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1
Rachal, David M., and Daniel P. Dugas. "Historical Dune Pattern Dynamics: White Sands Dune Field, New Mexico." Physical Geography 30, no. 1 (2009): 64–78. http://dx.doi.org/10.2747/0272-3646.30.1.64.
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Zhao, Feifei, Benjamin T. Cardenas, and Wonsuck Kim. "Controls of aeolian dune height on cross-strata architecture: White Sands Dune Field, New Mexico, U.S.A." Journal of Sedimentary Research 91, no. 5 (2021): 495–506. http://dx.doi.org/10.2110/jsr.2020.138.
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ABSTRACT The stratal types composing aeolian dunes preserve a record of the transport and sorting of grains and are categorized into: 1) grainflow strata, 2) grainfall laminae, and 3) wind-ripple laminae. The arrangement of these deposits in the cross beds of a formative dune is largely unexplored. Here, field results from White Sands Dune Field, New Mexico, USA, are used to test the hypothesis that dune height controls the arrangement, abundance, and geometry of cross-stratification types. Grainflow thicknesses and deposit widths were measured on wind-scoured stoss-side exposures of seven crescentic dunes with heights ranging from 1.7 m to 11.2 m. Dozens of grainflow thickness measurements were taken along transverse-oriented strata normal to the crest on each dune. The results show that grainflow thickness averages from 1 cm to 4 cm. These data show a positive trend between mean grainflow thickness and dune height but only for the grainflow thicknesses measured at the bases of dunes. The tallest dune (11.2 m) produced many thick grainflow packages of 10 cm to 30 cm in which individual grainflow strata were indistinguishable from each other. This amalgamation was also found to be characteristic of larger dunes—the product of a lack of grainfall deposits separating individual grainflows. These differences in grainflow strata at the bases of dune lee slopes are linked to the temporary storage of sediment along the upper parts of lee slopes. In taller dunes with longer lee slopes, amalgamated grainflows which require multiple avalanche events and take longer time to reach the base transport temporarily stored sediment at upper parts of the slope. This allows time for wind ripples to rework accumulations near the base, where grainfall deposition is also limited. Shorter dunes lack this temporary storage mechanism, as individual grainflows can move across the entire lee slope in a single event, and grainfall accumulates across the entire lee slope. These stratigraphic measurements and process-based understanding will be useful in estimating original dune height in ancient cross-strata and will lead to a better interpretation of aeolian stratigraphy.
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Kocurek, Gary, Mary Carr, Ryan Ewing, Karen G. Havholm, Y. C. Nagar, and A. K. Singhvi. "White Sands Dune Field, New Mexico: Age, dune dynamics and recent accumulations." Sedimentary Geology 197, no. 3-4 (2007): 313–31. http://dx.doi.org/10.1016/j.sedgeo.2006.10.006.
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Brothers, Sarah C., Gary Kocurek, Thomas C. Brothers, and Ilya V. Buynevich. "Stratigraphic architecture resulting from dune interactions: White Sands Dune Field, New Mexico." Sedimentology 64, no. 3 (2016): 686–713. http://dx.doi.org/10.1111/sed.12320.
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Pedersen, Anine, Gary Kocurek, David Mohrig, and Virginia Smith. "Dune deformation in a multi-directional wind regime: White Sands Dune Field, New Mexico." Earth Surface Processes and Landforms 40, no. 7 (2015): 925–41. http://dx.doi.org/10.1002/esp.3700.
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Dong, Pinliang, Jisheng Xia, Ruofei Zhong, Zhifang Zhao, and Shucheng Tan. "A New Method for Automated Measurement of Sand Dune Migration Based on Multi-Temporal LiDAR-Derived Digital Elevation Models." Remote Sensing 13, no. 16 (2021): 3084. http://dx.doi.org/10.3390/rs13163084.
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While remote sensing methods have long been used for coastal and desert sand dune studies, few methods have been developed for the automated measurement of dune migration in large dune fields. To overcome a major limitation of an existing method named “pairs of source and target points (PSTP)”, this paper proposes a toe line tracking (TLT) method for the automated measurement of dune migration rate and direction using multi-temporal digital elevation models (DEM) derived from light detection and ranging (LiDAR) data. Based on a few simple parameters, the TLT method automatically extracts the base level of a dune field and toe lines of individual dunes. The toe line polygons derived from two DEMs are processed using logical operators and other spatial analysis methods implemented in the Python programming language in a geographic information system. By generating thousands of random sampling points along source toe lines, dune migration distances and directions are calculated and saved with the sampling point feature class. The application of the TLT method was demonstrated using multi-temporal LiDAR-derived DEMs for a 9 km by 2.4 km area in the White Sands Dune Field in New Mexico (USA). Dune migration distances and directions for three periods (24 January 2009–26 September 2009, 26 September 2009–6 June 2010, and 24 January 2009–6 January 2010) were calculated. Sensitivity analyses were carried out using different window sizes and toe heights. The results suggest that both PSTP and TLT produce similar sand dune migration rates and directions, but TLT is a more generic method that works for dunes with or without slipfaces that reach the angle of repose.
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Baitis, Elke, Gary Kocurek, Virginia Smith, David Mohrig, Ryan C. Ewing, and A. P. B. Peyret. "Definition and origin of the dune-field pattern at White Sands, New Mexico." Aeolian Research 15 (December 2014): 269–87. http://dx.doi.org/10.1016/j.aeolia.2014.06.004.
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Pelletier, Jon D. "Controls on the large-scale spatial variations of dune field properties in the barchanoid portion of White Sands dune field, New Mexico." Journal of Geophysical Research: Earth Surface 120, no. 3 (2015): 453–73. http://dx.doi.org/10.1002/2014jf003314.
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Langford, Richard P. "The Holocene history of the White Sands dune field and influences on eolian deflation and playa lakes." Quaternary International 104, no. 1 (2003): 31–39. http://dx.doi.org/10.1016/s1040-6182(02)00133-7.
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Phillips, J. D., R. C. Ewing, R. Bowling, et al. "Low-angle eolian deposits formed by protodune migration, and insights into slipface development at White Sands Dune Field, New Mexico." Aeolian Research 36 (February 2019): 9–26. http://dx.doi.org/10.1016/j.aeolia.2018.10.004.
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Pelletier, Jon D., and Douglas J. Jerolmack. "Multiscale bed form interactions and their implications for the abruptness and stability of the downwind dune field margin at White Sands, New Mexico, USA." Journal of Geophysical Research: Earth Surface 119, no. 11 (2014): 2396–411. http://dx.doi.org/10.1002/2014jf003210.
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Langford, Richard P., Thomas E. Gill, and Slade B. Jones. "Transport and mixing of eolian sand from local sources resulting in variations in grain size in a gypsum dune field, White Sands, New Mexico, USA." Sedimentary Geology 333 (March 2016): 184–97. http://dx.doi.org/10.1016/j.sedgeo.2015.12.010.
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Rodríguez-Santalla, Inmaculada, David Gomez-Ortiz, Tomás Martín-Crespo, et al. "Study and Evolution of the Dune Field of La Banya Spit in Ebro Delta (Spain) Using LiDAR Data and GPR." Remote Sensing 13, no. 4 (2021): 802. http://dx.doi.org/10.3390/rs13040802.
