophysics Data System (ADS)

    Delorme, Pauline; Voller, Vaughan; Paola, Chris; Devauchelle, Olivier; Lajeunesse, Eric; Barrier, Laurie; Métivier, François

    2016-04-01

    At the outlet of mountain ranges, rivers flow onto flatter lowlands. The associated change of slope causes sediment deposition. As the river is free to move laterally, it builds conical sedimentary structures called alluvial fans. Their location at the interface between erosional and depositional areas makes them valuable sedimentary archives. To decipher these sedimentary records, we need to understand the dynamics of their growth. We carried out a series of experiments to investigate the growth of alluvial fans fed with mixed sediments. The density difference between silica and coal sediments mimics a bimodal grain-size distribution in nature. The sediment and water discharges are constant during an experiment. During the run, we track the evolution of the surface pattern by digital imaging. At the end of each run, we acquire the fan topography using a scanning laser. Finally, we cut a radial cross section to visualize the sedimentary deposit. We observe there is a distinct slope break at the transition that dominates the overall curvature of the fan surface. Based on mass conservation and observations, we propose that this alluvial fan grows in a self-similar way, thus causing the transition between silica and coal deposits to be a straight line. The shape of the experimental transition accords with this prediction.

  3. A Pleistocene coastal alluvial fan complex produced by Middle Pleistocene glacio-fluvial processes

    NASA Astrophysics Data System (ADS)

    Adamson, Kathryn; Woodward, Jamie; Hughes, Philip; Giglio, Federico; Del Bianco, Fabrizio

    2014-05-01

    A coarse-grained alluvial fan sequence at Lipci, Kotor Bay, in western Montenegro, provides a sedimentary record of meltwater streams draining from the Orjen Massif (1,894 m a.s.l.) to the coastal zone. At Lipci sedimentary evidence and U-series ages have been used alongside offshore bathymetric imagery and seismic profiles to establish the size of the fan and constrain the nature and timing of its formation. Establishing the depositional history of such coastal fans is important for our understanding of cold stage sediment flux from glaciated uplands to the offshore zone, and for exploring the impact of sea level change on fan reworking. There is evidence of at least four phases of Pleistocene glaciation on the Orjen massif, which have been U-series dated and correlated to MIS 12, MIS 6, MIS 5d-2 and the Younger Dryas. A series of meltwater channels delivered large volumes of coarse- and fine-grained limestone sediment from the glaciated uplands into the Bay of Kotor. At the southern margin of the Orjen massif, a series of large (>700 m long) alluvial fans has developed. Some of these extend offshore for up to 600 m. Lipci fan lies downstream of end moraines in the valley immediately above, which were formed by an extensive outlet glacier of the Orjen ice cap during MIS 12. The terrestrial deposits are part of the fan apex (50 m a.s.l.) that lies at the foot of a steep bedrock channel, but the majority of the fan is now more than 25 m below sea level. The terrestrial fan sediments are strongly cemented by multiple generations of calcite precipitates: the oldest U-series ages are infinite indicating that the fan is >350 ka in age. These ages are in agreement with alluvial sedimentary evidence and U-series ages from other fluvial units on Mount Orjen. The terrestrial portion of the Lipci fan surface contains several channels. These are well preserved due to cementation with calcium carbonate. Submarine imagery indicates that the now submerged portion of the fan also

  4. Geomorphic Processes and Remote Sensing Signatures of Alluvial Fans in the Kun Lun Mountains, China

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.; Chadwick, Oliver A.

    1996-01-01

    The timing of alluvial deposition in arid and semiarid areas is tied to land-surface instability caused by regional climate changes. The distribution pattern of dated deposits provides maps of regional land-surface response to past climate change. Sensitivity to differences in surface roughness and composition makes remote sensing techniques useful for regional mapping of alluvial deposits. Radar images from the Spaceborne Radar Laboratory and visible wavelength images from the French SPOT satellite were used to determine remote sensing signatures of alluvial fan units for an area in the Kun Lun Mountains of northwestern China. These data were combined with field observations to compare surface processes and their effects on remote sensing signatures in northwestern China and the southwestern United States. Geomorphic processes affecting alluvial fans in the two areas include aeolian deposition, desert varnish, and fluvial dissection. However, salt weathering is a much more important process in the Kun Lun than in the southwestern United States. This slows the formation of desert varnish and prevents desert pavement from forming. Thus the Kun Lun signatures are characteristic of the dominance of salt weathering, while signatures from the southwestern United States are characteristic of the dominance of desert varnish and pavement processes. Remote sensing signatures are consistent enough in these two regions to be used for mapping fan units over large areas.

  5. Alluvial Fans on Titan Reveal Atmosphere and Surface Interactions and Material Transport

    NASA Astrophysics Data System (ADS)

    Radebaugh, J.; Ventra, D.; Lorenz, R. D.; Farr, T. G.; Kirk, R. L.; Hayes, A.; Malaska, M. J.; Birch, S.; Liu, Z. Y. C.; Lunine, J. I.; Barnes, J. W.; Le Gall, A. A.; Lopes, R. M. C.; Stofan, E. R.; Wall, S. D.; Paillou, P.

    2015-12-01

    Alluvial fans, important depositional systems that record how sediment is stored and moved on planetary surfaces, are found on the surface of Titan, a body of significantly different materials and process rates than Earth. As seen by Cassini's Synthetic Aperture Radar (SAR) images at 350 m resolution, fans on Titan are found globally and are variable in size, shape and relationship to adjacent landforms. Their morphologies and SAR characteristics, which reveal roughness, textural patterns and other material properties, show similarities with fans in Death Valley seen by SAR and indicate there are regions of high relative relief locally, in the Ganesa, Xanadu and equatorial mountain belt regions. The Leilah Fluctus fans near Ganesa are ~30 km x 15 km, similar to the largest Death Valley fans, and revealing mountainous topography adjacent to plains. Others have gentle slopes over hundreds of kilometers, as in the high southern latitude lakes regions or the Mezzoramia southern midlatitudes, where a fan system is 200 km x 150 km, similar to the Qarn Alam fan emerging into the Rub al Khali in Oman. Additionally, there is evidence for a range of particle sizes, from relatively coarse (~2 cm or more) to fine, revealing long-term duration and variability in erosion by methane rainfall and transport. Some features have morphologies consistent with proximality to high-relief source areas and highly ephemeral runoff, while others appear to draw larger catchment areas and are perhaps characterized by more prolonged episodes of flow. The presence of many fans indicates the longevity of rainfall and erosion in Titan's surface processes and reveals that sediment transport and the precipitation that drives it are strongly episodic. Alluvial fans join rivers, lakes, eroded mountains, sand dunes and dissolution features in the list of surface morphologies derived from atmospheric and fluvial processes similar to those on Earth, strengthening comparisons between the two planetary

  6. Climatic and Tectonic Controls on Alluvial Fan Evolution: The Lost River Range, Idaho

    NASA Astrophysics Data System (ADS)

    Phillips, R. J.; Pierce, J. L.; Sharp, W. D.; Pierce, K. L.

    2006-12-01

    In the northern Basin &Range, alluvial fans developed along the Lost River range-front consist of several distinct inset fan segments with concave-up radial profiles. Multiple large radius (>5 km), shallow (2- 3°), alluvial fans extend across and beyond the active, ~140-km-long, normal Lost River fault. These large fans are relict features, formed by major sheetfloods that occurred intermittently between ~15-180 ka. More recent deposition has been dominated by debris-flows that form small-radius (<2 km), steep (8- 17°), fans closely confined to the mountain front [1,2]. In order to determine the timing of fan surface stabilization, we have undertaken precise mass spectrometric 230Th/U dating of pedogenic carbonate from calcic soils that mantle fan surfaces on the Arco fault segment. Careful selection of mg-size samples of dense soil carbonate pebble coats, from within a trench that cuts through gravelly fan deposits, indicates that the fan soils are geochemically suitable for uranium-series dating (median U=7ppm, 232Th=0.09ppm, 232Th/230Th=154). 230Th/U analysis of these calcic soils can thus provide precise temporal constraints on intervals of surface stability and subsequent soil formation. The oldest fan surface (Qfo1, 178+/-8 ka), exposed within the footwall of the trench, suggests an interval of surface stability, indicating that the fan was likely abandoned due to incision early in MIS 6. Incision may have resulted from surface faulting along the Arco segment of the Lost River fault, but could relate to changes in stream power or sediment supply associated with climatic change or with auto-cyclic variations within the drainage basin. A younger incised and faulted fan surface (Qfo2, 69+/-6 ka), likely represents active alluviation at the beginning of MIS 4 and, since it formed as hanging-wall alluvial gravel, provides age limits on an episode of fault displacement between Qfo1 and Qfo2. In situ pedogenic carbonate coats on sub-angular gravels within the

  7. Characterization and architecture of fluvial sand bodies in a intracratonic alluvial fan

    SciTech Connect

    Martinius, A.W.; Cuevas Gozalo, M.C. )

    1993-09-01

    The fluvial deposits of the Tortola alluvial fan of late Oligocene to early Miocene were deposited in the intracratonic Loranca Basin (Spain). the fluvial facies comprise individual and amalgamated sand bodies embedded in flood-plain fines. The succession is a labyrinth-type reservoir analog. A distal and proximal fan locality have been compared. The sand bodies were characterized and quantified by means of three-dimensional (3-D) morphology and facies analysis, sandbody size statistics, permeability and gamma-ray log profiles, and geometry of permeability baffles. A classification of the sand bodies in six genetic types was established: meander-loop, low-sinuosity channel-fill, braided channel-fill, deltaic, interchannel bar, and crevasse-splay deposits. This classification is conditioned by a set og geological rules. The external geometry, internal organization, and spatial arrangement of the genetic types is determined by variation in hydrodynamic conditions, sediment supply, fan morphology, and basin subsidence. Significant differences in reservoir quality exist between the genetic types, and between the two fan localities. Analysis of the sequential development of the two localities shows that the 3-D architecture is the result of coalescing fan depositional systems: a minor fluvial fan systems from the eastern basin margin, and local minor fluvial systems. Shifting of the channels on the fan surface due to avulsion processes, differential basin subsidence, and tectonic movements influenced fan formation and hence reservoir quality.

  8. Terrestrial Cosmogenic-Nuclide Dating of Alluvial Fans in Death Valley, California

    USGS Publications Warehouse

    Machette, Michael N.; Slate, Janet L.; Phillips, Fred M.

    2008-01-01

    We have used terrestrial cosmogenic nuclides (TCN) to establish the age of some of the most extensive Quaternary alluvial fans in Death Valley, California. These intermediate-age alluvial fans are most extensive on the western side of the valley, where tectonic deformation is considerably less pronounced than on the eastern side of the valley. These fans are characterized by a relatively smooth, densely packed desert pavement formed by well-varnished (blackened) clasts. These surfaces have been mapped as the Q2 gravel by previous workers and as unit Qai (intermediate age) by us. However, the intermediate-age gravels probably contain multiple subunits, as evidenced by slight differences in morphologic expression, soil formation, and inset geomorphic relations. The TCN technique used herein sums the cosmogenic 36Cl in approximately 2.5-meter-deep profiles through soil and host alluvium, thus avoiding some of the problems associated with the more typical surface-exposure dating of boulders or smaller clasts. Our TCN 36Cl dating of 12 depth profiles indicates that these intermediate-age (Qai) alluvial fans range from about 100 to 40 kilo-annum (ka), with a mean age of about 70 ka. An alternative interpretation is that alluvial unit Qai was deposited in two discrete episodes from 90 to 80 ka and from 60 to 50 ka, before and after MIS (marine oxygen-isotope stage) 4 (respectively). Without an intermediate-age unit, such as MIS 4 lake deposits, we can neither disprove nor prove that Qai was deposited in two discrete intervals or over a longer range of time. Thus, in Death Valley, alluvial unit Qai largely brackets MIS 4, which is not associated with a deep phase of Lake Manly. These Qai fans extend to elevations of about -46 meters (150 feet below sea level) and have not been transgressed by Lake Manly, suggesting that MIS 4 or MIS 2 lakes were rather shallow in Death Valley, perhaps because they lacked inflow from surface runoff of the Sierra Nevada drainages through

  9. Alluvial-fan and lacustrine fan-delta sedimentation in west-central California during the Middle Tertiary transition from subduction to transform tectonics

    SciTech Connect

    Cole, R.B. . Dept. of Geological Science); Stanley, R.G. )

    1992-01-01

    The Plush Ranch (PR) Formation was deposited in one of several sedimentary basins in west-central California. The PR consists of more than 1,800 m of nonmarine sedimentary rocks and interbedded basaltic volcanic rocks that together record a complicated history of synsedimentary faulting, volcanism, and deposition in alluvial-fan, fan-delta, and lacustrine depositional settings. The sedimentological analysis indicates that both the northern and southern margins of the PR basin apparently were controlled ENE-trending normal faults, but that the two margins are characterized from each other by distinctive depositional facies, provenance, and sediment transport directions. The northern basin margin is recorded by sandstone-dominated braidplain deposits, with interbedded lenses of boulder-rich breccia derived by landsliding from a nearby granitic provenance. The southern basin margin is represented by matrix- and clast-supported boulder- to pebble-conglomerate with interbedded trough-crossbedded sandstones; these represent debris-flow and stream-flow alluvial-fan deposits. The alluvial-fan deposits grade northward into lacustrine fan-delta facies and provide an excellent detailed record of interfingering between alluvial-fan and lacustrine fan-delta deposits on a bed-by-bed scale. Basalt are interbedded with turbidite sandstones and evaporite/carbonate-rich intervals, but not with alluvial-fan deposits. The analysis of the sedimentary record of the PR Formation permits documentation of detailed facies relations that are useful in understanding alluvial-fan and fan-delta transitions in fault-bounded lacustrine basins. In addition, results support the conclusion of earlier workers that the Big Pine fault was a down-to-the-north, normal-slip fault along the southern margin of the PR basin during late Oligocene-early Miocene time, and then became a predominantly left-slip fault during the Quaternary.

  10. Investigating the impact of vegetation on alluvial fans using laboratory experiments

    NASA Astrophysics Data System (ADS)

    Clarke, Lucy; McLelland, Stuart; Tom, Coutlhard

    2016-04-01

    Riparian vegetation can significantly influence the geomorphology of fluvial systems, affecting channel geometry and flow dynamics. However, there is still limited understanding of the role vegetation plays in the development of alluvial fans, despite the large number of vegetated fans located in temperate and humid climates. An understanding of the feedback loops between water flow, sediment dynamics and vegetation is key to understanding the geomorphological response of alluvial fans. But it is difficult to investigate these relationships in the natural world due to the complexity of the geomorphic and biological processes and timescales involved, whereas the controlled conditions afforded by laboratory experiments provide the ideal opportunity to explore these relationships. To examine the effects of vegetation on channel form, flow dynamics and morphology during fan evolution, a series of experiments were conducted using the Total Environment Simulator (operated by the University of Hull). The experiments followed a 'similarity of processes' approach and so were not scaled to a specific field prototype. Live vegetation (Medicago Sativa) was used to simulate the influence of vegetation on the fan development. A range of experiments were conducted on 2x2m fan plots, the same initial conditions and constant water discharge and sediment feed rates were used, but the vegetation density and amount of geomorphic time (when the sediment and water were running and there was active fan development) between seeding / vegetation growth varied between runs. The fan morphology was recorded at regular intervals using a laser scanner (at 1mm resolution) and high resolution video recording and overhead photography were used to gain near-continuous data quantifying fan topography, flow patterns, channel migration and avulsion frequency. Image analysis also monitored the spatial extent of vegetation establishment. The use of these techniques allowed collection of high resolution

  11. Shapefile of the Elevation of the Bedrock Surface Beneath the Rocky Flats Alluvial Fan, Boulder and Jefferson Counties, Colorado

    USGS Publications Warehouse

    Knepper, Daniel H.

    2003-01-01

    The Rocky Flats alluvial fan is a large early Pleistocene gravel deposit at the mouth of Coal Creek Canyon along the eastern flank of the Colorado Front Range in Jefferson and Boulder Counties, Colorado. Elevations of the bedrock surface beneath the alluvial fan gravels have been compiled at selected points from a variety of sources and recorded in a digital dataset suitable for importing into commonly used GIS and image processing software packages.

  12. Natural hazards on alluvial fans: the debris flow and flash flood disaster of December 1999, Vargas state, Venezuela

    USGS Publications Warehouse

    Larsen, Matthew C.; Wieczorek, Gerald F.; Eaton, L.S.; Torres-Sierra, Heriberto; Sylva, Walter F.

    2001-01-01

    Large populations live on or near alluvial fans in locations such as Los Angeles, California, Salt Lake City, Utah, Denver, Colorado, and lesser known areas such as Sarno, Italy, and Vargas, Venezuela. Debris flows and flash floods occur episodically in these alluvial fan environments, and place many communities at high risk during intense and prolonged rainfall. In December 1999, rainstorms induced thousands of landslides along the Cordillera de la Costa, Vargas, Venezuela. Rainfall accumulation of 293 mm during the first 2 weeks of December was followed by an additional 911 mm of rainfall on December 14 through 16. Debris flows and floods inundated coastal communities resulting in a catastrophic death toll of as many as 30,000 people. Flash floods and debris flows caused severe property destruction on alluvial fans at the mouths of the coastal mountain drainage network. In time scales spanning thousands of years, the alluvial fans along this Caribbean coastline are dynamic zones of high geomorphic activity. Because most of the coastal zone in Vargas consists of steep mountain fronts that rise abruptly from the Caribbean Sea, the alluvial fans provide practically the only flat areas upon which to build. Rebuilding and reoccupation of these areas requires careful determination of hazard zones to avoid future loss of life and property. KEY TERMS: Debris flows, flash floods, alluvial fans, natural hazards, landslides, Venezuela

  13. Debris-flow dominance of alluvial fans masked by runoff reworking and weathering

    NASA Astrophysics Data System (ADS)

    de Haas, Tjalling; Ventra, Dario; Carbonneau, Patrice E.; Kleinhans, Maarten G.

    2014-07-01

    Arid alluvial fan aggradation is highly episodic and fans often comprise active and inactive sectors. Hence the morphology and texture of fan surfaces are partly determined by secondary processes of weathering and erosion in addition to primary processes of aggradation. This introduces considerable uncertainty in the identification of formative processes of terrestrial and Martian fans from aerial and satellite imagery. The objectives of this study are (i) to develop a model to describe the sedimentological and morphological evolution of inactive fan surfaces in arid settings, and (ii) to assess the relative importance of primary processes of aggradation and secondary processes of weathering and reworking for surface morphology and sedimentology and for the stratigraphic record. We studied an alluvial fan characterized by a recently active sector and a long-abandoned, inactive sector along the coast of the hyperarid Atacama Desert. Here, rates of primary geomorphic activity are exceptionally low because of extreme aridity, while weathering rates are relatively high because of the effects of coastal fogs. Long-term processes of fan aggradation and reworking were determined through sedimentological facies analysis of stratigraphic sections. Ground surveys for textural and morphological patterns at the fan surface were integrated with remote-sensing by an Unmanned Airborne Vehicle (UAV). Discharges and sediment-transport capacities were calculated to estimate the efficiency of secondary runoff in reshaping the inactive fan sector. Stratigraphic sections reveal that the fan was dominantly aggraded by debris flows, whereas surface morphology is dominated by debris-flow signatures in the active sector and by weathering and runoff on the inactive sector. On the latter, rapid particle breakdown prevents the formation of a coarse desert pavement. Furthermore, relatively frequent local runoff events erode proximal debris-flow channels on the inactive sector to form local lag

  14. Drivers for the development of an alluvial fan in a high-altitude glaciated catchment

    NASA Astrophysics Data System (ADS)

    Steiner, Jakob; Miles, Evan; Ragettli, Silvan

    2016-04-01

    Alluvial fans have channelization and deposition dynamics that are not entirely understood but can have considerable impact on the local hydrological regime. Especially in high-altitude and glaciated catchments they are rather rarely investigated. During glaciological field work between 2012 and 2015 in the Langtang catchment in the Nepalese Himalaya, such an alluvial fan of ca. 0.35 km2 (4000 m a.s.l.) at the end of a very small glaciated subcatchment (~9km2) was observed. The subcatchment is the site of one of the presumed largest landslides in earth's history, that likely happened 40 000 years ago with a volume of approximately 10^10 m3 and land surface erosion is well visible. During the recent Gorkha earthquake in April 2015 (M=7.8), additional sediments were mobilized along the steep valley slopes. From 6 sets of concurrent high-resolution satellite images and DEMs between 2006 and 2015 and an additional image from 1974 we derive the evolution in space and volume of this fan and identify main sources of sediment supply. Precipitation data from a nearby Automatic Weather Station provides insight into strong rainfall events. We can compare the growth of the fan in the period without significant earthquakes until April 2014 to the change after the seismic event (image from May 2015) and after the following Monsoon season (image from October 2015) and determine dominant drivers of erosion.

  15. Tectonic controls of the North Anatolian Fault System (NAFS) on the geomorphic evolution of the alluvial fans and fan catchments in Erzincan pull-apart basin; Turkey

    NASA Astrophysics Data System (ADS)

    Sarp, Gulcan

    2015-02-01

    The Erzincan pull-apart basin is located in the eastern section of the North Anatolian Fault System (NAFS). The tectonic evolution of this basin is mostly controlled by strike slip master faults of the NAFS. This study examines the topography-structure relationships in an effort to evaluate the tectonic signatures in the landscape, paying special attention to recent tectonic activity. In the study, the main focus is on the tectonic controls of the NAFS on the geomorphic evolution of alluvial fans and fan catchments in the Erzincan pull-apart basin. The observations of the amount of tilting of the alluvial fans (β) and its relation with morphometric (Asymmetry Factor (AF), Hypsometric Integral (HI), Fractal analysis of drainage networks (D)) properties of the fan catchments provide valuable information about the tectonic evolution of the basin area. The results of the analyses showed that the alluvial fan and fan catchment morphology in the pull-apart basin are mainly controlled by the ongoing tectonic activity of the NAFS. The fault system in the basin has controlled the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration, channel incision and tilting the alluvial fans.

  16. Partially inverted, mixed grain size alluvial fans in the Atacama Desert as analogues for Martian sediment fans

    NASA Astrophysics Data System (ADS)

    Hobley, D. E.; Howard, A. D.

    2011-12-01

    Martian alluvial fans have now been recognized in many craters around the equatorial latitudes of Mars. HiRISE imagery reveals that their surfaces often show a radial pattern of narrow (10s to 100s of meters), long (km), low relief (<10 m), flat topped ridges. These may crosscut and superpose on each other, branch (especially at their downslope ends), and in nighttime thermal infrared imaging are brighter than the surrounding material, indicating a comparatively higher thermal inertia. These features among others suggest that these ridges are fluvial distributary channels, coarser grained than their surrounding material,now inverted by the postdepositional removal of many of these fines. This study focuses on a suite of alluvial fans in the Pampa de Tamarugal, part of the northern Atacama Desert. This site is an ideal analogue for the Martian examples, both in terms of the fan sedimentology and also the postdepositional inversion of flow deposits. The scales of both the fans and the channels associated with the flows approximate the Martian equivalents. The sediment sourced to the fans is a bimodal mixture of coarser (gravel to cobble) and finer (silt and mud) grain sizes, variable across both space and time and controlled by release from source rocks of highly variable lithology upstream. Such a bimodal grain size distribution is a match to the inferred sizes present in the Martian fans. We use WorldView-2 satellite visual imagery (0.6 m resolution) first to assess depositional processes and likely sediment grain sizes, then to reconstruct a history of activity across the fan surface and to assess the subsequent degradation of the deposits of each age. We infer the flow processes and grain size distribution of the deposits visually based on color, texture, and form in the images, groundtruthed with field reconnaissance. Active flow on the fan is strongly channelized, and near the rangefront commonly reoccupies earlier abandoned courses. Where unconfined by

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

    USGS Publications Warehouse

    Knepper, D.H.

    2005-01-01

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

  18. Laramide thrust-generated alluvial-fan sedimentation, Sphinx conglomerate, southwestern Montana

    SciTech Connect

    Decelles, P.G.; Tolson, R.B.; Graham, S.A.; Smith, G.A.; Ingersoll, R.V.; White, J.; Schmidt, C.J.; Rice, R.; Moxon, I.; Lemke, L.; handschy, J.W.; Follo, M.F.; Edwards, D.P.; Cavazza, W.; Caldwell, M.; Bargar, E. )

    1987-02-01

    The uppermost Cretaceous-lower Tertiary Sphinx Conglomerate crops out over an area of approximately 20 km{sup 2} (8 mi{sup 2}) in the Madison Range of southwestern Montana. The Sphinx consists of more than 1,000 m (3,300 ft) of synorogenic boulder and cobble conglomerate derived from a Late Cretaceous Laramide uplift that was located in the area presently occupied by the Madison River valley. Palynological and radiometric age data indicate that the Sphinx was deposited 75-58 Ma, and that thrusting and folding of the deposit had largely ceased by 56 Ma. Compositions of Sphinx clasts and paleocurrent data indicate that the Sphinx was produced by uplift and unroofing of Mesozoic and Paleozoic rocks located on two thrust sheets to the west and southwest. The lower Sphinx was deposited on the distal portions of an eastward prograding alluvial-fan system. Clast assemblages and lithofacies indicate that deposition of the middle Sphinx was controlled by a combination of progradation in response to ongoing thrusting and an influx of resistant clasts derived from middle Paleozoic carbonates in the source area. Deposition of the upper Sphinx was probably controlled by source lithology, as the influx of very coarse, resistant clasts from middle and lower Paleozoic carbonates overwhelmed the fan system's ability to organize its load of sediment by normal fan processes. A preliminary facies model for thrust-generated alluvial-fan deposits predicts intraformational deformation, cannibalization of proximal synorogenic fan facies, and abrupt compositional breaks in response to episodes of thrusting. 14 figs., 1 tab.

  19. Stochastic Spectral Analysis for Characterizing Hydraulic Diffusivity in an Alluvial Fan Aquifer with River Stimulus

    NASA Astrophysics Data System (ADS)

    Wang, Y. L.; Zha, Y.; Yeh, T. C. J.; Wen, J. C.

    2015-12-01

    Estimation of subsurface hydraulic diffusivity was carried out to understand the characteristics of Zhuoshui River alluvial fan, Taiwan. The fan, an important agricultural and industrial region with high water demand, is located at middle Taiwan with an area of 1800 km2. The prior geo-investigations suggest that the main recharge region of the fan is at an apex along the river. The distribution of soil hydraulic diffusivity was estimated by fusing naturally recurring stimulus provided by river and groundwater head. Specifically, the variance and power spectrum provided by temporal and spatial change of groundwater head in response to river stage variations are analyzed to estimate hydraulic diffusivity distribution. It is found that the hydraulic diffusivity of the fan is at the range from 0.08 to 16 m2/s. The average hydraulic diffusivity at the apex, middle, and tail of the fan along the river is about 0.4, 0.6, and 1.0 m2/s, respectively.

  20. Quaternary tilt of Death Valley determined from landform modelling of alluvial fans

    SciTech Connect

    West, R.B.; Wilson, D.S. . Dept. of Geology)

    1993-04-01

    Alluvial fans along the east side of central Death Valley are being actively back-tilted along the Death Valley fault zone. Initial modelling of the Copper Canyon and Furnace Creek fans led to recognition of distinct segments. Field reconnaissance and aerial photo mapping were conducted to check model results and improve segment discrimination. Surface roughness, relative position, vegetation distribution, and drainage patterns provided independent evidence for segment discrimination. Subsequent modelling of individual segments produced a range of tilt values from 0.275[degree] to 0.559[degree] down to the northeast. Continued analysis of these fan segments is concentrated on: (1) assigning confidence and error values to the tilt values; and (2) dating individual segments. Further work will compare the tilt rates of east-side fans with those from the west. The mean squared error (MSE) is currently being used as a first order assessment of the quality of the model's fit to data digitized from 1:24,000 scale USGS topographic maps. MSE values of 1 m or less can be expected for relatively young or actively aggrading segments. Previous fan models have found the expected range of misfits to be between 2 m and 5 m. This seven parameter least squares model has produced fits with less than 2 m total range in misfits. Previous models have not accounted for tilt or have relied on simplifying assumptions to fix apex position.

  1. Age and origin of the Gezira alluvial fan between the Blue and White Nile rivers

    NASA Astrophysics Data System (ADS)

    Williams, martin

    2014-05-01

    The Gezira is a low-angle alluvial fan bounded by the Blue Nile to the east and the White Nile to the west. It is the main agricultural region of Sudan and produces high quality long-staple cotton for export. Dark cracking clays (vertisols) cover much of the Gezira and range in age from 50 kyr to Holocene. The Gezira is traversed by a series of defunct sandy channels that originate between Sennar and Wad Medani on the present-day Blue Nile. With a radius of 300 km and an area of 40,000 km2 the Gezira is a mega-fan. The younger channels range in age from early Holocene to 100 kyr, while near surface channels filled with rolled quartz and carbonate gravels have ages back to >250 kyr. Boreholes in the Gezira reveal coarse alluvial sands and gravels in now buried channels overlain by alluvial clays, forming a repetitive sequence of fining-upwards alluvial units. that probably extend back to Pliocene times. The fan is up to 180 m thick with a volume of ~1,800 km3. The sandy or gravelly bed-load channels coincide with colder drier climates and sparse vegetation in the Ethiopian headwaters of the Blue Nile and the alluvial clays denote widespread flooding during times of stronger summer monsoon. The early stages of such flood events were often accompanied by mass burial of Nile oyster (Etheria elliptica) beds, such as the 45-50 kyr floods that deposited up to 5 m of clay in the northern Gezira. A unique feature of the eastern Gezira is a former Blue Nile channel at least 80 km long running parallel to the present river and entirely filled with volcanic ash. The channel was only 3-4 m deep and 20-30 m wide. Very fine laminations and cross-beds, together with locally abundant phytoliths and sponge spicules, suggest slow-moving water, with flow dispersed across many distributary channels. The ash geochemistry is similar to that in the lower part of the Kibish Formation in the lower Omo valley of southern Ethiopia and points to a minimum age of 100 kyr and a maximum age of

  2. Geotechnical Investigations on Sediments from Alluvial Fans in the Upper Sava River Valley, NW Slovenia

    NASA Astrophysics Data System (ADS)

    Petkovšek, A.; Maček, M.; Mikoš, M.

    2009-04-01

    In order to estimate whether any alluvial (torrential) fan should be rather classified as a debris cone (mainly formed by debris flows; at least occasionally threatened by debris flows) we performed a combined field and laboratory investigation on selected alluvial fans in the Upper Sava River valley between Rateče (border to Italy) and Jesenice in NW Slovenia. This work was done as a part of three year targeted research project "Debris flow risk assessment in Slovenia". This region was chosen due to its high potential for debris flow generation. In the distal or/and in the proximal part of each of the selected alluvial fans (Trebiža, Suhelj, Presušnik, Koroška Bela, Javorniški Rovt), one or two sedimentological trenches reaching over 5 m in depth were excavated. For each trench we assured qualitative geological (sedimentological) inventory and description of lithological structure, and in some trenches we tried to assess age of the sediments. From selected layers in different depths in the majority of trenches sediment samples have been taken for further geotechnical laboratory investigations. The main aim of the study was to assess transport properties of sediment material to flow in the form of a debris flow. We compared elaborated values of the main geotechnical parameters (grain size distribution, USCS classification, natural water content, Atterberg limits, plasticity index, density, dry density, shear strength as a function of sample water content) of these sediment samples with known corresponding values for samples taken in the past from other active landslides (Macesnik, Slano Blato) and debris flows (Stože, Strug) in Slovenia. The comparison of the samples' shear strengths as a function of sample water content has shown that samples from selected alluvial fans don't contain enough fines and are less sensitive to water content as the samples taken from the Stože debris flow, that was in November 2000 with the magnitude of over 1 million m3 the

  3. Grain size trends reveal alluvial fan sensitivity to late Pleistocene climate change

    NASA Astrophysics Data System (ADS)

    Whittaker, A. C.; D'Arcy, M. K.; Roda Boluda, D. C.

    2015-12-01

    The effects of climate change on eroding landscapes and the sedimentary record remain poorly understood. The measurement of grain size fining rates in stream-flow dominated deposits provides one way to address this issue because, in principle, these trends embed important information about the dynamics of sediment routing systems and their sensitivities to external forcing. At a fundamental level, downstream fining is often driven by selective deposition of sediment. The relative efficiency of this process is determined by the physical characteristics of the input sediment supply and the spatial distribution of subsidence rate, which generates the accommodation necessary for mass extraction. Here, we measure grain size fining rates from apex to toe on two alluvial fan systems in northern Death Valley, California, which have well-exposed modern and 70 ka surfaces, where the long-term tectonic boundary conditions are known and where climatic variation over this time period is well-constrained. We integrate a self-similar gravel fraction fining model, based on selective sediment extraction, with cosmogenically-derived catchment erosion rates and gravel fining data, to estimate the change in sediment flux that occurred between 70 ka and the present day. Our results show that a 30 % decrease in average precipitation rate led to a 20 % decrease in sediment flux and a clear increase in the down-fan rate of fining. This supports existing landscape evolution models that relate a decrease in precipitation rate to a decrease in sediment flux, but implies that this relationship may be sub-linear. This study offers a new approach to applying grain size fining models to mountain catchments and their alluvial fan systems, and shows fan stratigraphy can be highly sensitive to climate changes over <105 years. However we also observe that this sensitivity is lost when sediment is remobilised and recycled over a time period longer than the duration of the climatic perturbation.

  4. Contamination potential of nitrogen compounds in the heterogeneous aquifers of the Choushui River alluvial fan, Taiwan.

    PubMed

    Jang, Cheng-Shin; Liu, Chen-Wuing

    2005-10-01

    This study aimed to analyze the contamination potential associated with the reactive transport of nitrate-N and ammonium-N in the Choushui River alluvial fan, Taiwan and to evaluate a risk region in developing a groundwater protection policy in 2021. In this area, an aquifer redox sequence provided a good understanding of the spatial distributions of nitrate-N and ammonium-N and of aerobic and anaerobic environments. Equiprobable hydraulic conductivity (K) fields reproduced by geostatistical methods characterized the spatial uncertainty of contaminant transport in the heterogeneous aquifer. Nitrogen contamination potential fronts for high and low threshold concentrations based on a 95% risk probability were used to assess different levels of risk. The simulated result reveals that the spatial uncertainty of highly heterogeneous K fields governs the contamination potential assessment of the nitrogen compounds along the regional flow directions. The contamination potential of nitrate-N is more uncertain than that for ammonium-N. The high nitrate-N concentrations (> or =3 mg/L) are prevalent in the aerobic environment. The low concentration nitrate-N plumes (0.5-3 mg/L) gradually migrate to the mid-fan area and to a maximum distance of 15 km from the aerobic region. The nitrate-N plumes pose a potential human health risk in the aerobic and anaerobic environments. The ammonium-N plumes remain stably confined to the distal-fan and partial mid-fan areas. PMID:16095753

  5. Contamination potential of nitrogen compounds in the heterogeneous aquifers of the Choushui River alluvial fan, Taiwan.

    PubMed

    Jang, Cheng-Shin; Liu, Chen-Wuing

    2005-10-01

    This study aimed to analyze the contamination potential associated with the reactive transport of nitrate-N and ammonium-N in the Choushui River alluvial fan, Taiwan and to evaluate a risk region in developing a groundwater protection policy in 2021. In this area, an aquifer redox sequence provided a good understanding of the spatial distributions of nitrate-N and ammonium-N and of aerobic and anaerobic environments. Equiprobable hydraulic conductivity (K) fields reproduced by geostatistical methods characterized the spatial uncertainty of contaminant transport in the heterogeneous aquifer. Nitrogen contamination potential fronts for high and low threshold concentrations based on a 95% risk probability were used to assess different levels of risk. The simulated result reveals that the spatial uncertainty of highly heterogeneous K fields governs the contamination potential assessment of the nitrogen compounds along the regional flow directions. The contamination potential of nitrate-N is more uncertain than that for ammonium-N. The high nitrate-N concentrations (> or =3 mg/L) are prevalent in the aerobic environment. The low concentration nitrate-N plumes (0.5-3 mg/L) gradually migrate to the mid-fan area and to a maximum distance of 15 km from the aerobic region. The nitrate-N plumes pose a potential human health risk in the aerobic and anaerobic environments. The ammonium-N plumes remain stably confined to the distal-fan and partial mid-fan areas.

  6. Geophysical and Hydrological Characterization of Alluvial Fans in the Valle El Sauz Encinillas, Chihuahua, México.

    NASA Astrophysics Data System (ADS)

    Villalobos-Aragón, A.; Chávez-Aguirre, R.; Osuna-Vizcarra, A.; Espejel-García, V. V.

    2007-05-01

    The Valle El Sauz Encinillas (VESE) is located 92 km north of Chihuahua City, México. Despite being the principal aquifer feeding Chihuahua City, and being flanked by two well studied geological features (Bloque Calera-Del Nido to the West, and the Sierra Peña Blanca to the East), a lack of available hydrogeological data prevails in the valley. The goals of this study are two: 1) geomorphometrical analysis of the sub-basins and alluvial fans, and 2) determination of the alluvial fan geoelectrical units via electrical-resistivity soundings. The Basin and Range system forms a closed sub-basin with a lacustrine basin system in extinction process. The aquifer is located in alluvial Quaternary sediments, with varying granulometry, reaching a thickness of 600 meters at the center of the valley. The biggest alluvial fan in the VESE is located at the Cañón de Santa Clara, and intersects the playa-lake deposits of the Laguna de Encinillas. This fan has a surface of 73.2 km2 and an average slope of 0.437°. The geomorphometrical analysis included the sub-basins, currents, and the fans in the area. These analyses allow a comparison between alluvial fans in the VESE and those in Death Valley, California, USA. The alluvial fans in both areas show a similar behavior in all plots. Twenty electrical resistivity soundings (Schlumberger array, AB/2 distance of 400 m) were performed in the alluvial fan. The basement and four other geoelectrical units were identified in the fan. The geophysical data, granulometric determinations, plus geochemical information of twelve wells in the area were analyzed. These data show how the decrease in granulometry, both frontally and laterally in the fan, results in a rise of the hydraulic conductivity and transmisivity values (water wells in Los Sauces and El Faro). However, both the permeability and the water quality in its distal portion, are affected by the playa lake deposits, the raising ratio of clay-size sediments (and evaporites) in the

  7. Alluvial fan sensitivity to glacial-interglacial climate change: case studies from Death Valley.

    NASA Astrophysics Data System (ADS)

    Whittaker, Alexander; D'Arcy, Mitch; Roda-Boluda, Duna; Brooke, Sam

    2016-04-01

    The effects of climate change on eroding landscapes and the sedimentary record remain poorly understood. The measurement of regional grain size trends in stream-flow deposits provides one way to address this issue because, in principle, these trends embed important information on the dynamics of sediment routing systems and their sensitivity to external forcings. In many cases, downstream stratigraphic fining is primarily driven by selective deposition of sediment. The relative efficiency of this process is determined by the physical characteristics of the input sediment supply and the spatial distribution of subsidence rate, which generates the accommodation necessary for mass extraction. Here, we measure grain size fining rates from apex to toe for alluvial fan systems in Death Valley, California, which have well-exposed modern and late Pleistocene deposits, where the long-term tectonic boundary conditions are known and where climatic variation over this time period is well-constrained. Our field data demonstrate that input grain sizes and input fining rates do vary noticeably over the late Pleistocene-Holocene period in this study area, although there is little evidence for significant changes in rates of faulting in the last 200 ky. For two catchments in the Grapevine Mountains for which we have excellent stratigraphic constraints on modern and 70 ka fan deposits, we use a self-similarity based grain size fining model to understand changes in sediment flux to the fans over this time period. When calibrated with cosmogenically-derived catchment erosion rates, our results show that a 30 % decrease in average precipitation rate over this time-frame led to a 20 % decrease in sediment flux to the fans, and a clear increase in the down-fan rate of fining. This supports existing landscape evolution models that relate a decrease in precipitation rate to a decrease in sediment flux, but implies that the relationship between sediment flux and precipitation rate may be

  8. Occurrence of arsenic in ground water in the Choushui River alluvial fan, Taiwan.

    PubMed

    Liu, Chen-Wuing; Wang, Sheng-Wei; Jang, Cheng-Shin; Lin, Kao-Hong

    2006-01-01

    An investigation of shallow ground water quality revealed that high arsenic (As) concentrations were found in both aquifers and aquitards in the southern Choushui River alluvial fan of Taiwan. A total of 655 geological core samples from 13 drilling wells were collected and analyzed. High As contents were found primarily in aquitards, to a maximum of 590 mg/kg. The contents were correlated with the locations of the marine sequences. Additionally, strong correlations among the As concentrations of core samples, the clay, and the geological age of the Holocene transgression were identified. Most of the As in ground water originated from the aquitard of the marine sequence. The high As content in marine formations with high clay contents may be attributable to the bioaccumulation of As in the sea organisms, which accrued and were deposited in the formation. A preliminary geogenic model of the origin of the high As concentration in the shallow sedimentary basin of the Choushui River alluvial fan of Taiwan is proposed. PMID:16391278

  9. Fracture Detection in Alluvial Fan Deposits Using Near-Surface Seismic Reflection Techniques

    NASA Astrophysics Data System (ADS)

    Black, R. A.; Miller, B.

    2012-12-01

    In this study we document the observation of probable extensive shallow vertical fracture systems in unprocessed 2-D source gathers from near-surface seismic reflection surveys conducted over unconsolidated materials in alluvial fans environments. Mapping of fracture and fault systems within the sedimentary sections at hydrocarbon exploration scales has become common practice. This is due to the advent of post-stack attribute analysis of 3-D seismic images worldwide. However, examples of fracture detection and imaging in the near-surface are currently lacking in the literature. In addition, examples of fracture detection and mapping in the pre-stack domain are also lacking. In this study, unprocessed seismic source gathers from very high-resolution reflection surveys over alluvial fan deposits in tectonically active areas appear to display distinct patterns of amplitude drop off, geometrically similar to patterns expected for vertical fracture systems. The patterns can also be extracted by attribute analysis using techniques such as envelope and coherency analyses. Simple standard processing steps such as trace editing, muting, and bandpass filtering enhance interpretability. The patterns appear to be consistent and spatially fixed in the subsurface from source location to source location. These are observed in areas of obvious recent local large-scale fault movement. Examples are given from two areas, eastern Queen Valley in California and eastern Fish Lake Valley in Nevada. The stratigraphic and sedimentation patterns are quite complicated in both areas, and sediment characteristics vary considerably between sites. The surface sediments in the Queen Valley case are, in general, much coarser with many more boulder-sized clasts in the shallow subsurface. The seismic source consisted of a 30-06 rifle fired downhole at a depth of 0.5m. While the boulders interfered with seismic source operations, the record quality was excellent. The alluvial materials, especially

  10. Hydraulic Modeling of Alluvial Fans along the Truckee Canal using the 2-Dimensional Model SRH2D

    NASA Astrophysics Data System (ADS)

    Wright, J.; Kallio, R.; Sankovich, V.

    2013-12-01

    Alluvial fans are gently sloping, fan-shaped landforms created by sediment deposition at the ends of mountain valleys. Their gentle slopes and scenic vistas are attractive to developers. Unfortunately, alluvial fans are highly flood-prone, and the flow paths of flood events are highly variable, thereby placing human developments at risk. Many studies have been performed on alluvial fans in the arid west because of the uncertainty of their flow paths and flood extents. Most of these studies have been focused on flood elevations and mitigation. This study is not focused on the flood elevations. Rather, it is focused on the attenuation effects of alluvial fans on floods entering and potentially failing a Reclamation canal. The Truckee Canal diverts water from the Truckee River to Lahontan Reservoir. The drainage areas along the canal are alluvial fans with complex distributary channel networks . Ideally, in nature, the sediment grain-size distribution along the alluvial fan flow paths would provide enough infiltration and subsurface storage to attenuate floods entering the canal and reduce risk to low levels. Human development, however, can prevent the natural losses from occurring due to concentrated flows within the alluvial fan. While the concentrated flows might mitigate flood risk inside the fan, they do not lower the flood risk of the canal. A 2-dimensional hydraulic model, SRH-2D, was coupled to a 1-dimensional rainfall-runoff model to estimate the flood attenuation effects of the alluvial fan network surrounding an 11 mile stretch of the Truckee Canal near Fernley, Nevada. Floods having annual exceedance probabilities ranging from 1/10 to 1/100 were computed and analyzed. SRH-2D uses a zonal approach for modeling river systems, allowing areas to be divided into separate zones based on physical parameters such as surface roughness and infiltration. One of the major features of SRH-2D is the adoption of an unstructured hybrid mixed element mesh, which is based

  11. Using remotely-sensed multispectral imagery to build age models for alluvial fan surfaces

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Mason, Philippa J.; Roda Boluda, Duna C.; Whittaker, Alexander C.; Lewis, James

    2016-04-01

    Accurate exposure age models are essential for much geomorphological field research, and generally depend on laboratory analyses such as radiocarbon, cosmogenic nuclide, or luminescence techniques. These approaches continue to revolutionise geomorphology, however they cannot be deployed remotely or in situ in the field. Therefore other methods are still needed for producing preliminary age models, performing relative dating of surfaces, or selecting sampling sites for the laboratory analyses above. With the widespread availability of detailed multispectral imagery, a promising approach is to use remotely-sensed data to discriminate surfaces with different ages. Here, we use new Landsat 8 Operational Land Imager (OLI) multispectral imagery to characterise the reflectance of 35 alluvial fan surfaces in the semi-arid Owens Valley, California. Alluvial fans are useful landforms to date, as they are widely used to study the effects of tectonics, climate and sediment transport processes on source-to-sink sedimentation. Our target fan surfaces have all been mapped in detail in the field, and have well-constrained exposure ages ranging from modern to ~ 125 ka measured using a high density of 10Be cosmogenic nuclide samples. Despite all having similar granitic compositions, the spectral properties of these surfaces vary systematically with their exposure ages. Older surfaces demonstrate a predictable shift in reflectance across the visible and short-wave infrared spectrum. Simple calculations, such as the brightness ratios of different wavelengths, generate sensitive power law relationships with exposure age that depend on post-depositional alteration processes affecting these surfaces. We investigate what these processes might be in this dryland location, and evaluate the potential for using remotely-sensed multispectral imagery for developing surface age models. The ability to remotely sense relative exposure ages has useful implications for preliminary mapping, selecting

  12. Sedimentology and climatic environment of alluvial fans in the martian Saheki crater and a comparison with terrestrial fans in the Atacama Desert

    NASA Astrophysics Data System (ADS)

    Morgan, A. M.; Howard, A. D.; Hobley, D. E. J.; Moore, J. M.; Dietrich, W. E.; Williams, R. M. E.; Burr, D. M.; Grant, J. A.; Wilson, S. A.; Matsubara, Y.

    2014-02-01

    The deflated surfaces of the alluvial fans in Saheki crater reveal the most detailed record of fan stratigraphy and evolution found, to date, on Mars. During deposition of at least the uppermost 100 m of fan deposits, discharges from the source basin consisted of channelized flows transporting sediment (which we infer to be primarily sand- and gravel-sized) as bedload coupled with extensive overbank mud-rich flows depositing planar beds of sand-sized or finer sediment. Flow events are inferred to have been of modest magnitude (probably less than ∼60 m3/s), of short duration, and probably occupied only a few distributaries during any individual flow event. Occasional channel avulsions resulted in the distribution of sediment across the entire fan. A comparison with fine-grained alluvial fans in Chile’s Atacama Desert provides insights into the processes responsible for constructing the Saheki crater fans: sediment is deposited by channelized flows (transporting sand through boulder-sized material) and overbank mudflows (sand size and finer) and wind erosion leaves channels expressed in inverted topographic relief. The most likely source of water was snowmelt released after annual or epochal accumulation of snow in the headwater source basin on the interior crater rim during the Hesperian to Amazonian periods. We infer the Saheki fans to have been constructed by many hundreds of separate flow events, and accumulation of the necessary snow and release of meltwater may have required favorable orbital configurations or transient global warming.

  13. Minturn and Sangre de Cristo Formations of southern Colorado: a prograding fan-delta to alluvial-fan sequence shed from ancestral Rocky Mountains

    SciTech Connect

    Lindsey, D.A.; Clark, R.F.; Ashe, S.J.; Flores, R.J.

    1983-08-01

    The Pennsylvanian Minturn and Pennsylvanian-Permian Sangre de Cristo Formations of the northern Sangre de Cristo Mountains comprise a 3,800-m (12,500-ft) thick progradational sequence of coarse clastic sediments shed into a basin on the northeastern side of the late Paleozoic San Luis-Uncompahgre highland. From bottom to top, the mostly marine Minturn Formation contains probable deltaic (700 m, 2,300 ft), mixed fan-delta and prodelta (800 m, 2,600 ft), and fan-delta (600 m, 2,000 ft) deposits; the mostly continental Sangre de Cristo Formation contains distal alluvial fan (600 m, 2,000 ft) and proximal alluvial fan (1,100m 3,600 ft) deposits. At least three episodes of uplift are indicated by the distribution of unconformities, geometry of intertonguing facies, and abrupt vertical changes in facies. The deltaic and mixed fan-delta and prodelta deposits of the lower and middle parts of the Minturn Formation consist of coarsening-upward cycles 30 to 300 m (100 to 1,000 ft) thick of shale, siltstone, sandstone, and conglomeratic sandstone. The mixed deposits in the middle part of the Minturn contain cycles of shale, proximalturbidite sandstones, and conglomeratic sandstone; such cycles are interpreted as deposits of submarine fans overridden by fan deltas. Continental deposits of the lower member of the Sangre de Cristo Formation consist of fining-upward cycles 2 to 37 m (6.5 to 121 ft) thick of cross-bedded conglomerate, sandstone, and siltstone deposited by braided streams on the distal parts of alluvial fans.

  14. Late Quaternary alluviation and offset along the eastern Big Pine fault, southern California

    USGS Publications Warehouse

    DeLong, S.B.; Minor, S.A.; Arnold, L.J.

    2007-01-01

    Determining late Quaternary offset rates on specific faults within active mountain belts is not only a key component of seismic hazard analysis, but sheds light on regional tectonic development over geologic timescales. Here we report an estimate of dip-slip rate on the eastern Big Pine oblique-reverse fault in the upper Cuyama Valley within the western Transverse Ranges of southern California, and its relation to local landscape development. Optically stimulated luminescence (OSL) dating of sandy beds within coarse-grained alluvial deposits indicates that deposition of alluvium shed from the Pine Mountain massif occurred near the southern margin of the Cuyama structural basin at the elevation of the Cuyama River between 25 and 14??ka. This alluvial deposit has been offset ??? 10??m vertically by the eastern Big Pine fault, providing a latest Quaternary dip-slip rate estimate of ??? 0.9??m/ky based on a 50?? fault dip. Incision of the adjacent Cuyama River has exposed a section of older Cuyama River sediments beneath the Pine Mountain alluvium that accumulated between 45 and 30??ka on the down-thrown footwall block of the eastern Big Pine fault. Corroborative evidence for Holocene reverse-slip on the eastern Big Pine fault is ??? 1??m of incised bedrock that is characteristically exposed beneath 2-3.5??ka fill terraces in tributaries south of the fault. The eastern Big Pine fault in the Cuyama Valley area has no confirmed record of historic rupture; however, based on our results, we suggest the likelihood of multiple reverse-slip rupture events since 14??ka. ?? 2007 Elsevier B.V. All rights reserved.

  15. River path selection in response to uplift and interaction with alluvial fans

    NASA Astrophysics Data System (ADS)

    Grimaud, J. L.; Paola, C.; Voller, V. R.

    2015-12-01

    River systems construct stratigraphic successions and build land by depositing and redistributing sediments as they migrate across the entire basin. This mobility arises from the intrinsic variability of a river system but can also be forced by external changes. It is particularly observable in tectonically active basins where the basement can be partly uplifted and where sediments can come from multiple sources. Theoretically, the ability of these perturbations to steer channels depends on their capacity to create lateral topographic gradients at a faster rate than the aggradation. Following these lines, we present an experimental study on the impacts of lateral tilting by tectonics and lateral alluvial fans on rivers path. The experiment was conducted in the eXperimental Earth Scape facility, also known as the Jurassic tank, where the basement tilting rate can be monitored by controlling individually gravel subsidence through 108 hexagonal cells. The basin was relatively uplifted on one side of the tank according to an anticline-shape and sediments were input through two sources: a main, axial one and a lateral, secondary one. We analyzed the differences in the topographic signature and flow occupation of rivers in response to the uplift or the lateral sediment source as well as the competition of these forcing in the late stages of the experiments. We found that both tectonic tilting and fan activity tend to decrease the basin-wide channel mobility. Indeed, the area at the convergence of the two interacting fans is a long-lasting topographic low that tends to channelize the flow while areas away from it are less visited. The position of this boundary is correlated with the relative flow contribution from both fans. This highlights the self-healing capacity of fans that are able to rapidly restore a graded shape. As opposed to fans, an uplifted area will not heal but force rivers to carve long-lasting valleys and increase the relief. When eroded, these uplifted

  16. Geomorphic characterization of the Fortymile Wash alluvial fan, Nye County, Nevada, in support of the Yucca Mountain Project

    NASA Astrophysics Data System (ADS)

    Cline, M.; Delong, S.; Pelletier, J.

    2005-12-01

    In the event of an unlikely volcanic eruption through the proposed high-level radioactive waste repository at Yucca Mountain, contaminated ash may be deposited in portions of the Fortymile Wash drainage basin and subsequently redistributed to the Fortymile Wash alluvial fan by fluvial processes. Characterization of the Fortymile Wash alluvial fan has been undertaken as part of an effort to quantify the transport of contaminated ash throughout the fluvial system, especially to define the spatial distribution of fluvial activity over time scales of repository operation, and the rates of radionuclide migration into different soils on the fan. The Fortymile Wash alluvial fan consists of extremely low relief terraces as old as 70 ka. By conducting soils-geomorphic mapping and correlating relative surface ages with available geochronology from the Fortymile Wash fan and adjacent piedmonts, we identified 4 distinct surfaces on the fan. Surface ages are used to predict the relative stability of different areas of the fan to fluvial activity. Pleistocene-aged surfaces are assumed to be fluvially inactive over the 10 kyr time scale, for example. Our mapping and correlation provides a map of the depozone for contaminated ash that takes into account long-term channel migration for the time scales of repository operation, and it provides a geomorphic framework for predicting radionuclide dispersion rates into different soils across the fan. The standard model for vertical migration of radionuclides in soil is diffusion; therefore we used diffusion profiles derived from 137Cs fallout to determine radionuclide infiltration rates on the various geomorphic surfaces. The results show a strong inverse correlation of the geomorphic surface age and diffusivity values inferred from the 137Cs profiles collected on the different surfaces of the fan.

  17. Geomorphic Characterization of the FortyMile Wash Alluvial Fan, Nye County, Nevada, In Support of the Yucca Mountain Project

    SciTech Connect

    Cline; De Long; Pelletier; Harrington

    2005-09-06

    In the event of an unlikely volcanic eruption through the proposed high-level radioactive waste repository at Yucca Mountain, contaminated ash would be deposited in portions of the Fortymile Wash drainage basin and would subsequently be redistributed to the Fortymile Wash alluvial fan by fluvial processes. As part of an effort to quantify the transport of contaminated ash throughout the fluvial system, characterization of the Fortymile Wash alluvial fan is required, especially the spatial distribution of fluvial activity over time scales of repository operation, and the rates of radionuclide migration into different soils on the fan. The Fortymile Wash alluvial fan consists of extremely low relief terraces as old as 70 ka. By conducting soils-geomorphic mapping and correlating relative surface ages with available geochronology from the Fortymile Wash fan and adjacent piedmonts, we identified 4 distinct surfaces on the fan. Surface ages are used to predict the relative stability of different areas of the fan to fluvial activity. Pleistocene-aged surfaces are assumed to be fluvially inactive over the 10 kyr time scale, for example. Our mapping and correlation provides a map of the depozone for contaminated ash that takes into account long-term channel migration the time scales of repository operation, and it provides a geomorphic framework for predicting radionuclide dispersion rates into different soils across the fan. The standard model for vertical migration of radionuclides in soil is diffusion; therefore we used diffusion profiles derived from {sup 137}Cs fallout to determine infiltration rates on the various geomorphic surfaces. The results show a strong inverse correlation of the geomorphic surface age and diffusivity values inferred from the {sup 137}Cs profiles collected on the different surfaces of the fan.

  18. Ground-Water Geology and Hydrology of the Kern River Alluvial-Fan Area, California

    USGS Publications Warehouse

    Dale, R.H.; French, James J.; Gordon, G.V.

    1966-01-01

    The Kern River alluvial fan is the southernmost major alluvial fan built by the streams which drain the west side of the Sierra Nevada. The climate is semiarid with rainfall near 5 inches per year. Agricultural development within the area uses over half the 700,000 acre-feet per year flow of the Kern River, plus a considerable amount drawn from the ground-water reservoir particularly during periods of low flow. The area overlies a deep structural trough between crystalline rocks of the Sierra Nevada and the marine rocks of Tertiary age of the Coast Ranges. The top horizon of the marine rocks that lap on the Sierra Nevada block underlies the report area at an average depth of 2,000 feet. The overlying continental deposits that form the groundwater reservoir consist of alluvial-fan and lacustrine deposits. The continental deposits are subdivided into three lithologic units on the basis of grain size and sorting. The gravel and clay unit consists of older alluvial-fan material, of both Sierra Nevada and Coast Range provenance, that shows extremely poor sorting with some diagenetic decomposition through chemical weathering. The fine sand to clay unit consists principally of fine sand, silt, and clay deposited in a lacustrine environment, although some of the unit is of alluvial-fan origin derived from poorly consolidated marine shale of the Coast Ranges. Within the fine sand to clay unit three distinct clays, which affect ground-water conditions, can be recognized. The gravel to medium sand unit consists of unweathered alluvial-fan material that shows much better sorting than the gravel and clay unit. In the eastern part of the area the basal part of this unit is a gravel lentil that can be traced in the subsurface more than 250 square miles. The overlying deposits consist principally of medium sand. In the western part of the area the unit is a heterogeneous gravel and sand unit. Permeability in Meinzer units of the gravel and clay unit ranges between 10 and 100 with

  19. Characterization of land subsidence induced by groundwater withdrawals in Wenyu River alluvial fan, Beijing, China

    NASA Astrophysics Data System (ADS)

    Wang, R.; Luo, Y.; Yang, Y.; Tian, F.; Zhou, Y.; Tian, M.-Z.