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La Banya spit, located at the south of the River Ebro Delta, is a sandy formation, developed by annexation of bars forming successive beach ridges, which are oriented and modeled by the eastern and southern waves. The initial ridges run parallel to the coastline, and above them small dunes developed, the crests of which are oriented by dominant winds, forming foredune ridges and barchans. This study attempted to test a number of techniques in order to understand the dune dynamic on this coastal spit between 2004 and 2012: LiDAR data were used to reconstruct changes to the surface and volume of the barchan dunes and foredunes; ground-penetrating radar was applied to obtain an image of their internal structure, which would help to understand their recent evolution. GPS data taken on the field, together with application of GIS techniques, made possible the combination of results and their comparison. The results showed a different trend between the barchan dunes and the foredunes. While the barchan dunes increased in area and volume between 2004 and 2012, the foredunes lost thickness. This was also reflected in the radargrams: the barchan dunes showed reflectors related to the growth of the foresets while those associated with foredunes presented truncations associated with storm events. However, the global balance of dune occupation for the period 2004–2012 was positive.
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Glennie, K. W. "Exploration activities in the Netherlands and North-West Europe since Groningen." Netherlands Journal of Geosciences - Geologie en Mijnbouw 80, no. 1 (2001): 33–52. http://dx.doi.org/10.1017/s0016774600022150.
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AbstractOnce the great size of the Groningen Field was fully realized late in 1963, exploration in the southern North Sea was a natural development as the reservoir bedding dipped westward. The origin of that bedding was not certain, one possibility, dune sands, led immediately to a program of desert studies.Licensing regulations for Netherlands waters were not finalized until 1967, offshore exploration beginning with the award of First Round licenses in March 1968. In the UK area, the Continental Shelf Act came into force in May 1964, paving the way for offshore seismic, the first well being spudded late in that year. The first two wells were drilled on the large Mid North Sea High; both were dry, the targeted Rotliegend sandstones being absent. Then followed a series of Rotliegend gas discoveries, large and small, west of Groningen, so that by the time exploration began in Netherlands waters the UK monopoly market was saturated and exploration companies were already looking north for other targets including possible oil.The Rotliegend was targeted in the earliest wells of the UK central North Sea even though there had already been a series of intriguing oil shows in Chalk and Paleocene reservoirs in Danish and Norwegian waters. These were followed early in 1968 by the discovery of gas in Paleocene turbidites at Cod, near the UK-Norway median line. The first major discovery was Ekofisk in 1969, a billion-barrel Maastrichtian to Danian Chalk field. Forties (1970) confirmed the potential of the Paleocene sands as another billion barrel find, while the small Auk Field extended the oil-bearing stratigraphy down to the Permian. In 1971, discovery of the billion-barrel Brent field in a rotated fault block started a virtual ‘stampede’ to prove-up acreage awarded in the UK Fourth Round (1972) before the 50% statutory relinquishment became effective in 1978.Although the geology of much of the North Sea was reasonably well known by the end of the 1970s, new oil and gas reservoirs continued to be discovered during the next two decades. Exploration proved the Atlantic coast of Norway to be a gas and gas-condensate area. The stratigraphiC range of reservoirs extended down to the Carboniferous (gas) and Devonian (oil), while in the past decade, forays into the UK Atlantic Margin and offshore Ireland met with mixed success. During this hectic activity, Netherlands exploration confirmed a range of hydrocarbon-bearing reservoirs; Jurassic oil in the southern Central Graben, Jurassic-Cretaceous oil derived from a Liassic source mainly onshore and, of course, more gas from the Rotliegend. German exploration had mixed fortunes, with no commercial gas in the North Sea and high nitrogen content in Rotliegend gas in the east. Similarly in Poland, where several small Zechstein oil fields were discovered, the Rotliegend gas was nitrogen rich. The discovery of some 100 billion barrels of oil and oil equivalent beneath the waters of the North Sea since 1964 led to an enormous increase in geological knowledge, making it probably the best known area of comparable size in the World. The area had a varied history over the past 500 million years: platete-tonic movement, faulting, igneous activity, climatic change, and deposition in a variety of continental and marine environments, leading to complex geometrical relationships between source rock, reservoir and seal, and to the reasons for diagenetic changes in the quality of the reservoir sequences. Led by increasingly sophisticated seismic, drilling and wireline logging, and coupled with academic research, the North Sea developed into a giant geological laboratory where ideas were tested and extended industry-wide.
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Schenk, Christopher J., and Steven G. Fryberger. "Early diagenesis of eolian dune and interdune sands at White Sands, New Mexico." Sedimentary Geology 55, no. 1-2 (1988): 109–20. http://dx.doi.org/10.1016/0037-0738(88)90092-9.
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Stokes, Stephen, and David R. Gaylord. "Optical Dating of Holocene Dune Sands in the Ferris Dune Field, Wyoming." Quaternary Research 39, no. 3 (1993): 274–81. http://dx.doi.org/10.1006/qres.1993.1034.
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AbstractOptical dating of late Quaternary quartz dune sands from the Clear Creek portion of Ferris dune field, Wyoming, demonstrates the considerable potential of the technique as a chronostratigraphic tool. A sequence of radiocarbon-dated Holocene interdune strata permit optical dating of the intercalated dune sand to be tested; the concordance is good. The optical dates for the aeolian deposits not datable by radiocarbon suggest that aeolian sedimentation at Clear Creek peaked during two relatively short phases at ca. 8500 and 4000 yr B.P. The dates indicate that aeolian accumulation maxima (at least in the Clear Creek area) may not be synchronous with previously defined phases of marked aridity.
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Szynkiewicz, Anna, and Janice L. Bishop. "Assessment of Sulfate Sources under Cold Conditions as a Geochemical Proxy for the Origin of Sulfates in the Circumpolar Dunes on Mars." Minerals 11, no. 5 (2021): 507. http://dx.doi.org/10.3390/min11050507.
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Determining aqueous sulfate sources in terrestrial cold environments can provide an insight into the surface hydrological conditions and sulfur cycle on Mars. In this study, we analyzed sulfur and oxygen isotope compositions of secondary sulfate salts (e.g., gypsum, thenardite) in the surficial sediments and soils of the McMurdo Dry Valleys (MDV), Antarctica to determine contributions of sulfate from bedrock chemical weathering and atmospheric deposition under persistent dry polar conditions. The sulfate showed wider variation of δ34S (+15.8‰ to +32.5‰) compared to smaller ranges of δ18O (−8.9‰ to −4.1‰). In contrast, the δ34S of bedrock sulfide showed significantly lower and consistent values across the studied area (−0.6‰ to +3.3‰). Based on the δ34S trends, sulfide weathering may contribute up to 20–50% of secondary sulfate salts in the MDV. While the remaining 50–80% of sulfate inputs may originate from atmospheric deposition (e.g., sea aerosols, dimethulsulfide oxidation), the subglacial brines derived by relicts of seawater and/or lake/pond water influenced by microbial sulfate reduction could also be important sulfate endmembers particularly in the Antarctic lowland thaw zones. Additional field observations of frost, ponding water, and thin gypsum crusts on the terrestrial gypsum dunes at White Sands supports reactivity of gypsum on the surface of these dunes during cold winter conditions. Combined with our improved geochemical model of the sulfur cycle for cold Antarctic settings, we propose that transient liquid water or frost was available in near-surface environments at the time of gypsum formation in the north polar region on Mars. Ice and/or water interaction with basaltic sand of the basal unit (paleo-erg) would have enhanced leaching of sulfate from both sulfide oxidation and atmospheric deposition and resulted in formation of secondary gypsum salts.
18
Muhs, Daniel R., Josh Been, Shannon A. Mahan, et al. "Holocene eolian activity in the Minot dune field, North Dakota." Canadian Journal of Earth Sciences 34, no. 11 (1997): 1442–59. http://dx.doi.org/10.1139/e17-117.