    2015-11-01

    The Beijing plain area has suffered from severe land subsidence owing to groundwater overdraft. A major example is the Wenyu River alluvial fan in the Beijing plain area. This area has experienced as much as 10 m of land subsidence through 2000s. An integrated subsidence-monitoring program, including borehole extensometer and multilayer monitoring of groundwater, has been designed to meet the needs of monitoring land subsidence in this region. This work has allowed us to characterize land subsidence and understand the mechanical properties of the strata. The analysis results show the development of the land subsidence in this area is consistent with water-level change. The major strata contributing to compression deformation are Mid-Pleistocene stratum which contributed around 70 % of total subsidence. The shallow stratum and deep stratum show elastic mechanical behavior the intermediate stratum exhibit elastic-plastic mechanical behavior.

  20. Alluvial fans and megafans along the southern side of the Alps

    NASA Astrophysics Data System (ADS)

    Fontana, Alessandro; Mozzi, Paolo; Marchetti, Mauro

    2014-03-01

    The foreland basin of the southern European Alps is characterized by large fan-shaped alluvial systems fed by the main montane valleys and these depositional systems present an extent of 300-3000 km2, with a length of 30-70 km. Most of them are megafans, characterized by evident longitudinal differentiation in which steep piedmont sector consists of amalgamated gravels, while the distal portion has a gradient < 2‰ and is dominated by fine sediments. The major depositional phase occurred between 26 and 19 kyr cal BP during the Last Glacial Maximum (LGM) marine lowstand, when the Alpine glaciers reached the plain and fed the related fluvioglacial systems. The easternmost megafans also partly extended on the Adriatic shelf whereas, west from Garda Lake, their downstream development was limited by the Po River plain. The thickness of LGM alluvial sedimentation ranges between 30 and 15 m and pinches out about 25 km off the present coast. Soon after ice decay, after 19-17 kyr cal BP, sediment delivery from Alpine catchments to the plain dramatically decreased and in the central Alps large intramontane lakes formed, trapping almost all the bedload. Thus, the ratio between sediment and water discharge dramatically decreased and an erosive phase affected the LGM megafans and fans, leading the rivers to entrench for tens of meters. The funneling effect created by the fluvial incisions allowed the gravels to arrive tens of kilometers further downstream than in the LGM. In the Venetian-Friulian megafans a single valley formed in the piedmont sector, while 2-5 incised valleys developed in the distal sector. These latter valleys have been almost completely filled by a depositional lobe formed in the last 8 kyr, partly triggered by Holocene sea-level rise. The Alpine tributaries of the river Po still flow along a single incised valley from their megafan apex to the junction with the Po and they have not yet been affected by sea-level influence.

  1. Historical Ground-Water Development in the Salinas Alluvial Fan Area, Salinas, Puerto Rico, 1900-2005

    USGS Publications Warehouse

    Rodriguez, Jose M.; Gómez-Gómez, Fernando

    2008-01-01

    The Salinas alluvial fan area has historically been one of the most intensively used agricultural areas in the South Coastal Plain of Puerto Rico. Changes in agricultural practices and land use in the Salinas alluvial fan have also caused changes in the geographic distribution of ground-water withdrawals from the alluvial aquifer. As a result, the ground-water balance and ground-water flow pattern have changed throughout the years and may explain the presence of saline ground water along parts of the coast at present. By providing a reconstruction of historical ground-water development in the Salinas alluvial fan area, from the initial years of aquifer development at about 1900 to the most recent conditions existing in 2005, water resources managers and planners can use the results of the analysis for a more complete understanding of aquifer conditions especially pertaining to water quality. This study effort was conducted by the U.S. Geological Survey in cooperation with the Puerto Rico Department of Natural and Environmental Resources as a contribution in the management of the Jobos Bay National Estuarine Research Reserve. The study area encompasses about 20 mi2 (square miles) of the extensive South Coastal Plain alluvial aquifer system (fig. 1). The study area is bounded to the north by foothills of the Cordillera Central mountain chain, to the south by the Caribbean Sea, and to the east and west by the Rio Nigua de Salinas and the Quebrada Aguas Verdes, respectively. Fan-delta and alluvial deposits contain the principal aquifers in the study area.

  2. Tributary debris fans and the late Holocene alluvial chronology of the Colorado River, eastern Grand Canyon, Arizona

    USGS Publications Warehouse

    Hereford, R.; Thompson, K.S.; Burke, K.J.; Fairley, H.C.

    1996-01-01

    Bouldery debris fans and sandy alluvial terraces of the Colorado River developed contemporaneously during the late Holocene at the mouths of nine major tributaries in eastern Grand Canyon. The age of the debris fans and alluvial terraces contributes to understanding river hydraulics and to the history of human activity along the river, which has been concentrated on these surfaces for at least two to three millennia. Poorly sorted, coarse-grained debris-flow deposits of several ages are interbedded with, overlie, or are overlapped by three terrace-forming alluviums. The alluvial deposits are of three age groups: the striped alluvium, deposited from before 770 B.C. to about A.D. 300; the alluvium of Pueblo II age deposited from about A.D. 700 to 1200; and the alluvium of the upper mesquite terrace, deposited from about A.D. 1400 to 1880. Two elements define the geomorphology of a typical debris fan: the large, inactive surface of the fan and a smaller, entrenched, active debris-flow channel and fan that is about one-sixth the area of the inactive fan. The inactive fan is segmented into at least three surfaces with distinctive weathering characteristics. These surfaces are conformable with underlying debris-flow deposits that date from before 770 B.C. to around A.D. 660, A.D. 660 to before A.D. 1200, and from A.D. 1200 to slightly before 1890, respectively, based on late-19th-century photographs, radiocarbon and archaeologic dating of the three stratigraphically related alluviums, and radiocarbon dating of fine-grained debris-flow deposits. These debris flows aggraded the fans in at least three stages beginning about 2.8 ka, if not earlier in the late Holocene. Several main-stem floods eroded the margin of the segmented fans, reducing fan symmetry. The entrenched, active debris-flow channels contain deposits <100 yr old, which form debris fans at the mouth of the channel adjacent to the river. Early and middle Holocene debris-flow and alluvial deposits have not been

  3. Use of spectral data and Landsat TM for mapping alluvial fan deposits of the Rosillos Mountains in Brewster County, Texas

    SciTech Connect

    Bittick, S.M.; Morgan, K.M.; Busbey, A.B. . Dept. of Geology)

    1993-02-01

    The Rosillos Mountains consist of a large, highly faulted and fracture, exposed Tertiary igneous intrusion (laccolith) located adjacent to Big Bend National Park. This study examines the alluvial deposits that fan out over the 25,000 acre privately owned Rosillos Ranch located on the east side of the laccolith. Using a field spectrometer, spectral curves were generated for the various materials present. These surface reflectance patterns were used for spectral recognition and, along with Landsat digital data, for computer classification mapping of the alluvial fans. Several computer classification techniques will be presented along with mapping accuracies. Initial results indicate the resulting Landsat generated fan deposit maps are, in fact, related to the source areas and the age of deposition.

  4. Radon hazard in shallow groundwaters II: dry season fracture drainage and alluvial fan upwelling.

    PubMed

    Tommasone, F Pascale; De Francesco, S; Cuoco, E; Verrengia, G; Santoro, D; Tedesco, D

    2011-08-15

    ²²²Rn concentrations have been measured in a well located on the edge of a large Pleistocene-Holocene fan and belonging to the shallow pyroclastic aquifer of the Pietramelara Plain, southern Italy. The aim of this study has been both to characterise the hydrological inputs that determine the influx of ²²²Rn to the shallow aquifer and to understand the correlations between ²²²Rn, major ions, physical-chemical parameters and rainfall. Results obtained from the time series indicate that the studied well shows a ²²²Rn variability that is inconsistent with a mechanism of pure hydrological amplification, such as described in Radon hazard in shallow groundwaters: Amplification and long term variability induced by rainfall (De Francesco et al., 2010a). On the contrary, in this well hydrological amplification appears to be mainly tied to the upwelling of alluvial fan waters, rich in radon, in response to pistoning from recharge in the carbonate substrate. This upwelling of alluvial fan waters occurs during almost the whole period of the annual recharge and is also responsible of the constant increase in ²²²Rn levels during the autumn-spring period, when both the water table level and weekly rainfall totals drop. Furthermore, a rapid delivery mechanism for ²²²Rn likely operates through fracture drainage in concomitance with the very first late summer-early autumn rains, when rainfall totals appear largely insufficient to saturate the soil storage capacity. Results obtained from this study appear to be particularly significant in both radon hazard zoning in relation to the shallow aquifer and possibly also for indoor radon, owing to possible shallow aquifer-soil-building exchanges. Moreover, both the spike-like events and the long wave monthly scale background fluctuations detected can also have potential significance in interpreting ²²²Rn time series data as seismic and/or volcanic precursors. Finally, ²²²Rn has proved to be an excellent tracer for

  5. Radon hazard in shallow groundwaters II: dry season fracture drainage and alluvial fan upwelling.

    PubMed

    Tommasone, F Pascale; De Francesco, S; Cuoco, E; Verrengia, G; Santoro, D; Tedesco, D

    2011-08-15

    ²²²Rn concentrations have been measured in a well located on the edge of a large Pleistocene-Holocene fan and belonging to the shallow pyroclastic aquifer of the Pietramelara Plain, southern Italy. The aim of this study has been both to characterise the hydrological inputs that determine the influx of ²²²Rn to the shallow aquifer and to understand the correlations between ²²²Rn, major ions, physical-chemical parameters and rainfall. Results obtained from the time series indicate that the studied well shows a ²²²Rn variability that is inconsistent with a mechanism of pure hydrological amplification, such as described in Radon hazard in shallow groundwaters: Amplification and long term variability induced by rainfall (De Francesco et al., 2010a). On the contrary, in this well hydrological amplification appears to be mainly tied to the upwelling of alluvial fan waters, rich in radon, in response to pistoning from recharge in the carbonate substrate. This upwelling of alluvial fan waters occurs during almost the whole period of the annual recharge and is also responsible of the constant increase in ²²²Rn levels during the autumn-spring period, when both the water table level and weekly rainfall totals drop. Furthermore, a rapid delivery mechanism for ²²²Rn likely operates through fracture drainage in concomitance with the very first late summer-early autumn rains, when rainfall totals appear largely insufficient to saturate the soil storage capacity. Results obtained from this study appear to be particularly significant in both radon hazard zoning in relation to the shallow aquifer and possibly also for indoor radon, owing to possible shallow aquifer-soil-building exchanges. Moreover, both the spike-like events and the long wave monthly scale background fluctuations detected can also have potential significance in interpreting ²²²Rn time series data as seismic and/or volcanic precursors. Finally, ²²²Rn has proved to be an excellent tracer for

  6. Controls on morphometry and morphology of alluvial and colluvial fans in the high-Arctic setting, Petuniabukta, Svalbard.

    NASA Astrophysics Data System (ADS)

    Tomczyk, Aleksandra; Ewertowski, Marek

    2016-04-01

    The Petuniabukta (78o42' N, 16o32') is a bay in the northern part of Billefjorden in the central part of Spitsbergen Island, Svalbard. The bay is surrounded by six major, partly glaciated valleys. A numerous alluvial and colluvial fans have developed within valleys as well as along the fiord margins. Distribution and characterization of morphometric parameters of fans were investigated using time-series of orthophotos and digital elevation models (generated based on 1961, 1990, 2009 aerial photographs) and high resolution satellite imagery from 2013. In addition, a very detailed DEM and orthophoto (5 cm resolution) have been produced from unmanned aerial vehicle (UAV) imagery from 2014 and 2015, covering three fans characterised by different types of surface morphology. A 1:40,000 map showing the distribution of almost 300 alluvial and colluvial fans (ranging in area from 325 km2 to 451 275 km2), together with time-series of 1:5,000 geomorphological maps of sample fans enabled an assessment of the spatial and temporal evolution of processes responsible for delivery and erosion of sediments from the fans. The relationship between terrain parameters (e.g. slope, exposition) as well as geology was also investigated. Many of the studied alluvial fans were at least partly coupled and sediments were transferred from the upstream zone to the downstream zone, either due to debris-flow or channelized stream flow. In other cases, coarse sediments were stored within fans, and fines were transported downstream by sheet flows or sub-surface flows. In most of smaller colluvial fans and debris cones, sediments were delivered by mass movement processes (mainly rockfalls and snowfalls) and did not reach lower margin of landforms. Analysis of historical aerial photographs indicated recent increase in the activity of debris-flow modification of surface morphology of fans. Fans located outside limits of the Little Ice Age (LIA) glaciation are dominated by the secondary processes

  7. Synoptic snowfall as a possible source of water for late alluvial fan activity in southern Margaritifer Terra, Mars

    NASA Astrophysics Data System (ADS)

    Grant, J. A.; Wilson, S. A.

    2012-12-01

    Alluvial deposits on Mars provide an important record of the environmental conditions enabling their formation. A recent study of alluvial fans within large craters in southern Margaritifer Terra showed that deposition of exposed surfaces occurred late in Martian history, within the latest Hesperian or well into the early Amazonian. These fans typically display well developed alcoves and fan surfaces preserve distributary channels standing ~10-15 m in relief (via inversion of topography). Understanding whether the water responsible for fan emplacement was related to a local source (e.g., impact-related melting of ground ice) versus regional or global synoptic climatic events has implications for the nature of late water activity and potential habitability of Mars. Water released during and after impact events may be sufficient to cause runoff within and around newly formed craters and could contribute to late valley and fan formation without requiring changes in climate. For example, the impact forming the Amazonian-aged Hale crater (35.7S, 323.6E) produced valleys, but was not likely responsible for the alluvial fans because 1) alluvial fans occur in craters up to 700-800 km away from Hale; 2) craters with fans occur at a range of azimuths from Hale (and may not be consistent with downwind transport of volatiles under prevailing winds); and 3) many craters bearing older floor deposits and mantling deposits are closer to Hale than those containing fans. The impact forming the Hesperian-aged Holden crater (26.1S, 326E) is another possible local source of water, but like Hale, craters hosting fans occur at a range of azimuths and up to hundreds of km away from Holden. Moreover, at least six degraded craters on the relatively high relief rim of Holden suggest a gap in time between the Holden impact and the fluvial modification of these near-rim craters and the simultaneous fan activity within Holden. Fans within Holden also record evidence for multiple periods of

  8. Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages

    SciTech Connect

    Blair, T.C. ); McPherson, J.G. )

    1994-07-01

    Contrary to common contemporary usage, alluvial fans are a naturally unique phenomenon readily distinguishable from other sedimentary environments, including gravel-bed rivers, on the basis of morphology, hydraulic processes, sedimentologic processes, and facies assemblages. The piedmont setting of alluvial fans where the feeder channel of an upland drainage basin intersects the mountain front assures that catastrophic fluid gravity flows and sediment gravity flows, including sheetfloods, rock falls, rock slides, rock avalanches, and debris flows, are major constructional processes, regardless of climate. The unconfinement of these flows at the mountain front gives rise to the high-sloping, semiconical form that typifies fans. The plano-convex cross-profile geometry inherent in this form is the inverse of the toughlike cross-sectional form of river systems, and precludes the development of floodplains that characterize rivers. The relatively high slope of alluvial fans creates unique hydraulic conditions where passing fluid gravity flows attain high capacity, high competency, and upper flow regime, resulting in sheetfloods that deposit low-angle antidune or surface-parallel planar-stratified sequences. These waterlaid facies contrast with the typically lower-flow-regime thick-bedded, cross-bedded, and lenticular channel facies, and associated floodplain sequences, of rivers. The unconfinement of flows on fans causes a swift decrease in velocity, competency, and capacity as they attenuate, inducing rapid deposition that leads to the angular, poorly sorted textures and short radii typical of fans. This condition is markedly different than for rivers, where sediment gravity flows are rare and water flows remain confined by channel walls or spill into floodplains, and increase in depth downstream.

  9. Alluvial fan susceptibility to thermoerosion in a small arctic basin,Pangnirtung, NU

    NASA Astrophysics Data System (ADS)

    Gosselin, P.; Allard, M.; Falardeau-Marcoux, C.

    2011-12-01

    An exceptional rainstorm, high air temperature, thick snow cover and low soil permeability due to high permafrost table in early summer are some of the main causes that led to an extreme peak discharge of the Duval River, in Pangnirtung, Nunavut, on June 8, 2008. The 95 km2 catchment is located on mountainous terrain and the river flows in a steep channel down to a large Holocene alluvial fan on which the community is partially built. In a matter of several hours, an estimated volume of 91 000 m3 of sediments were eroded by the combined mechanical and thermal action of flowing water (thermoerosion). The bouldery main channel of the river was overdeepened by nearly 10 m while the permafrost river banks were undercut up to ~ 80 m laterally. The weight of the undercut bank eventually exceeded the strength of the permafrost and they collapsed, permanently damaging two bridges. As the Duval River flows through the community, the damage to the bridges resulted in limited access to some vital services such as distribution of drinking water and sewage transport. This event shows how climate change and, more specifically, the potential increase in the recurrence of extreme climatic events can trigger landscape hazards, raising safety concerns and infrastructure issues in northern communities. In order to help develop a more resilient community, this study focuses on understanding the process of thermal erosion and on assessing the potential risk of reoccurrence of a high magnitude fluvial event in Pangnirtung. The susceptibility to thermoerosion of the alluvial fan on which the river flows was determined by measuring the main characteristics of the permafrost (grain size, temperature profile, water and ice content) and of the Duval River (water temperature, discharge, channel slope). The unconsolidated sediments (silty-sand matrix till), the low ice-content and the relatively high permafrost temperature at the 12 m depth (-2.8 °C) are all factors promoting thermal erosion

  10. Jesse Ewing Canyon Formation, an interpreted alluvial fan deposit in the basal Uinta Mountain Group (Middle Proterozoic), Utah

    SciTech Connect

    Sanderson, I.D.; Wiley, M.T.

    1986-07-01

    The Jesse Ewing Canyon Formation, a member of the Middle Proterozic Uinta Mountain Group, is here proposed as a formal lithostratigraphic unit. It consists of interbedded dark reddish-brown to dark gray conglomerate with predominant white, pale green, gray, or pink metaquartzite clasts, light to dark brown or reddish-brown quartz arenite, and reddish-brown, red, or maroon shale. This represents the first proposal of a formation in the Uinta Mountain Group in the eastern part of the range and follows by only a few years beginning efforts to establish formations in the group in the western part. The Jesse Ewing Canyon Formation locally constitutes the basal member of the Uinta Mountain Group and is here reaffirmed as an alluvial fan deposit, based on a detailed comparison of observed features to those of modern alluvial fans. This interpretation supports the hypothesis that the Uinta Trough is an aulacogen.

  11. Architectural analysis and chronology of an Alpine alluvial fan using 3D ground penetrating radar investigation and quantitative outcrop analysis

    NASA Astrophysics Data System (ADS)

    Franke, D.; Hornung, J.; Hinderer, M.

    2012-04-01

    Alluvial fans represent sediment sinks directly at the outlet of the source area in mountain landscapes. They contain multiple information on short-term as well as on long-term changes of sediment supply and of environmental parameters like climate and vegetation. However, most studies on alluvial fans are restricted to selective surface analysis and almost no studies exist which aim to clear the subsurface geometry of an alluvial fan in total. Our study is embedded in the SedyMONT research program within the TOPO-EUROPE framework and aims to clarify the subsurface structure of an alluvial fan by a time-controlled 3D architectural model. The Illgraben fan is located in the Central Alps of Switzerland within the Rhone valley and covers an area of about 6.5 km2. Currently construction works for a highway cuts through the fan exposing its deposits (mainly gravel and diamicton) up to 15 m depth and therefore offers the unique opportunity to link ground penetrating radar (GPR) investigations with quantitative outcrop analysis. GPR measurements on the Illgraben fan have been carried out at two different scales: (i) a fan-wide scale with about 80 km radar sections forming a half spiderweb pattern to identify the fundamental architecture of the fan (using 100 MHz and 40 MHz antenna), and (ii) four orthogonal grids of about 50 m x 100 m for detailed architectural analysis (using a 200 MHz antenna). Penetration depth was up to 15 m for high and low frequency antennas. The radargrams were processed, georeferenced and transferred into a 3D-modeling software (GOCAD®) to map radar facies units. By means of quantitative sedimentological analyses and precisely scaled photo panels we could translate radar facies pattern into sedimentary facies, and interpret reflectors and their properties in terms of sedimentary units. These geobodies can be characterized in terms of volume, shape, geometrical key parameters, their spatial distribution, as well as internal sedimentary structures

  12. Constraints on Environmental Conditions on Mars during Periods of Alluvial Fan Formation: Results from Landform Evolution Modeling

    NASA Astrophysics Data System (ADS)

    Morgan, A. M.; Howard, A. D.; Moore, J. M.

    2015-12-01

    As depositional systems forming within enclosed crater basins, the Late Noachian and Hesperian -aged [1] alluvial fans on Mars (including the Peace Vallis fan in Gale crater) may be representative of the last vestiges of widespread fluvial activity on the planet's surface, an era during which the climate transitioned from a wetter early Mars to the cold and dry planet we observe today. We have constructed a landform evolution model that combines sediment transport with channel avulsion to study the evolution of a fan-forming channel network over timescales of decades to hundreds of thousands of years. We aim to address two related questions: (1) what were the characteristics of water discharge (flow magnitude and duration); and (2) what are the associated implications for the responsible climatic environment (e.g. amount and frequency of precipitation sourcing the fans). The model uses a cellular network with a grid spacing set equal to the channel width. Two end-members of sediment are transported through the channel network: gravel bedload and fine grained material that is deposited overbank as a function of distance and elevation difference from an active channel. Overbank deposition creates channel levees, which must be overtopped for the channel to undergo an avulsion. By recording the relative amounts of bedload and overbank deposition, the 3-D stratigraphy is recorded as the fan is constructed. Using measures such as channel width, relative proportions of channel versus overbank deposited sediment, and frequency of channel branching, output is statistically compared with digital elevation models that we been produced from high-resolution CTX and HiRISE stereo pairs. Our modeling suggests that the fans formed from many flow events over many thousands of years, in agreement with estimations based on geomorphological observations by [2]. We are continuing to refine the model to test for varying patterns of precipitation, duricrusts, and limits on sediment

  13. 230Th/U dating of a late Pleistocene alluvial fan along the southern San Andreas fault

    USGS Publications Warehouse

    Fletcher, Kathryn E.K.; Sharp, Warren D.; Kendrick, Katherine J.; Behr, Whitney M.; Hudnut, Kenneth W.; Hanks, Thomas C.

    2010-01-01

    U-series dating of pedogenic carbonate-clast coatings provides a reliable, precise minimum age of 45.1 ± 0.6 ka (2σ) for the T2 geomorphic surface of the Biskra Palms alluvial fan, Coachella Valley, California. Concordant ages for multiple subsamples from individual carbonate coatings provide evidence that the 238U-234U-230Th system has remained closed since carbonate formation. The U-series minimum age is used to assess previously published 10Be exposure ages of cobbles and boulders. All but one cobble age and some boulder 10Be ages are younger than the U-series minimum age, indicating that surface cobbles and some boulders were partially shielded after deposition of the fan and have been subsequently exhumed by erosion of fine-grained matrix to expose them on the present fan surface. A comparison of U-series and 10Be ages indicates that the interval between final alluvial deposition on the T2 fan surface and accumulation of dateable carbonate is not well resolved at Biskra Palms; however, the “time lag” inherent to dating via U-series on pedogenic carbonate can be no larger than ∼10 k.y., the uncertainty of the 10Be-derived age of the T2 fan surface. Dating of the T2 fan surface via U-series on pedogenic carbonate (minimum age, 45.1 ± 0.6 ka) and 10Be on boulder-top samples using forward modeling (preferred age, 50 ± 5 ka) provides broadly consistent constraints on the age of the fan surface and helps to elucidate its postdepositional development.

  14. 230Th/U dating of a late pleistocene alluvial fan along the southern san andreas fault

    USGS Publications Warehouse

    Fletcher, K.E.K.; Sharp, W.D.; Kendrick, K.J.; Behr, W.M.; Hudnut, K.W.; Hanks, T.C.

    2010-01-01

    U-series dating of pedogenic carbonate-clast coatings provides a reliable, precise minimum age of 45.1 ?? 0.6 ka (2??) for the T2 geomorphic surface of the Biskra Palms alluvial fan, Coachella Valley, California. Concordant ages for multiple subsamples from individual carbonate coatings provide evidence that the 238U-234U-230Th system has remained closed since carbonate formation. The U-series minimum age is used to assess previously published 10Be exposure ages of cobbles and boulders. All but one cobble age and some boulder 10Be ages are younger than the U-series minimum age, indicating that surface cobbles and some boulders were partially shielded after deposition of the fan and have been subsequently exhumed by erosion of fine-grained matrix to expose them on the present fan surface. A comparison of U-series and 10Be ages indicates that the interval between final alluvial deposition on the T2 fan surface and accumulation of dateable carbonate is not well resolved at Biskra Palms; however, the "time lag" inherent to dating via U-series on pedogenic carbonate can be no larger than ~10 k.y., the uncertainty of the 10Be-derived age of the T2 fan surface. Dating of the T2 fan surface via U-series on pedogenic carbonate (minimum age, 45.1 ?? 0.6 ka) and 10Be on boulder-top samples using forward modeling (preferred age, 50 ?? 5 ka) provides broadly consistent constraints on the age of the fan surface and helps to elucidate its postdepositional development. ?? 2010 Geological Society of America.

  15. Estimation of selenium concentration in shallow groundwater in alluvial fan area in Tsukui, Central Japan.

    PubMed

    Ham, Young-Sik; Tamiya, Sayaka; Choi, I-Song

    2007-02-01

    Total selenium (Se) and water-soluble Se in soil, and Se in a shallow groundwater were hydrogeochemically researched in an alluvial fan area in Tsukui, Central Japan. The water-soluble Se was estimated at average level of 2.6 +/- 1.2 microg Se kg(-1) dry soil (+/- SD, n = 25), showing less than 1% of the total Se (349-508 microg Se kg(-1) dry soil) in soil. The monthly Se concentration in groundwater was average 2.2 microg,L(-1), ranging 1.6-2.4 microg,L(-1) during 2001-2003. The Se in groundwater significantly decreased with increasing groundwater level after rainfall. This result indicated that Se-bearing water percolated with relatively low Se concentration through the soil layer. According to our prediction model of linear regression curve on the observation data, Se concentration in the groundwater was estimated to be increasing with the very low rate of 4.35 x 10(-3) microg Se L(-1),yr(-1). The hydrogeochemical research and the result of the prediction model showed that any explosive increase of Se will hardly occur in this groundwater without an anthropogenic Se contamination. PMID:16897511

  16. Integration of AIRSAR and AVIRIS data for Trail Canyon alluvial fan, Death Valley, California

    NASA Technical Reports Server (NTRS)

    Kierein-Young, Kathryn S.

    1995-01-01

    Combining quantitative geophysical information extracted from the optical and microwave wavelengths provides complementary information about both the surface mineralogy and morphology. This study combines inversion results from two remote sensing instruments, a polarimetric synthetic aperture radar, AIRSAR, and an imaging spectrometer, AVIRIS, for Trail Canyon alluvial fan in Death Valley, California. The NASA/JPL Airborne Synthetic Aperture Radar (AIRSAR) is a quad-polarization, three frequency instrument. AIRSAR collects data at C-band = 5.66 cm, L-band = 23.98 cm, and P-band = 68.13 cm. The data are processed to four-looks and have a spatial resolution of 10 m and a swath width of 12 km. The AIRSAR data used in this study were collected as part of the Geologic Remote Sensing Field Experiment (GRSFE) over Death Valley on 9/14/89. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) is a NASA/JPL instrument that flies in an ER-2 aircraft at an altitude of 20 km. AVIRIS uses four spectrometers to collect data in 224 spectral channels from 0.4 micrometer to 2.45 micrometer. The width of each spectral band is approximately 10 nm. AVIRIS collects data with a swath width of 11 km and a pixel size of 20 m. The AVIRIS data used in this study were collected over Death Valley on 5/31/92.

  17. Estimation of selenium concentration in shallow groundwater in alluvial fan area in Tsukui, Central Japan.

    PubMed

    Ham, Young-Sik; Tamiya, Sayaka; Choi, I-Song

    2007-02-01

    Total selenium (Se) and water-soluble Se in soil, and Se in a shallow groundwater were hydrogeochemically researched in an alluvial fan area in Tsukui, Central Japan. The water-soluble Se was estimated at average level of 2.6 +/- 1.2 microg Se kg(-1) dry soil (+/- SD, n = 25), showing less than 1% of the total Se (349-508 microg Se kg(-1) dry soil) in soil. The monthly Se concentration in groundwater was average 2.2 microg,L(-1), ranging 1.6-2.4 microg,L(-1) during 2001-2003. The Se in groundwater significantly decreased with increasing groundwater level after rainfall. This result indicated that Se-bearing water percolated with relatively low Se concentration through the soil layer. According to our prediction model of linear regression curve on the observation data, Se concentration in the groundwater was estimated to be increasing with the very low rate of 4.35 x 10(-3) microg Se L(-1),yr(-1). The hydrogeochemical research and the result of the prediction model showed that any explosive increase of Se will hardly occur in this groundwater without an anthropogenic Se contamination.

  18. Spatial patterns of ecohydrologic properties on a hillslope-alluvial fan transect, central New Mexico

    USGS Publications Warehouse

    Bedford, D.R.; Small, E.E.

    2008-01-01

    Spatial patterns of soil properties are linked to patchy vegetation in arid and semi-arid landscapes. The patterns of soil properties are generally assumed to be linked to the ecohydrological functioning of patchy dryland vegetation ecosystems. We studied the effects of vegetation canopy, its spatial pattern, and landforms on soil properties affecting overland flow and infiltration in shrublands at the Sevilleta National Wildlife Refuge/LTER in central New Mexico, USA. We studied the patterns of microtopography and saturated conductivity (Ksat), and generally found it to be affected by vegetation canopy and pattern, as well as landform type. On gently sloping alluvial fans, both microtopography and Ksat are high under vegetation canopy and decay with distance from plant center. On steeper hillslope landforms, only microtopography was significantly higher under vegetation canopy, while there was no significant difference in Ksat between vegetation and interspaces. Using geostatistics, we found that the spatial pattern of soil properties was determined by the spatial pattern of vegetation. Most importantly, the effects of vegetation were present in the unvegetated interspaces 2-4 times the extent of vegetation canopy, on the order of 2-3??m. Our results have implications for the understanding the ecohydrologic function of semi-arid ecosystems as well as the parameterization of hydrologic models. ?? 2007 Elsevier B.V. All rights reserved.

  19. Quaternary alluvial fans of Ciudad Juárez, Chihuahua, northern México: OSL ages and implications for climatic history of the region

    USGS Publications Warehouse

    Zúñiga de León, David; Kershaw, Stephen; Mahan, Shannon

    2016-01-01

    Alluvial fans formed from sediments derived from erosion of the Juárez Mountains in northernmost México have a significant flood impact on the Ciudad Juárez, which is built on the fan system. The northern part of Ciudad Juárez is the most active; further south, older parts of the fan, upon which the rest of the city is built, were largely eroded by natural processes prior to human habitation and subsequently modified only recently by human construction. Three aeolian sand samples, collected from the uppermost (youngest) parts of the fan system in the city area, in places where human intervention has not disturbed the sediment, and constrain the latest dates of fan building. Depositional ages of the Quaternary alluvial fans were measured using Optically Stimulated Luminescence (OSL) on aeolian sands that have inter-fingered with alluvial fan material. These dates are: a) sample P1, 31 ka; b) sample P2, 41 ka; c) sample P3, 74 ka, between Oxygen Isotope Stages (OIS) 3 to 5. They demonstrate that fan development, in the area now occupied by the city, terminated in the Late Pleistocene, immediately after what we interpret to have been an extended period of erosion without further deposition, lasting from the Late Pleistocene to Holocene. The three dates broadly correspond to global glacial periods, implying that the cool, dry periods may reflect periods of aeolian transport in northern México in between phases that were wetter to form the alluvial fans. Alluvial fan margins inter-finger with fluvial terrace sediments derived from the Río Bravo, indicating an additional component of fan dissection by Río Bravo lateral erosion, presumed to be active during earlier times than our OSL ages, but these are not yet dated. Further dating is required to ascertain the controls on the fan and fluvial system.

  20. Long-term interactions between man and the fluvial environment - case of the Diyala alluvial fan, Iraq

    NASA Astrophysics Data System (ADS)

    Heyvaert, Vanessa M. A.; Walstra, Jan; Mortier, Clément

    2014-05-01

    The Mesopotamian alluvial plain is dominated by large aggradading river systems (the Euphrates, Tigris and their tributaries), which are prone to avulsions. An avulsion can be defined as the diversion of flow from an existing channel onto the floodplain, eventually resulting in a new channel belt. Early civilizations depended on the position of rivers for their economic survival and hence the impact of channel shifts could be devastating (Wilkinson 2003; Morozova 2005; Heyvaert & Baeteman 2008). Research in the Iranian deltaic part of the Mesopotamian plain has demonstrated that deliberate human action (such as the construction of irrigation canals and dams) triggered or obstructed the alluvial processes leading to an avulsion on fluvial megafans (during preconditioning, triggering and post-triggering stages) (Walstra et al. 2010; Heyvaert et al. 2012, Heyvaert et al.2013). Thus, there is ample evidence that the present-day alluvial landscapes in the region are the result of complex interactions between natural and anthropogenic processes. Here we present a reconstruction of the Late Holocene evolution of the Diyala alluvial fan (one of the main tributaries of the Tigris in Iraq), with particular attention to the relations between alluvial fan development, changes in channel pattern, the construction of irrigation networks and the rise and collapse of societies through historic times. The work largely draws on the use of remote sensing and GIS techniques for geomorphological mapping, and previously published archaeological field data (Adams 1965). By linking archaeological sites of known age with traces of ancient irrigation networks we were able to establish a chronological framework of alluvial activity of the Diyala alluvial fan. Our results demonstrate that centralized and technologically advanced societies were able to maintain a rapidly aggradading distibutary channel system, supplying water and sediment across the entire alluvial fan. As a consequence

  1. Delineation of alluvial fans from Digital Elevation Models with a GIS algorithm for the geomorphological mapping of the Earth and Mars

    NASA Astrophysics Data System (ADS)

    Norini, Gianluca; Zuluaga, Maria Clara; Ortiz, Iris Jill; Aquino, Dakila T.; Lagmay, Alfredo Mahar F.

    2016-11-01

    Alluvial fans are prominent depositional geomorphic features present in nearly all global climates on Earth, and also found on Mars. In this study, we present a Geographic Information System (GIS) algorithm designed for the semi-automated detection of alluvial fans that are connected to their contributing upstream drainage network, from the analysis of Digital Elevation Models (DEMs). Through a combination of spatial analysis procedures, the GIS algorithm generates maps of alluvial fans and their upstream source drainage and watersheds. Tests of the algorithm in areas with well-known alluvial fans indicate that this new GIS procedure is capable of high-accuracy mapping of the fan apexes and correct delineation of fan deposits, in both arid and humid climates. Possible future applications of the GIS algorithm presented in this study include the systematic survey of alluvial fans at the local, regional and planetary scales, important for geologic hazard assessment, studies on the evolution of climate, analysis of continental sedimentary environments, understanding of the interplay between the endogenous dynamics and exogenous processes, and the evaluation of natural resources.

  2. Mapping Quaternary Alluvial Fans in the Southwestern United States based on Multi-Parameter Surface Roughness of LiDAR Topographic Data

    NASA Astrophysics Data System (ADS)

    Regmi, N. R.; McDonald, E.; Bacon, S. N.

    2012-12-01

    Quaternary alluvial fans, common landforms in hyper- to semi-arid regions, have diverse surface morphology, desert varnish accumulation, clasts rubification, desert pavement formation, soil development, and soil stratigraphy. Their age and surface topographic expression vary greatly within a single fan between adjacent fans. Numerous studies have demonstrated that the surface expression and morphometry of alluvial fans can be used as an indicator of their relative age of deposition, but only recently has there been an effort to utilize high resolution topographic data to differentiate alluvial fans with automated and quantifiable routines We developed a quantitative model for mapping the relative age of alluvial fan surfaces based on a multi-parameter surface roughness computed from 1-meter resolution LiDAR topographic data. Roughness is defined as a function of scale of observation and the integration of slope, curvature (tangential), and aspect topographic parameters. Alluvial fan roughness values were computed across multiple observation scales (3m×3m to 150m×150m moving observation windows) based on the standard deviation (STD) of slope, curvature, and aspect. Plots of roughness value versus size of observation scale suggest that the STD of each of the three topographic parameters at 7m×7m observation window best identified the signature of surface roughness elements. Roughness maps derived from the slope, curvature, and aspect at this scale were integrated using fuzzy logic operators (fuzzy OR and fuzzy gamma). The integrated roughness map was then classified into five relative morpho-stratigraphic surface age categories (active wash to ~400 ka) and statistically compared with a similar five-fold surface age map of alluvial fans developed using traditional field surveys and aerial photo interpretation. The model correctly predicted the distribution and relative surface age of ~61% of the observed alluvial fan map. The results of the multi-parameter model

  3. Modeling of Reactive Transport of Nitrate in a Heterogeneous Alluvial Fan Aquifer, San Joaquin Valley, California

    NASA Astrophysics Data System (ADS)

    Green, C. T.; Phillips, S. P.

    2005-12-01

    Fate of nitrate in an alluvial fan aquifer in the San Joaquin Valley, California, was investigated with combined laboratory analyses, field measurements, geostatistics, and flow and reactive transport modeling. In the summer of 2003, groundwater wells and lysimeters were installed along a 1-km transect extending upgradient from the Merced River through an unfarmed riparian zone, a corn field, and an orchard. Groundwater levels have been monitored continuously. Saturated and unsaturated pore waters were analyzed quarterly for nutrients, anions, and cations. Sediment core samples from above and below the water table were analyzed for organic matter, nutrients, inorganic chemistry, and potential denitrification using denitrification enzyme assays (DEA's) based on the acetylene block technique. Curve fitting of DEA's provided core-scale estimates of microbial populations and growth coefficients. DEA biomass was similar to values obtained with the most probable number technique. Growth coefficients were found to be relatively uniform across the site, while biomass varied by several orders of magnitude. Age dates estimated from Chlorofluorocarbon (CFC) and Sulfur Hexafluoride (SF6), together with analyses of nitrogen species and excess nitrogen gas, provided approximate aquifer-scale, zero-order denitrification rates. The field and laboratory measurements served as input for geostatistical realizations of sediment properties and simulations of reactive transport of nitrate in the saturated zone. Analyses of cores, drillers' logs, and previous interpretations of the local geology were used to generate transition probability models of hydrofacies distributions within Holocene alluvium and pre-Holocene fans, and maps of the boundaries between these stratigraphic sequences. Multiple 3-D realizations were created and ranked based on lateral and vertical bulk-flow properties. For realizations representing a range of geological conditions, 3-D flow was computed with boundary

  4. Applying Model Simulation to Identify The Importance of Protecting Groundwater Recharge Area - A Case Study of Choshuihsi Alluvial Fan, Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, Jui-Er; Huang, Chih-Chao; Wang, Yun-Shuen; Tsai, Jui-Pin; Chang, Liang-Cheng; Chen, Yu-Wen; Chen, You-Cheng; Wang, Yun-Chih

    2013-04-01

    Groundwater is an important source of water supply, especially for areas lacking in surface water. Many countries have delineated recharge areas to protect groundwater resources. If the areas were not protected, the groundwater quantity and quality would be affected because of human activities. To understand the importance of recharge areas, this study applied MODFLOW and MODPATH to qualify the effects after a recharge area was polluted. This study developed a steady state groundwater simulation model consisting of three aquifers to simulate the groundwater flow of Choshuihsi Alluvial Fan. The simulation heads from MODFLOW were used as input into MODPATH to estimate concentration field. The initial condition of MODPATH was that the contamination particles were distributed on the surface of the shallow aquifer inside the recharge area and the simulation period was set as 200 years. Results shows that parts of the particles flow into the deep aquifers and parts of them flow into the distal-fan of the shallow aquifer 200 years. The result also shows that 22.2%, 45.3% and 22.4% of the three aquifers were polluted, respectively. The second aquifer was polluted widest, this is because the confining bed at mid-fan and distal-fan between first aquifer and second aquifer were well developed. This caused the recharge of second aquifer to rely on the lateral recharge from recharge area and so does third aquifer. Furthermore, the large amount of pumpage at distal-fan of second aquifer caused groundwater level to lower. This situation makes a higher head difference between top-fan and distal-fan of second aquifer. Therefore, the contamination from recharge area has more opportunity to be transported to distal-fan.

  5. Hydrogeologic facies characterization of an alluvial fan near Fresno, California, using geophysical techniques

    USGS Publications Warehouse

    Burow, Karen R.; Weissmann, G.S.; Miller, R.D.; Placzek, Gary

    1997-01-01

    DBCP (1,2-dibromo-3-chloropropane) contamination in the sole source aquifer near Fresno, California, has significantly affected drinking-water supplies. Borehole and surface geophysical data were integrated with borehole textural data to characterize the Kings River alluvial fan sediments and to provide a framework for computer modeling of pesticide transport in ground water. Primary hydrogeologic facies units, such as gravel, coarse sand or gravel, fine sand, and silt and clay, were identified in cores collected from three borings located on a 4.6-kilometer transect of multilevel monitoring wells. Borehole geophysical logs collected from seven wells and surface geophysical surveys were used to extrapolate hydrogeologic facies to depths of about 82meters and to correlate the facies units with neighboring drilling sites. Thickness ranged from 0.3to 13 meters for sand and gravel units, and from 0.3 to 17 meters for silt and clay. The lateral extent of distinct silt and clay layers was mapped using shallow seismic reflection and ground-penetrating radar techniques. About 3.6 kilometers of seismic reflection data were collected; at least three distinct fine-grained layers were mapped. The depth of investigation of the seismic survey ranged from 34 to 107 meters below land surface, and vertical resolution was about 3.5 meters. The ground-penetrating radar survey covered 3.6kilometers and imaged a 1.5-meters thick, continuous fine-grained layer located at a depth of about 8 meters. Integrated results from the borehole sediment descriptions and geophysical surveys provided a detailed characterization over a larger areal extent than traditional hydrogeologic methods alone.

  6. Uranium-series comminution ages of continental sediments: Case study of a Pleistocene alluvial fan

    SciTech Connect

    Lee, Victoria E.; DePaolo, Donald J.; Christensen, John N.

    2010-04-30

    Obtaining quantitative information about the timescales associated with sediment transport, storage, and deposition in continental settings is important but challenging. The uranium-series comminution age method potentially provides a universal approach for direct dating of Quaternary detrital sediments, and can also provide estimates of the sediment transport and storage timescales. (The word"comminution" means"to reduce to powder," reflecting the start of the comminution age clock as reduction of lithic parent material below a critical grain size threshold of ~;;50 mu m.) To test the comminution age method as a means to date continental sediments, we applied the method to drill-core samples of the glacially-derived Kings River Fan alluvial deposits in central California. Sediments from the 45 m core have independently-estimated depositional ages of up to ~;;800 ka, based on paleomagnetism and correlations to nearby dated sediments. We characterized sequentially-leached core samples (both bulk sediment and grain size separates) for U, Nd, and Sr isotopes, grain size, surface texture, and mineralogy. In accordance with the comminution age model, where 234U is partially lost from small sediment grains due to alpha recoil, we found that (234U/238U) activity ratios generally decrease with age, depth, and specific surface area, with depletions of up to 9percent relative to radioactive equilibrium. The resulting calculated comminution ages are reasonable, although they do not exactly match age estimates from previous studies and also depend on assumptions about 234U loss rates. The results indicate that the method may be a significant addition to the sparse set of available tools for dating detrital continental sediments, following further refinement. Improving the accuracy of the method requires more advanced models or measurements for both the recoil loss factor fa and weathering effects. We discuss several independent methods for obtaining fa on individual samples

  7. Modeling analysis of ground water recharge potential on alluvial fans using limited data.

    PubMed

    Munévar, A; Mariño, M A

    1999-01-01

    A modeling approach is developed to evaluate the potential for artificial recharge on alluvial fans in the Salinas Valley, California, using limited data of soil texture, soil hydraulic properties, and interwell stratigraphy. Promising areas for surface recharge are identified and mapped on a broad-scale using soil surveys, geologic investigations, permeability tests, and seasonal ground water response to rainfall and runoff. Two-dimensional representations of the vadose zone at selected sites are then constructed from drillers'logs and soil material types are estimated. Next, hydraulic properties are assigned to each soil material type by comparing them to laboratory-tested cores of similar soils taken from one site. Finally, water flow through the vadose zone is modeled in two dimensions at seven sites using a transient, finite-difference, variably saturated flow model. Average infiltration rates range from 0.84 to 1.54 cm/hr and recharge efficiency, the percentage of infiltrated water that reaches the water table, varies from 51% to 79%. Infiltration rates and recharge efficiency are found to be relatively insensitive to recharge basin ponding depth due to the thickness of the vadose zones modeled (31 to 84 m). The impact of artificial recharge on the Salinas Valley ground water basin is investigated by simulating the regional ground water response to surface spreading and streamflow augmentation with a recently calibrated, finite-element, ground water-surface water model for the basin. It was determined that a combined approach of surface recharge and streamflow augmentation significantly reduces the state of ground water overdraft and, to a lesser extent, reduces the rate of sea water intrusion. PMID:19125917

  8. Modeling analysis of ground water recharge potential on alluvial fans using limited data.

    PubMed

    Munévar, A; Mariño, M A

    1999-01-01

    A modeling approach is developed to evaluate the potential for artificial recharge on alluvial fans in the Salinas Valley, California, using limited data of soil texture, soil hydraulic properties, and interwell stratigraphy. Promising areas for surface recharge are identified and mapped on a broad-scale using soil surveys, geologic investigations, permeability tests, and seasonal ground water response to rainfall and runoff. Two-dimensional representations of the vadose zone at selected sites are then constructed from drillers'logs and soil material types are estimated. Next, hydraulic properties are assigned to each soil material type by comparing them to laboratory-tested cores of similar soils taken from one site. Finally, water flow through the vadose zone is modeled in two dimensions at seven sites using a transient, finite-difference, variably saturated flow model. Average infiltration rates range from 0.84 to 1.54 cm/hr and recharge efficiency, the percentage of infiltrated water that reaches the water table, varies from 51% to 79%. Infiltration rates and recharge efficiency are found to be relatively insensitive to recharge basin ponding depth due to the thickness of the vadose zones modeled (31 to 84 m). The impact of artificial recharge on the Salinas Valley ground water basin is investigated by simulating the regional ground water response to surface spreading and streamflow augmentation with a recently calibrated, finite-element, ground water-surface water model for the basin. It was determined that a combined approach of surface recharge and streamflow augmentation significantly reduces the state of ground water overdraft and, to a lesser extent, reduces the rate of sea water intrusion.

  9. Organic matter sources and transport in an annually flooded alluvial fan, the Okavango Delta, Botswana.

    NASA Astrophysics Data System (ADS)

    Mladenov, N.; McKnight, D.; Wolski, P.

    2002-12-01

    The Okavango Delta of northwestern Botswana is a large inland delta and alluvial fan consisting of over 25,000 square kilometers of permanently and seasonally flooded wetland. Surface waters of the seasonal swamp contain high concentrations of dissolved organic matter (DOM) which vary significantly during inundation by the annual flood. Dissolved organic carbon (DOC), the largest pool of organic carbon in Okavango Delta waters, constitutes an important component of the carbon cycle and energy balance in water systems. Results from water chemistry sampling indicate flushing of DOC during the rising limb of the hydrograph and a dilution/consumption effect on DOC during the peak flood. This increase in DOC concentrations with the onset of flood correlates with an increase in conductivity, suggesting that two dominant hydrologic mechanisms are responsible: the concentrating of dissolved ions in the groundwater by evapotranspiration and the release of dissolved ions from the groundwater during flood and recharge of the groundwater aquifer. In the absence of surface inflows, the water table drops by 1.5 to 2 meters due to transpiration, and ions become so concentrated that the groundwater is saline. Inundation of the Okavango Delta by the annual flood replenishes the groundwater aquifer and mobilizes DOM. We postulate that DOM and ions are flushed from sediment interstitial waters with the onset of the flood. A decrease in conductivity and DOC concentrations at peak flood indicates a "dilution" effect and an increase in zooplankton concentrations at peak flood suggests consumption of newly released organic matter by zooplankton and higher trophic organisms. Spectral properties of fulvic acids isolated from filtered water samples were also analyzed and show that the sources of organic matter vary significantly between perennial and seasonal swamp areas.

  10. The impact of Quaternary sea-level and climatic change on coastal alluvial fans in the Cabo de Gata ranges, southeast Spain

    NASA Astrophysics Data System (ADS)

    Harvey, Adrian M.; Silva, Pablo G.; Mather, Anne E.; Goy, Jose L.; Stokes, Martin; Zazo, Cari

    1999-05-01

    Conventionally, a fall in base level is seen as stimulating incision into the distal zones of alluvial fans. In the Cabo de Gata ranges of southeast Spain evidence exists to the contrary. Two sets of Quaternary coastal alluvial fans demonstrate the interaction between climatically-driven variations in the supply of sediment and eustatically-driven changes in base level. The fans are supplied from Miocene volcanic terrain within which no evidence can be found for major tectonic deformation during the period of fan development. The evolution of the east-coast fans has been affected by variations in sediment supply and changes in sea level. The west-coast fans were buffered from the effects of changes in sea level by coastal barriers. Three phases of past sedimentation can be identified on the fans. These can be differentiated on the basis of field observations of soil profiles (particularly colour of the B horizons and accumulation of CaCO 3), and laboratory analyses of sequential iron oxide extractions and magnetic mineral properties. The two earlier (major) sedimentation phases were coincident with global glacials (>ca. 135 ka and ca. 85-10 ka, based on the stratigraphy and uranium/thorium dating of the coastal sediments). High sea levels during the intervening interglacial and during the Holocene caused erosion of the distal zones of the east-coast fans which led to channel incision into the fan surfaces. On the west-coast fans no such incision occurred, simply proximal incision by small fanhead trenches. The youngest (relatively minor) phase of fan sedimentation has occurred during the Holocene. These contrasting contexts have produced differing styles of fans, with telescopic fan morphology on the east-coast and stacked morphology on the west-coast fans. The differences are reflected in the fan profiles, with steeper gradients dominating the east-coast fans, and extensive lower gradient distal surfaces on the west-coast fans. Fan morphometry, based on analysis

  11. Alluvial fan facies in Death Valley: Contrasts with fluvial gravels and implications for the interpretation of ancient fan'' gravels

    SciTech Connect

    Middleton, G.V. . Dept. of Geology)

    1993-03-01

    Sedimentary environments in Death Valley belong to three major groups: fans, washes, and playas. Fans in Death Valley include both diamicts and bedded gravels. Seven facies may be recognized. The diamicts include: (1) matrix-rich, coarse wackestones; (2) thin, matrix-rich, fine wackestones, that may show grading; (3) matrix-poor, coarse packstones, transitional to wackestones. The bedded facies include: (4) weakly bedded, poorly sorted packstones or grainstones, that show patchy imbrication, and cut-and-fill structures; (5) packed, imbricated cobble lenses, generally interbedded in facies 4; (6) distinctly bedded gravels, that are better bedded, finer and better sorted, and show better imbrication than facies 4, but still do not show clear separation of sand and gravel beds; (7) backfill cross-bedded gravels. Sand beds are not seen in fan deposits. Sand is present in eolian deposits of the playa, as plane-laminated, back-eddy deposits in Death Valley Wash, and as laminated or rippled sand in the Amargosa River, which drains into the south end of Death Valley. The most remarkable features of the fan and wash deposits are the very weak segregation of sand and gravel, and the absence of any lower flow-regime structures produced by ripples or dunes. During floods, the slope of fan and wash surfaces is steep enough to produce upper regime flows. Most fans in Death Valley itself are not strongly dominated by debris flow deposits (diamicts). Within a fan, facies vary little from proximal to distal regions, but may differ strongly from facies seen in adjacent fans.

  12. Supercritical sheetflood deposits on the volcaniclastic alluvial fan: the Cretaceous upper Daeri Member, Wido Island, Korea

    NASA Astrophysics Data System (ADS)

    Gul Hwang, In; Gihm, Yong Sik; Kim, Min Cheol

    2016-04-01

    The upper Daeri Member is composed of subaerial primary and resedimented pyroclastic deposits. The upper Daeri Member accumulated under influence of tectonic subsidence, and the basin was divided into four blocks (Block 1 to 4) by intrabasinal normal faults (Fault A to C). Vertical separation of Fault B is estimated about 250 m and provided sufficient accommodation space on Block 3 with intrabasinal physiographic relief, resulting in conformable stacking of the upper Daeri Member on a volcaniclastic alluvial fan. The welded pumiceous lapilli tuff (primary one) was deposited by a pyroclastic density current during an explosive volcanic eruption. After the eruption, the resedimented pyroclastic deposits were deposited by episodic sediment gravity flows and are intercalated with the reddish, homogeneous mudstones. In Block 3 the resedimented pyroclastic deposits show an abrupt decrease in ten largest lithic clasts from within 3 km away from Fault B, reflecting rapid waning of parental sediment gravity flows. A wavy bedded lapilli tuff is one of the lithofacies of the resedimented pyroclastic deposits. The wavy bedded lapilli tuff is composed of symmetrical or nearly-symmetrical, wavy stratifications, forming undulatory bed geometry. The wavy stratifications are recognized by distinctive alternations of few cm to 10 cm thick, lapilli-rich and ash-rich layers. Beds of the wavy bedded lapilli tuff are 0.1 to 2 m thick (estimated in crests) and range in wavelength 1.3 m to 12 m (ave. 8 m). Both amplitude and wavelength gradually decrease away from Fault B. The wavy bedded lapilli tuff can laterally be traced over 90 m. Based on undulatory bed geometry and wavy stratifications, the wavy bedded lapilli tuff is interpreted as antidune bedforms, formed by supercritical sheetfloods. The symmetrical or nearly symmetrical wavy stratifications are due to maintenance of stationary state of standing waves of the sheetfloods. A down current decrease in both wavelength and thickness

  13. An integrated approach to flood hazard assessment on alluvial fans using numerical modeling, field mapping, and remote sensing

    USGS Publications Warehouse

    Pelletier, J.D.; Mayer, L.; Pearthree, P.A.; House, P.K.; Demsey, K.A.; Klawon, J.K.; Vincent, K.R.

    2005-01-01

    Millions of people in the western United States live near the dynamic, distributary channel networks of alluvial fans where flood behavior is complex and poorly constrained. Here we test a new comprehensive approach to alluvial-fan flood hazard assessment that uses four complementary methods: two-dimensional raster-based hydraulic modeling, satellite-image change detection, fieldbased mapping of recent flood inundation, and surficial geologic mapping. Each of these methods provides spatial detail lacking in the standard method and each provides critical information for a comprehensive assessment. Our numerical model simultaneously solves the continuity equation and Manning's equation (Chow, 1959) using an implicit numerical method. It provides a robust numerical tool for predicting flood flows using the large, high-resolution Digital Elevation Models (DEMs) necessary to resolve the numerous small channels on the typical alluvial fan. Inundation extents and flow depths of historic floods can be reconstructed with the numerical model and validated against field- and satellite-based flood maps. A probabilistic flood hazard map can also be constructed by modeling multiple flood events with a range of specified discharges. This map can be used in conjunction with a surficial geologic map to further refine floodplain delineation on fans. To test the accuracy of the numerical model, we compared model predictions of flood inundation and flow depths against field- and satellite-based flood maps for two recent extreme events on the southern Tortolita and Harquahala piedmonts in Arizona. Model predictions match the field- and satellite-based maps closely. Probabilistic flood hazard maps based on the 10 yr, 100 yr, and maximum floods were also constructed for the study areas using stream gage records and paleoflood deposits. The resulting maps predict spatially complex flood hazards that strongly reflect small-scale topography and are consistent with surficial geology. In

  14. Monitoring the lateral channel movements on the alluvial fan of Wadi Feiran drainage basin, South Sinai, Egypt using multi-temporal satellite imagery

    NASA Astrophysics Data System (ADS)

    Hermas, E. A.; Abou El-Magd, I. H.; Saleh, A. S.

    2010-08-01

    Human activities triggered various lateral channel movements over the alluvial fan of Wadi Feiran drainage basin, south Sinai, Egypt. Landsat TM images dated 1986, 1996, and 2001, along with a SPOT 4 XS image dated 2006 were acquired to monitor the lateral channel movement on the alluvial fan of Wadi Feiran through the last two decades. The lateral channel movements have been initiated by the channel avulsion of the incised channel of the alluvial fan as a result of obstructing the flow by developing a man-made barrier from the accumulated flood debris in the early years of 1990(s). The man-made barrier had evolved into an elevated concrete road of 3.75 m height with two culverts underneath directly south the fan apex by March 2007. These human activities enforced the incised channel to avulse in a new location leaving the original path and the active depositional lobe of the fan abandoned. Under the influence of successive flash flood events through the last twenty years, channel aggradations occurred resulting in channel braiding and channel widening processes in the reaches of the new formed distributary channels. The channel widening processes occurred on the expense of the inactive fan lobes located within and south the reaches of the new distributary channels. Observing the southward lateral growth of the reaches of the new formed distributary channels implies the possibility of forming a new active depositional lobe that could be merged with the abandoned depositional lobe of the fan.

  15. Using direct current resistivity sounding and geostatistics to aid in hydrogeological studies in the Choshuichi alluvial fan, Taiwan.

    PubMed

    Yang, Chieh-Hou; Lee, Wei-Feng

    2002-01-01

    Ground water reservoirs in the Choshuichi alluvial fan, central western Taiwan, were investigated using direct-current (DC) resistivity soundings at 190 locations, combined with hydrogeological measurements from 37 wells. In addition, attempts were made to calculate aquifer transmissivity from both surface DC resistivity measurements and geostatistically derived predictions of aquifer properties. DC resistivity sounding data are highly correlated to the hydraulic parameters in the Choshuichi alluvial fan. By estimating the spatial distribution of hydraulic conductivity from the kriged well data and the cokriged thickness of the correlative aquifer from both resistivity sounding data and well information, the transmissivity of the aquifer at each location can be obtained from the product of kriged hydraulic conductivity and computed thickness of the geoelectric layer. Thus, the spatial variation of the transmissivities in the study area is obtained. Our work is more comparable to Ahmed et al. (1988) than to the work of Niwas and Singhal (1981). The first "constraint" from Niwas and Singhal's work is a result of their use of linear regression. The geostatistical approach taken here (and by Ahmed et al. [1988]) is a natural improvement on the linear regression approach. PMID:11916121

  16. Analysis of Nitrogen Pollution Load by Domestic Waste Water Treatment in the Tedori River Alluvial Fan Areas

    NASA Astrophysics Data System (ADS)

    Maruyama, Toshisuke; Noto, Fumikazu; Takahashi, Tsuyoshi; Tsuchihara, Takeo; Tanaka, Tadashi

    An evaluation of the environment nitrogen pollution load with regard to domestic waste water treatment on the Tedori River Alluvial Fan Areas was conducted. The literature-based water quality data collected before and after the treatment and the basic outflow pollution unit was determined for the several water treatment systems. Next these data were applied for the entire alluvial fan areas resulting in an estimated total nitrogen pollution load of as 186 ton/year. 58% of the total nitrogen pollution load was estimated to be from the private residences that were not connected to the public sewage system (connecting ratio 90.5%) which thus had relation to the pollution of groundwater and water quality in the drainage canal in the region under consideration. The nitrogen pollution load was higher in the urban area more than the rural. The rural domestic waste water system accounted for about 17.9% of the total pollution load, which carried a high probability of groundwater pollution because of seepage or percolation. The pollution load from the direct flow of the public sewage treatment water to the middle stream of the Tedori River, together with the water from small companies and untreated water from local family dwellings made up about 3-10% of total pollution.

  17. Timing and distribution of alluvial fan sedimentation in response to strengthening of late Holocene ENSO variability in the Sonoran Desert, southwestern Arizona, USA

    NASA Astrophysics Data System (ADS)

    Bacon, Steven N.; McDonald, Eric V.; Caldwell, Todd G.; Dalldorf, Graham K.

    2010-05-01

    The integration of geomorphic mapping, soil stratigraphy, and radiocarbon dating of alluvial deposits offers insight to the timing, magnitude, and paleoclimatic context of Holocene fan sedimentation near Yuma, Arizona. Mapping of 3400 km 2 indicates about 10% of the area aggraded in the late Holocene and formed regionally extensive alluvial fan and alluvial plain cut-and-fill terraces. Fan deposits have weakly developed gravelly soils and yielded a date of 3200-2950 cal yr BP from carbonized wood. Alluvial plain deposits have weakly developed buried sandy soils and provided a date of 2460-2300 cal yr BP from a terrestrial snail shell. Precipitation records were analyzed to form historical analogues to the late Holocene aggradation and to consider the role of climatic variability and extreme hydrologic events as drivers of the sedimentation. The historical precipitation record indicates numerous above-average events correlated to the Southern Oscillation Index (SOI) in the region, but lacks any significant reactivation of alluvial fan surfaces. The timing of aggradation from 3200 to 2300 cal yr BP correlates well with other paleoclimatic proxy records in the southwestern U.S. and eastern Pacific region, which indicate an intensification of the El Niño-Southern Oscillation (ENSO) climatic pattern and rapid climate change during this period.

  18. Debris flood hazard documentation and mitigation on the Tilcara alluvial fan (Quebrada de Humahuaca, Jujuy province, North-West Argentina)

    NASA Astrophysics Data System (ADS)

    Marcato, G.; Bossi, G.; Rivelli, F.; Borgatti, L.

    2012-06-01

    For some decades, mass wasting processes such as landslides and debris floods have been threatening villages and transportation routes in the Rio Grande Valley, named Quebrada de Humauhuaca. One of the most significant examples is the urban area of Tilcara, built on a large alluvial fan. In recent years, debris flood phenomena have been triggered in the tributary valley of the Huasamayo Stream and reached the alluvial fan on a decadal basis. In view of proper development of the area, hazard and risk assessment together with risk mitigation strategies are of paramount importance. The need is urgent also because the Quebrada de Humahuaca was recently included in the UNESCO World Cultural Heritage. Therefore, the growing tourism industry may lead to uncontrolled exploitation and urbanization of the valley, with a consequent increase of the vulnerability of the elements exposed to risk. In this context, structural and non structural mitigation measures not only have to be based on the understanding of natural processes, but also have to consider environmental and sociological factors that could hinder the effectiveness of the countermeasure works. The hydrogeological processes are described with reference to present-day hazard and risk conditions. Considering the socio-economic context, some possible interventions are outlined, which encompass budget constraints and local practices. One viable solution would be to build a protecting dam upstream of the fan apex and an artificial channel, in order to divert the floodwaters in a gully that would then convey water and sediments into the Rio Grande, some kilometers downstream of Tilcara. The proposed remedial measures should employ easily available and relatively cheap technologies and local workers, incorporating low environmental and visual impacts issues, in order to ensure both the future conservation of the site and its safe exploitation for inhabitants and tourists.

  19. Sedimentary facies and tectonic implications of Lower Mesozoic alluvial-fan conglomerates of the Newark Basin, northeastern United States

    NASA Astrophysics Data System (ADS)

    Tevfik Arguden, A.; Rodolfo, Kelvin S.

    1986-12-01

    Upper Triassic to Lower Jurassic conglomeratic sequences of the Passaic and succeeding formations along the northwest-bounding fault of the Newark Basin in eastern Pennsylvania, New Jersey and New York, have six relatively distinct lithofacies that record continental basin filling under arid to semi-arid conditions. Matrix-supported conglomerates represent debris flows: clast-supported conglomerates are hyperconcentrated steamflood deposits. Coarse pebbly sandstones represent a braided-stream channel facies, and medium-to-fine sandstones are interpreted as a sheetflood facies, deposits normally succeeded by thin mudstones of a waning-flood facies. Associated with such mudstones at Milford, New Jersey is a sixth, pedogenic facies: caliches that document pauses in deposition. Areal lithologic variations and analyses of vertical changes, including Markov analyses of facies transitions, document intermittent, cyclical debris flows and streamfloods on alluvial fans prograding into the basin. The intermittency is best accounted for by episodic, localized tectonic rejuvenation of fan provenance at the northwest bounding fault of the Newark Basin during the late Triassic to early Jurassic, the final phase of basin filling. Penecontemporaneity of tectonism and fan deposition is corroborated by deformation of some conglomerate clasts which transmitted tectonic stresses to each other before their enclosing matrices were completely lithified. Some pebbles and cobbles are shattered at points of contact, and clasts of relatively soft lithologies became pocked while grinding against harder fragments during post-depositional tectonic episodes.

  20. New morpho-stratigraphic constraints for the evolution of the alluvial fan system along the northern slopes of the Taburno-Camposauro Mountains (Calore River basin, Southern Italy)

    NASA Astrophysics Data System (ADS)

    Leone, Natalia; Amato, Vincenzo; Aucelli, Pietro P. C.; Cesarano, Massimo; Filocamo, Francesca; Petrosino, Paola; Rosskopf, Carmen M.; Valente, Ettore; Giralt, Santiago; Casciello, Emilio

    2016-04-01

    The Lower Calore River Valley is a morphostructural depression located in the inner sector of the Campanian Apennine, between the Taburno-Camposauro and the Matese carbonate massifs. The river is the main left tributary of the Volturno River, it has a meandering channel partially structural-controlled. Numerous morphotectonic clues and historical seismicity data suggest that this part of the Apennine chain was particularly active during the late-Quaternary. In detail, the valley is E-W oriented and presents an asymmetry of the opposed valley slopes. The left side, corresponding to the northern flank of the Camposauro massif, is characterized by a steep slope (70°-35°), partially controlled by a ~E-W oriented fault system, and by a wide less-inclined piedmont aggradation zone. The latter started growing since middle Pleistocene, with the deposition of alluvial fans and slope deposits over the well cemented early Pleistocene breccias of Laiano Synthem. The alluvial fan deposition has been active until present giving rise to three main generations of alluvial fans. The right side of the valley, instead, is characterized by seven orders of fluvial terraces, both of erosional and depositional origin. The quaternary morpho-stratigraphic evolution of alluvial fans and fluvial terraces has been strongly conditioned by the interaction of tectonic phases and climatic variations. A detailed geomorphological study (1:5.000 in scale) was carried out with the aim to map the main depositional and erosional fluvial landforms and to identify the main tectonic lineaments of the area. A detailed field survey allowed to better define the stratigraphic and paleoenvironmental context in which the alluvial deposits developed and also to find chrono-stratigraphic markers. Tephra-stratigraphic analyses were performed on pyroclastic deposits interbedded into the alluvial fan and fluvial successions. At the moment the age of the first generation of alluvial fans is still under

  1. Using the Bidirectional Reflectance Distribution Function (BRDF) for remotely mapping surface roughness on alluvial fans: A comparison of Death Valley, CA to Mojave Crater on Mars

    NASA Astrophysics Data System (ADS)

    Doyle, S. L.; Wilkinson, M. J.; Scuderi, L. A.; Weissmann, G. S.; Scuderi, L. J.

    2011-12-01

    The Bidirectional Reflectance Distribution Function (BRDF) describes how incoming light from a given direction is reflected from specific surfaces in response to different incoming solar radiation angles. The amount and directionality of reflected light is a function of surface roughness and orientation. The goal of this study is to assess whether a BRDF based approach may be applicable for creating surface roughness maps for Martian alluvial fans. Landsat 7 satellite imagery is used to make classifications of surfaces with different roughness and spectral properties for alluvial fan surfaces in Death Valley, California. The resulting classes have been interpreted to represent surfaces of different ages and also different deposit types. In Death Valley, older surfaces are classified based on the amount of shadowing due to gully formation, differences in the amount of surface smoothness from desert pavement formation, and desert varnish color variations. In contrast, the most recently formed surfaces have an assemblage of classes that represent surface deposits of different grain size and sorting, as well as different landform types - incised channels and elevated bars. Many Death Valley fans have a telescoping morphology where progressively younger surfaces reach basin-ward. This is more evident on some fans using a BRDF classification. A similar map was made for depositional landforms within Mojave Crater on Mars, identified as sub-kilometer alluvial fans by Williams and Malin (2008). These alluvial fans are the youngest found on Mars (Amazonian age) and have topographic similarities to fans in the southwestern US. Any geomorphic similarities between Death Valley fans and those within Mojave Crater can be assessed using surface roughness. Imagery from both the High Resolution Imaging Experiment (HiRISE) and Context Camera (CTX) onboard the Mars Reconnaissance Orbiter (MRO) were used to compare differences in spatial resolution on BRDF classifications. The

  2. Non-Stationary Hydrostratigraphic Model of Cross-Cutting Alluvial Fans

    NASA Astrophysics Data System (ADS)

    Meirovitz, C.; Fogg, G. E.; Weissmann, G. S.; Labolle, E.; Sagar, J.; Roll, L.

    2009-12-01

    The groundwater system of southern Sacramento County was formed by the glacially dominated American River fan and the non-glacial Cosumnes River fan. Recent hydrostratigraphic analysis with borehole log data shows that the American River gravelly channels not only migrated to the south, cutting into the Cosumnes sediments in the Holocene, but also did the same during the Quaternary, leaving deep, coarse grained channels embedded in what would otherwise be considered Cosumnes fan sediments. Three dimensional Markov chain models are created for each of the two systems using transition probability geostatistics. Each system is simulated separately and then combined to produce a regional three-dimensional representation of subsurface heterogeneity which preserves cross-cutting relationships between American River coarse grained sediments and the Cosumnes River fan. This geologic model is incorporated into a simple flow model to investigate the impact of these channels on regional groundwater flow and transport.

  3. Magnetostratigraphy of The Astronomically-forced Alluvial Fan To Lacustrine Sequences of The Teruel Basin (late Miocene, Spain)

    NASA Astrophysics Data System (ADS)

    van Dam, J.; Aziz, H. Abdul; Hilgen, F. J.; Krijgsman, W.

    During the last years, more and more examples of allocyclic, astronomical forced variations in the continental record have been documented. Sedimentary hiatuses, tra- ditionally regarded as the primary reason for the absence of clear patterns of orbital signature in the terrestrial domain, may be absent or short, given the appropriate set- ting. Spanish endoreic basins, for instance, form a ideal setting for the registration of orbital-forced climate change, as has been demonstrated for the Middle Miocene distal-alluvial fan-floodplain to lacustrine deposits of the Calatayud Basin. Astronom- ical forcing of sedimentary cycles has also been demonstrated in the Late Miocene distal alluvial fan to lacustrine sequences of the Teruel Basin. The early Late Miocene Cascante and Cañizar sections South of the town of Teruel show distinct cyclic bed- ding of red and/or green mottled mudstones alternating with white carbonate beds, whereby the alternation is mainly controlled by precession and eccentricity. The car- bonate beds are interpreted as (shallow) lake highstands, which occur in response to submergence of the alluvial fan distal plain. Small mammal teeth have been recov- ered from organic-richer layers at the base of the carbonate cycles in the Cascante and Cañizar sections. The recovery of mammal remains in terrestrial Milankovitch forced settings is crucial for several reasons: 1) it provides a first approximate age estimation for the sequence, thereby constraining other sources of temporal information such as magnetostratigraphy; 2) it infers very accurate ages of the mammal localities after as- tronomical tuning of the cyclic patterns; 3) it formulates hypotheses on the climatic regime and its variability using precise correlations to the insolation curve and in- terpretation of phase relations; and 4) it confronts the astronomically-based climatic reconstruction with the paleoecological reconstructions and faunal changes observed in the mammals themselves

  4. Drinking Water Quality Criterion - Based site Selection of Aquifer Storage and Recovery Scheme in Chou-Shui River Alluvial Fan

    NASA Astrophysics Data System (ADS)

    Huang, H. E.; Liang, C. P.; Jang, C. S.; Chen, J. S.

    2015-12-01

    Land subsidence due to groundwater exploitation is an urgent environmental problem in Choushui river alluvial fan in Taiwan. Aquifer storage and recovery (ASR), where excess surface water is injected into subsurface aquifers for later recovery, is one promising strategy for managing surplus water and may overcome water shortages. The performance of an ASR scheme is generally evaluated in terms of recovery efficiency, which is defined as percentage of water injected in to a system in an ASR site that fulfills the targeted water quality criterion. Site selection of an ASR scheme typically faces great challenges, due to the spatial variability of groundwater quality and hydrogeological condition. This study proposes a novel method for the ASR site selection based on drinking quality criterion. Simplified groundwater flow and contaminant transport model spatial distributions of the recovery efficiency with the help of the groundwater quality, hydrological condition, ASR operation. The results of this study may provide government administrator for establishing reliable ASR scheme.

  5. A possible synoptic source of water for alluvial fan formation in southern Margaritifer Terra, Mars

    NASA Astrophysics Data System (ADS)

    Grant, John A.; Wilson, Sharon A.

    2012-11-01

    The morphometry and occurrence of crater-bound fans in southern Margaritifer Terra that were active from around the Hesperian-Amazonian boundary into the Early Amazonian is consistent with emplacement related to synoptic precipitation. Precipitation, possibly occurring as snow, may have been locally influenced by topography and (or) orbital variations. It is not known how much of the total sediment inventory in the fans relates to this late activity versus possible earlier events where water may have been available from alternate sources such as impact-related melting of ground ice. Winds may have concentrated late occurring precipitation into existing relief and (or) preexisting alcoves that facilitated physical weathering to produce fine sediments later incorporated into fans. Two of the craters containing fan deposits, Holden and Eberswalde, were finalists for the MSL landing site. Results suggest that exposed and accessible fan sediments at both crater sites may record a late period of colder, drier conditions relative to early Mars that was punctuated by ephemeral water-driven activity.

  6. Geochemistry characterizations and arsenic species analysis of As-rich aquifers in the southern Choushui River alluvial fan

    NASA Astrophysics Data System (ADS)

    Lu, K.; Liu, C.; Wang, S.

    2009-12-01

    In Taiwan, Choushui River alluvial fan was an area enriched in groundwater resource. Due to the excessive usage of groundwater, long-term monitoring of local groundwater qualities was needed especially for the existence of high levels of As concentration which could cause severe damage for local residents. With the intention to characterize the compositions of high As concentration groundwater, comprehensive hydrogeochemistry of thirty-seven monitoring wells that located in the southern Choushui River alluvial fan were conducted. Furthermore, the concentrations of inorganic As species (As3+ and As5+) were also measured. High levels of bicarbonate, ammonium, arsenic and iron concentrations accompanying low concentrations of sulfate, nitrate and EH values were indicative of reducing condition. Arsenic concentrations, predominantly in the form As3+, among these wells ranged from 1.0 to 539.7 ug/L with the average concentration of 82.1 ug/L. Seven out of thirty-seven wells were characterized as salination via the Piper diagram,. Furthermore, salination was also the dominant factor affecting local groundwater quality via the factor analysis. Subsequently, Fe2+, Mn and As5+ ions among these wells were categorized into the same factor, revealing the reductive dissolution reaction of Fe and Mn hydroxides alone with the increase of As concentrations. Furthermore, the third factor comprised As3+, HCO3- and DOC concentrations indicated the microbial-mediated reduction of arsenate ion was followed by the reductive dissolution of iron oxyhydroxides. Hence, the presence of high As concentration groundwaters in this area were postulated to be related with reducing condition which enhanced the reductive dissolution of Fe minerals and the reduction

  7. Luminescence ages for alluvial-fan deposits in Southern Death Valley: Implications for climate-driven sedimentation along a tectonically active mountain front

    USGS Publications Warehouse

    Sohn, M.F.; Mahan, S.A.; Knott, J.R.; Bowman, D.D.

    2007-01-01

    Controversy exists over whether alluvial-fan sedimentation along tectonically active mountain fronts is driven by climatic changes or tectonics. Knowing the age of sedimentation is the key to understanding the relationship between sedimentation and its cause. Alluvial-fan deposits in Death Valley and throughout the arid southwestern United States have long been the subjects of study, but their ages have generally eluded researchers until recently. Most mapping efforts have recognized at least four major relative-age groupings (Q1 (oldest), Q2, Q3, and Q4 (youngest)), using observed changes in surface soils and morphology, relation to the drainage net, and development of desert pavement. Obtaining numerical age determinations for these morphologic stages has proven challenging. We report the first optically stimulated luminescence (OSL) ages for three of these four stages deposited within alluvial-fans along the tectonically active Black Mountains of Death Valley. Deposits showing distinct, remnant bar and swale topography (Q3b) have OSL ages from 7 to 4 ka., whereas those with moderate to poorly developed desert pavement and located farther above the active channel (Q3a) have OSL ages from 17 to 11 ka. Geomorphically older deposits with well-developed desert pavement (Q2d) have OSL ages ???25 ka. Using this OSL-based chronology, we note that alluvial-fan deposition along this tectonically active mountain front corresponds to both wet-to-dry and dry-to-wet climate changes recorded globally and regionally. These findings underscore the influence of climate change on alluvial fan deposition in arid and semi-arid regions. ?? 2007 Elsevier Ltd and INQUA.

  8. Fault-sourced alluvial fans and their interaction with axial fluvial drainage: An example from the Plio-Pleistocene Upper Valdarno Basin (Tuscany, Italy)

    NASA Astrophysics Data System (ADS)

    Fidolini, Francesco; Ghinassi, Massimiliano; Aldinucci, Mauro; Billi, Paolo; Boaga, Jacopo; Deiana, Rita; Brivio, Lara

    2013-05-01

    The present study deals with the fault-sourced, alluvial-fan deposits of the Plio-Pleistocene Upper Valdarno Basin (Northern Apennines, Italy). Different phases of alluvial fan aggradation, progradation and backstep are discussed as possible effects of the interaction among fault-generated accommodation space, sediment supply and discharge variations affecting the axial fluvial drainage. The Upper Valdarno Basin, located about 35 km SE of Florence, is filled with 550 m palustrine, lacustrine and alluvial deposits forming four main unconformity-bounded units (i.e. synthems). The study alluvial-fan deposits belong to the two uppermost synthems (Montevarchi and Torrente Ciuffenna synthems) and are Early to Middle Pleistocene in age. These deposits are sourced from the fault-bounded, NE margin of the basin and interfinger with axial fluvial deposits. Alluvial fan deposits of the Montevarchi Synthem consist of three main intervals: i) a lower interval, which lacks any evidence of a depositional trend and testify balance between the subsidence rate (i.e. fault activity) and the amount of sediment provided from the margin; ii) a coarsening-upward middle interval, pointing to a decrease in subsidence rate associated with an augment in sediment supply; iii) a fining-upward, upper interval (locally preserved), documenting a phase of tectonic quiescence associated with a progressive re-equilibration of the tectonically-induced morphological profile. The basin-scale unconformity, which separates the Montevarchi and Torrente Ciuffenna synthems was due to the entrance of the Arno River into the basin as consequence of a piracy. This event caused a dramatic increase in water discharge of the axial fluvial system, and its consequent embanking. Such an erosional surface started to develop in the axial areas, and propagated along the main tributaries, triggering erosion of the alluvial fan deposits. Alluvial-fan deposits of the Torrente Ciuffenna Synthem accumulated above the

  9. Evolution of the late Holocene terraces in the hanging wall of the Chihshang Fault: interactions between alluvial fan deposition and fault uplift

    NASA Astrophysics Data System (ADS)

    Chang, Q.; Lee, J.; Wang, S.; Chen, R.; Chen, Y.

    2012-12-01

    In this study, we aim at studying the interactions between alluvial fan deposition and reverse fault uplift through analyzing the genesis of the terraces and their evolution in Chihshang area. Located in eastern Taiwan, the NNE-SSW trending Longitudinal Valley is the plate suture between the Philippine Sea plate and Eurasia. The east-dipping Longitudinal Valley Fault (LVF), often on the eastern side of the valley, is the major fault of this suture zone. The Chihshang area is located in the central-southern Longitudinal Valley, where the Chihshang Fault cuts through the eastern edge of the Xinwulyu River alluvial fan, one of the major alluvial fans. The Chihshang Fault is one of the most active segments of the LVF with a continuous uplifting rate up to ~3 cm/yr. A series of fan terraces with different height distribute on the hanging wall, where the front of the alluvial fan was uplifted by the reverse fault. Because of the special geological settings of this area, by studying the evolution of the terraces we could get insights on both the deposition behavior of the alluvial fan and the long term uplift rate of Chihshang Fault, and furthermore, their interactions through the late Holocene. We used 5-m high-resolution DEM and aerial photographs to identify the terraces and characterize their geomorphic features. We also distinguished the Xinwulyu River alluvial fan terraces from other terraces formed by other tributary rivers based on the lithology of terrace deposit as well as the geomorphic characters. Several outcrops and six trenches of 3-6 m depth allow us to analyze the composition of the fan terraces and to collect dating materials. Fan terraces are distinguished into ten levels according to height difference relative to the present fan surface. Terraces belonging to same level were assumed to form at similar time period. The lower the terraces, the better the terraces preservation, and the larger the terraces surface area. Distribution of terrace is not

  10. Optically stimulated luminescence dating of Holocene alluvial fans, East Anatolian Fault System, Turkey

    NASA Astrophysics Data System (ADS)

    Dogan, Tamer; Cetin, Hasan; Yegingil, Zehra; Topaksu, Mustafa; Yüksel, Mehmet; Duygun, Fırat; Nur, Necmettin; Yegingil, İlhami

    2015-07-01

    In this study, the optically stimulated luminescence dating technique was used to determine the time of deposition of alluvial sediment samples from the Türkoğlu-Antakya segment of the East Anatolian Fault System (EAFS) in Turkey. The double-single aliquot regenerative dose protocol on fine grain samples was used to estimate equivalent doses (De). Annual dose rate was computed using elemental concentration of uranium (U) and thorium (Th) determined by using thick-source alpha counting and potassium (K) concentrations using X-ray fluorescence and/or atomic absorption spectroscopy. The environmental dose was measured in situ using α-Al2O3:C chips inside plastic tubes for a year. The two different bulk sediment samples collected from the Islahiye trench yielded ages of 4.54 ± 0.28 and 2.91 ± 0.23 ka. We also obtained a 2.60 ± 0.18 ka age for the alluvial deposit in the Kıranyurdu trench and 2.31 ± 0.14 ka age for an excavation area called Malzeme Ocağı. These ages were consistent with the corresponding calibrated Carbon-14 (14C) ages of the region. The differences between the determined ages were insufficient to clearly distinguish the disturbance event from the effects of bioturbation, biological mixing, or other sources of De variation in the region. They provide a record of alluvial aggradation in the region and may determine undocumented historical earthquake events.

  11. Physical stratigraphy and sedimentology of an alluvial fan delta complex (south Pyrenean basin, Spain)

    SciTech Connect

    Crumeyrolle, P.

    1988-08-01

    The Santa Liestra is comprised of four main stratigraphic units with a major stratigraphic unconformity separating unit 2 from unit 3. This unconformity is expressed by an abrupt facies change and large-scale shelf instability features, and it probably represents a depositional sequence boundary related to a phase of thrust movement within the Santa Liestra sequence. Field correlations on transverse cross sections through the basin show a typical foreland asymmetrical clastic wedge; these correlations also illustrate the sheet-like geometry of the fan delta-front deposits. This study of a large fan delta-front system furnishes insight into the complex interactions governing the geometry and sedimentological characteristics of potential petroleum reservoirs in foreland basin settings.

  12. Dating offset fans along the Mojave section of the San Andreas fault using cosmogenic 26Al and 10Be

    USGS Publications Warehouse

    Matmon, A.; Schwartz, D.P.; Finkel, R.; Clemmens, S.; Hanks, T.

    2005-01-01

    Analysis of cosmogenic 10Be and 26Al in samples collected from exposed boulders (n = 20) and from buried sediment (n = 3) from offset fans along the San Andreas fault near Little Rock, California, yielded ages, ranging from 16 to 413 ka, which increase with distance from their source at the mouth of Little Rock Creek. In order to determine the age of the relatively younger fans, the erosion rate of the boulders and the cosmogenic nuclide inheritance from exposure prior to deposition in the fan were established. Cosmogenic nuclide inheritance values that range between 8.5 ?? 103 and 196 ?? 103 atoms 10Be g-1 quartz were determined by measuring the concentrations and ratios of 10Be and 26Al in boulders (n = 10) and fine sediment (n = 7) at the outlet of the present active stream. Boulder erosion rate, ranging between 17 and 160 mm k.y.-1, was estimated by measuring 10Be and 26Al concentrations in nearby bedrock outcrops (n = 8). Since the boulders on the fans represent the most resistant rocks in this environment, we used the lowest rate for the age calculations. Monte Carlo simulations were used to determine ages of 16 ?? 5 and 29 ?? 7 ka for the two younger fan surfaces. Older fans (older than 100 ka) were dated by analyzing 10Be and 26Al concentrations in buried sand samples. The ages of the three oldest fans range between 227 ?? 242 and 413 ?? 185 ka. Although fan age determinations are accompanied by large uncertainties, the results of this study show a clear trend of increasing fan ages with increasing distance from the source near Little Rock Creek and provide a long-term slip rate along this section of the San Andreas fault. Slip rate along the Mojave section of the San Andreas fault for the past 413 k.y. can be determined in several ways. The average slip rate calculated from the individual fan ages is 4.2 ?? 0.9 cm yr-1. A linear regression through the data points implies a slip rate of 3.7 ?? 1.0 cm yr-1. A most probable slip rate of 3.0 ?? 1.0 cm yr-1 is

  13. Variations in rock types on alluvial fan surfaces as an indicator of source reach and geomorphic process, Fish Lake Valley, Nevada-California

    SciTech Connect

    Slate, J.L. )

    1993-04-01

    Lithologic composition of fan-surface clasts can reflect the source of alluvial fan deposits within those drainages where rock types vary with location in the basin, provided that clasts at the surface resemble the makeup of rocks within the deposit. Interpreting the reach from which deposits were derived may, in turn, be used to infer the relation of fan deposition to causal events and source-area conditions. A multiparameter study of alluvial fans in four drainage basins of Fish Lake Valley, Nevada-California, included assessing modal lithology and the lithologic ratio among three main rock types. The author tallied rock types of 100 surface pebbles described on geomorphic surfaces along 50-m-long transects oriented perpendicular to streamflow direction near the mountain fronts. Source areas for the fan deposits shifted from the Pleistocene to the late Holocene, and may be a result of changes in weathering and transport conditions. The middle and lower reach sources of the two youngest (late Holocene) units (based on 7 transects) suggest that they were deposited in response to events that were only sufficient to transport material from these areas and not the headwaters, or that insufficient material was available for transport from the headwaters. The presence of these units of apparently similar age in the four mapped areas rules out localized storms or isolated faulting events as causes of deposition. The headwater and drainage-basin wide sources of two Pleistocene fan units (based on 13 transects) indicate deposition of these units may have occurred in response to significant climatic events that weathered material in the headwaters areas and transported that material to the fans. Thus, climatic conditions or elapsed time or a combination of the two may control sources of fan deposits.

  14. Integrative geomorphological mapping approach for reconstructing meso-scale alluvial fan palaeoenvironments at Alborz southern foothill, Damghan basin, Iran

    NASA Astrophysics Data System (ADS)

    Büdel, Christian; Majid Padashi, Seyed; Baumhauer, Roland

    2013-04-01

    Alluvial fans and aprons are common depositional features in general Iranian geomorphology. The countries major cities as well as settlements and surrounding area have often been developed and been built up on this Quaternary sediment covers. Hence they periodically face the effects of varying fluvial and slope-fluvial activity occurring as part of this geosystem. The Geological Survey of Iran therefore supports considerable efforts in Quaternary studies yielding to a selection of detailed mapped Quaternary landscapes. The studied geomorphologic structures which are settled up around an endorheic basin in Semnan Province represent a typical type of landform configuration in the area. A 12-km-transect was laid across this basin and range formation. It is oriented in north-south direction from the southern saltpan, called "Kavir-e-Haj Aligholi"/"Chah-e-Jam" ("Damghan Kavir"), across a vast sandy braided river plain, which is entering from the north east direction of the city of Shahroud. At its northern rim it covers alluvial sediment bodies, which are mainly constituted by broad alluvial aprons, fed by watersheds in Alborz Mountains and having their genetic origins in Mio-/Pliocene times. During this study a fully analytical mapping system was used for developing a geodatabase capable of integrating geomorphological analyses. Therefore the system must provide proper differentiation of form, material and process elements as well as geometric separation. Hence the German GMK25 system was set up and slightly modified to fit to the specific project demands. Due to its structure it offers most sophisticated standards and scale independent hierarchies, which fit very well to the software-determinated possibilities of advanced geodatabase applications. One of the main aspects of mapping Quaternary sediments and structures is to acquire a proper description and systematic correlation and categorization of the belonging mapping-objects. Therefore the team from GSI and

  15. Tectonic significance of Upper Cretaceous alluvial-fan deposits in the Peninsular Ranges forearc basin complex, Baja California (Mexico)

    SciTech Connect

    Fulford, M.; Busby-Spera, C. )

    1990-05-01

    Recent evidence suggests that forearc basins, previously depicted as broad downwarps, may experience syndepositional faulting and/or folding. The upper Campanian El Gallo Formation, which was deposited along the northern margin of the Rosario embayment of the peninsula Ranges forearc basin complex, records tilting of the underlying arc massif basement contemporaneous with dissection of the arc source terrane. The La Escarpa member at the base of the El Gallo Formation consists of a 100-180-m thick upward-fining sequence, interpreted as a retrogradational proximal to distal alluvial-fan deposit. Overlying the La Escarpa member is the 1,000-m thick El Disecado member, which lies at the top of the El Gallo Formation and consists of sandy fluvial deposits. Conglomerate clast counts from the La Escarpa member and point-count data from sandstones throughout the El Gallo Formation show an upsection increase in granitic and metasedimentary rock fragments relative to volcanic/metavolcanic rock fragments, reflecting unroofing and progressive headward erosion of the source terranes in the Peninsular Ranges. Paleocurrent data from the La Escarpa and El Disecado members suggest a rotation of approximately 110{degree} with time, from west-northwesterly to southerly, reflecting tilting of the basin floor. This may have been accomplished by downdropping along an east-west-trending fault that divided the Rosario embayment into separate subbasins during the Cretaceous.

  16. Reconstructing the evolution of the Chamoson alluvial fan (Swiss Rhône Valley) from outcrop observations and geo-radar survey.

    NASA Astrophysics Data System (ADS)

    Boulicault, Lise; Moscariello, Andrea; Ventra, Dario; Moreau, Julien

    2014-05-01

    Following the withdrawal of the Wurmian glacier occupying the Rhône Valley (Swiss Alps), a complex of glacial sediments, alluvial fan deposits generated form tributary valleys, and lacustrine sediments were accumulated. Here, we focus on the Chamoson alluvial fan, the largest (ca. 8 km2) fan in the area , characterised by frequent floods (4 to 6 event per year) which are confined within its incised channel. The study aims to understand the spatial and temporal evolution of the fan in particular with respect to the larger trunk of the Rhône Valley. The methodology includes (1) the description of sedimentary logs and photo mosaics along both 400 metre-long walls in the incised channel, (2) a Ground Penetrating Radar (GPR) survey designed to obtain a 3D model for identifying the internal architecture and geometry of the alluvial fan complex, and (3) carbon-14 age-determinations on suitable material in order to constrain a chronological framework of the sedimentary events observed in outcrop. The Chamoson alluvial fan largely consists of a vertical stack of amalgamated waterline debris flow deposits alternated with graded gravels and coarse sandstones associated with bedload processes. Intercalated within the coarse debris flow succession, field observations revealed the presence of a ca. 2 m-thick lacustrine silty and clayey interval containing wood fragments and well-preserved fresh-water gastropod shells. The AMS 14C-dating on gastropods indicates a Late Bronze Age for the formation of these deposits. The GPR data also show the wide 3D spatial extension of a sharp horizontal reflector, which was interpreted to be the lacustrine deposit within the fan by correlation with the sedimentological logs. These lacustrine deposits are situated 40 m above the current altitude of the Rhône Valley, which may suggest a very different depositional and physiographic setting in this part of the Rhône Valley at the end of the Late Bronze Age. The finding of these extensive fine

  17. Late Quaternary landscape evolution in the Kunlun Mountains and Qaidam Basin, Northern Tibet: A framework for examining the links between glaciation, lake level changes and alluvial fan formation

    USGS Publications Warehouse

    Owen, L.A.; Finkel, R.C.; Haizhou, M.; Barnard, P.L.

    2006-01-01

    The Qaidam Basin in Northern Tibet is one of the largest hyper-arid intermontane basins on Earth. Alluvial fans, pediment surfaces, shorelines and a thick succession of sediments within the basin, coupled with moraines and associated landforms in the adjacent high mountain catchments of the Kunlun Mountains, record a complex history of Late Quaternary paleoenvironmental change and landscape evolution. The region provides an ideal natural laboratory to examine the interaction between tectonics and climate within a continent-continent collision zone, and to quantify rates of landscape evolution as controlled by climate and the associated glacial and hydrological changes in hyper-arid and adjacent high-altitude environments. Geomorphic mapping, analysis of landforms and sediments, and terrestrial cosmogenic radionuclide surface exposure and optically stimulated luminescence dating serve to define the timing of formation of Late Quaternary landforms along the southern and northwestern margins of the Qaidam Basin, and in the Burhan Budai Shan of the Kunlun Mountains adjacent to the basin on the south. These dates provide a framework that suggests links between climatic amelioration, deglaciation, lake desiccation and alluvial fan evolution. At least three glacial advances are defined in the Burham Budai Shan of the Kunlun Mountains. On the northern side of this range these occurred in the penultimate glacial cycle or early in the last glacial cycle, during the Last Glacial Maximum (LGM)/Lateglacial and during the Holocene. On the south side of the range, advances occurred during the penultimate glacial cycle, MIS-3, and possibly the LGM, Lateglacial or Holocene. Several distinct phases of alluvial fan sedimentation are likewise defined. Alluvial fans formed on the southern side of the Kunlun Mountains prior to 200 ka. Ice-contact alluvial fans formed during the penultimate glacial and during MIS-3. Extensive incised alluvial fans that form the main valley fills north of

  18. 137Cs Results and Interpretation of Cesium Soil Data on the Upper Fortymile Wash Alluvial Fan, Amargosa Valley, Nevada.

    NASA Astrophysics Data System (ADS)

    Harrington, C.

    2004-12-01

    Studies using 137Cs were used to produce soil Cs profiles and to use them to determine erosion rates on interchannel divides of the Fortymile Wash alluvial fan over the last 50 years. Sample locations whose 137Cs profiles most resemble the reference-sample (stable surface) profiles are located on interchannel divide areas between distributary channels. These profiles are similar to the reference profiles that have low 137Cs values (in the range of 0.02 to 0.08 pCi/g) in the 3 to 6 cm layers. However, the surface layers (1-3 cm depth) typically have values much less than the reference samples from equivalent depths (range from 0.251 to 0.421 pCi/g). The data indicate that many of these interchannel divide areas have had part of the upper layer removed. Interchannel divide areas have the least likelihood of having been submerged during floods over the last fifty years. Thus, the loss of material from these otherwise stable surfaces appears to be due to eolian processes. Erosion of an interchannel divide area with little evidence of recent water movement is most easily explained by eolian removal. Evidence for wind erosion as the predominant process on the interchannel divide areas includes the lack of new or developing stream channels and the presence of modern coppice dunes near channels on interchannel divides. The presence of nearby Big Dune and other eolian deposits provides strong support for eolian erosion and transport. The amount of material removed from the interchannel divide areas was estimated by comparing the 137Cs value of the upper 3 cm layer to that of the reference value and calculating the thickness of the layer that would have to be removed to obtain the lower value. Applying this method across the interchannel divide sample locations indicates 1 to 2 cm of material has been removed from the interchannel divide surfaces in the last 50 years. This results in erosion rates that range from 0.02 to 0.04 cm/yr. These rates are similar to erosion rates

  19. Evaluation of hydrologic conditions and nitrate concentrations in the Rio Nigua de Salinas alluvial fan aquifer, Salinas, Puerto Rico, 2002-03

    USGS Publications Warehouse

    Rodriguez, Jose M.

    2006-01-01

    A ground-water quality study to define the potential sources and concentration of nitrate in the Rio Nigua de Salinas alluvial fan aquifer was conducted between January 2002 and March 2003. The study area covers about 3,600 hectares of the coastal plain within the municipality of Salinas in southern Puerto Rico, extending from the foothills to the Caribbean Sea. Agriculture is the principal land use and includes cultivation of diverse crops, turf grass, bioengineered crops for seed production, and commercial poultry farms. Ground-water withdrawal in the alluvial fan was estimated to be about 43,500 cubic meters per day, of which 49 percent was withdrawn for agriculture, 42 percent for public supply, and 9 percent for industrial use. Ground-water flow in the study area was primarily to the south and toward a cone of depression within the south-central part of the alluvial fan. The presence of that cone of depression and a smaller one located in the northeastern quadrant of the study area may contribute to the increase in nitrate concentration within a total area of about 545 hectares by 'recycling' ground water used for irrigation of cultivated lands. In an area that covers about 405 hectares near the center of the Salinas alluvial fan, nitrate concentrations increased from 0.9 to 6.7 milligrams per liter as nitrogen in 1986 to 8 to 12 milligrams per liter as nitrogen in 2002. Principal sources of nitrate in the study area are fertilizers (used in the cultivated farmlands) and poultry farm wastes. The highest nitrogen concentrations were found at poultry farms in the foothills area. In the area of disposed poultry farm wastes, nitrate concentrations in ground water ranged from 25 to 77 milligrams per liter as nitrogen. Analyses for the stable isotope ratios of nitrogen-15/nitrogen-14 in nitrate were used to distinguish the source of nitrate in the coastal plain alluvial fan aquifer. Potential nitrate loads from areas under cultivation were estimated for the

  20. Stratigraphic architecture and fault offsets of alluvial terraces at Te Marua, Wellington fault, New Zealand, revealed by pseudo-3D GPR investigation

    NASA Astrophysics Data System (ADS)

    Beauprêtre, S.; Manighetti, I.; Garambois, S.; Malavieille, J.; Dominguez, S.

    2013-08-01

    earthquake slips on faults are commonly determined by measuring morphological offsets at current ground surface. Because those offsets might not always be well preserved, we examine whether the first 10 m below ground surface contains relevant information to complement them. We focus on the Te Marua site, New Zealand, where 11 alluvial terraces have been dextrally offset by the Wellington fault. We investigated the site using pseudo-3D Ground Penetrating Radar and also produced a high-resolution digital elevation model (DEM) of the zone to constrain the surface slip record. The GPR data reveal additional information: (1) they image the 3D stratigraphic architecture of the seven youngest terraces and show that they are strath terraces carved into graywacke bedrock. Each strath surface is overlain by 3-5 m of horizontally bedded gravel sheets, including two pronounced and traceable reflectors; (2) thanks to the multilayer architecture, terrace risers and channels are imaged at three depths and their lateral offsets can be measured three to four times, constraining respective offsets and their uncertainties more reliably; and (3) the offsets are better preserved in the subsurface than at the ground surface, likely due to subsequent erosion-deposition on the latter. From surface and subsurface data, we infer that Te Marua has recorded six cumulative offsets of 2.9, 7.6, 18, 23.2, 26, and 31 m (± 1-2 m). Large earthquakes on southern Wellington fault might produce 3-5 m of slip, slightly less than previously proposed. Pseudo-3D GPR thus provides a novel paleoseismological tool to complement and refine surface investigations.

  1. Quaternary migration of active extension revealed by a syn-tectonic alluvial fan shift. A case study in the Northern Apennines of Italy

    NASA Astrophysics Data System (ADS)

    Mirabella, Francesco; Bucci, Francesco; Cardinali, Mauro; Santangelo, Michele; Guzzetti, Fausto

    2016-04-01

    In areas characterized by the progressive migration of active extension through time, shifts in the position of the active depocenter occur. Such shifts through time produces peculiar geomorphological settings that are often characterized by wind gaps, abandoned valleys, streams captures and drainage inversions. These features provide the opportunity to investigate active areas by studying the recent-most geological history of the related nearby basins. We investigate this topic in a tectonically active area in the Northern Apennines of Italy, as indicated by both instrumental and historical seismicity (maximum epicentral intensity I0=VIII) and extension rates in the order of 2.5-2.7 mm/yr. In particular, we study the Montefalco ridge drainage inversion. Here, fluvial sands and imbricated conglomerates deposited in a lower Pleistocene depocenter constituted by an extensional subsiding basin, are presently uplifted more than 200 m above the present day alluvial plain. The Montefalco ridge drainage inversion, at about 400 m a.s.l., separates two valleys, the Gualdo Cattaneo - Bastardo valley to the West (300 m a.s.l.) and the Foligno present-day alluvial plain to the East (200 m a.s.l.). Seismic reflection data show that the maximum thickness of the continental sequence in the Foligno valley is in the order of 500 m. This valley is presently occupied by a 37 km2 alluvial fan produced by the Topino river flowing from NE to SW. To unravel the Quaternary tectonic evolution of the area, we integrate different data sets collected by field mapping, detailed photo-geological data, sediments provenance information, and subsurface data. We interpret the Montefalco ridge as a paleo-Foligno-like alluvial fan representing the evidence of the recent migration of the active extension to the East of around 7 km. Considering an age of deformation of 2.5 My, an extension rate of about 2.8 mm/yr is derived, which corresponds to the present-day geodetic rates. We stress the importance

  2. Field, Laboratory and Imaging spectroscopic Analysis of Landslide, Debris Flow and Flood Hazards in Lacustrine, Aeolian and Alluvial Fan Deposits Surrounding the Salton Sea, Southern California

    NASA Astrophysics Data System (ADS)

    Hubbard, B. E.; Hooper, D. M.; Mars, J. C.

    2015-12-01

    High resolution satellite imagery, field spectral measurements using a portable ASD spectrometer, and 2013 hyperspectral AVIRIS imagery were used to evaluate the age of the Martinez Mountain Landslide (MML) near the Salton Sea, in order to determine the relative ages of adjacent alluvial fan surfaces and the potential for additional landslides, debris flows, and floods. The Salton Sea (SS) occupies a pluvial lake basin, with ancient shorelines ranging from 81 meters to 113 meters above the modern lake level. The highest shoreline overlaps the toe of the 0.24 - 0.38 km3 MML deposit derived from hydrothermally altered granites exposed near the summit of Martinez Mountain. The MML was originally believed to be of early Holocene age. However, AVIRIS mineral maps show abundant desert varnish on the top and toe of the landslide. Desert varnish can provide a means of relative dating of alluvial fan (AF) or landslide surfaces, as it accumulates at determinable rates over time. Based on the 1) highest levels of desert varnish accumulation mapped within the basin, 2) abundant evaporite playa minerals on top of the toe of the landslide, and 3) the highest shoreline of the ancestral lake overtopping the toe of the landslide with gastropod and bivalve shells, we conclude that the MML predates the oldest alluvial fan terraces and lake sediments exposed in the Coachella and Imperial valleys and must be older than early Holocene (i.e. Late Pleistocene?). Thus, the MML landslide has the potential to be used as a spectral endmember for desert varnish thickness and thus proxy for age discrimination of active AF washes versus desert pavements. Given the older age of the MML landslide and low water levels in the modern SS, the risk from future rockslides of this size and related seiches is rather low. However, catastrophic floods and debris flows do occur along the most active AF channels; and the aftermath of such flows can be identified spectrally by montmorillonite crusts forming in

  3. The application of remotely sensed data to pedologic and geomorphic mapping on alluvial fan and playa surfaces in Saline Valley, California

    NASA Technical Reports Server (NTRS)

    Miller, D. A.; Petersen, G. W.; Kahle, A. B.

    1986-01-01

    Arid and semiarid regions yield excellent opportunities for the study of pedologic and geomorphic processes. The dominance of rock and soil exposure over vegetation not only provides the ground observer with observational possibilities but also affords good opportunities for measurement by aircraft and satellite remote sensor devices. Previous studies conducted in the area of pedologic and geomorphic mapping in arid regions with remotely sensed data have utilized information obtained in the visible to near-infrared portion of the spectrum. Thermal Infrared Multispectral Scanner (TIMS) and Thematic Mapping (TM) data collected in 1984 are being used in comjunction with maps compiled during a Bureau of Land Management (BLM) soil survey to aid in a detailed mapping of alluvial fan and playa surfaces within the valley. The results from this study may yield valuable information concerning the application of thermal data and thermal/visible data combinations to the problem of dating pedologic and geomorphic features in arid regions.

  4. Braidplain, floodplain and playa lake, alluvial-fan, aeolian and palaeosol facies composing a diversified lithogenetical sequence in the permian and triassic of South Devon (England)

    NASA Astrophysics Data System (ADS)

    Mader, Detlef

    The Permian and Triassic of South Devon (England) are a continental red bed sequence of very diversified lithogenetical composition. Within the thick series, the distribution of the main depositional environments being fluvial braidplain, fluvial floodplain and playa lake, alluvial fan, aeolian dune and calcrete palaeosol changes repeatedly in both horizontal and vertical direction. Significant sedimentary milieus such as aeolian dunes and calcrete palaeosols occur repeatedly within the succession, but are also lacking in several parts of the sequence. Fluvial braidplain deposits comprise conglomerates, sandstones, intraformational reworking horizons and mudstones and originate in channels and overbank plains of a braided river system. Conglomerates and sandstones are formed by migration of bars and spreading out of sheets during infilling of streams and aggradation of flats. Gravel is often enriched as lag pockets or veneers within steeper scour holes and kolk pots or on the plane floor of the watercourse. Finer-grained sandstones and mudstones are laid down by suspension settling in stagnant water bodies such as small lakes in the overbank area and residual pools in interbar depressions during low-stage or waning-flow in active channels or in abandoned streams. Spectacular bioturbation features in some sandstones with both horizontal tubes and vertical burrows testify to the colonization of the sediments at the bottom of the rivers with declining discharge and transport capacity. Intraformational reworking horizons with ghost-like remnants of degraded sandstones, mudstones and pedogenic carbonates document partially severe condensation of the sequence by removal of some facies elements from the depositional record. The occasionally occurring gravel-bearing mudstones or silty-clayey sandstones represent products of high-energy water surges overspilling the channel banks and transporting sandy and gravelly bed-load in limited amounts beyond the levee wall. The

  5. Magnetic stratigraphy of the Bucaramanga alluvial fan: Evidence for a ≤3 mm/yr slip rate for the Bucaramanga-Santa Marta Fault, Colombia

    NASA Astrophysics Data System (ADS)

    Jiménez, Giovanny; Speranza, Fabio; Faccenna, Claudio; Bayona, German; Mora, Andres

    2015-01-01

    The 550 km long Bucaramanga-Santa Marta Fault is one of the main active tectonic features of NW South America. It is a left-lateral strike-slip fault bounding the Maracaibo block, and straddling northern Colombia from the Caribbean Sea to the Eastern Cordillera. Variable total displacement values (from 40 to 110 km), and present-day slip rates (from 0.01 to 10 mm/yr) have been proposed so far for the Bucaramanga Fault. Here we report on the paleomagnetic investigation of a Plio-Pleistocene (?) continental alluvial fan juxtaposed to the Bucaramanga Fault, and horizontally displaced by 2.5 km with respect to its feeding river. Nine (out of fourteen) reliable paleomagnetic directions define a succession of six different magnetic polarity zones that, lacking additional age constraints, can be correlated with several tracks of the Plio-Pleistocene magnetic polarity time scale. If the youngest age model is considered, most recent sediments of the fan can be reasonably dated at 0.8 Ma (Brunhes-Matuyama chron transition), translating into a maximum 3 mm/yr slip rate for the Bucaramanga Fault. Older age models would obviously yield smaller slip rates. Our paleomagnetic sites, located at 4-10 km from the fault, do not show significant rotations, implying weak fault coupling and/or ductile upper crust behavior adjacent to the Bucaramanga Fault.

  6. Depositional conditions on an alluvial fan at the turn of the Weichselian to the Holocene - a case study in the Żmigród Basin, southwest Poland

    NASA Astrophysics Data System (ADS)

    Zieliński, Paweł; Sokołowski, Robert J.; Fedorowicz, Stanisław; Woronko, Barbara; Hołub, Beata; Jankowski, Michał; Kuc, Michał; Tracz, Michał

    2016-06-01

    Presented are the results of research into the fluvio-aeolian sedimentary succession at the site of Postolin in the Żmigród Basin, southwest Poland. Based on lithofacies analysis, textural analysis, Thermoluminescence and Infrared-Optical Stimulated Luminescence dating and GIS analysis, three lithofacies units were recognised and their stratigraphic succession identified: 1) the lower unit was deposited during the Pleni-Weichselian within a sand-bed braided river functioning under permafrost conditions within the central part of the alluvial fan; 2) the middle unit is the result of aeolian deposition and fluvial redeposition on the surface of the fan during long-term permafrost and progressive decrease of humidity of the climate at the turn of the Pleni- to the Late Weichselian; 3) the upper unit accumulated following the development of longitudinal dunes at the turn of the Late Weichselian to the Holocene; the development of dunes was interrupted twice by the form being stabilised by vegetation and soil development.

  7. Debris flow dominated alluvial fans in the Australian high country indicate that landscape denudation through the Holocene has been dominated by post-bushfire runoff events

    NASA Astrophysics Data System (ADS)

    Marren, Philip; Nyman, Petter; Kermode, Stephanie

    2016-04-01

    Bushfires play a major role in shaping landscapes across the globe. Whilst the role of fire in shaping and changing vegetation assemblages is relatively well understood, there is still debate about the significance of fire in driving landscape denudation, relative to other processes, such as major rainfall and flood events and questions remain about the frequency of extreme fire events over longer timescales in response to climate forcing. Studies of post-fire landscape impact of recent bushfires in southeast Australia indicate that where storm events occur shortly after a major bushfire, hillslope erosion is enhanced, due to debris flows and erosion of both primary hillslope sediment and sediment stored in hillslope channel networks. In Australia, knowledge of long-term bushfire frequency is largely derived from pollen and micro-charcoal records in lake-sediment archives and is not directly relevant to resolving questions regarding fire impacts on landscape denudation and sediment transfer. We excavated trenches in four alluvial fans at the base of hillslopes in the high country of northeast Victoria, Australia. This area was burnt by bushfires in 1939 and 2003, and regional climate and hydrology are strongly controlled by El Niño. The trenches were up to 3.5m deep, and in most cases intersected underlying floodplain sediment at the base of the trench, indicating that they provide a full record of sedimentation for that sector of the fan. Fan stratigraphy consisted of sub-horizontal (parallel to the fan surface) units 0.3-0.5m thick, with occasional units 1-1.2m thick, and cross-cutting channelized units. Debris flow deposits accounted for 70-80% of the observed sediments, with water-laid gravels and soil units forming the remainder. Most soil layers were burnt, and most (but not all) debris flow units contained charcoal. A typical stratigraphy consisted of 6-8 debris flow units per fan, with four units containing a fire signature or overlying a burnt soil layer

  8. A database on flood and debris-flow processes in alluvial fans: a preliminary analysis aimed at evaluation of the damage

    NASA Astrophysics Data System (ADS)

    Vennari, Carmela; Santangelo, Nicoletta; Santo, Antonio; Parise, Mario

    2015-04-01

    Debris-flow and flood events cause yearly wide damages to buildings and infrastructures, and produce many casualties and fatalities. These processes are very common in Italy, affecting mainly torrential stream basins with different geological and morphological settings: in the Alpine mountain areas they are quite well analysed, whilst much less attention is generally paid in contexts such as those of the Apennines mostly due to the minor frequency of the events. Nevertheless, debris-flows and flood processes occur along many alluvial fans, have greatly contributed to their building up, and are therefore worth to be studied. Along many areas of the Southern Apennines, coalescent alluvial fans are a widespread geomorphic unit, typically located at the foot of steep slopes. In most cases these areas correspond to the more highly urbanised sectors, generally considered to be safer than the bottom valley, as concerns the direct effects from flooding. During intense storms, villages and towns built on alluvial fans may be affected by flooding and/or debris flow processes originated in the above catchment, and rapidly transferred downslope due to the steep slopes and the torrential character of the streams. This creates a very high hazard to the population and is at the origin of the severe and recurrent damage to urban settlements. Starting from the above considerations, we compiled a catalogue of flood and debris-flow events occurred in Campania Region, southern Italy, by consulting very different information sources: national and local newspapers and journals, regional historical archives, scientific literature, internet blogs. More than 350 events, occurred in Campania from 1700 to present, were collected. Information on time of occurrence and location are available for each event, with different level of accuracy, that is typically lower going back to the oldest events for which only the year or the month of occurrence of the event was identified; nevertheless, for

  9. Hydrogeochemical zonation and its implication for arsenic mobilization in deep groundwaters near alluvial fans in the Hetao Basin, Inner Mongolia

    NASA Astrophysics Data System (ADS)

    Jia, Yongfeng; Guo, Huaming; Jiang, Yuxiao; Wu, Yang; Zhou, Yinzhu

    2014-10-01

    High As groundwater has been found in shallow aquifers of the flat plain of the Hetao basin, but little is known about As concentration in deep groundwaters around piedmont areas, which are the major drinking water resources. One hundred and three groundwater samples from wells with depths >50 m and seven samples from one multi-level monitoring well (89 m in depth) were analyzed for chemical compositions and 18O and D isotopes to examine the geochemical processes controlling As mobilization. According to hydrogeological setting, chemical and isotopic characteristics of deep groundwater, three distinguished hydrogeochemical zones are delineated, including Recharge-Oxic Zone (Zone I), Groundwater Flow-Moderate Reducing Zone (Zone II), and Groundwater Flow-Reducing Zone (Zone III). Zone I is located in proximal fans in the recharge area with oxic conditions, where low As groundwater generally occurs. In Zone II, located in the intermediate between the fans and the flat plain with Fe-reduction predominated, groundwater As is moderate. Zone III lies in the flat plain with the occurrence of SO42- reduction, where high As groundwater is mostly found. This indicates that release of As to groundwater is primarily determined by reduction sequences. Arsenic is immobilized in O2 /NO3- reduction stage in Zone I and released in Fe-reducing conditions of Zone II, and displays a significant elevated concentration in SO4-reducing stage in Zone III. Dissolution of carbonate minerals occurs in Zone I, while Ca2+ and Mg2+ are expected to precipitate in Zone II and Zone III. In the multi-level monitoring well, both chemical and isotopic compositions are dependent of sampling depths, with the similar trend to the hydrogeochemical zonation along the flow path. The apparent increases in δD and δ18O values in Zone III reveal the possibility of high As shallow groundwater recharge to deep groundwater. It indicates that deep groundwaters in proximal fans have low As concentrations and are

  10. 10Be, OSL/IRSL Luminescence and 14C Cross-Dating of a Series of Abandoned Alluvial Surfaces Laterally Offset by the Dead Sea Fault, Jordan

    NASA Astrophysics Data System (ADS)

    Le Beon, M.; Jaiswal, M.; Al-Qaryouti, M.; Moumani, K.; Burr, G. S.; Chen, Y.; Klinger, Y.; Abdelghafoor, M.; Suppe, J.