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Stabilized eolian sand is common over much of the Great Plains region of the United States and Canada, including a subhumid area of ~1500 km2 near Minot, North Dakota. Eolian landforms consist of sand sheets and northwest-trending parabolic dunes. Dunes and sand sheets in the Minot field are presently stabilized by a cover of prairie grasses or oak woodland. Stratigraphic studies and accelerator mass spectrometry radiocarbon dating of paleosols indicate at least two periods of eolian sand movement in the late Holocene. Pedologic data suggest that all of the dune field has experienced late Holocene dune activity, though not all parts of the dune field may have been active simultaneously. Similar immobile element (Ti, Zr, La, Ce) concentrations support the interpretation that eolian sands are derived from local glaciofluvial and glaciolacustrine sediments. However, glaciolacustrine and glaciofluvial source sediments have high Ca concentrations from carbonate minerals, whereas dune sands are depleted in Ca. Because noneolian-derived soils in the area are calcareous, these data indicate that the Minot dune field may have had extended periods of activity in the Holocene, such that eolian abrasion removed soft carbonate minerals. The southwest-facing parts of some presently stabilized dunes were active during the 1930s drought, but were revegetated during the wetter years of the 1940s. These observations indicate that severe droughts accompanied by high temperatures are the most likely cause of Holocene eolian activity.
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Root, J. Jeffrey, Eric E. Jorgensen, and Stephen Demarais. "Soil Texture Uses by Sympatric Kangaroo Rats on the White Sands Dune Complex." Southwestern Naturalist 45, no. 4 (2000): 533. http://dx.doi.org/10.2307/3672605.
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Lu, Huayu, Yali Zhou, Weiguo Liu, and Joseph Mason. "Organic stable carbon isotopic composition reveals late Quaternary vegetation changes in the dune fields of northern China." Quaternary Research 77, no. 3 (2012): 433–44. http://dx.doi.org/10.1016/j.yqres.2012.01.009.
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Vegetation changes during the late Quaternary in the dune fields of northern China are not well understood. We investigated organic carbon stable isotopic composition of surface soils, related mainly to the ratio of C3 and C4 plants, across a range of arid to subhumid climates in this region. Isotopic composition is weakly related to both temperature and moisture (multiple R2 = 0.53), with the highest δ13C (greatest C4 abundance) in the warm, subhumid Horqin dune field. In late Quaternary, eolian stratigraphic sections of the Mu Us and Horqin dune fields, but not in the much colder Otindag dune field, δ13C is higher in organic carbon from paleosols than in eolian sands. This contrast, most evident for paleosols recording a major early to middle Holocene phase of dune stabilization, is interpreted as evidence for expansion of C4 plants due to increased effective moisture, high temperature because of high insolation, and decreased disturbance related to eolian erosion and deposition.
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Alhozaimy, A., M. S. Jaafar, A. Al-Negheimish, et al. "Properties of high strength concrete using white and dune sands under normal and autoclaved curing." Construction and Building Materials 27, no. 1 (2012): 218–22. http://dx.doi.org/10.1016/j.conbuildmat.2011.07.057.
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Miles, A., M. Allen, L. Fairweather, J. Hilton, H. Sloan, and P. Zapico-Palmero. "The Tolmount Field, Block 42/28d, UK North Sea." Geological Society, London, Memoirs 52, no. 1 (2020): 262–72. http://dx.doi.org/10.1144/m52-2018-16.
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AbstractThe Tolmount Field is a lean gas condensate accumulation located in Block 42/28d of the UK Southern North Sea. The field was discovered in 2011 by well 42/28d-12, which encountered good-quality gas-bearing reservoir sandstones of the Permian Leman Sandstone Formation. The discovery was appraised in 2013 by wells 42/28d-13 and 42/28d-13Z, which logged the gas–water contact on the eastern flank of the field. The Tolmount structure is a four-way, dip-closed, faulted anticline, orientated NW to SE. The reservoir comprises mixed aeolian dune and fluvial sheetflood facies deposited within an arid continental basin. Dune sands display the best reservoir properties with porosities around 22% and permeabilities exceeding 100 mD. Only minor diagenetic alteration has occurred, primarily in the form of grain-coating illite. Superior reservoir quality is observed at Tolmount compared to adjacent areas, due to the preservation of dune facies, a hypothesized early gas emplacement and a relatively benign burial history. Current mapped gas initially-in-place estimates for the field are between 450 bcf and 800 bcf, with an estimated recovery factor between 70 and 90%. An initial four-well development is planned, with first gas expected in 2020.
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Hillier, A. P. "The Leman Field, Blocks 49/26, 49/27, 49/28, 53/1, 53/2, UK North Sea." Geological Society, London, Memoirs 20, no. 1 (2003): 761–70. http://dx.doi.org/10.1144/gsl.mem.2003.020.01.63.
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AbstractDiscovered in 1966 and starting production in 1968, Leman was the second gas field to come into production in the UK sector of the North Sea and is still producing gas today. It is classified as a giant field with an estimated initial gas-in-place of 397 BCM of gas in the aeolian dune sands of the Rotliegend Group. The field extends over five blocks and is being developed by two licence groups with Shell and Amoco (now BP Amoco) being the operators
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Hillier, A. P., and B. P. J. Williams. "The Leman Field, Blocks 49/26, 49/27, 49/28, 53/1, 53/2, UK North Sea." Geological Society, London, Memoirs 14, no. 1 (1991): 451–58. http://dx.doi.org/10.1144/gsl.mem.1991.014.01.56.
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AbstractDiscovered in 1966 and starting production in 1968, Leman was the second gas field to come into production in the UK sector of the North Sea. It is classified as a giant field with an estimated ultimate recovery of 11 500 BCF of gas in the aeolian dune sands of the Rotliegend Group. The field extends over five blocks and is being developed by two groups with Shell and Amoco being the operators. Despite being such an old field development drilling is still ongoing in the field with the less permeable northwest area currently being developed.
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Attar, S., and S. Samuel Li. "A simplified approach to computing flow and bedload along gravel dune-like bedforms." Canadian Journal of Civil Engineering 42, no. 6 (2015): 367–76. http://dx.doi.org/10.1139/cjce-2014-0255.
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River dunes are important bedforms. Problems associated with the development and evolution of dune bedforms include increased flood risks, channel erosion, and damage to fish habitats. The purpose of this paper is to investigate the near-bed flow structure and bedload transport along gavel dune-like bedforms. The velocity field is computed using a relatively simple multi-layer hydrodynamic model, with a parameterization of flow separation in the leeside of dunes. The computation is of high efficiency and avoids uncertainties caused by flow separation. Fractional transport rates for a sediment mixture of sands and gravel are calculated using surface-based techniques. The computed flow velocities and bed shear stresses are in good comparison with acoustic Doppler velocimeter measurements. Bedload transport is shown to increase non-linearly with distance toward the dune crest and reach the maximum at the crest. This implies that dune-length averaged bed shear stress is not suitable for bedload calculations. At low discharges, the bed shear stress is the limiting factor, resulting in insignificant bedload. At high discharges when the bed shear stress exceeds a threshold, the effect of sediment-grain hiding and sediment-size availability are important for bedload calculations. The discharge–transport relationship is highly non-linear. This paper has demonstrated selective transport and potential dune surface coarsening. The simplified modelling approach has a good potential for application to field conditions.
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Hussein, Mohammed L. "Sedimentological Properties of the Sand Dunes and Valley Sediments in Al-Muthanna, Southern Iraq." Iraqi Geological Journal 54, no. 1F (2021): 69–84. http://dx.doi.org/10.46717/igj.54.1f.7ms-2021-06-27.