    2010-12-01

    Active tectonics studies are often limited by the uncertainties in accurately and precisely dating Late Quaternary deposits, especially alluvial deposits that often lack organic matter datable by 14C method. This is the case along the Wadi Araba Fault (WAF), the southernmost segment of the Dead Sea Fault, which delineates the 1000-km long plate boundary between the Arabia plate and the Sinai sub-plate. Geodetic, geomorphic and geologic studies converge to a fault slip rate of 5 ± 2 mm/a. Yet, long-term Late Pleistocene slip rates cover a wide range due to large uncertainties, mostly related to the dispersion of 10Be cosmogenic radionuclide (CRN) ages. The maximum slip rate since ~100 ka is up to a value of 11 mm/a, possibly suggesting significant variations in fault activity with time. In order to reduce the uncertainty on the Late Pleistocene slip rate and draw further conclusions regarding the seismic behavior of the WAF, we targeted one of the sites previously investigated for detailed morphotectonic analysis and 10Be CRN dating and we apply other chronometers, such as Optically stimulated luminescence (OSL) dating on quartz and feldspar minerals, and 14C dating when possible. The site consists in an abandoned bajada composed of four alluvial surface levels, offset by the WAF. We extensively sampled the terraces F2 and F4, which are offset by 160 ± 8 m and 626 ± 37 m, respectively. Our samples are collected from ~50-cm deep pits on the top of the terraces. On F2, we collected one OSL sample downstream from the fault and two upstream, where land snail shells were also found. Preliminary OSL ages agree on ~8 ± 2 ka upstream, also consistent with a 14C date, whereas the OSL age downstream is much older, ~41 ± 4 ka. On F4, we collected three samples downstream from the fault and two upstream. Preliminary OSL ages cluster between ~32 ± 4 ka and ~46 ± 5 ka. Five of the OSL samples have been collected at a similar location to surficial cobbles for 10Be, both on

  11. Regional and local risk assessments of alluvial fans by combination of historical and geomorphological data on debris flows, the most damaging natural hazard in the Aosta Valley Region (NW-Italy)

    NASA Astrophysics Data System (ADS)

    Giardino, Marco; Ratto, Sara; Alberto, Walter; Armand, Marco; Cignetti, Martina; Palomba, Mauro; Navillod, Evelyne

    2010-05-01

    The Aosta Valley (NW-Italy) is a small alpine Region (area = 3262 km2) where alluvial fans occupy large sectors of the main valley bottom and also of the tributary valleys; most towns and villages lie in these sectors which are frequently affected by different geomorphological processes, including debris flows. For a best environmental hazard assessment and management of alluvial fans, a research project has been carried out with a particular attention to debris flows, responsible for causing major damages to human activities and infrastructures. A debris flows inventory on a regional scale has been created, combining historical data (1900 to present), technical maps and geomorphological analysis on the alluvial fans areas. A complex methodology for data collection and analysis has been organized in two different stages. As a first step, aerial photointerpretation and Digital Elevation Models (DEMs) analysis were conducted over the Aosta Valley Region to obtain a complete fans inventory and to identify the most affected sectors by debris flows. As a second step, data on debris flow events occurred in the Region has been collected from different sources, such as bibliographic and historical data, municipality hazard maps for land planning restriction and drainage basin technical studies. For each inventored debris flow, aerial photointerpretations have been performed to validate geomorphological and historical data, mostly collected during major regional flood events. Finally, the selected debris flow events has been formally organized in a GIS to perform spatial and statistical analysis. Application of the methodology to the complete Aosta Valley Region dataset involved the overcoming of some difficulties, such as: 1) correct identification of repeated events from different sources, 2) exact recognition of small phenomena by photointerpretation and 3) problems related to the rapid landforms obliteration. The preliminary results of the research activity are outlined

  12. Gradual diversions of the Rio Pastaza in the Ecuadorian piedmont of the Andes from 1906 to 2008: role of tectonics, alluvial fan aggradation, and ENSO events

    NASA Astrophysics Data System (ADS)

    Bernal, Carolina; Christophoul, Frédéric; Soula, Jean-Claude; Darrozes, José; Bourrel, Luc; Laraque, Alain; Burgos, José; Bès de Berc, Séverine; Baby, Patrice

    2012-10-01

    The successive courses of the Rio Pastaza in the upper Amazonian Puyo plateau (Ecuador) during the past century have been followed using historical maps, aerial photographs, satellite imagery, topographic and river long profiles, and field studies. The abrupt change in direction of the Rio Pastaza from transverse to longitudinal was a result of two avulsions occurred between 1906 and 1976 at the braided-meandering transition of the former alluvial plain. These avulsions are related to aggradation at the toe of a braided piedmont fan prograding on to a hinterland-dipping topographic slope formed by ongoing tectonic backtilting. The main avulsion proceeded by annexation of a south-dipping depression created in front of the cordillera by backtilting of the plateau. A partial and gradual avulsion having occurred upstream of the former site between 1976 and 2008 is marked by the progressive predominance of a newly formed inner branch. Tectonic backtilting enhanced aggradation upstream of the initial site while it offered the newly avulsed channel a still more favorable way along the cordillera by creating a westward lateral slope. The correlation between ENSO events and the occurrence of the 1976-2008 avulsions strongly suggests that the triggers of the avulsions were the floods caused by the high water and sediment discharges associated with ENSO (La Niña) events contrasting with the regular monthly discharge and the lack of actual `normal' floods during the inter-ENSO periods.

  13. Understanding space-time patterns of groundwater system by empirical orthogonal functions: A case study in the Choshui River alluvial fan, Taiwan

    NASA Astrophysics Data System (ADS)

    Yu, Hwa-Lung; Chu, Hone-Jay

    2010-02-01

    SummaryNatural or anthropogenic activities contribute to changes of groundwater levels in space and time. Understanding the major and significant driving forces to changes in space-time patterns of groundwater levels is essential to groundwater management. This study analyzes monthly observations of piezometric heads from 66 wells during 1997-2002 located in the Choshui River alluvial fan of Taiwan, where groundwater has been the important local water resource for myriads of agricultural or industrial demands. Following spatiotemporal estimations of piezometric heads by Bayesian Maximum Entropy method (BME), this work performs rotated empirical orthogonal function (REOF) analysis to decompose the obtained space-time heads into a set of spatially distributed empirical orthogonal functions (EOFs) and their associated uncorrelated time series. Results show that the leading EOFs represent the most significant driving forces to spatiotemporal changes of groundwater levels in the Choshui River aquifer. These include rainfall recharges from upstream Choshui and Pei-Kang River, pumping activities from aquaculture usages in the coastal areas, as well as water exchanges between surface and subsurface flow of Choshui River. In summary, this study shows the strength of the REOF analysis which can effectively provide integrative views of spatiotemporal changes of groundwater, gaining insights of interactions between the groundwater system and other natural and human activities.

  14. Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone

    NASA Astrophysics Data System (ADS)

    Gray, Harrison J.; Owen, Lewis A.; Dietsch, Craig; Beck, Richard A.; Caffee, Marc A.; Finkel, Robert C.; Mahan, Shannon A.

    2014-12-01

    Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of convergent uplifts along the San Andreas Fault with the initiation of the sub-parallel San Jacinto Fault suggest a possible link between the two tectonic events. The ages of alluvial fans and the rates of catchment-wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the Mecca Hills. Ages for major geomorphic surfaces based on 10Be surface exposure dating of boulders and 10Be depth profiles define the timing of surface stabilization to 2.6 +5.6/-1.3 ka (Qyf1 surface), 67.2 ± 5.3 ka (Qvof2 surface), and 280 ± 24 ka (Qvof1 surface). Comparison of 10Be measurements from active channel deposits (Qac) and fluvial terraces (Qt) illustrate a complex history of erosion, sediment storage, and sediment transport in this environment. Beryllium-10 catchment-wide denudation rates range from 19.9 ± 3.2 to 149 ± 22.5 m/Ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area. The lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control. The currently measured topography and denudation rates across the Mecca Hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust.

  15. Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone

    USGS Publications Warehouse

    Gray, Harrison J.; Owen, Lewis; Dietsch, Craig; Beck, Richard A.; Caffee, Marc A.; Finkelman, Robert B.; Mahan, Shannon

    2014-01-01

    Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of convergent uplifts along the San Andreas Fault with the initiation of the sub-parallel San Jacinto Fault suggest a possible link between the two tectonic events. The ages of alluvial fans and the rates of catchment-wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the Mecca Hills. Ages for major geomorphic surfaces based on 10Be surface exposure dating of boulders and 10Be depth profiles define the timing of surface stabilization to 2.6 +5.6/–1.3 ka (Qyf1 surface), 67.2 ± 5.3 ka (Qvof2 surface), and 280 ± 24 ka (Qvof1 surface). Comparison of 10Be measurements from active channel deposits (Qac) and fluvial terraces (Qt) illustrate a complex history of erosion, sediment storage, and sediment transport in this environment. Beryllium-10 catchment-wide denudation rates range from 19.9 ± 3.2 to 149 ± 22.5 m/Ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area. The lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control. The currently measured topography and denudation rates across the Mecca Hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust.

  16. Structure and climate controls on the evolution of a Mid-Late Jurassic alluvial fan-delta system in the western part of Yanshan fold-and-thrust belt

    NASA Astrophysics Data System (ADS)

    Lin, Chengfa; Liu, Shaofeng; Yao, Xiang; Ma, Pengfei

    2016-04-01

    The Yanshan fold-thrust belt experienced several significant tectonic events during Mesozoic time and developed thrust fault-bounded intramontane sedimentary basins. However, elaborate works of sedimentology is inadequate in the Yanshan belt, particularly in its western segment, leading to a failure in comprehensively understanding how bounding-faults and climate change influence the basin filling processes. Our detailed sedimentological study of the Middle Jurassic Xiahuayuan Formation and Upper Jurassic-Lower Cretaceous Jiulongshan Formation in the Xiahuayuan basin of northern Hebei province, indicates a genetic relationship between the evolution of an alluvial fan-delta system and the tectonic and climate setting. The Xiahuayuan Formation was assigned to a debris flow-dominated Gilbert-type fan-delta composed of topset conglomerates, foreset massive siltstone-fine grained sandstone interbedded with lenticular conglomerate units and bottomset/lake bottom fine-grained deposits, spatially restricted to the northern part of the basin. While the lower Jiulongshan Formation was considered as a relatively small debris flow- and turbidity currents-dominated fan-delta with a single-ramp portrait, prograding into the middle part of the basin. And the upper part of Jiulongshan Formation contributed to the lake bottom component of the delta system during the forming of the Jiulongshan Formation. Our results reveal a transformation of a fan-delta from Gilbert-type to single-ramp type and the basinward migration of this fan-delta during Mid-Late Jurassic in the Xiahuayuan basin. And it is assumed that the activity of a thrust fault along the northern basin margin and the rapid switch of climate conditions from warm and humid to hot and dry triggered the transformation and migration of this fan-delta system.

  17. Risk assessment based on a combination of historical analysis, a detailed field study and numerical modeling on the alluvial fan Gadeinerbach as a basis for a risk management concept

    NASA Astrophysics Data System (ADS)

    Moser, M.

    2009-04-01

    The catchment Gadeinerbach in the District of Lungau/Salzburg/Austria is prone to debris flows. Large debris flow events dates back from the years 1934 and 1953. In the upper catchment large mass movements represent debris sources. A field study shows the debris potential and the catchment looks like a "sleeping torrential giant". To carry out mitigation measures a detailed risk management concept, based on a risk assessment in combination of historical analysis, field study and numerical modeling on the alluvial fan was conducted. Human activities have partly altered the surface of the alluvial fan Gadeinerbach but nevertheless some important hazard indicators could be found. With the hazard indicators and photo analysis from the large debris flow event 1934 the catchment character could be pointed out. With the help of these historical data sets (hazard indicators, sediment and debris amount...) it is possible to calibrate the provided numerical models and to win useful knowledge over the pro and cons and their application. The results were used to simulate the design event and furthermore to derive mitigation measures. Therefore the most effective protection against debris with a reduction of the high energy level to a lower level under particular energy change in combination with a debris/bedload deposition place has been carried out. Expert opinion, the study of historical data and a field work is in addition to numerical simulation techniques very necessary for the work in the field of natural hazard management.

  18. Radiogenic 3He/4He Estimates and Their Effect on Calculating Plio-Pleistocene Cosmogenic 3He Ages of Alluvial-Fan Terraces in the Lower Colorado River Basin, USA

    NASA Astrophysics Data System (ADS)

    Fenton, C.; Pelletier, J.

    2005-12-01

    Several alluvial-fan terraces near Topock, AZ were created by successive entrenchment of Pliocene and Pleistocene alluvial-fan gravels shed from the adjacent Black Mountains along the lower Colorado River corridor below Hoover Dam. These fans interfinger with and overlie main-stem Colorado River sands and gravels and grade to terrace levels that correspond with pre-existing elevations of the Colorado River. Absolute dates for the ages of Quaternary deposits on the lower Colorado River are rare and cosmogenic 3He age estimates of these surfaces would help constrain the timing of aggradation and incision in the lower Colorado River corridor. We analyzed individual basalt boulders from several terrace surfaces for total 3He/4He concentrations to calculate cosmogenic 3He ages of each fan terrace; 3He/4He values, expressed as R/Ra where Ra is the 3He/4He of air, range from 0.29 to 590. Black Mountain volcanic rocks have reported K-Ar ages between 15 and 30 Ma and basalt samples from adjacent alluvial fans contain 0.42 to 47× 1012 at/g of 4He, which has likely accumulated due to nuclear processes. The amount of radiogenic 3He/4He can be significant in old rocks with young exposure ages and can complicate determination of cosmogenic 3 He content. Alpha-decay of U, Th, and their daughter isotopes produces large amounts of 4He, whereas significant amounts of radiogenic 3He are only produced through the neutron bombardment of Li and subsequent beta-decay of tritium. We measured Li, U, Th, major and rare-earth element concentrations in whole-rock basalts and mineral separates. These concentrations are used to estimate the ratio of radiogenic helium contributed to the total helium system in our samples. Li concentrations typically range from 6 to 17 ppm, with one outlier of 62 ppm. U contents range from <0.1 to 2.7 ppm and Th contents range from 0.4 to 15.3 ppm. Based on these values, our calculations predict that the average radiogenic helium (R/Ra) contributed to the total

  19. Variation in erosion/deposition rates over the last 50 years on alluvial fan surfaces of L. Pleistocene- Mid Holocene age, estimations using 137Cs soil profile data, Amargosa Valley, Nevada.

    NASA Astrophysics Data System (ADS)

    Harrington, C.; Kelley, R.; Ebert, T.; Delong, S.; Cline, M.; Pelletier, J.; Whitney, J.

    2005-12-01

    Variations in erosion and deposition for the last fifty years (based on estimates from 137Cs profiles) on surfaces (Late Pleistocene to Late Holocene in age) making up the Fortymile Wash alluvial fan south of Yucca Mountain, is a function of surface age and of desert pavement development or absence. For purposes of comparing erosion and deposition, the surfaces can be examined as three groups: (1) Late Pleistocene surfaces possess areas of desert pavement development with thin Av or sandy A horizons, formed by the trapping capabilities of the pavements. These zones of deposition are complemented by coppice dune formation on similar parts of the surface. Areas on the surface where no pavement development has occurred are erosional in nature with 0.0 +/- 0.0 cm to 1.5 +/- 0.5 cm of erosion occurring primarily by winds blowing across the surface. Overall these surfaces may show either a small net depositional gain or small erosional loss. (2) Early Holocene surfaces have no well-developed desert pavements, but may have residual gravel deposits in small areas on the surfaces. These surfaces show the most consistent erosional surface areas on which it ranges from1.0 +/-.01 cm to 2.0+/-.01 cm. Fewer depositional forms are found on this age of surface so there is probably a net loss of 1.5 cm across these surfaces. (3) The Late Holocene surfaces show the greatest variability in erosion and deposition. Overbank deposition during floods cover many edges of these surfaces and coppice dune formation also creates depositional features. Erosion rates are highly variable and range from 0.0 +/- 0.0 to a maximum of 2.0+/-.01. Erosion occurs because of the lack of protection of the surface. However, the common areas of deposition probably result in the surface having a small net depositional gain across these surfaces. Thus, the interchannel surfaces of the Fortymile Wash fan show a variety of erosional styles as well as areas of deposition. The fan, therefore, is a dynamic system

  20. VARIATION IN EROSION/DEPOSITION RATES OVER THE LAST FIFTTY YEARS ON ALLUVIAL FAN SURFACES OF L. PLEISTOCENE-MID HOLOCENE AGE, ESTIMATIONS USING 137CS SOIL PROFILE DATA, AMARGOSA VALLEY, NEVADA

    SciTech Connect

    C. Harrington; R. Kelly; K.T. Ebert

    2005-08-26

    Variations in erosion and deposition for the last fifty years (based on estimates from 137Cs profiles) on surfaces (Late Pleistocene to Late Holocene in age) making up the Fortymile Wash alluvial fan south of Yucca Mountain, is a function of surface age and of desert pavement development or absence. For purposes of comparing erosion and deposition, the surfaces can be examined as three groups: (1) Late Pleistocene surfaces possess areas of desert pavement development with thin Av or sandy A horizons, formed by the trapping capabilities of the pavements. These zones of deposition are complemented by coppice dune formation on similar parts of the surface. Areas on the surface where no pavement development has occurred are erosional in nature with 0.0 +/- 0.0 cm to 1.5 +/- 0.5 cm of erosion occurring primarily by winds blowing across the surface. Overall these surfaces may show either a small net depositional gain or small erosional loss. (2) Early Holocene surfaces have no well-developed desert pavements, but may have residual gravel deposits in small areas on the surfaces. These surfaces show the most consistent erosional surface areas on which it ranges from 1.0 +/-.01 cm to 2.0+/- .01 cm. Fewer depositional forms are found on this age of surface so there is probably a net loss of 1.5 cm across these surfaces. (3) The Late Holocene surfaces show the greatest variability in erosion and deposition. Overbank deposition during floods cover many edges of these surfaces and coppice dune formation also creates depositional features. Erosion rates are highly variable and range from 0.0 +/- 0.0 to a maximum of 2.0+/-.01. Erosion occurs because of the lack of protection of the surface. However, the common areas of deposition probably result in the surface having a small net depositional gain across these surfaces. Thus, the interchannel surfaces of the Fortymile Wash fan show a variety of erosional styles as well as areas of deposition. The fan, therefore, is a dynamic

  1. Late Pleistocene intraplate extension of the Central Anatolian Plateau, Turkey: Inferences from cosmogenic exposure dating of alluvial fan, landslide and moraine surfaces along the Ecemiş Fault Zone

    NASA Astrophysics Data System (ADS)

    Yildirim, Cengiz; Akif Sarikaya, Mehmet; Ciner, Attila

    2016-04-01

    Late Pleistocene activity of the Ecemiş Fault Zone is integrally tied to ongoing intraplate crustal deformation in the Central Anatolian Plateau. Here we document the vertical displacement, slip rate, extension rate, and geochronology of normal faults within a narrow strip along the main strand of the fault zone. The Kartal, Cevizlik and Lorut faults are normal faults that have evident surface expression within the strip. Terrestrial cosmogenic nuclide geochronology reveals that the Kartal Fault deformed a 104.2 ± 16.5 ka alluvial fan surface and the Cevizlik Fault deformed 21.9 ± 1.8 ka glacial moraine and talus fan surfaces. The Cevizlik Fault delimits mountain front of the Aladaglar and forms >1 km relief. Our topographic surveys indicate 13.1 ± 1.4 m surface breaking vertical displacements along Cevizlik Faults, respectively. Accordingly, we suggest a 0.60 ± 0.08 mm a-1 slip rate and 0.35 ± 0.05 mm a-1 extension rate for the last 21.9 ± 1.8 ka on the Cevizlik Fault. Taken together with other structural observations in the region, we believe that the Cevizlik, Kartal ve Lorut faults are an integral part of intraplate crustal deformation in Central Anatolia. They imply that intraplate structures such as the Ecemiş Fault Zone may change their mode through time; presently, the Ecemiş Fault Zone has been deformed predominantly by normal faults. The presence of steep preserved fault scarps along the Kartal, Cevizlik and Lorut faults point to surface breaking normal faulting away from the main strand and particularly signify that these structures need to be taken into account for regional seismic hazard assessments. This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Grant number: 112Y087).

  2. Late Pleistocene intraplate extension of the Central Anatolian Plateau, Turkey: Inferences from cosmogenic exposure dating of alluvial fan, landslide, and moraine surfaces along the Ecemiş Fault Zone

    NASA Astrophysics Data System (ADS)

    Yıldırım, Cengiz; Sarıkaya, M. Akif; ćiner, Attila

    2016-06-01

    Here we documented the vertical displacement, slip rate, extension rate, and geochronology of normal faults within a narrow strip along the main strand of the Ecemiş Fault Zone. The Kartal, Cevizlik, and Lorut Faults are normal faults that have evident surface expression within the strip. Terrestrial cosmogenic nuclide geochronology revealed that the Kartal Fault deformed the 104.2 ± 16.5 ka aged alluvial fan surface and the Cevizlik Fault deformed the 21.9 ± 1.8 ka old moraine and talus fan surfaces. Our topographic surveys indicated 120 ± 10 m and 13.1 ± 1.4 m surface-breaking vertical displacements along the Kartal and Cevizlik Faults, respectively. Accordingly, we suggest a 1.15 ± 0.21 mm a-1 slip rate and 0.66 ± 0.12 mm a-1 extension rate for the last 104.2 ± 16.5 ka on the Kartal Fault, and a 0.60 ± 0.08 mm a-1 slip rate and 0.35 ± 0.05 mm a-1 extension rate for the last 21.9 ± 1.8 ka on the Cevizlik Fault. We believe that these structures are an integral part of intraplate crustal deformation in the Central Anatolia. They imply that intraplate structures such as the Ecemiş Fault Zone may change their mode through time; presently, the Ecemiş Fault Zone has been deformed predominantly by normal faults. The presence of steep preserved fault scarps along the Kartal, Cevizlik, and Lorut Faults point to surface-breaking normal faulting away from the main strand and particularly signify that these structures need to be taken into account for regional seismic hazard assessments.

  3. Fan deltas and braid deltas: conceptual problems

    SciTech Connect

    McPherson, J.G.; Shanmugam, G.; Moiola, R.J.

    1986-05-01

    The concept of fan deltas has been widely misinterpreted in the geologic literature. A true fan delta is defined as an alluvial fan deposited into a standing body of water. Such sequences are of limited areal extent and are, as expected, uncommon in the rock record. By contrast, braid deltas (herein defined), formed by progradation of a braided fluvial system into a standing body of water, are a common geomorphic feature in many modern settings, and their deposits are common in the geologic record. Braid-delta sequences are often identified as fan deltas, on the false premise that coarse-grained deposits in a deltaic setting are always part of an alluvial fan complex. The authors find that most published examples of so called fan deltas contain no direct evidence for the presence of an alluvial fan. Even in examples where an alluvial fan could be documented, the authors found that, in many cases, the alluvial fan complex was far removed from the shoreline, separated by an extensive braid plain. The authors suggest that such systems are better classified as braid deltas. They consider that it is essential to distinguish the environmental setting of true fan deltas from that of braid deltas. Misclassification will lead to incorrect interpretations of expected facies, sandstone geometry, reservoir quality, and tectonic settings. Criteria based on geometry, vertical and lateral lithofacies associations, and paleocurrent patterns should be used to correctly identify and distinguish these depositional systems.

  4. A fan tale, modern and ancient fans - A comparison

    SciTech Connect

    Fischer, P.J. ); Thor, D.R. ); Cherven, V.B.

    1991-02-01

    The Quaternary Conception fan of the Santa Barbara basin and the Upper Cretaceous Lathrop fan of the northern San Joaquin basin tell an interesting tale. Both fans show a well defined sequence stratigraphy of alternating low-stand, sand-rich units that alternate with thin high-stand silt units that drape and in-fill the surface topography of the previous sand-cycle. Isopachs made from detailed well log correlations (Lathrop) and seismic reflection data tied to borings (Conception) show that the fans are composed of a series of offset-stacked, elongate fan lobes. These lobes are similar in size. A major difference in the development of the two fans is the timing of tectonism. Concomitant tectonism uplifted the Conception fan lobes and resulted in localized erosion of high-stand silts beds and sand-on-sand lobe contacts. Tectonism and Lathrop occurred after fan deposition and provided the trapping structure-the Lathrop anticlinal fold. Following are some lessons to be learned from these and other fans the authors have studied: (1) Quaternary or modern' fans and ancient fans are similar. (2) Elongate sand-rich fan lobes separated by highstand silt units are typical of fans. (3) In addition to well-known techniques (seismic stratigraphy and detailed well log correlations), original reservoir pressures may be used to differentiate sequences and lobes (e.g., Lathrop). (4) Tectonism and erosion along the margin may limit traps to the uppermost lobe sequence (e.g., Conception). (5) An offset-stacked elongate fan lobe model is a valuable exploration and production tool.

  5. Meander in valley crossing a deep-ocean fan.

    PubMed

    Shepard, F P

    1966-10-21

    Seaward of most submarine canyons there are large sediment fans comparable to the fans at the base of mountain ranges. Many of the submarine fans are cut by valleys called fan-valleys which usually connect with the mouths of submarine canyons. Loop-like bends or meanders characterize the channels of rivers in their lower flood plains, but have never been found in the shallow channels that cross the alluvial fans at the base of mountain canyons. Therefore, it was surprising to find that the channel in a very deep submarine fan-valley off Monterey Bay, California, has a tight meander. PMID:17751705

  6. Meander in valley crossing a deep-ocean fan.

    PubMed

    Shepard, F P

    1966-10-21

    Seaward of most submarine canyons there are large sediment fans comparable to the fans at the base of mountain ranges. Many of the submarine fans are cut by valleys called fan-valleys which usually connect with the mouths of submarine canyons. Loop-like bends or meanders characterize the channels of rivers in their lower flood plains, but have never been found in the shallow channels that cross the alluvial fans at the base of mountain canyons. Therefore, it was surprising to find that the channel in a very deep submarine fan-valley off Monterey Bay, California, has a tight meander.

  7. Late Holocene Soil Stratigraphy and Geochronology of Alluvial Sedimentation in the Sonoran Desert, Arizona

    NASA Astrophysics Data System (ADS)

    Bacon, S. N.; McDonald, E. V.; Dalldorf, G. K.; Caldwell, T. G.

    2007-12-01

    The integration of soil stratigraphic investigations and radiocarbon dating at two sites in combination with geomorphic mapping at scales of 1:50k and 1:5k offer insight to the timing and magnitude of alluvial sedimentation during the late Holocene within the Sonoran Desert near Yuma, Arizona. Mapping at 1:50k was performed over an area of 3400 km2 and alluvial landforms were labeled Qf1 to Qf5, from oldest to youngest, using 1- and 5-meter resolution satellite imagery within the U.S. Army Yuma Proving Ground (YPG). Approximately 70% of the identified landforms within YPG are Quaternary alluvial fans, alluvial plains, and active washes, whereas the other 30% consist of mountain highlands, pediments, and badlands. In the southwest portion of YPG near Muggins Mountains, alluvial fan terraces (Qf4) positioned 0.5 m above active washes are characterized as having moderate bar-and-swale microtopography, moderately developed desert pavement, and a Av/ Bw/ Cky/ Cky1/ Cky2/ Cky3 gravelly soil profile. A large piece of charcoalized Ironwood ( Olneya tesota) was recovered from a depth of 0.75 m and yielded three AMS 14C dates that range from 3330 to 2860 cal yr B.P. Geomorphic mapping at a scale of 1:5k indicates that in an area of 25 km2 at the site, the distribution of late Holocene alluvial fan terraces comprise 17% of the surrounding Quaternary alluvium. Similar aged alluvial features were observed about 70 km to the north near South Trigo Peak at YPG. Terraces of a broad and flat alluvial plain positioned 0.5 m above active channels are characterized as having moderate bar- and-swale microtopography, poorly developed desert pavement, and a AC/ C/ Bwkb1/ Bwk1b2/ Bwk2b2/ BCkb2/ Bwkb3 sandy soil profile. A terrestrial gastropod shell ( Lymnea sp.) fragment was recovered from a depth of 0.5 m and yielded an AMS 14C date of 2360-2310 cal yr B.P. Additional geomorphic mapping at 1:5k shows that in an area of 30 km2, the distribution of late Holocene alluvial plain terraces

  8. Constraining Quaternary offset of the Cady fault, eastern California shear zone, southern California, with geologic mapping, luminescence dating, and geophysics

    NASA Astrophysics Data System (ADS)

    Schmidt, K. M.; Mahan, S.; Langenheim, V. E.

    2012-12-01

    aggradation was constant to extrapolate a ground-surface age. IRSL ages from K-feldspar of 10,660 (0.52 m) and 12,940 years (1.15 m) were used to infer an aggradation rate of almost 0.3 mm/yr. If characteristic, the extrapolated ground-surface age pre-dating fault displacement is ~8,780 years. Supporting this inferred deposit age is the deduction that Holocene-aged alluvial fans along the Cady fault are typically friction-dominated granular media, composed primarily of sand and gravel, and consequently are poor candidates for tectonic scarp preservation. Earthquake-induced surface rupture is likely better preserved in deposits older than mid-Holocene, such as the dated deposit, because of the greater proportion of fine-grained, more cohesive sediment derived from pedogenesis. Adopting the extrapolated deposit age of ~8,780 years, and a measured offset of ~7 m, results in a time-averaged sinistral offset rate of 0.8 mm/yr. Therefore the tectonic block-bounding Cady fault is an active feature that may have similar offset rates using short- and long-term slip indicators.

  9. Large Fluvial Fans and Exploration for Hydrocarbons

    NASA Technical Reports Server (NTRS)

    Wilkinson, Murray Justin

    2005-01-01

    A report discusses the geological phenomena known, variously, as modern large (or large modern) fluvial fans or large continental fans, from a perspective of exploring for hydrocarbons. These fans are partial cones of river sediment that spread out to radii of 100 km or more. Heretofore, they have not been much recognized in the geological literature probably because they are difficult to see from the ground. They can, however, be seen in photographs taken by astronauts and on other remotely sensed imagery. Among the topics discussed in the report is the need for research to understand what seems to be an association among fluvial fans, alluvial fans, and hydrocarbon deposits. Included in the report is an abstract that summarizes the global distribution of large modern fluvial fans and a proposal to use that distribution as a guide to understanding paleo-fluvial reservoir systems where oil and gas have formed. Also included is an abstract that summarizes what a continuing mapping project has thus far revealed about the characteristics of large fans that have been found in a variety of geological environments.

  10. Development and maintenance of a telescoping debris flow fan in response to human-induced fan surface channelization, Chalk Creek Valley Natural Debris Flow Laboratory, Colorado, USA

    NASA Astrophysics Data System (ADS)

    Wasklewicz, T.; Scheinert, C.

    2016-01-01

    Channel change has been a constant theme throughout William L. Graf's research career. Graf's work has examined channel changes in the context of natural environmental fluctuations, but more often has focused on quantifying channel change in the context of anthropogenic modifications. Here, we consider how channelization of a debris flows along a bajada has perpetuated and sustained the development of 'telescoping' alluvial fan. Two-dimensional debris-flow modeling shows the importance of the deeply entrenched channelized flow in the development of a telescoping alluvial fan. GIS analyses of repeat (five different debris flows), high-resolution (5 cm) digital elevation models (DEMs) generated from repeat terrestrial laser scanning (TLS) data elucidate sediment and topographic dynamics of the new telescoping portion of the alluvial fan (the embryonic fan). Flow constriction from channelization helps to perpetuate debris-flow runout and to maintain the embryonic fan and telescoping nature of the alluvial fan complex. Embryonic fan development, in response to five debris flows, proceeds with a major portion of the flows depositing on the southern portion of the embryonic fan. The third through the fifth debris flows also begin to shift some deposition to the northern portion of the embryonic. The transfer of sediment from a higher portion of the embryonic fan to a lower portion continues currently on the embryonic fan. While channelized flow has been shown to be critical to the maintenance of the telescoping fan, the flow constriction has led to higher than background levels of sediment deposition in Chalk Creek, a tributary of the Arkansas River. A majority of the sediment from each debris flow is incorporated into Chalk Creek as opposed to being stored on the embryonic fan.

  11. Hydrogeologic features of the alluvial deposits in the Greybull River valley, Bighorn Basin, Wyoming

    USGS Publications Warehouse

    Cooley, M.E.; Head, W.J.

    1979-01-01

    The alluvial aquifer along the Greybull River in Wyoming, consists principally of the Greybull terrace doposits and flood-plain alluvium but also includes Burlington terrace deposits east of Burlington, the McKinnie terrace, and the younger, generally undissected alluvial-fan deposits. Well-log data and 18 surface-resistivity measurements at four localities indicate that the thickness of the alluvial aquifer is as much as 60 feet thick only near Burlington and Otto. The most favorable area for development of ground water from the alluvial aquifer is near Burlington and Otto where relatively large amounts of water can be obtained from the Greybull terrace deposits and the flood-plain alluvium. Elsewhere, the deposits of the alluvial aquifer yield only small amounts of water to wells. (Woodard-USGS)

  12. Large Fluvial Fans: Aspects of the Attribute Array

    NASA Technical Reports Server (NTRS)

    Wilkinson, Justin M.

    2015-01-01

    In arguing for a strict definition of the alluvial fan (coarse-grained with radii less than10 km, in mountain-front settings), Blair and McPherson (1994) proposed that there is no meaningful difference between large fluvial fans (LFF) and floodplains, because the building blocks of both are channel-levee-overbank deposits. Sediment bodies at the LFF scale (greater than 100 km long, fan-shaped in planform), are relatively unstudied although greater than 160 are now identified globally. The following perspectives suggest that the significance of LFF needs to be reconsidered.

  13. Adaptable DC offset correction

    NASA Technical Reports Server (NTRS)

    Golusky, John M. (Inventor); Muldoon, Kelly P. (Inventor)

    2009-01-01

    Methods and systems for adaptable DC offset correction are provided. An exemplary adaptable DC offset correction system evaluates an incoming baseband signal to determine an appropriate DC offset removal scheme; removes a DC offset from the incoming baseband signal based on the appropriate DC offset scheme in response to the evaluated incoming baseband signal; and outputs a reduced DC baseband signal in response to the DC offset removed from the incoming baseband signal.

  14. Layered Fan

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03692 Layered Fan

    This beautiful fan deposit is located at the end of a mega-gully that empties into the southern trough of Coprates Chasma.

    Image information: VIS instrument. Latitude -14.9N, Longitude 299.8E. 17 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.

  15. Debris-flow hazards on tributary junction fans, Chitral, Hindu Kush Range, northern Pakistan

    NASA Astrophysics Data System (ADS)

    Khan, M. Asif; Haneef, M.; Khan, Anwar S.; Tahirkheli, Tazeem

    2013-01-01

    The Chitral district of northern Pakistan lies in the eastern Hindu Kush Range. The population in this high-relief mountainous terrain is restricted to tributary-junction fans in the Chitral valley. Proximity to steep valley slopes renders these fans prone to hydrogeomorphic hazards, including landslides, floods and debris flows. This paper focuses on debris-flow hazards on tributary-junction fans in Chitral. Using field observations, satellite-image analyses and a preliminary morphometry, the tributary-junction fans in the Chitral valley are classified into (1) discrete and (2) composite. The discrete fans are modern-day active landforms and include debris cones associated with ephemeral gullies, debris fans associated with ephemeral channels and alluvial fans formed by perennial streams. The composite fans are a collage of sediment deposits of widely different ages and formed by diverse alluvial-fan forming processes. These include fans formed predominantly during MIS-2/Holocene interglacial stages superimposed by modern-day alluvial and debris fans. Composite fans are turned into relict fans when entrenched by modern-day perennial streams. These deeply incised channels discharge their sediment load directly into the trunk river without significant spread on fan surface. In comparison, when associated with ephemeral streams, active debris fans develop directly at composite-fan surfaces. Major settlements in Chitral are located on composite fans, as they provide large tracts of leveled land with easy accesses to water from the tributary streams. These fan surfaces are relatively more stable, especially when they are entrenched by perennial streams (e.g., Chitral, Ayun, and Reshun). When associated with ephemeral streams (e.g., Snowghar) or a combination of ephemeral and perennial streams (e.g., Drosh), these fans are subject to frequent debris-flow hazards. Fans associated with ephemeral streams are prone to high-frequency (˜10 years return period) debris

  16. Generation of waterfalls at intermittently alluviated fault scarps releases tectonic forcing on a climatic beat.

    NASA Astrophysics Data System (ADS)

    Malatesta, Luca C.; Lamb, Michael P.

    2016-04-01

    Normal or reverse faults bonding mountain catchments typically mark the transition from the erosional to the depositional domain where bedrock channels flow into alluvial fans. We show here that interactions between the two fluvial domains can result in knickpoints that convolve tectonic and climatic signals. Changes in the ratio of sediment and water fluxes (Qs/Qw) modify the equilibrium geometry of the system and in particular of the reactive alluvial reaches so that a larger Qs/Qw forces steepening of the fan, backfilling of the bedrock reach and a heightened base level. Under these conditions, slip on the fault - covered and shielded by alluvium - can accumulate over several seismic cycles before being released at once by incision of the alluvial fan back to a shallow geometry. We demonstrate in this study that climate-driven aggradation and incision of alluvial fans in the Death Valley area can account for otherwise unexplained waterfalls at the base of catchments manyfold the height of coseismic throw. As a consequence, in this common configuration, tectonic slip can accumulate and be released at once on a tempo set by climatic fluctuations. Such that the faster denudation rate that might follow from increased precipitations is accompanied by an important retreating knickpoint. We propose that this mechanism can increase catchment reactivity and broaden the range of external forcings potentially recorded in the stratigraphy.

  17. Rhone deep-sea fan: morphostructure and growth pattern

    SciTech Connect

    Droz, L.; Bellaiche, G.

    1985-03-01

    A detailed bathymetric survey of the Rhone deep-sea fan and its feeder canyon using Sea-Beam, reveals morphologic features such as very tight meanders of the canyon and channel courses, cutoff meanders, and downslope narrowing of the inner channel floor. Striking similarities exist between these deep-sea features and some continental landforms, especially in alluvial plain areas or desert environments. Sea-Beam also reveals evidence of huge slump scars affecting the slope and fan. The superficial structure of the Rhone Fan results from the stacking of numerous lenticular acoustic units displaying specific seismic characters in which the authors recognized channel and levee facies. Except in the upper fan area, these units have not been constant; they have generally migrated, owing to shifting of the channel throughout fan evolution. Construction of the fan probably began as early as the early Pliocene and continued to the close of the Wurmian (late Wisconsinian). The fan's growth pattern could be associated with climatic fluctuations. The principal sedimentary mechanism responsible for the growth of the fan appears to be turbidity currents, but mass gravity flows have also been an important factor in building the fan by occasionally blocking the main channel and forcing it to migrate.

  18. Minimizing fan energy costs

    SciTech Connect

    Monroe, R.C.

    1985-05-27

    Minimizing fan energy costs and maximizing fan efficiency is the subject of this paper. Blade design itself can cause poor flow distribution and inefficiency. A basic design criterion is that a blade should produce uniform flow over the entire plane of the fan. Also an inherent problem with the axial fan is swirl -- the tangential deflection of exit-flow caused by the effect of torque. Swirl can be prevented with an inexpensive hub component. Basic efficiency can be checked by means of the fan's performance curve. Generally, fewer blades translate into higher axial-fan efficiency. A crowded inboard area creates hub turbulence which lessens efficiency. Whether the pitch of fan blades is fixed or variable also affects energy consumption. Power savings of 50% per year or more can be realized by replacing fixed-pitch, continuously operating fans with fans whose blade pitch or speed is automatically varied.

  19. Supersonic throughflow fans

    NASA Technical Reports Server (NTRS)

    Ball, C. L.; Moore, R. D.

    1988-01-01

    Supersonic throughflow fan research, and technology needs are reviewed. The design of a supersonic throughflow fan stage, a facility inlet, and a downstream diffuser is described. The results from the analysis codes used in executing the design are shown. An engine concept intended to permit establishing supersonic throughflow within the fan on the runway and maintaining the supersonic throughflow condition within the fan throughout the flight envelope is presented.

  20. Influence of depositional processes on the composition of sandstone in a wave-dominated fan delta

    SciTech Connect

    Suttner, L.J.; Hood, L.A.; Dutta, P.K.

    1988-02-01

    Sandstone in the Lower Pennsylvanian (Morrowan-Atokan) portion of the Fountain Formation in the Manitou Springs, Colorado, area was derived from Precambrian granite gneiss and deposited in associated medial alluvial-fan, foreshore, shoreface, and offshore environments constituting a wave-dominated fan delta. The sandstone facies are arranged in six vertically stacked progradational sequences. The regressive marine portions of the sequences rest on a transgressive lag conglomerate and range from 5 to 9 m thick. The alluvial deposits capping each sequence are up to 20 m thick.

  1. Abo Formation alluvial facies and Associated Basin Fill, Sacramento Mountains, New Mexico

    SciTech Connect

    Speer, S.W.

    1986-03-01

    Outcrops of the Abo Formation (Wolfcampian to early Leonardian age) in the Sacramento Mountains of south-central New Mexico record the evolution of a dry alluvial fan system as it was deposited off the pedernal uplift into the Orogrande basin. The location and orientation of present-day outcrops allow us to observe an inferred east-to-west transverse facies tract consisting of: (1) proximal alluvial fans (lower Abo), which are contiguous in places with underlying Laborcita Formation fan-deltaic sediments; (2) medial anastomosed streams (middle Abo); and (3) distal low-gradient mud-dominated flood basins characterized by either distributary streams (upper Abo) or clastic tidal flats (Lee Ranch Tongue of the Abo) with associated marine carbonates (Pendejo Tongue of the Hueco Formation). Tectonism in the Pedernal highlands, which climaxed during the Late Pennsylvanian, apparently continued well into the Wolfcampian in this region, as evidenced by a major basal Abo unconformity and distinct stacked megasequences of lower Abo alluvial fan lithofacies. However, by the middle Abo, tectonic activity had quiesced and the uplift began eroding and retreating to the north and east. By the late Abo, a pediment surface had formed that was subsequently onlapped by upper Abo and eventually Yeso Formation sediments.

  2. Noise Prediction Module for Offset Stream Nozzles

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.

    2011-01-01

    A Modern Design of Experiments (MDOE) analysis of data acquired for an offset stream technology was presented. The data acquisition and concept development were funded under a Supersonics NRA NNX07AC62A awarded to Dimitri Papamoschou at University of California, Irvine. The technology involved the introduction of airfoils in the fan stream of a bypass ratio (BPR) two nozzle system operated at transonic exhaust speeds. The vanes deflected the fan stream relative to the core stream and resulted in reduced sideline noise for polar angles in the peak jet noise direction. Noise prediction models were developed for a range of vane configurations. The models interface with an existing ANOPP module and can be used or future system level studies.

  3. 2. EXTERIOR VIEW OF NEW FAN HOUSE AND HILLMAN FAN ...

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

    2. EXTERIOR VIEW OF NEW FAN HOUSE AND HILLMAN FAN HOUSE LOOKING NORTHEAST The New Fan House is in the foreground; the metal fan housing and updraft chimney are attached to the north side. The Hillman Fan House is in the background; the brick airway, fan housing, and updraft chimney are visible. - Dorrance Colliery Fan Complex, South side of Susquehanna River at Route 115 & Riechard Street, Wilkes-Barre, Luzerne County, PA

  4. Tectonic and climatic controls on fan systems: The Kohrud mountain belt, Central Iran

    NASA Astrophysics Data System (ADS)

    Jones, Stuart J.; Arzani, Nasser; Allen, Mark B.

    2014-04-01

    Late Pleistocene to Holocene fans of the Kohrud mountain belt (Central Iran) illustrate the problems of differentiating tectonic and climatic drivers for the sedimentary signatures of alluvial fan successions. It is widely recognised that tectonic processes create the topography that causes fan development. The existence and position of fans along the Kohrud mountain belt, NE of Esfahan, are controlled by faulting along the Qom-Zefreh fault system and associated fault zones. These faults display moderate amounts of historical and instrumental seismicity, and so may be considered to be tectonically active. However, fluvial systems on the fans are currently incising in response to low Gavkhoni playa lake levels since the mid-Holocene, producing incised gullies on the fans up to 30 m deep. These gullies expose an interdigitation of lake deposits (dominated by fine-grained silts and clays with evaporites) and coarse gravels that characterise the alluvial fan sediments. The boundaries of each facies are mostly sharp, with fan sediments superimposed on lake sediments with little to no evidence of reworking. In turn, anhydrite-glauberite, mirabilite and halite crusts drape over the gravels, recording a rapid return to still water, shallow ephemeral saline lake sedimentation. Neither transition can be explained by adjustment of the hinterland drainage system after tectonic uplift. The potential influence in Central Iran of enhanced monsoons, the northward drift of the Intertopical Convergence Zone (ITCZ) and Mediterranean climates for the early Holocene (~ 6-10 ka) point to episodic rainfall (during winter months) associated with discrete high magnitude floods on the fan surfaces. The fan sediments were deposited under the general influence of a highstand playa lake whose level was fluctuating in response to climate. This study demonstrates that although tectonism can induce fan development, it is the sensitive balance between aridity and humidity resulting from changes in

  5. Variable scale channel avulsion history using fan architecture and stratigraphy, and sediment provenance of Sutlej-Yamuna fans in northwest Gangetic plains during Late Quaternary

    NASA Astrophysics Data System (ADS)

    Singh, Ajit; Gupta, Sanjeev; Sinha, Rajiv; Densmore, Alexander; Buylaert, Jan-Pieter; Carter, Andrew; Van-Dijk, Wout M.; Joshi, Suneel; Nayak, Nibedita; Mason, Philippa J.; Kumar, Dewashish; Mondal, Setbandhu; Murray, Andrew; Rai, Shiv P.; Shekhar, Shashank

    2016-04-01

    Channel avulsion during fan development controls distribution and deposition of channel sandbodies and hence alluvial architecture of a fan system. Variable scale spatio-temporal information of fluvial responses to past climate changes is stored in these channel sandbodies. Further these channel sandbodies form fluvial aquifers in alluvial fans and therefore understanding of alluvial architecture and stratigraphy of a fan is crucial for development of groundwater management strategies. In this study we used multiple approaches to map subsurface fluvial aquifer architecture and alluvial stratigraphy, and to estimate sediment provenance using U-Pb dating of detrital zircon grains of Sutlej-Yamuna fan system in northwest India. Satellite imagery based geomorphic mapping shows two large fan system with interfan area. The fan surfaces show presence of major and minor paleochannels. 2D resistivity tomography along several transects across fan surfaces shows distinct layers with contrasting resistivity values. These geo-electric facies corresponds to presence of channel sandbodies beneath surface signature of paleochannels and finer floodplain deposits useful to demarcate lateral extent of subsurface channel sandbodies. A more detailed subsurface stratigraphy using ~50m deep sediment cores and their luminescence ages from across fan surface shows presence of multi-storey sandbodies (MSB) separated by floodplain fines. Within the MSB, individual channel deposits are identified by presence of channel scour surfaces located at coarse sand overlying fine sand layer. Depositional ages of MSB's ranges from ~81 ka (late MIS5) to ~15 ka (MIS2) with major depositional break during MIS3 in parts of the fans. Sediment aggradation rate varies laterally across fan surface as well as vertically down the depth with an average rate of 0.54 mm/year. Fluvial channel persistence for studied time interval (about last 81 ka BP) shows major depositional breaks (and possible incision) at ~41 ka

  6. Late Pleistocene eolian-alluvial interference in the Balearic Islands (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Pomar, Francisco; Del Valle, Laura; Fornós, Joan J.; Gómez-Pujol, Lluís; Anechitei-Deacu, Valentina; Timar-Gabor, Alida

    2016-04-01

    This study deals with alluvial fan and aeolian sediments interference. Although initially they are two different environments, with different processes and resulting forms, very often their interaction produces deposits that share characteristics and features from both environments, as well as, maintain inherited elements from one to each other. In this sense, the aeolian-alluvial interference is the geomorphological expression of the coincidence, disruption and/or overlapping of aeolian and alluvial environments. Climate appears to be one of the most important controls on the role and magnitude of each environment in terms of sediment supply, precipitation, runoff or aeolian transport. In this study, eight major sedimentary facies have been described involving the succession of coastal, aeolian, colluvial and alluvial environments. Carbonate sandstones, breccias, conglomerates and fine-grained deposits are the main component of these sequences. OSL dating of aeolian levels indicate that their deposition took place during the Late Pleistocene, establishing a paleoclimatic evolution of Balearic coastal areas during the last 125 ka. The sedimentological and chronological analysis of these deposits allows reconstructing the coastal environmental changes during the Late Pleistocene at the Balearic archipelago. Keywords: Alluvial sedimentation, eolian sedimentation, alluvial-eolian interference, sea level, Late Pleistocene, Balearic Islands.

  7. TOPOGRAPHICAL CHARACTERISTICS OF LOCATION OF SPARSE VILLAGE AT AN ALLUVIAL FUN

    NASA Astrophysics Data System (ADS)

    Hattori, Shuhei; Nii, Akiyoshi

    This paper aims to clarify the topographical characteristics of location of sparse village at an alluvial fan. For that purpose, using the map which can grasp microtopography, examined the relation between topographical location of head families and Shinto shrines, and their site devices. As a result, the following points are mainly clarified. 1) The way of catching called a geographical feature line is effective in an alluvial fan. 2) The head family tends to be located in advantageous topographical feature on prevention of floods. Especially head families chose the place which cannot suffer damage of a fl ood easily although it is lower than the surrounding land. 3) It suggested that the Shinto shrines were established in the position which protects a colony from a fl ood from the topographical location feature of them, spatial relationship with the village, and the tradition of them.

  8. Seismic offset balancing

    SciTech Connect

    Ross, C.P.; Beale, P.L.

    1994-01-01

    The ability to successfully predict lithology and fluid content from reflection seismic records using AVO techniques is contingent upon accurate pre-analysis conditioning of the seismic data. However, all too often, residual amplitude effects remain after the many offset-dependent processing steps are completed. Residual amplitude effects often represent a significant error when compared to the amplitude variation with offset (AVO) response that the authors are attempting to quantify. They propose a model-based, offset-dependent amplitude balancing method that attempts to correct for these residuals and other errors due to sub-optimal processing. Seismic offset balancing attempts to quantify the relationship between the offset response of back-ground seismic reflections and corresponding theoretical predictions for average lithologic interfaces thought to cause these background reflections. It is assumed that any deviation from the theoretical response is a result of residual processing phenomenon and/or suboptimal processing, and a simple offset-dependent scaling function is designed to correct for these differences. This function can then be applied to seismic data over both prospective and nonprospective zones within an area where the theoretical values are appropriate and the seismic characteristics are consistent. A conservative application of the above procedure results in an AVO response over both gas sands and wet sands that is much closer to theoretically expected values. A case history from the Gulf of Mexico Flexure Trend is presented as an example to demonstrate the offset balancing technique.

  9. Fire, climate, and alluvial system dynamics: A Holocene record from Yellowstone National Park

    SciTech Connect

    Meyer, G.A. . Dept. of Geology); Wells, S.G. . Dept. of Earth Sciences); Jull, A.J. . NSF-Arizona Accelerator Facility For Isotope Dating)

    1992-01-01

    Many large debris-flow, hyperconcentrated-flow, and flood-streamflow sediment transport events have been produced in steep basins that were burned in the 1988 fires in northeaster Yellowstone National Park. The charcoal- and fines-rich character of fire-related debris-flow deposits and the abundance of similar facies in Holocene fan sections have allowed them to construct a [sup 14]C-dated chronology of fire-related sedimentation in the Soda Butte and Slough Creek drainages for the last 3500 years. Major periods of fire-related alluvial fan aggradation are interpreted as drought-dominated with the support of local paleoenvironmental data and statistical analyses of historical climate-fire relations; however, some fire-related events may occur due to high climatic variability and severe short-term drought within generally moist intervals. The last major episode of fire-related debris-flow activity encompasses the Medieval Warm Period of 900--1300 AD and peaks ca. 1150 AD; a prior episode culminates ca. 350--100 BC. Wetter periods contain minimal fire-related fan sedimentation; however, floodplain broadening and aggradation occurs along axial streams. Higher average snowmelt runoff discharges are probably involved, such that the dominant alluvial activity shifts to removal of sediment from alluvial fan storage and transport to downstream floodplains. The Little Ice Age (ca. 1300--1900 AD) contains minimal fire-related debris0flow activity and is associated with floodplain aggradation of the T4 terrace, and independent evidence suggests substantially wetter conditions during T3 aggradation ca. 350--650 AD. Thus, small-scale climate changes of the late Holocene effectively control the dominant mode of alluvial activity.

  10. 1. EXTERIOR VIEW OF NEW FAN HOUSE AND HILLMAN FAN ...

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

    1. EXTERIOR VIEW OF NEW FAN HOUSE AND HILLMAN FAN HOUSE LOOKING NORTHWEST The building on the left, the New Fan House, houses a Corliss steam engine which powered a Buffalo Forge Company single inlet Duplex Conoidal centrifugal exhausted fan through a metal updraft chimney. Part of the brick airway leading to the Baltimore shaft is visible to its right rear. The Hillman Fan House, on the right, houses the 1883 double inlet Guibal fan. The south entry, the curve of the fan housing, and brick updraft chimney are visible in this view. - Dorrance Colliery Fan Complex, South side of Susquehanna River at Route 115 & Riechard Street, Wilkes-Barre, Luzerne County, PA

  11. Policy development for biodiversity offsets: a review of offset frameworks.

    PubMed

    McKenney, Bruce A; Kiesecker, Joseph M

    2010-01-01

    Biodiversity offsets seek to compensate for residual environmental impacts of planned developments after appropriate steps have been taken to avoid, minimize or restore impacts on site. Offsets are emerging as an increasingly employed mechanism for achieving net environmental benefits, with offset policies being advanced in a wide range of countries (i.e., United States, Australia, Brazil, Colombia, and South Africa). To support policy development for biodiversity offsets, we review a set of major offset policy frameworks-US wetlands mitigation, US conservation banking, EU Natura 2000, Australian offset policies in New South Wales, Victoria, and Western Australia, and Brazilian industrial and forest offsets. We compare how the frameworks define offset policy goals, approach the mitigation process, and address six key issues for implementing offsets: (1) equivalence of project impacts with offset gains; (2) location of the offset relative to the impact site; (3) "additionality" (a new contribution to conservation) and acceptable types of offsets; (4) timing of project impacts versus offset benefits; (5) offset duration and compliance; and (6) "currency" and mitigation replacement ratios. We find substantial policy commonalities that may serve as a sound basis for future development of biodiversity offsets policy. We also identify issues requiring further policy guidance, including how best to: (1) ensure conformance with the mitigation hierarchy; (2) identify the most environmentally preferable offsets within a landscape context; and (3) determine appropriate mitigation replacement ratios.

  12. Policy Development for Biodiversity Offsets: A Review of Offset Frameworks

    NASA Astrophysics Data System (ADS)

    McKenney, Bruce A.; Kiesecker, Joseph M.

    2010-01-01

    Biodiversity offsets seek to compensate for residual environmental impacts of planned developments after appropriate steps have been taken to avoid, minimize or restore impacts on site. Offsets are emerging as an increasingly employed mechanism for achieving net environmental benefits, with offset policies being advanced in a wide range of countries (i.e., United States, Australia, Brazil, Colombia, and South Africa). To support policy development for biodiversity offsets, we review a set of major offset policy frameworks—US wetlands mitigation, US conservation banking, EU Natura 2000, Australian offset policies in New South Wales, Victoria, and Western Australia, and Brazilian industrial and forest offsets. We compare how the frameworks define offset policy goals, approach the mitigation process, and address six key issues for implementing offsets: (1) equivalence of project impacts with offset gains; (2) location of the offset relative to the impact site; (3) “additionality” (a new contribution to conservation) and acceptable types of offsets; (4) timing of project impacts versus offset benefits; (5) offset duration and compliance; and (6) “currency” and mitigation replacement ratios. We find substantial policy commonalities that may serve as a sound basis for future development of biodiversity offsets policy. We also identify issues requiring further policy guidance, including how best to: (1) ensure conformance with the mitigation hierarchy; (2) identify the most environmentally preferable offsets within a landscape context; and (3) determine appropriate mitigation replacement ratios.

  13. Calibrated, late Quaternary age indices using clast rubification and soil development on alluvial surfaces in Pilot Knob Valley, Mojave Desert, southeastern California

    NASA Astrophysics Data System (ADS)

    Helms, John G.; McGill, Sally F.; Rockwell, Thomas K.

    2003-11-01

    The orange coating (varnish) that forms on the undersides (ventral sides) of clasts in desert pavements constitutes a potential relative-age indicator. Using Munsell color notation, we semiquantified the color of the orange, ventral varnish on the undersides of clasts from 15 different alluvial fan and terrace surfaces of various ages ranging from less than 500 to about 25,000 yr. All of the surfaces studied are located along the central portion of the left-lateral Garlock fault, in the Mojave Desert of southern California. The amount of left-lateral offset may be used to determine the relative ages of the surfaces. The previously published slip rate of the fault may also be used to estimate the absolute age of each surface. The color of the ventral varnish is strongly correlated with surface age and appears to be a more reliable age-indicator than the percentage coverage of dorsal varnish. Soil development indices also were not as strongly correlated with age, as were the colors of the ventral varnish. In particular, rubification appears to be more useful than soils for distinguishing relative ages among Holocene surfaces. Humidity sensors indicated that the undersides of clasts condensed moisture nightly for a period of several days to over a week after each rain. These frequent wet-dry cycles may be responsible for the rapid development of clast rubification on Holocene surfaces.

  14. Training SVMs without offset

    SciTech Connect

    Steinwart, Ingo; Hush, Don; Scovel, Clint

    2009-01-01

    We develop, analyze, and test a training algorithm for support vector machine cla.'>sifiers without offset. Key features of this algorithm are a new stopping criterion and a set of working set selection strategies that, although inexpensive, do not lead to substantially more iterations than the optimal working set selection strategy. For these working set strategies, we establish convergence rates that coincide with the best known rates for SYMs with offset. We further conduct various experiments that investigate both the run time behavior and the performed iterations of the new training algorithm. It turns out, that the new algorithm needs less iterations and run-time than standard training algorithms for SYMs with offset.

  15. High resolution sequence stratigraphy and reservoir architecture of proximal alluvial deposits: The Buntsandstein facies of central Spain

    SciTech Connect

    Oliver, L.; Desaubliaux, G.; Verdier, F.

    1995-08-01

    The Buntsandstein facies outcrops along a 12 km long, 150 m thick cuesta near Ayllon (Central Spain). The outcrop study is based on vertical sedimentological sections and continuous photo paneling, and demonstrates the presence of two depositional systems: an alluvial fan system in the lower half of the outcrop, and a straight and braided river system in the upper part of the outcrop. This overall evolution is probably related to base-level fall to base-level rise cycle, in which the reservoir architecture is linked to genetic units stacking pattern: during the base-level fall, the alluvial fan is prograding over sand flat and sandy alluvial plain deposits. Coarse and pebbly proximal sandsheets are interbedded with finer reddish distal deposits. Reservoirs units are laterally continuous, but silty alluvial plain deposits constitute vertical permeability barriers, during base-level stillstand, erosive channels and sandsheets are vertically amalgamated. Reservoirs units are laterally continuous and vertically connected, during the base-level rise, alluvial fan deposits are overlapped by straight river deposits. Reservoirs units are laterally connected but silty argillaceous alluvial plain horizons are preserved, at the end of the base-level rise, braided and straight river deposits are amalgamated. Fully connected, these reservoirs units have a very large lateral extension. A lithofacies database is compiled on this outcrop, and variograms, horizontal and vertical proportion curves are completed. Each stage of the base-level cycle is then quantitatively characterized by a specific heterogeneity pattern. The outcrop study will improve the prediction of reservoir extension and architecture in subsurface gas storage of the Paris basin.

  16. Fault-scarp morphology and amount of surface offset on late-Quaternary surficial deposits, eastern escarpment of the central Sierra Nevada, CA

    SciTech Connect

    Berry, M.E. . Dept. of Geology)

    1992-01-01

    Faults scarps, formed on glacial deposits and an alluvial fan near the east-central Sierra Nevada mountain front by late-Quaternary movement on the Hilton Creek (HCF), Wheeler Crest (WCFZ) and Coyote Warp (CWFZ) fault zones, were profiled to determine the amount and to estimate the recency of fault offset. Areas studied include McGee (N--near Lake Crowley), Pine, Mount Tom, Basin Mountain, McGee (S--near Bishop), and Bishop Creek drainages. The profile data indicate that movement of the range-front faults (HCF and WCFZ), which is characterized by normal slip, has offset Tioga-age deposits 6.5-26 m. Offset of Tahoe-age moraines cannot be measured directly because the landforms are buried at the mountain-front by moraines from later glaciations. However, the amount of offset is estimated at 52--130 m, based on crest-height differences between Tahoe and Tioga moraines. The rates of slip are highest on the northern end of the HCF, at McGee (N) Creek; the higher slip rates in this latter area may be related to its close proximity to the Long Valley caldera, where tectonic processes are complex and considered closely related to ongoing magmatic activity. The preservation of bevels on the fault scarps in both HCF and WCFZ, combined with the amounts of surface offset on the late-Pleistocene moraines, and AMS C-14 dates for charcoal found in fault-scarp colluvium, indicate that large ground-rupturing events have occurred on these faults during the Holocene. In contrast to the mountain-front faults, faults in the CWFZ, on a broad warp that separates the WCFZ from range-front faults to the south of Bishop, do not cross Tioga moraines, implying that surface rupture has not occurred in the CWFZ for at least 15,000-25,000 years. The degraded morphology of the fault scarps on adjacent Tahoe and pre-Tahoe moraines, which have been offset between 10.5 and 30 m, attests to the lack of late-Pleistocene and Holocene fault activity in this latter area.

  17. Late Quaternary sedimentation on the Leidy Creek fan, Nevada-California: Geomorphic responses to climate change

    USGS Publications Warehouse

    Reheis, M.C.; Slate, J.L.; Throckmorton, C.K.; McGeehin, J.P.; Sarna-Wojcicki, A. M.; Dengler, L.

    1996-01-01

    Well-dated surface and subsurface deposits in semiarid Fish Lake Valley, Nevada and California, demonstrate that alluvial-fan deposition is strongly associated with the warm dry climate of the last two interglacial intervals, and that fans were stable and (or) incised during the last glaciation. Fan deposition was probably triggered by a change from relatively moist to arid conditions causing a decrease in vegetation cover and increases in flash floods and sediment yield. We think that this scenario applies to most of the other valleys in the southern Basin and Range. Radiocarbon, tephra, and a few thermoluminescence and cosmogenic ages from outcrops throughout Fish Lake Valley and from cores on the Leidy Creek fan yield ages of > 100-50 ka and 11-0 ka for the last two periods of alluvial-fan deposition. Mapping, coring and shallow seismic profiling indicate that these periods were synchronous throughout the valley and on the proximal and distal parts of the fans. From 50 to 11 ka, fan deposition ceased, a soil formed on the older alluvium and the axial drainage became active as runoff and stream competence increased. Slow deposition due to sheet flow or aeolian processes locally continued during this interval, producing cumulic soil profiles. The soil was buried by debris-flow sediment beginning at about 11 ka, coincident with the onset of relatively dry and warm conditions in the region. However, ground-water discharge maintained a large freshwater marsh on the valley floor throughout the Holocene. Pulses of deposition during the Holocene are recorded in the marsh and fan deposits; some pulses coincided with periods of or transitions to warm, dry climate indicated by proxy climate records, whereas others may reflect local disturbances associated with volcanism and fires. Within the marsh deposits, much of the clastic material is probably desert loess. In addition, the deposition of coppice dunes within the fan deposits coincides with two dry periods during the

  18. Development of the Astoria Canyon-Fan physiography and comparison with similar systems

    USGS Publications Warehouse

    Nelson, C.H.; Carlson, P.R.; Byrne, J.V.; Alpha, T.R.

    1970-01-01

    A detailed bathymetric study of Astoria Canyon and Astoria Fan provides a model for typical submarine canyon-fan systems. The present canyon head is 9 miles (17 km) west of the Columbia River mouth but buried Pleistocene channels appear to have connected the two features in the past. The canyon, which is distinguished by its relief, V-shaped profiles, and numerous tributaries, winds sinuously and is coincident with apparent structural trends across the continental shelf and slope. At the fan apex, the canyon mouth merges smoothly into Astoria Channel, which is characterized by its U-shaped profiles, lower walls of even height, and levee development. Astoria Channel and the fan valley at the base of the continental slope are the most recently active of a series of main fan valleys that appear to have: (1) progressively "hooked left"; (2) migrated from north to south across the fan during its formation; and (3) been partly responsible for the asymmetrical shape of the fan. The deep, narrow upper fan valleys that characterize the steep (> 1:100, or 0??35???) and rough (10-30 fathoms, or 18-55 m) upper fan surface break into distributaries on the middle fan, where there is the sharpest change in gradient. The main valleys become broader and shallower down the fan, while the generally concave fan surface grades to nearly a flat seafloor (to gradients < 1:1000, or 0??0.5???), (< 10 fathoms, or 18 m relief). Similarity of Astoria Canyon-Fan system with other deep-sea fan and alluvial fan systems, suggests the hypothesis that size of drainage basin, sediment size, and sediment load control the size, gradient, and valley development of any fan system. Data from bathymetry, seismic refraction stations, and sediment load of the Columbia River indicate that the cutting of Astoria Canyon and the deposition of the unconsolidated sediment layer forming Astoria Fan could have been accomplished during the Pleistocene. A similar history can be suggested for other major submarine

  19. Smart Fan Modules And System

    DOEpatents

    Cipolla, Thomas M.; Kaufman, Richard I.; Mok, Lawrence S.

    2003-07-15

    A fan module including: two or more individual fans, each fan having an air movement means and a motor engaged with the air movement means for accelerating air entering each of the two or more individual fans; a temperature sensor for sensing a temperature associated with the two or more fans and for outputting a first signal corresponding to the temperature; rotational speed sensor for outputting a second signal corresponding to a rotational speed of each of the two or more fans; and a processor for receiving the first and second signals and controlling the two or more individual fans based on the first and second signals. A fan module including: two or more individual fans, each fan having an air movement means and a motor engaged with the air movement means for accelerating air entering each of the two or more individual fans; a temperature sensor for sensing a temperature associated with the two or more fans and for outputting a first signal corresponding to the temperature; rotational speed sensor for outputting a second signal corresponding to a rotational speed of each of the two or more fans; and a processor for receiving the first and second signals and controlling the two or more individual fans based on the first and second signals.

  20. Offset Compound Gear Drive

    NASA Technical Reports Server (NTRS)

    Stevens, Mark A.; Handschuh, Robert F.; Lewicki, David G.

    2010-01-01

    The Offset Compound Gear Drive is an in-line, discrete, two-speed device utilizing a special offset compound gear that has both an internal tooth configuration on the input end and external tooth configuration on the output end, thus allowing it to mesh in series, simultaneously, with both a smaller external tooth input gear and a larger internal tooth output gear. This unique geometry and offset axis permits the compound gear to mesh with the smaller diameter input gear and the larger diameter output gear, both of which are on the same central, or primary, centerline. This configuration results in a compact in-line reduction gear set consisting of fewer gears and bearings than a conventional planetary gear train. Switching between the two output ratios is accomplished through a main control clutch and sprag. Power flow to the above is transmitted through concentric power paths. Low-speed operation is accomplished in two meshes. For the purpose of illustrating the low-speed output operation, the following example pitch diameters are given. A 5.0 pitch diameter (PD) input gear to 7.50 PD (internal tooth) intermediate gear (0.667 reduction mesh), and a 7.50 PD (external tooth) intermediate gear to a 10.00 PD output gear (0.750 reduction mesh). Note that it is not required that the intermediate gears on the offset axis be of the same diameter. For this example, the resultant low-speed ratio is 2:1 (output speed = 0.500; product of stage one 0.667 reduction and stage two 0.750 stage reduction). The design is not restricted to the example pitch diameters, or output ratio. From the output gear, power is transmitted through a hollow drive shaft, which, in turn, drives a sprag during which time the main clutch is disengaged.

  1. 9. DETAIL OF THE FAN HOUSE INTERIOR, SHOWING FAN OPENINGS. ...

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

    9. DETAIL OF THE FAN HOUSE INTERIOR, SHOWING FAN OPENINGS. - Tower Hill No. 2 Mine, Approximately 0.47 mile Southwest of intersection of Stone Church Road & Township Route 561, Hibbs, Fayette County, PA

  2. Fan-surface dynamics and biogenic calcrete development: Interactions during ultimate phases of fan evolution in the semiarid SE Spain (Murcia)

    NASA Astrophysics Data System (ADS)

    Alonso-Zarza, Ana M.; Silva, Pablo G.; Goy, José L.; Zazo, Cari

    1998-08-01

    Pleistocene alluvial fan surfaces of the Campo de Cartagena-Mar Menor Basin (Murcia, SE Spain) are capped by thick mature calcretes. Calcrete profiles consist mainly of six different horizons: prismatic, chalky, nodular, massive, laminar and coated-gravels. Petrographic study of the calcretes has shown the occurrence of features such as alveolar septal structures, calcified filaments, coated grains, spherulites, calcified root cells and calcispheres that indicate the biogenic origin of the calcretes, mainly induced by plant root related microbial activity. The calcretes studied were formed initially in the soil and represented the K horizon. Development of the calcrete profiles took place in six main stages and was driven by multiple phases of soil formation, erosion and reworking. The relationships between these processes caused the formation of different calcrete profiles in proximal and distal fan areas. In the distal areas, which are controlled by limited distal fan aggradation, episodic sediment input, buried previously developed calcretes and generated new space for calcrete growth by plants growing in the overlying unconsolidated materials. This allowed the renewal of calcrete formation and it led to the development of complex composite profiles which are thicker than in proximal areas, where surface stabilisation and/or dissection enabled calcrete reworking and brecciation. These processes of erosion, sedimentation, reworking and renewed calcrete formation initiated by vegetation were repeated through time. They explain the complex macro- and microstructures of these calcretes and indicate that calcrete development, even reaching mature stages, can start before the fan surface is completely abandoned, but it requires episodic sedimentation. Eventually, distal fan aggradation and continuous calcrete development throughout the entire fan surface, led to the ultimate fan surface induration, controlling subsequent landscape evolution. So, fan surface calcretes

  3. Fan-delta and interdeltaic shoreline sediments of Middle Devonian Granite Wash and Keg River clastics, Red Earth field, north Alberta basin, Canada

    SciTech Connect

    Sabry, H.

    1989-03-01

    A detailed sedimentological investigation of over 4000 ft of core and 500 well logs of the Middle Devonian granite wash and Keg River clastics in the Red Earth field, North Alberta basin, Canada, has led to the recognition of a granite wash subaerial fan-delta system that is laterally continuous with a Keg River subaqueous delta component along an eastern shoreline of the ancestral Peace River arch. The subaerial fan delta includes alluvial fan facies, sheet wash and mud flows, and playa lakes. The subaqueous delta component includes lower shoreface, upper shoreface, beach-foreshore, eolian sand dunes, lagoon, washover sands, tidal channels and flats, and supratidal carbonates and anhydrites. Within this system, six mappable units are defined. A conceptual depositional model for the sequence depicts four main events. (1) Erosion of Peach River arch uplifted fault blocks, which produced coarse-grained fan-delta sediments in an adjacent fault-bounded margin. Subsequent fluvial reworking resulted in the deposition of thick, lenticular, wedge-shaped alluvial fans of granite wash. (2) Progradation of alluvial fans seaward into the Keg River Sea. (3) Transgression by Middle Devonian seas from the east, which reworked alluvial fans and led to deposition of discontinuous linear sand bodies represented by the Keg River regressive shoreline sediments. (4) Restriction of the sea by the Presqu'ile barrier reef to the north, which deposited evaporites of the Muskeg Formation over the whole sequence. Modern analog to this fan-delta system is the coastal fans of the Gulf of Aqaba, Red Sea. Red Earth field contains over 27 million bbl of recoverable oil, related to a combination structural-stratigraphic trap.

  4. Report from working group on alluvial pedogenesis

    USGS Publications Warehouse

    Autin, W.J.; Aslan, A.; Bettis, E.A.; Walthall, P.M.

    1998-01-01

    These uses illustrate the complexity of alluvial pedogenesis as it relates to the analysis and interpretation of paleosols. Difficulties with interpretations of alluvial paleosols are probably greatest when applied to the preserved sedimentary record, where direct evidence of paleolandscape variability is scanty or lacking.

  5. Noise generated by quiet engine fans. 1: FanB

    NASA Technical Reports Server (NTRS)

    Montegani, F. J.

    1972-01-01

    Acoustical tests of full scale fans for jet engines are presented. The fans are described and some aerodynamic operating data are given. Far field noise around the fan was measured for a variety of configurations over a range of operating conditions. Complete results of one third octave band analysis are presented in tabular form. Power spectra and sideline perceived noise levels are included.

  6. 4. DOORS TO FAN ROOM IN FAN HOUSE, FROM NORTH ...

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

    4. DOORS TO FAN ROOM IN FAN HOUSE, FROM NORTH - Sublet Mine No. 6, Fan House, North structure, west side of Willow Creek Valley, east of County Road No. 306, 3 miles north of U.S. Highway 189, Kemmerer, Lincoln County, WY

  7. 3. STEVENS 10 FT FAN IN FAN HOUSE, FROM NORTHEAST ...

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

    3. STEVENS 10 FT FAN IN FAN HOUSE, FROM NORTHEAST - Sublet Mine No. 6, Fan House, North structure, west side of Willow Creek Valley, east of County Road No. 306, 3 miles north of U.S. Highway 189, Kemmerer, Lincoln County, WY

  8. Flight effects of fan noise

    NASA Astrophysics Data System (ADS)

    Chestnutt, D.

    1982-09-01

    Simulation of inflight fan noise and flight effects was discussed. The status of the overall program on the flight effects of fan noise was reviewed, and flight to static noise comparisons with the JT15D engine were displayed.

  9. Flight effects of fan noise

    NASA Technical Reports Server (NTRS)

    Chestnutt, D. (Editor)

    1982-01-01

    Simulation of inflight fan noise and flight effects was discussed. The status of the overall program on the flight effects of fan noise was reviewed, and flight to static noise comparisons with the JT15D engine were displayed.

  10. Hydrogeologic features of the alluvial deposits in the Owl Creek Valley, Bighorn Basin, Wyoming

    USGS Publications Warehouse

    Cooley, M.E.; Head, W.J.

    1982-01-01

    The alluvial acquifer principally of the flood-plain alluvium and part of the Arapahoe Ranch terrace deposits and consists subordinately of alluvial-fan deposits. Thickness of the alluvial aquifer is generally 20 to 40 feet. Dissolved-solids concentration of water in the alluvial aquifer ranges from about 500 to more than 3,000 milligrams per liter. The most favorable areas for groundwater development are the flood-plain alluvium and part of the Arapahoe Ranch terrace deposits; however, in much of these units, the water contains more than 2,000 milligrams per liter of dissolved solids. Measurements of specific conductance of the flow of Owl Creek indicate a progressive increase in the down stream direction and range between 15 and 355 micromhos per centimeter at 25C per mile. The increases are due to return flow of irrigation water, inflow from tributaries, and inflow from groundwater. Conspicuous terraces in Owl Creek Valley included an unnamed terrace at 500 feet above Owl Creek, the Embar Ranch terrace 160 to 120 feet above the creek, and the Arapahoe Ranch terrace 50 to 20 feet above the creek. (USGS)

  11. Reservoir Characterization, Production Characteristics, and Research Needs for Fluvial/Alluvial Reservoirs in the United States

    SciTech Connect

    Cole, E.L.; Fowler, M.L.; Jackson, S.R.; Madden, M.P.; Raw-Schatzinger, V.; Salamy, S.P.; Sarathi, P.; Young, M.A.

    1999-04-28

    The Department of Energy's (DOE's) Oil Recovery Field Demonstration Program was initiated in 1992 to maximize the economically and environmentally sound recovery of oil from known domestic reservoirs and to preserve access to this resource. Cost-shared field demonstration projects are being initiated in geology defined reservoir classes which have been prioritized by their potential for incremental recovery and their risk of abandonment. This document defines the characteristics of the fifth geological reservoir class in the series, fluvial/alluvial reservoirs. The reservoirs of Class 5 include deposits of alluvial fans, braided streams, and meandering streams. Deposit morphologies vary as a complex function of climate and tectonics and are characterized by a high degree of heterogeneity to fluid flow as a result of extreme variations in water energy as the deposits formed.

  12. Architecture of a Coarse-Grained Upper Middle Cambrian Alluvial Delta Dominated by Braidplain and Gilbert-Style Delta Components

    NASA Astrophysics Data System (ADS)

    Pound, K. S.

    2014-12-01

    The ~500-m thick upper Middle Cambrian Lockett Conglomerate was deposited as part of an alluvial delta that includes Gilbert-type mega-crossbeds as well as braidplain conglomerates, and was constructed across an accretionary prism. Internal Lockett Conglomerate architecture indicates at least three phases of progradation are recorded by Gilbert-type, delta-front deposits that are separated by delta-top distributaries and/or braidplain deposits, all of which form discontinuous sheets and lenses, and record aggradation. Evaluation of sedimentary features (particle size and organization, bedding features) allows identification of eight facies within the Lockett Conglomerate; sedimentary features were used to infer transportational and depositional mechanisms. Conglomerate facies HL-1 - HL-8 were assigned to one or more of the following depositional associations: Beachface/shoreface, Deltafront, Alluvial fan, Braidplain (fluvial, unchannelized), Delta-top distributaries, and Mouth-bars. A series of Depositional Packages was identified, and mapped; integration with measured sections allowed development of a facies model for an alluvial delta in which the subaerial component is dominated by the braidplain association, and the subaqueous component by the (Gilbert-type) deltafront association as well as the delta-top distributary and mouthbar associations. Locally, the beachface association marks the transition between the subaqueous and subaerial components of the alluvial delta. Alluvial fan deposits are absent, but the rounded pebbles, cobbles and boulders with a new and distinctive provenance signature indicate derivation from a newly exposed igneous and metamorphic basement, and abrasion during transport through the fluvial (braidplain) system prior to deposition as part of the alluvial delta.

  13. 30 CFR 57.4504 - Fan installations.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Fan installations. 57.4504 Section 57.4504... Control Installation/construction/maintenance § 57.4504 Fan installations. (a) Fan houses, fan bulkheads for main and booster fans, and air ducts connecting main fans to underground openings shall...

  14. 30 CFR 57.4504 - Fan installations.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Fan installations. 57.4504 Section 57.4504... Control Installation/construction/maintenance § 57.4504 Fan installations. (a) Fan houses, fan bulkheads for main and booster fans, and air ducts connecting main fans to underground openings shall...

  15. 30 CFR 57.4504 - Fan installations.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Fan installations. 57.4504 Section 57.4504... Control Installation/construction/maintenance § 57.4504 Fan installations. (a) Fan houses, fan bulkheads for main and booster fans, and air ducts connecting main fans to underground openings shall...

  16. 30 CFR 57.4504 - Fan installations.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Fan installations. 57.4504 Section 57.4504... Control Installation/construction/maintenance § 57.4504 Fan installations. (a) Fan houses, fan bulkheads for main and booster fans, and air ducts connecting main fans to underground openings shall...

  17. 30 CFR 57.4504 - Fan installations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Fan installations. 57.4504 Section 57.4504... Control Installation/construction/maintenance § 57.4504 Fan installations. (a) Fan houses, fan bulkheads for main and booster fans, and air ducts connecting main fans to underground openings shall...

  18. Bedload transport in alluvial channels

    USGS Publications Warehouse

    Bravo-Espinosa, M.; Osterkamp, W.R.; Lopes, V.L.

    2003-01-01

    Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams.

  19. Landscape evolution, alluvial architecture, environmental history, and the archaeological record of the Upper Mississippi River Valley

    NASA Astrophysics Data System (ADS)

    Bettis, E. Arthur, III; Benn, David W.; Hajic, Edwin R.

    2008-10-01

    The alluvial fill in the Upper Mississippi River Valley (UMV) is a palimpsest of past landscapes, environments, and physical evidence of human life ways. The valley has undergone significant changes in fluvial style during the time humans have occupied its landscapes, including changes in channel pattern, location of depocenters, and sediment lithology. Remnants of late-glacial braidplains that predate human presence in the Upper Midwest occur as sandy terraces and terrace fills. A subsequent major change in alluvial architecture resulted from fundamental changes in seasonal water and sediment input that marked the end of glacial meltwater input into the valley about 12.4 ka (10,500 14C yr B.P.). A shift to net transport of sandy bedload and storage of fine-grained overbank sediment on the floodplain accompanied the change to an island-braided channel pattern at that time. The Holocene channel belt has been significantly narrower, and the zone of sediment storage is reduced relative to that of the late-glacial river. Major Holocene depocenters include alluvial fans and colluvial slopes, floodbasins, natural levees, and fluvial fans at the junction of large tributaries. Climate models, and paleobotanical, and isotopic studies indicate that shifts in large-scale patterns of atmospheric circulation and moisture transport into the mid-continent of North America induced hydrologic and vegetation changes that strongly influenced flood frequency and magnitude, the delivery of sediment from tributary basins, and the evolution of the UMV landscape. Understanding the alluvial architecture of the valley, and the temporal/spatial distribution of biotic environments and processes that have buried, mixed, altered, or destroyed archaeological deposits is essential to develop strategies for sampling the valley for evidence of past human activity and for properly interpreting the archaeological record.

  20. Coseismic surface displacements from optical and SAR image offset tracking, fault modeling and geomorphological analysis of the Sept. 24th, 2013 M7.7 Balochistan earthquake

    NASA Astrophysics Data System (ADS)

    Harrington, Jonathan; Wang, Teng; Feng, Guangcai; Akoglu, Ahmet; Jónsson, Sigurjón; Motagh, Mahdi

    2014-05-01

    The M 7.7 earthquake in the Balochistan province of Pakistan on September 24th, 2013 took place along a subsidiary fault in the transition area between the Makran accretionary prism and the Chaman transform fault. This tectonics of the Indian and Arabian plate collisions with Eurasia produce primarily oblique left-lateral strike slip in this region. In this work, measurements of displacement and mapping of the rupture trace are achieved through image correlation of Landsat 8 images and SAR offset tracking of TerraSAR-X data. Horizontal displacements from both methods and derived vertical displacements are used to constrain a fault rupture model for the earthquake. Preliminary results show a surprisingly uniform slip distribution with maximum displacement near the surface. The total fault rupture length is ~210 km, with up to 9 m of left-lateral strike-slip and 3 m of reverse faulting. Additionally, mapping of the rupture trace is made use of for geomorphological observations relating to slip rates and identification of transpressional and transtensional features. Our results indicate a mostly smooth rupture trace, with the presence of two restraining steps, a releasing bend and a 3 km long sliver where the surface rupture jumped from the foot of the range-front into the alluvial fans at their base. A small block at one of the restraining steps shows intermediate displacement in both data sets. At the southern end of the rupture we observe that displacement from the earthquake cuts across a fold-and-thrust belt of the Makran accretionary prism. Preliminary results show a minimum of 12 km of repeated section of the accretionary wedge, and within the southern repeated section we find an offset of 600 m between two parallel ridges across the rupture trace. We relate these observations to conceptual models of fault segmentation and growth.

  1. Pennsylvanian fan-delta and carbonate deposition, Mobeetie Field, Texas panhandle

    SciTech Connect

    Dutton, S.P.

    1982-04-01

    Fan deltas prograded repeatedly onto a shallow, carbonate-shelf environment in the Anadarko basin during Late Pennsylvanian (Missourian) time. These fan-delta sandstones were part of a thick wedge of coarse clastics which were derived from the Amarillo uplift. Similar fault-bounded basement uplifts found throughout the west-central United States at this time formed an intracratonic tectonic setting in which alluvial-fan and fan-delta sedimentation was common. Missourian reservoirs at Mobeetie field consist of three alternating limestone and sandstone units. Limestones accumulated along strike in elongate, phylloid-algal mounds that separated the open shelf from a more restricted lagoonal environment. Algal-mound cores consist of a algae-foraminifer wackestone and packstone, and mounds are capped by coral boundstone and encrusting algae-foraminifer wackestone. Progradation of coarse-grained terrigenous clastics onto the carbonate shelf halted carbonate production. Braided streams breached low areas along the algal-mound trend and deposited fan-delta sediments on the shelf basinward of the mounds. Distal-fan-delta deposits in the two younger sandstones were reworked along strike into spits and bars. Carbonate deposition recommenced following waning of clastic influx and subsidence of the fan-delta sediments. Algal mounds were reestablished preferentially on shallow platforms formed by terrigenous clastics of the previous cycle. 22 figures, 1 table.

  2. Comparison of modern Mississippi fan with selected ancient fans

    SciTech Connect

    Shanmugam, G.; Moiola, R.J.; McPherson, J.G.; O'Connell, S.

    1988-09-01

    A comparison of the modern passive-margin Mississippi fan (DSDP Leg 96) with selected ancient active-margin fans reveals major differences in turbidite facies associations and seismic characteristics of the lower fan area. The lower Mississippi fan is composed of channel (facies B and F) and nonchannel sequences (facies C. and D), whereas lower fan areas of ancient active-margin fans are characterized by nonchannelized, thickening-upward depositional lobes (facies C and D) with sheetlike geometry. An absence of depositional lobes in the lower Mississippi fan is also suggested by a lack of mounded seismic reflections. Continuous and parallel seismic reflections of the lower Mississippi fan may represent sheet sands, but not those of true depositional lobes. In mature passive-margin fans, long, sinuous channels develop as a consequence of low gradients and the transport of sediment with a relatively low sand/mud ratio, and these channels develop lenticular sand bodies. In contrast, channels in active-margin fans are short and commonly braided as a result of high gradients and the transport of sediment with a relatively high sand/mud ratio. Braided channels characteristically develop sheetlike sand bodies.

  3. Morphology and sedimentology of two contemporary fan deltas on the southeastern Baja California Peninsula, Mexico

    NASA Astrophysics Data System (ADS)

    Nava-Sanchez, Enrique; Cruz-Orozco, Rodolfo; Gorsline, Donn S.

    1995-08-01

    The San Juan de Los Planes drainage basin is located on the southeastern margin of the Baja California Peninsula, approximately 20 km southeast of the city of La Paz. Pleistocene alluvial fans have been built into the basin from the surrounding areas of high relief and are presently being eroded. At the fan apex, the dissection depth ranges from 20 to 40 m, and is 6 to 15 m at the coast. The sediments have been redeposited in several active modern fan deltas built out into the narrow shelf of La Ventana Bay. Shelf width ranges from 0 to 5 km (average 3 km). Wave energy is delivered from southeasterly storms and from the local sea breeze winds; the respective wave heights average 2 and 1 m. The Agua Caliente and Las Canoas fan deltas, the subjects of this paper, are located on the active El Sargento Fault Zone and are fed by channels that deeply dissect the older fan surfaces. The Agua Caliente fan delta is a classic Gilbert-type delta with a steeply inclined delta front. Wave reworking and redistribution of the sediments at the delta face are important and a wave-cut terrace has developed at about 6 m depth. The Las Canoas fan delta is a shoal-water-profile, Hjulstrom type with a gently inclined delta front. Wave energy is less important. The alignments of the coasts of both fans are controlled by the fault line. Sediment supply is largest for the Las Canoas fan delta. The fan deltas are examples of this depositional form as it has developed in an arid, tectonically active, high-relief and narrow neo-trailing edge margin.

  4. Influence of depositional processes on the composition of sandstone in a wave-dominated fan delta

    SciTech Connect

    Suttner, L.J.; Hood, L.A.; Dutta, P.K.

    1988-01-01

    Sandstone in the Lower Pennsylvanian (Morrowan-Atokan) portion of the Fountain Formation in the Manitou Springs, Colorado, area was derived from Precambrian granite gneiss and deposited in associated medial alluvial-fan, foreshore, shoreface, and offshore environments constituting a wave-dominated fan delta. The sandstone facies are arranged in six vertically stacked progradational sequences. The regressive marine portions of the sequences rest on a transgressive lag conglomerate and range from 5 to 9 m thick. The alluvial deposits capping each sequence are up to 20 m thick. The different sandstone facies of the fan delta system show variations in mineralogical composition. Because all of the sandstone facies share a common first-cycle provenance and burial history, differences in composition largely reflect differences in depositional-process control on composition. Foreshore sandstones possess maximum compositional maturity; offshore sandstone is most immature. Apparently feldspar is winnowed out of the foreshore sand, bypasses the shoreface, and is concentrated in offshore, storm-deposited sand. Alluvial and shoreface sandstone are intermediate in composition with QFR content of 55:35:10 and 60:35:5, respectively.

  5. Geologic Characterization of Young Alluvial Basin-Fill Deposits from Drill Hole Data in Yucca Flat, Nye County, Nevada

    USGS Publications Warehouse

    Sweetkind, Donald S.; Drake II, Ronald M.

    2007-01-01

    Yucca Flat is a topographic and structural basin in the northeastern part of the Nevada Test Site (NTS) in Nye County, Nevada, that has been the site of numerous underground nuclear tests; many of these tests occurred within the young alluvial basin-fill deposits. The migration of radionuclides to the Paleozoic carbonate aquifer involves passage through this thick, heterogeneous section of Tertiary and Quaternary rock. An understanding of the lateral and vertical changes in the material properties of young alluvial basin-fill deposits will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating ground-water flow in the Yucca Flat area. This report by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, presents data and interpretation regarding the three-dimensional variability of the shallow alluvial aquifers in areas of testing at Yucca Flat, data that are potentially useful in the understanding of the subsurface flow system. This report includes a summary and interpretation of alluvial basin-fill stratigraphy in the Yucca Flat area based on drill hole data from 285 selected drill holes. Spatial variations in lithology and grain size of the Neogene basin-fill sediments can be established when data from numerous drill holes are considered together. Lithologic variations are related to different depositional environments within the basin including alluvial fan, channel, basin axis, and playa deposits.

  6. Geologic Characterization of Young Alluvial Basin-Fill Deposits from Drill-Hole Data in Yucca Flat, Nye County, Nevada

    USGS Publications Warehouse

    Sweetkind, Donald S.; Drake II, Ronald M.

    2007-01-01

    Yucca Flat is a topographic and structural basin in the northeastern part of the Nevada Test Site in Nye County, Nevada, that has been the site of numerous underground nuclear tests; many of these tests occurred within the young alluvial basin-fill deposits. The migration of radionuclides to the Paleozoic carbonate aquifer involves passage through this thick, heterogeneous section of Tertiary and Quaternary rock. An understanding of the lateral and vertical changes in the material properties of young alluvial basin-fill deposits will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating ground-water flow in the Yucca Flat area. This report by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, presents data and interpretation regarding the three-dimensional variability of the shallow alluvial aquifers in areas of testing at Yucca Flat, data that are potentially useful in the understanding of the subsurface flow system. This report includes a summary and interpretation of alluvial basin-fill stratigraphy in the Yucca Flat area based on drill-hole data from 285 selected drill holes. Spatial variations in lithology and grain size of the Neogene basin-fill sediments can be established when data from numerous drill holes are considered together. Lithologic variations are related to different depositional environments within the basin such as alluvial fan, channel, basin axis, and playa deposits.

  7. Geologic Characterization of Young Alluvial Basin-Fill Deposits from Drill Hole Data in Yucca Flat, Nye County, Nevada.

    SciTech Connect

    Donald S. Sweetkind; Ronald M. Drake II

    2007-01-22

    Yucca Flat is a topographic and structural basin in the northeastern part of the Nevada Test Site (NTS) in Nye County, Nevada, that has been the site of numerous underground nuclear tests; many of these tests occurred within the young alluvial basin-fill deposits. The migration of radionuclides to the Paleozoic carbonate aquifer involves passage through this thick, heterogeneous section of Tertiary and Quaternary rock. An understanding of the lateral and vertical changes in the material properties of young alluvial basin-fill deposits will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating ground-water flow in the Yucca Flat area. This report by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, presents data and interpretation regarding the three-dimensional variability of the shallow alluvial aquifers in areas of testing at Yucca Flat, data that are potentially useful in the understanding of the subsurface flow system. This report includes a summary and interpretation of alluvial basin-fill stratigraphy in the Yucca Flat area based on drill hole data from 285 selected drill holes. Spatial variations in lithology and grain size of the Neogene basin-fill sediments can be established when data from numerous drill holes are considered together. Lithologic variations are related to different depositional environments within the basin including alluvial fan, channel, basin axis, and playa deposits.

  8. Dispersion in alluvial convergent estuaries

    NASA Astrophysics Data System (ADS)

    Zhang, Zhilin; Savenije, Hubert H. G.

    2016-04-01

    The Van der Burgh's equation for longitudinal effective dispersion is a purely empirical method with practical implications. Its application to the effective tidal average dispersion under equilibrium conditions appears to have excellent performance in a wide range of alluvial estuaries. In this research, we try to find out the physical meaning of Van der Burgh's coefficient. Researchers like MacCready, Fischer, Kuijper, Hansen and Rattray have tried to split up dispersion into its constituents which did not do much to explain overall behaviour. In addition, traditional literature on dispersion is mostly related to flumes with constant cross-section. This research is about understanding the Van der Burgh's coefficient facing the fact that natural estuaries have exponentially varying cross-section. The objective is to derive a simple 1-D model considering both longitudinal and lateral mixing processes based on field observations (theoretical derivation). To that effect, we connect dispersion with salinity using the salt balance equation. Then we calculate the salinity along the longitudinal direction and compare it to the observed salinity. Calibrated dispersion coefficients in a range of estuaries are then compared with new expressions for the Van der Burgh's coefficient K and it is analysed if K varies from estuary to estuary. The set of reliable data used will be from estuaries: Kurau, Perak, Bernam, Selangor, Muar, Endau, Maputo, Thames, Corantijn, Sinnamary, Mae Klong, Lalang, Limpopo, Tha Chin, Chao Phraya, Edisto and Elbe.

  9. Lateral Erosion Encourages Vertical Incision in a Bimodal Alluvial River

    NASA Astrophysics Data System (ADS)

    Gran, K. B.

    2015-12-01

    Sand can have a strong impact on gravel transport, increasing gravel transport rates by orders of magnitude as sand content increases. Recent experimental work by others indicates that adding sand to an armored bed can even cause armor to break-up and mobilize. These two elements together help explain observations from a bimodal sand and gravel-bedded river, where lateral migration into sand-rich alluvium breaks up the armor layer, encouraging further incision into the bed. Detailed bedload measurements were coupled with surface and subsurface grain size analyses and cross-sectional surveys in a seasonally-incised channel carved into the upper alluvial fan of the Pasig-Potrero River at Mount Pinatubo, Philippines. Pinatubo erupted in 1991, filling valleys draining the flanks of the volcano with primarily sand-sized pyroclastic flow debris. Twenty years after the eruption, sand-rich sediment inputs are strongly seasonal, with most sediment input to the channel during the rainy season. During the dry season, flow condenses from a wide braided planform to a single-thread channel in most of the upper basin, extending several km onto the alluvial fan. This change in planform creates similar unit discharge ranges in summer and winter. Lower sediment loads in the dry season drive vertical incision until the bed is sufficiently armored. Incision proceeds downstream in a wave, with increasing sediment transport rates and decreasing grain size with distance downstream, eventually reaching a gravel-sand transition and return to a braided planform. Incision depths in the gravel-bedded section exceeded 3 meters in parts of a 4 km-long study reach, a depth too great to be explained by predictions from simple winnowing during incision. Instead, lateral migration into sand-rich alluvium provides sufficient fine sediment to break up the armor surface, allowing incision to start anew and increasing the total depth of the seasonally-incised valley. Lateral migration is recorded in a

  10. Fan Cart: The Next Generation

    NASA Astrophysics Data System (ADS)

    Lamore, Brian

    2016-10-01

    For years the fan cart has provided physics students with an excellent resource for exploring fundamental mechanics concepts such as acceleration, Newton's laws, impulse, momentum, work-energy, and energy conversions. The Physics Teacher has even seen some excellent do-it-yourself (DIY) fan carts and activities. If you are interested in developing the `E' portion of your and your students' STEM (science, technology, engineering, and math) skills, one way to accomplish this is to revisit the DIY fan cart. In this article I share a design of a new edition of the DIY fan cart and some ideas for incorporating the engineering design process into your high school curriculum.

  11. Fan and pump noise control

    NASA Technical Reports Server (NTRS)

    Misoda, J.; Magliozzi, B.

    1973-01-01

    The development is described of improved, low noise level fan and pump concepts for the space shuttle. In addition, a set of noise design criteria for small fans and pumps was derived. The concepts and criteria were created by obtaining Apollo hardware test data to correlate and modify existing noise estimating procedures. A set of space shuttle selection criteria was used to determine preliminary fan and pump concepts. These concepts were tested and modified to obtain noise sources and characteristics which yield the design criteria and quiet, efficient space shuttle fan and pump concepts.

  12. Fan Noise Reduction: An Overview

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2001-01-01

    Fan noise reduction technologies developed as part of the engine noise reduction element of the Advanced Subsonic Technology Program are reviewed. Developments in low-noise fan stage design, swept and leaned outlet guide vanes, active noise control, fan flow management, and scarfed inlet are discussed. In each case, a description of the method is presented and, where available, representative results and general conclusions are discussed. The review concludes with a summary of the accomplishments of the AST-sponsored fan noise reduction research and a few thoughts on future work.

  13. Self similar growth of a 1D granular fan under laminar flow near threshold

    NASA Astrophysics Data System (ADS)

    Guerit, Laure; Métivier, François; Devauchelle, Olivier; Lajeunesse, Eric; Barrier, Laurie

    2014-05-01

    Alluvial fans are major sedimentary bodies that make the transition between the reliefs and the sedimentary basins. They are found at the outlet of some drainages catchments, where rivers are free to diverge and avulse, and to depose part of their sedimentary load. Understanding their dynamics of formation and evolution is a great problem of sediment transport. Rivers and fan profiles are usually described as diffusive systems but this is only true if the shear stress exerted on the bed is high compared to the critical shear stress. This might be the case for sand bed rivers, but not for gravel bed rivers, for which it is known that the shear stress is only slightly higher than the critical one. This is why we need to develop a new model to describe the evolution of alluvial fans built by gravel bed rivers. To do this analytically, we work in 1D, with a laminar flow and one grain-size in order to be able to describe both the fluid and the sediment transport. In addition, the conditions of the experiments insured that the boundary shear stress is near the critical value for motion inception of the granular material. Using Taylor expansion, we show that for asymptotically long times, the fan growth is self-similar and can be decomposed into a triangular ``threshold" shape plus a small quadratic deviation. We performed experiments with glass beads and glycerol to test and successfully validate this theory.

  14. Scatter correction in CBCT with an offset detector through a deconvolution method using data consistency

    NASA Astrophysics Data System (ADS)

    Kim, Changhwan; Park, Miran; Lee, Hoyeon; Cho, Seungryong

    2016-03-01

    Our earlier work has demonstrated that the data consistency condition can be used as a criterion for scatter kernel optimization in deconvolution methods in a full-fan mode cone-beam CT [1]. However, this scheme cannot be directly applied to CBCT system with an offset detector (half-fan mode) because of transverse data truncation in projections. In this study, we proposed a modified scheme of the scatter kernel optimization method that can be used in a half-fan mode cone-beam CT, and have successfully shown its feasibility. Using the first-reconstructed volume image from half-fan projection data, we acquired full-fan projection data by forward projection synthesis. The synthesized full-fan projections were partly used to fill the truncated regions in the half-fan data. By doing so, we were able to utilize the existing data consistency-driven scatter kernel optimization method. The proposed method was validated by a simulation study using the XCAT numerical phantom and also by an experimental study using the ACS head phantom.

  15. Field of Fans

    NASA Technical Reports Server (NTRS)

    2007-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Subimage #1 Figure 1 Subimage #2 Figure 2 [figure removed for brevity, see original site] [figure removed for brevity, see original site] Anaglyph Figure 3 Subimage #3 Figure 4

    At the very beginning of spring in the southern hemisphere on Mars the ground is covered with a seasonal layer of carbon dioxide ice. In this image there are two lanes of undisturbed ice bordered by two lanes peppered with fans of dark dust.

    When we zoom in to the subimage (figure 1), the fans are seen to be pointed in the same direction, dust carried along by the prevailing wind. The fans seem to emanate from spider-like features.

    The second subimage (figure 2) zooms in to full HiRISE resolution to reveal the nature of the 'spiders.' The arms are channels carved in the surface, blanketed by the seasonal carbon dioxide ice. The seasonal ice, warmed from below, evaporates and the gas is carried along the channels. Wherever a weak spot is found the gas vents to the top of the seasonal ice, carrying along dust from below.

    The anaglyph (figure 3) of this spider shows that these channels are deep, deepening and widening as they converge. Spiders like this are often draped over the local topography and often channels get larger as they go uphill. This is consistent with a gas eroding the channels.

    A different channel morphology is apparent in the lanes not showing fans. In these regions the channels are dense, more like lace, and are not radially organized. The third subimage (figure 4) shows an example of 'lace.'

    Observation Geometry Image PSP_002532_0935 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 09-Feb-2007. The complete image is centered at -86.4 degrees latitude, 99.1 degrees East longitude. The range to the target site was 276.1 km (172.6 miles). At this distance the image scale is

  16. Charcoal and the Record of Fire-related Sedimentation in Holocene Alluvial Sediments

    NASA Astrophysics Data System (ADS)

    Meyer, G. A.

    2006-12-01

    Over the last few decades, rising temperatures and ensuing severe wildfires in the western USA cordillera have provided the opportunity to examine processes and deposits of postfire sedimentation on alluvial fans and floodplains. Most events are generated by widespread surface runoff from intense convective-storm precipitation on severely burned slopes. Flow processes range from debris flow to sediment-charged water floods. Muddy debris flows best preserve coarse charcoal in fan deposits, whereas gravelly debris flows often comminute charcoal into fine particles. As charcoal remains suspended in high-energy hyperconcentrated and water floods, only their fine-grained deposits typically contain much charcoal. Charcoal is locally concentrated in low-energy fluvial deposits, but displays increasing evidence for reworking with distance from source. Charred vegetation and litter marking burned soil surfaces may be preserved under postfire fan and fluvial sediments. Modern deposits provide models for identification of Holocene fire-related sediments and estimates of paleofire severity. AMS 14C dating of discrete charcoal fragments allows sample selection to minimize errors of sample age > fire age. Fires are incompletely recorded in the event stratigraphy of one fan, but larger populations of 14C ages from numerous fans permit composite probability distributions that represent centennial- to millennial-scale changes in fire-related sedimentation across a study area. Records from Yellowstone and central Idaho indicate the large role of fire in episodic erosion across a range of conifer forests, most strongly during severe, multidecadal droughts in warmer periods (e.g. in Medieval time 900-1300 AD). In central Idaho, identification of charcoal macrofossils indicates broadly similar, aspect-controlled forest compositions over the last 3000 yr. Emerging data from the Sacramento Mountains, New Mexico, show rapid fan aggradation due to fire-related events in the warm middle

  17. Architectural elements of fan-delta complex in Pennsylvanian Taos Trough, New Mexico

    SciTech Connect

    Soegaard, K.

    1989-03-01

    Identification of architectural elements within alluvial-fan and subaqueous fan-delta gravel units is fundamental to resolving depositional processes within fan-delta complexes of the Pennsylvanian Taos trough, New Mexico. Subaqueous fan-delta deposits consist of lenticular gravel-body complexes encased by black, basinal shales. Gravel-body complexes are composed of a series of stacked gravel lenses, each of which is enveloped by fifth-order bounding surfaces. The central portion of individual gravel lenses contains a channel complex. Channels are outlined by third- and fourth-order bounding surfaces and are infilled by high-density gravity flow deposits. The fringe of submarine gravel lenses consists of stacked, laterally continuous Bouma sequences separated by second-order bounding surfaces. Bouma sequences were deposited by dilute turbidity flows during evacuation of submarine channels. Subaqueous channel complexes within gravel lenses represent midfan channels, whereas the fringe of lenticular gravel lenses represent outer-fan lobes. Recognition of depositional processes and architectural elements of fan deltas in the Sandia Formation enables distinction between these and other types of coarse-grained deltas in the Taos trough. This, in turn, has implications for resolving evolution of the trough.

  18. Developing a post-fire flood chronology and recurrence probability from alluvial stratigraphy in the Buffalo Creek watershed, Colorado, USA

    USGS Publications Warehouse

    Elliott, J.G.; Parker, R.S.

    2001-01-01

    Stratigraphic and geomorphic evidence indicate floods that occur soon after forest fires have been intermittent but common events in many mountainous areas during the past several thousand years. The magnitude and recurrence of these post-fire flood events reflects the joint probability between the recurrence of fires and the recurrence of subsequent rainfall events of varying magnitude and intensity. Following the May 1996 Buffalo Creek, Colorado, forest fire, precipitation amounts and intensities that generated very little surface runoff outside of the burned area resulted in severe hillslope erosion, floods, and streambed sediment entrainment in the rugged, severely burned, 48 km2 area. These floods added sediment to many existing alluvial fans, while simultaneously incising other fans and alluvial deposits. Incision of older fans revealed multiple sequences of fluvially transported sandy gravel that grade upward into charcoal-rich, loamy horizons. We interpret these sequences to represent periods of high sediment transport and aggradation during floods, followed by intervals of quiescence and relative stability in the watershed until a subsequent fire occurred. An alluvial sequence near the mouth of a tributary draining a 0??82 km2 area indicated several previous post-fire flood cycles in the watershed. Dendrochronologic and radiocarbon ages of material in this deposit span approximately 2900 years, and define three aggradational periods. The three general aggradational periods are separated by intervals of approximately nine to ten centuries and reflect a 'millennium-scale' geomorphic response to a closely timed sequence of events: severe and intense, watershed-scale, stand-replacing fires and subsequent rainstorms and flooding. Millennium-scale aggradational units at the study site may have resulted from a scenario in which the initial runoff from the burned watershed transported and deposited large volumes of sediment on downstream alluvial surfaces and

  19. Developing a post-fire flood chronology and recurrence probability from alluvial stratigraphy in the Buffalo Creek watershed, Colorado, USA

    NASA Astrophysics Data System (ADS)

    Elliott, John G.; Parker, R. S.

    2001-10-01

    Stratigraphic and geomorphic evidence indicate floods that occur soon after forest fires have been intermittent but common events in many mountainous areas during the past several thousand years. The magnitude and recurrence of these post-fire flood events reflects the joint probability between the recurrence of fires and the recurrence of subsequent rainfall events of varying magnitude and intensity. Following the May 1996 Buffalo Creek, Colorado, forest fire, precipitation amounts and intensities that generated very little surface runoff outside of the burned area resulted in severe hillslope erosion, floods, and streambed sediment entrainment in the rugged, severely burned, 48 km2 area. These floods added sediment to many existing alluvial fans, while simultaneously incising other fans and alluvial deposits. Incision of older fans revealed multiple sequences of fluvially transported sandy gravel that grade upward into charcoal-rich, loamy horizons. We interpret these sequences to represent periods of high sediment transport and aggradation during floods, followed by intervals of quiescence and relative stability in the watershed until a subsequent fire occurred.An alluvial sequence near the mouth of a tributary draining a 0·82 km2 area indicated several previous post-fire flood cycles in the watershed. Dendrochronologic and radiocarbon ages of material in this deposit span approximately 2900 years, and define three aggradational periods. The three general aggradational periods are separated by intervals of approximately nine to ten centuries and reflect a millennium-scale geomorphic response to a closely timed sequence of events: severe and intense, watershed-scale, stand-replacing fires and subsequent rainstorms and flooding. Millennium-scale aggradational units at the study site may have resulted from a scenario in which the initial runoff from the burned watershed transported and deposited large volumes of sediment on downstream alluvial surfaces and

  20. Common-offset ray tracing

    SciTech Connect

    Jannaud, L.R.

    1994-12-31

    In the SMART method, exact traveltimes, used as input of reflection tomography, are computed by tracing rays that are reflected on interpreted migrated events. Since picking migrated events is easier in common offset migrated images than in common shot migrated images, a common offset raytracing has been developed. It is based on a continuation method in the source position-shooting angle domain. It consists in following in this domain iso-offset lines and determining the points of these lines corresponding to the actual sources. It allows the user to compute all the arrivals even for complex media at a low computational cost.

  1. Fan Cart: The Next Generation

    ERIC Educational Resources Information Center

    Lamore, Brian

    2016-01-01

    For years the fan cart has provided physics students with an excellent resource for exploring fundamental mechanics concepts such as acceleration, Newton's laws, impulse, momentum, work-energy, and energy conversions. "The Physics Teacher" has even seen some excellent do-it-yourself (DIY) fan carts and activities. If you are interested…

  2. Holocene paleoearthquakes of the Daqingshan fault detected from knickpoint identification and alluvial soil profile

    NASA Astrophysics Data System (ADS)

    He, Zhongtai

    2016-04-01

    Are there any effective methods to reveal paleoearthquakes on normal faults except traditional trenching technique? In this paper, we study Holocene paleoearthquakes of the Daqingshan fault which is a normal fault along the Daqingshan piedmont of Inner Mongolia in China. We identify knickpoints from stream profiles and study alluvial soil profiles to reconstruct the Holocene paleoearthquakes of the fault. From the fault's footwall we extract 25 gullies from IRS-P5 DEM data, and identify knickpoints in the profile that result from fault motion disturbing each channel. We combine the retreat distances and the knickpoint retreat rates to determine each knickpoint's forming time. We study alluvial fan outcrops that contain various paleosol sequences. As three distinct Holocene paleosols developed in the Daqingshan piedmont alluvial fans, we assume that the soil profile development was interrupted by fault activity preserved by interbedded gravel between the paleosols. The gravel layer between two adjacent paleosol layers represents material transported there after a paleoseismic event. Thus we date paleosol layers which are above and below the gravel layer to constrain paleoseismic events. Since trenches had been made by our predecessors along the fault to reveal the Holocene paleoearthquakes, we identify the Holocene paleoearthquake records from both sides of the fault, and then compare the results with the results from the trenches. The final result demonstrates that the knickpoints' sequence in the footwall and the paleosols' ages in the hanging wall correspond very closely with the Holocene paleoearthquakes along the Daqingshan piedmont fault. Methods in this paper have future application value to study paleoearthquakes on other normal faults with similar structure to the Daqingshan fault.

  3. Submarine fan lobe models: Implications for reservoir properties

    SciTech Connect

    Shanmugam, G.; Moiola, R.J. )

    1990-09-01

    A multitude of submarine fan lobe models, advocating widely different reservoir properties, has been introduced into the sedimentologic literature. Four of these models are compared to show their differences in reservoir properties. Braided suprafan lobes are characterized by stacked sand bodies with good lateral and vertical communication, and they constitute excellent reservoir facies. The unchanneled depositional lobes, composed of sheetlike sand bodies with good lateral and moderate vertical communication, exhibit properties of good reservoir facies. Fanlobes, which refer to meandering channels and associated levee facies of large mud-rich submarine fans such as the Mississippi Fan in the Gulf of Mexico, are characterized by offset stacked sand bodies with poor lateral and vertical communication. These lenticular sands have the potential to be moderately good reservoir facies. Ponded lobes, which represent mud-rich slump facies of slope environments, comprise poor reservoir facies because of poor sand content and poor sand-body connectivity caused by chaotic bedding. Furthermore, the presence of slumped mud layers in ponded lobes is expected to hinder fluid flow. Because different lobe models vary significantly from one another in terms of reservoir properties, caution must be exercised to apply the proper lobe model to ancient fan sequences in hydrocarbon exploration and production.

  4. Silicate weathering in the Ganges alluvial plain

    NASA Astrophysics Data System (ADS)

    Frings, Patrick J.; Clymans, Wim; Fontorbe, Guillaume; Gray, William; Chakrapani, Govind J.; Conley, Daniel J.; De La Rocha, Christina

    2015-10-01

    The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimiting the Ganges alluvial plain. Despite constituting approximately 80% of the basin, weathering processes in the peninsula and alluvial plain have received little attention. Here we present an analysis of 51 water samples along a transect of the alluvial plain, including all major tributaries. We focus on the geochemistry of silicon and its isotopes. Area normalised dissolved Si yields are approximately twice as high in rivers of Himalaya origin than the plain and peninsular tributaries (82, 51 and 32 kmol SiO2 km-2 yr-1, respectively). Such dissolved Si fluxes are not widely used as weathering rate indicators because a large but variable fraction of the DSi mobilised during the initial weathering process is retained in secondary clay minerals. However, the silicon isotopic composition of dissolved Si (expressed as δ30Si) varies from + 0.8 ‰ in the Ganges mainstem at the Himalaya front to + 3.0 ‰ in alluvial plain streams and appears to be controlled by weathering congruency, i.e. by the degree of incorporation of Si into secondary phases. The higher δ30Si values therefore reflect decreasing weathering congruency in the lowland river catchments. This is exploited to quantify the degree of removal using a Rayleigh isotope mass balance model, and consequently derive initial silica mobilisation rates of 200, 150 and 107 kmol SiO2 km-2 yr-1, for the Himalaya, peninsular India and the alluvial plain, respectively. Because the non-Himalayan regions dominate the catchment area, the majority of initial silica mobilisation from primary minerals occurs in the alluvial plain and peninsular catchment (41% and 34%, respectively).

  5. Counter-Rotatable Fan Gas Turbine Engine with Axial Flow Positive Displacement Worm Gas Generator

    NASA Technical Reports Server (NTRS)

    Giffin, Rollin George (Inventor); Murrow, Kurt David (Inventor); Fakunle, Oladapo (Inventor)

    2014-01-01

    A counter-rotatable fan turbine engine includes a counter-rotatable fan section, a worm gas generator, and a low pressure turbine to power the counter-rotatable fan section. The low pressure turbine maybe counter-rotatable or have a single direction of rotation in which case it powers the counter-rotatable fan section through a gearbox. The gas generator has inner and outer bodies having offset inner and outer axes extending through first, second, and third sections of a core assembly. At least one of the bodies is rotatable about its axis. The inner and outer bodies have intermeshed inner and outer helical blades wound about the inner and outer axes and extending radially outwardly and inwardly respectively. The helical blades have first, second, and third twist slopes in the first, second, and third sections respectively. A combustor section extends through at least a portion of the second section.

  6. Quiet High-Speed Fan

    NASA Technical Reports Server (NTRS)

    Lieber, Lysbeth; Repp, Russ; Weir, Donald S.

    1996-01-01

    A calibration of the acoustic and aerodynamic prediction methods was performed and a baseline fan definition was established and evaluated to support the quiet high speed fan program. A computational fluid dynamic analysis of the NASA QF-12 Fan rotor, using the DAWES flow simulation program was performed to demonstrate and verify the causes of the relatively poor aerodynamic performance observed during the fan test. In addition, the rotor flowfield characteristics were qualitatively compared to the acoustic measurements to identify the key acoustic characteristics of the flow. The V072 turbofan source noise prediction code was used to generate noise predictions for the TFE731-60 fan at three operating conditions and compared to experimental data. V072 results were also used in the Acoustic Radiation Code to generate far field noise for the TFE731-60 nacelle at three speed points for the blade passage tone. A full 3-D viscous flow simulation of the current production TFE731-60 fan rotor was performed with the DAWES flow analysis program. The DAWES analysis was used to estimate the onset of multiple pure tone noise, based on predictions of inlet shock position as a function of the rotor tip speed. Finally, the TFE731-60 fan rotor wake structure predicted by the DAWES program was used to define a redesigned stator with the leading edge configured to minimize the acoustic effects of rotor wake / stator interaction, without appreciably degrading performance.