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Sedimentological properties of the dunes and valley terrigenous sediments in Al-Muthanna Governorate, southern Iraq were carried out. Ten samples were collected, where five samples from both sand dunes, and valley sediments. Grain size analysis revealed that sand, silt and clay fractions are the constituents of these sediments. Sand fractions predominant in the dunes and the texture is classified as silty sand, whereas clay fractions dominate in the valley sediments, with sandy clay texture. The mineralogy is determined by X-ray diffraction, which revealed that quartz is the main mineral in both study areas, followed by calcite, feldspars in lesser amount and evaporates (gypsum) in minor component of the light minerals. Petrographically, monocrystalline quartz dominates over polycrystalline quartz in both areas. Rock fragments in the valley sediments are higher than in the sand dunes, which are comprised of carbonate, chert, igneous, metamorphic, evaporate, and mudstone rock fragments. Feldspars are approximately similar in the study areas and comprised mainly alkali feldspar (potash feldspar) and plagioclase. Petrogenically, the sand dunes occupy the quartzose-recycled field, while the valley sediments fall in transitional recycled fields represented recycled orogeny.
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Chen, Fahu, Guoqiang Li, Hui Zhao, et al. "Landscape evolution of the Ulan Buh Desert in northern China during the late Quaternary." Quaternary Research 81, no. 3 (2014): 476–87. http://dx.doi.org/10.1016/j.yqres.2013.08.005.
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AbstractThe evolution of arid environments in northern China was a major environmental change during the Quaternary. Here we present the dating and environmental proxy results from a 35 m long core (A-WL10ZK-1) collected from the Ulan Buh Desert (UBD), along with supplemental data from four other cores. The UBD is one of the main desert dune fields in China and our results indicate the UBD has undergone complex evolution during the late Quaternary. Most of the present UBD was covered by a Jilantai-Hetao Mega-paleolake lasting until ~ 90 ka ago. A sandy desert environment prevailed throughout the UBD during the last glacial period and early Holocene. A wetland environment characterized by the formation of numerous interdunal ponds in the northern UBD occurred at ~ 8–7 ka, although a dune field persisted in the southern UBD. The modern UBD landscape formed after these wetlands dried up. During the last 2000 years, eolian sand from the Badain Jaran Desert has invaded the northern UBD, while farming and overgrazing resulted in the formation of the eastern UBD. We suggest that the formation of UBD landforms is related to the disintegration of the megalake Jilantai-Hetao and to summer monsoon changes during the last glaciation and Holocene.
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Fieller, N. R. J., E. C. Flenley, D. D. Gilbertson, and C. O. Hunt. "The Description and Classification of Grain Size Data from Ancient and Modern Shoreline Sands at Lepcis Magna using Log Skew Laplace Distributions." Libyan Studies 21 (1990): 49–59. http://dx.doi.org/10.1017/s0263718900001461.
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AbstractThe description and analysis of particle size distributions using log skew Laplace distributions is a new technique designed to overcome various mathematical and computational problems associated with other approaches. This paper presents an application of the method. In particular, it describes fitting log skew Laplace distributions to modern and ancient shoreline sands from Lepcis Magna (near Horns), Tripolitania, with the purpose of discriminating between modern environments and so classifying the ancient samples. Satisfactory discrimination was not always achieved between some of the modern ‘calibration’ shoreline sand samples of known provenance — possibly as a result of the presence of multimodal distributions. One layer in the harbour-infill sequence, previously of unknown provenance, was shown to have collected at, or close to, an ancient shoreline which developed within the ancient harbour. The majority of the ‘ancient’ samples of unknown depositional environments which were excavated from exposures in the Romano-Libyan harbour-infill sands, were shown by this analysis to be of neither beach nor aeolian origin. This conclusion supports field observations which suggested that the greater part of the harbour-infill sequence represented reworked dune palaeosols, developing dune soils and fluvial and lagoonal facies.
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Bubenzer, Olaf, Nabil S. Embabi, and Mahmoud M. Ashour. "Sand Seas and Dune Fields of Egypt." Geosciences 10, no. 3 (2020): 101. http://dx.doi.org/10.3390/geosciences10030101.
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The article reviews the state of knowledge about distribution, sizes, dynamics, and ages of all sand seas (N = 6) and dune fields (N = 10) in Egypt (1,001,450 km2). However, chronological data (Optically Stimulated Luminescence, Thermoluminescence), used in the INQUA (International Union for Quaternary Research) dune database, only exists from three of the five sand seas located in the Western Desert of Egypt. The North Sinai Sand Sea and four of the ten dune fields are located near the Nile Valley, the delta or the coast and therefore changed drastically due to land reclamation during the last decades. Here, but also in the oases, their sands pose a risk for settlements and farmland. Our comprehensive investigations of satellite images and our field measurements show that nearly all terrestrial dune forms can be observed in Egypt. Longitudinal dunes and barchans are dominant. Sand seas cover about 23.8% (with an average sand coverage of 74.8%), dune fields about 4.4% (with an average sand coverage of 31.7%) of its territory. For the Great Sand Sea and the Farafra Sand Sea, situated in the central and northern part of the Western Desert, a Late Glacial transformation by strong westerlies was found, but not for the Selima Sand Sea, situated in the south of Egypt. Regarding the sparse chronological data up to now, for a reasonable estimation of future sand mobility in the course of global climate change, further data are essential. Finally, further studies concerning sand mobility, local wind systems, and land use are needed.
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Fares, S., S. Mereu, G. Scarascia Mugnozza, et al. "The ACCENT-VOCBAS field campaign on biosphere-atmosphere interactions in a Mediterranean ecosystem of Castelporziano (Rome): site characteristics, climatic and meteorological conditions, and eco-physiology of vegetation." Biogeosciences 6, no. 6 (2009): 1043–58. http://dx.doi.org/10.5194/bg-6-1043-2009.
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Abstract. Biosphere-atmosphere interactions were investigated on a sandy dune Mediterranean ecosystem in a field campaign held in 2007 within the frame of the European Projects ACCENT and VOCBAS. The campaign was carried out in the Presidential estate of Castelporziano, a peri-urban park close to Rome. Former campaigns (e.g. BEMA) performed in Castelporziano investigated the emission of biogenic volatile organic compounds (BVOC). These campaigns focused on pseudosteppe and evergreen oak groves whereas the contribution of the largely biodiverse dune vegetation, a prominent component of the Mediterranean ecosystem, was overlooked. While specific aspects of the campaign will be discussed in companion papers, the general climatic and physiological aspects are presented here, together with information regarding BVOC emission from the most common plant species of the dune ecosystem. During the campaign regular air movements were observed, dominated by moderate nocturnal land breeze and diurnal sea breeze. A regular daily increase of ozone concentration in the air was also observed, but daily peaks of ozone were lower than those measured in summer on the same site. The site was ideal as a natural photochemical reactor to observe reaction, transport and deposition processes occurring in the Mediterranean basin, since the sea-land breeze circulation allowed a strong mixing between biogenic and anthropogenic emissions and secondary pollutants. Measurements were run in May, when plant physiological conditions were optimal, in absence of severe drought and heat stress. Foliar rates of photosynthesis and transpiration were as high as generally recorded in unstressed Mediterranean sclerophyllous plants. Most of the plant species emitted high level of monoterpenes, despite measurements being made in a period in which emissions of volatile isoprenoids could be restrained by developmental and environmental factors, such as leaf age and relatively low air temperature. Emission of isoprene was generally low. Accounting for the high monoterpene spring emission of the dune ecosystem may be important to correct algorithms at regional and ecosystem levels, and to interpret measurements of fluxes of volatile isoprenoids and secondary pollutants.
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Osbon, R. A., O. C. Werngren, A. Kyei, D. Manley, and J. Six. "The Gawain Field, Blocks 49/24, 49/29a, UK North Sea." Geological Society, London, Memoirs 20, no. 1 (2003): 713–22. http://dx.doi.org/10.1144/gsl.mem.2003.020.01.58.
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AbstractThe Gawain Field is located on the Inde shelf in the Southern North Sea, 85 km NE of the Norfolk coast. Gawain was discovered in 1970 by well 49/29-1 and a total of nine wells have been drilled on the structure. Gas is produced from the Leman Sandstone Formation of Early Permian age. The reservoir section is comprised predominantly of stacked aeolian dune sands possessing excellent poroperm characteristics. The structure is a complex NW-SE trending horst block with a common gas-water contact at 8904 ft TVDss. Low structural relief has presented a major challenge to field development, which has utilized extended reach wells to maximize drainage potential. Initial gas-in-place is estimated at 289 BCF with recoverable reserves in the order of 196 BCF. The field came on production in September 1995 via a sub-sea tie back to the Thames infrastructure and has an expected field life of 10 years
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Johnson, Jeffrey R., Cherie Achilles, James F. Bell, et al. "Visible/near-infrared spectral diversity from in situ observations of the Bagnold Dune Field sands in Gale Crater, Mars." Journal of Geophysical Research: Planets 122, no. 12 (2017): 2655–84. http://dx.doi.org/10.1002/2016je005187.
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Lopez, Oliver, Khan Jadoon, and Thomas Missimer. "Method of Relating Grain Size Distribution to Hydraulic Conductivity in Dune Sands to Assist in Assessing Managed Aquifer Recharge Projects: Wadi Khulays Dune Field, Western Saudi Arabia." Water 7, no. 11 (2015): 6411–26. http://dx.doi.org/10.3390/w7116411.
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POWELL, J. M., F. N. IKPE, Z. C. SOMDA, and S. FERNÁNDEZ-RIVERA. "URINE EFFECTS ON SOIL CHEMICAL PROPERTIES AND THE IMPACT OF URINE AND DUNG ON PEARL MILLET YIELD." Experimental Agriculture 34, no. 3 (1998): 259–76. http://dx.doi.org/10.1017/s0014479798343069.
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Most farming systems in semi-arid West Africa rely on organic matter recycling for maintaining soil fertility. The cycling of biomass through ruminant livestock into dung (faeces) and urine that fertilize the soil has long been an important factor in t he nutrient cycling processes of these integrated, mixed crop/livestock systems. While dung greatly improves soil properties and crop yields, little is known about the effects of urine on soil chemical properties and the impact of dung and urine on crop p roduction. An average voiding of sheep urine applied to a sandy, siliceous soil in the Republic of Niger increased soil pH, available phosphorus and ammonium levels dramatically in the upper 10–15 cm of soil, especially during the first week following application. Losses of applied urine nitrogen via volatilization were in the order of 30–50%. A four-year field trial was conducted on the same soil type to evaluate the effects on pearl millet and weed yields of corralling cattle o r sheep overnight on cropland (dung plus urine application) for one, two or three nights, every one, two or three years versus the effects of applying only dung at the same application rates and intervals achieved with corralling. The main results of this field trial were that (1) urine had large positive effects on millet grain, threshed panicle, leaf, stem and weed yields, (2) sheep dung was more effective than cattle dung in increasing yield, (3) two nights of dung application was adequate for maximum yield and (4) the positive effects of dung and urine on yield lasted two to three cropping seasons after application.
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Dulias, Renata. "The disappearance of inland dunes landscape – a case study from southern Poland." Environmental & Socio-economic Studies 9, no. 2 (2021): 72–79. http://dx.doi.org/10.2478/environ-2021-0012.
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Abstract The paper presents changes in the landscape of inland dunes in one of the basins in the eastern part of Silesian Upland. Based on the analysis of archival maps and historical sources, the former dune landscape of Dąbrowa Basin was reconstructed. The current state of its preservation was determined based on contemporary cartographic materials and field research. It was established that the dunes occur on the floodplain, under-slope flattening, and cuesta escarpment (Ząbkowice Hummock)). The source of aeolian sands was fluvioglacial and alluvial deposits, which, as a result of aeolian transport, were moved to higher and higher morphological levels and stabilized on a substrate of different lithology and age. The impermeability of the bedrock – tills, clays, mudstones, siltstones had a significant influence on the dune landscape. It resulted in the presence of wetlands and peat bogs in the vicinity of most dunes. Consequently, the landscape of the valley was distinguished by a lot of contrast in terms of vegetation - dry pine forests or grassy areas on the dunes and moisture-loving vegetation in their surroundings. However, this landscape was under strong human pressure. Most of the dunes (3/4) have been destroyed in the last hundred years due to sand mining and industrial and residential construction. One of the largest dune fields in the Przemsza River basin and most floodplain and under-slope flattening dunes were utterly destroyed. In addition, an interesting dune at Triassic clays was almost fully exploited, and a rare case on the Silesian Upland where a dune entered the Triassic limestones was partially covered with concrete. There are only 25 dunes in the study area - they deserve protection both as the last fragments of the inland dunes landscape in this part of the Silesian Upland and for historical and natural reasons.
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Bradley, Richard, Aaron Watson, Ronnie Scott, and Annette Jack. "Littleferry, Sutherland." Proceedings of the Society of Antiquaries of Scotland 147 (November 30, 2018): 17–28. http://dx.doi.org/10.9750/psas.147.1248.
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The paper considers the significance of one of the largest collections of earlier prehistoric artefacts associated with a Scottish dune system. It came from a narrow spit, formerly an offshore island, at the mouth of Loch Fleet and was dominated by large numbers of arrowheads dating from the Early Neolithic period and the Beaker phase. They seem to have been made there, and many were unfinished. The original findspots are inaccessible today, but a programme of field walking in the surrounding area confirmed their exceptional character. Perhaps this remote location was chosen as a production site because of the specialised roles played by the artefacts made there. The results of this project are compared with similar evidence from the Culbin and Luce Sands.
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Hardwick, Kayla M., Luke J. Harmon, Scott D. Hardwick, and Erica Bree Rosenblum. "When Field Experiments Yield Unexpected Results: Lessons Learned from Measuring Selection in White Sands Lizards." PLOS ONE 10, no. 2 (2015): e0118560. http://dx.doi.org/10.1371/journal.pone.0118560.
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Yang, Ze-Yuan, Kai Wang, Yue Yuan, Jinting Huang, Zhi-Jun Chen, and Chen Li. "Non-Negligible Lag of Groundwater Infiltration Recharge: A Case in Mu Us Sandy Land, China." Water 11, no. 3 (2019): 561. http://dx.doi.org/10.3390/w11030561.
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Groundwater is often the main source of available water, and precipitation is one of the main recharge sources of groundwater in arid and semi-arid regions. This paper studies a fixed dune in Mu Us Sandy Land in China, establishes a numerical model, acquires hydraulic parameters and heat parameters of the vadose zone, and calculates the recharge coefficient based on field observation data and numerical modelling. These measurement results show that the response depths of storm rain are more than 90 cm, while those of small rain events are less than 10 cm. The numerical results show that infiltration depths are 10 cm for small rain and more than 90 cm for middle rain respectively. The lag time of the water content at 90 cm below the surface was 25 h following a middle rain, 18–19 h following a heavy rain, and 16–18 h following a storm rainfall. Groundwater recharge lag times (matrix flow) varied from 11 h to 48 h. Excluded precipitation for groundwater recharge was 11.25–11.75 mm in 1 h when groundwater depth was 120 cm and 15–15.5 mm when 140 cm, showing significant influence in groundwater resource evaluation.