  7. Backwater number scaling of alluvial bed forms

    NASA Astrophysics Data System (ADS)

    Shaw, John B.; McElroy, Brandon

    2016-08-01

    The backwater number, Bw, compares the backwater length scale to the length scale of alluvial bed forms. We derive theory to show that Bw plays an important role in determining the behavior and scaling of morphodynamic systems. When Bw ≫ 1, spatial patterns in deposition and erosion derive from flow accelerations associated with changes in flow depth, and bed evolution is akin to a kinematic wave. When Bw ≪ 1, the spatial pattern of shear stress is determined by variations in energy slope, and alluvial beds experience topographic dispersion. This theory is confirmed using a numerical model and data compiled from the literature. We present a data set of Bw for bed forms ranging from dunes to river deltas, including field and experimental measurements. For field-scale measurements, we find that dunes have Bw > 49, braid bars exist in the range Bw = [7.1,17], meanders have a range Bw = [7.1,18], and river mouth deposition ranges over Bw = [7.4,29]. Further, alluvial morphologies that are easily recreated in the laboratory (dunes and avulsions) have overlapping field and laboratory Bw ranges. In contrast, alluvial forms that have traditionally been difficult to recreate (meanders and river mouth processes) have field Bw that are difficult to match in laboratory settings. Large experimental Froude numbers are shown to reduce experimental Bw and incite diffusional behavior. Finally, we demonstrate the utility of Bw scaling for estimating fundamental scales in sedimentary systems.

  8. Variations in alluvial style of Tertiary units in response to tectonism, Las Monas area, middle Magdalena valley, Colombia

    SciTech Connect

    Jordan, D.W.; Siemers, C.T.

    1989-03-01

    Detailed sedimentologic and petrographic analyses of Tertiary alluvial sandstone outcrops within and east of producing oil fields in the Las Monas area in Colombia, South America, indicate that depositional style changed from fluvial-deltaic to braided streams atop alluvial fans to high-sinuosity meandering streams in response to uplifts in the surrounding areas. Diverse paleocurrent trends in the Tertiary formations in the perimeter area demonstrate that streams flowed northeast and northwest. Streams in the oil field had easterly and southerly components. Source areas contributing sediment were different and reflected uplifts to the west and south of the Las Monas area. Petrographic composition of sandstones that have easterly and southerly paleocurrent trends in the field area contain more feldspar and less polycrystalline strained quartz than sandstones having a northerly trend in the perimeter area. Sandstones in the field area represent an unroofing of a western granitic terrain, possibly in the ancestral Central Cordillera.

  9. Alluvial Fans on Dunes in Kaiser Crater Suggest Niveo-Aeolian and Denivation Processes on Mars

    NASA Technical Reports Server (NTRS)

    Bourke, M. C.

    2005-01-01

    On Earth, cold region sand dunes often contain inter-bedded sand, snow, and ice. These mixed deposits of wind-driven snow, sand, silt, vegetal debris, or other detritus have been termed Niveo-aeolian deposits. These deposits are often coupled with features that are due to melting or sublimation of snow, called denivation features. Snow and ice may be incorporated into dunes on Mars in three ways. Diffusion of water vapour into pore spaces is the widely accepted mechanism for the accretion of premafrost ice. Additional mechanisms may include the burial by sand of snow that has fallen on the dune surface or the synchronous transportation and deposition of snow, sand and ice. Both of these mechanisms have been reported for polar dunes on Earth. Niveo-aeolian deposits in polar deserts on Earth have unique morphologies and sedimentary structures that are generally not found in warm desert dunes. Recent analysis of MOC-scale data have found evidence for potential niveo-aeolian and denivation deposits in sand dunes on Mars.

  10. Artificial recharge experiments on the Ship Creek alluvial fan, Anchorage, Alaska

    USGS Publications Warehouse

    Anderson, Gary S.

    1977-01-01

    During the summers of 1973 and 174, water from Ship Creek, Alaska, was diverted at an average rate of approximately 6 cfs (cubic feet per second) to an 11-acre recharge basin. Maximum sustained unit recharge for the basin was approximately 1.4 feet per day. During 1975 a second basin of 8 acres was also used for recharge, and the total diversion rate was increased to as much as 30 cfs. The second basin was never completely filled, but the unit recharge rate was at least four times as great as that in the first basin. During 1973 and 1974, when only one recharge basin was in operation, a maximum rise of 18 feet was observed in the ground-water table near the basin. In 1975, when both basins were being used, the maximum rise was 30 feet in the same area. During 1973 and 1974, the water-level rise was 12 and 8 feet in the unconfined and confined systems, respectively, at a point 4,400 feet downgradient from the basins; in 1975 the rise at the same point was 31 and 16 feet, respectively. The potentiometric rise that was achieved in the confined aquifer during summer operation of the recharge basins was quickly dissipated when diversion stopped and the basins drained. Thus the benefits of recharge would not persist into late winter, the critical period for water availability in Anchorage, unless diversion to the basins could be continued until January or February. (Woodard-USGS)

  11. Laramide tectonics and humid alluvial fan sedimentation, Ne Uinta uplift, Utah and Wyoming

    SciTech Connect

    Crews, S.G.; Ethridge, F.G. )

    1993-05-01

    This paper describes and interprets a sequence of syntectonic conglomerates and sandstones shed from the northeast flank of the Uinta Mountains during an early Eocene phase of the Laramide orogeny. The study area centers around a cuesta 10 km long known as Richards Mountain located on the Utah-Wyoming border about 3 km north of the Uinta fault zone. Conglomerates and sandstones of the basal Wasatch Formation that crop out on Richards Mountain constitute an exhumed, strike-parallel deposit of carose sediments that formed adjacent to the rising Uinta Mountains uplift. These rocks are an example of sedimentation in a proximal, humid piedmont setting and provide clues to the relative rate and timing of a major cycle of uplift and erosion of the Uinta Mountains. Topics specifically addressed in this study include: (1) sedimentary facies, fluvial architecture, depositional processes, paleocurrents, and grain-size trends at Richards Mountain, based on detailed measured sections; (2) tectonic significance of the richards Mountain sequence, including tectonic and geomorphic explanations for several scales of cyclicity within the sequence; and (3) Early Paleogene tectonic and depositional history of the northeastern flank of the Uinta Uplift and the southern Green River Basin.

  12. GIS Analysis of Size Relationships between Drainage Basins and Alluvial Fans

    NASA Astrophysics Data System (ADS)

    Wright, S. N.; Scuderi, L. A.; Weissmann, G. S.; Hartley, A. J.

    2014-12-01

    Imagery from the global database of modern sedimentary basins compiled by Weissman et al. (2010) allows us to test whether a size relationship between drainage basin area and distributive fluvial system (DFS) area exists. We are testing this hypothesis using a combination of SRTM-based digital elevation models and Landsat satellite imagery in ArcGIS. Sedimentary basins are delineated by preforming a Gaussian smoothing on the DEM, followed by optimal edge detection through application of a modified Canny edge detector. The pour points defining the link between contributing hydrologic basins and these sedimentary basins are then located by generating a stream network in ArcGIS and intersecting the stream network arcs with the sedimentary basin polygons. From these pour points we delineate the adjacent contributing drainage basin using the watershed tool in ArcGIS. We manually digitize the boundary and geometry of the DFS identified for each drainage basin, using the higher resolution imagery found on Google Earth for visual confirmation if the scale or resolution of the Landsat imagery requires it. We then extract drainage basins and DFS polygon parameters and calculate areal extents in order to evaluate whether such a size relationship exists within basins, regionally across several basins, or across different basin types (e.g., endorheic vs exhoreic). A limitation of this approach is that we cannot evaluate sediment volumes, only aerial coverage. Results from this study may provide a better understanding of extrabasinal processes that control DFS shape and size.

  13. Modeling groundwater-surface water interaction in cross-cutting alluvial fan system

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Sager, J. C.; Fogg, G. E.

    2011-12-01

    In the classic interpretation, a deep water table can cause hydraulic 'disconnection' between a river and an underlying aquifer, with the lack of a saturated zone connection between them. Previous research indicates that in such cases heterogeneity may create localized saturated connections between the river and a deep water table. The dynamics of groundwater and surface water interaction under such circumstances has not been adequately investigated. This basin- scale modeling study of the Cosumnes River and American River groundwater systems of the Central Valley of California, which includes both high-resolution (200m×200m×0.5m) modeling of the hydro-facies (~18 million nodes) and variably saturated flow modeling with the parallel computing code ParFlow, investigates how the textual heterogeneity (e.g., connected channels and abundant aquitard facies) affects interplay between the groundwater and surface water, including possible mechanisms for enhancing both stream base flow and recharge through surface spreading. The possible influence of perched aquifers created by low permeability layers on river base flow is also investigated. Optimal locations of floodplain and flooding time frames are being examined. Results of this study will enhance our understanding of the mechanism of water dynamics in the variably saturated zone coupling with heterogeneity. Ultimately, the results will also help restore or better manage the stream base flow and the ecosystem that depends on it.

  14. 14 CFR 29.908 - Cooling fans.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Cooling fans. 29.908 Section 29.908... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.908 Cooling fans. For cooling fans that are a part of a powerplant installation the following apply: (a) Category A. For cooling fans...

  15. 14 CFR 29.908 - Cooling fans.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 14 Aeronautics and Space 1 2014-01-01 2014-01-01 false Cooling fans. 29.908 Section 29.908... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.908 Cooling fans. For cooling fans that are a part of a powerplant installation the following apply: (a) Category A. For cooling fans...

  16. 14 CFR 29.908 - Cooling fans.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Cooling fans. 29.908 Section 29.908... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.908 Cooling fans. For cooling fans that are a part of a powerplant installation the following apply: (a) Category A. For cooling fans...

  17. 14 CFR 29.908 - Cooling fans.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Cooling fans. 29.908 Section 29.908... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.908 Cooling fans. For cooling fans that are a part of a powerplant installation the following apply: (a) Category A. For cooling fans...

  18. 14 CFR 29.908 - Cooling fans.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Cooling fans. 29.908 Section 29.908... STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Powerplant General § 29.908 Cooling fans. For cooling fans that are a part of a powerplant installation the following apply: (a) Category A. For cooling fans...

  19. Central Fan Integrated Ventilation Systems

    SciTech Connect

    2009-05-12

    This information sheet describes one example of a ventilation system design, a central fan integrated supply (CFIS) system, a mechanical ventilation and pollutant source control to ensure that there is reasonable indoor air quality inside the house.

  20. Fan noise research at NASA

    NASA Astrophysics Data System (ADS)

    Groeneweg, John F.

    Results of recent NASA research to reduce aircraft turbofan noise are described. As the bypass ratio of a turbofan engine increases from 5 to as much as 20, the dominant source of engine noise is the fan. A primary mechanism of tone noise generation is the rotor blade wakes interacting with downstream stator vanes. Methods of analyzing rotor-stator tone noise generation are described and sample results are given. The role of an acoustic modal description is emphasized. Wind tunnel tests of model fans and nacelles are described including a novel rotating microphone technique for modal measurement. Sample far field results are given showing the effects of inlet length, and modal measurements are shown which point to a new generation mechanism. Concepts for active fan noise control at the source are addressed. Implications of the research which have general relevance to fan noise generation and control are discussed.

  1. Fan noise research at NASA

    NASA Technical Reports Server (NTRS)

    Groeneweg, John F.

    1994-01-01

    Results of recent NASA research to reduce aircraft turbofan noise are described. As the bypass ratio of a turbofan engine increases from 5 to as much as 20, the dominant source of engine noise is the fan. A primary mechanism of tone noise generation is the rotor blade wakes interacting with downstream stator vanes. Methods of analyzing rotor-stator tone noise generation are described and sample results are given. The role of an acoustic modal description is emphasized. Wind tunnel tests of model fans and nacelles are described including a novel rotating microphone technique for modal measurement. Sample far field results are given showing the effects of inlet length, and modal measurements are shown which point to a new generation mechanism. Concepts for active fan noise control at the source are addressed. Implications of the research which have general relevance to fan noise generation and control are discussed.

  2. Vehicle hydraulic cooling fan system

    SciTech Connect

    Nilson, C.A.

    1993-06-08

    A hydraulic cooling system for vehicles having an internal combustion engine cooled by a radiator and a coolant is described, comprising, in combination, a shroud adapted to be mounted adjacent the radiator having a wall forming an air passage and defining a first port disposed adjacent the radiator and a second port spaced from the first port, a fan located within the second port, a hydraulic fan motor operatively connected to the fan, a hydraulic pump operatively connected to the engine for producing a pressurized hydraulic fluid flow, a hydraulic circuit interconnecting the pump to the fan motor, the circuit including a control valve, a hydraulic fluid reservoir and a heat exchanger, the heat exchanger being mounted within the shroud air passage.

  3. Back Down to Earth: Reconstructing the Timescale of a Catastrophically-formed Fan from Sedimentary Data

    NASA Astrophysics Data System (ADS)

    Duller, R. A.; Warner, N. H.; De Angelis, S.; Armitage, J. J.; Poyatos-More, M.

    2015-12-01

    Alluvial fans and deltas on Mars, collectively termed fans, are formed by the transport and deposition of sediment by running water. Sediment transport models have been used to calculate the timescales of fan formation on Mars using orbital or rover-based imagery. These models provide a constraint on the total volume of water involved which has major implications for understanding the hydrologic history of early Mars. However, while the robustness of sediment transport models are not in doubt, the usefulness of their application to fans on Mars still requires testing using a terrestrial system of similar type, scale and possibly origin. The 1918 volcanically-generated catastrophic jökulhlaup (glacier outburst flood), southern Iceland deposited a ≤2 km3 fan over a known observed timescale of 6-8 hr. Predicted timescales using standard sediment transport models are in excellent agreement with the known timescale. This close agreement between observed and predicted timescales was arrived at only because key parameters related to the 1918 jökulhlaup are well known and tightly constrained from ground-based observations of the sedimentology and sedimentary architecture. Crucially, the latter provided independent estimates of hydraulic parameters. This work highlights the need for more detailed stratigraphic and sedimentary analysis of units on Mars (and Earth), which can provide constraints on the nature of water flow (magnitude, frequency, intermittency) and on hydraulic parameters. Such information cannot be gleaned from the final snapshot of surface geomorphology using remote imagery.

  4. Fluvial response in a sequence stratigraphic framework: Example from the Montserrat fan delta, Spain

    SciTech Connect

    Burns, B.A.; Heller, P.L.; Marzo, M.; Paola, C.

    1997-03-01

    Exceptional exposure of the Montserrat fan-delta system (Eocene) in northeastern Spain provides an excellent framework to evaluate the alluvial response to sea-level changes over two different time scales. The alluvial system contains multiple fifth-order cycles ({approximately}10{sup 4} yr) and eight fourth-order cycles ({approximately}10{sup 4} yr). Fifth-order cycles are characterized by long-distance shoreline migrations and, occasionally, by incised basal scour surfaces but not by changes in fluvial style, lithofacies, or channel stacking pattern. Fourth-order cycles are composed of stacked fifth-order cycles and have non-erosional basal boundaries. Changes in the alluvial system during fourth-order cycles are most pronounced adjacent to shoreline and die away upstream over just a few kilometers--indicating that the base-level signal decays away over the distance of a few backwater lengths. Higher-frequency (fifth-order) changes in relative sea level appear to produce the largest shoreline migrations, but lower-frequency (fourth-order) changes have more impact on the channel stacking architecture of the alluvial systems. Observed changes in alluvial stacking pattern may be most commonly found in tectonically active, rapidly subsiding, foreland basins because of their back-tilted geometry. The authors propose a model in which sediment is trapped in the proximal basin during times of rapid tectonic subsidence and attendant relative sea-level rise. Progradation occurs as erosion rates in the mountain belt increase, and rates of subsidence and relative sea-level rise diminish. Changes in alluvial architecture reflect an increase in sediment flux towards the shoreline as less sediment is trapped upstream. Hence, changes in channel-stacking pattern coincident with transgressions and regressions likely reflect the interplay between subsidence and sediment supply in the proximal part of the basin and are not necessarily driven by eustatic sea-level changes.

  5. 16 CFR 260.5 - Carbon offsets.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 16 Commercial Practices 1 2013-01-01 2013-01-01 false Carbon offsets. 260.5 Section 260.5... ENVIRONMENTAL MARKETING CLAIMS § 260.5 Carbon offsets. (a) Given the complexities of carbon offsets, sellers... deceptive to misrepresent, directly or by implication, that a carbon offset represents emission...

  6. 16 CFR 260.5 - Carbon offsets.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 16 Commercial Practices 1 2014-01-01 2014-01-01 false Carbon offsets. 260.5 Section 260.5... ENVIRONMENTAL MARKETING CLAIMS § 260.5 Carbon offsets. (a) Given the complexities of carbon offsets, sellers... deceptive to misrepresent, directly or by implication, that a carbon offset represents emission...

  7. Shallow subsurface stratigraphy and alluvial architecture of the Kosi and Gandak megafans in the Himalayan foreland basin, India

    NASA Astrophysics Data System (ADS)

    Sinha, Rajiv; Ahmad, Jawed; Gaurav, Kumar; Morin, Guillaume

    2014-03-01

    The Kosi and the Gandak are two major Himalayan tributaries of the Ganga River in the north Bihar plains India. With a large hinterland in the Nepal Himalaya, both these rivers have generated megafans in the plains over the Quaternary time scale. Both these rivers are known to be highly dynamic and sediment-charged. A few conceptual models and limited field data suggested that these megafans have produced thick sand sheets over Late Quaternary period but these ideas have remained speculative and there is no data on the size and dimension of these sand bodies. This paper attempts to reconstruct the subsurface stratigraphy and alluvial architecture for the upper ~ 100 m of the megafans based on electrical resistivity soundings, borehole data and drill cores. Alluvial architecture of the Kosi megafan shows significant variability from proximal to medial parts of the fan in terms of sediment grain size and layer thicknesses. While the medial part shows ~ 20-30 m thick medium to coarse sand sheets which are laterally stacked, the proximal part of the fan has a dominantly gravel unit below ~ 15 m depth that is underlain and overlain by medium to coarse sand units. Further, the medial fan also shows significant vertical and lateral variability in alluvial stratigraphy. The near-surface (< 20 m depth) deposits from the Kosi megafan have pockets of clay and silt within large amalgamated sand bodies whereas the shallow sub-surface (50-100 m depth) sediments are largely sandy and devoid of clay and silt pockets. Alluvial architecture of the Gandak megafan shows two major lithounits; the upper fan succession has a higher stacking density of smaller sand bodies perhaps reflecting the migratory behavior of the river whereas the lower succession shows narrow but thick sand fills reflecting incised channels. The western part of the Gandak megafan has more abundant sand bodies compared to the eastern side of the river along both transects. There are no significant differences

  8. Graphic Arts/Offset Lithography.

    ERIC Educational Resources Information Center

    Hoisington, James; Metcalf, Joseph

    This revised curriculum for graphic arts is designed to provide secondary and postsecondary students with entry-level skills and an understanding of current printing technology. It contains lesson plans based on entry-level competencies for offset lithography as identified by educators and industry representatives. The guide is divided into 15…

  9. Phonation Offset in Tracheoesophageal Speech

    ERIC Educational Resources Information Center

    Searl, Jeff; Ousley, Teri

    2004-01-01

    Tracheoesophageal (TE) speakers often have difficulty producing the voiced-voiceless distinction. Phonation offset (POff) as a TE speaker transitions from a vowel to a stop consonant may be altered, possibly contributing to listener misperceptions. The purposes of this study were to: (1) compare the duration of POff in TE versus laryngeal…

  10. Longitudinal profiles in simple alluvial systems

    NASA Astrophysics Data System (ADS)

    Rice, Stephen P.; Church, Michael

    2001-02-01

    Theoretical considerations suggest that exponential or quadratic functions are apt for describing the longitudinal profiles of aggrading, alluvial systems that are unaffected by significant lateral inputs of water or sediment. A new set of field data confirms this for individual sedimentary links along a wandering gravel-bed river in British Columbia, Canada. Each link is viewed as a simple alluvial system, without major water or sediment inputs, within which grain size typically fines downstream in a relatively systematic manner. Such homogeneous reaches are suitable for the investigation of simple profile form. It is found that quadratic approximations are the most flexible descriptor for link longitudinal profiles. Overall, the river forms an irregularly cuspate long profile structured by these fundamental length-scale units. Both link gradients and link fining rate reflect size-selective aggradation associated with the bounding lateral inputs.

  11. Interaction of fine sediment with alluvial streambeds

    USGS Publications Warehouse

    Jobson, H.E.; Carey, W.P.

    1989-01-01

    An alluvial streambed can have a large capacity to store fine sediments that are extracted from the flow when instream concentrations are high and it can gradually release fine sediment to the flow when the instream concentrations are low. Several types of storage mechanisms are available depending on the relative size distribution of the suspended load and bed material, as well as the flow hydraulics. -from Authors

  12. The Alternative Low Noise Fan

    NASA Technical Reports Server (NTRS)

    Dittmar, James H.; Elliott, David M.; Jeracki, Robert J.; Moore, Royce D.; Parrott, Tony L.

    2000-01-01

    A 106 bladed fan with a design takeoff tip speed of 1100 ft/sec was hypothesized as reducing perceived noise because of the shift of the blade passing harmonics to frequencies beyond the perceived noise rating range. A 22 in. model of this Alternative Low Noise Fan, ALNF, was tested in the NASA Glenn 9x 15 Wind Tunnel. 'Me fan was tested with a 7 vane long chord stator assembly and a 70 vane conventional stator assembly in both hard and acoustically treated configurations. In addition a partially treated 7 vane configuration was tested wherein the acoustic material between the 7 long chord stators was made inactive. The noise data from the 106 bladed fan with 7 long chord stators in a hard configuration was shown to be around 4 EPNdB quieter than a low tip speed Allison fan at takeoff and around 5 EPNdB quieter at approach. Although the tone noise behaved as hypothesized, the majority of this noise reduction was from reduced broadband noise related to the large number of rotor blades. This 106 bladed ALNF is a research fan designed to push the technology limits and as such is probably not a practical device with present materials technology. However, a low tip speed fan with around 50 blades would be a practical device and calculations indicate that it could be 2 to 3 EPNdB quieter at takeoff and 3 to 4 EPNdB quieter at approach than the Allison fan. 7 vane data compared with 70 vane data indicated that the tone noise was controlled by rotor wake-stator interaction but that the broadband noise is probably controlled by the interaction of the rotor with incoming flows. A possible multiple pure tone noise reduction technique for a fan/acoustic treatment system was identified. The data from the fully treated configuration showed significant noise reductions over a large frequency range thereby providing a real tribute to this bulk absorber treatment design. The tone noise data with the partially treated 7 vane configuration indicated that acoustic material in the

  13. Two-Stage Centrifugal Fan

    NASA Technical Reports Server (NTRS)

    Converse, David

    2011-01-01

    Fan designs are often constrained by envelope, rotational speed, weight, and power. Aerodynamic performance and motor electrical performance are heavily influenced by rotational speed. The fan used in this work is at a practical limit for rotational speed due to motor performance characteristics, and there is no more space available in the packaging for a larger fan. The pressure rise requirements keep growing. The way to ordinarily accommodate a higher DP is to spin faster or grow the fan rotor diameter. The invention is to put two radially oriented stages on a single disk. Flow enters the first stage from the center; energy is imparted to the flow in the first stage blades, the flow is redirected some amount opposite to the direction of rotation in the fixed stators, and more energy is imparted to the flow in the second- stage blades. Without increasing either rotational speed or disk diameter, it is believed that as much as 50 percent more DP can be achieved with this design than with an ordinary, single-stage centrifugal design. This invention is useful primarily for fans having relatively low flow rates with relatively high pressure rise requirements.

  14. Preliminary Geological Map of the Peace Vallis Fan Integrated with In Situ Mosaics From the Curiosity Rover, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Sumner, D. Y.; Palucis, M.; Dietrich, B.; Calef, F.; Stack, K. M.; Ehlmann, B.; Bridges, J.; Dromart, J.; Eigenbrode, J.; Farmer, J.; Grant, J.; Grotzinger, J.; Hamilton, V.; Hardgrove, C.; Kah, L.; Leveille, R.; Mangold, N.; Rowland, S.; Williams, R.

    2013-01-01

    A geomorphically defined alluvial fan extends from Peace Vallis on the NW wall of Gale Crater, Mars into the Mars Science Laboratory (MSL) Curiosity rover landing ellipse. Prior to landing, the MSL team mapped the ellipse and surrounding areas, including the Peace Vallis fan. Map relationships suggest that bedded rocks east of the landing site are likely associated with the fan, which led to the decision to send Curiosity east. Curiosity's mast camera (Mastcam) color images are being used to refine local map relationships. Results from regional mapping and the first 100 sols of the mission demonstrate that the area has a rich geological history. Understanding this history will be critical for assessing ancient habitability and potential organic matter preservation at Gale Crater.

  15. Sediment transport and fan deposition in the Gulf of Alaska: Effects of transform motion on deep sea sedimentation

    SciTech Connect

    Stevenson, A.J.; Bruns, T.R.; Carlson, P.R. ); Dobson, M.R. )

    1990-06-01

    GLORIA side-scan sonar images and two channel seismic profiles recently collected in the Gulf of Alaska reveal a major site of late Miocene to Recent terrigenous sediment accumulation on the oceanic plate adjacent to the Fairweather-Queen Charlotte transform and the Yakutat Terrane. Sediment moving across this margin has formed several large channel dominated fan systems that blanket the entire gulf and spill westward onto the Tufts Abyssal Plain. The Surveyor Fan, fed by the glaciers of the Yakutat Terrane and insulated from transform sediment source offset by the Terrane, has maintained a single channel course over the entire life of the fan. The Chirikov and Baranof fans receive their sediment supply from glaciofluvial point sources along the SE Alaska margin, separated from the fans by an active transform. The fans show a southward younging of channel ages consistent with the sense of plate motion. Early (late Miocene) deposition within the gulf was limited to the structural basin between the continental margin and the Kodiak-Bowie seamount chain. The geometry of these early depositional systems is poorly known, but available data suggest their channels were oriented NW-SE. Subsequent establishment of a depositional slope between the margin and the seamount chain, coupled with the filling of the basin, led to a reorganization into SW-NE channel systems. The fan bodies of the Gulf of Alaska are members of a distinct class of fans that are characterized by long distributary channels which persist to near the fan limits. This type of fan morphology is most often attributed to a predominantly fine-grained sediment supply. This is difficult to reconcile with the obvious proximal glacial source for much of the sediment supplied to these fans.

  16. Geostatistical simulations of alluvial sandbodies in the Triassic series of the Chaunoy field, France

    SciTech Connect

    Eschard, R.; Desaubliaux, G.; Eemouzy, P. ); Bacchiana, C.; Parpant, J.; Chautru, J.M.

    1993-09-01

    Chaunoy field, the largest oil field of the Paris basin, is exploiting heterogeneous reservoirs deposited during the Triassic in a large alluvial fan/lacustrine complex. The construction of a realistic reservoir model is difficult in such a setting because of the highly complex architecture of single reservoir units. Geostatistical simulations therefore have been performed to take into account the reservoir heterogeneities in the fluid flow modeling. A first layering has been determined from sedimentological and sequence stratigraphic analysis. The series was deposited in an alluvial outer fan environment. A lower siliciclastic member shows four heterogeneous sand sheets (7 m thick), which have been correlated across the field. Each of them is made up of stacked single channel sequences. The sand sheets are separated by extensive lacustrine and flood plain mudstone layers acting as permeability barriers. An upper siliciclastic/dolomitic member has been divided into two units with porous conglomeratic channels interfingered with cemented lagoonal dolomites. Proportional curves in lithofacies have confirmed this layering, showing the continuity of the permeability barriers, and the variogram analysis has shown that the well spacing is larger than the channel width. Simulations in lithofacies have been performed with the Heresim software using three different variogram ranges (small, medium, and large values). Because a good correlation exists between the lithofacies and the petrophysical attributes, a transcription of the lithofacies simulations into petrophysical attributes therefore was easy and realistic. Scaling-up techniques have given fluid-flow models corresponding to the three correlation ranges. Comparison of the global results of the fluid flow simulations with the observed production history enabled us to choose the more relevant case. The the model using the selected correlation range helped determine optimum well spacing.

  17. The preliminary study on the alluvial stratigraphy of Peinan archaeological site, Taiwan

    NASA Astrophysics Data System (ADS)

    Yang, Hsiaochin; Chen, Wenshan; Yeh, Changkeng

    2015-04-01

    Many of the activities of prehistoric people who lived in Taiwan were concentrated around river terrace environments and seldom in alluvial environments which are resulting from the rapid tectonic uplift and high erosion rate of the late Cenozoic mountain belt. However, the Peinan archaeological site, one of the most important Neolithic sites in Taiwan because of the great amount of slate slab coffins and nephrite artifacts unearthed, is located at the bottom of Peinan Hill which is formed by the activity of Lichi and Luyeh Faults. According to the radioactive carbon dating results, the Peinan alluvial fan used as cemetery was lasted over 3,700 years (5700-2000 yr BP) but the related cultural formation was only lasted 400 years (3500-3100 yr BP). What have happened to the prehistoric people? As the stratigraphic record allows archaeologists to ascertain the effects of geological processes on the preservation of the archaeological record, determining which parts of the archaeological records are absent, which have potentially been preserved, and how fragmentary are the preserved portions of the records. The limitations that geologic processes impose on the archaeological record must be recognized and understood before meaningful interpretations of prehistory can be made. Therefore, the reconstruction of the landscape and stratigraphic records in archaeological site not only provides the paleo-environmental context but also helps to explain changes that occurred to human cultures over time.

  18. Sound maintenance practices protect fan investments

    SciTech Connect

    Bauer, M.

    2009-11-15

    Since underground coal miners depend on axial fans, lack of maintenance could prove costly. A number of pre-emptive actions that can help keep fans running at optimal performance can also be taken. 2 photos.

  19. Prop-fan with improved stability

    NASA Technical Reports Server (NTRS)

    Rothman, Edward A. (Inventor); Violette, John A. (Inventor)

    1988-01-01

    Improved prop-fan stability is achieved by providing each blade of the prop-fan with a leading edge which, outwardly, from a location thereon at the mid-span of the blade, occupy generally a single plane.

  20. Depositional processes and facies of Trail Fan sandflat: Death Valley, California

    SciTech Connect

    Malicse, A.E.; Mazzullo, J.M.; Eide, M.G. )

    1992-01-01

    A study was conducted of the alluvial fan to playa transition along Trail fan in Death Valley, California with the primary objectives of documenting sedimentary facies and textural features of so-called arid region sandflat. The study involved description of sedimentary structures along trenches and meter-deep cores, description of surficial bedforms, and collection of samples for lithological analyses. Surficial features of Trail Fan sandflat gradually change downdip as a function of texture, ground water depth, and runoff. They include: (1) tongues of mudflows; (2) shallow braided channels that taper out into mudflat or coalesced into single channels; (3) puffy grounds; and (4) flat-smooth surface of the mudflat. The sediment's texture shows a fining downdip trend except when the surface are draped by mudflows. Four facies are distinguished downdip from the alluvial fan to playa mudflat. Facies 1 consists of massive, light gray, matrix to grain supported gravel, and is interpreted as debris flow or streamflow deposit. Facies 2 consists of thin-bedded (0.6--0.06 m), tan, massive, gravelly mud and is interpreted as mudflow deposit. Facies 2 consists of repeated sequences of thick-bedded (0.15 to 0.3 m), massive to planar stratified, graveliferous sand with mud drape and is interpreted as poorly sorted sheetflood or streamflow deposit. Facies 4 consist of light gray, planar laminated, coarsening upward mud to muddy sand, and is interpreted as mudflat facies. This study shows that arid region sandflat facies is a mosaic of mudflow, debris flow, sheetflood and streamflow deposits and is more complex than previous sandflat models described.

  1. Can Exercise Offset Alcohol's Damaging Effects?

    MedlinePlus

    ... gov/news/fullstory_160853.html Can Exercise Offset Alcohol's Damaging Effects? Even gardening, brisk walking may reduce ... study says moderate exercise may offset some of alcohol's harmful effects. Normally, drinking raises the risk of ...

  2. 5 CFR 1215.28 - Administrative offset.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... effective or has significant deterrent value; and (4) Offset is best suited to further and protect the...: (1) The nature and amount of the debt and the agency's intention to collect the debt by offset...

  3. Advance Noise Control Fan II: Test Rig Fan Risk Management Study

    NASA Technical Reports Server (NTRS)

    Lucero, John

    2013-01-01

    Since 1995 the Advanced Noise Control Fan (ANCF) has significantly contributed to the advancement of the understanding of the physics of fan tonal noise generation. The 9'x15' WT has successfully tested multiple high speed fan designs over the last several decades. This advanced several tone noise reduction concepts to higher TRL and the validation of fan tone noise prediction codes.

  4. Review of Aircraft Engine Fan Noise Reduction

    NASA Technical Reports Server (NTRS)

    VanZante, Dale

    2008-01-01

    Aircraft turbofan engines incorporate multiple technologies to enhance performance and durability while reducing noise emissions. Both careful aerodynamic design of the fan and proper installation of the fan into the system are requirements for achieving the performance and acoustic objectives. The design and installation characteristics of high performance aircraft engine fans will be discussed along with some lessons learned that may be applicable to spaceflight fan applications.

  5. 10 CFR 429.32 - Ceiling fans.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 3 2014-01-01 2014-01-01 false Ceiling fans. 429.32 Section 429.32 Energy DEPARTMENT OF... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.32 Ceiling fans. (a) Sampling plan for selection of units for testing. The requirements of § 429.11 are applicable to ceiling fans. (b)...

  6. 10 CFR 429.32 - Ceiling fans.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 3 2012-01-01 2012-01-01 false Ceiling fans. 429.32 Section 429.32 Energy DEPARTMENT OF... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.32 Ceiling fans. (a) Sampling plan for selection of units for testing. The requirements of § 429.11 are applicable to ceiling fans. (b)...

  7. 10 CFR 429.32 - Ceiling fans.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 3 2013-01-01 2013-01-01 false Ceiling fans. 429.32 Section 429.32 Energy DEPARTMENT OF... COMMERCIAL AND INDUSTRIAL EQUIPMENT Certification § 429.32 Ceiling fans. (a) Sampling plan for selection of units for testing. The requirements of § 429.11 are applicable to ceiling fans. (b)...

  8. Online Fan Fiction and Critical Media Literacy

    ERIC Educational Resources Information Center

    Black, Rebecca W.

    2010-01-01

    This article explores English-language-learning (ELL) youths' engagement with popular media through composing and publicly posting stories in an online fan fiction writing space. Fan fiction is a genre that lends itself to critical engagement with media texts as fans repurpose popular media to design their own narratives. Analyses describe how…

  9. 7 CFR 1951.111 - Salary offset.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... employees from loss of federal funds through negligence and other matters. Salary offset may also be used by... 7 CFR part 766. In addition, for Farm Loan Programs direct loans, salary offset will not be... Programs guaranteed debtors, salary offset can not begin until a final loss claim has been paid....

  10. 45 CFR 1177.8 - Administrative offset.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES CLAIMS COLLECTION § 1177.8 Administrative offset. (a) The... administrative offset, the National Endowment for the Humanities will send the debtor written notice of the... interest. (d) The National Endowment for the Humanities may effect an administrative offset against...

  11. 45 CFR 1177.8 - Administrative offset.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES CLAIMS COLLECTION § 1177.8 Administrative offset. (a) The... administrative offset, the National Endowment for the Humanities will send the debtor written notice of the... interest. (d) The National Endowment for the Humanities may effect an administrative offset against...

  12. 26 CFR 1.812-5 - Offset.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... and Loss from Operations § 1.812-5 Offset. (a) Offset defined. Section 812(d) defines the term “offset... is necessary to reduce the life insurance company taxable income (computed without regard to section... taxable year as were sustained in taxable years preceding the taxable year in which the life...

  13. 31 CFR 285.7 - Salary offset.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... offsets directly from a paying agency, rather than through TOP. See 5 CFR 550.1101 through 550.1108. (2... the same meaning as that term is defined in 5 CFR 550.1103. Federal employee means a current employee... disposable pay in accordance with 5 CFR 550.1103. (g) Offset amount. (1) The amount offset from a...

  14. 45 CFR 1177.8 - Administrative offset.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES CLAIMS COLLECTION § 1177.8 Administrative offset. (a) The... administrative offset, the National Endowment for the Humanities will send the debtor written notice of the... interest. (d) The National Endowment for the Humanities may effect an administrative offset against...

  15. 45 CFR 1177.8 - Administrative offset.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... HUMANITIES NATIONAL ENDOWMENT FOR THE HUMANITIES CLAIMS COLLECTION § 1177.8 Administrative offset. (a) The... administrative offset, the National Endowment for the Humanities will send the debtor written notice of the... interest. (d) The National Endowment for the Humanities may effect an administrative offset against...

  16. CHANNEL EVOLUTION IN MODIFIED ALLUVIAL STREAMS.

    USGS Publications Warehouse

    Simon, Andrew; Hupp, Cliff R.

    1987-01-01

    This study (a) assesses the channel changes and network trends of bed level response after modifications between 1959 and 1972 of alluvial channels in western Tennessee and (b) develops a conceptual model of bank slope development to qualitatively assess bank stability and potential channel widening. A six-step, semiquantitative model of channel evolution in disturbed channels was developed by quantifying bed level trends and recognizing qualitative stages of bank slope development. Development of the bank profile is defined in terms of three dynamic and observable surfaces: (a) vertical face (70 to 90 degrees), (b) upper bank (25 to 50 degrees), and (c) slough line (20 to 25 degrees).

  17. Overlapping of pedogenesis and meteoric diagenesis in distal alluvial and shallow lacustrine deposits in the Madrid Miocene Basin, Spain

    NASA Astrophysics Data System (ADS)

    Bustillo, M. a.. A.; Alonso-Zarza, A. M. a..

    2007-06-01

    The Miocene distal alluvial fan and palustrine deposits of the Madrid Basin (Paracuellos de Jarama area) were examined to establish the sequence of its pedogenic-diagenetic processes and the main factors controlling them. In this area the diagenetic processes operated not only on carbonates, as commonly studied, but also in high magnesium clays and opaline cherts. This paper provides a dynamic model for saline-alkaline lake margins that complements the existing freshwater palustrine model. Three sections (BER, PEL and UPC) containing limestones, sepiolite, dolostones and opaline cherts were examined; these represent the entire transition from alluvial fan deposit to lake environment. The alluvial fan deposits (PEL section) show the most complex sequence of processes. After a weak edaphic imprint, the primary mudstone and siltstones are affected by silicification (opaline levels formed mainly by selective replacement of sepiolites) and later dolomitization. Several types of dolomite are present, rounded crystals, spherules and globular bodies being the most characteristic. In the ponds situated at the foot of the alluvial fans or in interfan areas, sepiolite precipitated within free water bodies (BER section) and an intense pedogenesis led to the formation of palustrine sepiolite deposits. Later, the intense silicification of the sepiolite produced lenticular opaline levels that were locally transformed to quartz by aging. In the shallow lakes (UPC section), palustrine limestones and sepiolite were deposited. The carbonates are partially affected by silicification, the sepiolite becoming completely silicified. The opaline levels clearly preserve the structure of the limestones and sepiolite host rocks. All the opaline levels show local aging processes. The silicification processes were different in the three settings due to the interplay of groundwater with sedimentary environments and facies. In the distal alluvial fan sediments of the PEL section, the initial host

  18. The role of tropical cyclones on landscape dynamics in southern Baja California, Mexico based on Late Pleistocene-Holocene alluvial stratigraphy

    NASA Astrophysics Data System (ADS)

    McDonald, Eric; Antinao, Jose Luis; Rhodes, Edward J.; Brown, Nathan; Gosse, John

    2015-04-01

    Region-wide alluvial records provide evidence that time-transgressive changes in climate can be a major driver of landscape evolution. Historically, landfall of eastern Pacific tropical cyclones in southwestern North America during the late summer and early fall provide the strongest storms that have demonstrated geomorphic impact on the landscape. The alluvial fan record of the southern portion of Baja California (Mexico) was investigated to determine if linkages exist between region-wide fluvial deposits and tropical cyclones. The regional distribution and Pleistocene to Holocene morphostratigraphy of alluvial fans has been established for the southern portion of Baja California with primary focus on the La Paz and San José del Cabo basins. Six discrete morphopedosedimentary alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development further reinforced with geochronology using radiocarbon, optically stimulated luminescence and cosmogenic depth-profiles. A first phase of regional aggradation began before ~ 100 ka (Qt1) and culminated ~10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units are conformed of multiple 1-3 m thick alluvial packages deposited in upper-flow regime and representing individual storms. Aggradational units (Qt1-Qt4) covered broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are mostly confined to channels of ~0.5-2 km width. Continuous deposition of the thicker sequences is demonstrated by closely spaced luminescence dates in vertical profiles. In a few places disconformities between major units are evident and indicated by partly eroded buried soils. Analysis of historical terraces as part of the younger units

  19. Fluvial fan evolution during Late Quaternary climate changes: field and chronological constraints from the Indo-Gangetic basin

    NASA Astrophysics Data System (ADS)

    Singh, A.; Gupta, S.; Sinha, R.; Densmore, A.; Thomsen, K. J.; Nayak, N.; Joshi, S. K.; van Dijk, W. M.; Buylaert, J. P.; Mondal, S.; Kumar, D.; Mason, P. J.; Murray, A. S.; Kumar, M.; Shekhar, S.; Rai, S. P.

    2015-12-01

    The stratigraphic evolution of fluvial fans is to a large extent governed by channel avulsion. Spatial variations in alluvial architecture are influenced by avulsion magnitude and frequency. However due to the absence of long-term chronostratigraphic records of fan stratigraphy, it has proved difficult to test patterns of fan evolution against records of climate variability. In order to understand the processes of channel avulsion during fan evolution, it is important to determine the spatio-temporal pattern of fluvial channel aggradation, incision, and migration. In this study, we reconstruct the shallow sub-surface alluvial stratigraphy of fluvial fan systems formed by the major Himalayan rivers, the Sutlej and Yamuna, in the northwestern Indo-Gangetic basin. We map the spatial distribution of channel sand bodies deposited by these rivers and develop a chronostratigraphic model for the fluvial succession in a depositional dip perpendicular transect. Sediment cores up to ~50 m deep along two transects are used to reconstruct the shallow stratigraphy of the fan systems. Discontinuous channel sand bodies are separated by floodplain fines which occasionally show weak pedogenesis that mark the end of episodes of channel aggradation. Optically stimulated luminescence (OSL) dating is used to bracket the timing of channel-filling episodes, and their spatial distribution. Mapping of sand bodies coupled with chronostratigraphic constraints allows reconstruction of channel migration patterns and their timing across the Sutlej-Yamuna fans. Chronostratigraphy permits temporal correlation with published measures of monsoon variability. We find that fluvial aggradation at the western end of studied transects, near the middle of the Sutlej fan, terminated around ~20 ka. We also show that abandonment of the paleo-Sutlej and major fan-scale avulsion occurred after ~15 ka, and was followed by formation of incised valleys that confined the modern fluvial system in northwestern Indo

  20. Fertilizers mobilization in alluvial aquifer: laboratory experiments

    NASA Astrophysics Data System (ADS)

    Mastrocicco, M.; Colombani, N.; Palpacelli, S.

    2009-02-01

    In alluvial plains, intensive farming with conspicuous use of agrochemicals, can cause land pollution and groundwater contamination. In central Po River plain, paleo-channels are important links between arable lands and the underlaying aquifer, since the latter is often confined by clay sediments that act as a barrier against contaminants migration. Therefore, paleo-channels are recharge zones of particular interest that have to be protected from pollution as they are commonly used for water supply. This paper focuses on fertilizer mobilization next to a sand pit excavated in a paleo-channel near Ferrara (Italy). The problem is approached via batch test leaking and columns elution of alluvial sediments. Results from batch experiments showed fast increase in all major cations and anions, suggesting equilibrium control of dissolution reactions, limited availability of solid phases and geochemical homogeneity of samples. In column experiments, early elution and tailing of all ions breakthrough was recorded due to preferential flow paths. For sediments investigated in this study, dispersion, dilution and chemical reactions can reduce fertilizers at concentration below drinking standards in a reasonable time frame, provided fertilizer loading is halted or, at least, reduced. Thus, the definition of a corridor along paleo-channels is recommended to preserve groundwater quality.

  1. Low Noise Research Fan Stage Design

    NASA Technical Reports Server (NTRS)

    Hobbs, David E.; Neubert, Robert J.; Malmborg, Eric W.; Philbrick, Daniel H.; Spear, David A.

    1995-01-01

    This report describes the design of a Low Noise ADP Research Fan stage. The fan is a variable pitch design which is designed at the cruise pitch condition. Relative to the cruise setting, the blade is closed at takeoff and opened for reverse thrust operation. The fan stage is a split flow design with fan exit guide vanes and core stators. This fan stage design was combined with a nacelle and engine core duct to form a powered fan/nacelle, subscale model. This model is intended for use in aerodynamic performance, acoustic and structural testing in a wind tunnel. The model has a 22-inch outer fan diameter and a hub-to-top ratio of 0.426 which permits the use of existing NASA fan and cowl force balance designs and rig drive system. The design parameters were selected to permit valid acoustic and aerodynamic comparisons with the PW 17-inch rig previously tested under NASA contract. The fan stage design is described in detail. The results of the design axisymmetric analysis at aerodynamic design condition are included. The structural analysis of the fan rotor and attachment is described including the material selections and stress analysis. The blade and attachment are predicted to have adequate low cycle fatigue life, and an acceptable operating range without resonant stress or flutter. The stage was acoustically designed with airfoil counts in the fan exit guide vane and core stator to minimize noise. A fan-FEGV tone analysis developed separately under NASA contract was used to determine these airfoil counts. The fan stage design was matched to a nacelle design to form a fan/nacelle model for wind tunnel testing. The nacelle design was developed under a separate NASA contract. The nacelle was designed with an axisymmetric inlet, cowl and nozzle for convenience in testing and fabrication. Aerodynamic analysis of the nacelle confirmed the required performance at various aircraft operating conditions.

  2. Flutter of swept fan blades

    NASA Technical Reports Server (NTRS)

    Kielb, R. E.; Kaza, K. R. V.

    1984-01-01

    The effect of sweep on fan blade flutter is studied by applying the analytical methods developed for aeroelastic analysis of advance turboprops. Two methods are used. The first method utilizes an approximate structural model in which the blade is represented by a swept, nonuniform beam. The second method utilizes a finite element technique to conduct modal flutter analysis. For both methods the unsteady aerodynamic loads are calculated using two dimensional cascade theories which are modified to account for sweep. An advanced fan stage is analyzed with 0, 15 and 30 degrees of sweep. It is shown that sweep has a beneficial effect on predominantly torsional flutter and a detrimental effect on predominantly bending flutter. This detrimental effect is shown to be significantly destabilizing for 30 degrees of sweep.

  3. Characteristics of some submarine fan channels, Permian Ecca Group, South Africa

    SciTech Connect

    Bouma, A.H. ); Dev Wickens, H. )

    1991-03-01

    The vary well exposed submarine fan complex in the southwestern part of the Karoo basin permits close examination of channel-fills and in places their associated overbank deposits. The complex comprises five arenaceous fan systems some of which attain 60 m in thickness. The fans are vertically stacked and separated by basinal shale deposits; each system with its own direction of growth. The association of channelized sandstone bodies and thin-bedded sandstone and shale packages in an updip position from predominantly stacked lobe deposits suggest preservation of middle fan settings. A 500 m wide, 20 m thick channel-fill consisting massive amalgamated sandstone beds occupying the channel thalweg occurs in a setting dominated by thin-bedded, ripple-laminated sandstone and shale. Gradual thinning of the channel-fill beds toward the channel edges, lack of internal lateral accretion, and a high width to depth ratio suggests a low sinuous to straight channel. The channel-fill is capped by an abandonment facies characterized by ripple-laminated sandstone and shale. Stacked, laterally offset channel-fill deposits with highly erosional contacts and typical well-bedded overbank deposits form channel-overbank complexes and characterize the mid-fan region of the uppermost fan system. Palaeocurrent directions and gradual diminishing of bed-thickness away from the generally massively bedded, amalgamated channel-fill sandstones confirm a simultaneous channel/overbank origin for these deposits. Levee morphology has not been recognized. Both examples of channel-fills cited reveal part of the complexity of the channelized portions of submarine fans and hence the implications thereof in exploring for hydrocarbon reservoirs.

  4. Surface mine fan installations at Inco Limited

    SciTech Connect

    Stachulak, J.S.

    1995-12-31

    Inco Limited operates 11 underground mines in the Sudbury District. The mines are located on the rim of the Sudbury Basin, an oval with the axis in the range of 27 and 60 km. The ore dips to at least 3000 m below surface. The ores are mined primarily for nickel and copper. Total ore production from underground is in excess of 55,000 tons per day. Over 40 surface fans have been installed since the late 1960`s. All of the fans are adjustable pitch, axial flow units. A major factor influencing ventilation design in the last 30 years has been the introduction of diesel equipment underground. Volumes per fan have ranged from 60 to 330 (cubic metres per second), with motors from 100 to 2500 hp. Fans of the axial flow type have been in common use for main fan installations at Canadian mines for many years. The standard arrangement has been to mount these fans horizontally, i.e. with the fan shaft and the long axis of the housing horizontal. This is a natural arrangement for an underground fan, but for a surface installation, a vertically mounted fan has definite advantages. The surface area taken up by a typical vertical fan installation is generally about one quarter of that with a horizontal fan of the same capacity. This is not a problem with isolated fans and flat surface outcrop sites, but where the installation is to be near existing buildings, or where there are poor surface soil conditions, space and cost considerations greatly favour vertical fans.

  5. Seismic definition of fan lobe types of Mississippi Fan, Gulf of Mexico

    SciTech Connect

    Weimer, P.; Buffler, R.T.

    1986-05-01

    Detailed seismic stratigraphic studies in the upper and middle Mississippi Fan identified 12 fan lobes. Three different types of fan lobes are present. The type 1 fan lobe consists of two seismic sequences. At the base of the lower sequence are mounded reflectors that change upward to hummocky reflectors. The upper sequence has stacked high-amplitude reflectors flanked on either side by low-amplitude, laterally continuous reflectors. These type 1 fan lobes are interpreted as mass transport deposits overlain by a single channel with extensive overbank deposits. The type 2 fan lobe has seismic and geologic facies similar to the upper sequence of type 1. Both type 1 and type 2 fan lobes have a single channel that is sinuous in the middle fan. The type 3 fan lobe is characterized by several stacked high-amplitude reflectors, flanked by laterally continuous low-amplitude reflectors. These represent a bifurcating channel system showing several episodes of deposition and abandonment. Most of the sediments in the Mississippi Fan were deposited in type 2 or the upper sequence of type 1 fan lobes. Sediments in the lower sequence of the type 1 lobe are areally and volumetrically limited. Of the 12 fan lobes, 7 are type 1, 4 are type 2, and 1 is type 3. Deep Sea Drilling Project Leg 96 drilling penetrated only the modern lobe, which is a type 2 fan lobe.

  6. Impact of the alluvial style on the geoarcheology of stream valleys

    NASA Astrophysics Data System (ADS)

    Guccione, Margaret J.

    2008-10-01

    The extensive archeological record within river valleys provides an environment long favored for study by the archeologic community. This record of human occupation varies with the alluvial style of the river, resulting in each river valley having a unique archeological record controlled by three factors; location of occupation sites, preservation of those sites, and recognition of the sites. If problems of site preservation and recognition in a river valley can be recognized and addressed, a better insight into settlement patterns and complex human-environment interactions can result. This study represents a synthesis of extensive published and secondary data sets pertaining to archaeology and alluvial geomorphology of the lower Missouri, Red, and Mississippi Rivers, to examine the relationship of prehistoric site distribution with fluvial geomorphology. The archeologic data are from published literature and government agencies. The geomorphic data are from a variety of published and unpublished investigations, including maps of alluvial geomorphology, digital elevation models, aerial photographs, and topographic maps. The data were input into spreadsheets and a GIS for qualitative and quantitative analysis. Prehistoric human occupation of the narrow Missouri valley floor is limited, with only 0.061 recorded sites/km 2. Additional sites are likely buried by thick vertical accretion sediment on the limited prehistoric portions of the floodplain and within alluvial/colluvial fans along the valley margin. Non-random preservation patterns, such as the absence of sites from the youngest cultural period, are attributed to shifts in settlement patterns. In comparison to the lower Missouri River valley, prehistoric occupation of the lower Red and Mississippi rivers was much more extensive and the density of occupation was 0.274 sites/km 2 and 0.277 sites/km 2 respectively. Significant differences do exist in the age of sites and their relationship to different floodplain

  7. Alluvial Bars of the Obed Wild and Scenic River, Tennessee

    USGS Publications Warehouse

    Wolfe, W.J.; Fitch, K.C.; Ladd, D.E.

    2007-01-01

    In 2004, the U.S. Geological Survey (USGS) and the National Park Service (NPS) initiated a reconnaissance study of alluvial bars along the Obed Wild and Scenic River (Obed WSR), in Cumberland and Morgan Counties, Tennessee. The study was partly driven by concern that trapping of sand by upstream impoundments might threaten rare, threatened, or endangered plant habitat by reducing the supply of sediment to the alluvial bars. The objectives of the study were to: (1) develop a preliminary understanding of the distribution, morphology, composition, stability, and vegetation structure of alluvial bars along the Obed WSR, and (2) determine whether evidence of human alteration of sediment dynamics in the Obed WSR warrants further, more detailed examination. This report presents the results of the reconnaissance study of alluvial bars along the Obed River, Clear Creek, and Daddys Creek in the Obed WSR. The report is based on: (1) field-reconnaissance visits by boat to 56 alluvial bars along selected reaches of the Obed River and Clear Creek; (2) analysis of aerial photographs, topographic and geologic maps, and other geographic data to assess the distribution of alluvial bars in the Obed WSR; (3) surveys of topography, surface particle size, vegetation structure, and ground cover on three selected alluvial bars; and (4) analysis of hydrologic records.

  8. Fan Noise Source Diagnostic Test: Tone Modal Structure Results

    NASA Technical Reports Server (NTRS)

    Heidelberg, Laurence J.

    2002-01-01

    This investigation is part of a test series that was extremely comprehensive and included aerodynamic and acoustic testing of a fan stage using two different fan rotors and three different stator designs. The test series is known as the Source Diagnostic Test (SDT) and was conducted by NASA Glenn as part of the Advanced Subsonic Technology (AST) Noise Reduction Program. Tone mode measurements of one of the rotors with three different stators were made. The stator designs involve changes in vane count and sweep at constant solidity. The results of both inlet and exhaust tone mode measurements are presented in terms of mode power for both circumferential and radial mode orders. The results show benefits of vane sweep to be large, up to 13 dB in total tone power. At many conditions, the increase in power due to cutting on the rotor/stator interaction is more than offset by vane sweep. The rotor locked mode is shown as an important contributor to tone power when the blade tip speed is near and above Mach one. This is most evident in the inlet when the direct rotor field starts to cut on.

  9. 30 CFR 57.8518 - Main and booster fans.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Main and booster fans. 57.8518 Section 57.8518... and Underground § 57.8518 Main and booster fans. (a) All mine main and booster fans installed and used...-cycle shutdowns or planned or scheduled fan maintenance or fan adjustments where air quality...

  10. 30 CFR 57.8518 - Main and booster fans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Main and booster fans. 57.8518 Section 57.8518... and Underground § 57.8518 Main and booster fans. (a) All mine main and booster fans installed and used...-cycle shutdowns or planned or scheduled fan maintenance or fan adjustments where air quality...

  11. 30 CFR 57.8518 - Main and booster fans.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Main and booster fans. 57.8518 Section 57.8518... and Underground § 57.8518 Main and booster fans. (a) All mine main and booster fans installed and used...-cycle shutdowns or planned or scheduled fan maintenance or fan adjustments where air quality...

  12. 30 CFR 57.8518 - Main and booster fans.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Main and booster fans. 57.8518 Section 57.8518... and Underground § 57.8518 Main and booster fans. (a) All mine main and booster fans installed and used...-cycle shutdowns or planned or scheduled fan maintenance or fan adjustments where air quality...

  13. 30 CFR 57.8518 - Main and booster fans.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Main and booster fans. 57.8518 Section 57.8518... and Underground § 57.8518 Main and booster fans. (a) All mine main and booster fans installed and used...-cycle shutdowns or planned or scheduled fan maintenance or fan adjustments where air quality...

  14. Quaternary conception fan, Santa Barbara, California: two distinct canyon(s)-fan systems

    SciTech Connect

    Kraemer, S.M.C.

    1987-05-01

    The Quaternary Conception fan forms the gentle northwestern slope of the Santa Barbara basin, California. Two distinct canyon(s)-fan systems which show conspicuous differences in growth pattern coalesced to form this sediment wedge. The older Cojo canyon-fan system fed a typical radial fan characterized by (1) a single persistent conduit, (2) rhythmic interbedded levees in the upper and mid-fan built by frequent episodic turbidity flows, (3) an apparently well-developed distributary system, and (4) distal sand deposition on the lower fan and basin plain. Subsequently, the Gaviota canyons formed a radial fan/slope apron system. Two subparallel canyons were incised along fault zones where headward erosion was enhanced by slumping and increased fluvial sediment supply during the Pleistocene due to the capture of the Santa Ynez River near Gaviota Creek. Tectonism produced channel aggradation, which resulted in a series of en echelon channels. The eastern channel is associated with slumping and numerous coalescing slope gullies. These features resulted from oversteepening of the fan slope. Due to the absence of distinct gradient breaks, recent channel morphology was used to define fan divisions: (1) upper fan, broad channel with levees, gradient range from 1:25 to 1:40, (2) middle fan, levee heights decrease and channels narrow, gradients range from 1:40 to 1:100, and (3) lower fan, relatively smooth surface morphology, gradients less than 1:100. These higher gradients on the present Conception fan are unlike radial fan systems and have resulted in (1) relatively straight incised channels, (2) no distinct distributary system with evidence of channel braiding or avulsion, and (3) no suprafan bulge despite high sand supply. Morphology of the Cojo canyon-fan system suggests gradients were lower during deposition than presently observed on the fan.