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Enzel, Yehouda, Rivka Amit, Onn Crouvi, and Naomi Porat. "Abrasion-derived sediments under intensified winds at the latest Pleistocene leading edge of the advancing Sinai–Negev erg." Quaternary Research 74, no. 1 (2010): 121–31. http://dx.doi.org/10.1016/j.yqres.2010.04.002.
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AbstractQuaternary desert loess and sandstone–loessite relationships in the geological record raise questions regarding causes and mechanisms of silt formation and accretion. In the northern Sinai–Negev desert carbonate terrain, only sand abrasion in active erg could have produced the large quantities of quartzo-feldspathic silts constituting the late Quaternary northwestern Negev loess. In the continuum of source (medium to fine sand of dunes) to sink (silts in loess) the very fine sand is unaccounted for in the record. This weakens the sand abrasion model of silt formation as a global process. Here, we demonstrate that, as predicted by experiments, abrasion by advancing dunes generated large quantities of very fine sand (60–110 μm) deposited within the dune field and in close proximity downwind. This very fine sand was generated 13–11 ka, possibly synchronous with the Younger Dryas under gusty sand/dust storms in the southeastern Mediterranean and specifically in the northern Sinai–Negev erg. These very fine sands were washed down slope and filled small basins blocked by the advancing dunes; outside these sampling basins it is difficult to identify these sands as a distinct product. We conclude that ergs are mega-grinders of sand into very fine sand and silt under windy Quaternary and ancient aeolian desert environments.
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Frati, Giovanni, Patrick Launeau, Marc Robin, et al. "Coastal Sand Dunes Monitoring by Low Vegetation Cover Classification and Digital Elevation Model Improvement Using Synchronized Hyperspectral and Full-Waveform LiDAR Remote Sensing." Remote Sensing 13, no. 1 (2020): 29. http://dx.doi.org/10.3390/rs13010029.
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Due to the coastal morphodynamic being impacted by climate change there is a need for systematic and large-scale monitoring. The monitoring of sandy dunes in Pays-de-la-Loire (France) requires a simultaneous mapping of (i) its morphology, allowing to assess the sedimentary stocks and (ii) its low vegetation cover, which constitutes a significant proxy of the dune dynamics. The synchronization of hyperspectral imaging (HSI) with full-waveform (FWF) LiDAR is possible with an airborne platform. For a more intimate combination, we aligned the 1064 nm laser beam of a bi-spectral Titan FWF LiDAR with 401 bands and the 15 cm range resolution on the Hyspex VNIR camera with 160 bands and a 4.2 nm spectral resolution, making both types of data follow the same emergence angle. A ray tracing procedure permits to associate the data while keeping the acquisition angles. Stacking multiple shifted FWFs, which are linked to the same pixel, enables reaching a 5 cm range resolution grid. The objectives are (i) to improve the accuracy of the digital terrain models (DTM) obtained from an FWF analysis by calibrating it on dGPS field measurements and correcting it from local deviations induced by vegetation and (ii) in combination with airborne reflectances obtained with PARGE and ATCOR-4 corrections, to implement a supervised hierarchic classification of the main foredune vegetation proxies independently of the acquisition year and the physiological state. The normalization of the FWF LiDAR range to a dry sand reference waveform and the centering on their top canopy echoes allows to isolate Ammophilia arenaria from other vegetation types using two FWF indices, without confusion with slope effects. Fourteen HSI reflectance indices and 19 HSI Spectral Angle Mapping (SAM) indices based on 2017 spectral field measurements performed with the same Hyspex VNIR camera were stacked with both FWF indices into a single co-image for each acquisition year. A simple straightforward hierarchical classification of all 35 pre-classified co-image bands was successfully applied along 20 km, out of the 250 km of coastline acquired from 2017 to 2019, prefiguring its systematic application to the whole 250 km every year.
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Ineich, Ivan, and Charles P. Blanc. "Etudes sur les Acanthodactyles de Tunisie: VII - Les Acanthodactyles de l'Extrême-Sud tunisien." Amphibia-Reptilia 6, no. 1 (1985): 45–52. http://dx.doi.org/10.1163/156853885x00173.
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AbstractA multidimensional analysis of 34 characters of the colouring and scale pattern, providing 101 mathematical variables, applied to 77 Acanthodactylus collected in ten field stations in the Saharien Far-South of Tunisia, reveals a gradual and continuous morphological variation from populations of Acanthodactylus inornatus (with the back and sides of their body blackly reticulated and short legs) to populations with a A. longipes habitus (orange light body with small dorsal white spots, faint or nul black marks on their flanks and longer legs). Variation axis, approximately directed from North to South, also express an habitat difference between the populations dwelling on the reg nebkhas and sandy knolls in the beds and edges of the rivers (oueds) and those restricted to the high sand dunes of the Great Eastern Erg. The taxonomic status of the Acanthodactylus populations living in the Southern Tunisia should obviously be revised in relation with a high and mostly uncorrelated variability of the morphological characters of diagnostic use.
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Arciszewski, Tim J., Kelly R. Munkittrick, Bruce W. Kilgour, Heather M. Keith, Janice E. Linehan, and Mark E. McMaster. "Increased size and relative abundance of migratory fishes observed near the Athabasca oil sands." FACETS 2, no. 2 (2017): 833–58. http://dx.doi.org/10.1139/facets-2017-0028.
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Responses to chemical and physical stressors are commonly expected among organisms residing near the Athabasca oil sands. Physiological effects have been observed in fishes during field studies; but further effects associated with development are not clear or consistent among species. For instance, data from a fish fence in 2009 show declines in the relative abundances of some species, including Arctic grayling ( Thymallus arcticus). In contrast, increases were seen in white sucker ( Catostomus commersoni). This divergence suggests incomplete understanding of the status of fishes residing near the oil sands. However, an important challenge limiting understanding is the lack of reliable baseline or reference data. To overcome this challenge, we used iterative normal ranges and a historical data set (electrofishing surveys done from 1987 to 2014) to determine if changes have occurred in fishes captured in the lower Athabasca River. These analyses revealed clear increases in the lengths of white sucker and walleye ( Sander vitreus) and their relative abundances during the spawning season. The occurrence of these changes may be associated with overwintering location, but reduced fishing pressure in Lake Athabasca, eutrophication, or a cumulative effect may explain the form of changes detected in this study.
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Vrkoč, F., M. Vach, and V. Veleta. "Influence of different cultivation factors on the yield structure and on changes of soil properties." Plant, Soil and Environment 48, No. 5 (2011): 208–11. http://dx.doi.org/10.17221/4227-pse.
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The monitoring was carried on in the years 1996&ndash;2000 in the polyfactorial P-A&nbsp;field trial in Lukavec, Pelhřimov district. The given locality is characterized by low fertility sandy-loamy cambisoils, by long-term average annual rainfall of 653 mm, by average annual temperature of 7&deg;C and its altitude is 620 m. The field trial included different organic fertilizations; graduate N-doses, different soil tillage as well as different forecrops. It manifested in this group of field trials that the forecrop value of red clover and dung manured potatoes before winter wheat was practically the same in the given locality. The optimal N dose for potato yields was about 80 kg N.ha<sup>&ndash;1</sup>. In oats the yields after red clover with using the Horsch system in spring were significantly lower than after embedding of red clover in autumn. In cereals, graduated N doses increased the numbers of ears (panicles) per m2, but the mass of 1000 grains often decreased. In addition, N content in grain and straw increased with N doses, while pH annually decreased by 0.1 to 0.4.
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Shahed, A. B. M., M. A. Hossen, Al Mamun M. R., T. A. Tamanna, and M. Mizanur. "Impact of organic substance on growth attributes of mat type rice seedlings in the trays for machine transplanting." Journal of Science Technology and Environment Informatics 10, no. 1 (2020): 694–708. http://dx.doi.org/10.18801/jstei.100120.70.
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Rice seedling for mechanical transplanting must fulfill the prerequisites of guideline seedling block with uniform density of seedlings and between bending pulls for rolling. The present study was carried out at the Farm Power and Machinery Department, Sylhet Agricultural University, Sylhet during Boro season/2018-19 with the objective to assess the impact of organic substance on agronomic attributes of mat type rice seedling. The seedling was raised on plastic rigid tray utilizing sandy clay loam (SCL) and sandy clay (SC) soil blending with the organic fertilizer of cow-dung (CD), rice bran (RB), rice husk (RH) and tea wastage (TW) at the rate of 0.0, 5, 10, 15 and 20%, respectively. Averaged across the rate of soil mixture, 5 to 15% of CD and RB with the both types of soil gave higher seedling height, leaf length and stem length while 20% of CD and TW also showed better result for number of leaves and stem thickness. Considering all parameters, 15 to 20% rice husk and tea wastage mixed with the sandy clay loam soil and 10 to 15% with the sandy loam soil gave good result. Be that as it may, seedling quality differed among the natural composts with the two kinds of soil more or less like CD > RB > TW > RH. Water requirement in the SC soil was more compared to SCL soil. It was observed that crack was formed on the sandy clay soil in tray. For both types of soil, the density of seeds in the mat at the rate of 6-7 seeds cm-2 was found at 80% of soil mixture along with rice bran. The findings of the study could be promoted widely in farmer’s field to raise better quality of mat type seedling for better performance of the mechanical rice transplanter which ultimately leads to getting better rice yield.
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Fares, S., S. Mereu, G. Scarascia Mugnozza, et al. "The ACCENT-VOCBAS field campaign on biosphere-atmosphere interactions in a Mediterranean ecosystem of Castelporziano (Rome): site characteristics, climatic and meteorological conditions, and eco-physiology of vegetation." Biogeosciences Discussions 6, no. 1 (2009): 1185–227. http://dx.doi.org/10.5194/bgd-6-1185-2009.
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Abstract. Biosphere-atmosphere interactions were investigated on a sandy dune Mediterranean ecosystem in a field campaign held in 2007 within the frame of the European Projects ACCENT and VOCBAS. The campaign was carried out in the Presidential estate of Castelporziano, a peri-urban park close to Rome where several investigations on the emission of biogenic volatile organic compounds (BVOC) in Mediterranean area were performed in the past 15 y. While specific aspects of the campaign will be discussed in companion papers, the general climatic and physiological aspects will be presented here together with information regarding BVOC emission from the most common plants present in this ecosystem. During the campaign regular air movements were observed, dominated by moderate nocturnal land breeze and diurnal sea breeze. A regular daily increase of ozone concentration in the air was also observed, but daily peaks of ozone were much lower than those measured downwind of the Rome conurbation. The site was ideal as a natural photochemical reactor to observe reaction, transport and deposition processes occurring in the Mediterranean basin, where a sea-land breeze circulation system allows a strong mixing between biogenic and anthropogenic emissions and secondary pollutants. The campaign investigated emissions from a poorly studied and largely biodiverse ecosystem, often subjected to a combination of environmental stresses and to anthropogenic pollution. Measurements were run in May, when plant physiological conditions were still optimal, in absence of severe drought and heat stress. Foliar rates of photosynthesis and transpiration were as high as generally recorded in unstressed Mediterranean sclerophyllous plants. Most of the plant species emitted high level of monoterpenes, despite measurements being made in a period in which emissions of volatile isoprenoids could be restrained by developmental and environmental factors, such as leaf age and relatively low air temperature. No high isoprene emitting plants were found in the ecosystem. It is speculated that environmental stresses limit the emission during summer, differently than in other Mediterranean ecosystems. Accounting for the high spring emission of the dune ecosystem may be important to correct current algorithms at regional, ecosystem levels, and to interpret measurements of fluxes of volatile isoprenoids and pollutants.
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Attia, Ahmed, Salim Guettala, and Rebih Zaitri. "Using mixture design method to optimizing concretes characteristics made with binary and ternary sands." World Journal of Engineering 18, no. 2 (2021): 194–205. http://dx.doi.org/10.1108/wje-05-2020-0184.
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Purpose The purpose of this paper is to implement the mathematical models to predict concretes physico-mechanical characteristics made with binary and ternary sands using a mixture design method. It is a new technique that optimizes mixtures without being obliged to do a lot of experiments. The goal is to find the law governing the responses depending on mixture composition and capable of taking into account the effect of each parameter separately and in interaction between several parameters on the characteristics studied. Design/methodology/approach Mixture design method was used for optimizing concretes characteristics and studying the effects of river sand (RS), dune sand (DS) and crushed sand (CS) in combinations of binary system and ternary on workability, the compressive and flexural strengths of concretes at 7 and 28 days. A total of 21 mixtures of concrete were prepared for this investigation. The modeling was carried out by using JMP7 statistical software. Findings Mixture design method made it possible to obtain, with good precision, the statistical models and the prediction curves of studied responses. The models have relatively good correlation coefficients (R2 = 0.70) for all studied responses. The use of binary and ternary mixtures sands improves the workability and their mechanical strengths. The obtained results proved that concrete, based on binary mixture C15, presents the maximum compressive strength (MCS) on 28 day with an improvement of around 20%, compared to reference concrete (C21). For ternary mixtures, MCS on 28 day was obtained for the mixture C10 with an improvement of around 15% compared to C21. Increase in compressive strength during the progress of hydration reactions was accompanied by an increase in the flexural strength, but in different proportions. Originality/value The partial incorporation of DS (= 40%) in the concrete formulation can provide a solution for some work in the southern regions of country. In addition, the CS is an interesting alternative source for replacing 60% of RS. The concrete formulation based on local materials is really capable of solving the economic and technical problems encountered in the building field, as well as environmental problems. Local resources therefore constitute an economic, technological and environmental alternative.
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Miller, Mark A., and H. J. Ramey. "Effect of Temperature on Oil/Water Relative Permeabilities of Unconsolidated and Consolidated Sands." Society of Petroleum Engineers Journal 25, no. 06 (1985): 945–53. http://dx.doi.org/10.2118/12116-pa.