  15. Turbulent dispersion via fan-generated flows.

    PubMed

    Halloran, Siobhan K; Wexler, Anthony S; Ristenpart, William D

    2014-05-01

    Turbulent dispersion of passive scalar quantities has been extensively studied in wind tunnel settings, where the flow is carefully conditioned using flow straighteners and grids. Much less is known about turbulent dispersion in the "unconditioned" flows generated by fans that are ubiquitous in indoor environments, despite the importance of these flows to pathogen and contaminant transport. Here, we demonstrate that a point source of scalars released into an airflow generated by an axial fan yields a plume whose width is invariant with respect to the fan speed. The results point toward a useful simplification in modeling of disease and pollution spread via fan-generated flows.

  16. Noise suppression by flexible fan silencers

    SciTech Connect

    Partyka, J.; Kelly, T.R.J.

    1995-12-31

    This paper presents the results on noise testing of a fan only, as well as the results of a steel silencer and of flexible silencers that were connected directly to a fan. On-site facilities and free-field method set by the British Standards Institution were used to measure and then compare the fan only and different practical silencer configuration setups. In order to determine the fan-silencer combination that would give the maximum noise attenuation, total noise intensity, noise contributed to by the fan motor only, as well as aerodynamical noise created through air interacting with the fan parts were considered to obtain decibel readings for the octave bands. Subsequently, the optimal configuration found was the setup with flexible silencers on the fan inlet and the fan outlet. If only one silencer is used, it should be installed on the fan inlet. The aerodynamic noise affects the low frequencies. The flow noise is then overtaken at 1 kHz by the mechanical noise.

  17. Turbulent dispersion via fan-generated flows

    PubMed Central

    Halloran, Siobhan K.; Wexler, Anthony S.; Ristenpart, William D.

    2014-01-01

    Turbulent dispersion of passive scalar quantities has been extensively studied in wind tunnel settings, where the flow is carefully conditioned using flow straighteners and grids. Much less is known about turbulent dispersion in the “unconditioned” flows generated by fans that are ubiquitous in indoor environments, despite the importance of these flows to pathogen and contaminant transport. Here, we demonstrate that a point source of scalars released into an airflow generated by an axial fan yields a plume whose width is invariant with respect to the fan speed. The results point toward a useful simplification in modeling of disease and pollution spread via fan-generated flows. PMID:24932096

  18. Enhanced Fan Noise Modeling for Turbofan Engines

    NASA Technical Reports Server (NTRS)

    Krejsa, Eugene A.; Stone, James R.

    2014-01-01

    This report describes work by consultants to Diversitech Inc. for the NASA Glenn Research Center (GRC) to revise the fan noise prediction procedure based on fan noise data obtained in the 9- by 15 Foot Low-Speed Wind Tunnel at GRC. The purpose of this task is to begin development of an enhanced, analytical, more physics-based, fan noise prediction method applicable to commercial turbofan propulsion systems. The method is to be suitable for programming into a computational model for eventual incorporation into NASA's current aircraft system noise prediction computer codes. The scope of this task is in alignment with the mission of the Propulsion 21 research effort conducted by the coalition of NASA, state government, industry, and academia to develop aeropropulsion technologies. A model for fan noise prediction was developed based on measured noise levels for the R4 rotor with several outlet guide vane variations and three fan exhaust areas. The model predicts the complete fan noise spectrum, including broadband noise, tones, and for supersonic tip speeds, combination tones. Both spectra and directivity are predicted. Good agreement with data was achieved for all fan geometries. Comparisons with data from a second fan, the ADP fan, also showed good agreement.

  19. The lift-fan aircraft: Lessons learned

    NASA Technical Reports Server (NTRS)

    Deckert, Wallace H.

    1995-01-01

    This report summarizes the highlights and results of a workshop held at NASA Ames Research Center in October 1992. The objective of the workshop was a thorough review of the lessons learned from past research on lift fans, and lift-fan aircraft, models, designs, and components. The scope included conceptual design studies, wind tunnel investigations, propulsion systems components, piloted simulation, flight of aircraft such as the SV-5A and SV-5B and a recent lift-fan aircraft development project. The report includes a brief summary of five technical presentations that addressed the subject The Lift-Fan Aircraft: Lessons Learned.

  20. Flow visualization around axial flow fan blades

    NASA Astrophysics Data System (ADS)

    Kawaguchi, K.; Matsui, K.

    1986-02-01

    The flow around the blades of an axial flow fan was visualized by using a drum camera. The distribution of the flow velocity about the blades was determined by combining the spark tracing method with the smoke wire method, making it possible to determine the blade element efficiency. The efficiencies and noise levels of radiator cooling fans can be determined using this technique. The method was applied to two types of fans with different performances, and the flow around the wing was correlated with the wing tip efficiency. The effect of tip vortex on the total fan noise was quantified.

  1. Prototype Morphing Fan Nozzle Demonstrated

    NASA Technical Reports Server (NTRS)

    Lee, Ho-Jun; Song, Gang-Bing

    2004-01-01

    Ongoing research in NASA Glenn Research Center's Structural Mechanics and Dynamics Branch to develop smart materials technologies for aeropropulsion structural components has resulted in the design of the prototype morphing fan nozzle shown in the photograph. This prototype exploits the potential of smart materials to significantly improve the performance of existing aircraft engines by introducing new inherent capabilities for shape control, vibration damping, noise reduction, health monitoring, and flow manipulation. The novel design employs two different smart materials, a shape-memory alloy and magnetorheological fluids, to reduce the nozzle area by up to 30 percent. The prototype of the variable-area fan nozzle implements an overlapping spring leaf assembly to simplify the initial design and to provide ease of structural control. A single bundle of shape memory alloy wire actuators is used to reduce the nozzle geometry. The nozzle is subsequently held in the reduced-area configuration by using magnetorheological fluid brakes. This prototype uses the inherent advantages of shape memory alloys in providing large induced strains and of magnetorheological fluids in generating large resistive forces. In addition, the spring leaf design also functions as a return spring, once the magnetorheological fluid brakes are released, to help force the shape memory alloy wires to return to their original position. A computerized real-time control system uses the derivative-gain and proportional-gain algorithms to operate the system. This design represents a novel approach to the active control of high-bypass-ratio turbofan engines. Researchers have estimated that such engines will reduce thrust specific fuel consumption by 9 percent over that of fixed-geometry fan nozzles. This research was conducted under a cooperative agreement (NCC3-839) at the University of Akron.

  2. Avalanche sedimentation in seas and oceans, paper 4: sedimentogenesis stages at the second global level (preparation, transport, and accumulation). Models of submarine alluvial cones

    SciTech Connect

    Lisitsyn, A.P.

    1986-07-01

    This paper demonstrates that, in the terminal discharge basins, the ordinary sedimentogenesis stages are combined with gravity effects. The models of submerged alluvial cones--fans--are considered, which are constructed on the basis of studies of recent and ancient fans of different sizes. An important feature of the sedimentary process in this case is the relationship between the influx of the bulk of sedimentary matter and the repeated variations of the ocean level in the past (up to 8-12 times within the Quaternary alone), leading to massive discharges of sedimentary matter from upper (recent, short-lived) levels of avalanche sedimentation (in river mouths) to a lower level (to sites of constant storage of the material at the base of the continental slope).

  3. Containment of composite fan blades

    NASA Technical Reports Server (NTRS)

    Stotler, C. L.; Coppa, A. P.

    1979-01-01

    A lightweight containment was developed for turbofan engine fan blades. Subscale ballistic-type tests were first run on a number of concepts. The most promising configuration was selected and further evaluated by larger scale tests in a rotating test rig. Weight savings made possible by the use of this new containment system were determined and extrapolated to a CF6-size engine. An analytical technique was also developed to predict the released blades motion when involved in the blade/casing interaction process. Initial checkout of this procedure was accomplished using several of the tests run during the program.

  4. Offset truss hex solar concentrator

    NASA Technical Reports Server (NTRS)

    White, John E. (Inventor); Sturgis, James D. (Inventor); Erikson, Raymond J. (Inventor); Waligroski, Gregg A. (Inventor); Scott, Michael A. (Inventor)

    1991-01-01

    A solar energy concentrator system comprises an offset reflector structure made up of a plurality of solar energy reflector panel sections interconnected with one another to form a piecewise approximation of a portion of a (parabolic) surface of revolution rotated about a prescribed focal axis. Each panel section is comprised of a plurality of reflector facets whose reflective surfaces effectively focus reflected light to preselected surface portions of the interior sidewall of a cylindrically shaped solar energy receiver. The longitudinal axis of the receiver is tilted at an acute angle with respect to the optical axis such that the distribution of focussed solar energy over the interior surface of the solar engine is optimized for dynamic solar energy conversion. Each reflector panel section comprises a flat, hexagonally shaped truss support framework and a plurality of beam members interconnecting diametrically opposed corners of the hexagonal framework recessed within which a plurality of (spherically) contoured reflector facets is disposed. The depth of the framework and the beam members is greater than the thickness of a reflector facet such that a reflector facet may be tilted (for controlling the effective focus of its reflected light through the receiver aperture) without protruding from the panel section.

  5. Adjustments of Alluvial Rivers to Flood Flows

    NASA Astrophysics Data System (ADS)

    Pitlick, J.; Marr, J.; Pizzuto, J.

    2002-12-01

    Alluvial river channels appear to be formed and maintained by discharges that occur relatively often; in the typical case bankfull flows occur roughly once every 2 or 3 years, and a rough equilibrium is maintained between sediment transport and channel form. This observation is somewhat at odds with contemporary theories for self-formed channels. In theory the equilibrium bankfull width and depth are set by flows that produce sufficient shear stress to move the sediment on the bed, but otherwise are not competent to erode the banks. However, it follows that flows above bankfull should exceed this threshold, causing the channel to widen. If so, successively larger flows would be required to reach the bankfull level and channels would be sized to the largest flood of recent record. This is clearly not the case in nature. To reconcile theory and observation we have initiated an experimental study of the response of self-formed channels to floods. The experiments are run in a 16-meter straight channel with an erodible bank adjacent to a floodplain. In typical runs the channel is first allowed to equilibrate with a steady discharge and sediment feed, and then it is subjected to a flood of approximately two times the bankfull flow. The channel widens rapidly in response to the higher shear stresses produced by overbank flows. As time goes on the rate of widening decreases and the channel equilibrates to the new discharge. Eventually, most of the flow is contained within the banks, and the centerline shear stress has returned to the initial bankfull value; the bankfull width is thus limited only by the discharge we specify. These experiments suggest that without a mechanism to control bank erosion (e.g. vegetation) alluvial channels will widen indefinitely in response to floods. Alternatively, our experiments are not simulating the effects of channel curvature, which would allow for deposition and provide a mechanism to recover the space lost by erosion, such that the

  6. 45 CFR 1177.8 - Administrative offset.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... administrative offset, the National Endowment for the Humanities will send the debtor written notice of the... determination of indebtedness; and to enter into a written agreement to repay the debt and; (3) The applicable interest. (d) The National Endowment for the Humanities may effect an administrative offset against...

  7. 48 CFR 225.7306 - Offset arrangements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Offset arrangements. 225.7306 Section 225.7306 Federal Acquisition Regulations System DEFENSE ACQUISITION REGULATIONS SYSTEM....7306 Offset arrangements. In accordance with the Presidential policy statement of April 16, 1990,...

  8. 7 CFR 1951.102 - Administrative offset.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... administrative offset will be taken in accordance with 7 CFR part 3, subpart B and § 1951.106. (b) Definitions... under the purview of 7 CFR part 11. (12) Offsetting agency means an agency that withholds from its... CFR 3.29. FSA District Directors or other State Executive Director designees are designated to...

  9. 45 CFR 608.3 - Administrative offset.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 4 CFR 102.3(a). Before employing administrative offset, NSF will comply with the notice, hearing, review, or other procedural requirements of 31 U.S.C. 3716(a) and 4 CFR 102.3(b) and (c). Furthermore... certification required by 4 CFR 102.3(f) and offset would not be contrary to law. Before imposing...

  10. 45 CFR 608.3 - Administrative offset.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 4 CFR 102.3(a). Before employing administrative offset, NSF will comply with the notice, hearing, review, or other procedural requirements of 31 U.S.C. 3716(a) and 4 CFR 102.3(b) and (c). Furthermore... certification required by 4 CFR 102.3(f) and offset would not be contrary to law. Before imposing...

  11. 5 CFR 179.307 - Administrative offset.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 179.307 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS CLAIMS... administrative offset regulations, and the applicable provisions of 4 CFR part 102 with respect to providing the... administrative offset regulations and with the applicable provisions of 4 CFR part 102, including providing...

  12. 7 CFR 1951.111 - Salary offset.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... waiving the debt, the debtor requests waiver of the debt, and the waiver determination turns on an issue...; for example, when the validity of the debt turns on an issue of credibility or truth. (iii) The....111 Salary offset. Salary offset may be used to collect debts arising from delinquent USDA...

  13. 7 CFR 1951.111 - Salary offset.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... waiving the debt, the debtor requests waiver of the debt, and the waiver determination turns on an issue...; for example, when the validity of the debt turns on an issue of credibility or truth. (iii) The....111 Salary offset. Salary offset may be used to collect debts arising from delinquent USDA...

  14. Empirical assessment of theory for bankfull characteristics of alluvial channels

    NASA Astrophysics Data System (ADS)

    Trampush, S. M.; Huzurbazar, S.; McElroy, B.

    2014-12-01

    We compiled a data set of 541 bankfull measurements of alluvial rivers (see supporting information) and used Bayesian linear regression to examine empirical and theoretical support for the hypothesis that alluvial channels adjust to a predictable condition of basal shear stress as a function of sediment transport mode. An empirical closure based on channel slope, bankfull channel depth, and median grain size is proposed and results in the scaling of bankfull Shields stress with the inverse square root of particle Reynolds number. The empirical relationship is sufficient for purposes of quantifying paleohydraulic conditions in ancient alluvial channels. However, it is not currently appropriate for application to alluvial channels on extraterrestrial bodies because it depends on constant-valued, Earth-based coefficients.

  15. Microbial communities of alluvial soils in the Volga River delta

    NASA Astrophysics Data System (ADS)

    Sal'Nikova, N. A.; Polyanskaya, L. M.; Tyugai, Z. N.; Sal'Nikov, A. N.; Egorov, M. A.

    2009-01-01

    The number and biomass of the microbial community in the upper humus horizon (0-20 cm) were determined in the main types of alluvial soils (mucky gley, desertified soddy calcareous, hydrometamorphic dark-humus soils) in the Volga River delta. Fungal mycelium and alga cells predominate in the biomass of the microorganisms (35-50% and 30-47%, respectively). The proportion of prokaryotes in the microbial biomass of the alluvial soils amounts to 2-6%. No significant seasonal dynamics in the number and biomass of microorganisms were revealed in the alluvial soils. The share of carbon of the microbial biomass in the total carbon content of the soil organic matter is 1.4-2.3% in the spring. High coefficients of microbial mineralization and oligotrophy characterize the processes of organic matter decomposition in the alluvial soils of the mucky gley, desertified soddy calcareous, and hydrometamorphic dark humus soil types.

  16. Contribution of alluvial groundwater to the outflow of mountainous catchments

    NASA Astrophysics Data System (ADS)

    Käser, Daniel; Hunkeler, Daniel

    2016-02-01

    Alluvial aquifers in mountainous regions cover typically a limited area. Their contribution to catchment storage and outflow is rarely isolated; alluvial groundwater discharge under gauging stations is generally assumed negligible; and hydrological models tend to lump alluvial storage with other units. The role of alluvial aquifers remains therefore unclear: can they contribute significantly to outflow when they cover a few percent of catchment area? Should they be considered a dynamic storage unit or merely a transmission zone? We address these issues based on the continuous monitoring of groundwater discharge, river discharge (one year), and aquifer storage (6 months) in the 6 km2 alluvial system of a 194 km2 catchment. River and groundwater outflow were measured jointly through "coupled gauging stations." The contribution of alluvial groundwater to outflow was highest at the outlet of a subcatchment (52 km2), where subsurface discharge amounted to 15% of mean annual outflow, and 85% of outflow during the last week of a drought. In this period, alluvial-aquifer depletion supported 75% of the subcatchment outflow and 35% of catchment outflow—thus 3% of the entire catchment supported a third of the outflow. Storage fluctuations occurred predominantly in the aquifer's upstream part, where heads varied over 6 m. Not only does this section act as a significant water source, but storage recovers also rapidly at the onset of precipitation. Storage dynamics were best conceptualized along the valley axis, rather than across the more conventional riparian-channel transect. Overall the contribution of alluvial aquifers to catchment outflow deserves more attention.

  17. 1. SCAFFOLD, LEPLEY VENTILATOR, AND AEROVANE FAN (LEFT TO RIGHT) ...

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

    1. SCAFFOLD, LEPLEY VENTILATOR, AND AEROVANE FAN (LEFT TO RIGHT) FROM EAST. AEROVANE FAN HOOD AT REAR OF AEROVANE FAN. - Consolidation Coal Company Mine No. 11, East side of State Route 936, Midlothian, Allegany County, MD

  18. Effects of alluvial knickpoint migration on floodplain ecology and geomorphology

    NASA Astrophysics Data System (ADS)

    Larsen, Annegret; May, Jan-Hendrick

    2016-04-01

    Alluvial knickpoints are well described as erosional mechanism within discontinuous ephemeral streams in the semi-arid SW USA. However, alluvial knickpoints occur globally in a wide range of settings and of climate zones, including temperate SE Australia, subtropical Africa, and tropical Australia. Much attention has been given in the scientific literature to the trigger mechanisms of alluvial knickpoints, which can be summarized as: i) threshold phenomena, ii) climate variability and iii) land-use change, or to a combination of these factors. Recently, studies have focused on the timescale of alluvial knickpoint retreat, and the processes, mechanisms and feedbacks with ecology, geomorphology and hydrology. In this study, we compile data from a global literature review with a case study on a tropical river system in Australia affected by re-occurring, fast migrating (140 myr-1) alluvial knickpoint. We highlight the importance of potential water table declines due to channel incision following knickpoint migration, which in turn leads to the destabilization of river banks, and a shift in floodplain vegetation and fire incursion. We hypothesize that the observed feedbacks might also help to understand the broader impacts of alluvial knickpoint migration in other regions, and might explain the drastic effects of knickpoint migration on land cover and land-use in semi-arid areas.

  19. Active control of automotive fan noise

    NASA Astrophysics Data System (ADS)

    Gerard, Anthony; Berry, Alain; Masson, Patrice

    2002-11-01

    Active control for globally reducing the noise radiated by automotive axial engine cooling fans is investigated. First, an aeroacoutic model of the fan is combined with acoustic directivity measurements to derive a distribution of equivalent dipole sources on the fan surface. The results reveal that the fan behaves like a distributed dipole at blade passage tones when the upstream flow through the fan is spatially nonuniform. Numerical simulations of active noise control in the free field have been carried out using the previous aeroacoustic model of the fan and a dipole secondary source in front of the fan. The numerical results show that a single dipole control source is effective in globally controlling the sound radiation of the fan at the blade passage frequency and its first harmonic. Last, an experimental investigation of active control is presented. It consists of a SISO feedforward configuration with either a LMS algorithm (for FIR filters) or a back-retropopagation algorithm (for neural networks) using the Simulink/Dspace environment for real-time implementation.

  20. The Right to Be a Fan

    ERIC Educational Resources Information Center

    Gutierrez, Peter

    2011-01-01

    Reading experts have consistently cited the importance of independent reading, reading for pleasure, and fostering "a love of reading." Unfortunately, fanning the fire of fan readership is not so easy in the service of our clear-cut and standards-aligned curricula, except perhaps in small, carefully channeled doses. Moreover, the impetus for such…

  1. Fiber composite fan blade impact improvement program

    NASA Technical Reports Server (NTRS)

    Oller, T. L.

    1976-01-01

    The results of a 20-month program, designed to investigate parameters which effect the foreign object damage resulting from ingestion of birds into fan blades are described. Work performed on this program included the design, fabrication, and impact testing of QCSEE fan blades to demonstrate improvement in resistance relative to existing blades and also the design and demonstration of a pin root attachment concept.

  2. Early Holocene catastrophic mass-wasting event and fan-delta development on the Hua-tung coast, eastern Taiwan

    NASA Astrophysics Data System (ADS)

    Hsieh, Meng-Long; Liew, Ping-Mei; Chen, Hua-Wen

    2011-11-01

    Landslides and debris flows rarely occurred during historical times in the tectonically active Coastal Range of eastern Taiwan. This topographic stability, however, contrasts greatly with the widespread existence of terraced alluvial fans and fan-deltas on the Hua-tung coast which fringes the range. This study focuses on the two largest fan-terrace systems on the Hua-tung coast, both of which consist of alluvial fans (plane-view areas up to 8 km 2) larger than their contributing catchments. Stratigraphic data show that both systems were in sandy, wave-dominated settings during de-glacial times. The systems were then disturbed by a catastrophic landslide/debris-flow event (or events), which brought enormous amounts of gravel (Facies Gm) into the systems, deforming previously-deposited marine sands (Facies Sm) and shallowing the seafloor. The combined Gm/Sm complex yields multiple radiocarbon dates ranging from 11.3 to 8.3 ka cal BP, with a cluster around 8.6 ka cal BP. This mass-wasting event has been unique since the emergence of its contributing catchment 0.2-0.3 Ma ago. The low frequency of such an event could reflect the great resistance of rock mass in the source areas to weathering and erosion. The common blockage of valley floors by giant-boulder piles, which limits channel incision and sediment transport, could also increase the apparent stability of the mountain. The trigger of landslides in the Coastal Range has been linked to large earthquakes. Additionally, we propose that the great magnitude and duration of the observed early Holocene event were caused by the contemporaneous prolonged rainfall (and/or high frequency of typhoons) associated with the East Asian summer monsoon maximum.

  3. Supersonic through-flow fan assessment

    NASA Technical Reports Server (NTRS)

    Kepler, C. E.; Champagne, G. A.

    1988-01-01

    A study was conducted to assess the performance potential of a supersonic through-flow fan engine for supersonic cruise aircraft. It included a mean-line analysis of fans designed to operate with in-flow velocities ranging from subsonic to high supersonic speeds. The fan performance generated was used to estimate the performance of supersonic fan engines designed for four applications: a Mach 2.3 supersonic transport, a Mach 2.5 fighter, a Mach 3.5 cruise missile, and a Mach 5.0 cruise vehicle. For each application an engine was conceptualized, fan performance and engine performance calculated, weight estimates made, engine installed in a hypothetical vehicle, and mission analysis was conducted.

  4. Advanced Noise Control Fan Aerodynamic Performance

    NASA Technical Reports Server (NTRS)

    Bozak, Richard F., Jr.

    2009-01-01

    The Advanced Noise Control Fan at the NASA Glenn Research Center is used to experimentally analyze fan generated acoustics. In order to determine how a proposed noise reduction concept affects fan performance, flow measurements can be used to compute mass flow. Since tedious flow mapping is required to obtain an accurate mass flow, an equation was developed to correlate the mass flow to inlet lip wall static pressure measurements. Once this correlation is obtained, the mass flow for future configurations can be obtained from the nonintrusive wall static pressures. Once the mass flow is known, the thrust and fan performance can be evaluated. This correlation enables fan acoustics and performance to be obtained simultaneously without disturbing the flow.

  5. Blade Vibration Measurement System for Unducted Fans

    NASA Technical Reports Server (NTRS)

    Marscher, William

    2014-01-01

    With propulsion research programs focused on new levels of efficiency and noise reduction, two avenues for advanced gas turbine technology are emerging: the geared turbofan and ultrahigh bypass ratio fan engines. Both of these candidates are being pursued as collaborative research projects between NASA and the engine manufacturers. The high bypass concept from GE Aviation is an unducted fan that features a bypass ratio of over 30 along with the accompanying benefits in fuel efficiency. This project improved the test and measurement capabilities of the unducted fan blade dynamic response. In the course of this project, Mechanical Solutions, Inc. (MSI) collaborated with GE Aviation to (1) define the requirements for fan blade measurements; (2) leverage MSI's radar-based system for compressor and turbine blade monitoring; and (3) develop, validate, and deliver a noncontacting blade vibration measurement system for unducted fans.

  6. Fan-fold shielded electrical leads

    DOEpatents

    Rohatgi, Rajeev R.; Cowan, Thomas E.

    1996-01-01

    Fan-folded electrical leads made from copper cladded Kapton, for example, with the copper cladding on one side serving as a ground plane and the copper cladding on the other side being etched to form the leads. The Kapton is fan folded with the leads located at the bottom of the fan-folds. Electrical connections are made by partially opening the folds of the fan and soldering, for example, the connections directly to the ground plane and/or the lead. The fan folded arrangement produces a number of advantages, such as electrically shielding the leads from the environment, is totally non-magnetic, and has a very low thermal conductivity, while being easy to fabricate.

  7. Fan-fold shielded electrical leads

    DOEpatents

    Rohatgi, R.R.; Cowan, T.E.

    1996-06-11

    Disclosed are fan-folded electrical leads made from copper cladded Kapton, for example, with the copper cladding on one side serving as a ground plane and the copper cladding on the other side being etched to form the leads. The Kapton is fan folded with the leads located at the bottom of the fan-folds. Electrical connections are made by partially opening the folds of the fan and soldering, for example, the connections directly to the ground plane and/or the lead. The fan folded arrangement produces a number of advantages, such as electrically shielding the leads from the environment, is totally non-magnetic, and has a very low thermal conductivity, while being easy to fabricate. 3 figs.

  8. Advanced Prop-fan Engine Technology (APET) single- and counter-rotation gearbox/pitch change mechanism

    NASA Technical Reports Server (NTRS)

    Reynolds, C. N.

    1985-01-01

    The preliminary design of advanced technology (1992) prop-fan engines for single-rotation prop-fans, the conceptual design of the entire propulsion system, and an aircraft evaluation of the resultant designs are discussed. Four engine configurations were examined. A two-spool engine with all axial compressors and a three-spool engine with axial/centrifugal compressors were selected. Integrated propulsion systems were designed in conjunction with airframe manufacturers. The design efforts resulted in 12,000 shaft horsepower engines installed in over the installations with in-line and offset gearboxes. The prop-fan powered aircraft used 21 percent less fuel and cost 10 percent less to operate than a similar aircraft powered by turbofan engines with comparable technology.

  9. 41 CFR 105-56.029 - Offset amount.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false Offset amount. 105-56... Offset (CSO) Procedures-GSA as Paying Agency § 105-56.029 Offset amount. (a) The minimum dollar amount of salary offset under this subpart is $100. (b) The amount offset from a salary payment under this...

  10. 41 CFR 105-56.029 - Offset amount.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Offset amount. 105-56... Offset (CSO) Procedures-GSA as Paying Agency § 105-56.029 Offset amount. (a) The minimum dollar amount of salary offset under this subpart is $100. (b) The amount offset from a salary payment under this...

  11. 41 CFR 105-56.019 - Offset amount.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 41 Public Contracts and Property Management 3 2010-07-01 2010-07-01 false Offset amount. 105-56... Offset (CSO) Procedures-GSA as Creditor Agency § 105-56.019 Offset amount. (a) The minimum dollar amount referred for offset under this subpart is $100. (b) The amount offset from a salary payment under...

  12. 41 CFR 105-56.019 - Offset amount.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 41 Public Contracts and Property Management 3 2011-01-01 2011-01-01 false Offset amount. 105-56... Offset (CSO) Procedures-GSA as Creditor Agency § 105-56.019 Offset amount. (a) The minimum dollar amount referred for offset under this subpart is $100. (b) The amount offset from a salary payment under...

  13. Turbine blade tip with offset squealer

    DOEpatents

    Bunker, Ronald Scott

    2001-01-01

    An industrial turbine assembly comprises a plurality of rotating blade portions in a spaced relation with a stationary shroud. The rotating blade includes a root section, an airfoil having a pressure sidewall and a suction sidewall defining an outer periphery and a tip portion having a tip cap. An offset squealer is disposed on the tip cap. The offset squealer is positioned inward from the outer periphery of the rotating blade. The offset squealer increases the flow resistance and reduces the flow of hot gas flow leakage for a given pressure differential across the blade tip portion so as to improve overall turbine efficiency.

  14. Fan beam generated by a linear-array fed parabolic reflector

    NASA Technical Reports Server (NTRS)

    Huang, John; Rahmat-Samii, Yahya

    1990-01-01

    The theoretical background and the results of computer simulations and experimental studies for a parabolic reflector fed by a linear array are detailed. The concept of using a parabolic reflector antenna fed by a small linear array to generate fan-beam patterns is validated. Large angle scan along the broad-beam direction of the fan beam can be achieved by offsetting the linear array laterally. It is both empirically and numerically demonstrated that the array feed must be displaced in the reflector's axial direction to an optimum location from the focal plane in order to achieve the best antenna gain performance. As a result, the linear-array-fed parabolic reflector can be used in place of a long planar array in a multifunctional reflector antenna system.

  15. The provenance of Borneo's enigmatic alluvial diamonds

    NASA Astrophysics Data System (ADS)

    White, Lloyd; Graham, Ian; Tanner, Dominique; Hall, Robert; Armstrong, Richard; Yaxley, Greg; Barron, Larry; Spencer, Lee; van Leeuwen, Theo

    2016-04-01

    Gem-quality diamonds occur in several alluvial deposits across central and southern Borneo. Borneo has been a known source of diamonds for centuries, but the location of their primary igneous source remains enigmatic. Numerous geological models have been proposed to explain the distribution of Borneo's diamonds. To assess these models, we used a variety of techniques to examine heavy minerals from Kalimantan's Cempaka paleoalluvial diamond deposit. This involved collecting U-Pb isotopic data, fission track and trace element geochemistry of zircon as well as major element geochemical data of spinels and morphological descriptions of zircon and diamond. Our results indicate that the Cempaka diamonds were likely derived from at least two sources, one which was relatively local and/or involved little reworking, and the other more distal recording several periods of reworking. The distal diamond source is interpreted to be diamond-bearing pipes that intruded the basement of a block that: (1) rifted from northwest Australia (East Java or SW Borneo) and the diamonds were recycled into its sedimentary cover, or: (2) were emplaced elsewhere (e.g. NW Australia) and transported to a block (e.g. East Java or SW Borneo). Both of these scenarios require the diamonds to be transported with the block when it rifted from NW Australia in the Late Jurassic. The 'local' diamonds could be associated with ophiolitic rocks that are exposed in the nearby Meratus Mountains, or could be diamondiferous diatremes associated with eroded Miocene high-K alkaline intrusions north of the Barito Basin. If this were the case, these intrusions would indicate that the lithosphere beneath SW Borneo is thick (~150 km or greater).

  16. TBCC Fan Stage Operability and Performance

    NASA Technical Reports Server (NTRS)

    Suder, Kenneth L.

    2007-01-01

    NASA s Fundamental Aeronautics Program is investigating turbine-based propulsion systems for access to space because it provides the potential for aircraft-like, space-launch operations that may significantly reduce launch costs and improve safety. Studies performed under NASA s NGLT and the NASP High Speed Propulsion Assessment (HiSPA) program indicated a variable cycle turbofan/ramjet was the best configuration to satisfy access-to-space mission requirements because this configuration maximizes the engine thrust-to-weight ratio while minimizing frontal area. To this end, NASA and GE teamed to design a Mach 4 variable cycle turbofan/ramjet engine for access to space. To enable the wide operating range of a Mach 4+ variable cycle turbofan ramjet required the development of a unique fan stage design capable of multi-point operation to accommodate variations in bypass ratio (10X), fan speed (7X), inlet mass flow (3.5X), inlet pressure (8X), and inlet temperature (3X). The primary goal of the fan stage was to provide a high pressure ratio level with good efficiency at takeoff through the mid range of engine operation, while avoiding stall and losses at the higher flight Mach numbers, without the use of variable inlet guide vanes. Overall fan performance and operability therefore requires major consideration, as competing goals at different operating points and aeromechanical issues become major drivers in the design. To mitigate risk of meeting the unique design requirements for the fan stage, NASA and GE teamed to design and build a 57% engine scaled fan stage to be tested in NASA s transonic compressor facility. The objectives of this test are to assess the aerodynamic and aero mechanic performance and operability characteristics of the fan stage over the entire range of engine operation including: 1) sea level static take-off, 2) transition over large swings in fan bypass ratio, 3) transition from turbofan to ramjet, and 4) fan windmilling operation at high Mach

  17. Turbofan gas turbine engine with variable fan outlet guide vanes

    NASA Technical Reports Server (NTRS)

    Wood, Peter John (Inventor); Zenon, Ruby Lasandra (Inventor); LaChapelle, Donald George (Inventor); Mielke, Mark Joseph (Inventor); Grant, Carl (Inventor)

    2010-01-01

    A turbofan gas turbine engine includes a forward fan section with a row of fan rotor blades, a core engine, and a fan bypass duct downstream of the forward fan section and radially outwardly of the core engine. The forward fan section has only a single stage of variable fan guide vanes which are variable fan outlet guide vanes downstream of the forward fan rotor blades. An exemplary embodiment of the engine includes an afterburner downstream of the fan bypass duct between the core engine and an exhaust nozzle. The variable fan outlet guide vanes are operable to pivot from a nominal OGV position at take-off to an open OGV position at a high flight Mach Number which may be in a range of between about 2.5-4+. Struts extend radially across a radially inwardly curved portion of a flowpath of the engine between the forward fan section and the core engine.

  18. Chemical and Physical Weathering in a Hot-arid, Tectonically Active Alluvial System (Anza-Borrego Desert, CA)

    NASA Astrophysics Data System (ADS)

    Joo, Y. J.; Elwood Madden, M.; Soreghan, G. S.

    2014-12-01

    Climate and tectonics are primary controls on bedrock erosion, and sediment production, transport, and deposition. Additionally, silicate weathering in tectonically active regions is known to play a significant role in global climate owing to the high rates of physical erosion and exposure of unweathered bedrock to chemical weathering, which removes CO2 from the atmosphere. Therefore, the feedback between weathering and climate is key to understanding climate change through Earth history. This study investigates chemical and physical weathering of alluvial sediments in the Anza-Borrego Desert, California, located in the southern part of the San Andreas Fault System. This setting provides an ideal opportunity to study weathering in a hot and arid climate with mean annual temperatures of ~23 °C and mean annual precipitation of ~160 mm in the basin. Samples were collected along a proximal-to-distal transect of an alluvial-fan system sourced exclusively from Cretaceous tonalite of the Peninsular Range. The single bedrock lithology enables exploration of the effects of other variables — climate, transport distance, drainage area, and tectonics— on the physical and chemical properties of the sediments. Although minimal overall (CIA = 56-61), the degree of chemical weathering increases down transect, dominated by plagioclase dissolution. BET surface area of the mud (<63µm) fraction decreases distally, which is consistent with coarsening grain-size. Chemical alteration and BET surface area both increase in a distal region, within the active Elsinore Fault zone. Extensive fracturing here, together with a more-humid Pleistocene climate likely facilitated in-situ bedrock weathering; specifically, dissolution of primary minerals (e.g. plagioclase), preceding the arid alluvial erosion, transport, and deposition in the Holocene. This study further seeks to disentangle the complex record of the climate and tectonic signals imprinted in these sediments.

  19. Great apes and biodiversity offset projects in Africa: the case for national offset strategies.

    PubMed

    Kormos, Rebecca; Kormos, Cyril F; Humle, Tatyana; Lanjouw, Annette; Rainer, Helga; Victurine, Ray; Mittermeier, Russell A; Diallo, Mamadou S; Rylands, Anthony B; Williamson, Elizabeth A

    2014-01-01

    The development and private sectors are increasingly considering "biodiversity offsets" as a strategy to compensate for their negative impacts on biodiversity, including impacts on great apes and their habitats in Africa. In the absence of national offset policies in sub-Saharan Africa, offset design and implementation are guided by company internal standards, lending bank standards or international best practice principles. We examine four projects in Africa that are seeking to compensate for their negative impacts on great ape populations. Our assessment of these projects reveals that not all apply or implement best practices, and that there is little standardization in the methods used to measure losses and gains in species numbers. Even if they were to follow currently accepted best-practice principles, we find that these actions may still fail to contribute to conservation objectives over the long term. We advocate for an alternative approach in which biodiversity offset and compensation projects are designed and implemented as part of a National Offset Strategy that (1) takes into account the cumulative impacts of development in individual countries, (2) identifies priority offset sites, (3) promotes aggregated offsets, and (4) integrates biodiversity offset and compensation projects with national biodiversity conservation objectives. We also propose supplementary principles necessary for biodiversity offsets to contribute to great ape conservation in Africa. Caution should still be exercised, however, with regard to offsets until further field-based evidence of their effectiveness is available.

  20. Frequency-offset separated oscillatory fields

    NASA Astrophysics Data System (ADS)

    Vutha, A. C.; Hessels, E. A.

    2015-11-01

    A frequency-offset separated-oscillatory-field technique is presented. The technique is a modification of the Ramsey method of separated oscillatory fields [Phys. Rev. 76, 996 (1949), 10.1103/PhysRev.76.996], in which the frequencies of the two separated oscillatory fields are slightly offset from each other, so that the relative phase of the two fields varies continuously with time. With this technique, the detection signal oscillates in time at the offset frequency, and the resonance frequency is obtained by using a simple straight-line fit of the phase of this signal. The technique has the advantages of being insensitive to the frequency response of the experimental system, of being sensitive only to noise at the offset frequency, and of allowing systematic effects to be more cleanly resolved due to the simple lineshape.

  1. Influence of Lift Offset on Rotorcraft Performance

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne

    2008-01-01

    The influence of lift offset on the performance of several rotorcraft configurations is explored. A lift-offset rotor, or advancing blade concept, is a hingeless rotor that can attain good efficiency at high speed, by operating with more lift on the advancing side than on the retreating side of the rotor disk. The calculated performance capability of modern-technology coaxial rotors utilizing a lift offset is examined, including rotor performance optimized for hover and high-speed cruise. The ideal induced power loss of coaxial rotors in hover and twin rotors in forward flight is presented. The aerodynamic modeling requirements for performance calculations are evaluated, including wake and drag models for the high speed flight condition. The influence of configuration on the performance of rotorcraft with lift-offset rotors is explored, considering tandem and side-by-side rotorcraft as well as wing-rotor lift share.

  2. Influence of Lift Offset on Rotorcraft Performance

    NASA Technical Reports Server (NTRS)

    Johnson, Wayne

    2009-01-01

    The influence of lift offset on the performance of several rotorcraft configurations is explored. A lift-offset rotor, or advancing blade concept, is a hingeless rotor that can attain good efficiency at high speed by operating with more lift on the advancing side than on the retreating side of the rotor disk. The calculated performance capability of modern-technology coaxial rotors utilizing a lift offset is examined, including rotor performance optimized for hover and high-speed cruise. The ideal induced power loss of coaxial rotors in hover and twin rotors in forward flight is presented. The aerodynamic modeling requirements for performance calculations are evaluated, including wake and drag models for the high-speed flight condition. The influence of configuration on the performance of rotorcraft with lift-offset rotors is explored, considering tandem and side-by-side rotorcraft as well as wing-rotor lift share.

  3. Using major ions and δ15N-NO3(-) to identify nitrate sources and fate in an alluvial aquifer of the Baiyangdian lake watershed, North China Plain.

    PubMed

    Wang, Shiqin; Tang, Changyuan; Song, Xianfang; Yuan, Ruiqiang; Wang, Qinxue; Zhang, Yinghua

    2013-07-01

    In semi-arid regions, most human activities occur in alluvial fan areas; however, NO3(-) pollution has greatly threatened the shallow groundwater quality. In this paper, δ(15)N-NO3(-) and multi-tracers were used to identify the origin and fate of NO3(-) in groundwater of the Baiyangdian lake watershed, North China Plain. The investigation was conducted in two typical regions: one is the agricultural area located in the upstream of the watershed and another is the region influenced by urban wastewater in the downstream of the watershed. Results indicate that the high NO3(-) concentrations of the upstream shallow groundwater were sourced from fertilizer and manure or sewage leakage, whilst the mixture and denitrification caused the decrease in the NO3(-) concentration along the flow path of the groundwater. In the downstream, industrial and domestic effluent has a great impact on groundwater quality. The contaminated rivers contributed from 45% to 76% of the total recharge to the groundwater within a distance of 40 m from the river. The mixture fraction of the wastewater declined with the increasing distance away from the river. However, groundwater with NO3(-) concentrations larger than 20 mg l(-1) was only distributed in areas near to the polluted river or the sewage irrigation area. It is revealed that the frontier and depression regions of an alluvial fan in a lake watershed with abundant organics, silt and clay sediments have suitable conditions for denitrification in the downstream. PMID:23743546

  4. Dynamic response of Hovercraft lift fans

    NASA Astrophysics Data System (ADS)

    Moran, D. D.

    1981-08-01

    Hovercraft lift fans are subjected to varying back pressure due to wave action and craft motions when these vehicles are operating in a seaway. The oscillatory back pressure causes the fans to perform dynamically, exhibiting a hysteresis type of response and a corresponding degradation in mean performance. Since Hovercraft motions are influenced by variations in lift fan pressure and discharge, it is important to understand completely the nature of the dynamic performance of lift fans in order to completely solve the Hovercraft seakeeping problem. The present study was performed to determine and classify the instabilities encountered in a centrifugal fan operating against time-varying back pressure. A model-scale experiment was developed in which the fan discharge was directed into a flow-measuring device, terminating in a rotating valve which produced an oscillatory back pressure superimposed upon a mean aerodynamic resistance. Pressure and local velocity were measured as functions of time at several locations in the fan volute. The measurements permitted the identification of rotating (or propagating) stall in the impeller. One cell and two cell configurations were classified and the transient condition connecting these two configurations was observed. The mechanisms which lead to rotating stall in a centrifugal compressor are presented and discussed with specific reference to Hovercraft applications.

  5. UHB Engine Fan Broadband Noise Reduction Study

    NASA Technical Reports Server (NTRS)

    Gliebe, Philip R.; Ho, Patrick Y.; Mani, Ramani

    1995-01-01

    A study has been completed to quantify the contribution of fan broadband noise to advanced high bypass turbofan engine system noise levels. The result suggests that reducing fan broadband noise can produce 3 to 4 EPNdB in engine system noise reduction, once the fan tones are eliminated. Further, in conjunction with the elimination of fan tones and an increase in bypass ratio, a potential reduction of 7 to 10 EPNdB in system noise can be achieved. In addition, an initial assessment of engine broadband noise source mechanisms has been made, concluding that the dominant source of fan broadband noise is the interaction of incident inlet boundary layer turbulence with the fan rotor. This source has two contributors, i.e., unsteady life dipole response and steady loading quadrupole response. The quadrupole contribution was found to be the most important component, suggesting that broadband noise reduction can be achieved by the reduction of steady loading field-turbulence field quadrupole interaction. Finally, for a controlled experimental quantification and verification, the study recommends that further broadband noise tests be done on a simulated engine rig, such as the GE Aircraft Engine Universal Propulsion Simulator, rather than testing on an engine statically in an outdoor arena The rig should be capable of generating forward and aft propagating fan noise, and it needs to be tested in a large freejet or a wind tunnel.

  6. UHB engine fan broadband noise reduction study

    NASA Astrophysics Data System (ADS)

    Gliebe, Philip R.; Ho, Patrick Y.; Mani, Ramani

    1995-06-01

    A study has been completed to quantify the contribution of fan broadband noise to advanced high bypass turbofan engine system noise levels. The result suggests that reducing fan broadband noise can produce 3 to 4 EPNdB in engine system noise reduction, once the fan tones are eliminated. Further, in conjunction with the elimination of fan tones and an increase in bypass ratio, a potential reduction of 7 to 10 EPNdB in system noise can be achieved. In addition, an initial assessment of engine broadband noise source mechanisms has been made, concluding that the dominant source of fan broadband noise is the interaction of incident inlet boundary layer turbulence with the fan rotor. This source has two contributors, i.e., unsteady life dipole response and steady loading quadrupole response. The quadrupole contribution was found to be the most important component, suggesting that broadband noise reduction can be achieved by the reduction of steady loading field-turbulence field quadrupole interaction. Finally, for a controlled experimental quantification and verification, the study recommends that further broadband noise tests be done on a simulated engine rig, such as the GE Aircraft Engine Universal Propulsion Simulator, rather than testing on an engine statically in an outdoor arena The rig should be capable of generating forward and aft propagating fan noise, and it needs to be tested in a large freejet or a wind tunnel.

  7. 45 CFR 30.12 - Administrative offset.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ....S.C. 3716(c), and implementing regulation at 31 CFR 285.4; (iii) Debts arising under, or payments... such offsets under 5 U.S.C. 5514 and 31 U.S.C. 3716 (see 5 CFR part 550, subpart K; 31 CFR 285.7; and... centralized administrative offset pursuant to and in accordance with 31 CFR 901.3(b). Debts which are...

  8. 45 CFR 30.12 - Administrative offset.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ....S.C. 3716(c), and implementing regulation at 31 CFR 285.4; (iii) Debts arising under, or payments... such offsets under 5 U.S.C. 5514 and 31 U.S.C. 3716 (see 5 CFR part 550, subpart K; 31 CFR 285.7; and... centralized administrative offset pursuant to and in accordance with 31 CFR 901.3(b). Debts which are...

  9. 34 CFR 31.11 - Offset process.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... provisions of 4 CFR 102.4. (e) The Secretary effects an offset under this part against payments owing to an... the provisions of 5 CFR 550.1108. (Authority: 5 U.S.C. 5514; 31 U.S.C. 3716) ... 34 Education 1 2010-07-01 2010-07-01 false Offset process. 31.11 Section 31.11 Education Office...

  10. 34 CFR 31.11 - Offset process.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... provisions of 4 CFR 102.4. (e) The Secretary effects an offset under this part against payments owing to an... the provisions of 5 CFR 550.1108. (Authority: 5 U.S.C. 5514; 31 U.S.C. 3716) ... 34 Education 1 2012-07-01 2012-07-01 false Offset process. 31.11 Section 31.11 Education Office...

  11. 34 CFR 31.11 - Offset process.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... provisions of 4 CFR 102.4. (e) The Secretary effects an offset under this part against payments owing to an... the provisions of 5 CFR 550.1108. (Authority: 5 U.S.C. 5514; 31 U.S.C. 3716) ... 34 Education 1 2014-07-01 2014-07-01 false Offset process. 31.11 Section 31.11 Education Office...

  12. Late Quaternary mass-wasting records and formation of alluvial terraces in the actively uplifting Lao-nong catchment, southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Tsui, H. K.; Hsieh, M. L.; Li, W. L.; Hsiao, Y. T.

    2014-12-01

    Although dominated by erosion over long term, the tectonically active mountains of Taiwan commonly contain thick landslide and debris-flow gravels capping hillslopes or forming alluvial terraces. These deposits and their associated landforms serve to study ancient mass-wasting histories and their controls on fluvial processes. This study focuses on the Lao-nong River draining the 1000-3000 m high mountain areas in southwestern Taiwan (current tectonic uplift: 10-20 mm/yr). The Lao-nong River exhibits numerous terraces, many of which are of tributary-fan origins and consist of fluvial/debris-flow gravels 20-200 m thick. The development of such alluvial terraces can be observed during 2009 Typhoon Morakot, which brought record-setting 2000 mm of rain. Triggered by this heavy rain, almost all the tributaries of the Lao-nong generated alluvial fans at their mouths and consequently caused up-to-30 m aggradation along the trunk river. The Lao-nong has yielded >100 radiocarbon dates (all <20 ka).These data reveal that the formation of the observed alluvial terraces (from deposition of thick gravels to subsequent incision) could proceed very rapidly (<1 ky), and that the trunk river has been characterized by repeated aggradation and incision. This fact highlights the significance of event-driven sediment supply in governing the river behavior, which has strongly obscured the effect of the concurrent tectonic uplift. Among the terraces consisting of thick gravels, the six with 100-200 m-thick gravels are dated~18ka, ~12ka (for two terraces), ~5.5ka, ~3.4ka, and ~1.4 ka. The seven terraces with 50-100 m-thick gravels are dated ~12ka, ~8.3ka, ~5.7ka, ~1.3ka and 0.2-1.6ka (two undated). These dates (and others) suggest the clusters of mass-wasting events around ~12ka, 5.5-5.7 ka, and <1.6 ka. However, note that most of the recorded mass-wasting events vary in time and magnitude among tributary catchments, which implies the controls of internal factors on the timing, magnitude

  13. Fan-structure waves in shear ruptures

    NASA Astrophysics Data System (ADS)

    Tarasov, Boris

    2016-04-01

    This presentation introduces a recently identified shear rupture mechanism providing a paradoxical feature of hard rocks - the possibility of shear rupture propagation through the highly confined intact rock mass at shear stress levels significantly less than frictional strength. According to the fan-mechanism the shear rupture propagation is associated with consecutive creation of small slabs in the fracture tip which, due to rotation caused by shear displacement of the fracture interfaces, form a fan-structure representing the fracture head. The fan-head combines such unique features as: extremely low shear resistance (below the frictional strength), self-sustaining stress intensification in the rupture tip (providing easy formation of new slabs), and self-unbalancing conditions in the fan-head (making the failure process inevitably spontaneous and violent). An important feature of the fan-mechanism is the fact that for the initial formation of the fan-structure an enhanced local shear stress is required, however, after completion of the fan-structure it can propagate as a dynamic wave through intact rock mass at shear stresses below the frictional strength. Paradoxically low shear strength of pristine rocks provided by the fan-mechanism determines the correspondingly low transient strength of the lithosphere, which favours generation of new earthquake faults in the intact rock mass adjoining pre-existing faults in preference to frictional stick-slip instability along these faults. The new approach reveals an alternative role of pre-existing faults in earthquake activity: they represent local stress concentrates in pristine rock adjoining the fault where special conditions for the fan-mechanism nucleation are created, while further dynamic propagation of the new fault (earthquake) occurs at low field stresses even below the frictional strength.

  14. Submarine fans in a sequence stratigraphic framework

    SciTech Connect

    Posamentier, H.W.; Erskine, R.D.; Mitchum, R.M.; Vail, P.R.

    1987-05-01

    Submarine fans are fan- or cone-shaped turbiditic deposits formed in upper bathyal or deeper water depths. Within a sequence stratigraphic framework, these basin-floor turbidites can occur during lowstand-fan or lowstand-wedge systems tract time. During lowstand fan time, streams are rejuvenated and depocenters shift from the coastal plain to the upper slope, causing retrogradational slope failure and canyon formation. The sediment delivered here bypasses the canyon and continues down the slope as a succession of gravity flows and is deposited as fan-shaped turbiditic deposits at the base of the slope. Seismic and outcrop evidence suggest that these sand-prone deposits are abruptly introduced into the basin and are generally characterized by subtle external mounding and internal bidirectionally down lapping seismic reflections where seismically resolvable. Deep-water sediment deposited during this interval has no coeval shelf equivalent. During lowstand wedge time, streams cease down cutting and valleys which have been freshly incised begin to fill. Because coarse sediment will preferentially be deposited within these incised valleys, the sand-to-mud ratio delivered to the upper slope will be decreased and, consequently, there is an inherent difference between submarine fans deposited at this time and those deposited during lowstand fan time. Deposition during lowstand wedge time is characterized seismically by slope front fill or wedge-shaped geometries down lapping the earlier submarine fan (i.e., deposited during lowstand fan time). These shale-prone deposits are largely comprised of thinner-bedded turbidites as well as the occasional leveed channel.

  15. Supersonic through-flow fan design

    NASA Technical Reports Server (NTRS)

    Schmidt, James F.; Moore, Royce D.; Wood, Jerry R.; Steinke, Ronald J.

    1987-01-01

    The NASA Lewis Research Center has embarked on a program to experimentally prove the concept of a supersonic through-flow fan which is to maintain supersonic velocities throughout the compression system with only weak shock-wave flow losses. The detailed design of a supersonic through-flow fan and estimated off-design performance with the use of advanced computational codes are described. A multistage compressor facility is being modified for the newly designed supersonic through-flow fan and the major aspects of this modification are briefly described.

  16. Fan Database and Web-tool for Choosing Quieter Spaceflight Fans

    NASA Technical Reports Server (NTRS)

    Allen, Christopher S.; Burnside, Nathan J.

    2007-01-01

    One critical aspect of designing spaceflight hardware is the selection of fans to provide the necessary cooling. And with efforts to minimize cost and the tendancy to be conservative with the amount of cooling provided, it is easy to choose an overpowered fan. One impact of this is that the fan uses more energy than is necessary. But, the more significant impact is that the hardware produces much more acoustic noise than if an optimal fan was chosen. Choosing the right fan for a specific hardware application is no simple task. It requires knowledge of cooling requirements and various fan performance characteristics as well as knowledge of the aerodynamic losses of the hardware in which the fan is to be installed. Knowledge of the acoustic emissions of each fan as a function of operating condition is also required in order to choose a quieter fan for a given design point. The purpose of this paper is to describe a database and design-tool that have been developed to aid spaceflight hardware developers in choosing a fan for their application that is based on aerodynamic performance and reduced acoustic emissions as well. This web-based-tool provides a limited amount of fan-data, provides a method for selecting a fan based on its projected operating point, and also provides a method for comparing and contrasting aerodynamic performance and acoustic data from different fans. Drill-down techniques are used to display details of the spectral noise characteristics of the fan at specific operation conditions. The fan aerodynamic and acoustic data were acquired at Ames Research Center in the Experimental Aero-Physics Branch's Anechoic Chamber. Acoustic data were acquired according to ANSI Standard S12.11-1987, "Method for the Measurement of Noise Emitted by Small Air-Moving Devices." One significant improvement made to this technique included automation that allows for a significant increase in flow-rate resolution. The web-tool was developed at Johnson Space Center and is

  17. 30 CFR 57.8519 - Underground main fan controls.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Underground main fan controls. 57.8519 Section... Ventilation Surface and Underground § 57.8519 Underground main fan controls. All underground main fans shall have controls placed at a suitable protected location remote from the fan and preferably on the...

  18. 30 CFR 75.302 - Main mine fans.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Main mine fans. 75.302 Section 75.302 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.302 Main mine fans. Each coal mine shall be ventilated by one or more main mine fans. Booster fans shall not be installed underground to assist main...

  19. 30 CFR 75.310 - Installation of main mine fans.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Installation of main mine fans. 75.310 Section... mine fans. (a) Each main mine fan shall be— (1) Installed on the surface in an incombustible housing... that gives a signal at the mine when the fan either slows or stops. A responsible person designated...

  20. 30 CFR 75.310 - Installation of main mine fans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Installation of main mine fans. 75.310 Section... mine fans. (a) Each main mine fan shall be— (1) Installed on the surface in an incombustible housing... that gives a signal at the mine when the fan either slows or stops. A responsible person designated...

  1. 30 CFR 75.331 - Auxiliary fans and tubing.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Auxiliary fans and tubing. 75.331 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.331 Auxiliary fans and tubing. (a) When auxiliary fans and tubing are used for face ventilation, each auxiliary fan shall be—...

  2. 30 CFR 75.302 - Main mine fans.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Main mine fans. 75.302 Section 75.302 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.302 Main mine fans. Each coal mine shall be ventilated by one or more main mine fans. Booster fans shall not be installed underground to assist main...

  3. 30 CFR 75.302 - Main mine fans.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Main mine fans. 75.302 Section 75.302 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.302 Main mine fans. Each coal mine shall be ventilated by one or more main mine fans. Booster fans shall not be installed underground to assist main...

  4. 30 CFR 75.331 - Auxiliary fans and tubing.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Auxiliary fans and tubing. 75.331 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.331 Auxiliary fans and tubing. (a) When auxiliary fans and tubing are used for face ventilation, each auxiliary fan shall be—...

  5. 30 CFR 75.302 - Main mine fans.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Main mine fans. 75.302 Section 75.302 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.302 Main mine fans. Each coal mine shall be ventilated by one or more main mine fans. Booster fans shall not be installed underground to assist main...

  6. 30 CFR 57.8519 - Underground main fan controls.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Underground main fan controls. 57.8519 Section... Ventilation Surface and Underground § 57.8519 Underground main fan controls. All underground main fans shall have controls placed at a suitable protected location remote from the fan and preferably on the...

  7. 30 CFR 75.310 - Installation of main mine fans.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Installation of main mine fans. 75.310 Section... mine fans. (a) Each main mine fan shall be— (1) Installed on the surface in an incombustible housing... that gives a signal at the mine when the fan either slows or stops. A responsible person designated...

  8. 30 CFR 75.331 - Auxiliary fans and tubing.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Auxiliary fans and tubing. 75.331 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.331 Auxiliary fans and tubing. (a) When auxiliary fans and tubing are used for face ventilation, each auxiliary fan shall be—...

  9. 30 CFR 75.302 - Main mine fans.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Main mine fans. 75.302 Section 75.302 Mineral... SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.302 Main mine fans. Each coal mine shall be ventilated by one or more main mine fans. Booster fans shall not be installed underground to assist main...

  10. 30 CFR 75.331 - Auxiliary fans and tubing.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Auxiliary fans and tubing. 75.331 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.331 Auxiliary fans and tubing. (a) When auxiliary fans and tubing are used for face ventilation, each auxiliary fan shall be—...

  11. 30 CFR 75.331 - Auxiliary fans and tubing.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Auxiliary fans and tubing. 75.331 Section 75... HEALTH MANDATORY SAFETY STANDARDS-UNDERGROUND COAL MINES Ventilation § 75.331 Auxiliary fans and tubing. (a) When auxiliary fans and tubing are used for face ventilation, each auxiliary fan shall be—...

  12. 30 CFR 57.8519 - Underground main fan controls.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Underground main fan controls. 57.8519 Section... Ventilation Surface and Underground § 57.8519 Underground main fan controls. All underground main fans shall have controls placed at a suitable protected location remote from the fan and preferably on the...

  13. 30 CFR 57.8519 - Underground main fan controls.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Underground main fan controls. 57.8519 Section... Ventilation Surface and Underground § 57.8519 Underground main fan controls. All underground main fans shall have controls placed at a suitable protected location remote from the fan and preferably on the...

  14. 30 CFR 57.8519 - Underground main fan controls.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Underground main fan controls. 57.8519 Section... Ventilation Surface and Underground § 57.8519 Underground main fan controls. All underground main fans shall have controls placed at a suitable protected location remote from the fan and preferably on the...