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Abstract Over the past 20 years, a number of studies have reported temperature effects on two-phase relative permeabilities in porous media. Some of the reported results, however, have been contradictory. Also, observed effects have not been explained in terms of fundamental properties known to govern two-phase flow. The purpose of this study was to attempt to isolate the fundamental properties affecting two-phase relative permeabilities at elevated temperatures. Laboratory dynamic-displacement relative permeability measurements were made on unconsolidated and consolidated sand cores with water and a refined white mineral oil. Experiments were run on 2-in. [5.1-cm] -diameter, 20-in. [52.-cm] -long cores from room temperature to 300F [149C]. Unlike previous researchers, we observed essentially no changes with temperature in either residual saturations or relative permeability relationships. We concluded that previous results may have been affected by viscous previous results may have been affected by viscous instabilities, capillary end effects, and/or difficulties in maintaining material balances. Introduction Interest in measuring relative permeabilities at elevated temperatures began in the 1960's with petroleum industry interest in thermal oil recovery. Early thermal oil recovery field operations (well heaters, steam injection, in-situ combustion) indicated oil flow rate increases far in excess of what was predicted by viscosity reductions resulting from heating. This suggested that temperature affects relative permeabilities. One of the early studies of temperature effects on relative permeabilities was presented by Edmondson, who performed dynamic displacement measurements with crude performed dynamic displacement measurements with crude and white oils and distilled water in Berea sandstone cores. Edmondson reported that residual oil saturations (ROS's) (at the end of 10 PV's of water injected) decreased with increasing temperature. Relative permeability ratios decreased with temperature at high water saturations but increased with temperature at low water saturations. A series of elevated-temperature, dynamic-displacement relative permeability measurements on clean quartz and "natural" unconsolidated sands were reported by Poston et al. Like Edmondson, Poston et al. reported a decrease in the "practical" ROS (at less than 1 % oil cut) as temperature increased. Poston et al. also reported an increase in irreducible water saturation. Although irreducible water saturations decreased with decreasing temperature, they did not revert to the original room temperature values. It was assumed that the cores became increasingly water-wet with an increase in both temperature and time; measured changes of the IFT and the contact angle with temperature increase, however, were not sufficient to explain observed effects. Davidson measured dynamic-displacement relative permeability ratios on a coarse sand and gravel core with permeability ratios on a coarse sand and gravel core with white oil displaced by distilled water, nitrogen, and superheated steam at temperatures up to 540F [282C]. Starting from irreducible water saturation, relative permeability ratio curves were similar to Edmondson's. permeability ratio curves were similar to Edmondson's. Starting from 100% oil saturation, however, the curves changed significantly only at low water saturations. A troublesome aspect of Davidson's work was that he used a hydrocarbon solvent to clean the core between experiments. No mention was made of any consideration of wettability changes, which could explain large increases in irreducible water saturations observed in some runs. Sinnokrot et al. followed Poston et al.'s suggestion of increasing water-wetness and performed water/oil capillary pressure measurements on consolidated sandstone and limestone cores from room temperature up to 325F [163C]. Sinnokrot et al confirmed that, for sandstones, irreducible water saturation appeared to increase with temperature. Capillary pressures increased with temperature, and the hysteresis between drainage and imbibition curves reduced to essentially zero at 300F [149C]. With limestone cores, however, irreducible water saturations remained constant with increase in temperature, as did capillary pressure curves. Weinbrandt et al. performed dynamic displacement experiments on small (0.24 to 0.49 cu in. [4 to 8 cm3] PV) consolidated Boise sandstone cores to 175F [75C] PV) consolidated Boise sandstone cores to 175F [75C] with distilled water and white oil. Oil relative permeabilities shifted toward high water saturations with permeabilities shifted toward high water saturations with increasing temperature, while water relative permeabilities exhibited little change. Weinbrandt et al. confirmed the findings of previous studies that irreducible water saturation increases and ROS decreases with increasing temperature. SPEJ P. 945
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Perissoratis, C., and D. Mitropoulos. "Late Quaternary Evolution of the Northern Aegean Shelf." Quaternary Research 32, no. 1 (1989): 36–50. http://dx.doi.org/10.1016/0033-5894(89)90030-6.
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AbstractA dense network of 3.5 kHz and Uniboom seismic profiles revealed the geological evolution of the Ierissos-Alexandroupolis Shelf area of the northern Aegean during the latest sea-level rise. Near the end of the Pleistocene, ca. 14,000 yr B.P., the sea was at about − 120 m, and almost 5300 km2 of shelf was exposed to subaerial erosion. Two permanet lakes existed in the Ierissos and Kavalla Gulfs, as well as a number of ephemeral lakes scattered throughout the rest of the area. Kavalla Gulf was drained by the Nestos River which joined the Strymon River at the outer Strymonikos Plateau. On the flat Samothraki Plateau were dune fields, marshes, and a number of minor seasonal rivers, while the Evros River flowed east of the plateau. By ca. 13,000 yr B.P. the sea had risen to − 70 m and covered 30% of the previously exposed shelf. The lakes at Ierissos and Strymonikos Gulfs were shallower and the sea approached to within about 5 km of them. Kavalla Gulf and the adjacent eastern Strymonikos Plateau lay 10 m above sea level, while the sea intruded along river mouths at the Samothraki Plateau. During this transgression of the sea river-bed gravels and sands were covered by silts and clays. At the Pleistocene-Holocene transition, ca. 10,500 yr B.P., the sea lay at about − 50 m and in areas of steep slope the coast was close to its present position. At Kavalla Gulf, the sea advanced along the paleochannel of the Nestos River, and the island of Samothraki was separated from the mainland. By ca. 7500 yr B.P. the sea was only 15 m below its present level and the northeastern Aegean shelf assumed nearly its present morphology. The Nestos River changed course to the east and Thassos Island was separated from the mainland. Coarse sediment formed wedges nearshore, whereas fine-grained sediments were distributed widely by current action. In many areas, relict sediments are present.
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Sobrado, M. A. "Leaf tissue water relations and hydraulic properties of sclerophyllous vegetation on white sands of the upper Rio Negro in the Amazon region." Journal of Tropical Ecology 25, no. 3 (2009): 271–80. http://dx.doi.org/10.1017/s026646740900604x.
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Abstract:The objective of this study was to explore the leaf tissue water relations in terminal branches, as well as the relations between xylem structure and function of five sclerophyllous species coexisting on white sands within the Amazon region. In these species, which possess costly leaves and thrive in an extremely nutrient-poor habitat, the preservation of leaf survival would be of comparable importance to the preservation of xylem vessels. Three trees per species were tagged in the field for all measurements. Minimum leaf water potential (Ψ) was −1.53 ± 0.61 and −0.94 ± 0.10 MPa during rainless and rainy days, respectively. The Ψ for turgor loss averaged −1.92 ± 0.05 MPa. Therefore, minimum Ψ was maintained within a safety range above the critical value for turgor loss. Xylem (Kx) and leaf (Kl) specific conductivity averaged 1.4 ± 0.22 and 0.00033 ± 0.000045 kg m−1 s−1 MPa−1, respectively. Water supply was favoured in species with higher vessel density, and all species depended on relatively less abundant larger vessels for water transport. This would be advantageous because leaves were unable to develop very negative water potentials in order to maintain transpiration. High transpiration rates may be restricted to a few hours daily so as to prevent cavitation of widest vessels.
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Holliday, Vance T., and David J. Meltzer. "Geoarchaeology of the Midland (Paleoindian) Site, Texas." American Antiquity 61, no. 4 (1996): 755–71. http://dx.doi.org/10.2307/282016.
Full textAbstract:
In 1953 human remains and a new type of Paleoindian artifact were discovered eroding from a "blowout" in a small dune field along Monahans Draw, near Midland, Texas, on the Southern High Plains. The projectile points became the type “Midland” collection. Stratigraphy, radiometric dating, paleontology, and geochemistry suggested that the artifacts and bones dated to at least 10,000 B.P. and that the human remains were possibly as old as 20,000 B.P. The researchers believed that the human bones were from below a red sand that in turn was below a Folsom occupation. The dating of the human remains has long been problematic, however, and recent attempts to apply U-series dating further confuse the story. Geoarchaeological investigations were carried out at the site from 1989 to 1992 to reevaluate the geochronology, with particular reference to the age of the skeletal material. We reach several conclusions: (1) there are two Red Sands; (2) the human remains are from below the upper Red Sand, but the Folsom material is from above the lower Red Sand and, therefore, the Red Sand stratigraphy is not relevant to the age of the human remains; (3) the human remains were associated with the valley-margin facies of a lacustrine carbonate that is well dated in the region and rarely is > 10,000 B.P.; and (4) all numerical dating methods applied at the site produced unreliable results. We find no compelling evidence that the human remains from the Midland site are older than Folsom age; they may be contemporary with or younger than the Folsom occupation.