  15. 30 CFR 75.310 - Installation of main mine fans.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Installation of main mine fans. 75.310 Section... mine fans. (a) Each main mine fan shall be— (1) Installed on the surface in an incombustible housing... that gives a signal at the mine when the fan either slows or stops. A responsible person designated...

  16. Great Apes and Biodiversity Offset Projects in Africa: The Case for National Offset Strategies

    PubMed Central

    Kormos, Rebecca; Kormos, Cyril F.; Humle, Tatyana; Lanjouw, Annette; Rainer, Helga; Victurine, Ray; Mittermeier, Russell A.; Diallo, Mamadou S.; Rylands, Anthony B.; Williamson, Elizabeth A.

    2014-01-01

    The development and private sectors are increasingly considering “biodiversity offsets” as a strategy to compensate for their negative impacts on biodiversity, including impacts on great apes and their habitats in Africa. In the absence of national offset policies in sub-Saharan Africa, offset design and implementation are guided by company internal standards, lending bank standards or international best practice principles. We examine four projects in Africa that are seeking to compensate for their negative impacts on great ape populations. Our assessment of these projects reveals that not all apply or implement best practices, and that there is little standardization in the methods used to measure losses and gains in species numbers. Even if they were to follow currently accepted best-practice principles, we find that these actions may still fail to contribute to conservation objectives over the long term. We advocate for an alternative approach in which biodiversity offset and compensation projects are designed and implemented as part of a National Offset Strategy that (1) takes into account the cumulative impacts of development in individual countries, (2) identifies priority offset sites, (3) promotes aggregated offsets, and (4) integrates biodiversity offset and compensation projects with national biodiversity conservation objectives. We also propose supplementary principles necessary for biodiversity offsets to contribute to great ape conservation in Africa. Caution should still be exercised, however, with regard to offsets until further field-based evidence of their effectiveness is available. PMID:25372894

  17. New Fan Engine Noise-Reduction Concept Using Trailing Edge Blowing of Fan Blades Demonstrated

    NASA Technical Reports Server (NTRS)

    Heidelberg, Laurence J.

    2002-01-01

    A major source of noise in commercial turbofan engines is the interaction of the fan blade wakes with the fan exit vanes (stators). These wakes can be greatly reduced by filling them with air blown out of the blade trailing edge. Extensive testing of this concept has demonstrated significant noise reductions. These tests were conducted on a low-speed, 4- ft-diameter fan using hollow blades at NASA Glenn Research Center's Aeroacoustic Propulsion Laboratory (AAPL).

  18. Navy Fan, California Borderland: Growth pattern and depositional processes

    USGS Publications Warehouse

    Normark, W.R.; Piper, D.J.W.

    1984-01-01

    Navy Fan is a Late Pleistocene sand-rich fan prograding into an irregularly shaped basin in the southern California Borderland. The middle fan, characterized by one active and two abandoned 'distributary' channels and associated lobe deposits, at present onlaps part of the basin slope directly opposite from the upper-fan valley, thus dividing the lower-fan/basin-plain regions into two separate parts of different depths. Fine-scale mesotopographic relief on the fan surface and correlation of individual turbidite beds through nearly 40 cores on the middle and lower fan provide data for evaluating the Late Pleistocene and Holocene depositional processes. ?? 1984 Springer-Verlag New York Inc.

  19. 11. EXTERIOR VIEW OF NEW FAN HOUSE LOOKING EAST The ...

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

    11. EXTERIOR VIEW OF NEW FAN HOUSE LOOKING EAST The airway (on the left) leads from the Baltimore shaft to the New Fan House. The metal housing (center foreground) encases a single entry Duplex Conoidal fan, made by the Buffalo Forge Company. The Duplex Conoidal fan had two parts: a disk fan which drew air up the airway and a centrifugal fan set at a right angle to it which exhausted the air. The engine house (on the right) contains a direct connected Corliss engine. - Dorrance Colliery Fan Complex, South side of Susquehanna River at Route 115 & Riechard Street, Wilkes-Barre, Luzerne County, PA

  20. Design and Test of Fan/Nacelle Models Quiet High-Speed Fan Design

    NASA Technical Reports Server (NTRS)

    Miller, Christopher J. (Technical Monitor); Repp, Russ; Gentile, David; Hanson, David; Chunduru, Srinivas

    2003-01-01

    The primary objective of the Quiet High-Speed Fan (QHSF) program was to develop an advanced high-speed fan design that will achieve a 6 dB reduction in overall fan noise over a baseline configuration while maintaining similar performance. The program applies and validates acoustic, aerodynamic, aeroelastic, and mechanical design tools developed by NASA, US industry, and academia. The successful fan design will be used in an AlliedSignal Engines (AE) advanced regional engine to be marketed in the year 2000 and beyond. This technology is needed to maintain US industry leadership in the regional turbofan engine market.

  1. Active Vibration Reduction of Titanium Alloy Fan Blades (FAN1) Using Piezoelectric Materials

    NASA Technical Reports Server (NTRS)

    Choi, Benjamin; Kauffman, Jeffrey; Duffy, Kirsten; Provenza, Andrew; Morrison, Carlos

    2010-01-01

    The NASA Glenn Research Center is developing smart adaptive structures to improve fan blade damping at resonances using piezoelectric (PE) transducers. In this paper, a digital resonant control technique emulating passive shunt circuits is used to demonstrate vibration reduction of FAN1 Ti real fan blade at the several target modes. Single-mode control and multi-mode control using one piezoelectric material are demonstrated. Also a conceptual study of how to implement this digital control system into the rotating fan blade is discussed.

  2. Operation and maintenance guidelines for draft fans

    SciTech Connect

    Henry, R.E.; Basile, J.F. )

    1993-01-01

    Large draft fans typically account for more than one-fourth of a generating unit's auxiliary output. Industry data indicates that failure of draft fans is among the top 15 causes of outages. These guidelines offer comprehensive coverage of major topics, such as fan operation, maintenance, troubleshooting, wheel inspection, and weld repairs. Each section provides extensive road maps describing step-by-step procedures for implementing mutually supportive operating and maintenance strategies. The guidelines emphasize preventive maintenance through checks and predictive maintenance through vibration and temperature monitoring. Moreover, the guidelines present a tri-level maintenance structure of prestart checks, operational checks, and out-of-service checks. Utilities may use the guidelines in developing and refining overall operation and maintenance procedures for large draft fans in power plant applications.

  3. Supersonic fan engines for military aircraft

    NASA Technical Reports Server (NTRS)

    Franciscus, L. C.

    1983-01-01

    Engine performance and mission studies were performed for turbofan engines with supersonic through-flow fans. A Mach 2.4 CTOL aircraft was used in the study. Two missions were considered: a long range penetrator mission and a long range intercept mission. The supersonic fan engine is compared with an augmented mixed flow turbofan in terms of mission radius for a fixed takeoff gross weight of 75,000 lbm. The mission radius of aircraft powered by supersonic fan engines could be 15 percent longer than aircraft powered with conventional turbofan engines at moderate thrust to gross weight ratios. The climb and acceleration performance of the supersonic fan engines is better than that of the conventional turbofan engines.

  4. Supersonic fan engines for military aircraft

    NASA Technical Reports Server (NTRS)

    Franciscus, L. C.

    1983-01-01

    Engine performance and mission studies were performed for turbofan engines with supersonic through-flow fans. A Mach 2.4 CTOL aircraft was used in the study. Two missions were considered: a long range penetrator mission and a long range intercept mission. The supersonic fan engine is compared with an augmented mixed flow turbofan in terms of mission radius for a fixed takeoff gross weight of 75,000 lbm. The mission radius of aircraft powered by supersonic fan engines could be 15 percent longer than aircraft powered with conventional turbofan engines at moderate thrust to gross weight ratios. The climb and acceleration performance of the supersonic fan engines is better than that of the conventional turbofan engines. Previously announced in STAR as N83-34947

  5. Delgada Fan: Preliminary interpretation of channel development

    USGS Publications Warehouse

    Normark, W.R.; Gutmacher, C.E.

    1984-01-01

    The Delgada Fan, an irregularly shaped turbidite deposit extending more than 350 km offshore from northern California, consists of two large leveed-valley units each fed by a separate complex of coalescing submarine canyons and slope gullies. Although the leveed-valley units head within 25 km of each other, both appear to have developed independently during fan growth. The larger southern leveed-valley system has not developed middle-fan distributary channels and appears to illustrate a period of progressive valley abandonment. Although the lower-fan area is underlain by sandy sediments, little sand has been recovered in piston cores from the leveed-valley unit. ?? 1984 Springer-Verlag New York Inc.

  6. Synchronous and Cogged Fan Belt Performance Assessment

    SciTech Connect

    Cutler, D.; Dean, J.; Acosta, J.

    2014-02-01

    The GSA Regional GPG Team commissioned the National Renewable Energy Laboratory (NREL) to perform monitoring of cogged V-belts and synchronous belts on both a constant volume and a variable air volume fan at the Byron G. Rodgers Federal Building and U.S. Courthouse in Denver, Colorado. These motor/fan combinations were tested with their original, standard V-belts (appropriately tensioned by an operation and maintenance professional) to obtain a baseline for standard operation. They were then switched to the cogged V-belts, and finally to synchronous belts. The power consumption by the motor was normalized for both fan speed and air density changes. This was necessary to ensure that the power readings were not influenced by a change in rotational fan speed or by the power required to push denser air. Finally, energy savings and operation and maintenance savings were compiled into an economic life-cycle cost analysis of the different belt options.

  7. 7. EXTERIOR VIEW OF BALTIMORE FAN HOUSE, AIRWAY, AND HILLMAN ...

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

    7. EXTERIOR VIEW OF BALTIMORE FAN HOUSE, AIRWAY, AND HILLMAN FAN HOUSE LOOKING SOUTHEAST The roof of the 1908 Baltimore Fan House is to the left; the doorway opens onto the rear of the metal fan housing. In the immediate foreground is a section of the blast doors installed in the airway directly over the shaft to protect the fans in case of a mine explosion. The sloping airway, to the right, connects with the New Fan House, whose metal updraft chimney is evident in the right background. The engine house of the Hillman Fan House is in the left background with the fan housing and updraft chimney connected. The boiler house stack is in the background. All of the engines in the fan complex were powered by the boiler house. - Dorrance Colliery Fan Complex, South side of Susquehanna River at Route 115 & Riechard Street, Wilkes-Barre, Luzerne County, PA

  8. CF6 jet engine performance improvement: New fan

    NASA Technical Reports Server (NTRS)

    Fasching, W. A.

    1980-01-01

    As part of the NASA sponsored engine component improvement program, and fan package was developed to reduce fuel consumption in current CF6 turbofan aircraft engine. The new fan package consist of an improved fan blade, reduced fan tip clearance due to a fan case stiffener, and a smooth fan casing tip shroud. CF6 engine performance and acoustic tests demonstrated the predicted 1.8% improvement in cruise sfc without an increase in engine noise. Power management thrust/fan speed characteristics were defined. Mechanical and structural integrity was demonstrated in model fan rotor photoelastic stress tests, full-size fan blade bench fatigue tests, and CF6 engine bird ingestion, crosswind, and cyclic endurance tests. The fan was certified in the CF6-500c2/E2 engines and is in commerical service on the Boeing 747-200, Douglas DC-10-30, and Atrbus industrie A300B aircraft.

  9. The Advanced Noise Control Fan Baseline Measurements

    NASA Technical Reports Server (NTRS)

    McAllister, Joseph; Loew, Raymond A.; Lauer, Joel T.; Stuliff, Daniel L.

    2009-01-01

    The NASA Glenn Research Center s (NASA Glenn) Advanced Noise Control Fan (ANCF) was developed in the early 1990s to provide a convenient test bed to measure and understand fan-generated acoustics, duct propagation, and radiation to the farfield. As part of a complete upgrade, current baseline and acoustic measurements were documented. Extensive in-duct, farfield acoustic, and flow field measurements are reported. This is a follow-on paper to documenting the operating description of the ANCF.

  10. Flutter Calculations for an Experimental Fan

    NASA Technical Reports Server (NTRS)

    Bakhle, Milind A.; Srivastava, Rakesh; Panovsky, Josef; Keith, Theo G., Jr.; Stefko, George L.

    2003-01-01

    During testing, an experimental forward-swept fan encountered flutter at part-speed conditions. A three-dimensional propulsion aeroelasticity code, based on a computational fluid dynamics (CFD) approach, was used to model the aeroelastic behavior of this fan. This paper describes the flutter calculations and compares the results to the experimental measurements. Results of sensitivity studies are also presented that show the relative importance of different aspects of aeroelastic modeling.

  11. Noise Radiation from Engine Cooling Fans

    NASA Astrophysics Data System (ADS)

    Wu, S. F.; Su, S.; Shah, H.

    1998-09-01

    The semi-empirical formulation previously derived by the authors (Journal of Sound and Vibration200,379-399) for predicting noise spectra of axial flow fans running in a free field is extended to engine cooling fans installed in full-size vehicles. Because of the presence of shroud, upstream radiator/condenser, and downstream engine block, the ingested and discharged flow fields around the fan blades are completely different from those in a free field. Accordingly, the noise generation mechanisms become much more difficult to analyze and model. The shroud may significantly increase the unsteady fluctuating forces exerted on the fan blades, thus greatly enhancing the levels of the discrete sounds centred at the blade passage frequency and its harmonics. The upstream radiator/condenser set may induce a significant amount of intake turbulence, thus raising the levels of the broadband sounds. The downstream engine block may force the airflow to recirculate to the front and more importantly, raise the static pressure drop across the fan assembly, which has a direct impact on the resulting flow rate. Obviously, an exact description of the effects of these factors on the resulting noise spectra is not possible. In this paper it is shown that these factors can be approximated by using certain shapes and functions. The computer model thus developed is used to predict the noise spectra from different fan assemblies under various working conditions, and the results thus obtained are compared with the measured data. Also, this model is used to calculate the overall sound pressure levels from dimensionally similar fans running under different working conditions, and the results are compared with those predicted by the fan laws currently in use by engineers in the automotive industry.

  12. Holocene alluvial fills in the South Loup Valley, Nebraska

    NASA Astrophysics Data System (ADS)

    May, David W.

    1989-07-01

    Four Holocene alluvial fills are present in Nebraska's South Loup River valley. Fill IV, the oldest and thickest, was deposited between 10,200 and 4800 14C yr B.P.; Fill III has an age of about 3000 14C yr B.P.; Fill II is younger than 2100 and older than 900 14C yr B.P.; and Fill I is younger than 900 14C yr B.P. Regional contemporaneity of valley alluviation in the eastcentral Great Plains suggests that climate has controlled long-term sediment storage in the South Loup River valley.

  13. Radiated noise of ducted fans

    NASA Technical Reports Server (NTRS)

    Eversman, Walter

    1992-01-01

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  14. Radiated noise of ducted fans

    NASA Astrophysics Data System (ADS)

    Eversman, Walter

    The differences in the radiated acoustic fields of ducted and unducted propellers of the same thrust operating under similar conditions are investigated. An FEM model is created for the generation, propagation, and radiation of steady, rotor alone noise and exit guide vane interaction noise of a ducted fan. For a specified number of blades, angular mode harmonic, and rotor angular velocity, the acoustic field is described in a cylindrical coordinate system reduced to only the axial and radial directions. It is found that, contrary to the usual understanding of the Tyler and Sofrin (1962) result, supersonic tip speed rotor noise can be cut off if the tip Mach number is only slightly in excess of unity and if the number of blades is relatively small. If there are many blades, the fundamental angular mode number is large, and the Tyler and Sofrin result for thin annuli becomes more relevant. Shrouding of subsonic tip speed propellers is a very effective means of controlling rotor alone noise.

  15. High-frequency cyclicity in quaternary fan-delta deposits of the Andean fore-arc: Relative sea level changes and aseismic ridge subduction

    SciTech Connect

    Flint, S. ); Jolley, E.J.; Turner, P.; Williams, G.D.; Buddin, T. )

    1990-05-01

    The coast of northern Chile comprises Mesozoic magmatic rocks and Cenozoic-Holocene shallow-marine and alluvial fan/fan-delta sediments. The structure, landform development, and sedimentary response of the coast between Antofagasta in the south and Arica (600 km to the north) have been investigated to evaluate the influence of Nazca plate subduction on sea level changes over Quaternary to Holocene times. At Arica the coastal range is in net extension characterized by extensional normal faulting and subsidence, similar to much of Chile. South of Arica, uplift is recorded by marine terrace development and incision of alluvial fan surfaces; uplift reaches a maximum south of Iquiqui. The boundary between regions in net subsidence and net uplift is marked by north-facing neotectonic normal fault scarps. Variations in apparent uplift and subsidence are consistent with recently published oceanographic records on relative sea level changes over a 30 yr period. The authors data suggest that these regionally variable patterns of coastal uplift along the north Chilean coast are controlled by the subduction of an aseismic ridge, which overprints the effect of eustatic sea level fluctuations. Subduction of oceanic plate heterogeneities may provide a mechanism for producing cyclicity in sedimentary sequences at a frequency equal to or higher than glacio-eustacy in fore-arc and possibly back-arc sedimentary basins. These sequences will be neither of global extent nor of global synchroneity.

  16. Alluvial deposition and lake-level fluctuations forced by Late Quaternary climate change: the Dead Sea case example

    NASA Astrophysics Data System (ADS)

    Klinger, Y.; Avouac, J. P.; Bourles, D.; Tisnerat, N.

    2003-11-01

    Based on geomorphic observations, we discuss lake-level fluctuations, alluvial deposition and river entrenchment in the Dead Sea-Wadi Araba area. The bulk of alluvium in the northern Wadi Araba was probably deposited before the Lisan period of lake transgression that started at about 70 kyears B.P. The lake reached a maximum elevation about 150 m below sea level (b.s.l.), possibly around 15 cal. kyears B.P. as indicated by the highest preserved beach ridges. Cosmogenic exposure dates show that the ridge material consists mainly of remobilized Pleistocene gravel indicating little sediment supply during most of the Lisan period. During this period, a reduced sediment flux fed subaquatic fan deltas along the margin of the Dead Sea. Wetter conditions settled at the end of this period, the water level rose to about 280 m b.s.l. around 15 kyears B.P. and prevailed in the early Holocene (10.5-7 cal. kyears B.P.). Following that humid period, the lake level dropped and two major episodes of fluvial aggradation occurred during periods of relative low lake level. The first aggradational episode took place between about 7.0 and 6.2 cal. kyears B.P. Beach bars indicate a subsequent lake transgression between 6.2 and 4.4 kyears B.P. up to 350 m b.s.l. The second aggradational episode happened between 4.4 and 2.0 cal. kyears B.P., and was also followed by a late transgression up to 375 m b.s.l., dated to 1960-1715 cal. years B.P. The correlation between low lake level and fluvial aggradation is taken to reflect the synchronous change of the fluvial regime and of the lake hydrologic balance, forced by climate changes, rather than a base-level control. We also exclude large tectonic forcing on fan emplacement and river entrenchment. Alluviation appears in this setting as a very irregular process, characterized by long periods of quiescence alternating with periods of fan build-up, reflecting the transient response of the water drainage system to climate change.

  17. Influence of water and sediment supply on the stratigraphic record of alluvial fans and deltas: Process controls on stratigraphic completeness

    NASA Astrophysics Data System (ADS)

    Straub, Kyle M.; Esposito, Christopher R.

    2013-06-01

    contains the most complete record of information necessary to quantitatively reconstruct paleolandscape dynamics, but this record contains significant gaps over a range of time and space scales. These gaps result from stasis on geomorphic surfaces and erosional events that remove previously deposited sediment. Building on earlier statistical studies, we examine stratigraphic completeness in three laboratory experiments where the topography of aggrading deltas was monitored at high temporal and spatial scales. The three experiments cover unique combinations in the absolute magnitudes of sediment and water discharge in addition to generation of accommodation space through base-level rise. This analysis centers on three time scales: (1) the time at which a record is discretized (t), (2) the time necessary to build a deposit with mean thickness equivalent to the maximum roughness on a surface (Tc), and (3) the time necessary for channelized flow to migrate over all locations in a basin (Tch). These time scales incorporate information pertaining to the time-variant topography of actively changing surfaces, kinematics by which the surfaces are changing, and net deposition rate. We find that stratigraphic completeness increases as a function of t/Tc but decreases as a function of Tc/Tch over the parameter space covered in the experiments. Our results suggest that environmental signals disconnected from a sediment routing system are best preserved in systems with low Tc values. Nondimensionalizing t by Tc, however, shows that preservation of information characterizing system morphodynamics is best preserved in stratigraphy constructed by systems with low water to sediment flux ratios.

  18. Field Measurements of Electro-osmotic Transport of Ground Water Contaminants in a Lithologically Heterogeneous Alluvial-Fan Setting

    SciTech Connect

    McNab,W; Karachewski,J; Weismann,G

    2001-07-31

    Remediation of contaminated ground water by pump-and-treat approaches is often problematic because the heterogeneous distributions of lithologies, and hence hydraulic conductivities, characterizing many aquifers result in complex flow paths. Consequently, contaminants are removed readily from the most permeable regions of the subsurface but the less permeable sediments, rich in clay and silt, remain largely undisturbed. These continue to act as diffusion-limited sources for further contamination of the permeable sediments. Under certain circumstances, specialized technologies, such as electrokinetic approaches, may be useful for enhancing the removal of ground water from low-permeability sediments. These circumstances generally include high contaminant concentrations--hence posing a chronic source threat--and a relatively small area requiring treatment. At Lawrence Livermore National Laboratory (LLNL) in Livermore, California, electro-osmosis (EO) is being evaluated as a means for extracting ground water containing trichloroethylene (TCE) and other chlorinated hydrocarbons from fine-grained sediments in a plume source area.

  19. Investigations on alluvial deposits through borehole stratigraphy, radiocarbon dating and passive seismic technique (Carnic Alps, NE Italy)

    NASA Astrophysics Data System (ADS)

    Viero, Alessia; Marchi, Lorenzo; Cavalli, Marco; Crema, Stefano; Fontana, Alessandro; Mozzi, Paolo; Venturini, Corrado

    2016-04-01

    Alluvial sediment investigations provide fundamental tools to infer the processes that control geomorphological evolution of mountain environments. By analyzing sediment stratigraphy in depth, it is possible to retrieve the source, the geology, the time of deposition, the relative distance travelled by material as well as to distinguish among different type of transport (i.e., gravitational, fluvial or glacial). In this work, we present a combination of log stratigraphy, radiocarbon dating and geophysical surveys carried out on the valley floor of the But River (Carnic Alps, North East Italy). The But River basin drains an area of 326 km2 with a range in elevation from 2769 to 323 m a.s.l.; the bedrock mainly consists of carbonates and quartz arenites with minor inclusions of effusive rocks. After Pleistocene the gravitational deposits from mountain slopes have impounded the But River several times. In particular, we analyzed a sector of the upper portion of the But valley close to the confluence of the Moscardo Torrent, frequently affected by debris flows. A borehole was drilled in the But River floodplain, at the intersection with the Moscardo Torrent alluvial fan, down to a depth of 80 m. The analysis of the core samples allowed discerning three sedimentary levels rich in clay and organic materials, which testify the presence of small dam lakes, originated from the Moscardo debris-flow deposits. Three samples of wood and plant debris were collected from 13, 14 and 23 m of depth, respectively. They were analyzed through radiocarbon dating in order to determine the age of the lakes and, thus, to infer the activity of the debris flows building the Moscardo cone. The calibrated ages of the 3 samples are close to the younger limit of the radiocarbon method indicating a fast aggradation of the valley floor, starting from a period ranging between 1450 - 1632 AD. Historical maps and documents confirm the presence of the lakes until 19th century and they permit to assess

  20. Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona

    USGS Publications Warehouse

    Schmidt, John C.; Graf, Julia B.

    1990-01-01

    Alluvial sand deposits along the Colorado River in Grand Canyon National Park are used as campsites and are substrate for vegetation. The largest and most numerous of these deposits are formed in zones of recirculating current that are created downstream from where the channel is constricted by debris fans at tributary mouths. Alluvial sand deposits are classified by location and form. Separation and reattachment deposits are downstream from constrictions within recirculation zones. Separation deposits are near the point of flow separation and typically mantle large debris fans. Reattachment deposits are near the point of flow reattachment and project upstream beneath much of the zone of recirculating current. Upper-pool deposits are upstream from a constriction and are associated with backwaters. Channel-margin deposits line the channel and have the form of terraces. Some are created in small recirculation zones. Reattachment and channel-margin deposits are largest and most numerous in wide reaches, although small channel-margin deposits are used as campsites in the narrow Muav Gorge. Separation deposits are more uniformly distributed throughout Grand Canyon National Park than are other types of deposits. In some narrow reaches where the number of alluvial sand deposits used as campsites is small, separation deposits are a high percentage of the total. During high flows, both separation and reattachment deposits are initially scoured but are subsequently redeposited during flow recession. Sand is also exchanged between the main channel and recirculation zones. The rate of recession of high flows can affect the elevation of alluvial deposits that are left exposed after a flood has passed. Fluctuating flows that follow a period of steady discharge cause initial erosion of separation and reattachment deposits. A part of this eroded sand is transported to the main channel. Therefore, sand is exchanged between the main channel and recirculation zones and redistributed

  1. The paradox of large alluvial rivers (Invited)

    NASA Astrophysics Data System (ADS)

    Latrubesse, E. M.

    2010-12-01

    Large alluvial rivers exhibit large floodplains, very gentle slopes, a good selection of bed materials (generally sand), low specific stream power, and could represent the ultimate examples of “dynamic equilibrium” in fluvial systems. However, equilibrium can be discussed at different temporal scales. Base level changes by tectonic or climatic effects, modifications in sediment and water supply or different kinds of human impacts are the traditional causes that could trigger “disequilibrium” and changes in the longitudinal profile. Simultaneously, adjustments of longitudinal profiles were thought to be evolving from downstream to upstream by several processes, being the most common receding erosion. Some authors,have demonstrated that when changes in base level happen, a variety of adjustments can be reached in the lower course in function of the available sediment and water discharge, slopes articulations between the fluvial reach and the continental shelve, among others, and that the adjustments can be transferred upstream significantly in small rivers but not far upstream along large fluvial systems. When analyzing the Quaternary fluvial belts of large rivers in the millennium scale, paleohydrological changes and modifications in floodplain constructional processes or erosion, are associated normally to late Quaternary climatic changes. The study of several of the largest rivers demonstrates that climatic changes and fluvial responses are not always working totally in phase and those direct cause-consequences relations are not a rule. This paper describes floodplain evolution and the lagged geomorphic responses of some large river system to recent climatic changes. Information from some of the largest rivers of the world such as the Amazon, Parana, several tributaries of the Amazon (Negro, Xingú, Tapajos) as well as some large Siberian Rivers was used. Since the last deglaciation, these large fluvial systems have not had enough time to reach equilibrium

  2. The significance of avulsion phenomena in the alluvial filling configuration of a mountain stream: Venero Claro (Central Spain)

    NASA Astrophysics Data System (ADS)

    Ruiz-Villanueva, V.; Díez-Herrero, A.; Bodoque, J. M.; Fernández-García, P.; Ballesteros, J. A.

    2009-04-01

    In the dynamics and evolution of large river floodplains, alluvial fans and debris cones, avulsion phenomena have been considered very important. However, traditionally, in mountain streams, avulsion phenomena have been underestimated because they are not very frequent, and usually they are restricted to little chute cut-off. Nevertheless, there are mountainous areas where the valley bottom gets wider, and the alluvial filling works like an elongated debris cone. The Cabrera Stream in the Venero Claro reach (Spanish Central System) is one of these special areas. In this case, avulsion phenomena took place triggered by flash floods, and they were usually associated with hyperconcentrated flows, which exceeded the upper level of levees and banks, redefining the sedimentary architecture of the alluvial filling. In this study, an analysis of geomorphologic and sedymentological evolution of the alluvial filling in Venero Claro have been carried out. On this way, cartography made from the 19th Century until ninety ages were compared, and a stereoscopic analysis of aerial photographs and digital ortoimages were applied. Furthermore, the sedimentary filling was studied applying classic sedimentological techniques, such as a description and interpretation of sedimentary structures and facies analysis at field. As a result of the geomorphologic evolution analysis, a straightforward evolution model is proposed. This model enhances the relevant importance of the avulsion phenomena in the geomorphologic configuration of the Cabrera Stream in the Venero Claro reach. From the river pattern point of view, the avulsion phenomena originate capture processes in the main stream and its tributaries. As a result of these processes, the drainage network pattern changes successively from dendritic to sub-parallel. On other hand, from the sedimentologic point of view, the stratigraphy is composed of channel facies (debris flow facies and fluvial-torrential gravelbars) and back

  3. Degradation of the Mitchell River fluvial megafan by alluvial gully erosion increased by post-European land use change, Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Shellberg, J. G.; Spencer, J.; Brooks, A. P.; Pietsch, T. J.

    2016-08-01

    Along low gradient rivers in northern Australia, there is widespread gully erosion into unconfined alluvial deposits of active and inactive floodplains. On the Mitchell River fluvial megafan in northern Queensland, river incision and fan-head trenching into Pleistocene and Holocene megafan units with sodic soils created the potential energy for a secondary cycle of erosion. In this study, rates of alluvial gully erosion into incipiently-unstable channel banks and/or pre-existing floodplain features were quantified to assess the influence of land use change following European settlement. Alluvial gully scarp retreat rates were quantified at 18 sites across the megafan using recent GPS surveys and historic air photos, demonstrating rapid increases in gully area of 1.2 to 10 times their 1949 values. Extrapolation of gully area growth trends backward in time suggested that the current widespread phase of gullying initiated between 1880 and 1950, which is post-European settlement. This is supported by young optically stimulated luminescence (OSL) dates of gully inset-floodplain deposits, LiDAR terrain analysis, historic explorer accounts of earlier gully types, and archival records of cattle numbers and land management. It is deduced that intense cattle grazing and associated disturbance concentrated in the riparian zones during the dry season promoted gully erosion in the wet season along steep banks, adjacent floodplain hollows and precursor gullies. This is a result of reduced native grass cover, increased physical disturbance of soils, and the concentration of water runoff along cattle tracks, in addition to fire regime modifications, episodic drought, and the establishment of exotic weed and grass species. Geomorphic processes operating over geologic time across the fluvial megafan predisposed the landscape to being pushed by land used change across an intrinsically close geomorphic threshold towards instability. The evolution of these alluvial gullies is discussed

  4. 5 CFR 1215.8 - Procedures for salary offset.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 3 2010-01-01 2010-01-01 false Procedures for salary offset. 1215.8... MANAGEMENT Salary Offset § 1215.8 Procedures for salary offset. (a) Deductions to liquidate an employee's debt will be by the method and in the amount stated in the Chairman's notice of intention to offset...

  5. 6 CFR 11.4 - Collection by administrative offset.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 6 Domestic Security 1 2010-01-01 2010-01-01 false Collection by administrative offset. 11.4 Section 11.4 Domestic Security DEPARTMENT OF HOMELAND SECURITY, OFFICE OF THE SECRETARY CLAIMS § 11.4 Collection by administrative offset. (a) General Provisions for Offset. DHS will collect debts by administrative offset pursuant to 31 CFR parts...

  6. 7 CFR 3.46 - Offset against tax refunds.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 1 2010-01-01 2010-01-01 false Offset against tax refunds. 3.46 Section 3.46 Agriculture Office of the Secretary of Agriculture DEBT MANAGEMENT Administrative Offset § 3.46 Offset against tax refunds. USDA will take action to effect administrative offset against tax refunds due to...

  7. Multiple Episodes of Recent Gully Activity Indicated by Gully Fan Stratigraphy in Eastern Promethei Terra, Mars.

    NASA Astrophysics Data System (ADS)

    Schon, S.; Head, J.; Fassett, C.

    2008-09-01

    Introduction Gullies are considered among the youngest geomorphic features on Mars based upon their stratigraphic relationships, superposition on steep slopes and distinctive morphology in unconsolidated sediment. Multiple formation hypotheses have been proposed, which can be divided into three broad classes: entirely dry mechanisms (e.g., [1,2]), wet mechanisms invoking groundwater or ground ice (e.g., [3,4]) and wet mechanisms invoking surficial meltwater (e.g., [5,6,7,8]). It has been difficult to differentiate between these hypotheses based upon past observations and it remains possible that gullies are polygenetic landforms. This study presents stratigraphic relationships in the depositional fan of a crater wall gully system that suggest: (1) multiple episodes of alluvial fan-style deposition, (2) very recent depositional activity that is younger than a newly recognized rayed crater, and (3) surficial snowmelt as the most likely source of these multiple episodes of recent gully activity. Gully-Fan Stratigraphy In Eastern Promethei Terra an ~5 km-diameter crater is observed with a well-developed gully system (Fig. 1) and several smaller gullies in its northnortheast wall. The large gully system (composed of a small western gully and larger eastern gully) shows evidence for incision into the crater wall country rock and has multiple contributory sub-alcoves and channels. The depositional fan associated with this gully system is bounded on its western side by a small arcuate ridge swell that is not observed on the eastern side of the fan. This ridge is interpreted as a moraine-like structure that may have bounded a glacially-formed depression into which the fan is deposited [8]. Similar depressions with bounding ridges are commonly observed in this latitude band (~30-50°S) in association with deeply incised gully alcoves [9,10,11]. This gully fan is composed of multiple lobes with distinct lobe contacts, incised channels, and cut-andfill deposits - all features

  8. Provenance of the Heavy Mineral-enriched Alluvial Deposits at the West Coast of Red Sea. Implications to the Evolution of Arabian-Nubian Crust

    NASA Astrophysics Data System (ADS)

    Mahar, M. A.; Ibrahim, T.; Goodell, P.

    2014-12-01

    Here we present the LA-ICP-MS U-Pb ages and Hf isotopic record of detrital zircons from the active alluvial fans at the west coast of the Red Sea. The Ras Manazal alluvial fan (primarily composed of zircon, magnetite with some rutile, ilmenite and monazite) yielded a relatively restricted age population ranges from 765 to 666 Ma. These ages and present-day drainage pattern is consistent that the sediments are primarily derived from erosion of nearby subduction related granitoids in the immediate west (i.e., not more than 50 km from the Red Sea coast) of the fan. In contrast, approximately 160 km south, at the Egypt-Sudan border, the Wadi Diit fan is relatively more enriched in ilmenite and REE-bearing phases (e.g., thorite, monazite, xenotime, garnet etc.) and yielded five zircon age populations of 1) 824-733 Ma, 2) 730-705 Ma, 3) 646-608 Ma, 4) 516-500 Ma, and 5) 134-114 Ma. The age populations 1-3 if coupled with the present-day drainage pattern can be related to the earlier subduction related and later post collision granitoids in the southern part of the South Eastern Desert and Gebeit terrane of northern Sudan. Sparse Early Cretaceous zircons (134-114 Ma) are derived from the Mesozoic volcanic suits in the source region. However, the age group 516-500 Ma is enigmatic. Wadi Diit zircons are primarily derived from granitoids in the broad S-N directed Hamisana Shear Zone and its subordinate SW to NE directed Onib-Sol-Hamed Suture Zone. These shear zones provided pathways for the present-day drainage system for sediment transportation to the Wadi Diit and adjacent coastal region. We infer that the ca. 500 Ma late-stage magmatic zircons represent a hitherto unknown magmatic event, possibly related to the shear heating associated with the crustal scale shear zones. This implies that the shear zones in the South Eastern Desert and northern Sudan remained thermally active as late as ~500 Ma. The time resolved hafnium composition (ɛHf (t)) of both fans varies from +3

  9. Provenance of the heavy mineral-enriched alluvial deposits at the west coast of the Red Sea. Implications for evolution of Arabian-Nubian crust

    NASA Astrophysics Data System (ADS)

    Mahar, Munazzam Ali; Ibrahim, Tarek M. M.; Goodell, Philip C.

    2014-12-01

    Here we present the LA-ICP-MS U-Pb ages and Hf isotopic record of detrital zircons from the active alluvial fans at the west coast of the Red Sea. The Ras Manazal alluvial fan (primarily composed of zircon, magnetite with some rutile, ilmenite and monazite) yielded a relatively restricted age population ranges from 765 to 666 Ma. These ages and present-day drainage pattern is consistent that the sediments are primarily derived from erosion of nearby subduction related granitoids in the immediate west (i.e., not more than 50 km from the Red Sea coast) of the fan. In contrast, approximately 160 km south, at the Egypt-Sudan border, the Wadi Diit fan is relatively more enriched in ilmenite and REE-bearing phases (e.g., thorite, monazite, xenotime, garnet, etc.) and yielded five zircon age populations of (1) 824-733 Ma, (2) 730-705 Ma, (3) 646-608 Ma, (4) 516-500 Ma, and (5) 134-114 Ma. The age populations 1-3 if coupled with the present-day drainage pattern can be related to the earlier subduction related and later post collision granitoids in the southern part of the South Eastern Desert and Gebeit terrane of northern Sudan. Sparse Early Cretaceous zircons (134-114 Ma) are derived from the Mesozoic volcanic suits in the source region. However, the age group 516-500 Ma is enigmatic. Wadi Diit zircons are primarily derived from granitoids in the broad S-N directed Hamisana Shear Zone and its subordinate SW to NE directed Onib-Sol-Hamed Suture Zone. These shear zones provided pathways for the present-day drainage system for sediment transportation to the Wadi Diit and adjacent coastal region. We infer that the ca. 500 Ma late-stage magmatic zircons represent a hitherto unknown magmatic event, possibly related to the shear heating associated with the crustal scale shear zones. This implies that the shear zones in the South Eastern Desert and northern Sudan remained thermally active as late as ∼500 Ma. The time resolved hafnium composition (εHf (t)) of both fans varies

  10. Off-set stabilizer for comparator output

    DOEpatents

    Lunsford, James S.

    1991-01-01

    A stabilized off-set voltage is input as the reference voltage to a comparator. In application to a time-interval meter, the comparator output generates a timing interval which is independent of drift in the initial voltage across the timing capacitor. A precision resistor and operational amplifier charge a capacitor to a voltage which is precisely offset from the initial voltage. The capacitance of the reference capacitor is selected so that substantially no voltage drop is obtained in the reference voltage applied to the comparator during the interval to be measured.

  11. 75 FR 43878 - Airworthiness Directives; DASSAULT AVIATION Model Falcon 10 Airplanes; Model FAN JET FALCON, FAN...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-27

    ... products, which was published in the Federal Register on September 21, 2009 (74 FR 48021). That earlier... 12866; 2. Is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034... Model Falcon 10 Airplanes; Model FAN JET FALCON, FAN JET FALCON SERIES C, D, E, F, and G...

  12. 30 CFR 905.822 - Special performance standards-Operations in alluvial valley floors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... alluvial valley floors. 905.822 Section 905.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE CALIFORNIA § 905.822 Special performance standards—Operations in alluvial valley floors. Part 822 of this chapter, Special Permanent Program Performance Standards—Operations in Alluvial Valley...

  13. 30 CFR 947.822 - Special performance standards-operations on alluvial valley floors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... alluvial valley floors. 947.822 Section 947.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE WASHINGTON § 947.822 Special performance standards—operations on alluvial valley floors. Part 822 of this chapter, Special Performance Standards—Operations on Alluvial Valley Floors, shall apply...

  14. 30 CFR 903.822 - Special performance standards-Operations in alluvial valley floors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... alluvial valley floors. 903.822 Section 903.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE ARIZONA § 903.822 Special performance standards—Operations in alluvial valley floors. Part 822 of this chapter, Special Permanent Program Performance Standards—Operations in Alluvial Valley...

  15. 30 CFR 903.822 - Special performance standards-Operations in alluvial valley floors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... alluvial valley floors. 903.822 Section 903.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE ARIZONA § 903.822 Special performance standards—Operations in alluvial valley floors. Part 822 of this chapter, Special Permanent Program Performance Standards—Operations in Alluvial Valley...

  16. 30 CFR 947.822 - Special performance standards-operations on alluvial valley floors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... alluvial valley floors. 947.822 Section 947.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE WASHINGTON § 947.822 Special performance standards—operations on alluvial valley floors. Part 822 of this chapter, Special Performance Standards—Operations on Alluvial Valley Floors, shall apply...

  17. 30 CFR 905.822 - Special performance standards-Operations in alluvial valley floors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... alluvial valley floors. 905.822 Section 905.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE CALIFORNIA § 905.822 Special performance standards—Operations in alluvial valley floors. Part 822 of this chapter, Special Permanent Program Performance Standards—Operations in Alluvial Valley...

  18. 30 CFR 912.822 - Special performance standards-operations in alluvial valley floors.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... alluvial valley floors. 912.822 Section 912.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE IDAHO § 912.822 Special performance standards—operations in alluvial valley floors. Part 822 of this chapter, Special Permanent Program Performance Standards—Operations in Alluvial Valley...

  19. 30 CFR 912.822 - Special performance standards-operations in alluvial valley floors.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... alluvial valley floors. 912.822 Section 912.822 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STATE IDAHO § 912.822 Special performance standards—operations in alluvial valley floors. Part 822 of this chapter, Special Permanent Program Performance Standards—Operations in Alluvial Valley...

  20. MAP OF ECOREGIONS OF THE MISSISSIPPI ALLUVIAL PLAIN

    EPA Science Inventory

    The ecoregions of The Mississippi Alluvial Plain (73) have been identified, mapped, and described and provide a geographic structure for environmental resources research, assessment, monitoring, and management. This project is part of a larger effort by the U.S. EPA to create a ...

  1. HYDRAULIC ANALYSIS OF BASEFLOW AND BANK STORAGE IN ALLUVIAL STREAMS

    EPA Science Inventory

    This paper presents analytical solutions, which describe the effect of time-variable net recharge (net accretion to water table) and bank storage in alluvial aquifers on the sustenance of stream flows during storm and inter-storm events. The solutions relate the stream discharge,...

  2. Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 17. Geomorphology of the Red River Valley, Taos County, New Mexico, and Influence on Ground-Water Flow in the Shallow Alluvial Aquifer

    USGS Publications Warehouse

    Vincent, Kirk R.

    2008-01-01

    In April 2001, the U.S. Geological Survey (USGS) and the New Mexico Environment Department (NMED) began a cooperative study to infer the pre-mining ground-water chemistry at the Molycorp molybdenum mine site in the Red River Valley of north-central New Mexico. This report is one in a series of reports that can be used to determine pre-mining ground-water conditions at the mine site. Molycorp?s Questa molybdenum mine in the Red River Valley, northern New Mexico, is located near the margin of the Questa caldera in a highly mineralized region. The bedrock of the Taos Range surrounding the Red River is composed of Proterozoic rocks of various types, which are intruded and overlain by Oligocene volcanic rocks associated with the Questa caldera. Locally, these rocks were altered by hydrothermal activity. The alteration zones that contain sulfide minerals are particularly important because they constitute the commercial ore bodies of the region and, where exposed to weathering, form sites of rapid erosion referred to as alteration scars. Over the past thousand years, if not over the entire Holocene, erosion rates were spatially variable. Forested hillslopes eroded at about 0.04 millimeter per year, whereas alteration scars eroded at about 2.7 millimeters per year. The erosion rate of the alteration scars is unusually rapid for naturally occurring sites that have not been disturbed by humans. Watersheds containing large alteration scars delivered more sediment to the Red River Valley than the Red River could remove. Consequently, large debris fans, as much as 80 meters thick, developed within the valley. The geomorphology of the Red River Valley has had several large influences on the hydrology of the shallow alluvial aquifer, and those influences were in effect before the onset of mining within the watershed. Several reaches where alluvial ground water emerges to become Red River streamflow were observed by a tracer dilution study conducted in 2001. The aquifer narrows

  3. Fan Acoustic Issues in the NASA Space Flight Experience

    NASA Technical Reports Server (NTRS)

    Allen, Christopher S.; Goodman, Jerry

    2008-01-01

    Emphasis needs to be placed on choosing quiet fans compatible with systems design and specifications that control spec levels: a) Sound power; b) Choose quiet fan or plan to quiet it, early in program; c) Plan early verification that fan source allocations are met. Airborne noise: a) System design should function/play together with fans used (flow passages, restrictions, bends, expansions & contractions, and acoustics) vs. fan speed understood (nominal, worst case, & unplanned variances); b) Fan inlets treated, as required; c) Fan Outlets treated, as required; d) Ducted system inlets are outlets designed for acoustic compliance compatibility & designed so some late required modifications can be made without significant impacts. Structure Borne Noise: a) Structure borne noise dealt with as part of fan package or installation; b) Duct attachments and lines isolated. Case Radiated Noise: - Treatment added as much as possible to fan package (see example).

  4. Influence of provenance on detrital and diagenetic mineralogy of small tertiary fans in southwestern Montana

    SciTech Connect

    Olson, J.; Basu, A.

    1987-05-01

    In the North Boulder River basin in southwestern Montana, alluvial fans of the Renova (Oligocene-Miocene) and the Sixmile Creek (Miocene) Formations were deposited on the flanks of north-south-trending uplifts that also supplied the detritus. The Elkhorn Mountain volcanics (78 m.y.) overlying the Boulder batholith make up the western highlands, a small patch of Precambrian Belt Group rocks occur in the southwest and Paleozoic siliciclastic and carbonate rocks forming the eastern margin. The fan sediments thus allow adequate control for studying the influence of source rocks on detrital and diagenetic mineralogy. Modal analysis of 6228 grains in 31 thin sections shows a decrease of VRF away from the igneous sources (37% to 1% in a north-south transect; 37% to 7% in a west-east transect) along with an increase in quartz (8% to 24% and 3% to 13%) and plagioclase (2% to 16% and 2% to 10%); orthoclase abundance is low except in the southwest. Volcanic ash and glass shards are found in the younger sediments in the northern part of the basin. Their data show a positive correlation between the abundance of orthoclase and kaolinite (north-south transect); between SRF and carbonate cement (west-east transect) and between glass shards and smectite (both north-south and west-east transects). They infer that the diagenetic mineralogy of these sands was controlled essentially by the detrital particles, which were strongly controlled by source rocks in this area.

  5. Holocene sedimentation history of the major fan valleys of Monterey fan

    USGS Publications Warehouse

    Hess, G.R.; Normark, W.R.

    1976-01-01

    There are three major fan valleys on upper Monterey fan. Deep-tow geophysical profiles and 40 sediment cores provide the basis for evaluation of the sedimentation histories of these valleys. Monterey fan valley leads from Monterey canyon to a major suprafan and is bounded by levees that crest more than 400 m above the valley floor. The valley passes through a large z-bend or meander. Monterey East fan valley joins Monterey fan valley at the meander at about 150 m above the valley floor, and marks an earlier position of the lower Monterey fan valley. Ascension valley, a hanging contributary to the Monterey fan valley, appears to have once been the shoreward head of the lower part of the present Monterey fan valley. The relief of Monterey fan valley appears from deep-tow profiles to be erosional. The valley is floored with sand. Holocene turbidity currents do not overtop the levees 400 m above the valley floor, but do at times overflow and transport sand into Monterey East valley, producing a sandy floor. An 1100 m by 300 m dune field was observed on side scan sonar in Monterey East valley. Ascension fan valley was floored with sand during glacial intervals of lowered sea level, then was cut off from its sand source as sea level rose. A narrow (500 m), erosional, meandering channel was incised into the flat valley floor; the relief features otherwise appear depositional, with a hummocky topography perhaps produced in the manner of a braided riverbed. The sand is mantled by about 6 m of probable Holocene mud. Hummocky relief on the back side of the northwestern levees of both Ascension and Monterey valleys is characteristic of many turbidite valleys in the northeast Pacific. The hummocky topography is produced by dune-like features that migrate toward levee crests during growth. ?? 1976.

  6. Perceived Noise Analysis for Offset Jets Applied to Commercial Supersonic Aircraft

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.; Henderson, Brenda S.; Berton, Jeffrey J.; Seidel, Jonathan A.

    2016-01-01

    A systems analysis was performed with experimental jet noise data, engine/aircraft performance codes and aircraft noise prediction codes to assess takeoff noise levels and mission range for conceptual supersonic commercial aircraft. A parametric study was done to identify viable engine cycles that meet NASAs N+2 goals for noise and performance. Model scale data from offset jets was used as input to the aircraft noise prediction code to determine the expected sound levels for the lateral certification point where jet noise dominates over all other noise sources. The noise predictions were used to determine the optimal orientation of the offset nozzles to minimize the noise at the lateral microphone location. An alternative takeoff procedure called programmed lapse rate was evaluated for noise reduction benefits. Results show there are two types of engines that provide acceptable range performance; one is a standard mixed-flow turbofan with a single-stage fan, and the other is a three-stream variable-cycle engine with a multi-stage fan. The engine with a single-stage fan has a lower specific thrust and is 8 to 10 EPNdB quieter for takeoff. Offset nozzles reduce the noise directed toward the thicker side of the outer flow stream, but have less benefit as the core nozzle pressure ratio is reduced and the bypass-to-core area ratio increases. At the systems level for a three-engine N+2 aircraft with full throttle takeoff, there is a 1.4 EPNdB margin to Chapter 3 noise regulations predicted for the lateral certification point (assuming jet noise dominates). With a 10 reduction in thrust just after takeoff rotation, the margin increases to 5.5 EPNdB. Margins to Chapter 4 and Chapter 14 levels will depend on the cumulative split between the three certification points, but it appears that low specific thrust engines with a 10 reduction in thrust (programmed lapse rate) can come close to meeting Chapter 14 noise levels. Further noise reduction is possible with additional

  7. Impact resistance of composite fan blades

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Results are presented of a program to determine the impact resistance of composite fan blades subjected to foreign object damage (FOD) while operating under conditions simulating a short take-off and landing (STOL) engine at takeoff. The full-scale TF39 first-stage fan blade was chosen as the base design for the demonstration component since its configuration and operating tip speeds are similar to a typical STOL fan blade several composite configurations had already been designed and evaluated under previous programs. The first portion of the program was devoted toward fabricating and testing high impact resistant, aerodynamically acceptable composite blades which utilized only a single material system in any given blade. In order to increase the blade impact capability beyond this point, several mixed material (hybrid) designs were investigated using S-glass and Kevlar as well as boron and graphite fibers. These hybrid composite blades showed a marked improvement in resistance to bird impact over those blades made of a single composite material. The work conducted under this program has demonstrated substantial improvement in composite fan blades with respect to FOD resistance and has indicated that the hybrid design concept, which utilizes different types of fibers in various portions of a fan blade design depending on the particular requirements of the different areas and the characteristics of the different fibers involved, shows a significant improvement over those designs utilizing only one material system.

  8. Characterisation and modelling of washover fans

    USGS Publications Warehouse

    Donnelly, Chantal; Sallenger, Asbury H.

    2007-01-01

    Pre- and post-storm topography and aerial photography, collected in regions where new washover fans were formed, were studied to determine the extent of morphologic, vegetative and anthropogenic control on washover shape and extent. When overwash is funnelled through a gap in a dune ridge and then spreads laterally on the back barrier, decelerating and depositing sediment, it forms washover fans. Fans were shown to primarily occur at pre-existing gaps in the foredune. During overwash, these gaps, or overwash throats, widened and deepened. The shape and extent of the fan was shown to depend on not only the pre-storm topography, but also the existence of beach tracks, roads and other anthropogenic influences and vegetation. The cross-shore overwash profile change model by Larson et al. and Donnelly et al. was modified to include pre-storm throat widths and a lateral spreading angle estimated from the pre-storm topography as inputs and tested using cross-shore profiles through the fan centres. These new inputs make the model more generalised, such that the calibrated model is applicable to a wider range of cross-shore profiles.

  9. Survey of lift-fan aerodynamic technology

    NASA Technical Reports Server (NTRS)

    Hickey, David H.; Kirk, Jerry V.

    1993-01-01

    Representatives of NASA Ames Research Center asked that a summary of technology appropriate for lift-fan powered short takeoff/vertical landing (STOVL) aircraft be prepared so that new programs could more easily benefit from past research efforts. This paper represents one of six prepared for that purpose. The authors have conducted or supervised the conduct of research on lift-fan powered STOVL designs and some of their important components for decades. This paper will first address aerodynamic modeling requirements for experimental programs to assure realistic, trustworthy results. It will next summarize the results or efforts to develop satisfactory specialized STOVL components such as inlets and flow deflectors. It will also discuss problems with operation near the ground, aerodynamics while under lift-fan power, and aerodynamic prediction techniques. Finally, results of studies to reduce lift-fan noise will be presented. The paper will emphasize results from large scale experiments, where available, for reasons that will be brought out in the discussion. Some work with lift-engine powered STOVL aircraft is also applicable to lift-fan technology and will be presented herein. Small-scale data will be used where necessary to fill gaps.

  10. Offset compensation for A/D converters

    NASA Technical Reports Server (NTRS)

    Brokl, S. S.; Hurd, W. J.

    1979-01-01

    Analog-to-digital (A/D) converter eliminates dc offset in final digitized signal as well as in analog input by using digital feedback for compensation. Circuit could prove useful in data processing applications in which analog-format data are entered at high rates, as in point-of-sale data input systems.

  11. 45 CFR 608.3 - Administrative offset.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Welfare Regulations Relating to Public Welfare (Continued) NATIONAL SCIENCE FOUNDATION CLAIMS COLLECTION... 4 CFR 102.3(a). Before employing administrative offset, NSF will comply with the notice, hearing, review, or other procedural requirements of 31 U.S.C. 3716(a) and 4 CFR 102.3(b) and (c)....

  12. 20 CFR 627.708 - Offset process.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Offset process. 627.708 Section 627.708 Employees' Benefits EMPLOYMENT AND TRAINING ADMINISTRATION, DEPARTMENT OF LABOR GENERAL PROVISIONS GOVERNING... process. (a) In accordance with section 164(d) of the Act, the primary sanction for misexpenditure of...

  13. 20 CFR 627.708 - Offset process.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 20 Employees' Benefits 3 2012-04-01 2012-04-01 false Offset process. 627.708 Section 627.708 Employees' Benefits EMPLOYMENT AND TRAINING ADMINISTRATION, DEPARTMENT OF LABOR GENERAL PROVISIONS GOVERNING... process. (a) In accordance with section 164(d) of the Act, the primary sanction for misexpenditure of...

  14. 45 CFR 608.3 - Administrative offset.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Welfare Regulations Relating to Public Welfare (Continued) NATIONAL SCIENCE FOUNDATION CLAIMS COLLECTION... 4 CFR 102.3(a). Before employing administrative offset, NSF will comply with the notice, hearing, review, or other procedural requirements of 31 U.S.C. 3716(a) and 4 CFR 102.3(b) and (c)....

  15. 45 CFR 608.3 - Administrative offset.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Welfare Regulations Relating to Public Welfare (Continued) NATIONAL SCIENCE FOUNDATION CLAIMS COLLECTION... 4 CFR 102.3(a). Before employing administrative offset, NSF will comply with the notice, hearing, review, or other procedural requirements of 31 U.S.C. 3716(a) and 4 CFR 102.3(b) and (c)....

  16. Multiple bit differential detection of offset QPSK

    NASA Technical Reports Server (NTRS)

    Simon, M.

    2003-01-01

    Analogous to multiple symbol differential detection of quadrature phase-shift-keying, a multiple bit differential detection scheme is described for offset QPSK that also exhibits continuous improvement in performance with increasing observation interval. Being derived from maximum-likelihood (ML) considerations, the proposed scheme is purported to be the most power efficient scheme for such a modulation and detection method.

  17. 10. EXTERIOR VIEW OF STONE RETAINING WALL, AIRWAY, BALTIMORE FAN ...

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

    10. EXTERIOR VIEW OF STONE RETAINING WALL, AIRWAY, BALTIMORE FAN HOUSE AND HILLMAN FAN HOUSE LOOKING EAST The stone retaining wall encloses a pit which may have been the original site of the Hillman Fan House steam engine. The concrete foundations in the left foreground are more recent (c. 1930) additions which may be supports for a porch or stairway. The sloping airshaft, in the middle ground, connected the Baltimore shaft to the New Fan House (not shown) and Hillman Fan House in the background. The Hillman engine house is on the left. - Dorrance Colliery Fan Complex, South side of Susquehanna River at Route 115 & Riechard Street, Wilkes-Barre, Luzerne County, PA

  18. 20. INTERIOR VIEW OF NO. 4 AIRWAY AND NEW FAN ...

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

    20. INTERIOR VIEW OF NO. 4 AIRWAY AND NEW FAN HOUSE LOOKING SOUTH The No. 4 (Baltimore) shaft would be directly behind the viewer. The ventilating doors leading to the Hillman Fan House are to the left. The floor of the airway, once covered with concrete, has deteriorated. In the background is the metal disk fan, part of the Duplex Conoidal Fan installed in the New Fan House. The ladder provides access to the shaft bearings. - Dorrance Colliery Fan Complex, South side of Susquehanna River at Route 115 & Riechard Street, Wilkes-Barre, Luzerne County, PA

  19. 22. INTERIOR VIEW OF NEW FAN HOUSE UPSHAFT CHIMNEY LOOKING ...

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

    22. INTERIOR VIEW OF NEW FAN HOUSE UPSHAFT CHIMNEY LOOKING WEST The Duplex Conoidal Fan is a single entry disk fan (see PA 61-21 and PA 61-22) which drew air from the No. 4 (Baltimore) shaft up the air-way through the cone, seen on the right, into the centrifugal fan, pictured here. The curved metal blades forced the air from the center of the fan to the tips of the blades and out the sheet metal exhaust chimney. - Dorrance Colliery Fan Complex, South side of Susquehanna River at Route 115 & Riechard Street, Wilkes-Barre, Luzerne County, PA

  20. Design Guidelines for Quiet Fans and Pumps for Space Vehicles

    NASA Technical Reports Server (NTRS)

    Lovell, John S.; Magliozzi, Bernard

    2008-01-01

    This document presents guidelines for the design of quiet fans and pumps of the class used on space vehicles. A simple procedure is presented for the prediction of fan noise over the meaningful frequency spectrum. A section also presents general design criteria for axial flow fans, squirrel cage fans, centrifugal fans, and centrifugal pumps. The basis for this report is an experimental program conducted by Hamilton Standard under NASA Contract NAS 9-12457. The derivations of the noise predicting methods used in this document are explained in Hamilton Standard Report SVHSER 6183, "Fan and Pump Noise Control," dated May 1973 (6).